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Sample records for acid receptor nmdar

  1. Early Growth Response 1 (Egr-1) Regulates N-Methyl-d-aspartate Receptor (NMDAR)-dependent Transcription of PSD-95 and α-Amino-3-hydroxy-5-methyl-4-isoxazole Propionic Acid Receptor (AMPAR) Trafficking in Hippocampal Primary Neurons.

    PubMed

    Qin, Xike; Jiang, Yongjun; Tse, Yiu Chung; Wang, Yunling; Wong, Tak Pan; Paudel, Hemant K

    2015-12-01

    The N-methyl-d-aspartate receptor (NMDAR) controls synaptic plasticity and memory function and is one of the major inducers of transcription factor Egr-1 in the hippocampus. However, how Egr-1 mediates the NMDAR signal in neurons has remained unclear. Here, we show that the hippocampus of mice lacking Egr-1 displays electrophysiology properties and ultrastructure that are similar to mice overexpressing PSD-95, a major scaffolding protein of postsynaptic density involved in synapse formation, synaptic plasticity, and synaptic targeting of AMPA receptors (AMPARs), which mediate the vast majority of excitatory transmission in the CNS. We demonstrate that Egr-1 is a transcription repressor of the PSD-95 gene and is recruited to the PSD-95 promoter in response to NMDAR activation. Knockdown of Egr-1 in rat hippocampal primary neurons blocks NMDAR-induced PSD-95 down-regulation and AMPAR endocytosis. Likewise, overexpression of Egr-1 in rat hippocampal primary neurons causes reduction in PSD-95 protein level and promotes AMPAR endocytosis. Our data indicate that Egr-1 is involved in NMDAR-mediated PSD-95 down-regulation and AMPAR endocytosis, a process important in the expression of long term depression. PMID:26475861

  2. N-methyl-d-aspartate glutamate receptor (NMDA-R) antibodies in mild cognitive impairment and dementias.

    PubMed

    Busse, Stefan; Brix, Britta; Kunschmann, Ralf; Bogerts, Bernhard; Stoecker, Winfried; Busse, Mandy

    2014-08-01

    The N-methyl-d-aspartate glutamate receptor (NMDA-R) plays a central role in learning and memory and has therefore a potential role in the pathophysiology of neuropsychiatric disorders. Recently, we detected NMDA-R autoantibodies in aged healthy volunteers without neuropsychiatric disorders. Since studies showing the involvement of NMDA-R antibodies in mild cognitive impairment and different forms of dementia are rare, we examined NMDA-R antibodies (Abs) in serum of 46 patients with Alzheimer's disease (AD), 26 patients with subcortical ischemic vascular dementia (SIVD), 18 patients with frontotemporal dementia (FTD), 11 patients with Lewy body disease (LBD) and 33 patients with mild cognitive impairment (MCI) and in 21 healthy aged, gender-matched volunteers. While IgM and/or IgA NMDA-R Abs were present in all groups, IgG was only detected in one AD sample. Seropositivity could be correlated with the presence of co-symptoms: MCI and AD patients suffering from depression and AD and SIVD patients with a psychosis were almost all NMDA-R Ab positive. We conclude that the presence of NMDA-R Abs in dementia could influence the incidence of comorbid depressive and/or psychotic states.

  3. The involvement of N-methyl-D-aspartate receptor (NMDAR) subunit NR1 in the pathophysiology of schizophrenia.

    PubMed

    Ju, Peijun; Cui, Donghong

    2016-03-01

    Schizophrenia is a severe mental illness that afflicts nearly 1% of the world population. Although the exact pathophysiology of schizophrenia is unknown, the N-methyl-d-aspartate receptor (NMDAR), a major glutamate receptor subtype, has received great attention. The NR1 subunit is often considered indispensable for functional NMDAR assemblies, abnormal modulation of which is found in patients with schizophrenia. In this review, we discuss how disrupted function of NR1 subunits in NMDAR leads to the progression and development of symptoms of schizophrenia-like behaviors in a variety of genetically modified mouse models. We also discuss some of the susceptible genes and shared signaling pathways among the schizophrenia, and how their mutations lead to NR1 subunits hypofunction. Finally, we suggest that the subunit-selective modulators of NR1 subunits in NMDA receptors may be promising tools for the therapy of schizophrenia.

  4. Transient receptor potential channel 1/4 reduces subarachnoid hemorrhage-induced early brain injury in rats via calcineurin-mediated NMDAR and NFAT dephosphorylation

    PubMed Central

    Wang, Zhong; Wang, Yibin; Tian, Xiaodi; Shen, Haitao; Dou, Yang; Li, Haiying; Chen, Gang

    2016-01-01

    Transient receptor potential channel 1/4 (TRPC1/4) are considered to be related to subarachnoid hemorrhage (SAH)-induced cerebral vasospasm. In this study, a SAH rat model was employed to study the roles of TRPC1/4 in the early brain injury (EBI) after SAH. Primary cultured hippocampal neurons were exposed to oxyhemoglobin to mimic SAH in vitro. The protein levels of TRPC1/4 increased and peaked at 5 days after SAH in rats. Inhibition of TRPC1/4 by SKF96365 aggravated SAH-induced EBI, such as cortical cell death (by TUNEL staining) and degenerating (by FJB staining). In addition, TRPC1/4 overexpression could increase calcineurin activity, while increased calcineurin activity could promote the dephosphorylation of N-methyl-D-aspartate receptor (NMDAR). Calcineurin antagonist FK506 could weaken the neuroprotection and the dephosphorylation of NMDAR induced by TRPC1/4 overexpression. Contrarily, calcineurin agonist chlorogenic acid inhibited SAH-induced EBI, even when siRNA intervention of TRPC1/4 was performed. Moreover, calcineurin also could lead to the nuclear transfer of nuclear factor of activated T cells (NFAT), which is a transcription factor promoting the expressions of TRPC1/4. TRPC1/4 could inhibit SAH-induced EBI by supressing the phosphorylation of NMDAR via calcineurin. TRPC1/4-induced calcineurin activation also could promote the nuclear transfer of NFAT, suggesting a positive feedback regulation of TRPC1/4 expressions. PMID:27641617

  5. Transient receptor potential channel 1/4 reduces subarachnoid hemorrhage-induced early brain injury in rats via calcineurin-mediated NMDAR and NFAT dephosphorylation.

    PubMed

    Wang, Zhong; Wang, Yibin; Tian, Xiaodi; Shen, Haitao; Dou, Yang; Li, Haiying; Chen, Gang

    2016-01-01

    Transient receptor potential channel 1/4 (TRPC1/4) are considered to be related to subarachnoid hemorrhage (SAH)-induced cerebral vasospasm. In this study, a SAH rat model was employed to study the roles of TRPC1/4 in the early brain injury (EBI) after SAH. Primary cultured hippocampal neurons were exposed to oxyhemoglobin to mimic SAH in vitro. The protein levels of TRPC1/4 increased and peaked at 5 days after SAH in rats. Inhibition of TRPC1/4 by SKF96365 aggravated SAH-induced EBI, such as cortical cell death (by TUNEL staining) and degenerating (by FJB staining). In addition, TRPC1/4 overexpression could increase calcineurin activity, while increased calcineurin activity could promote the dephosphorylation of N-methyl-D-aspartate receptor (NMDAR). Calcineurin antagonist FK506 could weaken the neuroprotection and the dephosphorylation of NMDAR induced by TRPC1/4 overexpression. Contrarily, calcineurin agonist chlorogenic acid inhibited SAH-induced EBI, even when siRNA intervention of TRPC1/4 was performed. Moreover, calcineurin also could lead to the nuclear transfer of nuclear factor of activated T cells (NFAT), which is a transcription factor promoting the expressions of TRPC1/4. TRPC1/4 could inhibit SAH-induced EBI by supressing the phosphorylation of NMDAR via calcineurin. TRPC1/4-induced calcineurin activation also could promote the nuclear transfer of NFAT, suggesting a positive feedback regulation of TRPC1/4 expressions. PMID:27641617

  6. Transient receptor potential channel 1/4 reduces subarachnoid hemorrhage-induced early brain injury in rats via calcineurin-mediated NMDAR and NFAT dephosphorylation.

    PubMed

    Wang, Zhong; Wang, Yibin; Tian, Xiaodi; Shen, Haitao; Dou, Yang; Li, Haiying; Chen, Gang

    2016-01-01

    Transient receptor potential channel 1/4 (TRPC1/4) are considered to be related to subarachnoid hemorrhage (SAH)-induced cerebral vasospasm. In this study, a SAH rat model was employed to study the roles of TRPC1/4 in the early brain injury (EBI) after SAH. Primary cultured hippocampal neurons were exposed to oxyhemoglobin to mimic SAH in vitro. The protein levels of TRPC1/4 increased and peaked at 5 days after SAH in rats. Inhibition of TRPC1/4 by SKF96365 aggravated SAH-induced EBI, such as cortical cell death (by TUNEL staining) and degenerating (by FJB staining). In addition, TRPC1/4 overexpression could increase calcineurin activity, while increased calcineurin activity could promote the dephosphorylation of N-methyl-D-aspartate receptor (NMDAR). Calcineurin antagonist FK506 could weaken the neuroprotection and the dephosphorylation of NMDAR induced by TRPC1/4 overexpression. Contrarily, calcineurin agonist chlorogenic acid inhibited SAH-induced EBI, even when siRNA intervention of TRPC1/4 was performed. Moreover, calcineurin also could lead to the nuclear transfer of nuclear factor of activated T cells (NFAT), which is a transcription factor promoting the expressions of TRPC1/4. TRPC1/4 could inhibit SAH-induced EBI by supressing the phosphorylation of NMDAR via calcineurin. TRPC1/4-induced calcineurin activation also could promote the nuclear transfer of NFAT, suggesting a positive feedback regulation of TRPC1/4 expressions.

  7. Seroprevalence of N-methyl-D-aspartate glutamate receptor (NMDA-R) autoantibodies in aging subjects without neuropsychiatric disorders and in dementia patients.

    PubMed

    Busse, Stefan; Busse, Mandy; Brix, Britta; Probst, Christian; Genz, Axel; Bogerts, Bernhard; Stoecker, Winfried; Steiner, Johann

    2014-09-01

    N-methyl-D-aspartate glutamate receptors (NMDA-R) play a key role in learning and memory. Therefore, they may be involved in the pathophysiology of dementia. NMDA-R autoantibodies directed against the NR1a subunit of the NMDA-R, which were first identified as a specific marker for a severe form of encephalitis, cause a decrease in NMDA-Rs, resulting in cognitive impairment and psychosis. We examined the prevalence of NR1a NMDA-R autoantibodies in the serum and cerebrospinal fluid (CSF) of 24 patients with Alzheimer's disease (AD), 20 patients with subcortical ischemic vascular dementia (SIVD), and 274 volunteers without neuropsychiatric disorder. The latter cases showed an association of seropositivity with age. Notably, the overall seroprevalence was not statistically different between dementia patients and matched controls. Further analysis of the patient samples showed that four patients with AD and three patients with SIVD had positive NMDA-R IgM, IgG, and/or IgA autoantibody titers in serum. These patients suffered from psychosis (with the exception of one case). CSF samples were negative for NMDA-R autoantibodies. We conclude that the seroprevalence of NMDA-R-directed autoantibodies is age-related. It has to be clarified by larger studies whether NMDA-R autoantibodies in peripheral blood may predispose patients with AD and SIVD to susceptibility for psychotic episodes if disturbances of blood-brain-barrier integrity occur.

  8. Expression of N-methyl-D-aspartate receptor subunits in the bovine ovum: ova as a potential source of autoantigens causing anti-NMDAR encephalitis.

    PubMed

    Tachibana, Naoko; Kinoshita, Michiaki; Kametani, Fuyuki; Tanaka, Keiko; Une, Yumi; Komatsu, Yotaro; Kobayashi, Yukihiro; Ikeda, Shu-ichi

    2015-01-01

    Autoimmune synaptic encephalitis is characterized by the presence of autoantibodies against synaptic constituent receptors and manifests as neurological and psychiatric disorders. Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is such an autoimmune disorder that predominantly affects young women. It is associated with antibodies against the extracellular region of the NR1 subunit of postsynaptic NMDAR. Each NMDAR functions as a heterotetrameric complex that is composed of four subunits, including NR1 and NR2A, NR2B, or NR2C. Importantly, ovarian teratoma is a typical complication of anti-NMDAR encephalitis in female patients and may contain antigenic neural tissue; however, antigenic sites remain unknown in female patients without ovarian teratoma. The purpose of this study was to investigate the expression of NMDARs in the ovum. We detected NR1 and NR2B immunoreactivity in protein fractions extracted from the bovine ovary and ova by SDS-polyacrylamide gel electrophoresis and immunoblotting analysis. Immunoprecipitates digested with trypsin were analyzed by reverse phase liquid chromatography coupled to tandem mass spectrometry. We obtained the following five peptides: SPFGRFK and KNLQDR, which are consistent with partial sequences of human NR1, and GVEDALVSLK, QPTVAGAPK, and NEVMSSK, which correspond to those of NR2A, NR2B and NR2C, respectively. Immunocytochemical analysis revealed that the bovine ovum was stained with the immunoglobulin G purified from the serum of a patient with anti-NMDAR encephalitis. Taken together, we propose that the normal ovum expresses NMDARs that have strong affinity for the disease-specific IgG. The presence of NMDARs in ova may help explain why young females without ovarian teratomas are also affected by anti-NMDAR encephalitis.

  9. Hydroxysafflor Yellow A Protects Neurons From Excitotoxic Death through Inhibition of NMDARs

    PubMed Central

    Wang, Xingtao; Ma, Zhiyuan; Fu, Zhongxiao; Gao, Su; Yang, Liu; Jin, Yan; Sun, Hui; Wang, Chaoyun; Fan, Weiming; Chen, Lin; Zheng, Qing-Yin; Bi, Guoqiang

    2016-01-01

    Excessive glutamate release causes overactivation of N-methyl d-aspartate receptors (NMDARs), leading to excitatory neuronal damage in cerebral ischemia. Hydroxysafflor yellow A (HSYA), a compound extracted from Carthamus tinctorius L., has been reported to exert a neuroprotective effect in many pathological conditions, including brain ischemia. However, the underlying mechanism of HSYA's effect on neurons remains elusive. In the present study, we conducted experiments using patch-clamp recording of mouse hippocampal slices. In addition, we performed Ca2+ imaging, Western blots, as well as mitochondrial-targeted circularly permuted yellow fluorescent protein transfection into cultured hippocampal neurons in order to decipher the physiological mechanism underlying HSYA's neuroprotective effect. Through the electrophysiology experiments, we found that HSYA inhibited NMDAR-mediated excitatory postsynaptic currents without affecting α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor and γ-aminobutyric acid A-type receptor-mediated currents. This inhibitory effect of HSYA on NMDARs was concentration dependent. HSYA did not show any preferential inhibition of either N-methyl d-aspartate receptor subtype 2A- or N-methyl d-aspartate receptor subtype 2B- subunit-containing NMDARs. Additionally, HSYA exhibits a facilitatory effect on paired NMDAR-mediated excitatory postsynaptic currents. Furthermore, HSYA reduced the magnitude of NMDAR-mediated membrane depolarization currents evoked by oxygen-glucose deprivation, and suppressed oxygen-glucose deprivation–induced and NMDAR-dependent ischemic long-term potentiation, which is believed to cause severe reperfusion damage after ischemia. Through the molecular biology experiments, we found that HSYA inhibited the NMDA-induced and NMDAR-mediated intracellular Ca2+ concentration increase in hippocampal cultures, reduced apoptotic and necrotic cell deaths, and prevented mitochondrial damage. Together, our data

  10. Hydroxysafflor Yellow A Protects Neurons From Excitotoxic Death through Inhibition of NMDARs.

    PubMed

    Wang, Xingtao; Ma, Zhiyuan; Fu, Zhongxiao; Gao, Su; Yang, Liu; Jin, Yan; Sun, Hui; Wang, Chaoyun; Fan, Weiming; Chen, Lin; Zheng, Qing-Yin; Bi, Guoqiang; Ma, Chun-Lei

    2016-01-01

    Excessive glutamate release causes overactivation of N-methyld-aspartate receptors (NMDARs), leading to excitatory neuronal damage in cerebral ischemia. Hydroxysafflor yellow A (HSYA), a compound extracted from Carthamus tinctorius L., has been reported to exert a neuroprotective effect in many pathological conditions, including brain ischemia. However, the underlying mechanism of HSYA's effect on neurons remains elusive. In the present study, we conducted experiments using patch-clamp recording of mouse hippocampal slices. In addition, we performed Ca(2+) imaging, Western blots, as well as mitochondrial-targeted circularly permuted yellow fluorescent protein transfection into cultured hippocampal neurons in order to decipher the physiological mechanism underlying HSYA's neuroprotective effect.Through the electrophysiology experiments, we found that HSYA inhibited NMDAR-mediated excitatory postsynaptic currents without affecting α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor and γ-aminobutyric acid A-type receptor-mediated currents. This inhibitory effect of HSYA on NMDARs was concentration dependent. HSYA did not show any preferential inhibition of either N-methyld-aspartate receptor subtype 2A- or N-methyld-aspartate receptor subtype 2B- subunit-containing NMDARs. Additionally, HSYA exhibits a facilitatory effect on paired NMDAR-mediated excitatory postsynaptic currents. Furthermore, HSYA reduced the magnitude of NMDAR-mediated membrane depolarization currents evoked by oxygen-glucose deprivation, and suppressed oxygen-glucose deprivation-induced and NMDAR-dependent ischemic long-term potentiation, which is believed to cause severe reperfusion damage after ischemia. Through the molecular biology experiments, we found that HSYA inhibited the NMDA-induced and NMDAR-mediated intracellular Ca(2+)concentration increase in hippocampal cultures, reduced apoptotic and necrotic cell deaths, and prevented mitochondrial damage. Together, our data

  11. Ethanol Attenuates Peripheral NMDAR-Mediated Vascular Oxidative Stress and Pressor Response

    PubMed Central

    McGee, Marie A.; Abdel-Rahman, Abdel A.

    2015-01-01

    There are no studies on the acute effect of ethanol on peripheral N-methyl-D-aspartate receptor (NMDAR)-mediated increases in reactive oxygen species (ROS) and blood pressure (BP). We tested the hypothesis that ethanol antagonism of peripheral NMDAR dampens systemic NMDA-evoked increases in vascular ROS and BP. We investigated the effect of ethanol (1 g/kg) on BP and heart rate (HR) responses elicited by systemic bolus (125–1000 μg/kg, intra-venous [i.v.]) or infused (180 μg/kg/min) NMDA in conscious male Sprague-Dawley rats. We also hypothesized that peripheral NMDAR blockade with DL-2-Amino-5-phosphonopentanoic acid (AP-5; 5 mg/kg, i.v.) uncovers an ethanol- (1 or 1.5 g/kg) evoked hypotensive response. Ethanol attenuated the peripheral NMDAR-mediated pressor and bradycardic responses caused by NMDA infusion, and ex vivo studies revealed parallel ethanol attenuation of peripheral NMDAR-mediated increases in vascular ROS. While ethanol (1 or 1.5 g/kg) alone had no effect on BP, the higher dose caused a hypotensive response in the presence of NMDAR blockade (AP-5). Blood ethanol concentrations were not statistically different in the groups that received ethanol alone or along with NMDA or AP-5. These findings are the first to demonstrate ethanol attenuation of peripheral NMDAR-mediated pressor response, and the uncovering of ethanol-evoked hypotension in the presence of peripheral NMDAR blockade. PMID:25986731

  12. α7nAchR/NMDAR coupling affects NMDAR function and object recognition.

    PubMed

    Li, Shupeng; Nai, Qiang; Lipina, Tatiana V; Roder, John C; Liu, Fang

    2013-12-20

    The α7 nicotinic acetylcholine receptor (nAchR) and NMDA glutamate receptor (NMDAR) are both ligand-gated ion channels permeable to Ca2+ and Na+. Previous studies have demonstrated functional modulation of NMDARs by nAchRs, although the molecular mechanism remains largely unknown. We have previously reported that α7nAchR forms a protein complex with the NMDAR through a protein-protein interaction. We also developed an interfering peptide that is able to disrupt the α7nAchR-NMDAR complex and blocks cue-induced reinstatement of nicotine-seeking in rat models of relapse. In the present study, we investigated whether the α7nAchR-NMDAR interaction is responsible for the functional modulation of NMDAR by α7nAchR using both electrophysiological and behavioral tests. We have found that activation of α7nAchR upregulates NMDAR-mediated whole cell currents and LTP of mEPSC in cultured hippocampal neurons, which can be abolished by the interfering peptide that disrupts the α7nAchR-NMDAR interaction. Moreover, administration of the interfering peptide in mice impairs novel object recognition but not Morris water maze performance. Our results suggest that α7nAchR/NMDAR coupling may selectively affect some aspects of learning and memory.

  13. In vitro effects of glutamate and N-methyl-D-aspartate receptor (NMDAR) antagonism on human tendon derived cells.

    PubMed

    Dean, Benjamin John Floyd; Snelling, Sarah J B; Dakin, Stephanie Georgina; Javaid, Muhammad Kassim; Carr, Andrew Jonathan

    2015-10-01

    It is known that extracellular glutamate concentrations are increased in tendinopathy but the effects of glutamate upon human tendon derived cells are unknown. The primary purpose was to investigate the effect of glutamate exposure on human tendon-derived cells in terms of viability, protein, and gene expression. The second purpose was to assess whether NMDAR antagonism would affect the response of tendon-derived cells to glutamate exposure. Human tendon-derived cells were obtained from supraspinatus tendon tissue obtained during rotator cuff repair (tendon tear derived cells) and from healthy hamstring tendon tissue (control cells). The in vitro impact of glutamate exposure and NMDAR antagonism (MK-801) was measured using the Alamar blue cell viability assay, immunocytochemistry, and quantitative real-time PCR. Glutamate reduced cell viability at 24 h in tendon tear derived cells but not in control cells at concentrations of 7.5 mM and above. Cell viability was significantly reduced after 72 h of 1.875 mM glutamate in both cell groups; this deleterious effect was attenuated by NMDAR antagonism with 10 µM MK-801. Both 24 and 72 h of 1.875 mM glutamate exposure reduced Type 1 alpha 1 collagen (COL1A1) and Type 3 alpha 1 collagen (COL3A1) gene expression, but increased Aggrecan gene expression. We propose that these effects of glutamate on tendon derived cells including reduced cell viability and altered matrix gene expression contribute to the pathogenesis of tendinopathy. PMID:26041147

  14. Suppression of NMDA receptor function in mice prenatally exposed to valproic acid improves social deficits and repetitive behaviors

    PubMed Central

    Kang, Jaeseung; Kim, Eunjoon

    2015-01-01

    Animals prenatally exposed to valproic acid (VPA), an antiepileptic agent, have been used as a model for autism spectrum disorders (ASDs). Previous studies have identified enhanced NMDA receptor (NMDAR) function in the brain of VPA rats, and demonstrated that pharmacological suppression of NMDAR function normalizes social deficits in these animals. However, whether repetitive behavior, another key feature of ASDs, can be rescued by NMDAR inhibition remains unknown. We report here that memantine, an NMDAR antagonist, administered to VPA mice rescues both social deficits and repetitive behaviors such as self-grooming and jumping. These results suggest that suppression of elevated NMDAR function in VPA animals normalizes repetitive behaviors in addition to social deficits. PMID:26074764

  15. Ethanol attenuates peripheral NMDAR-mediated vascular oxidative stress and pressor response.

    PubMed

    McGee, Marie A; Abdel-Rahman, Abdel A

    2015-08-01

    There are no studies on the acute effect of ethanol on peripheral N-methyl-d-aspartate receptor (NMDAR)-mediated increases in reactive oxygen species (ROS) and blood pressure (BP). We tested the hypothesis that ethanol antagonism of peripheral NMDAR dampens systemic NMDA-evoked increases in vascular ROS and BP. We investigated the effect of ethanol (1 g/kg) on BP and heart rate (HR) responses elicited by systemic bolus (125-1000 μg/kg, intra-venous [i.v.]) or infused (180 μg/kg/min) NMDA in conscious male Sprague-Dawley rats. We also hypothesized that peripheral NMDAR blockade with DL-2-Amino-5-phosphonopentanoic acid (AP-5; 5 mg/kg, i.v.) uncovers an ethanol- (1 or 1.5 g/kg) evoked hypotensive response. Ethanol attenuated the peripheral NMDAR-mediated pressor and bradycardic responses caused by NMDA infusion, and ex vivo studies revealed parallel ethanol attenuation of peripheral NMDAR-mediated increases in vascular ROS. While ethanol (1 or 1.5 g/kg) alone had no effect on BP, the higher dose caused a hypotensive response in the presence of NMDAR blockade (AP-5). Blood ethanol concentrations were not statistically different in the groups that received ethanol alone or along with NMDA or AP-5. These findings are the first to demonstrate ethanol attenuation of peripheral NMDAR-mediated pressor response, and the uncovering of ethanol-evoked hypotension in the presence of peripheral NMDAR blockade.

  16. Trafficking of the NMDAR2B Receptor Subunit Distal Cytoplasmic Tail from Endoplasmic Reticulum to the Synapse

    PubMed Central

    Standley, Steve; Petralia, Ronald S.; Hamilton, Rebecca; Wang, Ya-Xian; Schubert, Manfred

    2012-01-01

    NMDA receptor NR2A/B subunits have PDZ-binding domains on their extreme C-termini that are known to interact with the PSD-95 family and other PDZ proteins. We explore the interactions between PSD-95 family proteins and the NR2A/B cytoplasmic tails, and the consequences of these interactions, from the endoplasmic reticulum (ER) through delivery to the synapse in primary rat hippocampal and cortical cultured neurons. We find that the NR2A/B cytoplasmic tails cluster very early in the secretory pathway and interact serially with SAP102 beginning at the intermediate compartment, and then PSD-95. We further establish that colocalization of the distal C-terminus of NR2B and PSD-95 begins at the trans-Golgi Network (TGN). Formation of NR2B/PSD-95/SAP102 complexes is dependent on the PDZ binding domain of NR2B subunits, but association with SAP102 and PSD-95 plays no distinguishable role in cluster pre-formation or initial targeting to the vicinity of the synapse. Instead the PDZ binding domain plays a role in restricting cell-surface clusters to postsynaptic targets. PMID:22761831

  17. Acetylsalicylic acid and ascorbic acid combination improves cognition; via antioxidant effect or increased expression of NMDARs and nAChRs?

    PubMed

    Kara, Yusuf; Doguc, Duygu Kumbul; Kulac, Esin; Gultekin, Fatih

    2014-05-01

    Chronic inflammation occurs systematically in the central nervous system during ageing, it has been shown that neuroinflammation plays an important role in the pathogenesis of many neurodegenerative disorders. Aspirin, a nonselective COX inhibitor, as well as ascorbic acid, has been purported to protect cerebral tissue. We investigated the effects of subchronic aspirin and ascorbic acid usage on spatial learning, oxidative stress and expressions of NR2A, NR2B, nAChRα7, α4 and β2. Forty male rats (16-18 months) were divided into 4 groups, namely, control, aspirin-treated, ascorbic acid-treated, aspirin+ascorbic acid-treated groups. Following 10-weeks administration period, rats were trained and tested in the Morris water maze. 8-Hydroxy-2-deoxyguanosine and malondialdehyde were evaluated by ELISA and HPLC, respectively. Receptor expressions were assessed by western blotting of hippocampi. Spatial learning performance improved partially in the aspirin group, but significant improvement was seen in the aspirin+ascorbic acid group (p < 0.05). While 8-hydroxy-2-deoxyguanosine and malondialdehyde levels were significantly decreased, NR2B and nAChRα7 expressions were significantly increased in the aspirin+ascorbic acid group as compared to the control group (p < 0.05). Subchronic treatment with aspirin+ascorbic acid in aged rats was shown to enhance cognitive performance and increase the expressions of several receptors related to learning and memory process.

  18. Learning in the Absence of Experience-Dependent Regulation of NMDAR Composition

    ERIC Educational Resources Information Center

    Lebel, David; Sidhu, Nishchal; Barkai, Edi; Quinlan, Elizabeth M.

    2006-01-01

    Olfactory discrimination (OD) learning consists of two phases: an initial N-methyl-d-aspartate (NMDA) receptor--sensitive rule-learning phase, followed by an NMDA receptor (NMDAR)--insensitive pair-learning phase. The rule-learning phase is accompanied by changes in the composition and function of NMDARs at synapses in the piriform cortex,…

  19. N-Methyl D-Aspartate Receptor Antagonist Kynurenic Acid Affects Human Cortical Development

    PubMed Central

    Bagasrawala, Inseyah; Zecevic, Nada; Radonjić, Nevena V.

    2016-01-01

    Kynurenic acid (KYNA), a neuroactive metabolite of tryptophan degradation, acts as an endogenous N-methyl-D-aspartate receptor (NMDAR) antagonist. Elevated levels of KYNA have been observed in pregnant women after viral infections and are considered to play a role in neurodevelopmental disorders. However, the consequences of KYNA-induced NMDAR blockade in human cortical development still remain elusive. To study the potential impact of KYNA on human neurodevelopment, we used an in vitro system of multipotent cortical progenitors, i.e., radial glia cells (RGCs), enriched from human cerebral cortex at mid-gestation (16–19 gestational weeks). KYNA treatment significantly decreased RGCs proliferation and survival by antagonizing NMDAR. This alteration resulted in a reduced number of cortical progenitors and neurons while number and activation of astrocytes increased. KYNA treatment reduced differentiation of RGCs into GABAergic neurons, while differentiation into glutamatergic neurons was relatively spared. Furthermore, in mixed cortical cultures KYNA triggered an inflammatory response as evidenced by increased levels of the pro-inflammatory cytokine IL-6. In conclusion, elevated levels of KYNA play a significant role in human RGC fate determination by antagonizing NMDARs and by activating an inflammatory response. The altered cell composition observed in cell culture following exposure to elevated KYNA levels suggests a mechanism for impairment of cortical circuitry formation in the fetal brain after viral infection, as seen in neurodevelopmental disorders such as schizophrenia. PMID:27746712

  20. Traces of Memory: Reacquisition of Fear Following Forgetting Is NMDAr-Independent

    ERIC Educational Resources Information Center

    Li, Stella; Richardson, Rick

    2013-01-01

    Recent research shows that while initial learning is dependent on "N"-methyl-D-aspartate receptors (NMDArs), relearning can be NMDAr-independent. In the present study we examined whether this switch also occurs following forgetting. The developing animal exhibits much more rapid rates of forgetting than adults, so infant rats were used. It was…

  1. Basic roles of key molecules connected with NMDAR signaling pathway on regulating learning and memory and synaptic plasticity.

    PubMed

    Wang, Hui; Peng, Rui-Yun

    2016-01-01

    With key roles in essential brain functions ranging from the long-term potentiation (LTP) to synaptic plasticity, the N-methyl-D-aspartic acid receptor (NMDAR) can be considered as one of the fundamental glutamate receptors in the central nervous system. The role of NMDA R was first identified in synaptic plasticity and has been extensively studied. Some molecules, such as Ca(2+), postsynaptic density 95 (PSD-95), calcium/calmodulin-dependent protein kinase II (CaMK II), protein kinase A (PKA), mitogen-activated protein kinase (MAPK) and cyclic adenosine monophosphate (cAMP) responsive element binding protein (CREB), are of special importance in learning and memory. This review mainly focused on the new research of key molecules connected with learning and memory, which played important roles in the NMDAR signaling pathway. PMID:27583167

  2. Activation of Extrasynaptic NMDARs at Individual Parallel Fiber–Molecular Layer Interneuron Synapses in Cerebellum

    PubMed Central

    Nahir, Ben

    2013-01-01

    NMDA receptors (NMDARs) expressed by cerebellar molecular layer interneurons (MLIs) are not activated by single exocytotic events but can respond to glutamate spillover following coactivation of adjacent parallel fibers (PFs), indicating that NMDARs are perisynaptic. Several types of synaptic plasticity rely on these receptors but whether they are activated at isolated synapses is not known. Using a combination of electrophysiological and optical recording techniques in acute slices of rat cerebellum, along with modeling, we find that repetitive activation of single PF–MLI synapses can activate NMDARs in MLIs. High-frequency stimulation, multivesicular release (MVR), or asynchronous release can each activate NMDARs. Frequency facilitation was found at all PF–MLI synapses but, while some showed robust MVR with increased release probability, most were limited to univesicular release. Together, these results reveal a functional diversity of PF synapses, which use different mechanisms to activate NMDARs. PMID:24107963

  3. Neuroleptic intolerance in patients with anti-NMDAR encephalitis

    PubMed Central

    Lejuste, Florian; Thomas, Laure; Picard, Géraldine; Desestret, Virginie; Ducray, François; Rogemond, Veronique; Psimaras, Dimitri; Antoine, Jean-Christophe; Delattre, Jean-Yves; Groc, Laurent; Leboyer, Marion

    2016-01-01

    Objective: To precisely describe the initial psychiatric presentation of patients with anti-NMDA receptor (NMDAR) antibodies encephalitis (anti-NMDAR encephalitis) to identify potential clues enhancing its early diagnosis. Methods: We retrospectively studied the French Reference Centre medical records of every adult patient with anti-NMDAR encephalitis to specify the patients' initial psychiatric symptoms leading to hospitalization in a psychiatric department and the reasons underlying the diagnosis of anti-NMDAR encephalitis. Results: The medical records of 111 adult patients were reviewed. Psychiatric features were the initial presentation in 65 patients (59%). Among them, several psychiatric manifestations were observed, including visual and auditory hallucinations (n = 26, 40%), depression (n = 15, 23%), mania (n = 5, 8%), acute schizoaffective episode (n = 15, 23%), and eating disorder or addiction (n = 4; 6%). Forty-five patients (40% of total cohort) were first hospitalized in a psychiatric institution (91% women), with a median duration of stay of 9 days (range 0.25–239 days). Among them, 24 patients (53%) had associated discreet neurologic signs at the first evaluation, while 17 additional patients (38%) developed neurologic signs within a few days. Twenty-one patients (47%) were transferred to a medical unit for a suspicion of antipsychotic intolerance characterized by high temperature, muscle rigidity, mutism or coma, and biological results suggesting rhabdomyolysis. Conclusions: Several psychiatric presentations were observed in patients with anti-NMDAR encephalitis, although none was specific; however, patients, mostly women, also had discreet neurologic signs that should be carefully assessed as well as signs of antipsychotic intolerance that should raise suspicion for anti-NMDAR encephalitis.

  4. Neuroleptic intolerance in patients with anti-NMDAR encephalitis

    PubMed Central

    Lejuste, Florian; Thomas, Laure; Picard, Géraldine; Desestret, Virginie; Ducray, François; Rogemond, Veronique; Psimaras, Dimitri; Antoine, Jean-Christophe; Delattre, Jean-Yves; Groc, Laurent; Leboyer, Marion

    2016-01-01

    Objective: To precisely describe the initial psychiatric presentation of patients with anti-NMDA receptor (NMDAR) antibodies encephalitis (anti-NMDAR encephalitis) to identify potential clues enhancing its early diagnosis. Methods: We retrospectively studied the French Reference Centre medical records of every adult patient with anti-NMDAR encephalitis to specify the patients' initial psychiatric symptoms leading to hospitalization in a psychiatric department and the reasons underlying the diagnosis of anti-NMDAR encephalitis. Results: The medical records of 111 adult patients were reviewed. Psychiatric features were the initial presentation in 65 patients (59%). Among them, several psychiatric manifestations were observed, including visual and auditory hallucinations (n = 26, 40%), depression (n = 15, 23%), mania (n = 5, 8%), acute schizoaffective episode (n = 15, 23%), and eating disorder or addiction (n = 4; 6%). Forty-five patients (40% of total cohort) were first hospitalized in a psychiatric institution (91% women), with a median duration of stay of 9 days (range 0.25–239 days). Among them, 24 patients (53%) had associated discreet neurologic signs at the first evaluation, while 17 additional patients (38%) developed neurologic signs within a few days. Twenty-one patients (47%) were transferred to a medical unit for a suspicion of antipsychotic intolerance characterized by high temperature, muscle rigidity, mutism or coma, and biological results suggesting rhabdomyolysis. Conclusions: Several psychiatric presentations were observed in patients with anti-NMDAR encephalitis, although none was specific; however, patients, mostly women, also had discreet neurologic signs that should be carefully assessed as well as signs of antipsychotic intolerance that should raise suspicion for anti-NMDAR encephalitis. PMID:27606355

  5. ER to synapse trafficking of NMDA receptors

    PubMed Central

    Horak, Martin; Petralia, Ronald S.; Kaniakova, Martina; Sans, Nathalie

    2014-01-01

    Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. There are three distinct subtypes of ionotropic glutamate receptors (GluRs) that have been identified including 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl)propanoic acid receptors (AMPARs), N-methyl-D-aspartate receptors (NMDARs) and kainate receptors. The most common GluRs in mature synapses are AMPARs that mediate the fast excitatory neurotransmission and NMDARs that mediate the slow excitatory neurotransmission. There have been large numbers of recent reports studying how a single neuron regulates synaptic numbers and types of AMPARs and NMDARs. Our current research is centered primarily on NMDARs and, therefore, we will focus in this review on recent knowledge of molecular mechanisms occurring (1) early in the biosynthetic pathway of NMDARs, (2) in the transport of NMDARs after their release from the endoplasmic reticulum (ER); and (3) at the plasma membrane including excitatory synapses. Because a growing body of evidence also indicates that abnormalities in NMDAR functioning are associated with a number of human psychiatric and neurological diseases, this review together with other chapters in this issue may help to enhance research and to gain further knowledge of normal synaptic physiology as well as of the etiology of many human brain diseases. PMID:25505872

  6. Restoration of contractility in hyperhomocysteinemia by cardiac-specific deletion of NMDA-R1.

    PubMed

    Moshal, Karni S; Kumar, Munish; Tyagi, Neetu; Mishra, Paras K; Metreveli, Naira; Rodriguez, Walter E; Tyagi, Suresh C

    2009-03-01

    Homocysteine (HCY) activated mitochondrial matrix metalloproteinase-9 and led to cardiomyocyte dysfunction, in part, by inducing mitochondrial permeability (MPT). Treatment with MK-801 [N-methyl-d-aspartate (NMDA) receptor antagonist] ameliorated the HCY-induced decrease in myocyte contractility. However, the role of cardiomyocyte NMDA-receptor 1 (R1) activation in hyperhomocysteinemia (HHCY) leading to myocyte dysfunction was not well understood. We tested the hypothesis that the cardiac-specific deletion of NMDA-R1 mitigated the HCY-induced decrease in myocyte contraction, in part, by decreasing nitric oxide (NO). Cardiomyocyte-specific knockout of NMDA-R1 was generated using cre/lox technology. NMDA-R1 expression was detected by Western blot and confocal microscopy. MPT was determined using a spectrophotometer. Myocyte contractility and calcium transients were studied using the IonOptix video-edge detection system and fura 2-AM loading. We observed that HHCY induced NO production by agonizing NMDA-R1. HHCY induced the MPT by agonizing NMDA-R1. HHCY caused a decrease in myocyte contractile performance, maximal rate of contraction and relaxation, and prolonged the time to 90% peak shortening and 90% relaxation by agonizing NMDA-R1. HHCY decreased contraction amplitude with the increase in calcium concentration. The recovery of calcium transient was prolonged in HHCY mouse myocyte by agonizing NMDA-R1. It was suggested that HHCY increased mitochondrial NO levels and induced MPT, leading to the decline in myocyte mechanical function by agonizing NMDA-R1.

  7. Neuropsychiatric autoimmune encephalitis without VGKC-complex, NMDAR, and GAD autoantibodies: case report and literature review.

    PubMed

    Najjar, Souhel; Pearlman, Daniel; Devinsky, Orrin; Najjar, Amanda; Nadkarni, Siddhartha; Butler, Tracy; Zagzag, David

    2013-03-01

    We report a patient with a seronegative autoimmune panencephalitis, adding a subtype to the emerging spectrum of seronegative autoimmune encephalitis, and we review the sparse literature on isolated psychiatric presentations of autoimmune encephalitis. (A PubMed search for "seronegative autoimmune encephalitis," "nonvasculitic autoimmune inflammatory meningoencephalitis," and related terms revealed <25 cases.) A 15-year-old girl developed an acute-onset isolated psychosis with prominent negative symptoms and intermittent encephalopathy. Despite clinical worsening, her brain magnetic resonance imaging (MRI) scans remained normal for 7 years. Serology was negative for voltage-gated potassium channel (VGKC)-complex, N-methyl-D-aspartate receptor (NMDAR), and glutamic acid decarboxylase (GAD) autoantibodies. We excluded genetic, metabolic, paraneoplastic, degenerative, and infectious etiologies. The patient's symptoms remitted fully with immune therapy, but recurred in association with widespread bihemispheric brain lesions. Brain biopsy revealed mild nonvasculitic inflammation and prominent vascular hyalinization. Immune therapy with plasma exchanges cleared the MRI abnormalities but, 10 years after onset, the patient still suffers neuropsychiatric sequelae. We conclude that autoimmune panencephalitis seronegative for VGKC-complex, NMDAR, and GAD autoantibodies is a subtype of autoimmune encephalitis that can present with pure neuropsychiatric features and a normal brain MRI. Immunologic mechanisms may account for psychiatric symptoms in a subset of patients now diagnosed with classical psychotic disorders. Delay in starting immune therapy can lead to permanent neuropsychiatric sequelae. We propose a standardized classification system for the autoimmune encephalitides, integrating earlier pathology-oriented terms with more recently defined serologic and clinical phenotypes.

  8. The Relative Contribution of NMDARs to Excitatory Postsynaptic Currents is Controlled by Ca2+-Induced Inactivation

    PubMed Central

    Valiullina, Fliza; Zakharova, Yulia; Mukhtarov, Marat; Draguhn, Andreas; Burnashev, Nail; Rozov, Andrei

    2016-01-01

    NMDA receptors (NMDARs) are important mediators of excitatory synaptic transmission and plasticity. A hallmark of these channels is their high permeability to Ca2+. At the same time, they are themselves inhibited by the elevation of intracellular Ca2+ concentration. It is unclear however, whether the Ca2+ entry associated with single NMDAR mediated synaptic events is sufficient to self-inhibit their activation. Such auto-regulation would have important effects on the dynamics of synaptic excitation in several central neuronal networks. Therefore, we studied NMDAR-mediated synaptic currents in mouse hippocampal CA1 pyramidal neurons. Postsynaptic responses to subthreshold Schaffer collateral stimulation depended strongly on the absence or presence of intracellular Ca2+ buffers. Loading of pyramidal cells with exogenous Ca2+ buffers increased the amplitude and decay time of NMDAR mediated EPSCs (EPSPs) and prolonged the time window for action potential (AP) generation. Our data indicate that the Ca2+ influx mediated by unitary synaptic events is sufficient to produce detectable self-inhibition of NMDARs even at a physiological Mg2+ concentration. Therefore, the contribution of NMDARs to synaptic excitation is strongly controlled by both previous synaptic activity as well as by the Ca2+ buffer capacity of postsynaptic neurons. PMID:26858606

  9. The Relative Contribution of NMDARs to Excitatory Postsynaptic Currents is Controlled by Ca(2+)-Induced Inactivation.

    PubMed

    Valiullina, Fliza; Zakharova, Yulia; Mukhtarov, Marat; Draguhn, Andreas; Burnashev, Nail; Rozov, Andrei

    2016-01-01

    NMDA receptors (NMDARs) are important mediators of excitatory synaptic transmission and plasticity. A hallmark of these channels is their high permeability to Ca(2+). At the same time, they are themselves inhibited by the elevation of intracellular Ca(2+) concentration. It is unclear however, whether the Ca(2+) entry associated with single NMDAR mediated synaptic events is sufficient to self-inhibit their activation. Such auto-regulation would have important effects on the dynamics of synaptic excitation in several central neuronal networks. Therefore, we studied NMDAR-mediated synaptic currents in mouse hippocampal CA1 pyramidal neurons. Postsynaptic responses to subthreshold Schaffer collateral stimulation depended strongly on the absence or presence of intracellular Ca(2+) buffers. Loading of pyramidal cells with exogenous Ca(2+) buffers increased the amplitude and decay time of NMDAR mediated EPSCs (EPSPs) and prolonged the time window for action potential (AP) generation. Our data indicate that the Ca(2+) influx mediated by unitary synaptic events is sufficient to produce detectable self-inhibition of NMDARs even at a physiological Mg(2+) concentration. Therefore, the contribution of NMDARs to synaptic excitation is strongly controlled by both previous synaptic activity as well as by the Ca(2+) buffer capacity of postsynaptic neurons. PMID:26858606

  10. N-Methyl-D-Aspartate Receptor Signaling and Function in Cardiovascular Tissues.

    PubMed

    McGee, Marie A; Abdel-Rahman, Abdel A

    2016-08-01

    Excellent reviews on central N-methyl-D-aspartate receptor (NMDAR) signaling and function in cardiovascular regulating neuronal pools have been reported. However, much less attention has been given to NMDAR function in peripheral tissues, particularly the heart and vasculature, although a very recent review discusses such function in the kidney. In this short review, we discuss the NMDAR expression and complexity of its function in cardiovascular tissues. In conscious (contrary to anesthetized) rats, activation of the peripheral NMDAR triggers cardiovascular oxidative stress through the PI3K-ERK1/2-NO signaling pathway, which ultimately leads to elevation in blood pressure. Evidence also implicates Ca release, in the peripheral NMDAR-mediated pressor response. Despite evidence of circulating potent ligands (eg, D-aspartate and L-aspartate, L-homocysteic acid, and quinolinic acid) and also their coagonist (eg, glycine or D-serine), the physiological role of peripheral cardiovascular NMDAR remains elusive. Nonetheless, the cardiovascular relevance of the peripheral NMDAR might become apparent when its signaling is altered by drugs, such as alcohol, which interact with the NMDAR or its downstream signaling mechanisms. PMID:27046337

  11. Neuroadaptive changes in NMDAR1 gene expression after extinction of cocaine self-administration.

    PubMed

    Crespo, José A; Oliva, José M; Ghasemzadeh, M Benham; Kalivas, Peter W; Ambrosio, E

    2002-06-01

    The aim of the present work was to study the time course effects in levels of mRNA encoding N-methyl-d-aspartate receptor subunit 1 (NMDAR1) after long-term cocaine self-administration (1 mg/kg/ injection) and its extinction using a yoked-box procedure. NMDAR1 content was measured by quantitative in situ hybridization histochemistry in prefrontal cortex, caudate-putamen, nucleus accumbens, olfactory tubercle, and piriform cortex immediately after cessation of the last session of cocaine self-administration (Day 0) and 1, 5, and 10 days after the extinction period. The results show that long-term cocaine self-administration and its extinction alter NMDAR1 gene expression in these forebrain regions, and that the changes depend upon the brain region examined and the type of cocaine administration (contingent, noncontingent, and saline). Compared to saline and noncontingent cocaine administration, contingent cocaine produced an up-regulation in NMDAR1 gene expression on Day 0 in all the brain regions analyzed. NMDAR1 levels of contingent animals decreased progressively in the absence of cocaine, and the decrement persisted 10 days after the extinction of cocaine self-administration behavior in all the forebrain areas, with the exception of olfactory tubercle. In contrast, noncontingent cocaine administration did not produce any change in NMDAR1 gene expression on Day 0, and extinction resulted in an increase of NMDAR1 mRNA content on Days 1 and 5 and returned to control (saline) values on Day 10. These results suggest that an interaction between environmental stimuli and the pharmacological action of cocaine during drug self-administration and its extinction may represent an important factor in the regulation of cocaine effects on NMDAR1 gene expression.

  12. Role of the NR2A/2B subunits of the N-methyl-D-aspartate receptor in glutamate-induced glutamic acid decarboxylase alteration in cortical GABAergic neurons in vitro.

    PubMed

    Monnerie, H; Hsu, F-C; Coulter, D A; Le Roux, P D

    2010-12-29

    The vulnerability of brain neuronal cell subpopulations to neurologic insults varies greatly. Among cells that survive a pathological insult, for example ischemia or brain trauma, some may undergo morphological and/or biochemical changes that may compromise brain function. The present study is a follow-up of our previous studies that investigated the effect of glutamate-induced excitotoxicity on the GABA synthesizing enzyme glutamic acid decarboxylase (GAD65/67)'s expression in surviving DIV 11 cortical GABAergic neurons in vitro [Monnerie and Le Roux, (2007) Exp Neurol 205:367-382, (2008) Exp Neurol 213:145-153]. An N-methyl-D-aspartate receptor (NMDAR)-mediated decrease in GAD expression was found following glutamate exposure. Here we examined which NMDAR subtype(s) mediated the glutamate-induced change in GAD protein levels. Western blotting techniques on cortical neuron cultures showed that glutamate's effect on GAD proteins was not altered by NR2B-containing diheteromeric (NR1/NR2B) receptor blockade. By contrast, blockade of triheteromeric (NR1/NR2A/NR2B) receptors fully protected against a decrease in GAD protein levels following glutamate exposure. When receptor location on the postsynaptic membrane was examined, extrasynaptic NMDAR stimulation was observed to be sufficient to decrease GAD protein levels similar to that observed after glutamate bath application. Blocking diheteromeric receptors prevented glutamate's effect on GAD proteins after extrasynaptic NMDAR stimulation. Finally, NR2B subunit examination with site-specific antibodies demonstrated a glutamate-induced, calpain-mediated alteration in NR2B expression. These results suggest that glutamate-induced excitotoxic NMDAR stimulation in cultured GABAergic cortical neurons depends upon subunit composition and receptor location (synaptic vs. extrasynaptic) on the neuronal membrane. Biochemical alterations in surviving cortical GABAergic neurons in various disease states may contribute to the altered

  13. Clinical experience and laboratory investigations in patients with anti-NMDAR encephalitis

    PubMed Central

    Dalmau, Josep; Lancaster, Eric; Martinez-Hernandez, Eugenia; Rosenfeld, Myrna R; Balice-Gordon, Rita

    2011-01-01

    Since its discovery in 2007, the encephalitis associated with antibodies against the N-methyl-D-aspartate receptor (NMDAR) has entered the mainstream of neurology and other disciplines. Most patients with anti-NMDAR encephalitis develop a multistage illness that progresses from psychosis, memory deficits, seizures, and language disintegration into a state of unresponsiveness with catatonic features often associated with abnormal movements, and autonomic and breathing instability. The disorder predominantly affects children and young adults, occurs with or without tumour association, and responds to treatment but can relapse. The presence of a tumour (usually an ovarian teratoma) is dependent on age, sex, and ethnicity, being more frequent in women older than 18 years, and slightly more predominant in black women than it is in white women. Patients treated with tumour resection and immunotherapy (corticosteroids, intravenous immunoglobulin, or plasma exchange) respond faster to treatment and less frequently need second-line immunotherapy (cyclophosphamide or rituximab, or both) than do patients without a tumour who receive similar initial immunotherapy. More than 75% of all patients have substantial recovery that occurs in inverse order of symptom development and is associated with a decline of antibody titres. Patients’ antibodies cause a titre-dependent, reversible decrease of synaptic NMDAR by a mechanism of crosslinking and internalisation. On the basis of models of pharmacological or genetic disruption of NMDAR, these antibody effects reveal a probable pathogenic relation between the depletion of receptors and the clinical features of anti-NMDAR encephalitis. PMID:21163445

  14. Disruption of hippocampal–prefrontal cortex activity by dopamine D2R-dependent LTD of NMDAR transmission

    PubMed Central

    Banks, Paul James; Burroughs, Amelia Caroline; Barker, Gareth Robert Isaac; Brown, Jon Thomas; Warburton, Elizabeth Clea; Bashir, Zafar Iqbal

    2015-01-01

    Functional connectivity between the hippocampus and prefrontal cortex (PFC) is essential for associative recognition memory and working memory. Disruption of hippocampal–PFC synchrony occurs in schizophrenia, which is characterized by hypofunction of NMDA receptor (NMDAR)-mediated transmission. We demonstrate that activity of dopamine D2-like receptors (D2Rs) leads selectively to long-term depression (LTD) of hippocampal–PFC NMDAR-mediated synaptic transmission. We show that dopamine-dependent LTD of NMDAR-mediated transmission profoundly disrupts normal synaptic transmission between hippocampus and PFC. These results show how dopaminergic activation induces long-term hypofunction of NMDARs, which can contribute to disordered functional connectivity, a characteristic that is a hallmark of psychiatric disorders such as schizophrenia. PMID:26286993

  15. Disruption of hippocampal-prefrontal cortex activity by dopamine D2R-dependent LTD of NMDAR transmission.

    PubMed

    Banks, Paul James; Burroughs, Amelia Caroline; Barker, Gareth Robert Isaac; Brown, Jon Thomas; Warburton, Elizabeth Clea; Bashir, Zafar Iqbal

    2015-09-01

    Functional connectivity between the hippocampus and prefrontal cortex (PFC) is essential for associative recognition memory and working memory. Disruption of hippocampal-PFC synchrony occurs in schizophrenia, which is characterized by hypofunction of NMDA receptor (NMDAR)-mediated transmission. We demonstrate that activity of dopamine D2-like receptors (D2Rs) leads selectively to long-term depression (LTD) of hippocampal-PFC NMDAR-mediated synaptic transmission. We show that dopamine-dependent LTD of NMDAR-mediated transmission profoundly disrupts normal synaptic transmission between hippocampus and PFC. These results show how dopaminergic activation induces long-term hypofunction of NMDARs, which can contribute to disordered functional connectivity, a characteristic that is a hallmark of psychiatric disorders such as schizophrenia.

  16. N-methyl-D-aspartate (NMDA) receptor dysfunction or dysregulation: the final common pathway on the road to schizophrenia?

    PubMed Central

    Kantrowitz, Joshua T.; Javitt, Daniel C.

    2010-01-01

    Schizophrenia is a severe mental disorder associated with a characteristic constellation of symptoms and neurocognitive deficits. At present, etiological mechanisms remain relatively unknown, although multiple points of convergence have been identified over recent years. One of the primary convergence points is dysfunction of N-methyl-D-aspartate (NMDAR)-type glutamate receptors. Antagonists of NMDAR produce a clinical syndrome that closely resembles, and uniquely incorporates negative and cognitive symptoms of schizophrenia, along with the specific pattern of neurocognitive dysfunction seen in schizophrenia. Genetic polymorphisms involving NMDAR subunits, particularly the GRIN2B subunit have been described. In addition, polymorphisms have been described in modulatory systems involving the NMDAR, including the enzymes serine racemase and D-amino acid oxidase/G72 that regulate brain D-serine synthesis. Reductions in plasma and brain glycine, D-serine and glutathione levels have been described as well, providing potential mechanisms underlying NMDAR dysfunction. Unique characteristics of the NMDAR are described that may explain the characteristic pattern of symptoms and neurocognitive deficits observed in schizophrenia. Finally, the NMDAR complex represents a convergence point for potential new treatment approaches in schizophrenia aimed at correcting underlying abnormalities in synthesis and regulation of allosteric modulators, as well as more general potentiation of pre- and post-synaptic glutamatergic and NMDAR function. PMID:20417696

  17. Cellular Plasticity Induced by Anti–α-Amino-3-Hydroxy-5-Methyl-4-Isoxazolepropionic Acid (AMPA) Receptor Encephalitis Antibodies

    PubMed Central

    Peng, Xiaoyu; Hughes, Ethan G; Moscato, Emilia H; Parsons, Thomas D; Dalmau, Josep; Balice-Gordon, Rita J

    2015-01-01

    Objective Autoimmune-mediated anti–α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis is a severe but treatment-responsive disorder with prominent short-term memory loss and seizures. The mechanisms by which patient antibodies affect synapses and neurons leading to symptoms are poorly understood. Methods The effects of patient antibodies on cultures of live rat hippocampal neurons were determined with immunostaining, Western blot, and electrophysiological analyses. Results We show that patient antibodies cause a selective decrease in the total surface amount and synaptic localization of GluA1- and GluA2-containing AMPARs, regardless of receptor subunit binding specificity, through increased internalization and degradation of surface AMPAR clusters. In contrast, patient antibodies do not alter the density of excitatory synapses, N-methyl-D-aspartate receptor (NMDAR) clusters, or cell viability. Commercially available AMPAR antibodies directed against extracellular epitopes do not result in a loss of surface and synaptic receptor clusters, suggesting specific effects of patient antibodies. Whole-cell patch clamp recordings of spontaneous miniature postsynaptic currents show that patient antibodies decrease AMPAR-mediated currents, but not NMDAR-mediated currents. Interestingly, several functional properties of neurons are also altered: inhibitory synaptic currents and vesicular γ-aminobutyric acid transporter (vGAT) staining intensity decrease, whereas the intrinsic excitability of neurons and short-interval firing increase. Interpretation These results establish that antibodies from patients with anti-AMPAR encephalitis selectively eliminate surface and synaptic AMPARs, resulting in a homeostatic decrease in inhibitory synaptic transmission and increased intrinsic excitability, which may contribute to the memory deficits and epilepsy that are prominent in patients with this disorder. PMID:25369168

  18. Expression pattern of NMDA receptors reveals antiepileptic potential of apigenin 8-C-glucoside and chlorogenic acid in pilocarpine induced epileptic mice.

    PubMed

    Aseervatham, G Smilin Bell; Suryakala, U; Doulethunisha; Sundaram, S; Bose, P Chandra; Sivasudha, T

    2016-08-01

    The present study was aimed to evaluate the effect of apigenin 8-C-glucoside (Vitexin) and chlorogenic acid on epileptic mice induced by pilocarpine and explored its possible mechanisms. Intraperitonial administration of pilocarpine (85mg/kg) induced seizure in mice was assessed by behavior observations, which is significantly (p>0.05) reduced by apigenin 8-C-glucoside (AP8CG) (10mg/kg) and chlorogenic acid (CA) (5mg/kg), similar to diazepam. Seizure was accompanied by an imbalance in the levels of Gamma-aminobutyric acid (GABA) and glutamate in the pilocarpine administered group. Moreover, convulsion along with reduced acetylcholinesterase, increased monoamine oxidase and oxidative stress was observed in epileptic mice brain. AP8CG and CA significantly restored back to normal levels even at lower doses. Further, increased lipid peroxidation and nitrite content was also significantly attenuated by AP8CG and CA. However, CA was found to be more effective when compared to AP8CG. In addition, the mRNA expression of N-methyl-d-aspartate receptor (NMDAR), mGluR1 and mGlu5 was significantly (P≤0.05) inhibited by AP8CG and CA in a lower dose. The mRNA expression of GRIK1 did not differ significantly in any of the group and showed a similar pattern of expression. Our result shows that AP8CG and CA selectively inhibit NMDAR, mGluR1 and mGlu5 expression. Modification in the provoked NMDAR calcium response coupled with neuronal death. Hence, these findings underline that the polyphenolics, AP8CG and CA have exerted antiepileptic and neuroprotective activity by suppressing glutamate receptors. PMID:27470339

  19. Modulation of N-methyl-d-aspartate receptor function by glycine transport

    PubMed Central

    Bergeron, Richard; Meyer, Torsten M.; Coyle, Joseph T.; Greene, Robert W.

    1998-01-01

    The recent discovery of glycine transporters in both the central nervous system and the periphery suggests that glycine transport may be critical to N-methyl-d-aspartate receptor (NMDAR) function by controlling glycine concentration at the NMDAR modulatory glycine site. Data obtained from whole-cell patch–clamp recordings of hippocampal pyramidal neurons, in vitro, demonstrated that exogenous glycine and glycine transporter type 1 (GLYT1) antagonist selectively enhanced the amplitude of the NMDA component of a glutamatergic excitatory postsynaptic current. The effect was blocked by 2-amino-5-phosphonovaleric acid and 7-chloro-kynurenic acid but not by strychnine. Thus, the glycine-binding site was not saturated under the control conditions. Furthermore, GLYT1 antagonist enhanced NMDAR function during perfusion with medium containing 10 μM glycine, a concentration similar to that in the cerebrospinal fluid in vivo, thereby supporting the hypothesis that the GLYT1 maintains subsaturating concentration of glycine at synaptically activated NMDAR. The enhancement of NMDAR function by specific GLYT1 antagonism may be a feasible target for therapeutic agents directed toward diseases related to hypofunction of NMDAR. PMID:9861038

  20. Cysteine Substitution of Transmembrane Domain Amino Acids Alters the Ethanol Inhibition of GluN1/GluN2A N-Methyl-d-Aspartate Receptors

    PubMed Central

    Xu, Minfu; Smothers, C. Thetford

    2015-01-01

    N-Methyl-d-aspartate receptors (NMDARs) are inhibited by behaviorally relevant concentrations of ethanol, and residues within transmembrane (TM) domains of NMDARs, including TM3 GluN1 phenylalanine 639 (F639), regulate this sensitivity. In the present study, we used cysteine (C) mutagenesis to determine whether there are additional residues within nearby TM domains that regulate ethanol inhibition on NMDARs. GluN1(F639C)/GluN2A receptors were less inhibited by ethanol than wild-type receptors, and inhibition was restored to wild-type levels following treatment with ethanol-like methanethiosulfonate reagents. Molecular modeling identified six residues in the GluN1 TM1 domain (valine V566; serine S569) and the GluN2A TM4 domain (methionine, M817; V820, F821, and leucine, L824) that were in close vicinity to the TM3 F639 residue, and these were individually mutated to cysteine and tested for ethanol inhibition and receptor function. The F639C-induced decrease in ethanol inhibition was blunted by coexpression of GluN1 TM1 mutants V566C and S569C, and statistically significant interactions were observed for ethanol inhibition among V566C, F639C, and GluN2A TM4 mutants V820C and F821C and S569C, F639C, and GluN2A TM4 mutants F821C and L824C. Ethanol inhibition was also reduced when either GluN1 TM1 mutant V566C or S569C was combined with GluN2A V820C, suggesting a novel TM1:TM4 intrasubunit site of action for ethanol. Cysteines substituted at TM3 and TM4 sites previously suggested to interact with ethanol had less dramatic effects on ethanol inhibition. Overall, the results from these studies suggest that interactions among TM1, TM3, and TM4 amino acids in NMDARs are important determinants of ethanol action at these receptors. PMID:25635140

  1. Anti-NMDAR antibodies in new-onset psychosis. Positive results in an HIV-infected patient.

    PubMed

    Arboleya, Susana; Clemente, Antonio; Deng, Savannah; Bedmar, Marta; Salvador, Isabel; Herbera, Patricia; Cunill, Vanessa; Vives-Bauza, Cristòfol; Haro, Josep Maria; Canellas, Francesca; Julià, Maria Rosa

    2016-08-01

    The role of neuronal surface autoantibodies (NSAs) in non-encephalitic psychosis is of recent and controversial interest. Most of the studies relating NSAs with psychosis are retrospective and only focused on the N-methyl-d-aspartate glutamate receptor (NMDAR). Our goal was to evaluate the prevalence of IgG antibodies against the NMDAR NR1 subunit (NMDAR-Abs) along with five additional NSAs in 61 first psychotic episode patients and 47 matched controls. We found two patients positive for NMDAR-Abs (3.3%). One of them was eventually considered to have been misdiagnosed and reclassified as encephalitis. The other met the criteria for bipolar I disorder, presented no neurological symptoms and had a comorbid HIV infection of vertical transmission. This is the first reported case of an HIV-infected patient with psychosis associated with NSAs. This study shows that patients presenting with clinically incomplete forms of anti-NMDAR encephalitis, with predominant or isolated psychiatric symptoms, can remain undetected if no ancillary tests are performed. To improve patient diagnosis and treatment of individuals with a first psychotic episode, more detailed neurological examinations might be needed. Further studies are required to better clarify the role of NSAs in the neuropsychiatric effects of HIV infection.

  2. Trans-synaptic zinc mobilization improves social interaction in two mouse models of autism through NMDAR activation

    PubMed Central

    Lee, Eun-Jae; Lee, Hyejin; Huang, Tzyy-Nan; Chung, Changuk; Shin, Wangyong; Kim, Kyungdeok; Koh, Jae-Young; Hsueh, Yi-Ping; Kim, Eunjoon

    2015-01-01

    Genetic aspects of autism spectrum disorders (ASDs) have recently been extensively explored, but environmental influences that affect ASDs have received considerably less attention. Zinc (Zn) is a nutritional factor implicated in ASDs, but evidence for a strong association and linking mechanism is largely lacking. Here we report that trans-synaptic Zn mobilization rapidly rescues social interaction in two independent mouse models of ASD. In mice lacking Shank2, an excitatory postsynaptic scaffolding protein, postsynaptic Zn elevation induced by clioquinol (a Zn chelator and ionophore) improves social interaction. Postsynaptic Zn is mainly derived from presynaptic pools and activates NMDA receptors (NMDARs) through postsynaptic activation of the tyrosine kinase Src. Clioquinol also improves social interaction in mice haploinsufficient for the transcription factor Tbr1, which accompanies NMDAR activation in the amygdala. These results suggest that trans-synaptic Zn mobilization induced by clioquinol rescues social deficits in mouse models of ASD through postsynaptic Src and NMDAR activation. PMID:25981743

  3. Trans-synaptic zinc mobilization improves social interaction in two mouse models of autism through NMDAR activation.

    PubMed

    Lee, Eun-Jae; Lee, Hyejin; Huang, Tzyy-Nan; Chung, Changuk; Shin, Wangyong; Kim, Kyungdeok; Koh, Jae-Young; Hsueh, Yi-Ping; Kim, Eunjoon

    2015-01-01

    Genetic aspects of autism spectrum disorders (ASDs) have recently been extensively explored, but environmental influences that affect ASDs have received considerably less attention. Zinc (Zn) is a nutritional factor implicated in ASDs, but evidence for a strong association and linking mechanism is largely lacking. Here we report that trans-synaptic Zn mobilization rapidly rescues social interaction in two independent mouse models of ASD. In mice lacking Shank2, an excitatory postsynaptic scaffolding protein, postsynaptic Zn elevation induced by clioquinol (a Zn chelator and ionophore) improves social interaction. Postsynaptic Zn is mainly derived from presynaptic pools and activates NMDA receptors (NMDARs) through postsynaptic activation of the tyrosine kinase Src. Clioquinol also improves social interaction in mice haploinsufficient for the transcription factor Tbr1, which accompanies NMDAR activation in the amygdala. These results suggest that trans-synaptic Zn mobilization induced by clioquinol rescues social deficits in mouse models of ASD through postsynaptic Src and NMDAR activation.

  4. Circuit analysis of NMDAR hypofunction in the hippocampus, in vitro, and psychosis of schizophrenia.

    PubMed

    Greene, R

    2001-01-01

    NMDA antagonists provide the best pharmacological model of psychosis-related schizophrenia. Data from circuit analysis of the effects of the antagonism of NMDA receptors in the CA1 region of the hippocampus of rats in vitro suggest a hypothesis concerning cortical circuit dysfunction responsible for NMDA antagonist-dependent psychosis, relevant to the psychosis associated with schizophrenia. The NMDA antagonists may act by causing a selective, partial, disinhibition of cortical projection cells. The effects are partially due to the partial role of NMDA-dependent transmission in the excitatory glutamate drive of interneurons. Characterization of the selectivity is incomplete, but includes disinhibition of the recurrent inhibitory circuit and is concentration-sensitive. It may result from differences in NMDA receptors (NMDARs) on interneurons. At higher concentrations, antagonism of all NMDA-dependent transmission results in anesthesia. At low concentration, selective blockade of NMDA-dependent LTP of the recurrent inhibitory circuit may disrupt particular aspects of information processing involving learning and/or memory, consistent with the generation of abnormal associations. An endogenous peptide, NAAG, is shown to antagonize NMDARs in a manner similar to known psychotogenic agents like ketamine or phencyclidine. Finally, mechanisms that could enhance NMDAR function are discussed as possible therapeutic strategies for psychosis.

  5. The σ1 Receptor Engages the Redox-Regulated HINT1 Protein to Bring Opioid Analgesia Under NMDA Receptor Negative Control

    PubMed Central

    Rodríguez-Muñoz, María; Sánchez-Blázquez, Pilar; Herrero-Labrador, Raquel; Martínez-Murillo, Ricardo; Merlos, Manuel; Vela, José Miguel

    2015-01-01

    Abstract Aims: The in vivo pharmacology of the sigma 1 receptor (σ1R) is certainly complex; however, σ1R antagonists are of therapeutic interest, because they enhance mu-opioid receptor (MOR)-mediated antinociception and reduce neuropathic pain. Thus, we investigated whether the σ1R is involved in the negative control that glutamate N-methyl-d-aspartate acid receptors (NMDARs) exert on opioid antinociception. Results: The MOR C terminus carries the histidine triad nucleotide-binding protein 1 (HINT1) coupled to the regulator of G-protein signaling RGSZ2-neural nitric oxide synthase assembly. Activated MORs stimulate the production of nitric oxide (NO), and the redox zinc switch RGSZ2 converts this signal into free zinc ions that are required to recruit the redox sensor PKCγ to HINT1 proteins. Then, PKCγ impairs HINT1-RGSZ2 association and enables σ1R-NR1 interaction with MOR-HINT1 complexes to restrain opioid signaling. The inhibition of NOS or the absence of σ1Rs prevents HINT1-PKCγ interaction, and MOR-NMDAR cross-regulation fails. The σ1R antagonists transitorily remove the binding of σ1Rs to NR1 subunits, facilitate the entrance of negative regulators of NMDARs, likely Ca2+-CaM, and prevent NR1 interaction with HINT1, thereby impairing the negative feedback of glutamate on opioid analgesia. Innovation: A redox-regulated process situates MOR signaling under NMDAR control, and in this context, the σ1R binds to the cytosolic C terminal region of the NMDAR NR1 subunit. Conclusion: The σ1R antagonists enhance opioid analgesia in naïve mice by releasing MORs from the negative influence of NMDARs, and they also reset antinociception in morphine tolerant animals. Moreover, σ1R antagonists alleviate neuropathic pain, probably by driving the inhibition of up-regulated NMDARs. Antioxid. Redox Signal. 22, 799–818. PMID:25557043

  6. Effects of enriched environment on gene expression and signal pathways in cortex of hippocampal CA1 specific NMDAR1 knockout mice.

    PubMed

    Li, Chunxia; Niu, Wenze; Jiang, Cecilia H; Hu, Yinghe

    2007-03-30

    N-methyl-D-aspartate glutamate receptor 1 (NMDAR1) plays a pivotal role in different forms of memory. Indeed, hippocampal CA1 region specific knockout (KO) of NMDAR1 in mice showed memory impairment. Recently, it has been reported that environmental enrichment enhanced memory and rescued the memory deficits of the NMDAR1-KO mice. It is well known that cortex has synaptic connections with hippocampus and is the storage region of the brain for long-term memory. To understand the molecular mechanisms of the memory impairments in the NMDAR1-KO mice, we have examined gene expression profiles in cortex from the receptor KO mice compared to wild type mice. Furthermore, since memory deficits were rescued after exposure of the NMDAR1-KO mice to enriched environment, we also analyzed the gene expression in the cortex of the KO mice after 3 hours, 2 days and 2 weeks enrichment. We found that the expression levels of 104 genes were altered in the cortex of NMDAR1-KO mice. Environmental enrichment for 3 hours, 2 days and 2 weeks affected the expression of 45, 34 and 56 genes, respectively. Genes involved in multiple signal pathways were regulated in the NMDAR1-KO mice, such as neurotransmission, structure, transcription, protein synthesis and protein processing. It is not surprising that since enriched environment rescued the memory decline in the NMDAR1-KO mice, the expression changes of a number of genes involved in these signal pathways were recovered or even reversed after enrichment. Our results further demonstrated that reelin and Notch signal pathways could be involved in the enrichment effects on memory improvement in the KO mice.

  7. First Bahraini adolescent with anti-NMDAR-Ab encephalitis.

    PubMed

    Almuslamani, Ahood; Mahmood, Fatima

    2015-01-01

    Anti-N-methyl-D-aspartate-receptor (NMDA-R) encephalitis is a new autoimmune, often paraneoplastic disorder that presents with complex neuropsychiatric symptoms. It was first described in 2007 by Dalmau et al. Our patient presented with headache, behavioral changes and then seizures with hallucinations. She was initially misdiagnosed to have schizophrenia and was prescribed antipsychotics. She deteriorated and developed further seizures with hypoventilation and choreoathetosis. Her blood investigations were positive for mycoplasma IGM. Her CSF studies showed high white cell counts, predominantly lymphocytes, and high anti-NMDA-R titre. Her brain MRI scans showed high tbl2 and FLAIR intensities in the grey and white matter of the left cerebellar hemisphere suggestive of acute disseminated encephalomyelitis. She responded to treatment with antibiotics, multiple antiepileptics, steroids and needed five sessions of plasmapheresis. There was no underlying malignancy on repeated scanning of the abdomen. She needed around one year for full recovery with intensive rehabilitation. The objective of this paper was to highlight the occurrence of this fairly new, challenging, easily missed, not-so-rare form of encephalitis often occurring in the absence of fever.

  8. First Bahraini adolescent with anti-NMDAR-Ab encephalitis

    PubMed Central

    Almuslamani, Ahood; Mahmood, Fatima

    2015-01-01

    Anti-N-methyl-D-aspartate-receptor (NMDA-R) encephalitis is a new autoimmune, often paraneoplastic disorder that presents with complex neuropsychiatric symptoms. It was first described in 2007 by Dalmau et al. Our patient presented with headache, behavioral changes and then seizures with hallucinations. She was initially misdiagnosed to have schizophrenia and was prescribed antipsychotics. She deteriorated and developed further seizures with hypoventilation and choreoathetosis. Her blood investigations were positive for mycoplasma IGM. Her CSF studies showed high white cell counts, predominantly lymphocytes, and high anti-NMDA-R titre. Her brain MRI scans showed high tbl2 and FLAIR intensities in the grey and white matter of the left cerebellar hemisphere suggestive of acute disseminated encephalomyelitis. She responded to treatment with antibiotics, multiple antiepileptics, steroids and needed five sessions of plasmapheresis. There was no underlying malignancy on repeated scanning of the abdomen. She needed around one year for full recovery with intensive rehabilitation. The objective of this paper was to highlight the occurrence of this fairly new, challenging, easily missed, not-so-rare form of encephalitis often occurring in the absence of fever. PMID:26535170

  9. The role of NMDAR antibody in the etiopathogenesis of schizophrenia

    PubMed Central

    Timucin, Damla; Ozdemir, Osman; Parlak, Mehmet

    2016-01-01

    Many authors have reported the presence of serum NMDAR antibodies in varying proportions of patients with schizophrenia; however, many others have not been able to confirm this. Because of the contradictory findings reported in various studies, more definitive research on this issue is required. Hence, we have investigated the NR1 subunit of NMDAR antibodies in patients with schizophrenia (n=49) and healthy controls (n=48). None of the investigated patients with schizophrenia and none of the healthy controls showed positive antibody against the NR1 subunit of the NMDAR. On the basis of this result, we conclude that the NR1 subunit of the NMDAR antibodies does not seem to have a role in schizophrenia. PMID:27695333

  10. The role of NMDAR antibody in the etiopathogenesis of schizophrenia

    PubMed Central

    Timucin, Damla; Ozdemir, Osman; Parlak, Mehmet

    2016-01-01

    Many authors have reported the presence of serum NMDAR antibodies in varying proportions of patients with schizophrenia; however, many others have not been able to confirm this. Because of the contradictory findings reported in various studies, more definitive research on this issue is required. Hence, we have investigated the NR1 subunit of NMDAR antibodies in patients with schizophrenia (n=49) and healthy controls (n=48). None of the investigated patients with schizophrenia and none of the healthy controls showed positive antibody against the NR1 subunit of the NMDAR. On the basis of this result, we conclude that the NR1 subunit of the NMDAR antibodies does not seem to have a role in schizophrenia.

  11. Essential involvement of the NMDA receptor in ethanol preconditioning-dependent neuroprotection from amyloid-betain vitro.

    PubMed

    Mitchell, Robert M; Neafsey, Edward J; Collins, Michael A

    2009-10-01

    In several epidemiological studies, moderate ethanol consumption has been associated with reduced risks of cognitive decline or Alzheimer's dementia. Of potential relevance is that brain cultures preconditioned with moderate ethanol concentrations are resistant to neurotoxic Alzheimer's amyloid-beta (Abeta) peptides. Using rat cerebellar mixed cultures we investigated whether certain membrane receptors were early 'sensors' in moderate ethanol preconditioning (MEP). In a 6-day MEP protocol (30 mM ethanol), neuroprotection from Abeta25-35 was undiminished by antagonism during the first 3 days of either adenosine A(1) or Galpha(i/o) protein-coupled receptors. However, similar cotreatment with memantine or DL-2-amino-5-phosphono-pentanoic acid (AP-5), antagonists of NMDA receptors (NMDAR), abolished neuroprotection, indicating key early involvement of this ionotropic glutamate receptor. Also in these cultures, directly activating NMDAR using subexcitotoxic NMDA preconditioning prevented Abeta neurotoxicity. By day 2 of MEP, we observed increased levels of NMDAR subunits NR1, NR2B, and NR2C that persisted through day 6. Interestingly, memantine co-exposure blocked elevations in the obligatory NR1 subunit. Furthermore, 2 days of MEP significantly increased two indicators of synaptic NMDAR localization, NR2B phospho-Tyr1472, and post-synaptic density 95 scaffolding protein. The results indicate that ethanol preconditioning-dependent neuroprotection is associated with early increases in NR subunits concomitant with enhancement of synaptic localization and activity of NMDAR. PMID:19694907

  12. Essential involvement of the NMDA receptor in ethanol preconditioning–dependent neuroprotection from amyloid–β in vitro

    PubMed Central

    Mitchell, Robert M.; Neafsey, Edward J.; Collins, Michael A.

    2010-01-01

    In several epidemiological studies, moderate ethanol consumption has been associated with reduced risks of cognitive decline or Alzheimer’s dementia. Of potential relevance is that brain cultures preconditioned with moderate ethanol concentrations are resistant to neurotoxic Alzheimer’s amyloid-β (Aβ) peptides. Using rat cerebellar mixed cultures we investigated whether certain membrane receptors were early ‘sensors’ in moderate ethanol preconditioning (MEP). In a 6-day MEP protocol (30 mM ethanol), neuroprotection from Aβ25–35 was undiminished by antagonism during the first 3 days of either adenosine A1 or Gαi/o protein-coupled receptors. However, similar cotreatment with memantine or DL-2-amino-5-phosphono-pentanoic acid (AP-5), antagonists of NMDA receptors (NMDAR), abolished neuroprotection, indicating key early involvement of this ionotropic glutamate receptor. Also in these cultures, directly activating NMDAR using subexcitotoxic NMDA preconditioning prevented Aβ neurotoxicity. By day 2 of MEP, we observed increased levels of NMDAR subunits NR1, NR2B, and NR2C that persisted through day 6. Interestingly, memantine co-exposure blocked elevations in the obligatory NR1 subunit. Furthermore, 2 days of MEP significantly increased two indicators of synaptic NMDAR localization, NR2B phospho-Tyr1472, and post-synaptic density 95 scaffolding protein. The results indicate that ethanol preconditioning-dependent neuroprotection is associated with early increases in NR subunits concomitant with enhancement of synaptic localization and activity of NMDAR. PMID:19694907

  13. Dysbindin-1 loss compromises NMDAR-dependent synaptic plasticity and contextual fear conditioning.

    PubMed

    Glen, W Bailey; Horowitz, Bryant; Carlson, Gregory C; Cannon, Tyrone D; Talbot, Konrad; Jentsch, J David; Lavin, Antonieta

    2014-02-01

    Genetic variants in DTNBP1 encoding the protein dysbindin-1 have often been associated with schizophrenia and with the cognitive deficits prominent in that disorder. Because impaired function of the hippocampus is thought to play a role in these memory deficits and because NMDAR-dependent synaptic plasticity in this region is a proposed biological substrate for some hippocampal-dependent memory functions in schizophrenia, we hypothesized that reduced dysbindin-1 expression would lead to impairments in NMDAR-dependent synaptic plasticity and in contextual fear conditioning. Acute slices from male mice carrying 0, 1, or 2 null mutant alleles of the Dtnbp1 gene were prepared, and field recordings from the CA1 striatum radiatum were obtained before and after tetanization of Schaffer collaterals of CA3 pyramidal cells. Mice homozygous for the null mutation in Dtnbp1 exhibited significantly reduced NMDAR-dependent synaptic potentiation compared to wild type mice, an effect that could be rescued by bath application of the NMDA receptor coagonist glycine (10 μM). Behavioral testing in adult mice revealed deficits in hippocampal memory processes. Homozygous null mice exhibited lower conditional freezing, without a change in the response to shock itself, indicative of a learning and memory deficit. Taken together, these results indicate that a loss of dysbindin-1 impairs hippocampal plasticity which may, in part, explain the role dysbindin-1 plays in the cognitive impairments of schizophrenia. PMID:24446171

  14. The indirect NMDAR inhibitor flupirtine induces sustained post-ischemic recovery, neuroprotection and angioneurogenesis

    PubMed Central

    Jaeger, Hanna M.; Pehlke, Jens R.; Kaltwasser, Britta; Kilic, Ertugrul; Bähr, Mathias; Hermann, Dirk M.; Doeppner, Thorsten R.

    2015-01-01

    N-methyl-D-aspartate receptor (NMDAR) activation induces excitotoxicity, contributing to post-stroke brain injury. Hitherto, NMDAR deactivation failed in clinical trials due to insufficient pre-clinical study designs and drug toxicity. Flupirtine is an indirect NMDAR antagonist being used as analgesic in patients. Taking into account its tolerability profile, we evaluated effects of flupirtine on post-stroke tissue survival, neurological recovery and brain remodeling. Mice were exposed to stroke and intraperitoneally treated with saline (control) or flupirtine at various doses (1-10 mg/kg) and time-points (0-12 hours). Tissue survival and cell signaling were studied on day 2, whereas neurological recovery and tissue remodeling were analyzed until day 84. Flupirtine induced sustained neuroprotection, when delivered up to 9 hours. The latter yielded enhanced neurological recovery that persisted over three months and which was accompanied by enhanced angioneurogenesis. On the molecular level, inhibition of calpain activation was noted, which was associated with increased signal-transducer-and-activator-of-transcription-6 (STAT6) abundance, reduced N-terminal-Jun-kinase and NF-κB activation, as well as reduced proteasomal activity. Consequently, blood-brain-barrier integrity was stabilized, oxidative stress was reduced and brain leukocyte infiltration was diminished. In view of its excellent tolerability, considering its sustained effects on neurological recovery, brain tissue survival and remodeling, flupirtine is an attractive candidate for stroke therapy. PMID:26050199

  15. A Metabotropic-Like Flux-Independent NMDA Receptor Regulates Ca2+ Exit from Endoplasmic Reticulum and Mitochondrial Membrane Potential in Cultured Astrocytes

    PubMed Central

    Montes de Oca Balderas, Pavel; Aguilera, Penélope

    2015-01-01

    Astrocytes were long thought to be only structural cells in the CNS; however, their functional properties support their role in information processing and cognition. The ionotropic glutamate N-methyl D-aspartate (NMDA) receptor (NMDAR) is critical for CNS functions, but its expression and function in astrocytes is still a matter of research and debate. Here, we report immunofluorescence (IF) labeling in rat cultured cortical astrocytes (rCCA) of all NMDAR subunits, with phenotypes suggesting their intracellular transport, and their mRNA were detected by qRT-PCR. IF and Western Blot revealed GluN1 full-length synthesis, subunit critical for NMDAR assembly and transport, and its plasma membrane localization. Functionally, we found an iCa2+ rise after NMDA treatment in Fluo-4-AM labeled rCCA, an effect blocked by the NMDAR competitive inhibitors D(-)-2-amino-5-phosphonopentanoic acid (APV) and Kynurenic acid (KYNA) and dependent upon GluN1 expression as evidenced by siRNA knock down. Surprisingly, the iCa2+ rise was not blocked by MK-801, an NMDAR channel blocker, or by extracellular Ca2+ depletion, indicating flux-independent NMDAR function. In contrast, the IP3 receptor (IP3R) inhibitor XestosponginC did block this response, whereas a Ryanodine Receptor inhibitor did so only partially. Furthermore, tyrosine kinase inhibition with genistein enhanced the NMDA elicited iCa2+ rise to levels comparable to those reached by the gliotransmitter ATP, but with different population dynamics. Finally, NMDA depleted the rCCA mitochondrial membrane potential (mΔψ) measured with JC-1. Our results demonstrate that rCCA express NMDAR subunits which assemble into functional receptors that mediate a metabotropic-like, non-canonical, flux-independent iCa2+ increase. PMID:25954808

  16. A Metabotropic-Like Flux-Independent NMDA Receptor Regulates Ca2+ Exit from Endoplasmic Reticulum and Mitochondrial Membrane Potential in Cultured Astrocytes.

    PubMed

    Montes de Oca Balderas, Pavel; Aguilera, Penélope

    2015-01-01

    Astrocytes were long thought to be only structural cells in the CNS; however, their functional properties support their role in information processing and cognition. The ionotropic glutamate N-methyl D-aspartate (NMDA) receptor (NMDAR) is critical for CNS functions, but its expression and function in astrocytes is still a matter of research and debate. Here, we report immunofluorescence (IF) labeling in rat cultured cortical astrocytes (rCCA) of all NMDAR subunits, with phenotypes suggesting their intracellular transport, and their mRNA were detected by qRT-PCR. IF and Western Blot revealed GluN1 full-length synthesis, subunit critical for NMDAR assembly and transport, and its plasma membrane localization. Functionally, we found an iCa2+ rise after NMDA treatment in Fluo-4-AM labeled rCCA, an effect blocked by the NMDAR competitive inhibitors D(-)-2-amino-5-phosphonopentanoic acid (APV) and Kynurenic acid (KYNA) and dependent upon GluN1 expression as evidenced by siRNA knock down. Surprisingly, the iCa2+ rise was not blocked by MK-801, an NMDAR channel blocker, or by extracellular Ca2+ depletion, indicating flux-independent NMDAR function. In contrast, the IP3 receptor (IP3R) inhibitor XestosponginC did block this response, whereas a Ryanodine Receptor inhibitor did so only partially. Furthermore, tyrosine kinase inhibition with genistein enhanced the NMDA elicited iCa2+ rise to levels comparable to those reached by the gliotransmitter ATP, but with different population dynamics. Finally, NMDA depleted the rCCA mitochondrial membrane potential (mΔψ) measured with JC-1. Our results demonstrate that rCCA express NMDAR subunits which assemble into functional receptors that mediate a metabotropic-like, non-canonical, flux-independent iCa2+ increase.

  17. Non-Ionotropic NMDA Receptor Signaling Drives Activity-Induced Dendritic Spine Shrinkage

    PubMed Central

    Stein, Ivar S.; Gray, John A.

    2015-01-01

    The elimination of dendritic spine synapses is a critical step in the refinement of neuronal circuits during development of the cerebral cortex. Several studies have shown that activity-induced shrinkage and retraction of dendritic spines depend on activation of the NMDA-type glutamate receptor (NMDAR), which leads to influx of extracellular calcium ions and activation of calcium-dependent phosphatases that modify regulators of the spine cytoskeleton, suggesting that influx of extracellular calcium ions drives spine shrinkage. Intriguingly, a recent report revealed a novel non-ionotropic function of the NMDAR in the regulation of synaptic strength, which relies on glutamate binding but is independent of ion flux through the receptor (Nabavi et al., 2013). Here, we tested whether non-ionotropic NMDAR signaling could also play a role in driving structural plasticity of dendritic spines. Using two-photon glutamate uncaging and time-lapse imaging of rat hippocampal CA1 neurons, we show that low-frequency glutamatergic stimulation results in shrinkage of dendritic spines even in the presence of the NMDAR d-serine/glycine binding site antagonist 7-chlorokynurenic acid (7CK), which fully blocks NMDAR-mediated currents and Ca2+ transients. Notably, application of 7CK or MK-801 also converts spine enlargement resulting from a high-frequency uncaging stimulus into spine shrinkage, demonstrating that strong Ca2+ influx through the NMDAR normally overcomes a non-ionotropic shrinkage signal to drive spine growth. Our results support a model in which NMDAR signaling, independent of ion flux, drives structural shrinkage at spiny synapses. SIGNIFICANCE STATEMENT Dendritic spine elimination is vital for the refinement of neural circuits during development and has been linked to improvements in behavioral performance in the adult. Spine shrinkage and elimination have been widely accepted to depend on Ca2+ influx through NMDA-type glutamate receptors (NMDARs) in conjunction with long

  18. Interactions of methoxyacetic acid with androgen receptor

    SciTech Connect

    Bagchi, Gargi; Hurst, Christopher H.; Waxman, David J.

    2009-07-15

    Endocrine disruptive compounds (EDC) alter hormone-stimulated, nuclear receptor-dependent physiological and developmental processes by a variety of mechanisms. One recently identified mode of endocrine disruption is through hormone sensitization, where the EDC modulates intracellular signaling pathways that control nuclear receptor function, thereby regulating receptor transcriptional activity indirectly. Methoxyacetic acid (MAA), the primary, active metabolite of the industrial solvent ethylene glycol monomethyl ether and a testicular toxicant, belongs to this EDC class. Modulation of nuclear receptor activity by MAA could contribute to the testicular toxicity associated with MAA exposure. In the present study, we evaluated the impact of MAA on the transcriptional activity of several nuclear receptors including the androgen receptor (AR), which plays a pivotal role in the development and maturation of spermatocytes. AR transcriptional activity is shown to be increased by MAA through a tyrosine kinase signaling pathway that involves PI3-kinase. In a combinatorial setting with AR antagonists, MAA potentiated the AR response without significantly altering the EC{sub 50} for androgen responsiveness, partially alleviating the antagonistic effect of the anti-androgens. Finally, MAA treatment of TM3 mouse testicular Leydig cells markedly increased the expression of Cyp17a1 and Shbg while suppressing Igfbp3 expression by {approx} 90%. Deregulation of these genes may alter androgen synthesis and action in a manner that contributes to MAA-induced testicular toxicity.

  19. Piperazine-2,3-dicarboxylic acid Derivatives as Dual Antagonists of NMDA and GluK1-Containing Kainate Receptors

    PubMed Central

    Irvine, Mark W.; Costa, Blaise M.; Dlaboga, Daniel; Culley, Georgia; Hulse, Richard; Scholefield, Caroline L.; Atlason, Palmi; Fang, Guangyu; Eaves, Richard; Morley, Richard; Mayo-Martin, Maria B.; Amici, Mascia; Bortolotto, Zuner A.; Donaldson, Lucy; Collingridge, Graham L.; Molnár, Elek; Monaghan, Daniel T.; Jane, David E.

    2011-01-01

    Competitive N-methyl-D-aspartate receptor (NMDAR) antagonists bind to the GluN2 subunit, of which there are four types (GluN2A-D). We report that some N1-substituted derivatives of cis-piperazine-2,3-dicarboxylic acid display improved relative affinity for GluN2C and GluN2D versus GluN2A and GluN2B. These derivatives also display subtype-selectivity among the more distantly related kainate receptor family. Compounds 18i and (−)-4 were the most potent kainate receptor antagonists and 18i was selective for GluK1 versus GluK2, GluK3 and AMPA receptors. Modeling studies revealed structural features required for activity at GluK1 subunits and suggested that S674 was vital for antagonist activity. Consistent with this hypothesis, replacing the equivalent residue in GluK3 (alanine) with a serine imparts 18i antagonist activity. Antagonists with dual GluN2D and GluK1 antagonist activity may have beneficial effects in various neurological disorders. Consistent with this idea, antagonist 18i (30 mg/Kg i.p.) showed antinociceptive effects in an animal model of mild nerve injury. PMID:22111545

  20. NMDA receptor antibodies

    PubMed Central

    Ramberger, Melanie; Bsteh, Gabriel; Schanda, Kathrin; Höftberger, Romana; Rostásy, Kevin; Baumann, Matthias; Aboulenein-Djamshidian, Fahmy; Lutterotti, Andreas; Deisenhammer, Florian; Berger, Thomas

    2015-01-01

    Objectives: To analyze the frequency of NMDA receptor (NMDAR) antibodies in patients with various inflammatory demyelinating diseases of the CNS and to determine their clinical correlates. Methods: Retrospective case-control study from 2005 to 2014 with the detection of serum IgG antibodies to NMDAR, aquaporin-4, and myelin oligodendrocyte glycoprotein by recombinant live cell-based immunofluorescence assays. Fifty-one patients with acute disseminated encephalomyelitis, 41 with neuromyelitis optica spectrum disorders, 34 with clinically isolated syndrome, and 89 with multiple sclerosis (MS) were included. Due to a known association of NMDAR antibodies with seizures and behavioral symptoms, patients with those clinical manifestations were preferentially included and are therefore overrepresented in our cohort. Nine patients with NMDAR encephalitis, 94 patients with other neurologic diseases, and 48 healthy individuals were used as controls. Results: NMDAR antibodies were found in all 9 patients with NMDAR encephalitis but in only 1 of 215 (0.5%) patients with inflammatory demyelination and in none of the controls. This patient had relapsing-remitting MS with NMDAR antibodies present at disease onset, with an increase in NMDAR antibody titer with the onset of psychiatric symptoms and cognitive deficits. Conclusion: In demyelinating disorders, NMDAR antibodies are uncommon, even in those with symptoms seen in NMDAR encephalitis. PMID:26309901

  1. Time and space profiling of NMDA receptor co-agonist functions.

    PubMed

    Mothet, Jean-Pierre; Le Bail, Matildé; Billard, Jean-Marie

    2015-10-01

    The N-Methyl D-Aspartic acid (NMDA) receptors (NMDAR) are key tetrameric ionotropic glutamate receptors that transduce glutamatergic signals throughout the central nervous system (CNS) and spinal cord. Although NMDARs are diverse in their subunit composition, subcellular localization, and biophysical and pharmacological properties, their activation always requires the binding of a co-agonist that has long been thought to be glycine. However, intense research over the last decade has challenged this classical model by showing that another amino acid, d-serine, is the preferential co-agonist for a subset of synaptic NMDARs in many areas of the adult brain. Nowadays, a totally new picture of glutamatergic synapses at work is emerging where both glycine and d-serine are involved in a complex interplay to regulate NMDAR functions in the CNS following time and space constraints. The purpose of this review was to highlight the particular role of each co-agonist in modulating NMDAR-dependent activities in healthy and diseased brains. We have herein integrated our most advanced knowledge of how glycine and d-serine may orchestrate synapse dynamics and drive neuronal network activity in a time- and synapse-specific manner and how changes in synaptic availability of these amino acids may contribute to cognitive impairments such as those associated with healthy aging, epilepsy, and schizophrenia. The N-Methyl D-Aspartic acid (NMDA) subtype of glutamate receptors are central to many physiological functions and are linked to brain disorders. Their functions require glutamate and a co-agonist d-serine or glycine. After years of intense research and controversy on the identity of the amino acid that serves as the right co-agonist, we are just entering a new era of consensus where glycine and d-serine are teaming up to regulate the function of different subsets of NMDA receptors and at different synapses during different time windows of brain development. PMID:26088787

  2. N-methyl-D-aspartate receptor-mediated glutamate transmission in nucleus accumbens plays a more important role than that in dorsal striatum in cognitive flexibility

    PubMed Central

    Ding, Xuekun; Qiao, Yanhua; Piao, Chengji; Zheng, Xigeng; Liu, Zhengkui; Liang, Jing

    2014-01-01

    Cognitive flexibility is a critical ability for adapting to an ever-changing environment in humans and animals. Deficits in cognitive flexibility are observed in most schizophrenia patients. Previous studies reported that the medial prefrontal cortex-to-ventral striatum and orbital frontal cortex-to-dorsal striatum circuits play important roles in extra- and intra-dimensional strategy switching, respectively. However, the precise function of striatal subregions in flexible behaviors is still unclear. N-methyl-D-aspartate receptors (NMDARs) are major glutamate receptors in the striatum that receive glutamatergic projections from the frontal cortex. The membrane insertion of Ca2+-permeable α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptors (AMPARs) depends on NMDAR activation and is required in learning and memory processes. In the present study, we measured set-shifting and reversal learning performance in operant chambers in rats and assessed the effects of blocking NMDARs and Ca2+-permeable AMPARs in striatal subregions on behavioral flexibility. The blockade of NMDARs in the nucleus accumbens (NAc) core by AP5 impaired set-shifting ability by causing a failure to modify prior learning. The suppression of NMDAR-mediated transmission in the NAc shell induced a deficit in set-shifting by disrupting the learning and maintenance of novel strategies. During reversal learning, infusions of AP5 into the NAc shell and core impaired the ability to learn and maintain new strategies. However, behavioral flexibility was not significantly affected by blocking NMDARs in the dorsal striatum. We also found that the blockade of Ca2+-permeable AMPARs by NASPM in any subregion of the striatum did not affect strategy switching. These findings suggest that NMDAR-mediated glutamate transmission in the NAc contributes more to cognitive execution compared with the dorsal striatum. PMID:25249952

  3. Effect of monocular deprivation on NMDAR1 immunostaining in ocular dominance columns of the marmoset Callithrix jacchus.

    PubMed

    Fonta, C; Chappert, C; Imbert, M

    2000-01-01

    We previously showed that immunoreactivity to N-Methyl-D-aspartate (NMDA) receptors in primary visual cortex of Callithrix jacchus is regulated by visual activity during the second and third postnatal months (Fonta et al., 1997). The purpose of the present study was to show that the columnar pattern of high and low NMDAR1 immunoreactivity observed in monocularly deprived animals corresponds to ocular dominance columns linked to the nondeprived and deprived eye, respectively. We compared cortical distribution of NMDAR1 receptors and the projection zones of thalamic afferents, revealed by transneuronal transport of tritiated proline, in 2-month-old, either monocularly deprived or control, marmosets. The data show that ocular dominance columns exist in 2-month-old marmosets and that a 2-week monocular deprivation by means of eyelid suture leads to a modification of the thalamo-cortical afferents organization. Experiments of neuronal tracing and immunohistochemistry performed on the same animals demonstrated that cortical domains with decreased NMDAR1 level correspond to the deprived eye columns. These investigations, coupled to the previous results, strongly suggest that the NMDA receptors, regulated by visual activity, are involved in the refining of ocular dominance columns in the primary visual cortex of juvenile marmoset.

  4. NMDA Receptors of Gastric-Projecting Neurons in the Dorsal Motor Nucleus of the Vagus Mediate the Regulation of Gastric Emptying by EA at Weishu (BL21).

    PubMed

    Zhang, Xin; Cheng, Bin; Jing, Xianghong; Qiao, Yongfa; Gao, Xinyan; Yu, Huijuan; Zhu, Bing; Qiao, Haifa

    2012-01-01

    A large number of studies have been conducted to explore the efficacy of electroacupuncture (EA) for the treatment of gastrointestinal motility. While several lines of evidence addressed the basic mechanism of EA on gastrointestinal motility regarding effects of limb and abdomen points, the mechanism for effects of the back points on gastric motility still remains unclear. Here we report that the NMDA receptor (NMDAR) antagonist kynurenic acid inhibited the gastric emptying increase induced by high-intensity EA at BL21 and agonist NMDA enhanced the effect of the same treatment. EA at BL21 enhanced NMDAR, but not AMPA receptor (AMPAR) component of miniature excitatory postsynaptic current (mEPSC) in gastric-projecting neurons of the dorsal motor nucleus of the vagus (DMV). In sum, our data demonstrate an important role of NMDAR-mediated synaptic transmission of gastric-projecting DMV neurons in mediating EA at BL21-induced enhancement of gastric emptying. PMID:22654955

  5. Postnatal NMDA receptor ablation in corticolimbic interneurons confers schizophrenia-like phenotypes.

    PubMed

    Belforte, Juan E; Zsiros, Veronika; Sklar, Elyse R; Jiang, Zhihong; Yu, Gu; Li, Yuqing; Quinlan, Elizabeth M; Nakazawa, Kazu

    2010-01-01

    Cortical GABAergic dysfunction may underlie the pathophysiology of psychiatric disorders, including schizophrenia. Here, we characterized a mouse strain in which the essential NR1 subunit of the NMDA receptor (NMDAR) was selectively eliminated in 40-50% of cortical and hippocampal interneurons in early postnatal development. Consistent with the NMDAR hypofunction theory of schizophrenia, distinct schizophrenia-related symptoms emerged after adolescence, including novelty-induced hyperlocomotion, mating and nest-building deficits, as well as anhedonia-like and anxiety-like behaviors. Many of these behaviors were exacerbated by social isolation stress. Social memory, spatial working memory and prepulse inhibition were also impaired. Reduced expression of glutamic acid decarboxylase 67 and parvalbumin was accompanied by disinhibition of cortical excitatory neurons and reduced neuronal synchrony. Postadolescent deletion of NR1 did not result in such abnormalities. These findings suggest that early postnatal inhibition of NMDAR activity in corticolimbic GABAergic interneurons contributes to the pathophysiology of schizophrenia-related disorders.

  6. Nutritional Signaling via Free Fatty Acid Receptors.

    PubMed

    Miyamoto, Junki; Hasegawa, Sae; Kasubuchi, Mayu; Ichimura, Atsuhiko; Nakajima, Akira; Kimura, Ikuo

    2016-01-01

    Excess energy is stored primarily as triglycerides, which are mobilized when demand for energy arises. Dysfunction of energy balance by excess food intake leads to metabolic diseases, such as obesity and diabetes. Free fatty acids (FFAs) provided by dietary fat are not only important nutrients, but also contribute key physiological functions via FFA receptor (FFAR)-mediated signaling molecules, which depend on FFAs' carbon chain length and the ligand specificity of the receptors. Functional analyses have revealed that FFARs are critical for metabolic functions, such as peptide hormone secretion and inflammation, and contribute to energy homeostasis. In particular, recent studies have shown that the administration of selective agonists of G protein-coupled receptor (GPR) 40 and GPR120 improved glucose metabolism and systemic metabolic disorders. Furthermore, the anti-inflammation and energy metabolism effects of short chain FAs have been linked to the activation of GPR41 and GPR43. In this review, we summarize recent progress in research on FFAs and their physiological roles in the regulation of energy metabolism. PMID:27023530

  7. Nutritional Signaling via Free Fatty Acid Receptors

    PubMed Central

    Miyamoto, Junki; Hasegawa, Sae; Kasubuchi, Mayu; Ichimura, Atsuhiko; Nakajima, Akira; Kimura, Ikuo

    2016-01-01

    Excess energy is stored primarily as triglycerides, which are mobilized when demand for energy arises. Dysfunction of energy balance by excess food intake leads to metabolic diseases, such as obesity and diabetes. Free fatty acids (FFAs) provided by dietary fat are not only important nutrients, but also contribute key physiological functions via FFA receptor (FFAR)-mediated signaling molecules, which depend on FFAs’ carbon chain length and the ligand specificity of the receptors. Functional analyses have revealed that FFARs are critical for metabolic functions, such as peptide hormone secretion and inflammation, and contribute to energy homeostasis. In particular, recent studies have shown that the administration of selective agonists of G protein-coupled receptor (GPR) 40 and GPR120 improved glucose metabolism and systemic metabolic disorders. Furthermore, the anti-inflammation and energy metabolism effects of short chain FAs have been linked to the activation of GPR41 and GPR43. In this review, we summarize recent progress in research on FFAs and their physiological roles in the regulation of energy metabolism. PMID:27023530

  8. Identity of the NMDA receptor coagonist is synapse specific and developmentally regulated in the hippocampus

    PubMed Central

    Le Bail, Matildé; Martineau, Magalie; Sacchi, Silvia; Yatsenko, Natalia; Radzishevsky, Inna; Conrod, Sandrine; Ait Ouares, Karima; Wolosker, Herman; Pollegioni, Loredano; Billard, Jean-Marie; Mothet, Jean-Pierre

    2015-01-01

    NMDA receptors (NMDARs) require the coagonists d-serine or glycine for their activation, but whether the identity of the coagonist could be synapse specific and developmentally regulated remains elusive. We therefore investigated the contribution of d-serine and glycine by recording NMDAR-mediated responses at hippocampal Schaffer collaterals (SC)–CA1 and medial perforant path–dentate gyrus (mPP–DG) synapses in juvenile and adult rats. Selective depletion of endogenous coagonists with enzymatic scavengers as well as pharmacological inhibition of endogenous d-amino acid oxidase activity revealed that d-serine is the preferred coagonist at SC–CA1 mature synapses, whereas, unexpectedly, glycine is mainly involved at mPP–DG synapses. Nevertheless, both coagonist functions are driven by the levels of synaptic activity as inferred by recording long-term potentiation generated at both connections. This regional compartmentalization in the coagonist identity is associated to different GluN1/GluN2A to GluN1/GluN2B subunit composition of synaptic NMDARs. During postnatal development, the replacement of GluN2B- by GluN2A-containing NMDARs at SC–CA1 synapses parallels a change in the identity of the coagonist from glycine to d-serine. In contrast, NMDARs subunit composition at mPP–DG synapses is not altered and glycine remains the main coagonist throughout postnatal development. Altogether, our observations disclose an unprecedented relationship in the identity of the coagonist not only with the GluN2 subunit composition at synaptic NMDARs but also with astrocyte activity in the developing and mature hippocampus that reconciles the complementary functions of d-serine and glycine in modulating NMDARs during the maturation of tripartite glutamatergic synapses. PMID:25550512

  9. [Beta]-Adrenergic Receptor Activation Rescues Theta Frequency Stimulation-Induced LTP Deficits in Mice Expressing C-Terminally Truncated NMDA Receptor GluN2A Subunits

    ERIC Educational Resources Information Center

    Moody, Teena D.; Watabe, Ayako M.; Indersmitten, Tim; Komiyama, Noboru H.; Grant, Seth G. N.; O'Dell, Thomas J.

    2011-01-01

    Through protein interactions mediated by their cytoplasmic C termini the GluN2A and GluN2B subunits of NMDA receptors (NMDARs) have a key role in the formation of NMDAR signaling complexes at excitatory synapses. Although these signaling complexes are thought to have a crucial role in NMDAR-dependent forms of synaptic plasticity such as long-term…

  10. Enriched environment has limited capacity for the correction of hippocampal memory-dependent schizoid behaviors in rats with early postnatal NMDAR dysfunction.

    PubMed

    Melik, Enver; Babar, Emine; Kocahan, Sayad; Guven, Mustafa; Akillioglu, Kubra

    2014-04-01

    Pre- and early postnatal stress can cause dysfunction of the N-methyl-d-aspartate receptor (NMDAR) and thereby promote the development of hippocampus memory-dependent schizoid abnormalities of navigation in space, time, and knowledge. An enriched environment improves mental abilities in humans and animals. Whether an enriched environment can prevent the development of schizoid symptoms induced by neonatal NMDAR dysfunction was the central question of our paper. The experimental animals were Wistar rats. Early postnatal NMDAR dysfunction was created by systemic treatment of rat pups with the NMDAR antagonist MK-801 at PD10-20 days. During the development period (PD21-90 days), the rats were reared in cognitively and physically enriched cages. Adult age rats were tested on navigation based on pattern separation and episodic memory in the open field and on auto-hetero-associations based on episodic and semantic memory in a step-through passive avoidance task. The results showed that postnatal NMDAR antagonism caused abnormal behaviors in both tests. An enriched environment prevented deficits in the development of navigation in space based on pattern separation and hetero-associations based on semantic memory. However, an enriched environment was unable to rescue navigation in space and auto-associations based on episodic memory. These data may contribute to the understanding that an enriched environment has a limited capacity for therapeutic interventions in protecting the development of schizoid syndromes in children and adolescents. PMID:24184288

  11. Enriched environment has limited capacity for the correction of hippocampal memory-dependent schizoid behaviors in rats with early postnatal NMDAR dysfunction.

    PubMed

    Melik, Enver; Babar, Emine; Kocahan, Sayad; Guven, Mustafa; Akillioglu, Kubra

    2014-04-01

    Pre- and early postnatal stress can cause dysfunction of the N-methyl-d-aspartate receptor (NMDAR) and thereby promote the development of hippocampus memory-dependent schizoid abnormalities of navigation in space, time, and knowledge. An enriched environment improves mental abilities in humans and animals. Whether an enriched environment can prevent the development of schizoid symptoms induced by neonatal NMDAR dysfunction was the central question of our paper. The experimental animals were Wistar rats. Early postnatal NMDAR dysfunction was created by systemic treatment of rat pups with the NMDAR antagonist MK-801 at PD10-20 days. During the development period (PD21-90 days), the rats were reared in cognitively and physically enriched cages. Adult age rats were tested on navigation based on pattern separation and episodic memory in the open field and on auto-hetero-associations based on episodic and semantic memory in a step-through passive avoidance task. The results showed that postnatal NMDAR antagonism caused abnormal behaviors in both tests. An enriched environment prevented deficits in the development of navigation in space based on pattern separation and hetero-associations based on semantic memory. However, an enriched environment was unable to rescue navigation in space and auto-associations based on episodic memory. These data may contribute to the understanding that an enriched environment has a limited capacity for therapeutic interventions in protecting the development of schizoid syndromes in children and adolescents.

  12. Conformations of tissue plasminogen activator (tPA) orchestrate neuronal survival by a crosstalk between EGFR and NMDAR

    PubMed Central

    Bertrand, T; Lesept, F; Chevilley, A; Lenoir, S; Aimable, M; Briens, A; Hommet, Y; Bardou, I; Parcq, J; Vivien, D

    2015-01-01

    Tissue-type plasminogen activator (tPA) is a pleiotropic serine protease of the central nervous system (CNS) with reported neurotrophic and neurotoxic functions. Produced and released under its single chain form (sc), the sc-tPA can be cleaved by plasmin or kallikrein in a two chain form, tc-tPA. Although both sc-tPA and tc-tPA display a similar fibrinolytic activity, we postulated here that these two conformations of tPA (sc-tPA and tc-tPA) could differentially control the effects of tPA on neuronal survival. Using primary cultures of mouse cortical neurons, our present study reveals that sc-tPA is the only one capable to promote N-methyl-D-aspartate receptor (NMDAR)-induced calcium influx and subsequent excitotoxicity. In contrast, both sc-tPA and tc-tPA are capable to activate epidermal growth factor receptors (EGFRs), a mechanism mediating the antiapoptotic effects of tPA. Interestingly, we revealed a tPA dependent crosstalk between EGFR and NMDAR in which a tPA-dependent activation of EGFRs leads to downregulation of NMDAR signaling and to subsequent neurotrophic effects. PMID:26469972

  13. Phospho-dependent Accumulation of GABABRs at Presynaptic Terminals after NMDAR Activation.

    PubMed

    Hannan, Saad; Gerrow, Kim; Triller, Antoine; Smart, Trevor G

    2016-08-16

    Here, we uncover a mechanism for regulating the number of active presynaptic GABAB receptors (GABABRs) at nerve terminals, an important determinant of neurotransmitter release. We find that GABABRs gain access to axon terminals by lateral diffusion in the membrane. Their relative accumulation is dependent upon agonist activation and the presence of the two distinct sushi domains that are found only in alternatively spliced GABABR1a subunits. Following brief activation of NMDA receptors (NMDARs) using glutamate, GABABR diffusion is reduced, causing accumulation at presynaptic terminals in a Ca(2+)-dependent manner that involves phosphorylation of GABABR2 subunits at Ser783. This signaling cascade indicates how synaptically released glutamate can initiate, via a feedback mechanism, increased levels of presynaptic GABABRs that limit further glutamate release and excitotoxicity.

  14. Phospho-dependent Accumulation of GABABRs at Presynaptic Terminals after NMDAR Activation.

    PubMed

    Hannan, Saad; Gerrow, Kim; Triller, Antoine; Smart, Trevor G

    2016-08-16

    Here, we uncover a mechanism for regulating the number of active presynaptic GABAB receptors (GABABRs) at nerve terminals, an important determinant of neurotransmitter release. We find that GABABRs gain access to axon terminals by lateral diffusion in the membrane. Their relative accumulation is dependent upon agonist activation and the presence of the two distinct sushi domains that are found only in alternatively spliced GABABR1a subunits. Following brief activation of NMDA receptors (NMDARs) using glutamate, GABABR diffusion is reduced, causing accumulation at presynaptic terminals in a Ca(2+)-dependent manner that involves phosphorylation of GABABR2 subunits at Ser783. This signaling cascade indicates how synaptically released glutamate can initiate, via a feedback mechanism, increased levels of presynaptic GABABRs that limit further glutamate release and excitotoxicity. PMID:27498877

  15. Parvalbumin Cell Ablation of NMDA-R1 Causes Increased Resting Network Excitability with Associated Social and Self-Care Deficits

    PubMed Central

    Billingslea, Eddie N; Tatard-Leitman, Valerie M; Anguiano, Jaynie; Jutzeler, Catherine R; Suh, Jimmy; Saunders, John A; Morita, Susumu; Featherstone, Robert E; Ortinski, Pavel I; Gandal, Michael J; Lin, Robert; Liang, Yuling; Gur, Raquel E; Carlson, Gregory C; Hahn, Chang-Gyu; Siegel, Steven J

    2014-01-01

    NMDA-receptor (NMDAR) hypofunction is strongly implicated in the pathophysiology of schizophrenia. Several convergent lines of evidence suggest that net excitation propagated by impaired NMDAR signaling on GABAergic interneurons may be of particular interest in mediating several aspects of schizophrenia. However, it is unclear which behavioral domains are governed by a net increase of excitation and whether modulating downstream GABAergic signaling can reverse neural and thus behavioral deficits. The current study determines the selective contributions of NMDAR dysfunction on PV-containing interneurons to electrophysiological, cognitive, and negative-symptom-related behavioral phenotypes of schizophrenia using mice with a PVcre-NR1flox-driven ablation of NR1 on PV-containing interneurons. In addition, we assessed the efficacy of one agent that directly modulates GABAergic signaling (baclofen) and one agent that indirectly modifies NMDAR-mediated signaling through antagonism of mGluR5 receptors (2-methyl-6-(phenylethynyl) pyridine (MPEP)). The data indicate that loss of NMDAR function on PV interneurons impairs self-care and sociability while increasing N1 latency and baseline gamma power, and reducing induction and maintenance of long-term potentiation. Baclofen normalized baseline gamma power without corresponding effects on behavior. MPEP further increased N1 latency and reduced social behavior in PVcre/NR1+/+ mice. These two indices were negatively correlated before and following MPEP such that as N1 latency increases, sociability decreases. This finding suggests a predictive role for N1 latency with respect to social function. Although previous data suggest that MPEP may be beneficial for core features of autism spectrum disorders, current data suggest that such effects require intact function of NMDAR on PV interneurons. PMID:24525709

  16. NMDAR-regulated dynamics of layer 4 neuronal dendrites during thalamocortical reorganization in neonates.

    PubMed

    Mizuno, Hidenobu; Luo, Wenshu; Tarusawa, Etsuko; Saito, Yoshikazu M; Sato, Takuya; Yoshimura, Yumiko; Itohara, Shigeyoshi; Iwasato, Takuji

    2014-04-16

    Thalamocortical (TC) connectivity is reorganized by thalamic inputs during postnatal development; however, the dynamic characteristics of TC reorganization and the underlying mechanisms remain unexplored. We addressed this question using dendritic refinement of layer 4 (L4) stellate neurons in mouse barrel cortex (barrel cells) as a model; dendritic refinement of L4 neurons is a critical component of TC reorganization through which postsynaptic L4 neurons acquire their dendritic orientation toward presynaptic TC axon termini. Simultaneous labeling of TC axons and individual barrel cell dendrites allowed in vivo time-lapse imaging of dendritic refinement in the neonatal cortex. The barrel cells reinforced the dendritic orientation toward TC axons by dynamically moving their branches. In N-methyl-D-aspartate receptor (NMDAR)-deficient barrel cells, this dendritic motility was enhanced, and the orientation bias was not reinforced. Our data suggest that L4 neurons have "fluctuating" dendrites during TC reorganization and that NMDARs cell autonomously regulate these dynamics to establish fine-tuned circuits.

  17. Cyclin-dependent kinase 5 governs learning and synaptic plasticity via control of NMDAR degradation.

    PubMed

    Hawasli, Ammar H; Benavides, David R; Nguyen, Chan; Kansy, Janice W; Hayashi, Kanehiro; Chambon, Pierre; Greengard, Paul; Powell, Craig M; Cooper, Donald C; Bibb, James A

    2007-07-01

    Learning is accompanied by modulation of postsynaptic signal transduction pathways in neurons. Although the neuronal protein kinase cyclin-dependent kinase 5 (Cdk5) has been implicated in cognitive disorders, its role in learning has been obscured by the perinatal lethality of constitutive knockout mice. Here we report that conditional knockout of Cdk5 in the adult mouse brain improved performance in spatial learning tasks and enhanced hippocampal long-term potentiation and NMDA receptor (NMDAR)-mediated excitatory postsynaptic currents. Enhanced synaptic plasticity in Cdk5 knockout mice was attributed to reduced NR2B degradation, which caused elevations in total, surface and synaptic NR2B subunit levels and current through NR2B-containing NMDARs. Cdk5 facilitated the degradation of NR2B by directly interacting with both it and its protease, calpain. These findings reveal a previously unknown mechanism by which Cdk5 facilitates calpain-mediated proteolysis of NR2B and may control synaptic plasticity and learning.

  18. AMPA receptors undergo channel arrest in the anoxic turtle cortex.

    PubMed

    Pamenter, Matthew Edward; Shin, Damian Seung-Ho; Buck, Leslie Thomas

    2008-02-01

    Without oxygen, all mammals suffer neuronal injury and excitotoxic cell death mediated by overactivation of the glutamatergic N-methyl-D-aspartate receptor (NMDAR). The western painted turtle can survive anoxia for months, and downregulation of NMDAR activity is thought to be neuroprotective during anoxia. NMDAR activity is related to the activity of another glutamate receptor, the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR). AMPAR blockade is neuroprotective against anoxic insult in mammals, but the role of AMPARs in the turtle's anoxia tolerance has not been investigated. To determine whether AMPAR activity changes during hypoxia or anoxia in the turtle cortex, whole cell AMPAR currents, AMPAR-mediated excitatory postsynaptic potentials (EPSPs), and excitatory postsynaptic currents (EPSCs) were measured. The effect of AMPAR blockade on normoxic and anoxic NMDAR currents was also examined. During 60 min of normoxia, evoked peak AMPAR currents and the frequencies and amplitudes of EPSPs and EPSCs did not change. During anoxic perfusion, evoked AMPAR peak currents decreased 59.2 +/- 5.5 and 60.2 +/- 3.5% at 20 and 40 min, respectively. EPSP frequency (EPSP(f)) and amplitude decreased 28.7 +/- 6.4% and 13.2 +/- 1.7%, respectively, and EPSC(f) and amplitude decreased 50.7 +/- 5.1% and 51.3 +/- 4.7%, respectively. In contrast, hypoxic (Po(2) = 5%) AMPAR peak currents were potentiated 56.6 +/- 20.5 and 54.6 +/- 15.8% at 20 and 40 min, respectively. All changes were reversed by reoxygenation. AMPAR currents and EPSPs were abolished by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). In neurons pretreated with CNQX, anoxic NMDAR currents were reversibly depressed by 49.8 +/- 7.9%. These data suggest that AMPARs may undergo channel arrest in the anoxic turtle cortex. PMID:18056983

  19. NMDA receptor subunits and associated signaling molecules mediating antidepressant-related effects of NMDA-GluN2B antagonism

    PubMed Central

    Kiselycznyk, Carly; Jury, Nicholas; Halladay, Lindsay; Nakazawa, Kazu; Mishina, Masayoshi; Sprengel, Rolf; Grant, Seth G.N.; Svenningsson, Per; Holmes, Andrew

    2015-01-01

    Drugs targeting the glutamate N-methyl-D-aspartate receptor (NMDAR) may be efficacious for treating mood disorders, as exemplified by the rapid antidepressant effects produced by single administration of the NMDAR antagonist ketamine. Though the precise mechanisms underlying the antidepressant-related effects of NMDAR antagonism remain unclear, recent studies implicate specific NMDAR subunits, including GluN2A and GluN2B, as well as the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR) subunit glutamate receptor interacting molecule, PSD-95. Here, integrating mutant and pharmacological in mice, we investigated the contribution of these subunits and molecules to antidepressant-related behaviors and the antidepressant-related effects of the GluN2B blocker, Ro 25-6981. We found that global deletion of GluA1 or PSD-95 reduced forced swim test (FST) immobility, mimicking the antidepressant-related effect produced by systemically administered Ro 25-6981 in C57BL/6J mice. Moreover, the FST antidepressant-like effects of systemic Ro 25-6981 were intact in mutants with global GluA1 deletion or GluN1 deletion in forebrain interneurons, but were absent in mutants constitutively lacking GluN2A or PSD-95. Next, we found that microinfusing Ro 25-6981 into the medial prefrontal cortex (mPFC), but not basolateral amygdala, of C57BL/6J mice was sufficient to produce an antidepressant-like effect. Together, these findings extend and refine current understanding of the mechanisms mediating antidepressant-like effects produced by NMDAR-GluN2B antagonists, and may inform the development of a novel class of medications for treating depression that target the GluN2B subtype of NMDAR. PMID:25800971

  20. Pharmacology of bile acid receptors: Evolution of bile acids from simple detergents to complex signaling molecules.

    PubMed

    Copple, Bryan L; Li, Tiangang

    2016-02-01

    For many years, bile acids were thought to only function as detergents which solubilize fats and facilitate the uptake of fat-soluble vitamins in the intestine. Many early observations; however, demonstrated that bile acids regulate more complex processes, such as bile acids synthesis and immune cell function through activation of signal transduction pathways. These studies were the first to suggest that receptors may exist for bile acids. Ultimately, seminal studies by many investigators led to the discovery of several bile acid-activated receptors including the farnesoid X receptor, the vitamin D receptor, the pregnane X receptor, TGR5, α5 β1 integrin, and sphingosine-1-phosphate receptor 2. Several of these receptors are expressed outside of the gastrointestinal system, indicating that bile acids may have diverse functions throughout the body. Characterization of the functions of these receptors over the last two decades has identified many important roles for these receptors in regulation of bile acid synthesis, transport, and detoxification; regulation of glucose utilization; regulation of fatty acid synthesis and oxidation; regulation of immune cell function; regulation of energy expenditure; and regulation of neural processes such as gastric motility. Through these many functions, bile acids regulate many aspects of digestion ranging from uptake of essential vitamins to proper utilization of nutrients. Accordingly, within a short time period, bile acids moved beyond simple detergents and into the realm of complex signaling molecules. Because of the important processes that bile acids regulate through activation of receptors, drugs that target these receptors are under development for the treatment of several diseases, including cholestatic liver disease and metabolic syndrome. In this review, we will describe the various bile acid receptors, the signal transduction pathways activated by these receptors, and briefly discuss the physiological processes that

  1. Overlapping demyelinating syndromes and anti-NMDA receptor encephalitis

    PubMed Central

    Titulaer, Maarten J.; Höftberger, Romana; Iizuka, Takahiro; Leypoldt, Frank; McCracken, Lindsey; Cellucci, Tania; Benson, Leslie A.; Shu, Huidy; Irioka, Takashi; Hirano, Makito; Singh, Gagandeep; Calvo, Alvaro Cobo; Kaida, Kenichi; Morales, Pamela S.; Wirtz, Paul W.; Yamamoto, Tomotaka; Reindl, Markus; Rosenfeld, Myrna R.; Graus, Francesc; Saiz, Albert; Dalmau, Josep

    2014-01-01

    Objective To report the clinical, radiological, and immunological association of demyelinating disorders with anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. Methods Clinical and radiological analysis of a cohort of 691 patients with anti-NMDAR encephalitis. Determination of antibodies to NMDAR, aquaporin-4 (AQP4) and myelin oligodendrocyte glycoprotein (MOG) was performed using brain immunohistochemistry and cell-based assays. Results Twenty-three of 691 patients with anti-NMDAR encephalitis had prominent MRI and/or clinical features of demyelination. Group 1 included 12 patients in whom anti-NMDAR encephalitis was preceded or followed by independent episodes of NMO-spectrum disorder (5 cases, 4 anti-AQP4-positive), or brainstem or multifocal demyelinating syndromes (7 cases, all anti-MOG-positive). Group 2 included 11 patients in whom anti-NMDAR encephalitis occurred simultaneously with MRI and symptoms compatible with demyelination (5 AQ4-positive, 2 MOG-positive). Group 3 (136 controls) included 50 randomly selected patients with typical anti-NMDAR encephalitis, 56 with NMO, and 30 with multiple sclerosis: NMDAR-antibodies were detected only in the 50 anti-NMDAR patients, MOG-antibodies in 3/50 anti-NMDAR and 1/56 NMO patients, and AQP4-antibodies in 48/56 NMO and 1/50 anti-NMDAR patients (p<0.0001 for all comparisons with Groups 1 and 2). Most patients improved with immunotherapy, but compared with anti-NMDAR encephalitis the demyelinating episodes required more intensive therapy and resulted in more residual deficits. Only 1/23 NMDAR patients with signs of demyelination had ovarian teratoma compared with 18/50 anti-NMDAR controls (p=0.011) Interpretation Patients with anti-NMDAR encephalitis may develop concurrent or separate episodes of demyelinating disorders, and conversely patients with NMO or demyelinating disorders with atypical symptoms (e.g., dyskinesias, psychosis) may have anti-NMDAR encephalitis. PMID:24700511

  2. Anatomical and pharmacological characterization of excitatory amino acid receptors

    SciTech Connect

    Monaghan, D.T.

    1985-01-01

    The majority of the excitatory neurotransmission in the vertebrate Central Nervous System is thought to be mediated by acidic amino acid neurotransmitters. However, relatively little is known about the excitatory amino acid receptors and their distribution within the CNS. By analyzing radioligand binding to purified synaptic plasma membranes and to thin tissue sections processed for autoradiography, multiple distinct binding sites were found. These binding sites exhibited the pharmacological properties indicative of the excitatory amino acid receptors, which had been identified by electrophysiological techniques. Specifically, L-(/sup 3/H)-glutamate and D-(/sup 3/H)-amino-5-phosphonopentanoate appear to label N-methyl-D-aspartate receptors, L-(/sup 3/H)-glutamate and (/sup 3/H)-kainic acid appear to label kainic acid receptors, and L-(/sup 3/H)-glutamate and (/sup 3/H)-amino-3-hydroxy-5-methyl-4-isoxazolepropionate appear to label quisqualate receptors. Together, these results confirm the three receptor scheme proposed for excitatory amino acid neurotransmission. These results also show that these transmitter-receptor systems are differentially distributed in the brain, and that the total distribution is consistent with that found by other markers for excitatory amino acid-using neurons.

  3. Down-regulation of NR3A-containing NMDARs is required for synapse maturation and memory consolidation

    PubMed Central

    Roberts, Adam C.; Díez-García, Javier; Rodriguiz, Ramona M.; López, Iciar Paula; Luján, Rafael; Martínez-Turrillas, Rebeca; Picó, Esther; Henson, Maile A.; Bernardo, Danilo R.; Jarrett, Thomas M.; Clendeninn, Dallis J.; López-Mascaraque, Laura; Feng, Guoping; Lo, Donald C.; Wesseling, John F.; Wetsel, William C.; Philpot, Benjamin D.; Pérez-Otaño, Isabel

    2012-01-01

    SUMMARY NR3A is the only NMDA receptor (NMDAR) subunit that down-regulates sharply prior to the onset of sensitive periods for plasticity, yet the functional importance of this transient expression remains largely unknown. To investigate the possibility that removal/replacement of juvenile NR3A-containing NMDARs is involved in experience-driven synapse maturation, we used a reversible transgenic system that allowed persistent NR3A expression in the postnatal forebrain. We found that removal of NR3A is required to develop strong NMDAR currents, full expression of long-term synaptic plasticity, a mature synaptic organization characterized by more synapses and larger postsynaptic densities, and the ability to form long-term memories. Deficits associated with prolonged NR3A were reversible, as late-onset suppression of transgene expression rescued both the synaptic and memory impairments. Our results suggest that NR3A behaves as a molecular brake to prevent the premature strengthening and stabilization of excitatory synapses, and that NR3A removal might thereby initiate critical stages of synapse maturation during early postnatal neural development. PMID:19679074

  4. Does MAP2 have a role in predicting the development of anti-NMDAR encephalitis associated with benign ovarian teratoma? A report of six new pediatric cases.

    PubMed

    Cundiff, Caitlin A; Elawabdeh, Nancy; Naguib, Mina M; Jactel, Samuel N; Demellawy, Dina El; Abramowsky, Carlos R; Durham, Megan M; Youssef, Lara; Wittkamp, Michael L; Shehata, Bahig M

    2015-01-01

    Anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis is a potentially fatal neurologic syndrome in which patients present with a spectrum of central nervous system deficits. Sixty percent of the cases can be attributed to the presence of tumors, most often ovarian teratomas. This report examines 6 pediatric patients who presented with neurologic deficits associated with the presence of such tumors. These cases illustrate a perplexing phenomenon, where benign teratomas could have a possible association with anti-NMDAR encephalitis. The purpose of this study was to compare the histology and immunohistochemistry of tumors associated with this syndrome to ovarian teratomas found in patients presenting with no neurologic symptoms. After obtaining institutional review board approval, 57 cases of ovarian teratomas were identified at our institution over 12 years. Six patients were identified with anti-NMDAR encephalitis. A panel of immunostains, including S100, GFAP, MAP2, and NeuN was applied to patients' tumor sections as well as the 6 controls from age-matched patients. No qualitative histologic or immunohistochemical differences were seen between the study cases and control group. Because no qualitative differences were identified between the study cases and the control group, testing of paired serum and cerebrospinal fluid remains the best method for diagnosis of anti-NMDAR encephalitis. Tumor banking with molecular analysis of ovarian teratomas, including whole-genome sequencing and comparative genomic hybridization between ovarian tissue saved from patients with and without anti-NMDAR encephalitis, is necessary to fully understand the etiopathogenesis of anti-NMDAR encephalitis.

  5. Overexpression of αCaMKII impairs behavioral flexibility and NMDAR-dependent long-term depression in the medial prefrontal cortex.

    PubMed

    Ma, J; Duan, Y; Qin, Z; Wang, J; Liu, W; Xu, M; Zhou, S; Cao, X

    2015-12-01

    The medial prefrontal cortex (mPFC) participates in the behavioral flexibility. As a major downstream molecule in the NMDA receptor signaling, alpha-Ca(2+)/calmodulin-dependent protein kinase II (αCaMKII) is crucial for hippocampal long-term potentiation (LTP) and hippocampus-related memory. However, the role of αCaMKII in mPFC-related behavioral flexibility and mPFC synaptic plasticity remains elusive. In the present study, using chemical-genetic approaches to temporally up-regulate αCaMKII activity, we found that αCaMKII-F89G transgenic mice exhibited impaired behavioral flexibility in Y-water maze arm reversal task. Notably, in vitro electrophysiological analysis showed normal basal synaptic transmission, LTP and depotentiation, but selectively impaired NMDAR-dependent long-term depression (LTD) in the mPFC of αCaMKII-F89G transgenic mice. In accordance with the deficit in NMDAR-dependent LTD, αCaMKII-F89G transgenic mice exhibited impaired AMPAR internalization during NMDAR-dependent chemical LTD expression in the mPFC. Furthermore, the above deficits in behavioral flexibility, NMDAR-dependent LTD and AMPAR internalization could all be reversed by 1-naphthylmethyl (NM)-PP1, a specific inhibitor of exogenous αCaMKII-F89G activity. Taken together, our results for the first time indicate that αCaMKII overexpression in the forebrain impairs behavioral flexibility and NMDAR-dependent LTD in the mPFC, and supports the notion that there is a close relationship between NMDAR-dependent LTD and behavioral flexibility.

  6. Comparative analyses of lysophosphatidic acid receptor-mediated signaling.

    PubMed

    Fukushima, Nobuyuki; Ishii, Shoichi; Tsujiuchi, Toshifumi; Kagawa, Nao; Katoh, Kazutaka

    2015-06-01

    Lysophosphatidic acid (LPA) is a bioactive lipid mediator that activates G protein-coupled LPA receptors to exert fundamental cellular functions. Six LPA receptor genes have been identified in vertebrates and are classified into two subfamilies, the endothelial differentiation genes (edg) and the non-edg family. Studies using genetically engineered mice, frogs, and zebrafish have demonstrated that LPA receptor-mediated signaling has biological, developmental, and pathophysiological functions. Computational analyses have also identified several amino acids (aa) critical for LPA recognition by human LPA receptors. This review focuses on the evolutionary aspects of LPA receptor-mediated signaling by comparing the aa sequences of vertebrate LPA receptors and LPA-producing enzymes; it also summarizes the LPA receptor-dependent effects commonly observed in mouse, frog, and fish. PMID:25732591

  7. Environmental enrichment does not reverse the effects of maternal deprivation on NMDAR and Balb/c mice behaviors.

    PubMed

    Akillioglu, Kubra; Yilmaz, M Bertan; Boga, Ayper; Binokay, Secil; Kocaturk-Sel, Sabriye

    2015-10-22

    Early adverse life experiences have been associated with anxiety-like behavior and memory impairment. N-methyl-d-aspartate receptors (NMDARs) play an important role in brain development. Enriched environments are known to positively influence emotional and cognitive functions in the brain. We examined the effects of maternal deprivation (MD) on NMDAR subunits in the hippocampus, locomotor activity, anxiety behaviors, and learning-memory performance of Balb/c mice. We also examined whether these effects could be reversed by raising the offspring in an enriched environment. The mice were separated from their mothers for a single 24h episode on postnatal day (PND) 9. The mice were weaned on day 21 and were housed under either standard (SE) or enriched (EE) environmental conditions. Emotional behaviors and cognitive processes of mice were evaluated using an open field (OF) test, an elevated plus maze (EPM) test, and a Morris water-maze (MWM). NMDAR subunits (GluN1, GluN2A, and GluN2B) mRNA expression levels in the hippocampus were examined by real-time PCR. In OF, MD had no effect on horizontal locomotor activity. MD increased anxiety-like behaviors in the EPM and decreased spatial learning performance in MWM; however, these effects were not reversed by EE. MD (in SE and EE conditions) increased GluN1, GluN2A, and GluN2B mRNA expressions in the hippocampus. In conclusion, MD led to the deterioration of the emotional and cognitive processes during adulthood. Moreover, environmental enrichment did not reverse the deleterious effects of the MD on emotional and cognitive functions and increased the NMDAR levels.

  8. Transcription factor Sp4 regulates expression of nervous wreck 2 to control NMDAR1 levels and dendrite patterning.

    PubMed

    Sun, Xinxin; Pinacho, Raquel; Saia, Gregory; Punko, Diana; Meana, J Javier; Ramos, Belén; Gill, Grace

    2015-01-01

    Glutamatergic signaling through N-methyl-d-aspartate receptors (NMDARs) is important for neuronal development and plasticity and is often dysregulated in psychiatric disorders. Mice mutant for the transcription factor Sp4 have reduced levels of NMDAR subunit 1 (NR1) protein, but not mRNA, and exhibit behavioral and memory deficits (Zhou et al., [2010] Human Molecular Genetics 19: 3797-3805). In developing cerebellar granule neurons (CGNs), Sp4 controls dendrite patterning (Ramos et al., [2007] Proc Natl Acad Sci USA 104: 9882-9887). Sp4 target genes that regulate dendrite pruning or NR1 levels are not known. Here we report that Sp4 activates transcription of Nervous Wreck 2 (Nwk2; also known as Fchsd1) and, further, that Nwk2, an F-BAR domain-containing protein, mediates Sp4-dependent regulation of dendrite patterning and cell surface expression of NR1. Knockdown of Nwk2 in CGNs increased primary dendrite number, phenocopying Sp4 knockdown, and exogenous expression of Nwk2 in Sp4-depleted neurons rescued dendrite number. We observed that acute Sp4 depletion reduced levels of surface, but not total, NR1, and this was rescued by Nwk2 expression. Furthermore, expression of Nr1 suppressed the increase in dendrite number in Sp4- or Nwk2- depleted neurons. We previously reported that Sp4 protein levels were reduced in cerebellum of subjects with bipolar disorder (BD) (Pinacho et al., [2011] Bipolar Disorders 13: 474-485). Here we report that Nwk2 mRNA and NR1 protein levels were also reduced in postmortem cerebellum of BD subjects. Our data suggest a role for Sp4-regulated Nwk2 in NMDAR trafficking and identify a Sp4-Nwk2-NMDAR1 pathway that regulates neuronal morphogenesis during development and may be disrupted in bipolar disorder.

  9. Presynaptic N-Methyl-d-aspartate (NMDA) Receptor Activity Is Increased Through Protein Kinase C in Paclitaxel-induced Neuropathic Pain.

    PubMed

    Xie, Jing-Dun; Chen, Shao-Rui; Chen, Hong; Zeng, Wei-An; Pan, Hui-Lin

    2016-09-01

    Painful peripheral neuropathy is a severe adverse effect of chemotherapeutic drugs such as paclitaxel (Taxol). The glutamate N-methyl-d-aspartate receptors (NMDARs) are critically involved in the synaptic plasticity associated with neuropathic pain. However, paclitaxel treatment does not alter the postsynaptic NMDAR activity of spinal dorsal horn neurons. In this study, we determined whether paclitaxel affects presynaptic NMDAR activity by recording excitatory postsynaptic currents (EPSCs) of dorsal horn neurons in spinal cord slices. In paclitaxel-treated rats, the baseline frequency of miniature EPSCs (mEPSCs) was significantly increased; the NMDAR antagonist 2-amino-5-phosphonopentanoic acid (AP5) completely normalized this frequency. Also, AP5 significantly reduced the amplitude of monosynaptic EPSCs evoked by dorsal root stimulation and reversed the reduction in the paired-pulse ratio of evoked EPSCs in paclitaxel-treated rats. Blocking GluN2A-containing, but not GluN2B-containing, NMDARs largely decreased the frequency of mEPSCs and the amplitude of evoked EPSCs of dorsal horn neurons in paclitaxel-treated rats. Furthermore, inhibition of protein kinase C fully reversed the increased frequency of mEPSCs and the amplitude of evoked EPSCs in paclitaxel-treated rats. Paclitaxel treatment significantly increased the protein level of GluN2A and phosphorylated GluN1 in the dorsal root ganglion. In addition, intrathecal injection of AP5 or systemic administration of memantine profoundly attenuated pain hypersensitivity induced by paclitaxel. Our findings indicate that paclitaxel treatment induces tonic activation of presynaptic NMDARs in the spinal cord through protein kinase C to potentiate nociceptive input from primary afferent nerves. Targeting presynaptic NMDARs at the spinal cord level may be an effective strategy for treating chemotherapy-induced neuropathic pain. PMID:27458019

  10. Whole-Cell Patch-Clamp Analysis of Recombinant NMDA Receptor Pharmacology Using Brief Glutamate Applications

    PubMed Central

    Glasgow, Nathan G.; Johnson, Jon W.

    2015-01-01

    Summary NMDA receptors (NMDARs) are ionotropic glutamate receptors that are essential for synaptic plasticity, learning and memory. Dysfunction of NMDARs has been implicated in many nervous system disorders; therefore, pharmacological modulation of NMDAR activity has great therapeutic potential. However, given the broad physiological importance of NMDARs, modulating their activity often has detrimental side effects precluding pharmaceutical use of many NMDAR modulators. One approach to possibly improve the therapeutic potential of NMDAR modulators is to identify compounds that modulate subsets of NMDARs. An obvious target for modulating NMDAR subsets are the many NMDAR subtypes produced through different combinations of NMDAR subunits. With seven identified genes that encode NMDAR subunits, there are many neuronal NMDAR subtypes with distinct properties and potentially differential pharmacological sensitivities. Study of NMDAR subtype-specific pharmacology is complicated in neurons, however, because most neurons express at least three NMDAR subtypes. Thus, use of an approach that permits study in isolation of a single receptor subtype is preferred. Additionally, the effects of drugs on agonist-activated responses typically depend on duration of agonist exposure. To evaluate drug effects on synaptic transmission, an approach should be used that allows activation of receptor responses as brief as those observed during synaptic transmission, both in the absence and presence of drug. To address these issues, we designed a fast perfusion system capable of (1) delivering brief (~5 ms) and consistent applications of glutamate to recombinant NMDARs of known subunit composition, and (2) easily and quickly (~5 seconds) changing between glutamate applications in the absence and presence of drug. PMID:25023300

  11. [Antinociceptive effect of docosahexaenoic acid (DHA) through long fatty acid receptor G protein-coupled receptor 40 (GPR40)].

    PubMed

    Nakamoto, Kazuo; Nishinaka, Takashi; Sato, Naoya; Mankura, Mitsumasa; Koyama, Yutaka; Tokuyama, Shogo

    2014-01-01

    Fatty acids, one class of essential nutrients for humans, are an important source of energy and an essential component of cell membranes. They also function as signal transduction molecules in a variety of biological phenomena. The important functional role of fatty acids in both onset and suppression of pain has become increasingly apparent in recent years. Recently, we have also demonstrated that the release of an endogenous opioid peptide, β-endorphin, plays an important role in the induction of docosahexaenoic acid (DHA)-induced antinociception. It is well known that fatty acids affect intracellular and intercellular signaling as well as the membrane fluidity of neurons. In addition to intracellular actions, unbound free fatty acids (FFAs) can also carry out extracellular signaling by stimulating the G protein-coupled receptor (GPCR). Among these receptors, G protein-coupled receptor 40 (GPR40) has been reported to be activated by long-chain fatty acids such as DHA, eicosapentaenoic acid (EPA) and arachidonic acid. In the peripheral area, GPR40 is preferentially expressed in pancreatic β-cells and is known to relate to the secretion of hormone and peptides. On the other hand, even though this receptor is widely distributed in the central nervous system, reports studying the role and functions of GPR40 in the brain have not been found. In this review, we summarize the findings of our recent study about the long-chain fatty acid receptor GPR40 as a novel pain regulatory system. PMID:24584021

  12. Behavioral Deficits and Subregion-Specific Suppression of LTP in Mice Expressing a Population of Mutant NMDA Receptors throughout the Hippocampus

    ERIC Educational Resources Information Center

    Chen, Philip E.; Errington, Michael L.; Kneussel, Matthias; Chen, Guiquan; Annala, Alexander J.; Rudhard, York H.; Rast, Georg F.; Specht, Christian G.; Tigaret, Cezar M.; Nassar, Mohammed A.; Morris, Richard G.M.; Bliss, Timothy V. P.; Schoepfer, Ralf

    2009-01-01

    The NMDA receptor (NMDAR) subunit GluN1 is an obligatory component of NMDARs without a known functional homolog and is expressed in almost every neuronal cell type. The NMDAR system is a coincidence detector with critical roles in spatial learning and synaptic plasticity. Its coincidence detection property is crucial for the induction of…

  13. Synaptic and extrasynaptic plasticity in glutamatergic circuits involving dentate granule cells following chronic N-methyl-d-aspartate receptor inhibition

    PubMed Central

    He, Shuijin; Shao, Li-Rong; Wang, Yu

    2013-01-01

    Chronic global N-methyl-d-aspartate receptor (NMDAR) blockade leads to changes in glutamatergic transmission. The impact of more subunit-selective NMDAR inhibition on glutamatergic circuits remains incomplete. To this end, organotypic hippocampal slice cultures were treated for 17–21 days with the high-affinity competitive antagonist d-aminophosphonovaleric acid (d-APV), the allosteric GluN2B-selective antagonist Ro25-6981, or the newer competitive GluN2A-preferring antagonist NVP-AAM077. Electrophysiological recordings from dentate granule cells revealed that chronic d-APV treatment increased, whereas chronic Ro25-6981 reduced, epileptiform event-associated large-amplitude spontaneous excitatory postsynaptic currents (sEPSC) compared with all other treatment groups, consistent with opposite effects on glutamatergic networks. Presynaptically, chronic d-APV or Ro25-6981 increased small-amplitude sEPSCs and AMPA/kainate receptor-mediated miniature EPSCs (mEPSCAMPAR) frequency. Chronic d-APV or NVP-AAM077, but not Ro25-6981, increased putative vGlut1-positive glutamatergic synapses. Postsynaptically, chronic d-APV dramatically increased mEPSCAMPAR and profoundly decreased NMDAR-mediated mEPSC (mEPSCNMDAR) measures, suggesting increased AMPAR/NMDAR ratio. Ro25-6981 decreased mEPSCAMPAR charge transfer and modestly decreased mEPSCNMDAR frequency and decay, suggesting downward scaling of AMPAR and NMDAR function without dramatically altering AMPAR/NMDAR ratio. Extrasynaptically, threo-β-benzyloxyaspartate-enhanced “tonic” NMDAR current amplitude and activated channel number estimates were significantly increased only by chronic Ro25-6981. For intrinsic excitability, action potential threshold was slightly more negative following chronic d-APV or NVP-AAM077. The predominant pro-excitatory effects of chronic d-APV are consistent with increased glutamatergic transmission and network excitability. The minor effects of chronic NVP-AAM077 on action potential threshold

  14. Recognition of Legionella pneumophila nucleic acids by innate immune receptors.

    PubMed

    Cunha, Larissa D; Zamboni, Dario S

    2014-12-01

    Innate immune receptors evolved to sense conserved molecules that are present in microbes or are released during non-physiological conditions. Activation of these receptors is essential for early restriction of microbial infections and generation of adaptive immunity. Among the conserved molecules sensed by innate immune receptors are the nucleic acids, which are abundantly contained in all infectious organisms including virus, bacteria, fungi and parasites. In this review we focus in the innate immune proteins that function to sense nucleic acids from the intracellular bacterial pathogen Legionella pneumophila and the importance of these processes to the outcome of the infection.

  15. Receptor-level interrelationships of amino acids and the adequate amino acid type hormones in Tetrahymena: a receptor evolution model.

    PubMed

    Csaba, G; Darvas, Z

    1986-01-01

    Histidine stimulates the phagocytosis of Tetrahymena to the same extent as histamine, and also stimulates its division, which histamine does not. Tyrosine and diiodotyrosine equally stimulate the growth of the Tetrahymena. Both amino acids inhibit the characteristic influence of the adequate amino acid hormone when added to Tetrahymena culture 72 h in advance of it. Primary interaction with diiodotyrosine and tyrosine notably increases the cellular growth rate. Histamine has a similar, although less notable effect than histidine. In the light of these experimental observations there is reason to postulate that the receptors of the amino acid hormones have developed from amino acid receptors.

  16. Endogenous ion channel complexes: the NMDA receptor.

    PubMed

    Frank, René A W

    2011-06-01

    Ionotropic receptors, including the NMDAR (N-methyl-D-aspartate receptor) mediate fast neurotransmission, neurodevelopment, neuronal excitability and learning. In the present article, the structure and function of the NMDAR is reviewed with the aim to condense our current understanding and highlight frontiers where important questions regarding the biology of this receptor remain unanswered. In the second part of the present review, new biochemical and genetic approaches for the investigation of ion channel receptor complexes will be discussed.

  17. NMDA-R inhibition affects cellular process formation in Tilapia melanocytes; a model for pigmented adrenergic neurons in process formation and retraction.

    PubMed

    Ogundele, Olalekan Michael; Okunnuga, Adetokunbo Adedotun; Fabiyi, Temitope Deborah; Olajide, Olayemi Joseph; Akinrinade, Ibukun Dorcas; Adeniyi, Philip Adeyemi; Ojo, Abiodun Ayodele

    2014-06-01

    Parkinson's disease has long been described to be a product of dopamine and (or) melanin loss in the substanstia nigra (SN). Although most studies have focused on dopaminergic neurons, it is important to consider the role of pigment cells in the etiology of the disease and to create an in vitro live cell model for studies involving pigmented adrenergic cells of the SN in Parkinsonism. The Melanocytes share specific features with the pigmented adrenergic neurons as both cells are pigmented, contain adrenergic receptors and have cellular processes. Although the melanocyte cellular processes are relatively short and observable only when stimulated appropriately by epinephrine and other factors or molecules. This study employs the manipulation of N-Methyl-D-Aspartate Receptor (NMDA-R), a major receptor in neuronal development, in the process formation pattern of the melanocyte in order to create a suitable model to depict cellular process elongation and shortening in pigmented adrenergic cells. NMDA-R is an important glutamate receptor implicated in neurogenesis, neuronal migration, maturation and cell death, thus we investigated the role of NMDA-R potentiation by glutamate/KCN and its inhibition by ketamine in the behavior of fish scale melanocytes in vitro. This is aimed at establishing the regulatory role of NMDA-R in this cell type (melanocytes isolated form Tilapia) in a similar manner to what is observable in the mammalian neurons. In vitro live cell culture was prepared in modified Ringer's solution following which the cells were treated as follows; Control, Glutamate, Ketamine, Glutamate + Ketamine, KCN + Ketamine and KCN. The culture was maintained for 10 min and the changes were captured in 3D-Time frame at 0, 5 and 10 min for the control and 5, 7 and 10 min for each of the treatment category. Glutamate treatment caused formation of short cellular processes localized directly on the cell body while ketamine treatment (inhibition of NMDA-R) facilitated

  18. A structural biology perspective on NMDA receptor pharmacology and function.

    PubMed

    Regan, Michael C; Romero-Hernandez, Annabel; Furukawa, Hiro

    2015-08-01

    N-methyld-aspartate receptors (NMDARs) belong to the large family of ionotropic glutamate receptors (iGluRs), which are critically involved in basic brain functions as well as multiple neurological diseases and disorders. The NMDARs are large heterotetrameric membrane protein complexes. The extensive extracellular domains recognize neurotransmitter ligands and allosteric compounds and translate the binding information to regulate activity of the transmembrane ion channel. Here, we review recent advances in the structural biology of NMDARs with a focus on pharmacology and function. Structural analysis of the isolated extracellular domains in combination with the intact heterotetrameric NMDAR structure provides important insights into how this sophisticated ligand-gated ion channel may function.

  19. Modulation of low-frequency-induced synaptic depression in the developing CA3-CA1 hippocampal synapses by NMDA and metabotropic glutamate receptor activation.

    PubMed

    Strandberg, Joakim; Wasling, Pontus; Gustafsson, Bengt

    2009-05-01

    Brief test-pulse stimulation (0.2-0.05 Hz) of naïve (previously nonstimulated) developing hippocampal CA3-CA1 synapses leads to a substantial synaptic depression, explained by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) silencing. Using field recordings in hippocampal slices from P8 to P12 rats, we examined this depression of naïve synapses using more prolonged test-pulse stimulation as well as low-frequency (1 Hz) stimulation (LFS). We found that 900 stimuli produced depression during stimulation to approximately 40% of the naïve level independent of whether test-pulse stimulation or LFS was used. This result was also observed during combined blockade of N-methyl-d-aspartate/metabotropic glutamate receptors (NMDAR/mGluRs) although the depression was smaller (to approximately 55% of naïve level). Using separate blockade of either NMDARs or mGluRs, we found that this impairment of the depression resulted from the NMDAR, and not from the mGluR, blockade. In fact, during NMDAR blockade alone, depression was smaller even than that observed during combined blockade. We also found that mGluR blockade alone facilitated the LFS-induced depression. In conclusion, test-pulse stimulation produced as much depression as LFS when applied to naïve synapses even when allowing for NMDAR and mGluR activation. Our results seem in line with the notion that NMDARs and mGluRs may exert a bidirectional control on AMPA receptor recruitment to synapses.

  20. Altered mRNA editing and expression of ionotropic glutamate receptors after kainic acid exposure in cyclooxygenase-2 deficient mice.

    PubMed

    Caracciolo, Luca; Barbon, Alessandro; Palumbo, Sara; Mora, Cristina; Toscano, Christopher D; Bosetti, Francesca; Barlati, Sergio

    2011-01-01

    Kainic acid (KA) binds to the AMPA/KA receptors and induces seizures that result in inflammation, oxidative damage and neuronal death. We previously showed that cyclooxygenase-2 deficient (COX-2(-/-)) mice are more vulnerable to KA-induced excitotoxicity. Here, we investigated whether the increased susceptibility of COX-2(-/-) mice to KA is associated with altered mRNA expression and editing of glutamate receptors. The expression of AMPA GluR2, GluR3 and KA GluR6 was increased in vehicle-injected COX-2(-/-) mice compared to wild type (WT) mice in hippocampus and cortex, whereas gene expression of NMDA receptors was decreased. KA treatment decreased the expression of AMPA, KA and NMDA receptors in the hippocampus, with a significant effect in COX-2(-/-) mice. Furthermore, we analyzed RNA editing levels and found that the level of GluR3 R/G editing site was selectively increased in the hippocampus and decreased in the cortex in COX-2(-/-) compared with WT mice. After KA, GluR4 R/G editing site, flip form, was increased in the hippocampus of COX-2(-/-) mice. Treatment of WT mice with the COX-2 inhibitor celecoxib for two weeks decreased the expression of AMPA/KA and NMDAR subunits after KA, as observed in COX-2(-/-) mice. After KA exposure, COX-2(-/-) mice showed increased mRNA expression of markers of inflammation and oxidative stress, such as cytokines (TNF-α, IL-1β and IL-6), inducible nitric oxide synthase (iNOS), microglia (CD11b) and astrocyte (GFAP). Thus, COX-2 gene deletion can exacerbate the inflammatory response to KA. We suggest that COX-2 plays a role in attenuating glutamate excitotoxicity by modulating RNA editing of AMPA/KA and mRNA expression of all ionotropic glutamate receptor subunits and, in turn, neuronal excitability. These changes may contribute to the increased vulnerability of COX-2(-/-) mice to KA. The overstimulation of glutamate receptors as a consequence of COX-2 gene deletion suggests a functional coupling between COX-2 and the

  1. Novel human D-amino acid oxidase inhibitors stabilize an active-site lid-open conformation

    PubMed Central

    Terry-Lorenzo, Ryan T.; Chun, Lawrence E.; Brown, Scott P.; Heffernan, Michele L. R.; Fang, Q. Kevin; Orsini, Michael A.; Pollegioni, Loredano; Hardy, Larry W.; Spear, Kerry L.; Large, Thomas H.

    2014-01-01

    The NMDAR (N-methyl-D-aspartate receptor) is a central regulator of synaptic plasticity and learning and memory. hDAAO (human D-amino acid oxidase) indirectly reduces NMDAR activity by degrading the NMDAR co-agonist D-serine. Since NMDAR hypofunction is thought to be a foundational defect in schizophrenia, hDAAO inhibitors have potential as treatments for schizophrenia and other nervous system disorders. Here, we sought to identify novel chemicals that inhibit hDAAO activity. We used computational tools to design a focused, purchasable library of compounds. After screening this library for hDAAO inhibition, we identified the structurally novel compound, ‘compound 2’ [3-(7-hydroxy-2-oxo-4-phenyl-2H-chromen-6-yl)propanoic acid], which displayed low nM hDAAO inhibitory potency (Ki=7 nM). Although the library was expected to enrich for compounds that were competitive for both D-serine and FAD, compound 2 actually was FAD uncompetitive, much like canonical hDAAO inhibitors such as benzoic acid. Compound 2 and an analog were independently co-crystalized with hDAAO. These compounds stabilized a novel conformation of hDAAO in which the active-site lid was in an open position. These results confirm previous hypotheses regarding active-site lid flexibility of mammalian D-amino acid oxidases and could assist in the design of the next generation of hDAAO inhibitors. PMID:25001371

  2. Quantification of the Mg2+-induced potency shift of amantadine and memantine voltage-dependent block in human recombinant GluN1/GluN2A NMDARs.

    PubMed

    Otton, H J; Lawson McLean, A; Pannozzo, M A; Davies, C H; Wyllie, D J A

    2011-01-01

    Clinically, amantadine and memantine are drugs whose therapeutic utility is linked to their ability to block N-methyl-D-aspartate receptors (NMDARs) in a voltage-dependent manner. Nevertheless many studies that have characterized the pharmacological actions of amantadine and memantine have done so in the absence of physiological levels of Mg(2+) ions. This study quantifies the extent to which Mg(2+) alters the potency of the block produced by both amantadine and memantine at human recombinant GluN1/GluN2A NMDARs. Human recombinant GluN1/GluN2A NMDARs were expressed in Xenopus laevis oocytes and two-electrode voltage-clamp recordings were made at -80, -60 and -40 mV to quantify amantadine and memantine block in the absence and presence of Mg(2+). Amantadine and memantine blocked human GluN1/GluN2A NMDARs in a voltage-dependent manner with IC(50) values (at -80 mV) of 49 ± 6 μM (n = 7) and 1.0 ± 0.3 μM (n = 7), respectively. In the presence of Mg(2+) (1mM) the equivalent IC(50) values were 165 ± 10 μM (n=6) and 6.6 ± 0.3 μM (n = 5). Similarly in the presence of amantadine or memantine the potency of Mg(2+) in blocking GluN1/GluN2A NMDARs was reduced. The decrease in the potencies of both amantadine and memantine in the presence of physiological concentrations of Mg(2+) indicates that other targets (e.g. α7-nicotinic acetylcholine receptors and 5-HT(3) receptors) in addition to NMDARs may well be sites of the therapeutic action of these channel blockers.

  3. Activation of γ-aminobutyric Acid (A) Receptor Protects Hippocampus from Intense Exercise-induced Synapses Damage and Apoptosis in Rats

    PubMed Central

    Ding, Yi; Xie, Lan; Chang, Cun-Qing; Chen, Zhi-Min; Ai, Hua

    2015-01-01

    Background: Our previous study has confirmed that one bout of exhaustion (Ex) can cause hippocampus neurocyte damage, excessive apoptosis, and dysfunction. Its initial reason is intracellular calcium overload in hippocampus triggered by N-methyl-D-aspartic acid receptor (NMDAR) over-activation. NMDAR activation can be suppressed by γ-aminobutyric acid (A) receptor (GABAAR). Whether GABAAR can prevent intense exercise-induced hippocampus apoptosis, damage, or dysfunction will be studied in this study. Methods: According to dose test, rats were randomly divided into control (Con), Ex, muscimol (MUS, 0.1 mg/kg) and bicuculline (BIC, 0.5 mg/kg) groups, then all rats underwent once swimming Ex except ones in Con group only underwent training. Intracellular free calcium concentration ([Ca2+]i) was measured by Fura-2-acetoxymethyl ester; glial fibrillary acidic protein (GFAP) and synaptophysin (SYP) immunofluorescence were also performed; apoptosis were displayed by dUTP nick end labeling (TUNEL) stain; endoplasmic reticulum stress-induced apoptosis pathway was detected by Western blotting analysis; Morris water maze was used to detect learning ability and spatial memory. Results: The appropriate dose was 0.1 mg/kg for MUS and 0.5 mg/kg for BIC. Ex group showed significantly increased [Ca2+]i and astrogliosis; TUNEL positive cells and levels of GFAP, B cell lymphoma-2 (Bcl-2) associated X protein (Bax), caspase-3, caspase-12 cleavage, CCAAT/enhancer binding protein homologous protein (CHOP), and p-Jun amino-terminal kinase (p-JNK) in Ex group also raised significantly compared to Con group, while SYP, synapse plasticity, and Bcl-2 levels in Ex group were significantly lower than those in Con group. These indexes were back to normal in MUS group. BIC group had the highest levels of [Ca2+]i, astrogliosis, TUNEL positive cell, GFAP, Bax, caspase-3, caspase-12 cleavage, CHOP, and p-JNK, it also gained the lowest SYP, synapse plasticity, and Bcl-2 levels among all groups

  4. A thermodynamic switch modulates abscisic acid receptor sensitivity

    PubMed Central

    Dupeux, Florine; Santiago, Julia; Betz, Katja; Twycross, Jamie; Park, Sang-Youl; Rodriguez, Lesia; Gonzalez-Guzman, Miguel; Jensen, Malene Ringkjøbing; Krasnogor, Natalio; Blackledge, Martin; Holdsworth, Michael; Cutler, Sean R; Rodriguez, Pedro L; Márquez, José Antonio

    2011-01-01

    Abscisic acid (ABA) is a key hormone regulating plant growth, development and the response to biotic and abiotic stress. ABA binding to pyrabactin resistance (PYR)/PYR1-like (PYL)/Regulatory Component of Abscisic acid Receptor (RCAR) intracellular receptors promotes the formation of stable complexes with certain protein phosphatases type 2C (PP2Cs), leading to the activation of ABA signalling. The PYR/PYL/RCAR family contains 14 genes in Arabidopsis and is currently the largest plant hormone receptor family known; however, it is unclear what functional differentiation exists among receptors. Here, we identify two distinct classes of receptors, dimeric and monomeric, with different intrinsic affinities for ABA and whose differential properties are determined by the oligomeric state of their apo forms. Moreover, we find a residue in PYR1, H60, that is variable between family members and plays a key role in determining oligomeric state. In silico modelling of the ABA activation pathway reveals that monomeric receptors have a competitive advantage for binding to ABA and PP2Cs. This work illustrates how receptor oligomerization can modulate hormonal responses and more generally, the sensitivity of a ligand-dependent signalling system. PMID:21847091

  5. State-dependent changes in astrocyte regulation of extrasynaptic NMDA receptor signalling in neurosecretory neurons.

    PubMed

    Fleming, Tiffany M; Scott, Victoria; Naskar, Krishna; Joe, Natalie; Brown, Colin H; Stern, Javier E

    2011-08-15

    Despite the long-established presence of glutamate NMDA receptors at extrasynaptic sites (eNMDARs), their functional roles remain poorly understood. Factors influencing the concentration and time course of glutamate in the extrasynaptic space, such as the topography of the neuronal–glial microenvironment, as well as glial glutamate transporters, are expected to affect eNMDAR-mediated signalling strength. In this study, we used in vitro and in vivo electrophysiological recordings to assess the properties, functional relevance and modulation of a persistent excitatory current mediated by activation of eNMDARs in hypothalamic supraoptic nucleus (SON) neurons. We found that ambient glutamate of a non-synaptic origin activates eNMDARs to mediate a persistent excitatory current (termed tonic I(NMDA)), which tonically stimulates neuronal activity. Pharmacological blockade of GLT1 astrocyte glutamate transporters, as well as the gliotoxin α-aminodadipic acid, enhanced tonic I(NMDA) and neuronal activity, supporting an astrocyte regulation of tonic I(NMDA) strength. Dehydration, a physiological challenge known to increase SON firing activity and to induce neuroglial remodelling, including reduced neuronal ensheathment by astrocyte processes, resulted in blunted GLT1 efficacy, enhanced tonic I(NMDA) strength, and increased neuronal activity. Taken together, our studies support the view that glial modulation of tonic I(NMDA) activation contributes to regulation of SON neuronal activity, contributing in turn to neuronal homeostatic responses during a physiological challenge. PMID:21690192

  6. Bile acid receptors and nonalcoholic fatty liver disease

    PubMed Central

    Yuan, Liyun; Bambha, Kiran

    2015-01-01

    With the high prevalence of obesity, diabetes, and other features of the metabolic syndrome in United States, nonalcoholic fatty liver disease (NAFLD) has inevitably become a very prevalent chronic liver disease and is now emerging as one of the leading indications for liver transplantation. Insulin resistance and derangement of lipid metabolism, accompanied by activation of the pro-inflammatory response and fibrogenesis, are essential pathways in the development of the more clinically significant form of NAFLD, known as nonalcoholic steatohepatitis (NASH). Recent advances in the functional characterization of bile acid receptors, such as farnesoid X receptor (FXR) and transmembrane G protein-coupled receptor (TGR) 5, have provided further insight in the pathophysiology of NASH and have led to the development of potential therapeutic targets for NAFLD and NASH. Beyond maintaining bile acid metabolism, FXR and TGR5 also regulate lipid metabolism, maintain glucose homeostasis, increase energy expenditure, and ameliorate hepatic inflammation. These intriguing features have been exploited to develop bile acid analogues to target pathways in NAFLD and NASH pathogenesis. This review provides a brief overview of the pathogenesis of NAFLD and NASH, and then delves into the biological functions of bile acid receptors, particularly with respect to NASH pathogenesis, with a description of the associated experimental data, and, finally, we discuss the prospects of bile acid analogues in the treatment of NAFLD and NASH. PMID:26668692

  7. Effect of N-methyl-D-aspartic acid on activity of superoxide dismutase, catalase, glutathione peroxidase and reduced glutathione level in selected organs of the mouse.

    PubMed

    Szaroma, Waldemar; Dziubek, K; Kapusta, E

    2014-09-01

    One of the major classes of ionotropic glutamate receptors is the class of N-methyl-D-aspartate receptors (NMDARs). Receptor activation recruits, via calcium signal transduction mechanisms which play important roles in oxidative metabolism, mitochondrial free radical production and occurrence of other mitochondrial factors which potentially contribute to excitotoxicity and neuronal death. In the present study, the effects of stimulation of NMDARs by applying N-methyl-D-aspartic acid (NMDA) in the brain, liver, kidneys and pancreas on change of the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSHPx) and in the amount of reduced glutathione (GSH) in blood, brain, liver and kidneys has been investigated. Statistically significant decrease of the activity of SOD, CAT and GSHPx and in the amount of reduced glutathione (GSH) was found in the examined organs after administration of NMDA, an agonist of NMDA receptors, demonstrating that NMDA administration compromises the antioxidant status in the investigated organs of the mouse.

  8. Characterization of the hydroxycarboxylic acid receptor 2 in cats.

    PubMed

    Graff, E C; Norris, O C; Sandey, M; Kemppainen, R J; Judd, R L

    2015-10-01

    The hydroxycarboxylic acid receptor 2 (HCA2) belongs to a family of nutrient-sensing receptors that bind β-hydroxybutyrate, an alternative fuel source produced during a negative energy balance. The HCA2 receptor has not been identified or characterized in cats. Therefore, the following were the objectives of this study: (1) identify the feline HCA2 receptor protein sequence and compare against known human and rodent sequences, (2) determine tissue distribution and relative expression in lean, healthy cats, and (3) demonstrate in vitro functionality in feline adipose tissue. Tissues (n = 6) and primary adipocytes (n = 4) were collected from lean, healthy, female cats. The published genomic sequence for cats was used to design primers for polymerase chain reaction isolation of HCA2. Relative tissue distribution was evaluated using reverse transcriptase-polymerase chain reaction with RNA isolated from 9 different tissues (spleen, pancreas, lymph node, jejunum, kidney, liver, heart, and subcutaneous and abdominal adipose tissue). Receptor function was evaluated in primary feline adipocyte culture, and changes were compared with basal lipolysis. The in silico predicted feline HCA2 protein sequence exhibited 83.1% and 86.5% amino acid similarity to human and mouse sequences, respectively. The feline HCA2 receptor is predominantly expressed in adipose tissue and spleen. Exposure of feline adipocytes to niacin, a pharmacologic ligand of HCA2, inhibited lipolysis to a similar degree as insulin, a potent lipolytic inhibitor. In conclusion, the feline HCA2 receptor is similar to human and murine receptors in sequence, distribution, and functionality. By gaining a better understanding of the HCA2 receptor in cats, we will be able to better manage feline patients.

  9. Carbobenzoxy amino acids: Structural requirements for cholecystokinin receptor antagonist activity

    SciTech Connect

    Maton, P.N.; Sutliff, V.E.; Jensen, R.T.; Gardner, J.D.

    1985-04-01

    The authors used dispersed acini prepared from guinea pig pancreas to examine 28 carbobenzoxy (CBZ) amino acids for their abilities to function as cholecystokinin receptor antagonists. All amino acid derivatives tested, except for CBZ-alanine, CBZ-glycine, and N alpha-CBZ- lysine, were able to inhibit the stimulation of amylase secretion caused by the C-terminal octapeptide of cholecystokinin. In general, there was a good correlation between the ability of a carbobenzoxy amino acid to inhibit stimulated amylase secretion and the ability of the amino acid derivative to inhibit binding of /sup 125/I-cholecystokinin. The inhibition of cholecystokinin-stimulated amylase secretion was competitive, fully reversible, and specific for those secretagogues that interact with the cholecystokinin receptor. The potencies with which the various carbobenzoxy amino acids inhibited the action of cholecystokinin varied 100-fold and CBZ-cystine was the most potent cholecystokinin receptor antagonist. This variation in potency was primarily but not exclusively a function of the hydrophobicity of the amino acid side chain.

  10. High affinity retinoic acid receptor antagonists: analogs of AGN 193109.

    PubMed

    Johnson, A T; Wang, L; Gillett, S J; Chandraratna, R A

    1999-02-22

    A series of high affinity retinoic acid receptor (RAR) antagonists were prepared based upon the known antagonist AGN 193109 (2). Introduction of various phenyl groups revealed a preference for substitution at the para-position relative to the meta-site. Antagonists with the highest affinities for the RARs possessed hydrophobic groups, however, the presence of polar functionality was also well tolerated.

  11. In vivo activation of the SK channel in the spinal cord reduces the NMDA receptor antagonist dose needed to produce antinociception in an inflammatory pain model.

    PubMed

    Hipólito, Lucia; Fakira, Amanda K; Cabañero, David; Blandón, Rebecca; Carlton, Susan M; Morón, Jose A; Melyan, Zara

    2015-05-01

    N-methyl-D-aspartate receptor (NMDAR) antagonists have been shown to reduce mechanical hypersensitivity in animal models of inflammatory pain. However, their clinical use is associated with significant dose-limiting side effects. Small-conductance Ca-activated K channels (SK) have been shown to modulate NMDAR activity in the brain. We demonstrate that in vivo activation of SK channels in the spinal cord can alleviate mechanical hypersensitivity in a rat model of inflammatory pain. Intrathecal (i.t.) administration of the SK channel activator, 6,7-dichloro-1H-indole-2,3-dione 3-oxime (NS309), attenuates complete Freund adjuvant (CFA)-induced mechanical hypersensitivity in a dose-dependent manner. Postsynaptic expression of the SK channel subunit, SK3, and apamin-sensitive SK channel-mediated currents recorded from superficial laminae are significantly reduced in the dorsal horn (DH) after CFA. Complete Freund adjuvant-induced decrease in SK-mediated currents can be reversed in vitro by bath application of NS309. In addition, immunostaining for the SK3 subunit indicates that SK3-containing channels within DH neurons can have both somatic and dendritic localization. Double immunostaining shows coexpression of SK3 and NMDAR subunit, NR1, compatible with functional interaction. Moreover, we demonstrate that i.t. coadministration of NS309 with an NMDAR antagonist reduces the dose of NMDAR antagonist, DL-2-amino-5-phosphonopentanoic acid (DL-AP5), required to produce antinociceptive effects in the CFA model. This reduction could attenuate the unwanted side effects associated with NMDAR antagonists, giving this combination potential clinical implications.

  12. Retinoic Acid-mediated Nuclear Receptor Activation and Hepatocyte Proliferation

    PubMed Central

    Bushue, Nathan; Wan, Yu-Jui Yvonne

    2016-01-01

    Due to their well-known differentiation and apoptosis-inducing abilities, retinoic acid (RA) and its analogs have strong anti-cancer efficacy in human cancers. However, in vivo RA is a liver mitogen. While speculation has persisted that RA-mediated signaling is likely involved in hepatocyte proliferation during liver regeneration, direct evidence is still required. Findings in support of this proposition include observations that a release of retinyl palmitate (the precursor of RA) occurs in liver stellate cells following liver injury. Nevertheless, the biological action of this released vitamin A is virtually unknown. More likely is that the released vitamin A is converted to RA, the biological form, and then bound to a specific receptor (retinoid x receptor; RXRα), which is most abundantly expressed in the liver. Considering the mitogenic effects of RA, the RA-activated RXRα would likely then influence hepatocyte proliferation and liver tissue repair. At present, the mechanism by which RA stimulates hepatocyte proliferation is largely unknown. This review summarizes the activation of nuclear receptors (peroxisome proliferator activated receptor-α, pregnane x receptor, constitutive androstane receptor, and farnesoid x receptor) in an RXRα dependent manner to induce hepatocyte proliferation, providing a link between RA and its proliferative role.

  13. Effects of Subchronic Treatment with Ibuprofen and Nimesulide on Spatial Memory and NMDAR Subunits Expression in Aged Rats.

    PubMed

    Ozturk Bilgin, Ozlem; Kumbul Doguc, Duygu; Altuntas, Irfan; Sutcu, Recep; Delibas, Namık

    2013-01-01

    Several studies point to an important function of cyclooxygenase (COX) and prostaglandin signaling in models of synaptic plasticity which is associated with N-methyl-D-aspartate receptors (NMDARs). Cyclooxygenase gene is suggested to be an immediate early gene that is tightly regulated in neurons by NMDA dependent synaptic activity. Nonsteroid Antiinflammatory Drugs (NSAIDs) exert their antiinflammatory effect by the inhibion of COX have controversial effects on learning and memory. We administered ibuprofen as a non-selective COX-2 inhibitor and nimesulide as a selective COX-2 inhibitor for 8 weeks for determining the cognitive impact of subchronic administration of NSAIDs to aged rats. Wistar albino rats (16 mo, n = 30) were separated into control (n = 10), ibuprofen (n = 10) and nimesulide (n = 10) treated groups. First we evaluated hippocampus-dependent spatial memory in the radial arm maze (RAM) and than we evaluated the expression of the NMDAR subunits, NR2A and NR2B by western blotting to see if their expressions are effected by subchronic administration with these drugs. Ibuprofen and nimesulide treated rats completed the task in a statistically significant shorter time when compared with control group (p < 0.01), but there was no statistically significant difference between groups about choice accuracy data in RAM. Furthermore, no statistically significant difference was detected for the protein expressions of NR2A and NR2B of the subjects. Oral administration of ibuprofen and nimesulide for 8 weeks showed no impairment but partly improved spatial memory. PMID:24523767

  14. Rapid recovery from catastrophic paraneoplastic anti-NMDAR encephalitis secondary to an ovarian teratoma following ovarian cystectomy.

    PubMed

    Tantipalakorn, Charuwan; Soontornpun, Atiwat; Pongsuvareeyakul, Tip; Tongsong, Theera

    2016-01-01

    This report is aimed to describe a life-threatening case of anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis secondary to ovarian teratoma with rapid recovery in 1 day after the removal of the tumour. A 23-year-old woman presented with sudden headache, personality changes and seizure. After neurological assessment, limbic or herpes encephalitis was provisionally diagnosed and treated with intravenous immunoglobulin, acyclovir and steroids. The patient had progressive severe neurological symptoms, requiring prolonged intubation and mechanical ventilation. An anti-NMDAR antibody test revealed positive in serum and cerebrospinal fluid at 3 weeks of admission. Pelvic ultrasound examination and CT scan revealed bilateral small ovarian teratomas. Bilateral ovarian cystectomy was performed by open surgery. The patient showed rapid improvement and no longer needed intubation 2 days after the operation. In conclusion, we described a catastrophic case of ovarian teratoma-associated encephalitis with delayed diagnosis but rapid recovery after ovarian cystectomy. This information can probably be helpful to neurologists and gynaecologists. PMID:27511754

  15. Frequent rhabdomyolysis in anti-NMDA receptor encephalitis.

    PubMed

    Lim, Jung-Ah; Lee, Soon-Tae; Kim, Tae-Joon; Moon, Jangsup; Sunwoo, Jun-Sang; Byun, Jung-Ick; Jung, Keun-Hwa; Jung, Ki-Young; Chu, Kon; Lee, Sang Kun

    2016-09-15

    The aim of this study was to analyze the clinical presentation and provocation factors of rhabdomyolysis in anti-NMDAR encephalitis. Among the 16 patients with anti-NMDAR encephalitis in our institutional cohort, nine patients had elevated CK enzyme levels and clinical evidence of rhabdomyolysis. Rhabdomyolysis was more frequent after immunotherapy. The use of dopamine receptor blocker (DRB) increased the risk of rhabdomyolysis. None of the patients without rhabdomyolysis received DRBs. Rhabdomyolysis is a frequent complication in anti-NMDAR encephalitis and more common after immunotherapy and the use of DRBs increases the risk. Therefore, DRBs should be administered carefully in patients with anti-NMDAR encephalitis. PMID:27609293

  16. Bile acid nuclear receptor FXR and digestive system diseases

    PubMed Central

    Ding, Lili; Yang, Li; Wang, Zhengtao; Huang, Wendong

    2015-01-01

    Bile acids (BAs) are not only digestive surfactants but also important cell signaling molecules, which stimulate several signaling pathways to regulate some important biological processes. The bile-acid-activated nuclear receptor, farnesoid X receptor (FXR), plays a pivotal role in regulating bile acid, lipid and glucose homeostasis as well as in regulating the inflammatory responses, barrier function and prevention of bacterial translocation in the intestinal tract. As expected, FXR is involved in the pathophysiology of a wide range of diseases of gastrointestinal tract, including inflammatory bowel disease, colorectal cancer and type 2 diabetes. In this review, we discuss current knowledge of the roles of FXR in physiology of the digestive system and the related diseases. Better understanding of the roles of FXR in digestive system will accelerate the development of FXR ligands/modulators for the treatment of digestive system diseases. PMID:26579439

  17. Bile acid nuclear receptor FXR and digestive system diseases.

    PubMed

    Ding, Lili; Yang, Li; Wang, Zhengtao; Huang, Wendong

    2015-03-01

    Bile acids (BAs) are not only digestive surfactants but also important cell signaling molecules, which stimulate several signaling pathways to regulate some important biological processes. The bile-acid-activated nuclear receptor, farnesoid X receptor (FXR), plays a pivotal role in regulating bile acid, lipid and glucose homeostasis as well as in regulating the inflammatory responses, barrier function and prevention of bacterial translocation in the intestinal tract. As expected, FXR is involved in the pathophysiology of a wide range of diseases of gastrointestinal tract, including inflammatory bowel disease, colorectal cancer and type 2 diabetes. In this review, we discuss current knowledge of the roles of FXR in physiology of the digestive system and the related diseases. Better understanding of the roles of FXR in digestive system will accelerate the development of FXR ligands/modulators for the treatment of digestive system diseases. PMID:26579439

  18. Anti-NMDA Receptor Encephalitis Antibody Binding Is Dependent on Amino Acid Identity of a Small Region Within the GluN1 Amino Terminal Domain

    PubMed Central

    Gleichman, Amy J.; Spruce, Lynn A.; Dalmau, Josep; Seeholzer, Steven H.; Lynch, David R.

    2012-01-01

    Anti-NMDA receptor (NMDAR) encephalitis is a newly identified autoimmune disorder that targets NMDARs, causing severe neurological symptoms including hallucinations, psychosis, and seizures, and may result in death (Dalmau et al., 2008). However, the exact epitope to which these antibodies bind is unknown. A clearly defined antigenic region could provide more precise testing, allow for comparison of immunogenicity between patients to explore potential clinically relevant variations, elucidate the functional effects of antibodies, and make patients’ antibodies a more effective tool with which to study NMDAR function. Here, we use human cerebrospinal fluid to explore the antigenic region of the NMDAR. We created a series of mutants within the amino terminal domain of GluN1 that change patient antibody binding in transfected cells in stereotyped ways. These mutants demonstrate that the N368/G369 region of GluN1 is crucial for the creation of immunoreactivity. Mass spectrometry experiments show that N368 is glycosylated in transfected cells and rat brain regions; however, this glycosylation is not directly required for epitope formation. Mutations of residues N368/G369 change the closed time of the receptor in single channel recordings; more frequent channel openings correlates with the degree of antibody staining, and acute antibody exposure prolongs open time of the receptor. The staining pattern of mutant receptors is similar across subgroups of patients, indicating consistent immunogenicity, although we have identified one region that has a variable role in epitope formation. These findings provide tools for detailed comparison of antibodies across patients and suggest an interaction between antibody binding and channel function. PMID:22875940

  19. Ligand regulation of retinoic acid receptor-related orphan receptors: implications for development of novel therapeutics

    PubMed Central

    Solt, Laura A.; Griffin, Patrick R.; Burris, Thomas P.

    2016-01-01

    Purpose of review In the late 1980s, the cloning of several nuclear receptors led to the intense search and isolation of new members of this superfamily. Despite their identification, many of these receptors were dubbed ‘orphan’ receptors, as their physiological ligands remained unknown. Recent reports have presented evidence for one family of orphan receptors, the retinoic acid receptor-related orphan receptors (RORs), in several pathologies, including osteoporosis, several autoimmune diseases, asthma, cancer, diabetes and obesity. The present review summarizes the studies identifying ligands for the RORs and evaluates their role as targets for potential therapeutics. Recent findings Significant progress was made in the initial identification of ligands for the RORs when X-ray crystallographic studies identified several molecules within the ligand-binding pockets of RORα and RORβ. Recently, we identified endogenous and synthetic ligands for RORα and RORγ, thereby solidifying their function as ligand-dependent transcription factors. Summary Recent studies have established roles for the RORs in physiological development and the advent of disease. Identification of ligands for the RORs, both endogenous and synthetic, has established these receptors as attractive new therapeutic targets for the treatment of ROR-related diseases. PMID:20463469

  20. Allosteric regulation in NMDA receptors revealed by the genetically encoded photo-cross-linkers

    PubMed Central

    Tian, Meilin; Ye, Shixin

    2016-01-01

    Allostery is essential to neuronal receptor function, but its transient nature poses a challenge for characterization. The N-terminal domains (NTDs) distinct from ligand binding domains are a major locus for allosteric regulation of NMDA receptors (NMDARs), where different modulatory binding sites have been observed. The inhibitor ifenprodil, and related phenylethanoamine compounds specifically targeting GluN1/GluN2B NMDARs have neuroprotective activity. However, whether they use differential structural pathways than the endogenous inhibitor Zn2+ for regulation is unknown. We applied genetically encoded unnatural amino acids (Uaas) and monitored the functional changes in living cells with photo-cross-linkers specifically incorporated at the ifenprodil binding interface between GluN1 and GluN2B subunits. We report constraining the NTD domain movement, by a light induced crosslinking bond that introduces minimal perturbation to the ligand binding, specifically impedes the transduction of ifenprodil but not Zn2+ inhibition. Subtle distance changes reveal interfacial flexibility and NTD rearrangements in the presence of modulators. Our results present a much richer dynamic picture of allostery than conventional approaches targeting the same interface, and highlight key residues that determine functional and subtype specificity of NMDARs. The light-sensitive mutant neuronal receptors provide complementary tools to the photo-switchable ligands for opto-neuropharmacology. PMID:27713495

  1. Seizure control by decanoic acid through direct AMPA receptor inhibition.

    PubMed

    Chang, Pishan; Augustin, Katrin; Boddum, Kim; Williams, Sophie; Sun, Min; Terschak, John A; Hardege, Jörg D; Chen, Philip E; Walker, Matthew C; Williams, Robin S B

    2016-02-01

    The medium chain triglyceride ketogenic diet is an established treatment for drug-resistant epilepsy that increases plasma levels of decanoic acid and ketones. Recently, decanoic acid has been shown to provide seizure control in vivo, yet its mechanism of action remains unclear. Here we show that decanoic acid, but not the ketones β-hydroxybutryate or acetone, shows antiseizure activity in two acute ex vivo rat hippocampal slice models of epileptiform activity. To search for a mechanism of decanoic acid, we show it has a strong inhibitory effect on excitatory, but not inhibitory, neurotransmission in hippocampal slices. Using heterologous expression of excitatory ionotropic glutamate receptor AMPA subunits in Xenopus oocytes, we show that this effect is through direct AMPA receptor inhibition, a target shared by a recently introduced epilepsy treatment perampanel. Decanoic acid acts as a non-competitive antagonist at therapeutically relevant concentrations, in a voltage- and subunit-dependent manner, and this is sufficient to explain its antiseizure effects. This inhibitory effect is likely to be caused by binding to sites on the M3 helix of the AMPA-GluA2 transmembrane domain; independent from the binding site of perampanel. Together our results indicate that the direct inhibition of excitatory neurotransmission by decanoic acid in the brain contributes to the anti-convulsant effect of the medium chain triglyceride ketogenic diet. PMID:26608744

  2. Lysophosphatidic acid receptor (LPAR) modulators: The current pharmacological toolbox.

    PubMed

    Llona-Minguez, Sabin; Ghassemian, Artin; Helleday, Thomas

    2015-04-01

    Lysophosphatidic acids (LPA) are key lipid-signalling molecules that regulate a remarkably diverse set of cellular events, such as motility, chemotaxis, cell cycle progression, viability, and wound healing. The physiological and pathophysiological consequences of LPA signalling are evident and misregulation of LPA signalling can lead to pathologies like cancer, atherosclerosis, ischaemia, and fibrosis. LPA exerts its biological actions mainly through several types of G protein-coupled receptors, some of which display opposing or redundant effects. For this reason, selective LPA receptor small-molecule ligands can shine light on LPA biology and present an exciting opportunity for drug discovery endeavours. This review provides insights into the detailed chemical nature and pharmacological profile of the small-molecules thus far developed as LPA receptor modulators, as well as information on the preparation of key pharmaceuticals. This summary will facilitate future research efforts and nurture collaboration between chemists and biologists working in this emerging field. PMID:25704399

  3. Ventral Midbrain NMDA Receptor Blockade: From Enhanced Reward and Dopamine Inactivation

    PubMed Central

    Hernandez, Giovanni; Cossette, Marie-Pierre; Shizgal, Peter; Rompré, Pierre-Paul

    2016-01-01

    Glutamate stimulates ventral midbrain (VM) N-Methyl-D-Aspartate receptors (NMDAR) to initiate dopamine (DA) burst firing activity, a mode of discharge associated with enhanced DA release and reward. Blockade of VM NMDAR, however, enhances brain stimulation reward (BSR), the results can be explained by a reduction in the inhibitory drive on DA neurons that is also under the control of glutamate. In this study, we used fast-scan cyclic voltammetry (FSCV) in anesthetized animals to determine whether this enhancement is associated with a change in phasic DA release in the nucleus accumbens. Rats were implanted with a stimulation electrode in the dorsal-raphe (DR) and bilateral cannulae above the VM and trained to self-administer trains of electrical stimulation. The curve-shift method was used to evaluate the effect of a single dose (0.825 nmol/0.5 μl/side) of the NMDAR antagonist, (2R,4S)-4-(3-Phosphopropyl)-2-piperidinecarboxylic acid (PPPA), on reward. These animals were then anesthetized and DA release was measured during delivery of electrical stimulation before and after VM microinjection of the vehicle followed by PPPA. As expected, phasic DA release and operant responding depended similarly on the frequency of rewarding electrical stimulation. As anticipated, PPPA produced a significant reward enhancement. Unexpectedly, PPPA produced a decrease in the magnitude of DA transients at all tested frequencies. To test whether this decrease resulted from excessive activation of DA neurons, we injected apomorphine 20 min after PPPA microinjection. At a dose (100 μg s.c.) sufficient to reduce DA firing under control conditions, apomorphine restored electrical stimulation-induced DA transients. These findings show that combined electrical stimulation and VM NMDARs blockade induce DA inactivation, an effect that indirectly demonstrates that VM NMDARs blockade enhances reward by potentiating stimulation-induced excitation in the mesoaccumbens DA pathway. PMID:27616984

  4. Ventral Midbrain NMDA Receptor Blockade: From Enhanced Reward and Dopamine Inactivation.

    PubMed

    Hernandez, Giovanni; Cossette, Marie-Pierre; Shizgal, Peter; Rompré, Pierre-Paul

    2016-01-01

    Glutamate stimulates ventral midbrain (VM) N-Methyl-D-Aspartate receptors (NMDAR) to initiate dopamine (DA) burst firing activity, a mode of discharge associated with enhanced DA release and reward. Blockade of VM NMDAR, however, enhances brain stimulation reward (BSR), the results can be explained by a reduction in the inhibitory drive on DA neurons that is also under the control of glutamate. In this study, we used fast-scan cyclic voltammetry (FSCV) in anesthetized animals to determine whether this enhancement is associated with a change in phasic DA release in the nucleus accumbens. Rats were implanted with a stimulation electrode in the dorsal-raphe (DR) and bilateral cannulae above the VM and trained to self-administer trains of electrical stimulation. The curve-shift method was used to evaluate the effect of a single dose (0.825 nmol/0.5 μl/side) of the NMDAR antagonist, (2R,4S)-4-(3-Phosphopropyl)-2-piperidinecarboxylic acid (PPPA), on reward. These animals were then anesthetized and DA release was measured during delivery of electrical stimulation before and after VM microinjection of the vehicle followed by PPPA. As expected, phasic DA release and operant responding depended similarly on the frequency of rewarding electrical stimulation. As anticipated, PPPA produced a significant reward enhancement. Unexpectedly, PPPA produced a decrease in the magnitude of DA transients at all tested frequencies. To test whether this decrease resulted from excessive activation of DA neurons, we injected apomorphine 20 min after PPPA microinjection. At a dose (100 μg s.c.) sufficient to reduce DA firing under control conditions, apomorphine restored electrical stimulation-induced DA transients. These findings show that combined electrical stimulation and VM NMDARs blockade induce DA inactivation, an effect that indirectly demonstrates that VM NMDARs blockade enhances reward by potentiating stimulation-induced excitation in the mesoaccumbens DA pathway. PMID:27616984

  5. Ventral Midbrain NMDA Receptor Blockade: From Enhanced Reward and Dopamine Inactivation

    PubMed Central

    Hernandez, Giovanni; Cossette, Marie-Pierre; Shizgal, Peter; Rompré, Pierre-Paul

    2016-01-01

    Glutamate stimulates ventral midbrain (VM) N-Methyl-D-Aspartate receptors (NMDAR) to initiate dopamine (DA) burst firing activity, a mode of discharge associated with enhanced DA release and reward. Blockade of VM NMDAR, however, enhances brain stimulation reward (BSR), the results can be explained by a reduction in the inhibitory drive on DA neurons that is also under the control of glutamate. In this study, we used fast-scan cyclic voltammetry (FSCV) in anesthetized animals to determine whether this enhancement is associated with a change in phasic DA release in the nucleus accumbens. Rats were implanted with a stimulation electrode in the dorsal-raphe (DR) and bilateral cannulae above the VM and trained to self-administer trains of electrical stimulation. The curve-shift method was used to evaluate the effect of a single dose (0.825 nmol/0.5 μl/side) of the NMDAR antagonist, (2R,4S)-4-(3-Phosphopropyl)-2-piperidinecarboxylic acid (PPPA), on reward. These animals were then anesthetized and DA release was measured during delivery of electrical stimulation before and after VM microinjection of the vehicle followed by PPPA. As expected, phasic DA release and operant responding depended similarly on the frequency of rewarding electrical stimulation. As anticipated, PPPA produced a significant reward enhancement. Unexpectedly, PPPA produced a decrease in the magnitude of DA transients at all tested frequencies. To test whether this decrease resulted from excessive activation of DA neurons, we injected apomorphine 20 min after PPPA microinjection. At a dose (100 μg s.c.) sufficient to reduce DA firing under control conditions, apomorphine restored electrical stimulation-induced DA transients. These findings show that combined electrical stimulation and VM NMDARs blockade induce DA inactivation, an effect that indirectly demonstrates that VM NMDARs blockade enhances reward by potentiating stimulation-induced excitation in the mesoaccumbens DA pathway.

  6. Retinoic acid receptor alpha (RAralpha) Mutations in Human Leukemia.

    PubMed

    Parrado, A; Chomienne, C; Padua, R A

    2000-10-01

    The retinoic acid receptor alpha (RARalpha) plays a central role in the biology of the myeloid cellular compartment. Chromosomal translocations involving the RARalpha locus probably represent the malignant initiating events in acute promyelocytic leukemia (APL). Recent studies that identify novel interactions between RARalpha and the nuclear receptor co-activators and co-repressors, new functions of the oncogenic RARalpha fusion proteins and their catabolism in retinoic acid-induced differentiation, and the availability of new transgenic mice models have provided important insights into our understanding of the mechanisms by which mutant forms of RARalpha can be implicated in the development of leukemia. Novel alterations of the RARalpha gene identified in hematopoietic malignant disorders other than APL, such as myelodysplastic syndromes, non-APL acute myeloid leukemias and B-chronic lymphocytic leukemias, suggest that disruption of the RARalpha gene might predispose to myeloid and lymphoid disorders.

  7. Identification of COUP-TFII Orphan Nuclear Receptor as a Retinoic Acid-Activated Receptor

    SciTech Connect

    Kruse, Schoen W; Suino-Powell, Kelly; Zhou, X Edward; Kretschman, Jennifer E; Reynolds, Ross; Vonrhein, Clemens; Xu, Yong; Wang, Liliang; Tsai, Sophia Y; Tsai, Ming-Jer; Xu, H Eric

    2010-01-12

    The chicken ovalbumin upstream promoter-transcription factors (COUP-TFI and II) make up the most conserved subfamily of nuclear receptors that play key roles in angiogenesis, neuronal development, organogenesis, cell fate determination, and metabolic homeostasis. Although the biological functions of COUP-TFs have been studied extensively, little is known of their structural features or aspects of ligand regulation. Here we report the ligand-free 1.48 {angstrom} crystal structure of the human COUP-TFII ligand-binding domain. The structure reveals an autorepressed conformation of the receptor, where helix {alpha}10 is bent into the ligand-binding pocket and the activation function-2 helix is folded into the cofactor binding site, thus preventing the recruitment of coactivators. In contrast, in multiple cell lines, COUP-TFII exhibits constitutive transcriptional activity, which can be further potentiated by nuclear receptor coactivators. Mutations designed to disrupt cofactor binding, dimerization, and ligand binding, substantially reduce the COUP-TFII transcriptional activity. Importantly, retinoid acids are able to promote COUP-TFII to recruit coactivators and activate a COUP-TF reporter construct. Although the concentration needed is higher than the physiological levels of retinoic acids, these findings demonstrate that COUP-TFII is a ligand-regulated nuclear receptor, in which ligands activate the receptor by releasing it from the autorepressed conformation.

  8. A third human retinoic acid receptor, hRAR-. gamma

    SciTech Connect

    Krust, A.; Kastner, Ph.; Petkovich, M.; Zelent, A.; Chambon, P. )

    1989-07-01

    Retinoic acid receptors (RARs) are retinoic acid (RA)-inducible enhancer factors belonging to the superfamily of steroid/thyroid nuclear receptors. The authors have previously characterized two human RAR (hRAR-{alpha} and hRAR-{beta}) cDNAs and have recently cloned their murine cognates (mRAR-{alpha} and mRAR-{beta}) together with a third RAR (mRAR-{gamma}) whose RNA was detected predominantly in skin, a well-known target for RA. mRAR-{gamma} cDNA was used here to clone its human counterpart (hRAR-{gamma}) from a T47D breast cancer cell cDNA library. Using a transient transfection assay in HeLa cells and a reporter gene harboring a synthetic RA responsive element, they demonstrate that hRAR-{gamma} cDNA indeed encodes a RA-inducible transcriptional trans-activator. Interestingly, comparisons of the amino acid sequences of all six human and mouse RARs indicate that the interspecies conservation of a given member of the RAR subfamily (either {alpha}, {beta}, or {gamma}) is much higher than the conservation of all three receptors within a given species. These observations indicate that RAR-{alpha}, -{beta}, and -{gamma} may perform specific functions. They show also that hRAR-{gamma} RNA is the predominant RAR RNA species in human skin, which suggests that hRAR-{gamma} mediates some of the retinoid effects in this tissue.

  9. Adenovirus Type 37 Uses Sialic Acid as a Cellular Receptor

    PubMed Central

    Arnberg, Niklas; Edlund, Karin; Kidd, Alistair H.; Wadell, Göran

    2000-01-01

    Two cellular receptors for adenovirus, coxsackievirus-adenovirus receptor (CAR) and major histocompatibility complex class I (MHC-I) α2, have recently been identified. In the absence of CAR, MHC-I α2 has been suggested to serve as a cellular attachment protein for subgenus C adenoviruses, while members from all subgenera except subgenus B have been shown to interact with CAR. We have found that adenovirus type 37 (Ad37) attachment to CAR-expressing CHO cells was no better than that to CHO cells lacking CAR expression, suggesting that CAR is not used by Ad37 during attachment. Instead, we have identified sialic acid as a third adenovirus receptor moiety. First, Ad37 attachment to both CAR-expresing CHO cells and MHC-I α2-expressing Daudi cells was sensitive to neuraminidase treatment, which eliminates sialic acid on the cell surface. Second, Ad37 attachment to sialic acid-expressing Pro-5 cells was more than 10-fold stronger than that to the Pro-5 subline Lec2, which is deficient in sialic acid expression. Third, neuraminidase treatment of A549 cells caused a 60% decrease in Ad37 replication in a fluorescent-focus assay. Moreover, the receptor sialoconjugate is most probably a glycoprotein rather than a ganglioside, since Ad37 attachment to sialic acid-expressing Pro-5 cells was sensitive to protease treatment. Ad37 attachment to Pro-5 cells occurs via α(2→3)-linked sialic acid saccharides rather than α(2→6)-linked ones, since (i) α(2→3)-specific but not α(2→6)-specific lectins blocked Ad37 attachment to Pro-5 cells and (ii) pretreatment of Pro-5 cells with α(2→3)-specific neuraminidase resulted in decreased Ad37 binding. Taken together, these results suggest that, unlike Ad5, Ad37 makes use of α(2→3)-linked sialic acid saccharides on glycoproteins for entry instead of using CAR or MHC-I α2. PMID:10590089

  10. Cholestenoic acids regulate motor neuron survival via liver X receptors

    PubMed Central

    Theofilopoulos, Spyridon; Griffiths, William J.; Crick, Peter J.; Yang, Shanzheng; Meljon, Anna; Ogundare, Michael; Kitambi, Satish Srinivas; Lockhart, Andrew; Tuschl, Karin; Clayton, Peter T.; Morris, Andrew A.; Martinez, Adelaida; Reddy, M. Ashwin; Martinuzzi, Andrea; Bassi, Maria T.; Honda, Akira; Mizuochi, Tatsuki; Kimura, Akihiko; Nittono, Hiroshi; De Michele, Giuseppe; Carbone, Rosa; Criscuolo, Chiara; Yau, Joyce L.; Seckl, Jonathan R.; Schüle, Rebecca; Schöls, Ludger; Sailer, Andreas W.; Kuhle, Jens; Fraidakis, Matthew J.; Gustafsson, Jan-Åke; Steffensen, Knut R.; Björkhem, Ingemar; Ernfors, Patrik; Sjövall, Jan; Arenas, Ernest; Wang, Yuqin

    2014-01-01

    Cholestenoic acids are formed as intermediates in metabolism of cholesterol to bile acids, and the biosynthetic enzymes that generate cholestenoic acids are expressed in the mammalian CNS. Here, we evaluated the cholestenoic acid profile of mammalian cerebrospinal fluid (CSF) and determined that specific cholestenoic acids activate the liver X receptors (LXRs), enhance islet-1 expression in zebrafish, and increase the number of oculomotor neurons in the developing mouse in vitro and in vivo. While 3β,7α-dihydroxycholest-5-en-26-oic acid (3β,7α-diHCA) promoted motor neuron survival in an LXR-dependent manner, 3β-hydroxy-7-oxocholest-5-en-26-oic acid (3βH,7O-CA) promoted maturation of precursors into islet-1+ cells. Unlike 3β,7α-diHCA and 3βH,7O-CA, 3β-hydroxycholest-5-en-26-oic acid (3β-HCA) caused motor neuron cell loss in mice. Mutations in CYP7B1 or CYP27A1, which encode enzymes involved in cholestenoic acid metabolism, result in different neurological diseases, hereditary spastic paresis type 5 (SPG5) and cerebrotendinous xanthomatosis (CTX), respectively. SPG5 is characterized by spastic paresis, and similar symptoms may occur in CTX. Analysis of CSF and plasma from patients with SPG5 revealed an excess of the toxic LXR ligand, 3β-HCA, while patients with CTX and SPG5 exhibited low levels of the survival-promoting LXR ligand 3β,7α-diHCA. Moreover, 3β,7α-diHCA prevented the loss of motor neurons induced by 3β-HCA in the developing mouse midbrain in vivo.Our results indicate that specific cholestenoic acids selectively work on motor neurons, via LXR, to regulate the balance between survival and death. PMID:25271621

  11. Development of novel silicon-containing inverse agonists of retinoic acid receptor-related orphan receptors.

    PubMed

    Toyama, Hirozumi; Nakamura, Masaharu; Nakamura, Masahiko; Matsumoto, Yotaro; Nakagomi, Madoka; Hashimoto, Yuichi

    2014-03-15

    Retinoic acid receptor (RAR)-related orphan receptors (RORs) regulate a variety of physiological processes, including hepatic gluconeogenesis, lipid metabolism, circadian rhythm and immune function. The RAR agonist: all-trans retinoic acid was reported to be an RORβ inverse agonist, but no information is available regarding ROR activity of its synthetic analogue Am580. Therefore, we screened Am580 and some related tetramethyltetrahydronaphthalene derivatives and carried out structural development studies, including substitution of carbon atoms with silicon, with the aim of creating a potent ROR transcriptional inhibitor. The phenyl amide disila compound 22 showed the most potent ROR-inhibitory activity among the compounds examined. Its activity towards RORα, RORβ and RORγ was increased compared to that of Am580. The IC₅₀ values for RORα, RORβ and RORγ are 1.3, >10 and 4.5 μM, respectively.

  12. Receptor for protons: First observations on Acid Sensing Ion Channels.

    PubMed

    Krishtal, Oleg

    2015-07-01

    The history of ASICs began in 1980 with unexpected observation. The concept of highly selective Na(+) current gated by specific receptors for protons was not easily accepted. It took 16 years to get these receptor/channels cloned and start a new stage in their investigation. "The receptor for protons" became ASIC comprising under this name a family of receptor/channels ubiquitous for mammalian nervous system, both peripheral and central. The role of ASICs as putative nociceptors was suggested almost immediately after their discovery. This role subsequently was proven in many forms of pain-related phenomena. Many other functions of ASICs have been also found or primed for speculations both in physiology and in disease. Despite the width of field and strength of efforts, numerous basic questions are to be answered before we understand how the local changes in pH in the nervous tissue transform into electric and messenger signaling via ASICs as transducers. This article is part of the Special Issue entitled 'Acid-Sensing Ion Channels in the Nervous System'.

  13. Bridging cell surface receptor with nuclear receptors in control of bile acid homeostasis

    PubMed Central

    Li, Shuangwei; Ni, Andrew; Feng, Gen-sheng

    2015-01-01

    Bile acids (BAs) are traditionally considered as “physiological detergents” for emulsifying hydrophobic lipids and vitamins due to their amphipathic nature. But accumulating clinical and experimental evidence shows an association between disrupted BA homeostasis and various liver disease conditions including hepatitis infection, diabetes and cancer. Consequently, BA homeostasis regulation has become a field of heavy interest and investigation. After identification of the Farnesoid X Receptor (FXR) as an endogenous receptor for BAs, several nuclear receptors (SHP, HNF4α, and LRH-1) were also found to be important in regulation of BA homeostasis. Some post-translational modifications of these nuclear receptors have been demonstrated, but their physiological significance is still elusive. Gut secrets FGF15/19 that can activate hepatic FGFR4 and its downstream signaling cascade, leading to repressed hepatic BA biosynthesis. However, the link between the activated kinases and these nuclear receptors is not fully elucidated. Here, we review the recent literature on signal crosstalk in BA homeostasis. PMID:25500873

  14. Prefrontal NMDA receptors expressed in excitatory neurons control fear discrimination and fear extinction.

    PubMed

    Vieira, Philip A; Corches, Alex; Lovelace, Jonathan W; Westbrook, Kevin B; Mendoza, Michael; Korzus, Edward

    2015-03-01

    N-methyl-D-aspartate receptors (NMDARs) are critically involved in various learning mechanisms including modulation of fear memory, brain development and brain disorders. While NMDARs mediate opposite effects on medial prefrontal cortex (mPFC) interneurons and excitatory neurons, NMDAR antagonists trigger profound cortical activation. The objectives of the present study were to determine the involvement of NMDARs expressed specifically in excitatory neurons in mPFC-dependent adaptive behaviors, specifically fear discrimination and fear extinction. To achieve this, we tested mice with locally deleted Grin1 gene encoding the obligatory NR1 subunit of the NMDAR from prefrontal CamKIIα positive neurons for their ability to distinguish frequency modulated (FM) tones in fear discrimination test. We demonstrated that NMDAR-dependent signaling in the mPFC is critical for effective fear discrimination following initial generalization of conditioned fear. While mice with deficient NMDARs in prefrontal excitatory neurons maintain normal responses to a dangerous fear-conditioned stimulus, they exhibit abnormal generalization decrement. These studies provide evidence that NMDAR-dependent neural signaling in the mPFC is a component of a neural mechanism for disambiguating the meaning of fear signals and supports discriminative fear learning by retaining proper gating information, viz. both dangerous and harmless cues. We also found that selective deletion of NMDARs from excitatory neurons in the mPFC leads to a deficit in fear extinction of auditory conditioned stimuli. These studies suggest that prefrontal NMDARs expressed in excitatory neurons are involved in adaptive behavior.

  15. Retinoic acid receptor alpha is associated with tamoxifen resistance in breast cancer

    PubMed Central

    Johansson, Henrik J.; Sanchez, Betzabe C.; Mundt, Filip; Forshed, Jenny; Kovacs, Aniko; Panizza, Elena; Hultin-Rosenberg, Lina; Lundgren, Bo; Martens, Ulf; Máthé, Gyöngyvér; Yakhini, Zohar; Helou, Khalil; Krawiec, Kamilla; Kanter, Lena; Hjerpe, Anders; Stål, Olle; Linderholm, Barbro K.; Lehtiö, Janne

    2013-01-01

    About one-third of oestrogen receptor alpha-positive breast cancer patients treated with tamoxifen relapse. Here we identify the nuclear receptor retinoic acid receptor alpha as a marker of tamoxifen resistance. Using quantitative mass spectrometry-based proteomics, we show that retinoic acid receptor alpha protein networks and levels differ in a tamoxifen-sensitive (MCF7) and a tamoxifen-resistant (LCC2) cell line. High intratumoural retinoic acid receptor alpha protein levels also correlate with reduced relapse-free survival in oestrogen receptor alpha-positive breast cancer patients treated with adjuvant tamoxifen solely. A similar retinoic acid receptor alpha expression pattern is seen in a comparable independent patient cohort. An oestrogen receptor alpha and retinoic acid receptor alpha ligand screening reveals that tamoxifen-resistant LCC2 cells have increased sensitivity to retinoic acid receptor alpha ligands and are less sensitive to oestrogen receptor alpha ligands compared with MCF7 cells. Our data indicate that retinoic acid receptor alpha may be a novel therapeutic target and a predictive factor for oestrogen receptor alpha-positive breast cancer patients treated with adjuvant tamoxifen. PMID:23868472

  16. Transcriptional profiling of the mouse hippocampus supports an NMDAR-mediated neurotoxic mode of action for benzo[a]pyrene.

    PubMed

    Chepelev, Nikolai L; Long, Alexandra S; Bowers, Wayne J; Gagné, Rémi; Williams, Andrew; Kuo, Byron; Phillips, David H; Arlt, Volker M; White, Paul A; Yauk, Carole L

    2016-06-01

    Benzo[a]pyrene (BaP) is a genotoxic carcinogen and a neurotoxicant. The neurotoxicity of BaP is proposed to arise from either genotoxicity leading to neuronal cell death, or perturbed expression of N-methyl-d-aspartate receptor (NMDAR) subunits. To explore these hypotheses, we profiled hippocampal gene expression of adult male Muta(™) Mouse administered 0, 1, 35, or 70 mg BaP/kg bw per day by oral gavage for 3 days. Transcriptional profiles were examined by RNA-sequencing (RNA-seq), DNA microarrays, and real-time quantitative reverse transcription polymerase chain reaction (RT-PCR). BaP-DNA adducts in the cerebellum were quantified by (32) P-post-labeling to measure genotoxicity. RNA-seq revealed altered expression of 0, 260, and 219 genes (P-value < 0.05, fold-change ≥ ± 1.5) following exposure to the low, medium, and high doses, respectively; 54 genes were confirmed by microarrays. Microarray and RT-PCR analysis showed increased expression of NMDAR subunits Grina and Grin2a. In contrast, no effects on DNA-damage response genes were observed despite comparable BaP-DNA adduct levels in the cerebellum and in the lungs and livers of mice at similar BaP doses in previous studies. The results suggest that DNA-damage response does not play a major role in BaP-induced adult neurotoxicity. Meta-analysis revealed that BaP-induced transcriptional profiles are highly correlated with those from the hippocampus of transgenic mice exhibiting similar neurotoxicity outcomes to BaP-exposed mice and rats (i.e., defects in learning and memory). Overall, we suggest that BaP-induced neurotoxicity is more likely to be a consequence of NMDAR perturbation than genotoxicity, and identify other important genes potentially mediating this adverse outcome. Environ. Mol. Mutagen. 57:350-363, 2016. © 2016 Her Majesty the Queen in Right of Canada. Environmental and Molecular Mutagenesis © 2016 Environmental Mutagen Society.

  17. Fyn Kinase regulates GluN2B subunit-dominant NMDA receptors in human induced pluripotent stem cell-derived neurons

    PubMed Central

    Zhang, Wen-Bo; Ross, P. Joel; Tu, YuShan; Wang, Yongqian; Beggs, Simon; Sengar, Ameet S.; Ellis, James; Salter, Michael W.

    2016-01-01

    NMDA receptor (NMDAR)-mediated fast excitatory neurotransmission is implicated in a broad range of physiological and pathological processes in the mammalian central nervous system. The function and regulation of NMDARs have been extensively studied in neurons from rodents and other non-human species, and in recombinant expression systems. Here, we investigated human NMDARs in situ by using neurons produced by directed differentiation of human induced pluripotent stem cells (iPSCs). The resultant cells showed electrophysiological characteristics demonstrating that they are bona fide neurons. In particular, human iPSC-derived neurons expressed functional ligand-gated ion channels, including NMDARs, AMPA receptors, GABAA receptors, as well as glycine receptors. Pharmacological and electrophysiological properties of NMDAR-mediated currents indicated that these were dominated by receptors containing GluN2B subunits. The NMDAR currents were suppressed by genistein, a broad-spectrum tyrosine kinase inhibitor. The NMDAR currents were also inhibited by a Fyn-interfering peptide, Fyn(39–57), but not a Src-interfering peptide, Src(40–58). Together, these findings are the first evidence that tyrosine phosphorylation regulates the function of NMDARs in human iPSC-derived neurons. Our findings provide a basis for utilizing human iPSC-derived neurons in screening for drugs targeting NMDARs in neurological disorders. PMID:27040756

  18. Fyn Kinase regulates GluN2B subunit-dominant NMDA receptors in human induced pluripotent stem cell-derived neurons.

    PubMed

    Zhang, Wen-Bo; Ross, P Joel; Tu, YuShan; Wang, Yongqian; Beggs, Simon; Sengar, Ameet S; Ellis, James; Salter, Michael W

    2016-04-04

    NMDA receptor (NMDAR)-mediated fast excitatory neurotransmission is implicated in a broad range of physiological and pathological processes in the mammalian central nervous system. The function and regulation of NMDARs have been extensively studied in neurons from rodents and other non-human species, and in recombinant expression systems. Here, we investigated human NMDARs in situ by using neurons produced by directed differentiation of human induced pluripotent stem cells (iPSCs). The resultant cells showed electrophysiological characteristics demonstrating that they are bona fide neurons. In particular, human iPSC-derived neurons expressed functional ligand-gated ion channels, including NMDARs, AMPA receptors, GABAA receptors, as well as glycine receptors. Pharmacological and electrophysiological properties of NMDAR-mediated currents indicated that these were dominated by receptors containing GluN2B subunits. The NMDAR currents were suppressed by genistein, a broad-spectrum tyrosine kinase inhibitor. The NMDAR currents were also inhibited by a Fyn-interfering peptide, Fyn(39-57), but not a Src-interfering peptide, Src(40-58). Together, these findings are the first evidence that tyrosine phosphorylation regulates the function of NMDARs in human iPSC-derived neurons. Our findings provide a basis for utilizing human iPSC-derived neurons in screening for drugs targeting NMDARs in neurological disorders.

  19. Physiological Roles of Calpain 1 Associated to Multiprotein NMDA Receptor Complex

    PubMed Central

    Averna, Monica; Pellegrini, Matteo; Cervetto, Chiara; Pedrazzi, Marco; Bavestrello, Margherita; De Tullio, Roberta; Salamino, Franca; Pontremoli, Sandro; Melloni, Edon

    2015-01-01

    We have recently demonstrated that in resting conditions calpain 1, but not calpain 2, is specifically associated to the N-Methyl-D-Aspartate receptor (NMDAR) multiprotein complex. We are here reporting that in SKNBE neuroblastoma cells or in freshly isolated nerve terminals from adult rat hippocampus, the proteolytic activity of calpain 1 resident at the NMDAR is very low under basal conditions and greatly increases following NMDAR stimulation. Since the protease resides at the NMDAR in saturating amounts, variations in Ca2+ influx promote an increase in calpain 1 activity without affecting the amount of the protease originally associated to NMDAR. In all the conditions examined, resident calpain 1 specifically cleaves NR2B at the C-terminal region, leading to its internalization together with NR1 subunit. While in basal conditions intracellular membranes include small amounts of NMDAR containing the calpain-digested NR2B, upon NMDAR stimulation nearly all the receptor molecules are internalized. We here propose that resident calpain 1 is involved in NMDAR turnover, and following an increase in Ca2+ influx, the activated protease, by promoting the removal of NMDAR from the plasma membranes, can decrease Ca2+ entrance through this channel. Due to the absence of calpastatin in such cluster, the activity of resident calpain 1 may be under the control of HSP90, whose levels are directly related to the activation of this protease. Observations of different HSP90/calpain 1 ratios in different ultrasynaptic compartments support this conclusion. PMID:26431040

  20. Novel nootropic drug sunifiram enhances hippocampal synaptic efficacy via glycine-binding site of N-methyl-D-aspartate receptor.

    PubMed

    Moriguchi, Shigeki; Tanaka, Tomoya; Narahashi, Toshio; Fukunaga, Kohji

    2013-10-01

    Sunifiram is a novel pyrrolidone nootropic drug structurally related to piracetam, which was developed for neurodegenerative disorder like Alzheimer's disease. Sunifiram is known to enhance cognitive function in some behavioral experiments such as Morris water maze task. To address question whether sunifiram affects N-methyl-D-aspartate receptor (NMDAR)-dependent synaptic function in the hippocampal CA1 region, we assessed the effects of sunifiram on NMDAR-dependent long-term potentiation (LTP) by electrophysiology and on phosphorylation of synaptic proteins by immunoblotting analysis. In mouse hippocampal slices, sunifiram at 10-100 nM significantly enhanced LTP in a bell-shaped dose-response relationship which peaked at 10 nM. The enhancement of LTP by sunifiram treatment was inhibited by 7-chloro-kynurenic acid (7-ClKN), an antagonist for glycine-binding site of NMDAR, but not by ifenprodil, an inhibitor for polyamine site of NMDAR. The enhancement of LTP by sunifilam was associated with an increase in phosphorylation of α-amino-3-hydroxy-5-methylisozazole-4-propionate receptor (AMPAR) through activation of calcium/calmodulin-dependent protein kinase II (CaMKII) and an increase in phosphorylation of NMDAR through activation of protein kinase Cα (PKCα). Sunifiram treatments at 1-1000 nM increased the slope of field excitatory postsynaptic potentials (fEPSPs) in a dose-dependent manner. The enhancement was associated with an increase in phosphorylation of AMPAR receptor through activation of CaMKII. Interestingly, under the basal condition, sunifiram treatments increased PKCα (Ser-657) and Src family (Tyr-416) activities with the same bell-shaped dose-response curve as that of LTP peaking at 10 nM. The increase in phosphorylation of PKCα (Ser-657) and Src (Tyr-416) induced by sunifiram was inhibited by 7-ClKN treatment. The LTP enhancement by sunifiram was significantly inhibited by PP2, a Src family inhibitor. Finally, when pretreated with a high

  1. Pharmacological activation of lysophosphatidic acid receptors regulates erythropoiesis

    PubMed Central

    Lin, Kuan-Hung; Ho, Ya-Hsuan; Chiang, Jui-Chung; Li, Meng-Wei; Lin, Shi-Hung; Chen, Wei-Min; Chiang, Chi-Ling; Lin, Yu-Nung; Yang, Ya-Jan; Chen, Chiung-Nien; Lu, Jenher; Huang, Chang-Jen; Tigyi, Gabor; Yao, Chao-Ling; Lee, Hsinyu

    2016-01-01

    Lysophosphatidic acid (LPA), a growth factor-like phospholipid, regulates numerous physiological functions, including cell proliferation and differentiation. In a previous study, we have demonstrated that LPA activates erythropoiesis by activating the LPA 3 receptor subtype (LPA3) under erythropoietin (EPO) induction. In the present study, we applied a pharmacological approach to further elucidate the functions of LPA receptors during red blood cell (RBC) differentiation. In K562 human erythroleukemia cells, knockdown of LPA2 enhanced erythropoiesis, whereas knockdown of LPA3 inhibited RBC differentiation. In CD34+ human hematopoietic stem cells (hHSC) and K526 cells, the LPA3 agonist 1-oleoyl-2-methyl-sn-glycero-3-phosphothionate (2S-OMPT) promoted erythropoiesis, whereas the LPA2 agonist dodecyl monophosphate (DMP) and the nonlipid specific agonist GRI977143 (GRI) suppressed this process. In zebrafish embryos, hemoglobin expression was significantly increased by 2S-OMPT treatment but was inhibited by GRI. Furthermore, GRI treatment decreased, whereas 2S-OMPT treatment increased RBC counts and amount of hemoglobin level in adult BALB/c mice. These results indicate that LPA2 and LPA3 play opposing roles during RBC differentiation. The pharmacological activation of LPA receptor subtypes represent a novel strategies for augmenting or inhibiting erythropoiesis. PMID:27244685

  2. Tissue plasminogen activator inhibits NMDA-receptor-mediated increases in calcium levels in cultured hippocampal neurons

    PubMed Central

    Robinson, Samuel D.; Lee, Tet Woo; Christie, David L.; Birch, Nigel P.

    2015-01-01

    NMDA receptors (NMDARs) play a critical role in neurotransmission, acting as essential mediators of many forms of synaptic plasticity, and also modulating aspects of development, synaptic transmission and cell death. NMDAR-induced responses are dependent on a range of factors including subunit composition and receptor location. Tissue-type plasminogen activator (tPA) is a serine protease that has been reported to interact with NMDARs and modulate NMDAR activity. In this study we report that tPA inhibits NMDAR-mediated changes in intracellular calcium levels in cultures of primary hippocampal neurons stimulated by low (5 μM) but not high (50 μM) concentrations of NMDA. tPA also inhibited changes in calcium levels stimulated by presynaptic release of glutamate following treatment with bicucculine/4-aminopyridine (4-AP). Inhibition was dependent on the proteolytic activity of tPA but was unaffected by α2-antiplasmin, an inhibitor of the tPA substrate plasmin, and receptor-associated protein (RAP), a pan-ligand blocker of the low-density lipoprotein receptor, two proteins previously reported to modulate NMDAR activity. These findings suggest that tPA can modulate changes in intracellular calcium levels in a subset of NMDARs expressed in cultured embryonic hippocampal neurons through a mechanism that involves the proteolytic activity of tPA and synaptic NMDARs. PMID:26500501

  3. Retinoic acid receptors: from molecular mechanisms to cancer therapy.

    PubMed

    di Masi, Alessandra; Leboffe, Loris; De Marinis, Elisabetta; Pagano, Francesca; Cicconi, Laura; Rochette-Egly, Cécile; Lo-Coco, Francesco; Ascenzi, Paolo; Nervi, Clara

    2015-02-01

    Retinoic acid (RA), the major bioactive metabolite of retinol or vitamin A, induces a spectrum of pleiotropic effects in cell growth and differentiation that are relevant for embryonic development and adult physiology. The RA activity is mediated primarily by members of the retinoic acid receptor (RAR) subfamily, namely RARα, RARβ and RARγ, which belong to the nuclear receptor (NR) superfamily of transcription factors. RARs form heterodimers with members of the retinoid X receptor (RXR) subfamily and act as ligand-regulated transcription factors through binding specific RA response elements (RAREs) located in target genes promoters. RARs also have non-genomic effects and activate kinase signaling pathways, which fine-tune the transcription of the RA target genes. The disruption of RA signaling pathways is thought to underlie the etiology of a number of hematological and non-hematological malignancies, including leukemias, skin cancer, head/neck cancer, lung cancer, breast cancer, ovarian cancer, prostate cancer, renal cell carcinoma, pancreatic cancer, liver cancer, glioblastoma and neuroblastoma. Of note, RA and its derivatives (retinoids) are employed as potential chemotherapeutic or chemopreventive agents because of their differentiation, anti-proliferative, pro-apoptotic, and anti-oxidant effects. In humans, retinoids reverse premalignant epithelial lesions, induce the differentiation of myeloid normal and leukemic cells, and prevent lung, liver, and breast cancer. Here, we provide an overview of the biochemical and molecular mechanisms that regulate the RA and retinoid signaling pathways. Moreover, mechanisms through which deregulation of RA signaling pathways ultimately impact on cancer are examined. Finally, the therapeutic effects of retinoids are reported. PMID:25543955

  4. Molecular basis for amino acid sensing by family C G-protein-coupled receptors

    PubMed Central

    Wellendorph, P; Bräuner-Osborne, H

    2009-01-01

    Family C of human G-protein-coupled receptors (GPCRs) is constituted by eight metabotropic glutamate receptors, two γ-aminobutyric acid type B (GABAB1–2) subunits forming the heterodimeric GABAB receptor, the calcium-sensing receptor, three taste1 receptors (T1R1–3), a promiscuous L-α-amino acid receptor G-protein-coupled receptor family C, group 6, subtype A (GPRC6A) and seven orphan receptors. Aside from the orphan receptors, the family C GPCRs are dimeric receptors characterized by a large extracellular Venus flytrap domain which bind the endogenous agonists. Except from the GABAB1–2 and T1R2–3 receptor, all receptors are either activated or positively modulated by amino acids. In this review, we outline mutational, biophysical and structural studies which have elucidated the interaction of the amino acids with the Venus flytrap domains, molecular mechanisms of receptor selectivity and the initial steps in receptor activation. PMID:19298394

  5. Leveraging abscisic acid receptors for efficient water use in Arabidopsis.

    PubMed

    Yang, Zhenyu; Liu, Jinghui; Tischer, Stefanie V; Christmann, Alexander; Windisch, Wilhelm; Schnyder, Hans; Grill, Erwin

    2016-06-14

    Plant growth requires the influx of atmospheric CO2 through stomatal pores, and this carbon uptake for photosynthesis is inherently associated with a large efflux of water vapor. Under water deficit, plants reduce transpiration and are able to improve carbon for water exchange leading to higher water use efficiency (WUE). Whether increased WUE can be achieved without trade-offs in plant growth is debated. The signals mediating the WUE response under water deficit are not fully elucidated but involve the phytohormone abscisic acid (ABA). ABA is perceived by a family of related receptors known to mediate acclimation responses and to reduce transpiration. We now show that enhanced stimulation of ABA signaling via distinct ABA receptors can result in plants constitutively growing at high WUE in the model species Arabidopsis WUE was assessed by three independent approaches involving gravimetric analyses, (13)C discrimination studies of shoots and derived cellulose fractions, and by gas exchange measurements of whole plants and individual leaves. Plants expressing the ABA receptors RCAR6/PYL12 combined up to 40% increased WUE with high growth rates, i.e., are water productive. Water productivity was associated with maintenance of net carbon assimilation by compensatory increases of leaf CO2 gradients, thereby sustaining biomass acquisition. Leaf surface temperatures and growth potentials of plants growing under well-watered conditions were found to be reliable indicators for water productivity. The study shows that ABA receptors can be explored to generate more plant biomass per water transpired, which is a prime goal for a more sustainable water use in agriculture. PMID:27247417

  6. Leveraging abscisic acid receptors for efficient water use in Arabidopsis

    PubMed Central

    Yang, Zhenyu; Liu, Jinghui; Tischer, Stefanie V.; Christmann, Alexander; Windisch, Wilhelm; Schnyder, Hans; Grill, Erwin

    2016-01-01

    Plant growth requires the influx of atmospheric CO2 through stomatal pores, and this carbon uptake for photosynthesis is inherently associated with a large efflux of water vapor. Under water deficit, plants reduce transpiration and are able to improve carbon for water exchange leading to higher water use efficiency (WUE). Whether increased WUE can be achieved without trade-offs in plant growth is debated. The signals mediating the WUE response under water deficit are not fully elucidated but involve the phytohormone abscisic acid (ABA). ABA is perceived by a family of related receptors known to mediate acclimation responses and to reduce transpiration. We now show that enhanced stimulation of ABA signaling via distinct ABA receptors can result in plants constitutively growing at high WUE in the model species Arabidopsis. WUE was assessed by three independent approaches involving gravimetric analyses, 13C discrimination studies of shoots and derived cellulose fractions, and by gas exchange measurements of whole plants and individual leaves. Plants expressing the ABA receptors RCAR6/PYL12 combined up to 40% increased WUE with high growth rates, i.e., are water productive. Water productivity was associated with maintenance of net carbon assimilation by compensatory increases of leaf CO2 gradients, thereby sustaining biomass acquisition. Leaf surface temperatures and growth potentials of plants growing under well-watered conditions were found to be reliable indicators for water productivity. The study shows that ABA receptors can be explored to generate more plant biomass per water transpired, which is a prime goal for a more sustainable water use in agriculture. PMID:27247417

  7. Biological roles and therapeutic potential of hydroxy-carboxylic Acid receptors.

    PubMed

    Ahmed, Kashan

    2011-01-01

    In the recent past, deorphanization studies have described intermediates of energy metabolism to activate G protein-coupled receptors and to thereby regulate metabolic functions. GPR81, GPR109A, and GPR109B, formerly known as the nicotinic acid receptor family, are encoded by clustered genes and share a high degree of sequence homology. Recently, hydroxy-carboxylic acids were identified as endogenous ligands of GPR81, GPR109A, and GPR109B, and therefore these receptors have been placed into a novel receptor family of hydroxy-carboxylic acid (HCA) receptors. The HCA(1) receptor (GPR81) is activated by the glycolytic metabolite 2-hydroxy-propionic acid (lactate), the HCA(2) receptor is activated by the ketone body 3-hydroxy-butyric acid, and the HCA(3) receptor (GPR109B) is a receptor for the β-oxidation intermediate 3-hydroxy-octanoic acid. While HCA(1) and HCA(2) receptors are present in most mammalian species, the HCA(3) receptor is exclusively found in humans and higher primates. HCA receptors are expressed in adipose tissue and mediate anti-lipolytic effects in adipocytes through G(i)-type G protein-dependent inhibition of adenylyl cyclase. HCA(2) and HCA(3) inhibit lipolysis during conditions of increased β-oxidation such as prolonged fasting, whereas HCA(1) mediates the anti-lipolytic effects of insulin in the fed state. As HCA(2) is a receptor for the established anti-dyslipidemic drug nicotinic acid, HCA(1) and HCA(3) also represent promising drug targets and several synthetic ligands for HCA receptors have been developed. In this article, we will summarize the deorphanization and pharmacological characterization of HCA receptors. Moreover, we will discuss recent progress in elucidating the physiological and pathophysiological role to further evaluate the therapeutic potential of the HCA receptor family for the treatment of metabolic disease.

  8. Bile acid receptor agonist GW4064 regulates PPARγ coactivator-1α expression through estrogen receptor-related receptor α.

    PubMed

    Dwivedi, Shailendra Kumar Dhar; Singh, Nidhi; Kumari, Rashmi; Mishra, Jay Sharan; Tripathi, Sarita; Banerjee, Priyam; Shah, Priyanka; Kukshal, Vandana; Tyagi, Abdul Malik; Gaikwad, Anil Nilkanth; Chaturvedi, Rajnish Kumar; Mishra, Durga Prasad; Trivedi, Arun Kumar; Sanyal, Somali; Chattopadhyay, Naibedya; Ramachandran, Ravishankar; Siddiqi, Mohammad Imran; Bandyopadhyay, Arun; Arora, Ashish; Lundåsen, Thomas; Anakk, Sayee Priyadarshini; Moore, David D; Sanyal, Sabyasachi

    2011-06-01

    Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) is induced in energy-starved conditions and is a key regulator of energy homeostasis. This makes PGC-1α an attractive therapeutic target for metabolic syndrome and diabetes. In our effort to identify new regulators of PGC-1α expression, we found that GW4064, a widely used synthetic agonist for the nuclear bile acid receptor [farnesoid X receptor (FXR)] strongly enhances PGC-1α promoter reporter activity, mRNA, and protein expression. This induction in PGC-1α concomitantly enhances mitochondrial mass and expression of several PGC-1α target genes involved in mitochondrial function. Using FXR-rich or FXR-nonexpressing cell lines and tissues, we found that this effect of GW4064 is not mediated directly by FXR but occurs via activation of estrogen receptor-related receptor α (ERRα). Cell-based, biochemical and biophysical assays indicate GW4064 as an agonist of ERR proteins. Interestingly, FXR disruption alters GW4064 induction of PGC-1α mRNA in a tissue-dependent manner. Using FXR-null [FXR knockout (FXRKO)] mice, we determined that GW4064 induction of PGC-1α expression is not affected in oxidative soleus muscles of FXRKO mice but is compromised in the FXRKO liver. Mechanistic studies to explain these differences revealed that FXR physically interacts with ERR and protects them from repression by the atypical corepressor, small heterodimer partner in liver. Together, this interplay between ERRα-FXR-PGC-1α and small heterodimer partner offers new insights into the biological functions of ERRα and FXR, thus providing a knowledge base for therapeutics in energy balance-related pathophysiology.

  9. A widely used retinoic acid receptor antagonist induces peroxisome proliferator-activated receptor-gamma activity.

    PubMed

    Schupp, Michael; Curtin, Joshua C; Kim, Roy J; Billin, Andrew N; Lazar, Mitchell A

    2007-05-01

    Nuclear receptors (NRs) are transcription factors whose activity is regulated by the binding of small lipophilic ligands, including hormones, vitamins, and metabolites. Pharmacological NR ligands serve as important therapeutic agents; for example, all-trans retinoic acid, an activating ligand for retinoic acid receptor alpha (RARalpha), is used to treat leukemia. Another RARalpha ligand, (E)-S,S-dioxide-4-(2-(7-(heptyloxy)-3,4-dihydro-4,4-dimethyl-2H-1-benzothiopyran-6-yl)-1-propenyl)-benzoic acid (Ro 41-5253), is a potent antagonist that has been a useful and purportedly specific probe of RARalpha function. Here, we report that Ro 41-5253 also activates the peroxisome proliferator-activated receptor gamma (PPARgamma), a master regulator of adipocyte differentiation and target of widely prescribed antidiabetic thiazolidinediones (TZDs). Ro 41-5253 enhanced differentiation of mouse and human preadipocytes and activated PPARgamma target genes in mature adipocytes. Like the TZDs, Ro 41-5253 also down-regulated PPARgamma protein expression in adipocytes. In addition, Ro 41-5253 activated the PPARgamma-ligand binding domain in transiently transfected HEK293T cells. These effects were not prevented by a potent RARalpha agonist or by depleting cells of RARalpha, indicating that PPARgamma activation was not related to RARalpha antagonism. Indeed, Ro 41-5253 was able to compete with TZD ligands for binding to PPARgamma, suggesting that Ro 41-5253 directly affects PPAR activity. These results vividly demonstrate that pharmacological NR ligands may have "off-target" effects on other NRs. Ro 41-5253 is a PPARgamma agonist as well as an RARalpha antagonist whose pleiotropic effects on NRs may signify a unique spectrum of biological responses.

  10. Thyroid hormone receptor can modulate retinoic acid-mediated axis formation in frog embryogenesis.

    PubMed Central

    Banker, D E; Eisenman, R N

    1993-01-01

    Thyroid hormone receptor acts as a hormone-dependent transcriptional transactivator and as a transcriptional repressor in the absence of thyroid hormone. Specifically, thyroid hormone receptor can repress retinoic acid-induced gene expression through interactions with retinoic acid receptor. (Retinoic acid is a potent teratogen in the frog Xenopus laevis, acting at early embryonic stages to interfere with the formation of anterior structures. Endogenous retinoic acid is thought to act in normal anterior-posterior axis formation.) We have previously shown that thyroid hormone receptor RNA (alpha isotype) is expressed and polysome-associated during Xenopus embryogenesis preceding thyroid gland maturation and endogenous thyroid hormone production (D. E. Banker, J. Bigler, and R. N. Eisenman, Mol. Cell. Biol. 11:5079-5089, 1991). To determine whether thyroid hormone receptor might influence the effects of retinoic acid in early frog development, we have examined the results of ectopic thyroid hormone receptor expression on retinoic acid teratogenesis. We demonstrate that microinjections of full-length thyroid hormone receptor RNA protect injected embryos from retinoic acid teratogenesis. DNA binding is apparently essential to this protective function, as truncated thyroid hormone receptors, lacking DNA-binding domains but including hormone-binding and dimerization domains, do not protect from retinoic acid. We have shown that microinjections of these dominant-interfering thyroid hormone receptors, as well as anti-thyroid hormone receptor antibodies, increase retinoic acid teratogenesis in injected embryos, presumably by inactivating endogenous thyroid hormone receptor. This finding suggests that endogenous thyroid hormone receptors may act to limit retinoic acid sensitivity. On the other hand, after thyroid hormone treatment, ectopic thyroid hormone receptor mediates teratogenesis that is indistinguishable from the dorsoanterior deficiencies produced in retinoic acid

  11. FATTY ACIDS MODULATE TOLL-LIKE RECEPTOR 4 ACTIVATION THROUGH REGULATION OF RECEPTOR DIMERIZATION AND RECRUITMENT INTO LIPID RAFTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The saturated fatty acids acylated on Lipid A of lipopolysaccharide (LPS) or bacterial lipoproteins play critical roles in ligand recognition and receptor activation for Toll-like Receptor 4 (TLR4) and TLR2. The results from our previous studies (J Biol Chem 2003, 2004) demonstrated that saturated ...

  12. The NMDA receptor as a target for cognitive enhancement

    PubMed Central

    Collingridge, Graham L.; Volianskis, Arturas; Bannister, Neil; France, Grace; Hanna, Lydia; Mercier, Marion; Tidball, Patrick; Fang, Guangyu; Irvine, Mark W.; Costa, Blaise M.; Monaghan, Daniel T.; Bortolotto, Zuner A.; Molnár, Elek; Lodge, David; Jane, David E.

    2015-01-01

    NMDA receptors (NMDAR) play an important role in neural plasticity including long-term potentiation and long-term depression, which are likely to explain their importance for learning and memory. Cognitive decline is a major problem facing an ageing human population, so much so that its reversal has become an important goal for scientific research and pharmaceutical development. Enhancement of NMDAR function is a core strategy toward this goal. In this review we indicate some of the major ways of potentiating NMDAR function by both direct and indirect modulation. There is good evidence that both positive and negative modulation can enhance function suggesting that a subtle approach correcting imbalances in particular clinical situations will be required. Excessive activation and the resultant deleterious effects will need to be carefully avoided. Finally we describe some novel positive allosteric modulators of NMDARs, with some subunit selectivity, and show initial evidence of their ability to affect NMDAR mediated events. PMID:22796429

  13. Local N-Methyl-D-Aspartate Receptor Antagonism in the Prefrontal Cortex Attenuates Spatial Cognitive Deficits Induced by Gonadectomy in Adult Male Rats

    PubMed Central

    Locklear, Mallory N.; Bhamidipaty, Surya; Kritzer, Mary F.

    2015-01-01

    Gonadectomy in adult male rats significantly impairs spatial working memory, behavioral flexibility and other functions associated with the prefrontal cortex (PFC). However, the mechanisms through which this occurs are largely unknown. In this study, intracortical drug challenge with the selective N-methyl-D-aspartate glutamate receptor (NMDAR) antagonist D(-)-2-amino-5-phosphonopentanoic acid (APV) was combined with Barnes maze testing, gonadectomy and hormone replacement (17β estradiol, testosterone propionate) to explore the contributions of NMDAR-mediated activity within the PFC to hormone effects on spatial cognition in adult male rats. Previous studies have shown that Barnes maze testing reveals significant estrogen-dependent, gonadectomy-induced deficits in spatial working memory and androgen-sensitive, gonadectomy-induced deficits in spatial search strategy. Here we found that bilateral infusion of APV into the medial prefrontal cortex prior to testing significantly improved both sets of behaviors in gonadectomized rats and significantly worsened performance measures in gonadally intact controls. In hormone-replaced cohorts, we further found that behaviors that are normally similar to controls were significantly disrupted by APV, and those that are normally similar to gonadectomized rats were rescued by intracortical APV infusion. There were, however, no residual effects of APV on retention testing conducted 24 hours later. Together these findings suggest that hormone regulation of NMDAR-mediated activity specifically within the PFC may be fundamental to the effects of gonadal steroids on spatial cognition in males. Our findings further identify NMDAR antagonists as potentially novel, non-steroidal means of attenuating the cognitive deficits that can accompany gonadal hormone decline in human males in aging, clinical cases of hypogonadalism and in certain neurologic and psychiatric illnesses. Accordingly, it may be important to obtain in males the kind of

  14. Retinal pigment epithelial acid lipase activity and lipoprotein receptors: effects of dietary omega-3 fatty acids.

    PubMed Central

    Elner, Victor M

    2002-01-01

    PURPOSE: To show that fish oil-derived omega-3 polyunsaturated fatty acids, delivered to the retinal pigment epithelium (RPE) by circulating low-density lipoproteins (LDL), enhance already considerable RPE lysosomal acid lipase activity, providing for more efficient hydrolysis of intralysosomal RPE lipids, an effect that may help prevent development of age-related macular degeneration (ARMD). METHODS: Colorimetric biochemical and histochemical techniques were used to demonstrate RPE acid lipase in situ, in vitro, and after challenge with phagocytic stimuli. Receptor-mediated RPE uptake of fluorescently labeled native, aceto-acetylated, and oxidized LDL was studied in vitro and in vivo. LDL effects on RPE lysosomal enzymes were assessed. Lysosomal enzyme activity was compared in RPE cells from monkeys fed diets rich in fish oil to those from control animals and in cultured RPE cells exposed to sera from these monkeys. RESULTS: RPE acid lipase activity was substantial and comparable to that of mononuclear phagocytes. Acid lipase activity increased significantly following phagocytic challenge with photoreceptor outer segment (POS) membranes. Receptor-mediated RPE uptake of labeled lipoproteins was determined in vitro. Distinctive uptake of labeled lipoproteins occurred in RPE cells and mononuclear phagocytes in vivo. Native LDL enhanced RPE lysosomal enzyme activity. RPE lysosomal enzymes increased significantly in RPE cells from monkeys fed fish oil-rich diets and in cultured RPE cells exposed to their sera. CONCLUSIONS: RPE cells contain substantial acid lipase for efficient metabolism of lipids imbibed by POS phagocytosis and LDL uptake. Diets rich in fish oil-derived omega-3 fatty acids, by enhancing acid lipase, may reduce RPE lipofuscin accumulation, RPE oxidative damage, and the development of ARMD. PMID:12545699

  15. EMBO Retinoids 2011: mechanisms, biology and pathology of signaling by retinoic acid and retinoic acid receptors

    PubMed Central

    McKenna, Neil J.

    2012-01-01

    Retinoic acid (RA) is one of the principal active metabolites of vitamin A (retinol) which mediates a spectrum of critical physiological and developmental processes. Transcriptional regulation by RA is mediated primarily by members of the retinoic acid receptor (RAR) subfamily of the nuclear receptor (NR) superfamily of transcription factors. NRs bind specific genomic DNA sequence motifs and engage coregulators and components of the basal transcription machinery to effect transcriptional regulation at target gene promoters. Disruption of signaling by retinoic acid is thought to underlie the etiology of a number of inflammatory and neoplastic diseases including breast cancer and haematological malignancies. A meeting of international researchers in retinoid signaling was convened in Strasbourg in September 2011 under the auspices of the European Molecular Biology Organization (EMBO). Retinoids 2011 encompassed myriad mechanistic, biological and pathological aspects of these hormones and their cognate receptors, as well as setting these advances in the context of wider current questions on signaling by members of the NR superfamily. PMID:22438793

  16. Human N-methyl D-aspartate receptor antibodies alter memory and behaviour in mice

    PubMed Central

    Planagumà, Jesús; Leypoldt, Frank; Mannara, Francesco; Gutiérrez-Cuesta, Javier; Martín-García, Elena; Aguilar, Esther; Titulaer, Maarten J.; Petit-Pedrol, Mar; Jain, Ankit; Balice-Gordon, Rita; Lakadamyali, Melike; Graus, Francesc; Maldonado, Rafael

    2015-01-01

    on Days 13–18), that after acid extraction and characterization with GluN1-expressing human embryonic kidney cells were confirmed to be against the NMDAR. Confocal microscopy and immunoblot analysis of the hippocampus showed progressive decrease of the density of total and synaptic NMDAR clusters and total NMDAR protein concentration (maximal on Day 18), without affecting the post-synaptic density protein 95 (PSD95) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. These effects occurred in parallel with memory and other behavioural deficits and gradually improved after Day 18, with reversibility of symptoms accompanied by a decrease of brain-bound antibodies and restoration of NMDAR levels. Overall, these findings establish a link between memory and behavioural deficits and antibody-mediated reduction of NMDAR, provide the biological basis by which removal of antibodies and antibody-producing cells improve neurological function, and offer a model for testing experimental therapies in this and similar disorders. PMID:25392198

  17. Human N-methyl D-aspartate receptor antibodies alter memory and behaviour in mice.

    PubMed

    Planagumà, Jesús; Leypoldt, Frank; Mannara, Francesco; Gutiérrez-Cuesta, Javier; Martín-García, Elena; Aguilar, Esther; Titulaer, Maarten J; Petit-Pedrol, Mar; Jain, Ankit; Balice-Gordon, Rita; Lakadamyali, Melike; Graus, Francesc; Maldonado, Rafael; Dalmau, Josep

    2015-01-01

    13-18), that after acid extraction and characterization with GluN1-expressing human embryonic kidney cells were confirmed to be against the NMDAR. Confocal microscopy and immunoblot analysis of the hippocampus showed progressive decrease of the density of total and synaptic NMDAR clusters and total NMDAR protein concentration (maximal on Day 18), without affecting the post-synaptic density protein 95 (PSD95) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. These effects occurred in parallel with memory and other behavioural deficits and gradually improved after Day 18, with reversibility of symptoms accompanied by a decrease of brain-bound antibodies and restoration of NMDAR levels. Overall, these findings establish a link between memory and behavioural deficits and antibody-mediated reduction of NMDAR, provide the biological basis by which removal of antibodies and antibody-producing cells improve neurological function, and offer a model for testing experimental therapies in this and similar disorders.

  18. Medium-chain Fatty Acid-sensing Receptor, GPR84, Is a Proinflammatory Receptor

    PubMed Central

    Suzuki, Masakatsu; Takaishi, Sachiko; Nagasaki, Miyuki; Onozawa, Yoshiko; Iino, Ikue; Maeda, Hiroaki; Komai, Tomoaki; Oda, Tomiichiro

    2013-01-01

    G protein-coupled receptor 84 (GPR84) is a putative receptor for medium-chain fatty acids (MCFAs), whose pathophysiological roles have not yet been clarified. Here, we show that GPR84 was activated by MCFAs with the hydroxyl group at the 2- or 3-position more effectively than nonhydroxylated MCFAs. We also identified a surrogate agonist, 6-n-octylaminouracil (6-OAU), for GPR84. These potential ligands and the surrogate agonist, 6-OAU, stimulated [35S]GTP binding and accumulated phosphoinositides in a GPR84-dependent manner. The surrogate agonist, 6-OAU, internalized GPR84-EGFP from the cell surface. Both the potential ligands and 6-OAU elicited chemotaxis of human polymorphonuclear leukocytes (PMNs) and macrophages and amplified LPS-stimulated production of the proinflammatory cytokine IL-8 from PMNs and TNFα from macrophages. Furthermore, the intravenous injection of 6-OAU raised the blood CXCL1 level in rats, and the inoculation of 6-OAU into the rat air pouch accumulated PMNs and macrophages in the site. Our results indicate a proinflammatory role of GPR84, suggesting that the receptor may be a novel target to treat chronic low grade inflammation associated-disease. PMID:23449982

  19. Regulation of vitamin D receptor expression by retinoic acid receptor alpha in acute myeloid leukemia cells.

    PubMed

    Marchwicka, Aleksandra; Cebrat, Małgorzata; Łaszkiewicz, Agnieszka; Śnieżewski, Łukasz; Brown, Geoffrey; Marcinkowska, Ewa

    2016-05-01

    Acute myeloid leukemia (AML) is the predominant acute leukemia among adults, characterized by an accumulation of malignant immature myeloid precursors. A very promising way to treat AML is differentiation therapy using either all-trans-retinoic acid (ATRA) or 1,25-dihydroxyvitamin D3 (1,25D), or the use of both these differentiation-inducing agents. However, the effect of combination treatment varies in different AML cell lines, and this is due to ATRA either down- or up-regulating transcription of vitamin D receptor (VDR) in the cells examined. The mechanism of transcriptional regulation of VDR in response to ATRA has not been fully elucidated. Here, we show that the retinoic acid receptor α (RARα) is responsible for regulating VDR transcription in AML cells. We have shown that a VDR transcriptional variant, originating in exon 1a, is regulated by RARα agonists in AML cells. Moreover, in cells with a high basal level of RARα protein, the VDR gene is transcriptionally repressed as long as RARα agonist is absent. In these cells down-regulation of the level of RARα leads to increased expression of VDR. We consider that our findings provide a mechanistic background to explain the different outcomes from treating AML cell lines with a combination of ATRA and 1,25D. PMID:26969398

  20. Alcohol Related Changes in Regulation of NMDA Receptor Functions

    PubMed Central

    Nagy, József

    2008-01-01

    Long-term alcohol exposure may lead to development of alcohol dependence in consequence of altered neurotransmitter functions. Accumulating evidence suggests that the N-methyl-D-aspartate (NMDA) type of glutamate receptors is a particularly important site of ethanol’s action. Several studies showed that ethanol potently inhibits NMDA receptors (NMDARs) and prolonged ethanol exposition leads to a compensatory “up-regulation” of NMDAR mediated functions. Therefore, alterations in NMDAR function are supposed to contribute to the development of ethanol tolerance, dependence as well as to the acute and late signs of ethanol withdrawal. A number of publications report alterations in the expression and phosphorylation states of NMDAR subunits, in their interaction with scaffolding proteins or other receptors in consequence of chronic ethanol treatment. Our knowledge on the regulatory processes, which modulate NMDAR functions including factors altering transcription, protein expression and post-translational modifications of NMDAR subunits, as well as those influencing their interactions with different regulatory proteins or other downstream signaling elements are incessantly increasing. The aim of this review is to summarize the complex chain of events supposedly playing a role in the up-regulation of NMDAR functions in consequence of chronic ethanol exposure. PMID:19305787

  1. Biosynthesis, biological effects, and receptors of hydroxyeicosatetraenoic acids (HETEs) and oxoeicosatetraenoic acids (oxo-ETEs) derived from arachidonic acid.

    PubMed

    Powell, William S; Rokach, Joshua

    2015-04-01

    Arachidonic acid can be oxygenated by a variety of different enzymes, including lipoxygenases, cyclooxygenases, and cytochrome P450s, and can be converted to a complex mixture of oxygenated products as a result of lipid peroxidation. The initial products in these reactions are hydroperoxyeicosatetraenoic acids (HpETEs) and hydroxyeicosatetraenoic acids (HETEs). Oxoeicosatetraenoic acids (oxo-ETEs) can be formed by the actions of various dehydrogenases on HETEs or by dehydration of HpETEs. Although a large number of different HETEs and oxo-ETEs have been identified, this review will focus principally on 5-oxo-ETE, 5S-HETE, 12S-HETE, and 15S-HETE. Other related arachidonic acid metabolites will also be discussed in less detail. 5-Oxo-ETE is synthesized by oxidation of the 5-lipoxygenase product 5S-HETE by the selective enzyme, 5-hydroxyeicosanoid dehydrogenase. It actions are mediated by the selective OXE receptor, which is highly expressed on eosinophils, suggesting that it may be important in eosinophilic diseases such as asthma. 5-Oxo-ETE also appears to stimulate tumor cell proliferation and may also be involved in cancer. Highly selective and potent OXE receptor antagonists have recently become available and could help to clarify its pathophysiological role. The 12-lipoxygenase product 12S-HETE acts by the GPR31 receptor and promotes tumor cell proliferation and metastasis and could therefore be a promising target in cancer therapy. It may also be involved as a proinflammatory mediator in diabetes. In contrast, 15S-HETE may have a protective effect in cancer. In addition to GPCRs, higher concentration of HETEs and oxo-ETEs can activate peroxisome proliferator-activated receptors (PPARs) and could potentially regulate a variety of processes by this mechanism. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance".

  2. Tulane virus recognizes sialic acids as cellular receptors.

    PubMed

    Tan, Ming; Wei, Chao; Huang, Pengwei; Fan, Qiang; Quigley, Christina; Xia, Ming; Fang, Hao; Zhang, Xufu; Zhong, Weiming; Klassen, John S; Jiang, Xi

    2015-01-01

    The recent discovery that human noroviruses (huNoVs) recognize sialic acids (SAs) in addition to histo-blood group antigens (HBGAs) pointed to a new direction in studying virus-host interactions during calicivirus infection. HuNoVs remain difficult to study due to the lack of an effective cell culture model. In this study, we demonstrated that Tulane virus (TV), a cultivable primate calicivirus, also recognizes SAs in addition to the previously known TV-HBGA interactions. Evidence supporting this discovery includes that TV virions bound synthetic sialoglycoconjugates (SGCs) and that treatment of TV permissive LLC-MK2 cells with either neuraminidases or SA-binding lectins inhibited TV infectivity. In addition, we found that Maackia amurensis leukoagglutinin (MAL), a lectin that recognizes the α-2,3 linked SAs, bound LLC-MK2 cells, as well as TV, by which MAL promoted TV infectivity in cell culture. Our findings further highlight TV as a valuable surrogate for huNoVs, particularly in studying virus-host interactions that may involve two host carbohydrate receptors or co-receptors for infection. PMID:26146020

  3. Identification of the orphan GPCR, P2Y(10) receptor as the sphingosine-1-phosphate and lysophosphatidic acid receptor.

    PubMed

    Murakami, Masanori; Shiraishi, Akira; Tabata, Kenichi; Fujita, Norihisa

    2008-07-11

    Phylogenetic analysis of transmembrane regions of GPCRs using PHYLIP indicated that the orphan receptor P2Y(10) receptor was classified into the cluster consisting nucleotide and lipid receptors. Based on the results, we studied the abilities of nucleotides and lipids to activate the P2Y(10) receptors. As a result, sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA) evoked intracellular Ca(2+) increases in the CHO cells stably expressing the P2Y(10) fused with a G(16alpha) protein. These Ca(2+) responses were inhibited by S1P receptor and LPA receptor antagonists. The introduction of siRNA designed for P2Y(10) receptor into the P2Y(10)-CHO cells effectively blocked both S1P- and LPA-induced Ca(2+) increases. RT-PCR analysis showed that the mouse P2Y(10) was expressed in reproductive organs, brain, lung and skeletal muscle, suggesting the receptor plays physiological roles throughout the whole body. In conclusion, the P2Y(10) receptor is the first receptor identified as a dual lysophospholipid receptor. PMID:18466763

  4. N-methyl-D-Aspartate Receptors Contribute to Complex Spike Signaling in Cerebellar Purkinje Cells: An In vivo Study in Mice.

    PubMed

    Liu, Heng; Lan, Yan; Bing, Yan-Hua; Chu, Chun-Ping; Qiu, De-Lai

    2016-01-01

    N-methyl-D-aspartate receptors (NMDARs) are post-synaptically expressed at climbing fiber-Purkinje cell (CF-PC) synapses in cerebellar cortex in adult mice and contributed to CF-PC synaptic transmission under in vitro conditions. In this study, we investigated the role of NMDARs at CF-PC synapses during the spontaneous complex spike (CS) activity in cerebellar cortex in urethane-anesthetized mice, by in vivo whole-cell recording technique and pharmacological methods. Under current-clamp conditions, cerebellar surface application of NMDA (50 μM) induced an increase in the CS-evoked pause of simple spike (SS) firing accompanied with a decrease in the SS firing rate. Under voltage-clamp conditions, application of NMDA enhanced the waveform of CS-evoked inward currents, which expressed increases in the area under curve (AUC) and spikelet number of spontaneous CS. NMDA increased the AUC of spontaneous CS in a concentration-dependent manner. The EC50 of NMDA for increasing AUC of spontaneous CS was 33.4 μM. Moreover, NMDA significantly increased the amplitude, half-width and decay time of CS-evoked after-hyperpolarization (AHP) currents. Blockade of NMDARs with D-(-)-2-amino-5-phosphonopentanoic acid (D-APV, 250 μM) decreased the AUC, spikelet number, and amplitude of AHP currents. In addition, the NMDA-induced enhancement of CS activity could not be observed after α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors were blocked. The results indicated that NMDARs of CF-PC synapses contributed to the spontaneous CS activity by enhancing CS-evoked inward currents and AHP currents. PMID:27445699

  5. N-methyl-D-Aspartate Receptors Contribute to Complex Spike Signaling in Cerebellar Purkinje Cells: An In vivo Study in Mice

    PubMed Central

    Liu, Heng; Lan, Yan; Bing, Yan-Hua; Chu, Chun-Ping; Qiu, De-Lai

    2016-01-01

    N-methyl-D-aspartate receptors (NMDARs) are post-synaptically expressed at climbing fiber-Purkinje cell (CF-PC) synapses in cerebellar cortex in adult mice and contributed to CF-PC synaptic transmission under in vitro conditions. In this study, we investigated the role of NMDARs at CF-PC synapses during the spontaneous complex spike (CS) activity in cerebellar cortex in urethane-anesthetized mice, by in vivo whole-cell recording technique and pharmacological methods. Under current-clamp conditions, cerebellar surface application of NMDA (50 μM) induced an increase in the CS-evoked pause of simple spike (SS) firing accompanied with a decrease in the SS firing rate. Under voltage-clamp conditions, application of NMDA enhanced the waveform of CS-evoked inward currents, which expressed increases in the area under curve (AUC) and spikelet number of spontaneous CS. NMDA increased the AUC of spontaneous CS in a concentration-dependent manner. The EC50 of NMDA for increasing AUC of spontaneous CS was 33.4 μM. Moreover, NMDA significantly increased the amplitude, half-width and decay time of CS-evoked after-hyperpolarization (AHP) currents. Blockade of NMDARs with D-(-)-2-amino-5-phosphonopentanoic acid (D-APV, 250 μM) decreased the AUC, spikelet number, and amplitude of AHP currents. In addition, the NMDA-induced enhancement of CS activity could not be observed after α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors were blocked. The results indicated that NMDARs of CF-PC synapses contributed to the spontaneous CS activity by enhancing CS-evoked inward currents and AHP currents. PMID:27445699

  6. Cinnabarinic acid, an endogenous metabolite of the kynurenine pathway, activates type 4 metabotropic glutamate receptors.

    PubMed

    Fazio, F; Lionetto, L; Molinaro, G; Bertrand, H O; Acher, F; Ngomba, R T; Notartomaso, S; Curini, M; Rosati, O; Scarselli, P; Di Marco, R; Battaglia, G; Bruno, V; Simmaco, M; Pin, J P; Nicoletti, F; Goudet, C

    2012-05-01

    Cinnabarinic acid is an endogenous metabolite of the kynurenine pathway that meets the structural requirements to interact with glutamate receptors. We found that cinnabarinic acid acts as a partial agonist of type 4 metabotropic glutamate (mGlu4) receptors, with no activity at other mGlu receptor subtypes. We also tested the activity of cinnabarinic acid on native mGlu4 receptors by examining 1) the inhibition of cAMP formation in cultured cerebellar granule cells; 2) protection against excitotoxic neuronal death in mixed cultures of cortical cells; and 3) protection against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity in mice after local infusion into the external globus pallidus. In all these models, cinnabarinic acid behaved similarly to conventional mGlu4 receptor agonists, and, at least in cultured neurons, the action of low concentrations of cinnabarinic acid was largely attenuated by genetic deletion of mGlu4 receptors. However, high concentrations of cinnabarinic acid were still active in the absence of mGlu4 receptors, suggesting that the compound may have off-target effects. Mutagenesis and molecular modeling experiments showed that cinnabarinic acid acts as an orthosteric agonist interacting with residues of the glutamate binding pocket of mGlu4. Accordingly, cinnabarinic acid did not activate truncated mGlu4 receptors lacking the N-terminal Venus-flytrap domain, as opposed to the mGlu4 receptor enhancer, N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxamide (PHCCC). Finally, we could detect endogenous cinnabarinic acid in brain tissue and peripheral organs by high-performance liquid chromatography-tandem mass spectrometry analysis. Levels increased substantially during inflammation induced by lipopolysaccharide. We conclude that cinnabarinic acid is a novel endogenous orthosteric agonist of mGlu4 receptors endowed with neuroprotective activity. PMID:22311707

  7. Enhancement of arachidonic acid signaling pathway by nicotinic acid receptor HM74A

    SciTech Connect

    Tang, Yuting . E-mail: ytang@prdus.jnj.com; Zhou, Lubing; Gunnet, Joseph W.; Wines, Pamela G.; Cryan, Ellen V.; Demarest, Keith T.

    2006-06-23

    HM74A is a G protein-coupled receptor for nicotinic acid (niacin), which has been used clinically to treat dyslipidemia for decades. The molecular mechanisms whereby niacin exerts its pleiotropic effects on lipid metabolism remain largely unknown. In addition, the most common side effect in niacin therapy is skin flushing that is caused by prostaglandin release, suggesting that the phospholipase A{sub 2} (PLA{sub 2})/arachidonic acid (AA) pathway is involved. Various eicosanoids have been shown to activate peroxisome-proliferator activated receptors (PPAR) that play a diverse array of roles in lipid metabolism. To further elucidate the potential roles of HM74A in mediating the therapeutic effects and/or side effects of niacin, we sought to explore the signaling events upon HM74A activation. Here we demonstrated that HM74A synergistically enhanced UTP- and bradykinin-mediated AA release in a pertussis toxin-sensitive manner in A431 cells. Activation of HM74A also led to Ca{sup 2+}-mobilization and enhanced bradykinin-promoted Ca{sup 2+}-mobilization through Gi protein. While HM74A increased ERK1/2 activation by the bradykinin receptor, it had no effects on UTP-promoted ERK1/2 activation.Furthermore, UTP- and bradykinin-mediated AA release was significantly decreased in the presence of both MAPK kinase inhibitor PD 098059 and PKC inhibitor GF 109203X. However, the synergistic effects of HM74A were not dramatically affected by co-treatment with both inhibitors, indicating the cross-talk occurred at the receptor level. Finally, stimulation of A431 cells transiently transfected with PPRE-luciferase with AA significantly induced luciferase activity, mimicking the effects of PPAR{gamma} agonist rosiglitazone, suggesting that alteration of AA signaling pathway can regulate gene expression via endogenous PPARs.

  8. Obeticholic acid, a synthetic bile acid agonist of the farnesoid X receptor, attenuates experimental autoimmune encephalomyelitis

    PubMed Central

    Ho, Peggy P.; Steinman, Lawrence

    2016-01-01

    Bile acids are ligands for the nuclear hormone receptor, farnesoid X receptor (FXR). The bile acid–FXR interaction regulates bile acid synthesis, transport, and cholesterol metabolism. Recently, bile acid–FXR regulation has been reported to play an integral role in both hepatic and intestinal inflammation, and in atherosclerosis. In this study, we found that FXR knockout mice had more disease severity in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Obeticholic acid (6α-ethyl-chenodeoxycholic acid, 6-ECDCA), a synthetic FXR agonist, is an orally available drug that is currently in clinical trials for the treatment of inflammatory diseases such as alcoholic hepatitis, nonalcoholic steatohepatitis, and primary biliary cirrhosis. When we treated mice exhibiting established EAE with 6-ECDCA, or the natural FXR ligand chenodeoxycholic acid (CDCA), clinical disease was ameliorated by (i) suppressing lymphocyte activation and proinflammatory cytokine production; (ii) reducing CD4+ T cells and CD19+ B cell populations and their expression of negative checkpoint regulators programmed cell death protein 1 (PD1), programmed death-ligand 1 (PD-L1), and B and T lymphocyte attenuator (BTLA); (iii) increasing CD8+ T cells and PD1, PDl-1, and BTLA expression; and (iv) reducing VLA-4 expression in both the T- and B-cell populations. Moreover, adoptive transfer of 6-ECDCA– or CDCA-treated donor cells failed to transfer disease in naive recipients. Thus, we show that FXR functions as a negative regulator in neuroinflammation and we highlight that FXR agonists represent a potential previously unidentified therapy for MS. PMID:26811456

  9. Farnesoid X receptor, the bile acid sensing nuclear receptor, in liver regeneration

    PubMed Central

    Li, Guodong; L. Guo, Grace

    2015-01-01

    The liver is unique in regenerative potential, which could recover the lost mass and function after injury from ischemia and resection. The underlying molecular mechanisms of liver regeneration have been extensively studied in the past using the partial hepatectomy (PH) model in rodents, where 2/3 PH is carried out by removing two lobes. The whole process of liver regeneration is complicated, orchestrated event involving a network of connected interactions, which still remain fully elusive. Bile acids (BAs) are ligands of farnesoid X receptor (FXR), a nuclear receptor of ligand-activated transcription factor. FXR has been shown to be highly involved in liver regeneration. BAs and FXR not only interact with each other but also regulate various downstream targets independently during liver regeneration. Moreover, recent findings suggest that tissue-specific FXR also contributes to liver regeneration significantly. These novel findings suggest that FXR has much broader role than regulating BA, cholesterol, lipid and glucose metabolism. Therefore, these researches highlight FXR as an important pharmaceutical target for potential use of FXR ligands to regulate liver regeneration in clinic. This review focuses on the roles of BAs and FXR in liver regeneration and the current underlying molecular mechanisms which contribute to liver regeneration. PMID:26579433

  10. Lysophosphatidic Acid (LPA) Receptor 5 Inhibits B Cell Antigen Receptor Signaling and Antibody Response1

    PubMed Central

    Shotts, Kristin; Donovan, Erin E.; Strauch, Pamela; Pujanauski, Lindsey M.; Victorino, Francisco; Al-Shami, Amin; Fujiwara, Yuko; Tigyi, Gabor; Oravecz, Tamas; Pelanda, Roberta; Torres, Raul M.

    2014-01-01

    Lysophospholipids have emerged as biologically important chemoattractants capable of directing lymphocyte development, trafficking and localization. Lysophosphatidic acid (LPA) is a major lysophospholipid found systemically and whose levels are elevated in certain pathological settings such as cancer and infections. Here, we demonstrate that BCR signal transduction by mature murine B cells is inhibited upon LPA engagement of the LPA5 (GPR92) receptor via a Gα12/13 – Arhgef1 pathway. The inhibition of BCR signaling by LPA5 manifests by impaired intracellular calcium store release and most likely by interfering with inositol 1,4,5-trisphosphate receptor activity. We further show that LPA5 also limits antigen-specific induction of CD69 and CD86 expression and that LPA5-deficient B cells display enhanced antibody responses. Thus, these data show that LPA5 negatively regulates BCR signaling, B cell activation and immune response. Our findings extend the influence of lysophospholipids on immune function and suggest that alterations in LPA levels likely influence adaptive humoral immunity. PMID:24890721

  11. The neurobiology of D-amino acid oxidase (DAO) and its involvement in schizophrenia

    PubMed Central

    Verrall, L; Burnet, PWJ; Betts, JF; Harrison, PJ

    2010-01-01

    D-amino acid oxidase (DAO, DAAO) is a flavoenzyme that metabolises certain D-amino acids, notably the endogenous N-methyl D-aspartate receptor (NMDAR) co-agonist, D-serine. As such, it has the potential to modulate NMDAR function and to contribute to the widely hypothesized involvement of NMDAR signalling in schizophrenia. Three lines of evidence now provide support for this possibility: DAO shows genetic associations to the disorder in several, though not all, studies; the expression and activity of DAO are increased in schizophrenia; and DAO inactivation in rodents produces behavioural and biochemical effects suggestive of potential therapeutic benefits. However, several key issues remain unclear. These include the regional, cellular and subcellular localization of DAO, the physiological importance of DAO and of its substrates other than D-serine, and the causes and consequences of elevated DAO in schizophrenia. Here we critically review the neurobiology of DAO, its involvement in schizophrenia, and the therapeutic value of DAO inhibition. The review also illuminates issues that have a broader relevance beyond DAO itself: how should we weigh up convergent and cumulatively impressive, but individually inconclusive, pieces of evidence regarding the role that a given gene may play in the aetiology, pathophysiology, and pharmacotherapy of schizophrenia? PMID:19786963

  12. Direct activation of GABAA receptors by substances in the organic acid fraction of Japanese sake.

    PubMed

    Izu, Hanae; Shigemori, Kensuke; Eguchi, Masaya; Kawane, Shuhei; Fujii, Shouko; Kitamura, Yuji; Aoshima, Hitoshi; Yamada, Yasue

    2017-01-01

    We investigated the effect of substances present in Japanese sake on the response of ionotropic γ-aminobutyric acid (GABA)A receptors expressed in Xenopus oocytes. Sake was fractionated by ion-exchange chromatography. The fraction containing organic acids (OA fraction) showed agonist activities on the GABAA receptor. OA fractions from sake were analyzed by capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS). Of the 64 compounds identified, 13 compounds showed GABAA receptor agonist activities. Especially, l-lactic acid showed high agonist activity and its EC50 value was 37μM. Intraperitoneal injections of l-lactic acid, gluconic acid, and pyruvic acid (10, 10, and 5mg/kg BW, respectively), which showed agonistic activity on the GABAA receptor, led to significant anxiolytic effects during an elevated plus-maze test in mice. PMID:27507485

  13. Coantagonism of Glutamate Receptors and Nicotinic Acetylcholinergic Receptors Disrupts Fear Conditioning and Latent Inhibition of Fear Conditioning

    ERIC Educational Resources Information Center

    Gould, Thomas J.; Lewis, Michael C.

    2005-01-01

    The present study investigated the hypothesis that both nicotinic acetylcholinergic receptors (nAChRs) and glutamate receptors ([alpha]-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptors (AMPARs) and N-methyl-D-aspartate glutamate receptors (NMDARs)) are involved in fear conditioning, and may modulate similar processes. The effects of the…

  14. Effects of arsenic exposure from drinking water on spatial memory, ultra-structures and NMDAR gene expression of hippocampus in rats.

    PubMed

    Luo, Jiao-hua; Qiu, Zhi-qun; Shu, Wei-qun; Zhang, Yong-yan; Zhang, Liang; Chen, Ji-an

    2009-01-30

    Epidemiological investigations indicate that chronic arsenic exposure can damage neurobehavioral function in children. The present study was aimed to study the effects of arsenic exposure from drinking water on the spatial memory, and hippocampal ultra-structures and N-methyl-d-aspartate receptor (NMDAR) gene expression in rats. Sprague-Dawley rats were assigned to four groups: rats in control group drank regular water, rats in other groups drank water with final arsenic concentration of 2.72 mg/L (group A), 13.6 mg/L (group B) and 68 mg/L (group C), respectively, for 3 months. The levels of arsenic in blood serum and hippocampus were monitored. Rats were tested in Morris water maze (MWM) for memory status. Samples of hippocampus were collected from two rats in each group for transmission electron microscopic study and the detection of NMDAR expression by RT-PCR. The rats in group C showed a significant delay in hidden platform acquisition. Neurons and endothelial cells presented pathological changes and the expression of NR2A was down-regulated in hippocampus in arsenic exposed rats. Our data indicated that arsenic exposure of 68 mg/L caused spatial memory damage, of which the morphological and biochemical bases could be the ultra-structure changes and reduced NR2A expression in hippocampus.

  15. Polymorphisms in MicroRNA Genes And Genes Involving in NMDAR Signaling and Schizophrenia: A Case-Control Study in Chinese Han Population.

    PubMed

    Zhang, Yanxia; Fan, Mei; Wang, Qingzhong; He, Guang; Fu, Yingmei; Li, Huafang; Yu, Shunying

    2015-08-10

    Disturbances in glutamate signaling caused by disruption of N-methyl-D-aspartate-type glutamate receptor (NMDAR) have been implicated in schizophrenia. Findings suggested that miR-219, miR-132 and miR-107 could involve in NMDAR signaling by influencing the expression of pathway genes or the signaling transmission and single nucleotide polymorphisms (SNPs) within miRNA genes or miRNA target sites could result in their functional changes. Therefore, we hypothesized that SNPs in miRNAs and/or their target sites were associated with schizophrenia. 3 SNPs in hsa-pri-miR-219/132/107 and 6 SNPs in 3'UTRs of GRIN2A/2B/3A and CAMK2G were selected and genotyped in a case-control study of 1041 schizophrenia cases and 953 healthy controls in Chinese Han population. In the present study, GRIN2B rs890 showed significant associations with schizophrenia. Further functional analyses showed that the rs890 variant C allele led to significantly lower luciferase activity, compared with the A allele. MDR analysis showed that a 4-locus model including rs107822, rs2306327, rs890 and rs12342026 was the best model. These findings suggest that GRIN2B may be associated with schizophrenia and interaction effects of the polymorphisms in hsa-miR-219, CAKM2G, GRIN2B and GRIN3A may confer susceptibility to schizophrenia in the Chinese Han population.

  16. Genetic Inactivation of D-Amino Acid Oxidase Enhances Extinction and Reversal Learning in Mice

    ERIC Educational Resources Information Center

    Labrie, Viviane; Duffy, Steven; Wang, Wei; Barger, Steven W.; Baker, Glen B.; Roder, John C.

    2009-01-01

    Activation of the N-methyl-d-aspartate receptor (NMDAR) glycine site has been shown to accelerate adaptive forms of learning that may benefit psychopathologies involving cognitive and perseverative disturbances. In this study, the effects of increasing the brain levels of the endogenous NMDAR glycine site agonist D-serine, through the genetic…

  17. Identification of Hydroxybenzoic Acids as Selective Lactate Receptor (GPR81) Agonists with Antilipolytic Effects.

    PubMed

    Dvorak, Curt A; Liu, Changlu; Shelton, Jonathan; Kuei, Chester; Sutton, Steven W; Lovenberg, Timothy W; Carruthers, Nicholas I

    2012-08-01

    Following the characterization of the lactate receptor (GPR81), a focused screening effort afforded 3-hydroxybenzoic acid 1 as a weak agonist of both GPR81 and GPR109a (niacin receptor). An examination of structurally similar arylhydroxy acids led to the identification of 3-chloro-5-hydroxybenzoic acid 2, a selective GPR81 agonist that exhibited favorable in vivo effects on lipolysis in a mouse model of obesity.

  18. Identification of Hydroxybenzoic Acids as Selective Lactate Receptor (GPR81) Agonists with Antilipolytic Effects

    PubMed Central

    2012-01-01

    Following the characterization of the lactate receptor (GPR81), a focused screening effort afforded 3-hydroxybenzoic acid 1 as a weak agonist of both GPR81 and GPR109a (niacin receptor). An examination of structurally similar arylhydroxy acids led to the identification of 3-chloro-5-hydroxybenzoic acid 2, a selective GPR81 agonist that exhibited favorable in vivo effects on lipolysis in a mouse model of obesity. PMID:24900524

  19. NR2A- and NR2B-containing NMDA receptors in the prelimbic medial prefrontal cortex differentially mediate trace, delay, and contextual fear conditioning.

    PubMed

    Gilmartin, Marieke R; Kwapis, Janine L; Helmstetter, Fred J

    2013-05-15

    Activation of N-methyl-D-aspartate receptors (NMDAR) in the prelimbic medial prefrontal cortex (PL mPFC) is necessary for the acquisition of both trace and contextual fear memories, but it is not known how specific NR2 subunits support each association. The NR2B subunit confers unique properties to the NMDAR and may differentially regulate these two fear memories. Here we show that NR2A-containing NMDARs mediate trace, delay, and contextual fear memories, but NR2B-containing NMDARs are required only for trace conditioning, consistent with a role for PL mPFC in working memory.

  20. NMDA receptor surface mobility depends on NR2A-2B subunits

    PubMed Central

    Groc, Laurent; Heine, Martin; Cousins, Sarah L.; Stephenson, F. Anne; Lounis, Brahim; Cognet, Laurent; Choquet, Daniel

    2006-01-01

    The NR2 subunit composition of NMDA receptors (NMDARs) varies during development, and this change is important in NMDAR-dependent signaling. In particular, synaptic NMDAR switch from containing mostly NR2B subunit to a mixture of NR2B and NR2A subunits. The pathways by which neurons differentially traffic NR2A- and NR2B-containing NMDARs are poorly understood. Using single-particle and -molecule approaches and specific antibodies directed against NR2A and NR2B extracellular epitopes, we investigated the surface mobility of native NR2A and NR2B subunits at the surface of cultured neurons. The surface mobility of NMDARs depends on the NR2 subunit subtype, with NR2A-containing NMDARs being more stable than NR2B-containing ones, and NR2A subunit overexpression stabilizes surface NR2B-containing NMDARs. The developmental change in the synaptic surface content of NR2A and NR2B subunits was correlated with a developmental change in the time spent by the subunits within synapses. This suggests that the switch in synaptic NMDAR subtypes depends on the regulation of the receptor surface trafficking. PMID:17124177

  1. Distinct Phosphorylation Clusters Determine the Signaling Outcome of Free Fatty Acid Receptor 4/G Protein-Coupled Receptor 120.

    PubMed

    Prihandoko, Rudi; Alvarez-Curto, Elisa; Hudson, Brian D; Butcher, Adrian J; Ulven, Trond; Miller, Ashley M; Tobin, Andrew B; Milligan, Graeme

    2016-05-01

    It is established that long-chain free fatty acids includingω-3 fatty acids mediate an array of biologic responses through members of the free fatty acid (FFA) receptor family, which includes FFA4. However, the signaling mechanisms and modes of regulation of this receptor class remain unclear. Here, we employed mass spectrometry to determine that phosphorylation of mouse (m)FFAR4 occurs at five serine and threonine residues clustered in two separable regions of the C-terminal tail, designated cluster 1 (Thr(347), Thr(349), and Ser(350)) and cluster 2 (Ser(357)and Ser(361)). Mutation of these phosphoacceptor sites to alanine completely prevented phosphorylation of mFFA4 but did not limit receptor coupling to extracellular signal regulated protein kinase 1 and 2 (ERK1/2) activation. Rather, an inhibitor of Gq/11proteins completely prevented receptor signaling to ERK1/2. By contrast, the recruitment of arrestin 3, receptor internalization, and activation of Akt were regulated by mFFA4 phosphorylation. The analysis of mFFA4 phosphorylation-dependent signaling was extended further by selective mutations of the phosphoacceptor sites. Mutations within cluster 2 did not affect agonist activation of Akt but instead significantly compromised receptor internalization and arrestin 3 recruitment. Distinctly, mutation of the phosphoacceptor sites within cluster 1 had no effect on receptor internalization and had a less extensive effect on arrestin 3 recruitment but significantly uncoupled the receptor from Akt activation. These unique observations define differential effects on signaling mediated by phosphorylation at distinct locations. This hallmark feature supports the possibility that the signaling outcome of mFFA4 activation can be determined by the pattern of phosphorylation (phosphorylation barcode) at the C terminus of the receptor.

  2. Dominant negative retinoic acid receptor initiates tumor formation in mice

    PubMed Central

    Kupumbati, Tara S; Cattoretti, Giorgio; Marzan, Christine; Farias, Eduardo F; Taneja, Reshma; Mira-y-Lopez, Rafael

    2006-01-01

    Background Retinoic acid suppresses cell growth and promotes cell differentiation, and pharmacological retinoic acid receptor (RAR) activation is anti-tumorigenic. This begs the question of whether chronic physiological RAR activation by endogenous retinoids is likewise anti-tumorigenic. Results To address this question, we generated transgenic mice in which expression of a ligand binding defective dominant negative RARα (RARαG303E) was under the control of the mouse mammary tumor virus (MMTV) promoter. The transgene was expressed in the lymphoid compartment and in the mammary epithelium. Observation of aging mice revealed that transgenic mice, unlike their wild type littermates, developed B cell lymphomas at high penetrance, with a median latency of 40 weeks. MMTV-RARαG303E lymphomas were high grade Pax-5+, surface H+L Ig negative, CD69+ and BCL6- and cytologically and phenotypically resembled human adult high grade (Burkitt's or lymphoblastic) lymphomas. We postulated that mammary tumors might arise after a long latency period as seen in other transgenic models of breast cancer. We tested this idea by transplanting transgenic epithelium into the cleared fat pads of wild type hosts, thus bypassing lymphomagenesis. At 17 months post-transplantation, a metastatic mammary adenocarcinoma developed in one of four transplanted glands whereas no tumors developed in sixteen of sixteen endogenous glands with wild type epithelium. Conclusion These findings suggest that physiological RAR activity may normally suppress B lymphocyte and mammary epithelial cell growth and that global RAR inactivation is sufficient to initiate a stochastic process of tumor development requiring multiple transforming events. Our work makes available to the research community a new animal resource that should prove useful as an experimental model of aggressive sporadic lymphoma in immunologically uncompromised hosts. We anticipate that it may also prove useful as a model of breast cancer. PMID

  3. Expression of retinoic acid receptors in human endometrial carcinoma.

    PubMed

    Tanabe, Kojiro; Utsunomiya, Hiroki; Tamura, Mitsutoshi; Niikura, Hitoshi; Takano, Tadao; Yoshinaga, Kohsuke; Nagase, Satoru; Suzuki, Takashi; Ito, Kiyoshi; Matsumoto, Mitsuyo; Hayashi, Shin-ichi; Yaegashi, Nobuo

    2008-02-01

    The retinoids (vitamin A and its biologically active derivatives) are essential for the health and survival of the individual. Several studies have reported a strong rationale for the use of retinoids in cancer treatment and chemoprevention. It has been discovered that expression of retinoic acid receptor (RAR) beta is frequently silenced in epithelial carcinogenesis, which has led to the hypothesis that RAR beta could act as a tumor suppressor. However, the status of RAR beta in human endometrial carcinoma has not been examined. In the present study, we initially studied the effects of retinoic acid on cell proliferation and the expression of RAR alpha, RAR beta, and RAR gamma using AM580 (a RAR-specific agonist) in the Ishikawa endometrial cancer cell line. We also examined the expression of RAR in human eutopic endometrium (30 cases), endometrial hyperplasia (28 cases), and endometrial carcinoma (103 cases) using immunohistochemistry. Finally, we correlated these findings with the clinicopathological parameters. In vitro, cell growth was inhibited and RAR beta and RAR gamma mRNA was significantly induced by AM580, compared with vehicle controls, whereas RAR alpha mRNA was significantly attenuated by AM580, compared with vehicle. RAR beta was detected predominantly in endometrial hyperplasia, compared with endometrial carcinoma. No statistically significant correlation was obtained between the expression of any other RAR subtypes and clinicopathological parameters in human endometrial carcinoma. The results of our study demonstrate that AM580 inhibits cell growth and induces RAR beta mRNA expression in the Ishikawa cell line, and the expression level of RAR beta in endometrial carcinoma is significantly lower than that in endometrial hyperplasia. AM580 might therefore be considered as a potential treatment for endometrial carcinoma.

  4. Structural basis and functions of abscisic acid receptors PYLs

    PubMed Central

    Zhang, Xing L.; Jiang, Lun; Xin, Qi; Liu, Yang; Tan, Jian X.; Chen, Zhong Z.

    2015-01-01

    Abscisic acid (ABA) plays a key role in many developmental processes and responses to adaptive stresses in plants. Recently, a new family of nucleocytoplasmic PYR/PYL/RCAR (PYLs) has been identified as bona fide ABA receptors. PYLs together with protein phosphatases type-2C (PP2Cs), Snf1 (Sucrose-non-fermentation 1)-related kinases subfamily 2 (SnRK2s) and downstream substrates constitute the core ABA signaling network. Generally, PP2Cs inactivate SnRK2s kinases by physical interaction and direct dephosphorylation. Upon ABA binding, PYLs change their conformations and then contact and inhibit PP2Cs, thus activating SnRK2s. Here, we reviewed the recent progress in research regarding the structures of the core signaling pathways of ABA, including the (+)-ABA, (−)-ABA and ABA analogs pyrabactin as well as 6AS perception by PYLs, SnRK2s mimicking PYLs in binding PP2Cs. PYLs inhibited PP2Cs in both the presence and absence of ABA and activated SnRK2s. The present review elucidates multiple ABA signal perception and transduction by PYLs, which might shed light on how to design small chemical compounds for improving plant performance in the future. PMID:25745428

  5. Characterization of DNA Binding and Retinoic Acid Binding Properties of Retinoic Acid Receptor

    NASA Astrophysics Data System (ADS)

    Yang, Na; Schule, Roland; Mangelsdorf, David J.; Evans, Ronald M.

    1991-05-01

    High-level expression of the full-length human retinoic acid receptor (RAR) α and the DNA binding domain of the RAR in Escherichia coli was achieved by using a T7 RNA polymerase-directed expression system. After induction, full-length RAR protein was produced at an estimated level of 20% of the total bacterial proteins. Both intact RAR molecules and the DNA binding domain bind to the cognate DNA response element with high specificity in the absence of retinoic acid. However, this binding is enhanced to a great extent upon the addition of eukaryotic cell extracts. The factor responsible for this enhancement is heat-sensitive and forms a complex with RAR that binds to DNA and exhibits a distinct migration pattern in the gel-mobility-shift assay. The interaction site of the factor with RAR is localized in the 70-amino acid DNA binding region of RAR. The hormone binding ability of the RARα protein was assayed by a charcoal absorption assay and the RAR protein was found to bind to retinoic acid with a K_d of 2.1 x 10-10 M.

  6. Allosteric modulators of NR2B-containing NMDA receptors: molecular mechanisms and therapeutic potential.

    PubMed

    Mony, Laetitia; Kew, James N C; Gunthorpe, Martin J; Paoletti, Pierre

    2009-08-01

    N-methyl-D-aspartate receptors (NMDARs) are ion channels gated by glutamate, the major excitatory neurotransmitter in the mammalian central nervous system (CNS). They are widespread in the CNS and are involved in numerous physiological and pathological processes including synaptic plasticity, chronic pain and psychosis. Aberrant NMDAR activity also plays an important role in the neuronal loss associated with ischaemic insults and major degenerative disorders including Parkinson's and Alzheimer's disease. Agents that target and alter NMDAR function may, thus, have therapeutic benefit. Interestingly, NMDARs are endowed with multiple extracellular regulatory sites that recognize ions or small molecule ligands, some of which are likely to regulate receptor function in vivo. These allosteric sites, which differ from agonist-binding and channel-permeation sites, provide means to modulate, either positively or negatively, NMDAR activity. The present review focuses on allosteric modulation of NMDARs containing the NR2B subunit. Indeed, the NR2B subunit confers a particularly rich pharmacology with distinct recognition sites for exogenous and endogenous allosteric ligands. Moreover, NR2B-containing receptors, compared with other NMDAR subtypes, appear to contribute preferentially to pathological processes linked to overexcitation of glutamatergic pathways. The actions of extracellular H+, Mg2+, Zn2+, of polyamines and neurosteroids, and of the synthetic compounds ifenprodil and derivatives ('prodils') are presented. Particular emphasis is put upon the structural determinants and molecular mechanisms that underlie the effects exerted by these agents. A better understanding of how NR2B-containing NMDARs (and NMDARs in general) operate and how they can be modulated should help define new strategies to counteract the deleterious effects of dysregulated NMDAR activity.

  7. Block of NMDA receptor channels by endogenous neurosteroids: implications for the agonist induced conformational states of the channel vestibule

    PubMed Central

    Vyklicky, Vojtech; Krausova, Barbora; Cerny, Jiri; Balik, Ales; Zapotocky, Martin; Novotny, Marian; Lichnerova, Katarina; Smejkalova, Tereza; Kaniakova, Martina; Korinek, Miloslav; Petrovic, Milos; Kacer, Petr; Horak, Martin; Chodounska, Hana; Vyklicky, Ladislav

    2015-01-01

    N-methyl-D-aspartate receptors (NMDARs) mediate synaptic plasticity, and their dysfunction is implicated in multiple brain disorders. NMDARs can be allosterically modulated by numerous compounds, including endogenous neurosteroid pregnanolone sulfate. Here, we identify the molecular basis of the use-dependent and voltage-independent inhibitory effect of neurosteroids on NMDAR responses. The site of action is located at the extracellular vestibule of the receptor’s ion channel pore and is accessible after receptor activation. Mutations in the extracellular vestibule in the SYTANLAAF motif disrupt the inhibitory effect of negatively charged steroids. In contrast, positively charged steroids inhibit mutated NMDAR responses in a voltage-dependent manner. These results, in combination with molecular modeling, characterize structure details of the open configuration of the NMDAR channel. Our results provide a unique opportunity for the development of new therapeutic neurosteroid-based ligands to treat diseases associated with dysfunction of the glutamate system. PMID:26086919

  8. Autocrine activation of neuronal NMDA receptors by aspartate mediates dopamine- and cAMP-induced CREB-dependent gene transcription.

    PubMed

    Almeida, Luis E F; Murray, Peter D; Zielke, H Ronald; Roby, Clinton D; Kingsbury, Tami J; Krueger, Bruce K

    2009-10-01

    cAMP can stimulate the transcription of many activity-dependent genes via activation of the transcription factor, cAMP response element-binding protein (CREB). However, in mouse cortical neuron cultures, prior to synaptogenesis, neither cAMP nor dopamine, which acts via cAMP, stimulated CREB-dependent gene transcription when NR2B-containing NMDA receptors (NMDARs) were blocked. Stimulation of transcription by cAMP was potentiated by inhibitors of excitatory amino acid uptake, suggesting a role for extracellular glutamate or aspartate in cAMP-induced transcription. Aspartate was identified as the extracellular messenger: enzymatic scavenging of l-aspartate, but not glutamate, blocked stimulation of CREB-dependent gene transcription by cAMP; moreover, cAMP induced aspartate but not glutamate release. Together, these results suggest that cAMP acts via an autocrine or paracrine pathway to release aspartate, which activates NR2B-containing NMDARs, leading to Ca(2+) entry and activation of transcription. This cAMP/aspartate/NMDAR signaling pathway may mediate the effects of transmitters such as dopamine on axon growth and synaptogenesis in developing neurons or on synaptic plasticity in mature neural networks.

  9. NR2A- and NR2B-Containing NMDA Receptors in the Prelimbic Medial Prefrontal Cortex Differentially Mediate Trace, Delay, and Contextual Fear Conditioning

    ERIC Educational Resources Information Center

    Gilmartin, Marieke R.; Kwapis, Janine L.; Helmstetter, Fred J.

    2013-01-01

    Activation of "N"-methyl-D-aspartate receptors (NMDAR) in the prelimbic medial prefrontal cortex (PL mPFC) is necessary for the acquisition of both trace and contextual fear memories, but it is not known how specific NR2 subunits support each association. The NR2B subunit confers unique properties to the NMDAR and may differentially…

  10. Among the twenty classical L-amino acids, only glutamate directly activates metabotropic glutamate receptors.

    PubMed

    Frauli, Mélanie; Neuville, Pascal; Vol, Claire; Pin, Jean-Philippe; Prézeau, Laurent

    2006-02-01

    Under pathophysiological conditions, cellular amino acids can be profusely released from cells into the cerebral interstitial space. Because several class-C G protein coupled receptors (GPCRs) display a broad natural ligand spectrum, being sensitive to more than one endogenous ligand, we wondered whether the related metabotropic glutamate (mGlu) receptors could be modulated by various types of L-amino acids, allowing them to sense large increase in extracellular amino acid concentration. Here, the agonist, antagonist and allosteric effects of the twenty classical L-amino acids were evaluated on the eight mGlu receptor subtypes. We show that, in addition to glutamate (Glu), cysteine, aspartate and asparagine also lead to the activation of mGlu3, 4 and 5. Interestingly, our data demonstrate that the effect of these three amino acids did not result from a direct activation of the receptors, but from an indirect action involving Glu-transporters/exchangers. These data first demonstrate that mGlu receptors, unlike other class-C GPCRs, display an extremely high selectivity towards one ligand. Moreover, our results also show that Glu transport systems allow mGlu receptors to sense large increase in the extracellular concentration of some amino acids. Such a system will certainly lead to a large increase in some mGlu receptor activity under pathological conditions, such as seizure, ischemia or other brain injuries. PMID:16310227

  11. Interaction between retinoid acid receptor-related orphan receptor alpha (RORA) and neuropeptide S receptor 1 (NPSR1) in asthma.

    PubMed

    Acevedo, Nathalie; Sääf, Annika; Söderhäll, Cilla; Melén, Erik; Mandelin, Jami; Pietras, Christina Orsmark; Ezer, Sini; Karisola, Piia; Vendelin, Johanna; Gennäs, Gustav Boije af; Yli-Kauhaluoma, Jari; Alenius, Harri; von Mutius, Erika; Doekes, Gert; Braun-Fahrländer, Charlotte; Riedler, Josef; van Hage, Marianne; D'Amato, Mauro; Scheynius, Annika; Pershagen, Göran; Kere, Juha; Pulkkinen, Ville

    2013-01-01

    Retinoid acid receptor-related Orphan Receptor Alpha (RORA) was recently identified as a susceptibility gene for asthma in a genome-wide association study. To investigate the impact of RORA on asthma susceptibility, we performed a genetic association study between RORA single nucleotide polymorphisms (SNPs) in the vicinity of the asthma-associated SNP (rs11071559) and asthma-related traits. Because the regulatory region of a previously implicated asthma susceptibility gene, Neuropeptide S receptor 1 (NPSR1), has predicted elements for RORA binding, we hypothesized that RORA may interact biologically and genetically with NPSR1. 37 RORA SNPs and eight NPSR1 SNPs were genotyped in the Swedish birth cohort BAMSE (2033 children) and the European cross-sectional PARSIFAL study (1120 children). Seven RORA SNPs confined into a 49 kb region were significantly associated with physician-diagnosed childhood asthma. The most significant association with rs7164773 (T/C) was driven by the CC genotype in asthma cases (OR = 2.0, 95%CI 1.36-2.93, p = 0.0003 in BAMSE; and 1.61, 1.18-2.19, p = 0.002 in the combined BAMSE-PARSIFAL datasets, respectively), and strikingly, the risk effect was dependent on the Gln344Arg mutation in NPSR1. In cell models, stimulation of NPSR1 activated a pathway including RORA and other circadian clock genes. Over-expression of RORA decreased NPSR1 promoter activity further suggesting a regulatory loop between these genes. In addition, Rora mRNA expression was lower in the lung tissue of Npsr1 deficient mice compared to wildtype littermates during the early hours of the light period. We conclude that RORA SNPs are associated with childhood asthma and show epistasis with NPSR1, and the interaction between RORA and NPSR1 may be of biological relevance. Combinations of common susceptibility alleles and less common functional polymorphisms may modify the joint risk effects on asthma susceptibility. PMID:23565190

  12. Biochemical principles underlying the stable maintenance of LTP by the CaMKII/NMDAR complex

    PubMed Central

    Lisman, John; Raghavachari, Sridhar

    2014-01-01

    Memory involves the storage of information at synapses by an LTP-like process. This information storage is synapse specific and can endure for years despite the turnover of all synaptic proteins. There must, therefore, be special principles that underlie the stability of LTP. Recent experimental results suggest that LTP is maintained by the complex of CaMKII with the NMDAR. Here we consider the specifics of the CaMKII/NMDAR molecular switch, with the goal of understanding the biochemical principles that underlie stable information storage by synapses. Consideration of a variety of experimental results suggests that multiple principles are involved. One switch requirement is to prevent spontaneous transitions from the off to the on state. The highly cooperative nature of CaMKII autophosphorylation by Ca2+ (Hill coefficient of 8) and the fact that formation of the CaMKII/NMDAR complex requires release of CaMKII from actin are mechanisms that stabilize the off state. The stability of the on state depends critically on intersubunit autophosphorylation, a process that restores any loss of pT286 due to phosphatase activity. Intersubunit autophosphorylation is also important in explaining why on state stability is not compromised by protein turnover. Recent evidence suggests that turnover occurs by subunit exchange. Thus, stability could be achieved if a newly inserted unphosphorylated subunit was autophosphorylated by a neighboring subunit. Based on other recent work, we posit a novel mechanism that enhances the stability of the on state by protection of pT286 from phosphatases. We posit that the binding of the NMNDAR to CaMKII forces pT286 into the catalytic site of a neighboring subunit, thereby protecting pT286 from phosphatases. A final principle concerns the role of structural changes. The binding of CaMKII to the NMDAR may act as a tag to organize the binding of further proteins that produce the synapse enlargement that underlies late LTP. We argue that these

  13. Therapeutic role of bile acids and nuclear receptor agonists in fibrosing cholangiopathies.

    PubMed

    Trauner, Michael; Halilbasic, Emina; Kazemi-Shirazi, Lili; Kienbacher, Christian; Staufer, Katharina; Traussnigg, Stefan; Hofer, Harald

    2014-01-01

    Chronic inflammatory bile duct diseases such as primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) result in progressive fibrosis of the biliary tract and ultimately cirrhosis of the liver. Since the etiology and pathogenesis of these fibrosing cholangiopathies are still poorly understood, therapeutic options are rather limited at present. Ursodeoxycholic acid (UDCA) is the paradigm therapeutic bile acid and established standard treatment for PBC, but its role for medical therapy of PSC is still under debate. Promising novel bile acid-based therapeutic options include 24-norursodeoxycholic acid, a side chain-shortened C23 homologue of UDCA, and bile acid receptor/farnesoid X receptor agonists (e.g., obeticholic acid) which currently undergo clinical development for fibrosing cholangiopathies such as PBC and PSC. Other nuclear receptors such as vitamin D receptor and fatty acid-activated peroxisome proliferator-activated receptors are also of considerable interest. This review article is a summary of an overview talk given at Falk Symposium 191 on Advances in Pathogenesis and Treatment of Liver Diseases held in London, October 3-4, 2013, and summarizes the recent progress with novel therapeutic bile acids and bile acid derivatives as novel therapies for fibrosing cholangiopathies such as PBC and PSC.

  14. Long-term potentiation and the role of N-methyl-D-aspartate receptors.

    PubMed

    Volianskis, Arturas; France, Grace; Jensen, Morten S; Bortolotto, Zuner A; Jane, David E; Collingridge, Graham L

    2015-09-24

    N-methyl-D-aspartate receptors (NMDARs) are known for their role in the induction of long-term potentiation (LTP). Here we start by reviewing the early evidence for their role in LTP at CA1 synapses in the hippocampus. We then discuss more recent evidence that NMDAR dependent synaptic plasticity at these synapses can be separated into mechanistically distinct components. An initial phase of the synaptic potentiation, which is generally termed short-term potentiation (STP), decays in an activity-dependent manner and comprises two components that differ in their kinetics and NMDAR subtype dependence. The faster component involves activation of GluN2A and GluN2B subunits whereas the slower component involves activation of GluN2B and GluN2D subunits. The stable phase of potentiation, commonly referred to as LTP, requires activation of primarily triheteromeric NMDARs containing both GluN2A and GluN2B subunits. In new work, we compare STP with a rebound potentiation (RP) that is induced by NMDA application and conclude that they are different phenomena. We also report that NMDAR dependent long-term depression (NMDAR-LTD) is sensitive to a glycine site NMDAR antagonist. We conclude that NMDARs are not synonymous for either LTP or memory. Whilst important for the induction of LTP at many synapses in the CNS, not all forms of LTP require the activation of NMDARs. Furthermore, NMDARs mediate the induction of other forms of synaptic plasticity and are important for synaptic transmission. It is, therefore, not possible to equate NMDARs with LTP though they are intimately linked. This article is part of a Special Issue entitled SI: Brain and Memory.

  15. Long-term potentiation and the role of N-methyl-d-aspartate receptors

    PubMed Central

    Volianskis, Arturas; France, Grace; Jensen, Morten S.; Bortolotto, Zuner A.; Jane, David E.; Collingridge, Graham L.

    2015-01-01

    N-methyl-d-aspartate receptors (NMDARs) are known for their role in the induction of long-term potentiation (LTP). Here we start by reviewing the early evidence for their role in LTP at CA1 synapses in the hippocampus. We then discuss more recent evidence that NMDAR dependent synaptic plasticity at these synapses can be separated into mechanistically distinct components. An initial phase of the synaptic potentiation, which is generally termed short-term potentiation (STP), decays in an activity-dependent manner and comprises two components that differ in their kinetics and NMDAR subtype dependence. The faster component involves activation of GluN2A and GluN2B subunits whereas the slower component involves activation of GluN2B and GluN2D subunits. The stable phase of potentiation, commonly referred to as LTP, requires activation of primarily triheteromeric NMDARs containing both GluN2A and GluN2B subunits. In new work, we compare STP with a rebound potentiation (RP) that is induced by NMDA application and conclude that they are different phenomena. We also report that NMDAR dependent long-term depression (NMDAR-LTD) is sensitive to a glycine site NMDAR antagonist. We conclude that NMDARs are not synonymous for either LTP or memory. Whilst important for the induction of LTP at many synapses in the CNS, not all forms of LTP require the activation of NMDARs. Furthermore, NMDARs mediate the induction of other forms of synaptic plasticity and are important for synaptic transmission. It is, therefore, not possible to equate NMDARs with LTP though they are intimately linked. This article is part of a Special Issue entitled SI: Brain and Memory. PMID:25619552

  16. Effects of beer and hop on ionotropic gamma-aminobutyric acid receptors.

    PubMed

    Aoshima, Hitoshi; Takeda, Katsuichi; Okita, Yoichi; Hossain, Sheikh Julfikar; Koda, Hirofumi; Kiso, Yoshinobu

    2006-04-01

    Beer induced the response of the ionotropic gamma-aminobutyric acid receptors (GABA(A) receptors) expressed in Xenopus oocytes, indicating the presence of gamma-aminobutyric acid (GABA)-like activity. Furthermore, the pentane extract of the beer, hop (Humulus lupulus L.) oil, and myrcenol potentiated the GABA(A) receptor response elicited by GABA. The GABA(A) receptor responses were also potentiated by the addition of aliphatic esters, most of which are reported to be present in beer flavor. Aliphatic esters showed the tendency to decrease in the potentiation of the GABA(A) receptor response with an increase in their carbon chain length. When myrcenol was injected to mice prior to intraperitoneal administration of pentobarbital, the pentobarbital-induced sleeping time of mice increased additionally. Therefore, the beer contained not only GABA-like activity but also the modulator(s) of the GABA(A) receptor response.

  17. Phosphatidylinositol (4,5)-Bisphosphate Regulation of N-Methyl-d-aspartate Receptor Channels in Cortical Neurons

    PubMed Central

    Mandal, Madhuchhanda

    2009-01-01

    The membrane phospholipid phosphatidylinositol (4,5)-bisphosphate (PIP2) has been implicated in the regulation of several ion channels and transporters. In this study, we examined the impact of PIP2 on N-methyl-d-aspartate receptors (NMDARs) in cortical neurons. Blocking PIP2 synthesis by inhibiting phosphoinositide-4 kinase, or stimulating PIP2 hydrolysis via activation of phospholipase C (PLC), or blocking PIP2 function with an antibody caused a significant reduction of NMDAR-mediated currents. On the other hand, inhibition of PLC or application of PIP2 caused an enhancement of NMDAR currents. These electrophysiological effects were accompanied by changes in NMDAR surface clusters induced by agents that manipulate PIP2 levels. The PIP2 regulation of NMDAR currents was abolished by the dynamin inhibitory peptide, which blocks receptor internalization. Agents perturbing actin stability prevented PIP2 regulation of NMDAR currents, suggesting the actin-dependence of this effect of PIP2. Cofilin, a major actin depolymerizing factor, which has a common binding sequence for actin and PIP2, was required for PIP2 regulation of NMDAR currents. It is noteworthy that the PIP2 regulation of NMDAR channels was impaired in a transgenic mouse model of Alzheimer's disease, probably because of the amyloid-β disruption of PIP2 metabolism. Taken together, our data suggest that continuous synthesis of PIP2 at the membrane might be important for the maintenance of NMDARs at the cell surface. When PIP2 is lost, cofilin is released from the PIP2 complex and is rendered free to depolymerize actin. With the actin cytoskeleton no longer intact, NMDARs are internalized via a dynamin/clathrin-dependent mechanism, leading to reduced NMDAR currents. PMID:19770351

  18. Conformational signaling required for synaptic plasticity by the NMDA receptor complex.

    PubMed

    Aow, Jonathan; Dore, Kim; Malinow, Roberto

    2015-11-24

    The NMDA receptor (NMDAR) is known to transmit important information by conducting calcium ions. However, some recent studies suggest that activation of NMDARs can trigger synaptic plasticity in the absence of ion flow. Does ligand binding transmit information to signaling molecules that mediate synaptic plasticity? Using Förster resonance energy transfer (FRET) imaging of fluorescently tagged proteins expressed in neurons, conformational signaling is identified within the NMDAR complex that is essential for downstream actions. Ligand binding transiently reduces FRET between the NMDAR cytoplasmic domain (cd) and the associated protein phosphatase 1 (PP1), requiring NMDARcd movement, and persistently reduces FRET between the NMDARcd and calcium/calmodulin-dependent protein kinase II (CaMKII), a process requiring PP1 activity. These studies directly monitor agonist-driven conformational signaling at the NMDAR complex required for synaptic plasticity.

  19. Data for amino acid alignment of Japanese stingray melanocortin receptors with other gnathostome melanocortin receptor sequences, and the ligand selectivity of Japanese stingray melanocortin receptors.

    PubMed

    Takahashi, Akiyoshi; Davis, Perry; Reinick, Christina; Mizusawa, Kanta; Sakamoto, Tatsuya; Dores, Robert M

    2016-06-01

    This article contains structure and pharmacological characteristics of melanocortin receptors (MCRs) related to research published in "Characterization of melanocortin receptors from stingray Dasyatis akajei, a cartilaginous fish" (Takahashi et al., 2016) [1]. The amino acid sequences of the stingray, D. akajei, MC1R, MC2R, MC3R, MC4R, and MC5R were aligned with the corresponding melanocortin receptor sequences from the elephant shark, Callorhinchus milii, the dogfish, Squalus acanthias, the goldfish, Carassius auratus, and the mouse, Mus musculus. These alignments provide the basis for phylogenetic analysis of these gnathostome melanocortin receptor sequences. In addition, the Japanese stingray melanocortin receptors were separately expressed in Chinese Hamster Ovary cells, and stimulated with stingray ACTH, α-MSH, β-MSH, γ-MSH, δ-MSH, and β-endorphin. The dose response curves reveal the order of ligand selectivity for each stingray MCR. PMID:27408924

  20. Potentiation of Gamma Aminobutyric Acid Receptors (GABAAR) by Ethanol: How Are Inhibitory Receptors Affected?

    PubMed Central

    Förstera, Benjamin; Castro, Patricio A.; Moraga-Cid, Gustavo; Aguayo, Luis G.

    2016-01-01

    In recent years there has been an increase in the understanding of ethanol actions on the type A γ-aminobutyric acid chloride channel (GABAAR), a member of the pentameric ligand gated ion channels (pLGICs). However, the mechanism by which ethanol potentiates the complex is still not fully understood and a number of publications have shown contradictory results. Thus many questions still remain unresolved requiring further studies for a better comprehension of this effect. The present review concentrates on the involvement of GABAAR in the acute actions of ethanol and specifically focuses on the immediate, direct or indirect, synaptic and extra-synaptic modulatory effects. To elaborate on the immediate, direct modulation of GABAAR by acute ethanol exposure, electrophysiological studies investigating the importance of different subunits, and data from receptor mutants will be examined. We will also discuss the nature of the putative binding sites for ethanol based on structural data obtained from other members of the pLGICs family. Finally, we will briefly highlight the glycine gated chloride channel (GlyR), another member of the pLGIC family, as a suitable target for the development of new pharmacological tools. PMID:27199667

  1. Late onset deficits in synaptic plasticity in the valproic acid rat model of autism.

    PubMed

    Martin, Henry G S; Manzoni, Olivier J

    2014-01-01

    Valproic acid (VPA) is a frequently used drug in the treatment of epilepsy, bipolar disorders and migraines; however it is also a potent teratogen. Prenatal exposure increases the risk of childhood malformations and can result in cognitive deficits. In rodents in utero exposure to VPA also causes neurodevelopmental abnormalities and is an important model of autism. In early postnatal life VPA exposed rat pups show changes in medial prefrontal cortex (mPFC) physiology and synaptic connectivity. Specifically, principal neurons show decreased excitability but increased local connectivity, coupled with an increase in long-term potentiation (LTP) due to an up-regulation of NMDA receptor (NMDAR) expression. However recent evidence suggests compensatory homeostatic mechanisms lead to normalization of synaptic NMDARs during later postnatal development. Here we have extended study of mPFC synaptic physiology into adulthood to better understand the longitudinal consequences of early developmental abnormalities in VPA exposed rats. Surprisingly in contrast to early postnatal life and adolescence, we find that adult VPA exposed rats show reduced synaptic function. Both NMDAR mediated currents and LTP are lower in adult VPA rats, although spontaneous activity and endocannabinoid dependent long-term depression are normal. We conclude that rather than correcting, synaptic abnormalities persist into adulthood in VPA exposed rats, although a quite different synaptic phenotype is present. This switch from hyper to hypo function in mPFC may be linked to some of the neurodevelopmental defects found in prenatal VPA exposure and autism spectrum disorders in general.

  2. Late onset deficits in synaptic plasticity in the valproic acid rat model of autism

    PubMed Central

    Martin, Henry G. S.; Manzoni, Olivier J.

    2014-01-01

    Valproic acid (VPA) is a frequently used drug in the treatment of epilepsy, bipolar disorders and migraines; however it is also a potent teratogen. Prenatal exposure increases the risk of childhood malformations and can result in cognitive deficits. In rodents in utero exposure to VPA also causes neurodevelopmental abnormalities and is an important model of autism. In early postnatal life VPA exposed rat pups show changes in medial prefrontal cortex (mPFC) physiology and synaptic connectivity. Specifically, principal neurons show decreased excitability but increased local connectivity, coupled with an increase in long-term potentiation (LTP) due to an up-regulation of NMDA receptor (NMDAR) expression. However recent evidence suggests compensatory homeostatic mechanisms lead to normalization of synaptic NMDARs during later postnatal development. Here we have extended study of mPFC synaptic physiology into adulthood to better understand the longitudinal consequences of early developmental abnormalities in VPA exposed rats. Surprisingly in contrast to early postnatal life and adolescence, we find that adult VPA exposed rats show reduced synaptic function. Both NMDAR mediated currents and LTP are lower in adult VPA rats, although spontaneous activity and endocannabinoid dependent long-term depression are normal. We conclude that rather than correcting, synaptic abnormalities persist into adulthood in VPA exposed rats, although a quite different synaptic phenotype is present. This switch from hyper to hypo function in mPFC may be linked to some of the neurodevelopmental defects found in prenatal VPA exposure and autism spectrum disorders in general. PMID:24550781

  3. Aromatic L-amino acids activate the calcium-sensing receptor.

    PubMed

    Conigrave, Arthur D; Mun, Hee-Chang; Lok, Hiu-Chuen

    2007-06-01

    The calcium-sensing receptor (CaR) is recognized as a member of class 3 of the G-protein coupled receptor superfamily. Members of this subgroup, which have large N-terminal extracellular domains, include receptors that respond specifically to the amino acid glutamate; receptors that respond to the glutamate analogue, gamma-amino butyric acid; and several receptors that act as broad-spectrum amino acid sensors. The CaR is one of these broad-spectrum amino acid sensors that, along with several other members of the subgroup, also responds to extracellular Ca2+. In this mini-review, we consider evidence that the CaR is a sensor of aromatic amino acids, that it has broad-spectrum amino acid sensing properties, that it provides an amino acid binding site in its extracellular N-terminal Venus Fly Trap domain, and that amino acids have a physiological impact on systems in which the CaR is expressed.

  4. NMDA receptor antibodies associated with distinct white matter syndromes

    PubMed Central

    Hacohen, Yael; Absoud, Michael; Hemingway, Cheryl; Jacobson, Leslie; Lin, Jean-Pierre; Pike, Mike; Pullaperuma, Sunil; Siddiqui, Ata; Wassmer, Evangeline; Waters, Patrick; Irani, Sarosh R.; Buckley, Camilla

    2014-01-01

    Objective: To report the clinical and radiologic findings of children with NMDA receptor (NMDAR) antibodies and white matter disorders. Method: Ten children with significant white matter involvement, with or without anti-NMDAR encephalitis, were identified from 46 consecutive NMDAR antibody–positive pediatric patients. Clinical and neuroimaging features were reviewed and the treatment and outcomes of the neurologic syndromes evaluated. Results: Three distinct clinicoradiologic phenotypes were recognized: brainstem encephalitis (n = 3), leukoencephalopathy following herpes simplex virus encephalitis (HSVE) (n = 2), and acquired demyelination syndromes (ADS) (n = 5); 3 of the 5 with ADS had myelin oligodendrocyte glycoprotein as well as NMDAR antibodies. Typical NMDAR antibody encephalitis was seen in 3 patients remote from the first neurologic syndrome (2 brainstem, 1 post-HSVE). Six of the 7 patients (85%) who were treated acutely, during the original presentation with white matter involvement, improved following immunotherapy with steroids, IV immunoglobulin, and plasma exchange, either individually or in combination. Two patients had escalation of immunotherapy at relapse resulting in clinical improvement. The time course of clinical features, treatments, and recoveries correlated broadly with available serum antibody titers. Conclusion: Clinicoradiologic evidence of white matter involvement, often distinct, was identified in 22% of children with NMDAR antibodies and appears immunotherapy responsive, particularly when treated in the acute phase of neurologic presentation. When observed, this clinical improvement is often mirrored by reduction in NMDAR antibody levels, suggesting that these antibodies may mediate the white matter disease. PMID:25340058

  5. How Nox2-Containing NADPH Oxidase Affects Cortical Circuits in the NMDA Receptor Antagonist Model of Schizophrenia

    PubMed Central

    Wang, Xin; Pinto-Duarte, António; Sejnowski, Terrence J.

    2013-01-01

    Abstract Significance: Schizophrenia is a complex neuropsychiatric disorder affecting around 1% of the population worldwide. Its mode of inheritance suggests a multigenic neurodevelopmental disorder with symptoms appearing during late adolescence/early adulthood, with its onset strongly influenced by environmental stimuli. Many neurotransmitter systems, including dopamine, glutamate, and gamma-aminobutyric acid, show alterations in affected individuals, and the behavioral and physiological characteristics of the disease can be mimicked by drugs that produce blockade of N-methyl-d-aspartate glutamate receptors (NMDARs). Recent Advances: Mounting evidence suggests that drugs that block NMDARs specifically impair the inhibitory capacity of parvalbumin-expressing (PV+) fast-spiking neurons in adult and developing rodents, and alterations in these inhibitory neurons is one of the most consistent findings in the schizophrenic postmortem brain. Disruption of the inhibitory capacity of PV+ inhibitory neurons will alter the functional balance between excitation and inhibition in prefrontal cortical circuits producing impairment of working memory processes such as those observed in schizophrenia. Critical Issues: Mechanistically, the effect of NMDAR antagonists can be attributed to the activation of the Nox2-dependent reduced form of nicotinamide adenine dinucleotide phosphate oxidase pathway in cortical neurons, which is consistent with the emerging role of oxidative stress in the pathogenesis of mental disorders, specifically schizophrenia. Here we review the mechanisms by which NMDAR antagonists produce lasting impairment of the cortical PV+ neuronal system and the roles played by Nox2-dependent oxidative stress mechanisms. Future Directions: The discovery of the pathways by which oxidative stress leads to unbalanced excitation and inhibition in cortical neural circuits opens a new perspective toward understanding the biological underpinnings of schizophrenia. Antioxid

  6. Nuclear retinoic acid receptors: conductors of the retinoic acid symphony during development.

    PubMed

    Samarut, Eric; Rochette-Egly, Cécile

    2012-01-30

    The vitamin A derivative, retinoic acid (RA), is essential for embryonic development through the activation of cognate nuclear receptors, RARs, which work as ligand dependent regulators of transcription. In vitro studies revealed how RARs control gene expression at the molecular level and now it appears that it is fine-tuned by a phosphorylation code. In addition, several genetic approaches provided valuable insights on the functions of RARs during development and on the influence of other actors such as the enzymes involved in RA synthesis and degradation and other signaling pathways. It appears that RARs are the conductors of the RA signaling symphony through controlling the dynamics and the coordination of the different players and development steps.

  7. Castor oil induces laxation and uterus contraction via ricinoleic acid activating prostaglandin EP3 receptors.

    PubMed

    Tunaru, Sorin; Althoff, Till F; Nüsing, Rolf M; Diener, Martin; Offermanns, Stefan

    2012-06-01

    Castor oil is one of the oldest drugs. When given orally, it has a laxative effect and induces labor in pregnant females. The effects of castor oil are mediated by ricinoleic acid, a hydroxylated fatty acid released from castor oil by intestinal lipases. Despite the wide-spread use of castor oil in conventional and folk medicine, the molecular mechanism by which ricinoleic acid acts remains unknown. Here we show that the EP(3) prostanoid receptor is specifically activated by ricinoleic acid and that it mediates the pharmacological effects of castor oil. In mice lacking EP(3) receptors, the laxative effect and the uterus contraction induced via ricinoleic acid are absent. Although a conditional deletion of the EP(3) receptor gene in intestinal epithelial cells did not affect castor oil-induced diarrhea, mice lacking EP(3) receptors only in smooth-muscle cells were unresponsive to this drug. Thus, the castor oil metabolite ricinoleic acid activates intestinal and uterine smooth-muscle cells via EP(3) prostanoid receptors. These findings identify the cellular and molecular mechanism underlying the pharmacological effects of castor oil and indicate a role of the EP(3) receptor as a target to induce laxative effects.

  8. The ON:OFF switch, σ1R-HINT1 protein, controls GPCR-NMDA receptor cross-regulation: Implications in neurological disorders

    PubMed Central

    Rodríguez-Muñoz, María; Cortés-Montero, Elsa; Pozo-Rodrigálvarez, Andrea; Sánchez-Blázquez, Pilar; Garzón-Niño, Javier

    2015-01-01

    In the brain, the histidine triad nucleotide-binding protein 1 (HINT1) and sigma 1 receptors (σ1Rs) coordinate the activity of certain G-protein coupled receptors (GPCRs) with that of glutamate N-methyl-D-aspartate receptors (NMDARs). To determine the role of HINT1-σ1R in the plasticity of GPCR-NMDAR interactions, substances acting at MOR, cannabinoid CB1 receptor, NMDAR and σ1R were injected into mice, and their effects were evaluated through in vivo, ex vivo, and in vitro assays. It was observed that HINT1 protein binds to GPCRs and NMDAR NR1 subunits in a calcium-independent manner, whereas σ1R binding to these proteins increases in the presence of calcium. In this scenario, σ1R agonists keep HINT1 at the GPCR and stimulate GPCR-NMDAR interaction, whereas σ1R antagonists transfer HINT1 to NR1 subunits and disengage both receptors. This regulation is lost in σ1R−/− mice, where HINT1 proteins mostly associate with NMDARs, and GPCRs are physically and functionally disconnected from NMDARs. In HINT1−/− mice, ischemia produces low NMDAR-mediated brain damage, suggesting that several different GPCRs enhance glutamate excitotoxicity via HINT1-σ1R. Thus, several GPCRs associate with NMDARs by a dynamic process under the physiological control of HINT1 proteins and σ1Rs. The NMDAR-HINT1-σ1R complex deserves attention because it offers new therapeutic opportunities. PMID:26461475

  9. Induction of Memory Deficit in Mice with Chronic Exposure to Cerebrospinal Fluid from Patients with Anti-N-Methyl-D-Aspartate Receptor Encephalitis.

    PubMed

    Li, Yongzhi; Tanaka, Keiko; Wang, Li; Ishigaki, Yasuhito; Kato, Nobuo

    2015-01-01

    Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is now widely recognized and the patients with this disease show prominent psychiatric symptoms followed by seizures, respiratory failure, involuntary movement, autonomic instability, and amnesia. The anti-NMDAR antibody titer coincides with disease activity, and antibody-deprivation treatment ameliorates neurological symptoms. Previous studies have shown that clusters of NMDARs on the neuronal surface decrease in density upon incubation with the cerebrospinal fluid from patients (NMDAR-CSF), and that the induction of long-term potentiation, a cellular mechanism underlie learning and memory processes, was suppressed with NMDAR-CSF. In this study, we exposed mice to NMDAR-CSF in an attempt to reproduce the human symptoms in mice. CSF was continuously administered via a cannula placed in the lateral ventricle of the mouse that connected to an osmotic pump transplanted in the back of the mouse. From day 8-18, we evaluated the behavior of the mice using standardized tests that were performed serially. Mice exposed to NMDAR-CSF showed impaired spatial memory, as detected with the Morris water maze test. Brain tissue from mice with memory disturbances had decreased content of NMDAR protein in the hippocampal area shown by immunohistochemistry, which is consistent with the anti-NMDAR antibodies affect the expression and function of NMDARs, resulting in anti-NMDAR encephalitis-like symptoms. Also, the mice treated with the NMDAR-CSF did not show inflammatory cell infiltration or neuron loss in their brain tissue and this lack of nervous tissue destruction is encouraging as it is consistent with the idea that this disease can be treated through immunotherapy.

  10. Eicosopentaneoic Acid and Other Free Fatty Acid Receptor Agonists Inhibit Lysophosphatidic Acid- and Epidermal Growth Factor-Induced Proliferation of Human Breast Cancer Cells

    PubMed Central

    Hopkins, Mandi M.; Zhang, Zhihong; Liu, Ze; Meier, Kathryn E.

    2016-01-01

    Many key actions of ω-3 (n-3) fatty acids have recently been shown to be mediated by two G protein-coupled receptors (GPCRs) in the free fatty acid receptor (FFAR) family, FFA1 (GPR40) and FFA4 (GPR120). n-3 Fatty acids inhibit proliferation of human breast cancer cells in culture and in animals. In the current study, the roles of FFA1 and FFA4 were investigated. In addition, the role of cross-talk between GPCRs activated by lysophosphatidic acid (LPA), and the tyrosine kinase receptor activated by epidermal growth factor (EGF), was examined. In MCF-7 and MDA-MB-231 human breast cancer cell lines, both LPA and EGF stimulated proliferation, Erk activation, Akt activation, and CCN1 induction. LPA antagonists blocked effects of LPA and EGF on proliferation in MCF-7 and MDA-MB-231, and on cell migration in MCF-7. The n-3 fatty acid eicosopentaneoic acid inhibited LPA- and EGF-induced proliferation in both cell lines. Two synthetic FFAR agonists, GW9508 and TUG-891, likewise inhibited LPA- and EGF-induced proliferation. The data suggest a major role for FFA1, which was expressed by both cell lines. The results indicate that n-3 fatty acids inhibit breast cancer cell proliferation via FFARs, and suggest a mechanism involving negative cross-talk between FFARS, LPA receptors, and EGF receptor. PMID:26821052

  11. γ-Hydroxybutyric acid (GHB) is not an agonist of extrasynaptic GABAA receptors.

    PubMed

    Connelly, William M; Errington, Adam C; Crunelli, Vincenzo

    2013-01-01

    γ-Hydroxybutyric acid (GHB) is an endogenous compound and a drug used clinically to treat the symptoms of narcolepsy. GHB is known to be an agonist of GABAB receptors with millimolar affinity, but also binds with much higher affinity to another site, known as the GHB receptor. While a body of evidence has shown that GHB does not bind to GABAA receptors widely, recent evidence has suggested that the GHB receptor is in fact on extrasynaptic α4β1δ GABAA receptors, where GHB acts as an agonist with an EC50 of 140 nM. We investigated three neuronal cell types that express a tonic GABAA receptor current mediated by extrasynaptic receptors: ventrobasal (VB) thalamic neurons, dentate gyrus granule cells and striatal medium spiny neurons. Using whole-cell voltage clamp in brain slices, we found no evidence that GHB (10 µM) induced any GABAA receptor mediated current in these cell types, nor that it modulated inhibitory synaptic currents. Furthermore, a high concentration of GHB (3 mM) was able to produce a GABAB receptor mediated current, but did not induce any other currents. These results suggest either that GHB is not a high affinity agonist at native α4β1δ receptors, or that these receptors do not exist in classical areas associated with extrasynaptic currents.

  12. Expression and localization of the omega-3 fatty acid receptor GPR120 in human term placenta.

    PubMed

    Lager, S; Ramirez, V I; Gaccioli, F; Jansson, T; Powell, T L

    2014-07-01

    Fatty acids can function as signaling molecules, acting through receptors in the cytosol or on the cell surface. G-Protein Receptor (GPR)120 is a membrane-bound receptor mediating anti-inflammatory and insulin-sensitizing effects of the omega-3 fatty acid docohexaenoic acid (DHA). GPR120 dysfunction is associated with obesity in humans. Cellular localization of GPR120 and the influence of maternal obesity on GPR120 protein expression in the placenta are unknown. Herein we demonstrate that GPR120 is predominantly expressed in the microvillous membrane (MVM) of human placenta and that the expression level of this receptor in MVM is not altered by maternal body mass index (BMI).

  13. Genetically encoding a light switch in an ionotropic glutamate receptor reveals subunit-specific interfaces.

    PubMed

    Zhu, Shujia; Riou, Morgane; Yao, C Andrea; Carvalho, Stéphanie; Rodriguez, Pamela C; Bensaude, Olivier; Paoletti, Pierre; Ye, Shixin

    2014-04-22

    Reprogramming receptors to artificially respond to light has strong potential for molecular studies and interrogation of biological functions. Here, we design a light-controlled ionotropic glutamate receptor by genetically encoding a photoreactive unnatural amino acid (UAA). The photo-cross-linker p-azido-L-phenylalanine (AzF) was encoded in NMDA receptors (NMDARs), a class of glutamate-gated ion channels that play key roles in neuronal development and plasticity. AzF incorporation in the obligatory GluN1 subunit at the GluN1/GluN2B N-terminal domain (NTD) upper lobe dimer interface leads to an irreversible allosteric inhibition of channel activity upon UV illumination. In contrast, when pairing the UAA-containing GluN1 subunit with the GluN2A subunit, light-dependent inactivation is completely absent. By combining electrophysiological and biochemical analyses, we identify subunit-specific structural determinants at the GluN1/GluN2 NTD dimer interfaces that critically dictate UV-controlled inactivation. Our work reveals that the two major NMDAR subtypes differ in their ectodomain-subunit interactions, in particular their electrostatic contacts, resulting in GluN1 NTD coupling more tightly to the GluN2B NTD than to the GluN2A NTD. It also paves the way for engineering light-sensitive ligand-gated ion channels with subtype specificity through the genetic code expansion. PMID:24715733

  14. Genetically encoding a light switch in an ionotropic glutamate receptor reveals subunit-specific interfaces

    PubMed Central

    Zhu, Shujia; Riou, Morgane; Yao, C. Andrea; Carvalho, Stéphanie; Rodriguez, Pamela C.; Bensaude, Olivier; Paoletti, Pierre; Ye, Shixin

    2014-01-01

    Reprogramming receptors to artificially respond to light has strong potential for molecular studies and interrogation of biological functions. Here, we design a light-controlled ionotropic glutamate receptor by genetically encoding a photoreactive unnatural amino acid (UAA). The photo–cross-linker p-azido-l-phenylalanine (AzF) was encoded in NMDA receptors (NMDARs), a class of glutamate-gated ion channels that play key roles in neuronal development and plasticity. AzF incorporation in the obligatory GluN1 subunit at the GluN1/GluN2B N-terminal domain (NTD) upper lobe dimer interface leads to an irreversible allosteric inhibition of channel activity upon UV illumination. In contrast, when pairing the UAA-containing GluN1 subunit with the GluN2A subunit, light-dependent inactivation is completely absent. By combining electrophysiological and biochemical analyses, we identify subunit-specific structural determinants at the GluN1/GluN2 NTD dimer interfaces that critically dictate UV-controlled inactivation. Our work reveals that the two major NMDAR subtypes differ in their ectodomain-subunit interactions, in particular their electrostatic contacts, resulting in GluN1 NTD coupling more tightly to the GluN2B NTD than to the GluN2A NTD. It also paves the way for engineering light-sensitive ligand-gated ion channels with subtype specificity through the genetic code expansion. PMID:24715733

  15. Ca(2+)-permeable AMPA and NMDA receptor channels in basket cells of rat hippocampal dentate gyrus.

    PubMed Central

    Koh, D S; Geiger, J R; Jonas, P; Sakmann, B

    1995-01-01

    1. Glutamate receptor (GluR) channels were studied in basket cells in the dentate gyrus of rat hippocampal slices. Basket cells were identified by their location, dendritic morphology and high frequency of action potentials generated during sustained current injection. 2. Dual-component currents were activated by fast application of glutamate to outside-out membrane patches isolated from basket cell somata (10 microM glycine, no external Mg2+). The fast component was selectively blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), the slow component by D-2-amino-5-phosphonopentanoic acid (D-AP5). This suggests that the two components were mediated by alpha-amino-3- hydroxy-5-methyl-4-isoxazolepropionate receptor (AMPAR)/kainate receptor and N-methyl-D-aspartate receptor (NMDAR) channels, respectively. The mean ratio of the peak current of the NMDAR component to that of the AMPAR/kainate receptor component was 0.22 (1 ms pulses of 10 mM glutamate). 3. The AMPAR/kainate receptor component, which was studied in isolation in the presence of D-AP5, was identified as AMPAR mediated on the basis of the preferential activation by AMPA as compared with kainate, the weak desensitization of kainate-activated currents, the cross-desensitization between AMPA and kainate, and the reduction of desensitization by cyclothiazide. 4. Deactivation of basket cell AMPARs following 1 ms pulses of glutamate occurred with a time constant (tau) of 1.2 +/- 0.1 ms (mean +/- S.E.M.). During 100 ms glutamate pulses AMPARs desensitized with a tau of 3.7 +/- 0.2ms. 5. The peak current-voltage (I-V) relation of AMPAR-mediated currents in Na(+)-rich extracellular solution showed a reversal potential of -4.0 +/- 2.6 mV and was characterized by a a doubly rectifying shape. The conductance of single AMPAR channels was estimated as 22.6 +/- 1.6 pS using non-stationary fluctuation analysis. AMPARs expressed in hippocampal basket cells were highly Ca2+ permeable (PCa/PK = 1.79). 6. NMDARs in

  16. The effects of avermectin on amino acid neurotransmitters and their receptors in the pigeon brain.

    PubMed

    Chen, Li-Jie; Sun, Bao-Hong; Cao, Ye; Yao, Hai-Dong; Qu, Jian-Ping; Liu, Ci; Xu, Shi-Wen; Li, Shu

    2014-03-01

    The objective of this study was to examine the effects of avermectin (AVM) on amino acid neurotransmitters and their receptors in the pigeon brain. Four groups two-month-old American king pigeons (n=20/group) were fed either a commercial diet or an AVM-supplemented diet (20mg/kg·diet, 40 mg/kg·diet, or 60 mg/kg·diet) for 30, 60, or 90 days. The contents of aspartic acid (ASP), glutamate (GLU), glycine (GLY), and γ-aminobutyric acid (GABA) in the brain tissues were determined using ultraviolet high-performance liquid chromatography (HPLC). The expression levels of the GLU and GABA receptor genes were analyzed using real-time quantitative polymerase chain reaction (qPCR). The results indicate that AVM exposure significantly enhances the contents of GABA, GLY, GLU, and ASP in the cerebrum, cerebellum, and optic lobe. In addition, AVM exposure increases the mRNA expression levels of γ-aminobutyric acid type A receptor (GABAAR), γ-aminobutyric acid type B receptor (GABABR), N-methyl-d-aspartate 1 receptor (NR1), N-methyl-d-aspartate 2A receptor (NR2A), and N-methyl-d-aspartate 2B receptor (NR2B) in a dose- and time-dependent manner. Moreover, we found that the most damaged organ was the cerebrum, followed by the cerebellum, and then the optic lobe. These results show that the AVM-induced neurotoxicity may be associated with its effects on amino acid neurotransmitters and their receptors. The information presented in this study will help supplement the available data for future AVM toxicity studies.

  17. Developmental toxicity of perfluorononanoic acid is dependent on peroxisome proliferator activated receptor-alpha.

    EPA Science Inventory

    Perfluorononanoic acid (PFNA) is one of the predominant perfluoroalkyl acids in the environment and in tissues of humans and wildlife. PFNA strongly activates the mouse and human peroxisome proliferator-activated receptor-alpha (PPARα) in vitro and negatively impacts development ...

  18. REACTIVITY PROFILE OF LIGANDS OF MAMMALIAN RETINOIC ACID RECEPTORS: A PRELIMINARY COREPA ANALYSIS

    EPA Science Inventory

    Retinoic acid and associated derivatives comprise a class of endogenous hormones that bind to and activate different families of retinoic acid receptors (RARs, RXRs), and control many aspects of vertebrate development. Identification of potential RAR and RXR ligands is of interes...

  19. Amino acid sequence of the alpha subunit of human leukocyte adhesion receptor Mo1 (complement receptor type 3)

    PubMed Central

    1988-01-01

    Mo1 (complement receptor type 3, CR3; CD11b/CD18) is an adhesion- promoting human leukocyte surface membrane heterodimer (alpha subunit 155 kD [CD11b] noncovalently linked to a beta subunit of 95 kD [CD18]). The complete amino acid sequence deduced from cDNA of the human alpha subunit is reported. The protein consists of 1,136 amino acids with a long amino-terminal extracytoplasmic domain, a 26-amino acid hydrophobic transmembrane segment, and a 19-carboxyl-terminal cytoplasmic domain. The extracytoplasmic region has three putative Ca2+- binding domains with good homology and one with weak homology to the "lock washer" Ca2+-binding consensus sequence. These metal-binding domains explain the divalent cation-dependent functions mediated by Mo1. The alpha subunit is highly homologous to the alpha subunit of leukocyte p150,95 and to a lesser extent, to the alpha subunit of other "integrin" receptors such as fibronectin, vitronectin, and platelet IIb/IIIa receptors in humans and position-specific antigen-2 (PS2) in Drosophila. Mo1 alpha, like p150, contains a unique 187-amino acid stretch NH2-terminal to the metal-binding domains. This region could be involved in some of the specific functions mediated by these leukocyte glycoproteins. PMID:2454931

  20. The inimitable kynurenic acid: the roles of different ionotropic receptors in the action of kynurenic acid at a spinal level.

    PubMed

    Tuboly, Gabor; Tar, Lilla; Bohar, Zsuzsanna; Safrany-Fark, Arpad; Petrovszki, Zita; Kekesi, Gabriella; Vecsei, Laszlo; Pardutz, Arpad; Horvath, Gyongyi

    2015-03-01

    Kynurenic acid (KYNA) is a neuroactive metabolite that interacts with NMDA, AMPA/kainate and alpha 7 nicotinic receptors. The goal of this study was to clarify the roles of these receptors in the action of KYNA at a spinal level by using highly specific receptor antagonists alone or in triple combinations. Chronic osteoarthritis-like joint pain was induced with monosodium-iodoacetate in male Wistar rats. Mechanical allodynia and motor function were quantified. In the first series we determined the dose-response and time course effects of intrathecally administered KYNA (10-100 μg), D-(-)-2-amino-5-phosphonopentanoic acid (AP5; an NMDA receptor antagonist; 10-200 μg), methyllycaconitine (MLA; an alpha 7 nicotinic receptor antagonist; 100-200 μg) and 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzoquinoxaline-7-sulfonamide (NBQX; an AMPA/kainate receptor antagonist; 1-20 μg). In the second series, four different triple combinations of MLA, AP5 and NBQX were investigated. Intrathecal administration of KYNA caused a dose-dependent motor impairment and antinociception. The highly specific NMDA receptor antagonist AP5 caused a motor impairment and antinociception with lower potency. High doses of NBQX resulted in significant antinociception with a slight motor impairment, while only the highest dose of MLA gave rise to significant antinociception with a slight motor impairment. After the coadministration of these ligands as combinations, no potentiation was observed. It may be supposed that the effects of KYNA are primarily due to the inhibition of NMDA receptors at both glycine and phencyclidine (PCP) binding sites, and not to the interactions at the different ionotropic receptors, but the mechanisms behind its high bio-efficiency are still unknown.

  1. Optical control of NMDA receptors with a diffusible photoswitch.

    PubMed

    Laprell, Laura; Repak, Emilienne; Franckevicius, Vilius; Hartrampf, Felix; Terhag, Jan; Hollmann, Michael; Sumser, Martin; Rebola, Nelson; DiGregorio, David A; Trauner, Dirk

    2015-01-01

    N-methyl-D-aspartate receptors (NMDARs) play a central role in synaptic plasticity, learning and memory, and are implicated in various neuronal disorders. We synthesized a diffusible photochromic glutamate analogue, azobenzene-triazole-glutamate (ATG), which is specific for NMDARs and functions as a photoswitchable agonist. ATG is inactive in its dark-adapted trans-isoform, but can be converted into its active cis-isoform using one-photon (near UV) or two-photon (740 nm) excitation. Irradiation with violet light photo-inactivates ATG within milliseconds, allowing agonist removal on the timescale of NMDAR deactivation. ATG is compatible with Ca(2+) imaging and can be used to optically mimic synaptic coincidence detection protocols. Thus, ATG can be used like traditional caged glutamate compounds, but with the added advantages of NMDAR specificity, low antagonism of GABAR-mediated currents, and precise temporal control of agonist delivery. PMID:26311290

  2. Optical control of NMDA receptors with a diffusible photoswitch

    PubMed Central

    Laprell, Laura; Repak, Emilienne; Franckevicius, Vilius; Hartrampf, Felix; Terhag, Jan; Hollmann, Michael; Sumser, Martin; Rebola, Nelson; DiGregorio, David A.; Trauner, Dirk

    2015-01-01

    N-methyl-D-aspartate receptors (NMDARs) play a central role in synaptic plasticity, learning and memory, and are implicated in various neuronal disorders. We synthesized a diffusible photochromic glutamate analogue, azobenzene-triazole-glutamate (ATG), which is specific for NMDARs and functions as a photoswitchable agonist. ATG is inactive in its dark-adapted trans-isoform, but can be converted into its active cis-isoform using one-photon (near UV) or two-photon (740 nm) excitation. Irradiation with violet light photo-inactivates ATG within milliseconds, allowing agonist removal on the timescale of NMDAR deactivation. ATG is compatible with Ca2+ imaging and can be used to optically mimic synaptic coincidence detection protocols. Thus, ATG can be used like traditional caged glutamate compounds, but with the added advantages of NMDAR specificity, low antagonism of GABAR-mediated currents, and precise temporal control of agonist delivery. PMID:26311290

  3. Metabotropic NMDA receptor signaling couples Src family kinases to pannexin-1 during excitotoxicity.

    PubMed

    Weilinger, Nicholas L; Lohman, Alexander W; Rakai, Brooke D; Ma, Evelyn M M; Bialecki, Jennifer; Maslieieva, Valentyna; Rilea, Travis; Bandet, Mischa V; Ikuta, Nathan T; Scott, Lucas; Colicos, Michael A; Teskey, G Campbell; Winship, Ian R; Thompson, Roger J

    2016-03-01

    Overactivation of neuronal N-methyl-D-aspartate receptors (NMDARs) causes excitotoxicity and is necessary for neuronal death. In the classical view, these ligand-gated Ca(2+)-permeable ionotropic receptors require co-agonists and membrane depolarization for activation. We report that NMDARs signal during ligand binding without activation of their ion conduction pore. Pharmacological pore block with MK-801, physiological pore block with Mg(2+) or a Ca(2+)-impermeable NMDAR variant prevented NMDAR currents, but did not block excitotoxic dendritic blebbing and secondary currents induced by exogenous NMDA. NMDARs, Src kinase and Panx1 form a signaling complex, and activation of Panx1 required phosphorylation at Y308. Disruption of this NMDAR-Src-Panx1 signaling complex in vitro or in vivo by administration of an interfering peptide either before or 2 h after ischemia or stroke was neuroprotective. Our observations provide insights into a new signaling modality of NMDARs that has broad-reaching implications for brain physiology and pathology.

  4. NMDA receptor signaling in oligodendrocyte progenitors is not required for oligodendrogenesis and myelination

    PubMed Central

    De Biase, L. M.; Kang, S. H.; Baxi, E. G.; Fukaya, M.; Pucak, M. L.; Mishina, M.; Calabresi, P. A.; Bergles, D. E.

    2011-01-01

    Oligodendrocyte precursor cells (OPCs) express NMDA receptors (NMDARs) and form synapses with glutamatergic neurons throughout the central nervous system (CNS). Although glutamate influences the proliferation and maturation of these progenitors in vitro, the role of NMDAR signaling in oligodendrogenesis and myelination in vivo is not known. Here, we investigated the consequences of genetically deleting the obligatory NMDAR subunit NR1 from OPCs and their oligodendrocyte progeny in the CNS of developing and mature mice. NMDAR-deficient OPCs proliferated normally, achieved appropriate densities in gray and white matter, and differentiated to form major white matter tracts without delay. OPCs also retained their characteristic physiological and morphological properties in the absence of NMDAR signaling, and were able to form synapses with glutamatergic axons. However, expression of calcium permeable AMPA receptors was enhanced in NMDAR-deficient OPCs. These results suggest that NMDAR signaling is not used to control OPC development, but to regulate AMPAR-dependent signaling with surrounding axons, pointing to additional functions for these ubiquitous glial cells. PMID:21880926

  5. Sigma-1 and N-Methyl-d-Aspartate Receptors: A Partnership with Beneficial Outcomes

    PubMed Central

    Pabba, Mohan; Sibille, Etienne

    2015-01-01

    Sigma-1 receptors (σ-1R) are interorganelle signaling molecules, which have been implicated in synaptic plasticity, primarily by enhancing the function of N-methyl-d-aspartate receptors (NMDARs). On the other hand, excessive influx of calcium via activated NMDAR can cause excitotoxicity. Yet, despite their NMDAR-enhancing role, multiple lines of evidence suggest that σ-1Rs are involved in neuroprotection. The mechanism underlying these intriguing opposing effects is not known. Recent studies now suggest the possibility that σ-1Rs could exert neuroprotective effects via targeted disruption of protein-protein interactions between NMDARs and their associated intracellular signaling machinery, specifically the neuronal nitric oxide synthase (nNOS). This targeted disruption of protein-protein interactions between NMDARs and nNOS results in lower levels of nitric oxide generation, thus having a neuroprotective effect. Here, we briefly summarize aspects of σ-1R-mediated enhancement of NMDAR function and possible neuroprotection. In-depth mechanistic understanding of σ-1R modulation of NMDAR function, which preserves Ca2+ homoeostasis while limiting excitotoxicity would provide valuable information for designing novel as well as improving prevailing therapeutic strategies.

  6. Stimulation of acid secretion and phosphoinositol production by rat parietal cell muscarinic M sub 2 receptors

    SciTech Connect

    Pfeiffer, A.; Rochlitz, H.; Herz, A.; Paumgartner, G. )

    1988-04-01

    The muscarinic receptor system involved in hydrogen production by enriched rat gastric parietal cells was investigated. Muscarinic receptor density determined by (N-methyl-{sup 3}H)scopolamine binding was 8,100/cell. The receptor appeared to be of the M{sub 2} muscarinic receptor subtype, since it had a low affinity (K{sub d} 189 nM) for the M{sub 1} receptor antagonist pirenzepine compared with atropine. Receptor activation by carbachol rapidly augmented levels of polyphosphoinositides, indicating an activation of phospholipase C. The dose-response relations for the increase in inositol phosphates closely paralleled the binding of carbachol to muscarinic receptors. The inositol phosphate response was antagonized by pirenzepine with a K{sub i} of 177 nM. the stimulation of inositol phosphate levels by carbachol correlated well with the stimulation of ({sup 14}C)aminopyrine uptake, determine as an index of acid secretion. The muscarinic agonists oxotremorine, pilocarpine, and bethanechol elicited partial increases in inositol phosphates at maximal drug concentrations, and these partial increases correlated with their ability to stimulate ({sup 14}C)aminopyrine uptake. These data indicate that inositolpolyphosphates may be a second messenger of M{sub 2} receptors stimulating acid secretion.

  7. Stacking interaction and its role in kynurenic acid binding to glutamate ionotropic receptors.

    PubMed

    Zhuravlev, Alexander V; Zakharov, Gennady A; Shchegolev, Boris F; Savvateeva-Popova, Elena V

    2012-05-01

    Stacking interaction is known to play an important role in protein folding, enzyme-substrate and ligand-receptor complex formation. It has been shown to make a contribution into the aromatic antagonists binding with glutamate ionotropic receptors (iGluRs), in particular, the complex of NMDA receptor NR1 subunit with the kynurenic acid (KYNA) derivatives. The specificity of KYNA binding to the glutamate receptors subtypes might partially result from the differences in stacking interaction. We have calculated the optimal geometry and binding energy of KYNA dimers with the four types of aromatic amino acid residues in Rattus and Drosophila ionotropic iGluR subunits. All ab initio quantum chemical calculations were performed taking into account electron correlations at MP2 and MP4 perturbation theory levels. We have also investigated the potential energy surfaces (PES) of stacking and hydrogen bonds (HBs) within the receptor binding site and calculated the free energy of the ligand-receptor complex formation. The energy of stacking interaction depends both on the size of aromatic moieties and the electrostatic effects. The distribution of charges was shown to determine the geometry of polar aromatic ring dimers. Presumably, stacking interaction is important at the first stage of ligand binding when HBs are weak. The freedom of ligand movements and rotation within receptor site provides the precise tuning of the HBs pattern, while the incorrect stacking binding prohibits the ligand-receptor complex formation. PMID:21833825

  8. Developmental expression of N-methyl-D-aspartate (NMDA) receptor subunits in human white and gray matter: potential mechanism of increased vulnerability in the immature brain.

    PubMed

    Jantzie, Lauren L; Talos, Delia M; Jackson, Michele C; Park, Hyun-Kyung; Graham, Dionne A; Lechpammer, Mirna; Folkerth, Rebecca D; Volpe, Joseph J; Jensen, Frances E

    2015-02-01

    The pathophysiology of perinatal brain injury is multifactorial and involves hypoxia-ischemia (HI) and inflammation. N-methyl-d-aspartate receptors (NMDAR) are present on neurons and glia in immature rodents, and NMDAR antagonists are protective in HI models. To enhance clinical translation of rodent data, we examined protein expression of 6 NMDAR subunits in postmortem human brains without injury from 20 postconceptional weeks through adulthood and in cases of periventricular leukomalacia (PVL). We hypothesized that the developing brain is intrinsically vulnerable to excitotoxicity via maturation-specific NMDAR levels and subunit composition. In normal white matter, NR1 and NR2B levels were highest in the preterm period compared with adult. In gray matter, NR2A and NR3A expression were highest near term. NR2A was significantly elevated in PVL white matter, with reduced NR1 and NR3A in gray matter compared with uninjured controls. These data suggest increased NMDAR-mediated vulnerability during early brain development due to an overall upregulation of individual receptors subunits, in particular, the presence of highly calcium permeable NR2B-containing and magnesium-insensitive NR3A NMDARs. These data improve understanding of molecular diversity and heterogeneity of NMDAR subunit expression in human brain development and supports an intrinsic prenatal vulnerability to glutamate-mediated injury; validating NMDAR subunit-specific targeted therapies for PVL.

  9. N-Methyl-D-aspartate receptors are clustered and immobilized on dendrites of living cortical neurons.

    PubMed Central

    Benke, T A; Jones, O T; Collingridge, G L; Angelides, K J

    1993-01-01

    The response of nerve cells to synaptic inputs and the propagation of this activation is critically dependent on the cell-surface distribution of ion channels. In the hippocampus, Ca2+ influx through N-methyl-D-aspartate receptors (NMDAR) and/or voltage-dependent calcium channels on dendrites is thought to be critically involved in long-term potentiation, neurite outgrowth, epileptogenesis, synaptogenesis, and cell death. We report that conantokin-G (CntxG), a peptide from Conus geographus venom, competitively blocked with high affinity and specificity NMDAR-mediated currents in hippocampal neurons and is a reliable probe for exploring NMDAR distribution. Fluorescent derivatives of CntxG were prepared and used to directly determine NMDAR distribution on living hippocampal neurons by digital imaging and confocal fluorescence microscopy. In hippocampal slices, the CA1 dendritic subfield was strongly labeled by CntxG, whereas the CA3 mossy fiber region was not. On CA1 hippocampal neurons in culture, dendritic CntkG-sensitive NMDAR were clustered at sites of synaptic contacts, whereas somatic NMDAR were distributed diffusely and in patches. NMDAR distribution differed from the distribution of voltage-dependent calcium channels. A significant fraction of labeled NMDAR on somata and dendrites was found to be highly mobile: rates were consistent with the possible rapid recruitment of NMDAR to specific synaptic locations. The localization of NMDAR and modulation of this distribution demonstrated here may have important implications for the events that underlie neuronal processing and synaptic remodeling during associative synaptic modification. Images Fig. 3 Fig. 4 Fig. 5 Fig. 6 PMID:7689230

  10. Propofol protects hippocampal neurons from apoptosis in ischemic brain injury by increasing GLT-1 expression and inhibiting the activation of NMDAR via the JNK/Akt signaling pathway.

    PubMed

    Gong, Hong-Yan; Zheng, Fang; Zhang, Chao; Chen, Xi-Yan; Liu, Jing-Jing; Yue, Xiu-Qin

    2016-09-01

    Ischemic brain injury (IBI) can cause nerve injury and is a leading cause of morbidity and mortality worldwide. The neuroprotective effects of propofol against IBI have been previously demonstrated. However, the neuroprotective effects of propofol on hippocampal neurons are not yet entirely clear. In the present study, models of IBI were established in hypoxia-exposed hippocampal neuronal cells. Cell viability assay and apoptosis assay were performed to examine the neuroprotective effects of propofol on hippocampal neurons in IBI. A significant decrease in cell viability and a significant increase in cell apoptosis were observed in the IBI group compared with the control group, accompanied by a decrease in glial glutamate transporter-1 (GLT‑1) expression as determined by RT-qPCR and western blot analysis. The effects of IBI were reversed by propofol treatment. The siRNA-mediated knockdown of GLT‑1 in the hypoxia-exposed hippocampal neuronal cells led to an increase in cell apoptosis, Jun N-terminal kinase (JNK) activation and N-methyl-D‑aspartate (NMDA) receptor (NR1 and NR2B) activation, as well as to a decrease in cell viability and a decrease in Akt activation. The effects of RNA interference-mediated GLT‑1 gene silencing on cell viability, JNK activation, NMDAR activation, cell apoptosis and Akt activation in the hippocampal neuronal cells were slightly reversed by propofol treatment. The JNK agonist, anisomycin, and the Akt inhibitor, LY294002, both significantly blocked the effects of propofol on hippocampal neuronal cell viability and apoptosis in IBI. The decrease in JNK activation and the increase in Akt activation caused by GLT‑1 overexpression were reversed by NMDA. Collectively, our findings suggest that propofol treatment protects hippocampal neurons against IBI by enhancing GLT‑1 expression and inhibiting the activation of NMDAR via the JNK/Akt signaling pathway. PMID:27430327

  11. Properties and molecular identity of NMDA receptors at synaptic and non-synaptic inputs in cerebellar molecular layer interneurons

    PubMed Central

    Bidoret, Céline; Bouvier, Guy; Ayon, Annick; Szapiro, Germán; Casado, Mariano

    2015-01-01

    N-methyl-D-aspartate receptors (NMDARs) in cerebellar molecular layer interneurons (MLIs) are expressed and activated in unusual ways: at parallel fibre (PF) synapses they are only recruited by repetitive stimuli, suggesting an extrasynaptic location, whereas their activation by climbing fibre is purely mediated by spillover. NMDARs are thought to play an important role in plasticity at different levels of the cerebellar circuitry. Evaluation of the location, functional properties and physiological roles of NMDARs will be facilitated by knowledge of the NMDAR isoforms recruited. Here we show that MLI-NMDARs activated by both PF and climbing fibre inputs have similar kinetics and contain GluN2B but not GluN2A subunits. On the other hand, no evidence was found of functional NMDARs in the axons of MLIs. At the PF-Purkinje cell (PF-PC) synapse, the activation of GluN2A-containing NMDARs has been shown to be necessary for the induction of long-term depression (LTD). Our results therefore provide a clear distinction between the NMDARs located on MLIs and those involved in plasticity at PF-PC synapses. PMID:25750623

  12. Mechanisms for the activation of Toll-like receptor 2/4 by saturated fatty acids and inhibition by docosahexaenoic acid.

    PubMed

    Hwang, Daniel H; Kim, Jeong-A; Lee, Joo Young

    2016-08-15

    Saturated fatty acids can activate Toll-like receptor 2 (TLR2) and TLR4 but polyunsaturated fatty acids, particularly docosahexaenoic acid (DHA) inhibit the activation. Lipopolysaccharides (LPS) and lipopetides, ligands for TLR4 and TLR2, respectively, are acylated by saturated fatty acids. Removal of these fatty acids results in loss of their ligand activity suggesting that the saturated fatty acyl moieties are required for the receptor activation. X-ray crystallographic studies revealed that these saturated fatty acyl groups of the ligands directly occupy hydrophobic lipid binding domains of the receptors (or co-receptor) and induce the dimerization which is prerequisite for the receptor activation. Saturated fatty acids also induce the dimerization and translocation of TLR4 and TLR2 into lipid rafts in plasma membrane and this process is inhibited by DHA. Whether saturated fatty acids induce the dimerization of the receptors by interacting with these lipid binding domains is not known. Many experimental results suggest that saturated fatty acids promote the formation of lipid rafts and recruitment of TLRs into lipid rafts leading to ligand independent dimerization of the receptors. Such a mode of ligand independent receptor activation defies the conventional concept of ligand induced receptor activation; however, this may enable diverse non-microbial molecules with endogenous and dietary origins to modulate TLR-mediated immune responses. Emerging experimental evidence reveals that TLRs play a key role in bridging diet-induced endocrine and metabolic changes to immune responses.

  13. Upregulation of retinoic acid receptor-beta by the epidermal growth factor-receptor inhibitor PD153035 is not mediated by blockade of ErbB pathways.

    PubMed

    Grunt, Thomas W; Tomek, Katharina; Wagner, Renate; Puckmair, Klaudia; Kainz, Birgit; Rünzler, Dominik; Gaiger, Alexander; Köhler, Gottfried; Zielinski, Christoph C

    2007-06-01

    Inhibiting epidermal growth factor-receptor (ErbB-1) represents a powerful anticancer strategy. Activation of retinoid pathways is also in development for cancer treatment. Retinoic acid receptor-beta-the tumor suppressor and main retinoid mediator--is silenced in many tumors. The ErbB-1 inhibitor PD153035 cooperates with retinoic acid during growth inhibition and induces retinoic acid receptor-beta suggesting that ErbB-1 controls retinoic acid receptor-beta. However, here we demonstrate that ErbB pathways are not involved in PD153035-mediated retinoic acid receptor-beta-upregulation. PD153035 inhibits ErbB-1-phosphorylation, whereas its derivative EBE-A22 is inactive. Yet both inhibit cell growth and upregulate retinoic acid receptor-beta in ErbB-1-overexpressing (MDA-MB-468), moderately expressing (OVCAR-3), ErbB-1-negative (MDA-MB-453) or ErbB-negative cells (CEM, Jurkat). Both bind DNA, whereas the closely related ErbB-1 inhibitors AG1478 and ZD1839, which are inactive on retinoic acid receptor-beta, do not significantly bind DNA. None of the other ErbB-1/ErbB-2 inhibitors tested (RG-14620, LFM-A12, AG879, AG825) affect retinoic acid receptor-beta. PD153035 decreases methylation of the retinoic acid receptor-beta2 promoter. In OVCAR-3, it stimulates dislodgement of histone deacetylase 1 from the promoter and acetylation of histones H3 and H4. Consequently, PD153035 facilitates recruitment of RNA polymerase II to the promoter and stimulates transcriptional activity. Moreover, PD153035 increases the retinoic acid receptor-beta mRNA half-life. No other retinoid receptor, nor estrogen receptor-alpha, nor RASSF1A is upregulated by PD153035. Thus PD153035 induces retinoic acid receptor-beta by ErbB-independent transcriptional and post-transcriptional mechanisms. This report highlights a triple action for an ErbB-1 inhibitor (ErbB-1 inhibition, DNA intercalation, retinoic acid receptor-beta-induction). Such multitargeting drugs bear great potential for cancer

  14. Cell type-specific pharmacology of NMDA receptors using masked MK801

    PubMed Central

    Yang, Yunlei; Lee, Peter; Sternson, Scott M

    2015-01-01

    N-Methyl-D-aspartate receptors (NMDA-Rs) are ion channels that are important for synaptic plasticity, which is involved in learning and drug addiction. We show enzymatic targeting of an NMDA-R antagonist, MK801, to a molecularly defined neuronal population with the cell-type-selectivity of genetic methods and the temporal control of pharmacology. We find that NMDA-Rs on dopamine neurons are necessary for cocaine-induced synaptic potentiation, demonstrating that cell type-specific pharmacology can be used to dissect signaling pathways within complex brain circuits. DOI: http://dx.doi.org/10.7554/eLife.10206.001 PMID:26359633

  15. Developmental changes in NMDA receptor expression in the platyfish brain

    NASA Technical Reports Server (NTRS)

    Flynn, K. M.; Schreibman, M. P.; Magliulo-Cepriano, L.

    1997-01-01

    We have examined the distribution of the N-methyl-D-aspartate (NMDA) receptor in the brain of a freshwater teleost using an antibody against the R1 subunit of the receptor (NMDAR1). The primary site of localization was the nucleus olfactoretinalis (NOR), a significant gonadotropin releasing hormone (GnRH)-containing brain nucleus. The number of cells expressing NMDAR1 in this nucleus was dependent upon developmental stage, with pubescent and mature animals displaying significantly more stained cells than immature and senescent animals. This is the first reported observation of age- and maturity-related NMDA receptor association with GnRH-containing brain areas.

  16. Phytanic acid and pristanic acid, branched-chain fatty acids associated with Refsum disease and other inherited peroxisomal disorders, mediate intracellular Ca2+ signaling through activation of free fatty acid receptor GPR40.

    PubMed

    Kruska, Nicol; Reiser, Georg

    2011-08-01

    The accumulation of the two branched-chain fatty acids phytanic acid and pristanic acid is known to play an important role in several diseases with peroxisomal impairment, like Refsum disease, Zellweger syndrome and α-methylacyl-CoA racemase deficiency. Recent studies elucidated that the toxic activity of phytanic acid and pristanic acid is mediated by multiple mitochondrial dysfunctions, generation of reactive oxygen species and Ca2+ deregulation via the InsP3-Ca2+ signaling pathway in glial cells. However, the exact signaling mechanism through which both fatty acids mediate toxicity is still under debate. Here, we studied the ability of phytanic acid and pristanic acid to activate the free fatty acid receptor GPR40, a G-protein-coupled receptor, which was described to be involved in the Ca2+ signaling of fatty acids. We treated HEK 293 cells expressing the GPR40 receptor with phytanic acid or pristanic acid. This resulted in a significant increase in the intracellular Ca2+ level, similar to the effect seen after treatment with the synthetic GPR40 agonist GW9508. Furthermore, we demonstrate that the GPR40 activation might be due to an interaction of the carboxylate moiety of fatty acids with the receptor. Our findings indicate that the phytanic acid- and pristanic acid-mediated Ca2+ deregulation can involve the activation of GPR40. Therefore, we suppose that activation of GPR40 might be part of the signaling cascade of the toxicity of phytanic and pristanic acids.

  17. Bovine adenovirus serotype 3 utilizes sialic acid as a cellular receptor for virus entry.

    PubMed

    Li, Xiaoxin; Bangari, Dinesh S; Sharma, Anurag; Mittal, Suresh K

    2009-09-30

    Bovine adenovirus serotype 3 (BAd3) and porcine adenovirus serotype 3 (PAd3) entry into the host cells is independent of Coxsackievirus adenovirus receptor and integrins. The role of sialic acid in BAd3 and PAd3 entry was investigated. Removal of sialic acid by neuraminidase, or blocking sialic acid by wheat germ agglutinin lectin significantly inhibited BAd3, but not PAd3, transduction of Madin-Darby bovine kidney cells. Maackia amurensis agglutinin or Sambucus nigra (elder) agglutinin treatment efficiently blocked BAd3 transduction suggesting that BAd3 utilized alpha(2,3)-linked and alpha(2,6)-linked sialic acid as a cell receptor. BAd3 transduction of MDBK cells was sensitive to sodium periodate, bromelain, or trypsin treatment indicating that the receptor sialoconjugate was a glycoprotein rather than a ganglioside. To determine sialic acid-containing cell membrane proteins that bind to BAd3, virus overlay protein binding assay (VOPBA) was performed and showed that sialylated cell membrane proteins in size of approximately 97 and 34 kDa bind to BAd3. The results suggest that sialic acid serves as a primary receptor for BAd3.

  18. [Discovery of potential nicotinic acid receptor agonists from Chinese herbal medicines based on molecular simulation].

    PubMed

    Jiang, Lu-Di; He, Yu-Su; Zhang, Yan-Ling

    2014-12-01

    Nicotinic acid could increase high density lipoprotein and reduce serum total cholesterol, low density lipoprotein cholesterol and triglycerides in human bodies, thus is frequently applied in treating low high-density lipoprotein cholesterol and hypertriglyceridemia in clinic. However, according to the findings, nicotinic acid could also cause adverse effects, such as skin flush, beside its curative effects. In this study, bioisosterism, fragment-based search and Lipinski's Rule of Five were used to preliminarily screen out potential TCM ingredients that may have similar pharmacological effects with nicotinic acid from Traditional Chinese medicine database (TCMD). Afterwards, homology modeling and flexible docking were used to further screen out potential nicotinic acid receptor agonists. As a result, eleven candidate compounds were derived from eight commonly used traditional Chinese medicines. Specifically, all of the candidate compounds' interaction with nicotinic acid receptor was similar to nicotinic acid, and their docking scores were all higher than that of nicotinic acid, but their druggability remained to be further studied. Some of the eight source traditional Chinese medicines were used to lower lipid according to literature studies, implying that they may show effect through above means. In summary, this study provides basis and reference for extracting new nicotinic acid receptor agonists from traditional Chinese medicines and improving the medication status of hyperlipidemia.

  19. A Mollusk Retinoic Acid Receptor (RAR) Ortholog Sheds Light on the Evolution of Ligand Binding

    PubMed Central

    Gutierrez-Mazariegos, Juliana; Nadendla, Eswar Kumar; Lima, Daniela; Pierzchalski, Keely; Jones, Jace W.; Kane, Maureen; Nishikawa, Jun-Ichi; Hiromori, Youhei; Nakanishi, Tsuyoshi; Santos, Miguel M.; Castro, L. Filipe C.; Bourguet, William

    2014-01-01

    Nuclear receptors are transcription factors that regulate networks of target genes in response to small molecules. There is a strong bias in our knowledge of these receptors because they were mainly characterized in classical model organisms, mostly vertebrates. Therefore, the evolutionary origins of specific ligand-receptor couples still remain elusive. Here we present the identification and characterization of a retinoic acid receptor (RAR) from the mollusk Nucella lapillus (NlRAR). We show that this receptor specifically binds to DNA response elements organized in direct repeats as a heterodimer with retinoid X receptor. Surprisingly, we also find that NlRAR does not bind all-trans retinoic acid or any other retinoid we tested. Furthermore, NlRAR is unable to activate the transcription of reporter genes in response to stimulation by retinoids and to recruit coactivators in the presence of these compounds. Three-dimensional modeling of the ligand-binding domain of NlRAR reveals an overall structure that is similar to vertebrate RARs. However, in the ligand-binding pocket (LBP) of the mollusk receptor, the alteration of several residues interacting with the ligand has apparently led to an overall decrease in the strength of the interaction with the ligand. Accordingly, mutations of NlRAR at key positions within the LBP generate receptors that are responsive to retinoids. Altogether our data suggest that, in mollusks, RAR has lost its affinity for all-trans retinoic acid, highlighting the evolutionary plasticity of its LBP. When put in an evolutionary context, our results reveal new structural and functional features of nuclear receptors validated by millions of years of evolution that were impossible to reveal in model organisms. PMID:25116705

  20. Farnesoid X Receptor Agonists and Other Bile Acid Signaling Strategies for Treatment of Liver Disease.

    PubMed

    Halilbasic, Emina; Fuchs, Claudia; Traussnigg, Stefan; Trauner, Michael

    2016-01-01

    The intracellular nuclear receptor farnesoid X receptor (FXR) and the transmembrane G protein-coupled receptor 5 (TGR5) respond to bile acids (BAs) by activating transcriptional networks and/or signaling cascades. These cascades affect the expression of a great number of target genes relevant for BA, cholesterol, lipid and carbohydrate metabolism, as well as genes involved in inflammation, fibrosis and carcinogenesis. FXR activation in the liver tissue and beyond, such as the gut-liver axis, kidney and adipose tissue, plays a role in metabolic diseases. These BA receptors activators hold promise to become a new class of drugs to be used in the treatment of chronic liver disease, hepatocellular cancer and extrahepatic inflammatory and metabolic diseases. This review discusses the relevant BA receptors, the new drugs that target BA transport and signaling and their possible applications. PMID:27332721

  1. Imaging Cancer Cells Expressing the Folate Receptor with Carbon Dots Produced from Folic Acid.

    PubMed

    Bhunia, Susanta Kumar; Maity, Amit Ranjan; Nandi, Sukhendu; Stepensky, David; Jelinek, Raz

    2016-04-01

    Development of new imaging tools for cancer cells in vitro and in vitro is important for advancing cancer research, elucidating drug effects upon cancer cells, and studying cellular processes. We showed that fluorescent carbon dots (C-dots) synthesized from folic acid can serve as an effective vehicle for imaging cancer cells expressing the folate receptor on their surface. The C-dots, synthesized through a simple one-step process from folic acid as the carbon source, exhibited selectivity towards cancer cells displaying the folate receptor, making such cells easily distinguishable in fluorescence microscopy imaging. Biophysical measurements and competition experiments both confirmed the specific targeting and enhanced uptake of C-dots by the folate receptor-expressing cells. The folic acid-derived C-dots were not cytotoxic, and their use in bioimaging applications could aid biological studies of cancer cells, identification of agonists/antagonists, and cancer diagnostics.

  2. TRIP6 Enhances Lysophosphatidic Acid-induced Cell Migration by Interacting with the Lysophosphatidic Acid 2 Receptor*

    PubMed Central

    Xu, Jun; Lai, Yun-Ju; Lin, Weei-Chin; Lin, Fang-Tsyr

    2014-01-01

    Lysophosphatidic acid (LPA) induces actin rearrangement, focal adhesion assembly, and cell migration through the activation of small G protein Rho and its downstream effectors. These diverse cellular responses are mediated by its associated G protein-coupled receptors. However, the mechanisms and specificity by which these LPA receptors mediate LPA actions are still poorly understood. Here we show that LPA stimulation promotes the interaction of the LPA2 receptor with a focal adhesion molecule, TRIP6 (thyroid receptor interacting protein 6)/ZRP-1 (zyxin-related protein 1). TRIP6 directly binds to the carboxyl-terminal tail of the LPA2 receptor through its LIM domains. LPA-dependent recruitment of TRIP6 to the plasma membrane promotes its targeting to focal adhesions and co-localization with actin stress fibers. In addition, TRIP6 associates with the components of focal complexes including paxillin, focal adhesion kinase, c-Src, and p130cas in an agonist-dependent manner. Overexpression of TRIP6 augments LPA-induced cell migration; in contrast, suppression of endogenous TRIP6 expression by a TRIP6-specific small interfering RNA reduces it in SKOV3 ovarian cancer cells. Strikingly, the association with TRIP6 is specific to the LPA2 receptor but not LPA1 or LPA3 receptor, indicating a specific role for TRIP6 in regulating LPA2 receptor-mediated signaling. Taken together, our results suggest that TRIP6 functions at a point of convergence between the activated LPA2 receptor and downstream signals involved in cell adhesion and migration. PMID:14688263

  3. Glutamate receptor-like channels in plants: a role as amino acid sensors in plant defence?

    PubMed Central

    Roberts, Michael R.

    2014-01-01

    Plant glutamate receptor-like genes (GLRs) are homologous to the genes for mammalian ionotropic glutamate receptors (iGluRs), after which they were named, but in the 16 years since their existence was first revealed, progress in elucidating their biological role has been disappointingly slow. Recently, however, studies from a number of laboratories focusing on the model plant species Arabidopsis thaliana (L.) have thrown new light on the functional properties of some members of the GLR gene family. One important finding has been that plant GLR receptors have a much broader ligand specificity than their mammalian iGluR counterparts, with evidence that some individual GLR receptors can be gated by as many as seven amino acids. These results, together with the ubiquity of their expression throughout the plant, open up the possibility that GLR receptors could have a pervasive role in plants as non-specific amino acid sensors in diverse biological processes. Addressing what one of these roles could be, recent studies examining the wound response and disease susceptibility in GLR knockout mutants have provided evidence that some members of clade 3 of the GLR gene family encode important components of the plant's defence response. Ways in which this family of amino acid receptors might contribute to the plant's ability to respond to an attack from pests and pathogens are discussed. PMID:24991414

  4. The bile acid membrane receptor TGR5 as an emerging target in metabolism and inflammation.

    PubMed

    Pols, Thijs W H; Noriega, Lilia G; Nomura, Mitsunori; Auwerx, Johan; Schoonjans, Kristina

    2011-06-01

    Bile acids (BAs) are amphipathic molecules that facilitate the uptake of lipids, and their levels fluctuate in the intestine as well as in the blood circulation depending on food intake. Besides their role in dietary lipid absorption, bile acids function as signaling molecules capable to activate specific receptors. These BA receptors are not only important in the regulation of bile acid synthesis and their metabolism, but also regulate glucose homeostasis, lipid metabolism, and energy expenditure. These processes are important in diabetes and other facets of the metabolic syndrome, which represents a considerable increasing health burden. In addition to the function of the nuclear receptor FXRα in regulating local effects in the organs of the enterohepatic axis, increasing evidence points to a crucial role of the G-protein coupled receptor (GPCR) TGR5 in mediating systemic actions of BAs. Here we discuss the current knowledge on BA receptors, with a strong focus on the cell membrane receptor TGR5, which emerges as a valuable target for intervention in metabolic diseases. PMID:21145931

  5. Free fatty acids and protein kinase C activation induce GPR120 (free fatty acid receptor 4) phosphorylation.

    PubMed

    Sánchez-Reyes, Omar B; Romero-Ávila, M Teresa; Castillo-Badillo, Jean A; Takei, Yoshinori; Hirasawa, Akira; Tsujimoto, Gozoh; Villalobos-Molina, Rafael; García-Sáinz, J Adolfo

    2014-01-15

    GPR120, free fatty acid receptor 4, is a recently deorphanized G protein-coupled receptor that seems to play cardinal roles in the regulation of metabolism and in the pathophysiology of inflammatory and metabolic disorders. In the present work a GPR120-Venus fusion protein was expressed in HEK293 Flp-In T-REx cells and its function (increase in intracellular calcium) and phosphorylation were studied. It was observed that the fusion protein migrated in sodium dodecyl sulfate-polyacrylamide gels as a band with a mass of ≈70-75kDa, although other bands of higher apparent weight (>130kDa) were also detected. Cell stimulation with docosahexaenoic acid or α-linolenic acid induced concentration-dependent increases in intracellular calcium and GPR120 phosphorylation. Activation of protein kinase C with phorbol esters also induced a marked receptor phosphorylation but did not alter the ability of 1µM docosahexaenoic acid to increase the intracellular calcium concentration. Phorbol ester-induced GPR120 phosphorylation, but not that induced with docosahexaenoic acid, was blocked by protein kinase C inhibitors (bis-indolyl-maleimide I and Gö 6976) suggesting that conventional kinase isoforms mediate this action. The absence of effect of protein kinase C inhibitors on agonist-induced GPR120 phosphorylation indicates that this kinase does not play a major role in agonist-induced receptor phosphorylation. Docosahexaenoic acid action was associated with marked GPR120 internalization whereas that induced with phorbol esters was smaller at early times. PMID:24239485

  6. Statistical Mechanics Model for the Interaction between the Neurotransmitter γ-Aminobutyric acid and GABAA Receptors

    NASA Astrophysics Data System (ADS)

    Zafar, Sufi; Saxena, Nina C.; Conrad, Kevin A.; Hussain, Arif

    2004-07-01

    Interactions between the neurotransmitter γ-aminobutyric acid (GABA) and GABAA receptor ion channels play an important role in the central nervous system. A statistical mechanics model is proposed for the interaction between GABA and GABAA receptors. The model provides good fits to the electrophysiology data as well as an estimation of receptor activation energies, and predicts the temperature dependence consistent with measurements. In addition, the model provides insights into single channel conductance measurements. This model is also applicable to other ligand-gated ion channels with similar pentameric structures.

  7. Site-specific incorporation of keto amino acids into functional G protein-coupled receptors using unnatural amino acid mutagenesis.

    PubMed

    Ye, Shixin; Köhrer, Caroline; Huber, Thomas; Kazmi, Manija; Sachdev, Pallavi; Yan, Elsa C Y; Bhagat, Aditi; RajBhandary, Uttam L; Sakmar, Thomas P

    2008-01-18

    G protein-coupled receptors (GPCRs) are ubiquitous heptahelical transmembrane proteins involved in a wide variety of signaling pathways. The work described here on application of unnatural amino acid mutagenesis to two GPCRs, the chemokine receptor CCR5 (a major co-receptor for the human immunodeficiency virus) and rhodopsin (the visual photoreceptor), adds a new dimension to studies of GPCRs. We incorporated the unnatural amino acids p-acetyl-L-phenylalanine (Acp) and p-benzoyl-L-phenylalanine (Bzp) into CCR5 at high efficiency in mammalian cells to produce functional receptors harboring reactive keto groups at three specific positions. We obtained functional mutant CCR5, at levels up to approximately 50% of wild type as judged by immunoblotting, cell surface expression, and ligand-dependent calcium flux. Rhodopsin containing Acp at three different sites was also purified in high yield (0.5-2 microg/10(7) cells) and reacted with fluorescein hydrazide in vitro to produce fluorescently labeled rhodopsin. The incorporation of reactive keto groups such as Acp or Bzp into GPCRs allows their reaction with different reagents to introduce a variety of spectroscopic and other probes. Bzp also provides the possibility of photo-cross-linking to identify precise sites of protein-protein interactions, including GPCR binding to G proteins and arrestins, and for understanding the molecular basis of ligand recognition by chemokine receptors. PMID:17993461

  8. A differential fluorescent receptor for nucleic acid analysis.

    PubMed

    Bengtson, Hillary N; Kolpashchikov, Dmitry M

    2014-01-24

    Differential receptors use an array of sensors to recognize analytes. Each sensor in the array can recognize not one, but several analytes with different rates, so a single analyte triggers a response of several sensors in the array. The receptor thus produces a pattern of signals that is unique for each analyte, thereby enabling identification of a specific analyte by producing a "fingerprint" pattern. We applied this approach for the analysis of DNA sequences of Mycobacterium tuberculosis strains that differ by single nucleotide substitutions in the 81-bp hot-spot region that imparts rifampin resistance. The technology takes advantage of the new multicomponent, selfassembling sensor, which produces a fluorescent signal in the presence of specific DNA sequences. A differential fluorescent receptor (DFR) contained an array of three such sensors and differentiated at least eight DNA sequences. The approach requires only one molecular-beacon-like fluorescent reporter, which can be used by all three sensors. The DFR developed in this study represents a cost-efficient alternative to molecular diagnostic technologies that use fluorescent hybridization probes.

  9. The NMDA receptor functions independently and as an LRP1 co-receptor to promote Schwann cell survival and migration.

    PubMed

    Mantuano, Elisabetta; Lam, Michael S; Shibayama, Masataka; Campana, W Marie; Gonias, Steven L

    2015-09-15

    NMDA receptors (NMDA-Rs) are ionotropic glutamate receptors, which associate with LDL-receptor-related protein-1 (LRP1) to trigger cell signaling in response to protein ligands in neurons. Here, we demonstrate for the first time that the NMDA-R is expressed by rat Schwann cells and functions independently and with LRP1 to regulate Schwann cell physiology. The NR1 (encoded by GRIN1) and NR2b (encoded by GRIN2B) NMDA-R subunits were expressed by cultured Schwann cells and upregulated in sciatic nerves following crush injury. The ability of LRP1 ligands to activate ERK1/2 (also known as MAPK3 and MAPK1, respectively) and promote Schwann cell migration required the NMDA-R. NR1 gene silencing compromised Schwann cell survival. Injection of the LRP1 ligands tissue-type plasminogen activator (tPA, also known as PLAT) or MMP9-PEX into crush-injured sciatic nerves activated ERK1/2 in Schwann cells in vivo, and the response was blocked by systemic treatment with the NMDA-R inhibitor MK801. tPA was unique among the LRP1 ligands examined because tPA activated cell signaling and promoted Schwann cell migration by interacting with the NMDA-R independently of LRP1, albeit with delayed kinetics. These results define the NMDA-R as a Schwann cell signaling receptor for protein ligands and a major regulator of Schwann cell physiology, which may be particularly important in peripheral nervous system (PNS) injury. PMID:26272917

  10. The NMDA receptor functions independently and as an LRP1 co-receptor to promote Schwann cell survival and migration

    PubMed Central

    Mantuano, Elisabetta; Lam, Michael S.; Shibayama, Masataka; Campana, W. Marie; Gonias, Steven L.

    2015-01-01

    ABSTRACT NMDA receptors (NMDA-Rs) are ionotropic glutamate receptors, which associate with LDL-receptor-related protein-1 (LRP1) to trigger cell signaling in response to protein ligands in neurons. Here, we demonstrate for the first time that the NMDA-R is expressed by rat Schwann cells and functions independently and with LRP1 to regulate Schwann cell physiology. The NR1 (encoded by GRIN1) and NR2b (encoded by GRIN2B) NMDA-R subunits were expressed by cultured Schwann cells and upregulated in sciatic nerves following crush injury. The ability of LRP1 ligands to activate ERK1/2 (also known as MAPK3 and MAPK1, respectively) and promote Schwann cell migration required the NMDA-R. NR1 gene silencing compromised Schwann cell survival. Injection of the LRP1 ligands tissue-type plasminogen activator (tPA, also known as PLAT) or MMP9-PEX into crush-injured sciatic nerves activated ERK1/2 in Schwann cells in vivo, and the response was blocked by systemic treatment with the NMDA-R inhibitor MK801. tPA was unique among the LRP1 ligands examined because tPA activated cell signaling and promoted Schwann cell migration by interacting with the NMDA-R independently of LRP1, albeit with delayed kinetics. These results define the NMDA-R as a Schwann cell signaling receptor for protein ligands and a major regulator of Schwann cell physiology, which may be particularly important in peripheral nervous system (PNS) injury. PMID:26272917

  11. Reduction of brain kynurenic acid improves cognitive function.

    PubMed

    Kozak, Rouba; Campbell, Brian M; Strick, Christine A; Horner, Weldon; Hoffmann, William E; Kiss, Tamas; Chapin, Douglas S; McGinnis, Dina; Abbott, Amanda L; Roberts, Brooke M; Fonseca, Kari; Guanowsky, Victor; Young, Damon A; Seymour, Patricia A; Dounay, Amy; Hajos, Mihaly; Williams, Graham V; Castner, Stacy A

    2014-08-01

    The elevation of kynurenic acid (KYNA) observed in schizophrenic patients may contribute to core symptoms arising from glutamate hypofunction, including cognitive impairments. Although increased KYNA levels reduce excitatory neurotransmission, KYNA has been proposed to act as an endogenous antagonist at the glycine site of the glutamate NMDA receptor (NMDAR) and as a negative allosteric modulator at the α7 nicotinic acetylcholine receptor. Levels of KYNA are elevated in CSF and the postmortem brain of schizophrenia patients, and these elevated levels of KYNA could contribute to NMDAR hypofunction and the cognitive deficits and negative symptoms associated with this disease. However, the impact of endogenously produced KYNA on brain function and behavior is less well understood due to a paucity of pharmacological tools. To address this issue, we identified PF-04859989, a brain-penetrable inhibitor of kynurenine aminotransferase II (KAT II), the enzyme responsible for most brain KYNA synthesis. In rats, systemic administration of PF-04859989 dose-dependently reduced brain KYNA to as little as 28% of basal levels, and prevented amphetamine- and ketamine-induced disruption of auditory gating and improved performance in a sustained attention task. It also prevented ketamine-induced disruption of performance in a working memory task and a spatial memory task in rodents and nonhuman primates, respectively. Together, these findings support the hypotheses that endogenous KYNA impacts cognitive function and that inhibition of KAT II, and consequent lowering of endogenous brain KYNA levels, improves cognitive performance under conditions considered relevant for schizophrenia.

  12. Recent Progress on Bile Acid Receptor Modulators for Treatment of Metabolic Diseases.

    PubMed

    Xu, Yanping

    2016-07-28

    Bile acids are steroid-derived molecules synthesized in the liver, secreted from hepatocytes into the bile canaliculi, and subsequently stored in the gall bladder. During the feeding, bile flows into the duodenum, where it contributes to the solubilization and digestion of lipid-soluble nutrients. After a meal, bile-acid levels increase in the intestine, liver, and also in the systemic circulation. Therefore, serum bile-acid levels serve as an important sensing mechanism for nutrient and energy. Recent studies have described bile acids as versatile signaling molecules endowed with systemic endocrine functions. Bile acids are ligands for G-protein coupled receptors (GPCRs) such as TGR5 (also known as GPBAR1, M-BAR, and BG37) and nuclear hormone receptors including farnesoid X receptor (FXR; also known as NR1H4). Acting through these diverse signaling pathways, bile acids regulate triglyceride, cholesterol, glucose homeostasis, and energy expenditure. These bile-acid-controlled signaling pathways have become the source of promising novel drug targets to treat common metabolic and hepatic diseases. PMID:26878262

  13. Regulation of Expression of Citrate Synthase by the Retinoic Acid Receptor-Related Orphan Receptor α (RORα)

    PubMed Central

    Crumbley, Christine; Wang, Yongjun; Banerjee, Subhashis; Burris, Thomas P.

    2012-01-01

    The retinoic acid receptor-related orphan receptor α (RORα) is a member of the nuclear receptor superfamily of transcription factors that plays an important role in regulation of the circadian rhythm and metabolism. Mice lacking a functional RORα display a range of metabolic abnormalities including decreased serum cholesterol and plasma triglycerides. Citrate synthase (CS) is a key enzyme of the citric acid cycle that provides energy for cellular function. Additionally, CS plays a critical role in providing citrate derived acetyl-CoA for lipogenesis and cholesterologenesis. Here, we identified a functional RORα response element (RORE) in the promoter of the CS gene. ChIP analysis demonstrates RORα occupancy of the CS promoter and a putative RORE binds to RORα effectively in an electrophoretic mobility shift assay and confers RORα responsiveness to a reporter gene in a cotransfection assay. We also observed a decrease in CS gene expression and CS enzymatic activity in the staggerer mouse, which has a mutation of in the Rora gene resulting in nonfunctional RORα protein. Furthermore, we found that SR1001 a RORα inverse agonist eliminated the circadian pattern of expression of CS mRNA in mice. These data suggest that CS is a direct RORα target gene and one mechanism by which RORα regulates lipid metabolism is via regulation of CS expression. PMID:22485150

  14. Amiloride inhibition of gamma-aminobutyric acid(A) receptors depends upon the alpha subunit subtype.

    PubMed

    Fisher, Janet L

    2002-06-01

    gamma-Aminobutyric acid(A) (GABA(A)) receptors (GABARs) are responsible for most fast inhibitory neurotransmission in the mammalian brain. The GABARs contain several allosteric modulatory sites, many of which are useful clinically. The activity of most of these modulators depends upon the subunit composition of the receptor. The diuretic amiloride was previously reported to inhibit GABARs in frog sensory neurons. We measured its effects on recombinant GABARs to determine its mechanism of action at mammalian receptors and to examine the effect of subunit composition. Amiloride acted primarily as a competitive antagonist, reducing the sensitivity of the receptor to GABA without affecting the maximal current amplitude. Receptors containing an alpha6 subunit were about 10-fold more sensitive to amiloride than those containing other alpha subunits. In contrast, the identity of the beta or gamma subtype had little effect on amiloride sensitivity. Although several other modulators have specific effects at alpha6-containing receptors, amiloride is the first inhibitor to be reported with no additional dependence on the identity of the beta or gamma subunit. Therefore, it probably represents a unique modulatory site on the GABAR, which could be useful for developing drugs targeting these receptors. The selective activity of amiloride could also be helpful for isolating the contribution of receptors composed of alpha6 subtypes in heterogeneous native GABAR populations.

  15. Structural basis for molecular recognition of folic acid by folate receptors.

    PubMed

    Chen, Chen; Ke, Jiyuan; Zhou, X Edward; Yi, Wei; Brunzelle, Joseph S; Li, Jun; Yong, Eu-Leong; Xu, H Eric; Melcher, Karsten

    2013-08-22

    Folate receptors (FRα, FRβ and FRγ) are cysteine-rich cell-surface glycoproteins that bind folate with high affinity to mediate cellular uptake of folate. Although expressed at very low levels in most tissues, folate receptors, especially FRα, are expressed at high levels in numerous cancers to meet the folate demand of rapidly dividing cells under low folate conditions. The folate dependency of many tumours has been therapeutically and diagnostically exploited by administration of anti-FRα antibodies, high-affinity antifolates, folate-based imaging agents and folate-conjugated drugs and toxins. To understand how folate binds its receptors, we determined the crystal structure of human FRα in complex with folic acid at 2.8 Å resolution. FRα has a globular structure stabilized by eight disulphide bonds and contains a deep open folate-binding pocket comprised of residues that are conserved in all receptor subtypes. The folate pteroate moiety is buried inside the receptor, whereas its glutamate moiety is solvent-exposed and sticks out of the pocket entrance, allowing it to be conjugated to drugs without adversely affecting FRα binding. The extensive interactions between the receptor and ligand readily explain the high folate-binding affinity of folate receptors and provide a template for designing more specific drugs targeting the folate receptor system.

  16. Characterization of cDNAs encoding the chick retinoic acid receptor gamma 2 and preferential distribution of retinoic acid receptor gamma transcripts during chick skin development.

    PubMed

    Michaille, J J; Blanchet, S; Kanzler, B; Garnier, J M; Dhouailly, D

    1994-12-01

    Retinoic acid receptors alpha, beta and gamma (RAR alpha, beta and gamma) are ligand-inductible transcriptional activators which belong to the steroid/thyroid hormone receptor superfamily. At least two major isoforms (1 and 2) of each RAR arise by differential use of two promoters and alternative splicing. In mouse, the three RAR genes are expressed in stage- and tissue-specific patterns during embryonic development. In order to understand the role of the different RARs in chick, RAR gamma 2 cDNAs were isolated from an 8.5-day (stage 35 of Hamburger and Hamilton) chick embryo skin library. The deduced chick RAR gamma 2 amino acid sequence displays uncommon features such as 21 specific amino acid replacements, 12 of them being clustered in the amino-terminal region (domains A2 and B), and a truncated acidic carboxy-terminal region (F domain). However, the pattern of RAR gamma expression in chick embryo resembles that reported in mouse, particularly in skin where RAR gamma expression occurs in both the dermal and epidermal layers at the beginning of feather formation, and is subsequently restricted to the differentiating epidermal cells. Northern blot analysis suggests that different RAR gamma isoforms could be successively required during chick development.

  17. Regulation of Neuronal Gene Expression and Survival by Basal NMDA Receptor Activity: A Role for Histone Deacetylase 4

    PubMed Central

    Chen, Yelin; Wang, Yuanyuan; Modrusan, Zora

    2014-01-01

    Neuronal gene expression is modulated by activity via calcium-permeable receptors such as NMDA receptors (NMDARs). While gene expression changes downstream of evoked NMDAR activity have been well studied, much less is known about gene expression changes that occur under conditions of basal neuronal activity. In mouse dissociated hippocampal neuronal cultures, we found that a broad NMDAR antagonist, AP5, induced robust gene expression changes under basal activity, but subtype-specific antagonists did not. While some of the gene expression changes are also known to be downstream of stimulated NMDAR activity, others appear specific to basal NMDAR activity. The genes altered by AP5 treatment of basal cultures were enriched for pathways related to class IIa histone deacetylases (HDACs), apoptosis, and synapse-related signaling. Specifically, AP5 altered the expression of all three class IIa HDACs that are highly expressed in the brain, HDAC4, HDAC5, and HDAC9, and also induced nuclear accumulation of HDAC4. HDAC4 knockdown abolished a subset of the gene expression changes induced by AP5, and led to neuronal death under long-term tetrodotoxin or AP5 treatment in rat hippocampal organotypic slice cultures. These data suggest that basal, but not evoked, NMDAR activity regulates gene expression in part through HDAC4, and, that HDAC4 has neuroprotective functions under conditions of low NMDAR activity. PMID:25392500

  18. Minireview: The Effects of Species Ortholog and SNP Variation on Receptors for Free Fatty Acids

    PubMed Central

    Hudson, Brian D.; Murdoch, Hannah

    2013-01-01

    Although it is widely assumed that species orthologs of hormone-responsive G protein-coupled receptors will be activated by the same endogenously produced ligand(s), variation in potency, particularly in cases in which more than 1 receptor responds to the same hormone, can result in challenges in defining the contribution of individual receptors in different species. This can create considerably greater issues when using synthetic chemical ligands and, in some cases, may result in a complete lack of efficacy of such a ligand when used in animal models of pathophysiology. In man, the concept that distinct responses of individuals to medicines may reflect differences in the ability of such drugs to bind to or activate single nucleotide polymorphism variants of receptors is more established as a concept but, in many cases, clear links between such variants that are associated with disease phenotypes and substantial differences in receptor ligand pharmacology have been more difficult to obtain. Herein we consider each of these issues for the group of free fatty acid receptors, FFA1-FFA4, defined to be activated by free fatty acids of varying chain length, which, based on their production by 1 tissue or location and action in distinct locations, have been suggested to possess characteristics of hormones. PMID:23686113

  19. Spinal NMDA receptor activation constrains inactivity-induced phrenic motor facilitation in Charles River Sprague-Dawley rats

    PubMed Central

    Streeter, K. A.

    2014-01-01

    Reduced spinal synaptic inputs to phrenic motor neurons elicit a unique form of spinal plasticity known as inactivity-induced phrenic motor facilitation (iPMF). iPMF requires tumor necrosis factor-α (TNF-α) and atypical protein kinase C (aPKC) activity within spinal segments containing the phrenic motor nucleus to stabilize early, transient increases in phrenic burst amplitude into long-lasting iPMF. Here we tested the hypothesis that spinal N-methyl-d-aspartate receptor (NMDAR) activation constrains long-lasting iPMF in some rat substrains. Phrenic motor output was recorded in anesthetized, ventilated Harlan (HSD) and Charles River (CRSD) Sprague-Dawley rats exposed to a 30-min central neural apnea. HSD rats expressed a robust, long-lasting (>60 min) increase in phrenic burst amplitude (i.e., long-lasting iPMF) when respiratory neural activity was restored. By contrast, CRSD rats expressed an attenuated, transient (∼15 min) iPMF. Spinal NMDAR inhibition with DL-2-amino-5-phosphonopentanoic acid (APV) before neural apnea or shortly (4 min) prior to the resumption of respiratory neural activity revealed long-lasting iPMF in CRSD rats that was phenotypically similar to that in HSD rats. By contrast, APV did not alter iPMF expression in HSD rats. Spinal TNF-α or aPKC inhibition impaired long-lasting iPMF enabled by NMDAR inhibition in CRSD rats, suggesting that similar mechanisms give rise to long-lasting iPMF in CRSD rats with NMDAR inhibition as those giving rise to long-lasting iPMF in HSD rats. These results suggest that NMDAR activation can impose constraints on TNF-α-induced aPKC activation after neural apnea, impairing stabilization of transient iPMF into long-lasting iPMF. These data may have important implications for understanding differential responses to reduced respiratory neural activity in a heterogeneous human population. PMID:25103979

  20. Contribution of N-methyl-D-aspartate receptors to attention and episodic spatial memory during senescence.

    PubMed

    Guidi, Michael; Rani, Asha; Karic, Semir; Severance, Barrett; Kumar, Ashok; Foster, Thomas C

    2015-11-01

    A decrease in N-methyl-D-aspartate receptor (NMDAR) function is associated with age-related cognitive impairments. However, NMDAR antagonists are prescribed for cognitive decline associated with age-related neurodegenerative disease, raising questions as to the role of NMDAR activity in cognitive function during aging. The current studies examined effects of NMDAR blockade on cognitive task that are sensitive to aging. Young and middle-age rats were trained on the five-choice serial reaction time task (5-CSRTT) and challenged with MK-801 (0.025, 0.05, and 0.1mg/kg or vehicle). Attention deficits were apparent in middle-age and performance of young and middle-age rats was enhanced for low doses of MK-801 (0.025 and 0.05). The beneficial effects on attention were reversed by the highest dose of MK-801. Older animals exhibited a delay-dependent impairment of episodic spatial memory examined on a delayed-matching to place water maze task. Similarly, a low dose of MK-801 (0.05mg/kg) impaired performance with increasing delay and aged animals were more susceptible to disruption by NMDAR blockade. Despite MK-801 impairment of episodic spatial memory, MK-801 had minimal effects on spatial reference memory. Our results confirm that NMDARs contribute to rapidly acquired and flexible spatial memory and support the idea that a decline in NMDAR function contributes to the age-related impairments in cognition.

  1. Distinct roles of NMDA receptors at different stages of granule cell development in the adult brain

    PubMed Central

    Mu, Yangling; Zhao, Chunmei; Toni, Nicolas; Yao, Jun; Gage, Fred H

    2015-01-01

    NMDA receptor (NMDAR)-dependent forms of synaptic plasticity are thought to underlie the assembly of developing neuronal circuits and to play a crucial role in learning and memory. It remains unclear how NMDAR might contribute to the wiring of adult-born granule cells (GCs). Here we demonstrate that nascent GCs lacking NMDARs but rescued from apoptosis by overexpressing the pro-survival protein Bcl2 were deficient in spine formation. Insufficient spinogenesis might be a general cause of cell death restricted within the NMDAR-dependent critical time window for GC survival. NMDAR loss also led to enhanced mushroom spine formation and synaptic AMPAR activity throughout the development of newborn GCs. Moreover, similar elevated synapse maturation in the absence of NMDARs was observed in neonate-generated GCs and CA1 pyramidal neurons. Together, these data suggest that NMDAR operates as a molecular monitor for controlling the activity-dependent establishment and maturation rate of synaptic connections between newborn neurons and others. DOI: http://dx.doi.org/10.7554/eLife.07871.001 PMID:26473971

  2. NMDA receptor-dependent LTD is required for consolidation but not acquisition of fear memory.

    PubMed

    Liu, Xing; Gu, Qin-Hua; Duan, Kaizheng; Li, Zheng

    2014-06-25

    NMDA receptor-dependent long-term depression (NMDAR-LTD) is a form of synaptic plasticity leading to long-lasting decreases in synaptic strength. NMDAR-LTD is essential for spatial and working memory, but its role in hippocampus-dependent fear memory has yet to be determined. Induction of NMDAR-LTD requires the activation of caspase-3 by cytochrome c. Cytochrome c normally resides in mitochondria and during NMDAR-LTD is released from mitochondria, a process promoted by Bax (Bcl-2-associated X protein). Bax induces cell death in apoptosis, but it plays a nonapoptotic role in NMDAR-LTD. Here, we investigated the role of NMDAR-LTD in fear memory in CA1-specific Bax knock-out mice. In hippocampal slices from these knock-out mice, while long-term potentiation of synaptic transmission, basal synaptic transmission, and paired-pulse ratio are intact, LTD in both young and fear-conditioned adult mice is obliterated. Interestingly, in CA1-specific Bax knock-out mice, long-term contextual fear memory is impaired, but the acquisition of fear memory and innate fear are normal. Moreover, these conditional Bax knock-out mice exhibit less behavioral despair. These findings indicate that NMDAR-LTD is required for consolidation, but not the acquisition of fear memory. Our study also shows that Bax plays an important role in depressive behavior.

  3. Bile Acids Trigger GLP-1 Release Predominantly by Accessing Basolaterally Located G Protein–Coupled Bile Acid Receptors

    PubMed Central

    Brighton, Cheryl A.; Rievaj, Juraj; Kuhre, Rune E.; Glass, Leslie L.; Schoonjans, Kristina; Holst, Jens J.

    2015-01-01

    Bile acids are well-recognized stimuli of glucagon-like peptide-1 (GLP-1) secretion. This action has been attributed to activation of the G protein–coupled bile acid receptor GPBAR1 (TGR5), although other potential bile acid sensors include the nuclear farnesoid receptor and the apical sodium-coupled bile acid transporter ASBT. The aim of this study was to identify pathways important for GLP-1 release and to determine whether bile acids target their receptors on GLP-1–secreting L-cells from the apical or basolateral compartment. Using transgenic mice expressing fluorescent sensors specifically in L-cells, we observed that taurodeoxycholate (TDCA) and taurolithocholate (TLCA) increased intracellular cAMP and Ca2+. In primary intestinal cultures, TDCA was a more potent GLP-1 secretagogue than taurocholate (TCA) and TLCA, correlating with a stronger Ca2+ response to TDCA. Using small-volume Ussing chambers optimized for measuring GLP-1 secretion, we found that both a GPBAR1 agonist and TDCA stimulated GLP-1 release better when applied from the basolateral than from the luminal direction and that luminal TDCA was ineffective when intestinal tissue was pretreated with an ASBT inhibitor. ASBT inhibition had no significant effect in nonpolarized primary cultures. Studies in the perfused rat gut confirmed that vascularly administered TDCA was more effective than luminal TDCA. Intestinal primary cultures and Ussing chamber–mounted tissues from GPBAR1-knockout mice did not secrete GLP-1 in response to either TLCA or TDCA. We conclude that the action of bile acids on GLP-1 secretion is predominantly mediated by GPBAR1 located on the basolateral L-cell membrane, suggesting that stimulation of gut hormone secretion may include postabsorptive mechanisms. PMID:26280129

  4. Bile Acids Trigger GLP-1 Release Predominantly by Accessing Basolaterally Located G Protein-Coupled Bile Acid Receptors.

    PubMed

    Brighton, Cheryl A; Rievaj, Juraj; Kuhre, Rune E; Glass, Leslie L; Schoonjans, Kristina; Holst, Jens J; Gribble, Fiona M; Reimann, Frank

    2015-11-01

    Bile acids are well-recognized stimuli of glucagon-like peptide-1 (GLP-1) secretion. This action has been attributed to activation of the G protein-coupled bile acid receptor GPBAR1 (TGR5), although other potential bile acid sensors include the nuclear farnesoid receptor and the apical sodium-coupled bile acid transporter ASBT. The aim of this study was to identify pathways important for GLP-1 release and to determine whether bile acids target their receptors on GLP-1-secreting L-cells from the apical or basolateral compartment. Using transgenic mice expressing fluorescent sensors specifically in L-cells, we observed that taurodeoxycholate (TDCA) and taurolithocholate (TLCA) increased intracellular cAMP and Ca(2+). In primary intestinal cultures, TDCA was a more potent GLP-1 secretagogue than taurocholate (TCA) and TLCA, correlating with a stronger Ca(2+) response to TDCA. Using small-volume Ussing chambers optimized for measuring GLP-1 secretion, we found that both a GPBAR1 agonist and TDCA stimulated GLP-1 release better when applied from the basolateral than from the luminal direction and that luminal TDCA was ineffective when intestinal tissue was pretreated with an ASBT inhibitor. ASBT inhibition had no significant effect in nonpolarized primary cultures. Studies in the perfused rat gut confirmed that vascularly administered TDCA was more effective than luminal TDCA. Intestinal primary cultures and Ussing chamber-mounted tissues from GPBAR1-knockout mice did not secrete GLP-1 in response to either TLCA or TDCA. We conclude that the action of bile acids on GLP-1 secretion is predominantly mediated by GPBAR1 located on the basolateral L-cell membrane, suggesting that stimulation of gut hormone secretion may include postabsorptive mechanisms.

  5. Cross-talk between lysophosphatidic acid receptor 1 and tropomyosin receptor kinase A promotes lung epithelial cell migration.

    PubMed

    Nan, Ling; Wei, Jianxin; Jacko, Anastasia M; Culley, Miranda K; Zhao, Jing; Natarajan, Viswanathan; Ma, Haichun; Zhao, Yutong

    2016-02-01

    Lysophosphatidic acid (LPA) is a bioactive lysophospholipid, which plays a crucial role in the regulation of cell proliferation, migration, and differentiation. LPA exerts its biological effects mainly through binding to cell-surface LPA receptors (LPA1-6), which belong to the G protein-coupled receptor (GPCR) family. Recent studies suggest that cross-talk between receptor tyrosine kinases (RTKs) and GPCRs modulates GPCRs-mediated signaling. Tropomyosin receptor kinase A (TrkA) is a RTK, which mediates nerve growth factor (NGF)-induced biological functions including cell migration in neuronal and non-neuronal cells. Here, we show LPA1 transactivation of TrkA in murine lung epithelial cells (MLE12). LPA induced tyrosine phosphorylation of TrkA in both time- and dose-dependent manners. Down-regulation of LPA1 by siRNA transfection attenuated LPA-induced phosphorylation of TrkA, suggesting a cross-talk between LPA1 and TrkA. To investigate the molecular regulation of the cross-talk, we focused on the interaction between LPA1 and TrkA. We found that LPA induced interaction between LPA1 and TrkA. The LPA1/TrkA complex was localized on the plasma membrane and in the cytoplasm. The C-terminus of LPA1 was identified as the binding site for TrkA. Inhibition of TrkA attenuated LPA-induced phosphorylation of TrkA and LPA1 internalization, as well as lung epithelial cell migration. These studies provide a molecular mechanism for the transactivation of TrkA by LPA, and suggest that the cross-talk between LPA1 and TrkA regulates LPA-induced receptor internalization and lung epithelial cell migration. PMID:26597701

  6. Two N-glycosylation Sites in the GluN1 Subunit Are Essential for Releasing N-methyl-d-aspartate (NMDA) Receptors from the Endoplasmic Reticulum*

    PubMed Central

    Lichnerova, Katarina; Kaniakova, Martina; Park, Seung Pyo; Skrenkova, Kristyna; Wang, Ya-Xian; Petralia, Ronald S.; Suh, Young Ho; Horak, Martin

    2015-01-01

    NMDA receptors (NMDARs) comprise a subclass of neurotransmitter receptors whose surface expression is regulated at multiple levels, including processing in the endoplasmic reticulum (ER), intracellular trafficking via the Golgi apparatus, internalization, recycling, and degradation. With respect to early processing, NMDARs are regulated by the availability of GluN subunits within the ER, the presence of ER retention and export signals, and posttranslational modifications, including phosphorylation and palmitoylation. However, the role of N-glycosylation, one of the most common posttranslational modifications, in regulating NMDAR processing has not been studied in detail. Using biochemistry, confocal and electron microscopy, and electrophysiology in conjunction with a lentivirus-based molecular replacement strategy, we found that NMDARs are released from the ER only when two asparagine residues in the GluN1 subunit (Asn-203 and Asn-368) are N-glycosylated. Although the GluN2A and GluN2B subunits are also N-glycosylated, their N-glycosylation sites do not appear to be essential for surface delivery of NMDARs. Furthermore, we found that removing N-glycans from native NMDARs altered the receptor affinity for glutamate. Our results suggest a novel mechanism by which neurons ensure that postsynaptic membranes contain sufficient numbers of functional NMDARs. PMID:26045554

  7. Ubiquitin/proteasome pathway regulates levels of retinoic acid receptor gamma and retinoid X receptor alpha in human keratinocytes.

    PubMed

    Boudjelal, M; Wang, Z; Voorhees, J J; Fisher, G J

    2000-04-15

    Repeated exposure of human skin to solar UV radiation leads to premature aging (photoaging) and skin cancer. UV-induced skin damage can be ameliorated by all-trans retinoic acid treatment. The actions of retinoic acid in skin keratinocytes are mediated primarily by nuclear retinoic acid receptor gamma (RARgamma) and retinoid X receptor alpha (RXRalpha). We found that exposure of cultured primary human keratinocytes to UV irradiation (30 mJ/cm2) substantially reduced (50-90%) RARgamma and RXRalpha mRNA and protein within 8 h. The rates of disappearance of RARgamma and RXRalpha proteins after UV exposure or treatment with the protein synthesis inhibitor cycloheximide were similar. UV irradiation did not increase the rate of breakdown of RARgamma or RXRalpha but rather reduced their rate of synthesis. The addition of proteasome inhibitors MG132 and LLvL, but not the lysosomal inhibitor E64, prevented loss of RARgamma and RXRalpha proteins after exposure of keratinocytes to either UV radiation or cycloheximide. Soluble extracts from nonirradiated or UV-irradiated keratinocytes possessed similar levels of proteasome activity that degraded RARgamma and RXRalpha proteins in vitro. Furthermore, RARgamma and RXRalpha were polyubiquitinated in intact cells. RXRalpha was found to contain two proline, glutamate/aspartate, serine, and threonine (PEST) motifs, which confer rapid turnover of many short-lived regulatory proteins that are degraded by the ubiquitin/proteasome pathway. However, the PEST motifs in RXRalpha did not function to regulate its stability, because deletion of the PEST motifs individually or together did not alter ubiquitination or proteasome-mediated degradation of RXRalpha. These results demonstrate that loss of RARgamma and RXRalpha proteins after UV irradiation results from degradation via the ubiquitin/proteasome pathway. Taken together, the data here indicate that ubiquitin/proteasome-mediated breakdown is an important mechanism regulating the levels of

  8. Identification of dehydroabietc acid from Boswellia thurifera resin as a positive GABAA receptor modulator.

    PubMed

    Rueda, Diana C; Raith, Melanie; De Mieri, Maria; Schöffmann, Angela; Hering, Steffen; Hamburger, Matthias

    2014-12-01

    In a two-microelectrode voltage clamp assay with Xenopus laevis oocytes, a petroleum ether extract (100 μg/mL) of the resin of Boswellia thurifera (Burseraceae) potentiated GABA-induced chloride currents (IGABA) through receptors of the subtype α₁β₂γ₂s by 319.8% ± 79.8%. With the aid of HPLC-based activity profiling, three known terpenoids, dehydroabietic acid (1), incensole (2), and AKBA (3), were identified in the active fractions of the extract. Structure elucidation was achieved by means of HR-MS and microprobe 1D/2D NMR spectroscopy. Compound 1 induced significant receptor modulation in the oocyte assay, with a maximal potentiation of IGABA of 397.5% ± 34.0%, and EC₅₀ of 8.7 μM ± 1.3 μM. This is the first report of dehydroabietic acid as a positive GABAA receptor modulator. PMID:25200370

  9. Binding of retinoic acid receptor heterodimers to DNA. A role for histones NH2 termini.

    PubMed

    Lefebvre, P; Mouchon, A; Lefebvre, B; Formstecher, P

    1998-05-15

    The retinoic acid signaling pathway is controlled essentially through two types of nuclear receptors, RARs and RXRs. Ligand dependent activation or repression of retinoid-regulated genes is dependent on the binding of retinoic acid receptor (RAR)/9-cis-retinoic acid receptor (RXR) heterodimers to retinoic acid response element (RARE). Although unliganded RXR/RAR heterodimers bind constitutively to DNA in vitro, a clear in vivo ligand-dependent occupancy of the RARE present in the RARbeta2 gene promoter has been reported (Dey, A., Minucci, S., and Ozato, K. (1994) Mol. Cell. Biol. 14, 8191-8201). Nucleosomes are viewed as general repressors of the transcriptional machinery, in part by preventing the access of transcription factors to DNA. The ability of hRXRalpha/hRARalpha heterodimers to bind to a nucleosomal template in vitro has therefore been examined. The assembly of a fragment from the RARbeta2 gene promoter, which contains a canonical DR5 RARE, into a nucleosome core prevented hRXRalpha/hRARalpha binding to this DNA, in conditions where a strong interaction is observed with a linear DNA template. However, histone tails removal by limited proteolysis and histone hyperacetylation yielded nucleosomal RAREs able to bind to hRXRalpha/hRARalpha heterodimers. These data establish therefore the role of histones NH2 termini as a major impediment to retinoid receptors access to DNA, and identify histone hyperacetylation as a potential physiological regulator of retinoid-induced transcription.

  10. Myeloid differentiation and retinoblastoma phosphorylation changes in HL-60 cells induced by retinoic acid receptor- and retinoid X receptor-selective retinoic acid analogs.

    PubMed

    Brooks, S C; Kazmer, S; Levin, A A; Yen, A

    1996-01-01

    The ability of subtypes of retinoic acid receptors (RARs) and retinoid X receptors (RXRs) singly and in combination to elicit myeloid differentiation, G1/0-specific growth arrest, and retinoblastoma (RB) tumor suppressor protein dephosphorylation was determined in the human myeloblastic leukemia cell line HL-60 using subtype-selective retinoic acid (RA) analogs. RA analogs that selectively bind only to RARs (Am580 and/or TTNPB) or to RXRs (Ro 25-6603, SR11237, and/or SR11234) did not elicit the above-mentioned three cellular responses. In contrast, simultaneous treatment with both an RAR-selective ligand (Am580 or TTNPB) and an RXR-selective ligand (Ro 25-6603, SR11237, or SR11234) induced all three cellular processes. An RAR alpha-selective ligand used with an RXR-selective ligand generated the same responses as did all-trans RA or 9-cis RA, which affect both families of receptors, suggesting an important role for RAR alpha among RAR subtypes in eliciting cellular response. Consistent with this finding, the RAR alpha antagonist, Ro 41-5253, reduced the level of the cellular responses elicited by treatment with an RAR alpha-selective ligand plus RXR-selective ligand. The coupling of the shift of RB to its hypophosphorylated form with G1/0 arrest and differentiation in response to ligands is consistent with a possible role of RB as a downstream target or effector of RAR alpha and RXR in combination.

  11. Molecular basis of positive allosteric modulation of GluN2B NMDA receptors by polyamines.

    PubMed

    Mony, Laetitia; Zhu, Shujia; Carvalho, Stéphanie; Paoletti, Pierre

    2011-06-17

    NMDA receptors (NMDARs) form glutamate-gated ion channels that have central roles in neuronal communication and plasticity throughout the brain. Dysfunctions of NMDARs are involved in several central nervous system disorders, including stroke, chronic pain and schizophrenia. One hallmark of NMDARs is that their activity can be allosterically regulated by a variety of extracellular small ligands. While much has been learned recently regarding allosteric inhibition of NMDARs, the structural determinants underlying positive allosteric modulation of these receptors remain poorly defined. Here, we show that polyamines, naturally occurring polycations that selectively enhance NMDARs containing the GluN2B subunit, bind at a dimer interface between GluN1 and GluN2B subunit N-terminal domains (NTDs). Polyamines act by shielding negative charges present on GluN1 and GluN2B NTD lower lobes, allowing their close apposition, an effect that in turn prevents NTD clamshell closure. Our work reveals the mechanistic basis for positive allosteric modulation of NMDARs. It provides the first example of an intersubunit binding site in this class of receptors, a discovery that holds promise for future drug interventions.

  12. Expression and colocalization of NMDA receptor and FosB/ΔFosB in sensitive brain regions in rats after chronic morphine exposure.

    PubMed

    Zhang, Qiang; Liu, Qi; Li, Tongzhou; Liu, You; Wang, Lei; Zhang, Zhonghai; Liu, Hongzhi; Hu, Min; Qiao, Yuehua; Niu, Haichen

    2016-02-12

    Research in the last decade demonstrated that the NMDA receptor (NMDAR) has an important role in opiate-induced neural and behavioral plasticity. In addition, increased levels of FosB-like proteins (FosB/ΔFosB) were found to be related to morphine withdrawal behaviors. However, the relationship between NMDAR and FosB/ΔFosB in sensitive brain regions during morphine withdrawal is largely unknown. In this study, we aimed to investigate NMDAR dynamics and FosB/ΔFosB levels in multiple brain regions and whether they are related in sensitive brain regions during morphine abstinence. Quantitative immunohistochemistry was adopted to test NMDAR and FosB/ΔfosB levels during morphine withdrawal in rats. Increased NMDAR and FosB/ΔFosB levels were found in the nucleus accumbens core (AcbC), nucleus accumbens shell (AcbSh), central amygdaloid nucleuscapsular part (CeC), ventral tegmental area (VTA) and cingulate cortex (Cg). Double-immunofluorescence labeling indicated that NMDAR colocalized with Fos/ΔFosB in these five regions. These results suggest that multiple phenotypic regions are mediated by NMDAR and Fos/ΔFosB during morphine withdrawal, such as the motivational (AcbC, AcbSh), limbic (CeC, VTA) and executive (Cg) system pathways, and may be the primary targets of NMDAR and Fos/ΔfosB that impact morphine withdrawal behaviors.

  13. Γ-aminobutyric acid receptors affect the progression and migration of tumor cells.

    PubMed

    Zhang, Xiaoxue; Du, Zuoyi; Liu, Jun; He, Jianxing

    2014-12-01

    Γ-aminobutyric acid (GABA) is a multifunctional molecule found in the nervous system and non-neuronal tissues. GABA receptors combine with GABA molecules and transmit signal stimuli into cells. In addition to traditional neurotransmission and regulation of secretion, GABA and GABA receptors are involved in cell differentiation and proliferation throughout peripheral organs, as well as in tumorigenesis. The exact mechanism of the GABAergic system in regulating tumor development is unclear, but many studies have revealed that GABA receptors exert critical regulative effects on tumor cell proliferation and migration. In this review, the molecular structure, distribution and biological function of GABA receptors associated with tumorigenesis are described. Recent advances in the elucidation of mechanisms underlying GABAergic signaling control over tumor growth are also discussed.

  14. Amino acid coevolution reveals three-dimensional structure and functional domains of insect odorant receptors

    PubMed Central

    Hopf, Thomas A.; Morinaga, Satoshi; Ihara, Sayoko; Touhara, Kazushige; Marks, Debora S.; Benton, Richard

    2015-01-01

    Insect Odorant Receptors (ORs) comprise an enormous protein family that translates environmental chemical signals into neuronal electrical activity. These heptahelical receptors are proposed to function as ligand-gated ion channels and/or to act metabotropically as G protein-coupled receptors (GPCRs). Resolving their signalling mechanism has been hampered by the lack of tertiary structural information and primary sequence similarity to other proteins. We use amino acid evolutionary covariation across these ORs to define restraints on structural proximity of residue pairs, which permit de novo generation of three-dimensional models. The validity of our analysis is supported by the location of functionally important residues in highly constrained regions of the protein. Importantly, insect OR models exhibit a distinct transmembrane domain packing arrangement to that of canonical GPCRs, establishing the structural unrelatedness of these receptor families. The evolutionary couplings and models predict odour binding and ion conduction domains, and provide a template for rationale structure-activity dissection. PMID:25584517

  15. Specificity of the antibody receptor site to D-lysergamide: model of a physiological receptor for lysergic acid diethylamide.

    PubMed

    Van Vunakis, H; Farrow, J T; Gjika, H B; Levine, L

    1971-07-01

    Antibodies to D-lysergic acid have been produced in rabbits and guinea pigs and a radioimmunoassay for the hapten was developed. The specificity of this lysergamide-antilysergamide reaction was determined by competitive binding with unlabeled lysergic acid diethylamide (LSD), psychotomimetic drugs, neurotransmitters, and other compounds with diverse structures. LSD and several related ergot alkaloids were potent competitors, three to seven times more potent than lysergic acid itself. The N,N-dimethyl derivatives of several compounds, including tryptamine, 5-hydroxytryptamine, 4-hydroxytryptamine, 5-methoxytryptamine, tyramine, and mescaline, were only about ten times less effective than lysergic acid, even though these compounds lack some of the ring systems of lysergic acid. The pattern of inhibition by related compounds with various substituents suggests that the antibody receptor site recognizes structural features resembling the LSD molecule. In particular, the aromatic nucleus and the dimethylated ethylamine side chain in phenylethylamine and tryptamine derivatives may assume in solution a conformation resembling ring A and the methylated nitrogen in ring C of LSD. Among the tryptamine derivatives, a large percentage of the most potent competitors are also psychotomimetic compounds.

  16. Oleic acid stimulates system A amino acid transport in primary human trophoblast cells mediated by toll-like receptor 4.

    PubMed

    Lager, Susanne; Gaccioli, Francesca; Ramirez, Vanessa I; Jones, Helen N; Jansson, Thomas; Powell, Theresa L

    2013-03-01

    Obese women have an increased risk to deliver large babies. However, the mechanisms underlying fetal overgrowth in these pregnancies are not well understood. Obese pregnant women typically have elevated circulating lipid levels. We tested the hypothesis that fatty acids stimulate placental amino acid transport, mediated via toll-like receptor 4 (TLR4) and mammalian target of rapamycin (mTOR) signaling pathways. Circulating NEFA levels and placental TLR4 expression were assessed in women with varying prepregnancy body mass index (BMI). The effects of oleic acid on system A and system L amino acid transport, and on the activation of the mTOR (4EBP1, S6K1, rpS6), TLR4 (IĸB, JNK, p38 MAPK), and STAT3 signaling pathways were determined in cultured primary human trophoblast cells. Maternal circulating NEFAs (n = 33), but not placental TLR4 mRNA expression (n = 16), correlated positively with BMI (P < 0.05). Oleic acid increased trophoblast JNK and STAT3 phosphorylation (P < 0.05), whereas mTOR activity was unaffected. Furthermore, oleic acid doubled trophoblast system A activity (P < 0.05), without affecting system L activity. siRNA-mediated silencing of TLR4 expression prevented the stimulatory effect of oleic acid on system A activity. Our data suggest that maternal fatty acids can increase placental nutrient transport via TLR4, thereby potentially affecting fetal growth.

  17. CIH-induced neurocognitive impairments are associated with hippocampal Ca(2+) overload, apoptosis, and dephosphorylation of ERK1/2 and CREB that are mediated by overactivation of NMDARs.

    PubMed

    Wang, Jing; Ming, Hong; Chen, Rui; Ju, Jing-Mei; Peng, Wan-da; Zhang, Guo-Xing; Liu, Chun-Feng

    2015-11-01

    Chronic intermittent hypoxia (CIH) is commonly seen in patients with obstructive sleep apnea, and has been hypothesized to underlie the neurocognitive dysfunction in these patients. However, its cellular and molecular mechanisms remain to be defined. The present study aimed to investigate, in a mouse CIH model, the role of NMDA receptor (NMDAR) activation in mediating the CIH-induced neurocognitive impairments, caspase expression and dysregulated Ca(2+) signaling pathways in hippocampus. Male ICR mice (n=45) were exposed to CIH (8h/day) or room air (control) for 4 weeks. After 4-week treatment, neurobehavioral assessments were performed by Morris water maze test, hippocampal [Ca(2+)]i was evaluated by flow cytometry; and protein expressions of caspase-3, caspase-9, PARP, p-ERK1/2 and p-CREB in hippocampus were measured by Western blotting. Our results showed that, compared to control animals, 4-week exposure to CIH produced significant spatial learning and memory impairments in CIH mice. Increased caspase expression in hippocampus was observed in CIH mice associated with significant elevation of [Ca(2+)]i and dephosphorylation of ERK and CREB expression. When the NMDAR antagonist memantine was administered by intraperitoneal injection prior to daily exposure to CIH, at a sub-therapeutic dose of 5mg/kg/day not shown to impact the neurobehavioral performance in control animals, the neurocognitive impairments as well as the neurobiochemical changes were abolished or normalized in the CIH mice. Our study suggests that overactivation of NMDARs and the Ca(2+) overload-dependent ERK/CREB dysregulation is one of the important mechanisms in mediating the CIH-induced neurocognitive impairments.

  18. Phosphorylation and Internalization of Lysophosphatidic Acid Receptors LPA1, LPA2, and LPA3

    PubMed Central

    Alcántara-Hernández, Rocío; Hernández-Méndez, Aurelio; Campos-Martínez, Gisselle A.; Meizoso-Huesca, Aldo; García-Sáinz, J. Adolfo

    2015-01-01

    Results The lysophosphatidic acid receptors LPA1, LPA2, and LPA3 were individually expressed in C9 cells and their signaling and regulation were studied. Agonist-activation increases intracellular calcium concentration in a concentration-dependent fashion. Phorbol myristate acetate markedly inhibited LPA1- and LPA3-mediated effect, whereas that mediated by LPA2 was only partially diminished; the actions of the phorbol ester were inhibited by bisindolylmaleimide I and by overnight incubation with the protein kinase C activator, which leads to down regulation of this protein kinase. Homologous desensitization was also observed for the three LPA receptors studied, with that of LPA2 receptors being consistently of lesser magnitude; neither inhibition nor down-regulation of protein kinase C exerted any effect on homologous desensitization. Activation of LPA1–3 receptors induced ERK 1/2 phosphorylation; this effect was markedly attenuated by inhibition of epidermal growth factor receptor tyrosine kinase activity, suggesting growth factor receptor transactivation in this effect. Lysophosphatidic acid and phorbol myristate acetate were able to induce LPA1–3 phosphorylation, in time- and concentration-dependent fashions. It was also clearly observed that agonists and protein kinase C activation induced internalization of these receptors. Phosphorylation of the LPA2 subtype required larger concentrations of these agents and its internalization was less intense than that of the other subtypes. Conclusion Our data show that these three LPA receptors are phosphoproteins whose phosphorylation state is modulated by agonist-stimulation and protein kinase C-activation and that differences in regulation and cellular localization exist, among the subtypes. PMID:26473723

  19. Receptor-mediated uptake of low density lipoprotein stimulates bile acid synthesis by cultured rat hepatocytes

    SciTech Connect

    Junker, L.H.; Davis, R.A. )

    1989-12-01

    The cellular mechanisms responsible for the lipoprotein-mediated stimulation of bile acid synthesis in cultured rat hepatocytes were investigated. Adding 280 micrograms/ml of cholesterol in the form of human or rat low density lipoprotein (LDL) to the culture medium increased bile acid synthesis by 1.8- and 1.6-fold, respectively. As a result of the uptake of LDL, the synthesis of (14C)cholesterol from (2-14C)acetate was decreased and cellular cholesteryl ester mass was increased. Further studies demonstrated that rat apoE-free LDL and apoE-rich high density lipoprotein (HDL) both stimulated bile acid synthesis 1.5-fold, as well as inhibited the formation of (14C)cholesterol from (2-14C)acetate. Reductive methylation of LDL blocked the inhibition of cholesterol synthesis, as well as the stimulation of bile acid synthesis, suggesting that these processes require receptor-mediated uptake. To identify the receptors responsible, competitive binding studies using 125I-labeled apoE-free LDL and 125I-labeled apoE-rich HDL were performed. Both apoE-free LDL and apoE-rich HDL displayed an equal ability to compete for binding of the other, suggesting that a receptor or a group of receptors that recognizes both apolipoproteins is involved. Additional studies show that hepatocytes from cholestyramine-treated rats displayed 2.2- and 3.4-fold increases in the binding of apoE-free LDL and apoE-rich HDL, respectively. These data show for the first time that receptor-mediated uptake of LDL by the liver is intimately linked to processes activating bile acid synthesis.

  20. Intracrine prostaglandin E(2) signalling regulates hypoxia-inducible factor-1α expression through retinoic acid receptor-β.

    PubMed

    Fernández-Martínez, Ana B; Jiménez, María I Arenas; Manzano, Victoria Moreno; Lucio-Cazaña, Francisco J

    2012-12-01

    We have previously found in human renal proximal tubular HK-2 cells that hypoxia- and all-trans retinoic acid-induced hypoxia-inducible factor-1α up-regulation is accompanied by retinoic acid receptor-β up-regulation. Here we first investigated whether hypoxia-inducible factor-1α expression is dependent on retinoic acid receptor-β and our results confirmed it since (i) hypoxia-inducible factor-1α-inducing agents hypoxia, hypoxia-mimetic agent desferrioxamine, all-trans retinoic acid and interleukin-1β increased retinoic acid receptor-β expression, (ii) hypoxia-inducible factor-1α up-regulation was prevented by retinoic acid receptor-β antagonist LE-135 or siRNA retinoic acid receptor-β and (iii) there was direct binding of retinoic acid receptor-β to the retinoic acid response element in hypoxia-inducible factor-1α promoter upon treatment with all-trans retinoic acid and 16,16-dimethyl-prostaglandin E(2). Since intracellular prostaglandin E(2) mediates hypoxia-inducible factor-1α up-regulation in normoxia in HK-2 cells, we next investigated and confirmed, its role in the up-regulation of retinoic acid receptor-β in normoxia by hypoxia-inducible factor-1α-inducing agents all-trans retinoic acid, interleukin-1β and 16,16-dimethyl-prostaglandin E(2) by inhibiting cyclooxygenases, prostaglandin influx transporter or EP receptors. Interestingly, the hypoxia-induced increase in retinoic acid receptor-β expression and accumulation of hypoxia-inducible factor-1α was also blocked by the inhibitors tested. This is the first time, to our knowledge, that retinoic acid receptor-β signalling is involved in the control of the expression of transcription factor hypoxia-inducible factor-1α in both normoxia and hypoxia and that retinoic acid receptor-β expression is found to be strictly regulated by intracellular prostaglandin E(2). Given the relevance of hypoxia-inducible factor-1α in the kidney in terms of tumorigenesis, progressive renal failure, production

  1. The lactate receptor, G-protein-coupled receptor 81/hydroxycarboxylic acid receptor 1: Expression and action in brain.

    PubMed

    Morland, Cecilie; Lauritzen, Knut Husø; Puchades, Maja; Holm-Hansen, Signe; Andersson, Krister; Gjedde, Albert; Attramadal, Håvard; Storm-Mathisen, Jon; Bergersen, Linda Hildegard

    2015-07-01

    We have proposed that lactate is a "volume transmitter" in the brain and underpinned this by showing that the lactate receptor, G-protein-coupled receptor 81 (GPR81, also known as HCA1 or HCAR1), which promotes lipid storage in adipocytes, is also active in the mammalian brain. This includes the cerebral neocortex and the hippocampus, where it can be stimulated by physiological concentrations of lactate and by the HCAR1 agonist 3,5-dihydroxybenzoate to reduce cAMP levels. Cerebral HCAR1 is concentrated on the postsynaptic membranes of excitatory synapses and also is enriched at the blood-brain barrier. In synaptic spines and in adipocytes, HCAR1 immunoreactivity is also located on subplasmalemmal vesicular organelles, suggesting trafficking to and from the plasma membrane. Through activation of HCAR1, lactate can act as a volume transmitter that links neuronal activity, cerebral blood flow, energy metabolism, and energy substrate availability, including a glucose- and glycogen-saving response. HCAR1 may contribute to optimizing the cAMP concentration. For instance, in the prefrontal cortex, excessively high cAMP levels are implicated in impaired cognition in old age, fatigue, stress, and schizophrenia and in the deposition of phosphorylated tau protein in Alzheimer's disease. HCAR1 could serve to ameliorate these conditions and might also act through downstream mechanisms other than cAMP. Lactate exits cells through monocarboxylate transporters in an equilibrating manner and through astrocyte anion channels activated by depolarization. In addition to locally produced lactate, lactate produced by exercising muscle as well as exogenous HCAR1 agonists, e.g., from fruits and berries, might activate the receptor on cerebral blood vessels and brain cells. PMID:25881750

  2. The lactate receptor, G-protein-coupled receptor 81/hydroxycarboxylic acid receptor 1: Expression and action in brain.

    PubMed

    Morland, Cecilie; Lauritzen, Knut Husø; Puchades, Maja; Holm-Hansen, Signe; Andersson, Krister; Gjedde, Albert; Attramadal, Håvard; Storm-Mathisen, Jon; Bergersen, Linda Hildegard

    2015-07-01

    We have proposed that lactate is a "volume transmitter" in the brain and underpinned this by showing that the lactate receptor, G-protein-coupled receptor 81 (GPR81, also known as HCA1 or HCAR1), which promotes lipid storage in adipocytes, is also active in the mammalian brain. This includes the cerebral neocortex and the hippocampus, where it can be stimulated by physiological concentrations of lactate and by the HCAR1 agonist 3,5-dihydroxybenzoate to reduce cAMP levels. Cerebral HCAR1 is concentrated on the postsynaptic membranes of excitatory synapses and also is enriched at the blood-brain barrier. In synaptic spines and in adipocytes, HCAR1 immunoreactivity is also located on subplasmalemmal vesicular organelles, suggesting trafficking to and from the plasma membrane. Through activation of HCAR1, lactate can act as a volume transmitter that links neuronal activity, cerebral blood flow, energy metabolism, and energy substrate availability, including a glucose- and glycogen-saving response. HCAR1 may contribute to optimizing the cAMP concentration. For instance, in the prefrontal cortex, excessively high cAMP levels are implicated in impaired cognition in old age, fatigue, stress, and schizophrenia and in the deposition of phosphorylated tau protein in Alzheimer's disease. HCAR1 could serve to ameliorate these conditions and might also act through downstream mechanisms other than cAMP. Lactate exits cells through monocarboxylate transporters in an equilibrating manner and through astrocyte anion channels activated by depolarization. In addition to locally produced lactate, lactate produced by exercising muscle as well as exogenous HCAR1 agonists, e.g., from fruits and berries, might activate the receptor on cerebral blood vessels and brain cells.

  3. The NHR-8 nuclear receptor regulates cholesterol and bile acid homeostasis in C. elegans.

    PubMed

    Magner, Daniel B; Wollam, Joshua; Shen, Yidong; Hoppe, Caroline; Li, Dongling; Latza, Christian; Rottiers, Veerle; Hutter, Harald; Antebi, Adam

    2013-08-01

    Hormone-gated nuclear receptors (NRs) are conserved transcriptional regulators of metabolism, reproduction, and homeostasis. Here we show that C. elegans NHR-8 NR, a homolog of vertebrate liver X and vitamin D receptors, regulates nematode cholesterol balance, fatty acid desaturation, apolipoprotein production, and bile acid metabolism. Loss of nhr-8 results in a deficiency in bile acid-like steroids, called the dafachronic acids, which regulate the related DAF-12/NR, thus controlling entry into the long-lived dauer stage through cholesterol availability. Cholesterol supplementation rescues various nhr-8 phenotypes, including developmental arrest, unsaturated fatty acid deficiency, reduced fertility, and shortened life span. Notably, nhr-8 also interacts with daf-16/FOXO to regulate steady-state cholesterol levels and is synthetically lethal in combination with insulin signaling mutants that promote unregulated growth. Our studies provide important insights into nuclear receptor control of cholesterol balance and metabolism and their impact on development, reproduction, and aging in the context of larger endocrine networks.

  4. Endocytosis of hyaluronic acid by rat liver endothelial cells. Evidence for receptor recycling.

    PubMed Central

    McGary, C T; Raja, R H; Weigel, P H

    1989-01-01

    Hyaluronic acid (HA) is cleared from the blood by liver endothelial cells through receptor-mediated endocytosis [Eriksson, Fraser, Laurent, Pertoft & Smedsrod (1983) Exp. Cell Res. 144, 223-238]. We have measured the capacity of cultured rat liver endothelial cells to endocytose and degrade 125I-HA (Mr approximately 44,000) at 37 degrees C. Endocytosis was linear for 3 h and then reached a plateau. The rate of endocytosis was concentration-dependent and reached a maximum of 250 molecules/s per cell. Endocytosis of 125I-HA was inhibited more than 92% by a 150-fold excess of non-radiolabelled HA. HA, chondroitin sulphate and heparin effectively competed for endocytosis of 125I-HA, whereas glucuronic acid, N-acetylglucosamine, DNA, RNA, polygalacturonic acid and dextran did not compete. In the absence of cycloheximide, endothelial cells processed 13 times more 125I-HA in 6 h than their total (cell-surface and intracellular) specific HA-binding capacity. This result was not due to degradation and rapid replacement of receptors, because, even in the presence of cycloheximide, these cells processed 6 times more HA than their total receptor content in 6 h. Also, in the presence of cycloheximide, no decrease in 125I-HA-binding capacity was seen in cells processing or not processing HA for 6 h, indicating that receptors are not degraded after the endocytosis of HA. During endocytosis of HA at 37 degrees C, at least 65% of the intracellular HA receptors became occupied with HA within 30 min. This indicates that the intracellular HA receptors (75% of the total) function during continuous endocytosis. Hyperosmolarity inhibits endocytosis and receptor recycling in the asialoglycoprotein and low-density-lipoprotein receptor systems by disrupting the coated-pit pathway [Heuser & Anderson (1987) J. Cell Biol. 105, 230a; Oka & Weigel (1988) J. Cell. Biochem. 36, 169-183]. Hyperosmolarity inhibited 125I-HA endocytosis in liver endothelial cells by more than 90%, suggesting use of a

  5. Tetrahydro-iso-alpha Acids Antagonize Estrogen Receptor Alpha Activity in MCF-7 Breast Cancer Cells.

    PubMed

    Lempereur, Maëlle; Majewska, Claire; Brunquers, Amandine; Wongpramud, Sumalee; Valet, Bénédicte; Janssens, Philippe; Dillemans, Monique; Van Nedervelde, Laurence; Gallo, Dominique

    2016-01-01

    Tetrahydro-iso-alpha acids commonly called THIAA or Tetra are modified hop acids extracted from hop (Humulus lupulus L.) which are frequently used in brewing industry mainly in order to provide beer bitterness and foam stability. Interestingly, molecular structure of tetrahydro-iso-alpha acids is close to a new type of estrogen receptor alpha (ERα) antagonists aimed at disrupting the binding of coactivators containing an LxxLL motif (NR-box). In this work we show that THIAA decreases estradiol-stimulated proliferation of MCF-7 (ERα-positive breast cancer cells). Besides, we show that it inhibits ERα transcriptional activity. Interestingly, this extract fails to compete with estradiol for ERα binding and does not significantly impact the receptor turnover rate in MCF-7 cells, suggesting that it does not act like classical antiestrogens. Hence, we demonstrate that THIAA is able to antagonize ERα estradiol-induced recruitment of the LxxLL binding motif. PMID:27190515

  6. Tetrahydro-iso-alpha Acids Antagonize Estrogen Receptor Alpha Activity in MCF-7 Breast Cancer Cells

    PubMed Central

    Lempereur, Maëlle; Majewska, Claire; Brunquers, Amandine; Wongpramud, Sumalee; Valet, Bénédicte; Janssens, Philippe; Dillemans, Monique; Van Nedervelde, Laurence; Gallo, Dominique

    2016-01-01

    Tetrahydro-iso-alpha acids commonly called THIAA or Tetra are modified hop acids extracted from hop (Humulus lupulus L.) which are frequently used in brewing industry mainly in order to provide beer bitterness and foam stability. Interestingly, molecular structure of tetrahydro-iso-alpha acids is close to a new type of estrogen receptor alpha (ERα) antagonists aimed at disrupting the binding of coactivators containing an LxxLL motif (NR-box). In this work we show that THIAA decreases estradiol-stimulated proliferation of MCF-7 (ERα-positive breast cancer cells). Besides, we show that it inhibits ERα transcriptional activity. Interestingly, this extract fails to compete with estradiol for ERα binding and does not significantly impact the receptor turnover rate in MCF-7 cells, suggesting that it does not act like classical antiestrogens. Hence, we demonstrate that THIAA is able to antagonize ERα estradiol-induced recruitment of the LxxLL binding motif. PMID:27190515

  7. Mutations in the nuclear bile acid receptor FXR cause progressive familial intrahepatic cholestasis

    PubMed Central

    Gomez-Ospina, Natalia; Potter, Carol J.; Xiao, Rui; Manickam, Kandamurugu; Kim, Mi-Sun; Kim, Kang Ho; Shneider, Benjamin L.; Picarsic, Jennifer L.; Jacobson, Theodora A.; Zhang, Jing; He, Weimin; Liu, Pengfei; Knisely, A. S.; Finegold, Milton J.; Muzny, Donna M.; Boerwinkle, Eric; Lupski, James R.; Plon, Sharon E.; Gibbs, Richard A.; Eng, Christine M.; Yang, Yaping; Washington, Gabriel C.; Porteus, Matthew H.; Berquist, William E.; Kambham, Neeraja; Singh, Ravinder J.; Xia, Fan; Enns, Gregory M.; Moore, David D.

    2016-01-01

    Neonatal cholestasis is a potentially life-threatening condition requiring prompt diagnosis. Mutations in several different genes can cause progressive familial intrahepatic cholestasis, but known genes cannot account for all familial cases. Here we report four individuals from two unrelated families with neonatal cholestasis and mutations in NR1H4, which encodes the farnesoid X receptor (FXR), a bile acid-activated nuclear hormone receptor that regulates bile acid metabolism. Clinical features of severe, persistent NR1H4-related cholestasis include neonatal onset with rapid progression to end-stage liver disease, vitamin K-independent coagulopathy, low-to-normal serum gamma-glutamyl transferase activity, elevated serum alpha-fetoprotein and undetectable liver bile salt export pump (ABCB11) expression. Our findings demonstrate a pivotal function for FXR in bile acid homeostasis and liver protection. PMID:26888176

  8. Astrocytes increase the activity of synaptic GluN2B NMDA receptors

    PubMed Central

    Hahn, Junghyun; Wang, Xianhong; Margeta, Marta

    2015-01-01

    Astrocytes regulate excitatory synapse formation and surface expression of glutamate AMPA receptors (AMPARs) during development. Less is known about glial modulation of glutamate NMDA receptors (NMDARs), which mediate synaptic plasticity and regulate neuronal survival in a subunit- and subcellular localization-dependent manner. Using primary hippocampal cultures with mature synapses, we found that the density of NMDA-evoked whole-cell currents was approximately twice as large in neurons cultured in the presence of glia compared to neurons cultured alone. The glial effect was mediated by (an) astrocyte-secreted soluble factor(s), was Mg2+ and voltage independent, and could not be explained by a significant change in the synaptic density. Instead, we found that the peak amplitudes of total and NMDAR miniature excitatory postsynaptic currents (mEPSCs), but not AMPAR mEPSCs, were significantly larger in mixed than neuronal cultures, resulting in a decreased synaptic AMPAR/NMDAR ratio. Astrocytic modulation was restricted to synaptic NMDARs that contain the GluN2B subunit, did not involve an increase in the cell surface expression of NMDAR subunits, and was mediated by protein kinase C (PKC). Taken together, our findings indicate that astrocyte-secreted soluble factor(s) can fine-tune synaptic NMDAR activity through the PKC-mediated regulation of GluN2B NMDAR channels already localized at postsynaptic sites, presumably on a rapid time scale. Given that physiologic activation of synaptic NMDARs is neuroprotective and that an increase in the synaptic GluN2B current is associated with improved learning and memory, the astrocyte-induced potentiation of synaptic GluN2B receptor activity is likely to enhance cognitive function while simultaneously strengthening neuroprotective signaling pathways. PMID:25941471

  9. Evidence for impaired retinoic acid receptor-thyroid hormone receptor AF-2 cofactor activity in human lung cancer.

    PubMed Central

    Moghal, N; Neel, B G

    1995-01-01

    Retinoic acid (RA) is required for normal airway epithelial cell growth and differentiation both in vivo and in vitro. One of the earliest events following the exposure of bronchial epithelial cells to RA is the strong induction of RA receptor beta (RAR beta) mRNA. Previous work established that many lung cancer cell lines and primary tumors display abnormal RAR beta mRNA expression, most often absence or weak expression of the RAR beta 2 isoform, even after RA treatment. Restoration of RAR beta 2 into RAR beta-negative lung cancer cell lines has been reported to inhibit tumorigenicity. Since RAR beta 2 inactivation may contribute to lung cancer, we have investigated the molecular mechanism of defective RAR beta 2 expression. Nuclear run-on assays and transient transfections with RAR beta 2 promoter constructs indicate the presence of trans-acting transcriptional defects in most lung cancer cell lines, which map to the RA response element (RARE). These defects cannot be complemented by RAR-retinoid X receptor cotransfection and can be separated into two types: (i) one affecting transcription from direct repeat RAREs, but not palindromic RAREs, and (ii) another affecting transcription from both types of RARE. Studies using chimeras between RAR alpha, TR alpha, and other transcription factors suggest the existence of novel RAR-thyroid hormone receptor AF-2-specific cofactors, which are necessary for high levels of transcription. Furthermore, these factors may be frequently inactivated in human lung cancer. PMID:7791800

  10. Molecular recognition of amino acids with some fluorescent ditopic pyrylium- and pyridinium-based crown ether receptors

    NASA Astrophysics Data System (ADS)

    Moghimi, A.; Maddah, B.; Yari, A.; Shamsipur, M.; Boostani, M.; Fall Rastegar, M.; Ghaderi, A. R.

    2005-10-01

    The molecular recognition of L-amino acids such as asparagine, glutamine, lysine and arginine with some crownpyryliums, CP's, and a crownpyridinium compound, as receptors, were examined in methanol. 1H NMR spectroscopy was used to examine the structural stability of the receptors in the presence of the amino acids. The fluorimetric titration of the receptors by specified amino acids, other than arginine, was followed within a few minutes and the stoichiometry and stability of the resulting amino acid complexes were evaluated. The data analysis clearly demonstrated the critical role of the terminal amino group to carboxylic acid distance of amino acids for their proper fixation on the receptor molecules. Ion pairing for the two oppositely charged carboxylate anion and pyrylium (or pyridinium) cation, as well as the hydrogen bonding between crown ethers' oxygens and ammonium hydrogens are expected as the main interaction sources in the host-guest complexations.

  11. Peripheral tackykinin and excitatory amino acid receptors mediate hyperalgesia induced by Phoneutria nigriventer venom.

    PubMed

    Zanchet, Eliane Maria; Cury, Yara

    2003-04-25

    The generation of hyperalgesia by Phoneutria nigriventer venom was investigated in rats using the paw pressure test, through the intraplantar injection of the venom. Hyperalgesia was significantly inhibited by N-[2-(4-chlorophenyl) ethyl]-1,3,4,5-tetrahydro-7,8-dihydroxy-2H-2-benzazepine-2-carbothioamide (capsazepine), a vanilloid receptor antagonist, by the local administration of pGlu-Ala-Asp-Pro-Asn-Lys-Phe-Tyr-Pro (spiro-gamma-lactam) Leu-Trp-NH(2) (GR82334) or of Phenyl-CO-Ala-Ala-D-Trp-Phe-D-Pro-Pro-Nle-NH(2) (GR94800), inhibitors of tachykinin NK(1) and NK(2) receptors, respectively, or by the local injection of dizocilpine (MK 801), (+/-)-2-amino-5-phosphonopentanoic acid ((+/-)-AP-5), or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), antagonists of NMDA and non-NMDA excitatory amino acid receptors. The correlation between hyperalgesia and the inflammatory response induced by the venom was also investigated. The venom-induced edematogenic response was not modified by the pharmacological treatments. These results suggest that hyperalgesia induced by P. nigriventer venom is mediated by stimulation of capsaicin-sensitive neurons, with activation of peripheral tachykinin NK(1) and NK(2) receptors and of both the NMDA and AMPA receptors. Distinct mechanisms are involved in the development of hyperalgesia and edema induced by the venom.

  12. Signaling through retinoic acid receptors in cardiac development: Doing the right things at the right times.

    PubMed

    Xavier-Neto, José; Sousa Costa, Ângela M; Figueira, Ana Carolina M; Caiaffa, Carlo Donato; Amaral, Fabio Neves do; Peres, Lara Maldanis Cerqueira; da Silva, Bárbara Santos Pires; Santos, Luana Nunes; Moise, Alexander R; Castillo, Hozana Andrade

    2015-02-01

    Retinoic acid (RA) is a terpenoid that is synthesized from vitamin A/retinol (ROL) and binds to the nuclear receptors retinoic acid receptor (RAR)/retinoid X receptor (RXR) to control multiple developmental processes in vertebrates. The available clinical and experimental data provide uncontested evidence for the pleiotropic roles of RA signaling in development of multiple embryonic structures and organs such eyes, central nervous system, gonads, lungs and heart. The development of any of these above-mentioned embryonic organ systems can be effectively utilized to showcase the many strategies utilized by RA signaling. However, it is very likely that the strategies employed to transfer RA signals during cardiac development comprise the majority of the relevant and sophisticated ways through which retinoid signals can be conveyed in a complex biological system. Here, we provide the reader with arguments indicating that RA signaling is exquisitely regulated according to specific phases of cardiac development and that RA signaling itself is one of the major regulators of the timing of cardiac morphogenesis and differentiation. We will focus on the role of signaling by RA receptors (RARs) in early phases of heart development. This article is part of a Special Issue entitled: Nuclear receptors in animal development.

  13. G-CSF receptor-binding cyclic peptides designed with artificial amino-acid linkers

    SciTech Connect

    Shibata, Kenji . E-mail: kshibata@kyowa.co.jp; Maruyama-Takahashi, Kumiko; Yamasaki, Motoo; Hirayama, Noriaki . E-mail: hirayama@is.icc.u-tokai.ac.jp

    2006-03-10

    Designing small molecules that mimic the receptor-binding local surface structure of large proteins such as cytokines or growth factors is fascinating and challenging. In this study, we designed cyclic peptides that reproduce the receptor-binding loop structures of G-CSF. We found it is important to select a suitable linker to join two or more discontinuous sequences and both termini of the peptide corresponding to the receptor-binding loop. Structural simulations based on the crystallographic structure of KW-2228, a stable and potent analog of human G-CSF, led us to choose 4-aminobenzoic acid (Abz) as a part of the linker. A combination of 4-Abz with {beta}-alanine or glycine, and disulfide bridges between cysteins or homocysteins, gave a structure suitable for receptor binding. In this structure, the side-chains of several amino acids important for the interactions with the receptor are protruding from one side of the peptide ring. This artificial peptide showed G-CSF antagonistic activity in a cell proliferation assay.

  14. N-methyl-D-aspartate receptors strongly regulate postsynaptic activity levels during optic nerve regeneration.

    PubMed

    Kolls, Brad J; Meyer, Ronald L

    2013-10-01

    During development, neuronal activity is used as a cue to guide synaptic rearrangements to refine connections. Many studies, especially in the visual system, have shown that the N-methyl-D-aspartate receptor (NMDAr) plays a key role in mediating activity-dependent refinement through long-term potentiation (LTP)-like processes. Adult goldfish can regenerate their optic nerve and utilize neuronal activity to generate precise topography in their projection onto tectum. Although the NMDAr has been implicated in this process, its precise role in regeneration has not been extensively studied. In examining NMDAr function during regeneration, we found salient differences compared with development. By using field excitatory postsynaptic potential (fEPSP) recordings, the contribution of the NMDAr at the primary optic synapse was measured. In contrast to development, no increase in NMDAr function was detectable during synaptic refinement. Unlike development, LTP could not be reliably elicited during regeneration. Unexpectedly, we found that NMDAr exerted a major effect on regulating ongoing tectal (postsynaptic) activity levels during regeneration. Blocking NMDAr strongly suppressed spontaneous activity during regeneration but had no significant effect in the normal projection. This difference could be attributed to an occlusion effect of strong optic drive in the normal projection, which dominated ongoing tectal activity. During regeneration, this optic drive is largely absent. Optic nerve stimulation further indicated that the NMDAr had little effect on the ability of optic fibers to evoke early postsynaptic impulse activity but was important for late network activity. These results indicate that, during regeneration, the NMDAr may play a critical role in the homeostatic regulation of ongoing activity and network excitability. PMID:23873725

  15. Computer-aided design of a novel ligand for retinoic acid receptor in cancer chemotherapy

    NASA Astrophysics Data System (ADS)

    Silva, Carlos H. T. P.; Leopoldino, Andreia M.; Silva, Eloiza H. T.; Espinoza, V. A. A.; Taft, C. A.

    The isotypes of RAR and RXR are retinoic acid and retinoid X acid receptors, respectively, whose ligand-binding domain contains the ligand-dependent activation function, with distinct pharmacological targets for retinoids, involved in the treatment of various cancers and skin diseases. Due to the major challenge which cancer treatment and cure still imposes after many decades to the international scientific community, there is actually considerable interest in new ligands with increased bioactivity. We have focused on the retinoid acid receptor, which is considered an interesting target for drug design. In this work, we carried out density functional geometry optimizations and different docking procedures. We performed screening in a large database (hundreds of thousands of molecules which we optimized at the AM1 level) yielding a set of potential bioactive ligands. A new ligand was selected and optimized at the B3LYP/6-31G* level. A flexible docking program was used to investigate the interactions between the receptor and the new ligand. The result of this work is compared with several crystallographic ligands of RAR. Our theoretically more bioactive new ligand indicates stronger and more hydrogen bonds as well as hydrophobic interactions with the receptor.

  16. Structure-dependent effects of pyridine derivatives on mechanisms of intestinal fatty acid uptake: regulation of nicotinic acid receptor and fatty acid transporter expression.

    PubMed

    Riedel, Annett; Lang, Roman; Rohm, Barbara; Rubach, Malte; Hofmann, Thomas; Somoza, Veronika

    2014-07-01

    Pyridines are widely distributed in foods. Nicotinic acid (NA), a carboxylated pyridine derivative, inhibits lipolysis in adipocytes by activation of the orphan NA receptor (HM74A) and is applied to treat hyperlipidemia. However, knowledge on the impact of pyridine derivatives on intestinal lipid metabolism is scarce. This study was performed to identify the structural determinants of pyridines for their effects on fatty acid uptake in enterocyte-like Caco-2 cells and to elucidate the mechanisms of action. The impact of 17 pyridine derivatives on fatty acid uptake was tested. Multiple regression analysis revealed the presence of a methyl group to be the structural determinant at 0.1 mM, whereas at 1 mM, the presence of a carboxylic group and the N-methylation presented further structural characteristics to affect the fatty acid uptake. NA, showing a stimulating effect on FA uptake, and N-methyl-4-phenylpyridinium (MPP), inhibiting FA uptake, were selected for mechanistic studies. Gene expression of the fatty acid transporters CD36, FATP2 and FATP4, and the lipid metabolism regulating transcription factors peroxisome proliferator-activated receptor (PPAR) α and PPARγ was up-regulated upon NA treatment. Caco-2 cells were demonstrated to express the low-affinity NA receptor HM74 of which the gene expression was up-regulated upon NA treatment. We hypothesize that the NA-induced fatty acid uptake might result from NA receptor activation and related intracellular signaling cascades. In contrast, MPP increased transepithelial electrical resistance. We therefore conclude that NA and MPP, both sharing the pyridine motif core, exhibit their contrary effects on intestinal FA uptake by activation of different mechanisms.

  17. Structure-dependent effects of pyridine derivatives on mechanisms of intestinal fatty acid uptake: regulation of nicotinic acid receptor and fatty acid transporter expression.

    PubMed

    Riedel, Annett; Lang, Roman; Rohm, Barbara; Rubach, Malte; Hofmann, Thomas; Somoza, Veronika

    2014-07-01

    Pyridines are widely distributed in foods. Nicotinic acid (NA), a carboxylated pyridine derivative, inhibits lipolysis in adipocytes by activation of the orphan NA receptor (HM74A) and is applied to treat hyperlipidemia. However, knowledge on the impact of pyridine derivatives on intestinal lipid metabolism is scarce. This study was performed to identify the structural determinants of pyridines for their effects on fatty acid uptake in enterocyte-like Caco-2 cells and to elucidate the mechanisms of action. The impact of 17 pyridine derivatives on fatty acid uptake was tested. Multiple regression analysis revealed the presence of a methyl group to be the structural determinant at 0.1 mM, whereas at 1 mM, the presence of a carboxylic group and the N-methylation presented further structural characteristics to affect the fatty acid uptake. NA, showing a stimulating effect on FA uptake, and N-methyl-4-phenylpyridinium (MPP), inhibiting FA uptake, were selected for mechanistic studies. Gene expression of the fatty acid transporters CD36, FATP2 and FATP4, and the lipid metabolism regulating transcription factors peroxisome proliferator-activated receptor (PPAR) α and PPARγ was up-regulated upon NA treatment. Caco-2 cells were demonstrated to express the low-affinity NA receptor HM74 of which the gene expression was up-regulated upon NA treatment. We hypothesize that the NA-induced fatty acid uptake might result from NA receptor activation and related intracellular signaling cascades. In contrast, MPP increased transepithelial electrical resistance. We therefore conclude that NA and MPP, both sharing the pyridine motif core, exhibit their contrary effects on intestinal FA uptake by activation of different mechanisms. PMID:24767308

  18. PLZF is a negative regulator of retinoic acid receptor transcriptional activity.

    PubMed

    Martin, Perrine J; Delmotte, Marie-Hélène; Formstecher, Pierre; Lefebvre, Philippe

    2003-09-01

    BACKGROUND: Retinoic acid receptors (RARs) are ligand-regulated transcription factors controlling cellular proliferation and differentiation. Receptor-interacting proteins such as corepressors and coactivators play a crucial role in specifying the overall transcriptional activity of the receptor in response to ligand treatment. Little is known however on how receptor activity is controlled by intermediary factors which interact with RARs in a ligand-independent manner. RESULTS: We have identified the promyelocytic leukemia zinc finger protein (PLZF), a transcriptional corepressor, to be a RAR-interacting protein using the yeast two-hybrid assay. We confirmed this interaction by GST-pull down assays and show that the PLZF N-terminal zinc finger domain is necessary and sufficient for PLZF to bind RAR. The RAR ligand binding domain displayed the highest affinity for PLZF, but corepressor and coactivator binding interfaces did not contribute to PLZF recruitment. The interaction was ligand-independent and correlated to a decreased transcriptional activity of the RXR-RAR heterodimer upon overexpression of PLZF. A similar transcriptional interference could be observed with the estrogen receptor alpha and the glucocorticoid receptor. We further show that PLZF is likely to act by preventing RXR-RAR heterodimerization, both in-vitro and in intact cells. CONCLUSION: Thus RAR and PLZF interact physically and functionally. Intriguingly, these two transcription factors play a determining role in hematopoiesis and regionalization of the hindbrain and may, upon chromosomal translocation, form fusion proteins. Our observations therefore define a novel mechanism by which RARs activity may be controlled.

  19. G-Protein-Coupled Lysophosphatidic Acid Receptors and Their Regulation of AKT Signaling

    PubMed Central

    Riaz, Anjum; Huang, Ying; Johansson, Staffan

    2016-01-01

    A hallmark of G-protein-coupled receptors (GPCRs) is their ability to recognize and respond to chemically diverse ligands. Lysophospholipids constitute a relatively recent addition to these ligands and carry out their biological functions by activating G-proteins coupled to a large family of cell-surface receptors. This review aims to highlight salient features of cell signaling by one class of these receptors, known as lysophosphatidic acid (LPA) receptors, in the context of phosphatidylinositol 3-kinase (PI3K)–AKT pathway activation. LPA moieties efficiently activate AKT phosphorylation and activation in a multitude of cell types. The interplay between LPA, its receptors, the associated Gαi/o subunits, PI3K and AKT contributes to the regulation of cell survival, migration, proliferation and confers chemotherapy-resistance in certain cancers. However, detailed information on the regulation of PI3K–AKT signals induced by LPA receptors is missing from the literature. Here, some urgent issues for investigation are highlighted. PMID:26861299

  20. G-Protein-Coupled Lysophosphatidic Acid Receptors and Their Regulation of AKT Signaling.

    PubMed

    Riaz, Anjum; Huang, Ying; Johansson, Staffan

    2016-01-01

    A hallmark of G-protein-coupled receptors (GPCRs) is their ability to recognize and respond to chemically diverse ligands. Lysophospholipids constitute a relatively recent addition to these ligands and carry out their biological functions by activating G-proteins coupled to a large family of cell-surface receptors. This review aims to highlight salient features of cell signaling by one class of these receptors, known as lysophosphatidic acid (LPA) receptors, in the context of phosphatidylinositol 3-kinase (PI3K)-AKT pathway activation. LPA moieties efficiently activate AKT phosphorylation and activation in a multitude of cell types. The interplay between LPA, its receptors, the associated Gαi/o subunits, PI3K and AKT contributes to the regulation of cell survival, migration, proliferation and confers chemotherapy-resistance in certain cancers. However, detailed information on the regulation of PI3K-AKT signals induced by LPA receptors is missing from the literature. Here, some urgent issues for investigation are highlighted. PMID:26861299

  1. Cannabinoid receptor agonists reduce the short-term mitochondrial dysfunction and oxidative stress linked to excitotoxicity in the rat brain.

    PubMed

    Rangel-López, E; Colín-González, A L; Paz-Loyola, A L; Pinzón, E; Torres, I; Serratos, I N; Castellanos, P; Wajner, M; Souza, D O; Santamaría, A

    2015-01-29

    The endocannabinoid system (ECS) is involved in a considerable number of physiological processes in the Central Nervous System. Recently, a modulatory role of cannabinoid receptors (CBr) and CBr agonists on the reduction of the N-methyl-d-aspartate receptor (NMDAr) activation has been demonstrated. Quinolinic acid (QUIN), an endogenous analog of glutamate and excitotoxic metabolite produced in the kynurenine pathway (KP), selectively activates NMDAr and has been shown to participate in different neurodegenerative disorders. Since the early pattern of toxicity exerted by this metabolite is relevant to explain the extent of damage that it can produce in the brain, in this work we investigated the effects of the synthetic CBr agonist WIN 55,212-2 (WIN) and other agonists (anandamide or AEA, and CP 55,940 or CP) on early markers of QUIN-induced toxicity in rat striatal cultured cells and rat brain synaptosomes. WIN, AEA and CP exerted protective effects on the QUIN-induced loss of cell viability. WIN also preserved the immunofluorescent signals for neurons and CBr labeling that were decreased by QUIN. The QUIN-induced early mitochondrial dysfunction, lipid peroxidation and reactive oxygen species (ROS) formation were also partially or completely prevented by WIN pretreatment, but not when this CBr agonist was added simultaneously with QUIN to brain synaptosomes. These findings support a neuroprotective and modulatory role of cannabinoids in the early toxic events elicited by agents inducing excitotoxic processes.

  2. Nicotinic α7 receptor activation selectively potentiates the function of NMDA receptors in glutamatergic terminals of the nucleus accumbens.

    PubMed

    Zappettini, Stefania; Grilli, Massimo; Olivero, Guendalina; Chen, Jiayang; Padolecchia, Cristina; Pittaluga, Anna; Tomé, Angelo R; Cunha, Rodrigo A; Marchi, Mario

    2014-01-01

    We here provide functional and immunocytochemical evidence supporting the co-localization and functional interaction between nicotinic acetylcholine receptors (nAChRs) and N-methyl-D-aspartic acid receptors (NMDARs) in glutamatergic terminals of the nucleus accumbens (NAc). Immunocytochemical studies showed that a significant percentage of NAc terminals were glutamatergic and possessed GluN1 and α7-containing nAChR. A short-term pre-exposure of synaptosomes to nicotine (30 µM) or choline (1 mM) caused a significant potentiation of the 100 µM NMDA-evoked [(3)H]D-aspartate ([(3)H]D-Asp) outflow, which was prevented by α-bungarotoxin (100 nM). The pre-exposure to nicotine (100 µM) or choline (1 mM) also enhanced the NMDA-induced cytosolic free calcium levels, as measured by FURA-2 fluorescence imaging in individual NAc terminals, an effect also prevented by α-bungarotoxin. Pre-exposure to the α4-nAChR agonists 5IA85380 (10 nM) or RJR2429 (1 µM) did not modify NMDA-evoked ([(3)H]D-Asp) outflow and calcium transients. The NMDA-evoked ([(3)H]D-Asp) overflow was partially antagonized by the NMDAR antagonists MK801, D-AP5, 5,7-DCKA and R(-)CPP and unaffected by the GluN2B-NMDAR antagonists Ro256981 and ifenprodil. Notably, pre-treatment with choline increased GluN2A biotin-tagged proteins. In conclusion, our results show that the GluN2A-NMDA receptor function can be positively regulated in NAc terminals in response to a brief incubation with α7 but not α4 nAChRs agonists. This might be a general feature in different brain areas since a similar nAChR-mediated bolstering of NMDA-induced ([(3)H]D-Asp) overflow was also observed in hippocampal synaptosomes.

  3. Agonist binding to the NMDA receptor drives movement of its cytoplasmic domain without ion flow

    PubMed Central

    Dore, Kim; Aow, Jonathan; Malinow, Roberto

    2015-01-01

    The NMDA receptor (R) plays important roles in brain physiology and pathology as an ion channel. Here we examine the ion flow-independent coupling of agonist to the NMDAR cytoplasmic domain (cd). We measure FRET between fluorescently tagged cytoplasmic domains of GluN1 subunits of NMDARs expressed in neurons. Different neuronal compartments display varying levels of FRET, consistent with different NMDARcd conformations. Agonist binding drives a rapid and transient ion flow-independent reduction in FRET between GluN1 subunits within individual NMDARs. Intracellular infusion of an antibody targeting the GluN1 cytoplasmic domain blocks agonist-driven FRET changes in the absence of ion flow, supporting agonist-driven movement of the NMDARcd. These studies indicate that extracellular ligand binding to the NMDAR can transmit conformational information into the cell in the absence of ion flow. PMID:26553997

  4. Coordinated activation of distinct Ca2+ sources and metabotropic glutamate receptors encodes Hebbian synaptic plasticity

    PubMed Central

    Tigaret, Cezar M.; Olivo, Valeria; Sadowski, Josef H.L.P.; Ashby, Michael C.; Mellor, Jack R.

    2016-01-01

    At glutamatergic synapses, induction of associative synaptic plasticity requires time-correlated presynaptic and postsynaptic spikes to activate postsynaptic NMDA receptors (NMDARs). The magnitudes of the ensuing Ca2+ transients within dendritic spines are thought to determine the amplitude and direction of synaptic change. In contrast, we show that at mature hippocampal Schaffer collateral synapses the magnitudes of Ca2+ transients during plasticity induction do not match this rule. Indeed, LTP induced by time-correlated pre- and postsynaptic spikes instead requires the sequential activation of NMDARs followed by voltage-sensitive Ca2+ channels within dendritic spines. Furthermore, LTP requires inhibition of SK channels by mGluR1, which removes a negative feedback loop that constitutively regulates NMDARs. Therefore, rather than being controlled simply by the magnitude of the postsynaptic calcium rise, LTP induction requires the coordinated activation of distinct sources of Ca2+ and mGluR1-dependent facilitation of NMDAR function. PMID:26758963

  5. Anti-N-methyl-d-aspartate receptor encephalitis in a patient with neuromyelitis optica spectrum disorders.

    PubMed

    Luo, Jing-Jing; Lv, He; Sun, Wei; Zhao, Juan; Hao, Hong-Jun; Gao, Feng; Huang, Yi-Ning

    2016-07-01

    We described a female patient with anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis occurring sequentially with neuromyelitis optica spectrum disorders (NMOSD). The 19-year-old patient initially presented a diencephalic syndrome with aquaporin-4 immunoglobulin G antibodies (AQP4-IgG) and brain lesions which involving bilateral medial temporal lobes and periependymal surfaces of the third ventricle on magnetic resonance imaging (MRI). Ten months later, the patient developed cognitive impairment, psychiatric symptoms and dyskinesia with left basal ganglia lesions on brain MRI. Meanwhile, the anti-NMDAR antibodies were positive in the patient's serum and cerebrospinal fluid, while the screening tests for an ovarian teratoma and other tumors were all negative. Hence, the patient was diagnosed NMOSD and anti-NMDAR encephalitis followed by low-dose rituximab treatment with a good response. This case was another evidence for demyelinating syndromes overlapping anti-NMDAR encephalitis in Chinese patients. PMID:27456878

  6. Lysergic acid diethylamide-induced Fos expression in rat brain: role of serotonin-2A receptors.

    PubMed

    Gresch, P J; Strickland, L V; Sanders-Bush, E

    2002-01-01

    Lysergic acid diethylamide (LSD) produces altered mood and hallucinations in humans and binds with high affinity to serotonin-2A (5-HT(2A)) receptors. Although LSD interacts with other receptors, the activation of 5-HT(2A) receptors is thought to mediate the hallucinogenic properties of LSD. The goal of this study was to identify the brain sites activated by LSD and to determine the influence of 5-HT(2A) receptors in this activation. Rats were pretreated with the 5-HT(2A) receptor antagonist MDL 100907 (0.3 mg/kg, i.p.) or vehicle 30 min prior to LSD (500 microg/kg, i.p.) administration and killed 3 h later. Brain tissue was examined for Fos protein expression by immunohistochemistry. LSD administration produced a five- to eight-fold increase in Fos-like immunoreactivity in medial prefrontal cortex, anterior cingulate cortex, and central nucleus of amygdala. However, in dorsal striatum and nucleus accumbens no increase in Fos-like immunoreactivity was observed. Pretreatment with MDL 100907 completely blocked LSD-induced Fos-like immunoreactivity in medial prefrontal cortex and anterior cingulate cortex, but only partially blocked LSD-induced Fos-like immunoreactivity in amygdala. Double-labeled immunohistochemistry revealed that LSD did not induce Fos-like immunoreactivity in cortical cells expressing 5-HT(2A) receptors, suggesting an indirect activation of cortical neurons. These results indicate that the LSD activation of medial prefrontal cortex and anterior cingulate cortex is mediated by 5-HT(2A) receptors, whereas in amygdala 5-HT(2A) receptor activation is a component of the response. These findings support the hypothesis that the medial prefrontal cortex, anterior cingulate cortex, and perhaps the amygdala, are important regions involved in the production of hallucinations.

  7. Two isoforms of Xenopus retinoic acid receptor gamma 2 (B) exhibit differential expression and sensitivity to retinoic acid during embryogenesis.

    PubMed

    Crawford, M J; Liversage, R A; Varmuza, S L

    1995-01-01

    We report the isolation of two retinoic acid receptor isoforms (RAR gamma), which differ only in the 5'untranslated and putative N-terminus A regions. The two isoforms appear to serve as early markers for the presumptive neural axis; however, their expression patterns differ. RAR-gamma 2.1 is first expressed at gastrulation at the dorsal lip and subsequently along the presumptive neural axis. RAR- gamma 2.2 represents the full-length sequence of a receptor cDNA already partially characterized and present as a maternal transcript [Ellinger-Ziegelbauer and Dreyer (1991); Genes Dev 5:94-104, (1993): Mech Dev 41:31-46; Pfeffer and DeRobertis, (1994) Mech Dev: 45:147-153]. Unlike RAR-gamma 2.2, the 2.1 variant is not expressed either in pre-somitic mesoderm or notochord. RAR-gamma 2.1 is strongly expressed in branchial arches and to a lesser extent in the neural floor plate. The two isoforms also exhibit differential sensitivity to retinoic acid. Constitutive expression of RAR gamma 2.2 following neurulation appears to be depressed by treatment with retinoic acid, but domains of highest expression, namely, the head and tail, remain relatively unaffected, as do patterns of expression prior to late neurulation. By contrast, RAR-gamma 2.1 is not transcribed in retinoid-inhibited structures. Using microinjection techniques, we show that changes of RAR-gamma 2.1 expression in presumptive head structures occur as an early and local consequence of retinoic acid administration. Since RAR-gamma 2.1 expression is inhibited by retinoic acid, we tested to see if other treatments that perturb axis formation had any effect. Surprisingly, UV irradiation did not suppress that its inhibition by retinoic acid is not due solely to inhibition of anterior neural development. These experiments demonstrate a new subdivision of isoforms that undergo differential expression during development and that exhibit differential sensitivity to retinoic acid and to UV. This sensitivity and the presence

  8. Reelin, an extracellular matrix protein linked to early onset psychiatric diseases, drives postnatal development of the prefrontal cortex via GluN2B-NMDARs and the mTOR pathway.

    PubMed

    Iafrati, J; Orejarena, M J; Lassalle, O; Bouamrane, L; Gonzalez-Campo, C; Chavis, P

    2014-04-01

    Defective brain extracellular matrix (ECM) is a factor of vulnerability in various psychiatric diseases such as schizophrenia, depression and autism. The glycoprotein reelin is an essential building block of the brain ECM that modulates neuronal development and participates to the functions of adult central synapses. The reelin gene (RELN) is a strong candidate in psychiatric diseases of early onset, but its synaptic and behavioral functions in juvenile brain circuits remain unresolved. Here, we found that in juvenile reelin-haploinsufficient heterozygous reeler mice (HRM), abnormal fear memory erasure is concomitant to reduced dendritic spine density and anomalous long-term potentiation in the prefrontal cortex. In juvenile HRM, a single in vivo injection with ketamine or Ro25-6981 to inhibit GluN2B-N-methyl-D-aspartate receptors (NMDARs) restored normal spine density, synaptic plasticity and converted fear memory to an erasure-resilient state typical of adult rodents. The functional and behavioral rescue by ketamine was prevented by rapamycin, an inhibitor of the mammalian target of rapamycin pathway. Finally, we show that fear memory erasure persists until adolescence in HRM and that a single exposure to ketamine during the juvenile period reinstates normal fear memory in adolescent mice. Our results show that reelin is essential for successful structural, functional and behavioral development of juvenile prefrontal circuits and that this developmental period provides a critical window for therapeutic rehabilitation with GluN2B-NMDAR antagonists.

  9. Phosphorylation of Ser1166 on GluN2B by PKA Is Critical to Synaptic NMDA Receptor Function and Ca2+ Signaling in Spines

    PubMed Central

    Murphy, Jessica A.; Stein, Ivar S.; Lau, C. Geoffrey; Peixoto, Rui T.; Aman, Teresa K.; Kaneko, Naoki; Aromolaran, Kelly; Saulnier, Jessica L.; Popescu, Gabriela K.

    2014-01-01

    The NMDA-type glutamate receptor (NMDAR) is essential for synaptogenesis, synaptic plasticity, and higher cognitive function. Emerging evidence indicates that NMDAR Ca2+ permeability is under the control of cAMP/protein kinase A (PKA) signaling. Whereas the functional impact of PKA on NMDAR-dependent Ca2+ signaling is well established, the molecular target remains unknown. Here we identify serine residue 1166 (Ser1166) in the carboxy-terminal tail of the NMDAR subunit GluN2B to be a direct molecular and functional target of PKA phosphorylation critical to NMDAR-dependent Ca2+ permeation and Ca2+ signaling in spines. Activation of β-adrenergic and D1/D5-dopamine receptors induces Ser1166 phosphorylation. Loss of this single phosphorylation site abolishes PKA-dependent potentiation of NMDAR Ca2+ permeation, synaptic currents, and Ca2+ rises in dendritic spines. We further show that adverse experience in the form of forced swim, but not exposure to fox urine, elicits striking phosphorylation of Ser1166 in vivo, indicating differential impact of different forms of stress. Our data identify a novel molecular and functional target of PKA essential to NMDAR-mediated Ca2+ signaling at synapses and regulated by the emotional response to stress. PMID:24431445

  10. A critical role for PSD-95/AKAP interactions in endocytosis of synaptic AMPA receptors

    PubMed Central

    Bhattacharyya, Samarjit; Biou, Virginie; Xu, Weifeng; Schlüter, Oliver; Malenka, Robert C.

    2009-01-01

    The endocytosis of AMPA receptors (AMPARs) underlies several forms of synaptic plasticity including NMDA receptor (NMDAR)-dependent long-term depression (LTD) but the molecular mechanisms responsible for this trafficking remain unknown. Here we demonstrate that PSD-95, a major postsynaptic density protein, plays a key role in NMDAR-triggered endocytosis of synaptic AMPARs because of its binding to AKAP150, a scaffold for specific protein kinases and phosphatases. Knockdown of PSD-95 with shRNA blocks NMDAR-triggered, but not constitutive nor mGluR-triggered endocytosis of AMPARs. Deletion of PSD-95’s SH3 and GK domains as well as a point mutation (L460P), both of which inhibit binding of PSD-95 to AKAP150, also block NMDAR-triggered AMPAR endocytosis. Furthermore, expression of a mutant AKAP150 that does not bind calcineurin inhibits this NMDAR-triggered trafficking event. These results suggest that PSD-95’s interaction with AKAP150 is critical for NMDAR-triggered AMPAR endocytosis and LTD, possibly because these scaffolds position calcineurin in the appropriate subsynaptic domain. PMID:19169250

  11. NR2B-containing NMDA receptors promote neural progenitor cell proliferation through CaMKIV/CREB pathway

    SciTech Connect

    Li, Mei; Zhang, Dong-Qing; Wang, Xiang-Zhen; Xu, Tie-Jun

    2011-08-12

    Highlights: {yields} The NR2B component of the NMDARs is important for the NSPC proliferation. {yields} pCaMKIV and pCREB exist in NSPCs. {yields} The CaMKIV/CREB pathway mediates NSPC proliferation. -- Abstract: Accumulating evidence indicates the involvement of N-methyl-D-aspartate receptors (NMDARs) in regulating neural stem/progenitor cell (NSPC) proliferation. Functional properties of NMDARs can be markedly influenced by incorporating the regulatory subunit NR2B. Here, we aim to analyze the effect of NR2B-containing NMDARs on the proliferation of hippocampal NSPCs and to explore the mechanism responsible for this effect. NSPCs were shown to express NMDAR subunits NR1 and NR2B. The NR2B selective antagonist, Ro 25-6981, prevented the NMDA-induced increase in cell proliferation. Moreover, we demonstrated that the phosphorylation levels of calcium/calmodulin-dependent protein kinase IV (CaMKIV) and cAMP response element binding protein (CREB) were increased by NMDA treatment, whereas Ro 25-6981 decreased them. The role that NR2B-containing NMDARs plays in NSPC proliferation was abolished when CREB phosphorylation was attenuated by CaMKIV silencing. These results suggest that NR2B-containing NMDARs have a positive role in regulating NSPC proliferation, which may be mediated through CaMKIV phosphorylation and subsequent induction of CREB activation.

  12. Rapid attenuation of receptor-induced diacylglycerol and phosphatidic acid by phospholipase D-mediated transphosphatidylation: formation of bisphosphatidic acid.

    PubMed Central

    van Blitterswijk, W J; Hilkmann, H

    1993-01-01

    Generation and attenuation of lipid second messengers are key processes in cellular signalling. Receptor-mediated increase in 1,2-diacylglycerol (DG) levels is attenuated by DG kinase and DG lipase. We here report a novel mechanism of DG attenuation by phospholipase D (PLD), which also precludes the production of another (putative) second messenger, phosphatidic acid (PA). In the presence of an alcohol, PLD converts phosphatidylcholine (PC) into a phosphatidylalcohol (by transphosphatidylation) rather than into PA. We found in bradykinin-stimulated human fibroblasts that PLD mediates transphosphatidylation from PC (donor) to the endogenous 'alcohol' DG (acceptor), yielding bis(1,2-diacylglycero)-3-sn-phosphate (bisphosphatidic acid; bisPA). This uncommon phospholipid is thus a condensation product of the phospholipase C (PLC) and PLD signalling pathways, where PLC produces DG and PLD couples this DG to a phosphatidyl moiety. Long-term phorbol ester treatment blocks bradykinin-induced activation of PLD and consequent bisPA formation, thereby unveiling rapid formation of DG. BisPA formation is rapid (15 s) and transient (peaks at 2-10 min) and is also induced by other stimuli capable of raising DG and activating PLD simultaneously, e.g. endothelin, lysophosphatidic acid, fetal calf serum, phorbol ester, dioctanoylglycerol or bacterial PLC. This novel metabolic route counteracts rapid accumulation of receptor-induced DG and PA, and assigns for the first time a physiological role to the transphosphatidylation activity of PLD, that is signal attenuation. Images PMID:8392931

  13. Hydroxycarboxylic acid receptors are essential for breast cancer cells to control their lipid/fatty acid metabolism

    PubMed Central

    Stäubert, Claudia; Broom, Oliver Jay; Nordström, Anders

    2015-01-01

    Cancer cells exhibit characteristic changes in their metabolism with efforts being made to address them therapeutically. However, targeting metabolic enzymes as such is a major challenge due to their essentiality for normal proliferating cells. The most successful pharmaceutical targets are G protein-coupled receptors (GPCRs), with more than 40% of all currently available drugs acting through them. We show that, a family of metabolite-sensing GPCRs, the Hydroxycarboxylic acid receptor family (HCAs), is crucial for breast cancer cells to control their metabolism and proliferation. We found HCA1 and HCA3 mRNA expression were significantly increased in breast cancer patient samples and detectable in primary human breast cancer patient cells. Furthermore, siRNA mediated knock-down of HCA3 induced considerable breast cancer cell death as did knock-down of HCA1, although to a lesser extent. Liquid Chromatography Mass Spectrometry based analyses of breast cancer cell medium revealed a role for HCA3 in controlling intracellular lipid/fatty acid metabolism. The presence of etomoxir or perhexiline, both inhibitors of fatty acid β-oxidation rescues breast cancer cells with knocked-down HCA3 from cell death. Our data encourages the development of drugs acting on cancer-specific metabolite-sensing GPCRs as novel anti-proliferative agents for cancer therapy. PMID:25839160

  14. Hydroxycarboxylic acid receptors are essential for breast cancer cells to control their lipid/fatty acid metabolism.

    PubMed

    Stäubert, Claudia; Broom, Oliver Jay; Nordström, Anders

    2015-08-14

    Cancer cells exhibit characteristic changes in their metabolism with efforts being made to address them therapeutically. However, targeting metabolic enzymes as such is a major challenge due to their essentiality for normal proliferating cells. The most successful pharmaceutical targets are G protein-coupled receptors (GPCRs), with more than 40% of all currently available drugs acting through them.We show that, a family of metabolite-sensing GPCRs, the Hydroxycarboxylic acid receptor family (HCAs), is crucial for breast cancer cells to control their metabolism and proliferation.We found HCA1 and HCA3 mRNA expression were significantly increased in breast cancer patient samples and detectable in primary human breast cancer patient cells. Furthermore, siRNA mediated knock-down of HCA3 induced considerable breast cancer cell death as did knock-down of HCA1, although to a lesser extent. Liquid Chromatography Mass Spectrometry based analyses of breast cancer cell medium revealed a role for HCA3 in controlling intracellular lipid/fatty acid metabolism. The presence of etomoxir or perhexiline, both inhibitors of fatty acid β-oxidation rescues breast cancer cells with knocked-down HCA3 from cell death.Our data encourages the development of drugs acting on cancer-specific metabolite-sensing GPCRs as novel anti-proliferative agents for cancer therapy.

  15. Unsurmountable antagonism of brain 5-hydroxytryptamine2 receptors by (+)-lysergic acid diethylamide and bromo-lysergic acid diethylamide.

    PubMed

    Burris, K D; Sanders-Bush, E

    1992-11-01

    Lysergic acid diethylamide (LSD) and its structural analogue 2-bromo-lysergic acid diethylamide (BOL) act as unsurmountable antagonists of serotonin-elicited contractions in smooth muscle preparations. Two different models, allosteric and kinetic, have been invoked to explain these findings. The present studies investigate the mechanism of antagonism of brain 5-hydroxytryptamine (5HT)2 receptors, utilizing cells transfected with 5HT2 receptor cDNA cloned from rat brain. A proximal cellular response, phosphoinositide hydrolysis, was examined in order to minimize possible postreceptor effects. Even though LSD behaved as a partial agonist and BOL as a pure antagonist, both drugs blocked the effect of serotonin in an unsurmountable manner, i.e., increasing concentrations of serotonin could not overcome the blocking effect of LSD or BOL. Radioligand binding studies showed that preincubation of membranes with either LSD or BOL reduced the density of [3H]ketanserin binding sites, suggesting that the drugs bind tightly to the 5HT2 receptor and are not displaced during the binding assay. Two additional experiments supported this hypothesis. First, the off-rate of [3H] LSD was slow (20 min), relative to that of [3H]ketanserin (approximately 4 min). Second, when the length of incubation with [3H]ketanserin was increased to 60 min, the LSD-induced decrease in Bmax was essentially eliminated. The possibility that LSD and BOL decrease [3H]ketanserin binding by interacting with an allosteric site was rejected, because neither drug altered the rate of dissociation of [3H]ketanserin. The most parsimonious interpretation of these results is that unsurmountable antagonism reflects prolonged occupancy of the receptor by slowly reversible antagonists.

  16. Metabotropic glutamate receptor signaling is required for NMDA receptor-dependent ocular dominance plasticity and LTD in visual cortex.

    PubMed

    Sidorov, Michael S; Kaplan, Eitan S; Osterweil, Emily K; Lindemann, Lothar; Bear, Mark F

    2015-10-13

    A feature of early postnatal neocortical development is a transient peak in signaling via metabotropic glutamate receptor 5 (mGluR5). In visual cortex, this change coincides with increased sensitivity of excitatory synapses to monocular deprivation (MD). However, loss of visual responsiveness after MD occurs via mechanisms revealed by the study of long-term depression (LTD) of synaptic transmission, which in layer 4 is induced by acute activation of NMDA receptors (NMDARs) rather than mGluR5. Here we report that chronic postnatal down-regulation of mGluR5 signaling produces coordinated impairments in both NMDAR-dependent LTD in vitro and ocular dominance plasticity in vivo. The data suggest that ongoing mGluR5 signaling during a critical period of postnatal development establishes the biochemical conditions that are permissive for activity-dependent sculpting of excitatory synapses via the mechanism of NMDAR-dependent LTD.

  17. Metabotropic glutamate receptor signaling is required for NMDA receptor-dependent ocular dominance plasticity and LTD in visual cortex.

    PubMed

    Sidorov, Michael S; Kaplan, Eitan S; Osterweil, Emily K; Lindemann, Lothar; Bear, Mark F

    2015-10-13

    A feature of early postnatal neocortical development is a transient peak in signaling via metabotropic glutamate receptor 5 (mGluR5). In visual cortex, this change coincides with increased sensitivity of excitatory synapses to monocular deprivation (MD). However, loss of visual responsiveness after MD occurs via mechanisms revealed by the study of long-term depression (LTD) of synaptic transmission, which in layer 4 is induced by acute activation of NMDA receptors (NMDARs) rather than mGluR5. Here we report that chronic postnatal down-regulation of mGluR5 signaling produces coordinated impairments in both NMDAR-dependent LTD in vitro and ocular dominance plasticity in vivo. The data suggest that ongoing mGluR5 signaling during a critical period of postnatal development establishes the biochemical conditions that are permissive for activity-dependent sculpting of excitatory synapses via the mechanism of NMDAR-dependent LTD. PMID:26417096

  18. LE135, a retinoid acid receptor antagonist, produces pain through direct activation of TRP channels

    PubMed Central

    Yin, Shijin; Luo, Jialie; Qian, Aihua; Yu, Weihua; Hu, Hongzhen

    2014-01-01

    Background and PurposeRetinoids, through their activation of retinoic acid receptors (RARs) and retinoid X receptors, regulate diverse cellular processes, and pharmacological intervention in their actions has been successful in the treatment of skin disorders and cancers. Despite the many beneficial effects, administration of retinoids causes irritating side effects with unknown mechanisms. Here, we demonstrate that LE135 [4-(7,8,9,10-tetrahydro-5,7,7,10,10-pentamethyl-5H-benzo[e]naphtho[2,3-b][1,4]diazepin-13-yl)benzoic acid], a selective antagonist of RARβ, is a potent activator of the capsaicin (TRPV1) and wasabi (TRPA1) receptors, two critical pain-initiating cation channels. Experimental ApproachWe performed to investigate the excitatory effects of LE135 on TRPV1 and TRPA1 channels expressed in HEK293T cells and in dorsal root ganglia neurons with calcium imaging and patch-clamp recordings. We also used site-directed mutagenesis of the channels to determine the structural basis of LE135-induced activation of TRPV1 and TRPA1 channels and behavioural testing to examine if pharmacological inhibition and genetic deletion of the channels affected LE135-evoked pain-related behaviours. Key ResultsLE135 activated both the capsaicin receptor (TRPV1) and the allyl isothiocyanate receptor (TRPA1) heterologously expressed in HEK293T cells and endogenously expressed by sensory nociceptors. Mutations disrupting the capsaicin-binding site attenuated LE135 activation of TRPV1 channels and a single mutation (K170R) eliminated TRPA1 activity evoked by LE135. Intraplantar injection of LE135 evoked pain-related behaviours. Both TRPV1 and TRPA1 channels were involved in LE135-elicited pain-related responses, as shown by pharmacological and genetic ablation studies. Conclusions and ImplicationsThis blocker of retinoid acid signalling also exerted non-genomic effects through activating the pain-initiating TRPV1 and TRPA1 channels. PMID:24308840

  19. The fate of P2Y-related orphan receptors: GPR80/99 and GPR91 are receptors of dicarboxylic acids.

    PubMed

    Gonzalez, Nathalie Suarez; Communi, Didier; Hannedouche, Sébastien; Boeynaems, Jean-Marie

    2004-12-01

    Several orphan G protein-coupled receptors are structurally close to the family of P2Y nucleotide receptors: GPR80/99 and GPR91 are close to P2Y(1/2/4/6/11) receptors, whereas GPR87, H963 and GPR34 are close to P2Y(12/13/14). Over the years, several laboratories have attempted without success to identify the ligands of those receptors. In early 2004, two papers have been published: One claiming that GPR80/99 is an AMP receptor, called P2Y(15), and the other one showing that GPR80/99 is a receptor for alpha-ketoglutarate, while GPR91 is a succinate receptor. The accompanying paper by Qi et al. entirely supports that GPR80/99 is an alpha-ketoglutarate receptor and not an AMP receptor. The closeness of dicarboxylic acid and P2Y nucleotide receptors might be linked to the negative charges of both types of ligands and the involvement of conserved Arg residues in their neutralization. PMID:18404396

  20. Regulation of antibacterial defense in the small intestine by the nuclear bile acid receptor

    NASA Astrophysics Data System (ADS)

    Inagaki, Takeshi; Moschetta, Antonio; Lee, Youn-Kyoung; Peng, Li; Zhao, Guixiang; Downes, Michael; Yu, Ruth T.; Shelton, John M.; Richardson, James A.; Repa, Joyce J.; Mangelsdorf, David J.; Kliewer, Steven A.

    2006-03-01

    Obstruction of bile flow results in bacterial proliferation and mucosal injury in the small intestine that can lead to the translocation of bacteria across the epithelial barrier and systemic infection. These adverse effects of biliary obstruction can be inhibited by administration of bile acids. Here we show that the farnesoid X receptor (FXR), a nuclear receptor for bile acids, induces genes involved in enteroprotection and inhibits bacterial overgrowth and mucosal injury in ileum caused by bile duct ligation. Mice lacking FXR have increased ileal levels of bacteria and a compromised epithelial barrier. These findings reveal a central role for FXR in protecting the distal small intestine from bacterial invasion and suggest that FXR agonists may prevent epithelial deterioration and bacterial translocation in patients with impaired bile flow. bacteria | biliary obstruction | epithelial barrier | ileum

  1. Role of farnesoid X receptor and bile acids in alcoholic liver disease

    PubMed Central

    Manley, Sharon; Ding, Wenxing

    2015-01-01

    Alcoholic liver disease (ALD) is one of the major causes of liver morbidity and mortality worldwide. Chronic alcohol consumption leads to development of liver pathogenesis encompassing steatosis, inflammation, fibrosis, cirrhosis, and in extreme cases, hepatocellular carcinoma. Moreover, ALD may also associate with cholestasis. Emerging evidence now suggests that farnesoid X receptor (FXR) and bile acids also play important roles in ALD. In this review, we discuss the effects of alcohol consumption on FXR, bile acids and gut microbiome as well as their impacts on ALD. Moreover, we summarize the findings on FXR, FoxO3a (forkhead box-containing protein class O3a) and PPARα (peroxisome proliferator-activated receptor alpha) in regulation of autophagy-related gene transcription program and liver injury in response to alcohol exposure. PMID:26579442

  2. Role of farnesoid X receptor and bile acids in alcoholic liver disease.

    PubMed

    Manley, Sharon; Ding, Wenxing

    2015-03-01

    Alcoholic liver disease (ALD) is one of the major causes of liver morbidity and mortality worldwide. Chronic alcohol consumption leads to development of liver pathogenesis encompassing steatosis, inflammation, fibrosis, cirrhosis, and in extreme cases, hepatocellular carcinoma. Moreover, ALD may also associate with cholestasis. Emerging evidence now suggests that farnesoid X receptor (FXR) and bile acids also play important roles in ALD. In this review, we discuss the effects of alcohol consumption on FXR, bile acids and gut microbiome as well as their impacts on ALD. Moreover, we summarize the findings on FXR, FoxO3a (forkhead box-containing protein class O3a) and PPARα (peroxisome proliferator-activated receptor alpha) in regulation of autophagy-related gene transcription program and liver injury in response to alcohol exposure. PMID:26579442

  3. Retinoic acid receptor alpha mediates growth inhibition by retinoids in human colon carcinoma HT29 cells.

    PubMed

    Nicke, B; Kaiser, A; Wiedenmann, B; Riecken, E O; Rosewicz, S

    1999-08-11

    Although retinoids have been suggested to inhibit chemically induced colon carcinogenesis, the molecular mechanisms underlying retinoid-mediated growth regulation in colon carcinoma cells are unknown. Therefore, we investigated the biological effects of retinoids on growth in HT29 colon carcinoma cells. All-trans retinoic acid (ATRA) treatment of HT29 cells resulted in a profound inhibition of anchorage-independent growth without biochemical or morphological evidence for induction of differentiation. Treatment with the selective RARalpha agonist Ro 40-6055 completely mimicked the effects of ATRA on growth and transactivation of a betaRAREx2-luciferase reporter construct, while RARbeta- and gamma-specific analogues were ineffective. Furthermore, ATRA-regulated growth and transactivation could be completely blocked by a RARalpha-selective receptor antagonist. Thus, ATRA potently inhibits anchorage-independent growth in HT29 cells and this effect is mainly if not exclusively mediated by the retinoic acid receptor alpha.

  4. Pharmacological Modulation of NMDA Receptor Activity and the Advent of Negative and Positive Allosteric Modulators

    PubMed Central

    Monaghan, Daniel T.; Irvine, Mark W.; Costa, Blaise Mathias; Fang, Guangyu; Jane, David E.

    2012-01-01

    The NMDA receptor (NMDAR) family of L-glutamate receptors are well known to have diverse roles in CNS function as well as in various neuropathological and psychiatric conditions. Until recently, the types of agents available to pharmacologically regulate NMDAR function have been quite limited in terms of mechanism of action and subtype selectivity. This has changed significantly in the past two years. The purpose of this review is to summarize the many drug classes now available for modulating NMDAR activity. Previously, this included competitive antagonists at the L-glutamate and glycine binding sites, high and low affinity channel blockers, and GluN2B-selective N-terminal domain binding site antagonists. More recently, we and others have identifed new classes of NMDAR agents that are either positive or negative allosteric modulators (PAMs and NAMs, respectively). These compounds include the pan potentiator UBP646, the GluN2A-selective potentiator/GluN2C & GluN2D inhibitor UBP512, the GluN2D-selective potentiator UBP551, the GluN2C/GluN2D-selective potentiator CIQ as well as the new NMDAR-NAMs such as the pan-inhibitor UBP618, the GluN2C/GluN2D-selective inhibitor QZN46 and the GluN2A inhibitors UBP608 and TCN201. These new agents do not bind within the L-glutamate or glycine binding sites, the ion channel pore or the N-terminal regulatory domain. Collectively, these new allosteric modulators appear to be acting at multiple novel sites on the NMDAR complex. Importantly, these agents display improved subtype-selectivity and as NMDAR PAMs and NAMs, they represent a new generation of potential NMDAR therapeutics. PMID:22269804

  5. Oleanolic acid acrylate elicits antidepressant-like effect mediated by 5-HT1A receptor.

    PubMed

    Fajemiroye, James O; Polepally, Prabhakar R; Chaurasiya, Narayan D; Tekwani, Babu L; Zjawiony, Jordan K; Costa, Elson A

    2015-01-01

    The development of new drugs for the treatment of depression is strategic to achieving clinical needs of patients. This study evaluates antidepressant-like effect and neural mechanisms of four oleanolic acid derivatives i.e. acrylate (D1), methacrylate (D2), methyl fumarate (D3) and ethyl fumarate (D4). All derivatives were obtained by simple one-step esterification of oleanolic acid prior to pharmacological screening in the forced swimming (FS) and open field (OF) tests. Pharmacological tools like α-methyl-p-tyrosine (AMPT, catecholamine depletor), p-chlorophenylalanine (serotonin depletor), prazosin (PRAZ, selective α1-receptor antagonist), WAY-100635 (selective serotonin 5-HT1A receptor antagonist) as well as monoamine oxidase (MAO) and functional binding assays were conducted to investigate possible neural mechanisms. In the FS test, D1 showed the most promising antidepressant-like effect without eliciting locomotor incoordination. Unlike group of mice pretreated with AMPT 100 mg/kg, PCPA 100 mg/kg or PRAZ 1 mg/kg, the effect of D1 was attenuated by WAY-100635 0.3 mg/kg pretreatment. D1 demonstrated moderate inhibition of MAO-A (IC50 = 48.848 ± 1.935 μM), potency (pEC50 = 6.1 ± 0.1) and intrinsic activity (E max = 26 ± 2.0%) on 5-HT1A receptor. In conclusion, our findings showed antidepressant-like effect of D1 and possible involvement of 5-HT1A receptor.

  6. Specific interaction of aurintricarboxylic acid with the human immunodeficiency virus/CD4 cell receptor

    SciTech Connect

    Schols, D.; Baba, M.; Pauwels, R.; Desmyter, J.; De Clercq, E. )

    1989-05-01

    The triphenylmethane derivative aurintricarboxylic acid (ATA), but not aurin, selectively prevented the binding of OKT4A/Leu-3a monoclonal antibody (mAb) and, to a lesser extent, OKT4 mAb to the CD4 cell receptor for human immunodeficiency virus type 1 (HIV-1). The effect was seen within 1 min at an ATA concentration of 10 {mu}M in various T4{sup +} cells (MT-4, U-937, peripheral blood lymphocytes, and monocytes). It was dose-dependent and reversible. ATA prevented the attachment of radiolabeled HIV-1 particles to MT-4 cells, which could be expected as the result of its specific binding to the HIV/CD4 receptor. Other HIV inhibitors such as suramin, fuchsin acid, azidothymidine, dextran sulfate, heparin, and pentosan polysulfate did not affect OKT4A/Leu-3a mAb binding to the CD4 receptor, although the sulfated polysaccharides suppressed HIV-1 adsorption to the cells at concentrations required for complete protection against HIV-1 cytopathogenicity. Thus, ATA is a selective marker molecule for the CD4 receptor. ATA also interfered with the staining of membrane-associated HIV-1 glycoprotein gp120 by a mAb against it. These unusual properties of a small molecule of nonimmunological origin may have important implications for the study of CD4/HIV/AIDS pathogenesis and possibly treatment.

  7. The myeloperoxidase product hypochlorous acid generates irreversible high-density lipoprotein receptor inhibitors

    PubMed Central

    Binder, Veronika; Ljubojevic, Senka; Haybaeck, Johannes; Holzer, Michael; El-Gamal, Dalia; Schicho, Rudolf; Pieske, Burkert; Heinemann, Akos; Marsche, Gunther

    2014-01-01

    Objective Elevated levels of advanced oxidation protein products (AOPPs) have been described in several chronic inflammatory diseases, like chronic renal insufficiency, rheumatoid arthritis and atherosclerosis. Recent findings revealed that AOPPs are inhibitors of the major high-density lipoprotein (HDL) receptor, scavenger receptor class B, type 1 (SR-BI). Here we investigated what oxidation induced structural alterations convert plasma albumin into an HDL-receptor inhibitor. Approach and Results Exposure of albumin to the physiological oxidant, hypochlorous acid, generated high affinity SR-BI ligands. Protection of albumin lysine-residues prior exposure to hypochlorous acid as well as regeneration of N-chloramines after oxidation of albumin completely prevented binding of oxidized albumin to SR-BI, indicating that modification of albumin lysine-residues is required to generate SR-BI ligands. Of particular interest, N-chloramines within oxidized albumin promoted irreversible binding to SR-BI, resulting in permanent receptor blockade. We observed that the SR-BI inhibitory activity of albumin isolated from chronic kidney disease patients correlated with the content of the myeloperoxidase-specific oxidation product 3-chlorotyrosine and was associated with alterations in the composition of HDL. Conclusion Given that several potential atheroprotective activities of HDL are mediated by SR-BI, the present results raise the possibility that oxidized plasma albumin, through permanent SR-BI blockade, contributes to the pathophysiology of cardiovascular disease. PMID:23493288

  8. The acidic domains of the Toc159 chloroplast preprotein receptor family are intrinsically disordered protein domains

    PubMed Central

    2009-01-01

    Background The Toc159 family of proteins serve as receptors for chloroplast-destined preproteins. They directly bind to transit peptides, and exhibit preprotein substrate selectivity conferred by an unknown mechanism. The Toc159 receptors each include three domains: C-terminal membrane, central GTPase, and N-terminal acidic (A-) domains. Although the function(s) of the A-domain remains largely unknown, the amino acid sequences are most variable within these domains, suggesting they may contribute to the functional specificity of the receptors. Results The physicochemical properties of the A-domains are characteristic of intrinsically disordered proteins (IDPs). Using CD spectroscopy we show that the A-domains of two Arabidopsis Toc159 family members (atToc132 and atToc159) are disordered at physiological pH and temperature and undergo conformational changes at temperature and pH extremes that are characteristic of IDPs. Conclusions Identification of the A-domains as IDPs will be important for determining their precise function(s), and suggests a role in protein-protein interactions, which may explain how these proteins serve as receptors for such a wide variety of preprotein substrates. PMID:20042108

  9. SIGNALLING THROUGH RETINOIC ACID RECEPTORS IN CARDIAC DEVELOPMENT: DOING THE RIGHT THINGS AT THE RIGHT TIMES

    PubMed Central

    Xavier-Neto, José; Costa, Ângela M. Sousa; Figueira, Ana Carolina M.; Caiaffa, Carlo Donato; do Amaral, Fabio Neves; Peres, Lara Maldanis Cerqueira; da Silva, Bárbara Santos Pires; Santos, Luana Nunes; Moise, Alexander R.; Castillo, Hozana Andrade

    2015-01-01

    Retinoic acid (RA) is a terpenoid that is synthesized from Vitamin A/retinol (ROL) and binds to the nuclear receptors retinoic acid receptor (RAR)/retinoid X receptor (RXR) to control multiple developmental processes in vertebrates. The available clinic and experimental data provide uncontested evidence for the pleiotropic roles of RA signalling in development of multiple embryonic structures and organs such eyes, central nervous system, gonads, lungs and heart. The development of any of these above-mentioned embryonic organ systems can be effectively utilized to showcase the many strategies utilized by RA signalling. However, it is very likely that the strategies employed to transfer RA signals during cardiac development comprise the majority of the relevant and sophisticated ways through which retinoid signals can be conveyed in a complex biological system. Here, we provide the reader with arguments indicating that RA signalling is exquisitely regulated according to specific phases of cardiac development and that RA signalling itself is one of the major regulators of the timing of cardiac morphogenesis and differentiation. We will focus on the role of signalling by RA receptors (RARs) in early phases of heart development. PMID:25134739

  10. Retinoic acid and retinoid receptors: potential chemopreventive and therapeutic role in cervical cancer.

    PubMed

    Abu, Jafaru; Batuwangala, Madu; Herbert, Karl; Symonds, Paul

    2005-09-01

    Retinoids are natural and synthetic derivatives of vitamin A, which can be obtained from animal products (milk, liver, beef, fish oils, and eggs) and vegetables (carrots, mangos, sweet potatoes, and spinach). Retinoids regulate various important cellular functions in the body through specific nuclear retinoic-acid receptors and retinoid-X receptors, which are encoded by separate genes. Retinoic-acid receptors specifically bind tretinoin and alitretinoin, whereas retinoid-X receptors bind only alitretinoin. Retinoids have long been established as crucial for several essential life processes-healthy growth, vision, maintenance of tissues, reproduction, metabolism, tissue differentiation (normal, premalignant cells, and malignant cells), haemopoiesis, bone development, spermatogenesis, embryogenesis, and overall survival. Therefore, deficiency of vitamin A can lead to various unwanted biological effects. Several experimental and epidemiological studies have shown the antiproliferative activity of retinoids and their potential use in cancer treatment and chemoprevention. Emerging clinical trials have shown the chemotherapeutic and chemopreventive potential of retinoids in cancerous and precancerous conditions of the uterine cervix. In this review, we explore the potential chemopreventive and therapeutic roles of retinoids in preinvasive and invasive cervical neoplasia.

  11. Synthesis and evaluation of a (68)Ga labeled folic acid derivative for targeting folate receptors.

    PubMed

    Jain, Akanksha; Mathur, Anupam; Pandey, Usha; Bhatt, Jyotsna; Mukherjee, Archana; Ram, Ramu; Sarma, Haladhar Dev; Dash, Ashutosh

    2016-10-01

    Present work evaluates the potential of a newly synthesized (68)Ga-NOTA-folic acid conjugate for PET imaging of tumors over-expressing folate receptors (FRs). NOTA-folic acid conjugate was synthesized and characterized. It was radiolabeled with (68)Ga in ≥ 95% radiolabeling yields. In vitro cell binding studies showed a maximum cell uptake of 1.7±0.4% per million KB cells which was completely blocked on addition of cold folic acid showing specificity towards the FRs. However, further studies in tumor xenografts are warranted in order to assess the potential of (68)Ga-folic acid complex for imaging tumors over-expressing FRs. PMID:27501138

  12. The evolution of bat nucleic acid-sensing Toll-like receptors.

    PubMed

    Escalera-Zamudio, Marina; Zepeda-Mendoza, M Lisandra; Loza-Rubio, Elizabeth; Rojas-Anaya, Edith; Méndez-Ojeda, Maria L; Arias, Carlos F; Greenwood, Alex D

    2015-12-01

    We characterized the nucleic acid-sensing Toll-like receptors (TLR) of a New World bat species, the common vampire bat (Desmodus rotundus), and through a comparative molecular evolutionary approach searched for general adaptation patterns among the nucleic acid-sensing TLRs of eight different bats species belonging to three families (Pteropodidae, Vespertilionidae and Phyllostomidae). We found that the bat TLRs are evolving slowly and mostly under purifying selection and that the divergence pattern of such receptors is overall congruent with the species tree, consistent with the evolution of many other mammalian nuclear genes. However, the chiropteran TLRs exhibited unique mutations fixed in ligand-binding sites, some of which involved nonconservative amino acid changes and/or targets of positive selection. Such changes could potentially modify protein function and ligand-binding properties, as some changes were predicted to alter nucleic acid binding motifs in TLR 9. Moreover, evidence for episodic diversifying selection acting specifically upon the bat lineage and sublineages was detected. Thus, the long-term adaptation of chiropterans to a wide variety of environments and ecological niches with different pathogen profiles is likely to have shaped the evolution of the bat TLRs in an order-specific manner. The observed evolutionary patterns provide evidence for potential functional differences between bat and other mammalian TLRs in terms of resistance to specific pathogens or recognition of nucleic acids in general. PMID:26503258

  13. Autoradiographic localization and characterization of [125I]lysergic acid diethylamide binding to serotonin receptors in Aplysia.

    PubMed

    Kadan, M J; Hartig, P R

    1988-03-01

    The sensitive serotonergic radioligand 2-[125I]lysergic acid diethylamide was used to study the distribution and pharmacological binding properties of serotonin receptors in Aplysia californica. The high specific activity of this radioligand allowed us to develop a methodology for the investigation of receptor binding properties and receptor distribution in a single ganglion. [125I]Lysergic acid diethylamide labels a population of high-affinity serotonergic sites (Kd = 0.41 nM) in Aplysia ganglia whose regional distribution matches that expected from previous electrophysiological and immunohistochemical studies. The properties of [125I]lysergic acid diethylamide binding sites in Aplysia are in general agreement with previous studies on [3H]lysergic acid diethylamide binding in this system but these sites differ from the serotonergic receptor subtypes described in the mammalian brain. Guanine nucleotides were shown to modulate agonist but not antagonist affinity for the [125I]lysergic acid diethylamide binding site in Aplysia, suggesting that this site is coupled to a G-protein. Images of serotonin receptor distribution in the Aplysia nervous system were obtained from autoradiograms of [125I]lysergic acid diethylamide binding. Serotonin receptors in ganglia tissue sections are located primarily within the neuropil. In addition, a subset of neuronal soma are specifically labeled by [125I]lysergic acid diethylamide. These studies indicate that [125I]lysergic acid diethylamide binds to sites in the Aplysia nervous system which display a regional distribution, pharmacological binding properties and evidence of coupling to a G-protein consistent with labeling of a subset of functional serotonin receptors. In addition, the techniques used in this investigation provide a general approach for rapidly characterizing the pharmacological properties and anatomical distribution of receptor binding sites in single invertebrate ganglia. Individual neurons containing these receptor

  14. Spinal D1-like dopamine receptors modulate NMDA receptor-induced hyperexcitability and NR1 subunit phosphorylation at serine 889.

    PubMed

    Aira, Zigor; Barrenetxea, Teresa; Buesa, Itsaso; Martínez, Endika; Azkue, Jon Jatsu

    2016-04-01

    Activation of the N-methyl-d-aspartate receptor (NMDAR) in dorsal horn neurons is recognized as a fundamental mechanism of central sensitization and pathologic pain. This study assessed the influence of dopaminergic, D1-like receptor-mediated input to the spinal dorsal horn on NMDAR function. Spinal superfusion with selective NMDAR agonist cis-ACPD significantly increased C-fiber-evoked field potentials in rats subjected to spinal nerve ligation (SNL), but not in sham-operated rats. Simultaneous application of D1LR antagonist SCH 23390 dramatically reduced hyperexcitability induced by cis-ACPD. Furthermore, cis-ACPD-induced hyperexcitability seen in nerve-ligated rats could be mimicked in unin-jured rats during stimulation of D1LRs by agonist SKF 38393 at subthreshold concentration. Phosphorylation of NMDAR subunit NR1 at serine 889 at postsynaptic sites was found to be increased in dorsal horn neurons 90 min after SNL, as assessed by increased co-localization with postsynaptic marker PSD-95. Increased NR1 phosphorylation was attenuated in the presence of SCH 23390 in the spinal superfusate. The present results support that D1LRs regulate most basic determinants of NMDAR function in dorsal horn neurons, suggesting a potential mechanism whereby dopaminergic input to the dorsal horn can modulate central sensitization and pathologic pain.

  15. Agrochemical control of plant water use using engineered abscisic acid receptors.

    PubMed

    Park, Sang-Youl; Peterson, Francis C; Mosquna, Assaf; Yao, Jin; Volkman, Brian F; Cutler, Sean R

    2015-04-23

    Rising temperatures and lessening fresh water supplies are threatening agricultural productivity and have motivated efforts to improve plant water use and drought tolerance. During water deficit, plants produce elevated levels of abscisic acid (ABA), which improves water consumption and stress tolerance by controlling guard cell aperture and other protective responses. One attractive strategy for controlling water use is to develop compounds that activate ABA receptors, but agonists approved for use have yet to be developed. In principle, an engineered ABA receptor that can be activated by an existing agrochemical could achieve this goal. Here we describe a variant of the ABA receptor PYRABACTIN RESISTANCE 1 (PYR1) that possesses nanomolar sensitivity to the agrochemical mandipropamid and demonstrate its efficacy for controlling ABA responses and drought tolerance in transgenic plants. Furthermore, crystallographic studies provide a mechanistic basis for its activity and demonstrate the relative ease with which the PYR1 ligand-binding pocket can be altered to accommodate new ligands. Thus, we have successfully repurposed an agrochemical for a new application using receptor engineering. We anticipate that this strategy will be applied to other plant receptors and represents a new avenue for crop improvement. PMID:25652827

  16. Abscisic Acid Analogues That Act as Universal or Selective Antagonists of Phytohormone Receptors.

    PubMed

    Rajagopalan, Nandhakishore; Nelson, Ken M; Douglas, Amy F; Jheengut, Vishal; Alarcon, Idralyn Q; McKenna, Sean A; Surpin, Marci; Loewen, Michele C; Abrams, Suzanne R

    2016-09-13

    The plant hormone abscisic acid (ABA) plays many important roles in controlling plant development and physiology, from flowering to senescence. ABA is now known to exert its effects through a family of soluble ABA receptors, which in Arabidopsis thaliana has 13 members divided into three clades. Homologues of these receptors are present in other plants, also in relatively large numbers. Investigation of the roles of each homologue in mediating the diverse physiological roles of ABA is hampered by this genetic redundancy. We report herein the in vitro screening of a targeted ABA-like analogue library and identification of novel antagonist hits, including the analogue PBI686 that had been developed previously as a probe for identifying ABA-binding proteins. Further in vitro characterization of PBI686 and development of second-generation leads yielded both receptor-selective and universal antagonist hits. In planta assays in different species have demonstrated that these antagonist leads can overcome various ABA-induced physiological changes. While the general antagonists open up a hitherto unexplored avenue for controlling plant growth through inhibition of ABA-regulated physiological processes, the receptor-selective antagonist can be developed into chemical probes to explore the physiological roles of individual receptors.

  17. Nuclear receptors for retinoic acid and thyroid hormone regulate transcription of keratin genes.

    PubMed Central

    Tomic, M; Jiang, C K; Epstein, H S; Freedberg, I M; Samuels, H H; Blumenberg, M

    1990-01-01

    In the epidermis, retinoids regulate the expression of keratins, the intermediate filament proteins of epithelial cells. We have cloned the 5' regulatory regions of four human epidermal keratin genes, K#5, K#6, K#10, and K#14, and engineered constructs in which these regions drive the expression of the CAT reporter gene. By co-transfecting the constructs into epithelial cells along with the vectors expressing nuclear receptors for retinoic acid (RA) and thyroid hormone, we have demonstrated that the receptors can suppress the promoters of keratin genes. The suppression is ligand dependent; it is evident both in established cell lines and in primary cultures of epithelial cells. The three RA receptors have similar effects on keratin gene transcription. Our data indicate that the nuclear receptors for RA and thyroid hormone regulate keratin synthesis by binding to negative recognition elements in the upstream DNA sequences of the keratin genes. RA thus has a twofold effect on epidermal keratin expression: qualitatively, it regulates the regulators that effect the switch from basal cell-specific keratins to differentiation-specific ones; and quantitatively, it determines the level of keratin synthesis within the cell by direct interaction of its receptors with the keratin gene promoters. Images PMID:1712634

  18. Abscisic Acid Analogues That Act as Universal or Selective Antagonists of Phytohormone Receptors.

    PubMed

    Rajagopalan, Nandhakishore; Nelson, Ken M; Douglas, Amy F; Jheengut, Vishal; Alarcon, Idralyn Q; McKenna, Sean A; Surpin, Marci; Loewen, Michele C; Abrams, Suzanne R

    2016-09-13

    The plant hormone abscisic acid (ABA) plays many important roles in controlling plant development and physiology, from flowering to senescence. ABA is now known to exert its effects through a family of soluble ABA receptors, which in Arabidopsis thaliana has 13 members divided into three clades. Homologues of these receptors are present in other plants, also in relatively large numbers. Investigation of the roles of each homologue in mediating the diverse physiological roles of ABA is hampered by this genetic redundancy. We report herein the in vitro screening of a targeted ABA-like analogue library and identification of novel antagonist hits, including the analogue PBI686 that had been developed previously as a probe for identifying ABA-binding proteins. Further in vitro characterization of PBI686 and development of second-generation leads yielded both receptor-selective and universal antagonist hits. In planta assays in different species have demonstrated that these antagonist leads can overcome various ABA-induced physiological changes. While the general antagonists open up a hitherto unexplored avenue for controlling plant growth through inhibition of ABA-regulated physiological processes, the receptor-selective antagonist can be developed into chemical probes to explore the physiological roles of individual receptors. PMID:27523384

  19. A gate-latch-lock mechanism for hormone signalling by abscisic acid receptors

    SciTech Connect

    Melcher, Karsten; Ng, Ley-Moy; Zhou, X Edward; Soon, Fen-Fen; Xu, Yong; Suino-Powell, Kelly M; Park, Sang-Youl; Weiner, Joshua J; Fujii, Hiroaki; Chinnusamy, Viswanathan; Kovach, Amanda; Li, Jun; Wang, Yonghong; Li, Jiayang; Peterson, Francis C; Jensen, Davin R; Yong, Eu-Leong; Volkman, Brian F; Cutler, Sean R; Zhu, Jian-Kang; Xu, H Eric

    2010-01-12

    Abscisic acid (ABA) is a ubiquitous hormone that regulates plant growth, development and responses to environmental stresses. Its action is mediated by the PYR/PYL/RCAR family of START proteins, but it remains unclear how these receptors bind ABA and, in turn, how hormone binding leads to inhibition of the downstream type 2C protein phosphatase (PP2C) effectors. Here we report crystal structures of apo and ABA-bound receptors as well as a ternary PYL2-ABA-PP2C complex. The apo receptors contain an open ligand-binding pocket flanked by a gate that closes in response to ABA by way of conformational changes in two highly conserved β-loops that serve as a gate and latch. Moreover, ABA-induced closure of the gate creates a surface that enables the receptor to dock into and competitively inhibit the PP2C active site. A conserved tryptophan in the PP2C inserts directly between the gate and latch, which functions to further lock the receptor in a closed conformation. Together, our results identify a conserved gate-latch-lock mechanism underlying ABA signalling.

  20. Aldose Reductase acts as a Selective Derepressor of PPARγ and Retinoic Acid Receptor

    PubMed Central

    Thiagarajan, Devi; Ananthakrishnan, Radha; Zhang, Jinghua; O’Shea, Karen M.; Quadri, Nosirudeen; Li, Qing; Sas, Kelli; Jing, Xiao; Rosario, Rosa; Pennathur, Subramaniam; Schmidt, Ann Marie; Ramasamy, Ravichandran

    2016-01-01

    Summary Histone deacetylase 3 (HDAC3), a chromatin modifying enzyme, requires association with the deacetylase containing domain (DAD) of the nuclear receptor co-repressors NCOR1 and SMRT for its stability and activity. Here we show that aldose reductase (AR), the rate-limiting enzyme of the polyol pathway, competes with HDAC3 to bind the NCOR1/SMRT DAD. Increased AR expression leads to HDAC3 degradation followed by increased PPARγ signaling resulting in lipid accumulation in the heart. AR also downregulates expression of nuclear corepressor complex cofactors including Gps2 and Tblr1, thus affecting activity of the nuclear corepressor complex itself. Though AR reduces HDAC3-corepressor complex formation, it specifically de-represses the retinoic acid receptor (RAR), but not other nuclear receptors such as the thyroid receptor (TR) and liver X receptor (LXR). In summary, this work defines a distinct role for AR in lipid and retinoid metabolism through HDAC3 regulation and consequent de-repression of PPARγ and RAR. PMID:27052179

  1. The nuclear receptor PPARγ individually responds to serotonin- and fatty acid-metabolites

    PubMed Central

    Waku, Tsuyoshi; Shiraki, Takuma; Oyama, Takuji; Maebara, Kanako; Nakamori, Rinna; Morikawa, Kosuke

    2010-01-01

    The nuclear receptor, peroxisome proliferator-activated receptor γ (PPARγ), recognizes various synthetic and endogenous ligands by the ligand-binding domain. Fatty-acid metabolites reportedly activate PPARγ through conformational changes of the Ω loop. Here, we report that serotonin metabolites act as endogenous agonists for PPARγ to regulate macrophage function and adipogenesis by directly binding to helix H12. A cyclooxygenase inhibitor, indomethacin, is a mimetic agonist of these metabolites. Crystallographic analyses revealed that an indole acetate functions as a common moiety for the recognition by the sub-pocket near helix H12. Intriguingly, a serotonin metabolite and a fatty-acid metabolite each bind to distinct sub-pockets, and the PPARγ antagonist, T0070907, blocked the fatty-acid agonism, but not that of the serotonin metabolites. Mutational analyses on receptor-mediated transcription and coactivator binding revealed that each metabolite individually uses coregulator and/or heterodimer interfaces in a ligand-type-specific manner. Furthermore, the inhibition of the serotonin metabolism reduced the expression of the endogenous PPARγ-target gene. Collectively, these results suggest a novel agonism, in which PPARγ functions as a multiple sensor in response to distinct metabolites. PMID:20717101

  2. Dopamine D2High receptors stimulated by phencyclidines, lysergic acid diethylamide, salvinorin A, and modafinil.

    PubMed

    Seeman, Philip; Guan, Hong-Chang; Hirbec, Hélène

    2009-08-01

    Although it is commonly stated that phencyclidine is an antagonist at ionotropic glutamate receptors, there has been little measure of its potency on other receptors in brain tissue. Although we previously reported that phencyclidine stimulated cloned-dopamine D2Long and D2Short receptors, others reported that phencyclidine did not stimulate D2 receptors in homogenates of rat brain striatum. This study, therefore, examined whether phencyclidine and other hallucinogens and psychostimulants could stimulate the incorporation of [(35)S]GTP-gamma-S into D2 receptors in homogenates of rat brain striatum, using the same conditions as previously used to study the cloned D2 receptors. Using 10 microM dopamine to define 100% stimulation, phencyclidine elicited a maximum incorporation of 46% in rat striata, with a half-maximum concentration of 70 nM for phencyclidine, when compared with 80 nM for dopamine, 89 nM for salvinorin A (48 nM for D2Long), 105 nM for lysergic acid diethylamide (LSD), 120 nM for R-modafinil, 710 nM for dizocilpine, 1030 nM for ketamine, and >10,000 nM for S-modafinil. These compounds also inhibited the binding of the D2-selective ligand [(3)H]domperidone. The incorporation was inhibited by the presence of 200 microM guanylylimidodiphosphate and also by D2 blockade, using 10 microM S-sulpiride, but not by D1 blockade with 10 microM SCH23390. Hypertonic buffer containing 150 mM NaCl inhibited the stimulation by phencyclidine, which may explain negative results by others. It is concluded that phencyclidine and other psychostimulants and hallucinogens can stimulate dopamine D2 receptors at concentrations related to their behavioral actions.

  3. Structure-based drug design targeting the cell membrane receptor GPBAR1: exploiting the bile acid scaffold towards selective agonism

    NASA Astrophysics Data System (ADS)

    di Leva, Francesco Saverio; Festa, Carmen; Renga, Barbara; Sepe, Valentina; Novellino, Ettore; Fiorucci, Stefano; Zampella, Angela; Limongelli, Vittorio

    2015-11-01

    Bile acids can regulate nutrient metabolism through the activation of the cell membrane receptor GPBAR1 and the nuclear receptor FXR. Developing an exogenous control over these receptors represents an attractive strategy for the treatment of enterohepatic and metabolic disorders. A number of dual GPBAR1/FXR agonists are known, however their therapeutic use is limited by multiple unwanted effects due to activation of the diverse downstream signals controlled by the two receptors. On the other hand, designing selective GPBAR1 and FXR agonists is challenging since the two proteins share similar structural requisites for ligand binding. Here, taking advantage of our knowledge of the two targets, we have identified through a rational drug design study a series of amine lithocholic acid derivatives as selective GPBAR1 agonists. The presence of the 3α-NH2 group on the steroidal scaffold is responsible for the selectivity over FXR unveiling unprecedented structural insights into bile acid receptors activity modulation.

  4. Structure-based drug design targeting the cell membrane receptor GPBAR1: exploiting the bile acid scaffold towards selective agonism

    PubMed Central

    Di Leva, Francesco Saverio; Festa, Carmen; Renga, Barbara; Sepe, Valentina; Novellino, Ettore; Fiorucci, Stefano; Zampella, Angela; Limongelli, Vittorio

    2015-01-01

    Bile acids can regulate nutrient metabolism through the activation of the cell membrane receptor GPBAR1 and the nuclear receptor FXR. Developing an exogenous control over these receptors represents an attractive strategy for the treatment of enterohepatic and metabolic disorders. A number of dual GPBAR1/FXR agonists are known, however their therapeutic use is limited by multiple unwanted effects due to activation of the diverse downstream signals controlled by the two receptors. On the other hand, designing selective GPBAR1 and FXR agonists is challenging since the two proteins share similar structural requisites for ligand binding. Here, taking advantage of our knowledge of the two targets, we have identified through a rational drug design study a series of amine lithocholic acid derivatives as selective GPBAR1 agonists. The presence of the 3α-NH2 group on the steroidal scaffold is responsible for the selectivity over FXR unveiling unprecedented structural insights into bile acid receptors activity modulation. PMID:26567894

  5. Benzodiazepine receptor agonists affect both binding and gating of recombinant alpha1beta2gamma2 gamma-aminobutyric acid-A receptors.

    PubMed

    Mercik, Katarzyna; Piast, Michał; Mozrzymas, Jerzy W

    2007-05-28

    Benzodiazepines are known to act by enhancing the effect of gamma-aminobutyric acid-A receptor agonists. Positive modulation by benzodiazepines is typically ascribed to upregulation of agonist binding affinity but their effect on gamma-aminobutyric acid-A receptor gating remain unclear. In this work, we have used the ultrafast application system to examine the impact of flurazepam and zolpidem on recombinant alpha1beta2gamma2 gamma-aminobutyric acid-A receptors. As expected, both drugs strongly enhanced currents evoked by low [gamma-aminobutyric acid]. These compounds, however, also affected currents elicited by saturating agonist concentration. In particular, flurazepam and zolpidem reduced current amplitudes and slowed down the recovery process in paired-pulse experiments. Moreover, flurazepam accelerated the current rise time and zolpidem enhanced the rate and extent of desensitization. We propose that flurazepam and zolpidem modulate gamma-aminobutyric acid-A receptors by strong enhancement of agonist binding with a superimposed limited effect on the receptor gating.

  6. Essential role for retinoic acid in the promotion of CD4+ T cell effector responses via retinoic acid receptor alpha

    PubMed Central

    Hall, J.A.; Cannons, J.L.; Grainger, J.R.; Santos, L.M. Dos; Hand, T.W.; Naik, S.; Wohlfert, E.A.; Chou, D.B.; Oldenhove, G.; Robinson, M.; Grigg, M.E.; Kastenmayer, R.; Schwartzberg, P.L.; Belkaid, Y.

    2012-01-01

    SUMMARY Vitamin A and its metabolite, retinoic acid (RA), have recently been implicated in the regulation of immune homeostasis via the peripheral induction of regulatory T cells. Here we show that RA is also required to elicit proinflammatory CD4+ helper T cell responses to infection and mucosal vaccination. Retinoic acid receptor alpha (RARα) is the critical mediator of these effects. Strikingly, antagonism of RAR signaling and deficiency in RARα(Rara−/−) results in a cell autonomous CD4+ T cell activation defect. Altogether, these findings reveal a fundamental role for the RA/RARα axis in the development of both regulatory and inflammatory arms of adaptive immunity and establish nutritional status as a broad regulator of adaptive T cell responses. PMID:21419664

  7. Design, synthesis and biological activity of phenoxyacetic acid derivatives as novel free fatty acid receptor 1 agonists.

    PubMed

    Li, Zheng; Wang, Xuekun; Xu, Xue; Yang, Jianyong; Xia, Wenting; Zhou, Xianhao; Huang, Wenlong; Qian, Hai

    2015-11-15

    The free fatty acid receptor 1 (FFA1) is a novel antidiabetic target for the treatment of type 2 diabetes based on particular mechanism in amplifying glucose-stimulated insulin secretion. We have previously identified a series of phenoxyacetic acid derivatives. Herein, we describe the further chemical modification of this series directed by ligand efficiency and ligand lipophilicity efficiency. All of these efforts lead to the discovery of the promising candidate 16, an excellent FFA1 agonist with robust agonistic activity (43.6 nM), desired LE and LLE values. Moreover, compound 16 revealed a great potential for improving the hyperglycemia levels in both normal and type 2 diabetic mice without the risk of hypoglycemia even at the high dose of 40 mg/kg. PMID:26482570

  8. Modulation of GABA receptors expressed in Xenopus oocytes by 13-L-hydroxylinoleic acid and food additives.

    PubMed

    Aoshima, H; Tenpaku, Y

    1997-12-01

    To study the effects of 13-L-hydroxylinoleic acid (LOH) and food additives on gamma-aminobutyric acid (GABA) receptors, ionotropic GABA receptors were expressed in Xenopus oocytes by injecting mRNAs prepared from rat whole brain. LOH, which was prepared by reduction of 13-L-hydroperoxylinoleic acid (LOOH), inhibited the response of GABA receptors in the presence of high concentrations of GABA. LOH also inhibited nicotinic acetylcholine, glycine, and kainate receptors, while it had little effect on NMDA receptors expressed in Xenopus oocytes. However, LOH potentiated the response of GABA receptors as well as LOOH in the presence of low concentrations of GABA, possibly increasing the affinity of GABA for the receptors, while linoleic acid did not. Since some modification of the compounds seemed to change their effects on GABA receptors, the responses of GABA receptors elicited by 10 microM GABA were measured in the presence of compounds with various kinds of functional groups or the structural isomers of pentanol. Potentiation of GABA receptors depended strongly on the species of functional groups and also depended on the structure of the isomers. Then effects of various kinds of food additives on GABA receptors were also examined; perfumes such as alcohols or esters potentiated the responses strongly, while hexylamine, nicotinamide, or caffeine inhibited the responses, mainly in a competitive manner, and vanillin inhibited the responses noncompetitively. These results suggest the possibility that production of LOOH and LOH, or intake of much of some food additives, modulates the neural transmission in the brain, especially through ionotropic GABA receptors and changes the frame of the human mind, as alcohol or tobacco does.

  9. PTH1 Receptor Is Involved in Mediating Cellular Response to Long-Chain Polyunsaturated Fatty Acids

    PubMed Central

    Chachisvilis, Mirianas

    2012-01-01

    The molecular pathways by which long chain polyunsaturated fatty acids (LCPUFA) influence skeletal health remain elusive. Both LCPUFA and parathyroid hormone type 1 receptor (PTH1R) are known to be involved in bone metabolism while any direct link between the two is yet to be established. Here we report that LCPUFA are capable of direct, PTH1R dependent activation of extracellular ligand-regulated kinases (ERK). From a wide range of fatty acids studied, varying in chain length, saturation, and position of double bonds, eicosapentaenoic (EPA) and docosahexaenoic fatty acids (DHA) caused the highest ERK phosphorylation. Moreover, EPA potentiated the effect of parathyroid hormone (PTH(1–34)) in a superagonistic manner. EPA or DHA dependent ERK phosphorylation was inhibited by the PTH1R antagonist and by knockdown of PTH1R. Inhibition of PTH1R downstream signaling molecules, protein kinases A (PKA) and C (PKC), reduced EPA and DHA dependent ERK phosphorylation indicating that fatty acids predominantly activate G-protein pathway and not the β-arrestin pathway. Using picosecond time-resolved fluorescence microscopy and a genetically engineered PTH1R sensor (PTH-CC), we detected conformational responses to EPA similar to those caused by PTH(1–34). PTH1R antagonist blocked the EPA induced conformational response of the PTH-CC. Competitive binding studies using fluorescence anisotropy technique showed that EPA and DHA competitively bind to and alter the affinity of PTH1 receptor to PTH(1–34) leading to a superagonistic response. Finally, we showed that EPA stimulates protein kinase B (Akt) phosphorylation in a PTH1R-dependent manner and affects the osteoblast survival pathway, by inhibiting glucocorticoid-induced cell death. Our findings demonstrate for the first time that LCPUFAs, EPA and DHA, can activate PTH1R receptor at nanomolar concentrations and consequently provide a putative molecular mechanism for the action of fatty acids in bone. PMID:23300710

  10. Histamine (H3) receptors modulate the excitatory amino acid receptor response of the vestibular afferents.

    PubMed

    Chávez, Hortencia; Vega, Rosario; Soto, Enrique

    2005-12-01

    Although the effectiveness of histamine-related drugs in the treatment of peripheral and central vestibular disorders may be explained by their action on the vestibular nuclei, it has also been shown that antivertigo effects can take place at the peripheral level. In this work, we examined the actions of H3 histaminergic agonists and antagonists on the afferent neuron electrical discharge in the isolated inner ear of the axolotl. Our results indicate that H3 antagonists such as thioperamide, clobenpropit, and betahistine (BH) decreased the electrical discharge of afferent neurons by interfering with the postsynaptic response to excitatory amino acid agonists. These results lend further support to the idea that the antivertigo action of histamine-related drugs may be caused, at least in part, by a decrease in the sensory input from the vestibular endorgans. The present data show that the inhibitory action of the afferent neurons discharge previously described for BH is not restricted to this molecule but is also shared by other H3 antagonists.

  11. A Comparison of the Roles of Peroxisome Proliferator-Activated Receptor and Retinoic Acid Receptor on CYP26 Regulation

    PubMed Central

    Tay, Suzanne; Dickmann, Leslie; Dixit, Vaishali

    2010-01-01

    The cytochrome P450 26 family is believed to be responsible for all-trans-retinoic acid (atRA) metabolism and elimination in the human fetus and adults. CYP26A1 and CYP26B1 mRNA is expressed in a tissue-specific manner, and mice in which the CPY26 isoform has been knocked out show distinct malformations and lethality. The aim of this study was to determine differences in CYP26A1 and CYP26B1 regulation and expression. Analysis of CYP26A1 and CYP26B1 expression in a panel of 57 human livers showed CYP26A1 to be the major CYP26 isoform present in the liver, and its expression to be subject to large interindividual variability between donors. CYP26A1 and retinoic acid receptor (RAR) β were found to be greatly inducible by atRA in HepG2 cells, whereas CYP26B1, RARα, and RARγ were induced to a much lesser extent. Based on treatments with RAR isoform-selective ligands, RARα is the major isoform responsible for CYP26A1 and RARβ induction in HepG2 cells. Classic cytochrome P450 inducers did not affect CYP26 transcription, whereas the peroxisome proliferator-activated receptor (PPAR) γ agonists pioglitazone and rosiglitazone up-regulated CYP26B1 transcription by as much as 209- ± 80-fold and CYP26A1 by 10-fold. RARβ was also up-regulated by pioglitazone and rosiglitazone. CYP26B1 induction by PPARγ agonists was abolished by the irreversible PPARγ antagonist 2-chloro-5-nitrobenzanilide (GW9662), whereas RARβ and CYP26A1 induction was unaffected by GW9662. Overall, the results of this study suggest that CYP26B1 and CYP26A1 are regulated by different nuclear receptors, resulting in tissue-specific expression patterns. The fact that drugs can alter the expression of CYP26 enzymes may have toxicological and therapeutic importance. PMID:19884280

  12. Fatty Acid Amide Hydrolase (FAAH) Inhibition Enhances Memory Acquisition through Activation of PPAR-alpha Nuclear Receptors

    ERIC Educational Resources Information Center

    Mazzola, Carmen; Medalie, Julie; Scherma, Maria; Panlilio, Leigh V.; Solinas, Marcello; Tanda, Gianluigi; Drago, Filippo; Cadet, Jean Lud; Goldberg, Steven R.; Yasar, Sevil

    2009-01-01

    Inhibitors of fatty acid amide hydrolase (FAAH) increase endogenous levels of anandamide (a cannabinoid CB[subscript 1]-receptor ligand) and oleoylethanolamide and palmitoylethanolamide (OEA and PEA, ligands for alpha-type peroxisome proliferator-activated nuclear receptors, PPAR-alpha) when and where they are naturally released in the brain.…

  13. Coexistence of NMDA and AMPA receptor subunits with nNOS in the nucleus tractus solitarii of rat.

    PubMed

    Lin, Li-Hsien; Talman, William T

    2002-11-01

    We previously showed that most neuronal nitric oxide synthase (nNOS)-containing neurons in the nucleus tractus solitarii (NTS) contain NMDAR1, the fundamental subunit for functional N-methyl-D-aspartate (NMDA) receptors. Likewise, we found that almost all nNOS-containing neurons in the NTS contain GluR1, the calcium permeable AMPA receptor subunit. These data suggest that AMPA and NMDA receptors may colocalize in NTS neurons that contain nNOS. However, other investigators have suggested that non-NMDA receptors are located primarily on second-order neurons and NMDA receptors are located predominantly on higher-order neurons in NTS. We now seek to test the hypothesis that NMDA receptors, AMPA receptors and nNOS are colocalized in NTS cells. We performed triple fluorescent immunohistochemical staining of nNOS, NMDAR1 and GluR1, and performed confocal laser scanning microscopic analysis of the NTS. The distributions of nNOS immunoreactivity (IR), NMDAR1-IR and GluR1-IR in the NTS were similar to those we reported earlier. Superimposed images revealed that almost all NMDAR1-IR cells contained GluR1-IR and almost all GluR1-IR cells contained NMDAR1-IR. Some double-labeled cells were additionally labeled for nNOS-IR. All nNOS-IR neurons contained both GluR1-IR and NMDAR1-IR. These studies support our hypothesis that NMDA and AMPA receptors are colocalized in NTS neurons and are consistent with a role of both types of ionotropic receptors in transmission of afferent signals in NTS. In addition, these data provide support for an anatomical link between ionotropic glutamate receptors and nitric oxide in the NTS.

  14. Skin Barrier Recovery by Protease-Activated Receptor-2 Antagonist Lobaric Acid.

    PubMed

    Joo, Yeon Ah; Chung, Hyunjin; Yoon, Sohyun; Park, Jong Il; Lee, Ji Eun; Myung, Cheol Hwan; Hwang, Jae Sung

    2016-09-01

    Atopic dermatitis (AD) results from gene and environment interactions that lead to a range of immunological abnormalities and breakdown of the skin barrier. Protease-activated receptor 2 (PAR2) belongs to a family of G-protein coupled receptors and is expressed in suprabasal layers of the epidermis. PAR2 is activated by both trypsin and a specific agonist peptide, SLIGKV-NH₂ and is involved in both epidermal permeability barrier homeostasis and epithelial inflammation. In this study, we investigated the effect of lobaric acid on inflammation, keratinocyte differentiation, and recovery of the skin barrier in hairless mice. Lobaric acid blocked trypsin-induced and SLIGKV-NH2-induced PAR2 activation resulting in decreased mobilization of intracellular Ca²⁺ in HaCaT keratinocytes. Lobaric acid reduced expression of interleukin-8 induced by SLIGKV-NH₂ and thymus and activation regulated chemokine (TARC) induced by tumor necrosis factor-a (TNF-α) and IFN-γ in HaCaT keratinocytes. Lobaric acid also blocked SLIGKV-NH₂-induced activation of ERK, which is a downstream signal of PAR2 in normal human keratinocytes (NHEKs). Treatment with SLIGKV-NH₂ downregulated expression of involucrin, a differentiation marker protein in HaCaT keratinocytes, and upregulated expression of involucrin, transglutamase1 and filaggrin in NHEKs. However, lobaric acid antagonized the effect of SLIGKV-NH₂ in HaCaT keratinocytes and NHEKs. Topical application of lobaric acid accelerated barrier recovery kinetics in a SKH-1 hairless mouse model. These results suggested that lobaric acid is a PAR2 antagonist and could be a possible therapeutic agent for atopic dermatitis. PMID:27169822

  15. Folic acid mediates activation of the pro-oncogene STAT3 via the Folate Receptor alpha.

    PubMed

    Hansen, Mariann F; Greibe, Eva; Skovbjerg, Signe; Rohde, Sarah; Kristensen, Anders C M; Jensen, Trine R; Stentoft, Charlotte; Kjær, Karina H; Kronborg, Camilla S; Martensen, Pia M

    2015-07-01

    The signal transducer and activator of transcription 3 (STAT3) is a well-described pro-oncogene found constitutively activated in several cancer types. Folates are B vitamins that, when taken up by cells through the Reduced Folate Carrier (RFC), are essential for normal cell growth and replication. Many cancer cells overexpress a glycophosphatidylinositol (GPI)-anchored Folate Receptor α (FRα). The function of FRα in cancer cells is still poorly described, and it has been suggested that transport of folate is not its primary function in these cells. We show here that folic acid and folinic acid can activate STAT3 through FRα in a Janus Kinase (JAK)-dependent manner, and we demonstrate that gp130 functions as a transducing receptor for this signalling. Moreover, folic acid can promote dose dependent cell proliferation in FRα-positive HeLa cells, but not in FRα-negative HEK293 cells. After folic acid treatment of HeLa cells, up-regulation of the STAT3 responsive genes Cyclin A2 and Vascular Endothelial Growth Factor (VEGF) were verified by qRT-PCR. The identification of this FRα-STAT3 signal transduction pathway activated by folic and folinic acid contributes to the understanding of the involvement of folic acid in preventing neural tube defects as well as in tumour growth. Previously, the role of folates in these diseases has been attributed to their roles as one-carbon unit donors following endocytosis into the cell. Our finding that folic acid can activate STAT3 via FRα adds complexity to the established roles of B9 vitamins in cancer and neural tube defects.

  16. Skin Barrier Recovery by Protease-Activated Receptor-2 Antagonist Lobaric Acid

    PubMed Central

    Joo, Yeon Ah; Chung, Hyunjin; Yoon, Sohyun; Park, Jong Il; Lee, Ji Eun; Myung, Cheol Hwan; Hwang, Jae Sung

    2016-01-01

    Atopic dermatitis (AD) results from gene and environment interactions that lead to a range of immunological abnormalities and breakdown of the skin barrier. Protease-activated receptor 2 (PAR2) belongs to a family of G-protein coupled receptors and is expressed in suprabasal layers of the epidermis. PAR2 is activated by both trypsin and a specific agonist peptide, SLIGKV-NH2 and is involved in both epidermal permeability barrier homeostasis and epithelial inflammation. In this study, we investigated the effect of lobaric acid on inflammation, keratinocyte differentiation, and recovery of the skin barrier in hairless mice. Lobaric acid blocked trypsin-induced and SLIGKV-NH2-induced PAR2 activation resulting in decreased mobilization of intracellular Ca2+ in HaCaT keratinocytes. Lobaric acid reduced expression of interleukin-8 induced by SLIGKV-NH2 and thymus and activation regulated chemokine (TARC) induced by tumor necrosis factor-a (TNF-α) and IFN-γ in HaCaT keratinocytes. Lobaric acid also blocked SLIGKV-NH2-induced activation of ERK, which is a downstream signal of PAR2 in normal human keratinocytes (NHEKs). Treatment with SLIGKV-NH2 downregulated expression of involucrin, a differentiation marker protein in HaCaT keratinocytes, and upregulated expression of involucrin, transglutamase1 and filaggrin in NHEKs. However, lobaric acid antagonized the effect of SLIGKV-NH2 in HaCaT keratinocytes and NHEKs. Topical application of lobaric acid accelerated barrier recovery kinetics in a SKH-1 hairless mouse model. These results suggested that lobaric acid is a PAR2 antagonist and could be a possible therapeutic agent for atopic dermatitis. PMID:27169822

  17. Amino acid sequence coevolution in the insect bursicon ligand-receptor system.

    PubMed

    Hughes, Austin L

    2012-06-01

    The pattern of amino acid residue replacement in the components of the bursicon signaling system (involving the BURSα/BURSβ heterodimer and its receptor BURSrec) was reconstructed across a phylogeny of 17 insect species, in order to test for the co-occurrence of replacements at sets of individual sites. Sets of three or more branches with perfectly concordant changes occurred to a greater extent than expected by chance, given the observed level of amino acid change. The latter sites (SPC sites) were found to have distinctive characteristics: (1) the mean number of changes was significantly lower at SPC sites than that at other sites with multiple changes; (2) SPC sites had a significantly greater tendency toward parallel amino acid changes than other sites with multiple changes, but no greater tendency toward convergent changes; and (3) parallel changes tended to involve relatively similar amino acids, as indicated by relatively low mean chemical distances. The results implicated functional constraint, permitting only a limited subset of amino acids in a given site, as a major factor in causing both parallel amino acid replacement and coordinated amino acid changes in different sites of the same protein and of interacting proteins in this system.

  18. Role of the retinoic acid receptor-α in HIV-associated nephropathy.

    PubMed

    Ratnam, Krishna K; Feng, Xiaobei; Chuang, Peter Y; Verma, Vikram; Lu, Ting-Chi; Wang, Jinshan; Jin, Yuanmeng; Farias, Eduardo F; Napoli, Joseph L; Chen, Nan; Kaufman, Lewis; Takano, Tomoko; D'Agati, Vivette D; Klotman, Paul E; He, John C

    2011-03-01

    All-trans retinoic acid protects against the development of HIV-associated nephropathy (HIVAN) in HIV-1 transgenic mice (Tg26). In vitro, all-trans retinoic acid inhibits HIV-induced podocyte proliferation and restores podocyte differentiation markers by activating its receptor-α (RARα). Here, we report that Am580, a water-soluble RARα-specific agonist, attenuated proteinuria, glomerosclerosis, and podocyte proliferation, and restored podocyte differentiation markers in kidneys of Tg26 mice. Furthermore, RARα-/- Tg26 mice developed more severe kidney and podocyte injury than did RARα+/- Tg26 mice. Am580 failed to ameliorate kidney injury in RARα-/- Tg26 mice, confirming our hypothesis that Am580 acts through RARα. Although the expression of RARα-target genes was suppressed in the kidneys of Tg26 mice and of patients with HIVAN, the expression of RARα in the kidney was not different between patients with HIVAN and minimal change disease. However, the tissue levels of retinoic acid were reduced in the kidney cortex and isolated glomeruli of Tg26 mice. Consistent with this, the expression of two key enzymes in the retinoic acid synthetic pathway, retinol dehydrogenase type 1 and 9, and the overall enzymatic activity for retinoic acid synthesis were significantly reduced in the glomeruli of Tg26 mice. Thus, a defect in the endogenous synthesis of retinoic acid contributes to loss of the protection by retinoic acid in HIVAN. Hence, RARα agonists may be potential agents for the treatment of HIVAN.

  19. NMDA-like receptors in the nervous system of the crab Neohelice granulata: a neuroanatomical description.

    PubMed

    Hepp, Yanil; Tano, Martín Carbó; Pedreira, María Eugenia; Freudenthal, Ramiro A M

    2013-07-01

    N-Methyl-D-aspartate receptors (NMDARs) are involved in learning and memory processes in vertebrates and invertebrates. In Neohelice granulata, NMDARs are involved in the storage of associative memories (see references in text). The aim of this work was to characterize this type of glutamate receptor in Neohelice and to describe its distribution in the central nervous system (CNS). As a first step, a detailed study of the CNS of N. granulata was performed at the neuropil level, with special focus on one of the main structures involved in this type of memory, the supraesophageal ganglion, called central brain. The characterization of the NMDAR was achieved by identifying the essential subunit of these receptors, the NR1-like subunit. The NR1-like signals were found via western blot and immunohistochemistry techniques in each of the major ganglia: the eyestalk ganglia, the central brain, and the thoracic ganglion. Western blots yielded two bands for the crab NR1-like subunit, at ∼88 and ∼84 kDa. This subunit is present in all the major ganglia, and shows a strong localization in synaptosomal membranes. NMDARs are distributed throughout the majority of each ganglion but show prominent signal intensity in some distinguishable neuropils and neurons. This is the first general description of the N. granulata nervous system as a whole and the first study of NMDARs in the CNS of decapods. The preferential localization of the receptor in some neuropils and neurons indicates the presence of possible new targets for memory processing and storage.

  20. Salicylic acid receptors activate jasmonic acid signalling through a non-canonical pathway to promote effector-triggered immunity

    PubMed Central

    Liu, Lijing; Sonbol, Fathi-Mohamed; Huot, Bethany; Gu, Yangnan; Withers, John; Mwimba, Musoki; Yao, Jian; He, Sheng Yang; Dong, Xinnian

    2016-01-01

    It is an apparent conundrum how plants evolved effector-triggered immunity (ETI), involving programmed cell death (PCD), as a major defence mechanism against biotrophic pathogens, because ETI-associated PCD could leave them vulnerable to necrotrophic pathogens that thrive on dead host cells. Interestingly, during ETI, the normally antagonistic defence hormones, salicylic acid (SA) and jasmonic acid (JA) associated with defence against biotrophs and necrotrophs respectively, both accumulate to high levels. In this study, we made the surprising finding that JA is a positive regulator of RPS2-mediated ETI. Early induction of JA-responsive genes and de novo JA synthesis following SA accumulation is activated through the SA receptors NPR3 and NPR4, instead of the JA receptor COI1. We provide evidence that NPR3 and NPR4 may mediate this effect by promoting degradation of the JA transcriptional repressor JAZs. This unique interplay between SA and JA offers a possible explanation of how plants can mount defence against a biotrophic pathogen without becoming vulnerable to necrotrophic pathogens. PMID:27725643

  1. Molecular basis for designing selective modulators of retinoic acid receptor transcriptional activities.

    PubMed

    Lefebvre, P

    2001-08-01

    Retinoic acid receptors are ligand-regulated transcription factors belonging to the nuclear receptor superfamily, which comprises 49 members in the human genome. all-trans retinoic acid and 9-cis retinoic acid receptors (RARs and RXRs) are each encoded by three distinct genes and several isoforms arise from alternative splicing and the use of different promoters. While RXRs are promiscuous dimerization partners of several other nuclear receptors, RARs are active, in-vivo, when associated to RXRs. Retinoids are therefore regulators of multiple physiological processes, from embryogenesis to metabolism. Different combinations of RXR:RAR heterodimers occur as a function of their tissue-specific expression and their activity is mostly conditioned by the activation status of RAR. These heterodimers are defined as non permissive heterodimers, in opposition to permissive dimers whose transcriptional activity may be modulated through RXR and its dimerization partner. The transcriptional activity of these dimers also relies on their ability to recruit nuclear coactivators and corepressors, which function as multi proteic complexes harboring several enzymatic activities (acetylases, kinases). The structure of the ligand bound to the RAR moiety of the dimer, as well as the nature of the DNA sequence to which dimers are bound, dictate the relative affinity of dimers for coactivators and thus its overall transcriptional activity. RARs are also able to repress the activity of unrelated transcription factors such as AP1 and NF-kappa-B, and therefore have potent anti proliferative and anti inflammatory properties. This review summarizes our current view of molecular mechanisms governing these various activities and emphasizes the need for a detailed understanding of how retinoids may dictate transactivating and transrepressive properties of RARs and RXRs, which may be considered as highly valuable therapeutic targets in many diseases such as cancer, skin hyperproliferation and

  2. Novel Retinoic Acid Receptor Alpha Agonists for Treatment of Kidney Disease

    PubMed Central

    Liu, Ruijie; Li, Zhengzhe; Chen, Yibang; Evans, Todd; Chuang, Peter; Das, Bhaskar; He, John Cijiang

    2011-01-01

    Development of pharmacologic agents that protect podocytes from injury is a critical strategy for the treatment of kidney glomerular diseases. Retinoic acid reduces proteinuria and glomerulosclerosis in multiple animal models of kidney diseases. However, clinical studies are limited because of significant side effects of retinoic acid. Animal studies suggest that all trans retinoic acid (ATRA) attenuates proteinuria by protecting podocytes from injury. The physiological actions of ATRA are mediated by binding to all three isoforms of the nuclear retinoic acid receptors (RARs): RARα, RARβ, and RARγ. We have previously shown that ATRA exerts its renal protective effects mainly through the agonism of RARα. Here, we designed and synthesized a novel boron-containing derivative of the RARα-specific agonist Am580. This new derivative, BD4, binds to RARα receptor specifically and is predicted to have less toxicity based on its structure. We confirmed experimentally that BD4 binds to RARα with a higher affinity and exhibits less cellular toxicity than Am580 and ATRA. BD4 induces the expression of podocyte differentiation markers (synaptopodin, nephrin, and WT-1) in cultured podocytes. Finally, we confirmed that BD4 reduces proteinuria and improves kidney injury in HIV-1 transgenic mice, a model for HIV-associated nephropathy (HIVAN). Mice treated with BD4 did not develop any obvious toxicity or side effect. Our data suggest that BD4 is a novel RARα agonist, which could be used as a potential therapy for patients with kidney disease such as HIVAN. PMID:22125642

  3. Novel retinoic acid receptor alpha agonists for treatment of kidney disease.

    PubMed

    Zhong, Yifei; Wu, Yingwei; Liu, Ruijie; Li, Zhengzhe; Chen, Yibang; Evans, Todd; Chuang, Peter; Das, Bhaskar; He, John Cijiang

    2011-01-01

    Development of pharmacologic agents that protect podocytes from injury is a critical strategy for the treatment of kidney glomerular diseases. Retinoic acid reduces proteinuria and glomerulosclerosis in multiple animal models of kidney diseases. However, clinical studies are limited because of significant side effects of retinoic acid. Animal studies suggest that all trans retinoic acid (ATRA) attenuates proteinuria by protecting podocytes from injury. The physiological actions of ATRA are mediated by binding to all three isoforms of the nuclear retinoic acid receptors (RARs): RARα, RARβ, and RARγ. We have previously shown that ATRA exerts its renal protective effects mainly through the agonism of RARα. Here, we designed and synthesized a novel boron-containing derivative of the RARα-specific agonist Am580. This new derivative, BD4, binds to RARα receptor specifically and is predicted to have less toxicity based on its structure. We confirmed experimentally that BD4 binds to RARα with a higher affinity and exhibits less cellular toxicity than Am580 and ATRA. BD4 induces the expression of podocyte differentiation markers (synaptopodin, nephrin, and WT-1) in cultured podocytes. Finally, we confirmed that BD4 reduces proteinuria and improves kidney injury in HIV-1 transgenic mice, a model for HIV-associated nephropathy (HIVAN). Mice treated with BD4 did not develop any obvious toxicity or side effect. Our data suggest that BD4 is a novel RARα agonist, which could be used as a potential therapy for patients with kidney disease such as HIVAN.

  4. Predicting G-protein-coupled receptors families using different physiochemical properties and pseudo amino acid composition.

    PubMed

    Rehman, Zia-Ur; Mirza, Muhammad Tayyeb; Khan, Asifullah; Xhaard, Henri

    2013-01-01

    G-protein-coupled receptors (GPCRs) initiate signaling pathways via trimetric guanine nucleotide-binding proteins. GPCRs are classified based on their ligand-binding properties and molecular phylogenetic analyses. Nonetheless, these later analyses are in most case dependent on multiple sequence alignments, themselves dependent on human intervention and expertise. Alignment-free classifications of GPCR sequences, in addition to being unbiased, present many applications uncovering hidden physicochemical parameters shared among specific groups of receptors, to being used in automated workflows for large-scale molecular modeling applications. Current alignment-free classification methods, however, do not reach a full accuracy. This chapter discusses how GPCRs amino acid sequences can be classified using pseudo amino acid composition and multiscale energy representation of different physiochemical properties of amino acids. A hybrid feature extraction strategy is shown to be suitable to represent GPCRs and to be able to exploit GPCR amino acid sequence discrimination capability in spatial as well as transform domain. Classification strategies such as support vector machine and probabilistic neural network are then discussed in regards to GPCRs classification. The work of GPCR-Hybrid web predictor is also discussed.

  5. Mg2+ imparts NMDA receptor subtype selectivity to the Alzheimer's drug memantine.

    PubMed

    Kotermanski, Shawn E; Johnson, Jon W

    2009-03-01

    N-methyl-D-aspartate receptors (NMDARs) mediate interneuronal communication and are broadly involved in nervous system physiology and pathology (Dingledine et al., 1999). Memantine, a drug that blocks the ion channel formed by NMDARs, is a widely prescribed treatment of Alzheimer's disease (Schmitt, 2005; Lipton, 2006; Parsons et al., 2007). Research on memantine's mechanism of action has focused on the NMDAR subtypes most highly expressed in adult cerebral cortex, NR1/2A and NR1/2B receptors (Cull-Candy and Leszkiewicz, 2004), and has largely ignored interactions with extracellular Mg(2+) (Mg(2+)(o)). Mg(2+)(o) is an endogenous NMDAR channel blocker that binds near memantine's binding site (Kashiwagi et al., 2002; Chen and Lipton, 2005). We report that a physiological concentration (1 mM) of Mg(2+)(o) decreased memantine inhibition of NR1/2A and NR1/2B receptors nearly 20-fold at a membrane voltage near rest. In contrast, memantine inhibition of the other principal NMDAR subtypes, NR1/2C and NR1/2D receptors, was decreased only approximately 3-fold. As a result, therapeutic memantine concentrations should have negligible effects on NR1/2A or NR1/2B receptor activity but pronounced effects on NR1/2C and NR1/2D receptors. Quantitative modeling showed that the voltage dependence of memantine inhibition also is altered by 1 mM Mg(2+)(o). We report similar results with the NMDAR channel blocker ketamine, a drug used to model schizophrenia (Krystal et al., 2003). These results suggest that currently hypothesized mechanisms of memantine and ketamine action should be reconsidered and that NR1/2C and/or NR1/2D receptors play a more important role in cortical physiology and pathology than previously appreciated.

  6. PLZF is a negative regulator of retinoic acid receptor transcriptional activity

    PubMed Central

    Martin, Perrine J; Delmotte, Marie-Hélène; Formstecher, Pierre; Lefebvre, Philippe

    2003-01-01

    Background Retinoic acid receptors (RARs) are ligand-regulated transcription factors controlling cellular proliferation and differentiation. Receptor-interacting proteins such as corepressors and coactivators play a crucial role in specifying the overall transcriptional activity of the receptor in response to ligand treatment. Little is known however on how receptor activity is controlled by intermediary factors which interact with RARs in a ligand-independent manner. Results We have identified the promyelocytic leukemia zinc finger protein (PLZF), a transcriptional corepressor, to be a RAR-interacting protein using the yeast two-hybrid assay. We confirmed this interaction by GST-pull down assays and show that the PLZF N-terminal zinc finger domain is necessary and sufficient for PLZF to bind RAR. The RAR ligand binding domain displayed the highest affinity for PLZF, but corepressor and coactivator binding interfaces did not contribute to PLZF recruitment. The interaction was ligand-independent and correlated to a decreased transcriptional activity of the RXR-RAR heterodimer upon overexpression of PLZF. A similar transcriptional interference could be observed with the estrogen receptor alpha and the glucocorticoid receptor. We further show that PLZF is likely to act by preventing RXR-RAR heterodimerization, both in-vitro and in intact cells. Conclusion Thus RAR and PLZF interact physically and functionally. Intriguingly, these two transcription factors play a determining role in hematopoiesis and regionalization of the hindbrain and may, upon chromosomal translocation, form fusion proteins. Our observations therefore define a novel mechanism by which RARs activity may be controlled. PMID:14521715

  7. Ginseng pharmacology: a new paradigm based on gintonin-lysophosphatidic acid receptor interactions

    PubMed Central

    Choi, Sun-Hye; Jung, Seok-Won; Lee, Byung-Hwan; Kim, Hyeon-Joong; Hwang, Sung-Hee; Kim, Ho-Kyoung; Nah, Seung-Yeol

    2015-01-01

    Ginseng, the root of Panax ginseng, is used as a traditional medicine. Despite the long history of the use of ginseng, there is no specific scientific or clinical rationale for ginseng pharmacology besides its application as a general tonic. The ambiguous description of ginseng pharmacology might be due to the absence of a predominant active ingredient that represents ginseng pharmacology. Recent studies show that ginseng abundantly contains lysophosphatidic acids (LPAs), which are phospholipid-derived growth factor with diverse biological functions including those claimed to be exhibited by ginseng. LPAs in ginseng form a complex with ginseng proteins, which can bind and deliver LPA to its cognate receptors with a high affinity. As a first messenger, gintonin produces second messenger Ca2+ via G protein-coupled LPA receptors. Ca2+ is an intracellular mediator of gintonin and initiates a cascade of amplifications for further intercellular communications by activation of Ca2+-dependent kinases, receptors, gliotransmitter, and neurotransmitter release. Ginsenosides, which have been regarded as primary ingredients of ginseng, cannot elicit intracellular [Ca2+]i transients, since they lack specific cell surface receptor. However, ginsenosides exhibit non-specific ion channel and receptor regulations. This is the key characteristic that distinguishes gintonin from ginsenosides. Although the current discourse on ginseng pharmacology is focused on ginsenosides, gintonin can definitely provide a mode of action for ginseng pharmacology that ginsenosides cannot. This review article introduces a novel concept of ginseng ligand-LPA receptor interaction and proposes to establish a paradigm that shifts the focus from ginsenosides to gintonin as a major ingredient representing ginseng pharmacology. PMID:26578955

  8. Oxidative stress upregulates the NMDA receptor on cerebrovascular endothelium.

    PubMed

    Betzen, Christian; White, Robin; Zehendner, Christoph M; Pietrowski, Eweline; Bender, Bianca; Luhmann, Heiko J; Kuhlmann, Christoph R W

    2009-10-15

    N-methyl-d-aspartate receptor (NMDA-R)-mediated oxidative stress has been implicated in blood-brain barrier (BBB) disruption in a variety of neuropathological diseases. Although some interactions between both phenomena have been elucidated, possible influences of reactive oxygen species (ROS) on the NMDA-R itself have so far been neglected. The objective of this study was to examine how the cerebroendothelial NMDA-R is affected by exposure to oxidative stress and to assess possible influences on BBB integrity. RT-PCR confirmed several NMDA-R subunits (NR1, NR2B-D) expressed in the bEnd3 cell line (murine cerebrovascular endothelial cells). NR1 protein expression after exposure to ROS was observed via in-cell Western. The functionality of the expressed NMDA-R was determined by measuring DiBAC fluorescence in ROS-preexposed cells upon stimulation with the specific agonist NMDA. Finally, the effects on barrier integrity were evaluated using the ECIS system to detect changes in monolayer impedance upon NMDA-R stimulation after exposure to ROS. The expression of NR1 significantly (p<0.001) increased 72 h after 30 min exposure to superoxide (+33.8+/-7.5%), peroxynitrite (+84.9+/-10.7%), or hydrogen peroxide (+92.8+/-7.6%), resulting in increased cellular response to NMDA-R stimulation and diminished monolayer impedance. We conclude that oxidative stress upregulates NMDA-R on cerebrovascular endothelium and thus heightens susceptibility to glutamate-induced BBB disruption.

  9. Oxidative stress upregulates the NMDA receptor on cerebrovascular endothelium.

    PubMed

    Betzen, Christian; White, Robin; Zehendner, Christoph M; Pietrowski, Eweline; Bender, Bianca; Luhmann, Heiko J; Kuhlmann, Christoph R W

    2009-10-15

    N-methyl-d-aspartate receptor (NMDA-R)-mediated oxidative stress has been implicated in blood-brain barrier (BBB) disruption in a variety of neuropathological diseases. Although some interactions between both phenomena have been elucidated, possible influences of reactive oxygen species (ROS) on the NMDA-R itself have so far been neglected. The objective of this study was to examine how the cerebroendothelial NMDA-R is affected by exposure to oxidative stress and to assess possible influences on BBB integrity. RT-PCR confirmed several NMDA-R subunits (NR1, NR2B-D) expressed in the bEnd3 cell line (murine cerebrovascular endothelial cells). NR1 protein expression after exposure to ROS was observed via in-cell Western. The functionality of the expressed NMDA-R was determined by measuring DiBAC fluorescence in ROS-preexposed cells upon stimulation with the specific agonist NMDA. Finally, the effects on barrier integrity were evaluated using the ECIS system to detect changes in monolayer impedance upon NMDA-R stimulation after exposure to ROS. The expression of NR1 significantly (p<0.001) increased 72 h after 30 min exposure to superoxide (+33.8+/-7.5%), peroxynitrite (+84.9+/-10.7%), or hydrogen peroxide (+92.8+/-7.6%), resulting in increased cellular response to NMDA-R stimulation and diminished monolayer impedance. We conclude that oxidative stress upregulates NMDA-R on cerebrovascular endothelium and thus heightens susceptibility to glutamate-induced BBB disruption. PMID:19660541

  10. Copper blocks quinolinic acid neurotoxicity in rats: contribution of antioxidant systems.

    PubMed

    Santamaría, Abel; Flores-Escartín, Abigail; Martínez, Juan Carlos; Osorio, Laura; Galván-Arzate, Sonia; Pedraza-Chaverrí, José; Chaverrí, José Pedraza; Maldonado, Perla D; Medina-Campos, Omar N; Jiménez-Capdeville, María E; Manjarrez, Joaquín; Ríos, Camilo

    2003-08-15

    Reactive oxygen species and oxidative stress are involved in quinolinic acid (QUIN)-induced neurotoxicity. QUIN, a N-methyl-D-aspartate receptor (NMDAr) agonist and prooxidant molecule, produces NMDAr overactivation, excitotoxic events, and direct reactive oxygen species formation. Copper is an essential metal exhibiting both modulatory effects on neuronal excitatory activity and antioxidant properties. To investigate whether this metal is able to counteract the neurotoxic and oxidative actions of QUIN, we administered copper (as CuSO(4)) intraperitoneally to rats (2.5, 5.0, 7.5, and 10.0 mg/kg) 30 min before the striatal infusion of 1 microliter of QUIN (240 nmol). A 5.0 mg/kg CuSO(4) dose significantly increased the copper content in the striatum, reduced the neurotoxicity measured both as circling behavior and striatal gamma-aminobutyric acid (GABA) depletion, and blocked the oxidative injury evaluated as striatal lipid peroxidation (LP). In addition, copper reduced the QUIN-induced decreased striatal activity of Cu,Zn-dependent superoxide dismutase, and increased the ferroxidase activity of ceruloplasmin in cerebrospinal fluid from QUIN-treated rats. However, copper also produced significant increases of plasma lactate dehydrogenase activity and mortality at the highest doses employed (7.5 and 10.0 mg/kg). These results show that at low doses, copper exerts a protective effect on in vivo QUIN neurotoxicity.

  11. Spike-timing-dependent plasticity at resting and conditioned lateral perforant path synapses on granule cells in the dentate gyrus: different roles of N-methyl-D-aspartate and group I metabotropic glutamate receptors.

    PubMed

    Lin, Yi-Wen; Yang, Hsiu-Wen; Wang, Hui-Ju; Gong, Chi-Li; Chiu, Tsai-Hsien; Min, Ming-Yuan

    2006-05-01

    We examined the mechanisms underlying spike-timing-dependent plasticity induction at resting and conditioned lateral perforant pathway (LPP) synapses in the rat dentate gyrus. Two stimulating electrodes were placed in the outer third of the molecular layer and in the granule cell layer in hippocampal slices to evoke field excitatory postsynaptic potentials (fEPSPs) and antidromic field somatic spikes (afSSs), respectively. Long-term potentiation (LTP) of LPP synapses was induced by paired stimulation with fEPSP preceding afSS. Reversal of the temporal order of fEPSP and afSS stimulation resulted in long-term depression (LTD). Induction of LTP or LTD was blocked by D,L-2-amino-5-phosphonopentanoic acid (AP5), showing that both effects were N-methyl-D-aspartate receptor (NMDAR)-dependent. Induction of LTP was also blocked by inhibitors of calcium-calmodulin kinase II, protein kinase C or mitogen-activated/extracellular-signal regulated kinase, suggesting that these are downstream effectors of NMDAR activation, whereas induction of LTD was blocked by inhibitors of protein kinase C and protein phosphatase 2B. At LPP synapses previously potentiated by high-frequency stimulation or depressed by low-frequency stimulation, paired fEPSP-afSS stimulation resulted in 'de-depression' at depressed LPP synapses but had no effect on potentiated synapses, whereas reversal of the temporal order of fEPSP-afSS stimulation resulted in 'de-potentiation' at potentiated synapses but had no effect on depressed synapses. Induction of de-depression and de-potentiation was unaffected by ap5 but was blocked by 2-methyl-6-(phenylethynyl) pyridine hydrochloride, a group I metabotropic glutamate receptor blocker, showing that both were NMDAR-independent but group I metabotropic glutamate receptor-dependent. In conclusion, our results show that spike-timing-dependent plasticity can occur at both resting and conditioned LPP synapses, its induction in the former case being NMDAR-dependent and, in

  12. Developmental Changes in NMDA Receptor Subunit Composition at ON and OFF Bipolar Cell Synapses onto Direction-Selective Retinal Ganglion Cells

    PubMed Central

    Stafford, Benjamin K.; Park, Silvia J. H.; Wong, Kwoon Y.

    2014-01-01

    In the developing mouse retina, spontaneous and light-driven activity shapes bipolar→ganglion cell glutamatergic synapse formation, beginning around the time of eye-opening (P12–P14) and extending through the first postnatal month. During this time, glutamate release can spill outside the synaptic cleft and possibly stimulate extrasynaptic NMDA-type glutamate receptors (NMDARs) on ganglion cells. Furthermore, the role of NMDARs during development may differ between ON and OFF bipolar synapses as in mature retina, where ON synapses reportedly include extrasynaptic NMDARs with GluN2B subunits. To better understand the function of glutamatergic synapses during development, we made whole-cell recordings of NMDAR-mediated responses, in vitro, from two types of genetically identified direction-selective ganglion cells (dsGCs): TRHR (thyrotropin-releasing hormone receptor) and Drd4 (dopamine receptor 4). Both dsGC types responded to puffed NMDA between P7 and P28; and both types exhibited robust light-evoked NMDAR-mediated responses at P14 and P28 that were quantified by conductance analysis during nicotinic and GABAA receptor blockade. For a given cell type and at a given age, ON and OFF bipolar cell inputs evoked similar NMDAR-mediated responses, suggesting that ON-versus-OFF differences in mature retina do not apply to the cell types or ages studied here. At P14, puff- and light-evoked NMDAR-mediated responses in both dsGCs were partially blocked by the GluN2B antagonist ifenprodil, whereas at P28 only TRHR cells remained ifenprodil-sensitive. NMDARs contribute at both ON and OFF bipolar cell synapses during a period of robust activity-dependent synaptic development, with declining GluN2B involvement over time in specific ganglion cell types. PMID:24478373

  13. Developmental changes in NMDA receptor subunit composition at ON and OFF bipolar cell synapses onto direction-selective retinal ganglion cells.

    PubMed

    Stafford, Benjamin K; Park, Silvia J H; Wong, Kwoon Y; Demb, Jonathan B

    2014-01-29

    In the developing mouse retina, spontaneous and light-driven activity shapes bipolar→ganglion cell glutamatergic synapse formation, beginning around the time of eye-opening (P12-P14) and extending through the first postnatal month. During this time, glutamate release can spill outside the synaptic cleft and possibly stimulate extrasynaptic NMDA-type glutamate receptors (NMDARs) on ganglion cells. Furthermore, the role of NMDARs during development may differ between ON and OFF bipolar synapses as in mature retina, where ON synapses reportedly include extrasynaptic NMDARs with GluN2B subunits. To better understand the function of glutamatergic synapses during development, we made whole-cell recordings of NMDAR-mediated responses, in vitro, from two types of genetically identified direction-selective ganglion cells (dsGCs): TRHR (thyrotropin-releasing hormone receptor) and Drd4 (dopamine receptor 4). Both dsGC types responded to puffed NMDA between P7 and P28; and both types exhibited robust light-evoked NMDAR-mediated responses at P14 and P28 that were quantified by conductance analysis during nicotinic and GABA(A) receptor blockade. For a given cell type and at a given age, ON and OFF bipolar cell inputs evoked similar NMDAR-mediated responses, suggesting that ON-versus-OFF differences in mature retina do not apply to the cell types or ages studied here. At P14, puff- and light-evoked NMDAR-mediated responses in both dsGCs were partially blocked by the GluN2B antagonist ifenprodil, whereas at P28 only TRHR cells remained ifenprodil-sensitive. NMDARs contribute at both ON and OFF bipolar cell synapses during a period of robust activity-dependent synaptic development, with declining GluN2B involvement over time in specific ganglion cell types.

  14. Glutamic acid decarboxylase and glutamate receptor changes during tolerance and dependence to benzodiazepines

    PubMed Central

    Izzo, Emanuela; Auta, James; Impagnatiello, Francesco; Pesold, Christine; Guidotti, Alessandro; Costa, Erminio

    2001-01-01

    Protracted administration of diazepam elicits tolerance, whereas discontinuation of treatment results in signs of dependence. Tolerance to the anticonvulsant action of diazepam is present in an early phase (6, 24, and 36 h) but disappears in a late phase (72–96 h) of withdrawal. In contrast, signs of dependence such as decrease in open-arm entries on an elevated plus-maze and increased susceptibility to pentylenetetrazol-induced seizures were apparent 96 h (but not 12, 24, or 48 h) after diazepam withdrawal. During the first 72 h of withdrawal, tolerance is associated with changes in the expression of GABAA (γ-aminobutyric acid type A) receptor subunits (decrease in γ2 and α1; increase in α5) and with an increase of mRNA expression of the most abundant form of glutamic acid decarboxylase (GAD), GAD67. In contrast, dl-α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor GluR1 subunit mRNA and cognate protein, which are normal during the early phase of diazepam withdrawal, increase by approximately 30% in cortex and hippocampus in association with the appearance of signs of dependence 96 h after diazepam withdrawal. Immunohistochemical studies of GluR1 subunit expression with gold-immunolabeling technique reveal that the increase of GluR1 subunit protein is localized to layer V pyramidal neurons and their apical dendrites in the cortex, and to pyramidal neurons and in their dendritic fields in hippocampus. The results suggest an involvement of GABA-mediated processes in the development and maintenance of tolerance to diazepam, whereas excitatory amino acid-related processes (presumably via AMPA receptors) may be involved in the expression of signs of dependence after withdrawal. PMID:11248104

  15. Glutamic acid decarboxylase and glutamate receptor changes during tolerance and dependence to benzodiazepines.

    PubMed

    Izzo, E; Auta, J; Impagnatiello, F; Pesold, C; Guidotti, A; Costa, E

    2001-03-13

    Protracted administration of diazepam elicits tolerance, whereas discontinuation of treatment results in signs of dependence. Tolerance to the anticonvulsant action of diazepam is present in an early phase (6, 24, and 36 h) but disappears in a late phase (72-96 h) of withdrawal. In contrast, signs of dependence such as decrease in open-arm entries on an elevated plus-maze and increased susceptibility to pentylenetetrazol-induced seizures were apparent 96 h (but not 12, 24, or 48 h) after diazepam withdrawal. During the first 72 h of withdrawal, tolerance is associated with changes in the expression of GABA(A) (gamma-aminobutyric acid type A) receptor subunits (decrease in gamma(2) and alpha(1); increase in alpha(5)) and with an increase of mRNA expression of the most abundant form of glutamic acid decarboxylase (GAD), GAD(67). In contrast, dl-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor GluR1 subunit mRNA and cognate protein, which are normal during the early phase of diazepam withdrawal, increase by approximately 30% in cortex and hippocampus in association with the appearance of signs of dependence 96 h after diazepam withdrawal. Immunohistochemical studies of GluR1 subunit expression with gold-immunolabeling technique reveal that the increase of GluR1 subunit protein is localized to layer V pyramidal neurons and their apical dendrites in the cortex, and to pyramidal neurons and in their dendritic fields in hippocampus. The results suggest an involvement of GABA-mediated processes in the development and maintenance of tolerance to diazepam, whereas excitatory amino acid-related processes (presumably via AMPA receptors) may be involved in the expression of signs of dependence after withdrawal.

  16. Pregnenolone sulfate and its enantiomer: differential modulation of memory in a spatial discrimination task using forebrain NMDA receptor deficient mice

    PubMed Central

    Petit, Géraldine H.; Tobin, Christine; Krishnan, Kathiresan; Moricard, Yves; Covey, Douglas F.; Rondi-Reig, Laure; Akwa, Yvette

    2010-01-01

    This study examined the role of forebrain N-methyl-D-aspartate receptors (NMDA-Rs) in the promnesiant effects of natural (+) pregnenolone sulfate (PREGS) and its synthetic (−) enantiomer ent-PREGS in young adult mice. Using the two-trial arm discrimination task in a Y-maze, PREGS and ent-PREGS administration to control mice increased memory performances. In mice with a knock-out of the NR1 subunit of NMDA-Rs in the forebrain, the promnesiant effect of ent-PREGS was maintained whereas the activity of PREGS was lost. Memory enhancement by PREGS involves the NMDA-R activity in the hippocampal CA1 area and possibly in some locations of the cortical layers, whereas ent-PREGS acts independently of NMDA-R function. PMID:21036556

  17. The brain as immunoprecipitator of serum autoantibodies against N-Methyl-D-aspartate receptor subunit NR1.

    PubMed

    Castillo-Gomez, Esther; Kästner, Anne; Steiner, Johann; Schneider, Anja; Hettling, Bilke; Poggi, Giulia; Ostehr, Kristin; Uhr, Manfred; Asif, Abdul R; Matzke, Mike; Schmidt, Ulrike; Pfander, Viktoria; Hammer, Christian; Schulz, Thomas F; Binder, Lutz; Stöcker, Winfried; Weber, Frank; Ehrenreich, Hannelore

    2016-01-01

    Autoantibodies (AB) against N-methyl-D-aspartate receptor subunit NR1 (NMDAR1) are highly seroprevalent in health and disease. Symptomatic relevance may arise upon compromised blood-brain barrier (BBB). However, it remained unknown whether circulating NMDAR1 AB appear in the cerebrospinal fluid (CSF). Of n = 271 subjects with CSF-serum pairs, 26 were NMDAR1 AB seropositive, but only 1 was CSF positive. Contrariwise, tetanus AB (non-brain-binding) were present in serum and CSF of all subjects, with CSF levels higher upon BBB dysfunction. Translational mouse experiments proved the hypothesis that the brain acts as an 'immunoprecipitator'; simultaneous injection of NMDAR1 AB and the non-brain-binding green fluorescent protein AB resulted in high detectability of the former in brain and the latter in CSF. PMID:26505629

  18. Retinoic Acid Receptor-Mediated Induction of ABCA1 in Macrophages

    PubMed Central

    Costet, Philippe; Lalanne, Florent; Gerbod-Giannone, Marie C.; Molina, Jennifer R.; Fu, Xuan; Lund, Erik G.; Gudas, Lorraine J.; Tall, Alan R.

    2003-01-01

    ABCA1, the mutant molecule in Tangier Disease, mediates efflux of cellular cholesterol to apoA-I and is induced by liver X receptor (LXR)/retinoid X receptor (RXR) transcription factors. Retinoic acid receptor (RAR) activators (all-trans-retinoic acid [ATRA] and TTNPB) were found to increase ATP-binding cassette transporter 1 (ABCA1) mRNA and protein in macrophages. In cellular cotransfection assays, RARγ/RXR activated the human ABCA1 promoter, via the same direct repeat 4 (DR4) promoter element as LXR/RXR. Chromatin immunoprecipitation analysis in macrophages confirmed the binding of RARγ/RXR to the ABCA1 promoter DR4 element in the presence of ATRA, with weaker binding of RARα/RXR, and no binding of RARβ/RXR. However, in macrophages from RARγ−/− mice, TTNPB still induced ABCA1, in association with marked upregulation of RARα, suggesting that high levels of RARα can compensate for the absence of RARγ. Dose-response experiments with ATRA in mouse primary macrophages showed that other LXR target genes were weakly induced (ABCG1 and SREBP-1c) or not induced (apoE and LXRα). The more specific RAR activator TTNPB did not induce SREBP-1c in mouse primary macrophages or liver. These studies indicate a direct role of RARγ/RXR in induction of macrophage ABCA1. PMID:14560020

  19. Functional Analysis of Free Fatty Acid Receptor GPR120 in Human Eosinophils: Implications in Metabolic Homeostasis

    PubMed Central

    Konno, Yasunori; Ueki, Shigeharu; Takeda, Masahide; Kobayashi, Yoshiki; Tamaki, Mami; Moritoki, Yuki; Oyamada, Hajime; Itoga, Masamichi; Kayaba, Hiroyuki; Omokawa, Ayumi; Hirokawa, Makoto

    2015-01-01

    Recent evidence has shown that eosinophils play an important role in metabolic homeostasis through Th2 cytokine production. GPR120 (FFA4) is a G protein-coupled receptor (GPCR) for long-chain fatty acids that functions as a regulator of physiological energy metabolism. In the present study, we aimed to investigate whether human eosinophils express GPR120 and, if present, whether it possesses a functional capacity on eosinophils. Eosinophils isolated from peripheral venous blood expressed GPR120 at both the mRNA and protein levels. Stimulation with a synthetic GPR120 agonist, GW9508, induced rapid down-regulation of cell surface expression of GPR120, suggesting ligand-dependent receptor internalization. Although GPR120 activation did not induce eosinophil chemotactic response and degranulation, we found that GW9508 inhibited eosinophil spontaneous apoptosis and Fas receptor expression. The anti-apoptotic effect was attenuated by phosphoinositide 3-kinase (PI3K) inhibitors and was associated with inhibition of caspase-3 activity. Eosinophil response investigated using ELISpot assay indicated that stimulation with a GPR120 agonist induced IL-4 secretion. These findings demonstrate the novel functional properties of fatty acid sensor GPR120 on human eosinophils and indicate the previously unrecognized link between nutrient metabolism and the immune system. PMID:25790291

  20. Recognition and sequestration of ω-fatty acids by a cavitand receptor

    PubMed Central

    Mosca, Simone; Ajami, Dariush; Rebek, Julius

    2015-01-01

    One of the largest driving forces for molecular association in aqueous solution is the hydrophobic effect, and many synthetic receptors with hydrophobic interiors have been devised for molecular recognition studies in water. Attempts to create the longer, narrower cavities appropriate for long-chain fatty acids have been thwarted by solvophobic collapse of the synthetic receptors, giving structures that have no internal spaces. The collapse generally involves the stacking of aromatic panels onto themselves. We describe here the synthesis and application of a deep cavitand receptor featuring “prestacked” aromatic panels at the upper rim of the binding pocket. The cavitand remains open and readily sequesters biologically relevant long-chain molecules—unsaturated ω-3, -6, and -9 fatty acids and derivatives such as anandamide—from aqueous media. The cavitand exists in isomeric forms with different stacking geometries and n-alkanes were used to characterize the binding modes and conformational properties. Long alkyl chains are accommodated in inverted J-shaped conformations. An analogous cavitand with electron-rich aromatic walls was prepared and comparative binding experiments indicated the role of intramolecular stacking in the binding properties of these deep container molecules. PMID:26305974

  1. Recognition and sequestration of ω-fatty acids by a cavitand receptor.

    PubMed

    Mosca, Simone; Ajami, Dariush; Rebek, Julius

    2015-09-01

    One of the largest driving forces for molecular association in aqueous solution is the hydrophobic effect, and many synthetic receptors with hydrophobic interiors have been devised for molecular recognition studies in water. Attempts to create the longer, narrower cavities appropriate for long-chain fatty acids have been thwarted by solvophobic collapse of the synthetic receptors, giving structures that have no internal spaces. The collapse generally involves the stacking of aromatic panels onto themselves. We describe here the synthesis and application of a deep cavitand receptor featuring "prestacked" aromatic panels at the upper rim of the binding pocket. The cavitand remains open and readily sequesters biologically relevant long-chain molecules-unsaturated ω-3, -6, and -9 fatty acids and derivatives such as anandamide-from aqueous media. The cavitand exists in isomeric forms with different stacking geometries and n-alkanes were used to characterize the binding modes and conformational properties. Long alkyl chains are accommodated in inverted J-shaped conformations. An analogous cavitand with electron-rich aromatic walls was prepared and comparative binding experiments indicated the role of intramolecular stacking in the binding properties of these deep container molecules.

  2. Comparison of the effects of pelargonic acid vanillylamide and capsaicin on human vanilloid receptors.

    PubMed

    Weiser, Thomas; Roufogalis, Basil; Chrubasik, Sigrun

    2013-07-01

    Pelargonic acid vanillylamide is like capsaicin a natural capsaicinoid from chili peppers and commonly used in food additives to create a hot sensation, even in self-defense pepper sprays and as an alternative to capsaicin in medical products for topical treatment of pain. Although the chemical structures of both compounds are similar, preclinical data suggest that capsaicin is the more potent compound. We therefore performed voltage-clamp recordings using cells transfected with the human vanilloid receptor TRPV1 in order to assess the responses of pelargonic acid vanillylamide and capsaicin at the receptor level. We provide evidence that at the molecular target TRPV1, the concentration-response curves, kinetics of current activation, as well as inhibition by the competitive antagonist capsazepine were not significantly different between the two capsaicinoids. We suggest that the different effects of the two capsaicinoids observed in previous studies may rather be due to different physicochemical or pharmacokinetic properties than to different pharmacological profiles at the receptor level. PMID:22961689

  3. Comparison of the effects of pelargonic acid vanillylamide and capsaicin on human vanilloid receptors.

    PubMed

    Weiser, Thomas; Roufogalis, Basil; Chrubasik, Sigrun

    2013-07-01

    Pelargonic acid vanillylamide is like capsaicin a natural capsaicinoid from chili peppers and commonly used in food additives to create a hot sensation, even in self-defense pepper sprays and as an alternative to capsaicin in medical products for topical treatment of pain. Although the chemical structures of both compounds are similar, preclinical data suggest that capsaicin is the more potent compound. We therefore performed voltage-clamp recordings using cells transfected with the human vanilloid receptor TRPV1 in order to assess the responses of pelargonic acid vanillylamide and capsaicin at the receptor level. We provide evidence that at the molecular target TRPV1, the concentration-response curves, kinetics of current activation, as well as inhibition by the competitive antagonist capsazepine were not significantly different between the two capsaicinoids. We suggest that the different effects of the two capsaicinoids observed in previous studies may rather be due to different physicochemical or pharmacokinetic properties than to different pharmacological profiles at the receptor level.

  4. Development and Characterization of a Potent Free Fatty Acid Receptor 1 (FFA1) Fluorescent Tracer.

    PubMed

    Christiansen, Elisabeth; Hudson, Brian D; Hansen, Anders Højgaard; Milligan, Graeme; Ulven, Trond

    2016-05-26

    The free fatty acid receptor 1 (FFA1/GPR40) is a potential target for treatment of type 2 diabetes. Although several potent agonists have been described, there remains a strong need for suitable tracers to interrogate ligand binding to this receptor. We address this by exploring fluorophore-tethering to known potent FFA1 agonists. This led to the development of 4, a high affinity FFA1 tracer with favorable and polarity-dependent fluorescent properties. A close to ideal overlap between the emission spectrum of the NanoLuciferase receptor tag and the excitation spectrum of 4 enabled the establishment of a homogeneous BRET-based binding assay suitable for both detailed kinetic studies and high throughput competition binding studies. Using 4 as a tracer demonstrated that the compound acts fully competitively with selected synthetic agonists but not with lauric acid and allowed for the characterization of binding affinities of a diverse selection of known FFA1 agonists, indicating that 4 will be a valuable tool for future studies at FFA1. PMID:27074625

  5. Expression and distribution of sialic acid influenza virus receptors in wild birds

    PubMed Central

    França, M.; Stallknecht, D. E.; Howerth, E. W.

    2013-01-01

    Avian influenza (AI) viruses have been detected in more than 105 wild bird species from 12 different orders but species-related differences in susceptibility to AI viruses exist. Expression of α2,3-linked (avian-type) and α2,6linked (human type) sialic acid (SA) influenza virus receptors in tissues is considered to be one of the determinants of the host range and tissue tropism of influenza viruses. We investigated the expression of these SA receptors in 37 wild bird species from 11 different orders by lectin histochemistry. Two isoforms of Maackia amurensis (MAA) lectin, MAA1 and MAA2, were used to detect α2,3-linked SA and Sambucus nigra (SNA) lectin was used to detect α2,6-linked SA. All species evaluated expressed α2,3-linked and α2,6-linked SA receptors in endothelial cells and renal tubular epithelial cells. Both α2,3-linked and α-2,6-linked SA receptors were expressed in respiratory and intestinal tract tissues of aquatic and terrestrial wild bird species from different taxa, but differences in SA expression and in the predominant isoform of MAA lectin bound were observed. With a few possible exceptions, these observed differences were not generally predictive of reported species susceptibility to AI viruses based on published experimental and field data. PMID:23391183

  6. Effects of perfluoroalkyl acids on the function of the thyroid hormone and the aryl hydrocarbon receptor.

    PubMed

    Long, Manhai; Ghisari, Mandana; Bonefeld-Jørgensen, Eva Cecilie

    2013-11-01

    Perfluoroalkyl acids (PFAAs) are perfluorinated compounds that widely exist in the environment and can elicit adverse effects including endocrine disruption in humans and animals. This study investigated the effect of seven PFAAs on the thyroid hormone (TH) system assessing the proliferation of the 3,3',5-triiodo-L-thryonine (T3)-dependent rat pituitary GH3 cells using the T-screen assay and the effect on the aryl hydrocarbon receptor (AhR) transactivation in the AhR-luciferase reporter gene bioassay. A dose-dependent impact on GH3 cells was observed in the range 1×10(-9)-1×10(-4) M: seven PFAAs (perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), perfluorooctanoic acid, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnA), and perfluorododecanoic acid (PFDoA)) inhibited the GH3 cell growth, and four PFAAs (PFOS, PFHxS, PFNA, and PFUnA) antagonized the T3-induced GH3 cell proliferation. At the highest test concentration, PFHxS showed a further increase of the T3-induced GH3 growth. Among the seven tested PFAAs, only PFDoA and PFDA elicited an activating effect on the AhR. In conclusion, PFAAs possess in vitro endocrine-disrupting potential by interfering with TH and AhR functions, which need to be taken into consideration when assessing the impact on human health. PMID:23539207

  7. Mapping amino acids of the measles virus hemagglutinin responsible for receptor (CD46) downregulation.

    PubMed

    Bartz, R; Brinckmann, U; Dunster, L M; Rima, B; Ter Meulen, V; Schneider-Schaulies, J

    1996-10-01

    We compared the amino acid sequences of groups of receptor (CD46) downregulating and nondownregulating measles virus (MV) hemagglutinins (Hs) and identified seven group-specific differences as candidates for the mediation of the observed differential effects. Using site-directed mutagenesis, we mutated the chosen amino acids of the H of MV-strain WTF (WTF-H), a nondownregulating H, and Introduced the corresponding amino acids of Edmonston-H (Edm-H), a downregulating H. We identified four amino acids, 211G, 243R, 451V, and 481Y, which influenced the downregulative function when introduced into WTF-H. The double mutation 451V and 481Y in WTF-H led to a degree of CD46 downregulation comparable to that of Edm-H. Conversely, introducing amino acids 451E and 481N into Edm-H resulted in a loss of the downregulative function. These results indicate that these amino acids play a decisive role in the H-CD46 interaction. PMID:8862431

  8. Linking γ-aminobutyric acid A receptor to epidermal growth factor receptor pathways activation in human prostate cancer.

    PubMed

    Wu, Weijuan; Yang, Qing; Fung, Kar-Ming; Humphreys, Mitchell R; Brame, Lacy S; Cao, Amy; Fang, Yu-Ting; Shih, Pin-Tsen; Kropp, Bradley P; Lin, Hsueh-Kung

    2014-03-01

    Neuroendocrine (NE) differentiation has been attributed to the progression of castration-resistant prostate cancer (CRPC). Growth factor pathways including the epidermal growth factor receptor (EGFR) signaling have been implicated in the development of NE features and progression to a castration-resistant phenotype. However, upstream molecules that regulate the growth factor pathway remain largely unknown. Using androgen-insensitive bone metastasis PC-3 cells and androgen-sensitive lymph node metastasis LNCaP cells derived from human prostate cancer (PCa) patients, we demonstrated that γ-aminobutyric acid A receptor (GABA(A)R) ligand (GABA) and agonist (isoguvacine) stimulate cell proliferation, enhance EGF family members expression, and activate EGFR and a downstream signaling molecule, Src, in both PC-3 and LNCaP cells. Inclusion of a GABA(A)R antagonist, picrotoxin, or an EGFR tyrosine kinase inhibitor, Gefitinib (ZD1839 or Iressa), blocked isoguvacine and GABA-stimulated cell growth, trans-phospohorylation of EGFR, and tyrosyl phosphorylation of Src in both PCa cell lines. Spatial distributions of GABAAR α₁ and phosphorylated Src (Tyr416) were studied in human prostate tissues by immunohistochemistry. In contrast to extremely low or absence of GABA(A)R α₁-positive immunoreactivity in normal prostate epithelium, elevated GABA(A)R α₁ immunoreactivity was detected in prostate carcinomatous glands. Similarly, immunoreactivity of phospho-Src (Tyr416) was specifically localized and limited to the nucleoli of all invasive prostate carcinoma cells, but negative in normal tissues. Strong GABAAR α₁ immunoreactivity was spatially adjacent to the neoplastic glands where strong phospho-Src (Tyr416)-positive immunoreactivity was demonstrated, but not in adjacent to normal glands. These results suggest that the GABA signaling is linked to the EGFR pathway and may work through autocrine or paracine mechanism to promote CRPC progression.

  9. NMDA receptors in mouse anterior piriform cortex initialize early odor preference learning and L-type calcium channels engage for long-term memory

    PubMed Central

    Mukherjee, Bandhan; Yuan, Qi

    2016-01-01

    The interactions of L-type calcium channels (LTCCs) and NMDA receptors (NMDARs) in memories are poorly understood. Here we investigated the specific roles of anterior piriform cortex (aPC) LTCCs and NMDARs in early odor preference memory in mice. Using calcium imaging in aPC slices, LTCC activation was shown to be dependent on NMDAR activation. Either D-APV (NMDAR antagonist) or nifedipine (LTCC antagonist) reduced somatic calcium transients in pyramidal cells evoked by lateral olfactory tract stimulation. However, nifedipine did not further reduce calcium in the presence of D-APV. In mice that underwent early odor preference training, blocking NMDARs in the aPC prevented short-term (3 hr) and long-term (24 hr) odor preference memory, and both memories were rescued when BayK-8644 (LTCC agonist) was co-infused. However, activating LTCCs in the absence of NMDARs resulted in loss of discrimination between the conditioned odor and a similar odor mixture at 3 hr. Elevated synaptic AMPAR expression at 3 hr was prevented by D-APV infusion but restored when LTCCs were directly activated, mirroring the behavioral outcomes. Blocking LTCCs prevented 24 hr memory and spared 3 hr memory. These results suggest that NMDARs mediate stimulus-specific encoding of odor memory while LTCCs mediate intracellular signaling leading to long-term memory. PMID:27739540

  10. Anti-NMDA receptor antibodies in patients with a first episode of schizophrenia

    PubMed Central

    Masopust, Jiří; Andrýs, Ctirad; Bažant, Jan; Vyšata, Oldřich; Kuca, Kamil; Vališ, Martin

    2015-01-01

    Background Encephalitis with antibodies against N-methyl-D-aspartate receptor (NMDA-R) is classified as an autoimmune disorder with psychotic symptoms, which are frequently dominant. However, it remains unclear how frequently NMDA-R antibodies lead to a condition that mimics psychosis and first-episode schizophrenia. In our work, we investigated the presence of antibodies against NMDA-R in patients with first-episode psychosis (FEP) in comparison with healthy volunteers. Methods This study included 50 antipsychotic-naïve patients with FEP (including 21 women) and 50 healthy volunteers (including 21 women). The mean age of the patients was 27.4 (±7.4) years and that of the healthy controls was 27.0 (±7.3) years. Antibodies against NMDA-R in the serum were detected by immunofluorescence. Results None of the investigated patients with an FEP and none of the healthy controls showed positive antibodies against NMDA-Rs. Conclusion According to results of studies, a small proportion of patients with an FEP possess antibodies against NMDA-R. However, the extent to which this finding contributes to the etiopathogenesis of the response to antipsychotic medication and whether immunomodulatory therapy is indicated in these cases remains uncertain. PMID:25834440

  11. Bidirectional NMDA receptor plasticity controls CA3 output and heterosynaptic metaplasticity

    PubMed Central

    Hunt, David L.; Puente, Nagore; Grandes, Pedro; Castillo, Pablo E.

    2013-01-01

    N–methyl–d–aspartate glutamate receptors (NMDARs) are classically known as coincidence detectors for the induction of long–term synaptic plasticity, and have been implicated in hippocampal CA3–dependent spatial memory functions that likely rely on dynamic cellular ensemble encoding of space. The unique functional properties of both NMDARs and mossy fiber (MF) projections to CA3 pyramidal cells place MF–NMDARs in a prime position to influence CA3 ensemble dynamics. By mimicking pre and postsynaptic activity patterns observed in–vivo, we report a burst timing–dependent paradigm for bidirectional long–term NMDAR plasticity at MF–CA3 synapses in rat hippocampal slices. This form of plasticity imparts bimodal control of MF–driven CA3 burst–firing and spike temporal fidelity. Moreover, we show that MF–NMDARs mediate heterosynaptic metaplasticity between MF and associational/commissural synapses. Thus, bidirectional NMDAR plasticity at MF–CA3 synapses could significantly contribute to the formation, storage, and recall of CA3 cell assembly patterns. PMID:23852115

  12. Ursodeoxycholic acid exerts farnesoid X receptor-antagonistic effects on bile acid and lipid metabolism in morbid obesity

    PubMed Central

    Mueller, Michaela; Thorell, Anders; Claudel, Thierry; Jha, Pooja; Koefeler, Harald; Lackner, Carolin; Hoesel, Bastian; Fauler, Guenter; Stojakovic, Tatjana; Einarsson, Curt; Marschall, Hanns-Ulrich; Trauner, Michael

    2015-01-01

    Background & Aims Bile acids (BAs) are major regulators of hepatic BA and lipid metabolism but their mechanisms of action in non-alcoholic fatty liver disease (NAFLD) are still poorly understood. Here we aimed to explore the molecular and biochemical mechanisms of ursodeoxycholic acid (UDCA) in modulating the cross-talk between liver and visceral white adipose tissue (vWAT) regarding BA and cholesterol metabolism and fatty acid/lipid partitioning in morbidly obese NAFLD patients. Methods In this randomized controlled pharmacodynamic study, we analyzed serum, liver and vWAT samples from 40 well-matched morbidly obese patients receiving UDCA (20 mg/kg/day) or no treatment three weeks prior to bariatric surgery. Results Short term UDCA administration stimulated BA synthesis by reducing circulating fibroblast growth factor 19 and farnesoid X receptor (FXR) activation, resulting in cholesterol 7α-hydroxylase induction mirrored by elevated C4 and 7α-hydroxycholesterol. Enhanced BA formation depleted hepatic and LDL-cholesterol with subsequent activation of the key enzyme of cholesterol synthesis 3-hydroxy-3-methylglutaryl-CoA reductase. Blunted FXR anti-lipogenic effects induced lipogenic stearoyl-CoA desaturase (SCD) in the liver, thereby increasing hepatic triglyceride content. In addition, induced SCD activity in vWAT shifted vWAT lipid metabolism towards generation of less toxic and more lipogenic monounsaturated fatty acids such as oleic acid. Conclusion These data demonstrate that by exerting FXR-antagonistic effects, UDCA treatment in NAFLD patients strongly impacts on cholesterol and BA synthesis and induces neutral lipid accumulation in both liver and vWAT. PMID:25617503

  13. Programmable Multivalent Display of Receptor Ligands using Peptide Nucleic Acid Nanoscaffolds

    PubMed Central

    Englund, Ethan A.; Wang, Deyun; Fujigaki, Hidetsugu; Sakai, Hiroyasu; Micklitsch, Christopher M.; Ghirlando, Rodolfo; Martin-Manso, Gema; Pendrak, Michael L.; Roberts, David D.; Durell, Stewart R.; Appella, Daniel H.

    2012-01-01

    Multivalent effects dictate the binding affinity of multiple ligands on one molecular entity to receptors. Integrins are receptors that mediate cell attachment through multivalent binding to peptide sequences within the extracellular matrix, and overexpression promotes the metastasis of some cancers. Multivalent display of integrin antagonists enhances their efficacy, but current scaffolds have limited ranges and precision for the display of ligands. Here we present an approach to study multivalent effects across wide ranges of ligand number, density, and three-dimensional arrangement. Using L-lysine γ-substituted peptide nucleic acids, the multivalent effects of an integrin antagonist were examined over a range of 1 to 45 ligands. The optimal construct improves the inhibitory activity of the antagonist by two orders of magnitude against the binding of melanoma cells to the extracellular matrix in both in vitro and in vivo models. PMID:22233624

  14. Dissecting the Role of Retinoic Acid Receptor Isoforms in the CD8 Response to Infection

    PubMed Central

    Guo, Yanxia; Lee, Yu-Chi; Brown, Chrysothemis; Zhang, Weijun; Usherwood, Edward; Noelle, Randolph J.

    2015-01-01

    Vitamin A deficiency leads to increased susceptibility to a spectrum of infectious diseases. The studies presented dissect the intrinsic role of each of the retinoic acid receptor (RAR) isoforms in the clonal expansion, differentiation, and survival of pathogen-specific CD8 T cells in vivo. The data show that RARα is required for the expression of gut-homing receptors on CD8+ T cells and survival of CD8+ T cells in vitro. Furthermore, RARα is essential for survival of CD8+ T cells in vivo following Listeria monocytogenes infection. In contrast, RARβ deletion leads to modest deficiency in Ag-specific CD8+ T cell expansion during infection. The defective survival of RARα-deficient CD8+ T cells leads to a deficiency in control of L. monocytogenes expansion in the spleen. To our knowledge, these are the first comparative studies of the role of RAR isoforms in CD8+ T cell immunity. PMID:24610012

  15. Bile acid transporters and regulatory nuclear receptors in the liver and beyond

    PubMed Central

    Halilbasic, Emina; Claudel, Thierry; Trauner, Michael

    2013-01-01

    Summary Bile acid (BA) transporters are critical for maintenance of the enterohepatic BA circulation where BAs exert their multiple physiological functions including stimulation of bile flow, intestinal absorption of lipophilic nutrients, solubilization and excretion of cholesterol, as well as antimicrobial and metabolic effects. Tight regulation of BA transporters via nuclear receptors is necessary to maintain proper BA homeostasis. Hereditary and acquired defects of BA transporters are involved in the pathogenesis of several hepatobiliary disorders including cholestasis, gallstones, fatty liver disease and liver cancer, but also play a role in intestinal and metabolic disorders beyond the liver. Thus, pharmacological modification of BA transporters and their regulatory nuclear receptors opens novel treatment strategies for a wide range of disorders. PMID:22885388

  16. G-protein coupling and nuclear translocation of the human abscisic acid receptor LANCL2

    PubMed Central

    Fresia, Chiara; Vigliarolo, Tiziana; Guida, Lucrezia; Booz, Valeria; Bruzzone, Santina; Sturla, Laura; Di Bona, Melody; Pesce, Mattia; Usai, Cesare; De Flora, Antonio; Zocchi, Elena

    2016-01-01

    Abscisic acid (ABA), a long known phytohormone, has been recently demonstrated to be present also in humans, where it targets cells of the innate immune response, mesenchymal and hemopoietic stem cells and cells involved in the regulation of systemic glucose homeostasis. LANCL2, a peripheral membrane protein, is the mammalian ABA receptor. We show that N-terminal glycine myristoylation causes LANCL2 localization to the plasmamembrane and to cytoplasmic membrane vesicles, where it interacts with the α subunit of a Gi protein and starts the ABA signaling pathway via activation of adenylate cyclase. Demyristoylation of LANCL2 by chemical or genetic means triggers its nuclear translocation. Nuclear enrichment of native LANCL2 is also induced by ABA treatment. Therefore human LANCL2 is a non-transmembrane G protein-coupled receptor susceptible to hormone-induced nuclear translocation. PMID:27222287

  17. Inhibitory effects of lysophosphatidic acid receptor-5 on cellular functions of sarcoma cells.

    PubMed

    Araki, Mutsumi; Kitayoshi, Misaho; Dong, Yan; Hirane, Miku; Ozaki, Shuhei; Mori, Shiori; Fukushima, Nobuyuki; Honoki, Kanya; Tsujiuchi, Toshifumi

    2014-06-01

    Lysophosphatidic acid (LPA) is a bioactive lipid that interacts with G protein-coupled LPA receptors (LPA receptor-1 (LPA1) to LPA6). Here, we investigated the effects of LPA signaling via LPA5 on cellular functions of sarcoma cells by generating Lpar5 overexpressing and Lpar5 knockdown cells from rat osteosarcoma and malignant fibrous histiocytoma cells, respectively. The cell motility activity of Lpar5 overexpressing cells was significantly lower, while Lpar5 knockdown cells showed high cell motility, compared with respective controls. Gelatin zymography showed that LPA5 suppressed the activation of matrix metalloproteinase-2. LPA5 also inhibited the cell motility activity of endothelial cells, correlating with the expression levels of vascular endothelial growth factor genes. These results suggest that LPA signaling via LPA5 negatively regulates the cellular functions of rat sarcoma cells. PMID:24798396

  18. Stoichiometry of N-methyl-D-aspartate receptors within the suprachiasmatic nucleus.

    PubMed

    Clark, J P; Kofuji, P

    2010-06-01

    The circadian pacemaker within the suprachiasmatic nucleus (SCN) confers daily rhythms to bodily functions. In nature, the circadian clock will adopt a 24-h period by synchronizing to the solar light/dark cycle. This light entrainment process is mediated, in part, at glutamatergic synapses formed between retinal ganglion afferents and SCN neurons. N-methyl-D-aspartate receptors (NMDARs) located on SCN neurons gate light-induced phase resetting. Despite their importance in circadian physiology, little is known about their functional stoichiometry. We investigated the NR2-subunit composition with whole cell recordings of SCN neurons within the murine hypothalamic brain slice using a combination of subtype-selective NMDAR antagonists and voltage-clamp protocols. We found that extracellular magnesium ([Mg](o)) strongly blocks SCN NMDARs exhibiting affinities and voltage sensitivities associated with NR2A and NR2B subunits. These NMDAR currents were inhibited strongly by NR2B-selective antagonists, Ro 25-6981 (3.5 microM, 55.0 +/- 9.0% block; mean +/- SE) and ifenprodil (10 microM, 55.8 +/- 3.0% block). The current remaining showed decreased [Mg](o) affinities reminiscent of NR2C and NR2D subunits but was highly sensitive to [Zn](o), a potent NR2A blocker, showing a approximately 44.2 +/- 1.1% maximal inhibition at saturating concentrations with an IC(50) of 7.8 +/- 1.1 nM. Considering the selectivity, efficacy, and potency of the drugs used in combination with [Mg](o)-block characteristics of the NMDAR, our data show that both diheteromeric NR2B NMDARs and triheteromeric NR2A NMDARs (paired with an NR2C or NR2D subunits) account for the vast majority of the NMDAR current within the SCN.

  19. Nipecotic acid ethyl ester: a cholinergic agonist that may differentiate muscarinic receptor subtypes

    SciTech Connect

    Zorn, S.H.; Duman, R.S.; Enna, S.J.; Krogsgaard-Larsen, P.; Micheletti, R.; Giraldo, E.; Giachetti, A.

    1986-03-05

    Reports indicate that nipecotic acid ethyl ester (NAEE) displays cholinomimetic properties in vivo. In the present study a series of physiological and biochemical tests were conducted to characterize this action. NAEE had a negative inotropic effect on the guinea pig atrium, and stimulated contraction of the guinea pig ileum and isolated mouse stomach strip at concentrations similar to bethanechol (BCH). The atrial and ilial effects were reversed by atropine. Unlike BCH, NAEE had no effect on basal acid secretion in the isolated mouse stomach at concentrations < 100 ..mu..M. NAEE was more potent than carbachol (CCH) in displacing /sup 3/H-ONB binding from rat brain membranes. The potency of NAEE to inhibit antagonist binding in rat heart membranes was enhanced by Mg/sup + +/ (Hill coefficient < 1.0) and reduced by Gpp(NH)p. Like CCH, NAEE inhibited GTP-stimulated adenylate cyclase in rat brain striatal membranes. As compared to CCH, NAEE had little effect (< 5%) as a stimulator of inositol phosphate (IP) production in rat brain slices. The results indicate that NAEE is a direct-acting muscarinic receptor agonist. Moreover, its differential effects on acid secretion, IP accumulation, and adenylate cyclase suggest that it may be useful for defining cholinergic receptor subclasses.

  20. Membrane bile acid receptor TGR5 predicts good prognosis in ampullary adenocarcinoma patients with hyperbilirubinemia

    PubMed Central

    Chen, Min-Chan; Chen, Yi-Ling; Wang, Tzu-Wen; Hsu, Hui-Ping; Lai, Ming-Derg

    2016-01-01

    Bile acids are potential carcinogens in gastrointestinal cancer, and interact with nuclear and membrane receptors to initiate downstream signaling. The effect of TGR5 [also known as G protein-coupled bile acid receptor 1 (GPBAR1)] on cancer progression is dependent on the tissue where it is activated. In this report, the function of TGR5 expression in cancer was studied using a bioinformatic approach. TGR5 expression in ampullary adenocarcinoma and normal duodenum was compared by western blotting, reverse transcription polymerase chain reaction, and immunohistochemistry (IHC). High GPBAR1 gene expression was found to be an indicator of worse prognosis in gastric and breast cancer patients, and an indication of better prognosis in ovarian cancer patients. The level of GPBAR1 gene expression was higher in bile-acid exposed cancer than in other types of cancer, and was increased in well-differentiated ampullary adenocarcinoma. Negative, weak or mild expression of TGR5 was correlated with younger age, higher plasma level of total/direct bilirubin, higher plasma concentration of CA-125, advanced tumor stage and advanced AJCC TNM stage. The disease-specific survival rate was highest in ampullary adenocarcinoma patients with high TGR5 expression and high total bilirubin level. In summary, TGR5 functions as a tumor-suppressor in patients with ampullary adenocarcinoma and preoperative hyperbilirubinemia. Further study of the suppressive mechanism may provide a new therapeutic option for patients with ampullary adenocarcinoma. PMID:27510297

  1. Identification of Darmstoff analogs as selective agonists and antagonists of lysophosphatidic acid receptors.

    PubMed

    Gududuru, Veeresa; Zeng, Kui; Tsukahara, Ryoko; Makarova, Natalia; Fujiwara, Yuko; Pigg, Kathryn R; Baker, Daniel L; Tigyi, Gabor; Miller, Duane D

    2006-01-15

    Darmstoff describes a family of gut smooth muscle-stimulating acetal phosphatidic acids initially isolated and characterized from the bath fluid of stimulated gut over 50 years ago. Despite similar structural and biological profiles, Darmstoff analogs have not previously been examined as potential LPA mimetics. Here, we report a facile method for the synthesis of potassium salts of Darmstoff analogs. To understand the effect of stereochemistry on lysophosphatidic acid mimetic activity, synthesis of optically pure stereoisomers of selected Darmstoff analogs was achieved starting with chiral methyl glycerates. Each Darmstoff analog was evaluated for subtype-specific LPA receptor agonist/antagonist activity, PPARgamma activation, and autotaxin inhibition. From this study we identified compound 12 as a pan-antagonist and several pan-agonists for the LPA(1-3) receptors. Introduction of an aromatic ring in the lipid chain such as analog 22 produced a subtype-specific LPA(3) agonist with an EC(50) of 692 nM. Interestingly, regardless of their LPA(1/2/3) ligand properties all of the Darmstoff analogs tested activated PPARgamma. However, these compounds are weak inhibitors of autotaxin. The results indicate that Darmstoff analogs constitute a novel class of lysophosphatidic acid mimetics. PMID:16290140

  2. Membrane bile acid receptor TGR5 predicts good prognosis in ampullary adenocarcinoma patients with hyperbilirubinemia.

    PubMed

    Chen, Min-Chan; Chen, Yi-Ling; Wang, Tzu-Wen; Hsu, Hui-Ping; Lai, Ming-Derg

    2016-10-01

    Bile acids are potential carcinogens in gastrointestinal cancer, and interact with nuclear and membrane receptors to initiate downstream signaling. The effect of TGR5 [also known as G protein-coupled bile acid receptor 1 (GPBAR1)] on cancer progression is dependent on the tissue where it is activated. In this report, the function of TGR5 expression in cancer was studied using a bioinformatic approach. TGR5 expression in ampullary adenocarcinoma and normal duodenum was compared by western blotting, reverse transcription polymerase chain reaction, and immunohistochemistry (IHC). High GPBAR1 gene expression was found to be an indicator of worse prognosis in gastric and breast cancer patients, and an indication of better prognosis in ovarian cancer patients. The level of GPBAR1 gene expression was higher in bile‑acid exposed cancer than in other types of cancer, and was increased in well-differentiated ampullary adenocarcinoma. Negative, weak or mild expression of TGR5 was correlated with younger age, higher plasma level of total/direct bilirubin, higher plasma concentration of CA-125, advanced tumor stage and advanced AJCC TNM stage. The disease-specific survival rate was highest in ampullary adenocarcinoma patients with high TGR5 expression and high total bilirubin level. In summary, TGR5 functions as a tumor-suppressor in patients with ampullary adenocarcinoma and preoperative hyperbilirubinemia. Further study of the suppressive mechanism may provide a new therapeutic option for patients with ampullary adenocarcinoma. PMID:27510297

  3. Identification of Darmstoff analogs as selective agonists and antagonists of lysophosphatidic acid receptors.

    PubMed

    Gududuru, Veeresa; Zeng, Kui; Tsukahara, Ryoko; Makarova, Natalia; Fujiwara, Yuko; Pigg, Kathryn R; Baker, Daniel L; Tigyi, Gabor; Miller, Duane D

    2006-01-15

    Darmstoff describes a family of gut smooth muscle-stimulating acetal phosphatidic acids initially isolated and characterized from the bath fluid of stimulated gut over 50 years ago. Despite similar structural and biological profiles, Darmstoff analogs have not previously been examined as potential LPA mimetics. Here, we report a facile method for the synthesis of potassium salts of Darmstoff analogs. To understand the effect of stereochemistry on lysophosphatidic acid mimetic activity, synthesis of optically pure stereoisomers of selected Darmstoff analogs was achieved starting with chiral methyl glycerates. Each Darmstoff analog was evaluated for subtype-specific LPA receptor agonist/antagonist activity, PPARgamma activation, and autotaxin inhibition. From this study we identified compound 12 as a pan-antagonist and several pan-agonists for the LPA(1-3) receptors. Introduction of an aromatic ring in the lipid chain such as analog 22 produced a subtype-specific LPA(3) agonist with an EC(50) of 692 nM. Interestingly, regardless of their LPA(1/2/3) ligand properties all of the Darmstoff analogs tested activated PPARgamma. However, these compounds are weak inhibitors of autotaxin. The results indicate that Darmstoff analogs constitute a novel class of lysophosphatidic acid mimetics.

  4. Oleanolic acid acrylate elicits antidepressant-like effect mediated by 5-HT1A receptor

    PubMed Central

    Fajemiroye, James O.; Polepally, Prabhakar R.; Chaurasiya, Narayan D.; Tekwani, Babu L.; Zjawiony, Jordan K.; Costa, Elson A.

    2015-01-01

    The development of new drugs for the treatment of depression is strategic to achieving clinical needs of patients. This study evaluates antidepressant-like effect and neural mechanisms of four oleanolic acid derivatives i.e. acrylate (D1), methacrylate (D2), methyl fumarate (D3) and ethyl fumarate (D4). All derivatives were obtained by simple one-step esterification of oleanolic acid prior to pharmacological screening in the forced swimming (FS) and open field (OF) tests. Pharmacological tools like α-methyl-p-tyrosine (AMPT, catecholamine depletor), p-chlorophenylalanine (serotonin depletor), prazosin (PRAZ, selective α1-receptor antagonist), WAY-100635 (selective serotonin 5-HT1A receptor antagonist) as well as monoamine oxidase (MAO) and functional binding assays were conducted to investigate possible neural mechanisms. In the FS test, D1 showed the most promising antidepressant-like effect without eliciting locomotor incoordination. Unlike group of mice pretreated with AMPT 100 mg/kg, PCPA 100 mg/kg or PRAZ 1 mg/kg, the effect of D1 was attenuated by WAY-100635 0.3 mg/kg pretreatment. D1 demonstrated moderate inhibition of MAO-A (IC50 = 48.848 ± 1.935 μM), potency (pEC50 = 6.1 ± 0.1) and intrinsic activity (Emax = 26 ± 2.0%) on 5-HT1A receptor. In conclusion, our findings showed antidepressant-like effect of D1 and possible involvement of 5-HT1A receptor. PMID:26199018

  5. Distinct Pathways of ERK1/2 Activation by Hydroxy-Carboxylic Acid Receptor-1

    PubMed Central

    Li, Guo; Wang, Hui-qian; Wang, Li-hui; Chen, Ru-ping; Liu, Jun-ping

    2014-01-01

    Mechanistic investigations have shown that, upon agonist activation, hydroxy-carboxylic acid receptor-1(HCA1) couples to a Gi protein and inhibits adenylate cyclase activity, leading to inhibition of liberation of free fatty acid. However, the underlying molecular mechanisms for HCA1 signaling remain largely unknown. Using CHO-K1 cells stably expressing HCA1, and L6 cells, which endogenously express rat HCA1 receptors, we found that activation of ERK1/2 by HCA1 was rapid, peaking at 5 min, and was significantly blocked by pertussis toxin. Furthermore, time course experiments with different kinase inhibitors demonstrated that HCA1 induced ERK1/2 activation via the extracellular Ca2+, PKC and IGF-I receptor transactivation-dependent pathways. In addition, we observed that pretreated the cells with M119K, an inhibitor of Gβγ subunit-dependent signaling, effectively attenuated the ERK1/2 activation triggered by HCA1, suggesting a critical role for βγ-subunits in HCA1-activated ERK1/2 phosphorylation. Furthermore, the present results also indicated that the arrestin2/3 were not required for ERK1/2 activation. In conclusion, our findings demonstrate that upon binding to agonist, HCA1 receptors initially activate Gi, leading to dissociation of the Gβγ subunit from activated Gi, and subsequently induce ERK1/2 activation via two distinct pathways: one PKC-dependent pathway and the other IGF-IR transactivation-dependent pathway. Our results provide the first in-depth evidence that defines the molecular mechanism of HCA1-mediated ERK1/2 activation. PMID:24671202

  6. Elicidation by a H-2-receptor antagonist of the significance of mucosal histamine mobilization in exciting acid secretion.

    PubMed Central

    Lundell, L

    1975-01-01

    1. The consequence of H-2-receptor blockade for the secretory responses of the gastric mucosa to hormonal or cholinergic stimulation was studied in conscious rats with Heindenhain pouches or Pavlov pouches with the antrum retained or resected. 2. Metiamide almost completely abolished acid secretion induced by pentagastrin without altering significantly the amount of histamine excreted in the urine. Histamine mobilization on pentagastrin infusion determined in vitro, seemed to be larger during H-2-receptor blockade than with pentagastrin alone. 3. CCK-PZ mobilized mucosal histamine to a considerable extent; the secretory response to this hormone was completely abolished by H-2-receptor blockade. 4. Acid secretion in response to 2-deoxy-D-glucose was inhibited by H-2-receptor blockade in the presence or absence of the antrum; however the inhibition was less complete than with hormone-induced secretion. 5. The acid secretory response to 100 mg/kg of 2-deoxy-D-glucose appeared to be less susceptible to H-2-receptor blockade than that of 50-mg/kg of 2-deoxy-D-glucose. 6. Feeding induced a secretory response in the Pavlov pouch which initially was more effectively inhibited by H-2-receptor blockade than the response to 2-deoxy-D-glucose. In the absence of antral gastrin secretion by either stimulus was equally inhibited. 7. Methacholine-induced acid secretion was inhibited by infusion of the H-2-receptor antagonist, an inhibition that was absent when pentagastrin was concomitantly infused. 8. Although acid secretion induced by cholinergic stimuli was readily inhibited by the H-2-receptor antagonist, slight or nor inhibition was noted on pepsin secretion. 9. The role of histamine as a physiological stimulus for the parietal cell is discussed in view of the fact that the secretory effect of natural stimuli, known or demonstrated to mobilize mucosal histamine, is restrained by H-2-receptor blockade. PMID:49418

  7. Neuroligin1: a cell adhesion molecule that recruits PSD-95 and NMDA receptors by distinct mechanisms during synaptogenesis

    PubMed Central

    2009-01-01

    Background The cell adhesion molecule pair neuroligin1 (Nlg1) and β-neurexin (β-NRX) is a powerful inducer of postsynaptic differentiation of glutamatergic synapses in vitro. Because Nlg1 induces accumulation of two essential components of the postsynaptic density (PSD) – PSD-95 and NMDA receptors (NMDARs) – and can physically bind PSD-95 and NMDARs at mature synapses, it has been proposed that Nlg1 recruits NMDARs to synapses through its interaction with PSD-95. However, PSD-95 and NMDARs are recruited to nascent synapses independently and it is not known if Nlg1 accumulates at synapses before these PSD proteins. Here, we investigate how a single type of cell adhesion molecule can recruit multiple types of synaptic proteins to new synapses with distinct mechanisms and time courses. Results Nlg1 was present in young cortical neurons in two distinct pools before synaptogenesis, diffuse and clustered. Time-lapse imaging revealed that the diffuse Nlg1 aggregated at, and the clustered Nlg1 moved to, sites of axodendritic contact with a rapid time course. Using a patching assay that artificially induced clusters of Nlg, the time course and mechanisms of recruitment of PSD-95 and NMDARs to those Nlg clusters were characterized. Patching Nlg induced clustering of PSD-95 via a slow palmitoylation-dependent step. In contrast, NMDARs directly associated with clusters of Nlg1 during trafficking. Nlg1 and NMDARs were highly colocalized in dendrites before synaptogenesis and they became enriched with a similar time course at synapses with age. Patching of Nlg1 dramatically decreased the mobility of NMDAR transport packets. Finally, Nlg1 was biochemically associated with NMDAR transport packets, presumably through binding of NMDARs to MAGUK proteins that, in turn, bind Nlg1. This interaction was essential for colocalization and co-transport of Nlg1 with NMDARs. Conclusion Our results suggest that axodendritic contact leads to rapid accumulation of Nlg1, recruitment of

  8. G-protein-coupled receptors for neurotransmitter amino acids: C-terminal tails, crowded signalosomes.

    PubMed Central

    El Far, Oussama; Betz, Heinrich

    2002-01-01

    G-protein-coupled receptors (GPCRs) represent a superfamily of highly diverse integral membrane proteins that transduce external signals to different subcellular compartments, including nuclei, via trimeric G-proteins. By differential activation of diffusible G(alpha) and membrane-bound G(beta)gamma subunits, GPCRs might act on both cytoplasmic/intracellular and plasma-membrane-bound effector systems. The coupling efficiency and the plasma membrane localization of GPCRs are regulated by a variety of interacting proteins. In this review, we discuss recently disclosed protein interactions found with the cytoplasmic C-terminal tail regions of two types of presynaptic neurotransmitter receptors, the group III metabotropic glutamate receptors and the gamma-aminobutyric acid type-B receptors (GABA(B)Rs). Calmodulin binding to mGluR7 and other group III mGluRs may provide a Ca(2+)-dependent switch for unidirectional (G(alpha)) versus bidirectional (G(alpha) and G(beta)gamma) signalling to downstream effector proteins. In addition, clustering of mGluR7 by PICK1 (protein interacting with C-kinase 1), a polyspecific PDZ (PSD-95/Dlg1/ZO-1) domain containing synaptic organizer protein, sheds light on how higher-order receptor complexes with regulatory enzymes (or 'signalosomes') could be formed. The interaction of GABA(B)Rs with the adaptor protein 14-3-3 and the transcription factor ATF4 (activating transcription factor 4) suggests novel regulatory pathways for G-protein signalling, cytoskeletal reorganization and nuclear gene expression: processes that may all contribute to synaptic plasticity. PMID:12006104

  9. Gintonin enhances performance of mice in rotarod test: Involvement of lysophosphatidic acid receptors and catecholamine release.

    PubMed

    Lee, Byung-Hwan; Kim, Jisu; Lee, Ra Mi; Choi, Sun-Hye; Kim, Hyeon-Joong; Hwang, Sung-Hee; Lee, Myung Koo; Bae, Chun-Sik; Kim, Hyoung-Chun; Rhim, Hyewon; Lim, Kiwon; Nah, Seung-Yeol

    2016-01-26

    Ginseng has a long history of use as a tonic for restoration of vigor. One example of ginseng-derived tonic effect is that it can improve physical stamina under conditions of stress. However, the active ingredient and the underlying molecular mechanism responsible for the ergogenic effect are unknown. Recent studies show that ginseng contains a novel ingredient, gintonin, which consists of a unique class of herbal-medicine lysophosphatidic acids (LPAs). Gintonin activates G protein-coupled LPA receptors to produce a transient [Ca(2+)]i signal, which is coupled to diverse intra- and inter-cellular signal transduction pathways that stimulate hormone or neurotransmitter release. However, relatively little is known about how gintonin-mediated cellular modulation is linked to physical endurance. In the present study, systemic administration of gintonin, but not ginsenosides, in fasted mice increased blood glucose concentrations in a dose-dependent manner. Gintonin treatment elevated blood glucose to a maximum level after 30min. This elevation in blood glucose level could be abrogated by the LPA1/3 receptor antagonist, Ki16425, or the β-adrenergic receptor antagonist, propranolol. Furthermore, gintonin-dependent enhanced performance of fasted mice in rotarod test was likewise abrogated by Ki16425. Gintonin also elevated plasma epinephrine and norepinephrine concentrations. The present study shows that gintonin mediates catecholamine release through activation of the LPA receptor and that activation of the β-adrenergic receptor is coupled to liver glycogenolysis, thereby increasing the supply of glucose and enhancing performance in the rotarod test. Thus, gintonin acts via the LPA-catecholamine-glycogenolysis axis, representing a candidate mechanism that can explain how ginseng treatment enhances physical stamina. PMID:26706688

  10. Arginine of retinoic acid receptor beta which coordinates with the carboxyl group of retinoic acid functions independent of the amino acid residues responsible for retinoic acid receptor subtype ligand specificity.

    PubMed

    Zhang, Zeng Ping; Hutcheson, Juliet M; Poynton, Helen C; Gabriel, Jerome L; Soprano, Kenneth J; Soprano, Dianne Robert

    2003-01-15

    The biological actions of retinoic acid (RA) are mediated by retinoic acid receptors (RARalpha, RARbeta, and RARgamma) and retinoid X receptors (RXRalpha, RXRbeta, and RXRgamma). Consistent with the X-ray crystal structures of RARalpha and RARgamma, site-directed mutagenesis studies have demonstrated the importance of a conserved Arg residue (alphaArg(276), betaArg(269), and gammaArg(278)) for coordination with the carboxyl group of RA. However, mutation of Arg(269) to Ala in RARbeta causes only a 3- to 6-fold increase in the K(d) for RA and EC(50) in RA-dependent transcriptional transactivation assays while the homologous mutation in either RARalpha or RARgamma causes a 110-fold and a 45-fold increase in EC(50) value, respectively. To further investigate the nature of this difference, we prepared mutant RARs to determine the effect of conversion of betaR269A to a mutant which mimics either RARalpha ligand selectivity (betaA225S/R269A) or RARgamma ligand selectivity (betaI263M/R269A/V338A). Our results demonstrate that in RARbeta mutants that acquire either RARalpha or RARgamma ligand specificity the Arg(269) position responsible for coordination with the carboxyl group of retinoids continued to function like that of RARbeta. Furthermore, three mutant receptors (betaA225S/R269A, betaA225S/F279, and alphaF286A) were found to have a greater than wild-type affinity for the RARalpha-selective ligand Am580. Finally, a homology-based computer model of the ligand binding domain (LBD) of RARbeta and the X-ray crystal structures of the LBD of both RARalpha and RARgamma are used to describe potential mechanisms responsible for the increased affinity of some mutants for Am580 and for the difference in the effect of mutation of Arg(269) in RARbeta compared to its homologous Arg in RARalpha and RARgamma.

  11. Recessive and dominant mutations in retinoic acid receptor beta in cases with microphthalmia and diaphragmatic hernia.

    PubMed

    Srour, Myriam; Chitayat, David; Caron, Véronique; Chassaing, Nicolas; Bitoun, Pierre; Patry, Lysanne; Cordier, Marie-Pierre; Capo-Chichi, José-Mario; Francannet, Christine; Calvas, Patrick; Ragge, Nicola; Dobrzeniecka, Sylvia; Hamdan, Fadi F; Rouleau, Guy A; Tremblay, André; Michaud, Jacques L

    2013-10-01

    Anophthalmia and/or microphthalmia, pulmonary hypoplasia, diaphragmatic hernia, and cardiac defects are the main features of PDAC syndrome. Recessive mutations in STRA6, encoding a membrane receptor for the retinol-binding protein, have been identified in some cases with PDAC syndrome, although many cases have remained unexplained. Using whole-exome sequencing, we found that two PDAC-syndrome-affected siblings, but not their unaffected sibling, were compound heterozygous for nonsense (c.355C>T [p.Arg119(∗)]) and frameshift (c.1201_1202insCT [p.Ile403Serfs(∗)15]) mutations in retinoic acid receptor beta (RARB). Transfection studies showed that p.Arg119(∗) and p.Ile403Serfs(∗)15 altered RARB had no transcriptional activity in response to ligands, confirming that the mutations induced a loss of function. We then sequenced RARB in 15 subjects with anophthalmia and/or microphthalmia and at least one other feature of PDAC syndrome. Surprisingly, three unrelated subjects with microphthalmia and diaphragmatic hernia showed de novo missense mutations affecting the same codon; two of the subjects had the c.1159C>T (Arg387Cys) mutation, whereas the other one carried the c.1159C>A (p.Arg387Ser) mutation. We found that compared to the wild-type receptor, p.Arg387Ser and p.Arg387Cys altered RARB induced a 2- to 3-fold increase in transcriptional activity in response to retinoic acid ligands, suggesting a gain-of-function mechanism. Our study thus suggests that both recessive and dominant mutations in RARB cause anophthalmia and/or microphthalmia and diaphragmatic hernia, providing further evidence of the crucial role of the retinoic acid pathway during eye development and organogenesis.

  12. The short-chain fatty acid receptor, FFA2, contributes to gestational glucose homeostasis.

    PubMed

    Fuller, Miles; Priyadarshini, Medha; Gibbons, Sean M; Angueira, Anthony R; Brodsky, Michael; Hayes, M Geoffrey; Kovatcheva-Datchary, Petia; Bäckhed, Fredrik; Gilbert, Jack A; Lowe, William L; Layden, Brian T

    2015-11-15

    The structure of the human gastrointestinal microbiota can change during pregnancy, which may influence gestational metabolism; however, a mechanism of action remains unclear. Here we observed that in wild-type (WT) mice the relative abundance of Actinobacteria and Bacteroidetes increased during pregnancy. Along with these changes, short-chain fatty acids (SCFAs), which are mainly produced through gut microbiota fermentation, significantly changed in both the cecum and peripheral blood throughout gestation in these mice. SCFAs are recognized by G protein-coupled receptors (GPCRs) such as free fatty acid receptor-2 (FFA2), and we have previously demonstrated that the fatty acid receptor-2 gene (Ffar2) expression is higher in pancreatic islets during pregnancy. Using female Ffar2-/- mice, we explored the physiological relevance of signaling through this GPCR and found that Ffar2-deficient female mice developed fasting hyperglycemia and impaired glucose tolerance in the setting of impaired insulin secretion compared with WT mice during, but not before, pregnancy. Insulin tolerance tests were similar in Ffar2-/- and WT mice before and during pregnancy. Next, we examined the role of FFA2 in gestational β-cell mass, observing that Ffar2-/- mice had diminished gestational expansion of β-cells during pregnancy. Interestingly, mouse genotype had no significant impact on the composition of the gut microbiome, but did affect the observed SCFA profiles, suggesting a functional difference in the microbiota. Together, these results suggest a potential link between increased Ffar2 expression in islets and the alteration of circulating SCFA levels, possibly explaining how changes in the gut microbiome contribute to gestational glucose homeostasis. PMID:26394664

  13. Inhibitory effects of bile acids and synthetic farnesoid X receptor agonists on rotavirus replication.

    PubMed

    Kim, Yunjeong; Chang, Kyeong-Ok

    2011-12-01

    Rotaviruses (group A rotaviruses) are the most important cause of severe gastroenteritis in infants and children worldwide. Currently, an antiviral drug is not available and information on therapeutic targets for antiviral development is limited for rotavirus infection. Previously, it was shown that lipid homeostasis is important in rotavirus replication. Since farnesoid X receptor (FXR) and its natural ligands bile acids (such as chenodeoxycholic acid [CDCA]) play major roles in cholesterol and lipid homeostasis, we examined the effects of bile acids and synthetic FXR agonists on rotavirus replication in association with cellular lipid levels. In a mouse model of rotavirus infection, effects of oral administration of CDCA on fecal rotavirus shedding were investigated. The results demonstrate the following. First, the intracellular contents of triglycerides were significantly increased by rotavirus infection. Second, CDCA, deoxycholic acid (DCA), and other synthetic FXR agonists, such as GW4064, significantly reduced rotavirus replication in cell culture in a dose-dependent manner. The reduction of virus replication correlated positively with activation of the FXR pathway and reduction of cellular triglyceride contents (r(2) = 0.95). Third, oral administration of CDCA significantly reduced fecal virus shedding in mice (P < 0.05). We conclude that bile acids and FXR agonists play important roles in the suppression of rotavirus replication. The inhibition mechanism is proposed to be the downregulation of lipid synthesis induced by rotavirus infection.

  14. Pharmacologically targeted NMDA receptor antagonism by NitroMemantine for cerebrovascular disease

    PubMed Central

    Takahashi, Hiroto; Xia, Peng; Cui, Jiankun; Talantova, Maria; Bodhinathan, Karthik; Li, Wenjun; Holland, Emily A.; Tong, Gary; Piña-Crespo, Juan; Zhang, Dongxian; Nakanishi, Nobuki; Larrick, James W.; McKercher, Scott R.; Nakamura, Tomohiro; Wang, Yuqiang; Lipton, Stuart A.

    2015-01-01

    Stroke and vascular dementia are leading causes of morbidity and mortality. Neuroprotective therapies have been proposed but none have proven clinically tolerated and effective. While overstimulation of N-methyl-d-aspartate-type glutamate receptors (NMDARs) is thought to contribute to cerebrovascular insults, the importance of NMDARs in physiological function has made this target, at least in the view of many in ‘Big Pharma,’ ‘undruggable’ for this indication. Here, we describe novel NitroMemantine drugs, comprising an adamantane moiety that binds in the NMDAR-associated ion channel that is used to target a nitro group to redox-mediated regulatory sites on the receptor. The NitroMemantines are both well tolerated and effective against cerebral infarction in rodent models via a dual allosteric mechanism of open-channel block and NO/redox modulation of the receptor. Targeted S-nitrosylation of NMDARs by NitroMemantine is potentiated by hypoxia and thereby directed at ischemic neurons. Allosteric approaches to tune NMDAR activity may hold therapeutic potential for cerebrovascular disorders. PMID:26477507

  15. Retinoic Acid-Related Orphan Receptors (RORs): Regulatory Functions in Immunity, Development, Circadian Rhythm, and Metabolism

    PubMed Central

    Cook, Donald N.; Kang, Hong Soon; Jetten, Anton M.

    2015-01-01

    In this overview, we provide an update on recent progress made in understanding the mechanisms of action, physiological functions, and roles in disease of retinoic acid related orphan receptors (RORs). We are particularly focusing on their roles in the regulation of adaptive and innate immunity, brain function, retinal development, cancer, glucose and lipid metabolism, circadian rhythm, metabolic and inflammatory diseases and neuropsychiatric disorders. We also summarize the current status of ROR agonists and inverse agonists, including their regulation of ROR activity and their therapeutic potential for management of various diseases in which RORs have been implicated. PMID:26878025

  16. Redox control of retinoic acid receptor activity: a novel mechanism for retinoic acid resistance in melanoma cells.

    PubMed

    Demary, K; Wong, L; Liou, J S; Faller, D V; Spanjaard, R A

    2001-06-01

    Retinoic acid (RA) slows growth and induces differentiation of tumor cells through activation of RA receptors (RARs). However, melanoma cell lines display highly variable responsiveness to RA, which is a poorly understood phenomenon. By using Northern and Western blot analyses, we show that RA-resistant A375 and RA-responsive S91 melanoma cells express comparable levels of major components of RAR-signaling pathways. However, A375 cells have substantially higher intracellular reactive oxygen species (ROS) levels than S91 cells. Lowering ROS levels in A375 cells through hypoxic culture conditions restores RAR-dependent trans-activity, which could be further enhanced by addition of the antioxidant N-acetyl-cysteine. Hypoxia also enhances RAR activity in the moderately RA-responsive C32 cells, which have intermediate ROS levels. Conversely, increasing oxidative stress in highly RA-responsive S91 and B16 cells, which have low ROS levels, by treatment with H(2)O(2) impairs RAR activity. Consistent with these observations, RA more potently inhibited the proliferation of hypoxic A375 cells than that of normoxic cells. Oxidative states diminish, whereas reducing conditions enhance, DNA binding of retinoid X receptor/RAR heterodimers in vitro, providing a molecular basis for the observed inverse correlation between RAR activity and ROS levels. The redox state of melanoma cells provides a novel, epigenetic control mechanism of RAR activity and RA resistance. PMID:11356710

  17. Genetic deletion of TNF receptor suppresses excitatory synaptic transmission via reducing AMPA receptor synaptic localization in cortical neurons

    PubMed Central

    He, Ping; Liu, Qiang; Wu, Jie; Shen, Yong

    2012-01-01

    The distribution of postsynaptic glutamate receptors has been shown to be regulated by proimmunocytokine tumor necrosis factor α (TNF-α) signaling. The role of TNF-α receptor subtypes in mediating glutamate receptor expression, trafficking, and function still remains unclear. Here, we report that TNF receptor subtypes (TNFR1 and TNFR2) differentially modulate α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) clustering and function in cultured cortical neurons. We find that genetic deletion of TNFR1 decreases surface expression and synaptic localization of the AMPAR GluA1 subunit, reduces the frequency of miniature excitatory postsynaptic current (mEPSC), and reduces AMPA-induced maximal whole-cell current. In addition, these results are not observed in TNFR2-deleted neurons. The decreased AMPAR expression and function in TNFR1-deleted cells are not significantly restored by short (2 h) or long (24 h) term exposure to TNF-α. In TNFR2-deleted cells, TNF-α promotes AMPAR trafficking to the synapse and increases mEPSC frequency. In the present study, we find no significant change in the GluN1 subunit of NMDAR clusters, location, and mEPSC. This includes applying or withholding the TNF-α treatment in both TNFR1- and TNFR2-deleted neurons. Our results indicate that TNF receptor subtype 1 but not 2 plays a critical role in modulating AMPAR clustering, suggesting that targeting TNFR1 gene might be a novel approach to preventing neuronal AMPAR-mediated excitotoxicity.—He, P., Liu, Q., Wu, J., Shen, Y. Genetic deletion of TNF receptor suppresses excitatory synaptic transmission via reducing AMPA receptor synaptic localization in cortical neurons. PMID:21982949

  18. Gene Interaction Network Suggests Dioxin Induces a Significant Linkage between Aryl Hydrocarbon Receptor and Retinoic Acid Receptor Beta

    PubMed Central

    Toyoshiba, Hiroyoshi; Yamanaka, Takeharu; Sone, Hideko; Parham, Frederick M.; Walker, Nigel J.; Martinez, Jeanelle; Portier, Christopher J.

    2004-01-01

    Gene expression arrays (gene chips) have enabled researchers to roughly quantify the level of mRNA expression for a large number of genes in a single sample. Several methods have been developed for the analysis of gene array data including clustering, outlier detection, and correlation studies. Most of these analyses are aimed at a qualitative identification of what is different between two samples and/or the relationship between two genes. We propose a quantitative, statistically sound methodology for the analysis of gene regulatory networks using gene expression data sets. The method is based on Bayesian networks for direct quantification of gene expression networks. Using the gene expression changes in HPL1A lung airway epithelial cells after exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin at levels of 0.1, 1.0, and 10.0 nM for 24 hr, a gene expression network was hypothesized and analyzed. The method clearly demonstrates support for the assumed network and the hypothesis linking the usual dioxin expression changes to the retinoic acid receptor system. Simulation studies demonstrated the method works well, even for small samples. PMID:15345368

  19. Phosphatase inhibitors remove the run-down of γ-aminobutyric acid type A receptors in the human epileptic brain

    PubMed Central

    Palma, E.; Ragozzino, D. A.; Di Angelantonio, S.; Spinelli, G.; Trettel, F.; Martinez-Torres, A.; Torchia, G.; Arcella, A.; Di Gennaro, G.; Quarato, P. P.; Esposito, V.; Cantore, G.; Miledi, R.; Eusebi, F.

    2004-01-01

    The properties of γ-aminobutyric acid (GABA) type A receptors (GABAA receptors) microtransplanted from the human epileptic brain to the plasma membrane of Xenopus oocytes were compared with those recorded directly from neurons, or glial cells, in human brains slices. Cell membranes isolated from brain specimens, surgically obtained from six patients afflicted with drug-resistant temporal lobe epilepsy (TLE) were injected into frog oocytes. Within a few hours, these oocytes acquired GABAA receptors that generated GABA currents with an unusual run-down, which was inhibited by orthovanadate and okadaic acid. In contrast, receptors derived from membranes of a nonepileptic hippocampal uncus, membranes from mouse brain, or recombinant rat α1β2γ2-GABA receptors exhibited a much less pronounced GABA-current run-down. Moreover, the GABAA receptors of pyramidal neurons in temporal neocortex slices from the same six epileptic patients exhibited a stronger run-down than the receptors of rat pyramidal neurons. Interestingly, the GABAA receptors of neighboring glial cells remained substantially stable after repetitive activation. Therefore, the excessive GABA-current run-down observed in the membrane-injected oocytes recapitulates essentially what occurs in neurons, rather than in glial cells. Quantitative RT-PCR analyses from the same TLE neocortex specimens revealed that GABAA-receptor β1, β2, β3, and γ2 subunit mRNAs were significantly overexpressed (8- to 33-fold) compared with control autopsy tissues. Our results suggest that an abnormal GABA-receptor subunit transcription in the TLE brain leads to the expression of run-down-enhanced GABAA receptors. Blockage of phosphatases stabilizes the TLE GABAA receptors and strengthens GABAergic inhibition. It may be that this process can be targeted to develop new treatments for intractable epilepsy. PMID:15218107

  20. GPR109A, GPR109B and GPR81, a family of hydroxy-carboxylic acid receptors.

    PubMed

    Ahmed, Kashan; Tunaru, Sorin; Offermanns, Stefan

    2009-11-01

    G-protein-coupled receptors (GPCRs) are the most versatile receptor family as they have the ability to respond to chemically diverse ligands. Despite intensive efforts during the past two decades, there are still more than 100 orphan GPCRs for which endogenous ligands are unknown. Recently, GPR109A, GPR109B and GPR81, which form a GPCR subfamily, have been deorphanized. The physiological ligands of these receptors are the ketone body 3-hydroxy-butyrate, the metabolite 2-hydroxy-propanoate (lactate) as well as the beta-oxidation intermediate 3-hydroxy-octanoate. Thus, this receptor subfamily is activated by hydroxy-carboxylic acid ligands which are intermediates of energy metabolism. All three receptors are predominantly expressed in adipocytes and mediate antilipolytic effects. In this article, we propose that the hydroxy-carboxylic acid structure of their endogenous ligands is the defining property of this receptor subfamily and that hydroxy-carboxylic acid receptors function as metabolic sensors which fine-tune the regulation of metabolic pathways.

  1. Structure-activity relationships of fatty acid amide ligands in activating and desensitizing G protein-coupled receptor 119

    PubMed Central

    Kumar, Pritesh; Kumar, Akhilesh; Song, Zhao-Hui

    2016-01-01

    The purpose of the current study was to apply a high throughput assay to investigate the structure-activity relationships of fatty acid amides for activating and desensitizing G protein-coupled receptor 119, a promising therapeutic target for both type 2 diabetes and obesity. A cell-based, homogenous time resolved fluorescence (HTRF) method for measuring G protein-coupled receptor 119-mediated increase of cyclic adenosine monophosphate (cAMP) levels was validated and applied in this study. Using novel fatty acid amides and detailed potency and efficacy analyses, we have demonstrated that degree of saturation in acyl chain and charged head groups of fatty acid amides have profound effects on the ability of these compounds to activate G protein-coupled receptor 119. In addition, we have demonstrated for the first time that pretreatments with G protein-coupled receptor 119 agonists desensitize the receptor and the degrees of desensitization caused by fatty acid amides correlate well with their structure-activity relationships in activating the receptor. PMID:24184668

  2. A novel role for the dioxin receptor in fatty acid metabolism and hepatic steatosis

    PubMed Central

    Lee, Jung Hoon; Wada, Taira; Febbraio, Maria; He, Jinhan; Matsubara, Tsutomu; Lee, Min Jae; Gonzalez, Frank J.; Xie, Wen

    2010-01-01

    Background & Aims The aryl hydrocarbon receptor (AhR) is a PAS domain transcription factor previously known as the “dioxin receptor” or “xenobiotic receptor.” The goal of this study is to determine the endobiotic role of AhR in hepatic steatosis. Methods Wild type, constitutively activated AhR (CA-AhR) transgenic, AhR null (AhR-/-), and fatty acid translocase CD36/FAT null (CD36-/-) mice were used to investigate the role of AhR in steatosis and the involvement of CD36 in the steatotic effect of AhR. The promoters of the mouse and human CD36 genes were cloned and their regulation by AhR was analyzed. Results Activation of AhR induced spontaneous hepatic steatosis characterized by the accumulation of triglycerides. The steatotic effect of AhR is likely due to the combined upregulation of CD36 and fatty acid transport proteins (FATPs), suppression of fatty acid oxidation, inhibition of hepatic export of triglycerides, increase in peripheral fat mobilization, and increased hepatic oxidative stress. Promoter analysis established CD36 as a novel transcriptional target of AhR. Activation of AhR in liver cells induced CD36 gene expression and enhanced fatty acid uptake. The steatotic effect of an AhR agonist was inhibited in CD36-/- mice. Conclusions Our study reveals a novel link between AhR-induced steatosis and the expression of CD36. Industrial or military exposures to dioxin and related compounds have been linked to increased prevalence of fatty liver in humans. Results from this study may help to establish AhR and its target CD36 as novel therapeutic and preventive targets for fatty liver disease. PMID:20303349

  3. Human sweet taste receptor mediates acid-induced sweetness of miraculin.

    PubMed

    Koizumi, Ayako; Tsuchiya, Asami; Nakajima, Ken-ichiro; Ito, Keisuke; Terada, Tohru; Shimizu-Ibuka, Akiko; Briand, Loïc; Asakura, Tomiko; Misaka, Takumi; Abe, Keiko

    2011-10-01

    Miraculin (MCL) is a homodimeric protein isolated from the red berries of Richadella dulcifica. MCL, although flat in taste at neutral pH, has taste-modifying activity to convert sour stimuli to sweetness. Once MCL is held on the tongue, strong sweetness is sensed over 1 h each time we taste a sour solution. Nevertheless, no molecular mechanism underlying the taste-modifying activity has been clarified. In this study, we succeeded in quantitatively evaluating the acid-induced sweetness of MCL using a cell-based assay system and found that MCL activated hT1R2-hT1R3 pH-dependently as the pH decreased from 6.5 to 4.8, and that the receptor activation occurred every time an acid solution was applied. Although MCL per se is sensory-inactive at pH 6.7 or higher, it suppressed the response of hT1R2-hT1R3 to other sweeteners at neutral pH and enhanced the response at weakly acidic pH. Using human/mouse chimeric receptors and molecular modeling, we revealed that the amino-terminal domain of hT1R2 is required for the response to MCL. Our data suggest that MCL binds hT1R2-hT1R3 as an antagonist at neutral pH and functionally changes into an agonist at acidic pH, and we conclude this may cause its taste-modifying activity. PMID:21949380

  4. Human sweet taste receptor mediates acid-induced sweetness of miraculin

    PubMed Central

    Koizumi, Ayako; Tsuchiya, Asami; Nakajima, Ken-ichiro; Ito, Keisuke; Terada, Tohru; Shimizu-Ibuka, Akiko; Briand, Loïc; Asakura, Tomiko; Misaka, Takumi; Abe, Keiko

    2011-01-01

    Miraculin (MCL) is a homodimeric protein isolated from the red berries of Richadella dulcifica. MCL, although flat in taste at neutral pH, has taste-modifying activity to convert sour stimuli to sweetness. Once MCL is held on the tongue, strong sweetness is sensed over 1 h each time we taste a sour solution. Nevertheless, no molecular mechanism underlying the taste-modifying activity has been clarified. In this study, we succeeded in quantitatively evaluating the acid-induced sweetness of MCL using a cell-based assay system and found that MCL activated hT1R2-hT1R3 pH-dependently as the pH decreased from 6.5 to 4.8, and that the receptor activation occurred every time an acid solution was applied. Although MCL per se is sensory-inactive at pH 6.7 or higher, it suppressed the response of hT1R2-hT1R3 to other sweeteners at neutral pH and enhanced the response at weakly acidic pH. Using human/mouse chimeric receptors and molecular modeling, we revealed that the amino-terminal domain of hT1R2 is required for the response to MCL. Our data suggest that MCL binds hT1R2-hT1R3 as an antagonist at neutral pH and functionally changes into an agonist at acidic pH, and we conclude this may cause its taste-modifying activity. PMID:21949380

  5. Excitatory amino acid receptors and synaptic transmission in the rat ventrobasal thalamus.

    PubMed

    Salt, T E

    1987-10-01

    1. Extracellular single-neurone recordings were made in the ventrobasal thalamus (v.b.t.) of urethane-anaesthetized rats with multi-barrel ionophoretic electrodes in order to test the hypothesis that excitatory amino acid receptors are involved in the responses of these neurones to stimulation of sensory afferents. 2. Responses of neurones to either physiological stimulation of hair and vibrissa follicle sensory afferents and to ionophoretically applied excitatory amino acids were challenged with the antagonists D-2-amino-5-phosphonovalerate (APV), kynurenate and gamma-D-glutamylaminomethyl sulphonate (GAMS). 3. In agreement with previous findings in other brain areas, ionophoretically applied APV was found to selectively antagonize responses of v.b.t. neurones to N-methylaspartate (NMA), whereas GAMS was found to be moderately kainate selective. Kynurenate was found to be relatively non-selective. 4. Responses of neurones to short-duration (10-20 ms) physiological stimulation of afferents were resistant to APV when this antagonist was applied with NMA-selective ionophoretic currents. In contrast, these APV currents were adequate to antagonize responses to maintained physiological stimulation. 5. The broad spectrum excitatory amino acid antagonist kynurenate was found to block synaptic responses of v.b.t. neurones to both short-duration and maintained stimuli when it was applied with currents which were sufficient to reduce responses to ionophoretic quisqualate. 6. GAMS was found to selectively block kainate responses in a proportion of the neurones tested. In such cases, there was little effect of the antagonist on the responses evoked by either short-duration or maintained sensory stimuli. 7. It is concluded that excitatory amino acid receptors of both the NMDA and non-NMDA type are involved in the synaptic responses of v.b.t. neurones to sensory afferent stimulation, and that the apparent synaptic pharmacology depends on the mode of stimulation of the afferent

  6. Effect of retinoic acid and ethanol on retinoic acid receptor beta and glial fibrillary acidic protein mRNA expression in human astrocytoma cells.

    PubMed

    Grummer, M A; Salih, Z N; Zachman, R D

    2000-11-17

    This work explores the hypothesis that perturbations caused by ethanol on the regulatory role of retinoids in brain development may be a mechanism involved in the neuropathology of fetal alcohol syndrome. The interaction of ethanol and retinoic acid (RA) on RA receptor (RAR) beta and glial fibrillary acidic protein (GFAP) mRNA expression is evaluated. In the U-373 MG astrocytoma, mRNA expression of RAR beta was increased and GFAP was decreased by RA. Ethanol decreased the expression of RAR beta mRNA, but increased that of GFAP. The RA-stimulated increase in RAR beta was not affected by the presence of ethanol. RA prevented the ethanol-induced increase in GFAP mRNA. Cycloheximide abolished only the GFAP response to ethanol. This work shows that an interrelationship between ethanol and RA exists in the astrocyte. PMID:11058790

  7. Pharmacodynamics of long-acting folic acid-receptor targeted ritonavir boosted atazanavir nanoformulations

    PubMed Central

    Puligujja, Pavan; Balkundi, Shantanu; Kendrick, Lindsey; Baldridge, Hannah; Hilaire, James; Bade, Aditya N.; Dash, Prasanta K.; Zhang, Gang; Poluektova, Larisa; Gorantla, Santhi; Liu, Xin-Ming; Ying, Tianlei; Feng, Yang; Wang, Yanping; Dimitrov, Dimiter S.; McMillan, JoEllyn M.; Gendelman, Howard E.

    2014-01-01

    Long-acting nanoformulated antiretroviral therapy (nanoART) that target monocyte-macrophage could improve the drug’s half-life and protein binding capacities while facilitating cell and tissue depots. To this end, ART nanoparticles that target the folic acid (FA) receptor and permit cell-based drug depots were examined using pharmacokinetic and pharmacodynamic (PD) tests. FA receptor-targeted poloxamer 407 nanocrystals, containing ritonavir-boosted atazanavir (ATV/r), significantly affected several therapeutic factors: drug bioavailability increased as much as 5 times and PD activity improved as much as 100 times. Drug particles administered to human peripheral blood lymphocyte reconstituted NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ mice and infected with HIV-1ADA at a tissue culture infective dose50 of 104 infectious viral particles/ml led to ATV/r drug concentrations that paralleled FA receptor beta staining in both the macrophage-rich parafollicular areas of spleen and lymph nodes. Drug levels were higher in these tissues than what could be achieved by either native drug or untargeted nanoART particles. The data also mirrored potent reductions in viral loads, tissue viral RNA and numbers of HIV-1p24+ cells in infected and treated animals. We conclude that FA-P407 coating of ART nanoparticles readily facilitate drug carriage and facilitate antiretroviral responses. PMID:25522973

  8. Cellular localization of retinoic acid receptor-gamma expression in normal and neoplastic skin.

    PubMed Central

    Finzi, E.; Blake, M. J.; Celano, P.; Skouge, J.; Diwan, R.

    1992-01-01

    Retinoids profoundly affect the normal growth and differentiation of epithelial tissues. Retinoic acid receptor-gamma (RAR-gamma) is a member of a family of retinoid receptors, and has been shown to be expressed almost exclusively in skin. However, little is known about the cellular localization of this receptor in human skin. The authors studied the expression of RAR-gamma in normal skin and human skin tumors by Northern blot analysis and in situ hybridization. RAR-gamma mRNA was detected in normal skin as well as in cultures of neonatal keratinocytes. Using an oligonucleotide specific for the RAR-gamma cDNA isoform 1 (RAR-gamma 1), RAR-gamma 1 mRNA was localized to all layers of the epidermis, the outer root sheath of hair follicles, follicular hair bulbs, eccrine and sebaceous glands. Basal cell carcinoma constitutively expressed gamma-1 mRNA and one of seven squamous cell carcinomas showed loss of gamma-1 mRNA expression, relative to adjacent epithelium. By contrast, normal melanocytic nevi and tumor-associated lymphocytes expressed little or no RAR-gamma mRNA. These results suggest that RAR-gamma 1 may play an important role in the maintenance and differentiation of normal epidermis and skin appendages. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 PMID:1318641

  9. Asymmetrical macromolecular complex formation of lysophosphatidic acid receptor 2 (LPA2) mediates gradient sensing in fibroblasts.

    PubMed

    Ren, Aixia; Moon, Changsuk; Zhang, Weiqiang; Sinha, Chandrima; Yarlagadda, Sunitha; Arora, Kavisha; Wang, Xusheng; Yue, Junming; Parthasarathi, Kaushik; Heil-Chapdelaine, Rick; Tigyi, Gabor; Naren, Anjaparavanda P

    2014-12-26

    Chemotactic migration of fibroblasts toward growth factors relies on their capacity to sense minute extracellular gradients and respond to spatially confined receptor-mediated signals. Currently, mechanisms underlying the gradient sensing of fibroblasts remain poorly understood. Using single-particle tracking methodology, we determined that a lysophosphatidic acid (LPA) gradient induces a spatiotemporally restricted decrease in the mobility of LPA receptor 2 (LPA2) on chemotactic fibroblasts. The onset of decreased LPA2 mobility correlates to the spatial recruitment and coupling to LPA2-interacting proteins that anchor the complex to the cytoskeleton. These localized PDZ motif-mediated macromolecular complexes of LPA2 trigger a Ca(2+) puff gradient that governs gradient sensing and directional migration in response to LPA. Disruption of the PDZ motif-mediated assembly of the macromolecular complex of LPA2 disorganizes the gradient of Ca(2+) puffs, disrupts gradient sensing, and reduces the directional migration of fibroblasts toward LPA. Our findings illustrate that the asymmetric macromolecular complex formation of chemoattractant receptors mediates gradient sensing and provides a new mechanistic basis for models to describe gradient sensing of fibroblasts.

  10. Asymmetrical macromolecular complex formation of lysophosphatidic acid receptor 2 (LPA2) mediates gradient sensing in fibroblasts.

    PubMed

    Ren, Aixia; Moon, Changsuk; Zhang, Weiqiang; Sinha, Chandrima; Yarlagadda, Sunitha; Arora, Kavisha; Wang, Xusheng; Yue, Junming; Parthasarathi, Kaushik; Heil-Chapdelaine, Rick; Tigyi, Gabor; Naren, Anjaparavanda P

    2014-12-26

    Chemotactic migration of fibroblasts toward growth factors relies on their capacity to sense minute extracellular gradients and respond to spatially confined receptor-mediated signals. Currently, mechanisms underlying the gradient sensing of fibroblasts remain poorly understood. Using single-particle tracking methodology, we determined that a lysophosphatidic acid (LPA) gradient induces a spatiotemporally restricted decrease in the mobility of LPA receptor 2 (LPA2) on chemotactic fibroblasts. The onset of decreased LPA2 mobility correlates to the spatial recruitment and coupling to LPA2-interacting proteins that anchor the complex to the cytoskeleton. These localized PDZ motif-mediated macromolecular complexes of LPA2 trigger a Ca(2+) puff gradient that governs gradient sensing and directional migration in response to LPA. Disruption of the PDZ motif-mediated assembly of the macromolecular complex of LPA2 disorganizes the gradient of Ca(2+) puffs, disrupts gradient sensing, and reduces the directional migration of fibroblasts toward LPA. Our findings illustrate that the asymmetric macromolecular complex formation of chemoattractant receptors mediates gradient sensing and provides a new mechanistic basis for models to describe gradient sensing of fibroblasts. PMID:25542932

  11. MHC class I immune proteins are critical for hippocampus-dependent memory and gate NMDAR-dependent hippocampal long-term depression

    PubMed Central

    Nelson, P. Austin; Sage, Jennifer R.; Wood, Suzanne C.; Davenport, Christopher M.; Anagnostaras, Stephan G.; Boulanger, Lisa M.

    2013-01-01

    Memory impairment is a common feature of conditions that involve changes in inflammatory signaling in the brain, including traumatic brain injury, infection, neurodegenerative disorders, and normal aging. However, the causal importance of inflammatory mediators in cognitive impairments in these conditions remains unclear. Here we show that specific immune proteins, members of the major histocompatibility complex class I (MHC class I), are essential for normal hippocampus-dependent memory, and are specifically required for NMDAR-dependent forms of long-term depression (LTD) in the healthy adult hippocampus. In β2m−/−TAP−/−mice, which lack stable cell-surface expression of most MHC class I proteins, NMDAR-dependent LTD in area CA1 of adult hippocampus is abolished, while NMDAR-independent forms of potentiation, facilitation, and depression are unaffected. Altered NMDAR-dependent synaptic plasticity in the hippocampus of β2m−/−TAP−/−mice is accompanied by pervasive deficits in hippocampus-dependent memory, including contextual fear memory, object recognition memory, and social recognition memory. Thus normal MHC class I expression is essential for NMDAR-dependent hippocampal synaptic depression and hippocampus-dependent memory. These results suggest that changes in MHC class I expression could be an unexpected cause of disrupted synaptic plasticity and cognitive deficits in the aging, damaged, and diseased brain. PMID:23959708

  12. Surface expression of NMDA receptor changes during memory consolidation in the crab Neohelice granulata.

    PubMed

    Hepp, Yanil; Salles, Angeles; Carbo-Tano, Martin; Pedreira, Maria Eugenia; Freudenthal, Ramiro

    2016-08-01

    The aim of the present study was to analyze the surface expression of the NMDA-like receptors during the consolidation of contextual learning in the crab Neohelice granulata Memory storage is based on alterations in the strength of synaptic connections between neurons. The glutamatergic synapses undergo various forms of N-methyl-D aspartate receptor (NMDAR)-dependent changes in strength, a process that affects the abundance of other receptors at the synapse and underlies some forms of learning and memory. Here we propose a direct regulation of the NMDAR. Changes in NMDAR's functionality might be induced by the modification of the subunit's expression or cellular trafficking. This trafficking does not only include NMDAR's movement between synaptic and extra-synaptic localizations but also the cycling between intracellular compartments and the plasma membrane, a process called surface expression. Consolidation of contextual learning affects the surface expression of the receptor without affecting its general expression. The surface expression of the GluN1 subunit of the NMDAR is down-regulated immediately after training, up-regulated 3 h after training and returns to naïve and control levels 24 h after training. The changes in NMDAR surface expression observed in the central brain are not seen in the thoracic ganglion. A similar increment in surface expression of GluN1 in the central brain is observed 3 h after administration of the competitive GABAA receptor antagonist, bicuculline. These consolidation changes are part of a plasticity event that first, during the down-regulation, stabilizes the trace and later, at 3-h post-training, changes the threshold for synapse activation.

  13. Surface expression of NMDA receptor changes during memory consolidation in the crab Neohelice granulata.

    PubMed

    Hepp, Yanil; Salles, Angeles; Carbo-Tano, Martin; Pedreira, Maria Eugenia; Freudenthal, Ramiro

    2016-08-01

    The aim of the present study was to analyze the surface expression of the NMDA-like receptors during the consolidation of contextual learning in the crab Neohelice granulata Memory storage is based on alterations in the strength of synaptic connections between neurons. The glutamatergic synapses undergo various forms of N-methyl-D aspartate receptor (NMDAR)-dependent changes in strength, a process that affects the abundance of other receptors at the synapse and underlies some forms of learning and memory. Here we propose a direct regulation of the NMDAR. Changes in NMDAR's functionality might be induced by the modification of the subunit's expression or cellular trafficking. This trafficking does not only include NMDAR's movement between synaptic and extra-synaptic localizations but also the cycling between intracellular compartments and the plasma membrane, a process called surface expression. Consolidation of contextual learning affects the surface expression of the receptor without affecting its general expression. The surface expression of the GluN1 subunit of the NMDAR is down-regulated immediately after training, up-regulated 3 h after training and returns to naïve and control levels 24 h after training. The changes in NMDAR surface expression observed in the central brain are not seen in the thoracic ganglion. A similar increment in surface expression of GluN1 in the central brain is observed 3 h after administration of the competitive GABAA receptor antagonist, bicuculline. These consolidation changes are part of a plasticity event that first, during the down-regulation, stabilizes the trace and later, at 3-h post-training, changes the threshold for synapse activation. PMID:27421895

  14. The effect of folic acid on GABA(A)-B 1 receptor subunit.

    PubMed

    Vasquez, Kizzy; Kuizon, Salomon; Junaid, Mohammed; Idrissi, Abdeslem El

    2013-01-01

    Autism contains a spectrum of behavioral and cognitive disturbances of childhood development that is manifested by deficits in social interaction, impaired communication, repetitive behavior, and/or restricted interest. Much research has been dedicated to finding the genes that are responsible for autism, but less than 10% of the cases can be attributed to one gene. Autism prevalence has increased in the last decade and there may be environmental components that are leading to this increase. There are reports of disruption of epigenetic mechanisms controlling the regulation of gene expression as probable cause for autism. Folic acid (FA) is prescribed to women during pregnancy, and can cause epigenetic changes. GABAergic pathway is involved in inhibitory neurotransmission in the central nervous system and plays a crucial role during early embryonic development. Autism may entail defect or deregulation of the GABAergic receptor pathway in the brain. Gamma-aminobutyric acid (type A) beta 1 receptor (GABRB1) disruption has been implicated in autism. In the present study, we investigated GABRB1 expression in response to FA supplementation in neuronal cells. Western blot analysis showed GABRB1 protein levels increased in the FA-treated cells in a concentration-dependent manner. FA-dependent increased expression of GABRB1 was further confirmed at the mRNA level using quantitative RT-PCR. These results suggest that epigenetic control of gene expression may affect the expression of GABRB1 and disrupt inhibitory synaptic transmission during embryonic development. PMID:23392927

  15. Kynurenic acid, an aryl hydrocarbon receptor ligand, is elevated in serum of Zucker fatty rats

    PubMed Central

    Oxenkrug, G; Cornicelli, J; van der Hart, M; Roeser, J; Summergrad, P

    2016-01-01

    Obesity is an increasingly urgent global problem and the molecular mechanisms of obesity are not fully understood. Dysregulation of the tryptophan (Trp) – kynurenine (Kyn) metabolic pathway (TKP) have been suggested as a mechanism of obesity and described in obese humans and in animal models of obesity. However, to the best of our knowledge, TKP metabolism has not been studied in leptin-receptor-deficient Zucker fatty rats (ZFR) (fa/fa), the best-known and most widely used rat model of obesity. We were interested to determine if there are any deviations of TKP in ZFR. Concentrations of major TKP metabolites were evaluated (HPLC- MS method) in serum of ZFR (fa/fa) and age-matched lean rats (FA/-). Concentrations of kynurenic acid (KYNA) were 50% higher in ZFR than in lean rats (p<0.004, Mann-Whitney two-tailed test). Anthranilic acid (AA) concentrations, while elevated by 33%, did not reach statistical significance (p<0.04, one-tailed test). Elevated KYNA serum concentrations might contribute to development of obesity via KYNA-induced activation of aryl hydrocarbon receptor. Present results warrant further studies of KYNA and AA in ZFR and other animal models of obesity. PMID:27738521

  16. Mutations of lysophosphatidic acid receptor-1 gene during progression of lung tumors in rats

    SciTech Connect

    Yamada, Takanori; Obo, Yumi; Furukawa, Mami; Hotta, Mayuko; Yamasaki, Ayako; Honoki, Kanya; Fukushima, Nobuyuki; Tsujiuchi, Toshifumi

    2009-01-16

    Lysophosphatidic acid (LPA) is a bioactive phospholipid that stimulates cell proliferation, migration, and protects cells from apoptosis. It interacts with specific G protein-coupled transmembrane receptors. In this study, mutations of lysophosphatidic acid receptor-1 (LPA1) gene were investigated to clarify the possible molecular mechanisms underlying the development of lung tumors induced by N-nitrosobis(2-hydroxypropyl)amine (BHP) in rats. Male Wistar rats, 6 weeks of age, were given 2000 ppm BHP in their drinking water for 12 weeks and then maintained without further treatment until sacrifice at 25 weeks. Genomic DNAs were extracted from paraffin-embedded tissues and exons 2-4 were examined for mutations, using polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) analysis. No LPA1 mutations were detected in 15 hyperplasias, but 2 out of 12 adenomas (16.7%) and 7 out of 17 adenocarcinomas (41.2%). These results suggest that mutations of LPA1 gene may be involved in the acquisition of growth advantage from adenomas to adenocarcinomas in lung carcinogenesis induced in rats by BHP.

  17. Molecular mechanism of the assembly of an acid-sensing receptor ion channel complex.

    PubMed

    Yu, Yong; Ulbrich, Maximilian H; Li, Ming-Hui; Dobbins, Scott; Zhang, Wei K; Tong, Liang; Isacoff, Ehud Y; Yang, Jian

    2012-01-01

    Polycystic kidney disease (PKD) family proteins associate with transient receptor potential (TRP) channel family proteins to form functionally important complexes. PKD proteins differ from known ion channel-forming proteins and are generally thought to act as membrane receptors. Here we find that PKD1L3, a PKD protein, functions as a channel-forming subunit in an acid-sensing heteromeric complex formed by PKD1L3 and TRPP3, a TRP channel protein. Single amino-acid mutations in the putative pore region of both proteins alter the channel's ion selectivity. The PKD1L3/TRPP3 complex in the plasma membrane of live cells contains one PKD1L3 and three TRPP3. A TRPP3 C-terminal coiled-coil domain forms a trimer in solution and in crystal, and has a crucial role in the assembly and surface expression of the PKD1L3/TRPP3 complex. These results demonstrate that PKD subunits constitute a new class of channel-forming proteins, enriching our understanding of the function of PKD proteins and PKD/TRPP complexes. PMID:23212381

  18. Acid-responsive PEGylated doxorubicin prodrug nanoparticles for neuropilin-1 receptor-mediated targeted drug delivery.

    PubMed

    Song, Huijuan; Zhang, Ju; Wang, Weiwei; Huang, Pingsheng; Zhang, Yumin; Liu, Jianfeng; Li, Chen; Kong, Deling

    2015-12-01

    Self-assembled prodrug nanoparticles have demonstrated great promise in cancer chemotherapy. In the present study, we developed a new kind of prodrug nanoparticles for targeted drug delivery. PEGylated doxorubicin conjugate with an acid-cleavable cis-aconityl spacer was prepared. Then it was functionalized with a tumor-penetrating peptide, Cys-Arg-Gly-Asp-Lys (CRGDK), providing the prodrug nanoparticles with the specific binding ability to neurophilin-1 receptor. In acid mediums, doxorubicin could be released from the prodrug nanoparticles with an accumulative release around 60% through the acid-triggered hydrolysis of cis-aconityl bond and nanoparticle disassembly. Whereas, drug release was slow under a neutral pH and the accumulative drug release was less than 16%. In the cell culture tests, our prodrug nanoparticles showed enhanced endocytosis and cytotoxicity in cancer cells including HepG2, MCF-7 and MDA-MB-231 cells, but lower cytotoxicity in human cardiomyocyte H2C9. In the animal experiments, the prodrug nanoparticles were intravenously injected into Balb/c nude mice bearing MDA-MB-231 tumors. Enhanced drug penetration and accumulation in tumors, accompanying with a rapid early tumor-binding behavior, was observed after intravenous injection of the peptide modified prodrug nanoparticles. These data suggests that the acid-sensitive and tumor-targeting PEGylated doxorubicin prodrug nanoparticle may be an efficient drug delivery system for cancer chemotherapy.

  19. GPR34 is a receptor for lysophosphatidylserine with a fatty acid at the sn-2 position.

    PubMed

    Kitamura, Hajime; Makide, Kumiko; Shuto, Akira; Ikubo, Masaya; Inoue, Asuka; Suzuki, Kensuke; Sato, Yusuke; Nakamura, Sho; Otani, Yuko; Ohwada, Tomohiko; Aoki, Junken

    2012-05-01

    GPR34 is a G protein-coupled receptor belonging to the P2Y family. Here, we attempted to resolve conflicting reports about whether it is a functional lysophosphatidylserine (LysoPS) receptor. In HEK293 cells expressing human, mouse or rat GPR34 and Gα chimera between Gαq and Gαi1(Gq/i1), LysoPS quickly elevated intracellular Ca(2+) ion levels ([Ca(2+)](i)). LysoPS also stimulated alkaline phosphatase (AP)-tagged TGFα (AP-TGFα) release in GPR34-expressing HEK293 cells and induced the migration of CHO-K1 cells expressing GPR34. Other lysophospholipids did not induce these actions. Replacement of the serine residue of LysoPS abolished the reactivity of LysoPS with GPR34, indicating that GPR34 strictly recognizes the serine head group of LysoPS. Recombinant phosphatidylserine-specific phospholipase A(1) (PS-PLA(1)) that deacylates fatty acid at the sn-1 position of PS and produces 2-acyl-LysoPS, but not catalytically inactive mutant PS-PLA(1), stimulated the release of AP-TGFα from GPR34-expressing cells. Consistent with the result, LysoPS was detected in the cells treated with wild-type PS-PLA(1) but not with the mutant PS-PLA(1). PS treated with PLA(1) was much more effective at stimulating AP-TGFα release than PS treated with PLA(2). In addition, migration-resistant 2-acyl-1-deoxy-LysoPS, a 2-acyl-LysoPS analogue, was much more potent than 1-acyl-2-deoxy-LysoPS. The present studies confirm that GPR34 is a cellular receptor for LysoPS, especially with a fatty acid at the sn-2 position. PMID:22343749

  20. A Novel Allosteric Activator of Free Fatty Acid 2 Receptor Displays Unique Gi-functional Bias.

    PubMed

    Bolognini, Daniele; Moss, Catherine E; Nilsson, Karolina; Petersson, Annika U; Donnelly, Iona; Sergeev, Eugenia; König, Gabriele M; Kostenis, Evi; Kurowska-Stolarska, Mariola; Miller, Ashley; Dekker, Niek; Tobin, Andrew B; Milligan, Graeme

    2016-09-01

    The short chain fatty acid receptor FFA2 is able to stimulate signaling via both Gi- and Gq/G11-promoted pathways. These pathways are believed to control distinct physiological end points but FFA2 receptor ligands appropriate to test this hypothesis have been lacking. Herein, we characterize AZ1729, a novel FFA2 regulator that acts as a direct allosteric agonist and as a positive allosteric modulator, increasing the activity of the endogenously produced short chain fatty acid propionate in Gi-mediated pathways, but not at those transduced by Gq/G11 Using AZ1729 in combination with direct inhibitors of Gi and Gq/G11 family G proteins demonstrated that although both arms contribute to propionate-mediated regulation of phospho-ERK1/2 MAP kinase signaling in FFA2-expressing 293 cells, the Gq/G11-mediated pathway is predominant. We extend these studies by employing AZ1729 to dissect physiological FFA2 signaling pathways. The capacity of AZ1729 to act at FFA2 receptors to inhibit β-adrenoreceptor agonist-promoted lipolysis in primary mouse adipocytes and to promote chemotaxis of isolated human neutrophils confirmed these as FFA2 processes mediated by Gi signaling, whereas, in concert with blockade by the Gq/G11 inhibitor FR900359, the inability of AZ1729 to mimic or regulate propionate-mediated release of GLP-1 from mouse colonic preparations defined this physiological response as an end point transduced via activation of Gq/G11. PMID:27385588

  1. A Novel Allosteric Activator of Free Fatty Acid 2 Receptor Displays Unique Gi-functional Bias*

    PubMed Central

    Bolognini, Daniele; Moss, Catherine E.; Nilsson, Karolina; Petersson, Annika U.; Donnelly, Iona; Sergeev, Eugenia; König, Gabriele M.; Kostenis, Evi; Kurowska-Stolarska, Mariola; Miller, Ashley; Dekker, Niek; Tobin, Andrew B.

    2016-01-01

    The short chain fatty acid receptor FFA2 is able to stimulate signaling via both Gi- and Gq/G11-promoted pathways. These pathways are believed to control distinct physiological end points but FFA2 receptor ligands appropriate to test this hypothesis have been lacking. Herein, we characterize AZ1729, a novel FFA2 regulator that acts as a direct allosteric agonist and as a positive allosteric modulator, increasing the activity of the endogenously produced short chain fatty acid propionate in Gi-mediated pathways, but not at those transduced by Gq/G11. Using AZ1729 in combination with direct inhibitors of Gi and Gq/G11 family G proteins demonstrated that although both arms contribute to propionate-mediated regulation of phospho-ERK1/2 MAP kinase signaling in FFA2-expressing 293 cells, the Gq/G11-mediated pathway is predominant. We extend these studies by employing AZ1729 to dissect physiological FFA2 signaling pathways. The capacity of AZ1729 to act at FFA2 receptors to inhibit β-adrenoreceptor agonist-promoted lipolysis in primary mouse adipocytes and to promote chemotaxis of isolated human neutrophils confirmed these as FFA2 processes mediated by Gi signaling, whereas, in concert with blockade by the Gq/G11 inhibitor FR900359, the inability of AZ1729 to mimic or regulate propionate-mediated release of GLP-1 from mouse colonic preparations defined this physiological response as an end point transduced via activation of Gq/G11. PMID:27385588

  2. Triphenyl phosphate-induced developmental toxicity in zebrafish: Potential role of the retinoic acid receptor

    PubMed Central

    Isales, Gregory M.; Hipszer, Rachel A.; Raftery, Tara D.; Chen, Albert; Stapleton, Heather M.; Volz, David C.

    2015-01-01

    Using zebrafish as a model, we previously reported that developmental exposure to triphenyl phosphate (TPP) – a high-production volume organophosphate-based flame retardant – results in dioxin-like cardiac looping impairments that are independent of the aryl hydrocarbon receptor. Using a pharmacologic approach, the objective of this study was to investigate the potential role of retinoic acid receptor (RAR) – a nuclear receptor that regulates vertebrate heart morphogenesis – in mediating TPP-induced developmental toxicity in zebrafish. We first revealed that static exposure of zebrafish from 5-72 hours post-fertilization (hpf) to TPP in the presence of non-toxic concentrations of an RAR antagonist (BMS493) significantly enhanced TPP-induced toxicity (relative to TPP alone), even though identical non-toxic BMS493 concentrations mitigated retinoic acid (RA)-induced toxicity. BMS493-mediated enhancement of TPP toxicity was not a result of differential TPP uptake or metabolism, as internal embryonic doses of TPP and diphenyl phosphate (DPP) – a primary TPP metabolite - were not different in the presence or absence of BMS493. Using real-time PCR, we then quantified the relative change in expression of cytochrome P450 26a1 (cyp26a1) – a major target gene for RA-induced RAR activation in zebrafish – and found that RA and TPP exposure resulted in a ∼5-fold increase and decrease in cyp26a1 expression, respectively, relative to vehicle-exposed embryos. To address whether TPP may interact with human RARs, we then exposed Chinese hamster ovary cells stably transfected with chimeric human RARα-, RARβ-, or RARγ to TPP in the presence of RA, and found that TPP significantly inhibited RA-induced luciferase activity in a concentration-dependent manner. Overall, our findings suggest that zebrafish RARs may be involved in mediating TPP-induced developmental toxicity, a mechanism of action that may have relevance to humans. PMID:25725299

  3. Effects of bile acids and the bile acid receptor FXR agonist on the respiratory rhythm in the in vitro brainstem medulla slice of neonatal Sprague-Dawley rats.

    PubMed

    Zhao, Cong; Wang, Xianbao; Cong, Yuling; Deng, Yi; Xu, Yijun; Chen, Aihua; Yin, Yanru

    2014-01-01

    Intrahepatic cholestasis of pregnancy is always accompanied by adverse fetal outcomes such as malfunctions of respiration. Farnesoid X receptor (FXR) plays a critical role in the homeostasis of bile acids. Thus, we are determined to explore the effects of farnesoid X receptor (FXR) and five bile acids on respiratory rhythm generation and modulation of neonatal rats. Spontaneous periodic respiratory-related rhythmical discharge activity (RRDA) was recorded from hypoglossal nerves during the perfusion of modified Krebs solution. Group 1-6 was each given GW4064 and five bile acids of chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), lithocholic acid (LCA), cholic acid (CA) as well as ursodeoxycholic acid (UDCA) at different concentrations to identify their specific functions on respiratory rhythm modulations. Group 7 was applied to receive FXR blocker Z-guggulsterone and Z-guggulsterone with the above bile acids separately to explore the role of FXR in the respiratory rhythm modulation. Group 8 was given dimethyl sulfoxide (DMSO) as controls. Apart from UDCA, CDCA, DCA LCA and CA all exerted effects on RRDA recorded from hypoglossal nerves in a concentration-dependent manner. Respiratory cycle (RC), Inspiratory time (TI), Expiratory Time (TE) and Integral Amplitude (IA) were influenced and such effects could be reversed by Z-guggulsterone. FXR may contribute to the effects on the modulation of respiratory rhythm exerted by bile acids.

  4. Efficient Modulation of γ-Aminobutyric Acid Type A Receptors by Piperine Derivatives

    PubMed Central

    2014-01-01

    Piperine activates TRPV1 (transient receptor potential vanilloid type 1 receptor) receptors and modulates γ-aminobutyric acid type A receptors (GABAAR). We have synthesized a library of 76 piperine analogues and analyzed their effects on GABAAR by means of a two-microelectrode voltage-clamp technique. GABAAR were expressed in Xenopus laevis oocytes. Structure–activity relationships (SARs) were established to identify structural elements essential for efficiency and potency. Efficiency of piperine derivatives was significantly increased by exchanging the piperidine moiety with either N,N-dipropyl, N,N-diisopropyl, N,N-dibutyl, p-methylpiperidine, or N,N-bis(trifluoroethyl) groups. Potency was enhanced by replacing the piperidine moiety by N,N-dibutyl, N,N-diisobutyl, or N,N-bistrifluoroethyl groups. Linker modifications did not substantially enhance the effect on GABAAR. Compound 23 [(2E,4E)-5-(1,3-benzodioxol-5-yl)-N,N-dipropyl-2,4-pentadienamide] induced the strongest modulation of GABAA (maximal GABA-induced chloride current modulation (IGABA-max = 1673% ± 146%, EC50 = 51.7 ± 9.5 μM), while 25 [(2E,4E)-5-(1,3-benzodioxol-5-yl)-N,N-dibutyl-2,4-pentadienamide] displayed the highest potency (EC50 = 13.8 ± 1.8 μM, IGA