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Sample records for anaphylatoxin receptor cd88

  1. C5a receptor (CD88) inhibition improves hypothermia-induced neuroprotection in an in vitro ischemic model.

    PubMed

    Thundyil, John; Pavlovski, Dale; Hsieh, Yu-Hsuan; Gelderblom, Mathias; Magnus, Tim; Fairlie, David P; Arumugam, Thiruma V

    2012-03-01

    The concept of 'salvageble penumbra' has prompted both scientists and physicians to explore various neuroprotective approaches that could be beneficial during stroke therapy. Unfortunately, most of them have proved ineffective in targeting multiple cellular death cascades incited within the ischemic penumbra. Hypothermia has been shown to be capable of addressing this problem to some extent. Although many studies have shown that hypothermia targets several cellular processes, its effects on innate immune receptor-mediated apoptotic death still remain unclear. Moreover, whether inhibiting the signaling of innate immune receptors like complement anaphylatoxin C5a receptor (CD88) plays a role in this hypothermic neuroprotection still need to be deciphered. Using various types of ischemic insults in different neuronal cells, we confirm that hypothermia does indeed attenuate apoptotic neuronal cell death in vitro and this effect can be further enhanced by pharmacologically blocking or knocking out CD88. Thus, our study raises a promising therapeutic possibility of adding CD88 antagonists along with hypothermia to improve stroke outcomes.

  2. The complement anaphylatoxin receptors are not required for the development of experimental autoimmune uveitis.

    PubMed

    Read, Russell W; Vogt, Susan D; Barnum, Scott R

    2013-11-15

    To determine if complement anaphylatoxin-mediated inflammation contributes to the development and progression of experimental autoimmune uveitis (EAU), we induced disease in wild type and complement anaphylatoxin receptor-deficient mice (C3a receptor(-/-), C5a receptor(-/-) and C3aR(-/-)/C5aR(-/-)) and evaluated the eyes three weeks post-induction. No differences in disease severity or in disease incidence were seen between wild type controls and anaphylatoxin receptor-deficient mice. Our data indicate that C3a and C5a-mediated functions are not critical to the development of EAU.

  3. The Complement Anaphylatoxin Receptors Are Not Required for the Development of Experimental Autoimmune Uveitis

    PubMed Central

    Read, Russell W.; Vogt, Susan D.; Barnum, Scott R.

    2013-01-01

    To determine if complement anaphylatoxin-mediated inflammation contributes to the development and progression of experimental autoimmune uveitis (EAU), we induced disease in wild type and complement anaphylatoxin receptor-deficient mice (C3a receptor−/−, C5a receptor−/− and C3aR−/−/C5aR−/−) and evaluated eyes three weeks post-induction. No differences in disease severity or in disease incidence were seen between wild type controls and anaphylatoxin receptor-deficient mice. Our data indicate that C3a and C5a-mediated functions are not critical to the development of EAU. PMID:24035596

  4. Molecular analysis of the bovine anaphylatoxin C5a receptor

    PubMed Central

    Nemali, Sailasree; Siemsen, Daniel W.; Nelson, Laura K.; Bunger, Peggy L.; Faulkner, Craig L.; Rainard, Pascal; Gauss, Katherine A.; Jutila, Mark A.; Quinn, Mark T.

    2008-01-01

    Recruitment of phagocytes to inflammatory sites involves the coordinated action of several chemoattractants, including the anaphylatoxin C5a. While the C5a receptor (C5aR) has been well characterized in humans and rodents, little is known about the bovine C5aR. Here, we report cloning of bovine C5R1, the gene encoding bovine C5aR. We also analyzed genomic sequence upstream of the C5R1 translation start site. Although the bovine C5aR amino acid sequence was well conserved among species, significant differences in conserved features were found, including major differences in the N terminus, intracellular loop 3, and transmembrane domain VII. Analysis of C5aR expression by flow cytometry and confocal microscopy demonstrated high levels of C5aR on all bovine neutrophils and a subset of bovine monocytes. C5aR was not expressed on resting or activated bovine lymphocytes, although C5aR message was present in these cells. C5aR was also expressed on a small subset of bovine mammary epithelial cells. Pharmacological analysis of bovine C5aR-mediated responses showed that bovine C5a and C5adesArg both induced dose-dependent calcium fluxes and chemotaxis in bovine neutrophils, with similar efficacy for both agonists. Treatment of bovine neutrophils with C5a or C5adesArg resulted in homologous desensitization of bovine C5aR and cross-desensitization to interleukin 8 (IL-8) and platelet-activating factor (PAF); whereas, treatment with IL-8 or PAF did not cross-desensitize the cells to C5a or C5adesArg. Overall, these studies provide important information regarding distinct structural and functional features that may contribute to the unique pharmacological properties of bovine C5aR. PMID:18480166

  5. C5a receptor (CD88) promotes motility and invasiveness of gastric cancer by activating RhoA

    PubMed Central

    Kaida, Takayoshi; Nitta, Hidetoshi; Kitano, Yuki; Yamamura, Kensuke; Arima, Kota; Izumi, Daisuke; Higashi, Takaaki; Kurashige, Junji; Imai, Katsunori; Hayashi, Hiromitsu; Iwatsuki, Masaaki; Ishimoto, Takatsugu; Hashimoto, Daisuke; Yamashita, Yoichi; Chikamoto, Akira; Imanura, Takahisa; Ishiko, Takatoshi; Beppu, Toru; Baba, Hideo

    2016-01-01

    Purpose Anaphylatoxin C5a is a strong chemoattractant of the complement system that binds the C5a receptor (C5aR). The expression of C5aR is associated with poor prognosis in several cancers. However, the role of C5aR in gastric cancer (GC) is unknown. The aim of this study was to examine the role of C5aR on GC cell motility and invasion. Experimental Design The mechanism of invasion via C5aR was assessed by analyzing cytoskeletal rearrangement and RhoA activity after C5a treatment. Moreover, we investigated the relationship between C5aR expression and the prognosis of GC patients. Results Two human GC cell lines (MKN1 and MKN7) had high C5aR expression. An invasion assay revealed that C5a stimulation promoted the invasive ability of MKN1 and MKN7 cells and that this was suppressed by knockdown of C5aR using siRNA or a C5aR-antagonist. Moreover, overexpression of C5aR in GC cells enhanced the conversion of RhoA-guanosine diphosphate (RhoA-GDP) to RhoA-guanosine triphosphate (RhoA-GTP) after C5a stimulation and caused morphological changes, including increased expression of stress fibers and filopodia. Examination of tumor specimens from 100 patients with GC revealed that high C5aR expression (35 of 100 samples, 35.0%) was associated with increased invasion depth, vascular invasion and advanced stage. The 5-year overall survival of patients with high or low C5aR expression was 58.2% and 88.5%, respectively (p=0.008). Conclusions This study is the first to demonstrate that C5aR promotes GC cell invasion by activating RhoA and is associated with a poor prognosis in GC patients. Therefore, this study provides a biomarker for GC patients who require an advanced therapeutic strategy. PMID:27756879

  6. Expression cloning of a receptor for C5a anaphylatoxin on differentiated HL-60 cells

    SciTech Connect

    Boulay, F.; Mery, L.; Tardif, M.; Brouchon, L.; Vignais, P. )

    1991-03-26

    A cDNA clone encoding the human C5a anaphylatoxin receptor has been isolated by expression cloning from a CDM8 expression library prepared from mRNA of human myeloid HL-60 cells differentiated to the granulocyte phenotype with dibutyryladenosine cyclic monophosphate. The cDNA clone was able to transfer to COS-7 cells the capacity to specifically bind iodinated human recombinant C5a. The cDNA was 2.3 kb long, with an open reading frame encoding a 350-residue polypeptide. Cross-linking of iodinated C5a to the plasma membrane of transfected COS cells revealed a complex with an apparent molecular mass of 52-55 kDa, similar to that observed for the constitutively expressed receptor in differentiated HL-60 cells or human neutrophils. Although differentiated HL-60 cells display a single class of binding sites, with a dissociation constant of approximately 800-900 pM, the C5a-R cDNA, expressed in COS cells, generates both high-affinity (1.7 nM) and low-affinity (20-25 nM) receptors. Sequence comparison established that the degree of sequence identity between the C5a receptor and the N-formlypeptide receptor is 34%.

  7. Complement anaphylatoxin receptors C3aR and C5aR are required in the pathogenesis of experimental autoimmune uveitis.

    PubMed

    Zhang, Lingjun; Bell, Brent A; Yu, Minzhong; Chan, Chi-Chao; Peachey, Neal S; Fung, John; Zhang, Xiaoming; Caspi, Rachel R; Lin, Feng

    2016-03-01

    Recent studies have suggested that reagents inhibiting complement activation could be effective in treating T cell mediated autoimmune diseases such as autoimmune uveitis. However, the precise role of the complement anaphylatoxin receptors (C3a and C5a receptors) in the pathogenesis of autoimmune uveitis remains elusive and controversial. We induced experimental autoimmune uveitis in mice deficient or sufficient in both C3a and C5a receptors and rigorously compared their retinal phenotype using various imaging techniques, including indirect ophthalmoscopy, confocal scanning laser ophthalmoscopy, spectral domain optical coherence tomography, topical endoscopic fundus imaging, and histopathological analysis. We also assessed retinal function using electroretinography. Moreover, we performed Ag-specific T cell recall assays and T cell adoptive transfer experiments to compare pathogenic T cell activity between wild-type and knockout mice with experimental autoimmune uveitis. These experiments showed that C3a receptor/C5a receptor-deficient mice developed much less severe uveitis than did control mice using all retinal examination methods and that these mice had reduced pathogenic T cell responses. Our data demonstrate that both complement anaphylatoxin receptors are important for the development of experimental autoimmune uveitis, suggesting that targeting these receptors could be a valid approach for treating patients with autoimmune uveitis.

  8. Expression and modulation of C5a receptor (CD88) on skin dendritic cells. Chemotactic effect of C5a on skin migratory dendritic cells.

    PubMed Central

    Morelli, A; Larregina, A; Chuluyán, I; Kolkowski, E; Fainboim, L

    1996-01-01

    Although it is known that dendritic cells (DC) migrate in response to inflammatory stimuli. There is little information about the expression of receptors for chemotactic factors on DC. The present study has demonstrated by double immunostaining and flow cytometry of Langerhan's cell (LC)-enriched epidermal cell suspensions that a small subpopulation (5-6%) of epidermal resident DC (rLC) expresses receptors for C5a (C5aR). Epidermal rLC positive for C5aR show a round-shape morphology, were located next to the basement membrane and express HLA-DR molecules higher than C5aR negative rLC. These observations suggest that rLC would express C5aR as part of their process of maturation during tissue trafficking. To investigate whether epidermal LC up-regulate C5aR along their differentiation pathway. LC were differentiated in vitro after culture in epidermal cell suspensions supplemented with granulocyte macrophage colony-stimulating factor (GM-CSF). As a result, in vitro differentiated LC increased the expression of C5aR up to 69% of the DC population. In accordance with this observation, interdigitating DC of secondary lymphoid organs (lymph node and tonsil) also expressed (5aR. Migratory CD1a positive DC that spontaneously migrated out of dermal or split-skin organ explants were also positive for C5aR and were used for chemotaxis and chemokinesis assays in response to human recombinant C5a (rC5a). Optimum migration to rC5a was observed at 10(-8)M with a sigmoidal dose response curve. Checkboard analysis demonstrated that locomotion in response to rC5a was chemotaxis and not chemokinesis. Images Figure 3 Figure 6 Figure 7 Figure 10 Figure 11 PMID:8911150

  9. The complement anaphylatoxin C3a receptor (C3aR) contributes to the inflammatory response in dextran sulfate sodium (DSS)-induced colitis in mice.

    PubMed

    Wende, Elisabeth; Laudeley, Robert; Bleich, André; Bleich, Eva; Wetsel, Rick A; Glage, Silke; Klos, Andreas

    2013-01-01

    Inflammatory bowel diseases are a critical public health issue, and as treatment options remain limited, there is a need to unravel the underlying pathomechanisms in order to identify new therapeutic targets. Complement activation was found in patients suffering from inflammatory bowel disease, and the complement anaphylatoxin C5a and its receptor C5aR have been implicated in disease pathogenesis in animal models of bowel inflammation. To further characterize complement-related pathomechanisms in inflammatory bowel disease, we have investigated the role of the anaphylatoxin C3a receptor in acute dextran sulfate sodium-induced colitis in mice. For this, colitis was induced in C3a receptor-deficient BALB/c and C57BL/6 mice, and disease severity was evaluated by clinical and histological examination, and by measuring the mRNA expression or protein levels of inflammatory mediators in the tissue. C3a receptor deficiency was partially protective in BALB/c mice, which had significantly reduced weight loss, clinical and histological scores, colon shortening, and CXCL-1/KC mRNA, myeloperoxidase and interleukin-6 tissue levels compared to the corresponding wild type mice. In C57BL/6 mice the differences between wild type and C3a receptor-deficient animals were much smaller and reached no significance. Our data demonstrate that the contribution of C3a receptor to disease pathogenesis and severity of dextran sulfate sodium-induced colitis in mice depends on the genetic background. Further studies will be required to clarify whether targeting of C3a receptor, possibly in combination with C5a receptor, might be considered as a therapeutic strategy for inflammatory bowel disease.

  10. Cloning and preliminary pharmacological characterization of the anaphylatoxin C5a receptor in the rabbit.

    PubMed

    Bachvarov, D R; Houle, S; Bachvarova, M; Bouthillier, J; St-Pierre, S A; Fukuoka, Y; Ember, J A; Marceau, F

    1999-09-01

    1 The rabbit receptor for C5a was cloned from a genomic library and found to be 79.5% identical to the human homologue, the highest degree of similarity found so far in nonprimate laboratory animals. 2 The rabbit C5a receptor stably expressed in RBL cells binds human 125I-C5a (2 nM). Unlabelled C5a and the C-terminal analogue N-acetyl-Tyr-Ser-Phe-Lys-Pro-Met-Pro-Leu-D-Ala-Arg (Ac-YSFKPMPLaR) were found to be competitors of that binding, the peptide analogue retaining approximately 0.1% of the affinity of human C5a. 3 The order of potency human C5a>Ac-YSFKPMPLaR was conserved in bioassays based on rabbits (relaxation of the isolated portal vein and pulmonary artery; acute in vivo neutropenia), but with a decreasing potency gap between the two compounds, a likely consequence of the resistance to peptidases of the analogue. 4 The molecular definition of the rabbit C5a receptor evidenced a high preservation degree of sequence and pharmacologic properties relative to the human ortholog receptor, thus defining a set of molecular tools for the investigation of the role of C5a in physiologic and pathologic models based on the rabbit (e.g. atherosclerosis, inflammation).

  11. The receptor for the complement C3a anaphylatoxin (C3aR) provides host protection against Listeria monocytogenes-induced apoptosis.

    PubMed

    Mueller-Ortiz, Stacey L; Morales, John E; Wetsel, Rick A

    2014-08-01

    Listeria monocytogenes is a Gram-positive intracellular bacterium that is acquired through tainted food and may lead to systemic infection and possible death. Despite the importance of the innate immune system in fighting L. monocytogenes infection, little is known about the role of complement and its activation products, including the potent C3a anaphylatoxin. In a model of systemic L. monocytogenes infection, we show that mice lacking the receptor for C3a (C3aR(-/-)) are significantly more sensitive to infection compared with wild-type mice, as demonstrated by decreased survival, increased bacterial burden, and increased damage to their livers and spleens. The inability of the C3aR(-/-) mice to clear the bacterial infection was not caused by defective macrophages or by a reduction in cytokines/chemokines known to be critical in the host response to L. monocytogenes, including IFN-γ and TNF-α. Instead, TUNEL staining, together with Fas, active caspase-3, and Bcl-2 expression data, indicates that the increased susceptibility of C3aR(-/-) mice to L. monocytogenes infection was largely caused by increased L. monocytogenes-induced apoptosis of myeloid and lymphoid cells in the spleen that are required for ultimate clearance of L. monocytogenes, including neutrophils, macrophages, dendritic cells, and T cells. These findings reveal an unexpected function of C3a/C3aR signaling during the host immune response that suppresses Fas expression and caspase-3 activity while increasing Bcl-2 expression, thereby providing protection to both myeloid and lymphoid cells against L. monocytogenes-induced apoptosis. Copyright © 2014 by The American Association of Immunologists, Inc.

  12. The Receptor for the Complement C3a Anaphylatoxin (C3aR) Provides Host Protection against Listeria monocytogenes Induced Apoptosis

    PubMed Central

    Mueller-Ortiz, Stacey L.; Morales, John E.; Wetsel, Rick A.

    2014-01-01

    Listeria monocytogenes (LM) is a Gram-positive intracellular bacterium that is acquired through tainted food and may lead to systemic infection and possible death. Despite the importance of the innate immune system in fighting LM infection, little is known about the role of complement and its activation products, including the potent C3a anaphylatoxin. In a model of systemic LM infection, we show here that mice lacking the receptor for C3a (C3aR-/-) are significantly more sensitive to infection compared to WT mice as demonstrated by decreased survival, increased bacterial burden, and increased damage to their livers and spleens. The inability of the C3aR-/- mice to clear the bacterial infection was not caused by defective macrophages or by reduction of cytokines/chemokines known to be critical in the host response to LM, including IFN-γ and TNF-α. Instead, TUNEL staining together with Fas, active caspase-3, and Bcl-2 expression data indicate that the increased susceptibility of C3aR-/- mice to LM infection was largely caused by increased LM-induced apoptosis of myeloid and lymphoid cells in the spleen that are required for ultimate clearance of LM, including neutrophils, macrophages, dendritic cells, and T cells. These findings reveal an unexpected function of C3a/C3aR signaling during the host immune response that suppresses Fas expression and caspase-3 activity while increasing Bcl-2 expression, thereby providing protection to both myeloid and lymphoid cells against LM-induced apoptosis. PMID:24981453

  13. C5L2, the Second C5a Anaphylatoxin Receptor, Suppresses LPS-Induced Acute Lung Injury.

    PubMed

    Wang, Ruobing; Lu, Bao; Gerard, Craig; Gerard, Norma P

    2016-11-01

    LPS-induced lung injury in the mouse is one of the most robust experimental models used for studies of acute lung injury (ALI) and acute respiratory distress syndrome in humans. Prior clinical and experimental studies support an important role for complement activation, particularly production of C5a, in the pathophysiology of human ALI/acute respiratory distress syndrome. In the mouse model, however, the precise role of C5a and its receptors is unclear. C5L2, an enigmatic second receptor for C5a, has been characterized, and results have generated substantial debate regarding its in vivo function. Our previous work with human neutrophils revealed a unique role for C5L2 in negatively modulating C5a-C5a receptor (C5aR)-mediated cellular activation, in which antibody-mediated blockade of C5L2 resulted in augmented C5a-C5aR responses. Here, we demonstrate that C5L2(-/-) mice (BALB/c background) administered intranasal LPS exhibit significantly more airway edema and hemorrhage than do wild-type animals. Bronchoalveolar lavage fluid and lung homogenates have significantly more neutrophils and myeloperoxidase activity, as well as proinflammatory cytokines and chemokines. When a blocking antibody against the C5aR was administered before LPS administration, the increased neutrophilic infiltration and cytokine levels were reversed. Thus, our data show not only that C5a contributes significantly to LPS-induced ALI in the mouse, but also that C5L2 plays an important antiinflammatory role in this model through actions resulting at least in part from negative modulation of C5a receptor activation.

  14. C4a: An Anaphylatoxin in Name Only.

    PubMed

    Barnum, Scott R

    2015-01-01

    Activation of complement leads to generation of the 3 anaphylatoxins C3a, C4a, and C5a. Although all 3 peptides are structurally similar, only C3a and C5a share a similar functional profile that includes the classic inflammatory activities and, more recently, developmental homing and regenerative properties among others. In contrast, the functional profile of C4a is questionable in most cases owing to contamination of C4a preparations with physiologically relevant levels of C3a and/or C5a. Combined with the absence of an identified C4a receptor and the inability of C4a to signal through the C3a and C5a receptors, it is clear that C4a should not be included in the family of complement anaphylatoxins.

  15. THE MECHANISM OF ANAPHYLATOXIN FORMATION

    PubMed Central

    Jobling, James W.; Petersen, William

    1914-01-01

    1. The unsaturated lipoids (serum antitrypsin) can be adsorbed from guinea pig serum, rabbit serum, and horse serum by kaolin, starch, agar, and bacteria. 2. Diphtheria toxin and cobra venom also reduce the serum antitrypsin, possibly because of their affinity for lipoids. 3. Anaphylatoxins represent sera rendered toxic by partial removal of serum antitrypsin. 4. The matrix of the protein split products lies in the serum proteins so exposed. 5. The amount of removal of serum antitrypsin depends on definite quantitative relations; very large amounts and very small amounts of adsorbing substances are least effective (kaolin, starch, and bacteria). 6. Bacteria previously treated with serum or with oils do not adsorb serum antitrypsin. 7. Bacteria treated with serum become more resistant to the action of trypsin. PMID:19867801

  16. *C5a/CD88 signaling alters blood-brain barrier integrity in lupus through NFκb

    PubMed Central

    Jacob, Alexander; Hack, Bradley; Chen, Peili; Quigg, Richard J.; Alexander, Jessy J.

    2011-01-01

    Inflammation is a key factor in a number of neurodegenerative diseases including systemic lupus erythematosus (SLE). The complement system is an important mechanism in initiating and amplifying inflammation. Our recent studies demonstrate that C5a, a protein fragment generated during complement activation could alter the blood-brain barrier (BBB) integrity, and thereby disturb the brain microenvironment. To understand the mechanism by which this occurs, we examined the effects of C5a on apoptosis, translocation of nuclear factor-κB (NFκb) and the expression of Iκbα, MAPK, CREB and TJ protein, zona occludens (ZO-1) in mouse brain endothelial cells. Apoptosis was examined by DNA laddering and caspase-3 activity and the distribution of the ZO-1 and the p65 subunit of NFκB were determined by immunofluorescence. Inhibition of CD88 reduced translocation of NFκb into the nucleus, altered ZO-1 at the interfaces of neighboring cells, decreased caspase-3 activity and prevented apoptosis in these cells. Our results indicate that signaling through CD88 regulates the BBB in a NFκb dependent manner. These studies suggest that the C5a receptor, CD88 is a promising therapeutic target that will reduce NFκb signaling cascades in inflammatory settings. PMID:21929539

  17. The C5a anaphylatoxin receptor (C5aR1) protects against Listeria monocytogenes infection by inhibiting type 1 IFN expression.

    PubMed

    Calame, Daniel G; Mueller-Ortiz, Stacey L; Morales, John E; Wetsel, Rick A

    2014-11-15

    Listeria monocytogenes is a major cause of mortality resulting from food poisoning in the United States. In mice, C5 has been genetically linked to host resistance to listeriosis. Despite this genetic association, it remains poorly understood how C5 and its activation products, C5a and C5b, confer host protection to this Gram-positive intracellular bacterium. In this article, we show in a systemic infection model that the major receptor for C5a, C5aR1, is required for a normal robust host immune response against L. monocytogenes. In comparison with wild-type mice, C5aR1(-/-) mice had reduced survival and increased bacterial burden in their livers and spleens. Infected C5aR1(-/-) mice exhibited a dramatic reduction in all major subsets of splenocytes, which was associated with elevated caspase-3 activity and increased TUNEL staining. Because type 1 IFN has been reported to impede the host response to L. monocytogenes through the promotion of splenocyte death, we examined the effect of C5aR1 on type 1 IFN expression in vivo. Indeed, serum levels of IFN-α and IFN-β were significantly elevated in L. monocytogenes-infected C5aR1(-/-) mice. Similarly, the expression of TRAIL, a type 1 IFN target gene and a proapoptotic factor, was elevated in NK cells isolated from infected C5aR1(-/-) mice. Treatment of C5aR1(-/-) mice with a type 1 IFNR blocking Ab resulted in near-complete rescue of L. monocytogenes-induced mortality. Thus, these findings reveal a critical role for C5aR1 in host defense against L. monocytogenes through the suppression of type 1 IFN expression. Copyright © 2014 by The American Association of Immunologists, Inc.

  18. Degradation of C3a anaphylatoxins by rat mast cells

    SciTech Connect

    Fukuoka, Y.; Hugli, T.E.

    1986-05-01

    Incubation of /sup 125/I-human C3a with rat peritoneal mast cells (RMC) causes extensive degradation of the ligand. Both cell-bound and free /sup 125/I-C3a (hu) was degraded by RMC, even at 0/sup 0/C, based on SDS-PAGE analysis. The authors examined several protease inhibitors for their ability to prevent degradation of /sup 125/I-C3a (hu). Degradation of /sup 125/I-C3a (hu) by RMC was not inhibited by leupeptin, antipain, elastatinal, pepstatin, ..cap alpha../sub 1/-antitrypsin or EDTA. TPCK and TLCK were only partially effective. PMSF, chymostatin and SBTI were most effective in preventing /sup 125/I-C3a (hu) degradation. These latter compounds are effective inhibitors of the chymotrypsin-like enzyme chymase extracted from RMC, as is TPCK, based on hydrolysis of the substrate BTEE. Degradation of cell-bound ligand is totally prevented only by PMSF (or DFP). Therefore, /sup 125/I-C3a (hu) bound to the RMC appears to be degraded predominantly by chymase; however the cell-bound ligand is attacked by other surface proteases. Degradation of rat C3a by RMC was examined. After incubation with RMC, cell-bound and free /sup 125/I-C3a (rat) showed no evidence of degradation with or without inhibitors present. From these results, the authors conclude that chymase may not play a significant role in regulating anaphylatoxin activity. Furthermore, the authors propose that rat C3a is a preferred ligand for identifying receptors on mast cells because of its resistance to proteolysis.

  19. 27-Oxygenated cholesterol induces expression of CXCL8 in macrophages via NF-κB and CD88

    SciTech Connect

    Kim, Sun-Mi; Lee, Chung Won; Kim, Bo-Young; Jung, Young-Suk; Eo, Seong-Kug; Park, Young Chul; Kim, Koanhoi

    2015-08-07

    We attempted to determine the effects of a milieu rich in cholesterol molecules on expression of chemokine CXCL8. A high-cholesterol diet led to an increased transcription of the IL-8 gene in the arteries and elevated levels of CXCL8 in sera of ApoE{sup −/−} mice, compared with those of wild-type C57BL/6 mice. Treatment of THP-1 monocyte/macrophage cells with 27-hydroxycholesterol (27OHChol) resulted in transcription of the IL-8 gene and increased secretion of its corresponding gene product whereas cholesterol did not induce expression of CXCL8 in THP-1 cells. 27OHChol-induced transcription of the IL-8 gene was blocked by cycloheximide, but not by polymyxin B. Treatment of THP-1 cells with 27OHChol caused translocation of p65 NF-κB subunit into the nucleus and up-regulation of CD88. Inhibition of NF-κB and CD88 using SN50 and W-54011, respectively, resulted in reduced transcription of the IL-8 gene and attenuated secretion of CXCL8 induced by 27OHChol. We propose that oxidatively modified cholesterol like 27OHChol, rather than cholesterol, is responsible for sustained expression of CXCL8 in monocytes/macrophages in atherosclerotic arteries. - Highlights: • Consumption of a high-cholesterol diet leads to increased CXCL8 expression in ApoE{sup −/−} mice. • 27OHChol, but not cholesterol, up-regulates expression of CXCL8 in macrophages. • 27OHChol enhances nuclear translocation of NF-κB and expression of CD88 in macrophages. • Inhibition of NF-κB or CD88 results in decreased CXCL8 expression induced by 27OHChol. • 27OHChol up-regulates CXCL8 expression via NF-κB and CD88 in macrophages.

  20. Cloning, expression, cellular distribution, and role in chemotaxis of a C5a receptor in rainbow trout: the first identification of a C5a receptor in a nonmammalian species

    USGS Publications Warehouse

    Boshra, Hani; Li, Jun; Peters, Rodney; Hansen, John; Matlapudi, Anjan; Sunyer, J. Oriol

    2004-01-01

    C3a, C4a, and C5a anaphylatoxins generated during complement activation play a key role in inflammation. C5a is the most potent of the three anaphylatoxins in eliciting biological responses. The effects of C5a are mediated by its binding to C5a receptor (C5aR, CD88). To date, C5aR has only been identified and cloned in mammalian species, and its evolutionary history remains ill-defined. To gain insights into the evolution, conserved structural domains, and functions of C5aR, we have cloned and characterized a C5aR in rainbow trout, a teleost fish. The isolated cDNA encoded a 350-aa protein that showed the highest sequence similarity to C5aR from other species. Genomic analysis revealed the presence of one continuous exon encoding the entire open reading frame. Northern blot analysis showed significant expression of the trout C5a receptor (TC5aR) message in PBLs and kidney. Flow cytometric analysis showed that two Abs generated against two different areas of the extracellular N-terminal region of TC5aR positively stained the same leukocyte populations from PBLs. B lymphocytes and granulocytes comprised the majority of cells recognized by the anti-TC5aR. More importantly, these Abs inhibited chemotaxis of PBLs toward a chemoattractant fraction purified from complement-activated trout serum. Our data suggest that the split between C5aR and C3aR from a common ancestral molecule occurred before the emergence of teleost fish. Moreover, we demonstrate that the overall structure of C5aR as well as its role in chemotaxis have remained conserved for >300 million years.

  1. Complement anaphylatoxin C3a is a potent inducer of embryonic chick retina regeneration

    PubMed Central

    Haynes, Tracy; Luz-Madrigal, Agustin; Reis, Edimara S.; Echeverri Ruiz, Nancy P.; Grajales-Esquivel, Erika; Tzekou, Apostolia; Tsonis, Panagiotis A.; Lambris, John D.; Del Rio-Tsonis, Katia

    2013-01-01

    Identifying the initiation signals for tissue regeneration in vertebrates is one of the major challenges in regenerative biology. Much of the research thus far has indicated that certain growth factors have key roles. Here we show that complement fragment C3a is sufficient to induce complete regeneration of the embryonic chick retina from stem/progenitor cells present in the eye, independent of fibroblast growth factor receptor signaling. Instead, C3a induces retina regeneration via STAT3 activation, which in turn activates the injury- and inflammation-responsive factors, IL-6, IL-8 and TNF-α. This activation sets forth regulation of Wnt2b, Six3 and Sox2, genes associated with retina stem and progenitor cells. Thus, our results establish a mechanism for retina regeneration based on injury and inflammation signals. Furthermore, our results indicate a unique function for complement anaphylatoxins that implicate these molecules in the induction and complete regeneration of the retina, opening new avenues of experimentation in the field. PMID:23942241

  2. Micrurus snake venoms activate human complement system and generate anaphylatoxins

    PubMed Central

    2012-01-01

    Background The genus Micrurus, coral snakes (Serpentes, Elapidae), comprises more than 120 species and subspecies distributed from the south United States to the south of South America. Micrurus snake bites can cause death by muscle paralysis and further respiratory arrest within a few hours after envenomation. Clinical observations show mainly neurotoxic symptoms, although other biological activities have also been experimentally observed, including cardiotoxicity, hemolysis, edema and myotoxicity. Results In the present study we have investigated the action of venoms from seven species of snakes from the genus Micrurus on the complement system in in vitro studies. Several of the Micrurus species could consume the classical and/or the lectin pathways, but not the alternative pathway, and C3a, C4a and C5a were generated in sera treated with the venoms as result of this complement activation. Micrurus venoms were also able to directly cleave the α chain of the component C3, but not of the C4, which was inhibited by 1,10 Phenanthroline, suggesting the presence of a C3α chain specific metalloprotease in Micrurus spp venoms. Furthermore, complement activation was in part associated with the cleavage of C1-Inhibitor by protease(s) present in the venoms, which disrupts complement activation control. Conclusion Micrurus venoms can activate the complement system, generating a significant amount of anaphylatoxins, which may assist due to their vasodilatory effects, to enhance the spreading of other venom components during the envenomation process. PMID:22248157

  3. Peptidyl arginine deiminase from Porphyromonas gingivalis abolishes anaphylatoxin C5a activity.

    PubMed

    Bielecka, Ewa; Scavenius, Carsten; Kantyka, Tomasz; Jusko, Monika; Mizgalska, Danuta; Szmigielski, Borys; Potempa, Barbara; Enghild, Jan J; Prossnitz, Eric R; Blom, Anna M; Potempa, Jan

    2014-11-21

    Evasion of killing by the complement system, a crucial part of innate immunity, is a key evolutionary strategy of many human pathogens. A major etiological agent of chronic periodontitis, the Gram-negative bacterium Porphyromonas gingivalis, produces a vast arsenal of virulence factors that compromise human defense mechanisms. One of these is peptidylarginine deiminase (PPAD), an enzyme unique to P. gingivalis among bacteria, which converts Arg residues in polypeptide chains into citrulline. Here, we report that PPAD citrullination of a critical C-terminal arginine of the anaphylatoxin C5a disabled the protein function. Treatment of C5a with PPAD in vitro resulted in decreased chemotaxis of human neutrophils and diminished calcium signaling in monocytic cell line U937 transfected with the C5a receptor (C5aR) and loaded with a fluorescent intracellular calcium probe: Fura-2 AM. Moreover, a low degree of citrullination of internal arginine residues by PPAD was also detected using mass spectrometry. Further, after treatment of C5 with outer membrane vesicles naturally shed by P. gingivalis, we observed generation of C5a totally citrullinated at the C-terminal Arg-74 residue (Arg74Cit). In stark contrast, only native C5a was detected after treatment with PPAD-null outer membrane vesicles. Our study suggests reduced antibacterial and proinflammatory capacity of citrullinated C5a, achieved via lower level of chemotactic potential of the modified molecule, and weaker cell activation. In the context of previous studies, which showed crosstalk between C5aR and Toll-like receptors, as well as enhanced arthritis development in mice infected with PPAD-expressing P. gingivalis, our findings support a crucial role of PPAD in the virulence of P. gingivalis.

  4. Peptidyl Arginine Deiminase from Porphyromonas gingivalis Abolishes Anaphylatoxin C5a Activity*

    PubMed Central

    Bielecka, Ewa; Scavenius, Carsten; Kantyka, Tomasz; Jusko, Monika; Mizgalska, Danuta; Szmigielski, Borys; Potempa, Barbara; Enghild, Jan J.; Prossnitz, Eric R.; Blom, Anna M.; Potempa, Jan

    2014-01-01

    Evasion of killing by the complement system, a crucial part of innate immunity, is a key evolutionary strategy of many human pathogens. A major etiological agent of chronic periodontitis, the Gram-negative bacterium Porphyromonas gingivalis, produces a vast arsenal of virulence factors that compromise human defense mechanisms. One of these is peptidylarginine deiminase (PPAD), an enzyme unique to P. gingivalis among bacteria, which converts Arg residues in polypeptide chains into citrulline. Here, we report that PPAD citrullination of a critical C-terminal arginine of the anaphylatoxin C5a disabled the protein function. Treatment of C5a with PPAD in vitro resulted in decreased chemotaxis of human neutrophils and diminished calcium signaling in monocytic cell line U937 transfected with the C5a receptor (C5aR) and loaded with a fluorescent intracellular calcium probe: Fura-2 AM. Moreover, a low degree of citrullination of internal arginine residues by PPAD was also detected using mass spectrometry. Further, after treatment of C5 with outer membrane vesicles naturally shed by P. gingivalis, we observed generation of C5a totally citrullinated at the C-terminal Arg-74 residue (Arg74Cit). In stark contrast, only native C5a was detected after treatment with PPAD-null outer membrane vesicles. Our study suggests reduced antibacterial and proinflammatory capacity of citrullinated C5a, achieved via lower level of chemotactic potential of the modified molecule, and weaker cell activation. In the context of previous studies, which showed crosstalk between C5aR and Toll-like receptors, as well as enhanced arthritis development in mice infected with PPAD-expressing P. gingivalis, our findings support a crucial role of PPAD in the virulence of P. gingivalis. PMID:25324545

  5. Expression of cytokines by human astrocytomas following stimulation by C3a and C5a anaphylatoxins: specific increase in interleukin-6 mRNA expression.

    PubMed

    Sayah, S; Ischenko, A M; Zhakhov, A; Bonnard, A S; Fontaine, M

    1999-06-01

    C3a and C5a anaphylatoxins are two proinflammatory peptides generated during complement activation that act through distinct Gi protein-coupled receptors named C3aR and C5aR, respectively. We have demonstrated previously that human astrocytes expressed C3aR and C5aR constitutively and were able to produce a functional complement. In this study, we examined the effect of an anaphylatoxin stimulation on cytokine expression by human astrocyte cell lines. Interleukin (IL)-1beta, IL-6, tumor necrosis factor-alpha, and transforming growth factor-beta mRNA expression was studied by quantitative RT-PCR. Whereas IL-1beta, tumor necrosis factor-alpha, and transforming growth factor-beta mRNA levels remained unchanged, stimulation of astrocytoma cells (T98G, CB193, U118MG) by C3a, C5a, and peptidic C3aR and C5aR agonists induced an increase in the IL-6 mRNA level. The amount of IL-6 was markedly increased at 3 and 6 h and returned to the basal level at 9 h of stimulation. This response was specific, because pretreatment of cells with pertussis toxin or with polyclonal anti-C3aR or anti-C5aR antibodies completely blocked the IL-6 mRNA increase. The IL-6 response was also investigated at the protein level, but IL-6 protein was detected neither in cell lysates nor in supernatants of stimulated cells. The anaphylatoxin-mediated transcriptional activation of IL-6 gene suggests that C3a and C5a could play a role in priming glial cells during the inflammatory process in the brain.

  6. Control of the collective migration of enteric neural crest cells by the Complement anaphylatoxin C3a and N-cadherin

    PubMed Central

    Broders-Bondon, Florence; Paul-Gilloteaux, Perrine; Gazquez, Elodie; Heysch, Julie; Piel, Matthieu; Mayor, Roberto; Lambris, John D.; Dufour, Sylvie

    2016-01-01

    We analyzed the cellular and molecular mechanisms governing the adhesive and migratory behavior of enteric neural crest cells (ENCCs) during their collective migration within the developing mouse gut. We aimed to decipher the role of the complement anaphylatoxin C3a during this process, because this well-known immune system attractant has been implicated in cephalic NCC co-attraction, a process controlling directional migration. We used the conditional Ht-PA-cre transgenic mouse model allowing a specific ablation of the N-cadherin gene and the expression of a fluorescent reporter in migratory ENCCs without affecting the central nervous system. We performed time-lapse videomicroscopy of ENCCs from control and N-cad-herin mutant gut explants cultured on fibronectin (FN) and micropatterned FN-stripes with C3a or C3aR antagonist, and studied cell migration behavior with the use of triangulation analysis to quantify cell dispersion. We performed ex vivo gut cultures with or without C3aR antagonist to determine the effect on ENCC behavior. Confocal microscopy was used to analyze the cell-matrix adhesion properties. We provide the first demonstration of the localization of the complement anaphylatoxin C3a and its receptor on ENCCs during their migration in the embryonic gut. C3aR receptor inhibition alters ENCC adhesion and migration, perturbing directionality and increasing cell dispersion both in vitro and ex vivo. N-cad-herin-null ENCCs do not respond to C3a co-attraction. These findings indicate that C3a regulates cell migration in a N-cadherin-dependent process. Our results shed light on the role of C3a in regulating collective and directional cell migration, and in ganglia network organization during enteric nervous system ontogenesis. The detection of an immune system chemokine in ENCCs during ENS development may also shed light on new mechanisms for gastrointestinal disorders. PMID:27041467

  7. Control of the collective migration of enteric neural crest cells by the Complement anaphylatoxin C3a and N-cadherin.

    PubMed

    Broders-Bondon, Florence; Paul-Gilloteaux, Perrine; Gazquez, Elodie; Heysch, Julie; Piel, Matthieu; Mayor, Roberto; Lambris, John D; Dufour, Sylvie

    2016-06-01

    We analyzed the cellular and molecular mechanisms governing the adhesive and migratory behavior of enteric neural crest cells (ENCCs) during their collective migration within the developing mouse gut. We aimed to decipher the role of the complement anaphylatoxin C3a during this process, because this well-known immune system attractant has been implicated in cephalic NCC co-attraction, a process controlling directional migration. We used the conditional Ht-PA-cre transgenic mouse model allowing a specific ablation of the N-cadherin gene and the expression of a fluorescent reporter in migratory ENCCs without affecting the central nervous system. We performed time-lapse videomicroscopy of ENCCs from control and N-cadherin mutant gut explants cultured on fibronectin (FN) and micropatterned FN-stripes with C3a or C3aR antagonist, and studied cell migration behavior with the use of triangulation analysis to quantify cell dispersion. We performed ex vivo gut cultures with or without C3aR antagonist to determine the effect on ENCC behavior. Confocal microscopy was used to analyze the cell-matrix adhesion properties. We provide the first demonstration of the localization of the complement anaphylatoxin C3a and its receptor on ENCCs during their migration in the embryonic gut. C3aR receptor inhibition alters ENCC adhesion and migration, perturbing directionality and increasing cell dispersion both in vitro and ex vivo. N-cadherin-null ENCCs do not respond to C3a co-attraction. These findings indicate that C3a regulates cell migration in a N-cadherin-dependent process. Our results shed light on the role of C3a in regulating collective and directional cell migration, and in ganglia network organization during enteric nervous system ontogenesis. The detection of an immune system chemokine in ENCCs during ENS development may also shed light on new mechanisms for gastrointestinal disorders.

  8. Negative regulation of pulmonary Th17 responses by C3a anaphylatoxin during allergic inflammation in mice.

    PubMed

    Lim, Hoyong; Kim, Young Uk; Drouin, Scott M; Mueller-Ortiz, Stacey; Yun, Kyoungah; Morschl, Eva; Wetsel, Rick A; Chung, Yeonseok

    2012-01-01

    Activation of complement is one of the earliest immune responses to exogenous threats, resulting in various cleavage products including anaphylatoxin C3a. In addition to its contribution to host defense, C3a has been shown to mediate Th2 responses in animal models of asthma. However, the role of C3a on pulmonary Th17 responses during allergic inflammation remains unclear. Here, we show that mice deficient in C3a receptor (C3aR) exhibited (i) higher percentages of endogenous IL-17-producing CD4(+) T cells in the lungs, (ii) higher amounts of IL-17 in the bronchoalveolar lavage fluid, and (iii) more neutrophils in the lungs than wild-type mice when challenged with intranasal allergens. Moreover, adoptive transfer experiments showed that the frequencies of antigen-specific IL-17-producing CD4(+) T cells were significantly higher in the lungs and bronchial lymph nodes of C3aR-deficient recipients than those of wild-types recipients. Bone-marrow reconstitution study indicated that C3aR-deficiency on hematopoietic cells was required for the increased Th17 responses. Furthermore, C3aR-deficient mice exhibited increased percentages of Foxp3(+) regulatory T cells; however, depletion of these cells minimally affected the induction of antigen-specific Th17 cell population in the lungs. Neutralization of IL-17 significantly reduced the number of neutrophils in bronchoalveolar lavage fluid of C3aR-deficient mice. Our findings demonstrate that C3a signals negatively regulate antigen-specific Th17 responses during allergic lung inflammation and the size of Foxp3(+) regulatory T cell population in the periphery.

  9. Human C5a anaphylatoxin: gene cloning and expression in Escherichia coli.

    PubMed

    Bautsch, W; Emde, M; Kretzschmar, T; Köhl, J; Suckau, D; Bitter-Suermann, D

    1992-06-01

    A gene coding for the human anaphylatoxin C5a was cloned and expressed in Escherichia coli. A combination of reverse transcription of mRNA of the U937 cell line with subsequent preparative polymerase chain reaction was employed to obtain the gene. The sequence was cloned into the plasmid vector pKK 233-2 behind an ATG initiation codon under the control of a trc promotor. After purification by ion exchange chromatography and reversed phase FPLC a mixture of predominantly non-glycosylated recombinant human C5a with a beta-mercaptoethanol adduct at cysteine 27 and the N-methionyl derivative was obtained which was homogeneous on silver-stained gels, immunoreactive with C5a-specific monoclonal antibodies and functionally active in releasing myeloperoxidase from human granulocytes and ATP from guinea pig platelets. The final yield was about 0.4-0.8 mg purified recombinant C5a per liter bacterial culture.

  10. Intratracheal administration of anaphylatoxin C5a potentiates antigen-induced pulmonary reactions through the prolonged production of cysteinyl-leukotrienes.

    PubMed

    Kodani, M; Sakata, N; Takano, Y; Kamiya, H; Katsuragi, T; Hugli, T E; Abe, M

    2000-09-01

    The effects of intratracheal administration of anaphylatoxin C5a on airway inflammation have been studied using two sources of material, zymosan activated serum (ZAS) and purified rat C5a des Arg, in order to determine the influence of complement activation on allergic airway disorders.The intratracheal administration of ovalbumin (OA) to OA-sensitized rats generated two phases of airway response, an immediate airway response (IAR) occurring within 15 min and a late airway response (LAR) beginning 4-6 h after the allergen challenge. The simultaneous administration of ZAS and OA into the trachea generated a sustained elevation of airway resistance (Raw) following IAR, while that of OA or ZAS alone resulted in Raw returning nearly to the baseline just after the IAR. The elevation of Raw after the combined challenge of OA and ZAS was significantly inhibited by pretreatment with a CysLT(1) receptor antagonist, pranlukast 30 mg/kg, but after that OA or ZAS alone was not significantly inhibited by pranlukast. The intratracheal administration of purified C5a produced an airway response that was similar to, but higher than, that evoked by ZAS. Namely, the challenge with OA plus C5a resulted in a higher IAR than OA plus ZAS, and also caused an early animal death up to 6 h, which was prevented by a combined pretreatment with pranlukast and the H(1) receptor antagonist, diphenhydramine.A histological examination at 6 h after the OA challenge identified an infiltration of inflammatory cells into the bronchial submucosal tissue, with a predominance of neutrophils and fewer eosinophils. On the other hand, a histological examination after the OA and ZAS challenge showed more severe infiltration of granulocytes into the bronchial submucosal tissue than that with OA or ZAS alone. The challenge with OA plus C5a was associated with severe perivascular leakage in the lungs and the combined pretreatment with both the antagonists led to a marked reduction in perivascular leakage. The

  11. Inhibition by prostaglandin E(2) of anaphylatoxin C5a- but not zymosan-induced prostanoid release from rat Kupffer cells.

    PubMed

    Pestel, Sabine; Jungermann, Kurt; Götze, Otto; Schieferdecker, Henrike L

    2002-04-01

    The proinflammatory anaphylatoxin C5a induces the release of prostanoids, ie, prostaglandins (PG) and thromboxane (TX), from the resident liver macrophages (Kupffer cells [KC]). Because KC themselves express prostanoid receptors, prostanoids--besides having paracrine functions--might regulate their own release in an autocrine loop. So far, such a possible feedback regulation has not been investigated systematically, probably because of methodological difficulties to measure newly synthesized prostanoids in the presence of added prostanoids. Here, after prelabeling of phospholipids with [(14)C]arachidonate, cellularly formed [(14)C]prostanoids were determined in the presence of added unlabelled prostanoids by thin layer chromatography. In cultured KC, recombinant rat C5a (rrC5a) rapidly increased PGD(2), PGE(2), and TXA(2) release, which was strongly reduced by PGE(2), but neither by PGD(2) nor by the TXA(2) analog U46619. The inhibitory effect of PGE(2) was mimicked by cAMP, indicating that the G(s)-coupled PGE(2) receptors type 2 or 4 were involved. Zymosan also enhanced prostanoid release from KC, but with slightly slower kinetics; this action was neither inhibited by PGE(2) nor by cAMP. Also in perfused rat livers, rrC5a enhanced prostanoid release from KC as shown by prostanoid overflow and thereby indirectly increased glucose output from hepatocytes. Again, PGE(2), but not PGD(2), inhibited rrC5a-elicited prostanoid overflow. This resulted in a complete inhibition of rrC5a-induced, prostanoid-mediated glucose output. Thus, PGE(2) can inhibit specifically the C5a-induced prostanoid release from KC via a feedback mechanism and thereby limit prostanoid-mediated hepatocellular defense reactions, eg, glucose release.

  12. Differences in the involvement of prostanoids from Kupffer cells in the mediation of anaphylatoxin C5a-, zymosan-, and lipopolysaccharide-dependent hepatic glucose output and flow reduction.

    PubMed

    Pestel, Sabine; Schlaf, Gerald; Götze, Otto; Jungermann, Kurt; Schieferdecker, Henrike L

    2003-12-01

    Various inflammatory stimuli such as anaphylatoxin C5a, zymosan, and lipopolysaccharides (LPSs) have been reported both to enhance glucose output in the perfused rat liver and to induce prostanoid (ie, prostaglandin and thromboxane) release from Kupffer cells, the resident liver macrophages. Because prostanoids can enhance glucose output from hepatocytes, it was the aim of this study to compare the possible roles of prostanoids released after C5a, zymosan, and LPS in the mediation of hepatic glucose output. In perfused livers both C5a and zymosan immediately enhanced glucose output, reduced flow, and induced prostanoid overflow into the hepatic vein, but with different quantities and kinetics. Only the C5a-induced but not the zymosan-induced effects were abrogated by inhibitors of prostanoid signaling as the prostanoid synthesis inhibitor indomethacin and the thromboxane receptor antagonist daltroban. In contrast to C5a and zymosan, LPS had no effect on glucose output, flow rate, or prostanoid overflow. In isolated Kupffer cells, C5a and zymosan induced maximal release of prostaglandins D(2) and E(2) and of thromboxane A(2) within a period of 0 to 2 minutes and 5 to 15 minutes, respectively. In pulse-chase experiments, maximal prostanoid release was already observed after 2 minutes of continuous stimulation with C5a, but only after 10 to 15 minutes of continuous stimulation with zymosan. LPS-dependent prostanoid release was not seen before 1 hour. Thus, even though C5a, zymosan, and LPS induced prostanoid release from Kupffer cells, only C5a quickly regulated hepatic glucose metabolism in a prostanoid-dependent manner (due to the kinetics and quantities of prostanoids released).

  13. C5a of Cynoglossus semilaevis has anaphylatoxin-like properties and promotes antibacterial and antiviral defense.

    PubMed

    Li, Mo-fei; Hu, Yong-hua

    2016-07-01

    Activation of the complement system leads to the cleavage of component factor C5 into C5a and C5b. C5a can induce chemotaxis and inflammatory responses in mammals. The function of C5a in fish is poorly understood. In this study, we report the identification and analysis of a C5 homologue, CsC5, from tongue sole (Cynoglossus semilaevis). CsC5 is composed of 1683 amino acid residues that include an anaphylatoxin homologous domain. Expression of CsC5 could be detected in a variety of tissues and was up-regulated by bacterial or viral pathogen infection. Purified recombinant CsC5a (rCsC5a) could bind to peripheral blood leukocytes (PBL) and stimulate PBL chemotaxis, proliferation, respiratory burst, acid phosphatase activity, and phagocytosis. Tongue sole administered rCsC5a exhibited enhanced resistance against bacterial and viral infections. These results indicate that CsC5a is an anaphylatoxin with a role in innate immune defense against bacterial and viral infections.

  14. Potentiation of the anaphylatoxins in vivo using an inhibitor of serum carboxypeptidase N (SCPN). I. Lethality and pathologic effects on pulmonary tissue.

    PubMed Central

    Huey, R.; Bloor, C. M.; Kawahara, M. S.; Hugli, T. E.

    1983-01-01

    Carboxypeptidase N (EC 3.4.12.7) (SCPN) is a plasma enzyme that efficiently inactivates the anaphylatoxins C3a and C4a and significantly reduces C5a spasmogenic activity by removing the C-terminal arginyl residue from each of these factors. The arginine analog DL-2-mercaptomethyl-3-guanidinoethylthiopropanoic acid (SCPN-INH) is a potent competitive inhibitor of SCPN with a Ki for this carboxypeptidase in serum of 2 x 10(-9) M. Therefore, we have used the SCPN inhibitor to potentiate biologic activity of the anaphylatoxins in vivo. Infusion via the carotid artery of about 40 mg of SCPN-INH into each of 8 adult guinea pigs inactivated the SCPN for at least 3 hours and caused no measurable toxic effects. When cobra venom factor (CVF) is infused into guinea pigs, it activates the alternative pathway of complement, thereby generating the anaphylatoxins C3a and C5a. Ordinarily, infusion of CVF is nonlethal, because the generated anaphylatoxins are rapidly converted to C3a des Arg and C5a des Arg by SCPN. However, CVF (200 micrograms) plus SCPN-INH delivered intravenously in 5 animals induced a lethal reaction in less than 5 minutes. The authors conclude that the lethal effect is due largely to the anaphylatoxins. Histologic sections of the lungs from treated animals show dramatic structural changes consistent with peripheral small airway constriction, bronchial constriction, and vasoconstriction of small muscular arteries. Also, cell aggregates are present in blood vessels. Other histologic changes include severe congestion, pulmonary edema, and an interstitial infiltrate of mononuclear cells. Large doses of chlorpheniramine prevent this lethal reaction. Lethality is apparently attributable to asphyxia and is dependent on the level of CVF administered: eg, 100 micrograms CVF was not lethal in 4 animals given SCPN inhibitor, although signs of respiratory distress were observed. On histologic examination of lungs from guinea pigs given CVF and SCPN-INH, the features are

  15. Structural basis for the targeting of complement anaphylatoxin C5a using a mixed L-RNA/L-DNA aptamer

    NASA Astrophysics Data System (ADS)

    Yatime, Laure; Maasch, Christian; Hoehlig, Kai; Klussmann, Sven; Andersen, Gregers R.; Vater, Axel

    2015-04-01

    L-Oligonucleotide aptamers (Spiegelmers) consist of non-natural L-configured nucleotides and are of particular therapeutic interest due to their high resistance to plasma nucleases. The anaphylatoxin C5a, a potent inflammatory mediator generated during complement activation that has been implicated with organ damage, can be efficiently targeted by Spiegelmers. Here, we present the first crystallographic structures of an active Spiegelmer, NOX-D20, bound to its physiological targets, mouse C5a and C5a-desArg. The structures reveal a complex 3D architecture for the L-aptamer that wraps around C5a, including an intramolecular G-quadruplex stabilized by a central Ca2+ ion. Functional validation of the observed L-aptamer:C5a binding mode through mutational studies also rationalizes the specificity of NOX-D20 for mouse and human C5a against macaque and rat C5a. Finally, our structural model provides the molecular basis for the Spiegelmer affinity improvement through positional L-ribonucleotide to L-deoxyribonucleotide exchanges and for its inhibition of the C5a:C5aR interaction.

  16. Functional analysis and quantification of the complement C3 derived anaphylatoxin C3a with a monoclonal antibody.

    PubMed Central

    Burger, R; Bader, A; Kirschfink, M; Rother, U; Schrod, L; Wörner, I; Zilow, G

    1987-01-01

    The C3 fragment C3a belongs to the anaphylatoxins. It has immune regulatory activity and contributes to the pathogenesis of the adult respiratory distress syndrome (ARDS). The low molecular weight (9 kD) of C3a complicates the production of antibodies to C3a. We obtained a monoclonal antibody (designated H13) to human C3a. It reacts with C3a or C3a-desArg and with native C3 but not with C5 or C5a. In immunoblot analysis it reacts with the alpha- but not with beta-chain of C3 and binds to a protein with a mol. wt of about 10 kD present in zymosan-activated sera which is only marginally detectable in nonactivated serum and absent in plasma. H13 crossreacts with the analogous proteins of rabbit, guinea pig and sheep. H13 has the capacity to bind 125I-radiolabelled C3a efficiently but fails totally to react with 125I-C5a or with other C3 alpha-chain fragments. H13 blocks C3a functional activity. It markedly inhibits C3a-induced 3H-serotonin release from platelets in vitro and similarly inhibits the C3a-induced extravasation of Evans blue into the skin in vivo. H13 does not interfere with the haemolytic activity of C3. An ELISA system was established using H13 which permits quantification of C3a in sera of polytrauma patients. The antibody H13 should facilitate further functional analysis of C3a in experimental systems. It should be useful for quantification of C3a in diagnostic assays and also for application in immunopathology. Images Fig. 3 PMID:3498585

  17. A regulatory role for the C5a anaphylatoxin in type 2 immunity in asthma

    PubMed Central

    Köhl, Jörg; Baelder, Ralf; Lewkowich, Ian P.; Pandey, Manoj K.; Hawlisch, Heiko; Wang, Lihua; Best, Jennifer; Herman, Nancy S.; Sproles, Alyssa A.; Zwirner, Jörg; Whitsett, Jeffrey A.; Gerard, Craig; Sfyroera, Georgia; Lambris, John D.; Wills-Karp, Marsha

    2006-01-01

    Complement component 5 (C5) has been described as either promoting or protecting against airway hyperresponsiveness (AHR) in experimental allergic asthma, suggesting pleomorphic effects of C5. Here we report that local pharmacological targeting of the C5a receptor (C5aR) prior to initial allergen sensitization in murine models of inhalation tolerance or allergic asthma resulted in either induction or marked enhancement of Th2-polarized immune responses, airway inflammation, and AHR. Importantly, C5aR-deficient mice exhibited a similar, increased allergic phenotype. Pulmonary allergen exposure in C5aR-targeted mice resulted in increased sensitization and accumulation of CD4+CD69+ T cells associated with a marked increase in pulmonary myeloid, but not plasmacytoid, DC numbers. Pulmonary DCs from C5aR-targeted mice produced large amounts of CC chemokine ligand 17 (CCL17) and CCL22 ex vivo, suggesting a negative impact of C5aR signaling on pulmonary homing of Th2 cells. In contrast, C5aR targeting in sensitized mice led to suppressed airway inflammation and AHR but was still associated with enhanced production of Th2 effector cytokines. These data suggest a dual role for C5a in allergic asthma, i.e., protection from the development of maladaptive type 2 immune responses during allergen sensitization at the DC/T cell interface but enhancement of airway inflammation and AHR in an established inflammatory environment. PMID:16511606

  18. Targeted Disruption of the Gene Encoding the Murine Small Subunit of Carboxypeptidase N (CPN1) Causes Susceptibility to C5a Anaphylatoxin-Mediated Shock1

    PubMed Central

    Mueller-Ortiz, Stacey L.; Wang, Dachun; Morales, John E.; Li, Li; Chang, Jui-Yoa; Wetsel, Rick A.

    2015-01-01

    Carboxypeptidase N (CPN) is a plasma zinc metalloprotease, which consists of two enzymatically active small subunits (CPN1) and two large subunits (CPN2) that protect the protein from degradation. Historically, CPN has been implicated as a major regulator of inflammation by its enzymatic cleavage of functionally important arginine and lysine amino acids from potent phlogistic molecules, such as the complement anaphylatoxins C3a and C5a. Because of no known complete CPN deficiencies, the biological impact of CPN in vivo has been difficult to evaluate. Here, we report the generation of a mouse with complete CPN deficiency by targeted disruption of the CPN1 gene. CPN1−/− mice were hypersensitive to lethal anaphylactic shock due to acute complement activation by cobra venom factor. This hypersensitivity was completely resolved in CPN1−/−/C5aR−/− but not in CPN1−/−/C3aR−/− mice. Moreover, CPN1−/− mice given C5a i.v., but not C3a, experienced 100% mortality. This C5a-induced mortality was reduced to 20% when CPN1−/− mice were treated with an antihistamine before C5a challenge. These studies describe for the first time a complete deficiency of CPN and demonstrate 1) that CPN plays a requisite role in regulating the lethal effects of anaphylatoxin-mediated shock, 2) that these lethal effects are mediated predominantly by C5a-induced histamine release, and 3) that C3a does not contribute significantly to shock following acute complement activation. PMID:19414808

  19. Crystal Structure of Glyceraldehyde-3-Phosphate Dehydrogenase from the Gram-Positive Bacterial Pathogen A. vaginae, an Immunoevasive Factor that Interacts with the Human C5a Anaphylatoxin

    PubMed Central

    Querol-García, Javier; Fernández, Francisco J.; Marin, Ana V.; Gómez, Sara; Fullà, Daniel; Melchor-Tafur, Cecilia; Franco-Hidalgo, Virginia; Albertí, Sebastián; Juanhuix, Jordi; Rodríguez de Córdoba, Santiago; Regueiro, José R.; Vega, M. Cristina

    2017-01-01

    The Gram-positive anaerobic human pathogenic bacterium Atopobium vaginae causes most diagnosed cases of bacterial vaginosis as well as opportunistic infections in immunocompromised patients. In addition to its well-established role in carbohydrate metabolism, D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from Streptococcus pyogenes and S. pneumoniae have been reported to act as extracellular virulence factors during streptococcal infections. Here, we report the crystal structure of GAPDH from A. vaginae (AvGAPDH) at 2.19 Å resolution. The refined model has a crystallographic Rfree of 22.6%. AvGAPDH is a homotetramer wherein each subunit is bound to a nicotinamide adenine dinucleotide (NAD+) molecule. The AvGAPDH enzyme fulfills essential glycolytic as well as moonlight (non-glycolytic) functions, both of which might be targets of chemotherapeutic intervention. We report that AvGAPDH interacts in vitro with the human C5a anaphylatoxin and inhibits C5a-specific granulocyte chemotaxis, thereby suggesting the participation of AvGAPDH in complement-targeted immunoevasion in a context of infection. The availability of high-quality structures of AvGAPDH and other homologous virulence factors from Gram-positive pathogens is critical for drug discovery programs. In this study, sequence and structural differences between AvGAPDH and related bacterial and eukaryotic GAPDH enzymes are reported in an effort to understand how to subvert the immunoevasive properties of GAPDH and evaluate the potential of AvGAPDH as a druggable target. PMID:28443070

  20. Identification of classical anaphylatoxin as the des-Arg form of the C5a molecule: Evidence of a modulator role for the oligosaccharide unit in human des-Arg74-C5a

    PubMed Central

    Gerard, Craig; Hugli, Tony E.

    1981-01-01

    A functionally active and potentially lethal fragment of the fifth component of complement (C5) is generated during complement activation in serum from animals of various species. This factor, termed the “classical” anaphylatoxin, was isolated from porcine serum and was identified chemically as the des-Arg derivative of the well-characterized C5a molecule. Unlike the C3a and C4a anaphylatoxins, porcine C5a does not require the COOH-terminal arginyl residue for spasmogenic activity. Further degradation of porcine des-Arg74-C5a by carboxypeptidase Y removed glycine-73 and leucine-72 and decreased the intrinsic spasmogenic activity by >90%. Hence, we conclude that, although the arginyl residue is not essential, the COOH-terminal sequence Leu-Gly-Arg contributes structural information that accounts for >90% of C5a activity. Human des-Arg74-C5a, like its porcine counterpart, has instrinsic anaphylatoxin activity; however, higher concentrations were needed to contract the guinea pig ileal tissue (i.e., 1 μM for human des-Arg74-C5a versus 1 nM for porcine des-Arg74-C5a). Furthermore, the des-Arg form of human C5a was only 0.1% as active as porcine des-Arg74-C5a for enhancing vascular permeability in guinea pig skin. In addition to these biological differences, numerous chemical differences exist between the human and porcine des-Arg74-C5a molecules, the most prominent feature being an oligosaccharide entity associated uniquely with the human C5a. When the oligosaccharide unit of human des-Arg74-C5a was removed by glycosidases, leaving a single glucosamine residue attached to the side chain of asparagine-64, activity was enhanced. The human des-Arg74-C5a molecule devoid of the complex oligosaccharide unit exhibited 10-fold stronger spasmogenic activity and 20- to 50-fold greater permeability-enhancing activity than did human des-Arg74-C5a containing the oligosaccharide. Consequently, the oligosaccharide associated with human C5a modulates or suppresses potentially

  1. Contribution of anaphylatoxin C5a to late airway responses after repeated exposure of antigen to allergic rats.

    PubMed

    Abe, M; Shibata, K; Akatsu, H; Shimizu, N; Sakata, N; Katsuragi, T; Okada, H

    2001-10-15

    We attempted to elucidate the contribution of complement to allergic asthma. Rat sensitized to OVA received repeated intratracheal exposures to OVA for up to 3 consecutive days, and pulmonary resistance was then estimated for up to 6 h after the last exposure. Whereas the immediate airway response (IAR) in terms of R(L) tended to decrease in proportion to the number of OVA exposures, late airway response (LAR) became prominent only after three. Although premedication with two kinds of complement inhibitors, soluble complement receptor type 1 (sCR1) or nafamostat mesylate, resulted in inhibition of the IAR after either a single or a double exposure, the LAR was inhibited after the triple. Premedication with a C5a receptor antagonist (C5aRA) before every exposure to OVA also inhibited the LAR after three. Repeated OVA exposure resulted in eosinophil and neutrophil infiltration into the bronchial submucosa which was suppressed by premedication with sCR1 or C5aRA. Up-regulation of C5aR mRNA was shown in lungs after triple OVA exposure, but almost no up-regulation of C3aR. Pretreatment with sCR1 or C5aRA suppressed the up-regulation of C5aR expression as well as cytokine messages in the lungs. The suppression of LAR by pretreatment with sCR1 was reversed by intratracheal instillation of rat C5a desArg the action of which was inhibited by C5aRA. In contrast, rat C3a desArg or cytokine-induced neutrophil chemoattractant-1 induced cellular infiltration into the bronchial submucosa by costimulation with OVA, but these had no influence on the LAR. These differences might be explained by the fact that costimulation with OVA and C5a synergistically potentiated IAR, whereas that with OVA and either C3a or cytokine-induced neutrophil chemoattractant-1 did not. C5a generated by Ag-Ab complexes helps in the production of cytokines and contributes to the LAR after repeated exposure to Ag.

  2. Immune receptors and adhesion molecules in human pulmonary leptospirosis.

    PubMed

    Del Carlo Bernardi, Fabiola; Ctenas, Bruno; da Silva, Luiz Fernando Ferraz; Nicodemo, Antonio Carlos; Saldiva, Paulo Hilário Nascimento; Dolhnikoff, Marisa; Mauad, Thais

    2012-10-01

    Pulmonary involvement in leptospirosis has been increasingly reported in the last 20 years, being related to the severity and mortality of the disease. The pathogenesis of pulmonary hemorrhage in leptospirosis is not understood. Lung endothelial cells have been proposed as targets in the pathogenesis of lung involvement in leptospirosis through the activation of Toll-like receptor 2 or the complement system, which stimulates the release of cytokines that lead to the activation of adhesion molecules. The aim of this study was to investigate the involvement of immune pathways and of the intercellular and vascular cell adhesion molecules (intercellular adhesion molecule and vascular cell adhesion molecule, respectively) in the lungs of patients with pulmonary involvement of leptospirosis. We studied the lungs of 18 patients who died of leptospirosis and compared them with 2 groups of controls: normal and noninfectious hemorrhagic lungs. Using immunohistochemistry and image analysis, we quantified the expression of the C3a anaphylatoxin receptor, intercellular adhesion molecule, vascular cell adhesion molecule, and Toll-like receptor 2 in small pulmonary vessels and in the alveolar septa. There was an increased expression of intercellular adhesion molecule (P < .03) and C3a anaphylatoxin receptor (P < .008) in alveolar septa in the leptospirosis group compared with the normal and hemorrhagic controls. In the vessels of the leptospirosis group, there was an increased expression of intercellular adhesion molecule (P = .004), vascular cell adhesion molecule (P = .030), and Toll-like receptor 2 (P = .042) compared with the normal group. Vascular cell adhesion molecule expression in vessels was higher in the leptospirosis group compared with the hemorrhagic group (P = .015). Our results indicate that immune receptors and adhesion molecules participate in the phenomena leading to pulmonary hemorrhage in leptospirosis. Copyright © 2012 Elsevier Inc. All rights reserved.

  3. Antagonism of the prostaglandin D2 receptor CRTH2 attenuates asthma pathology in mouse eosinophilic airway inflammation

    PubMed Central

    Uller, Lena; Mathiesen, Jesper Mosolff; Alenmyr, Lisa; Korsgren, Magnus; Ulven, Trond; Högberg, Thomas; Andersson, Gunnar; Persson, Carl GA; Kostenis, Evi

    2007-01-01

    Background Mast cell-derived prostaglandin D2 (PGD2), may contribute to eosinophilic inflammation and mucus production in allergic asthma. Chemoattractant receptor homologous molecule expressed on TH2 cells (CRTH2), a high affinity receptor for prostaglandin D2, mediates trafficking of TH2-cells, mast cells, and eosinophils to inflammatory sites, and has recently attracted interest as target for treatment of allergic airway diseases. The present study involving mice explores the specificity of CRTH2 antagonism of TM30089, which is structurally closely related to the dual TP/CRTH2 antagonist ramatroban, and compares the ability of ramatroban and TM30089 to inhibit asthma-like pathology. Methods Affinity for and antagonistic potency of TM30089 on many mouse receptors including thromboxane A2 receptor mTP, CRTH2 receptor, and selected anaphylatoxin and chemokines receptors were determined in recombinant expression systems in vitro. In vivo effects of TM30089 and ramatroban on tissue eosinophilia and mucus cell histopathology were examined in a mouse asthma model. Results TM30089, displayed high selectivity for and antagonistic potency on mouse CRTH2 but lacked affinity to TP and many other receptors including the related anaphylatoxin C3a and C5a receptors, selected chemokine receptors and the cyclooxygenase isoforms 1 and 2 which are all recognized players in allergic diseases. Furthermore, TM30089 and ramatroban, the latter used as a reference herein, similarly inhibited asthma pathology in vivo by reducing peribronchial eosinophilia and mucus cell hyperplasia. Conclusion This is the first report to demonstrate anti-allergic efficacy in vivo of a highly selective small molecule CRTH2 antagonist. Our data suggest that CRTH2 antagonism alone is effective in mouse allergic airway inflammation even to the extent that this mechanism can explain the efficacy of ramatroban. PMID:17328802

  4. Deletion of both the C3a and C5a receptors fails to protect against experimental autoimmune encephalomyelitis.

    PubMed

    Ramos, Theresa N; Wohler, Jillian E; Barnum, Scott R

    2009-12-31

    Multiple sclerosis (MS) is an autoimmune disease in which inflammation, leukocyte infiltration, and ultimately, demyelination occur as a result of innate and adaptive immune-mediated mechanisms. The pathophysiological role of the complement system, a major component of innate immunity, in the development and progression of experimental autoimmune encephalomyelitis (EAE), the animal model for MS has been extensively examined. Previous studies from our lab have shown that the complement receptor for the anaphylatoxin C3a, but not for C5a plays an important role in EAE. Based on the important contributions of the complement anaphylatoxin receptors to other inflammatory conditions in the CNS, we reasoned that deletion of both receptors may reveal underlying interactions between them that are important to EAE pathology. We performed EAE in C3aR/C5aR double knockout mice (C3aR/C5aR(-/-)) and observed delayed onset of disease but no attenuation of disease severity compared to wild type mice. Interestingly there was trend toward greater infiltration of CD4(+), but not CD8(+) T cells, in C3aR/C5aR(-/-) mice with EAE, suggesting altered trafficking of these cells. Antigen-specific T cells isolated from C3aR/C5aR(-/-) mice during acute EAE produced elevated levels of TNF-alpha, but markedly reduced levels of IFN-gamma and IL-12 compared to wild type mice. It remains unclear how the changes in these disease parameters contribute to the loss of the protective effect seen in C3aR(-/-) mice, however our data indicate a level of cross-modulation between the C3aR and C5aR during EAE.

  5. Deletion of Both the C3a and C5a Receptors Fails to Protect Against Experimental Autoimmune Encephalomyelitis

    PubMed Central

    Ramos, Theresa N.; Wohler, Jillian E.; Barnum, Scott R.

    2009-01-01

    Multiple sclerosis (MS) is an autoimmune disease in which inflammation, leukocyte infiltration, and ultimately, demyelination occur as a result of innate and adaptive immune-mediated mechanisms. The pathophysiological role of the complement system, a major component of innate immunity, in the development and progression of experimental autoimmune encephalomyelitis (EAE), the animal model for MS has been extensively examined. Previous studies from our lab have shown that the complement receptor for the anaphylatoxin C3a, but not for C5a plays an important role in EAE. Based on the important contributions of the complement anaphylatoxin receptors to other inflammatory conditions in the CNS, we reasoned that deletion of both receptors may reveal underlying interactions between them that are important to EAE pathology. We performed EAE in C3aR/C5aR double knockout mice (C3aR/C5aR−/−) and observed delayed onset of disease but no attenuation of disease severity compared to wild type mice. Interestingly there was trend toward greater infiltration of CD4+, but not CD8+ T cells, in C3aR/C5aR−/− mice with EAE, suggesting altered trafficking of these cells. Antigen-specific T cells isolated from C3aR/C5aR−/− mice during acute EAE produced elevated levels of TNF-α, but markedly reduced levels of IFN-γ and IL-12 compared to wild type mice. It remains unclear how the changes in these disease parameters contribute to the loss of the protective effect seen in C3aR−/− mice, however our data indicate a level of cross modulation between the C3aR and C5aR during EAE. PMID:19850104

  6. Connecting the innate and adaptive immune responses in mouse choroidal neovascularization via the anaphylatoxin C5a and γδT-cells

    PubMed Central

    Coughlin, Beth; Schnabolk, Gloriane; Joseph, Kusumam; Raikwar, Himanshu; Kunchithapautham, Kannan; Johnson, Krista; Moore, Kristi; Wang, Yi; Rohrer, Bärbel

    2016-01-01

    Neovascular age-related macular degeneration (AMD) is characterized by choroidal neovascularization (CNV). An overactive complement system is associated with AMD pathogenesis, and serum pro-inflammatory cytokines, including IL-17, are elevated in AMD patients. IL-17 is produced by complement C5a-receptor-expressing T-cells. In murine CNV, infiltrating γδT- rather than Th17-cells produce the IL-17 measurable in lesioned eyes. Here we asked whether C5a generated locally in response to CNV recruits IL-17-producing T-cells to the eye. CNV lesions were generated using laser photocoagulation and quantified by imaging; T-lymphocytes were characterized by QRT-PCR. CNV resulted in an increase in splenic IL-17-producing γδT- and Th17-cells; yet in the CNV eye, only elevated levels of γδT-cells were observed. Systemic administration of anti-C5- or anti-C5a-blocking antibodies blunted the CNV-induced production of splenic Th17- and γδT-cells, reduced CNV size and eliminated ocular γδT-cell infiltration. In ARPE-19 cell monolayers, IL-17 triggered a pro-inflammatory state; and splenocyte proliferation was elevated in response to ocular proteins. Thus, we demonstrated that CNV lesions trigger a systemic immune response, augmenting local ocular inflammation via the infiltration of IL-17-producing γδT-cells, which are presumably recruited to the eye in a C5a-dependent manner. Understanding the complexity of complement-mediated pathological mechanisms will aid in the development of an AMD treatment. PMID:27029558

  7. Demonstration of a specific C3a receptor on guinea pig platelets

    SciTech Connect

    Fukuoka, Y.; Hugli, T.E.

    1988-05-15

    Guinea pig platelets reportedly contain receptors specific for the anaphylatoxin C3a based on both ligand-binding studies and functional responses. A portion of the human 125I-C3a that binds to guinea pig platelets is competitively displaced by excess unlabeled C3a; however, the majority of ligand uptake was nonspecific. Uptake of 125I-C3a by guinea pig platelets is maximal in 1 min, and stimulation of guinea pig platelets by thrombin, ADP, or the Ca2+ ionophore A23187 showed little influence on binding of the ligand. Scatchard analysis indicated that approximately 1200 binding sites for C3a exist per cell with an estimated Kd of 8 x 10(-10) M. Human C3a des Arg also binds to guinea pig platelets, but Scatchard analysis indicated that no specific binding occurred. Because the ligand-binding studies were complicated by high levels of nonspecific uptake, we attempted to chemically cross-link the C3a molecule to a specific component on the platelet surface. Cross-linkage of 125I-C3a to guinea pig platelets with bis(sulfosuccinimidyl)suberate revealed radioactive complexes at 105,000 and 115,000 m.w. on SDS-PAGE gels by autoradiographic analysis. In the presence of excess unlabeled C3a, complex formation was inhibited. No cross-linkage could be demonstrated between the inactive 125I-C3a des Arg and the putative C3a-R on guinea pig platelets. Human C3a, but not C3a des Arg induces serotonin release and aggregation of the guinea pig platelets. Human C3a was unable to induce either serotonin release or promote aggregation of human platelets. Uptake of human 125I-C3a by human platelets was not saturable, and Scatchard analysis was inconclusive. Attempts to cross-link 125I-C3a to components on the surface of human platelets also failed to reveal a ligand-receptor complex. Therefore, we conclude that guinea pig platelets have specific surface receptors to C3a and that human platelets appear devoid of receptors to the anaphylatoxin.

  8. Renal expression of the C3a receptor and functional responses of primary human proximal tubular epithelial cells.

    PubMed

    Braun, Michael C; Reins, Rose Y; Li, Tong-Bin; Hollmann, Travis J; Dutta, Ranjan; Rick, Wetsel A; Teng, Ba-Bie; Ke, Baozhen

    2004-09-15

    Although complement activation and deposition have been associated with a variety of glomerulopathies, the pathogenic mechanisms by which complement directly mediates renal injury remain to be fully elucidated. Renal parenchymal tissues express a limited repertoire of receptors that directly bind activated complement proteins. We report the renal expression of the receptor for the C3 cleavage product C3a, a member of the anaphylatoxin family. C3aR is highly expressed in normal human and murine kidney, as demonstrated by immunohistochemistry and in situ hybridization. Its distribution is limited to epithelial cells only, as glomerular endothelial and mesangial cells showed no evidence of C3aR expression. The C3aR is also expressed by primary renal proximal tubular epithelial cells in vitro as demonstrated by FACS, Western blot, and RT-PCR. In vitro C3aR is functional in terms of its capacity to bind 125I-labeled C3a and generate inositol triphosphate. Finally, using microarray analysis, four novel genes were identified and confirmed as transcriptionally regulated by C3aR activation in proximal tubular cells. These studies define a new pathway by which complement activation may directly modulate the renal response to immunologic injury.

  9. The complement C3a receptor is critical in defense against Chlamydia psittaci in mouse lung infection and required for antibody and optimal T cell response.

    PubMed

    Dutow, Pavel; Fehlhaber, Beate; Bode, Jenny; Laudeley, Robert; Rheinheimer, Claudia; Glage, Silke; Wetsel, Rick A; Pabst, Oliver; Klos, Andreas

    2014-04-15

    The complement system protects against extracellular pathogens and links innate and adaptive immunity. In this study, we investigated the anaphylatoxin C3a receptor (C3aR) in Chlamydia psittaci lung infection and elucidated C3a-dependent adaptive immune mechanisms. Survival, body weight, and clinical score were monitored in primary mouse infection and after serum transfer. Bacterial load, histology, cellular distribution, cytokines, antibodies, and lymphocytes were analyzed. C3aR(-/-) mice showed prolonged pneumonia with decreased survival, lower weight, and higher clinical score. Compared to wild-type mice bacterial clearance was impaired, and inflammatory parameters were increased. In lung-draining lymph nodes of C3aR(-/-) mice the total number of B cells, CD4(+) T cells, and Chlamydia-specific IFN-γ(+) (CD4(+) or CD8(+)) cells was reduced upon infection, and the mice were incapable of Chlamydia-specific immunoglobulin M or immunoglobulin G production. Performed before infection, transfer of hyperimmune serum prolonged survival of C3aR(-/-) mice. C3a and its receptor are critical for defense against C. psittaci in mouse lung infection. In this model, C3a acts via its receptor as immune modulator. Enhancement of specific B and T cell responses upon infection with an intracellular bacterium were identified as hitherto unknown features of C3a/C3aR. These new functions might be of general immunological importance.

  10. A soluble deletion mutant of the human complement receptor type 1, which lacks the C4b binding site, is a selective inhibitor of the alternative complement pathway.

    PubMed

    Scesney, S M; Makrides, S C; Gosselin, M L; Ford, P J; Andrews, B M; Hayman, E G; Marsh, H C

    1996-08-01

    The human complement receptor type 1 (CR1, CD35), is a single-chain glycoprotein consisting of 30 repeating homologous protein domains known as short consensus repeats (SCR) followed by transmembrane and cytoplasmic domains. The SCR themselves, considered in groups of seven, form long homologous repeats (LHR) which have been designated LHR-A, -B, -C, and -D for the most common human allotype of CR1. A soluble deletion mutant of CR1 which lacks the first seven N-terminal SCR (LHR-A) as well as the transmembrane and cytoplasmic domains was produced and characterized. The resulting protein, designated sCR1[desLHR-A], lacks the C4b binding site found in LHR-A, but retains the two C3b binding sites found in LHR-B and -C, respectively. The functional activities of sCR1[desLHR-A] were quantitatively compared in vitro to those of soluble complement receptor type 1 (sCR1) which has been shown to retain all known functions of the native cell surface receptor. sCR1[desLHR-A] and sCR1 competed equally for the binding of dimeric C3b to erythrocyte CR1. sCR1[desLHR-A] and sCR1 were similar in their capacity to serve as a cofactor in the factor I-mediated degradation of the C3b and C4b alpha chains. sCR1[desLHR-A] and sCR1 were comparable in their capacity to inhibit erythrocyte lysis and anaphylatoxin production mediated by the alternative complement pathway. sCR1[desLHR-A], however, was significantly less effective an inhibitor of erythrocyte lysis and anaphylatoxin production than sCR1 under conditions which allow classical pathway activation. These results demonstrate sCR1[desLHR-A] to be a selective inhibitor of the alternative complement pathway in vitro.

  11. The Complement Anaphylatoxins C5a and C3a Suppress IFN-β Production in Response to Listeria monocytogenes by Inhibition of the Cyclic Dinucleotide-Activated Cytosolic Surveillance Pathway.

    PubMed

    Mueller-Ortiz, Stacey L; Calame, Daniel G; Shenoi, Nancy; Li, Yi-Dong; Wetsel, Rick A

    2017-04-15

    Listeria monocytogenes is an intracellular Gram-positive bacterium that induces expression of type I IFNs (IFN-α/IFN-β) during infection. These cytokines are detrimental to the host during infection by priming leukocytes to undergo L. monocytogenes-mediated apoptosis. Our previous studies showed that C5aR1(-/-) and C3aR(-/-) mice are highly susceptible to L. monocytogenes infection as a result of increased IFN-β-mediated apoptosis of major leukocyte cell populations, including CD4(+) and CD8(+) T cells. However, the mechanisms by which C3a and C5a modulate IFN-β expression during L. monocytogenes infection were not examined in these initial investigations. Accordingly, we report in this article that C5a and C3a suppress IFN-β production in response to L. monocytogenes via cyclic di-AMP (c-di-AMP), a secondary messenger molecule of L. monocytogenes, in J774A.1 macrophage-like cells and in bone marrow-derived dendritic cells (BMDCs). Moreover, C5a and C3a suppress IFN-β production by acting through their respective receptors, because no inhibition was seen in C5aR1(-/-) or C3aR(-/-) BMDCs, respectively. C5a and C3a suppress IFN-β production in a manner that is dependent on Bruton's tyrosine kinase, p38 MAPK, and TANK-binding kinase 1 (TBK1), as demonstrated by the individual use of Bruton's tyrosine kinase, p38 MAPK, and TBK1 inhibitors. Pretreatment of cells with C5a and C3a reduced the expression of the IFN-β signaling molecules DDX41, STING, phosphorylated TBK1, and phosphorylated p38 MAPK in wild-type BMDCs following treatment with c-di-AMP. Collectively, these data demonstrate that C3a and C5a, via direct signaling through their specific receptors, suppress IFN-β expression by modulation of a distinct innate cytosolic surveillance pathway involving DDX41, STING, and other downstream molecular targets of L. monocytogenes-generated c-di-AMP. Copyright © 2017 by The American Association of Immunologists, Inc.

  12. Protease-activated receptor-2 deficient mice have reduced house dust mite-evoked allergic lung inflammation.

    PubMed

    de Boer, J Daan; Van't Veer, Cornelis; Stroo, Ingrid; van der Meer, Anne J; de Vos, Alex F; van der Zee, Jaring S; Roelofs, Joris J T H; van der Poll, Tom

    2014-08-01

    Protease-activated receptor-2 (PAR2) is abundantly expressed in the pulmonary compartment. House dust mite (HDM) is a common cause of allergic asthma and contains multiple PAR2 agonistic proteases. The aim of this study was to determine the role of PAR2 in HDM-induced allergic lung inflammation. For this, the extent of allergic lung inflammation was studied in wild type (Wt) and PAR2 knockout (KO) mice after repeated airway exposure to HDM. HDM exposure of Wt mice resulted in a profound influx of eosinophils in bronchoalveolar lavage fluid (BALF) and accumulation of eosinophils in lung tissue, which both were strongly reduced in PAR2 KO mice. PAR2 KO mice demonstrated attenuated lung pathology and protein leak in the bronchoalveolar space, accompanied by lower BALF levels of the anaphylatoxins C3a and C5a. This study reveals, for the first time, an important role for PAR2 in allergic lung inflammation induced by the clinically relevant allergens contained in HDM.

  13. C5a receptor is cleaved by metalloproteases induced by sphingomyelinase D from Loxosceles spider venom.

    PubMed

    van den Berg, Carmen W; Gonçalves-de-Andrade, Rute M; Okamoto, Cinthya K; Tambourgi, Denise V

    2012-09-01

    Neutrophils are involved in numerous pathologies and are considered to be major contributors to the establishment of cutaneous loxoscelism after envenomation by the Loxosceles spider. Neutrophils are attracted to the site of envenomation by locally generated C5a and contribute to the tissue destruction. We have investigated the effects of this spider venom on the receptor for C5a: C5aR/CD88, a seven transmembrane G-protein coupled receptor. We show here that the Loxosceles venom induces the cleavage of the C5aR at two sites, resulting in the release of the extracellular N-terminus, while retaining part of the transmembrane regions. Using specific inhibitors, it was shown that the cleavage was induced by activation of an endogenous metalloprotease of the adamalysin (ADAM) family, which was activated by the sphingomyelinase D in the venom. Although it resulted in the near complete loss of the N-terminus, C5a was still able to induce a small increase in intracellular calcium and increase secretion of IL-8. The cleavage of the C5aR may well be a protective response after envenomation, rather than contributing to the pathology of Loxosceles envenomation and may represent a general mechanism for how the body protects itself against excess C5a generation in pathological circumstances such as sepsis. Copyright © 2012 Elsevier GmbH. All rights reserved.

  14. Complement C3a enhances CXCL12 (SDF-1)-mediated chemotaxis of bone marrow hematopoietic cells independently of C3a receptor.

    PubMed

    Honczarenko, Marek; Ratajczak, Mariusz Z; Nicholson-Weller, Anne; Silberstein, Leslie E

    2005-09-15

    Complement C3a promotes CXCL12-induced migration and engraftment of human and murine hemopoietic progenitor cells, suggesting a cross-influence between anaphylatoxin and chemokine axes. Here we have explored the underlying mechanism(s) of complement anaphylatoxin and chemokine cooperation. In addition to C3a, C3a-desArg and C4a but not C5a, are potent enhancers of CXCL12-induced chemotaxis of human and murine bone marrow (BM) stem/progenitor cells and B lineage cells. C3a enhancement of chemotaxis is chemokine specific because it is also observed for chemotaxis to CCL19 but not to CXCL13. The potentiating effect of C3a on CXCL12 is independent of the classical C3a receptor (C3aR). First, human BM CD34(+) and B lineage cells do not express C3aR by flow cytometry. Second, the competitive C3aR inhibitor SB290157 does not affect C3a-mediated enhancement of CXCL12-induced chemotaxis. Third, enhancement of chemotaxis of hemopoietic cells is also mediated by C3a-desArg, which does not bind to C3aR. Finally, C3a enhances CXCL12-induced chemotaxis of BM cells from C3aR knockout mice similar to BM cells from wild-type mice. Subsequent studies revealed that C3a increased the binding affinity of CXCL12 to human CXCR4(+)/C3aR(-), REH pro-B cells, which is compatible with a direct interaction between C3a and CXCL12. BM stromal cells were able to generate C3a, C3a-desArg, C4a, as well as CXCL12, suggesting that this pathway could function in vivo. Taken together, we demonstrate a C3a-CXCL12 interaction independent of the C3aR, which may provide a mechanism to modulate the function of CXCL12 in the BM microenvironment.

  15. Anaphylatoxin C3a induced mediator release from mast cells

    SciTech Connect

    Herrscher, R.; Hugli, T.E.; Sullivan, T.J.

    1986-03-01

    The authors investigated the biochemical and functional consequences of the binding of highly purified human C3a to isolated rat serosal mast cells. C3a caused a dose-dependent (1-30 ..mu..M), noncytotoxic release of up to 64% (+/- 7 SEM) of the mast cell histamine content. C3a (10..mu..M) increased /sup 45/Ca/sup + +/ uptake 8.2- fold (+/- 2.2 SEM) above unstimulated control values within 10 minutes. Arachidonyl-diacylglycerol and arachidonyl-monoacylglycerol levels increased significantly within 2 minutes after C3a (10 ..mu..M) stimulation. Turnover of phosphatidylinositol, phosphatidic acid, and phosphatidylcholine were increased within 15 minutes. In contrast to antigen, C3a stimulation (10 ..mu..M) was not enhanced by exogenous phosphatidylserine, and was not inhibited by ethanol (100 ..mu..mM). C3a suppressed arachidonic acid (AA) release to 38% (+/- 9 SEM) below baseline, and did not cause PGD/sub 2/ formation. C3a and the desarginine form of C3a caused identical responses in all experiments. These studies indicate that C3a stimulation activates mast cell preformed mediator release in a manner very similar to antigen-IgE stimulation, but C3a suppresses free AA levels and does not stimulate PGD/sub 2/ synthesis.

  16. The Complement C3a Receptor Is Critical in Defense against Chlamydia psittaci in Mouse Lung Infection and Required for Antibody and Optimal T Cell Response

    PubMed Central

    Dutow, Pavel; Fehlhaber, Beate; Bode, Jenny; Laudeley, Robert; Rheinheimer, Claudia; Glage, Silke; Wetsel, Rick A.; Pabst, Oliver; Klos, Andreas

    2014-01-01

    Background. The complement system protects against extracellular pathogens and links innate and adaptive immunity. In this study, we investigated the anaphylatoxin C3a receptor (C3aR) in Chlamydia psittaci lung infection and elucidated C3a-dependent adaptive immune mechanisms. Methods. Survival, body weight, and clinical score were monitored in primary mouse infection and after serum transfer. Bacterial load, histology, cellular distribution, cytokines, antibodies, and lymphocytes were analyzed. Results. C3aR−/− mice showed prolonged pneumonia with decreased survival, lower weight, and higher clinical score. Compared to wild-type mice bacterial clearance was impaired, and inflammatory parameters were increased. In lung-draining lymph nodes of C3aR−/− mice the total number of B cells, CD4+ T cells, and Chlamydia-specific IFN-γ+ (CD4+ or CD8+) cells was reduced upon infection, and the mice were incapable of Chlamydia-specific immunoglobulin M or immunoglobulin G production. Performed before infection, transfer of hyperimmune serum prolonged survival of C3aR−/− mice. Conclusions. C3a and its receptor are critical for defense against C. psittaci in mouse lung infection. In this model, C3a acts via its receptor as immune modulator. Enhancement of specific B and T cell responses upon infection with an intracellular bacterium were identified as hitherto unknown features of C3a/C3aR. These new functions might be of general immunological importance. PMID:24273177

  17. Inhibition of prostaglandin D2 clearance in rat hepatocytes by the thromboxane receptor antagonists daltroban and ifetroban and the thromboxane synthase inhibitor furegrelate.

    PubMed

    Pestel, Sabine; Nath, Annegret; Jungermann, Kurt; Schieferdecker, Henrike L

    2003-08-15

    Prostanoids, i.e. prostaglandins and thromboxane, regulate liver-specific functions both in homeostasis and during defense reactions. For example, prostanoids are released from Kupffer cells, the resident liver macrophages, in response to the inflammatory mediator anaphylatoxin C5a, and mediate an enhanced glucose output from hepatocytes as energy supply. In perfused rat livers, the thromboxane receptor antagonist daltroban enhanced C5a-induced prostanoid overflow and reduced glucose output. It was the aim of this study to elucidate whether daltroban interfered with prostanoid release from Kupffer cells or prostanoid clearance by hepatocytes, and/or whether it directly influenced prostanoid-dependent glucose metabolism in these cells. In perfused rat livers, daltroban enhanced prostaglandin (PG)D(2) overflow not only after infusion of C5a (15-fold), but also after PGD(2) (10-fold). Neither daltroban nor another receptor antagonist, ifetroban, or the thromboxane synthase inhibitor furegrelate enhanced prostanoid release from Kupffer cells. In contrast, all inhibitors reduced clearance, i.e. uptake and degradation, of PGD(2) by hepatocytes: within 5 min uptake of 1 nmol/L PGD(2) was reduced from 43+/-5 fmol (controls) to 22+/-6 fmol (daltroban), 24+/-6 fmol (ifetroban) and 21+/-6 fmol (furegrelate). PGD(2) in the medium was reduced to 39+/-7% in the controls, but remained at 93+/-9%, 93+/-11% and 60+/-3% in the presence of the inhibitors. PGD(2)-dependent glucose output in the perfused liver or activation of glycogen phosphorylase in isolated hepatocytes remained unaffected by daltroban. These data clearly demonstrate that the thromboxane-inhibitors reduced PGD(2) clearance by hepatocytes, presumably by inhibition of prostanoid transport into the cells. In contrast, they did not interfere with PGD(2)-dependent glucose metabolism, suggesting an independent mechanism for the inhibition of glucose output from the liver.

  18. Opioid Receptors.

    PubMed

    Stein, Christoph

    2016-01-01

    Opioids are the oldest and most potent drugs for the treatment of severe pain. Their clinical application is undisputed in acute (e.g., postoperative) and cancer pain, but their long-term use in chronic pain has met increasing scrutiny. This article reviews mechanisms underlying opioid analgesia and other opioid actions. It discusses the structure, function, and plasticity of opioid receptors; the central and peripheral sites of analgesic actions and side effects; endogenous and exogenous opioid receptor ligands; and conventional and novel opioid compounds. Challenging clinical situations, such as the tension between chronic pain and addiction, are also illustrated.

  19. Roundabout receptors.

    PubMed

    Ypsilanti, Athéna R; Chedotal, Alain

    2014-01-01

    Roundabout receptors (Robo) and their Slit ligands were discovered in the 1990s and found to be key players in axon guidance. Slit was initially described s an extracellular matrix protein that was expressed by midline glia in Drosophila. A few years later, it was shown that, in vertebrates and invertebrates, Slits acted as chemorepellents for axons crossing the midline. Robo proteins were originally discovered in Drosophila in a mutant screen for genes involved in the regulation of midline crossing. This ligand-receptor pair has since been implicated in a variety of other neuronal and non-neuronal processes ranging from cell migration to angiogenesis, tumourigenesis and even organogenesis of tissues such as kidneys, lungs and breasts.

  20. Influence of the C5a-C5a receptor system on breast cancer progression and patient prognosis.

    PubMed

    Imamura, Takahisa; Yamamoto-Ibusuki, Mutsuko; Sueta, Aiko; Kubo, Tatsuko; Irie, Atsushi; Kikuchi, Ken; Kariu, Toru; Iwase, Hirotaka

    2016-11-01

    Emerging evidence has shown activation of the complement system in cancer tissues and anaphylatoxin C5a release from C5 by cancer cells, suggesting C5a as a component in the cancer microenvironment. We revealed aberrant expression of C5a receptor (C5aR) in various human cancers and C5a-elicited enhancement of C5aR-expressing cancer cell invasion. To explore an influence of the C5a-C5aR system in breast cancer (BC), we investigated BC C5aR expression in relation to clinicopathological parameters of the patients and an effect of C5a on BC cell proliferation. BC cell C5aR expression was observed immunohistochemically in 22 of 171 patients (13 %) and related to larger tumor size, higher nuclear grade and Ki-67 labeling index, presence of lymph node metastasis and advanced clinical stages. Interestingly, BC cells were C5aR-negative in all patients with BC in situ and C5aR-positive rate was high (38 %) in patients with hormone receptor-negative, namely triple-negative BC. For BC cells in metastasized lymph nodes, 12 of 22 patients (55 %) were C5aR-positive and included 7 patients with C5aR-negative BC in the primary site. Survival rate of patients with C5aR-positive BC was lower than that of patients with C5aR-negative BC. C5a enhanced proliferation of C5aR-expressing triple-negative BC cells in a C5aR-dependent manner. Relation of BC C5aR expression to tumor development and poor prognosis of the patients and proliferation enhancing effect of C5a on C5aR-expressing BC cells suggest that the C5a-C5aR system is closely associated with BC progression. This system may be a new target to treat BC patients, particularly with triple-negative BC.

  1. CGRP and its receptors.

    PubMed

    Hay, Debbie L; Walker, Christopher S

    2017-02-24

    The calcitonin gene-related peptide (CGRP) neuropeptide system is an important but still evolving target for migraine. A fundamental consideration for all of the current drugs in clinical trials and for ongoing development in this area is the identity, expression pattern, and function of CGRP receptors because this knowledge informs safety and efficacy considerations. In recent years, only the calcitonin receptor-like receptor/receptor activity-modifying protein 1 (RAMP1) complex, known as the CGRP receptor, has generally been considered relevant. However, CGRP is capable of activating multiple receptors and could have more than one endogenous receptor. The recent identification of the CGRP-responsive calcitonin receptor/RAMP1 complex (AMY1 receptor - amylin subtype 1 receptor) in the trigeminovascular system warrants a deeper consideration of the molecular identity of CGRP receptor(s) involved in the pathophysiology, and thus potential treatment of migraine. This perspective considers some of the issues and implications.

  2. The LDL receptor.

    PubMed

    Goldstein, Joseph L; Brown, Michael S

    2009-04-01

    In this article, the history of the LDL receptor is recounted by its codiscoverers. Their early work on the LDL receptor explained a genetic cause of heart attacks and led to new ways of thinking about cholesterol metabolism. The LDL receptor discovery also introduced three general concepts to cell biology: receptor-mediated endocytosis, receptor recycling, and feedback regulation of receptors. The latter concept provides the mechanism by which statins selectively lower plasma LDL, reducing heart attacks and prolonging life.

  3. Differential Contributions of the Complement Anaphylotoxin Receptors C5aR1 and C5aR2 to the Early Innate Immune Response against Staphylococcus aureus Infection

    PubMed Central

    Horst, Sarah A.; Itzek, Andreas; Klos, Andreas; Beineke, Andreas; Medina, Eva

    2015-01-01

    The complement anaphylatoxin C5a contributes to host defense against Staphylococcus aureus. In this study, we investigated the functional role of the two known C5a receptors, C5aR1 and C5aR2, in the host response to S. aureus. We found that C5aR1−/− mice exhibited greater susceptibility to S. aureus bloodstream infection than wild type and C5aR2−/− mice, as demonstrated by the significantly higher bacterial loads in the kidneys and heart at 24 h of infection, and by the higher levels of inflammatory IL-6 in serum. Histological and immunohistochemistry investigation of infected kidneys at 24 h after bacterial inoculation revealed a discrete infiltration of neutrophils in wild type mice but already well-developed abscesses consisting of bacterial clusters surrounded by a large number of neutrophils in both C5aR1−/− and C5aR2−/− mice. Furthermore, blood neutrophils from C5aR1−/− mice were less efficient than those from wild type or C5aR2−/− mice at killing S. aureus. The requirement of C5aR1 for efficient killing of S. aureus was also demonstrated in human blood after disrupting C5a-C5aR1 signaling using specific inhibitors. These results demonstrated a role for C5aR1 in S. aureus clearance as well as a role for both C5aR1 and C5aR2 in the orchestration of the inflammatory response during infection. PMID:26512700

  4. Differential Contributions of the Complement Anaphylotoxin Receptors C5aR1 and C5aR2 to the Early Innate Immune Response against Staphylococcus aureus Infection.

    PubMed

    Horst, Sarah A; Itzek, Andreas; Klos, Andreas; Beineke, Andreas; Medina, Eva

    2015-10-23

    The complement anaphylatoxin C5a contributes to host defense against Staphylococcus aureus. In this study, we investigated the functional role of the two known C5a receptors, C5aR1 and C5aR2, in the host response to S. aureus. We found that C5aR1(-/)(-) mice exhibited greater susceptibility to S. aureus bloodstream infection than wild type and C5aR2(-/)(-) mice, as demonstrated by the significantly higher bacterial loads in the kidneys and heart at 24 h of infection, and by the higher levels of inflammatory IL-6 in serum. Histological and immunohistochemistry investigation of infected kidneys at 24 h after bacterial inoculation revealed a discrete infiltration of neutrophils in wild type mice but already well-developed abscesses consisting of bacterial clusters surrounded by a large number of neutrophils in both C5aR1(-/)(-) and C5aR2(-/)(-) mice. Furthermore, blood neutrophils from C5aR1(-/)(-) mice were less efficient than those from wild type or C5aR2(-/)(-) mice at killing S. aureus. The requirement of C5aR1 for efficient killing of S. aureus was also demonstrated in human blood after disrupting C5a-C5aR1 signaling using specific inhibitors. These results demonstrated a role for C5aR1 in S. aureus clearance as well as a role for both C5aR1 and C5aR2 in the orchestration of the inflammatory response during infection.

  5. Evaluation of C3a receptor expression on human leucocytes by the use of novel monoclonal antibodies

    PubMed Central

    ZWIRNER, J; GÖTZE, O; BEGEMANN, G; KAPP, A; KIRCHHOFF, K; WERFEL, T

    1999-01-01

    Varying results have been published in the past regarding the reactivity of different leucocyte subpopulations, including neutrophils, monocytes and B lymphocytes, to the anaphylatoxin C3a and its degradation product C3a(desArg). To better characterize the cellular distribution of C3a receptor (C3aR) expression, monoclonal antibodies against two different epitopes on the third extracellular domain of the human C3aR were generated. Quantification of C3aR as compared with C5aR densities was performed on peripheral blood leucocytes by quantitative indirect immunofluorescence. Eosinophils and basophils expressed similar numbers of C3aR and C5aR molecules/cell. On eosinophils 10 700±4500 (mean±SD) C3aR and 14 700±4100 C5aR were found, whereas basophils carried 8100±2100 C3aR and 13 500±3800 C5aR. Monocytes expressed approximately six times more C5aR than C3aR molecules on their surface (6000±2500 C3aR versus 34 100±9300 C5aR molecules) whereas on neutrophils, the expression of C5aR was more than 20 times higher than the expression of C3aR (3100±1000 C3aR versus 63 500±12 200 C5aR). No C3aR expression was detectable on peripheral blood-derived B lymphocytes and on tonsillar B cells before and after stimulation with interleukin-2/Staphylococcus aureus Cowan strain I. Our findings correspond well with the paucity of data on C3a-induced functional activities in monocytes and neutrophils and suggest that eosinophilic and basophilic granulocytes represent the primary effector cells in the peripheral blood which can be stimulated by C3a. PMID:10447728

  6. Brain receptor imaging.

    PubMed

    Heiss, Wolf-Dieter; Herholz, Karl

    2006-02-01

    Receptors have a prominent role in brain function, as they are the effector sites of neurotransmission at the postsynaptic membrane, have a regulatory role on presynaptic sites for transmitter reuptake and feedback, and are modulating various functions on the cell membrane. Distribution, density, and activity of receptors in the brain can be visualized by radioligands labeled for SPECT and PET, and the receptor binding can be quantified by appropriate tracer kinetic models, which can be modified and simplified for particular application. Selective radioligands are available for the various transmitter systems, by which the distribution of these receptors in the normal brain and changes in receptor binding during various physiologic activities or resulting from pathologic conditions can be visualized. The quantitative imaging for several receptors has gained clinical importance-for example, dopamine (D2)) receptors for differential diagnosis of movement disorders and for assessment of receptor occupancy by neuroleptics drugs; serotonin (5-hydroxytryptamine, 5-HT) receptors and the 5-HT transporter in affective disorders and for assessment of activity of antidepressants; nicotinic receptors and acetylcholinesterase as markers of cognitive and memory impairment; central benzodiazepine-binding sites at the gamma-aminobutyric acid A (GABAA) receptor complex as markers of neuronal integrity in neurodegenerative disorders, epilepsy, and stroke and as the site of action of benzodiazepines; peripheral benzodiazepine receptors as indicators of inflammatory changes; opioid receptors detecting increased cortical excitability in focal epilepsy but also affected in perception of and emotional response to pain; and several receptor systems affected in drug abuse and craving. Further studies of the various transmitter/receptor systems and their balance and infraction will improve our understanding of complex brain functions and will provide more insight into the pathophysiology of

  7. [Melatonin receptor agonist].

    PubMed

    Uchiyama, Makoto

    2015-06-01

    Melatonin is a hormone secreted by the pineal gland and is involved in the regulation of human sleep-wake cycle and circadian rhythms. The melatonin MT1 and MT2 receptors located in the suprachiasmatic nucleus in the hypothalamus play a pivotal role in the sleep-wake regulation. Based on the fact that MT1 receptors are involved in human sleep onset process, melatonin receptor agonists have been developed to treat insomnia. In this article, we first reviewed functions of melatonin receptors with special reference to MT1 and MT2, and properties and clinical application of melatonin receptor agonists as hypnotics.

  8. Standardizing scavenger receptor nomenclature.

    PubMed

    Prabhudas, Mercy; Bowdish, Dawn; Drickamer, Kurt; Febbraio, Maria; Herz, Joachim; Kobzik, Lester; Krieger, Monty; Loike, John; Means, Terry K; Moestrup, Soren K; Post, Steven; Sawamura, Tatsuya; Silverstein, Samuel; Wang, Xiang-Yang; El Khoury, Joseph

    2014-03-01

    Scavenger receptors constitute a large family of proteins that are structurally diverse and participate in a wide range of biological functions. These receptors are expressed predominantly by myeloid cells and recognize a variety of ligands, including endogenous and modified host-derived molecules and microbial pathogens. There are currently eight classes of scavenger receptors, many of which have multiple names, leading to inconsistencies and confusion in the literature. To address this problem, a workshop was organized by the U.S. National Institute of Allergy and Infectious Diseases, National Institutes of Health to help develop a clear definition of scavenger receptors and a standardized nomenclature based on that definition. Fifteen experts in the scavenger receptor field attended the workshop and, after extensive discussion, reached a consensus regarding the definition of scavenger receptors and a proposed scavenger receptor nomenclature. Scavenger receptors were defined as cell surface receptors that typically bind multiple ligands and promote the removal of non-self or altered-self targets. They often function by mechanisms that include endocytosis, phagocytosis, adhesion, and signaling that ultimately lead to the elimination of degraded or harmful substances. Based on this definition, nomenclature and classification of these receptors into 10 classes were proposed. The discussion and nomenclature recommendations described in this report only refer to mammalian scavenger receptors. The purpose of this article is to describe the proposed mammalian nomenclature and classification developed at the workshop and to solicit additional feedback from the broader research community.

  9. Serum transferrin receptor.

    PubMed

    Cook, J D; Skikne, B S; Baynes, R D

    1993-01-01

    The transferrin receptor plays a critical role in iron metabolism by precisely controlling the flow of transferrin iron into body cells. A soluble truncated form of the receptor can be detected in human serum using sensitive immunoassays, and the initial clinical experience with this new measurement indicates that it reflects the total body mass of tissue receptor. Serum receptor levels rise significantly with tissue iron deficiency and the heightened demand for iron associated with expansion of the erythroid marrow. The serum receptor provides a quantitative measure of functional iron deficiency and distinguishes the associated anemia from that of chronic disease. If iron deficiency is excluded, the serum receptor provides a quantitative measure of total erythropoiesis that is more sensitive and less invasive than bone marrow examination currently used to assess red cell precursor mass. Performed in conjunction with serum ferritin measurements, the serum receptor will be useful in establishing the true prevalence of iron deficiency anemia in population studies.

  10. Effect of repetitive high-dose treatment with soluble complement receptor type 1 and cobra venom factor on discordant xenograft survival.

    PubMed

    Candinas, D; Lesnikoski, B A; Robson, S C; Miyatake, T; Scesney, S M; Marsh, H C; Ryan, U S; Dalmasso, A P; Hancock, W W; Bach, F H

    1996-08-15

    Hyperacute xenograft rejection may be modified by the activation and depletion of complement (C) using cobra venom factor (CVF). This method of prolonging xenograft survival is toxic and associated with systemic inflammation, which may potentially contribute to the pathologic features of delayed xenograft rejection. Soluble complement receptor type 1 (sCR1) inhibits both the classical and alternative C pathways and thus limits the production of proinflammatory products such as the anaphylatoxins. Hence, we investigated the effects of various sCR1 and CVF regimens, and combinations thereof, in the discordant guinea pig-to-Lewis rat cardiac xenograft model. Mean graft survival time (MST) was significantly prolonged with repetitive dosing (MST=22 hr) or continuous infusion of sCR1 (MST=32 hr) as compared with unmodified controls (MST=15 min). However, sCR1 did not prevent intragraft deposition of C3 or neutrophil infiltration and resulted in only partial inhibition of C-mediated hemolytic activity in vitro. Grafts in rats treated with a single dose of CVF (MST=67 hr) or repetitive doses of CVF (MST=69 hr) survived significantly longer than those treated with sCR1 alone, and lacked C3 deposition or neutrophil accumulation. Sera from these animals were completely depleted of C-mediated hemolytic activity. Animals treated with a single dose of CVF, or sCRI plus a single dose of CVF (MST=64 hr), had similar xenograft survival times. However, immunohistologic studies showed that addition of sCR1 to a single dose of CVF resulted in decreased macrophage activation and reduced levels of cytokines (tumor necrosis factor-alpha and interleukin-1beta) within xenografts as compared with that in recipients treated with CVF alone. Such decreased macrophage activation may result from the binding of C4b by sCR1, since combination therapy was associated with decreased intragraft C4b as compared with either therapy alone. High doses of sCR1 were well tolerated by rats and significantly

  11. Chicken NK cell receptors.

    PubMed

    Straub, Christian; Neulen, Marie-Luise; Sperling, Beatrice; Windau, Katharina; Zechmann, Maria; Jansen, Christine A; Viertlboeck, Birgit C; Göbel, Thomas W

    2013-11-01

    Natural killer cells are innate immune cells that destroy virally infected or transformed cells. They recognize these altered cells by a plethora of diverse receptors and thereby differ from other lymphocytes that use clonally distributed antigen receptors. To date, several receptor families that play a role in either activating or inhibiting NK cells have been identified in mammals. In the chicken, NK cells have been functionally and morphologically defined, however, a conclusive analysis of receptors involved in NK cell mediated functions has not been available. This is partly due to the low frequencies of NK cells in blood or spleen that has hampered their intensive characterization. Here we will review recent progress regarding the diverse NK cell receptor families, with special emphasis on novel families identified in the chicken genome with potential as chicken NK cell receptors.

  12. Receptor distribution studies.

    PubMed

    Carletti, Renzo; Tacconi, Stefano; Mugnaini, Manolo; Gerrard, Philip

    2017-08-10

    Receptor distribution studies have played a key role in the characterization of receptor systems (e.g. GABAB, NMDA (GluNRs), and Neurokinin 1) and in generating hypotheses to exploit these systems as potential therapeutic targets. Distribution studies can provide important information on the potential role of candidate receptors in normal physiology/disease and alert for possible adverse effects of targeting the receptors. Moreover, they can provide valuable information relating to quantitative target engagement (e.g. % receptor occupancy) to drive mechanistic pharmacokinetic/pharmacodynamic (PK/PD) hypotheses for compounds in the Drug Discovery process. Finally, receptor distribution and quantitative target engagement studies can be used to validate truly translational technologies such as PET ligands and pharmacoEEG paradigms to facilitate bridging of the preclinical/clinical interface and thus increase probability of success. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Selective Glucocorticoid Receptor modulators.

    PubMed

    De Bosscher, Karolien

    2010-05-31

    The ancient two-faced Roman god Janus is often used as a metaphor to describe the characteristics of the Glucocorticoid Receptor (NR3C1), which exhibits both a beneficial side, that serves to halt inflammation, and a detrimental side responsible for undesirable effects. However, recent developments suggest that the Glucocorticoid Receptor has many more faces with the potential to express a range of different functionalities, depending on factors that include the tissue type, ligand type, receptor variants, cofactor surroundings and target gene promoters. This behavior of the receptor has made the development of safer ligands, that trigger the expression program of only a desirable subset of genes, a real challenge. Thus more knowledge-based fundamental research is needed to ensure the design and development of selective Glucocorticoid Receptor modulators capable of reaching the clinic. Recent advances in the characterization of novel selective Glucocorticoid Receptor modulators, specifically in the context of anti-inflammatory strategies, will be described in this review.

  14. Anaphylatoxin C5a fails to promote prostacyclin release from cultured human endothelial cells

    SciTech Connect

    Lunberg, C.; Marceau, F.; Huey, R.; Hugli, T.E.

    1986-03-01

    A predominantly relaxing effect of C5a on isolated blood vessels has been reported, which is associated with prostacyclin release from the vessel wall. Further, the well known hypothensive effect of C5a, also associated with increased prostacyclin output and preventable by indomethacin, indicates an involvement of endothelial cells in this reaction. In this study the authors characterized the response to C5a of cultured human endothelial cells from umbilical vein as measured by prostacyclin release. Prostacyclin was quantitated by radioimmunoassay as 6-keto-PGF/sub 1..cap alpha../. Subcultured cells respond to histamine and mellitin with increased prostacyclin production, but do not respond to leukotriene C4 (LTC/sub 4/). Primary cultures, on the other hand, respond to LTC/sub 4/ and the histamine response is 7-fold greater for these cells than for subcultured cells. However, neither primary nor subcultured cells release prostacyclin following application of either human C5a (100 nM) or C3a (1 ..mu..M). Also, these cells fail to show specific binding sites for /sup 125/I-C5a. In contrast, endothelial cells in the presence of human PMNs challenged with C5a release prostacyclin. These data suggest that C5a has no direct effect on the endothelial cell, but rather activates this cell indirectly via mediators from other cells known to respond to C5a.

  15. [The LDL receptor family].

    PubMed

    Meilinger, Melinda

    2002-12-29

    The members of the LDL receptor family are structurally related endocytic receptors. Our view on these receptors has considerably changed in recent years. Not only have new members of the family been identified, but also several interesting observations have been published concerning the biological function of these molecules. The LDL receptor family members are able to bind and internalize a plethora of ligands; as a consequence, they play important roles in diverse physiological processes. These receptors are key players in the lipoprotein metabolism, vitamin homeostasis, Ca2+ homeostasis, cell migration, and embryonic development. Until recently, LDL receptor family members were thought to be classic endocytic receptors that provide cells with metabolites on one hand, while regulating the concentration of their ligands in the extracellular fluids on the other hand. However, recent findings indicate that in addition to their cargo transport function, LDL receptor family members can act as signal transducers, playing important roles in the development of the central nervous system or the skeleton. Better understanding of physiological and pathophysiological functions of these molecules may open new avenues for the treatment or prevention of many disorders.

  16. Cannabis and cannabinoid receptors.

    PubMed

    Nocerino, E; Amato, M; Izzo, A A

    2000-08-01

    Cannabis and cannabinoids exert many of their biological functions through receptor-mediated mechanisms. Two types of cannabinoid receptors have been identified, namely CB(1) and CB(2), both coupled to a G protein. CB(1) receptors have been detected in the central nervous system (where they are responsible for the characteristic effects of Cannabis, including catalepsy, depression of motor activity, analgesia and feelings of relaxation and well being) and in peripheral neurons (where their activation produces a suppression in neurotransmitter release in the heart, bladder, intestine and vas deferens). Cannabinoid CB(2) receptors have only been detected outside the central nervous system, mostly in cells of the immune system, presumably mediating cannabinoid-induced immunosuppression and antinflammatory effects. With the discovery of cannabinoid receptors for exogenous cannabinoids, also endogenous cannabinoids (anandamide, 2-arachidonylglycerol) have been described.

  17. Historical overview of nuclear receptors.

    PubMed

    Gustafsson, Jan-Ake

    2016-03-01

    This review summarizes the birth of the field of nuclear receptors, from Jensen's discovery of estrogen receptor alpha, Gustafsson's discovery of the three-domain structure of the glucocorticoid receptor, the discovery of the glucocorticoid response element and the first partial cloning of the glucocorticoid receptor. Furthermore the discovery of the novel receptors called orphan receptors is described. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Receptors in disease: an overview.

    PubMed

    Amino, N

    1990-02-01

    Hormones and certain other signal molecules bind to plasma membrane or intracellular receptors producing signals that initiate their physiological effects. Recent understanding of receptors has resulted in recognition of several categories of receptor-related abnormalities. (a) Congenital receptor abnormalities such as receptor deficiency syndrome. LDL receptor defect in familial hypercholesteremia and primary androgen resistance are examples. (b) Postreceptor coupling abnormalities such as pseudohypoparathyroidism type Ia where there are reduced levels of guanine nucleotide receptor cyclase coupling protein. (c) Acquired receptor abnormalities, such as presence of circulating antireceptor antibodies. Such antibodies have been implicated in the pathophysiology of many diseases including Graves' disease and myasthenia gravis.

  19. Signaling by Sensory Receptors

    PubMed Central

    Julius, David; Nathans, Jeremy

    2012-01-01

    Sensory systems detect small molecules, mechanical perturbations, or radiation via the activation of receptor proteins and downstream signaling cascades in specialized sensory cells. In vertebrates, the two principal categories of sensory receptors are ion channels, which mediate mechanosensation, thermosensation, and acid and salt taste; and G-protein-coupled receptors (GPCRs), which mediate vision, olfaction, and sweet, bitter, and umami tastes. GPCR-based signaling in rods and cones illustrates the fundamental principles of rapid activation and inactivation, signal amplification, and gain control. Channel-based sensory systems illustrate the integration of diverse modulatory signals at the receptor, as seen in the thermosensory/pain system, and the rapid response kinetics that are possible with direct mechanical gating of a channel. Comparisons of sensory receptor gene sequences reveal numerous examples in which gene duplication and sequence divergence have created novel sensory specificities. This is the evolutionary basis for the observed diversity in temperature- and ligand-dependent gating among thermosensory channels, spectral tuning among visual pigments, and odorant binding among olfactory receptors. The coding of complex external stimuli by a limited number of sensory receptor types has led to the evolution of modality-specific and species-specific patterns of retention or loss of sensory information, a filtering operation that selectively emphasizes features in the stimulus that enhance survival in a particular ecological niche. The many specialized anatomic structures, such as the eye and ear, that house primary sensory neurons further enhance the detection of relevant stimuli. PMID:22110046

  20. [PPAR receptors: recent data].

    PubMed

    Vidal, H

    2005-04-01

    The nuclear receptors PPAR (Peroxisome Proliferator-Activated Receptors) are transcription factors which form with the retinoid receptor RXR, a PPAR/RXR heterodimer, the functional transcription factor within cells. PPAR receptors are activated by their ligands, either naturals or synthetics, and modulate target gene transcription. There are three PPAR subtypes (PPARalpha, PPARbeta/delta et PPARgamma) coded by different genes, and two isoforms of PPARgamma proteins have been detected in humans (PPARgamma1 and PPARgamma2). PPAR are mainly modulators of lipid metabolism, but each receptor subtype is pharmacologically distinct, and development of synthetic PPAR agonists has shown their role in cellular (mainly adipocyte) differentiation and in glucose homeostasis. This review summarise the main data, currently available, on expression, biological functions, natural and synthetic (activators) ligands for the PPAR receptor subtypes. PPAR receptors key-role in lipid and glucose métabolisms, has lead to a large clinical use of pharmacological agents acting as PPAR ligands: fibrates, PPARalpha agonists as hypolipidaemic treatment, thiazolidinediones (glitazones), PPARalpha agonists as antidiabetics. Lipid metabolism is impaired in insulin resistant skeletal muscles, fatty acids role in the pathophysiology of insulin resistance generates several hypothesis we briefly describe. Finally, we present and discuss experimental data, suggesting the activation of PPARbeta/delta in skeletal muscle to be a potential new approach in the treatment of insulin resistance and metabolic syndrome.

  1. Serotonin Receptors in Hippocampus

    PubMed Central

    Berumen, Laura Cristina; Rodríguez, Angelina; Miledi, Ricardo; García-Alcocer, Guadalupe

    2012-01-01

    Serotonin is an ancient molecular signal and a recognized neurotransmitter brainwide distributed with particular presence in hippocampus. Almost all serotonin receptor subtypes are expressed in hippocampus, which implicates an intricate modulating system, considering that they can be localized as autosynaptic, presynaptic, and postsynaptic receptors, even colocalized within the same cell and being target of homo- and heterodimerization. Neurons and glia, including immune cells, integrate a functional network that uses several serotonin receptors to regulate their roles in this particular part of the limbic system. PMID:22629209

  2. Angiotensin II Receptor Blockers

    MedlinePlus

    ... side effects include: Dizziness Elevated blood potassium level (hyperkalemia) Localized swelling of tissues (angioedema) There have been ... 31, 2016. Townsend RR. Major side effects of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers. http://www.uptodate. ...

  3. Pituitary Somatostatin Receptor Signaling

    PubMed Central

    Ben-Shlomo, Anat; Melmed, Shlomo

    2010-01-01

    Somatostatin (SRIF) is a major regulator of pituitary function, mostly inhibiting hormone secretion and to a lesser extent pituitary cell growth. Five SRIF receptor subtypes (SSTR1–5) are ubiquitously expressed G-protein coupled receptors. In the pituitary, SSTR1, SSTR2, SSTR3 and SSTR5 are expressed, with SSTR2 and SSTR5 predominating. As new SRIF-analogs have recently been introduced for treatment of pituitary disease, we evaluate the current knowledge of cell-specific pituitary SRIF receptor signaling and highlight areas of future research for comprehensive understanding of these mechanisms. Elucidating pituitary SRIF receptor signaling enables understanding of pituitary hormone secretion and cell growth, and also points to future therapeutic development for pituitary disorders. PMID:20149677

  4. Sigma Receptor Binding Assays.

    PubMed

    Chu, Uyen B; Ruoho, Arnold E

    2015-12-08

    Sigma receptors, both Sigma-1(S1R) and Sigma-2 (S2R), are small molecule-regulated, primarily endoplasmic reticulum (ER) membrane-associated sites. A number of drugs bind to sigma receptors, including the antipsychotic haloperidol and (+)-pentazocine, an opioid analgesic. Sigma receptors are implicated in many central nervous system disorders, in particular Alzheimer's disease and conditions associated with motor control, such as Amyotrophic Lateral Sclerosis (ALS). Described in this unit are radioligand binding assays used for the pharmacological characterization of S1R and S2R. Methods detailed include a radioligand saturation binding assay for defining receptor densities and a competitive inhibition binding assay employing [³H]-(+)-pentazocine for identifying and characterizing novel ligands that interact with S1R. Procedures using [³H]-1,3-di(2-tolyl)guanidine ([³H]-DTG), a nonselective sigma receptor ligand, are described for conducting a saturation binding and competitive inhibition assays for the S2R site. These protocols are of value in drug discovery in identifying new sigma ligands and in the characterization of these receptors.

  5. Muscarinic Receptor Antagonists.

    PubMed

    Matera, Maria Gabriella; Cazzola, Mario

    2017-01-01

    Parasympathetic activity is increased in patients with chronic obstructive pulmonary disease (COPD) and asthma and appears to be the major reversible component of airway obstruction. Therefore, treatment with muscarinic receptor antagonists is an effective bronchodilator therapy in COPD and also in asthmatic patients. In recent years, the accumulating evidence that the cholinergic system controls not only contraction by airway smooth muscle but also the functions of inflammatory cells and airway epithelial cells has suggested that muscarinic receptor antagonists could exert other effects that may be of clinical relevance when we must treat a patient suffering from COPD or asthma. There are currently six muscarinic receptor antagonists licenced for use in the treatment of COPD, the short-acting muscarinic receptor antagonists (SAMAs) ipratropium bromide and oxitropium bromide and the long-acting muscarinic receptor antagonists (LAMAs) aclidinium bromide, tiotropium bromide, glycopyrronium bromide and umeclidinium bromide. Concerns have been raised about possible associations of muscarinic receptor antagonists with cardiovascular safety, but the most advanced compounds seem to have an improved safety profile. Further beneficial effects of SAMAs and LAMAs are seen when added to existing treatments, including LABAs, inhaled corticosteroids and phosphodiesterase 4 inhibitors. The importance of tiotropium bromide in the maintenance treatment of COPD, and likely in asthma, has spurred further research to identify new LAMAs. There are a number of molecules that are being identified, but only few have reached the clinical development.

  6. Genetics of Taste Receptors

    PubMed Central

    Bachmanov, Alexander A.; Bosak, Natalia P.; Lin, Cailu; Matsumoto, Ichiro; Ohmoto, Makoto; Reed, Danielle R.; Nelson, Theodore M.

    2016-01-01

    Taste receptors function as one of the interfaces between internal and external milieus. Taste receptors for sweet and umami (T1R [taste receptor, type 1]), bitter (T2R [taste receptor, type 2]), and salty (ENaC [epithelial sodium channel]) have been discovered in the recent years, but transduction mechanisms of sour taste and ENaC-independent salt taste are still poorly understood. In addition to these five main taste qualities, the taste system detects such noncanonical “tastes” as water, fat, and complex carbohydrates, but their reception mechanisms require further research. Variations in taste receptor genes between and within vertebrate species contribute to individual and species differences in taste-related behaviors. These variations are shaped by evolutionary forces and reflect species adaptations to their chemical environments and feeding ecology. Principles of drug discovery can be applied to taste receptors as targets in order to develop novel taste compounds to satisfy demand in better artificial sweeteners, enhancers of sugar and sodium taste, and blockers of bitterness of food ingredients and oral medications. PMID:23886383

  7. Dopamine Receptors and Neurodegeneration

    PubMed Central

    Rangel-Barajas, Claudia; Coronel, Israel; Florán, Benjamín

    2015-01-01

    Dopamine (DA) is one of the major neurotransmitters and participates in a number of functions such as motor coordination, emotions, memory, reward mechanism, neuroendocrine regulation etc. DA exerts its effects through five DA receptors that are subdivided in 2 families: D1-like DA receptors (D1 and D5) and the D2-like (D2, D3 and D4). All DA receptors are widely expressed in the central nervous system (CNS) and play an important role in not only in physiological conditions but also pathological scenarios. Abnormalities in the DAergic system and its receptors in the basal ganglia structures are the basis Parkinson’s disease (PD), however DA also participates in other neurodegenerative disorders such as Huntington disease (HD) and multiple sclerosis (MS). Under pathological conditions reorganization of DAergic system has been observed and most of the times, those changes occur as a mechanism of compensation, but in some cases contributes to worsening the alterations. Here we review the changes that occur on DA transmission and DA receptors (DARs) at both levels expression and signals transduction pathways as a result of neurotoxicity, inflammation and in neurodegenerative processes. The better understanding of the role of DA receptors in neuropathological conditions is crucial for development of novel therapeutic approaches to treat alterations related to neurodegenerative diseases. PMID:26425390

  8. Adenosine receptor neurobiology: overview.

    PubMed

    Chen, Jiang-Fan; Lee, Chien-fei; Chern, Yijuang

    2014-01-01

    Adenosine is a naturally occurring nucleoside that is distributed ubiquitously throughout the body as a metabolic intermediary. In the brain, adenosine functions as an important upstream neuromodulator of a broad spectrum of neurotransmitters, receptors, and signaling pathways. By acting through four G-protein-coupled receptors, adenosine contributes critically to homeostasis and neuromodulatory control of a variety of normal and abnormal brain functions, ranging from synaptic plasticity, to cognition, to sleep, to motor activity to neuroinflammation, and cell death. This review begun with an overview of the gene and genome structure and the expression pattern of adenosine receptors (ARs). We feature several new developments over the past decade in our understanding of AR functions in the brain, with special focus on the identification and characterization of canonical and noncanonical signaling pathways of ARs. We provide an update on functional insights from complementary genetic-knockout and pharmacological studies on the AR control of various brain functions. We also highlight several novel and recent developments of AR neurobiology, including (i) recent breakthrough in high resolution of three-dimension structure of adenosine A2A receptors (A2ARs) in several functional status, (ii) receptor-receptor heterodimerization, (iii) AR function in glial cells, and (iv) the druggability of AR. We concluded the review with the contention that these new developments extend and strengthen the support for A1 and A2ARs in brain as therapeutic targets for neurologic and psychiatric diseases. © 2014 Elsevier Inc. All rights reserved.

  9. SIGMA RECEPTOR BINDING ASSAYS

    PubMed Central

    CHU, UYEN B.; RUOHO, ARNOLD E.

    2016-01-01

    Sigma receptors belong to a class of small molecule-regulated, primarily endoplasmic reticulum (ER) membrane-associated receptors, of which there are two subtypes: the Sigma-1 receptor (S1R) and the Sigma-2 receptor (S2R). Both S1R and S2R bind to a number of drugs including antipsychotic, haloperidol, and the opioid analgesic, (+)-pentazocine. Sigma receptors are implicated in multiple disease pathologies associated with the nervous system including diseases affecting motor control such as Amyotrophic Lateral Sclerosis (ALS) and Alzeimher's disease. This unit describes methods for the pharmacological characterization of S1R and S2R using radioligand-binding assays. In the first section, radioligand saturation binding assay to determine receptor densities and competitive inhibition assays to characterize affinities of novel compounds are presented for S1R using the selective S1R ligand, [3H]-(+)-pentazocine. The second section describes radioligand saturation binding assay and competitive inhibition assays for the S2R using a non-selective S1R and S2R ligand, [3H]-1,3-di(2-tolyl)guanidine ([3H]-DTG). PMID:26646191

  10. Chemokine Receptor Oligomerization and Allostery

    PubMed Central

    Stephens, Bryan; Handel, Tracy M.

    2014-01-01

    Oligomerization of chemokine receptors has been reported to influence many aspects of receptor function through allosteric communication between receptor protomers. Allosteric interactions within chemokine receptor hetero-oligomers have been shown to cause negative cooperativity in the binding of chemokines and to inhibit receptor activation in the case of some receptor pairs. Other receptor pairs can cause enhanced signaling and even activate entirely new, hetero-oligomer-specific signaling complexes and responses downstream of receptor activation. Many mechanisms contribute to these effects including direct allosteric coupling between the receptors, G protein mediated allostery, G protein stealing, ligand sequestration and recruitment of new intracellular proteins by exposing unique binding interfaces on the oligomerized receptors. These effects present both challenges as well as exciting opportunities for drug discovery. One of the most difficult challenges will involve determining if and when hetero-oligomers versus homo-oligomers are involved in specific disease states. PMID:23415099

  11. Adenosine A1 receptor: Functional receptor-receptor interactions in the brain

    PubMed Central

    Sichardt, Kathrin

    2007-01-01

    Over the past decade, many lines of investigation have shown that receptor-mediated signaling exhibits greater diversity than previously appreciated. Signal diversity arises from numerous factors, which include the formation of receptor dimers and interplay between different receptors. Using adenosine A1 receptors as a paradigm of G protein-coupled receptors, this review focuses on how receptor-receptor interactions may contribute to regulation of the synaptic transmission within the central nervous system. The interactions with metabotropic dopamine, adenosine A2A, A3, neuropeptide Y, and purinergic P2Y1 receptors will be described in the first part. The second part deals with interactions between A1Rs and ionotropic receptors, especially GABAA, NMDA, and P2X receptors as well as ATP-sensitive K+ channels. Finally, the review will discuss new approaches towards treating neurological disorders. PMID:18404442

  12. The cannabinoid receptors.

    PubMed

    Howlett, Allyn C

    2002-08-01

    Cannabinoid receptors were named because they have affinity for the agonist delta9-tetrahydrocannabinol (delta9-THC), a ligand found in organic extracts from Cannabis sativa. The two types of cannabinoid receptors, CB1 and CB2. are G protein coupled receptors that are coupled through the Gi/o family of proteins to signal transduction mechanisms that include inhibition of adenylyl cyclase, activation of mitogen-activated protein kinase, regulation of calcium and potassium channels (CB1 only), and other signal transduction pathways. A class of the eicosanoid ligands are relevant to lipid-mediated cellular signaling because they serve as endogenous agonists for cannabinoid receptors, and are thus referred to as endocannabinoids. Those compounds identified to date include the eicosanoids arachidonoylethanolamide (anandamide), 2-arachidonoylglycerol and 2-arachidonylglyceryl ether (noladin ether). Several excellent reviews on endocannabinoids and their synthesis, metabolism and function have appeared in recent years. This paper will describe the biological activities, pharmacology, and signal transduction mechanisms for the cannabinoid receptors, with particular emphasis on the responses to the eicosanoid ligands.

  13. Biomembrane and receptor mechanisms

    SciTech Connect

    Chapman, D.; Bertoli, E.

    1987-01-01

    This book cover the reviews on biomembrane dynamics; recent spectroscopic studies. Topics covered are freeze fracture: Seeing and thinking biological membranes, membrane proteins and receptors: structure and organisation; techniques to determine the transbilayer distribution and mobility of phospholipids in biological membranes, transbilayer organisation of phospholipids in the plasma membranes of pro-erythroblasts and normal and abnormal red cells, aminophospholipid translocation in the erythroctye membrane is mediated by a specific AIP-dependent enzyme; membrane protein interactions, lipid-protein interactions: selectively and receptor binding, membrane fluidity in the regulation of membrane-linked enzymes, the lipid regulation of receptor functions, microheterogencity of biological membrane: structural and functional implications, fusion-fission reactions in biological membranes and in phospholpid bilayers, methods for studying the structure and function of the mitochondrial uncoupling protein, methods for studying metabolite transport in mitochondria, transport of metabolites in mitochondria, membrane gangliosides and allied glycosphingolipids: Biochemical features and physicochemical properties, the use of merocyanine 540 for monitoring aggregation properties of sialogangliosides in solution, hormone reception at the cell surface - an overview, double role for GIP in the stimulus secretion sequence of mast cells and neurophils, tumor promoters and hormone receptor coupling mechanisms in the anterior pituitary. The regulation of hormone-dependent adenylate cyclase in native membranes and systems reconstituted from purified components.- Immunological tools for the study of plasma membrane receptors.

  14. Receptor strategies in pancreatitis.

    PubMed Central

    Grendell, J. H.

    1992-01-01

    A variety of receptors on pancreatic acinar and duct cells regulate both pancreatic exocrine secretion and intracellular processes. These receptors are potential sites of action for therapeutic agents in the treatment of pancreatitis. Cholecystokinin (CCK) receptor antagonists, which may reduce the level of metabolic "stress" on acinar cells, have been shown to mitigate the severity of acute pancreatitis in a number of models. Not all studies have shown a benefit, however, and differences may exist between different structural classes of antagonists. Because increased pancreatic stimulation due to loss of feedback inhibition of CCK has been proposed to contribute to the pain of some patients with chronic pancreatitis, CCK receptor antagonists could also be of benefit in this setting. Somatostatin and its analogs diminish pancreatic secretion of water and electrolytes and have been effective in treating pancreatic fistulas and pseudocysts. These agents are also being evaluated for their ability to reduce pain in chronic pancreatitis (perhaps by reducing ductal pressure by diminishing secretory volume) and mitigating the severity of acute pancreatitis (possibly by reducing the metabolic load on acinar cells). Recently described secretin receptor antagonists may also have therapeutic value as a means of selectively inhibiting pancreatic secretion of water and electrolytes. PMID:1340060

  15. Ionotropic Crustacean Olfactory Receptors

    PubMed Central

    Corey, Elizabeth A.; Bobkov, Yuriy; Ukhanov, Kirill; Ache, Barry W.

    2013-01-01

    The nature of the olfactory receptor in crustaceans, a major group of arthropods, has remained elusive. We report that spiny lobsters, Panulirus argus, express ionotropic receptors (IRs), the insect chemosensory variants of ionotropic glutamate receptors. Unlike insects IRs, which are expressed in a specific subset of olfactory cells, two lobster IR subunits are expressed in most, if not all, lobster olfactory receptor neurons (ORNs), as confirmed by antibody labeling and in situ hybridization. Ligand-specific ORN responses visualized by calcium imaging are consistent with a restricted expression pattern found for other potential subunits, suggesting that cell-specific expression of uncommon IR subunits determines the ligand sensitivity of individual cells. IRs are the only type of olfactory receptor that we have detected in spiny lobster olfactory tissue, suggesting that they likely mediate olfactory signaling. Given long-standing evidence for G protein-mediated signaling in activation of lobster ORNs, this finding raises the interesting specter that IRs act in concert with second messenger-mediated signaling. PMID:23573266

  16. Taste Receptors in Innate Immunity

    PubMed Central

    Lee, Robert J.

    2014-01-01

    Taste receptors were first identified on the tongue, where they initiate a signaling pathway that communicates information to the brain about the nutrient content or potential toxicity of ingested foods. However, recent research has shown that taste receptors are also expressed in a myriad of other tissues, from the airway and gastrointestinal epithelia to the pancreas and brain. The functions of many of these extraoral taste receptors remain unknown, but emerging evidence suggests that bitter and sweet taste receptors in the airway are important sentinels of innate immunity. This review discusses taste receptor signaling, focusing on the G-protein coupled–receptors that detect bitter, sweet, and savory tastes, followed by an overview of extraoral taste receptors and in-depth discussion of studies demonstrating the roles of taste receptors in airway innate immunity. Future research on extraoral taste receptors has significant potential for identification of novel immune mechanisms and insights into host-pathogen interactions. PMID:25323130

  17. Human presynaptic receptors.

    PubMed

    Schlicker, Eberhard; Feuerstein, Thomas

    2017-04-01

    Presynaptic receptors are sites at which transmitters, locally formed mediators or hormones inhibit or facilitate the release of a given transmitter from its axon terminals. The interest in the identification of presynaptic receptors has faded in recent years and it may therefore be justified to give an overview of their occurrence in the autonomic and central nervous system; this review will focus on presynaptic receptors in human tissues. Autoreceptors are presynaptic receptors at which a given transmitter restrains its further release, though in some instances may also increase its release. Inhibitory autoreceptors represent a typical example of a negative feedback; they are tonically activated by the respective endogenous transmitter and/or are constitutively active. Autoreceptors also play a role under pathophysiological conditions, e.g. by limiting the massive noradrenaline release occurring during congestive heart failure. They can be used for therapeutic purposes; e.g., the α2-adrenoceptor antagonist mirtazapine is used as an antidepressant and the inverse histamine H3 receptor agonist pitolisant has been marketed as a new drug for the treatment of narcolepsy in 2016. Heteroreceptors are presynaptic receptors at which transmitters from adjacent neurons, locally formed mediators (e.g. endocannabinoids) or hormones (e.g. adrenaline) can inhibit or facilitate transmitter release; they may be subject to an endogenous tone. The constipating effect of the sympathetic nervous system or of the antihypertensive drug clonidine is related to the activation of inhibitory α2-adrenoceptors on postganglionic parasympathetic neurons. Part of the stimulating effect of adrenaline on the sympathetic nervous system during stress is related to its facilitatory effect on noradrenaline release via β2-adrenoceptors.

  18. Biomimetic receptors and sensors.

    PubMed

    Dickert, Franz L

    2014-11-27

    In biomimetics, living systems are imitated to develop receptors for ions, molecules and bioparticles. The most pertinent idea is self-organization in analogy to evolution in nature, which created the key-lock principle. Today, modern science has been developing host-guest chemistry, a strategy of supramolecular chemistry for designing interactions of analytes with synthetic receptors. This can be realized, e.g., by self-assembled monolayers (SAMs) or molecular imprinting. The strategies are used for solid phase extraction (SPE), but preferably in developing recognition layers of chemical sensors.

  19. Assays for calcitonin receptors

    SciTech Connect

    Teitelbaum, A.P.; Nissenson, R.A.; Arnaud, C.D.

    1985-01-01

    The assays for calcitonin receptors described focus on their use in the study of the well-established target organs for calcitonin, bone and kidney. The radioligand used in virtually all calcitonin binding studies is /sup 125/I-labelled salmon calcitonin. The lack of methionine residues in this peptide permits the use of chloramine-T for the iodination reaction. Binding assays are described for intact bone, skeletal plasma membranes, renal plasma membranes, and primary kidney cell cultures of rats. Studies on calcitonin metabolism in laboratory animals and regulation of calcitonin receptors are reviewed.

  20. Rabies virus receptors.

    PubMed

    Lafon, Monique

    2005-02-01

    There is convincing in vitro evidence that the muscular form of the nicotinic acetylcholine receptor (nAChR), the neuronal cell adhesion molecule (NCAM), and the p75 neurotrophin receptor (p75NTR) bind rabies virus and/or facilitate rabies virus entry into cells. Other components of the cell membrane, such as gangliosides, may also participate in the entry of rabies virus. However, little is known of the role of these molecules in vivo. This review proposes a speculative model that accounts for the role of these different molecules in entry and trafficking of rabies virus into the nervous system.

  1. The liver X receptors.

    PubMed

    Lala, Deepak S

    2005-09-01

    The liver X receptors (LXRs), members of the nuclear receptor superfamily, are potential targets for a variety of diseases. While there are many opportunities for the development of LXR-based therapeutics, there are some major hurdles, such as the ability of LXRs to cause hypertriglyceridemia, as well as some species-dependent aspects of LXR-mediated gene regulation. In addition to classical pharmacological approaches using relevant cellular and animal models, systematic molecular-based strategies will be important in overcoming these obstacles.

  2. Biomimetic Receptors and Sensors

    PubMed Central

    Dickert, Franz L.

    2014-01-01

    In biomimetics, living systems are imitated to develop receptors for ions, molecules and bioparticles. The most pertinent idea is self-organization in analogy to evolution in nature, which created the key-lock principle. Today, modern science has been developing host-guest chemistry, a strategy of supramolecular chemistry for designing interactions of analytes with synthetic receptors. This can be realized, e.g., by self-assembled monolayers (SAMs) or molecular imprinting. The strategies are used for solid phase extraction (SPE), but preferably in developing recognition layers of chemical sensors. PMID:25436653

  3. CONTAMINANT INTERACTIONS WITH STEROID RECEPTORS: EVIDENCE FOR RECEPTOR BINDING.

    EPA Science Inventory

    Steroid receptors are important determinants of endocrine disrupter consequences. As the most frequently proposed mechanism of endocrine-disrupting contaminant (EDC) action, steroid receptors are not only targets of natural steroids but are also commonly sites of nonsteroidal com...

  4. Pharmacology of mammalian olfactory receptors.

    PubMed

    Smith, Richard S; Peterlin, Zita; Araneda, Ricardo C

    2013-01-01

    Mammalian species have evolved a large and diverse number of odorant receptors (ORs). These proteins comprise the largest family of G-protein-coupled receptors (GPCRs) known, amounting to ~1,000-different receptors in the rodent. From the perspective of olfactory coding, the availability of such a vast number of chemosensory receptors poses several fascinating questions; in addition, such a large repertoire provides an attractive biological model to study ligand-receptor interactions. The limited functional expression of these receptors in heterologous systems, however, has greatly hampered attempts to deorphanize them. We have employed a successful approach that combines electrophysiological and imaging techniques to analyze the response profiles of single sensory neurons. Our approach has enabled us to characterize the "odor space" of a population of native aldehyde receptors and the molecular range of a genetically engineered receptor, OR-I7.

  5. Synaptic Neurotransmitter-Gated Receptors

    PubMed Central

    Smart, Trevor G.; Paoletti, Pierre

    2012-01-01

    Since the discovery of the major excitatory and inhibitory neurotransmitters and their receptors in the brain, many have deliberated over their likely structures and how these may relate to function. This was initially satisfied by the determination of the first amino acid sequences of the Cys-loop receptors that recognized acetylcholine, serotonin, GABA, and glycine, followed later by similar determinations for the glutamate receptors, comprising non-NMDA and NMDA subtypes. The last decade has seen a rapid advance resulting in the first structures of Cys-loop receptors, related bacterial and molluscan homologs, and glutamate receptors, determined down to atomic resolution. This now provides a basis for determining not just the complete structures of these important receptor classes, but also for understanding how various domains and residues interact during agonist binding, receptor activation, and channel opening, including allosteric modulation. This article reviews our current understanding of these mechanisms for the Cys-loop and glutamate receptor families. PMID:22233560

  6. Characterization of melanocortin receptors.

    PubMed

    Goetz, Aaron S; Ignar, Diane M

    2003-11-01

    This unit describes a Scintillation Proximity Assay (SPA) for the measurement of ligand binding to melanocortin receptors (MCRs) using membranes prepared from cell lines stably expressing recombinant MCRs. It provides a facile method for determining the affinity of compounds at MC1R, MC3R, MC4R, or MC5R.

  7. Calcitonin and calcitonin receptors

    PubMed Central

    Masi, Laura; Brandi, Maria Luisa

    2007-01-01

    Calcitonin (CT) is a polypeptide hormone with 32 aminoacids syntetized primarily by the thyroid. Several evidences support the existence of nonthyroidal CT like peptide. The CT gene transcript also encodes a distinct peptide known as calcitonin gene related peptide (CGRP) which is a potent vasodilator and responsible for the stimulation of the glomerular filtration rate. In addition, a 37 aminoacid peptide amylin has been originally isolated by pancreatic β-cells. Amylin is able to inhibit insulin secretion, glucose transport into the skeletal musculature and gluconeogenesis. It is also able to inhibit gastric emptying. In the kidney it is able to modulate Calcium (Ca2+) excretion and increases renin activity. Finally, high affinity amylin receptors have been identified in the brain of the rat. The calcitonin receptor (CTR) is a member of a subfamily of the seven-transmembrane domain G-protein coupled receptor super family that includes several peptides. Members of this family have a similar structure with other seven-membrane-spanning domain G-protein coupled receptors. The genetic contribution to osteoporosis susceptibility is well documented and many studies demonstrated that genetic factors play important roles in the regulation of bone metabolism. Restriction Fragment Length Polymorphisms (RFLPs) for the CTR gene have been described in the literature with a positive association with the lumbar bone mineral density (BMD), femoral neck BMD and with a lower incidence of vertebral fractures. PMID:22461211

  8. Label-Free Receptor Assays

    PubMed Central

    Fang, Ye

    2010-01-01

    Label-free biosensors offer integrated, kinetic and multi-parametric measures of receptor biology and ligand pharmacology in whole cells. Being highly sensitive and pathway-unbiased, label-free receptor assays can be used to probe the systems cell biology including pleiotropic signaling of receptors, and to characterize the functional selectivity and phenotypic pharmacology of ligand molecules. These assays provide a new dimension for elucidating receptor biology and for facilitating drug discovery. PMID:21221420

  9. Label-Free Receptor Assays.

    PubMed

    Fang, Ye

    2011-01-01

    Label-free biosensors offer integrated, kinetic and multi-parametric measures of receptor biology and ligand pharmacology in whole cells. Being highly sensitive and pathway-unbiased, label-free receptor assays can be used to probe the systems cell biology including pleiotropic signaling of receptors, and to characterize the functional selectivity and phenotypic pharmacology of ligand molecules. These assays provide a new dimension for elucidating receptor biology and for facilitating drug discovery.

  10. P2 receptors and immunity

    PubMed Central

    Rayah, Amel; Kanellopoulos, Jean M.; Di Virgilio, Francesco

    2012-01-01

    Immune cells express receptors for extracellular nucleotides named P2 receptors. P2 receptors transduce signals delivered by nucleotides present in the extracellular environment. Accruing evidence shows that purinergic signalling has a profound effect on multiple immune cell responses such as T lymphocyte proliferation, chemotaxis, cytokine release, phagocytosis, Ag presentation and cytotoxicity. This makes P2 receptors an attractive target for the therapy of immuno-mediated disease and cancer. PMID:22909902

  11. Functional Characterization of Odorant Receptors

    DTIC Science & Technology

    1994-02-07

    94 IFINAL REPORT 9/1/92-11/30/93 4. TITLE AND SUBTITLE S. FUNDING NUMBERS Functional Characterization of Odorant Receptors DAAL03-92-G-0390 6. AUTHOR(S...characterization of odorant receptors have developed in two directions. One direction is concerned with the characterization of the ligand specificity of... receptor have been replaced by the equivalent regions of odorant receptor 1-15 (Buck and Axel, 1991), thus forming a chimaeric seven transmembrane domain

  12. Universality of receptor channel responses.

    PubMed

    Kardos, J; Nyikos, L

    2001-12-01

    Rate parameters estimated for neurotransmitter-gated receptor channel opening and receptor desensitization are classified according to their dependence on the temporal resolution of the techniques applied in the measurements. Because allosteric proteins constituting receptor channels impose restrictions on the types of model suitable to describe the dynamic response of channels to neurotransmitters, Markovian, non-linear or fractal dynamic models and their possible extension to receptor channel response in excitable membranes are discussed.

  13. Histamine H3-receptor isoforms.

    PubMed

    Bakker, R A

    2004-10-01

    Increasing evidence supports a role for HA as a neurotransmitter and neuromodulator in various brain functions, including emotion, cognition, and feeding. The recent cloning of the histamine H3 receptor allowed for the subsequent cloning of a variety of H3 receptor isoforms from different species as well as the H4 receptor. As a result a wide variety of H3-receptor isoforms are now known that display differential brain expression patterns and signalling properties. These recent discoveries are discussed in view of the growing interest of the H3 receptor as a target for the development of potential therapeutics.

  14. Receptor tyrosine kinases in carcinogenesis.

    PubMed

    Zhang, Xiao-Ying; Zhang, Pei-Ying

    2016-11-01

    Receptor tyrosine kinases (RTKs) are cell surface glycoproteins with enzymatic activity involved in the regulation of various important functions. In all-important physiological functions including differentiation, cell-cell interactions, survival, proliferation, metabolism, migration and signaling these receptors are the key players of regulation. Additionally, mutations of RTKs or their overexpression have been described in many human cancers and are being explored as a novel avenue for a new therapeutic approach. Some of the deregulated RTKs observed to be significantly affected in cancers included vascular endothelial growth factor receptor, epidermal growth factor receptor, fibroblast growth factor receptor, RTK-like orphan receptor 1 (ROR1) and the platelet-derived growth factor receptor. These deregulated RTKs offer attractive possibilities for the new anticancer therapeutic approach involving specific targeting by monoclonal antibodies as well as kinase. The present review aimed to highlight recent perspectives of RTK ROR1 in cancer.

  15. Taste Receptor Genes

    PubMed Central

    Bachmanov, Alexander A.; Beauchamp, Gary K.

    2009-01-01

    In the past several years, tremendous progress has been achieved with the discovery and characterization of vertebrate taste receptors from the T1R and T2R families, which are involved in recognition of bitter, sweet, and umami taste stimuli. Individual differences in taste, at least in some cases, can be attributed to allelic variants of the T1R and T2R genes. Progress with understanding how T1R and T2R receptors interact with taste stimuli and with identifying their patterns of expression in taste cells sheds light on coding of taste information by the nervous system. Candidate mechanisms for detection of salts, acids, fat, complex carbohydrates, and water have also been proposed, but further studies are needed to prove their identity. PMID:17444812

  16. Thyroid Stimulating Hormone Receptor

    PubMed Central

    Tuncel, Murat

    2017-01-01

    Thyroid stimulating hormone receptor (TSHR) plays a pivotal role in thyroid hormone metabolism. It is a major controller of thyroid cell function and growth. Mutations in TSHR may lead to several thyroid diseases, most commonly hyperthyroidism. Although its genetic and epigenetic alterations do not directly lead to carcinogenesis, it has a crucial role in tumor growth, which is initiated by several oncogenes. This article will provide a brief review of TSHR and related diseases. PMID:28117293

  17. Quantitative receptor autoradiography

    SciTech Connect

    Boast, C.A.; Snowhill, E.W.; Altar, C.A.

    1986-01-01

    Quantitative receptor autoradiography addresses the topic of technical and scientific advances in the sphere of quantitative autoradiography. The volume opens with a overview of the field from a historical and critical perspective. Following is a detailed discussion of in vitro data obtained from a variety of neurotransmitter systems. The next section explores applications of autoradiography, and the final two chapters consider experimental models. Methodological considerations are emphasized, including the use of computers for image analysis.

  18. Thyroid Stimulating Hormone Receptor.

    PubMed

    Tuncel, Murat

    2016-01-05

    Thyroid stimulating hormone receptor (TSHR) plays a pivotal role in thyroid hormone metabolism. It is a major controller of thyroid cell function and growth. Mutations in TSHR may lead to several thyroid diseases, most commonly hyperthyroidism. Although its genetic and epigenetic alterations do not directly lead to carcinogenesis, it has a crucial role in tumor growth, which is initiated by several oncogenes. This article will provide a brief review of TSHR and related diseases.

  19. Metabotropic Glutamate Receptors

    PubMed Central

    Dillon, James; Franks, Christopher J.; Murray, Caitriona; Edwards, Richard J.; Calahorro, Fernando; Ishihara, Takeshi; Katsura, Isao; Holden-Dye, Lindy; O'Connor, Vincent

    2015-01-01

    Glutamatergic neurotransmission is evolutionarily conserved across animal phyla. A major class of glutamate receptors consists of the metabotropic glutamate receptors (mGluRs). In C. elegans, three mGluR genes, mgl-1, mgl-2, and mgl-3, are organized into three subgroups, similar to their mammalian counterparts. Cellular reporters identified expression of the mgls in the nervous system of C. elegans and overlapping expression in the pharyngeal microcircuit that controls pharyngeal muscle activity and feeding behavior. The overlapping expression of mgls within this circuit allowed the investigation of receptor signaling per se and in the context of receptor interactions within a neural network that regulates feeding. We utilized the pharmacological manipulation of neuronally regulated pumping of the pharyngeal muscle in the wild-type and mutants to investigate MGL function. This defined a net mgl-1-dependent inhibition of pharyngeal pumping that is modulated by mgl-3 excitation. Optogenetic activation of the pharyngeal glutamatergic inputs combined with electrophysiological recordings from the isolated pharyngeal preparations provided further evidence for a presynaptic mgl-1-dependent regulation of pharyngeal activity. Analysis of mgl-1, mgl-2, and mgl-3 mutant feeding behavior in the intact organism after acute food removal identified a significant role for mgl-1 in the regulation of an adaptive feeding response. Our data describe the molecular and cellular organization of mgl-1, mgl-2, and mgl-3. Pharmacological analysis identified that, in these paradigms, mgl-1 and mgl-3, but not mgl-2, can modulate the pharyngeal microcircuit. Behavioral analysis identified mgl-1 as a significant determinant of the glutamate-dependent modulation of feeding, further highlighting the significance of mGluRs in complex C. elegans behavior. PMID:25869139

  20. The interleukin-4 receptor: signal transduction by a hematopoietin receptor.

    PubMed

    Keegan, A D; Pierce, J H

    1994-02-01

    Over the last several years, the receptors for numerous cytokines have been molecularly characterized. Analysis of their amino acid sequences shows that some of these receptors bear certain motifs in their extracellular domains that define a family of receptors called the Hematopoietin receptor superfamily. Significant advances in characterizing the structure, function, and mechanisms of signal transduction have been made for several members of this family. The purpose of this review is to discuss the recent advances made for one of the family members, the interleukin (IL) 4 receptor. Other receptor systems have recently been reviewed elsewhere. The IL-4 receptor consists of, at the minimum, the cloned 140 kDa IL-4-binding chain with the potential for associating with other chains. The IL-4 receptor transduces its signal by activating a tyrosine kinase that phosphorylates cellular substrates, including the receptor itself, and the 170 kDa substrate called 4PS. Phosphorylated 4PS interacts with the SH2 domain of the enzyme PI-3'-kinase and increases its enzymatic activity. These early events in the IL-4 receptor initiated signaling pathway may trigger a series of signals that will ultimately lead to an IL-4 specific biologic outcome.

  1. Investigational melatonin receptor agonists.

    PubMed

    Hardeland, Rüdiger

    2010-06-01

    Melatonin is a major chronobiological regulator involved in circadian phasing, sleep, and numerous other functions including cyto-/neuroprotection, immune modulation, and energy metabolism. The suitability of melatonin as a drug is limited because of its short half-life. Therefore, various indolic and non-indolic melatonergic agonists have been developed. Frequent health problems such as sleep disturbances, neuropsychiatric disorders related to circadian dysphasing, and metabolic diseases associated with insulin resistance are targeted by melatonergic agonists. Various synthetic melatonergic drugs are compared with regard to receptor affinities, selectivity, effects on sleep, endogenous melatonin, circadian phase and insulin-related metabolism. The chemical design of melatonin receptor agonists is discussed in relation to consequences for receptor affinity, selectivity, metabolism, and spectrum of effects. Melatonergic agonists are suitable for phase-shifting circadian rhythms, and may be used for treating disorders related to circadian dysfunction including sleep difficulties. Facilitation of sleep onset is a general property, whereas promotion of sleep maintenance is demonstrable but not always fully sufficient. Details are especially available for tasimelteon. Support of insulin sensitivity may become a new area of application for compounds such as NEU-P11. Some drugs acting additionally as serotonergic antagonists display antidepressant properties.

  2. [Lipoprotein receptors. Old acquaintances and newcomers].

    PubMed

    Ducobu, J

    1997-02-01

    Lipoprotein receptors are plasma membrane proteins of high affinity which interact with circulating lipoprotein particles. The well characterized LDL receptor continues to be analysed and some new findings on its intracellular mechanisms of action have emerged. New lipoprotein receptors have recently been described: the chylomicron remnant receptor or LDL-related protein (LRP), the lipolysis stimulated receptor (LSR), the very low density lipoprotein receptor (VLDLR), the HDL receptor (HDLR) and the scavenger receptor (SR). The molecular details of the receptors will facilitate the development of new therapeutic means to improve receptor-mediated clearance of lipoproteins.

  3. Complement fragments C3a and C5a: the salt and pepper of the immune response.

    PubMed

    Sacks, Steven H

    2010-03-01

    The influence of complement on B-cell responses has been known for many years, but the notion that T-cell recognition, expansion and differentiation are complement dependent has only recently gained impetus. DC, and to a lesser extent T cells, produce a range of complement components necessary for complement activation, and these cells also express receptors that detect complement-activation products such as C3a and C5a (anaphylatoxins). In the absence of C3a-receptor (C3aR) signalling, DC lose their capacity to induce potent Th1 responses against alloantigen and also favour the emergence of Treg. A study in this issue of the European Journal of Immunology not only spotlights the importance of C5aR signalling in DC interaction with T cells, but also shows how cooperation with other signalling pathways determines the outcome of T-cell activation. Remove C5aR from the equation, TLR2-stimulated DC induce naive CD4(+) Th cells to undergo differentiation not only mainly to Th17 cells but also to Treg, via a TGF-beta-dependent pathway. Thus, anaphylatoxins in conjunction with other danger signalling pathways modify the function of DC in antigen presentation and help to shape the primary immune response. Future work will need to address the impact of anaphylatoxins on protective immunity in vivo and determine the wider implications of anaphylatoxins for allo- and autoimmunity.

  4. Generation of complement component C5a by ischemic neurons promotes neuronal apoptosis.

    PubMed

    Pavlovski, Dale; Thundyil, John; Monk, Peter N; Wetsel, Rick A; Taylor, Stephen M; Woodruff, Trent M

    2012-09-01

    C5a receptors are found in the central nervous system (CNS), on both neurons and glia. However, the origin of the C5a, which activates these receptors, is unclear. In the present study, we show that primary cultured mouse cortical neurons constitutively express C5, the precursor of C5a, and express the classical receptor for C5a, CD88. With cell ischemia caused by 12 h glucose deprivation, or oxygen-glucose deprivation (OGD), neurons demonstrated increased apoptosis, up-regulation of CD88, and increased levels of C5a in the media. Exogenous murine C5a (100 nM) added to the neuronal cultures resulted in apoptosis, without affecting cell necrosis. Pretreatment of the cells with the specific CD88 receptor antagonist PMX53 (100 nM) significantly blocked ischemia-induced apoptosis (∼50%), and neurons from CD88(-/-) mice were similarly protected. In a murine model of stroke, using middle cerebral artery occlusion (MCAO), we found that C5a levels in the brain increased; this also occurred in cerebral slice cultures exposed to OGD. CD88(-/-) mice subjected to MCAO had significantly reduced infarct volumes and improved neurological scores. Taken together, our results demonstrate that neurons in the CNS have the capability to generate C5a following ischemic stress, and this has the potential to activate their C5a receptors, with deleterious consequences.

  5. Is the acetylcholine receptor a rabies virus receptor?

    PubMed

    Lentz, T L; Burrage, T G; Smith, A L; Crick, J; Tignor, G H

    1982-01-08

    Rabies virus was found on mouse diaphragms and on cultured chick myotubes in a distribution coinciding with that of the acetylcholine receptor. Treatment of the myotubes with alpha-bungarotoxin and d-tubocurarine before the addition of the virus reduced the number of myotubes that became infected with rabies virus. These findings together suggest that acetylcholine receptors may serve as receptors for rabies virus. The binding of virus to acetylcholine receptors, which are present in high density at the neuromuscular junction, would provide a mechanism whereby the virus could be locally concentrated at sites in proximity to peripheral nerves facilitating subsequent uptake and transfer to the central nervous system.

  6. Muscarinic receptor family interacting proteins: role in receptor function.

    PubMed

    Borroto-Escuela, Dasiel O; Correia, Patrícia A; Romero-Fernandez, Wilber; Narvaez, Manuel; Fuxe, Kjell; Ciruela, Francisco; Garriga, Pere

    2011-02-15

    G protein-coupled receptors constitute one of the most important families of membrane receptors through which cells respond to extracellular stimuli. Receptors of this superfamily likely function as signal transduction complexes. The identification and analysis of their components provide new insights into a better understanding of these receptors' function and regulation. We used tandem-affinity purification and mass spectrometry as a systematic approach to characterize multiprotein complexes in the acetylcholine muscarinic receptor subfamily. To overcome the limitations associated with membrane protein receptor solubilization with detergents, we developed a strategy in which receptors are co-expressed with a cytoplasmic minigene construct, encoding the third intracellular loop and the C-terminal tail tagged to the tandem-affinity-cassette of each receptor subtype. Numerous protein complexes were identified, including many new interactions in various signalling pathways. Systematic identification data set together with protein interactions reported in the literature revealed a high degree of connectivity. These allow the proposal, for the first time, of an outline of the muscarinic interactome as a network of protein complexes and a context for a more reasoned and informed approach to drug discovery and muscarinic receptor subtype specificities.

  7. Angiotensin II receptors in testes

    SciTech Connect

    Millan, M.A.; Aguilera, G.

    1988-05-01

    Receptors for angiotensin II (AII) were identified and characterized in testes of rats and several primate species. Autoradiographic analysis of the binding of 125I-labeled (Sar1,Ile8)AII to rat, rhesus monkey, cebus monkey, and human testicular slide-mounted frozen sections indicated specific binding to Leydig cells in the interstitium. In rat collagenase-dispersed interstitial cells fractionated by Percoll gradient, AII receptor content was parallel to that of hCG receptors, confirming that the AII receptors are in the Leydig cells. In rat dispersed Leydig cells, binding was specific for AII and its analogs and of high affinity (Kd, 4.8 nM), with a receptor concentration of 15 fmol/10(6) cells. Studies of AII receptors in rat testes during development reveals the presence of high receptor density in newborn rats which decreases toward the adult age (4934 +/- 309, 1460 +/- 228, 772 +/- 169, and 82 +/- 12 fmol/mg protein at 5, 15, 20, and 30 days of age, respectively) with no change in affinity. At all ages receptors were located in the interstitium, and the decrease in binding was parallel to the decrease in the interstitial to tubular ratio observed with age. AII receptor properties in membrane-rich fractions from prepuberal testes were similar in the rat and rhesus monkey. Binding was time and temperature dependent, reaching a plateau at 60 min at 37 C, and was increased by divalent cations, EGTA, and dithiothreitol up to 0.5 mM. In membranes from prepuberal monkey testes, AII receptors were specific for AII analogs and of high affinity (Kd, 4.2 nM) with a receptor concentration of 7599 +/- 1342 fmol/mg protein. The presence of AII receptors in Leydig cells in rat and primate testes in conjunction with reports of the presence of other components of the renin-angiotensin system in the testes suggests that the peptide has a physiological role in testicular function.

  8. Targeting the androgen receptor.

    PubMed

    Friedlander, Terence W; Ryan, Charles J

    2012-11-01

    Androgen receptor (AR)-mediated signaling is critical to the growth and survival of prostate cancer. Although medical castration and antiandrogen therapy can decrease AR activity and lower PSA, castration resistance eventually develops. Recent work exploring the molecular structure and evolution of AR in response to hormonal therapies has revealed novel mechanisms of progression of castration-resistant prostate cancer and yielded new targets for drug development. This review focuses on understanding the mechanisms of persistent AR signaling in the castrate environment, and highlights new therapies either currently available or in clinical trials, including androgen synthesis inhibitors and novel direct AR inhibitors.

  9. Engineering Chimeric Antigen Receptors

    PubMed Central

    Kulemzin, S. V.; Kuznetsova, V. V.; Mamonkin, M.; Taranin, A. V.; Gorchakov, A. A.

    2017-01-01

    Chimeric antigen receptors (CARs) are recombinant protein molecules that redirect cytotoxic lymphocytes toward malignant and other target cells. The high feasibility of manufacturing CAR-modified lymphocytes for the therapy of cancer has spurred the development and optimization of new CAR T cells directed against a broad range of target antigens. In this review, we describe the main structural and functional elements constituting a CAR, discuss the roles of these elements in modulating the anti-tumor activity of CAR T cells, and highlight alternative approaches to CAR engineering. PMID:28461969

  10. GABAρ1/GABAAα1 receptor chimeras to study receptor desensitization

    PubMed Central

    Martínez-Torres, Ataúlfo; Demuro, Angelo; Miledi, Ricardo

    2000-01-01

    γ-Aminobutyrate type C (GABAC) receptors are ligand-gated ion channels that are expressed preponderantly in the vertebrate retina and are characterized, among other things, by a very low rate of desensitization and resistance to the specific GABAA antagonist bicuculline. To examine which structural elements determine the nondesensitizing character of the human homomeric ρ1 receptor, we used a combination of gene chimeras and electrophysiology of receptors expressed in Xenopus oocytes. Two chimeric genes were constructed, made up of portions of the ρ1-subunit and of the α1-subunit of the GABAA receptor. When expressed in Xenopus oocytes, one chimeric gene (ρ1/α1) formed functional homooligomeric receptors that were fully resistant to bicuculline and were blocked by the specific GABAC antagonist (1,2,5,6-tetrahydropyridine-4-yl)methylphosphinic acid and by zinc. Moreover, these chimeric receptors had a fast-desensitizing component, even faster than that of heterooligomeric GABAA receptors, in striking contrast to the almost nil desensitization of wild-type ρ1 (wt ρ1) receptors. To see whether the fast-desensitizing characteristic of the chimera was determined by the amino acids forming the ion channels, we replaced the second transmembrane segment (TM2) of ρ1 by that of the α1-subunit of GABAA. Although the α1-subunit forms fast-desensitizing receptors when coexpressed with other GABAA subunits, the sole transfer of the α1TM2 segment to ρ1 was not sufficient to form desensitizing receptors. All this suggests that the slow-desensitizing trait of ρ1 receptors is determined by a combination of several interacting domains along the molecule. PMID:10725369

  11. Opioid receptor heteromers in analgesia

    PubMed Central

    Costantino, Cristina M.; Gomes, Ivone; Stockton, Steven D.; Lim, Maribel P.; Devi, Lakshmi A.

    2013-01-01

    Opiates such as morphine and fentanyl, a major class of analgesics used in the clinical management of pain, exert their effects through the activation of opioid receptors. Opioids are among the most commonly prescribed and frequently abused drugs in the USA; however, the prolonged use of opiates often leads to the development of tolerance and addiction. Although blockade of opioid receptors with antagonists such as naltrexone and naloxone can lessen addictive impulses and facilitate recovery from overdose, systemic disruption of endogenous opioid receptor signalling through the use of these antagonistic drugs can have severe side effects. In the light of these challenges, current efforts have focused on identifying new therapeutic targets that selectively and specifically modulate opioid receptor signalling and function so as to achieve analgesia without the adverse effects associated with chronic opiate use. We have previously reported that opioid receptors interact with each other to form heteromeric complexes and that these interactions affect morphine signalling. Since chronic morphine administration leads to an enhanced level of these heteromers, these opioid receptor heteromeric complexes represent novel therapeutic targets for the treatment of pain and opiate addiction. In this review, we discuss the role of heteromeric opioid receptor complexes with a focus on mu opioid receptor (MOR) and delta opioid receptor (DOR) heteromers. We also highlight the evidence for altered pharmacological properties of opioid ligands and changes in ligand function resulting from the heteromer formation. PMID:22490239

  12. [Olfactory receptors and odour coding].

    PubMed

    Pernollet, Jean-Claude; Sanz, Guenhaël; Briand, Loïc

    2006-09-01

    The first step of olfactory detection involves interactions between odorant molecules and neuronal protein receptors. Odour coding results from the combinatory activation of a set of receptors and rests on their clonal expression and olfactory neurone connexion, which lead to formation of a specific sensory map in the cortex. This system, sufficient to discriminate myriads of odorants with a mere 350 different receptors, allows humans to smell molecules that are not natural (new cooking flavours, synthetic chemicals...). The extreme olfactory genome diversity explains the absence of odour semantics. Olfactory receptors are also involved in cellular chemotaxis.

  13. Nuclear Receptors in Skeletal Homeostasis.

    PubMed

    Zuo, Hao; Wan, Yihong

    2017-01-01

    Nuclear receptors are a family of transcription factors that can be activated by lipophilic ligands. They are fundamental regulators of development, reproduction, and energy metabolism. In bone, nuclear receptors enable bone cells, including osteoblasts, osteoclasts, and osteocytes, to sense their dynamic microenvironment and maintain normal bone development and remodeling. Our views of the molecular mechanisms in this process have advanced greatly in the past decade. Drugs targeting nuclear receptors are widely used in the clinic for treating patients with bone disorders such as osteoporosis by modulating bone formation and resorption rates. Deficiency in the natural ligands of certain nuclear receptors can cause bone loss; for example, estrogen loss in postmenopausal women leads to osteoporosis and increases bone fracture risk. In contrast, excessive ligands of other nuclear receptors, such as glucocorticoids, can also be detrimental to bone health. Nonetheless, the ligand-induced osteoprotective effects of many other nuclear receptors, e.g., vitamin D receptor, are still in debate and require further characterizations. This review summarizes previous studies on the roles of nuclear receptors in bone homeostasis and incorporates the most recent findings. The advancement of our understanding in this field will help researchers improve the applications of agonists, antagonists, and selective modulators of nuclear receptors for therapeutic purposes; in particular, determining optimal pharmacological drug doses, preventing side effects, and designing new drugs that are more potent and specific. © 2017 Elsevier Inc. All rights reserved.

  14. Calcium-sensing receptors.

    PubMed

    Goodman, William G

    2004-01-01

    It is now known that variations in extracellular calcium concentration exert diverse physiologic effects in a variety of tissues that are mediated by a calcium-sensing receptor (CaSRs). In parathyroid tissue, the CaSR represents the molecular mechanism by which parathyroid cells detect changes in blood ionized calcium concentration, modulate parathyroid hormone (PTH) secretion accordingly, and thus maintain serum calcium levels within a narrow physiologic range. In the kidney, the CaSR regulates renal calcium excretion and influences the transepithelial movement of water and other electrolytes. More generally, activation of the CaSR represents an important signal transduction pathway in intestine, placenta, brain, and perhaps bone. Some of these actions involve cell cycle regulation, changes that may be relevant to understanding the pathogenesis of parathyroid gland hyperplasia in secondary hyperparathyroidism caused by chronic kidney disease. The CaSR represents an appealing target for therapeutic agents designed to modify parathyroid gland function in vivo, offering the prospect of novel therapies for selected disorders of bone and mineral metabolism. Other receptors capable of responding to extracellular calcium ions also have been identified, but the functional importance of these interactions remains to be determined.

  15. Angiotensin II receptor heterogeneity

    SciTech Connect

    Herblin, W.F.; Chiu, A.T.; McCall, D.E.; Ardecky, R.J.; Carini, D.J.; Duncia, J.V.; Pease, L.J.; Wong, P.C.; Wexler, R.R.; Johnson, A.L. )

    1991-04-01

    The possibility of receptor heterogeneity in the angiotensin II (AII) system has been suggested previously, based on differences in Kd values or sensitivity to thiol reagents. One of the authors earliest indications was the frequent observation of incomplete inhibition of the binding of AII to adrenal cortical membranes. Autoradiographic studies demonstrated that all of the labeling of the rat adrenal was blocked by unlabeled AII or saralasin, but not by DuP 753. The predominant receptor in the rat adrenal cortex (80%) is sensitive to dithiothreitol (DTT) and DuP 753, and is designated AII-1. The residual sites in the adrenal cortex and almost all of the sites in the rat adrenal medulla are insensitive to both DTT and DuP 753, but were blocked by EXP655. These sites have been confirmed by ligand binding studies and are designated AII-2. The rabbit adrenal cortex is unique in yielding a nonuniform distribution of AII-2 sites around the outer layer of glomerulosa cells. In the rabbit kidney, the sites on the glomeruli are AII-1, but the sites on the kidney capsule are AII-2. Angiotensin III appears to have a higher affinity for AII-2 sites since it inhibits the binding to the rabbit kidney capsule but not the glomeruli. Elucidation of the distribution and function of these diverse sites should permit the development of more selective and specific therapeutic strategies.

  16. The Multifaceted Mineralocorticoid Receptor

    PubMed Central

    Gomez-Sanchez, Elise; Gomez-Sanchez, Celso E.

    2015-01-01

    The primary adrenal cortical steroid hormones, aldosterone, and the glucocorticoids cortisol and corticosterone, act through the structurally similar mineralocorticoid (MR) and glucocorticoid receptors (GRs). Aldosterone is crucial for fluid, electrolyte, and hemodynamic homeostasis and tissue repair; the significantly more abundant glucocorticoids are indispensable for energy homeostasis, appropriate responses to stress, and limiting inflammation. Steroid receptors initiate gene transcription for proteins that effect their actions as well as rapid non-genomic effects through classical cell signaling pathways. GR and MR are expressed in many tissues types, often in the same cells, where they interact at molecular and functional levels, at times in synergy, others in opposition. Thus the appropriate balance of MR and GR activation is crucial for homeostasis. MR has the same binding affinity for aldosterone, cortisol, and corticosterone. Glucocorticoids activate MR in most tissues at basal levels and GR at stress levels. Inactivation of cortisol and corticosterone by 11β-HSD2 allows aldosterone to activate MR within aldosterone target cells and limits activation of the GR. Under most conditions, 11β-HSD1 acts as a reductase and activates cortisol/corticosterone, amplifying circulating levels. 11β-HSD1 and MR antagonists mitigate inappropriate activation of MR under conditions of oxidative stress that contributes to the pathophysiology of the cardiometabolic syndrome; however, MR antagonists decrease normal MR/GR functional interactions, a particular concern for neurons mediating cognition, memory, and affect. PMID:24944027

  17. Axonal GABAA receptors.

    PubMed

    Trigo, Federico F; Marty, Alain; Stell, Brandon M

    2008-09-01

    Type A GABA receptors (GABA(A)Rs) are well established as the main inhibitory receptors in the mature mammalian forebrain. In recent years, evidence has accumulated showing that GABA(A)Rs are prevalent not only in the somatodendritic compartment of CNS neurons, but also in their axonal compartment. Evidence for axonal GABA(A)Rs includes new immunohistochemical and immunogold data: direct recording from single axonal terminals; and effects of local applications of GABA(A)R modulators on action potential generation, on axonal calcium signalling, and on neurotransmitter release. Strikingly, whereas presynaptic GABA(A)Rs have long been considered inhibitory, the new studies in the mammalian brain mostly indicate an excitatory action. Depending on the neuron that is under study, axonal GABA(A)Rs can be activated by ambient GABA, by GABA spillover, or by an autocrine action, to increase either action potential firing and/or transmitter release. In certain neurons, the excitatory effects of axonal GABA(A)Rs persist into adulthood. Altogether, axonal GABA(A)Rs appear as potent neuronal modulators of the mammalian CNS.

  18. Discoidin Domain Receptor 1

    PubMed Central

    Song, Sunmi; Shackel, Nicholas A.; Wang, Xin M.; Ajami, Katerina; McCaughan, Geoffrey W.; Gorrell, Mark D.

    2011-01-01

    Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase that binds and is activated by collagens. Transcriptional profiling of cirrhosis in human liver using a DNA array and quantitative PCR detected elevated mRNA expression of DDR1 compared with that in nondiseased liver. The present study characterized DDR1 expression in cirrhotic and nondiseased human liver and examined the cellular effects of DDR1 expression. mRNA expression of all five isoforms of DDR1 was detected in human liver, whereas DDR1a demonstrated differential expression in liver with hepatitis C virus and primary biliary cirrhosis compared with nondiseased liver. In addition, immunoblot analysis detected shed fragments of DDR1 more readily in cirrhotic liver than in nondiseased liver. Inasmuch as DDR1 is subject to protease-mediated cleavage after prolonged interaction with collagen, this differential expression may indicate more intense activation of DDR1 protein in cirrhotic compared with nondiseased liver. In situ hybridization and immunofluorescence localized intense DDR1 mRNA and protein expression to epithelial cells including hepatocytes at the portal-parenchymal interface and the luminal aspect of the biliary epithelium. Overexpression of DDR1a altered hepatocyte behavior including increased adhesion and less migration on extracelular matrix substrates. DDR1a regulated extracellular expression of matrix metalloproteinases 1 and 2. These data elucidate DDR1 function pertinent to cirrhosis and indicate the importance of epithelial cell–collagen interactions in chronic liver injury. PMID:21356365

  19. Trace amine-associated receptors are olfactory receptors in vertebrates.

    PubMed

    Liberles, Stephen D

    2009-07-01

    The mammalian nose is a powerful chemosensor, capable of detecting and distinguishing a myriad of chemicals. Sensory neurons in the olfactory epithelium contain two types of chemosensory G protein-coupled receptors (GPCRs): odorant receptors (ORs), which are encoded by the largest gene family in mammals, and trace amine-associated receptors (TAARs), a smaller family of receptors distantly related to biogenic amine receptors. Do TAARs play a specialized role in olfaction distinct from that of ORs? Genes encoding TAARs are found in diverse vertebrates, from fish to mice to humans. Like OR genes, each Taar gene defines a unique population of canonical sensory neurons dispersed in a single zone of the olfactory epithelium. Ligands for mouse TAARs include a number of volatile amines, several of which are natural constituents of mouse urine, a rich source of rodent social cues. One chemical, 2-phenylethylamine, is reported to be enriched in the urine of stressed animals, and two others, trimethylamine and isoamylamine, are enriched in male versus female urine. Furthermore, isoamylamine has been proposed to be a pheromone that induces puberty acceleration in young female mice. These data raise the possibility that some TAARs are pheromone receptors in the nose, a hypothesis consistent with recent data suggesting that the olfactory epithelium contains dedicated pheromone receptors, separate from pheromone receptors in the vomeronasal organ. Future experiments will clarify the roles of TAARs in olfaction.

  20. Kinin receptor classification.

    PubMed

    Regoli, D; Jukic, D; Tousignant, C; Rhaleb, N E

    1992-01-01

    Apparent affinities of kinin agonists and antagonists were determined in terms of pD2 and pA2 respectively, on three isolated smooth muscles: rabbit jugular vein (Rb.J.V.), rabbit aorta (Rb.A.) and guinea pig ileum (G.P.I.). Both kinin agonists and antagonists were evaluated for their ability to induce the release of histamine from rat mastocytes. Our results indicate that the kininase I metabolites (desArg9-BK and desArg10-KD) were inactive on Rb.J.V. and G.P.I. (B2 preparations) and were full agonists on Rb.A. (B1) while [Tyr(Me)8]-BK and [Hyp3,Tyr(Me)8]-BK were inactive on Rb.A. and maintain a high affinity on Rb.J.V. and G.P.I. In addition, [Hyp3]-BK was a potent agonist on Rb.J.V. (pD2 = 8.88) and was of a moderate affinity on G.P.I. (pD2 = 7.27). On the other hand, the affinity of [Aib7]-BK was identical to that of BK on G.P.I. (pD2 = 7.90) but drastically reduced in Rb.J.V. (pD2 = 6.28). Conctractile effects of kinins in the Rb.J.V. and G.P.I. were reduced or eliminated by B2 receptor antagonists but at different concentration levels (e.g. DArg[Hyp3,DPhe7,Leu8]-BK showed pA2 values of 8.86 on Rb.J.V., but only 6.77 on G.P.I. DArg[Hyp3,Gly6,Leu8]BK showed high affinity on Rb.J.V. (pA2 = 7.60) but was a full agonist on G.P.I. Conversely, DArg[Tyr3,DPhe7,Leu8,BK] showed high agonistic activity on Rb.J.V. (pD2 = 8.30, alpha E = 1.0) and showed a pA2 value of 6.80 on G.P.I. All compounds (agonists and antagonists) were quite potent on histamine release induced in rat mastocytes. [Arg1(Tos),Hyp3,Thi5,DTic7,Oic8]-BK and DArg[Hyp3,Thi5,DTic7,Oic8]-BK showed almost similar pA2 values on both Rb.J.V. and G.P.I., but were inactive on Rb.A. (B1). These results suggest that kinins act on at least four functional sites: B1 (Rb.A.), B2A (Rb.J.V.), B2B (G.P.I.) and BH. However, there is no clear evidence of a kinin receptor on rat mast cells and the release of histamine may simply be a non-receptor phenomenon. Our data also show that B2A and B2B receptor subtypes might

  1. Sensory receptors in monotremes.

    PubMed Central

    Proske, U; Gregory, J E; Iggo, A

    1998-01-01

    This is a summary of the current knowledge of sensory receptors in skin of the bill of the platypus, Ornithorhynchus anatinus, and the snout of the echidna, Tachyglossus aculeatus. Brief mention is also made of the third living member of the monotremes, the long-nosed echidna, Zaglossus bruijnii. The monotremes are the only group of mammals known to have evolved electroreception. The structures in the skin responsible for the electric sense have been identified as sensory mucous glands with an expanded epidermal portion that is innervated by large-diameter nerve fibres. Afferent recordings have shown that in both platypuses and echidnas the receptors excited by cathodal (negative) pulses and inhibited by anodal (positive) pulses. Estimates give a total of 40,000 mucous sensory glands in the upper and lower bill of the platypus, whereas there are only about 100 in the tip of the echidna snout. Recording of electroreceptor-evoked activity from the brain of the platypus have shown that the largest area dedicated to somatosensory input from the bill, S1, shows alternating rows of mechanosensory and bimodal neurons. The bimodal neurons respond to both electrosensory and mechanical inputs. In skin of the platypus bill and echidna snout, apart from the electroreceptors, there are structures called push rods, which consist of a column of compacted cells that is able to move relatively independently of adjacent regions of skin. At the base of the column are Merkel cell complexes, known to be type I slowly adapting mechanoreceptors, and lamellated corpuscles, probably vibration receptors. It has been speculated that the platypus uses its electric sense to detect the electromyographic activity from moving prey in the water and for obstacle avoidance. Mechanoreceptors signal contact with the prey. For the echidna, a role for the electrosensory system has not yet been established during normal foraging behaviour, although it has been shown that it is able to detect the presence

  2. Sensory receptors in monotremes.

    PubMed

    Proske, U; Gregory, J E; Iggo, A

    1998-07-29

    This is a summary of the current knowledge of sensory receptors in skin of the bill of the platypus, Ornithorhynchus anatinus, and the snout of the echidna, Tachyglossus aculeatus. Brief mention is also made of the third living member of the monotremes, the long-nosed echidna, Zaglossus bruijnii. The monotremes are the only group of mammals known to have evolved electroreception. The structures in the skin responsible for the electric sense have been identified as sensory mucous glands with an expanded epidermal portion that is innervated by large-diameter nerve fibres. Afferent recordings have shown that in both platypuses and echidnas the receptors excited by cathodal (negative) pulses and inhibited by anodal (positive) pulses. Estimates give a total of 40,000 mucous sensory glands in the upper and lower bill of the platypus, whereas there are only about 100 in the tip of the echidna snout. Recording of electroreceptor-evoked activity from the brain of the platypus have shown that the largest area dedicated to somatosensory input from the bill, S1, shows alternating rows of mechanosensory and bimodal neurons. The bimodal neurons respond to both electrosensory and mechanical inputs. In skin of the platypus bill and echidna snout, apart from the electroreceptors, there are structures called push rods, which consist of a column of compacted cells that is able to move relatively independently of adjacent regions of skin. At the base of the column are Merkel cell complexes, known to be type I slowly adapting mechanoreceptors, and lamellated corpuscles, probably vibration receptors. It has been speculated that the platypus uses its electric sense to detect the electromyographic activity from moving prey in the water and for obstacle avoidance. Mechanoreceptors signal contact with the prey. For the echidna, a role for the electrosensory system has not yet been established during normal foraging behaviour, although it has been shown that it is able to detect the presence

  3. Zinc Modulation of Glycine Receptors

    PubMed Central

    Trombley, Paul Q.; Blakemore, Laura J.; Hill, Brook J.

    2011-01-01

    Glycine receptors are widely expressed in the mammalian central nervous system, and previous studies have demonstrated that glycine receptors are modulated by endogenous zinc. Zinc is concentrated in synaptic vesicles in several brain regions but is particularly abundant in the hippocampus and olfactory bulb. In the present study, we used patch-clamp electrophysiology of rat hippocampal and olfactory bulb neurons in primary culture to examine the effects of zinc on glycine receptors. Although glycine has been reported to reach millimolar concentrations during synaptic transmission, most previous studies on the effects of zinc on glycine receptors have used relatively low concentrations of glycine. High concentrations of glycine cause receptor desensitization. Our current results extend our previous demonstration that the modulatory actions of zinc are largely prevented when co-applied with desensitizing concentrations of glycine (300 μM), suggesting that the effects of zinc are dependent on the state of the receptor. In contrast, pre-application of 300 μM zinc, prior to glycine (300 μM) application, causes a slowly developing inhibition with a slow rate of recovery, suggesting that the timing of zinc and glycine release also influences the effects of zinc. Furthermore, previous evidence suggests that synaptically released zinc can gain intracellular access, and we provide the first demonstration that low concentrations of intracellular zinc can potentiate glycine receptors. These results support the notion that zinc has complex effects on glycine receptors and multiple factors may interact to influence the efficacy of glycinergic transmission. PMID:21530619

  4. [Interceptors:--"silent" chemokine receptors].

    PubMed

    Grodecka, Magdalena; Waśniowska, Kazimiera

    2007-01-01

    The physiological effect caused by chemokines is regulated by interactions with a group of rodopsin-like G protein-coupled receptors (GPCRs). These receptors share a number of common features: the polypeptide chain is a 7-transmembrane ?-helix (7 TMD motif) and the region involved in G-protein interaction (the DRYLAIV sequence) is located in the second transmembrane loop. So far, 19 chemokine receptors have been identified. Three of them (Duffy glycoprotein, D6, and CCX-CKR proteins), although structurally related to other GPCRs, lack the ability of G-protein signal transduction. Instead, they efficiently internalize their cognate ligands, regulating chemokine levels in various body compartments. These three proteins are suggested to form a distinct chemokine receptor family, designated "interceptors" or "silent" chemokine receptors.

  5. Dopamine Receptors and Parkinson's Disease

    PubMed Central

    Hisahara, Shin; Shimohama, Shun

    2011-01-01

    Parkinson's disease (PD) is a progressive extrapyramidal motor disorder. Pathologically, this disease is characterized by the selective dopaminergic (DAergic) neuronal degeneration in the substantia nigra. Correcting the DA deficiency in PD with levodopa (L-dopa) significantly attenuates the motor symptoms; however, its effectiveness often declines, and L-dopa-related adverse effects emerge after long-term treatment. Nowadays, DA receptor agonists are useful medication even regarded as first choice to delay the starting of L-dopa therapy. In advanced stage of PD, they are also used as adjunct therapy together with L-dopa. DA receptor agonists act by stimulation of presynaptic and postsynaptic DA receptors. Despite the usefulness, they could be causative drugs for valvulopathy and nonmotor complication such as DA dysregulation syndrome (DDS). In this paper, physiological characteristics of DA receptor familyare discussed. We also discuss the validity, benefits, and specific adverse effects of pharmaceutical DA receptor agonist. PMID:25954517

  6. Allosteric Modulation of Chemoattractant Receptors

    PubMed Central

    Allegretti, Marcello; Cesta, Maria Candida; Locati, Massimo

    2016-01-01

    Chemoattractants control selective leukocyte homing via interactions with a dedicated family of related G protein-coupled receptor (GPCR). Emerging evidence indicates that the signaling activity of these receptors, as for other GPCR, is influenced by allosteric modulators, which interact with the receptor in a binding site distinct from the binding site of the agonist and modulate the receptor signaling activity in response to the orthosteric ligand. Allosteric modulators have a number of potential advantages over orthosteric agonists/antagonists as therapeutic agents and offer unprecedented opportunities to identify extremely selective drug leads. Here, we resume evidence of allosterism in the context of chemoattractant receptors, discussing in particular its functional impact on functional selectivity and probe/concentration dependence of orthosteric ligands activities. PMID:27199992

  7. Antibodies to cardiac receptors.

    PubMed

    Boivin-Jahns, V; Schlipp, A; Hartmann, S; Panjwani, P; Klingel, K; Lohse, M J; Ertl, G; Jahns, R

    2012-12-01

    Inflammation of cardiac tissue is generally associated with an activation of the host's immune system. On the one hand, this activation is mandatory to protect the heart by fighting the invading microbial agents or toxins and by engaging myocardial reparation and healing processes. On the other hand, uncontrolled activation of the immune defense has the risk of an arousal of auto- or cross-reactive immune cells, which in some cases bring more harm than good. Dependent on the individual genetic predisposition, such heart-directed autoimmune reactions most likely occur as a result of myocyte apoptosis or necrosis and subsequent liberation of self-antigens previously hidden to the immune system. During the past two decades, evidence for a pathogenic relevance of autoimmunity in human heart disease has substantially increased. Conformational cardiac (auto)antibodies affecting cardiac function and, in particular, (auto)antibodies that target G protein-coupled cardiac membrane receptors are thought to play a key role in the development of heart failure. Clinical pilot studies even suggest that such antibodies negatively affect survival in heart failure patients. However, the true prevalence and clinical impact of many cardiac (auto)antibodies in human heart diseases are still unclear, as are the events triggering their formation, their titer course, and their patterns of clearance and/or persistence. The present article summarizes current knowledge in the field of cardiac receptor (auto)antibodies including recent efforts to address some of the aforementioned gaps of knowledge, thereby attempting to pave the way for novel, more specific therapeutic approaches.

  8. Molecular characterization of opioid receptors

    SciTech Connect

    Howard, A.D.

    1986-01-01

    The aim of this research was to purify and characterize active opioid receptors and elucidate molecular aspects of opioid receptor heterogeneity. Purification to apparent homogeneity of an opioid binding protein from bovine caudate was achieved by solubilization in the non-ionic detergent, digitonin, followed by sequential chromatography on the opiate affinity matrix, ..beta..-naltrexylethylenediamine-CH-Sepharose 4B, and on the lectine affinity matrix, wheat germ agglutinin-agarose. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE) followed by autoradiography revealed that radioiodinated purified receptor gave a single band. Purified receptor preparations showed a specific activity of 12,000-15,000 fmol of opiate bound per mg of protein. Radioiodinated human beta-endorphin (/sup 125/I-beta-end/sub H/) was used as a probe to investigate the ligand binding subunits of mu and delta opioid receptors. /sup 125/I-beta-end/sub H/ was shown to bind to a variety of opioid receptor-containing tissues with high affinity and specificity with preference for mu and delta sites, and with little, if any, binding to kappa sites. Affinity crosslinking techniques were employed to covalently link /sup 125/I-beta-end/sub H/ to opioid receptors, utilizing derivatives of bis-succinimidyl esters that are bifunctional crosslinkers with specificities for amino and sulfhydryl groups. This, and competition experiments with high type-selective ligands, permitted the assignment of two labeled peptides to their receptor types, namely a peptide of M/sub r/ = 65,000 for mu receptors and one of M/sub r/ = 53,000 for delta receptors.

  9. Receptor dependent multidimensional QSAR for modeling drug--receptor interactions.

    PubMed

    Polanski, Jaroslaw

    2009-01-01

    Quantitative Structure Activity Relationship (QSAR) is an approach of mapping chemical structure to properties. A significant development can be observed in the last two decades in this method which originated from the Hansch analysis based on the logP data and Hammett constant towards a growing importance of the molecular descriptors derived from 3D structure including conformational dynamics and solvation scenarios. However, molecular interactions in biological systems are complex phenomena generating extremely noisy data, if simulated in silico. This decides that activity modeling and predictions are a risky business. Molecular recognition uncertainty in traditional receptor independent (RI) m-QSAR cannot be eliminated but by the inclusion of the receptor data. Modeling ligand-receptor interactions is a complex computational problem. This has limited the development of the receptor dependent (RD) m-QSAR. However, a steady increase of computational power has also improved modeling ability in chemoinformatics and novel RD QSAR methods appeared. Following the RI m-QSAR terminology this is usually classified as RD 3/6D-QSAR. However, a clear systematic m-QSAR classification can be proposed, where dimension m refers to, the static ligand representation (3D), multiple ligand representation (4D), ligand-based virtual or pseudo receptor models (5D), multiple solvation scenarios (6D) and real receptor or target-based receptor model data (7D).

  10. Estrogen-related receptor β (ERRβ) – renaissance receptor or receptor renaissance?

    PubMed Central

    Divekar, Shailaja D.; Tiek, Deanna M.; Fernandez, Aileen; Riggins, Rebecca B.

    2016-01-01

    Estrogen-related receptors (ERRs) are founding members of the orphan nuclear receptor (ONR) subgroup of the nuclear receptor superfamily. Twenty-seven years of study have yet to identify cognate ligands for the ERRs, though they have firmly placed ERRα and ERRγ at the intersection of cellular metabolism and oncogenesis. The pace of discovery for novel functions of ERRβ, however, has until recently been somewhat slower than that of its family members. ERRβ has also been largely ignored in summaries and perspectives of the ONR literature. Here, we provide an overview of established and emerging knowledge of ERRβ in mouse, man, and other species, highlighting unique aspects of ERRβ biology that set it apart from the other two estrogen-related receptors, with a focus on the impact of alternative splicing on the structure and function of this receptor. PMID:27507929

  11. Estrogen-related receptor β (ERRβ) - renaissance receptor or receptor renaissance?

    PubMed

    Divekar, Shailaja D; Tiek, Deanna M; Fernandez, Aileen; Riggins, Rebecca B

    2016-01-01

    Estrogen-related receptors (ERRs) are founding members of the orphan nuclear receptor (ONR) subgroup of the nuclear receptor superfamily. Twenty-seven years of study have yet to identify cognate ligands for the ERRs, though they have firmly placed ERRα and ERRγ at the intersection of cellular metabolism and oncogenesis. The pace of discovery for novel functions of ERRβ, however, has until recently been somewhat slower than that of its family members. ERRβ has also been largely ignored in summaries and perspectives of the ONR literature. Here, we provide an overview of established and emerging knowledge of ERRβ in mouse, man, and other species, highlighting unique aspects of ERRβ biology that set it apart from the other two estrogen-related receptors, with a focus on the impact of alternative splicing on the structure and function of this receptor.

  12. Vascular dopamine-I receptors.

    PubMed

    Yasunari, K; Kohno, M; Yokokawa, K; Horio, T; Kano, H; Takeda, T

    1995-06-01

    The modulation of dopamine DA1 receptors of cultured rat renal arterial smooth muscle cells by phorbol ester, glucocorticoid and sodium chloride was studied. The extent of [3H]Sch-23390 binding to phorbol ester-treated cell was increased without any change in the dissociation constant (Kd). At a concentration of 10 nmol/l, the synthetic glucocorticoid dexamethasone increased maximum receptor binding (Bmax) but had no effect on the Kd. 100 mmol/l sodium chloride did not change Bmax, but increased the Kd for DA1 receptor. The production of cAMP in response to DA1 receptor stimulation was enhanced without any change of the adenylate cyclase activity. The glucocorticoid effect on DA1 of arterial smooth muscle cells became apparent after hours of incubation in the presence of the steroid and was significantly inhibited by cycloheximide (10 micrograms/ml) and by the glucocorticoid receptor antagonist RU-38486, indicating that the effect required protein synthesis through glucocorticoid receptors. Treatment of cells with 1 mumol/l dexamethasone for 24 h increased basal and DA1-stimulated adenylate cyclase activity. Basal adenylate cyclase was decreased by sodium chloride in a dose-dependent manner. These results suggest differential control of DA1 receptors on vascular smooth muscle cells by protein kinase C, glucocorticoid or sodium chloride.

  13. Pulmonary and respiratory tract receptors.

    PubMed

    Widdicombe, J G

    1982-10-01

    Nervous receptors in the lungs and respiratory tract can be grouped into four general categories. 1. Deep, slowly adapting end-organs, which respond to stretch of the airway wall and have large-diameter myelinated fibres; those in the lungs are responsible for the Breuer-Hering reflex. 2. Endings in and under the epithelium which respond to a variety of chemical and mechanical stimuli (i.e. are polymodal), usually with a rapidly adapting discharge, and with small-diameter myelinated fibres; they are responsible for defensive reflexes such as cough and sneeze, and for the reflex actions to inhaled irritants and to some respiratory disease processes. 3. Receptors with nonmyelinated nerve fibres which, being polymodal, are stimulated by tissue damage and oedema and by the mediators released in these conditions; these receptors may be similar in function to 'nociceptors' in other viscera, and set up appropriate reflexes as a reaction to respiratory damage. 4. Specialized receptors such as those for taste and swallowing, and those around joints and in skeletal muscle. Stimulation of any group of receptors may cause reflex changes in breathing (including defensive reflexes), bronchomotor tone, airway mucus secretion, the cardiovascular system (including the vascular bed of the airways), laryngeal calibre, spinal reflexes and sensation. The total pattern of motor responses is unique for each group of receptors, although it is probably unusual for one type of receptor to be stimulated in isolation. The variety of patterns of motor responses must reflect the complexity of brainstem organization of these systems.

  14. Sigma receptors and cocaine abuse.

    PubMed

    Narayanan, Sanju; Mesangeau, Christophe; Poupaert, Jacques H; McCurdy, Christopher R

    2011-01-01

    Sigma receptors have been well documented as a protein target for cocaine and have been shown to be involved in the toxic and stimulant actions of cocaine. Strategies to reduce the access of cocaine to sigma receptors have included antisense oligonucleotides to the sigma-1 receptor protein as well as small molecule ligand with affinity for sigma receptor sites. These results have been encouraging as novel protein targets that can attenuate the actions of cocaine are desperately needed as there are currently no medications approved for treatment of cocaine toxicity or addiction. Many years of research in this area have yet to produce an effective treatment and much focus was on dopamine systems. A flurry of research has been carried out to elucidate the role of sigma receptors in the blockade of cocaine effects but this research has yet to yield a clinical agent. This review summarizes the work to date on the linkage of sigma receptors and the actions of cocaine and the progress that has been made with regard to small molecules. Although there is still a lack of an agent in clinical trials with a sigma receptor mechanism of action, work is progressing and the ligands are becoming more selective for sigma systems and the potential remains high.

  15. Cytokine receptors and hematopoietic differentiation.

    PubMed

    Robb, L

    2007-10-15

    Colony-stimulating factors and other cytokines signal via their cognate receptors to regulate hematopoiesis. In many developmental systems, inductive signalling determines cell fate and, by analogy with this, it has been postulated that cytokines, signalling via their cognate receptors, may play an instructive role in lineage specification in hematopoiesis. An alternative to this instructive hypothesis is the stochastic or permissive hypothesis. The latter proposes that commitment to a particular hematopoietic lineage is an event that occurs independently of extrinsic signals. It predicts that the role of cytokines is to provide nonspecific survival and proliferation signals. In this review, we look at the role of cytokine receptor signalling in hematopoiesis and consider the evidence for both hypotheses. Data from experiments that genetically manipulate receptor gene expression in vitro or in vivo are reviewed. Experiments in which cytokine receptors were installed in multipotential cells showed that, in some cases, stimulation with the cognate ligand could lead to alterations in lineage output. The creation of genetically manipulated mouse strains demonstrated that cytokine receptors are required for expansion and survival of single lineages but did not reveal a role in lineage commitment. We conclude that hematopoietic differentiation involves mainly stochastic events, but that cytokine receptors also have some instructive role.

  16. Estrogen receptor and aryl hydrocarbon receptor signaling pathways

    PubMed Central

    Matthews, Jason; Gustafsson, Jan-Åke

    2006-01-01

    Estrogen receptors (ERs) and the aryl hydrocarbon receptor (AhR) are ligand activated transcription factors and members of the nuclear receptor and bHLH-PAS superfamilies, respectively. AhR is involved in xenobiotic metabolism and in mediating the toxic effects of dioxin-like compounds. Crosstalk has been observed among AhR and nuclear receptors, but has been most well studied with respect to ER signaling. Activated AhR inhibits ER activity through a number of different mechanisms, whereas ERα has been reported to have a positive role in AhR signaling. Here we will discuss recent data revealing that dioxin bound AhR recruits ERα to AhR regulated genes. We will also consider the implications of ER recruitment to AhR target genes on ER and AhR signaling. PMID:16862222

  17. Nuclear hormone receptors in podocytes

    PubMed Central

    2012-01-01

    Nuclear receptors are a family of ligand-activated, DNA sequence-specific transcription factors that regulate various aspects of animal development, cell proliferation, differentiation, and homeostasis. The physiological roles of nuclear receptors and their ligands have been intensively studied in cancer and metabolic syndrome. However, their role in kidney diseases is still evolving, despite their ligands being used clinically to treat renal diseases for decades. This review will discuss the progress of our understanding of the role of nuclear receptors and their ligands in kidney physiology with emphasis on their roles in treating glomerular disorders and podocyte injury repair responses. PMID:22995171

  18. Chemosensory Receptor Specificity and Regulation

    PubMed Central

    Dalton, Ryan P.; Lomvardas, Stavros

    2016-01-01

    The senses provide a means by which data on the physical and chemical properties of the environment may be collected and meaningfully interpreted. Sensation begins at the periphery, where a multitude of different sensory cell types are activated by environmental stimuli as different as photons and odorant molecules. Stimulus sensitivity is due to expression of different cell surface sensory receptors, and therefore the receptive field of each sense is defined by the aggregate of expressed receptors in each sensory tissue. Here, we review current understanding on patterns of expression and modes of regulation of sensory receptors. PMID:25938729

  19. Simulation model of defective insulin receptors as byproducts of receptor recycling.

    PubMed

    Kurbel, B; Kurbel, S; Kristek, Z; Jakić, M; Jurić, M; Sulava, D

    1997-08-01

    Our simulation model assumes that the defective insulin-binding receptors in non-insulin-dependent diabetes (NIDDM) patients result from functional receptor recycling. The model is a short program written in MS DOS 5.0 Qbasic. MODEL DESIGN: Receptors with intracellular portions damaged in the process of recycling are considered defective since they bind insulin but do mediate insulin effects, or recycle. Their occurrence depends on the average activation rate of functional receptors. The insulin-binding receptors (defective and functional) are objects of slow and time-dependent turnover defined by the turnover rate. Recycled receptors rejoin functional receptors or enter the pool of defective receptors. The waste in the functional receptors' pool is covered by a limited amount of newly synthesized receptors. The defective receptors often accumulate in cases of increased activation of functional receptors. SIMULATION RESULTS: The insulin-binding receptor quantity is determined, in the model, only by the number of newly synthesized receptors, reflecting the intensity of insulin stimulation. Synthesis is increased following variable insulin stimulations and decreased after sustained, intensive insulin stimulation. The number of functional receptors inversely reflects the average activation rate of functional receptors compared with the insulin-binding receptors turnover rate. High activation rates can diminish the proportion of functional receptors to less than 5% of that of all insulin-binding receptors. The model predicts that cells bearing only functional receptors show progressively shortened half-lives of receptors, reflecting the receptor activation intensity. On the other hand, cells bearing both defective and functional receptors show stable receptors' half-lives (20-36% of the defective receptors' half-life). Simulation results suggest that reduced functional receptor proportions in NIDDM patients might reflect the imbalance between the activation of

  20. Triterpenes from Alisma orientalis act as androgen receptor agonists, progesterone receptor antagonists, and glucocorticoid receptor antagonists.

    PubMed

    Lin, Hsiang-Ru

    2014-08-01

    Alisma orientalis, a well-known traditional medicine, exerts numerous pharmacological effects including anti-diabetes, anti-hepatitis, and anti-diuretics but its bioactivity is not fully clear. Androgen receptor (AR), progesterone receptor (PR), and glucocorticoid receptor (GR) are three members of nuclear receptor superfamily that has been widely targeted for developing treatments for essential diseases including prostate cancer and breast cancer. In this study, two triterpenes, alisol M 23-acetate and alisol A 23-acetate from Alisma orientalis were determined whether they may act as androgen receptor (AR), progesterone receptor (PR), or glucocorticoid receptor (GR) modulators. Indeed, in the transient transfection reporter assays, alisol M 23-acetate and alisol A 23-acetate transactivated AR in dose-dependent manner, while they transrepressed the transactivation effects exerted by agonist-activated PR and GR. Through molecular modeling docking studies, they were shown to respectively interact with AR, PR, or GR ligand binding pocket fairly well. All these results indicate that alisol M 23-acetate and alisol A 23-acetate from Alisma orientalis might possess therapeutic effects through their modulation of AR, PR, and GR pathways. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Recombinant soluble adenovirus receptor

    DOEpatents

    Freimuth, Paul I.

    2002-01-01

    Disclosed are isolated polypeptides from human CAR (coxsackievirus and adenovirus receptor) protein which bind adenovirus. Specifically disclosed are amino acid sequences which corresponds to adenovirus binding domain D1 and the entire extracellular domain of human CAR protein comprising D1 and D2. In other aspects, the disclosure relates to nucleic acid sequences encoding these domains as well as expression vectors which encode the domains and bacterial cells containing such vectors. Also disclosed is an isolated fusion protein comprised of the D1 polypeptide sequence fused to a polypeptide sequence which facilitates folding of D1 into a functional, soluble domain when expressed in bacteria. The functional D1 domain finds application for example in a therapeutic method for treating a patient infected with a virus which binds to D1, and also in a method for identifying an antiviral compound which interferes with viral attachment. Also included is a method for specifically targeting a cell for infection by a virus which binds to D1.

  2. Selective Estrogen Receptor Modulators

    PubMed Central

    2016-01-01

    Selective estrogen receptor modulators (SERMs) are now being used as a treatment for breast cancer, osteoporosis and postmenopausal symptoms, as these drugs have features that can act as an estrogen agonist and an antagonist, depending on the target tissue. After tamoxifen, raloxifene, lasofoxifene and bazedoxifene SERMs have been developed and used for treatment. The clinically decisive difference among these drugs (i.e., the key difference) is their endometrial safety. Compared to bisphosphonate drug formulations for osteoporosis, SERMs are to be used primarily in postmenopausal women of younger age and are particularly recommended if there is a family history of invasive breast cancer, as their use greatly reduces the incidence of this type of cancer in women. Among the above mentioned SERMs, raloxifene has been widely used in prevention and treatment of postmenopausal osteoporosis and vertebral compression fractures, and clinical studies are now underway to test the comparative advantages of raloxifene with those of bazedoxifene, a more recently developed SERM. Research on a number of adverse side effects of SERM agents is being performed to determine the long-term safety of this class of compouds for treatment of osteoporosis. PMID:27559463

  3. Autoimmune NMDA receptor encephalitis.

    PubMed

    Lazar-Molnar, Eszter; Tebo, Anne E

    2015-01-01

    Anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis is a treatable autoimmune disease of the central nervous system (CNS) with prominent neurologic and psychiatric features at disease onset. The disease is associated with the production of autoantibodies to NMDAR, a protein involved in memory function and synaptic plasticity. Affected patients develop a multistage progressive illness with symptoms ranging from memory deficits, seizures and psychosis, to potentially lethal catatonia, and autonomic and breathing instability. The outcome can be much improved with accurate diagnosis and early treatment using adequate immunosuppressive therapy. However, since the neurological and psychiatric symptoms as well as the clinical examination results can be non-specific, the disease is probably under-recognized. Reliable and accurate clinical testing for the identification of NMDAR autoantibodies is crucial for diagnosis, timely treatment selection, and monitoring. Recently, a cell-based indirect immunofluorescent antibody test for the detection of IgG antibodies to NMDAR has become available for diagnostic use. This review highlights the progress and challenges of laboratory testing in the evaluation and management anti-NMDAR encephalitis, and perspectives for the future.

  4. 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

  5. Lamin B receptor

    PubMed Central

    Olins, Ada L; Rhodes, Gale; Welch, David B Mark; Zwerger, Monika

    2010-01-01

    Lamin B receptor (LBR) is an integral membrane protein of the interphase nuclear envelope (NE). The N-terminal end resides in the nucleoplasm, binding to lamin B and heterochromatin, with the interactions disrupted during mitosis. The C-terminal end resides within the inner nuclear membrane, retreating with the ER away from condensing chromosomes during mitotic NE breakdown. Some of these properties are interpretable in terms of our current structural knowledge of LBR, but many of the structural features remain unknown. LBR apparently has an evolutionary history which brought together at least two ancient conserved structural domains (i.e., Tudor and sterol reductase). This convergence may have occurred with the emergence of the chordates and echinoderms. It is not clear what survival values have maintained LBR structure during evolution. But it seems likely that roles in post-mitotic nuclear reformation, interphase NE growth and compartmentalization of nuclear architecture might have provided some evolutionary advantage to preservation of the LBR gene. PMID:21327105

  6. A threading receptor for polysaccharides

    NASA Astrophysics Data System (ADS)

    Mooibroek, Tiddo J.; Casas-Solvas, Juan M.; Harniman, Robert L.; Renney, Charles M.; Carter, Tom S.; Crump, Matthew P.; Davis, Anthony P.

    2016-01-01

    Cellulose, chitin and related polysaccharides are key renewable sources of organic molecules and materials. However, poor solubility tends to hamper their exploitation. Synthetic receptors could aid dissolution provided they are capable of cooperative action, for example by multiple threading on a single polysaccharide molecule. Here we report a synthetic receptor designed to form threaded complexes (polypseudorotaxanes) with these natural polymers. The receptor binds fragments of the polysaccharides in aqueous solution with high affinities (Ka up to 19,000 M-1), and is shown—by nuclear Overhauser effect spectroscopy—to adopt the threading geometry. Evidence from induced circular dichroism and atomic force microscopy implies that the receptor also forms polypseudorotaxanes with cellulose and its polycationic analogue chitosan. The results hold promise for polysaccharide solubilization under mild conditions, as well as for new approaches to the design of biologically active molecules.

  7. AIDS and the death receptors.

    PubMed

    Peter, M E; Ehret, A; Berndt, C; Krammer, P H

    1997-01-01

    Activation-induced cell death (AICD) of T cells involves the CD95 receptor/ligand system. T cell activation through the T cell receptor results in expression of the CD95 ligand (CD95L) that acts on CD95+ cells by direct binding and in a paracrine or autocrine fashion. In AIDS, upregulation of CD95L in T cells is accelerated by two viral gene products, HIV-1 Tat and gp120. The CD95 signaling pathway is, therefore, likely to represent an important road to cell death of the CD4+ T cells in AIDS. Recently, the early events in the CD95 signaling pathway have been identified. A key role hereby plays a receptor-interacting member of the interleukin 1 beta-converting enzymes (ICE), FLICE, that could be a target for therapeutic intervention. In addition to CD95, the role of other members of the TNF receptor superfamily in AIDS is discussed.

  8. Anthrax receptors position the spindle.

    PubMed

    Minc, Nicolas; Piel, Matthieu

    2013-01-01

    Spindle orientation plays a pivotal role in tissue morphogenesis. An asymmetric anthrax receptor cap is revealed to promote activation of a formin to orient the spindle along the planar cell polarity (PCP) axis in zebrafish dorsal epiblast cells.

  9. A nonsteroidal glucocorticoid receptor antagonist.

    PubMed

    Miner, Jeffrey N; Tyree, Curtis; Hu, Junlian; Berger, Elaine; Marschke, Keith; Nakane, Masaki; Coghlan, Michael J; Clemm, Dave; Lane, Ben; Rosen, Jon

    2003-01-01

    Selective intracellular receptor antagonists are used clinically to ameliorate hormone-dependent disease states. Patients with Cushing's syndrome have high levels of the glucocorticoid, cortisol, and suffer significant consequences from this overexposure. High levels of this hormone are also implicated in exacerbating diabetes and the stress response. Selectively inhibiting this hormone may have clinical benefit in these disease states. To this end, we have identified the first selective, nonsteroidal glucocorticoid receptor (GR) antagonist. This compound is characterized by a tri-aryl methane core chemical structure. This GR-specific antagonist binds with nanomolar affinity to the GR and has no detectable binding affinity for the highly related receptors for mineralocorticoids, androgens, estrogens, and progestins. We demonstrate that this antagonist inhibits glucocorticoid-mediated transcriptional regulation. This compound binds competitively with steroids, likely occupying a similar site within the ligand-binding domain. Once bound, however, the compound fails to induce critical conformational changes in the receptor necessary for agonist activity.

  10. [Nucleotide receptors and renal function].

    PubMed

    Jankowski, Maciej

    2014-01-01

    Kidney plays a key role in homeostasis of human body. It has heterogenic structure and is characterized by complicated vascular beds and numbers of sympathetic nerves endings. Nucleotides receptors are involved in the regulation of blood flow, a fundamental process for renal function. Plasma is filtrated in renal glomerulus and activity of nucleotides receptors located on cells of glomerular filter modifies the physi- cochemical properties of filter and affects the filtration process. Electrolytes, water and low molecular weight molecules are reabsorbed from tubular fluid or secreted into fluid in proximal and distal tubules. Glomerular filtration rate and activity of tubular processes are regulated via nucleotides receptors by glomerulotubularbalance and tubuloglomerular feedback. Nucleotides receptors are involved in systemic regulation of blood pressure and carbohydrate metabolism.

  11. Sialic Acid Receptors of Viruses.

    PubMed

    Matrosovich, Mikhail; Herrler, Georg; Klenk, Hans Dieter

    2015-01-01

    Sialic acid linked to glycoproteins and gangliosides is used by many viruses as a receptor for cell entry. These viruses include important human and animal pathogens, such as influenza, parainfluenza, mumps, corona, noro, rota, and DNA tumor viruses. Attachment to sialic acid is mediated by receptor binding proteins that are constituents of viral envelopes or exposed at the surface of non-enveloped viruses. Some of these viruses are also equipped with a neuraminidase or a sialyl-O-acetyl-esterase. These receptor-destroying enzymes promote virus release from infected cells and neutralize sialic acid-containing soluble proteins interfering with cell surface binding of the virus. Variations in the receptor specificity are important determinants for host range, tissue tropism, pathogenicity, and transmissibility of these viruses.

  12. The interleukin 1 receptor family.

    PubMed

    Subramaniam, Sumathi; Stansberg, Christine; Cunningham, Charles

    2004-05-03

    Interleukin-1 is a key inflammatory cytokine that mediates its effects through a type I receptor and a receptor accessory protein. These two molecules are members of a wider family of proteins that have in common the presence of immunoglobulin domains in the extracellular region of the protein and a TIR domain in the cytoplasmic region. The nature of this family of proteins and their signal transduction pathway is discussed in this review.

  13. History of retinoic acid receptors.

    PubMed

    Benbrook, Doris M; Chambon, Pierre; Rochette-Egly, Cécile; Asson-Batres, Mary Ann

    2014-01-01

    The discovery of retinoic acid receptors arose from research into how vitamins are essential for life. Early studies indicated that Vitamin A was metabolized into an active factor, retinoic acid (RA), which regulates RNA and protein expression in cells. Each step forward in our understanding of retinoic acid in human health was accomplished by the development and application of new technologies. Development cDNA cloning techniques and discovery of nuclear receptors for steroid hormones provided the basis for identification of two classes of retinoic acid receptors, RARs and RXRs, each of which has three isoforms, α, β and ɣ. DNA manipulation and crystallographic studies revealed that the receptors contain discrete functional domains responsible for binding to DNA, ligands and cofactors. Ligand binding was shown to induce conformational changes in the receptors that cause release of corepressors and recruitment of coactivators to create functional complexes that are bound to consensus promoter DNA sequences called retinoic acid response elements (RAREs) and that cause opening of chromatin and transcription of adjacent genes. Homologous recombination technology allowed the development of mice lacking expression of retinoic acid receptors, individually or in various combinations, which demonstrated that the receptors exhibit vital, but redundant, functions in fetal development and in vision, reproduction, and other functions required for maintenance of adult life. More recent advancements in sequencing and proteomic technologies reveal the complexity of retinoic acid receptor involvement in cellular function through regulation of gene expression and kinase activity. Future directions will require systems biology approaches to decipher how these integrated networks affect human stem cells, health, and disease.

  14. Receptor-targeted metalloradiopharmaceuticals. Final technical report

    SciTech Connect

    Green, Mark A.

    2000-03-22

    Copper (II) and platinum (II) coordination complexes were prepared and characterized. These complexes were designed to afford structural homology with steroidal and non-steroidal estrogens for possible use as receptor-targeted radiopharmaceuticals. While weak affinity for the estrogen receptor was detectable, none would appear to have sufficient receptor-affinity for estrogen-receptor-targeted imaging or therapy.

  15. L-glutamate Receptor In Paramecium

    NASA Astrophysics Data System (ADS)

    Bernal-Martínez, Juan; Ortega-Soto, Arturo

    2004-09-01

    Behavioral, electrophysiological and biochemical experiments were performed in order to establish the presence of a glutamate receptor in the ciliate Paramecium. It was found that an AMPA/KA receptor is functionally expressed in Paramecium and that this receptor is immunologically and fillogenetically related to the AMPA/KA receptor present in vertebrates.

  16. Estrogen receptors in breast carcinoma.

    PubMed

    Huaman, A

    1979-11-01

    On the basis of estrogen receptor assays, breast carcinomas are presently classified as estrogen-dependent tumors, which respond to endocrine therapy, and autonomous tumors, for which endocrine therapy is useless. This paper presents a short review of the biochemical principles of estrogen dependence, the procedures used to determine estrogen receptors, and the clinical applications of the findings of these assay procedures. Biobhemically, the estroogen dependence of normal breast cells is explained as a biochemical reaction occurring between the circulating estradiol and the breast cell, which occurs in 3 steps: 1) circulating estradiol penetrates the cellular membrane by passive diffusion, followed by 2) combining of estradiol with the estrogen-binding protein (estrophilin) and formation of an estrogen receptor complex which undergoes activation and translocation into the nucleus, to result in 3) the activated steroid receptor which combines with the nuclear charomatin and stimulates ribonucleic acid synthesis for the formation of estradiol binding proteins or estradiol receptors. The cytosol method of Wittliff et al. is described in brief and entails radioactive competitive analysis; the other available laboratory procedure is immunofluorescence of tumor sections. Quantification of estrogen receptor content can be used clinically to decide on ablative endocrine therapy, to determine the effectiveness of anti-estrogen administration, to determine the primary site of metastatic carcinoma, and as a screenng device.

  17. Nuclear Receptors, RXR, and the Big Bang.

    PubMed

    Evans, Ronald M; Mangelsdorf, David J

    2014-03-27

    Isolation of genes encoding the receptors for steroids, retinoids, vitamin D, and thyroid hormone and their structural and functional analysis revealed an evolutionarily conserved template for nuclear hormone receptors. This discovery sparked identification of numerous genes encoding related proteins, termed orphan receptors. Characterization of these orphan receptors and, in particular, of the retinoid X receptor (RXR) positioned nuclear receptors at the epicenter of the "Big Bang" of molecular endocrinology. This Review provides a personal perspective on nuclear receptors and explores their integrated and coordinated signaling networks that are essential for multicellular life, highlighting the RXR heterodimer and its associated ligands and transcriptional mechanism. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. Nuclear Receptors, RXR & the Big Bang

    PubMed Central

    Evans, Ronald M.; Mangelsdorf, David J.

    2014-01-01

    Summary Isolation of genes encoding the receptors for steroids, retinoids, vitamin D and thyroid hormone, and their structural and functional analysis revealed an evolutionarily conserved template for nuclear hormone receptors. This discovery sparked identification of numerous genes encoding related proteins, termed orphan receptors. Characterization of these orphan receptors, and in particular of the retinoid X receptor (RXR), positioned nuclear receptors at the epicenter of the “Big Bang” of molecular endocrinology. This review provides a personal perspective on nuclear receptors and explores their integrated and coordinated signaling networks that are essential for multi-cellular life, highlighting the RXR heterodimer and its associated ligands and transcriptional mechanism. PMID:24679540

  19. Gravity receptors and responses

    NASA Technical Reports Server (NTRS)

    Brown, Allan H.

    1989-01-01

    The overall process of gravity sensing and response processes in plants may be divided conveniently into at least four components or stages: Stimulus susception (a physical event, characteristically the input to the G receptor system of environmental information about the G force magnitude, its vector direction, or both); information perception (an influence of susception on some biological structure or process that can be described as the transformation of environmental information into a biologicallly meaningful change); information transport (the export, if required, of an influence (often chemical) to cells and organs other than those at the sensor location); and biological response (almost always (in plants) a growth change of some kind). Some analysts of the process identify, between information perception and information transport, an additional stage, transduction, which would emphasize the importance of a transformation from one form of information to another, for example from mechanical statolith displacement to an electric, chemical, or other alteration that was its indirect result. These four (or five) stages are temporally sequential. Even if all that occurs at each stage can not be confidently identified, it seems evident that during transduction and transport, matters dealt with are found relatively late in the information flow rather than at the perception stage. As more and more is learned about the roles played by plant hormones which condition the G responses, the mechanism(s) of perception which should be are not necessarily better understood. However, if by asking the right questions and being lucky with experiments perhaps the discovery of how some process (such as sedimentation of protoplasmic organelles) dictates what happens down stream in the information flow sequence may be made.

  20. Oxytocin receptor signalling.

    PubMed

    Devost, Dominic; Wrzal, Paulina; Zingg, Hans H

    2008-01-01

    The great diversity of the expression sites and proposed function of the oxytocin (OXT) receptor (OXTR) is paralleled by a diversity of its signalling pathways, many of which have still remained unexplored. We have used different approaches to discover novel pathways. By means of a phosphoproteomics approach, we have detected several distinct OXT-induced changes in tyrosine as well as threonine phosphorylation states of intracellular protein in myometrial cells. The most prominent change involved dephosphorylation of a 95-kDa phosphothreonine moiety. By N-terminal amino acid microsequence analysis, this moiety was shown to correspond to eukaryotic translation factor eEF2. This protein is a key regulator of protein synthesis and mediates, upon dephosphorylation, the translocation step of peptide chain elongation. These findings define a novel mechanism by which OXT assumes a so far unrecognized trophic function. We next elucidated the intracellular pathway(s) involved. We found that this effect is not mediated by any of the known pathways known to induce eEF2 dephosphorylation (mTOR, ERK1/2 or p38) but by protein kinase C. Consistent with this idea, we also found that direct stimulation of protein kinase C with a phorbol ester induced eEF2 dephosphorylation in myometrial cells. Using phosphoERK antibodies, we discovered by Western blotting that OXT induced phosphorylation of a higher molecular weight ERK-related protein. We were able to show that this band corresponded to "big MAP kinase1" or ERK5. ERK5 is part of a distinct MAPK cascade and promotes expression of the myosin light chain gene and plays an obligatory role in muscle cell development and differentiation. The role of ERK5 in myometrium has remained unexplored, but it is likely to represent an important novel pathway mediating OXT's effects on smooth muscle function. Further elucidation of these novel signalling pathways will have significant relevance for the development of novel pathway-specific OXTR

  1. The acetylcholine receptor as a cellular receptor for rabies virus.

    PubMed

    Lentz, T L; Burrage, T G; Smith, A L; Tignor, G H

    1983-01-01

    Characterization of specific host cell receptors for enveloped viruses is a difficult problem because many enveloped viruses bind to a variety of substrates which are not obviously related to tissue tropisms in the intact host. Viruses with a limited cellular tropism in infected animals present useful models for studying the mechanisms by which virus attachment regulates the disease process. Rabies virus is a rhabdovirus which exhibits a marked neuronotropism in infected animals. Limited data suggest that spread occurs by transsynaptic transfer of virus. The results of recent experiments at Yale suggest that viral antigen is localized very soon after injection at neuromuscular junctions, the motor nerve endings on muscle tissue. On cultured muscle cells, similar co-localization with the acetylcholine receptor is seen both before and after virus multiplication. Pretreatment of these cells with some ligands of the acetylcholine receptor results in reduced viral infection. These findings suggest that a neurotransmitter receptor or a closely associated molecule may serve as a specific host cell receptor for rabies virus and thus may be responsible for the tissue tropism exhibited by this virus. In addition to clarifying aspects of rabies virus pathogenesis, these studies have broad implications regarding the mechanism by which other viruses or viral immunizations might mediate autoimmune diseases such as myasthenia gravis.

  2. Insulin receptor-related receptor as an extracellular alkali sensor.

    PubMed

    Deyev, Igor E; Sohet, Fabien; Vassilenko, Konstantin P; Serova, Oxana V; Popova, Nadezhda V; Zozulya, Sergey A; Burova, Elena B; Houillier, Pascal; Rzhevsky, Dmitry I; Berchatova, Anastasiya A; Murashev, Arkady N; Chugunov, Anton O; Efremov, Roman G; Nikol'sky, Nikolai N; Bertelli, Eugenio; Eladari, Dominique; Petrenko, Alexander G

    2011-06-08

    The insulin receptor-related receptor (IRR), an orphan receptor tyrosine kinase of the insulin receptor family, can be activated by alkaline media both in vitro and in vivo at pH >7.9. The alkali-sensing property of IRR is conserved in frog, mouse, and human. IRR activation is specific, dose-dependent and quickly reversible and demonstrates positive cooperativity. It also triggers receptor conformational changes and elicits intracellular signaling. The pH sensitivity of IRR is primarily defined by its L1F extracellular domains. IRR is predominantly expressed in organs that come in contact with mildly alkaline media. In particular, IRR is expressed in the cell subsets of the kidney that secrete bicarbonate into urine. Disruption of IRR in mice impairs the renal response to alkali loading attested by development of metabolic alkalosis and decreased urinary bicarbonate excretion in response to this challenge. We therefore postulate that IRR is an alkali sensor that functions in the kidney to manage metabolic bicarbonate excess. Copyright © 2011 Elsevier Inc. All rights reserved.

  3. Insulin receptor-related receptor as an extracellular alkali sensor

    PubMed Central

    Deyev, Igor E.; Sohet, Fabien; Vassilenko, Konstantin P.; Serova, Oxana V.; Popova, Nadezhda V.; Zozulya, Sergey A.; Burova, Elena B.; Houillier, Pascal; Rzhevsky, Dmitry I.; Berchatova, Anastasiya A.; Murashev, Arkady N.; Chugunov, Anton O.; Efremov, Roman G.; Nikol’sky, Nikolai N.; Bertelli, Eugenio; Eladari, Dominique; Petrenko, Alexander G.

    2011-01-01

    SUMMARY The insulin receptor-related receptor (IRR), an orphan receptor tyrosine kinase of the insulin receptor family, can be activated by alkaline media both in vitro and in vivo at pH>7.9. The alkali-sensing property of IRR is conserved in frog, mouse and human. IRR activation is specific, dose-dependent, quickly reversible and demonstrates positive cooperativity. It also triggers receptor conformational changes and elicits intracellular signaling. The pH sensitivity of IRR is primarily defined by its L1F extracellular domains. IRR is predominantly expressed in organs that come in contact with mildly alkaline media. In particular, IRR is expressed in the cell subsets of the kidney that secrete bicarbonate into urine. Disruption of IRR in mice impairs the renal response to alkali loading attested by development of metabolic alkalosis and decreased urinary bicarbonate excretion in response to this challenge. We therefore postulate that IRR is an alkali sensor that functions in the kidney to manage metabolic bicarbonate excess. PMID:21641549

  4. Phenobarbital and Insulin Reciprocate Activation of the Nuclear Receptor Constitutive Androstane Receptor through the Insulin Receptor

    PubMed Central

    Yasujima, Tomoya; Saito, Kosuke; Moore, Rick

    2016-01-01

    Phenobarbital (PB) antagonized insulin to inactivate the insulin receptor and attenuated the insulin receptor downstream protein kinase B (AKT)–forkhead box protein O1 and extracellular signal-regulated kinase 1/2 signals in mouse primary hepatocytes and HepG2 cells. Hepatic AKT began dephosphorylation in an early stage of PB treatment, and blood glucose levels transiently increased in both wild-type and constitutive androstane receptor (CAR) knockout (KO) mice. On the other hand, blood glucose levels increased in wild-type mice, but not KO mice, in later stages of PB treatment. As a result, PB, acting as an insulin receptor antagonist, elicited CAR-independent increases and CAR-dependent decreases of blood glucose levels at these different stages of treatment, respectively. Reciprocally, insulin activation of the insulin receptor repressed CAR activation and induction of its target CYP2B6 gene in HepG2 cells. Thus, PB and insulin cross-talk through the insulin receptor to regulate glucose and drug metabolism reciprocally. PMID:26994072

  5. Phenobarbital and Insulin Reciprocate Activation of the Nuclear Receptor Constitutive Androstane Receptor through the Insulin Receptor.

    PubMed

    Yasujima, Tomoya; Saito, Kosuke; Moore, Rick; Negishi, Masahiko

    2016-05-01

    Phenobarbital (PB) antagonized insulin to inactivate the insulin receptor and attenuated the insulin receptor downstream protein kinase B (AKT)-forkhead box protein O1 and extracellular signal-regulated kinase 1/2 signals in mouse primary hepatocytes and HepG2 cells. Hepatic AKT began dephosphorylation in an early stage of PB treatment, and blood glucose levels transiently increased in both wild-type and constitutive androstane receptor (CAR) knockout (KO) mice. On the other hand, blood glucose levels increased in wild-type mice, but not KO mice, in later stages of PB treatment. As a result, PB, acting as an insulin receptor antagonist, elicited CAR-independent increases and CAR-dependent decreases of blood glucose levels at these different stages of treatment, respectively. Reciprocally, insulin activation of the insulin receptor repressed CAR activation and induction of its target CYP2B6 gene in HepG2 cells. Thus, PB and insulin cross-talk through the insulin receptor to regulate glucose and drug metabolism reciprocally. Copyright © 2016 by U.S. Government work not protected by U.S. copyright.

  6. Radiopharmaceuticals for somatostatin receptor imaging.

    PubMed

    Mikołajczak, Renata; Maecke, Helmut R

    2016-01-01

    The aim of this review is to summarize the developments and briefly characterize the somatostatin analogs which are currently used for somatostatin receptor imaging in clinical routine or in early phase clinical trials. Somatostatin (sst) receptor targeting with radiolabeled peptides has become an integral part in nuclear oncology during the last 20 years. This integration process has been initiated in Europe with the introduction to the market of 111In-DTPA-DPhe1-octreotide [111In-pentetreotide]. Introducing 99mTc in somatostatin receptor targeting radiopeptides resulted in much better image quality, higher sensitivity of tumor detection and lower mean effective dose for the examined patient. The next generation are 68Ga labeled somatostatin analogs. Due to the spatial resolution of PET technique and increasing number of PET scanners, the PET or PET/CT technique became very important in somatostatin receptor imaging. Until up to a couple of years ago the analogs of somatostatin were constructed aiming at their agonistic behavior, expecting that their internalization with the receptor acti-vated by the radiolabeled ligand and its retention within the tumor cell are crucial for efficient imaging and therapy. Recently it has been shown that the antagonists recognize more binding sites at the tumor cell membrane and hence offer an improved diagnostic efficacy, especially when the density of sst receptors is low. This approach may in future improve diagnostic value of somatostatin receptor imaging techniques. The developments in tracer design are followed by the improvements in imaging techniques. The new SPECT scanners offer resolution close to that of PET, which might open a new era for 99mTc and other SPECT radiotracers.

  7. Proteinase-activated receptors (PARs) – focus on receptor-receptor-interactions and their physiological and pathophysiological impact

    PubMed Central

    2013-01-01

    Proteinase-activated receptors (PARs) are a subfamily of G protein-coupled receptors (GPCRs) with four members, PAR1, PAR2, PAR3 and PAR4, playing critical functions in hemostasis, thrombosis, embryonic development, wound healing, inflammation and cancer progression. PARs are characterized by a unique activation mechanism involving receptor cleavage by different proteinases at specific sites within the extracellular amino-terminus and the exposure of amino-terminal “tethered ligand“ domains that bind to and activate the cleaved receptors. After activation, the PAR family members are able to stimulate complex intracellular signalling networks via classical G protein-mediated pathways and beta-arrestin signalling. In addition, different receptor crosstalk mechanisms critically contribute to a high diversity of PAR signal transduction and receptor-trafficking processes that result in multiple physiological effects. In this review, we summarize current information about PAR-initiated physical and functional receptor interactions and their physiological and pathological roles. We focus especially on PAR homo- and heterodimerization, transactivation of receptor tyrosine kinases (RTKs) and receptor serine/threonine kinases (RSTKs), communication with other GPCRs, toll-like receptors and NOD-like receptors, ion channel receptors, and on PAR association with cargo receptors. In addition, we discuss the suitability of these receptor interaction mechanisms as targets for modulating PAR signalling in disease. PMID:24215724

  8. Transferrin Receptor Controls AMPA Receptor Trafficking Efficiency and Synaptic Plasticity

    PubMed Central

    Liu, Ke; Lei, Run; Li, Qiong; Wang, Xin-Xin; Wu, Qian; An, Peng; Zhang, Jianchao; Zhu, Minyan; Xu, Zhiheng; Hong, Yang; Wang, Fudi; Shen, Ying; Li, Hongchang; Li, Huashun

    2016-01-01

    Transferrin receptor (TFR) is an important iron transporter regulating iron homeostasis and has long been used as a marker for clathrin mediated endocytosis. However, little is known about its additional function other than iron transport in the development of central nervous system (CNS). Here we demonstrate that TFR functions as a regulator to control AMPA receptor trafficking efficiency and synaptic plasticity. The conditional knockout (KO) of TFR in neural progenitor cells causes mice to develop progressive epileptic seizure, and dramatically reduces basal synaptic transmission and long-term potentiation (LTP). We further demonstrate that TFR KO remarkably reduces the binding efficiency of GluR2 to AP2 and subsequently decreases AMPA receptor endocytosis and recycling. Thus, our study reveals that TFR functions as a novel regulator to control AMPA trafficking efficiency and synaptic plasticity. PMID:26880306

  9. Purinergic receptors in ocular inflammation.

    PubMed

    Guzman-Aranguez, Ana; Gasull, Xavier; Diebold, Yolanda; Pintor, Jesús

    2014-01-01

    Inflammation is a complex process that implies the interaction between cells and molecular mediators, which, when not properly "tuned," can lead to disease. When inflammation affects the eye, it can produce severe disorders affecting the superficial and internal parts of the visual organ. The nucleoside adenosine and nucleotides including adenine mononucleotides like ADP and ATP and dinucleotides such as P(1),P(4)-diadenosine tetraphosphate (Ap4A), and P(1),P(5)-diadenosine pentaphosphate (Ap5A) are present in different ocular locations and therefore they may contribute/modulate inflammatory processes. Adenosine receptors, in particular A2A adenosine receptors, present anti-inflammatory action in acute and chronic retinal inflammation. Regarding the A3 receptor, selective agonists like N(6)-(3-iodobenzyl)-5'-N-methylcarboxamidoadenosine (CF101) have been used for the treatment of inflammatory ophthalmic diseases such as dry eye and uveoretinitis. Sideways, diverse stimuli (sensory stimulation, large intraocular pressure increases) can produce a release of ATP from ocular sensory innervation or after injury to ocular tissues. Then, ATP will activate purinergic P2 receptors present in sensory nerve endings, the iris, the ciliary body, or other tissues surrounding the anterior chamber of the eye to produce uveitis/endophthalmitis. In summary, adenosine and nucleotides can activate receptors in ocular structures susceptible to suffer from inflammatory processes. This involvement suggests the possible use of purinergic agonists and antagonists as therapeutic targets for ocular inflammation.

  10. Purinergic Receptors in Ocular Inflammation

    PubMed Central

    Guzman-Aranguez, Ana; Gasull, Xavier; Diebold, Yolanda; Pintor, Jesús

    2014-01-01

    Inflammation is a complex process that implies the interaction between cells and molecular mediators, which, when not properly “tuned,” can lead to disease. When inflammation affects the eye, it can produce severe disorders affecting the superficial and internal parts of the visual organ. The nucleoside adenosine and nucleotides including adenine mononucleotides like ADP and ATP and dinucleotides such as P1,P4-diadenosine tetraphosphate (Ap4A), and P1,P5-diadenosine pentaphosphate (Ap5A) are present in different ocular locations and therefore they may contribute/modulate inflammatory processes. Adenosine receptors, in particular A2A adenosine receptors, present anti-inflammatory action in acute and chronic retinal inflammation. Regarding the A3 receptor, selective agonists like N6-(3-iodobenzyl)-5′-N-methylcarboxamidoadenosine (CF101) have been used for the treatment of inflammatory ophthalmic diseases such as dry eye and uveoretinitis. Sideways, diverse stimuli (sensory stimulation, large intraocular pressure increases) can produce a release of ATP from ocular sensory innervation or after injury to ocular tissues. Then, ATP will activate purinergic P2 receptors present in sensory nerve endings, the iris, the ciliary body, or other tissues surrounding the anterior chamber of the eye to produce uveitis/endophthalmitis. In summary, adenosine and nucleotides can activate receptors in ocular structures susceptible to suffer from inflammatory processes. This involvement suggests the possible use of purinergic agonists and antagonists as therapeutic targets for ocular inflammation. PMID:25132732

  11. Ionotropic Glutamate Receptors & CNS Disorders

    PubMed Central

    Bowie, Derek

    2008-01-01

    Disorders of the central nervous system (CNS) are complex disease states that represent a major challenge for modern medicine. Although etiology is often unknown, it is established that multiple factors such as defects in genetics and/or epigenetics, the environment as well as imbalance in neurotransmitter receptor systems are all at play in determining an individual’s susceptibility to disease. Gene therapy is currently not available and therefore, most conditions are treated with pharmacological agents that modify neurotransmitter receptor signaling. Here, I provide a review of ionotropic glutamate receptors (iGluRs) and the roles they fulfill in numerous CNS disorders. Specifically, I argue that our understanding of iGluRs has reached a critical turning point to permit, for the first time, a comprehensive re-evaluation of their role in the cause of disease. I illustrate this by highlighting how defects in AMPA receptor trafficking are important to Fragile X mental retardation and ectopic expression of kainate (KA) receptor synapses contributes to the pathology of temporal lobe epilepsy. Finally, I discuss how parallel advances in studies of other neurotransmitter systems may allow pharmacologists to work towards a cure for many CNS disorders rather than developing drugs to treat their symptoms. PMID:18537642

  12. The Mosquito Aedes aegypti (L.) leucokinin Receptor is a Multiligand Receptor for the three Aedes kinins

    DTIC Science & Technology

    2004-09-07

    receptors for the three Aedes kinins. Keywords: insect GPCR (G protein-coupled receptor ) (myo)kinin receptor ... receptor 57 © 2005 The Royal Entomological Society, Insect Molecular Biology , 14 , 55–67 58 P. V. Pietrantonio et al. © 2005 The... receptor 59 © 2005 The Royal Entomological Society, Insect Molecular Biology , 14 , 55–67 further support to the role of this receptor

  13. Brain CB₂ Receptors: Implications for Neuropsychiatric Disorders.

    PubMed

    Roche, Michelle; Finn, David P

    2010-08-10

    Although previously thought of as the peripheral cannabinoid receptor, it is now accepted that the CB₂ receptor is expressed in the central nervous system on microglia, astrocytes and subpopulations of neurons. Expression of the CB₂ receptor in the brain is significantly lower than that of the CB₁ receptor. Conflicting findings have been reported on the neurological effects of pharmacological agents targeting the CB₂ receptor under normal conditions. Under inflammatory conditions, CB₂ receptor expression in the brain is enhanced and CB2 receptor agonists exhibit potent anti-inflammatory effects. These findings have prompted research into the CB₂ receptor as a possible target for the treatment of neuroinflammatory and neurodegenerative disorders. Neuroinflammatory alterations are also associated with neuropsychiatric disorders and polymorphisms in the CB₂ gene have been reported in depression, eating disorders and schizophrenia. This review will examine the evidence to date for a role of brain CB₂ receptors in neuropsychiatric disorders.

  14. Photo-antagonism of the GABAA receptor.

    PubMed

    Mortensen, Martin; Iqbal, Favaad; Pandurangan, Arun P; Hannan, Saad; Huckvale, Rosemary; Topf, Maya; Baker, James R; Smart, Trevor G

    2014-07-29

    Neurotransmitter receptor trafficking is fundamentally important for synaptic transmission and neural network activity. GABAA receptors and inhibitory synapses are vital components of brain function, yet much of our knowledge regarding receptor mobility and function at inhibitory synapses is derived indirectly from using recombinant receptors, antibody-tagged native receptors and pharmacological treatments. Here we describe the use of a set of research tools that can irreversibly bind to and affect the function of recombinant and neuronal GABAA receptors following ultraviolet photoactivation. These compounds are based on the competitive antagonist gabazine and incorporate a variety of photoactive groups. By using site-directed mutagenesis and ligand-docking studies, they reveal new areas of the GABA binding site at the interface between receptor β and α subunits. These compounds enable the selected inactivation of native GABAA receptor populations providing new insight into the function of inhibitory synapses and extrasynaptic receptors in controlling neuronal excitation.

  15. Interactions between effectors linked to serotonin receptors.

    PubMed

    Berg, K A; Maayani, S; Clarke, W P

    1998-12-15

    In general, there are two types of interactions between effector signaling pathways. "Homologous" interactions are those that occur within a receptor system to alter its own responsiveness, for example the loss of responsiveness (desensitization) that can occur upon agonist occupancy of a receptor. "Heterologous" interactions are those that occur between different receptor systems where the responsiveness of one receptor system is regulated (positively or negatively) by activation of another receptor system (i.e., "cross-talk"). Many, if not all receptors, couple to multiple cellular effector pathways and alterations in the responsiveness of a receptor system can be effector pathway-dependent which underscores the importance of studying each effector coupled to a receptor. Regulation of receptor system responsiveness, and consequently the efficacy of drugs, is a highly dynamic process. Perhaps by exploiting these interactions, new targets for pharmacotherapy may be uncovered which will provide for increased efficacy and specificity of drug action.

  16. Identification and mechanism of ABA receptor antagonism

    SciTech Connect

    Melcher, Karsten; Xu, Yong; Ng, Ley-Moy; Zhou, X. Edward; Soon, Fen-Fen; Chinnusamy, Viswanathan; Suino-Powell, Kelly M; Kovach, Amanda; Tham, Fook S.; Cutler, Sean R.; Li, Jun; Yong, Eu-Leong; Zhu, Jian-Kang; Xu, H. Eric

    2010-11-11

    The phytohormone abscisic acid (ABA) functions through a family of fourteen PYR/PYL receptors, which were identified by resistance to pyrabactin, a synthetic inhibitor of seed germination. ABA activates these receptors to inhibit type 2C protein phosphatases, such as ABI1, yet it remains unclear whether these receptors can be antagonized. Here we demonstrate that pyrabactin is an agonist of PYR1 and PYL1 but is unexpectedly an antagonist of PYL2. Crystal structures of the PYL2-pyrabactin and PYL1-pyrabactin-ABI1 complexes reveal the mechanism responsible for receptor-selective activation and inhibition, which enables us to design mutations that convert PYL1 to a pyrabactin-inhibited receptor and PYL2 to a pyrabactin-activated receptor and to identify new pyrabactin-based ABA receptor agonists. Together, our results establish a new concept of ABA receptor antagonism, illustrate its underlying mechanisms and provide a rational framework for discovering novel ABA receptor ligands.

  17. Epidermal Growth Factor Receptor Transactivation by the Cannabinoid Receptor (CB1) and Transient Receptor Potential Vanilloid 1 (TRPV1) Induces Differential Responses in Corneal Epithelial Cells

    DTIC Science & Technology

    2010-01-01

    Epidermal growth factor receptor transactivation by the cannabinoid receptor (CB1) and transient receptor potential vanilloid 1 ( TRPV1 ) induces...Available online 7 July 2010 Keywords: cannabinoid receptor 1 (CB1) transient receptor potential vanilloid 1 ( TRPV1 ) epidermal growth factor receptor (EGFR...release of endogenous metabolites that are cannabinoid receptor 1 (CB1) and transient receptor potential vanilloid 1 ( TRPV1 ) agonists. We determined

  18. An Update on GABAρ Receptors

    PubMed Central

    Martínez-Delgado, Gustavo; Estrada-Mondragón, Argel; Miledi, Ricardo; Martínez-Torres, Ataúlfo

    2010-01-01

    The present review discusses the functional and molecular diversity of GABAρ receptors. These receptors were originally described in the mammalian retina, and their functional role in the visual pathway has been recently elucidated; however new studies on their distribution in the brain and spinal cord have revealed that they are more spread than originally thought, and thus it will be important to determine their physiological contribution to the GABAergic transmission in other areas of the central nervous system. In addition, molecular modeling has revealed peculiar traits of these receptors that have impacted on the interpretations of the latest pharmacolgical and biophysical findings. Finally, sequencing of several vertebrate genomes has permitted a comparative analysis of the organization of the GABAρ genes. PMID:21629448

  19. Cannabinoids, cannabinoid receptors and tinnitus.

    PubMed

    Smith, Paul F; Zheng, Yiwen

    2016-02-01

    One hypothesis suggests that tinnitus is a form of sensory epilepsy, arising partly from neuronal hyperactivity in auditory regions of the brain such as the cochlear nucleus and inferior colliculus. Although there is currently no effective drug treatment for tinnitus, anti-epileptic drugs are used in some cases as a potential treatment option. There is increasing evidence to suggest that cannabinoid drugs, i.e. cannabinoid receptor agonists, can also have anti-epileptic effects, at least in some cases and in some parts of the brain. It has been reported that cannabinoid CB1 receptors and the endogenous cannabinoid, 2-arachidonylglycerol (2-AG), are expressed in the cochlear nucleus and that they are involved in the regulation of plasticity. This review explores the question of whether cannabinoid receptor agonists are likely to be pro- or anti-epileptic in the cochlear nucleus and therefore whether cannabinoids and Cannabis itself are likely to make tinnitus better or worse.

  20. History of Discovery: The LDL Receptor

    PubMed Central

    Goldstein, Joseph L.; Brown, Michael S.

    2009-01-01

    Summary In this article, the history of the LDL receptor is recounted by its co-discoverers. Their early work on the LDL receptor explained a genetic cause of heart attacks and led to new ways of thinking about cholesterol metabolism. The LDL receptor discovery also introduced three general concepts to cell biology: receptor-mediated endocytosis, receptor recycling, and feedback regulation of receptors. The latter concept provides the mechanism by which statins selectively lower plasma LDL, reducing heart attacks and prolonging life. PMID:19299327

  1. Glutamate receptors at atomic resolution

    SciTech Connect

    Mayer, Mark L.

    2010-12-03

    At synapses throughout the brain and spinal cord, the amino-acid glutamate is the major excitatory neurotransmitter. During evolution, a family of glutamate-receptor ion channels seems to have been assembled from a kit consisting of discrete ligand-binding, ion-channel, modulatory and cytoplasmic domains. Crystallographic studies that exploit this unique architecture have greatly aided structural analysis of the ligand-binding core, but the results also pose a formidable challenge, namely that of resolving the allosteric mechanisms by which individual domains communicate and function in an intact receptor.

  2. Liver X receptors and atherosclerosis.

    PubMed

    Lala, Deepak S

    2004-06-01

    Cardiovascular disease, the primary cause of death and illness in the industrialized world, is typically due to complications of atherosclerosis, a multifactorial disease of the arterial intima. The liver X receptors (LXRs), LXRalpha and LXRbeta, are intracellular receptors that appear to play an important role in protection against atherosclerosis; however, LXR activation also leads to a dramatic increase in liver and serum triglycerides. This presents a challenge to developing drugs via these targets. This article discusses the role of LXRs in atherosclerosis and lipid regulation and the possibility of designing LXR ligands that may be anti-atherogenic without side effects.

  3. Receptor regulation of senile phenoptosis.

    PubMed

    Skulachev, M V; Severin, F F; Skulachev, V P

    2014-10-01

    Here we present a concept that considers organism aging as an additional facultative function promoting evolution, but counterproductive for an individual. We hypothesize that aging can be inhibited or even arrested when full mobilization of all resources is needed for the survival of an individual. We believe that the organism makes such a decision based on the analysis of signals of special receptors that monitor a number of parameters of the internal and external environment. The amount of available food is one of these parameters. Food restriction is perceived by the organism as a signal of coming starvation; in response to it, the organism inhibits its counterproductive programs, in particular, aging. We hypothesize that the level of protein obtained with food is estimated based on blood concentration of one of the essential amino acids (methionine), of carbohydrates - via glucose level, and fats - based on the level of one of the free fatty acids. When the amount of available food is sufficient, these receptors transmit the signal allowing aging. In case of lack of food, this signal is cancelled, and as a result aging is inhibited, i.e. age-related weakening of physiological functions is inhibited, and lifespan increases (the well-known geroprotective effect of partial food restriction). In Caenorhabditis elegans, lowering of the ambient temperature has a similar effect. This geroprotective effect is removed by the knockout of one of the cold receptors, and replacement of the C. elegans receptor by a similar human receptor restores the ability of low temperature to increase the lifespan of the nematode. A chain of events linking the receptor with the aging mechanism has been discovered in mice - for one of the pain receptors in neurons, the nerve endings of which entwine pancreas β-cells. Age-related activation of these receptors inhibits the work of insulin genes in β-cells. Problems with insulin secretion lead to oxidative stress, chronic inflammation

  4. Nuclear receptors and nonalcoholic fatty liver disease.

    PubMed

    Cave, Matthew C; Clair, Heather B; Hardesty, Josiah E; Falkner, K Cameron; Feng, Wenke; Clark, Barbara J; Sidey, Jennifer; Shi, Hongxue; Aqel, Bashar A; McClain, Craig J; Prough, Russell A

    2016-09-01

    Nuclear receptors are transcription factors which sense changing environmental or hormonal signals and effect transcriptional changes to regulate core life functions including growth, development, and reproduction. To support this function, following ligand-activation by xenobiotics, members of subfamily 1 nuclear receptors (NR1s) may heterodimerize with the retinoid X receptor (RXR) to regulate transcription of genes involved in energy and xenobiotic metabolism and inflammation. Several of these receptors including the peroxisome proliferator-activated receptors (PPARs), the pregnane and xenobiotic receptor (PXR), the constitutive androstane receptor (CAR), the liver X receptor (LXR) and the farnesoid X receptor (FXR) are key regulators of the gut:liver:adipose axis and serve to coordinate metabolic responses across organ systems between the fed and fasting states. Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease and may progress to cirrhosis and even hepatocellular carcinoma. NAFLD is associated with inappropriate nuclear receptor function and perturbations along the gut:liver:adipose axis including obesity, increased intestinal permeability with systemic inflammation, abnormal hepatic lipid metabolism, and insulin resistance. Environmental chemicals may compound the problem by directly interacting with nuclear receptors leading to metabolic confusion and the inability to differentiate fed from fasting conditions. This review focuses on the impact of nuclear receptors in the pathogenesis and treatment of NAFLD. Clinical trials including PIVENS and FLINT demonstrate that nuclear receptor targeted therapies may lead to the paradoxical dissociation of steatosis, inflammation, fibrosis, insulin resistance, dyslipidemia and obesity. Novel strategies currently under development (including tissue-specific ligands and dual receptor agonists) may be required to separate the beneficial effects of nuclear receptor activation from unwanted metabolic

  5. Lectins in the investigation of receptors

    NASA Astrophysics Data System (ADS)

    Lakhtin, V. M.; Yamskov, Igor A.

    1991-08-01

    Problems of the purification and characterisation are considered for approximately 270 receptors (including cell surface and organelle enzymes), which are glycoconjugates (mainly glycoproteins) from animals, plants and microorganisms, using various lectins (mainly lectin sorbents). An analysis has been carried out of the stages of lectin affinity chromatography of receptors (choice of detergent, use of organic solvents, elution with carbohydrates, etc.). Examples are given of procedures for the purification of receptors, including the use of paired columns and combination chromatography on lectins. The possibility of separating sub-populations of receptors using lectins has been demonstrated. Examples are given of the use of lectins in the analysis of the oligosaccharide structure of receptors. Cases are recorded of the interaction of receptors with endogenous lectins and of receptor lectins with endogenous glycoconjugates. It has been shown that lectins, in combination with glycosidases and antibodies, may be useful in the investigation of receptors. The bibliography contains 406 references.

  6. Glutamate Receptor Dynamics in Dendritic Microdomains

    PubMed Central

    Newpher, Thomas M.; Ehlers, Michael D.

    2008-01-01

    Among diverse factors regulating excitatory synaptic transmission, the abundance of postsynaptic glutamate receptors figures prominently in molecular memory and learning-related synaptic plasticity. To allow for both long-term maintenance of synaptic transmission and acute changes in synaptic strength, the relative rates of glutamate receptor insertion and removal must be tightly regulated. Interactions with scaffolding proteins control the targeting and signaling properties of glutamate receptors within the postsynaptic membrane. In addition, extrasynaptic receptor populations control the equilibrium of receptor exchange at synapses and activate distinct signaling pathways involved in plasticity. Here, we review recent findings that have shaped our current understanding of receptor mobility between synaptic and extrasynaptic compartments at glutamatergic synapses, focusing on AMPA and NMDA receptors. We also examine the cooperative relationship between intracellular trafficking and surface diffusion of glutamate receptors that underlies the expression of learning-related synaptic plasticity. PMID:18498731

  7. Mechanism for the activation of glutamate receptors

    Cancer.gov

    Scientists at the NIH have used a technique called cryo-electron microscopy to determine a molecular mechanism for the activation and desensitization of ionotropic glutamate receptors, a prominent class of neurotransmitter receptors in the brain and spina

  8. Henipavirus receptor usage and tropism.

    PubMed

    Pernet, Olivier; Wang, Yao E; Lee, Benhur

    2012-01-01

    Nipah (NiV) and Hendra (HeV) viruses are the deadliest human pathogens within the Paramyxoviridae family, which include human and animal pathogens of global biomedical importance. NiV and HeV infections cause respiratory and encephalitic illness with high mortality rates in humans. Henipaviruses (HNV) are the only Paramyxoviruses classified as biosafety level 4 (BSL4) pathogens due to their extreme pathogenicity, potential for bioterrorism, and lack of licensed vaccines and therapeutics. HNV use ephrin-B2 and ephrin-B3, highly conserved proteins, as viral entry receptors. This likely accounts for their unusually broad species tropism, and also provides opportunities to study how receptor usage, cellular tropism, and end-organ pathology relates to the pathobiology of HNV infections. The clinical and pathologic manifestations of NiV and HeV virus infections are reviewed in the chapters by Wong et al. and Geisbert et al. in this issue. Here, we will review the biology of the HNV receptors, and how receptor usage relates to HNV cell tropism in vitro and in vivo.

  9. Recombinant lymphokines and their receptors

    SciTech Connect

    Gillis, S.

    1987-01-01

    This book contains 15 selections. Some of the chapter titles are: Human Interleukin-2, Molecular Analysis of the Murine Interleukin-2 Receptor, Bovine Interleukin-2, Molecular Organization and Expression of the Prointerleukin-1..beta.. Gene, Human Erythroid-Portentiating Activity, and Tumor Necrosis Factors Alpha and Beta.

  10. Receptor sensitivity in bacterial chemotaxis

    NASA Astrophysics Data System (ADS)

    Sourjik, Victor; Berg, Howard C.

    2002-01-01

    Chemoreceptors in Escherichia coli are coupled to the flagella by a labile phosphorylated intermediate, CheY~P. Its activity can be inferred from the rotational bias of flagellar motors, but motor response is stochastic and limited to a narrow physiological range. Here we use fluorescence resonance energy transfer to monitor interactions of CheY~P with its phosphatase, CheZ, that reveal changes in the activity of the receptor kinase, CheA, resulting from the addition of attractants or repellents. Analyses of cheR and/or cheB mutants, defective in receptor methylation/demethylation, show that response sensitivity depends on the activity of CheB and the level of receptor modification. In cheRcheB mutants, the concentration of attractant that generates a half-maximal response is equal to the dissociation constant of the receptor. In wild-type cells, it is 35 times smaller. This amplification, together with the ultrasensitivity of the flagellar motor, explains previous observations of high chemotactic gain.

  11. [Serotoninergic receptors and cardiovascular diseases].

    PubMed

    Hong, E; Castillo, C; Flores, E; Mercedes, F

    1994-01-01

    The seronin or 5-hydroxytryptamine (5-HT) is a biogenic amine involved in diverse physiologic and physiopathological processes in the cardiovascular system. 5-HT may lower the arterial blood pressure by an action on central 5-HT1A receptors, or may increase it by stimulation of 5-HT2 receptors located in vascular smooth muscle. It has been postulated that hypofunction of 5-HT1A receptors, or the exaggerated stimulation of 5-HT2 receptor may be associated with arterial hypertension and that agonists of the first type (indorenate or 8-OH-DPAT) or antagonists of the second type (ketanserin or pelanserin) allow the control of arterial hypertension. On the other land, ketanserin and pelanserin attenuated the hemodynamic manifestations in an experimental model of thromboembolism, suggesting that 5-HT is involved in such phenomenon. Finally, 5-HT could be related with the presence of angor pectoris during hypertension or atherosclerosis, diseases that are associated with a lesional of the vascular endothelium, a condition that favors the 5-HT induced vasoconstriction in coronary arteries.

  12. Laminin receptors for neurite formation

    SciTech Connect

    Kleinman, H.K.; Ogle, R.C.; Cannon, F.B.; Little, C.D.; Sweeney, T.M.; Luckenbill-Edds, L.

    1988-02-01

    Laminin, a basement membrane glycoprotein promotes both cell attachment and neurite outgrowth. Separate domains on laminin elicit these responses, suggesting that distinct receptors occur on the surface of cells. NG108-15 neuroblastoma-glioma cells rapidly extend long processes in the presence of laminin. The authors report here that /sup 125/I-labeled laminin specifically binds to these cells and to three membrane proteins of 67, 110, and 180 kDa. These proteins were isolated by affinity chromatography on laminin-Sepharose. The 67-kDa protein reacted with antibody to the previously characterized receptor for cell attachment to laminin. Antibodies to the 110-kDa and 180-kDa bands demonstrated that the 110-kDa protein was found in a variety of epithelial cell lines and in brain, whereas the 180-kDa protein was neural specific. Antibodies prepared against the 110-kDa and 180-kDa proteins inhibited neurite outgrowth induced by the neurite-promoting domain of laminin, whereas antibodies to the 67-kDa laminin receptor had no effect on neurite outgrowth. They conclude that neuronal cells have multiple cell-surface laminin receptors and that the 110-kDa and 180-kDa proteins are involved in neurite formation.

  13. Steroid receptor coupling becomes nuclear.

    PubMed

    Galigniana, Mario D

    2012-06-22

    In this issue of Chemistry & Biology, Grossman et al. report a study on aldosterone-dependent nuclear translocation of the mineralocorticoid receptor (MR). They analyze the dependency of MR retrotransport, DNA-binding, and transcriptional activity on Hsp90 and demonstrate that MR dimerization is a nuclear event. Copyright © 2012 Elsevier Ltd. All rights reserved.

  14. Interleukin-24 and its receptors.

    PubMed

    Wang, Mai; Liang, Peng

    2005-02-01

    Interleukin 24 (IL-24) is a new member of the IL-10 family of cytokines and it signals through two heterodimeric receptors: IL-20R1/IL-20R2 and IL-22R1/IL-20R2. Upon binding to its receptors, IL-24 induces rapid activation of Stat-1 and Stat-3 transcription factors, which appear to play a role in cell survival and proliferation. Under physiological conditions, the major sources of IL-24 are the activated monocytes and T helper 2 cells, whereas the major IL-24 target tissues, based on the receptor expression pattern, are non-haematopoietic in origin, and include skin, lung and reproductive tissues. Structurally and functionally, IL-24 is highly conserved across species. This review highlights our current knowledge of IL-24 as a cytokine, with much less emphasis placed on the non-receptor-mediated functions (a subject of several reviews) focused on in much of the earlier literature on IL-24. The potential roles of IL-24 as part of a complex cytokine network in wound healing, psoriasis and cancer are discussed.

  15. Cannabinoid receptor localization in brain

    SciTech Connect

    Herkenham, M.; Lynn, A.B.; Little, M.D.; Johnson, M.R.; Melvin, L.S.; de Costa, B.R.; Rice, K.C. )

    1990-03-01

    (3H)CP 55,940, a radiolabeled synthetic cannabinoid, which is 10-100 times more potent in vivo than delta 9-tetrahydrocannabinol, was used to characterize and localize a specific cannabinoid receptor in brain sections. The potencies of a series of natural and synthetic cannabinoids as competitors of (3H)CP 55,940 binding correlated closely with their relative potencies in several biological assays, suggesting that the receptor characterized in our in vitro assay is the same receptor that mediates behavioral and pharmacological effects of cannabinoids, including human subjective experience. Autoradiography of cannabinoid receptors in brain sections from several mammalian species, including human, reveals a unique and conserved distribution; binding is most dense in outflow nuclei of the basal ganglia--the substantia nigra pars reticulata and globus pallidus--and in the hippocampus and cerebellum. Generally high densities in forebrain and cerebellum implicate roles for cannabinoids in cognition and movement. Sparse densities in lower brainstem areas controlling cardiovascular and respiratory functions may explain why high doses of delta 9-tetrahydrocannabinol are not lethal.

  16. Neuroexcitatory Drug Receptors in Mammals and Invertebrates

    DTIC Science & Technology

    1990-03-16

    several animal species investigated. We identified the codfish as having a single polypeptide/gene for CABA -A receptors, as compared to 10-15 different...through blocking of CABA receptor functions. The CABA receptor-chloride channel system is important in wide-spread regions of the mammalian nervous... CABA receptor distribution was quantitated and mapped (14). For this analysis, we employed an image analyzer purchased by Drs. Olsen and de Vellis under

  17. Opiate Receptor Binding Properties of Carfentanil

    DTIC Science & Technology

    1987-11-01

    CHEMICAL O [RE CORN r RESEARCHL co -DEVELOPMENT & ENGINEERING CENTER,CRDEC-TR-88029 OPIATE RECEPTOR BINDING PROPERTIES OF CARFENTANIL DTIC .4J...TITLE (Include Security Classification) Opiate Receptor Binding Properties of Carfentanil 12. PERSONAL AUTHOR(S) Thompson, Roy G., Menking, Darrel...FIELD GROUP SUB-GROUP Opiates DELTA receptor 07 03 Carfentanil KAPPA receptor 15 06 03 Mil rpcentnr 19. ABSTRACT (Continue on reverse if necessary and

  18. Receptors of anthrax toxin and cell entry.

    PubMed

    van der Goot, Gisou; Young, John A T

    2009-12-01

    Anthrax toxin-receptor interactions are critical for toxin delivery to the host cell cytoplasm. This review summarizes what is known about the molecular details of the protective antigen (PA) toxin subunit interaction with either the ANTXR1 and ANTXR2 cellular receptors, and how receptor-type can dictate the low pH threshold of PA pore formation. The roles played by cellular factors in regulating the endocytosis of toxin-receptor complexes is also discussed.

  19. Characterization of the thyrotropin receptor

    SciTech Connect

    McQuade, R.D.

    1986-01-01

    Scatchard analysis of the binding of (/sup 125/I)TSH to thyroid plasma membranes results in a curvilinear, concave-upward plot. This phenomenon could be indicative of several conditions, including radioligand heterogeneity, negative cooperativity, or multiple binding sites. To investigate the first of these possibilities, (/sup 125/I)TSH was purified by chromatography on Sepharose 6B. The receptor active (/sup 125/I)TSH continued to yield a curvilinear Scatchard plot in equilibrium binding analyses, indicating that this phenomenon was not the result of radioligand impurities of heterogeneity. To determine the contribution of the receptor to this complex behavior, the TSH receptor was solubilized and subjected to concanavalin A chromatography. Two populations of binding sites were recovered. The pass-through fraction contained 70% of the total sites and exhibited a linear Scatchard plot with a K/sub D/ of 67 nM, while 0.2 M methylmannoside eluted 10% of the sites which exhibited a single K/sub D/ of 0.3 nM. To characterize its structure, the TSH receptor was labeled with (/sup 125/I)TSH and cross-linked with disuccinimidyl suberate. Analysis by electrophoresis and autoradiography demonstrated the labeling of two hormone-receptor complexes with M/sub r/ of 80,000 and 68,000. These two bands were demonstrated to be TSH-specific and were present in plasma membranes from thyroid, but not from muscle or liver. Furthermore, antibodies isolated from the sera of Graves' disease patients, which inhibit the bindings of (/sup 125/I)TSH, blocked the labeling of the two complexes. When the separated high and low affinity TSH binding components were similarly analyzed, both components exhibited the 80,000 and 68,000 bands. Furthermore, the autoantibodies from Graves' disease sera inhibited the binding of (/sup 125/I)TSH to both the high and low affinity species.

  20. The Role of Estrogen Related Receptor in Modulating Estrogen Receptor Mediated Transcription in Breast Cancer Cells

    DTIC Science & Technology

    2005-04-01

    receptors ) by demonstrating that mitochondrial biogenesis and fatty acid P- oxidation , processes ERRa is known to regulate , are robustly...gluconeogenesis, and fatty acid oxidation (Lin 2003; Puigserver 1998; Wu 1999; Yoon 2001). In addition to its activity on a number of nuclear receptors , this...in target cells. They were generated by replacing the receptor interaction domains in peroxisome proliferator activated receptor

  1. Cell surface receptors for CCN proteins.

    PubMed

    Lau, Lester F

    2016-06-01

    The CCN family (CYR61; CTGF; NOV; CCN1-6; WISP1-3) of matricellular proteins in mammals is comprised of six homologous members that play important roles in development, inflammation, tissue repair, and a broad range of pathological processes including fibrosis and cancer. Despite considerable effort to search for a high affinity CCN-specific receptor akin to growth factor receptors, no such receptor has been found. Rather, CCNs bind several groups of multi-ligand receptors as characteristic of other matricellular proteins. The most extensively documented among CCN-binding receptors are integrins, including αvβ3, αvβ5, α5β1, α6β1, αIIbβ3, αMβ2, and αDβ2, which mediate diverse CCN functions in various cell types. CCNs also bind cell surface heparan sulfate proteoglycans (HSPGs), low density liproprotein receptor-related proteins (LRPs), and the cation-independent mannose-6-phosphate (M6P) receptor, which are endocytic receptors that may also serve as co-receptors in cooperation with other cell surface receptors. CCNs have also been reported to bind FGFR-2, Notch, RANK, and TrkA, potentially altering the affinities of these receptors for their ligands. The ability of CCNs to bind a multitude of receptors in various cell types may account for the remarkable versatility of their functions, and underscore the diverse signaling pathways that mediate their activities.

  2. Neurotransmitter Receptor Binding in Bovine Cerebral Microvessels

    NASA Astrophysics Data System (ADS)

    Peroutka, Stephen J.; Moskowitz, Michael A.; Reinhard, John F.; Synder, Solomon H.

    1980-05-01

    Purified preparations of microvessels from bovine cerebral cortex contain substantial levels of alpha-adrenergic, beta-adrenergic, and histamine 1 receptor binding sites but only negligible serotonin, muscarinic cholinergic, opiate, and benzodiazepine receptor binding. Norepinephrine and histamine may be endogenous regulators of the cerebral microcirculation at the observed receptors.

  3. The Physiology and Biochemistry of Receptors.

    ERIC Educational Resources Information Center

    Spitzer, Judy A., Ed.

    1983-01-01

    The syllabus for a refresher course on the physiology and biochemistry of receptors (presented at the 1983 American Physiological Society meeting) is provided. Topics considered include receptor regulation, structural/functional aspects of receptors for insulin and insulin-like growth factors, calcium channel inhibitors, and role of lipoprotein…

  4. Function of Estrogen Receptor Tryosine Phosphorylation

    DTIC Science & Technology

    1997-07-01

    localization of the receptors, ligand binding, DNA binding, transcriptional activation, and receptor turnover ( LeGoff et al. 1994; Lahooti et al. 1994...1040-1049 (1995). LeGoff P., M.M. Montano, D.J. Schodin, and B. Katzenellenbogen. Phosphorylation of the Human Estrogen Receptor. J. Biol. Chem

  5. The Physiology and Biochemistry of Receptors.

    ERIC Educational Resources Information Center

    Spitzer, Judy A., Ed.

    1983-01-01

    The syllabus for a refresher course on the physiology and biochemistry of receptors (presented at the 1983 American Physiological Society meeting) is provided. Topics considered include receptor regulation, structural/functional aspects of receptors for insulin and insulin-like growth factors, calcium channel inhibitors, and role of lipoprotein…

  6. Triheteromeric NMDA Receptors at Hippocampal Synapses

    PubMed Central

    Tovar, Kenneth R.; McGinley, Matthew J.; Westbrook, Gary L.

    2013-01-01

    NMDA receptors are composed of two GluN1 (N1) and two GluN2 (N2) subunits. Constituent N2 subunits control the pharmacological and kinetic characteristics of the receptor. NMDA receptors in hippocampal or cortical neurons are often thought of as diheteromeric, i.e., containing only one type of N2 subunit. However, triheteromeric receptors with more than one type of N2 subunit also have been reported and the relative contribution of di- and triheteromeric NMDA receptors at synapses has been difficult to assess. Because wild-type hippocampal principal neurons express N1, N2A and N2B, we used cultured hippocampal principal neurons from N2A and N2B-knockout mice as templates for diheteromeric synaptic receptors. Summation of N1/N2B and N1/N2A excitatory postsynaptic currents could not account for the deactivation kinetics of wild-type excitatory postsynaptic currents (EPSCs) however. To make a quantitative estimate of NMDA receptor subtypes at wild-type synapses, we used the deactivation kinetics, as well as the effects of the competitive antagonist NVP-AAM077. Our results indicate that three types of NMDA receptors contribute to the wild-type EPSC, with at least two-thirds being triheteromeric receptors. Functional isolation of synaptic triheteromeric receptors revealed deactivation kinetics and pharmacology distinct from either diheteromeric receptor subtype. Because of differences in open probability, synaptic triheteromeric receptors outnumbered N1/N2A receptors by 5.8 to 1 and N1/N2B receptors by 3.2 to 1. Our results suggest that triheteromeric NMDA receptors must be either preferentially assembled or preferentially localized at synapses. PMID:23699525

  7. Dopamine receptor oligomerization visualized in living cells.

    PubMed

    O'Dowd, Brian F; Ji, Xiaodong; Alijaniaram, Mohammad; Rajaram, Ryan D; Kong, Michael M C; Rashid, Asim; Nguyen, Tuan; George, Susan R

    2005-11-04

    G protein-coupled receptors occur as dimers within arrays of oligomers. We visualized ensembles of dopamine receptor oligomers in living cells and evaluated the contributions of receptor conformation to the dynamics of oligomer association and dissociation, using a strategy of trafficking a receptor to another cellular compartment. We incorporated a nuclear localization sequence into the D1 dopamine receptor, which translocated from the cell surface to the nucleus. Receptor inverse agonists blocked this translocation, retaining the modified receptor, D1-nuclear localization signal (NLS), at the cell surface. D1 co-translocated with D1-NLS to the nucleus, indicating formation of homooligomers. (+)-Butaclamol retained both receptors at the cell surface, and removal of the drug allowed translocation of both receptors to the nucleus. Agonist-nonbinding D1(S198A/S199A)-NLS, containing two substituted serine residues in transmembrane 5 also oligomerized with D1, and both were retained on the cell surface by (+)-butaclamol. Drug removal disrupted these oligomerized receptors so that D1 remained at the cell surface while D1(S198A/S199A)-NLS trafficked to the nucleus. Thus, receptor conformational differences permitted oligomer disruption and showed that ligand-binding pocket occupancy by the inverse agonist induced a conformational change. We demonstrated robust heterooligomerization between the D2 dopamine receptor and the D1 receptor. The heterooligomers could not be disrupted by inverse agonists targeting either one of the receptor constituents. However, D2 did not heterooligomerize with the structurally modified D1(S198A/S199A), indicating an impaired interface for their interaction. Thus, we describe a novel method showing that a homogeneous receptor conformation maintains the structural integrity of oligomers, whereas conformational heterogeneity disrupts it.

  8. [Structure and Function of the Nuclear Receptor Constitutive Androstane Receptor].

    PubMed

    Inouye, Yoshio

    2016-01-01

    Animal defense mechanisms against both endogenous and exogenous toxic compounds function mainly through receptor-type transcription factors, including the constitutive androstane receptor (CAR). Following xenobiotic stimulation, CAR translocates into the nucleus and transactivates its target genes including oxygenic and conjugative enzymes and transporters in hepatocytes. We identified subcellular localization signals in the rat CAR: two nuclear localization signals (NLS1 and 2); two nuclear export signals (NES1 and 2); and a cytoplasmic retention region. The nuclear import of CAR is regulated by the importin-Ran system and microtubule network. Five splice variants (SV1-5) were identified in rat liver in addition to wild-type CAR. When expressed in immortalized cells, their artificial transcripts were inactive as transcription factors. A CAR mutant with three consecutive alanine residues inserted into the ligand-binding domain of CAR showed ligand-dependent activation of target genes in immortalized cells, which is in marked contrast to the constitutive transactivating nature of wild-type CAR. Using this assay system, androstenol and clotrimazole, both of which are inverse agonists of CAR, were classified as an antagonist and weak agonist, respectively. A member of the DEAD box DNA/RNA helicase family (DP97) and protein arginine methyltransferase 5 (PRMT5) were found to be gene (or promotor)-specific coactivators of CAR. The expression of the CAR gene might be under the control of clock genes mediated by the nuclear receptor Rev-erb-α.

  9. GABAB receptor modulation of synaptic function

    PubMed Central

    Chalifoux, Jason R.; Carter, Adam G.

    2011-01-01

    Neuromodulators have complex effects on both the presynaptic release and postsynaptic detection of neurotransmitters. Here we describe recent advances in our understanding of synaptic modulation by metabotropic GABAB receptors. By inhibiting multivesicular release from the presynaptic terminal, these receptors decrease the synaptic glutamate signal. GABAB receptors also inhibit the Ca2+ permeability of NMDA receptors to decrease Ca2+ signals in postsynaptic spines. These new findings highlight the importance of GABAB receptors in regulating many aspects of synaptic transmission. They also point to novel questions about the spatiotemporal dynamics and sources of synaptic modulation in the brain. PMID:21376567

  10. New concepts of histamine receptors and actions.

    PubMed

    Repka-Ramirez, Maria Susana

    2003-05-01

    Histamine and antihistamines are so deeply woven into the fabric of allergic diseases that it is sometimes difficult to see how this field could advance beyond our current, potent histamine H1-receptor drugs. Investigations of other actions of histamine and the identification of H2, H3, and now H4 receptors have suddenly reignited the search for new mono- and multi-receptor-specific agonists and antagonists. There is great excitement due to preliminary findings that H3 receptors act as neural inhibitory autoreceptors, and H4 receptors might modulate immune cell functions.

  11. Variable Lymphocyte Receptors: A Current Overview.

    PubMed

    Kasahara, Masanori

    2015-01-01

    Jawless vertebrates represented by lampreys and hagfish mount antigen-specific immune responses using variable lymphocyte receptors. These receptors generate diversity comparable to that of T-cell and B-cell receptors by assembling multiple leucine-rich repeat modules with highly variable sequences. Although it is true that jawed and jawless vertebrates have structurally unrelated antigen receptors, their adaptive immune systems have much in common. Most notable is the conservation of lymphocyte lineages. It appears that specialized lymphocyte lineages emerged in a common vertebrate ancestor and that jawed and jawless vertebrates co-opted different antigen receptors within the context of such lymphocyte lineages.

  12. Recycling Endosomes Supply AMPA Receptors for LTP

    NASA Astrophysics Data System (ADS)

    Park, Mikyoung; Penick, Esther C.; Edwards, Jeffrey G.; Kauer, Julie A.; Ehlers, Michael D.

    2004-09-01

    Long-term potentiation (LTP) of synaptic strength, the most established cellular model of information storage in the brain, is expressed by an increase in the number of postsynaptic AMPA receptors. However, the source of AMPA receptors mobilized during LTP is unknown. We report that AMPA receptors are transported from recycling endosomes to the plasma membrane for LTP. Stimuli that triggered LTP promoted not only AMPA receptor insertion but also generalized recycling of cargo and membrane from endocytic compartments. Thus, recycling endosomes supply AMPA receptors for LTP and provide a mechanistic link between synaptic potentiation and membrane remodeling during synapse modification.

  13. Sugars, Sweet Taste Receptors, and Brain Responses.

    PubMed

    Lee, Allen A; Owyang, Chung

    2017-06-24

    Sweet taste receptors are composed of a heterodimer of taste 1 receptor member 2 (T1R2) and taste 1 receptor member 3 (T1R3). Accumulating evidence shows that sweet taste receptors are ubiquitous throughout the body, including in the gastrointestinal tract as well as the hypothalamus. These sweet taste receptors are heavily involved in nutrient sensing, monitoring changes in energy stores, and triggering metabolic and behavioral responses to maintain energy balance. Not surprisingly, these pathways are heavily regulated by external and internal factors. Dysfunction in one or more of these pathways may be important in the pathogenesis of common diseases, such as obesity and type 2 diabetes mellitus.

  14. Evolutionary vignettes of natural killer cell receptors.

    PubMed

    Sambrook, Jennifer G; Beck, Stephan

    2007-10-01

    The discovery of novel immune receptors has led to a recent renaissance of research into the innate immune system, following decades of intense research of the adaptive immune system. Of particular interest has been the discovery of the natural killer (NK) cell receptors which, depending on type, interact with classical or non-classical MHC class I antigens of the adaptive immune system, thus functioning at the interface of innate and adaptive immunity. Here, we review recent progress with respect to two such families of NK receptors, the killer immunoglobulin-like receptors (KIRs) and the killer cell lectin-like receptors (KLRs), and attempt to trace their evolution across vertebrates.

  15. Receptor crosstalk protein, calcyon, regulates affinity state of dopamine D1 receptors.

    PubMed

    Lidow, M S; Roberts, A; Zhang, L; Koh, P O; Lezcano, N; Bergson, C

    2001-09-21

    The recently cloned protein, calcyon, potentiates crosstalk between G(s)-coupled dopamine D1 receptors and heterologous G(q/11)-coupled receptors allowing dopamine D1 receptors to stimulate intracellular Ca(2+) release, in addition to cAMP production. This crosstalk also requires the participating G(q/11)-coupled receptors to be primed by their agonists. We examined the ability of calcyon and priming to regulate the affinity of dopamine D1 receptors for its ligands. Receptor binding assays were performed on HEK293 cell membrane preparations expressing dopamine D1 receptors either alone or in combination with calcyon. Co-expression of dopamine D1 receptor and calcyon affected neither the affinity of this receptor for antagonists nor the affinity of agonist binding to this receptor high and low-affinity states. However, the presence of calcyon dramatically decreased the proportion of the high-affinity dopamine D1 receptor agonist binding sites. This decrease was reversed by carbachol, which primes the receptor crosstalk by stimulating endogenous G(q/11)-coupled muscarinic receptors. Our findings suggest that calcyon regulates the ability of dopamine D1 receptors to achieve the high-affinity state for agonists, in a manner that depends on priming of receptor crosstalk.

  16. Molecular Mechanisms of Prolactin and Its Receptor

    PubMed Central

    2012-01-01

    Prolactin and the prolactin receptors are members of a family of hormone/receptor pairs which include GH, erythropoietin, and other ligand/receptor pairs. The mechanisms of these ligand/receptor pairs have broad similarities, including general structures, ligand/receptor stoichiometries, and activation of several common signaling pathways. But significant variations in the structural and mechanistic details are present among these hormones and their type 1 receptors. The prolactin receptor is particularly interesting because it can be activated by three sequence-diverse human hormones: prolactin, GH, and placental lactogen. This system offers a unique opportunity to compare the detailed molecular mechanisms of these related hormone/receptor pairs. This review critically evaluates selected literature that informs these mechanisms, compares the mechanisms of the three lactogenic hormones, compares the mechanism with those of other class 1 ligand/receptor pairs, and identifies information that will be required to resolve mechanistic ambiguities. The literature describes distinct mechanistic differences between the three lactogenic hormones and their interaction with the prolactin receptor and describes more significant differences between the mechanisms by which other related ligands interact with and activate their receptors. PMID:22577091

  17. Structural determinants of sigma receptor affinity

    SciTech Connect

    Largent, B.L.; Wikstroem, H.G.; Gundlach, A.L.; Snyder, S.H.

    1987-12-01

    The structural determinants of sigma receptor affinity have been evaluated by examining a wide range of compounds related to opioids, neuroleptics, and phenylpiperidine dopaminergic structures for affinity at sigma receptor-binding sites labeled with (+)-(/sup 3/H)3-PPP. Among opioid compounds, requirements for sigma receptor affinity differ strikingly from the determinants of affinity for conventional opiate receptors. Sigma sites display reverse stereoselectivity to classical opiate receptors. Multi-ringed opiate-related compounds such as morphine and naloxone have negligible affinity for sigma sites, with the highest sigma receptor affinity apparent for benzomorphans which lack the C ring of opioids. Highest affinity among opioids and other compounds occurs with more lipophilic N-substituents. This feature is particularly striking among the 3-PPP derivatives as well as the opioids. The butyrophenone haloperidol is the most potent drug at sigma receptors we have detected. Among the series of butyrophenones, receptor affinity is primarily associated with the 4-phenylpiperidine moiety. Conformational calculations for various compounds indicate a fairly wide range of tolerance for distances between the aromatic ring and the amine nitrogen, which may account for the potency at sigma receptors of structures of considerable diversity. Among the wide range of structures that bind to sigma receptor-binding sites, the common pharmacophore associated with high receptor affinity is a phenylpiperidine with a lipophilic N-substituent.

  18. The evolution of vertebrate opioid receptors

    PubMed Central

    Stevens, Craig W.

    2011-01-01

    The proteins that mediate the analgesic and other effects of opioid drugs and endogenous opioid peptides are known as opioid receptors. Opioid receptors consist of a family of four closely-related proteins belonging to the large superfamily of G-protein coupled receptors. The three types of opioid receptors shown unequivocally to mediate analgesia in animal models are the mu (MOR), delta (DOR), and kappa (KOR) opioid receptor proteins. The role of the fourth member of the opioid receptor family, the nociceptin or orphanin FQ receptor (ORL), is not as clear as hyperalgesia, analgesia, and no effect was reported after administration of ORL agonists. There are now cDNA sequences for all four types of opioid receptors that are expressed in the brain of six species from three different classes of vertebrates. This review presents a comparative analysis of vertebrate opioid receptors using bioinformatics and data from recent human genome studies. Results indicate that opioid receptors arose by gene duplication, that there is a vector of opioid receptor divergence, and that MOR shows evidence of rapid evolution. PMID:19273128

  19. Signal transduction activated by cannabinoid receptors.

    PubMed

    Díaz-Laviada, Inés; Ruiz-Llorente, Lidia

    2005-07-01

    Since the discovery that cannabinoids exert biological actions through binding to specific receptors, signal mechanisms triggered by these receptors have been focus of extensive study. This review summarizes the current knowledge of the signalling events produced by cannabinoids from membrane receptors to downstream regulators. Two types of cannabinoid receptors have been identified to date: CB(1) and CB(2) both belonging to the heptahelichoidal receptor family but with different tissue distribution and signalling mechanisms. Coupling to inhibitory guanine nucleotide-binding protein and thus inhibition of adenylyl cyclase has been observed in both receptors but other signal transduction pathways that are regulated or not by these G proteins are differently activated upon ligand-receptor binding including ion channels, sphingomyelin hydrolysis, ceramide generation, phospholipases activation and downstream targets as MAP kinase cascade, PI3K, FAK or NOS regulation. Cannabinoids may also act independently of CB(1)or CB(2) receptors. The existence of new unidentified putative cannabinoid receptors has been claimed by many investigators. Endocannabinoids activate vanilloid TRPV1 receptors that may mediate some of the cannabinoid effects. Other actions of cannabinoids can occur through non-receptor-mediated mechanisms.

  20. Dopamine D4 receptors in psychostimulant addiction.

    PubMed

    Di Ciano, Patricia; Grandy, David K; Le Foll, Bernard

    2014-01-01

    Since the cloning of the D4 receptor in the 1990s, interest has been building in the role of this receptor in drug addiction, given the importance of dopamine in addiction. Like the D3 receptor, the D4 receptor has limited distribution within the brain, suggesting it may have a unique role in drug abuse. However, compared to the D3 receptor, few studies have evaluated the importance of the D4 receptor. This may be due, in part, to the relative lack of compounds selective for the D4 receptor; the early studies were mainly conducted in mice lacking the D4 receptor. In this review, we summarize the literature on the structure and localization of the D4 receptor before reviewing the data from D4 knockout mice that used behavioral models relevant to the understanding of stimulant use. We also present evidence from more recent pharmacological studies using selective D4 agonists and antagonists and animal models of drug-seeking and drug-taking. The data summarized here suggest a role for D4 receptors in relapse to stimulant use. Therefore, treatments based on antagonism of the D4 receptor may be useful treatments for relapse to nicotine, cocaine, and amphetamine use. © 2014 Elsevier Inc. All rights reserved.

  1. Xenobiotic receptor humanized mice and their utility.

    PubMed

    Scheer, Nico; Roland Wolf, C

    2013-02-01

    The nuclear receptors pregnane X receptor, constitutive androstane receptor, and peroxisome proliferator-activated receptor alpha have important endogenous functions and are also involved in the induction of drug-metabolizing enzymes and transporters in response to exogenous xenobiotics. Though not belonging to the same protein family, the Per-Sim-ARNT domain receptor aryl hydrocarbon receptor functionally overlaps with the three nuclear receptors in many aspects and is therefore included in this review. Significant species differences in ligand affinity and biological responses as a result of activation of these receptors have been described. Several xenobiotic receptor humanized mice have been created to overcome these species differences and to provide in vivo models that are more predictive for human responses. This review provides an overview of the different xenobiotic receptor humanized mouse models described to date and will summarize how these models can be applied in basic research and improve drug discovery and development. Some of the key applications in the evaluation of drug induction, drug-drug interactions, nongenotoxic carcinogenicity, other toxicity, or efficacy studies are described. We also discuss relevant considerations in the interpretation of such data and potential future directions for the use of xenobiotic receptor humanized mice.

  2. Prostanoid receptors and acute inflammation in skin.

    PubMed

    Hohjoh, Hirofumi; Inazumi, Tomoaki; Tsuchiya, Soken; Sugimoto, Yukihiko

    2014-12-01

    Prostanoids such as prostaglandins (PGs) and thromboxanes exert a wide variety of actions via nine types of G protein-coupled receptors, including four PGE2 receptors (EPs) and two PGD2 receptors (DPs). Recent studies have revealed that prostanoids trigger or modulate acute inflammation in the skin via multiple mechanisms involving distinct receptors and molecules; PGE2 elicits vascular permeability and edema formation via EP3 receptor on mast cells, and PGE2 increases blood flow by eliciting vasodilatation via EP2/EP4 receptors on smooth muscle cells. PGD2-DP1 signaling plays a role in mast cell maturation and mast cell-mediated inflammation. Therefore, the local inhibition of specific prostanoid receptor signaling is expected to be an effective strategy for the prevention and treatment of acute inflammation.

  3. Detection of cell surface dopamine receptors.

    PubMed

    Xiao, Jiping; Bergson, Clare

    2013-01-01

    Dopamine receptors are a class of metabotropic G protein-coupled receptors. Plasma membrane expression is a key determinant of receptor signaling, and one that is regulated both by extra and intracellular cues. Abnormal dopamine receptor signaling is implicated in several neuropsychiatric disorders, including schizophrenia and attention deficit hyperactivity disorder, as well as drug abuse. Here, we describe in detail the application of two complementary applications of protein biotinylation and enzyme-linked immunoabsorbent assay (ELISA) for detecting and quantifying levels of dopamine receptors expressed on the cell surface. In the biotinylation method, cell surface receptors are labeled with Sulfo-NHS-biotin. The charge on the sulfonyl facilitates water solubility of the reactive biotin compound and prevents its diffusion across the plasma membrane. In the ELISA method, surface labeling is achieved with antibodies specific to extracellular epitopes on the receptors, and by fixing the cells without detergent such that the plasma membrane remains intact.

  4. Detection of Cell Surface Dopamine Receptors

    PubMed Central

    Xiao, Jiping; Bergson, Clare

    2014-01-01

    Dopamine receptors are a class of metabotropic G protein-coupled receptors. Plasma membrane expression is a key determinant of receptor signaling, and one that is regulated both by extra and intracellular cues. Abnormal dopamine receptor signaling is implicated in several neuropsychiatric disorders, including schizophrenia and attention deficit hyperactivity disorder, as well as drug abuse. Here, we describe in detail the application of two complementary applications of protein biotinylation and enzyme-linked immunoabsorbant assay (ELISA) for detecting and quantifying levels of dopamine receptors expressed on the cell surface. In the biotinylation method, cell surface receptors are labeled with Sulfo-NHS-biotin. The charge on the sulfonyl facilitates water solubility of the reactive biotin compound and prevents its diffusion across the plasma membrane. In the ELISA method, cells surface labeling is achieved with antibodies specific to extracellular epitopes on the receptors, and by fixing the cells without detergent such that the plasma membrane remains intact. PMID:23296774

  5. Targeting nuclear receptors with marine natural products.

    PubMed

    Yang, Chunyan; Li, Qianrong; Li, Yong

    2014-01-27

    Nuclear receptors (NRs) are important pharmaceutical targets because they are key regulators of many metabolic and inflammatory diseases, including diabetes, dyslipidemia, cirrhosis, and fibrosis. As ligands play a pivotal role in modulating nuclear receptor activity, the discovery of novel ligands for nuclear receptors represents an interesting and promising therapeutic approach. The search for novel NR agonists and antagonists with enhanced selectivities prompted the exploration of the extraordinary chemical diversity associated with natural products. Recent studies involving nuclear receptors have disclosed a number of natural products as nuclear receptor ligands, serving to re-emphasize the translational possibilities of natural products in drug discovery. In this review, the natural ligands of nuclear receptors will be described with an emphasis on their mechanisms of action and their therapeutic potentials, as well as on strategies to determine potential marine natural products as nuclear receptor modulators.

  6. Receptor arrays optimized for natural odor statistics

    PubMed Central

    Zwicker, David; Murugan, Arvind; Brenner, Michael P.

    2016-01-01

    Natural odors typically consist of many molecules at different concentrations. It is unclear how the numerous odorant molecules and their possible mixtures are discriminated by relatively few olfactory receptors. Using an information theoretic model, we show that a receptor array is optimal for this task if it achieves two possibly conflicting goals: (i) Each receptor should respond to half of all odors and (ii) the response of different receptors should be uncorrelated when averaged over odors presented with natural statistics. We use these design principles to predict statistics of the affinities between receptors and odorant molecules for a broad class of odor statistics. We also show that optimal receptor arrays can be tuned to either resolve concentrations well or distinguish mixtures reliably. Finally, we use our results to predict properties of experimentally measured receptor arrays. Our work can thus be used to better understand natural olfaction, and it also suggests ways to improve artificial sensor arrays. PMID:27102871

  7. Hunting Viral Receptors Using Haploid Cells

    PubMed Central

    Pillay, Sirika; Carette, Jan E.

    2016-01-01

    Viruses have evolved intricate mechanisms to gain entry into the host cell. Identification of critical receptors has enabled insights into virus particle internalization, host and tissue tropism, and viral pathogenesis. In this review we discuss the most commonly employed methods for virus receptor discovery, specifically highlighting the use of forward genetic screens in human haploid cells. The ability to generate true knockout alleles at high saturation provides a sensitive means to study virus-host interactions. As an example, haploid genetic screens identified the lysosomal proteins, NPC1 and LAMP1, as intracellular receptors for Ebola virus and Lassa virus, respectively. From these studies emerges the notion that receptor usage by these viruses is highly dynamic involving a programmed switch from cell surface receptor to intracellular receptor. Broad application of genetic knockout approaches will chart functional landscapes of receptors and endocytic pathways hijacked by viruses. PMID:26958914

  8. The measurement of serum transferrin receptor.

    PubMed

    Cook, J D

    1999-10-01

    The concentration of the soluble fragment of transferrin receptor in serum is an important new hematological parameter. Clinical and laboratory studies have shown that this serum form of the receptor reflects the total body mass of cellular transferrin receptor, 80% of which is contained in the erythroid marrow. The two disorders that result in an elevation in the serum transferrin receptor are anemias associated with enhanced erythropoiesis and tissue iron deficiency. The concentration of soluble transferrin receptor provides a useful quantitative measure of the erythroid marrow mass and thereby assists clinically in categorizing the type of anemia. The most important clinical use of the serum transferrin receptor is in determining the cause of iron deficient erythropoiesis (that is, identifying iron deficiency anemia whether it occurs alone or in the presence of the anemia of chronic disease). Present evidence supports the routine use of the serum transferrin receptor in the clinical evaluation of anemic patients.

  9. Targeting Nuclear Receptors with Marine Natural Products

    PubMed Central

    Yang, Chunyan; Li, Qianrong; Li, Yong

    2014-01-01

    Nuclear receptors (NRs) are important pharmaceutical targets because they are key regulators of many metabolic and inflammatory diseases, including diabetes, dyslipidemia, cirrhosis, and fibrosis. As ligands play a pivotal role in modulating nuclear receptor activity, the discovery of novel ligands for nuclear receptors represents an interesting and promising therapeutic approach. The search for novel NR agonists and antagonists with enhanced selectivities prompted the exploration of the extraordinary chemical diversity associated with natural products. Recent studies involving nuclear receptors have disclosed a number of natural products as nuclear receptor ligands, serving to re-emphasize the translational possibilities of natural products in drug discovery. In this review, the natural ligands of nuclear receptors will be described with an emphasis on their mechanisms of action and their therapeutic potentials, as well as on strategies to determine potential marine natural products as nuclear receptor modulators. PMID:24473166

  10. Glycine receptors and brain development

    PubMed Central

    Avila, Ariel; Nguyen, Laurent; Rigo, Jean-Michel

    2013-01-01

    Glycine receptors (GlyRs) are ligand-gated chloride ion channels that mediate fast inhibitory neurotransmission in the spinal cord and the brainstem. There, they are mainly involved in motor control and pain perception in the adult. However, these receptors are also expressed in upper regions of the central nervous system, where they participate in different processes including synaptic neurotransmission. Moreover, GlyRs are present since early stages of brain development and might influence this process. Here, we discuss the current state of the art regarding GlyRs during embryonic and postnatal brain development in light of recent findings about the cellular and molecular mechanisms that control brain development. PMID:24155690

  11. Ligands for Ionotropic Glutamate Receptors

    NASA Astrophysics Data System (ADS)

    Swanson, Geoffrey T.; Sakai, Ryuichi

    Marine-derived small molecules and peptides have played a central role in elaborating pharmacological specificities and neuronal functions of mammalian ionotropic glutamate receptors (iGluRs), the primary mediators of excitatory syn-aptic transmission in the central nervous system (CNS). As well, the pathological sequelae elicited by one class of compounds (the kainoids) constitute a widely-used animal model for human mesial temporal lobe epilepsy (mTLE). New and existing molecules could prove useful as lead compounds for the development of therapeutics for neuropathologies that have aberrant glutamatergic signaling as a central component. In this chapter we discuss natural source origins and pharmacological activities of those marine compounds that target ionotropic glutamate receptors.

  12. What are Nuclear Receptor Ligands?

    PubMed Central

    Sladek, Frances M.

    2010-01-01

    Nuclear receptors (NRs) are a family of highly conserved transcription factors that regulate transcription in response to small lipophilic compounds. They play a role in every aspect of development, physiology and disease in humans. They are also ubiquitous in and unique to the animal kingdom suggesting that they may have played an important role in their evolution. In contrast to the classical endocrine receptors that originally defined the family, recent studies suggest that the first NRs might have been sensors of their environment, binding ligands that were external to the host organism. The purpose of this review is to provide a broad perspective on NR ligands and address the issue of exactly what constitutes a NR ligand from historical, biological and evolutionary perspectives. This discussion will lay the foundation for subsequent reviews in this issue as well as pose new questions for future investigation. PMID:20615454

  13. Ligands for Ionotropic Glutamate Receptors

    PubMed Central

    Swanson, Geoffrey T.; Sakai, Ryuichi

    2010-01-01

    Marine-derived small molecules and peptides have played a central role in elaborating pharmacological specificities and neuronal functions of mammalian ionotropic glutamate receptors (iGluRs), the primary mediators of excitatory synaptic transmission in the central nervous system (CNS). As well, the pathological sequelae elicited by one class of compounds (the kainoids) constitute a widely-used animal model for human mesial temporal lobe epilepsy (mTLE). New and existing molecules could prove useful as lead compounds for the development of therapeutics for neuropathologies that have aberrant glutamatergic signaling as a central component. In this chapter we discuss natural source origins and pharmacological activities of those marine compounds that target ionotropic glutamate receptors. PMID:19184587

  14. Endocannabinoids and cannabinoid receptor genetics.

    PubMed

    Onaivi, Emmanuel S; Leonard, Claire M; Ishiguro, Hiroki; Zhang, Ping Wu; Lin, Zhicheng; Akinshola, Babatunde E; Uhl, George R

    2002-04-01

    This review presents the remarkable advances that have been achieved in marijuana (cannabinoid) research, with the discovery of specific receptors and the existence of naturally occurring cannabis-like substances in the human body and brain. The last decade has seen more rapid progress in marijuana research than any time in the thousands of years that marijuana has been used by humans, particularly in cannabinoid genomics. The cDNA and genomic sequences encoding G protein-coupled cannabinoid receptors (Cnrs) from several species have now been cloned. Endogenous cannabinoids (endocannabinoids), synthetic and hydrolyzing enzymes and transporters that define neurochemically-specific cannabinoid brain pathways have been identified. Endocannabinoid lipid signaling molecules alter activity at G protein-coupled receptors (GPCR) and possibly at anandamide-gated ion channels, such as vanilloid receptors. Availability of increasingly-specific CB1 and CB2 Cnr antagonists and of CB1 and CB2 Cnr knockout mice have increased our understanding of these cannabinoid systems and provides tantalizing evidence for even more G protein-coupled Cnrs. Initial studies of the Cnr gene structure, regulation and polymorphisms whet our appetite for more information about these interesting genes, their variants and roles in vulnerabilities to addictions and other neuropsychiatric disorders. Behavioral studies of cannabinoids document the complex interactions between rewarding and aversive effects of these drugs. Pursuing cannabinoid-related molecular, pharmacological and behavioral leads will add greatly to our understanding of endogenous brain neuromodulator systems, abused substances and potential therapeutics. This review of CB1 and CB2 Cnr genes in human and animal brain and their neurobiological effects provide a basis for many of these studies. Therefore, understanding the physiological cannabinoid control system in the human body and brain will contribute to elucidating this natural

  15. Aza compounds as anion receptors

    DOEpatents

    Lee, Hung Sui; Yang, Xiao-Qing; McBreen, James

    1998-01-06

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of Li.sup.+ ion in alkali metal batteries.

  16. Aza compounds as anion receptors

    DOEpatents

    Lee, H.S.; Yang, X.Q.; McBreen, J.

    1998-01-06

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of Li{sup +} ion in alkali metal batteries. 3 figs.

  17. Endomorphins interact with tachykinin receptors.

    PubMed

    Kosson, Piotr; Bonney, Iwona; Carr, Daniel B; Lipkowski, Andrzej W

    2005-09-01

    Soon after the discovery of endomorphins several studies indicated differences between pharmacological effects of endomorphins and other MOR selective ligands, as well as differences between the effects of endomorphin I and endomorphin II. We now propose that these differences are the result of an additional non-opioid property of endomorphins, namely, their weak antagonist properties with respect to tachykinin NK1 and NK1 receptors.

  18. Neurotransmitter receptors as targets for pesticides.

    PubMed

    Eldefrawi, M E; Eldefrawi, A T

    1983-01-01

    Nicotinic and muscarinic acetylcholine (ACh) receptors have been identified biochemically by means of their specific binding of [3H] alpha-bungarotoxin ([3H]alpha-BGT) and [3H]quinuclidinyl benzilate, respectively. There are some differences in the drug specificities, and sensitivities to active group reagents, of these receptors in insects when compared to those in vertebrates. Also, insect brain contains more nicotinic than muscarinic receptors, while the reverse is found in mammalian brain. Insect brain contains a third kind of putative ACh-receptor that is relatively soluble and is both nicotinic and muscarinic in its pharmacology but does not bind alpha-BGT. Toxic nicotine and analogs bind to it with high affinities. Several organophosphorus and carbamate insecticides and nereistoxin bind with high affinities to the nicotinic ACh-receptor of the electric organ of Torpedo. A few chlorinated hydrocarbon insecticides and derivatives interact with Torpedo nicotinic ACh-receptors, not at their 'receptor' sites but at their allosteric or 'channel' sites (which are identified by their specific binding of [3H]perhydrohistrionicotoxin). A few also bind to mammalian brain muscarinic receptors. The most potent on both receptors is the acaricide chlorobenzilate. Pyrethrins and synthetic pyrethroids also bind with high affinities to the channel sites of the Torpedo nicotinic ACh-receptor, though not to its receptor sites. Another group that binds to ACh-receptors is the organic and inorganic mercury compounds, which interact with both the Torpedo nicotinic and rat brain muscarinic receptors. Thus, neurotransmitter receptors act as molecular targets, primary or secondary for different pesticides.

  19. A new family of insect tyramine receptors.

    PubMed

    Cazzamali, Giuseppe; Klaerke, Dan A; Grimmelikhuijzen, Cornelis J P

    2005-12-16

    The Drosophila Genome Project database contains a gene, CG7431, annotated to be an "unclassifiable biogenic amine receptor." We have cloned this gene and expressed it in Chinese hamster ovary cells. After testing various ligands for G protein-coupled receptors, we found that the receptor was specifically activated by tyramine (EC(50), 5x10(-7)M) and that it showed no cross-reactivity with beta-phenylethylamine, octopamine, dopa, dopamine, adrenaline, noradrenaline, tryptamine, serotonin, histamine, and a library of 20 Drosophila neuropeptides (all tested in concentrations up to 10(-5) or 10(-4)M). The receptor was also expressed in Xenopus oocytes, where it was, again, specifically activated by tyramine with an EC(50) of 3x10(-7)M. Northern blots showed that the receptor is already expressed in 8-hour-old embryos and that it continues to be expressed in all subsequent developmental stages. Adult flies express the receptor both in the head and body (thorax/abdomen) parts. In addition to the Drosophila tyramine receptor gene, CG7431, we found another closely related Drosophila gene, CG16766, that probably also codes for a tyramine receptor. Furthermore, we annotated similar tyramine-like receptor genes in the genomic databases from the malaria mosquito Anopheles gambiae and the honeybee Apis mellifera. These four tyramine or tyramine-like receptors constitute a new receptor family that is phylogenetically distinct from the previously identified insect octopamine/tyramine receptors. The Drosophila tyramine receptor is, to our knowledge, the first cloned insect G protein-coupled receptor that appears to be fully specific for tyramine.

  20. Intracellular trafficking of GABA(A) receptors.

    PubMed

    Barnes, E M

    2000-02-11

    Some of the mechanisms that control the intracellular trafficking of GABA(A) receptors have recently been described. Following the synthesis of alpha, beta, and gamma subunits in the endoplasmic reticulum, ternary receptor complexes assemble slowly and are inefficiently inserted into surface membranes of heterologous cells. While beta3, beta4, and gamma2S subunits appear to contain polypeptide sequences that alone are sufficient for surface targeting, these sequences are neither conserved nor essential for surface expression of heteromeric GABA(A) receptors formed from alpha1beta or alpha1betagamma subunits. At the neuronal surface, native GABA(A) receptor clustering and synaptic targeting require a gamma2 subunit and the participation of gephyrin, a clustering protein for glycine receptors. A linker protein, such as the GABA(A) receptor associated protein (GABARAP), may be necessary for the formation of GABA(A) receptor aggregates containing gephyrin. A substantial fraction of surface receptors are sequestered by endocytosis, another process which apparently requires a GABA(A) receptor gamma2 subunit. In heterologous cells, constitutive endocytosis seems to predominate while, in cortical neurons, internalization is evoked when receptors are occupied by GABA(A) agonists. After constitutive endocytosis, receptors are relatively stable and can be rapidly recycled to the cell surface, a process that may be regulated by protein kinase C. On the other hand, a portion of the intracellular GABA(A) receptors derived from ligand-dependent endocytosis is apparently degraded. The clustering of GABA(A) receptors at synapses and at coated pits are two mechanisms that may compete for a pool of diffusable receptors, providing a model for plasticity at inhibitory synapses.

  1. Targeting tachykinin receptors in neuroblastoma

    PubMed Central

    Szymansky, Annabell; Seiler, Marleen; Althoff, Kristina; Beckers, Anneleen; Speleman, Frank; Schäfers, Simon; De Preter, Katleen; Astrahanseff, Kathy; Struck, Joachim; Schramm, Alexander; Eggert, Angelika; Bergmann, Andreas; Schulte, Johannes H.

    2017-01-01

    Neuroblastoma is the most common extracranial tumor in children. Despite aggressive multimodal treatment, high-risk neuroblastoma remains a clinical challenge with survival rates below 50%. Adding targeted drugs to first-line therapy regimens is a promising approach to improve survival in these patients. TACR1 activation by substance P has been reported to be mitogenic in cancer cell lines. Tachykinin receptor (TACR1) antagonists are approved for clinical use as an antiemetic remedy since 2003. Tachykinin receptor inhibition has recently been shown to effectively reduce growth of several tumor types. Here, we report that neuroblastoma cell lines express TACR1, and that targeting TACR1 activity significantly reduced cell viability and induced apoptosis in neuroblastoma cell lines. Gene expression profiling revealed that TACR1 inhibition repressed E2F2 and induced TP53 signaling. Treating mice harboring established neuroblastoma xenograft tumors with Aprepitant also significantly reduced tumor burden. Thus, we provide evidence that the targeted inhibition of tachykinin receptor signaling shows therapeutic efficacy in preclinical models for high-risk neuroblastoma. PMID:27888795

  2. CB receptor ligands from plants.

    PubMed

    Woelkart, Karin; Salo-Ahen, Outi M H; Bauer, Rudolf

    2008-01-01

    Advances in understanding the physiology and pharmacology of the endogenous cannabinoid system have potentiated the interest of cannabinoid receptors as potential therapeutic targets. Cannabinoids have been shown to modulate a variety of immune cell functions and have therapeutic implications on central nervous system (CNS) inflammation, chronic inflammatory conditions such as arthritis, and may be therapeutically useful in treating autoimmune conditions such as multiple sclerosis. Many of these drug effects occur through cannabinoid receptor signalling mechanisms and the modulation of cytokines and other gene products. Further, endocannabinoids have been found to have many physiological and patho-physiological functions, including mood alteration and analgesia, control of energy balance, gut motility, motor and co-ordination activities, as well as alleviation of neurological, psychiatric and eating disorders. Plants offer a wide range of chemical diversity and have been a growing domain in the search for effective cannabinoid ligands. Cannabis sativa L. with the known plant cannabinoid, Delta(9-)tetrahydrocannabinol (THC) and Echinacea species with the cannabinoid (CB) receptor-binding lipophilic alkamides are the best known herbal cannabimimetics. This review focuses on the state of the art in CB ligands from plants, as well their possible therapeutic and immunomodulatory effects.

  3. Autophagy selectivity through receptor clustering

    NASA Astrophysics Data System (ADS)

    Rutenberg, Andrew; Brown, Aidan

    Substrate selectivity in autophagy requires an all-or-none cellular response. We focus on peroxisomes, for which autophagy receptor proteins NBR1 and p62 are well characterized. Using computational models, we explore the hypothesis that physical clustering of autophagy receptor proteins on the peroxisome surface provides an appropriate all-or-none response. We find that larger peroxisomes nucleate NBR1 clusters first, and lose them due to competitive coarsening last, resulting in significant size-selectivity. We then consider a secondary hypothesis that p62 inhibits NBR1 cluster formation. We find that p62 inhibition enhances size-selectivity enough that, even if there is no change of the pexophagy rate, the volume of remaining peroxisomes can significantly decrease. We find that enhanced ubiquitin levels suppress size-selectivity, and that this effect is more pronounced for individual peroxisomes. Sufficient ubiquitin allows receptor clusters to form on even the smallest peroxisomes. We conclude that NBR1 cluster formation provides a viable physical mechanism for all-or-none substrate selectivity in pexophagy. We predict that cluster formation is associated with significant size-selectivity. Now at Simon Fraser University.

  4. Pyrazole complexes as anion receptors.

    PubMed

    Nieto, Sonia; Pérez, Julio; Riera, Lucía; Riera, Víctor; Miguel, Daniel

    2006-03-01

    The behavior of the receptors [Re(CO)3(Hdmpz)3]BAr'4 (Hdmpz = 3,5-dimethylpyrazole) (1) and [Re(CO)3(HtBupz)3]BAr'4 (HtBupz = 3(5)-tert-butylpyrazole) (2; Ar' = 3,5-bis(trifluoromethyl)phenyl) toward the anions fluoride, chloride, bromide, iodide, hydrogensulfate, dihydrogenphosphate, nitrate, and perrhenate was studied in CD3CN solution. In most cases, the receptors were stable. Anion exchange was fast, and binding constants were calculated from the NMR titration profiles. The structure of the adduct [Re(CO)3(HtBupz)3] x NO3 (3) was determined by X-ray diffraction. Two pyrazole moieties are hydrogen-bonded to one nitrate oxygen atom, and the third pyrazole moiety is hydrogen-bonded to an oxygen atom of an adjacent nitrate, leading to infinite chains. The structure of the adduct [Re(CO)3(Hdmpz)3]BAr'4acetone (4), also determined by X-ray diffraction, showed a similar interaction of two pyrazole N-H groups with the acetone oxygen atom. F- and H2PO4(-) deprotonate the receptors, and HSO4(-) decomposed 1. The structure of one of the decomposition products (5), determined by X-ray diffraction, is consistent with pyrazole protonation and substitution by sulfate.

  5. Azilsartan: Novel Angiotensin Receptor Blocker.

    PubMed

    Dargad, Ramesh R; Parekh, Jai D; Dargad, Rohit R; Kukrety, Shweta

    2016-03-01

    To describe the efficacy and safety profile of the new angiotensin receptor blocker (ARB), "Azilsartan Medoxomil", reviewing data available from both clinical and pre-clinical studies. We completed a review of the English literature from PubMed using the keywords- azilsartan medoxomil, angiotensin receptor blockers (ARB), angiotensin converting enzyme inhibitors (ACEi) and hypertension. Many clinical trials have been conducted comparing the efficacy of azilsartan with other ARB's and also with the ACEi ramipril. The trials have shown azilsartan to be more effective in reducing the mean 24-hour systolic blood pressure compared to its counterparts. Azilsartan is a recently approved ARB and appears to be more efficacious in reducing blood pressure (BP) than the other ARBs with a similar safety and tolerability profile. Azilsartan's very high affinity to and slow dissociation from the angiotensin 1 receptor (AT1R) along with its inverse agonistic properties make it a very good candidate for clinical effects beyond simple BP control, potentially counteracting cardiac hypertrophy, cardiac fibrosis and insulin resistance, together with improved reno-protection and atherosclerotic plaque stabilization.

  6. Nuclear hormone receptors in chordates.

    PubMed

    Bertrand, Stéphanie; Belgacem, Mohamed R; Escriva, Hector

    2011-03-01

    In order to understand evolution of the endocrine systems in chordates, study of the evolution of the nuclear receptors (NRs), which mediate the cellular responses to several key hormones, is of major interest. Thanks to the sequencing of several complete genomes of different species in the three chordate phyla, we now have a global view of the evolution of the nuclear receptors gene content in this lineage. The challenge is now to understand how the function of the different receptors evolved during the invertebrate-chordate to vertebrate transition by studying the functional properties of the NRs using comparative approaches in different species. The best available model system to answer this question is the cephalochordate amphioxus which has a NR gene complement close to that of the chordate ancestor. Here we review the available data concerning the function of the amphioxus NRs, and we discuss some evolutionary scenarios that can be drawn from these results. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  7. Variable lymphocyte receptors in hagfish

    PubMed Central

    Pancer, Zeev; Saha, Nil Ratan; Kasamatsu, Jun; Suzuki, Takashi; Amemiya, Chris T.; Kasahara, Masanori; Cooper, Max D.

    2005-01-01

    A previously uncharacterized type of variable lymphocyte receptors (VLR) was identified recently in the Sea lamprey. This jawless vertebrate generates an extensive VLR repertoire through differential insertion of neighboring diverse leucine-rich repeat (LRR) cassettes into an incomplete germ-line VLR gene. We report here VLR homologs from two additional lamprey species and the presence of two types of VLR genes in hagfish, the only other order of contemporary jawless vertebrates. As in the Sea lamprey, the incomplete hagfish germ-line VLR-A and -B genes are modified in lymphocyte-like cells to generate highly diverse repertoires of VLR-A and -B proteins via a presently undetermined mechanism. This jawless-fish mode of VLR diversification starkly contrasts with the rearrangement of Ig V(D)J gene segments used by all jawed vertebrates to produce diverse repertoires of T and B lymphocyte antigen receptors. The development of two very different strategies for receptor diversification at the dawn of vertebrate evolution ≈500 million years ago attests to the fitness value of a lymphocyte-based system of anticipatory immunity. PMID:15964979

  8. Insulin receptor in Drosophila melanogaster

    SciTech Connect

    Petruzzelli, L.; Herrera, R.; Rosen, O.

    1986-05-01

    A specific, high affinity insulin receptor is present in both adult Drosophila and in Drosophila embryos. Wheat germ lectin-enriched extracts of detergent-solubilized membranes from embryos and adults bind insulin with a K/sub d/ of 15 nM. Binding is specific for insulin; micromolar concentrations of proinsulin, IGFI, and IGFII are required to displace bound /sup 125/I-insulin. Insulin-dependent protein tyrosine kinase activity appears during embryogenesis. It is evident between 6 and 12 hours of development, peaks between 12 and 18 hours and falls in the adult. During 0-6 hours of embryogenesis, and in the adult, a specific protein band (Mr = 135,000) is crosslinked to /sup 125/I-insulin. During 6-12 and 12-18 hours of embryogenesis stages in which insulin-dependent protein tyrosine kinase is high, an additional band (Mr = 100,000) becomes crosslinked to /sup 125/I-insulin. Isolation and DNA sequence analysis of genomic clones encoding the Drosophila insulin receptor will be presented as will the characterization of insulin receptor mRNA's during development.

  9. Modes of glutamate receptor gating

    PubMed Central

    Popescu, Gabriela K

    2012-01-01

    Abstract The time course of excitatory synaptic currents, the major means of fast communication between neurons of the central nervous system, is encoded in the dynamic behaviour of post-synaptic glutamate-activated channels. First-pass attempts to explain the glutamate-elicited currents with mathematical models produced reaction mechanisms that included only the most basic functionally defined states: resting vs. liganded, closed vs. open, responsive vs. desensitized. In contrast, single-molecule observations afforded by the patch-clamp technique revealed an unanticipated kinetic multiplicity of transitions: from microseconds-lasting flickers to minutes-long modes. How these kinetically defined events impact the shape of the synaptic response, how they relate to rearrangements in receptor structure, and whether and how they are physiologically controlled represent currently active research directions. Modal gating, which refers to the slowest, least frequently observed ion-channel transitions, has been demonstrated for representatives of all ion channel families. However, reaction schemes have been largely confined to the short- and medium-range time scales. For glutamate receptors as well, modal gating has only recently come under rigorous scrutiny. This article reviews the evidence for modal gating of glutamate receptors and the still developing hypotheses about the mechanism(s) by which modal shifts occur and the ways in which they may impact the time course of synaptic transmission. PMID:22106181

  10. [Anti-NMDA-receptor encephalitis].

    PubMed

    Engen, Kristine; Agartz, Ingrid

    2016-06-01

    BACKGROUND In 2007 a clinical disease caused by autoantibodies directed against the N-methyl-D-aspartate (NMDA) receptor was described for the first time. Anti-NMDA-receptor encephalitis is a subacute, autoimmune neurological disorder with psychiatric manifestations. The disease is a form of limbic encephalitis and is often paraneoplastic. The condition is also treatable. In this review article we examine the development of the disease, clinical practice, diagnostics and treatment.MATERIAL AND METHOD The article is based on references retrieved from searches in PubMed, and a discretionary selection of articles from the authors' own literature archive.RESULTS The disease most frequently affects young women. It may initially be perceived as a psychiatric condition, as it usually presents in the form of delusions, hallucinations or mania. The diagnosis should be suspected in patients who later develop neurological symptoms such as various movement disorders, epileptic seizures and autonomic instability. Examination of serum or cerebrospinal fluid for NMDA receptor antibodies should be included in the assessment of patients with suspected encephalitis. MRI, EEG and assessment for tumours are important tools in diagnosing the condition and any underlying malignancy.INTERPRETATION If treatment is initiated early, the prognosis is good. Altogether 75 % of patients will fully recover or experience significant improvement. Apart from surgical resection of a possible tumour, the treatment consists of immunotherapy. Because of good possibilities for treatment, it is important that clinicians, particularly those in acute psychiatry, are aware of and alert to this condition.

  11. Lymphocyte receptors for pertussis toxin

    SciTech Connect

    Clark, C.G.; Armstrong, G.D. )

    1990-12-01

    We have investigated human T-lymphocyte receptors for pertussis toxin by affinity isolation and photoaffinity labeling procedures. T lymphocytes were obtained from peripheral human blood, surface iodinated, and solubilized in Triton X-100. The iodinated mixture was then passed through pertussis toxin-agarose, and the fractions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Autoradiography of the fixed, dried gels revealed several bands in the pertussis toxin-bound fraction that were not observed in fractions obtained from histone or fetuin-agarose. Further investigations employed a photoaffinity labeling reagent, sulfosuccinimidyl 2-(p-azido-salicylamido)-1,3'-dithiopropionate, to identify pertussis toxin receptors in freshly isolated peripheral blood monocytic cells, T lymphocytes, and Jurkat cells. In all three cell systems, the pertussis toxin affinity probe specifically labeled a single protein species with an apparent molecular weight of 70,000 that was not observed when the procedure was performed in the presence of excess unmodified pertussis toxin. A protein comparable in molecular weight to the one detected by the photoaffinity labeling technique was also observed among the species that bound to pertussis toxin-agarose. The results suggest that pertussis toxin may bind to a 70,000-Da receptor in human T lymphocytes.

  12. High-throughput Analysis of Mammalian Olfactory Receptors: Measurement of Receptor Activation via Luciferase Activity

    PubMed Central

    Trimmer, Casey; Snyder, Lindsey L.; Mainland, Joel D.

    2014-01-01

    Odorants create unique and overlapping patterns of olfactory receptor activation, allowing a family of approximately 1,000 murine and 400 human receptors to recognize thousands of odorants. Odorant ligands have been published for fewer than 6% of human receptors1-11. This lack of data is due in part to difficulties functionally expressing these receptors in heterologous systems. Here, we describe a method for expressing the majority of the olfactory receptor family in Hana3A cells, followed by high-throughput assessment of olfactory receptor activation using a luciferase reporter assay. This assay can be used to (1) screen panels of odorants against panels of olfactory receptors; (2) confirm odorant/receptor interaction via dose response curves; and (3) compare receptor activation levels among receptor variants. In our sample data, 328 olfactory receptors were screened against 26 odorants. Odorant/receptor pairs with varying response scores were selected and tested in dose response. These data indicate that a screen is an effective method to enrich for odorant/receptor pairs that will pass a dose response experiment, i.e. receptors that have a bona fide response to an odorant. Therefore, this high-throughput luciferase assay is an effective method to characterize olfactory receptors—an essential step toward a model of odor coding in the mammalian olfactory system. PMID:24961834

  13. Characterization of functional urotensin II receptors in human skeletal muscle myoblasts: comparison with angiotensin II receptors.

    PubMed

    Qi, Jian-shen; Minor, Lisa K; Smith, Charles; Hu, Bing; Yang, Jing; Andrade-Gordon, Patricia; Damiano, Bruce

    2005-04-01

    The properties of urotensin II (U-II) receptor (UT receptor) and angiotensin II (ANG II) receptor (AT receptor) in primary human skeletal myoblasts (HSMM) and differentiated skeletal myotubes (HSMMT) were characterized. Radiolabeled U-II and ANG II bound specifically to HSMM with Kd's of 0.31 nM (2311 receptors/cell) and 0.61 nM (18,257 receptors/cell), respectively. The cyclic segment of U-II peptide, CFWKYC, was the minimal sequence required for binding, with the WKY residues essential. Inhibitor studies suggested AT1 is the predominant ANG II receptor. After radioligand binding, under conditions designed to minimize receptor internalization, half the bound U-II was resistant to acid washing suggesting that U-II binds tightly to its receptor in a quasi-irreversible fashion. The AT1 receptor-bound radioligand was completely removed under the same conditions. RT-PCR detected the expression of mRNAs for UT and AT1 receptors. Western blotting showed that U-II and ANG II signaled via ERK1/2 kinase. UT receptor was not lost upon differentiation into myotubes since both mRNA for UT receptor and U-II binding were still present. ANG II receptors were also present as shown by ANG II-induced calcium mobilization.

  14. The two-state dimer receptor model: a general model for receptor dimers.

    PubMed

    Franco, Rafael; Casadó, Vicent; Mallol, Josefa; Ferrada, Carla; Ferré, Sergi; Fuxe, Kjell; Cortés, Antoni; Ciruela, Francisco; Lluis, Carmen; Canela, Enric I

    2006-06-01

    Nonlinear Scatchard plots are often found for agonist binding to G-protein-coupled receptors. Because there is clear evidence of receptor dimerization, these nonlinear Scatchard plots can reflect cooperativity on agonist binding to the two binding sites in the dimer. According to this, the "two-state dimer receptor model" has been recently derived. In this article, the performance of the model has been analyzed in fitting data of agonist binding to A(1) adenosine receptors, which are an example of receptor displaying concave downward Scatchard plots. Analysis of agonist/antagonist competition data for dopamine D(1) receptors using the two-state dimer receptor model has also been performed. Although fitting to the two-state dimer receptor model was similar to the fitting to the "two-independent-site receptor model", the former is simpler, and a discrimination test selects the two-state dimer receptor model as the best. This model was also very robust in fitting data of estrogen binding to the estrogen receptor, for which Scatchard plots are concave upward. On the one hand, the model would predict the already demonstrated existence of estrogen receptor dimers. On the other hand, the model would predict that concave upward Scatchard plots reflect positive cooperativity, which can be neither predicted nor explained by assuming the existence of two different affinity states. In summary, the two-state dimer receptor model is good for fitting data of binding to dimeric receptors displaying either linear, concave upward, or concave downward Scatchard plots.

  15. Effect of nonpersistent pesticides on estrogen receptor, androgen receptor, and aryl hydrocarbon receptor.

    PubMed

    Medjakovic, Svjetlana; Zoechling, Alfred; Gerster, Petra; Ivanova, Margarita M; Teng, Yun; Klinge, Carolyn M; Schildberger, Barbara; Gartner, Michael; Jungbauer, Alois

    2014-10-01

    Nonpersistent pesticides are considered less harmful for the environment, but their impact as endocrine disruptors has not been fully explored. The pesticide Switch was applied to grape vines, and the maximum residue concentration of its active ingredients was quantified. The transactivation potential of the pesticides Acorit, Frupica, Steward, Reldan, Switch, Cantus, Teldor, and Scala and their active compounds (hexythiazox, mepanipyrim, indoxacarb, chlorpyrifos-methyl, cyprodinil, fludioxonil, boscalid, fenhexamid, and pyrimethanil) were tested on human estrogen receptor α (ERα), androgen receptor (AR) and arylhydrocarbon receptor (AhR) in vitro. Relative binding affinities of the pure pesticide constituents for AR and their effect on human breast cancer and prostate cancer cell lines were evaluated. Residue concentrations of Switch's ingredients were below maximum residue limits. Fludioxonil and fenhexamid were ERα agonists (EC50 -values of 3.7 and 9.0 μM, respectively) and had time-dependent effects on endogenous ERα-target gene expression (cyclin D1, progesterone receptor, and nuclear respiratory factor 1) in MCF-7 human breast cancer cells. Fludioxonil, mepanipyrim, cyprodinil, pyrimethanil, and chlorpyrifos-methyl were AhR-agonists (EC50 s of 0.42, 0.77, 1.4, 4.6, and 5.1 μM, respectively). Weak AR binding was shown for chlorpyrifos-methyl, cyprodinil, fenhexamid, and fludioxonil. Assuming a total uptake which does not take metabolism and clearance rates into account, our in vitro evidence suggests that pesticides could activate pathways affecting hormonal balance, even within permitted limits, thus potentially acting as endocrine disruptors. Copyright © 2013 Wiley Periodicals, Inc., a Wiley company.

  16. Constitutive receptor systems for drug discovery.

    PubMed

    Chen, G; Jayawickreme, C; Way, J; Armour, S; Queen, K; Watson, C; Ignar, D; Chen, W J; Kenakin, T

    1999-12-01

    This paper discusses the use of constitutively active G-protein-coupled receptor systems for drug discovery. Specifically, the ternary complex model is used to define the two major theoretical advantages of constitutive receptor screening-namely, the ability to detect antagonists as well as agonists directly and the fact that constitutive systems are more sensitive to agonists. In experimental studies, transient transfection of Chinese hamster ovary cyclic AMP response element (CRE) luciferase reporter cells with cDNA for human parathyroid hormone receptor, glucagon receptor, and glucagon-like peptide (GLP-1) receptor showed cDNA concentration-dependent constitutive activity with parathyroid hormone (PTH-1) and glucagon. In contrast, no constitutive activity was observed for GLP-1 receptor, yet responses to GLP-1 indicated that receptor expression had taken place. In another functional system, Xenopus laevi melanophores transfected with cDNA for human calcitonin receptor showed constitutive activity. Nine ligands for the calcitonin receptor either increased or decreased constitutive activity in this assay. The sensitivity of the system to human calcitonin increased with increasing constitutive activity. These data indicate that, for those receptors which naturally produce constitutive activity, screening in this mode could be advantageous over other methods.

  17. Update on melatonin receptors: IUPHAR Review 20

    PubMed Central

    Delagrange, Philippe; Dubocovich, Margarita L.; Markus, Regina P.; Renault, Nicolas; Tosini, Gianluca; Cecon, Erika; Zlotos, Darius P.

    2016-01-01

    Melatonin receptors are seven transmembrane‐spanning proteins belonging to the GPCR superfamily. In mammals, two melatonin receptor subtypes exist ‐ MT1 and MT2 ‐ encoded by the MTNR1A and MTNR1B genes respectively. The current review provides an update on melatonin receptors by the corresponding subcommittee of the International Union of Basic and Clinical Pharmacology. We will highlight recent developments of melatonin receptor ligands, including radioligands, and give an update on the latest phenotyping results of melatonin receptor knockout mice. The current status and perspectives of the structure of melatonin receptor will be summarized. The physiological importance of melatonin receptor dimers and biologically important and type 2 diabetes‐associated genetic variants of melatonin receptors will be discussed. The role of melatonin receptors in physiology and disease will be further exemplified by their functions in the immune system and the CNS. Finally, antioxidant and free radical scavenger properties of melatonin and its relation to melatonin receptors will be critically addressed. PMID:27314810

  18. Localization of mineralocorticoid receptors at mammalian synapses.

    PubMed

    Prager, Eric M; Brielmaier, Jennifer; Bergstrom, Hadley C; McGuire, Jennifer; Johnson, Luke R

    2010-12-15

    In the brain, membrane associated nongenomic steroid receptors can induce fast-acting responses to ion conductance and second messenger systems of neurons. Emerging data suggest that membrane associated glucocorticoid and mineralocorticoid receptors may directly regulate synaptic excitability during times of stress when adrenal hormones are elevated. As the key neuron signaling interface, the synapse is involved in learning and memory, including traumatic memories during times of stress. The lateral amygdala is a key site for synaptic plasticity underlying conditioned fear, which can both trigger and be coincident with the stress response. A large body of electrophysiological data shows rapid regulation of neuronal excitability by steroid hormone receptors. Despite the importance of these receptors, to date, only the glucocorticoid receptor has been anatomically localized to the membrane. We investigated the subcellular sites of mineralocorticoid receptors in the lateral amygdala of the Sprague-Dawley rat. Immunoblot analysis revealed the presence of mineralocorticoid receptors in the amygdala. Using electron microscopy, we found mineralocorticoid receptors expressed at both nuclear including: glutamatergic and GABAergic neurons and extra nuclear sites including: presynaptic terminals, neuronal dendrites, and dendritic spines. Importantly we also observed mineralocorticoid receptors at postsynaptic membrane densities of excitatory synapses. These data provide direct anatomical evidence supporting the concept that, at some synapses, synaptic transmission is regulated by mineralocorticoid receptors. Thus part of the stress signaling response in the brain is a direct modulation of the synapse itself by adrenal steroids.

  19. Cannabinoid Receptors: Nomenclature and Pharmacological Principles

    PubMed Central

    Console-Bram, Linda; Marcu, Jahan; Abood, Mary E.

    2012-01-01

    The CB1 and CB2 cannabinoid receptors are members of the G protein-coupled receptor (GPCR) family that are pharmacologically well defined. However, the discovery of additional sites of action for endocannabinoids as well as synthetic cannabinoid compounds suggests the existence of additional cannabinoid receptors. Here we review this evidence, as well as the current nomenclature for classifying a target as a cannabinoid receptor. Basic pharmacological definitions, principles and experimental conditions are discussed in order to place in context the mechanisms underlying cannabinoid receptor activation. Constitutive (agonist-independent) activity is observed with the overexpression of many GPCRs, including cannabinoid receptors. Allosteric modulators can alter the pharmacological responses of cannabinoid receptors. The complex molecular architecture of each of the cannabinoid receptors allows for a single receptor to recognize multiple classes of compounds and produce an array of distinct downstream effects. Natural polymorphisms and alternative splice variants may also contribute to their pharmacological diversity. As our knowledge of the distinct differences grows, we may be able to target select receptor conformations and their corresponding pharmacological responses. Importantly, the basic biology of the endocannabinoid system will continue to be revealed by ongoing investigations. PMID:22421596

  20. Receptor response in Venus's fly-trap.

    PubMed

    Jacobson, S L

    1965-09-01

    The insect-trapping movement of the plant Dionaea muscipula (Venus's fly-trap) is mediated by the stimulation of mechanosensory hairs located on the surface of the trap. It is known that stimulation of the hairs is followed by action potentials which are propagated over the surface of the trap. It has been reported that action potentials always precede trap closure. The occurrence of non-propagated receptor potentials is reported here. Receptor potentials always precede the action potentials. The receptor potential appears to couple the mechanical stimulation step to the action potential step of the preying sequence. Receptor potentials elicited by mechanical stimulation of a sensory hair were measured by using the hair as an integral part of the current-measuring path. The tip of the hair was cut off exposing the medullary tissue; this provided a natural extension of the measuring electrode into the receptor region at the base of the hair. A measuring pipette electrode was slipped over the cut tip of the hair. Positive and negative receptor potentials were measured. Evidence is presented which supports the hypothesis that the positive and negative receptor potentials originate from independent sources. An analysis is made of (a) the relation of the parameters of mechanical stimuli to the magnitude of the receptor potential, and (b) the relation of the receptor potentials to the action potential. The hypothesis that the positive receptor potential is the generator of the action potential is consistent with these data.

  1. Insulin receptors in normal and disease states.

    PubMed

    Grunberger, G; Taylor, S I; Dons, R F; Gorden, P

    1983-03-01

    The binding of insulin to its receptor has been studied under various physiological and pathological conditions. Quantitative studies have involved human circulating cells such as monocytes and erythrocytes, adipocytes, placental cells, and cultured cells such as fibroblasts and transformed lymphocytes. In animals, other target tissues such as liver and muscle have been studied and correlated with the human studies. Various physiological conditions such as diurnal rhythm, diet, age, exercise and the menstrual cycle affect insulin binding; in addition, many drugs perturb the receptor interaction. Disease affecting the insulin receptor can be divided into five general categories: (1) Receptor regulation--this involves diseases characterized by hyper- or hypoinsulinaemia. Hyperinsulinaemia in the basal state usually leads to receptor 'down' regulation as seen in obesity, type II diabetes, acromegaly and islet cell tumours. Hypoinsulinaemia such as seen in anorexia nervosa or type I diabetes may lead to elevated binding. (2) Antireceptor antibodies--these immunoglobulins bind to the receptor and competitively inhibit insulin binding. They may act as agonists, antagonists or partial agonists. (3) Genetic diseases which produce fixed alterations in both freshly isolated and cultured cells. (4) Diseases of receptor specificity where insulin may bind with different affinity to its own receptor or related receptors such as receptors for insulin-like growth factors. (5) Disease of affinity modulation where physical factors such as pH, temperature, ions, etc. may modify binding. In this review, we have considered primarily abnormality in insulin receptor binding. There are numerous other functions of the receptor such as coupling and transmission of the biological signal. These mechanisms are frequently referred to as postreceptor events, but more properly should be referred to as postbinding events since the receptor subserves other functions in addition to recognition and

  2. Assembly of PRR-containing receptors on scaffolds: a model for imidazoline I(1)-receptor action.

    PubMed

    Musgrave, I F; Dehle, F C; Piletz, J

    2003-12-01

    IRAS, a putative clone of the I(1)-imidazoline receptor, possesses a proline-rich region (PRR) motif, which might interact with SH3 regions on tyrosine kinases, and an integrin-binding motif. Receptors with a PRR motif can generally assemble onto multi-element signaling complexes (eg., the beta(3)-receptor on the EGF receptor) and thereby modulate signal transduction. Integrins serve as scaffolds for multi-element signaling complexes, similar to that assembled with the EGF receptor. It is therefore possible that IRAS signals through a complex with other receptors.

  3. Human native kappa opioid receptor functions not predicted by recombinant receptors: Implications for drug design

    PubMed Central

    Broad, John; Maurel, Damien; Kung, Victor W. S.; Hicks, Gareth A.; Schemann, Michael; Barnes, Michael R.; Kenakin, Terrence P.; Granier, Sébastien; Sanger, Gareth J.

    2016-01-01

    If activation of recombinant G protein-coupled receptors in host cells (by drugs or other ligands) has predictive value, similar data must be obtained with native receptors naturally expressed in tissues. Using mouse and human recombinant κ opioid receptors transfected into a host cell, two selectively-acting compounds (ICI204448, asimadoline) equi-effectively activated both receptors, assessed by measuring two different cell signalling pathways which were equally affected without evidence of bias. In mouse intestine, naturally expressing κ receptors within its nervous system, both compounds also equi-effectively activated the receptor, inhibiting nerve-mediated muscle contraction. However, whereas ICI204448 acted similarly in human intestine, where κ receptors are again expressed within its nervous system, asimadoline was inhibitory only at very high concentrations; instead, low concentrations of asimadoline reduced the activity of ICI204448. This demonstration of species-dependence in activation of native, not recombinant κ receptors may be explained by different mouse/human receptor structures affecting receptor expression and/or interactions with intracellular signalling pathways in native environments, to reveal differences in intrinsic efficacy between receptor agonists. These results have profound implications in drug design for κ and perhaps other receptors, in terms of recombinant-to-native receptor translation, species-dependency and possibly, a need to use human, therapeutically-relevant, not surrogate tissues. PMID:27492592

  4. Cannabinoid 2 receptor- and beta Arrestin 2-dependent upregulation of serotonin 2A receptors.

    PubMed

    Franklin, J M; Vasiljevik, T; Prisinzano, T E; Carrasco, G A

    2013-07-01

    Recent evidence suggests that cannabinoid receptor agonists may regulate serotonin 2A (5-HT(2A)) receptor neurotransmission in the brain, although no molecular mechanism has been identified. Here, we present experimental evidence that sustained treatment with a non-selective cannabinoid agonist (CP55,940) or selective CB2 receptor agonists (JWH133 or GP1a) upregulate 5-HT(2A) receptors in a neuronal cell line. Furthermore, this cannabinoid receptor agonist-induced upregulation of 5-HT(2A) receptors was prevented in cells stably transfected with either CB2 or β-Arrestin 2 shRNA lentiviral particles. Additionally, inhibition of clathrin-mediated endocytosis also prevented the cannabinoid receptor-induced upregulation of 5-HT(2A) receptors. Our results indicate that cannabinoid agonists might upregulate 5-HT(2A) receptors by a mechanism that requires CB2 receptors and β-Arrestin 2 in cells that express both CB2 and 5-HT(2A) receptors. 5-HT(2A) receptors have been associated with several physiological functions and neuropsychiatric disorders such as stress response, anxiety and depression, and schizophrenia. Therefore, these results might provide a molecular mechanism by which activation of cannabinoid receptors might be relevant to some cognitive and mood disorders in humans.

  5. Increased AT(1) receptors in adrenal gland of AT(2) receptor gene-disrupted mice.

    PubMed

    Saavedra, J M; Armando, I; Terrón, J A; Falcón-Neri, A; Jöhren, O; Häuser, W; Inagami, T

    2001-10-15

    Angiotensin II (Ang II) AT(2) receptor-gene disrupted mice have increased systemic blood pressure and response to exogenous Angiotensin II. To clarify the mechanism of these changes, we studied adrenal AT(1) receptor expression and mRNA by receptor autoradiography and in situ hybridization in female AT(2) receptor-gene disrupted mice (agtr 2-/-) and wild-type controls (agtr 2+/+). We found high expression of AT(1) receptor binding and mRNA in adrenal zona glomerulosa of female wild-type mice. AT(2) receptors and mRNA were highly expressed in adrenal medulla of wild-type mice, but were not detected in zona glomerulosa. There was no AT(2) receptor binding or mRNA in adrenal glands of AT(2) receptor-gene disrupted mice. In these animals, AT(1) receptor binding and mRNA were increased in adrenal zona glomerulosa and AT(1) receptor mRNA was increased in the adrenal medulla when compared with wild-type animals.The present data support the hypothesis of an interaction or cross talk between AT(2) and AT(1) receptors in adrenal gland. The significant increase in AT(1) receptor expression in the absence of AT(2) receptor transcription may be partially responsible for the increased blood pressure and for the enhanced response to exogenously administered Angiotensin II in this model.

  6. OXYTOCIN INDUCES SOCIAL COMMUNICATION BY ACTIVATING ARGININEVASOPRESSIN V1A RECEPTORS AND NOT OXYTOCIN RECEPTORS

    PubMed Central

    SONG, Zhimin; MCCANN, Katharine E.; MCNEILL, John K.; LARKIN, Tony E.; HUHMAN, Kim L.; ALBERS, H. Elliott

    2014-01-01

    Arginine-vasopressin (AVP) and oxytocin (OT) and their receptors are very similar in structure. As a result, at least some of the effects of these peptides may be the result of crosstalk between their canonical receptors. The present study investigated this hypothesis by determining whether the induction of flank marking, a form of social communication in Syrian hamsters, by OT is mediated by the OT receptor or the AVP V1a receptor. Intracerebroventricular (ICV) injections of OT or AVP induced flank marking in a dose-dependent manner although the effects of AVP were approximately 100 times greater than those of OT. Injections of highly selective V1a receptor agonists but not OT receptor agonists induced flank marking, and V1a receptor antagonists but not OT receptor antagonists significantly inhibited the ability of OT to induce flank marking. Lastly, injection of alpha-melanocyte-stimulating hormone (α-MSH), a peptide that stimulates OT but not AVP release, significantly increased odor-induced flank marking, and these effects were blocked by a V1a receptor antagonist. These data demonstrate that OT induces flank marking by activating AVP V1a and not OT receptors, suggesting that the V1a receptor should be considered to be an OT receptor as well as an AVP receptor. PMID:25173438

  7. Leukocyte chemoattractant receptors in human disease pathogenesis.

    PubMed

    Zabel, Brian A; Rott, Alena; Butcher, Eugene C

    2015-01-01

    Combinations of leukocyte attractant ligands and cognate heptahelical receptors specify the systemic recruitment of circulating cells by triggering integrin-dependent adhesion to endothelial cells, supporting extravasation, and directing specific intratissue localization via gradient-driven chemotaxis. Chemoattractant receptors also control leukocyte egress from lymphoid organs and peripheral tissues. In this article, we summarize the fundamental mechanics of leukocyte trafficking, from the evolution of multistep models of leukocyte recruitment and navigation to the regulation of chemoattractant availability and function by atypical heptahelical receptors. To provide a more complete picture of the migratory circuits involved in leukocyte trafficking, we integrate a number of nonchemokine chemoattractant receptors into our discussion. Leukocyte chemoattractant receptors play key roles in the pathogenesis of autoimmune diseases, allergy, inflammatory disorders, and cancer. We review recent advances in our understanding of chemoattractant receptors in disease pathogenesis, with a focus on genome-wide association studies in humans and the translational implications of mechanistic studies in animal disease models.

  8. Toll-Like Receptors in Chronic Pain

    PubMed Central

    Nicotra, Lauren; Loram, Lisa C; Watkins, Linda R; Hutchinson, Mark R

    2011-01-01

    Proinflammatory central immune signaling contributes significantly to the initiation and maintenance of heightened pain states. Recent discoveries have implicated the innate immune system, pattern recognition Toll-like receptors in triggering these proinflammatory central immune signaling events. These exciting developments have been complemented by the discovery of neuronal expression of Toll-like receptors, suggesting pain pathways can be activated directly by the detection of pathogen associated molecular patterns or danger associated molecular patterns. This review will examine the evidence to date implicating Toll-like receptors and their associated signaling components in heightened pain states. In addition, insights into the impact Toll-like receptors have on priming central immune signaling systems for heightened pain states will be discussed. The influence possible sex differences in Toll-like receptor signaling have for female pain and the recognition of small molecule xenobiotics by Toll-like receptors will also be reviewed. PMID:22001158

  9. Eph Receptors and Ephrins: Therapeutic Opportunities

    PubMed Central

    Barquilla, Antonio; Pasquale, Elena B.

    2015-01-01

    The Eph receptor tyrosine kinase family plays important roles in developmental processes, adult tissue homeostasis and various diseases. Interaction with ephrin ligands on the surface of neighboring cells triggers Eph receptor kinase-dependent signaling. The ephrins can also transmit signals, leading to bidirectional cell contact-dependent communication. Moreover, Eph receptors and ephrins can function independently of each other, through interplay with other signaling systems. Given their involvement in many pathological conditions ranging from neurological disorders to cancer and viral infections, Eph receptors and ephrins are increasingly recognized as attractive therapeutic targets and a variety of strategies are being explored to modulate their expression and function. Eph receptor/ephrin upregulation in cancer cells, the angiogenic vasculature, and injured or diseased tissues also offers opportunities for Eph/ephrin-based targeted drug delivery and imaging. Thus, despite the challenges presented by the complex biology of the Eph receptor/ephrin system, exciting possibilities exist for therapies exploiting these molecules. PMID:25292427

  10. Receptor Tyrosine Kinases in Drosophila Development

    PubMed Central

    Sopko, Richelle; Perrimon, Norbert

    2013-01-01

    Tyrosine phosphorylation plays a significant role in a wide range of cellular processes. The Drosophila genome encodes more than 20 receptor tyrosine kinases and extensive studies in the past 20 years have illustrated their diverse roles and complex signaling mechanisms. Although some receptor tyrosine kinases have highly specific functions, others strikingly are used in rather ubiquitous manners. Receptor tyrosine kinases regulate a broad expanse of processes, ranging from cell survival and proliferation to differentiation and patterning. Remarkably, different receptor tyrosine kinases share many of the same effectors and their hierarchical organization is retained in disparate biological contexts. In this comprehensive review, we summarize what is known regarding each receptor tyrosine kinase during Drosophila development. Astonishingly, very little is known for approximately half of all Drosophila receptor tyrosine kinases. PMID:23732470

  11. TAM receptor deficiency affects adult hippocampal neurogenesis

    PubMed Central

    Ji, Rui; Meng, Lingbin; Li, Qiutang; Lu, Qingxian

    2014-01-01

    The Tyro3, Axl and Mertk (TAM) subfamily of receptor protein tyrosine kinases functions in cell growth, differentiation, survival, and most recently found, in the regulation of immune responses and phagocytosis. All three receptors and their ligands, Gas6 (growth arrest-specific gene 6) and protein S, are expressed in the central nervous system (CNS). TAM receptors play pivotal roles in adult hippocampal neurogenesis. Loss of these receptors causes a comprised neurogenesis in the dentate gyrus of adult hippocampus. TAM receptors have a negative regulatory effect on microglia and peripheral antigen-presenting cells, and play a critical role in preventing overproduction of pro-inflammatory cytokines detrimental to the proliferation, differentiation, and survival of adult neuronal stem cells (NSCs). Besides, these receptors also play an intrinsic trophic function in supporting NSC survival, proliferation, and differentiation into immature neurons. All these events collectively ensure a sustained neurogenesis in adult hippocampus. PMID:25487541

  12. Early development of sigma-receptor ligands.

    PubMed

    Narayanan, Sanju; Bhat, Rohit; Mesangeau, Christophe; Poupaert, Jacques H; McCurdy, Christopher R

    2011-01-01

    Sigma receptors (σ-1 and σ-2) are non-opioid proteins implicated in the pathophysiology of various neurological disorders and cancer. The σ-1 subtype is a chaperon protein widely distributed in the CNS and peripheral tissues. These receptors are involved in the modulation of K(+)- and Ca(2+)-dependent signaling cascades at the endoplasmic reticulum and modulation of neurotransmitter release. σ-1 receptors are emerging targets for the treatment of neurophychiatric diseases (schizophrenia and depression) and cocaine addiction. σ-2 receptors are lipid raft proteins. They are highly expressed on many tumor cells and hence considered potential targets for anticancer drugs. σ receptors bind to a diverse class of pharmacological compounds like cocaine, methamphetamine, benzomorphans like (±)-pentazocine, (±)-SKF-10,047 and endogenous neurosteroids and sphingolipids. In this review we focus on the early development of σ receptor-specific ligands and radiolabeling agents.

  13. GABAA Receptors at Hippocampal Mossy Fibers

    PubMed Central

    Ruiz, Arnaud; Fabian-Fine, Ruth; Scott, Ricardo; Walker, Matthew C.; Rusakov, Dmitri A.; Kullmann, Dimitri M.

    2012-01-01

    Summary Presynaptic GABAA receptors modulate synaptic transmission in several areas of the CNS but are not known to have this action in the cerebral cortex. We report that GABAA receptor activation reduces hippocampal mossy fibers excitability but has the opposite effect when intracellular Cl− is experimentally elevated. Synaptically released GABA mimics the effect of exogenous agonists. GABAA receptors modulating axonal excitability are tonically active in the absence of evoked GABA release or exogenous agonist application. Presynaptic action potential-dependent Ca2+ transients in individual mossy fiber varicosities exhibit a biphasic dependence on membrane potential and are altered by GABAA receptors. Antibodies against the α2 subunit of GABAA receptors stain mossy fibers. Axonal GABAA receptors thus play a potentially important role in tonic and activity-dependent heterosynaptic modulation of information flow to the hippocampus. PMID:12971896

  14. The anatomy of mammalian sweet taste receptors.

    PubMed

    Chéron, Jean-Baptiste; Golebiowski, Jérôme; Antonczak, Serge; Fiorucci, Sébastien

    2017-02-01

    All sweet-tasting compounds are detected by a single G-protein coupled receptor (GPCR), the heterodimer T1R2-T1R3, for which no experimental structure is available. The sweet taste receptor is a class C GPCR, and the recently published crystallographic structures of metabotropic glutamate receptor (mGluR) 1 and 5 provide a significant step forward for understanding structure-function relationships within this family. In this article, we recapitulate more than 600 single point site-directed mutations and available structural data to obtain a critical alignment of the sweet taste receptor sequences with respect to other class C GPCRs. Using this alignment, a homology 3D-model of the human sweet taste receptor is built and analyzed to dissect out the role of key residues involved in ligand binding and those responsible for receptor activation. Proteins 2017; 85:332-341. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  15. Acetylcholine receptors in the human retina

    SciTech Connect

    Hutchins, J.B.; Hollyfield, J.G.

    1985-11-01

    Evidence for a population of acetylcholine (ACh) receptors in the human retina is presented. The authors have used the irreversible ligand TH-propylbenzilylcholine mustard (TH-PrBCM) to label muscarinic receptors. TH- or SVI-alpha-bungarotoxin (alpha-BTx) was used to label putative nicotinic receptors. Muscarinic receptors are apparently present in the inner plexiform layer of the retina. Autoradiographic grain densities are reduced in the presence of saturating concentrations of atropine, quinuclidinyl benzilate or scopolamine; this indicates that TH-PrBCM binding is specific for a population of muscarinic receptors in the human retina. Binding sites for radiolabeled alpha-BTx are found predominantly in the inner plexiform layer of the retina. Grain densities are reduced in the presence of d-tubocurarine, indicating that alpha-BTx may bind to a pharmacologically relevant nicotinic ACh receptor. This study provides evidence for cholinergic neurotransmission in the human retina.

  16. Sensing odorants and pheromones with chemosensory receptors.

    PubMed

    Touhara, Kazushige; Vosshall, Leslie B

    2009-01-01

    Olfaction is a critical sensory modality that allows living things to acquire chemical information from the external world. The olfactory system processes two major classes of stimuli: (a) general odorants, small molecules derived from food or the environment that signal the presence of food, fire, or predators, and (b) pheromones, molecules released from individuals of the same species that convey social or sexual cues. Chemosensory receptors are broadly classified, by the ligands that activate them, into odorant or pheromone receptors. Peripheral sensory neurons expressing either odorant or pheromone receptors send signals to separate odor- and pheromone-processing centers in the brain to elicit distinct behavioral and neuroendocrinological outputs. General odorants activate receptors in a combinatorial fashion, whereas pheromones activate narrowly tuned receptors that activate sexually dimorphic neural circuits in the brain. We review recent progress on chemosensory receptor structure, function, and circuitry in vertebrates and invertebrates from the point of view of the molecular biology and physiology of these sensory systems.

  17. Phosphorylation of GABAA receptors influences receptor trafficking and neurosteroid actions.

    PubMed

    Comenencia-Ortiz, Eydith; Moss, Stephen J; Davies, Paul A

    2014-09-01

    Gamma-aminobutyric acid type A receptors (GABAARs) are the principal mediators of inhibitory transmission in the mammalian central nervous system. GABAARs can be localized at post-synaptic inhibitory specializations or at extrasynaptic sites. While synaptic GABAARs are activated transiently following the release of GABA from presynaptic vesicles, extrasynaptic GABAARs are typically activated continuously by ambient GABA concentrations and thus mediate tonic inhibition. The tonic inhibitory currents mediated by extrasynaptic GABAARs control neuronal excitability and the strength of synaptic transmission. However, the mechanisms by which neurons control the functional properties of extrasynaptic GABAARs had not yet been explored. We review GABAARs, how they are assembled and trafficked, and the role phosphorylation has on receptor insertion and membrane stabilization. Finally, we review the modulation of GABAARs by neurosteroids and how GABAAR phosphorylation can influence the actions of neurosteroids. Trafficking and stability of functional channels to the membrane surface are critical for inhibitory efficacy. Phosphorylation of residues within GABAAR subunits plays an essential role in the assembly, trafficking, and cell surface stability of GABAARs. Neurosteroids are produced in the brain and are highly efficacious allosteric modulators of GABAAR-mediated current. This allosteric modulation by neurosteroids is influenced by the phosphorylated state of the GABAAR which is subunit dependent, adding temporal and regional variability to the neurosteroid response. Possible links between neurosteroid actions, phosphorylation, and GABAAR trafficking remain to be explored, but potential novel therapeutic targets may exist for numerous neurological and psychological disorders which are linked to fluctuations in neurosteroid levels and GABAA subunit expression.

  18. Targeted complement inhibition and microvasculature in transplants: a therapeutic perspective.

    PubMed

    Khan, M A; Hsu, J L; Assiri, A M; Broering, D C

    2016-02-01

    Active complement mediators play a key role in graft-versus-host diseases, but little attention has been given to the angiogenic balance and complement modulation during allograft acceptance. The complement cascade releases the powerful proinflammatory mediators C3a and C5a anaphylatoxins, C3b, C5b opsonins and terminal membrane attack complex into tissues, which are deleterious if unchecked. Blocking complement mediators has been considered to be a promising approach in the modern drug discovery plan, and a significant number of therapeutic alternatives have been developed to dampen complement activation and protect host cells. Numerous immune cells, especially macrophages, develop both anaphylatoxin and opsonin receptors on their cell surface and their binding affects the macrophage phenotype and their angiogenic properties. This review discusses the mechanism that complement contributes to angiogenic injury, and the development of future therapeutic targets by antagonizing activated complement mediators to preserve microvasculature in rejecting the transplanted organ. © 2015 British Society for Immunology.

  19. Cytokines: sources, receptors and signalling.

    PubMed

    Barrett, K E

    1996-03-01

    Cytokines are a family of protein mediators that are important in transducing information between various cell types. These messengers are synthesized by a broad spectrum of cells. Cellular sources of cytokines include those cell types considered to play pivotal roles in the immune system as well as in inflammatory responses, including lymphocytes, monocytes and mast cells. Emerging data indicate that non-immune cells, including epithelial cells and fibroblasts, may also be important sources of certain cytokines. Cytokines fulfill a number of roles during immune and inflammatory reactions, and may display overlapping or redundant functions. In part, this redundancy may arise from the fact that cytokine receptors are not all unique entities, but may be divided into families. Many cytokine receptors have a subunit structure, with common subunits shared between receptors, and serving as affinity modifiers/signal transducers. Cytokines exert their effects on target cells by activating intracellular signalling mechanisms. In addition to 'classical' signal transduction path-ways, new data indicate that cytokines may also exemplify molecules that utilize novel signalling mechanisms, including the Jak-STAT pathways of transcriptional regulation and pathways involving the novel lipid second messenger, ceramide. In conclusion, molecular techniques have enabled the identification of many new cytokines, and the elucidation of their binding sites and mechanisms of action. This information has provided new insights into this complex area. Moreover, an understanding of the molecular basis of cytokine action and the pathways that lead to their acute and chronic effects may, in turn, facilitate interventions to prevent or modify their actions in disease states.

  20. Nitrosamines as nicotinic receptor ligands.

    PubMed

    Schuller, Hildegard M

    2007-05-30

    Nitrosamines are carcinogens formed in the mammalian organism from amine precursors contained in food, beverages, cosmetics and drugs. The potent carcinogen, NNK, and the weaker carcinogen, NNN, are nitrosamines formed from nicotine. Metabolites of the nitrosamines react with DNA to form adducts responsible for genotoxic effects. We have identified NNK as a high affinity agonist for the alpha7 nicotinic acetylcholine receptor (alpha7nAChR) whereas NNN bound with high affinity to epibatidine-sensitive nAChRs. Diethylnitrosamine (DEN) bound to both receptors but with lower affinity. High levels of the alpha7nAChR were expressed in human small cell lung cancer (SCLC) cell lines and in hamster pulmonary neuroendocrine cells (PNECs), which serve as a model for the cell of origin of human SCLC. Exposure of SCLC or PNECs to NNK or nicotine increased expression of the alpha7nAChR and caused influx of Ca(2+), activation of PKC, Raf-1, ERK1/2, and c-myc, resulting in the stimulation of cell proliferation. Signaling via the alpha7nAChR was enhanced when cells were maintained in an environment of 10-15% CO(2) similar to that in the diseased lung. Hamsters with hyperoxia-induced pulmonary fibrosis developed neuroendocrine lung carcinomas similar to human SCLC when treated with NNK, DEN, or nicotine. The development of the NNK-induced tumors was prevented by green tea or theophylline. The beta-adrenergic receptor agonist, isoproterenol or theophylline blocked NNK-induced cell proliferation in vitro. NNK and nicotine-induced hyperactivity of the alpha7nAChR/RAF/ERK1/2 pathway thus appears to play a crucial role in the development of SCLC in smokers and could be targeted for cancer prevention.

  1. Nitrosamines as nicotinic receptor ligands

    PubMed Central

    Schuller, Hildegard M.

    2007-01-01

    Nitrosamines are carcinogens formed in the mammalian organism from amine precursors contained in food, beverages, cosmetics and drugs. The potent carcinogen, NNK, and the weaker carcinogen, NNN, are nitrosamines formed from nicotine. Metabolites of the nitrosamines react with DNA to form adducts responsible for genotoxic effects. We have identified NNK as a high affinity agonist for the alpha7 nicotinic acetylcholine receptor (α7nAChR) whereas NNN bound with high affinity to epibatidine-sensitive nAChRs. Diethylnitrosamine (DEN) bound to both receptors but with lower affinity. High levels of the α7nAChR were expressed in human small cell lung cancer (SCLC) cell lines and in hamster pulmonary neuroendocrine cells (PNECs), which serve as a model for the cell of origin of human SCLC. Exposure of SCLC or PNECs to NNK or nicotine increased expression of the a7nAChR and caused influx of Ca2+, activation of PKC, Raf-1, ERK1/2, and c-myc, resulting in the stimulation of cell proliferation. Signaling via the α7nAChR was enhanced when cells were maintained in an environment of 10–15% CO2 similar to that in the diseased lung. Hamsters with hyperoxia-induced pulmonary fibrosis developed neuroendocrine lung carcinomas similar to human SCLC when treated with NNK, DEN, or nicotine. The development of the NNK-induced tumors was prevented by green tea or theophylline. The beta-adrenergic receptor agonist, isoproterenol or theophylline blocked NNK-induced cell proliferation in vitro. NNK and nicotine-induced hyperactivity of the α7nAChR/RAF/ERK1/2 pathway thus appears to play a crucial role in the development of SCLC in smokers and could be targeted for cancer prevention. PMID:17459420

  2. Xenobiotics and the Glucocorticoid Receptor.

    PubMed

    Gulliver, Linda S M

    2017-03-15

    Glucocorticoid Receptor (GR) is present in virtually every human cell type. Representing a nuclear receptor superfamily, GR has several different isoforms essentially acting as ligand-dependent transcription factors, regulating glucocorticoid-responsive gene expression in both a positive and a negative manner. Although the natural ligand of the Glucocorticoid Receptor, glucocorticoids (GC) represent only some of the multiple ligands for GR. Xenobiotics, ubiquitous in the environment, bind to GR and are also capable of activating or repressing GR gene expression, thereby modulating GR cell and tissue-specific downstream effects in a multitude of ways that include responses to inflammatory, allergic, metabolic, neoplastic and autoimmune processes. Many xenobiotics, if inadequately metabolized by xenobiotic metabolizing enzymes and not wholly eliminated, could have deleterious toxic effects with potentially lethal consequences. This review examines GR, the genomic and non-genomic actions of natural and synthetic GC and the body's handling of xenobiotic compounds, before reviewing what is presently known about GR's interactions with many of the more commonly encountered and some of the less well known GR-associated xenobiotics. GR promiscuity and crosstalk with other signaling pathways is discussed, alongside novel roles for GR that include mood disorder and addiction. A knowledge of GR interactions with xenobiotics is increasingly relevant when considering aging populations and the related prevalence of neoplastic disease, together with growing concerns around human exposure to mixtures of chemicals in the environment. Furthermore, escalating rates of obesity, Type 2 diabetes; autoimmune, allergy, addiction and mood disorder-related pathologies, require novel targeted interventions and GR appears a promising pharmacological candidate. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Targeting Discoidin Domain Receptors in Prostate Cancer

    DTIC Science & Technology

    2016-08-01

    Agency: DOD-BCRP Grant #: Breakthrough Award L1 BC150621P Title: “Discoidin Domain Receptors: Novel Targets in Breast Cancer Bone Metastasis...1 AWARD NUMBER: W81XWH-15-1-0226 TITLE: Targeting Discoidin Domain Receptors in Prostate Cancer PRINCIPAL INVESTIGATOR: Dr. Rafael Fridman...4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER W81XWH-15-1-0226 Targeting Discoidin Domain Receptors in Prostate Cancer 5b. GRANT NUMBER W81XWH-15

  4. Angiotensin II receptors in the gonads

    SciTech Connect

    Aguilera, G.; Millan, M.A.; Harwood, J.P.

    1989-05-01

    The presence of components of the renin-angiotensin system in ovaries and testes suggests that angiotensin II (AII) is involved in gonadal function, and thus we sought to characterize receptors for AII in rat and primate gonads. In the testes, autoradiographic studies showed receptors in the interstitium in all species. In rat interstitial cells fractionated by Percoll gradient, AII receptors coincided with hCG receptors indicating that AII receptors are located on the Leydig cells. In Leydig cells and membranes from rat and rhesus monkey prepuberal testes, AII receptors were specific for AII analogues and of high affinity (Kd=nM). During development, AII receptor content in rat testes decreases with age parallel to a fall in the ratio of interstitial to tubular tissue. In the ovary, the distribution of AII receptors was dependent on the stage of development, being high in the germinal epithelium and stromal tissue between five and 15 days, and becoming localized in secondary follicles in 20-and 40-day-old rats. No binding was found in primordial or primary follicles. In rhesus monkey ovary, AII receptors were higher in stromal tissue and lower in granulosa and luteal cells of the follicles. Characterization of the binding in rat and monkey ovarian membranes showed a single class of sites with a Kd in the nmol/L range and specificity similar to that of the adrenal glomerulosa and testicular AII receptors. Receptors for AII were also present in membrane fractions from PMSG/hCG primed rat ovaries. Infusion of AII (25 ng/min) or captopril (1.4 micrograms/min) during the PMSG/hCG induction period had no effect on ovarian weight or AII receptor concentration in the ovaries.

  5. Measurement and Regulation of Central Noradrenergic Receptors

    DTIC Science & Technology

    1993-11-30

    study on stress-induced motor impairment we showed that both propranolol and betaxolol , a selective beta-i receptor blocker, mimic the inhibitory...impairment we showed that both propranolol and betaxolol , a selective beta-1 receptor blocker, mimic the inhibitory effect of stress on effortful motor...subjected mice to immobilization stress in the presence or absence of treatment with propranolol, or the selective beta-1 receptor antagonist, betaxolol and

  6. Gustatory receptors: not just for good taste.

    PubMed

    Montell, Craig

    2013-10-21

    A recent study has found that a Drosophila gustatory receptor is required for thermotaxis. With other fly gustatory receptors having been shown to act in the detection of CO2, nutrients in the brain, and light, the roles of the so-called 'gustatory receptors' clearly go way beyond peripheral detection of non-volatile chemicals. Copyright © 2013 Elsevier Ltd. All rights reserved.

  7. Membrane guanylyl cyclase receptors: an update

    PubMed Central

    Garbers, David L.; Chrisman, Ted D.; Wiegn, Phi; Katafuchi, Takeshi; Albanesi, Joseph P.; Bielinski, Vincent; Barylko, Barbara; Redfield, Margaret M.; Burnett, John C.

    2007-01-01

    Recent studies have demonstrated key roles for several membrane guanylyl cyclase receptors in the regulation of cell hyperplasia, hypertrophy, migration and extracellular matrix production, all of which having an impact on clinically relevant diseases, including tissue remodeling after injury. Additionally, cell differentiation, and even tumor progression, can be profoundly influenced by one or more of these receptors. Some of these receptors also mediate important communication between the heart and intestine, and the kidney to regulate blood volume and Na+ balance. PMID:16815030

  8. Nuclear Receptors: Decoding Metabolic Disease

    PubMed Central

    Sonoda, Junichiro; Pei, Liming; Evans, Ronald M.

    2008-01-01

    Nuclear receptors (NR) are a superfamily of ligand-activated transcription factors that regulate development, reproduction, and metabolism of lipids, drugs and energy. The importance of this family of proteins in metabolic disease is exemplified by NR ligands used in the clinic or under exploratory development for the treatment of diabetes mellitus, dyslipidemia, hypercholesterolemia, or other metabolic abnormalities. Genetic studies in humans and rodents support the notion that NRs control a wide variety of metabolic processes by regulating the expression of genes encoding key enzymes, transporters and other proteins involved in metabolic homeostasis. Current knowledge of complex NR metabolic networks is summarized here. PMID:18023286

  9. EGF receptor ligands: recent advances

    PubMed Central

    Singh, Bhuminder; Carpenter, Graham; Coffey, Robert J.

    2016-01-01

    Seven ligands bind to and activate the mammalian epidermal growth factor (EGF) receptor (EGFR/ERBB1/HER1): EGF, transforming growth factor-alpha (TGFA), heparin-binding EGF-like growth factor (HBEGF), betacellulin (BTC), amphiregulin (AREG), epiregulin (EREG), and epigen (EPGN). Of these, EGF, TGFA, HBEGF, and BTC are thought to be high-affinity ligands, whereas AREG, EREG, and EPGN constitute low-affinity ligands. This focused review is meant to highlight recent studies related to actions of the individual EGFR ligands, the interesting biology that has been uncovered, and relevant advances related to ligand interactions with the EGFR. PMID:27635238

  10. Oxytocin receptors and parturition. I. Control of oxytocin receptor concentration in the rat myometrium at term.

    PubMed

    Alexandrova, M; Soloff, M S

    1980-03-01

    Rat myometrium exhibited a marked rise in the concentration of oxytocin (OT) receptors during parturition. The elevation began several hours before labor, was maximal during labor, and declined several hours later. In the perinatal period, the change in OT receptor concentration was proportional to the ratio of plasma estradiol to progesterone levels. Several hours before the increase in OT receptor concentration, there was a proportional increase in estrogen receptor concentration in both the cytosol and nuclear fractions of the myometrium. In view of the known action of estrogens in increasing the concentration of OT receptors in rat uterus, we propose that the following sequence of events occurs in the initiation of labor in the rat. The decline in serum progesterone permits estradiol to stimulate the synthesis of estrogen receptors in the myometrium. This increased concentration of estrogen receptors and their occupancy by estradiol stimulates the appearance of more OT receptors, which then trigger labor by interacting with circulating OT.

  11. Human dopamine receptor and its uses

    DOEpatents

    Civelli, Olivier; Van Tol, Hubert Henri-Marie

    1999-01-01

    The present invention is directed toward the isolation, characterization and pharmacological use of the human D4 dopamine receptor. The nucleotide sequence of the gene corresponding to this receptor and alleleic variant thereof are provided by the invention. The invention also includes recombinant eukaryotic expression constructs capable of expressing the human D4 dopamine receptor in cultures of transformed eukaryotic cells. The invention provides cultures of transformed eukaryotic cells which synthesize the human D4 dopamine receptor, and methods for characterizing novel psychotropic compounds using such cultures.

  12. Protein kinase activity of the insulin receptor.

    PubMed Central

    Gammeltoft, S; Van Obberghen, E

    1986-01-01

    The insulin receptor is an integral membrane glycoprotein (Mr approximately 300,000) composed of two alpha-subunits (Mr approximately 130,000) and two beta-subunits (Mr approximately 95,000) linked by disulphide bonds. This oligomeric structure divides the receptor into two functional domains such that alpha-subunits bind insulin and beta-subunits possess tyrosine kinase activity. The amino acid sequence deduced from cDNA of the single polypeptide chain precursor of human placental insulin receptor revealed that alpha- and beta-subunits consist of 735 and 620 residues, respectively. The alpha-subunit is hydrophilic, disulphide-bonded, glycosylated and probably extracellular. The beta-subunit consists of a short extracellular region which links the alpha-subunit through disulphide bridges, a hydrophobic transmembrane region and a longer cytoplasmic region which is structurally homologous with other tyrosine kinases like the src oncogene product and EGF receptor kinases. The cellular function of insulin receptors is dual: transmembrane signalling and endocytosis of hormone. The binding of insulin to its receptor on the cell membrane induces transfer of signal from extracellular to cytoplasmic receptor domains leading to activation of cell metabolism and growth. In addition, hormone-receptor complexes are internalized leading to intracellular proteolysis of insulin, whereas receptors are recycled to the membrane. These phenomena are kinetically well-characterized, but their molecular mechanisms remain obscure. Insulin receptor in different tissues and animal species are homologous in their structure and function, but show also significant differences regarding size of alpha-subunits, binding kinetics, insulin specificity and receptor-mediated degradation. We suggest that this heterogeneity of receptors may be linked to the diversity in insulin effects on metabolism and growth in various cell types. The purified insulin receptor phosphorylates its own beta-subunit and

  13. Challenges in imaging cell surface receptor clusters

    NASA Astrophysics Data System (ADS)

    Medda, Rebecca; Giske, Arnold; Cavalcanti-Adam, Elisabetta Ada

    2016-01-01

    Super-resolution microscopy offers unique tools for visualizing and resolving cellular structures at the molecular level. STED microscopy is a purely optical method where neither complex sample preparation nor mathematical post-processing is required. Here we present the use of STED microscopy for imaging receptor cluster composition. We use two-color STED to further determine the distribution of two different receptor subunits of the family of receptor serine/threonine kinases in the presence or absence of their ligands. The implications of receptor clustering on the downstream signaling are discussed, and future challenges are also presented.

  14. Identification and Mechanism of ABA Receptor Antagonism

    PubMed Central

    Melcher, Karsten; Xu, Yong; Ng, Ley-Moy; Zhou, X. Edward; Soon, Fen-Fen; Chinnusamy, Viswanathan; Suino-Powell, Kelly M.; Kovach, Amanda; Tham, Fook S.; Cutler, Sean R.; Li, Jun; Yong, Eu-Leong; Zhu, Jian-Kang; Xu, H. Eric

    2010-01-01

    The phytohormone abscisic acid (ABA) functions through a family of fourteen PYR/PYL receptors, which were identified by resistance to pyrabactin, a synthetic inhibitor of seed germination. ABA activates these receptors to inhibit type 2C protein phosphatases, such as ABI1, yet it remains unclear whether these receptors can be antagonized. Here we demonstrate that pyrabactin is an agonist of PYR1 and PYL1, but unexpectedly an antagonist of PYL2. Crystal structures of the PYL2–pyrabactin and PYL1–pyrabactin–ABI1 complexes reveal the mechanism responsible for receptor-selective activation and inhibition, which enables us to design mutations that convert PYL1 to a pyrabactin-inhibited receptor and PYL2 to a pyrabactin-activated receptor, and to identify new pyrabactin-based ABA receptor agonists. Together, our results establish a new concept of ABA receptor antagonism, illustrate its underlying mechanisms, and provide a rational framework for discovering novel ABA receptor ligands. PMID:20729862

  15. Imaging sigma receptors: applications in drug development.

    PubMed

    Collier, Thomas Lee; Waterhouse, Rikki N; Kassiou, Michael

    2007-01-01

    Sigma receptors have been implicated in a myriad of cellular functions, biological processes and diseases. While the precise biological functions of sigma receptors have not been elucidated, recent work has shed some light on to these enigmatic systems. Sigma receptors have recently been a target of drug development related to psychiatric and neurological disorders. Sigma ligands have also been shown to modulate endothelial cell proliferation and can control angiogenesis which makes them a promising target for oncology applications. Other areas currently being investigated include treatment of gastrointestinal, cardiovascular, endocrine and immune system disorders. Of interest is that the human sigma-1 receptor gene contains a steroid binding component, and several gonadal steroids, including progesterone, testosterone and dehydroepiandrosterone (DHEA), interact with sigma-1 receptors. Of the steroids examined thus far, progesterone binds with the highest affinity to human sigma-1 receptors, with a reported affinity (Ki) as high as 30 nM while the other steroids exhibit lower affinity. For this and other reasons, sigma-1 receptors have been proposed as a link between the central nervous system and the endocrine and reproductive systems. Taken together, the above information highlights an important yet largely unexplored but promising area of research to examine the biological function and therapeutic potential of sigma receptors. This review provides an overview of the current knowledge of these sites with a focus on specific areas where in vivo sigma receptor imaging is currently being investigated.

  16. Characterization of the chicken muscle insulin receptor

    SciTech Connect

    Adamo, M.; Simon, J.; Rosebrough, R.W.; McMurtry, J.P.; Steele, N.C.; LeRoith, D.

    1987-12-01

    Insulin receptors are present in chicken skeletal muscle. Crude membrane preparations demonstrated specific /sup 125/I-insulin binding. The nonspecific binding was high (36-55% of total binding) and slightly lower affinity receptors were found than are typically observed for crude membrane insulin binding in other chicken tissues. Affinity crosslinking of /sup 125/I-insulin to crude membranes revealed insulin receptor alpha-subunits of Mr 128K, intermediate between those of liver (134K) and brain (124K). When solubilized and partially purified on wheat germ agglutinin (WGA) affinity columns, chicken muscle insulin receptors exhibited typical high affinity binding, with approximately 10(-10) M unlabeled insulin producing 50% inhibition of the specific /sup 125/I-insulin binding. WGA purified chicken muscle insulin receptors also exhibited insulin-stimulated autophosphorylation of the beta-subunit, which appeared as phosphorylated bands of 92- and 81K. Both bands were immunoprecipitated by anti-receptor antiserum (B10). WGA purified membranes also demonstrated dose-dependent insulin-stimulated phosphorylation of the exogenous substrate poly(Glu,Tyr)4:1. However, unlike chicken liver, chicken muscle insulin receptor number and tyrosine kinase activity were unaltered by 48 hr of fasting or 48 hr of fasting and 24 hr of refeeding. Thus, despite the presence of insulin receptors in chicken muscle showing normal coupling to receptor tyrosine kinase activity, nutritional alterations modulate these parameters in a tissue-specific manner in chickens.

  17. Neurobiology of central D - dopamine receptors

    SciTech Connect

    Breese, G.R.; Creese, I.

    1986-01-01

    The work described in this text is primarily stimulated by the development of two selective d/sub 1/ receptor drugs -- the antagonist SCH 23390 and the agonist SKF 38393. The studies described here show that D/sub 1/ receptors have many behavioral functions which, on the surface, are often similar to those responses mediated by D/sub 2/ receptors. These observations, according to the authors, hold hope for the development of new dopaminergic agents for use in treatment of psychiatric and neurologic diseases that may be more selective in their actions and lack some of the side effects of the D/sub 2/ receptor selective agents.

  18. Collective binding properties of receptor arrays.

    PubMed

    Agmon, N; Edelstein, A L

    1997-04-01

    Binding kinetics of receptor arrays can differ dramatically from that of the isolated receptor. We simulate synaptic transmission using a microscopically accurate Brownian dynamics routine. We study the factors governing the rise and decay of the activation probability as a function of the number of transmitter molecules released. Using a realistic receptor array geometry, the simulation reproduces the time course of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor-mediated excitatory postsynaptic currents. A consistent interpretation of experimentally observed synaptic currents in terms of rebinding and spatial correlations is discussed.

  19. Human olfactory receptor responses to odorants

    PubMed Central

    Mainland, Joel D; Li, Yun R; Zhou, Ting; Liu, Wen Ling L; Matsunami, Hiroaki

    2015-01-01

    Although the human olfactory system is capable of discriminating a vast number of odors, we do not currently understand what chemical features are encoded by olfactory receptors. In large part this is due to a paucity of data in a search space covering the interactions of hundreds of receptors with billions of odorous molecules. Of the approximately 400 intact human odorant receptors, only 10% have a published ligand. Here we used a heterologous luciferase assay to screen 73 odorants against a clone library of 511 human olfactory receptors. This dataset will allow other researchers to interrogate the combinatorial nature of olfactory coding. PMID:25977809

  20. Neuropeptide Receptor Transcriptome Reveals Unidentified Neuroendocrine Pathways

    PubMed Central

    Yamanaka, Naoki; Yamamoto, Sachie; Žitňan, Dušan; Watanabe, Ken; Kawada, Tsuyoshi; Satake, Honoo; Kaneko, Yu; Hiruma, Kiyoshi; Tanaka, Yoshiaki; Shinoda, Tetsuro; Kataoka, Hiroshi

    2008-01-01

    Neuropeptides are an important class of molecules involved in diverse aspects of metazoan development and homeostasis. Insects are ideal model systems to investigate neuropeptide functions, and the major focus of insect neuropeptide research in the last decade has been on the identification of their receptors. Despite these vigorous efforts, receptors for some key neuropeptides in insect development such as prothoracicotropic hormone, eclosion hormone and allatotropin (AT), remain undefined. In this paper, we report the comprehensive cloning of neuropeptide G protein-coupled receptors from the silkworm, Bombyx mori, and systematic analyses of their expression. Based on the expression patterns of orphan receptors, we identified the long-sought receptor for AT, which is thought to stimulate juvenile hormone biosynthesis in the corpora allata (CA). Surprisingly, however, the AT receptor was not highly expressed in the CA, but instead was predominantly transcribed in the corpora cardiaca (CC), an organ adjacent to the CA. Indeed, by using a reverse-physiological approach, we purified and characterized novel allatoregulatory peptides produced in AT receptor-expressing CC cells, which may indirectly mediate AT activity on the CA. All of the above findings confirm the effectiveness of a systematic analysis of the receptor transcriptome, not only in characterizing orphan receptors, but also in identifying novel players and hidden mechanisms in important biological processes. This work illustrates how using a combinatorial approach employing bioinformatic, molecular, biochemical and physiological methods can help solve recalcitrant problems in neuropeptide research. PMID:18725956

  1. Novel NMDA Receptor Modulators: An Update

    PubMed Central

    Santangelo, Rose M.; Acker, Timothy M.; Zimmerman, Sommer S.; Katzman, Brooke M.; Strong, Katie L.; Traynelis, Stephen F.; Liotta, Dennis C.

    2013-01-01

    Summary Introduction The NMDA receptor is a ligand-gated ion channel that plays a critical role in higher level brain processes and has been implicated in a range of neurological and psychiatric conditions. Although initial studies for the use of NMDA receptor antagonists in neuroprotection were unsuccessful, more recently, NMDA receptor antagonists have shown clinical promise in other indications such as Alzheimer’s disease, Parkinson’s disease, pain and depression. Based on the clinical observations and more recent insights into receptor pharmacology, new modulatory approaches are beginning to emerge, with potential therapeutic benefit. Areas Covered The article covers the known pharmacology and important features regarding NMDA receptors and their function. A discussion of pre-clinical and clinical relevance is included, as well. The subsequent patent literature review highlights the current state of the art targeting the receptor since the last review in 2010. Expert Opinion The complex nature of the NMDA receptor structure and function is becoming better understood. As knowledge about this receptor increases, it opens up new opportunities for targeting the receptor for many therapeutic indications. New strategies and advances in older technologies will need to be further developed before clinical success can be achieved. First-in-class potentiators and subunit-selective agents form the basis for most new strategies, complemented by efforts to limit off-target liability and fine-tune on-target properties. PMID:23009122

  2. ABA Receptors: Past, Present and Future

    SciTech Connect

    Guo, Jianjun; Yang, Xiaohan; Weston, David; Chen, Jay

    2011-01-01

    Abscisic acid (ABA) is the key plant stress hormone. Consistent with the earlier studies in support of the presence of both membrane- and cytoplasm-localized ABA receptors, recent studies have identified multiple ABA receptors located in various subcellular locations. These include a chloroplast envelope-localized receptor (the H subunit of Chloroplast Mg2+-chelatase/ABA Receptor), two plasma membrane-localized receptors (G-protein Coupled Receptor 2 and GPCR-type G proteins), and one cytosol/nucleus-localized Pyrabactin Resistant (PYR)/PYR-Like (PYL)/Regulatory Component of ABA Receptor 1 (RCAR). Although the downstream molecular events for most of the identified ABA receptors are currently unknown, one of them, PYR/PYL/RACR was found to directly bind and regulate the activity of a long-known central regulator of ABA signaling, the A-group protein phosphatase 2C (PP2C). Together with the Sucrose Non-fermentation Kinase Subfamily 2 (SnRK2s) protein kinases, a central signaling complex (ABA-PYR-PP2Cs-SnRK2s) that is responsible for ABA signal perception and transduction is supported by abundant genetic, physiological, biochemical and structural evidence. The identification of multiple ABA receptors has advanced our understanding of ABA signal perception and transduction while adding an extra layer of complexity.

  3. Clinical potential of GABAB receptor modulators.

    PubMed

    Ong, Jennifer; Kerr, David I B

    2005-01-01

    Metabotropic gamma-aminobutyric acid(B) (GABAB) receptors for the major inhibitory transmitter GABA, together with metabotropic glutamate (mGLuRs) receptors, the extracellular calcium-sensing receptors (CaSRs), some V2R pheromone receptors and T1R taste receptors, belong to the family of 3 G-protein-coupled receptors (GPCRs). GABAB receptors are known to control neuronal excitability and modulate synaptic neurotransmission, playing a very important role in many physiological activities. These receptors are widely expressed and distributed in the nervous system and have been implicated in a variety of neurodegenerative and pathophysiological disorders including epilepsy, spasticity, chronic pain, depression, schizophrenia and drug addiction. To form a functional receptor entity, GABAB receptors must exist as a heterodimer consisting of GABAB1 and GABAB2 receptor subtypes with two 7-transmembrane proteins, and these subunits arise from distinct genes. The GABAB1 subunit binds the endogenous ligand within its extracellular N-terminus, whilst the GABAB2 subunit is not only essential for the correct trafficking of the GABAB1 subunit to the cell surface, but is also responsible for the interaction of the receptor with its cognate G-protein. Allosteric modulation has recently been recognized as an alternative pharmacological approach to gain selectivity in drug action. It is now generally accepted that modulators acting at the allosteric sites provide a novel perspective for the development of subtype-selective agents acting at GPCRs. These agents interact with allosteric binding sites quite separate from the highly conserved agonist binding region. In this review, we present a new class of phenylalkylamines, based on the lead compound fendiline, that are potent positive potentiators of GABAB receptor-mediated function and discuss their putative clinical applications. It is proposed that these new modulators may have therapeutic value in GABAB receptor pharmacology and

  4. Identification of receptors for pig endogenous retrovirus.

    PubMed

    Ericsson, Thomas A; Takeuchi, Yasuhiro; Templin, Christian; Quinn, Gary; Farhadian, Shelli F; Wood, James C; Oldmixon, Beth A; Suling, Kristen M; Ishii, Jennifer K; Kitagawa, Yoshinori; Miyazawa, Takayuki; Salomon, Daniel R; Weiss, Robin A; Patience, Clive

    2003-05-27

    Xenotransplantation of porcine tissues has the potential to treat a wide variety of major health problems including organ failure and diabetes. Balanced against the potential benefits of xenotransplantation, however, is the risk of human infection with a porcine microorganism. In particular, the transmission of porcine endogenous retrovirus (PERV) is a major concern [Chapman, L. E. & Bloom, E. T. (2001) J. Am. Med. Assoc. 285, 2304-2306]. Here we report the identification of two, sequence-related, human proteins that act as receptors for PERV-A, encoded by genes located on chromosomes 8 and 17. We also describe homologs from baboon and porcine cells that also are active as receptors. Conversely, activity could not be demonstrated with a syntenic murine receptor homolog. Sequence analysis indicates that PERV-A receptors [human PERV-A receptor (HuPAR)-1, HuPAR-2, baboon PERV-A receptor 2, and porcine PERV-A receptor] are multiple membrane-spanning proteins similar to receptors for other gammaretroviruses. Expression is widespread in human tissues including peripheral blood mononuclear cells, but their biological functions are unknown. The identification of the PERV-A receptors opens avenues of research necessary for a more complete assessment of the retroviral risks of pig to human xenotransplantation.

  5. Knock-In Mice with NOP-eGFP Receptors Identify Receptor Cellular and Regional Localization

    PubMed Central

    Ozawa, Akihiko; Brunori, Gloria; Mercatelli, Daniela; Wu, Jinhua; Cippitelli, Andrea; Zou, Bende; Xie, Xinmin (Simon); Williams, Melissa; Zaveri, Nurulain T.; Low, Sarah; Scherrer, Grégory; Kieffer, Brigitte L.

    2015-01-01

    The nociceptin/orphanin FQ (NOP) receptor, the fourth member of the opioid receptor family, is involved in many processes common to the opioid receptors including pain and drug abuse. To better characterize receptor location and trafficking, knock-in mice were created by inserting the gene encoding enhanced green fluorescent protein (eGFP) into the NOP receptor gene (Oprl1) and producing mice expressing a functional NOP-eGFP C-terminal fusion in place of the native NOP receptor. The NOP-eGFP receptor was present in brain of homozygous knock-in animals in concentrations somewhat higher than in wild-type mice and was functional when tested for stimulation of [35S]GTPγS binding in vitro and in patch-clamp electrophysiology in dorsal root ganglia (DRG) neurons and hippocampal slices. Inhibition of morphine analgesia was equivalent when tested in knock-in and wild-type mice. Imaging revealed detailed neuroanatomy in brain, spinal cord, and DRG and was generally consistent with in vitro autoradiographic imaging of receptor location. Multicolor immunohistochemistry identified cells coexpressing various spinal cord and DRG cellular markers, as well as coexpression with μ-opioid receptors in DRG and brain regions. Both in tissue slices and primary cultures, the NOP-eGFP receptors appear throughout the cell body and in processes. These knock-in mice have NOP receptors that function both in vitro and in vivo and appear to be an exceptional tool to study receptor neuroanatomy and correlate with NOP receptor function. SIGNIFICANCE STATEMENT The NOP receptor, the fourth member of the opioid receptor family, is involved in pain, drug abuse, and a number of other CNS processes. The regional and cellular distribution has been difficult to determine due to lack of validated antibodies for immunohistochemical analysis. To provide a new tool for the investigation of receptor localization, we have produced knock-in mice with a fluorescent-tagged NOP receptor in place of the native

  6. Intrarenal dopamine D1-like receptor stimulation induces natriuresis via an angiotensin type-2 receptor mechanism.

    PubMed

    Salomone, Leslie J; Howell, Nancy L; McGrath, Helen E; Kemp, Brandon A; Keller, Susanna R; Gildea, John J; Felder, Robin A; Carey, Robert M

    2007-01-01

    We explored the effects of direct renal interstitial stimulation of dopamine D(1)-like receptors with fenoldopam, a selective D(1)-like receptor agonist, on renal sodium excretion and angiotensin type-2 (AT(2)) receptor expression and cellular distribution in rats on a high-sodium intake. In contrast to vehicle-infused rats, sodium excretion increased in fenoldopam-infused rats during each of three 1-hour experimental periods (<0.001). Blood pressure was unaffected by vehicle or fenoldopam. In plasma membranes of renal cortical cells, fenoldopam increased D(1) receptor expression by 38% (P<0.05) and AT(2) receptor expression by 69% (P<0.01). In plasma membranes of renal proximal tubule cells, fenoldopam increased AT(2) receptor expression by 108% (P<0.01). In outer apical membranes of proximal tubule cells, fenoldopam increased AT(2) receptor expression by 59% (P<0.01). No significant change in total AT(2) receptor protein expression was detectable in response to fenoldopam. Fenoldopam-induced natriuresis was abolished when either PD-123319, a specific AT(2) receptor antagonist, or SCH-23390, a potent D(1)-like receptor antagonist, was coinfused with F (P<0.001). In summary, direct renal D(1)-like receptor activation increased urinary sodium excretion and the plasma membrane expression of AT(2) receptors in renal cortical and proximal tubule cells. D(1)-like receptor-induced natriuresis was abolished by intrarenal AT(2) receptor inhibition. These findings suggest that dopaminergic regulation of sodium excretion involves recruitment of AT(2) receptors to the outer plasma membranes of renal proximal tubule cells and that dopamine-induced natriuresis requires AT(2) receptor activation.

  7. The endocrinology of taste receptors

    PubMed Central

    Santa-Cruz Calvo, Sara; Egan, Josephine M.

    2016-01-01

    Levels of obesity have reached epidemic proportions on a global scale, which has led to considerable increases in health problems and increased risk of several diseases, including cardiovascular and pulmonary diseases, cancer and diabetes mellitus. People with obesity consume more food than is needed to maintain an ideal body weight, despite the discrimination that accompanies being overweight and the wealth of available information that overconsumption is detrimental to health. The relationship between energy expenditure and energy intake throughout an individual’s lifetime is far more complicated than previously thought. An improved comprehension of the relationships between taste, palatability, taste receptors and hedonic responses to food might lead to increased understanding of the biological underpinnings of energy acquisition, as well as why humans sometimes eat more than is needed and more than we know is healthy. This Review discusses the role of taste receptors in the tongue, gut, pancreas and brain and their hormonal involvement in taste perception, as well as the relationship between taste perception, overeating and the development of obesity. PMID:25707779

  8. Prorenin receptor in kidney development.

    PubMed

    Yosypiv, Ihor V

    2017-03-01

    Prorenin receptor (PRR), a receptor for renin and prorenin and an accessory subunit of the vacuolar proton pump H(+)-ATPase, is expressed in the developing kidney. Global loss of PRR is lethal in mice, and PRR mutations are associated with a high blood pressure, left ventricular hypertrophy and X-linked mental retardation in humans. With the advent of modern gene targeting techniques, including conditional knockout approaches, several recent studies have demonstrated critical roles for the PRR in several lineages of the developing kidney. PRR signaling has been shown to be essential for branching morphogenesis of the ureteric bud (UB), nephron progenitor survival and nephrogenesis. PRR regulates these developmental events through interactions with other transcription and growth factors. Several targeted PRR knockout animal models have structural defects mimicking congenital anomalies of the kidney and urinary tract observed in humans. The aim of this review, is to highlight new insights into the cellular and molecular mechanisms by which PRR may regulate UB branching, terminal differentiation and function of UB-derived collecting ducts, nephron progenitor maintenance, progression of nephrogenesis and normal structural kidney development and function.

  9. Ryanodine receptors in smooth muscle.

    PubMed

    Guerrero-Hernández, Agustín; Gómez-Viquez, Leticia; Guerrero-Serna, Guadalupe; Rueda, Angélica

    2002-07-01

    The sarcoplasmic reticulum (SR) of smooth muscle is endowed with two different types of Ca2+ release channels, i.e. inositol 1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs). In general, both release channels mobilize Ca2+ from the same internal store in smooth muscle. While the importance of IP3Rs in agonist-induced contraction is well established, the role of RyRs in excitation-contraction coupling of smooth muscle is not clear. The participation of smooth muscle RyRs in the amplification of Ca2+ transients induced by either opening of Ca2+-permeable channels or IP3-triggered Ca2+ release has been studied. The efficacy of both processes to activate RyRs by calcium-induced calcium release (CICR) is highly variable and not widely present in smooth muscle. Although RyRs in smooth muscle generate Ca2+ sparks that are similar to those observed in striated muscles, the contribution of these local Ca2+ events to depolarization-induced global rise in [Ca2+]i is rather limited. Recent data suggest that RyRs are involved in regulating the luminal [Ca2+] of SR and also in smooth muscle relaxation. This review summarizes studies that were carried out mainly in muscle strips or in freshly isolated myocytes, and that were aimed to determine the physiological role of RyRs in smooth muscle.

  10. Leptin receptor in boar spermatozoa.

    PubMed

    De Ambrogi, Marco; Spinaci, Marcella; Galeati, Giovanna; Tamanini, Carlo

    2007-10-01

    Leptin is active in both metabolism and reproduction. In fact, it seems to exert an inhibitory action on gonadal functions by reducing testosterone production. The presence of leptin in human and boar seminal plasma and in human spermatozoa has been demonstrated; recently, leptin receptors (Ob-R) have been localized in human spermatozoa, thus suggesting a possible action of this hormone even on these cells. Our aim was to verify whether leptin receptor [the long form (Ob-Rb)] is present in boar spermatozoa. Immunofluorescence and reverse transcriptase-polymerase chain reaction (RT-PCR) techniques were employed. RNA was extracted from boar spermatozoa and a specific band (382 bp) for Ob-Rb was detected after RT-PCR. Ob-Rb was detected on acrosome, subequatorial area and either on the midpiece or on the whole tail. These localizations were maintained even in semen washed twice to eliminate seminal plasma. We conclude that Ob-R is present in boar spermatozoa where seminal plasma leptin can exert its effects.

  11. Nicotinic receptors in addiction pathways.

    PubMed

    Leslie, Frances M; Mojica, Celina Y; Reynaga, Daisy D

    2013-04-01

    Neuronal nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that consist of pentameric combinations of α and β subunits. These receptors are widely distributed throughout the brain and are highly expressed in addiction circuitry. The role of nAChRs in regulating neuronal activity and motivated behavior is complex and varies both in and among brain regions. The rich diversity of central nAChRs has hampered the characterization of their structure and function with use of classic pharmacological techniques. However, recent molecular approaches using null mutant mice with specific regional lentiviral re-expression, in combination with neuroanatomical and electrophysiological techniques, have allowed the elucidation of the influence of different nAChR types on neuronal circuit activity and behavior. This review will address the influence of nAChRs on limbic dopamine circuitry and the medial habenula-interpeduncular nucleus complex, which are critical mediators of reinforced behavior. Characterization of the mechanisms underlying regulation of addiction pathways by endogenous cholinergic transmission and by nicotine may lead to the identification of new therapeutic targets for treating tobacco dependence and other addictions.

  12. Evolution of insect olfactory receptors

    PubMed Central

    Missbach, Christine; Dweck, Hany KM; Vogel, Heiko; Vilcinskas, Andreas; Stensmyr, Marcus C; Hansson, Bill S; Grosse-Wilde, Ewald

    2014-01-01

    The olfactory sense detects a plethora of behaviorally relevant odor molecules; gene families involved in olfaction exhibit high diversity in different animal phyla. Insects detect volatile molecules using olfactory (OR) or ionotropic receptors (IR) and in some cases gustatory receptors (GRs). While IRs are expressed in olfactory organs across Protostomia, ORs have been hypothesized to be an adaptation to a terrestrial insect lifestyle. We investigated the olfactory system of the primary wingless bristletail Lepismachilis y-signata (Archaeognatha), the firebrat Thermobia domestica (Zygentoma) and the neopteran leaf insect Phyllium siccifolium (Phasmatodea). ORs and the olfactory coreceptor (Orco) are with very high probability lacking in Lepismachilis; in Thermobia we have identified three Orco candidates, and in Phyllium a fully developed OR/Orco-based system. We suggest that ORs did not arise as an adaptation to a terrestrial lifestyle, but evolved later in insect evolution, with Orco being present before the appearance of ORs. DOI: http://dx.doi.org/10.7554/eLife.02115.001 PMID:24670956

  13. Epac2: a sulfonylurea receptor?

    PubMed

    Rehmann, Holger

    2012-02-01

    Sulfonylureas are widely used oral drugs in the treatment of diabetes mellitus. They function by the inhibition of ATP-sensitive K+ channels in pancreatic β-cells, which are thus considered the 'classical' sulfonylurea receptor. Next to the ATP-sensitive K+ channels, additional sulfonylurea-interacting proteins were identified, which might contribute to the physiological effects of this drug family. Most recently, Epac2 (exchange protein directly activated by cAMP 2) was added to the list of sulfonylurea receptors. However, this finding caused controversy in the literature. The critical discussion of the present paper comes to the conclusion that sulfonylureas are not able to activate Epac2 directly and are unlikely to bind to Epac2. Increased blood glucose levels after food intake result in the secretion of insulin from pancreatic β-cells. Glucose levels are detected 'indirectly' by β-cells: owing to increased glycolysis rates, the ratio of cellular ATP/ADP increases and causes the closure of ATP-sensitive K+ channels. In consequence, cells depolarize and voltage-dependent Ca2+ channels open to cause an increase in the cellular Ca2+ concentration. Finally, Ca2+ induces the fusion of insulin-containing granules with the plasma membrane. Sulfonylureas, such as tolbutamide, glibenclamide or acetohexamide, form a class of orally applicable drugs used in the treatment of non-insulin-dependent diabetes mellitus.

  14. TVB Receptors for Cytopathic and Noncytopathic Subgroups of Avian Leukosis Viruses Are Functional Death Receptors

    PubMed Central

    Brojatsch, Jürgen; Naughton, John; Adkins, Heather B.; Young, John A. T.

    2000-01-01

    The identification of TVBS3, a cellular receptor for the cytopathic subgroups B and D of avian leukosis virus (ALV-B and ALV-D), as a tumor necrosis factor receptor-related death receptor with a cytoplasmic death domain, provides a compelling argument that viral Env-receptor interactions are linked to cell death (4). However, other TVB proteins have been described that appear to have similar death domains but are cellular receptors for the noncytopathic subgroup E of ALV (ALV-E): TVBT, a turkey subgroup E-specific ALV receptor, and TVBS1, a chicken receptor for subgroups B, D, and E ALV. To begin to understand the role of TVB receptors in the cytopathic effects associated with infection by specific ALV subgroups, we asked whether binding of a soluble ALV-E surface envelope protein (SU) to its receptor can lead to cell death. Here we report that ALV-E SU-receptor interactions can induce apoptosis in quail or turkey cells. We also show directly that TVBS1 and TVBT are functional death receptors that can trigger cell death by apoptosis via a mechanism involving their cytoplasmic death domains and activation of the caspase pathway. These data demonstrate that ALV-B and ALV-E use functional death receptors to enter cells, and it remains to be determined why only subgroups B and D viral infections lead specifically to cell death. PMID:11090145

  15. The role of the CGRP-receptor component protein (RCP) in adrenomedullin receptor signal transduction.

    PubMed

    Prado, M A; Evans-Bain, B; Oliver, K R; Dickerson, I M

    2001-11-01

    G protein-coupled receptors are usually thought to act as monomer receptors that bind ligand and then interact with G proteins to initiate signal transduction. In this study we report an intracellular peripheral membrane protein named the calcitonin gene-related peptide (CGRP)-receptor component protein (RCP) required for signal transduction at the G protein-coupled receptor for adrenomedullin. Cell lines were made that expressed an antisense construct of the RCP cDNA, and in these cells diminished RCP expression correlated with loss of adrenomedullin signal transduction. In contrast, loss of RCP did not diminish receptor density or affinity, therefore RCP does not appear to act as a chaperone protein. Instead, RCP represents a novel class of protein required to couple the adrenomedullin receptor to the cellular signal transduction pathway. A candidate adrenomedullin receptor named the calcitonin receptor-like receptor (CRLR) has been described, which forms high affinity adrenomedullin receptors when co-expressed with the accessory protein receptor-activity modifying protein 2 (RAMP2). RCP co-immunoprecipitated with CRLR and RAMP2, indicating that a functional adrenomedullin receptor is composed of at least three proteins: the ligand binding protein (CRLR), an accessory protein (RAMP2), and a coupling protein for signal transduction (RCP).

  16. Functional selectivity of dopamine D1 receptor agonists in regulating the fate of internalized receptors *

    PubMed Central

    Ryman-Rasmussen, Jessica P.; Griffith, Adam; Oloff, Scott; Vaidehi, Nagarajan; Brown, Justin T.; Goddard, William A.; Mailman, Richard B.

    2007-01-01

    Recently, we demonstrated that D1 agonists can cause functionally selective effects when the endpoints of receptor internalization and adenylate cyclase activation are compared. The present study was designed to probe the phenomenon of functional selectivity at the D1 receptor further by testing the hypothesis that structurally dissimilar agonists with efficacies at these endpoints that equal or exceed those of dopamine would differ in ability to influence receptor fate after internalization, a functional endpoint largely unexplored for the D1 receptor. We selected two novel agonists of therapeutic interest that meet these criteria (the isochroman A-77636, and the isoquinoline dinapsoline), and compared the fates of the D1 receptor after internalization in response to these two compounds with that of dopamine. We found that dopamine caused the receptor to be rapidly recycled to the cell surface within 1 h of removal. Conversely, A-77636 caused the receptor to be retained intracellularly up to 48 h after agonist removal. Most surprisingly, the D1 receptor recovered to the cell surface 48 h after removal of dinapsoline. Taken together, these data indicate that these agonists target the D1 receptor to different intracellular trafficking pathways, demonstrating that the phenomenon of functional selectivity at the D1 receptor is operative for cellular events that are temporally downstream of immediate receptor activation. We hypothesize that these differential effects result from interactions of the synthetic ligands with aspects of the D1 receptor that are distal from the ligand binding domain. PMID:17067639

  17. Selective antagonism of AMPA receptors unmasks kainate receptor-mediated responses in hippocampal neurons.

    PubMed

    Paternain, A V; Morales, M; Lerma, J

    1995-01-01

    Although both protein and mRNAs for kainate receptor subunits are abundant in several brain regions, the responsiveness of AMPA receptors to kainate has made it difficult to demonstrate the presence of functional kainate-type receptors in native cells. Recently, however, we have shown that many hippocampal neurons in culture express glutamate receptors of the kainate type. The large nondesensitizing response that kainate induces at AMPA receptors precludes detection and analysis of smaller, rapidly desensitizing currents induced by kainate at kainate receptors. Consequently, the functional significance of these strongly desensitizing glutamate receptors remains enigmatic. We report here that the family of new noncompetitive antagonists of AMPA receptors (GYKI 52466 and 53655) minimally affects kainate-induced responses at kainate receptors while completely blocking AMPA receptor-mediated currents, making it possible to separate the responses mediated by each receptor. These compounds will allow determination of the role played by kainate receptors in synaptic transmission and plasticity in the mammalian brain, as well as evaluation of their involvement in neurotoxicity.

  18. A second trigeminal CGRP receptor: function and expression of the AMY1 receptor

    PubMed Central

    Walker, Christopher S; Eftekhari, Sajedeh; Bower, Rebekah L; Wilderman, Andrea; Insel, Paul A; Edvinsson, Lars; Waldvogel, Henry J; Jamaluddin, Muhammad A; Russo, Andrew F; Hay, Debbie L

    2015-01-01

    Objective The trigeminovascular system plays a central role in migraine, a condition in need of new treatments. The neuropeptide, calcitonin gene-related peptide (CGRP), is proposed as causative in migraine and is the subject of intensive drug discovery efforts. This study explores the expression and functionality of two CGRP receptor candidates in the sensory trigeminal system. Methods Receptor expression was determined using Taqman G protein-coupled receptor arrays and immunohistochemistry in trigeminal ganglia (TG) and the spinal trigeminal complex of the brainstem in rat and human. Receptor pharmacology was quantified using sensitive signaling assays in primary rat TG neurons. Results mRNA and histological expression analysis in rat and human samples revealed the presence of two CGRP-responsive receptors (AMY1: calcitonin receptor/receptor activity-modifying protein 1 [RAMP1]) and the CGRP receptor (calcitonin receptor-like receptor/RAMP1). In support of this finding, quantification of agonist and antagonist potencies revealed a dual population of functional CGRP-responsive receptors in primary rat TG neurons. Interpretation The unexpected presence of a functional non-canonical CGRP receptor (AMY1) at neural sites important for craniofacial pain has important implications for targeting the CGRP axis in migraine. PMID:26125036

  19. Somatostatin and its receptor family.

    PubMed

    Patel, Y C

    1999-07-01

    Somatostatin (SST), a regulatory peptide, is produced by neuroendocrine, inflammatory, and immune cells in response to ions, nutrients, neuropeptides, neurotransmitters, thyroid and steroid hormones, growth factors, and cytokines. The peptide is released in large amounts from storage pools of secretory cells, or in small amounts from activated immune and inflammatory cells, and acts as an endogenous inhibitory regulator of the secretory and proliferative responses of target cells that are widely distributed in the brain and periphery. These actions are mediated by a family of seven transmembrane (TM) domain G-protein-coupled receptors that comprise five distinct subtypes (termed SSTR1-5) that are endoded by separate genes segregated on different chromosomes. The five receptor subtypes bind the natural SST peptides, SST-14 and SST-28, with low nanomolar affinity. Short synthetic octapeptide and hexapeptide analogs bind well to only three of the subtypes, 2, 3, and 5. Selective nonpeptide agonists with nanomolar affinity have been developed for four of the subtypes (SSTR1, 2, 3, and 4) and putative peptide antagonists for SSTR2 and SSTR5 have been identified. The ligand binding domain for SST ligands is made up of residues in TMs III-VII with a potential contribution by the second extracellular loop. SSTRs are widely expressed in many tissues, frequently as multiple subtypes that coexist in the same cell. The five receptors share common signaling pathways such as the inhibition of adenylyl cyclase, activation of phosphotyrosine phosphatase (PTP), and modulation of mitogen-activated protein kinase (MAPK) through G-protein-dependent mechanisms. Some of the subtypes are also coupled to inward rectifying K(+) channels (SSTR2, 3, 4, 5), to voltage-dependent Ca(2+) channels (SSTR1, 2), a Na(+)/H(+) exchanger (SSTR1), AMPA/kainate glutamate channels (SSTR1, 2), phospholipase C (SSTR2, 5), and phospholipase A(2) (SSTR4). SSTRs block cell secretion by inhibiting intracellular

  20. From anion receptors to transporters.

    PubMed

    Gale, Philip A

    2011-03-15

    Cystic fibrosis is the most well-known of a variety of diseases termed channelopathies, in which the regulation of ion transport across cell membranes is so disrupted that the threshold of a pathology is passed. The human toll exacted by these diseases has led a number of research groups, including our own, to create compounds that mediate ion transport across lipid bilayers. In this Account, we discuss three classes of synthetic compounds that were refined to bind and transport anions across lipid bilayer membranes. All of the compounds were originally designed as anion receptors, that is, species that would simply create stable complexes with anions, but were then further developed as transporters. By studying structurally simple systems and varying their properties to change the degree of preorganization, the affinity for anions, or the lipophilicity, we have begun to rationalize why particular anion transport mechanisms (cotransport or antiport processes) occur in particular cases. For example, we have studied the chloride transport properties of receptors based on the closely related structures of isophthalamide and pyridine-2,6-dicarboxamide: the central ring in each case was augmented with pendant methylimidazole groups designed to cotransport H(+) and Cl(-). We observed that the more preorganized pyridine-based receptor was the more efficient transporter, a finding replicated with a series of isophthalamides in which one contained hydroxyl groups designed to preorganize the receptor. This latter class of compound, together with the natural product prodigiosin, can transport bicarbonate (as part of a chloride/bicarbonate antiport process) across lipid bilayer membranes. We have also studied the membrane transport properties of calix[4]pyrroles. Although the parent meso-octamethylcalix[4]pyrrole functions solely as a Cs(+)/Cl(-) cotransporter, other compounds with increased anion affinities can function through an antiport process. One example is octafluoro

  1. Chemistry and pharmacology of GABAB receptor ligands.

    PubMed

    Froestl, Wolfgang

    2010-01-01

    This chapter presents new clinical applications of the prototypic GABA(B) receptor agonist baclofen for the treatment of addiction by drugs of abuse, such as alcohol, cocaine, nicotine, morphine, and heroin, a novel baclofen prodrug Arbaclofen placarbil, the GABA(B) receptor agonist AZD3355 (Lesogabaran) currently in Phase 2 clinical trials for the treatment of gastroesophageal reflux disease, and four positive allosteric modulators of GABA(B) receptors (CGP7930, GS39783, NVP-BHF177, and BHFF), which have less propensity for the development of tolerance due to receptor desensitization than classical GABA(B) receptor agonists. All four compounds showed anxiolytic affects. In the presence of positive allosteric modulators the "classical" GABA(B) receptor antagonists CGP35348 and 2-hydroxy-saclofen showed properties of partial GABA(B) receptor agonists. Seven micromolar affinity GABA(B) receptor antagonists, phaclofen; 2-hydroxy-saclofen; CGP's 35348, 36742, 46381, 51176; and SCH50911, are discussed. CGP36742 (SGS742) showed statistically significant improvements of working memory and attention in a Phase 2 clinical trial in mild, but not in moderate Alzheimer patients. Eight nanomolar affinity GABA(B) receptor antagonists are presented (CGP's 52432, 54626, 55845, 56433, 56999, 61334, 62349, and 63360) that were used by pharmacologists for numerous in vitro and in vivo investigations. CGP's 36742, 51176, 55845, and 56433 showed antidepressant effects. Several compounds are also available as radioligands, such as [(3)H]CGP27492, [(3)H]CGP54626, [(3)H]CGP5699, and [(3)H]CGP62349. Three novel fluorescent and three GABA(B) receptor antagonists with very high specific radioactivity (>2,000 Ci/mmol) are presented. [(125)I]CGP64213 and the photoaffinity ligand [(125)I]CGP71872 allowed the identification of GABA(B1a) and GABA(B1b) receptors in the expression cloning work.

  2. Receptor-Mediated Tobacco Toxicity

    PubMed Central

    Arredondo, Juan; Chernyavsky, Alexander I.; Marubio, Lisa M.; Beaudet, Arthur L.; Jolkovsky, David L.; Pinkerton, Kent E.; Grando, Sergei A.

    2005-01-01

    Tobacco is a known cause of oral disease but the mechanism remains elusive. Nicotine (Nic) is a likely culprit of pathobiological effects because it displaces the local cytotransmitter acetylcholine from the nicotinic receptors (nAChRs) expressed by oral keratinocytes (KCs). To gain a mechanistic insight into tobacco-induced morbidity in the oral cavity, we studied effects of exposures to environmental tobacco smoke (ETS) versus equivalent concentration of pure Nic on human and murine KCs. Both ETS and Nic up-regulated expression of cell cycle and apoptosis regulators, differentiation marker filaggrin, and signal transduction factors at both the mRNA and protein levels. These changes could be abolished in cultured human oral KCs transfected with anti-α3 small interfering RNA or treated with the α3β2-preferring antagonist α-conotoxin MII. Functional inactivation of α3-mediated signaling in α3−/− mutant KCs prevented most of the ETS/Nic-dependent changes in gene expression. To determine relevance of the in vitro findings to the in vivo situation, we studied gene expression in oral mucosa of neonatal α3+/+ and α3−/− littermates delivered by heterozygous mice soon after their exposures to ETS or equivalent concentration of pure Nic in drinking water. In addition to reverse transcriptase-polymerase chain reaction and Western blot, the ETS/Nic-dependent alterations in gene expression were also detected by semiquantitative immunofluorescence assay directly in KCs comprising murine oral mucosa. Only wild-type mice consistently developed significant (P < 0.05) changes in the gene expression. These results identified α3β2 nAChR as a major receptor mediating effects of tobacco products on KC gene expression. Real-time polymerase chain reaction demonstrated that in all three model systems the common genes targeted by α3β2-mediated ETS/Nic toxicity were p21, Bcl-2, NF-κB, and STAT-1. The expression of the nAChR subunits α5 and β2 and the muscarinic

  3. Identifying the receptor subtype selectivity of retinoid X and retinoic acid receptors via quantum mechanics.

    PubMed

    Tsuji, Motonori; Shudo, Koichi; Kagechika, Hiroyuki

    2017-03-01

    Understanding and identifying the receptor subtype selectivity of a ligand is an important issue in the field of drug discovery. Using a combination of classical molecular mechanics and quantum mechanical calculations, this report assesses the receptor subtype selectivity for the human retinoid X receptor (hRXR) and retinoic acid receptor (hRAR) ligand-binding domains (LBDs) complexed with retinoid ligands. The calculated energies show good correlation with the experimentally reported binding affinities. The technique proposed here is a promising method as it reveals the origin of the receptor subtype selectivity of selective ligands.

  4. Group I Metabotropic Glutamate Receptor Interacting Proteins: Fine-Tuning Receptor Functions in Health and Disease

    PubMed Central

    Kalinowska, Magdalena; Francesconi, Anna

    2016-01-01

    Group I metabotropic glutamate receptors mediate slow excitatory neurotransmission in the central nervous system and are critical to activity-dependent synaptic plasticity, a cellular substrate of learning and memory. Dysregulated receptor signaling is implicated in neuropsychiatric conditions ranging from neurodevelopmental to neurodegenerative disorders. Importantly, group I metabotropic glutamate receptor signaling functions can be modulated by interacting proteins that mediate receptor trafficking, expression and coupling efficiency to signaling effectors. These interactions afford cell- or pathway-specific modulation to fine-tune receptor function, thus representing a potential target for pharmacological interventions in pathological conditions. PMID:27296642

  5. Evidence of paired M2 muscarinic receptors

    SciTech Connect

    Potter, L.T.; Ballesteros, L.A.; Bichajian, L.H.; Ferrendelli, C.A.; Fisher, A.; Hanchett, H.E.; Zhang, R. )

    1991-02-01

    Binding assays involving various antagonists, including N-(3H) methylscopolamine, (3H)quinuclidinyl benzilate, AFDX-116, pirenzepine, and propylbenzilylcholine mustard, disclosed only a single population of M2 muscarinic receptors in membranes from the rat brainstem (medulla, pons, and colliculi). However, competition curves between N-(3H)methylscopolamine and various agonists, including oxotremorine, cis-dioxolane, and acetylethylcholine mustard, showed approximately equal numbers of guanine nucleotide-sensitive high affinity (H) sites and guanine nucleotide-insensitive low affinity (L) sites. This 50% H phenomenon persisted in different buffers, at different temperatures, after the number of receptors was halved (and, thus, the remaining receptor to guanine nucleotide-binding protein ratio was doubled), after membrane solubilization with digitonin, and when rabbit cardiac membranes were used instead of rat brainstem membranes. Preferential occupation of H sites with acetylethylcholine mustard, and of L sites with quinuclidinyl benzilate or either mustard, yielded residual free receptor populations showing predominantly L and H sites, respectively. Low concentrations of (3H)-oxotremorine-M labeled only H sites, and the Bmax for these sites was 49% of the Bmax found with (3H)quinuclidinyl benzilate plus guanine nucleotide. These and other results are most consistent with the idea that H and L receptor sites exist on separate but dimeric receptor molecules and with the hypothesis that only the H receptors cycle between high and low affinity, depending upon interactions between this receptor molecule and a guanine nucleotide-binding protein.

  6. Fine Structure of APLYSIA Statocyst Receptor Cells

    DTIC Science & Technology

    1974-08-01

    receptors. Cold Spring Harbor Symp. Quant. Biol. 30:133-145, 1965. 5. Flock, A. Sensory transduction in hair cells. In: Handbook of Sensory...and Lundquist, P.-G. Structural basis for directional sen- sitivity in cochlear and vestibular sensory receptors. Cold Spring Harbor Symp

  7. The exportomer: the peroxisomal receptor export machinery.

    PubMed

    Platta, Harald W; Hagen, Stefanie; Erdmann, Ralf

    2013-04-01

    Peroxisomes constitute a dynamic compartment of almost all eukaryotic cells. Depending on environmental changes and cellular demands peroxisomes can acquire diverse metabolic roles. The compartmentalization of peroxisomal matrix enzymes is a prerequisite to carry out their physiologic function. The matrix proteins are synthesized on free ribosomes in the cytosol and are ferried to the peroxisomal membrane by specific soluble receptors. Subsequent to cargo release into the peroxisomal matrix, the receptors are exported back to the cytosol to facilitate further rounds of matrix protein import. This dislocation step is accomplished by a remarkable machinery, which comprises enzymes required for the ubiquitination as well as the ATP-dependent extraction of the receptor from the membrane. Interestingly, receptor ubiquitination and dislocation are the only known energy-dependent steps in the peroxisomal matrix protein import process. The current view is that the export machinery of the receptors might function as molecular motor not only in the dislocation of the receptors but also in the import step of peroxisomal matrix protein by coupling ATP-dependent removal of the peroxisomal import receptor with cargo translocation into the organelle. In this review we will focus on the architecture and function of the peroxisomal receptor export machinery, the peroxisomal exportomer.

  8. Progesterone Receptor Scaffolding Function in Breast Cancer

    DTIC Science & Technology

    2012-10-01

    Progesterone Receptors Mediates Proliferative Signaling in Breast Cancer. Funding period: 2012- 2017 17 CONCLUSION Progesterone receptors (PR) are...National Cancer Institute): R01 CA123763 (formerly R01 DK53825; NIH/National Institute of Diabetes and Digestive and Kidney Diseases). The authors have

  9. The receptor concept: pharmacology's big idea

    PubMed Central

    Rang, H P

    2006-01-01

    Chemical signalling is the main mechanism by which biological function is controlled at all levels, from the single cell to the whole organism. Chemical recognition is the function of receptors, which, in addition to recognising endogenous chemical signals, are also the target of many important experimental and therapeutic drugs. Receptors, therefore, lie at the heart of pharmacology. This article describes the way in which the receptor concept originated early in the 20th century, and evolved through a highly innovative stage of quantitative theory based on chemical kinetics, to the point where receptors were first isolated and later cloned, until we now have a virtually complete catalogue of all the receptors present in the genome. Studies on signal transduction are revealing great complexity in the events linking ligand binding to the physiological or therapeutic response. Though some simple quantitative rules of ‘receptor theory' are still useful, the current emphasis is on unravelling the pathways that link receptors to responses, and it will be some time before we know enough about them to embark on the next phase of ‘receptor theory'. PMID:16402126

  10. Odorant and pheromone receptors in insects.

    PubMed

    Ha, Tal Soo; Smith, Dean P

    2009-01-01

    Since the emergence of the first living cells, survival has hinged on the ability to detect and localize chemicals in the environment. Modern animal species ranging from insects to mammals express large odorant receptor repertoires to detect the structurally diverse array of volatile molecules important for survival. Despite the essential nature of chemical detection, there is surprising diversity in the signaling mechanisms that different species use for odorant detection. In vertebrates, odorant receptors are classical G-protein coupled, seven transmembrane receptors that activate downstream effector enzymes that, in turn, produce second messengers that open ion channels. However, recent work reveals that insects have adopted different strategies to detect volatile chemicals. In Drosophila, the odorant receptors, predicted to have seven transmembrane domains, have reversed membrane topology compared to classical G-protein coupled receptors. Furthermore, insect odorant receptors appear to form odorant-gated ion channels. Pheromone detection in insects is even more unusual, utilizing soluble, extracellular receptors that undergo conformational activation. These alternate olfactory signaling strategies are discussed in terms of receptor design principles.

  11. Teaching Receptor Theory to Biochemistry Undergraduates

    ERIC Educational Resources Information Center

    Benore-Parsons, Marilee; Sufka, Kenneth J.

    2003-01-01

    Receptor:ligand interactions account for numerous reactions critical to biochemistry and molecular biology. While students are typically exposed to some examples, such as hemoglobin binding of oxygen and signal transduction pathways, the topic could easily be expanded. Theory and kinetic analysis, types of receptors, and the experimental assay…

  12. Chemotactic peptide receptor modulation in polymorphonuclear leukocytes

    PubMed Central

    1980-01-01

    The binding of the chemotactic peptide N- formylnorleucylleucylphenylalanine (FNLLP) to its receptor on rabbit polymorphonuclear leukocytes (PMNs) modulates the number of available peptide receptors. Incubation with FNLLP decreases subsequent binding capacity, a phenomenon that has been termed receptor down regulation. Down regulation of the chemotactic peptide receptor is concentration dependent in both the rate and extent of receptor loss. The dose response parallels that of FNLLP binding to the recptor. The time- course is rapid; even at concentrations of FNLLP as low as 3 x 10(-9) M, the new equilibrium concentration of receptors is reached within 15 min. Down regulation is temperature dependent, but does occur even at 4 degrees C. Concomitant with down regulation, some of the peptide becomes irreversibly cell associated. At 4 degrees C, there is a small accumulation of nondissociable peptide that rapidly reaches a plateau. At higher temperatures, accumulation of nondissociable peptide continues after the rceptor number has reached equilibrium, and the amount accumulated can exceed the initial number of receptors by as much as 300%. The dose response of peptide uptake at 37 degrees C reflects that of binding, suggesting that it is receptor mediated. This uptake may occur via a pinocytosis mechanism. Although PMNs have not been considered to be pinocytic, the addition of FNLLP causes a fourfold stimulation of the rate of pinocytosis as measured by the uptake of [3H]sucrose. PMID:7391138

  13. Thermogenic characterization of ghrelin receptor null mice

    USDA-ARS?s Scientific Manuscript database

    Ghrelin is the only known circulating orexigenic hormone that increases food intake and promotes adiposity, and these physiological functions of ghrelin are mediated through its receptor growth hormone secretagogue receptor (GHS-R). Ghrelin/GHS-R signaling plays a crucial role in energy homeostasis....

  14. Opioid receptor trafficking and interaction in nociceptors

    PubMed Central

    Zhang, X; Bao, L; Li, S

    2015-01-01

    Opiate analgesics such as morphine are often used for pain therapy. However, antinociceptive tolerance and dependence may develop with long-term use of these drugs. It was found that μ-opioid receptors can interact with δ-opioid receptors, and morphine antinociceptive tolerance can be reduced by blocking δ-opioid receptors. Recent studies have shown that μ- and δ-opioid receptors are co-expressed in a considerable number of small neurons in the dorsal root ganglion. The interaction of μ-opioid receptors with δ-opioid receptors in the nociceptive afferents is facilitated by the stimulus-induced cell-surface expression of δ-opioid receptors, and contributes to morphine tolerance. Further analysis of the molecular, cellular and neural circuit mechanisms that regulate the trafficking and interaction of opioid receptors and related signalling molecules in the pain pathway would help to elucidate the mechanism of opiate analgesia and improve pain therapy. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2 PMID:24611685

  15. Taste Receptors in Upper Airway Immunity.

    PubMed

    Carey, Ryan M; Lee, Robert J; Cohen, Noam A

    2016-01-01

    Taste receptors are well known for their role in communicating information from the tongue to the brain about nutritional value or potential toxicity of ingested substances. More recently, it has been shown that taste receptors are expressed in other locations throughout the body, including the airway, gastrointestinal tract, brain and pancreas. The roles of some 'extraoral' taste receptors are largely unknown, but emerging research suggests that bitter and sweet taste receptors in the airway are capable of sensing bacteria and modulating innate immunity. This chapter focuses on the role of bitter and sweet taste receptors in human airway innate immunity and their clinical relevance to rhinosinusitis. The bitter taste receptor T2R38 expressed in sinonasal cilia detects bitter bacterial quorum-sensing molecules and activates a nitric oxide-dependent innate immune response; moreover, there are polymorphisms in T2R38 that underlie susceptibility to chronic rhinosinusitis (CRS). Bitter and sweet receptors in sinonasal solitary chemosensory cells control secretion of antimicrobial peptides in the upper airway and may have a profound impact on airway infections in patients with CRS and diabetes. Future research on taste receptors in the airway has enormous potential to expand our understanding of host-pathogen immune interactions and provide novel therapeutic targets.

  16. The delta opioid receptor tool box.

    PubMed

    Vicente-Sanchez, Ana; Segura, Laura; Pradhan, Amynah A

    2016-12-03

    In recent years, the delta opioid receptor has attracted increasing interest as a target for the treatment of chronic pain and emotional disorders. Due to their therapeutic potential, numerous tools have been developed to study the delta opioid receptor from both a molecular and a functional perspective. This review summarizes the most commonly available tools, with an emphasis on their use and limitations. Here, we describe (1) the cell-based assays used to study the delta opioid receptor. (2) The features of several delta opioid receptor ligands, including peptide and non-peptide drugs. (3) The existing approaches to detect delta opioid receptors in fixed tissue, and debates that surround these techniques. (4) Behavioral assays used to study the in vivo effects of delta opioid receptor agonists; including locomotor stimulation and convulsions that are induced by some ligands, but not others. (5) The characterization of genetically modified mice used specifically to study the delta opioid receptor. Overall, this review aims to provide a guideline for the use of these tools with the final goal of increasing our understanding of delta opioid receptor physiology.

  17. [Central effects of ORL1 receptor ligands].

    PubMed

    Maslov, L N; Lishmanov, Iu B; Calo, G; Ma, L

    2003-01-01

    It has been discussed literature data on molecular structure of ORL1 receptor and its interaction with intracellular signal systems and neurotransmitters. Data on chemical structure of ORL1 receptor ligands and their central effects (nociception, locomotion, feeding, cognition) are presented.

  18. [Innate immunity, Toll receptor and sepsis].

    PubMed

    Carrillo-Esper, Raúl

    2003-01-01

    The innate immune response is the first line of defense against infection. Toll-like receptors (TLRs) recognize bacterial lipopolysaccharide and other pathogen-associated molecular patterns (PAMPs). Intracellular signals initiated by interaction between Toll receptors and specific PAMPs results in inflammatory response. Sepsis and septic shock are the result of an exaggerated inflammatory systemic response induced by innate immune dysregulation.

  19. Teaching Receptor Theory to Biochemistry Undergraduates

    ERIC Educational Resources Information Center

    Benore-Parsons, Marilee; Sufka, Kenneth J.

    2003-01-01

    Receptor:ligand interactions account for numerous reactions critical to biochemistry and molecular biology. While students are typically exposed to some examples, such as hemoglobin binding of oxygen and signal transduction pathways, the topic could easily be expanded. Theory and kinetic analysis, types of receptors, and the experimental assay…

  20. Neurosteroids and GABA-A Receptor Function

    PubMed Central

    Wang, Mingde

    2011-01-01

    Neurosteroids represent a class of endogenous steroids that are synthesized in the brain, the adrenals, and the gonads and have potent and selective effects on the GABAA-receptor. 3α-hydroxy A-ring reduced metabolites of progesterone, deoxycorticosterone, and testosterone are positive modulators of GABAA-receptor in a non-genomic manner. Allopregnanolone (3α-OH-5α-pregnan-20-one), 5α-androstane-3α, 17α-diol (Adiol), and 3α5α-tetrahydrodeoxycorticosterone (3α5α-THDOC) enhance the GABA-mediated Cl- currents acting on a site (or sites) distinct from the GABA, benzodiazepine, barbiturate, and picrotoxin binding sites. 3α5α-P and 3α5α-THDOC potentiate synaptic GABAA-receptor function and activate δ-subunit containing extrasynaptic receptors that mediate tonic currents. On the contrary, 3β-OH pregnane steroids and pregnenolone sulfate (PS) are GABAA-receptor antagonists and induce activation-dependent inhibition of the receptor. The activities of neurosteroid are dependent on brain regions and types of neurons. In addition to the slow genomic action of the parent steroids, the non-genomic, and rapid actions of neurosteroids play a significant role in the GABAA-receptor function and shift in mood and memory function. This review describes molecular mechanisms underlying neurosteroid action on the GABAA-receptor, mood changes, and cognitive functions. PMID:22654809

  1. In vivo studies of opiate receptors

    SciTech Connect

    Frost, J.J.; Dannals, R.F.; Duelfer, T.; Burns, H.D.; Ravert, H.T.; Langstroem, B.; Balasubramanian, V.; Wagner, H.N. Jr.

    1984-01-01

    To study opiate receptors noninvasively in vivo using positron emission tomography, techniques for preferentially labeling opiate receptors in vivo can be used. The rate at which receptor-bound ligand clears from the brain in vivo can be predicted by measuring the equilibrium dissociation constant (KD) at 37 degrees C in the presence of 100 mM sodium chloride and 100 microM guanyl-5'-imidodiphosphate, the drug distribution coefficient, and the molecular weight. A suitable ligand for labeling opiate receptors in vivo is diprenorphine, which binds to mu, delta, and kappa receptors with approximately equal affinity in vitro. However, in vivo diprenorphine may bind predominantly to one opiate receptor subtype, possibly the mu receptor. To predict the affinity for binding to the opiate receptor, a Hansch correlation was determined between the 50% inhibitory concentration for a series of halogen-substituted fentanyl analogs and electronic, lipophilic, and steric parameters. Radiochemical methods for the synthesis of carbon-11-labeled diprenorphine and lofentanil are presented.

  2. [Olfactory esthesioneuroblastoma: scintigraphic expression of somatostatin receptors].

    PubMed

    García Vicente, A; García Del Castillo, E; Soriano Castrejón, A; Alonso Farto, J

    1999-10-01

    Esthesioneuroblastoma is an uncommon tumor originating in the upper nasal cavity and constitutes 3% of all intranasal neoplasms. Few references exist about the expression of somatostatin receptors in these tumors. Our case demonstrates a good correlation between the somatostatin receptor scintigraphy and magnetic resonance imaging.

  3. Primary Structure of Nicotinic Acetylcholine Receptor

    DTIC Science & Technology

    1986-08-01

    quantities of starting material (for reviews of receptor, see Popot and Changeux, 1984; Stroud and Finer-Moore, 1985). This work led to the...Cloning of the Acetylcholine Receptor. Cold Spring Harbor Symp. on Quant. Biol. XLVIH: 71-78. 15. Popot , J-L. and Changeux, J-P. (1984) The

  4. Nuclear receptors in transgenerational epigenetic inheritance.

    PubMed

    Ozgyin, Lilla; Erdős, Edina; Bojcsuk, Dóra; Balint, Balint L

    2015-07-01

    Nuclear Receptors are ligand-activated transcription factors that translate information about the lipid environment into specific genetic programs, a property that renders them good candidates to be mediators of rapid adaptation changes of a species. Lipid-based morphogens, endocrine hormones, fatty acids and xenobiotics might act through this class of transcription factors making them regulators able to fine-tune physiological processes. Here we review the basic concepts and current knowledge on the process whereby small molecules act through nuclear receptors and contribute to transgenerational changes. Several molecules shown to cause transgenerational changes like phthalates, BPA, nicotine, tributylin bind and activate nuclear receptors like ERs, androgen receptors, glucocorticoid receptors or PPARγ. A specific subset of observations involving nuclear receptors has focused on the effects of environmental stress or maternal behaviour on the development of transgenerational traits. While these effects do not involve environmental ligands, they change the expression levels of Estrogen and glucocorticoid receptors of the second generation and consequently initiate an altered genetic program in the second generation. In this review we summarize the available literature about the role of nuclear receptors in transgenerational inheritance.

  5. Nuclear receptors and pathogenesis of pancreatic cancer

    PubMed Central

    Polvani, Simone; Tarocchi, Mirko; Tempesti, Sara; Galli, Andrea

    2014-01-01

    Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with a median overall survival time of 5 mo and the five years survival less than 5%, a rate essentially unchanged over the course of the years. A well defined progression model of accumulation of genetic alterations ranging from single point mutations to gross chromosomal abnormalities has been introduced to describe the origin of this disease. However, due to the its subtle nature and concurring events PDAC cure remains elusive. Nuclear receptors (NR) are members of a large superfamily of evolutionarily conserved ligand-regulated DNA-binding transcription factors functionally involved in important cellular functions ranging from regulation of metabolism, to growth and development. Given the nature of their ligands, NR are very tempting drug targets and their pharmacological modulation has been widely exploited for the treatment of metabolic and inflammatory diseases. There are now clear evidences that both classical ligand-activated and orphan NR are involved in the pathogenesis of PDAC from its very early stages; nonetheless many aspects of their role are not fully understood. The purpose of this review is to highlight the striking connections that link peroxisome proliferator activated receptors, retinoic acid receptors, retinoid X receptor, androgen receptor, estrogen receptors and the orphan NR Nur, chicken ovalbumin upstream promoter transcription factor II and the liver receptor homologue-1 receptor to PDAC development, connections that could lead to the identification of novel therapies for this disease. PMID:25232244

  6. Current Research on Opioid Receptor Function

    PubMed Central

    Feng, Yuan; He, Xiaozhou; Yang, Yilin; Chao, Dongman; Lazarus, Lawrence H.; Xia, Ying

    2012-01-01

    The use of opioid analgesics has a long history in clinical settings, although the comprehensive action of opioid receptors is still less understood. Nonetheless, recent studies have generated fresh insights into opioid receptor-mediated functions and their underlying mechanisms. Three major opioid receptors (μ-opioid receptor, MOR; δ-opioid receptor, DOR; and κ-opioid receptor, KOR) have been cloned in many species. Each opioid receptor is functionally sub-classified into several pharmacological subtypes, although, specific gene corresponding each of these receptor subtypes is still unidentified as only a single gene has been isolated for each opioid receptor. In addition to pain modulation and addiction, opioid receptors are widely involved in various physiological and pathophysiological activities, including the regulation of membrane ionic homeostasis, cell proliferation, emotional response, epileptic seizures, immune function, feeding, obesity, respiratory and cardiovascular control as well as some neurodegenerative disorders. In some species, they play an essential role in hibernation. One of the most exciting findings of the past decade is the opioid-receptor, especially DOR, mediated neuroprotection and cardioprotection. The up-regulation of DOR expression and DOR activation increase the neuronal tolerance to hypoxic/ischemic stress. The DOR signal triggers (depending on stress duration and severity) different mechanisms at multiple levels to preserve neuronal survival, including the stabilization of homeostasis and increased pro-survival signaling (e.g., PKC-ERK-Bcl 2) and anti-oxidative capacity. In the heart, PKC and KATP channels are involved in the opioid receptor-mediated cardioprotection. The DOR-mediated neuroprotection and cardioprotection have the potential to significantly alter the clinical pharmacology in terms of prevention and treatment of life-threatening conditions like stroke and myocardial infarction. The main purpose of this article

  7. Steroid Hormone Receptor Signals as Prognosticators for Urothelial Tumor

    PubMed Central

    Ide, Hiroki; Miyamoto, Hiroshi

    2015-01-01

    There is a substantial amount of preclinical or clinical evidence suggesting that steroid hormone receptor-mediated signals play a critical role in urothelial tumorigenesis and tumor progression. These receptors include androgen receptor, estrogen receptors, glucocorticoid receptor, progesterone receptor, vitamin D receptor, retinoid receptors, peroxisome proliferator-activated receptors, and others including orphan receptors. In particular, studies using urothelial cancer tissue specimens have demonstrated that elevated or reduced expression of these receptors as well as alterations of their upstream or downstream pathways correlates with patient outcomes. This review summarizes and discusses available data suggesting that steroid hormone receptors and related signals serve as biomarkers for urothelial carcinoma and are able to predict tumor recurrence or progression. PMID:26770009

  8. The ABA receptors -- we report you decide.

    PubMed

    McCourt, Peter; Creelman, Robert

    2008-10-01

    The plant hormone abscisic acid (ABA) has been implicated in a variety of physiological responses ranging from seed dormancy to stomatal conductance. Recently, three groups have reported the molecular identification of three disparate ABA receptors. Unlike the identification of other hormone receptors, in these three cases high affinity binding to ABA rather than the isolation of ABA insensitive mutants led to these receptor genes. Interestingly, two of the receptors encode genes involved in floral timing and chlorophyll biosynthesis, which are not considered traditional ABA responses. And the third receptor has been clouded in issues of its molecular identity. To clearly determine the roles of these genes in ABA perception it will require placing of these ABA-binding proteins into the rich ABA physiological context that has built up over the years.

  9. Metabotropic Glutamate Receptors: Physiology, Pharmacology, and Disease

    PubMed Central

    Niswender, Colleen M.; Conn, P. Jeffrey

    2010-01-01

    The metabotropic glutamate receptors (mGluRs) are family C G-protein-coupled receptors that participate in the modulation of synaptic transmission and neuronal excitability throughout the central nervous system. The mGluRs bind glutamate within a large extracellular domain and transmit signals through the receptor protein to intracellular signaling partners. A great deal of progress has been made in determining the mechanisms by which mGluRs are activated, proteins with which they interact, and orthosteric and allosteric ligands that can modulate receptor activity. The widespread expression of mGluRs makes these receptors particularly attractive drug targets, and recent studies continue to validate the therapeutic utility of mGluR ligands in neurological and psychiatric disorders such as Alzheimer’s disease, Parkinson’s disease, anxiety, depression, and schizophrenia. PMID:20055706

  10. T cell costimulation by chemokine receptors.

    PubMed

    Molon, Barbara; Gri, Giorgia; Bettella, Monica; Gómez-Moutón, Concepción; Lanzavecchia, Antonio; Martínez-A, Carlos; Mañes, Santos; Viola, Antonella

    2005-05-01

    Signals mediated by chemokine receptors may compete with T cell receptor stop signals and determine the duration of T cell-antigen-presenting cell interactions. Here we show that during T cell stimulation by antigen-presenting cells, T cell chemokine receptors coupled to G(q) and/or G(11) protein were recruited to the immunological synapse by a G(i)-independent mechanism. When chemokine receptors were sequestered at the immunological synapse, T cells became insensitive to chemotactic gradients, formed more stable conjugates and finally responded with enhanced proliferation and cytokine production. We suggest that chemokine receptor trapping at the immunological synapse enhances T cell activation by improving T cell-antigen-presenting cell attraction and impeding the 'distraction' of successfully engaged T cells by other chemokine sources.

  11. GABAA receptor subtype involvement in addictive behaviour.

    PubMed

    Stephens, D N; King, S L; Lambert, J J; Belelli, D; Duka, T

    2017-01-01

    GABAA receptors form the major class of inhibitory neurotransmitter receptors in the mammalian brain. This review sets out to summarize the evidence that variations in genes encoding GABAA receptor isoforms are associated with aspects of addictive behaviour in humans, while animal models of addictive behaviour also implicate certain subtypes of GABAA receptor. In addition to outlining the evidence for the involvement of specific subtypes in addiction, we summarize the particular contributions of these isoforms in control over the functioning of brain circuits, especially the mesolimbic system, and make a first attempt to bring together evidence from several fields to understanding potential involvement of GABAA receptor subtypes in addictive behaviour. While the weight of the published literature is on alcohol dependency, the underlying principles outlined are relevant across a number of different aspects of addictive behaviour. © 2016 John Wiley & Sons Ltd and International Behavioural and Neural Genetics Society.

  12. [Beta-adrenergic receptor blocker poisoning].

    PubMed

    Reingardiene, Dagmara

    2007-01-01

    Beta-adrenergic receptor blocking drugs are used in the treatment of hypertension, angina, myocardial infarction, cardiac dysrhythmia, cardiomyopathy, migraine headache, thyrotoxicosis, and glaucoma. beta-adrenergic receptor blocking agents are competitive antagonist at beta(1), beta(2), or both types of adrenergic receptors. Overdoses of beta-adrenergic receptor blockers are uncommon, but are associated with significant morbidity and mortality. This review article discusses the properties of beta-adrenergic receptor blockers, presents the doses of these drugs causing toxicity and doses, after ingestion of which, referral to an emergency department is recommended. Clinical presentation of overdose (the cardiovascular, neurologic manifestations, pulmonary and other complications), diagnosis, and treatment (gastrointestinal decontamination; the usage of atropine, phosphodiesterase inhibitors, glucagon, insulin; indications for cardiac pacing, extracorporeal procedures of drug removal, etc.) are analyzed. In addition, this article focuses on clinical course and prognosis of beta-blocker overdose.

  13. Ror receptor tyrosine kinases: orphans no more

    PubMed Central

    Green, Jennifer L.; Kuntz, Steven G.; Sternberg, Paul W.

    2015-01-01

    Ror proteins are a conserved family of tyrosine kinase receptors that function in developmental processes, including skeletal and neuronal development, cell movement, and cell polarity. While Ror (receptor tyrosine kinase-like orphan receptor) proteins were originally named because the associated ligand and signaling pathway were unknown, recent studies in multiple species now establish that Ror proteins are Wnt receptors. Depending on the cellular context, Ror proteins can either activate or repress transcription of Wnt target genes and can modulate Wnt signaling by sequestering Wnt ligands. New evidence implicates Ror proteins in planar cell polarity (PCP), an alternative Wnt pathway. Here, we review the progress made in understanding these mysterious proteins and in particular we focus on their function as Wnt receptors. PMID:18848778

  14. Endothelin ETA receptor antagonism in cardiovascular disease.

    PubMed

    Nasser, Suzanne A; El-Mas, Mahmoud M

    2014-08-15

    Since the discovery of the endothelin system in 1988, it has been implicated in numerous physiological and pathological phenomena. In the cardiovascular system, endothelin-1 (ET-1) acts through intracellular pathways of two endothelin receptors (ETA and ETB) located mainly on smooth muscle and endothelial cells to regulate vascular tone and provoke mitogenic and proinflammatory reactions. The endothelin ETA receptor is believed to play a pivotal role in the pathogenesis of several cardiovascular disease including systemic hypertension, pulmonary arterial hypertension (PAH), dilated cardiomyopathy, and diabetic microvascular dysfunction. Growing evidence from recent experimental and clinical studies indicates that the blockade of endothelin receptors, particularly the ETA subtype, grasps promise in the treatment of major cardiovascular pathologies. The simultaneous blockade of endothelin ETB receptors might not be advantageous, leading possibly to vasoconstriction and salt and water retentions. This review summarizes the role of ET-1 in cardiovascular modulation and the therapeutic potential of endothelin receptor antagonism.

  15. Atypical chemokine receptors: from silence to sound.

    PubMed

    Cancellieri, Cinzia; Vacchini, Alessandro; Locati, Massimo; Bonecchi, Raffaella; Borroni, Elena M

    2013-02-01

    ACRs (atypical chemokine receptors) were initially referred to as 'silent' receptors on the basis of a lack of signalling and functional activities that are typically observed with conventional chemokine receptors. Although ACRs do not directly induce cell migration, they indirectly control leucocyte recruitment by shaping chemokine gradients in tissues through degradation, transcytosis or local concentration of their cognate ligands. Recent evidence also suggests that these biological activities are supported by G-protein-independent, β-arrestin-dependent signalling events. In the present article, we review current knowledge on structural and signalling properties of ACRs that are changing our view on this entire class of receptors from silent to endogenous β-arrestin-biased signalling receptors.

  16. Sugars, Sweet Taste Receptors, and Brain Responses

    PubMed Central

    Lee, Allen A.; Owyang, Chung

    2017-01-01

    Sweet taste receptors are composed of a heterodimer of taste 1 receptor member 2 (T1R2) and taste 1 receptor member 3 (T1R3). Accumulating evidence shows that sweet taste receptors are ubiquitous throughout the body, including in the gastrointestinal tract as well as the hypothalamus. These sweet taste receptors are heavily involved in nutrient sensing, monitoring changes in energy stores, and triggering metabolic and behavioral responses to maintain energy balance. Not surprisingly, these pathways are heavily regulated by external and internal factors. Dysfunction in one or more of these pathways may be important in the pathogenesis of common diseases, such as obesity and type 2 diabetes mellitus. PMID:28672790

  17. Novel Identified Receptors on Mast Cells

    PubMed Central

    Migalovich-Sheikhet, Helena; Friedman, Sheli; Mankuta, David; Levi-Schaffer, Francesca

    2012-01-01

    Mast cells (MC) are major participants in the allergic reaction. In addition they possess immunomodulatory roles in the innate and adaptive immune reactions. Their functions are modulated through a number of activating and inhibitory receptors expressed on their surface. This review deals with some of the most recently described receptors, their expression patterns, ligand(s), signal transduction mechanisms, possible cross-talk with other receptors and, last but not least, regulatory functions that the MC can perform based on their receptor expression in health or in disease. Where the receptor role on MC is still not clear, evidences from other hematopoietic cells expressing them is provided as a possible insight for their function on MC. Suggested strategies to modulate these receptors’ activity for the purpose of therapeutic intervention are also discussed. PMID:22876248

  18. Chemical Approaches to Nuclear Receptors in Metabolism

    PubMed Central

    Margolis, Ronald N.; Moore, David D.; Willson, Timothy M.; Guy, R. Kip

    2017-01-01

    The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) sponsored a workshop, “Chemical Approaches to Nuclear Receptors and Metabolism,” in April 2009 to explore how chemical and molecular biology and physiology can be exploited to further our understanding of nuclear receptor structure, function, and role in disease. Signaling cascades involving nuclear receptors are more complex and interrelated than once thought. Nuclear receptors continue to be attractive targets for drug discovery. The overall goal of this workshop was to identify gaps in our understanding of the complexity of ligand activities and begin to address them by (i) increasing the collaboration of investigators from different disciplines, (ii) developing a better understanding of chemical modulation of nuclear receptor action, and (iii) identifying opportunities and roadblocks in the path of translating basic research to discovery of new therapeutics. PMID:19654413

  19. A highly selective receptor for zwitterionic proline.

    PubMed

    Temprano, Álvaro G; Monleón, Laura M; Rubio, Omayra H; Rubio, Luis Simón; Pérez, Asunción B; Sanz, Francisca; Morán, Joaquín R

    2016-01-28

    A chiral chromane receptor has been synthesized which mimics the oxyanion hole of the enzymes. In this receptor H-bonds and cation-π interactions team up to generate an apolar host-guest complex with zwitterionic proline. This complex allows the extraction of only proline to a chloroform phase, while no other natural amino acids are extracted. Due to the chiral nature of the receptor, enantioselective extraction from the aqueous proline solution to a chloroform phase takes place. L-Proline provided an easy method to resolve the receptor racemic mixture, while anisotropic effects, NOE and CD studies revealed the absolute configuration of the receptor. Modelling studies also support the proposed structures. The presence of an oxyanion-hole motif in this structure was corroborated by X-ray diffraction studies.

  20. Novel receptors for bacterial protein toxins.

    PubMed

    Schmidt, Gudula; Papatheodorou, Panagiotis; Aktories, Klaus

    2015-02-01

    While bacterial effectors are often directly introduced into eukaryotic target cells by various types of injection machines, toxins enter the cytosol of host cells from endosomal compartments or after retrograde transport via Golgi from the ER. A first crucial step of toxin-host interaction is receptor binding. Using optimized protocols and new methods novel toxin receptors have been identified, including metalloprotease ADAM 10 for Staphylococcus aureus α-toxin, laminin receptor Lu/BCAM for Escherichia coli cytotoxic necrotizing factor CNF1, lipolysis stimulated lipoprotein receptor (LSR) for Clostridium difficile transferase CDT and low-density lipoprotein receptor-related protein (LRP) 1 for Clostridium perfringens TpeL toxin. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Phenobarbital Meets Phosphorylation of Nuclear Receptors

    PubMed Central

    2017-01-01

    Phenobarbital was the first therapeutic drug to be characterized for its induction of hepatic drug metabolism. Essentially at the same time, cytochrome P450, an enzyme that metabolizes drugs, was discovered. After nearly 50 years of investigation, the molecular target of phenobarbital induction has now been delineated to phosphorylation at threonine 38 of the constitutive androstane receptor (NR1I3), a member of the nuclear receptor superfamily. Determining this mechanism has provided us with the molecular basis to understand drug induction of drug metabolism and disposition. Threonine 38 is conserved as a phosphorylation motif in the majority of both mouse and human nuclear receptors, providing us with an opportunity to integrate diverse functions of nuclear receptors. Here, I review the works and accomplishments of my laboratory at the National Institutes of Health National Institute of Environmental Health Sciences and the future research directions of where our study of the constitutive androstane receptor might take us. PMID:28356313

  2. Complexing receptor pharmacology: modulation of family B G protein-coupled receptor function by RAMPs.

    PubMed

    Sexton, Patrick M; Morfis, Maria; Tilakaratne, Nanda; Hay, Debbie L; Udawela, Madhara; Christopoulos, George; Christopoulos, Arthur

    2006-07-01

    The most well-characterized subgroup of family B G protein-coupledreceptors (GPCRs) comprises receptors for peptide hormones, such as secretin, calcitonin (CT), glucagon, and vasoactive intestinal peptide (VIP). Recent data suggest that many of these receptors can interact with a novel family of GPCR accessory proteins termed receptor activity modifying proteins (RAMPs). RAMP interaction with receptors can lead to a variety of actions that include chaperoning of the receptor protein to the cell surface as is the case for the calcitonin receptor-like receptor (CLR) and the generation of novel receptor phenotypes. RAMP heterodimerization with the CLR and related CT receptor is required for the formation of specific CT gene-related peptide, adrenomedullin (AM) or amylin receptors. More recent work has revealed that the specific RAMP present in a heterodimer may modulate other functions such as receptor internalization and recycling and also the strength of activation of downstream signaling pathways. In this article we review our current state of knowledge of the consequence of RAMP interaction with family B GPCRs.

  3. Gβ promotes pheromone receptor polarization and yeast chemotropism by inhibiting receptor phosphorylation

    PubMed Central

    Ismael, Amber; Tian, Wei; Waszczak, Nicholas; Wang, Xin; Cao, Youfang; Suchkov, Dmitry; Bar, Eli; Metodiev, Metodi V.; Liang, Jie; Arkowitz, Robert; Stone, David E.

    2016-01-01

    Gradient-directed cell migration (chemotaxis) and growth (chemotropism) are universal processes, which are essential to the development and life cycles of all species. Cells use surface receptors to sense the shallow chemical gradients that elicit chemotaxis and chemotropism. Slight asymmetries in receptor activation are amplified by downstream signaling systems, which ultimately induce dynamic reorganization of the cytoskeleton. During the mating response of budding yeast, a model chemotropic system, the pheromone receptor on the plasma membrane polarizes to the side of the cell closest to the stimulus. Although receptor polarization occurs before and independently of actin-cable dependent vesicle delivery (directed secretion), it requires receptor internalization. Phosphorylation of pheromone receptors by yeast casein kinase 1 or 2 (Yck1/2) stimulates their internalization. We showed that the pheromone-responsive Gβγ dimer promotes the polarization of the pheromone receptor by interacting with Yck1/2 and locally inhibiting receptor phosphorylation. We also found that receptor phosphorylation is essential for chemotropism, independent of its role in inducing receptor internalization. A mathematical model supports the idea that the interaction between Gβγ and Yck1/2 results in differential phosphorylation and internalization of the pheromone receptor and accounts for its polarization before the initiation of directed secretion. PMID:27072657

  4. Gβ promotes pheromone receptor polarization and yeast chemotropism by inhibiting receptor phosphorylation.

    PubMed

    Ismael, Amber; Tian, Wei; Waszczak, Nicholas; Wang, Xin; Cao, Youfang; Suchkov, Dmitry; Bar, Eli; Metodiev, Metodi V; Liang, Jie; Arkowitz, Robert A; Stone, David E

    2016-04-12

    Gradient-directed cell migration (chemotaxis) and growth (chemotropism) are processes that are essential to the development and life cycles of all species. Cells use surface receptors to sense the shallow chemical gradients that elicit chemotaxis and chemotropism. Slight asymmetries in receptor activation are amplified by downstream signaling systems, which ultimately induce dynamic reorganization of the cytoskeleton. During the mating response of budding yeast, a model chemotropic system, the pheromone receptors on the plasma membrane polarize to the side of the cell closest to the stimulus. Although receptor polarization occurs before and independently of actin cable-dependent delivery of vesicles to the plasma membrane (directed secretion), it requires receptor internalization. Phosphorylation of pheromone receptors by yeast casein kinase 1 or 2 (Yck1/2) stimulates their internalization. We showed that the pheromone-responsive Gβγ dimer promotes the polarization of the pheromone receptor by interacting with Yck1/2 and locally inhibiting receptor phosphorylation. We also found that receptor phosphorylation is essential for chemotropism, independently of its role in inducing receptor internalization. A mathematical model supports the idea that the interaction between Gβγ and Yck1/2 results in differential phosphorylation and internalization of the pheromone receptor and accounts for its polarization before the initiation of directed secretion.

  5. On the origin of the olfactory receptor family: receptor genes of the jawless fish (Lampetra fluviatilis).

    PubMed

    Freitag, J; Beck, A; Ludwig, G; von Buchholtz, L; Breer, H

    1999-01-21

    In vertebrates, recognition of odorous compounds is based on a large repertoire of receptor subtypes encoded by a multigene family. Towards an understanding of the phylogenetic origin of the vertebrate olfactory receptor family, attempts have been made to identify related receptor genes in the river lampreys (Lampetra fluviatilis), which are descendants of the earliest craniates and living representatives of the most ancient vertebrates. Employing molecular cloning approaches led to the discovery of four genes encoding heptahelical receptors, which share only a rather low overall sequence identity but several of the characteristic structural hallmarks with vertebrate olfactory receptors. Furthermore, in situ hybridization studies demonstrated that the identified genes are expressed in chemosensory cells of the singular lamprey olfactory organ. Molecular phylogenetic analysis confirmed a close relationship of the lamprey receptors to vertebrate olfactory receptors and in addition demonstrated that olfactory genes of the agnathostomes diverged from the gnathostome receptor genes before those split into class I and class II receptors. The data indicate that the lamprey receptors represent the most ancient family of the hitherto identified vertebrate olfactory receptors.

  6. Transmembrane signaling by a chimera of the Escherichia coli aspartate receptor and the human insulin receptor.

    PubMed Central

    Moe, G R; Bollag, G E; Koshland, D E

    1989-01-01

    Since many receptors apparently contain only one or two membrane-spanning segments, their transmembrane topology should be similar. This feature suggests that these receptors share common mechanisms of transmembrane signaling. To test the degree of conservation of signaling properties, a chimeric receptor containing the ligand-binding extracellular domain of the Escherichia coli aspartate chemoreceptor and the cytosolic portion of the human insulin receptor was constructed. This chimeric receptor is active as a tyrosine kinase, and aspartate stimulates its activity. Some interesting differences are noted in the target proteins phosphorylated by the chimera compared to the wild-type insulin receptor. These results indicate that features of the signaling mechanisms used by these diverse receptors are conserved, but that interesting changes in the protein properties are caused by differences in the neighboring domains. Images PMID:2548185

  7. The use of receptor-specific antibodies to study G-protein-coupled receptors.

    PubMed

    Gupta, Achla; Devi, Lakshmi A

    2006-07-01

    The identification of G-protein-coupled receptor (GPCR) cDNAs has facilitated a number of studies characterizing the biochemical properties of the receptor protein. Most of these studies have used antibodies directed against the epitope-tagged receptor expressed in heterologous cells, because of the lack of sensitive and selective antibodies capable of recognizing endogenous receptors in their native state. In order to facilitate studies with endogenous receptors, efforts have been made to generate receptor-type selective, sensitive antibodies that are able to recognize endogenous receptors. In this review, we discuss the strategies as well as the details of the techniques used for the generation of monoclonal and polyclonal antibodies with a focus on family A GPCRs.

  8. Enhanced sensitivity of muscarinic cholinergic receptor associated with dopaminergic receptor subsensitivity after chronic antidepressant treatment

    SciTech Connect

    Koide, T.; Matsushita, H.

    1981-03-09

    The chronic effects of antidepressant treatment on striatal dopaminergic (DA) and muscarinic cholinergic (mACh) receptors of the rat brain have been examined comparatively in this study using /sup 3/H-spiroperidol (/sup 3/H-SPD) and /sup 3/H-quinuclidinyl benzilate (/sup 3/H-QNB) as the respective radioactive ligands. Imipramine and desipramine were used as prototype antidepressants. Although a single administration of imipramine or desipramine did not affect each receptor sensitivity, chronic treatment with each drug caused a supersensitivity of mACh receptor subsequent to DA receptor subsensitivity. Furthermore, it has been suggested that anti-mACh properties of imipramine or desipramine may not necessarily be related to the manifestation of mACh receptor supersensitivity and that sustained DA receptor subsensitivity may play some role in the alterations of mACh receptor sensitivity.

  9. Biology of the TAM Receptors

    PubMed Central

    Lemke, Greg

    2013-01-01

    The TAM receptors—Tyro3, Axl, and Mer—comprise a unique family of receptor tyrosine kinases, in that as a group they play no essential role in embryonic development. Instead, they function as homeostatic regulators in adult tissues and organ systems that are subject to continuous challenge and renewal throughout life. Their regulatory roles are prominent in the mature immune, reproductive, hematopoietic, vascular, and nervous systems. The TAMs and their ligands—Gas6 and Protein S—are essential for the efficient phagocytosis of apoptotic cells and membranes in these tissues; and in the immune system, they act as pleiotropic inhibitors of the innate inflammatory response to pathogens. Deficiencies in TAM signaling are thought to contribute to chronic inflammatory and autoimmune disease in humans, and aberrantly elevated TAM signaling is strongly associated with cancer progression, metastasis, and resistance to targeted therapies. PMID:24186067

  10. Architecture of Eph receptor clusters

    SciTech Connect

    Himanen, Juha P.; Yermekbayeva, Laila; Janes, Peter W.; Walker, John R.; Xu, Kai; Atapattu, Lakmali; Rajashankar, Kanagalaghatta R.; Mensinga, Anneloes; Lackmann, Martin; Nikolov, Dimitar B.; Dhe-Paganon, Sirano

    2010-10-04

    Eph receptor tyrosine kinases and their ephrin ligands regulate cell navigation during normal and oncogenic development. Signaling of Ephs is initiated in a multistep process leading to the assembly of higher-order signaling clusters that set off bidirectional signaling in interacting cells. However, the structural and mechanistic details of this assembly remained undefined. Here we present high-resolution structures of the complete EphA2 ectodomain and complexes with ephrin-A1 and A5 as the base unit of an Eph cluster. The structures reveal an elongated architecture with novel Eph/Eph interactions, both within and outside of the Eph ligand-binding domain, that suggest the molecular mechanism underlying Eph/ephrin clustering. Structure-function analysis, by using site-directed mutagenesis and cell-based signaling assays, confirms the importance of the identified oligomerization interfaces for Eph clustering.

  11. Adenosine receptor targets for pain.

    PubMed

    Sawynok, J

    2016-12-03

    The main focus for the development of adenosine targets as analgesics to date has been A1Rs due to its antinociceptive profile in various preclinical pain models. The usefulness of systemic A1R agonists may be limited by other effects (cardiovascular, motor), but enhanced selectivity for pain might occur with partial agonists, potent and highly selective agonists, or allosteric modulators. A2AR agonists exhibit some peripheral pronociceptive effects, but also act on immune cells to suppress inflammation and on spinal glia to suppress pain signaling and may be useful for inflammatory and neuropathic pain. A2BR agonists exhibit peripheral proinflammatory effects on immune cells, but also spinal antinociceptive effects similar to A2AR agonists. A3Rs are now demonstrated to produce antinociception in several preclinical neuropathic pain models, with mechanistic actions on glial cells, and may be useful for neuropathic pain. Endogenous adenosine levels can be augmented by inhibition of metabolism (via adenosine kinase) or increased generation (via nucleotidases), and these approaches have implications for pain. Endogenous adenosine contributes to antinociception by several pharmacological agents, herbal remedies, acupuncture, transcutaneous electrical nerve stimulation, exercise, joint mobilization, and water immersion via spinal and/or peripheral effects, such that this system appears to constitute a major pain regulatory system. Finally, caffeine inhibits A1-, A2A- and A3Rs with similar potency, and dietary caffeine intake will need attention in trials of: (a) agonists and/or modulators acting at these receptors, (b) some pharmacological and herbal analgesics, and (c) manipulations that enhance endogenous adenosine levels, all of which are inhibited by caffeine and/or A1R antagonists in preclinical studies. All adenosine receptors have effects on spinal glial cells in regulating nociception, and gender differences in the involvement of such cells in chronic

  12. Orexin/hypocretin receptor signalling cascades

    PubMed Central

    Kukkonen, JP; Leonard, CS

    2014-01-01

    Orexin (hypocretin) peptides and their two known G-protein-coupled receptors play essential roles in sleep–wake control and powerfully influence other systems regulating appetite/metabolism, stress and reward. Consequently, drugs that influence signalling by these receptors may provide novel therapeutic opportunities for treating sleep disorders, obesity and addiction. It is therefore critical to understand how these receptors operate, the nature of the signalling cascades they engage and their physiological targets. In this review, we evaluate what is currently known about orexin receptor signalling cascades, while a sister review (Leonard & Kukkonen, this issue) focuses on tissue-specific responses. The evidence suggests that orexin receptor signalling is multifaceted and is substantially more diverse than originally thought. Indeed, orexin receptors are able to couple to members of at least three G-protein families and possibly other proteins, through which they regulate non-selective cation channels, phospholipases, adenylyl cyclase, and protein and lipid kinases. In the central nervous system, orexin receptors produce neuroexcitation by postsynaptic depolarization via activation of non-selective cation channels, inhibition of K+ channels and activation of Na+/Ca2+ exchange, but they also can stimulate the release of neurotransmitters by presynaptic actions and modulate synaptic plasticity. Ca2+ signalling is also prominently influenced by these receptors, both via the classical phospholipase C−Ca2+ release pathway and via Ca2+ influx, mediated by several pathways. Upon longer-lasting stimulation, plastic effects are observed in some cell types, while others, especially cancer cells, are stimulated to die. Thus, orexin receptor signals appear highly tunable, depending on the milieu in which they are operating. Linked ArticlesThis article is part of a themed section on Orexin Receptors. To view the other articles in this section visit http://dx.doi.org/10

  13. Solution assembly of cytokine receptor ectodomain complexes

    SciTech Connect

    Wu, Zining; Ciardelli, T.L.; Johnson, K.W.

    1995-09-01

    For the majority of single transmembrane-spanning cell surface receptors, signal transmission across the lipid bilayer barrier involves several discrete components of molecular recognition. The interaction between ligand and the extracellular segment of its cognate receptor (ectodomain) initiates either homomeric or heteromeric association of receptor subunits. Specific recognition among these subunits may then occur between ectodomain regions, within the membrane by interhelical contact or inside the cell between cytoplasmic domains. Any or all of these interactions may contribute to the stability of the signaling complex. It is the characteristics of ligand binding by the ectodomains of these receptors that controls the heteromeric or homomeric nature and the stoichiometry of the complex. Cytokines and their receptors belong to a growing family of macromolecular systems that exhibit these functional features and share many structural similarities as well. Interleukin-2 is a multifunctional cytokine that represents, perhaps, the most complex example to date of ligand recognition among the hematopoietin receptor family. It is the cooperative binding of IL-2 by all three proteins on the surface of activated T-lymphocytes, however, that ultimately results in crosslinking of the {beta}- and {gamma}-subunits and signaling via association of their cytoplasmic domains. Although the high-affinity IL-2R functions as a heterotrimer, heterodimers of the receptor subunits are also physiologically important. The {alpha}/{beta} heterodimer or {open_quotes}pseudo-high affinity{close_quotes} receptor captures IL-2 as a preformed cell surface complex while the {beta}/{gamma} intermediate affinity site exists, in the absence of the {alpha} subunit, on the majority of natural killer cells. We have begun to study stable complexes of cytokine receptor ectodomains of defined composition and that mimic the ligand binding characteristics of the equivalent cell surface receptor sites.

  14. Nicotine recruits glutamate receptors to postsynaptic sites.

    PubMed

    Duan, Jing-Jing; Lozada, Adrian F; Gou, Chen-Yu; Xu, Jing; Chen, Yuan; Berg, Darwin K

    2015-09-01

    Cholinergic neurons project throughout the nervous system and activate nicotinic receptors to modulate synaptic function in ways that shape higher order brain function. The acute effects of nicotinic signaling on long-term synaptic plasticity have been well-characterized. Less well understood is how chronic exposure to low levels of nicotine, such as those encountered by habitual smokers, can alter neural connections to promote addiction and other lasting behavioral effects. We show here that chronic exposure of hippocampal neurons in culture to low levels of nicotine recruits AMPA and NMDA receptors to the cell surface and sequesters them at postsynaptic sites. The receptors include GluA2-containing AMPA receptors, which are responsible for most of the excitatory postsynaptic current mediated by AMPA receptors on the neurons, and include NMDA receptors containing GluN1 and GluN2B subunits. Moreover, we find that the nicotine treatment also increases expression of the presynaptic component synapsin 1 and arranges it in puncta juxtaposed to the additional AMPA and NMDA receptor puncta, suggestive of increases in synaptic contacts. Consistent with increased synaptic input, we find that the nicotine treatment leads to an increase in the excitatory postsynaptic currents mediated by AMPA and NMDA receptors. Further, the increases skew the ratio of excitatory-to-inhibitory input that the cell receives, and this holds both for pyramidal neurons and inhibitory neurons in the hippocampal CA1 region. The GluN2B-containing NMDA receptor redistribution at synapses is associated with a significant increase in GluN2B phosphorylation at Tyr1472, a site known to prevent GluN2B endocytosis. These results suggest that chronic exposure to low levels of nicotine not only alters functional connections but also is likely to change excitability levels across networks. Further, it may increase the propensity for synaptic plasticity, given the increase in synaptic NMDA receptors.

  15. Stoichiometry of δ subunit containing GABAA receptors

    PubMed Central

    Patel, B; Mortensen, M; Smart, T G

    2014-01-01

    Background and Purpose Although the stoichiometry of the major synaptic αβγ subunit-containing GABAA receptors has consensus support for 2α:2β:1γ, a clear view of the stoichiometry of extrasynaptic receptors containing δ subunits has remained elusive. Here we examine the subunit stoichiometry of recombinant α4β3δ receptors using a reporter mutation and a functional electrophysiological approach. Experimental Approach Using site-directed mutagenesis, we inserted a highly characterized 9′ serine to leucine mutation into the second transmembrane (M2) region of α4, β3 and δ subunits that increases receptor sensitivity to GABA. Whole-cell, GABA-activated currents were recorded from HEK-293 cells co-expressing different combinations of wild-type (WT) and/or mutant α4(L297S), β3(L284S) and δ(L288S) subunits. Key Results Recombinant receptors containing one or more mutant subunits showed increased GABA sensitivity relative to WT receptors by approximately fourfold, independent of the subunit class (α, β or δ) carrying the mutation. GABA dose–response curves of cells co-expressing WT subunits with their respective L9′S mutants exhibited multiple components, with the number of discernible components enabling a subunit stoichiometry of 2α, 2β and 1δ to be deduced for α4β3δ receptors. Varying the cDNA transfection ratio by 10-fold had no significant effect on the number of incorporated δ subunits. Conclusions and Implications Subunit stoichiometry is an important determinant of GABAA receptor function and pharmacology, and δ subunit-containing receptors are important mediators of tonic inhibition in several brain regions. Here we demonstrate a preferred subunit stoichiometry for α4β3δ receptors of 2α, 2β and 1δ. PMID:24206220

  16. Nicotine Recruits Glutamate Receptors to Postsynaptic Sites

    PubMed Central

    Duan, Jing-jing; Lozada, Adrian F.; Gou, Chen-yu; Xu, Jing; Chen, Yuan; Berg, Darwin K.

    2015-01-01

    Cholinergic neurons project throughout the nervous system and activate nicotinic receptors to modulate synaptic function in ways that shape higher order brain function. The acute effects of nicotinic signaling on long-term synaptic plasticity have been well-characterized. Less well understood is how chronic exposure to low levels of nicotine, such as those encountered by habitual smokers, can alter neural connections to promote addiction and other lasting behavioral effects. We show here that chronic exposure of hippocampal neurons in culture to low levels of nicotine recruits AMPA and NMDA receptors to the cell surface and sequesters them at postsynaptic sites. The receptors include GluA2-containing AMPA receptors, which are responsible for most of the excitatory postsynaptic current mediated by AMPA receptors on the neurons, and include NMDA receptors containing GluN1 and GluN2B subunits. Moreover, we find that the nicotine treatment also increases expression of the presynaptic component synapsin 1 and arranges it in puncta juxtaposed to the additional AMPA and NMDA receptor puncta, suggestive of increases in synaptic contacts. Consistent with increased synaptic input, we find that the nicotine treatment leads to an increase in the excitatory postsynaptic currents mediated by AMPA and NMDA receptors. Further, the increases skew the ratio of excitatory-to-inhibitory input the cell receives, and this holds both for pyramidal neurons and inhibitory neurons in the hippocampal CA1 region. The GluN2B-containing NMDA receptor redistribution at synapses is associated with a significant increase in GluN2B phosphorylation at Tyr1472, a site known to prevent GluN2B endocytosis. These results suggest that chronic exposure to low levels of nicotine not only alters functional connections but also is likely to change excitability levels across networks. Further, it may increase the propensity for synaptic plasticity, given the increase in synaptic NMDA receptors. PMID:26365992

  17. Cocaine Inhibits Dopamine D2 Receptor Signaling via Sigma-1-D2 Receptor Heteromers

    PubMed Central

    Navarro, Gemma; Moreno, Estefania; Bonaventura, Jordi; Brugarolas, Marc; Farré, Daniel; Aguinaga, David; Mallol, Josefa; Cortés, Antoni; Casadó, Vicent; Lluís, Carmen; Ferre, Sergi

    2013-01-01

    Under normal conditions the brain maintains a delicate balance between inputs of reward seeking controlled by neurons containing the D1-like family of dopamine receptors and inputs of aversion coming from neurons containing the D2-like family of dopamine receptors. Cocaine is able to subvert these balanced inputs by altering the cell signaling of these two pathways such that D1 reward seeking pathway dominates. Here, we provide an explanation at the cellular and biochemical level how cocaine may achieve this. Exploring the effect of cocaine on dopamine D2 receptors function, we present evidence of σ1 receptor molecular and functional interaction with dopamine D2 receptors. Using biophysical, biochemical, and cell biology approaches, we discovered that D2 receptors (the long isoform of the D2 receptor) can complex with σ1 receptors, a result that is specific to D2 receptors, as D3 and D4 receptors did not form heteromers. We demonstrate that the σ1-D2 receptor heteromers consist of higher order oligomers, are found in mouse striatum and that cocaine, by binding to σ1 -D2 receptor heteromers, inhibits downstream signaling in both cultured cells and in mouse striatum. In contrast, in striatum from σ1 knockout animals these complexes are not found and this inhibition is not seen. Taken together, these data illuminate the mechanism by which the initial exposure to cocaine can inhibit signaling via D2 receptor containing neurons, destabilizing the delicate signaling balance influencing drug seeking that emanates from the D1 and D2 receptor containing neurons in the brain. PMID:23637801

  18. Secretin receptor oligomers form intracellularly during maturation through receptor core domains.

    PubMed

    Lisenbee, Cayle S; Miller, Laurence J

    2006-07-11

    Oligomerization of numerous G protein-coupled receptors has been documented, including the prototypic family B secretin receptor. The clinical significance of oligomerization of this receptor became clear with the recent observation that a misspliced form present in pancreatic cancer could associate with the wild-type receptor and act as a dominant negative inhibitor of its normal growth inhibitory function. Our goal was to explore the molecular mechanism of this interaction using bioluminescence (BRET) and fluorescence (FRET) resonance energy transfer and fluorescence microscopy with a variety of receptor constructs tagged with luciferase or cyan or yellow fluorescent proteins. BRET signals comparable to those obtained from cells coexpressing differentially tagged wild-type receptors were observed for similarly tagged secretin receptors in which all or part of the amino-terminal domain was deleted. As expected, neither of these constructs bound secretin, and only the partially truncated construct sorted to the plasma membrane. Receptors lacking the majority of the carboxyl-terminal domain, including that important for phosphorylation-mediated desensitization, also produced BRET signals above background. These findings suggested that the receptor's membrane-spanning core is responsible for secretin receptor oligomerization. Interestingly, alanine substitutions for a -GxxxG- helix interaction motif in transmembrane segment 7 created nonfunctional receptors that were capable of forming oligomers. Furthermore, treatment of receptor-expressing cells with brefeldin A did not eliminate the BRET signals, and morphologic FRET experiments confirmed the expected subcellular localizations of receptor oligomers. We conclude that secretin receptor oligomerization occurs through -GxxxG- motif-independent interactions of transmembrane segments during the maturation of nascent molecules.

  19. SIGIRR inhibits interleukin-1 receptor- and toll-like receptor 4-mediated signaling through different mechanisms.

    PubMed

    Qin, Jinzhong; Qian, Youcun; Yao, Jianhong; Grace, Cui; Li, Xiaoxia

    2005-07-01

    The Toll-interleukin-1 receptor (TIR) domain-containing orphan receptor SIGIRR (single immunoglobulin interleukin-1 receptor-related protein) acts as a negative regulator of interleukin (IL)-1 and lipopolysaccharide (LPS) signaling. Endogenous SIGIRR transiently interacted with IL-1 receptor and the receptor-proximal signaling components (MyD88, IRAK, and tumor necrosis factor receptor-associated factor 6) upon IL-1 stimulation, indicating that SIGIRR interacts with the IL-1 receptor complex in a ligand-dependent manner. Similar interaction was also observed between SIGIRR and Toll-like receptor 4 receptor complex upon LPS stimulation. To identify the domains of SIGIRR required for its interaction with the Toll-like receptor 4 and IL-1 receptor complexes, several SIGIRR deletion mutants were generated, including DeltaN (lacking the extracellular immunoglobulin (Ig) domain with deletion of amino acids 1-119), DeltaC (lacking the C-terminal domain with deletion of amino acids 313-410), and DeltaTIR (lacking the TIR domain with deletion of amino acids 161-313). Whereas both the extracellular Ig domain and the intracellular TIR domains are important for SIGIRR to inhibit IL-1 signaling, only the TIR domain is necessary for SIGIRR to inhibit LPS signaling. The extracellular Ig domain exerts its inhibitory role in IL-1 signaling by interfering with the heterodimerization of IL-1 receptor and IL-1RAcP, whereas the intracellular TIR domain inhibits both IL-1 and LPS signaling by attenuating the recruitment of receptor-proximal signaling components to the receptor. These results indicate that SIGIRR inhibits IL-1 and LPS signaling pathways through differential mechanisms.

  20. Feedback, receptor clustering, and receptor restriction to single cells yield large Turing spaces for ligand-receptor-based Turing models

    NASA Astrophysics Data System (ADS)

    Kurics, Tamás; Menshykau, Denis; Iber, Dagmar

    2014-08-01

    Turing mechanisms can yield a large variety of patterns from noisy, homogenous initial conditions and have been proposed as patterning mechanism for many developmental processes. However, the molecular components that give rise to Turing patterns have remained elusive, and the small size of the parameter space that permits Turing patterns to emerge makes it difficult to explain how Turing patterns could evolve. We have recently shown that Turing patterns can be obtained with a single ligand if the ligand-receptor interaction is taken into account. Here we show that the general properties of ligand-receptor systems result in very large Turing spaces. Thus, the restriction of receptors to single cells, negative feedbacks, regulatory interactions among different ligand-receptor systems, and the clustering of receptors on the cell surface all greatly enlarge the Turing space. We further show that the feedbacks that occur in the FGF10-SHH network that controls lung branching morphogenesis are sufficient to result in large Turing spaces. We conclude that the cellular restriction of receptors provides a mechanism to sufficiently increase the size of the Turing space to make the evolution of Turing patterns likely. Additional feedbacks may then have further enlarged the Turing space. Given their robustness and flexibility, we propose that receptor-ligand-based Turing mechanisms present a general mechanism for patterning in biology.

  1. G-protein receptor kinase 5 regulates the cannabinoid receptor 2-induced up-regulation of serotonin 2A receptors.

    PubMed

    Franklin, Jade M; Carrasco, Gonzalo A

    2013-05-31

    We have recently reported that cannabinoid agonists can up-regulate and enhance the activity of serotonin 2A (5-HT2A) receptors in the prefrontal cortex (PFCx). Increased expression and activity of cortical 5-HT2A receptors has been associated with neuropsychiatric disorders, such as anxiety and schizophrenia. Here we report that repeated CP55940 exposure selectively up-regulates GRK5 proteins in rat PFCx and in a neuronal cell culture model. We sought to examine the mechanism underlying the regulation of GRK5 and to identify the role of GRK5 in the cannabinoid agonist-induced up-regulation and enhanced activity of 5-HT2A receptors. Interestingly, we found that cannabinoid agonist-induced up-regulation of GRK5 involves CB2 receptors, β-arrestin 2, and ERK1/2 signaling because treatment with CB2 shRNA lentiviral particles, β-arrestin 2 shRNA lentiviral particles, or ERK1/2 inhibitor prevented the cannabinoid agonist-induced up-regulation of GRK5. Most importantly, we found that GRK5 shRNA lentiviral particle treatment prevented the cannabinoid agonist-induced up-regulation and enhanced 5-HT2A receptor-mediated calcium release. Repeated cannabinoid exposure was also associated with enhanced phosphorylation of CB2 receptors and increased interaction between β-arrestin 2 and ERK1/2. These latter phenomena were also significantly inhibited by GRK5 shRNA lentiviral treatment. Our results suggest that sustained activation of CB2 receptors, which up-regulates 5-HT2A receptor signaling, enhances GRK5 expression; the phosphorylation of CB2 receptors; and the β-arrestin 2/ERK interactions. These data could provide a rationale for some of the adverse effects associated with repeated cannabinoid agonist exposure.

  2. Modulators of the nuclear receptor retinoic acid receptor-related orphan receptor-γ (RORγ or RORc).

    PubMed

    Fauber, Benjamin P; Magnuson, Steven

    2014-07-24

    As the biology surrounding the nuclear receptor retinoic acid receptor-related orphan receptor-gamma (RORγ or RORc) continues to evolve, significant effort has been invested in discovering modulators of this potentially important target for the treatment of metabolic and immunological diseases. Several major pharmaceutical and biotechnology companies have disclosed RORc inhibitors or partnered with other players in the field. In this perspective, we discuss both the biology and the underlying structural biology of RORc, and summarize the RORc modulators disclosed in the scientific and patent literature.

  3. Cannabinoid receptor type-1: breaking the dogmas

    PubMed Central

    Busquets Garcia, Arnau; Soria-Gomez, Edgar; Bellocchio, Luigi; Marsicano, Giovanni

    2016-01-01

    The endocannabinoid system (ECS) is abundantly expressed in the brain. This system regulates a plethora of physiological functions and is composed of cannabinoid receptors, their endogenous ligands (endocannabinoids), and the enzymes involved in the metabolism of endocannabinoids. In this review, we highlight the new advances in cannabinoid signaling, focusing on a key component of the ECS, the type-1 cannabinoid receptor (CB 1). In recent years, the development of new imaging and molecular tools has demonstrated that this receptor can be distributed in many cell types (e.g., neuronal or glial cells) and intracellular compartments (e.g., mitochondria). Interestingly, cellular and molecular effects are differentially mediated by CB 1 receptors according to their specific localization (e.g., glutamatergic or GABAergic neurons). Moreover, this receptor is expressed in the periphery, where it can modulate periphery-brain connections. Finally, the better understanding of the CB 1 receptor structure led researchers to propose interesting and new allosteric modulators. Thus, the advances and the new directions of the CB 1 receptor field will provide new insights and better approaches to profit from its interesting therapeutic profile. PMID:27239293

  4. Assessment of estrogen receptor--histone interactions.

    PubMed Central

    Kallos, J; Fasy, T M; Hollander, V P

    1981-01-01

    Several different in vitro binding assays show that the estrogen receptor from rabbit uterus interacts selectively with purified histones from calf thymus. The estrogen receptor binds strongly to histones H2B and H2A, moderately to histones H3 and H4, and poorly to histone H1. In the presence of histones H2B or H2A, the position at which the estrogen receptor focuses in an isoelectric gradient is shifted to a more basic zone. Kinetic experiments show that, if histone H2B is bound to a DNA, the estrogen receptor dissociates more slowly from that DNA. The portion of the estrogen receptor molecule required for binding to histone H2B is relatively stable to tryptic digestion; in contrast, the portion of the receptor molecule responsible for DNA binding is promptly lost during limited tryptic digestion. These in vitro findings suggest that the mechanism by which the estrogen receptor selectively alters gene expression may involve specific contacts with histone molecules. PMID:6942408

  5. The evolution of natural killer cell receptors.

    PubMed

    Carrillo-Bustamante, Paola; Keşmir, Can; de Boer, Rob J

    2016-01-01

    Natural killer (NK) cells are immune cells that play a crucial role against viral infections and tumors. To be tolerant against healthy tissue and simultaneously attack infected cells, the activity of NK cells is tightly regulated by a sophisticated array of germline-encoded activating and inhibiting receptors. The best characterized mechanism of NK cell activation is "missing self" detection, i.e., the recognition of virally infected or transformed cells that reduce their MHC expression to evade cytotoxic T cells. To monitor the expression of MHC-I on target cells, NK cells have monomorphic inhibitory receptors which interact with conserved MHC molecules. However, there are other NK cell receptors (NKRs) encoded by gene families showing a remarkable genetic diversity. Thus, NKR haplotypes contain several genes encoding for receptors with activating and inhibiting signaling, and that vary in gene content and allelic polymorphism. But if missing-self detection can be achieved by a monomorphic NKR system why have these polygenic and polymorphic receptors evolved? Here, we review the expansion of NKR receptor families in different mammal species, and we discuss several hypotheses that possibly underlie the diversification of the NK cell receptor complex, including the evolution of viral decoys, peptide sensitivity, and selective MHC-downregulation.

  6. Action mechanisms of Liver X Receptors

    SciTech Connect

    Gabbi, Chiara; Warner, Margaret; Gustafsson, Jan-Åke

    2014-04-11

    Highlights: • LXRα and LXRβ are ligand-activated nuclear receptors. • They share oxysterol ligands and the same heterodimerization partner, RXR. • LXRs regulate lipid and glucose metabolism, CNS and immune functions, and water transport. - Abstract: The two Liver X Receptors, LXRα and LXRβ, are nuclear receptors belonging to the superfamily of ligand-activated transcription factors. They share more than 78% homology in amino acid sequence, a common profile of oxysterol ligands and the same heterodimerization partner, Retinoid X Receptor. LXRs play crucial roles in several metabolic pathways: lipid metabolism, in particular in preventing cellular cholesterol accumulation; glucose homeostasis; inflammation; central nervous system functions and water transport. As with all nuclear receptors, the transcriptional activity of LXR is the result of an orchestration of numerous cellular factors including ligand bioavailability, presence of corepressors and coactivators and cellular context i.e., what other pathways are activated in the cell at the time the receptor recognizes its ligand. In this mini-review we summarize the factors regulating the transcriptional activity and the mechanisms of action of these two receptors.

  7. 5-HT6 receptors and Alzheimer's disease

    PubMed Central

    2013-01-01

    During the past 20 years, the 5-HT6 receptor has received increasing attention and become a promising target for improving cognition. Several studies with structurally different compounds have shown that not only antagonists but also 5-HT6 receptor agonists improve learning and memory in animal models. A large number of publications describing the development of ligands for this receptor have come to light, and it is now quite evident that 5-HT6 receptors have great pharmaceutical potential in terms of related patents. However, 5-HT6 receptor functionality is much more complex than initially defined. According to the existing data, different cellular pathways may be activated, depending on the drug being used. This article reviews preclinical and clinical evidence of the effects that 5-HT6 receptor compounds have on cognition. In addition, the biochemical and neurochemical mechanisms of action through which 5-HT6 receptor compounds can influence cognition will be described. Overall, several 5-HT6-targeted compounds can reasonably be regarded as powerful drug candidates for the treatment of Alzheimer's disease. PMID:23607787

  8. Estrogen increases renal oxytocin receptor gene expression.

    PubMed

    Ostrowski, N L; Young, W S; Lolait, S J

    1995-04-01

    Estrogens have been implicated in the sodium and fluid imbalances associated with the menstrual cycle and late pregnancy. An estrogen-dependent role for renal oxytocin receptors in fluid homeostasis is suggested by the present findings which demonstrate that estradiol benzoate treatment increases the expression of the oxytocin receptor messenger ribonucleic acid and 125I-OTA binding to oxytocin receptors in the renal cortex and medullary collecting ducts of ovariectomized female rats. Moreover, estradiol induced high levels of oxytocin receptor expression in outer stripe proximal tubules of ovariectomized female and adrenalectomized male rats. Proximal tubule induction was inhibited in a dose-dependent manner by the antiestrogen tamoxifen, but cortical expression of oxytocin receptors in macula densa cells was unaffected by tamoxifen. These data demonstrate cell-specific regulation of oxytocin receptor expression in macula densa and proximal tubule cells, and suggest a important role for these receptors in mediating estrogen-induced alterations in renal fluid dynamics by possibly affecting glomerular filtration and water and solute reabsorption during high estrogen states.

  9. Glucagon receptors: effect of exercise and fasting.

    PubMed

    Lavoie, Carole

    2005-06-01

    One paradox of hormonal regulation during exercise is the maintenance of glucose homeostasis after endurance training despite a lower increase in plasma glucagon. One explanation could be that liver sensitivity to glucagon is increased by endurance training. Glucagon exerts its effect through a 62 KDa glycoprotein receptor, member of the G protein-coupled receptor. To determine whether changes with exercise in glucagon sensitivity occurred at the level of the glucagon receptor (GR), binding characteristics of hepatic glucagon receptors were ascertained in rat purified plasma membranes. Saturation kinetics indicated no difference in the dissociation constant or affinity of glucagon receptor, but a significantly higher glucagon receptor binding density in liver in endurance trained compared to untrained animals. Along with endurance training, it appears that fasting also changes GR binding characteristics. In animals fasting 24 hrs, a significant increase in glucagon receptor density was also reported. Although the exact mechanism remains unknown, there is no doubt that the liver can adapt to physiological stress through modulation of GR binding characteristics to enhance the hepatic glucose production responsiveness to glucagon.

  10. [The cellular receptors of exogenous RNA].

    PubMed

    Reniewicz, Patryk; Zyzak, Joanna; Siednienko, Jakub

    2016-04-21

    One of the key determinants of survival for organisms is proper recognition of exogenous and endogenous nucleic acids. Therefore, high eukaryotes developed a number of receptors that allow for discrimination between friend or foe DNA and RNA. Appearance of exogenous RNA in cytoplasm provides a signal of danger and triggers cellular responses that facilitate eradication of a pathogen. Recognition of exogenous RNA is additionally complicated by fact that large amount of endogenous RNA is present in cytoplasm Thus, number of different receptors, found in eukaryotic cells, is able to recognize that nucleic acid. First group of those receptors consist endosomal Toll like receptors, namely TLR3, TLR7, TLR8 and TLR13. Those receptors recognize RNA released from pathogens that enter the cell by endocytosis. The second group includes cytoplasmic sensors like PKR and the family of RLRs comprised of RIG-I, MDA5 and LGP2. Cytoplasmic receptors recognize RNA from pathogens invading the cell by non-endocytic pathway. In both cases binding of RNA by its receptors results in activation of the signalling cascades that lead to the production of interferon and other cytokines.

  11. Targeting the Fc receptor in autoimmune disease

    PubMed Central

    Li, Xinrui; Kimberly, Robert P

    2014-01-01

    Introduction The Fc receptors and their interaction with immunoglobulin and innate immune opsonins such as CRP are key players in humoral and cellular immune responses. As the effector mechanism for some therapeutic monoclonal antibodies and often a contributor to the pathogenesis and progression of autoimmunity, FcRs are promising targets for treating autoimmune diseases. Areas covered This review discusses the nature of different Fc receptors and the various mechanisms of their involvement in initiating and modulating immunocyte functions and their biological consequences. It describes a range of current strategies in targeting Fc receptors and manipulating their interaction with specific ligands while presenting the pros and cons of these approaches. This review also discusses potential new strategies including regulation of FcR expression and receptor cross-talk. Expert opinion Fc receptors are appealing targets in the treatment of inflammatory autoimmune diseases. However, there are still knowledge limitations and technical challenges, the most important being a better understanding of the individual roles of each of the Fc receptors and enhancement of the specificity in targeting particular cell types and specific Fc receptors. PMID:24521454

  12. Differential expression of somatostatin receptors in medulloblastoma.

    PubMed

    Guyotat, J; Champier, J; Pierre, G S; Jouvet, A; Bret, P; Brisson, C; Belin, M F; Signorelli, F; Montange, M F

    2001-01-01

    Somatostatin receptors have been found on a variety of tumours like neuroendocrine breast or brain tumours. Their detection opens new diagnostic and therapeutic paths. The aim of this work was to investigate their expression in medulloblastomas. Using both techniques, reverse transcriptase-polymerase chain reaction and immunohistochemistry, we analysed mRNA of different subtypes of somatostatin receptors in 15 medulloblastomas and the localisation of the subtype SSTR2 receptor at the cellular level in 13 medulloblastomas. All five subtypes mRNA were variably expressed in each medulloblastoma. The signal obtained after Southern blotting for SSTR2 receptor amplification was the highest as compared to the signal obtained for the other receptor subtypes. Immunostaining for SSTR2A receptor was present in every tumour specimen and was specifically located to the cellular membrane of neoplastic cells. No staining was identified at the level of peritumoral veins. The evidence of predominant expression of SSTR2 receptors in medulloblastomas opens interesting prospects for their diagnosis and therapy.

  13. Transferrin receptor function in hereditary hemochromatosis

    SciTech Connect

    Ward, J.H.; Kushner, J.P.; Ray, F.A.; Kaplan, J.

    1984-02-01

    The binding of /sup 125/I-diferric transferrin to cultured skin fibroblasts and phytohemagglutinin-stimulated lymphocytes was studied in cells derived from individuals homozygous for hereditary hemochromatosis and from normal individuals. Receptors with a high affinity for diferric transferrin were present on all cells. Transferrin receptor number decreased by more than 50% when fibroblasts from both normal and hemochromatotic subjects were maintained in iron-supplemented medium. The number of transferrin receptors expressed by normal and hemochromatotic lymphocytes after mitogen stimulation in iron-supplemented media was less than 50% that of lymphocytes which were mitogen stimulated in standard medium. No change in the affinity of the receptors of diferric transferrin was seen in cells maintained in iron-supplemented medium. Competition experiments in the presence of deferoxamine suggested that the transferrin receptors of fibroblasts and mitogen-stimulated lymphocytes have a 70- to 100-fold higher affinity for diferric transferrin than for apotransferrin. No differences in the properties of transferrin receptors were found between patients with hereditary hemochromatosis and normal individuals. Although transferrin binding decreases when cells are exposed to high levels of iron in the medium, the failure to totally abolish transferrin binding to the receptor suggests that the concentration of diferric transferrin to which cells are exposed may be a major determinant of cellular iron loading in hereditary hemochromatosis.

  14. Synaptic NMDA Receptors Mediate Hypoxic Excitotoxic Death

    PubMed Central

    Wroge, Christine M.; Hogins, Joshua; Eisenman, Larry; Mennerick, Steven

    2012-01-01

    Excessive NMDA receptor activation and excitotoxicity underlies pathology in many neuropsychiatric and neurological disorders, including hypoxia/ischemia. Thus, the development of effective therapeutics for these disorders demands a complete understanding of NMDA receptor (NMDAR) activation during excitotoxic insults. The extrasynaptic NMDAR hypothesis posits that synaptic NMDARs are neurotrophic/neuroprotective and extrasynaptic NMDARs are neurotoxic. In part, the extrasynaptic hypothesis is built on observed selectivity for extrasynaptic receptors of a neuroprotective use-dependent NMDAR channel blocker, memantine. In rat hippocampal neurons we found that a neuroprotective concentration of memantine shows little selectivity for extrasynaptic NMDARs when all receptors are tonically activated by exogenous glutamate. This led us to test the extrasynaptic NMDAR hypothesis using metabolic challenge, where the source of excitotoxic glutamate buildup may be largely synaptic. Three independent approaches suggest strongly that synaptic receptors participate prominently in hypoxic excitotoxicity. First, block of glutamate transporters with a non-substrate antagonist exacerbated rather than prevented damage, consistent with a primarily synaptic source of glutamate. Second, selective, preblock of synaptic NMDARs with a slowly reversible, use-dependent antagonist protected nearly fully against prolonged hypoxic insult. Third, glutamate pyruvate transaminase (GPT), which degrades ambient but not synaptic glutamate, did not protect against hypoxia but protected against exogenous glutamate damage. Together, these results suggest that synaptic NMDARs can mediate excitotoxicity, particularly when the glutamate source is synaptic and when synaptic receptor contributions are rigorously defined. Moreover, the results suggest that in some situations therapeutically targeting extrasynaptic receptors may be inappropriate. PMID:22573696

  15. Dopamine receptors – IUPHAR Review 13

    PubMed Central

    Beaulieu, Jean-Martin; Espinoza, Stefano; Gainetdinov, Raul R

    2015-01-01

    The variety of physiological functions controlled by dopamine in the brain and periphery is mediated by the D1, D2, D3, D4 and D5 dopamine GPCRs. Drugs acting on dopamine receptors are significant tools for the management of several neuropsychiatric disorders including schizophrenia, bipolar disorder, depression and Parkinson's disease. Recent investigations of dopamine receptor signalling have shown that dopamine receptors, apart from their canonical action on cAMP-mediated signalling, can regulate a myriad of cellular responses to fine-tune the expression of dopamine-associated behaviours and functions. Such signalling mechanisms may involve alternate G protein coupling or non-G protein mechanisms involving ion channels, receptor tyrosine kinases or proteins such as β-arrestins that are classically involved in GPCR desensitization. Another level of complexity is the growing appreciation of the physiological roles played by dopamine receptor heteromers. Applications of new in vivo techniques have significantly furthered the understanding of the physiological functions played by dopamine receptors. Here we provide an update of the current knowledge regarding the complex biology, signalling, physiology and pharmacology of dopamine receptors. PMID:25671228

  16. Effects of carbon dioxide on laryngeal receptors

    SciTech Connect

    Anderson, J.W.; Sant'Ambrogio, F.B.; Orani, G.P.; Sant'Ambrogio, G.; Mathew, O.P. )

    1990-02-26

    Carbon dioxide (CO{sub 2}) either stimulates or inhibits laryngeal receptors in the cat. The aim of this study was to correlate the CO{sub 2} response of laryngeal receptors with their response to other known stimuli (i.e. pressure, movement, cold, water and smoke). Single unit action potentials were recorded from fibers in the superior laryngeal nerve of 5 anesthetized, spontaneously breathing dogs together with CO{sub 2} concentration, esophageal and subglottic pressure. Constant streams of warm, humidified air or 10% CO{sub 2} in O{sub 2} were passed through the functionally isolated upper airway for 60 s. Eight of 13 randomly firing or silent receptors were stimulated by CO{sub 2} (from 0.4{plus minus}0.1 to 1.8{plus minus}0.4 imp.s). These non-respiratory-modulated receptors were more strongly stimulated by solutions lacking Cl{sup {minus}} and/or cigarette smoke. Six of 21 respiratory modulated receptors (responding to pressure and/or laryngeal motion) were either inhibited or stimulated by CO{sub 2}. Our results show that no laryngeal receptor responds only to CO{sub 2}. Silent or randomly active receptors were stimulated most often by CO{sub 2} consistent with the reflex effect of CO{sub 2} in the larynx.

  17. Renal tubular vasopressin receptors downregulated by dehydration

    SciTech Connect

    Steiner, M.; Phillips, M.I. )

    1988-03-01

    Receptors for arginine vasopressin (AVP) were characterized in tubular epithelial basolateral membranes (BL membranes) prepared from the kidneys of male Spraque-Dawley rats. Association of ({sup 3}H)AVP was rapid, reversible, and specific. Saturation studies revealed a single class of saturable binding sites with a maximal binding (B{sub max}) of 184 {plus minus} 15 fmol/mg protein. The V{sub 2} receptor antagonist was more than 3,700 times as effective in displacing ({sup 3}H)AVP than was the V{sub 1} antagonist. To investigate the physiological regulation of vasopressin receptors, the effects of elevated levels of circulating AVP on receptor characteristics were studied. Seventy-two-hour water deprivation significantly elevated plasma osmolality and caused an 11.5-fold increase in plasma (AVP). Scatchard analysis revealed a 38% decreased in the number of AVP receptors on the BL membranes from dehydrated animals. The high-affinity binding sites on the BL membranes fit the pharmacological profile for adenylate cyclase-linked vasopressin receptors (V{sub 2}), which mediate the antidiuretic action of the hormone. The authors conclude that physiologically elevated levels of AVP can downregulate vasopressin receptors in the kidney.

  18. 5-HT6 receptors and Alzheimer's disease.

    PubMed

    Ramírez, María Javier

    2013-01-01

    During the past 20 years, the 5-HT6 receptor has received increasing attention and become a promising target for improving cognition. Several studies with structurally different compounds have shown that not only antagonists but also 5-HT6 receptor agonists improve learning and memory in animal models. A large number of publications describing the development of ligands for this receptor have come to light, and it is now quite evident that 5-HT6 receptors have great pharmaceutical potential in terms of related patents. However, 5-HT6 receptor functionality is much more complex than initially defined. According to the existing data, different cellular pathways may be activated, depending on the drug being used. This article reviews preclinical and clinical evidence of the effects that 5-HT6 receptor compounds have on cognition. In addition, the biochemical and neurochemical mechanisms of action through which 5-HT6 receptor compounds can influence cognition will be described. Overall, several 5-HT6-targeted compounds can reasonably be regarded as powerful drug candidates for the treatment of Alzheimer's disease.

  19. [Nucleotide receptors in learning and neuronal plasticity].

    PubMed

    Czajkowski, Rafał

    2014-01-01

    Nucleotide signalling plays an important role in neuronal plasticity and learning. Nucleotides are released at the synaptic terminals and may act pre- and postsynaptically by activating Pland P2 receptors. The A1 receptor, activated tonically by resting concentration of adenosine regulates basal neurotransmission. The A2A receptor is activated by increased adenosine levels and participates in plastic changes. ATP may act as an independent neurotransmitter on the P2X1 receptor, or via P2X3 subtype as a neuromodulator that affects NMDA receptor signalling. The G protein coupled P2Y receptors also evoke neuromodulatory effect on the neuronal plasticity, inhibiting LTD in prefrontal cortex. P2X7 receptor is responsible for communication between astrocytes and for synchronizing their activity. ATP and adenosine released by astrocytes act as neuromodulators both at the release site and heterosynaptically. Taken together, these multiple actions of nucleotides constitute a mechanism regulating homeostatic processes that are necessary for proper brain functioning: synaptic scaling and metaplasticity.

  20. Characterization of a plant glutamate receptor activity.

    PubMed

    Teardo, Enrico; Segalla, Anna; Formentin, Elide; Zanetti, Manuela; Marin, Oriano; Giacometti, Giorgio Mario; Lo Schiavo, Fiorella; Zoratti, Mario; Szabò, Ildikò

    2010-01-01

    Bioinformatic approaches have allowed the identification of twenty genes, grouped into three subfamilies, encoding for homologues of animal ionotropic glutamate receptors (iGLRs) in the Arabidopsis thaliana model plant. Indirect evidence suggests that plant iGLRs function as non-selective cation channels. In the present work we provide biochemical and electrophysiological evidences for the chloroplast localization of glutamate receptor(s) of family 3 (iGLR3) in spinach. A specific antibody, recognizing putative receptors of family 3 locates iGLR3 to the inner envelope membrane of chloroplasts. In planar lipid bilayer experiments, purified inner envelope vesicles from spinach display a cation-selective electrophysiological activity which is inhibited by DNQX (6,7-dinitroquinoxaline-2,3-dione), considered to act as an inhibitor on both animal and plant iGLRs. These results identify for the first time the intracellular localization of plant glutamate receptor(s) and a DNQX-sensitive, glutamate-gated activity at single channel level in native membrane with properties compatible with those predicted for plant glutamate receptors. Copyright 2010 S. Karger AG, Basel.

  1. Lessons from crystal structures of kainate receptors.

    PubMed

    Møllerud, Stine; Frydenvang, Karla; Pickering, Darryl S; Kastrup, Jette Sandholm

    2017-01-01

    Kainate receptors belong to the family of ionotropic glutamate receptors. These receptors assemble from five subunits (GluK1-5) into tetrameric ion channels. Kainate receptors are located at both pre- and postsynaptic membranes in the central nervous system where they contribute to excitatory synaptic transmission and modulate network excitability by regulating neurotransmitter release. Dysfunction of kainate receptors has been implicated in several neurological disorders such as epilepsy, schizophrenia and depression. Here we provide a review on the current understanding of kainate receptor structure and how they bind agonists, antagonists and ions. The first structure of the ligand-binding domain of the GluK1 subunit was reported in 2005, seven years after publication of the crystal structure of a soluble construct of the ligand-binding domain of the AMPA-type subunit GluA2. Today, a full-length structure has been determined of GluK2 by cryo electron microscopy to 7.6 Å resolution as well as 84 high-resolution crystal structures of N-terminal domains and ligand-binding domains, including agonist and antagonist bound structures, modulatory ions and mutations. However, there are still many unanswered questions and challenges in front of us. This article is part of the Special Issue entitled 'Ionotropic glutamate receptors'.

  2. Pharmacological analysis of calcium antagonist receptors

    SciTech Connect

    Reynolds, I.J.

    1987-01-01

    This work focuses on two aspects of the action of calcium antagonist drugs, namely, the interaction of drugs with receptors for verapamil-like calcium antagonists, and the interactions of drugs with voltage-sensitive calcium fluxes in rat brain synaptosomes. From binding studies I have found that the ligand of choice for labeling the verapamil receptor is (-)(/sup 3/H)desmethoxy-verapamil. This drug labels potently, reversibly and stereoselectively two receptors in membranes prepared from rat brain and rabbit skeletal muscle tissues. In equilibrium studies dihydropyridine calcium antagonists interact in a non-competitive fashion, while many non-DHPs are apparently competitive. In-depth kinetic studies in skeletal muscle membranes indicate that the two receptors are linked in a negative heterotropic fashion, and that low-affinity binding of (-) (/sup 3/H)desmethoxy-verapamil may be to the diltiazem receptor. However, these studies were not able to distinguish between the hypothesis that diltiazem binds to spatially separate, allosterically coupled receptors, and the hypothesis that diltiazem binds to a subsite of the verapamil receptor.

  3. Neuromedin B receptors regulate EGF receptor tyrosine phosphorylation in lung cancer cells

    PubMed Central

    Moody, Terry W.; Berna, Marc J.; Mantey, Samuel; Sancho, Veronica; Ridnour, Lisa; Wink, David A.; Chan, Daniel; Giaccone, Giuseppe; Jensen, Robert T.

    2014-01-01

    Neuromedin B (NMB), a member of the bombesin family of peptides, is an autocrine growth factor for many lung cancer cells. The present study investigated the ability of NMB to cause transactivation of the epidermal growth factor (EGF) receptor in lung cancer cells. By Western blot, addition of NMB or related peptides to NCI-H1299 human non-small cell lung cancer (NSCLC) cells, caused phosphorylation of Tyr1068 of the EGF receptor. The signal was amplified using NCI-H1299 cells stably transected with NMB receptors. The transactivation of the EGF receptor or the tyrosine phosphorylation of ERK caused by NMB-like peptides was inhibited by AG1478 or gefitinib (tyrosine kinase inhibitors) and NMB receptor antagonist PD168368 but not the GRP receptor antagonist, BW2258U89. The transactivation of the EGF receptor caused by NMB-like peptides was inhibited by GM6001 (matrix metalloprotease inhibitor), PP2 (Src inhibitor), or transforming growth factor (TGF)α antibody. The transactivation of the EGF receptor and the increase in reactive oxygen species caused by NMB-like peptides was inhibited by N-acetylcysteine (NAC) or Tiron. Gefitinib inhibited the proliferation of NCI-H1299 cells and its sensitivity was increased by the addition of PD168368. The results indicate that the NMB receptor regulates EGF receptor transactivation by a mechanism dependent on Src as well as metalloprotease activation and generation of reactive oxygen species. PMID:20388507

  4. Cell receptors: definition, mechanisms and regulation of receptor-mediated endocytosis.

    PubMed

    Féger, J; Gil-Falgon, S; Lamaze, C

    1994-12-01

    Receptors allow the cells to recognize specific ligands and to receive extracellular messages. They can be classified into five families: 1) receptors for lipidic or lipophilic ligands; 2) the seven transmembrane receptors which mediate their messages by transduction through the activation of G-proteins, effectors and second messengers to amplify the response; 3) receptors which present an enzymatic activity on their transmembrane domains; 4) channel-receptors, transmembrane oligomeric molecules which let ions flow into the cell and 5) receptors which role is to internalize ligands, whatever their various functions. In parallel a concept of membrane plasticity was developed: vesicles are constantly formed from the plasma membrane, addressing complexes of ligand-receptors to specific intracellular compartments. This receptor-mediated endocytosis of ligand plays a critical role in regulating the number of a given receptor at the plasma membrane and in the cellular uptake of nutrients, growth factors and hormones. Many pathways exist for these transports but little is known about the signals which select the ligands or the receptors and direct them to their appropriate intracellular destination.

  5. Adenosine receptor antagonists alter the stability of human epileptic GABAA receptors

    PubMed Central

    Roseti, Cristina; Martinello, Katiuscia; Fucile, Sergio; Piccari, Vanessa; Mascia, Addolorata; Di Gennaro, Giancarlo; Quarato, Pier Paolo; Manfredi, Mario; Esposito, Vincenzo; Cantore, Gianpaolo; Arcella, Antonella; Simonato, Michele; Fredholm, Bertil B.; Limatola, Cristina; Miledi, Ricardo; Eusebi, Fabrizio

    2008-01-01

    We examined how the endogenous anticonvulsant adenosine might influence γ-aminobutyric acid type A (GABAA) receptor stability and which adenosine receptors (ARs) were involved. Upon repetitive activation (GABA 500 μM), GABAA receptors, microtransplanted into Xenopus oocytes from neurosurgically resected epileptic human nervous tissues, exhibited an obvious GABAA-current (IGABA) run-down, which was consistently and significantly reduced by treatment with the nonselective adenosine receptor antagonist CGS15943 (100 nM) or with adenosine deaminase (ADA) (1 units/ml), that inactivates adenosine. It was also found that selective antagonists of A2B (MRS1706, 10 nM) or A3 (MRS1334, 30 nM) receptors reduced IGABA run-down, whereas treatment with the specific A1 receptor antagonist DPCPX (10 nM) was ineffective. The selective A2A receptor antagonist SCH58261 (10 nM) reduced or potentiated IGABA run-down in ≈40% and ≈20% of tested oocytes, respectively. The ADA-resistant, AR agonist 2-chloroadenosine (2-CA) (10 μM) potentiated IGABA run-down but only in ≈20% of tested oocytes. CGS15943 administration again decreased IGABA run-down in patch-clamped neurons from either human or rat neocortex slices. IGABA run-down in pyramidal neurons was equivalent in A1 receptor-deficient and wt neurons but much larger in neurons from A2A receptor-deficient mice, indicating that, in mouse cortex, GABAA-receptor stability is tonically influenced by A2A but not by A1 receptors. IGABA run-down from wt mice was not affected by 2-CA, suggesting maximal ARs activity by endogenous adenosine. Our findings strongly suggest that cortical A2–A3 receptors alter the stability of GABAA receptors, which could offer therapeutic opportunities. PMID:18809912

  6. N-glycosylation of the β2 adrenergic receptor regulates receptor function by modulating dimerization.

    PubMed

    Li, Xiaona; Zhou, Mang; Huang, Wei; Yang, Huaiyu

    2017-07-01

    N-glycosylation is a common post-translational modification of G-protein-coupled receptors (GPCRs). However, it remains unknown how N-glycosylation affects GPCR signaling. β2 adrenergic receptor (β2 AR) has three N-glycosylation sites: Asn6, Asn15 at the N-terminus, and Asn187 at the second extracellular loop (ECL2). Here, we show that deletion of the N-glycan did not affect receptor expression and ligand binding. Deletion of the N-glycan at the N-terminus rather than Asn187 showed decreased effects on isoproterenol-promoted G-protein-dependent signaling, β-arrestin2 recruitment, and receptor internalization. Both N6Q and N15Q showed decreased receptor dimerization, while N187Q did not influence receptor dimerization. As decreased β2 AR homodimer accompanied with reduced efficiency for receptor function, we proposed that the N-glycosylation of β2 AR regulated receptor function by influencing receptor dimerization. To verify this hypothesis, we further paid attention to the residues at the dimerization interface. Studies of Lys60 and Glu338, two residues at the receptor dimerization interface, exhibited that the K60A/E338A showed decreased β2 AR dimerization and its effects on receptor signaling were similar to N6Q and N15Q, which further supported the importance of receptor dimerization for receptor function. This work provides new insights into the relationship among glycosylation, dimerization, and function of GPCRs. Peptide-N-glycosidase F (PNGase F, EC 3.2.2.11); endo-β-N-acetylglucosaminidase A (Endo-A, EC 3.2.1.96). © 2017 Federation of European Biochemical Societies.

  7. Evolution of endothelin receptors in vertebrates.

    PubMed

    Braasch, Ingo; Schartl, Manfred

    2014-12-01

    Endothelin receptors are G protein coupled receptors (GPCRs) of the β-group of rhodopsin receptors that bind to endothelin ligands, which are 21 amino acid long peptides derived from longer prepro-endothelin precursors. The most basal Ednr-like GPCR is found outside vertebrates in the cephalochordate amphioxus, but endothelin ligands are only present among vertebrates, including the lineages of jawless vertebrates (lampreys and hagfishes), cartilaginous vertebrates (sharks, rays, and chimaeras), and bony vertebrates (ray-finned fishes and lobe-finned vertebrates including tetrapods). A bona fide endothelin system is thus a vertebrate-specific innovation with important roles for regulating the cardiovascular system, renal and pulmonary processes, as well as for the development of the vertebrate-specific neural crest cell population and its derivatives. Expectedly, dysregulation of endothelin receptors and the endothelin system leads to a multitude of human diseases. Despite the importance of different types of endothelin receptors for vertebrate development and physiology, current knowledge on endothelin ligand-receptor interactions, on the expression of endothelin receptors and their ligands, and on the functional roles of the endothelin system for embryonic development and in adult vertebrates is very much biased towards amniote vertebrates. Recent analyses from a variety of vertebrate lineages, however, have shown that the endothelin system in lineages such as teleost fish and lampreys is more diverse and is divergent from the mammalian endothelin system. This diversity is mainly based on differential evolution of numerous endothelin system components among vertebrate lineages generated by two rounds of whole genome duplication (three in teleosts) during vertebrate evolution. Here we review current understanding of the evolutionary history of the endothelin receptor family in vertebrates supplemented with surveys on the endothelin receptor gene complement of

  8. Pharmacology of kinin receptors: recent developments.

    PubMed

    Regoli, D; Gobeil, F

    1995-07-01

    Fifteen years after the classification of kinin receptors into B1 and B2, both receptors have been shown to differ between species. New receptor types have been proposed and named B3, B4, and B5. However, it is not established whether different pharmacologic profiles describing B2 receptors in various species are indicative of different receptor types or of different subtypes (species dependent) subserving the same biological functions. To answer these questions, a systematic search of new pharmacologic tools was undertaken to find monoreceptor systems (isolated organs whose responses are contributed by a single receptor) as well as new selective agonists and competitive or noncompetitive antagonists. Classical pharmacologic experiments were performed in isolated organs for quantifying agonist activities in terms of pD2 and antagonist affinities in terms of pA2. Competitivity of antagonists was established from Schild plots. Results obtained in tissues from rabbits or guinea pigs indicate the existence of two different pharmacological entities, well characterized by selective agonists and competitive antagonists. In vivo experiments performed on anesthetized rabbits and guinea pigs have confirmed the B2 receptor heterogeneity between the two species. Correlations have been established between data obtained in rabbit and guinea pig tissues (biological assays) and in human receptors raised by genic transfection in Chinese hamster ovary (CHO) cells. A good correlation has been found between the IC50 values of kinins and derivatives to displace [3H]bradykinin from the membranes of CHO cells containing the human receptor and the pD2 or pA4 values of the same compounds in the rabbit jugular vein.

  9. Serotonin receptors involved in antidepressant effects.

    PubMed

    Artigas, Francesc

    2013-01-01

    The neurotransmitter serotonin (5-hdroxytryptamine; 5-HT) has been implicated in the pathophysiology and treatment of major depression since the serendipitous discovery of antidepressant drugs in the 1950s. However, despite the generalised use of serotonin-enhancing drugs, such as the selective serotonin reuptake inhibitors (SSRIs) and the dual serotonin and norepinephrine reuptake inhibitors (SNRIs), the exact neurobiological mechanisms involved in the therapeutic action of these drugs are poorly understood. Better knowledge of these mechanisms may help to identify new therapeutic targets and to overcome the two main limitations of current treatments: reduced efficacy and slowness of action. Here I review the preclinical and clinical evidence supporting the involvement of different 5-HT receptors in the therapeutic action of antidepressant drugs. Presynaptic 5-HT(1A) and 5-HT(1B) autoreceptors play a major detrimental role in antidepressant treatments, as their activation by the excess of the active (extracellular) 5-HT fraction produced by serotonin transporter (SERT) blockade reduces presynaptic serotonergic function. Conversely, stimulation of postsynaptic 5-HT(1A) receptors in corticolimbic networks appears beneficial for the antidepressant action. The 5-HT(2) receptor family is also involved as 5-HT(2A/2C) receptor blockade improves the antidepressant action of SSRIs, and recent data suggest that 5-HT(2B) receptor activation enhances serotonergic activity. Less is known from the rest of postsynaptic 5-HT receptors. However, 5-HT(3) receptor blockade augments the 5-HT increase evoked by SERT inhibition, and 5-HT(4) receptor activation may have antidepressant effects on its own. Finally, blockade of 5-HT(6) and 5-HT(7) receptors appears also to augment the antidepressant effects of SERT inhibition.

  10. Regulating hippocampal hyperexcitability through GABAB Receptors

    PubMed Central

    Lang, Min; Moradi‐Chameh, Homeira; Zahid, Tariq; Gane, Jonathan; Wu, Chiping; Valiante, Taufik; Zhang, Liang

    2014-01-01

    Abstract Disturbances of GABAergic inhibition are a major cause of epileptic seizures. GABA exerts its actions via ionotropic GABAA receptors and metabotropic G protein‐coupled GABAB receptors. Malfunction of GABAA inhibition has long been recognized in seizure genesis but the role of GABAB receptors in controlling seizure activity is still not well understood. Here, we examined the anticonvulsive, or inhibitory effects, of GABAB receptors in a mouse model of hippocampal kindling as well as mouse hippocampal slices through the use of GS 39783, a positive allosteric GABAB receptor modulator, and CGP 55845, a selective GABAB receptor antagonist. When administered via intraperitoneal injections in kindled mice, GS 39783 (5 mg/kg) did not attenuate hippocampal EEG discharges, but did reduce aberrant hippocampal spikes, whereas CGP 55845 (10 mg/kg) prolonged hippocampal discharges and increased spike incidences. When examined in hippocampal slices, neither GS 39783 at 5 μmol/L nor the GABAB receptor agonist baclofen at 0.1 μmol/L alone significantly altered repetitive excitatory field potentials, but GS 39783 and baclofen together reversibly abolished these field potentials. In contrast, CGP 55845 at 1 μmol/L facilitated induction and incidence of these field potentials. In addition, CGP 55845 attenuated the paired pulse depression of CA3 population spikes and increased the frequency of EPSCs in individual CA3 pyramidal neurons. Collectively, these data suggest that GABABB receptors regulate hippocampal hyperexcitability by inhibiting CA3 glutamatergic synapses. We postulate that positive allosteric modulation of GABAB receptors may be effective in reducing seizure‐related hyperexcitability. PMID:24771688

  11. Role of adenosine receptors in caffeine tolerance

    SciTech Connect

    Holtzman, S.G.; Mante, S.; Minneman, K.P. )

    1991-01-01

    Caffeine is a competitive antagonist at adenosine receptors. Receptor up-regulation during chronic drug treatment has been proposed to be the mechanism of tolerance to the behavioral stimulant effects of caffeine. This study reassessed the role of adenosine receptors in caffeine tolerance. Separate groups of rats were given scheduled access to drinking bottles containing plain tap water or a 0.1% solution of caffeine. Daily drug intake averaged 60-75 mg/kg and resulted in complete tolerance to caffeine-induced stimulation of locomotor activity, which could not be surmounted by increasing the dose of caffeine. 5'-N-ethylcarboxamidoadenosine (0.001-1.0 mg/kg) dose dependently decreased the locomotor activity of caffeine-tolerant rats and their water-treated controls but was 8-fold more potent in the latter group. Caffeine (1.0-10 mg/kg) injected concurrently with 5-N-ethylcarboxamidoadenosine antagonized the decreases in locomotor activity comparably in both groups. Apparent pA2 values for tolerant and control rats also were comparable: 5.05 and 5.11. Thus, the adenosine-antagonist activity of caffeine was undiminished in tolerant rats. The effects of chronic caffeine administration on parameters of adenosine receptor binding and function were measured in cerebral cortex. There were no differences between brain tissue from control and caffeine-treated rats in number and affinity of adenosine binding sites or in receptor-mediated increases (A2 adenosine receptor) and decreases (A1 adenosine receptor) in cAMP accumulation. These results are consistent with theoretical arguments that changes in receptor density should not affect the potency of a competitive antagonist. Experimental evidence and theoretical considerations indicate that up-regulation of adenosine receptors is not the mechanism of tolerance to caffeine-induced stimulation of locomotor activity.

  12. Drug interactions at GABA(A) receptors.

    PubMed

    Korpi, Esa R; Gründer, Gerhard; Lüddens, Hartmut

    2002-06-01

    Neurotransmitter receptor systems have been the focus of intensive pharmacological research for more than 20 years for basic and applied scientific reasons, but only recently has there been a better understanding of their key features. One of these systems includes the type A receptor for the gamma-aminobutyric acid (GABA), which forms an integral anion channel from a pentameric subunit assembly and mediates most of the fast inhibitory neurotransmission in the adult vertebrate central nervous system. Up to now, depending on the definition, 16-19 mammalian subunits have been cloned and localized on different genes. Their assembly into proteins in a poorly defined stoichiometry forms the basis of functional and pharmacological GABA(A) receptor diversity, i.e. the receptor subtypes. The latter has been well documented in autoradiographic studies using ligands that label some of the receptors' various binding sites, corroborated by recombinant expression studies using the same tools. Significantly less heterogeneity has been found at the physiological level in native receptors, where the subunit combinations have been difficult to dissect. This review focuses on the characteristics, use and usefulness of various ligands and their binding sites to probe GABA(A) receptor properties and to gain insight into the biological function from fish to man and into evolutionary conserved GABA(A) receptor heterogeneity. We also summarize the properties of the novel mouse models created for the study of various brain functions and review the state-of-the-art imaging of brain GABA(A) receptors in various human neuropsychiatric conditions. The data indicate that the present ligands are only partly satisfactory tools and further ligands with subtype-selective properties are needed for imaging purposes and for confirming the behavioral and functional results of the studies presently carried out in gene-targeted mice with other species, including man.

  13. Orexin/hypocretin receptor signalling cascades.

    PubMed

    Kukkonen, J P; Leonard, C S

    2014-01-01

    Orexin (hypocretin) peptides and their two known G-protein-coupled receptors play essential roles in sleep-wake control and powerfully influence other systems regulating appetite/metabolism, stress and reward. Consequently, drugs that influence signalling by these receptors may provide novel therapeutic opportunities for treating sleep disorders, obesity and addiction. It is therefore critical to understand how these receptors operate, the nature of the signalling cascades they engage and their physiological targets. In this review, we evaluate what is currently known about orexin receptor signalling cascades, while a sister review (Leonard & Kukkonen, this issue) focuses on tissue-specific responses. The evidence suggests that orexin receptor signalling is multifaceted and is substantially more diverse than originally thought. Indeed, orexin receptors are able to couple to members of at least three G-protein families and possibly other proteins, through which they regulate non-selective cation channels, phospholipases, adenylyl cyclase, and protein and lipid kinases. In the central nervous system, orexin receptors produce neuroexcitation by postsynaptic depolarization via activation of non-selective cation channels, inhibition of K⁺ channels and activation of Na⁺/Ca²⁺ exchange, but they also can stimulate the release of neurotransmitters by presynaptic actions and modulate synaptic plasticity. Ca²⁺ signalling is also prominently influenced by these receptors, both via the classical phospholipase C-Ca²⁺ release pathway and via Ca²⁺ influx, mediated by several pathways. Upon longer-lasting stimulation, plastic effects are observed in some cell types, while others, especially cancer cells, are stimulated to die. Thus, orexin receptor signals appear highly tunable, depending on the milieu in which they are operating.

  14. Pharmacological and autoradiographic characterization of sigma receptors

    SciTech Connect

    Largent, B.L.

    1986-01-01

    The existence of three types of opioid receptors - ..mu.., kappa, and sigma - was postulated to explain the effects of different opioids in the chronic spinal dog. Sigma receptors, named for the prototypic agonist SKF 10,047 (N-allylnormetazocine), were suggested to mediate the psychotomimetic-like effects of SKF 10,047 in the dog. 3-(3-Hydroxyphenyl)-N-(1-propyl)piperidine (3-PPP) has been proposed as a selective dopamine autoreceptor agonist. However, the drug specificity of (+)(/sup 3/H)3-PPP binding in brain is identical to that of sigma receptor binding sites which may mediate psychotomimetic effects of some opioids. Pharmacological and autoradiographic analyses reveal that (+)(/sup 3/H)SKF 10,047, the prototypic sigma agonist, labels two sites in brain. The drug specificity of the high affinity site for (+)(/sup 3/H)SKF 10,047 resembles that of putative sigma receptors labeled with (+)(/sup 3/H)3-PPP, being potently inhibited by (+)3-PPP, haloperidol, and (+/-)pentazocine, and demonstrating stereoselectivity for the (+) isomer of SKF 10,047. Autoradiographic localizations of high affinity (+)(/sup 3/H)SKF 10,047 binding sites closely resemble those of (+)(/sup 3/H)3-PPP labeled sites with high levels of binding in the hippocampal pyramidal cell layer, hypothalamus, and pontine and cranial nerve nuclei. Thus, putative sigma receptors and PCP receptors represent distinct receptor populations in brain. This proposal is supported by the presence of sigma binding sites - and absence of PCP receptors - on NCB-20 cell membranes, a hybrid neurotumor cell line that provides a model system for the physiological and biochemical study of sigma receptors.

  15. Revisiting AMPA receptors as an antiepileptic drug target.

    PubMed

    Rogawski, Michael A

    2011-03-01

    In the 1990s there was intense interest in ionotropic glutamate receptors as therapeutic targets for diverse neurological disorders, including epilepsy. NMDA receptors were thought to play a key role in the generation of seizures, leading to clinical studies of NMDA receptor blocking drugs in epilepsy. Disappointing results dampened enthusiasm for ionotropic glutamate receptors as a therapeutic target. Eventually it became appreciated that another type of ionotropic glutamate receptor, the AMPA receptor, is actually the predominant mediator of excitatory neurotransmission in the central nervous system and moreover that AMPA receptors are critical to the generation and spread of epileptic activity. As drugs became available that selectively target AMPA receptors, it was possible to demonstrate that AMPA receptor antagonists have powerful antiseizure activity in in vitro and in vivo models. A decade later, promising clinical studies with AMPA receptor antagonists, including the potent noncompetitive antagonist perampanel, are once again focusing attention on AMPA receptors as a drug target for epilepsy therapy.

  16. Direct imaging of lateral movements of AMPA receptors inside synapses

    PubMed Central

    Tardin, Catherine; Cognet, Laurent; Bats, Cécile; Lounis, Brahim; Choquet, Daniel

    2003-01-01

    Trafficking of AMPA receptors in and out of synapses is crucial for synaptic plasticity. Previous studies have focused on the role of endo/exocytosis processes or that of lateral diffusion of extra-synaptic receptors. We have now directly imaged AMPAR movements inside and outside synapses of live neurons using single- molecule fluorescence microscopy. Inside individual synapses, we found immobile and mobile receptors, which display restricted diffusion. Extra-synaptic receptors display free diffusion. Receptors could also exchange between these membrane compartments through lateral diffusion. Glutamate application increased both receptor mobility inside synapses and the fraction of mobile receptors present in a juxtasynaptic region. Block of inhibitory transmission to favor excitatory synaptic activity induced a transient increase in the fraction of mobile receptors and a decrease in the proportion of juxtasynaptic receptors. Altogether, our data show that rapid exchange of receptors between a synaptic and extra-synaptic localization occurs through regulation of receptor diffusion inside synapses. PMID:12970178

  17. Agonists and antagonists for P2 receptors

    PubMed Central

    Jacobson, Kenneth A.; Costanzi, Stefano; Joshi, Bhalchandra V.; Besada, Pedro; Shin, Dae Hong; Ko, Hyojin; Ivanov, Andrei A.; Mamedova, Liaman

    2015-01-01

    Recent work has identified nucleotide agonists selective for P2Y1, P2Y2 and P2Y6 receptors and nucleotide antagonists selective for P2Y1, P2Y12 and P2X1 receptors. Selective non-nucleotide antagonists have been reported for P2Y1, P2Y2, P2Y6, P2Y12, P2Y13, P2X2/3/P2X3 and P2X7 receptors. For example, the dinucleotide INS 37217 (Up4dC) potently activates the P2Y2 receptor, and the non-nucleotide antagonist A-317491 is selective for P2X2/3/P2X3 receptors. Nucleotide analogues in which the ribose moiety is substituted by a variety of novel ring systems, including conformation-ally locked moieties, have been synthesized as ligands for P2Y receptors. The focus on conformational factors of the ribose-like moiety allows the inclusion of general modifications that lead to enhanced potency and selectivity. At P2Y1,2,4,11 receptors, there is a preference for the North conformation as indicated with (N)-methanocarba analogues. The P2Y1 antagonist MRS2500 inhibited ADP-induced human platelet aggregation with an IC50 of 0.95 nM. MRS2365, an (N)-methanocarba analogue of 2-MeSADP, displayed potency (EC50) of 0.4 nM at the P2Y1 receptor, with >10 000-fold selectivity in comparison to P2Y12 and P2Y13 receptors. At P2Y6 receptors there is a dramatic preference for the South conformation. Three-dimensional structures of P2Y receptors have been deduced from structure activity relationships (SAR), mutagenesis and modelling studies. Detailed three-dimensional structures of P2X receptors have not yet been proposed. PMID:16805423

  18. Regulation of Plasma Cholesterol by Lipoprotein Receptors

    NASA Astrophysics Data System (ADS)

    Brown, Michael S.; Kovanen, Petri T.; Goldstein, Joseph L.

    1981-05-01

    The lipoprotein transport system holds the key to understanding the mechanisms by which genes, diet, and hormones interact to regulate the plasma cholesterol level in man. Crucial components of this system are lipoprotein receptors in the liver and extrahepatic tissues that mediate the uptake and degradation of cholesterol-carrying lipoproteins. The number of lipoprotein receptors, and hence the efficiency of disposal of plasma cholesterol, can be increased by cholesterol-lowering drugs. Regulation of lipoprotein receptors can be exploited pharmacologically in the therapy of hypercholesterolemia and atherosclerosis in man.

  19. Muscarinic Receptor Antagonists: Effects on Pulmonary Function

    PubMed Central

    Buels, Kalmia S.

    2014-01-01

    In healthy lungs, muscarinic receptors control smooth muscle tone, mucus secretion, vasodilation, and inflammation. In chronic obstructive pulmonary disease (COPD) and asthma, cholinergic mechanisms contribute to increased bronchoconstriction and mucus secretion that limit airflow. This chapter reviews neuronal and nonneuronal sources of acetylcholine in the lung and the expression and role of M1, M2, and M3 muscarinic receptor subtypes in lung physiology. It also discusses the evidence for and against the role of parasympathetic nerves in asthma, and the current use and therapeutic potential of muscarinic receptor antagonists in COPD and asthma. PMID:22222705

  20. Ghrelin Receptors in Non-Mammalian Vertebrates

    PubMed Central

    Kaiya, Hiroyuki; Kangawa, Kenji; Miyazato, Mikiya

    2012-01-01

    The growth hormone secretagogue-receptor (GHS-R) was discovered in humans and pigs in 1996. The endogenous ligand, ghrelin, was discovered 3 years later, in 1999, and our understanding of the physiological significance of the ghrelin system in vertebrates has grown steadily since then. Although the ghrelin system in non-mammalian vertebrates is a subject of great interest, protein sequence data for the receptor in non-mammalian vertebrates has been limited until recently, and related biological information has not been well organized. In this review, we summarize current information related to the ghrelin receptor in non-mammalian vertebrates. PMID:23882259

  1. Expression of Plant Receptor Kinases in Yeast.

    PubMed

    Barberini, María Laura; Muschietti, Jorge P

    2017-01-01

    The budding yeast Saccharomyces cerevisiae is a useful system to express recombinant proteins and analyze protein-protein interaction. Membrane-spanning proteins like plant receptor kinases find their way to the plasma membrane when expressed in yeast and seem to retain their structure and function. Here, we describe a general yeast DNA transformation procedure based on lithium acetate, salmon sperm DNA, and polyethylene glycol used to express recombinant proteins. Yeast cells expressing plant receptor kinases can be used for in vivo and in vitro studies of receptor function.

  2. Receptors useful for gas phase chemical sensing

    DOEpatents

    Jaworski, Justyn W; Lee, Seung-Wuk; Majumdar, Arunava; Raorane, Digvijay A

    2015-02-17

    The invention provides for a receptor, capable of binding to a target molecule, linked to a hygroscopic polymer or hydrogel; and the use of this receptor in a device for detecting the target molecule in a gaseous and/or liquid phase. The invention also provides for a method for detecting the presence of a target molecule in the gas phase using the device. In particular, the receptor can be a peptide capable of binding a 2,4,6-trinitrotoluene (TNT) or 2,4,-dinitrotoluene (DNT).

  3. AMPA receptor cycling in the synapse.

    PubMed

    Contractor, Anis; Heinemann, Stephen F

    2004-10-19

    Ionotropic glutamate receptors (GluRs) are involved in mediating signaling in response to synaptic activity. In addition to converting the chemical signal released from the presynaptic terminal to an electrical response in the postsynaptic neuron, these receptors are critically involved in activity-dependent, long-term changes in synaptic strength and, therefore, are central to processes thought to underlie learning and memory. The animation provides an interactive illustration of how activity-dependent changes in the glutamate receptor composition and numbers at the synapse may contribute to synaptic plasticity.

  4. Agonists at the δ-opioid receptor modify the binding of µ-receptor agonists to the µ–δ receptor hetero-oligomer

    PubMed Central

    Kabli, N; Martin, N; Fan, T; Nguyen, T; Hasbi, A; Balboni, G; O'Dowd, BF; George, SR

    2010-01-01

    BACKGROUND AND PURPOSE µ- and δ-opioid receptors form heteromeric complexes with unique ligand binding and G protein-coupling profiles linked to G protein α z-subunit (Gαz) activation. However, the mechanism of action of agonists and their regulation of the µ–δ receptor heteromer are not well understood. EXPERIMENTAL APPROACH Competition radioligand binding, cell surface receptor internalization in intact cells, confocal microscopy and receptor immunofluorescence techniques were employed to study the regulation of the µ–δ receptor heteromer in heterologous cells with and without agonist exposure. KEY RESULTS Gαz enhanced affinity of some agonists at µ–δ receptor heteromers, independent of agonist chemical structure. δ-Opioid agonists displaced µ-agonist binding with high affinity from µ–δ heteromers, but not µ receptor homomers, suggestive of δ-agonists occupying a novel µ-receptor ligand binding pocket within the heteromers. Also, δ-agonists induced internalization of µ-opioid receptors in cells co-expressing µ- and δ-receptors, but not those expressing µ-receptors alone, indicative of µ–δ heteromer internalization. This dose-dependent, Pertussis toxin-resistant and clathrin- and dynamin-dependent effect required agonist occupancy of both µ- and δ-opioid receptors. In contrast to µ-receptor homomers, agonist-induced internalization of µ–δ heteromers persisted following chronic morphine exposure. CONCLUSIONS AND IMPLICATIONS The µ–δ receptor heteromer may contain a novel δ-agonist-detected, high-affinity, µ-receptor ligand binding pocket and is regulated differently from the µ-receptor homomer following chronic morphine exposure. Occupancy of both µ- and δ-receptor binding pockets is required for δ-agonist-induced endocytosis of µ–δ receptor heteromers. δ-Opioid agonists target µ–δ receptor heteromers, and thus have a broader pharmacological specificity than previously identified. PMID:20977461

  5. Hypothyroidism affects D2 receptor-mediated breathing without altering D2 receptor expression.

    PubMed

    Schlenker, Evelyn H; Del Rio, Rodrigo; Schultz, Harold D

    2014-03-01

    Bromocriptine depressed ventilation in air and D2 receptor expression in the nucleus tractus solitaries (NTS) in male hypothyroid hamsters. Here we postulated that in age-matched hypothyroid female hamsters, the pattern of D2 receptor modulation of breathing and D2 receptor expression would differ from those reported in hypothyroid males. In females hypothyroidism did not affect D2 receptor protein levels in the NTS, carotid bodies or striatum. Bromocriptine, but not carmoxirole (a peripheral D2 receptor agonist), increased oxygen consumption and body temperature in awake air-exposed hypothyroid female hamsters and stimulated their ventilation before and following exposure to hypoxia. Carmoxirole depressed frequency of breathing in euthyroid hamsters prior to, during and following hypoxia exposures and stimulated it in the hypothyroid hamsters following hypoxia. Although hypothyroidism did not affect expression of D2 receptors, it influenced central D2 modulation of breathing in a disparate manner relative to euthyroid hamsters.

  6. Dynamics of the actin cytoskeleton mediates receptor cross talk: An emerging concept in tuning receptor signaling.

    PubMed

    Mattila, Pieta K; Batista, Facundo D; Treanor, Bebhinn

    2016-02-01

    Recent evidence implicates the actin cytoskeleton in the control of receptor signaling. This may be of particular importance in the context of immune receptors, such as the B cell receptor, where dysregulated signaling can result in autoimmunity and malignancy. Here, we discuss the role of the actin cytoskeleton in controlling receptor compartmentalization, dynamics, and clustering as a means to regulate receptor signaling through controlling the interactions with protein partners. We propose that the actin cytoskeleton is a point of integration for receptor cross talk through modulation of protein dynamics and clustering. We discuss the implication of this cross talk via the cytoskeleton for both ligand-induced and low-level constitutive (tonic) signaling necessary for immune cell survival.

  7. Hypothyroidism Affects D2 Receptor-mediated Breathing without altering D2 Receptor Expression

    PubMed Central

    Schlenker, Evelyn H.; Rio, Rodrigo Del; Schultz, Harold D.

    2015-01-01

    Bromocriptine depressed ventilation in air and D2 receptor expression in the nucleus tractus solitaries (NTS) in male hypothyroid hamsters. Here we postulated that in age- matched hypothyroid female hamsters, the pattern of D2 receptor modulation of breathing and D2 receptor expression would differ from those reported in hypothyroid males. In females hypothyroidism did not affect D2 receptor protein levels in the NTS, carotid bodies or striatum. Bromocriptine, but not carmoxirole (a peripheral D2 receptor agonist), increased oxygen consumption and body temperature in awake air-exposed hypothyroid female hamsters and stimulated their ventilation before and following exposure to hypoxia. Carmoxirole depressed frequency of breathing in euthyroid hamsters prior to, during and following hypoxia exposures and stimulated it in the hypothyroid hamsters following hypoxia. Although hypothyroidism did not affect expression of D2 receptors, it influenced central D2 modulation of breathing in a disparate manner relative to euthyroid hamsters. PMID:24434437

  8. Dynamics of the actin cytoskeleton mediates receptor cross talk: An emerging concept in tuning receptor signaling

    PubMed Central

    Mattila, Pieta K.; Batista, Facundo D.

    2016-01-01

    Recent evidence implicates the actin cytoskeleton in the control of receptor signaling. This may be of particular importance in the context of immune receptors, such as the B cell receptor, where dysregulated signaling can result in autoimmunity and malignancy. Here, we discuss the role of the actin cytoskeleton in controlling receptor compartmentalization, dynamics, and clustering as a means to regulate receptor signaling through controlling the interactions with protein partners. We propose that the actin cytoskeleton is a point of integration for receptor cross talk through modulation of protein dynamics and clustering. We discuss the implication of this cross talk via the cytoskeleton for both ligand-induced and low-level constitutive (tonic) signaling necessary for immune cell survival. PMID:26833785

  9. Model for growth hormone receptor activation based on subunit rotation within a receptor dimer

    SciTech Connect

    Brown, Richard J.; Adams, Julian J.; Pelekanos, Rebecca A.; Wan, Yu; McKinstry, William J.; Palethorpe, Kathryn; Seeber, Ruth M.; Monks, Thea A.; Eidne, Karin A.; Parker, Michael W.; Waters, Michael J.

    2010-07-13

    Growth hormone is believed to activate the growth hormone receptor (GHR) by dimerizing two identical receptor subunits, leading to activation of JAK2 kinase associated with the cytoplasmic domain. However, we have reported previously that dimerization alone is insufficient to activate full-length GHR. By comparing the crystal structure of the liganded and unliganded human GHR extracellular domain, we show here that there is no substantial change in its conformation on ligand binding. However, the receptor can be activated by rotation without ligand by inserting a defined number of alanine residues within the transmembrane domain. Fluorescence resonance energy transfer (FRET), bioluminescence resonance energy transfer (BRET) and coimmunoprecipitation studies suggest that receptor subunits undergo specific transmembrane interactions independent of hormone binding. We propose an activation mechanism involving a relative rotation of subunits within a dimeric receptor as a result of asymmetric placement of the receptor-binding sites on the ligand.

  10. Nicotinic receptors, memory, and hippocampus.

    PubMed

    Kutlu, Munir Gunes; Gould, Thomas J

    2015-01-01

    Nicotinic acetylcholine receptors (nAChRs) modulate the neurobiological processes underlying hippocampal learning and memory. In addition, nicotine's ability to desensitize and upregulate certain nAChRs may alter hippocampus-dependent memory processes. Numerous studies have examined the effects of nicotine on hippocampus-dependent learning, as well as the roles of low- and high-affinity nAChRs in mediating nicotine's effects on hippocampus-dependent learning and memory. These studies suggested that while acute nicotine generally acts as a cognitive enhancer for hippocampus-dependent learning, withdrawal from chronic nicotine results in deficits in hippocampus-dependent memory. Furthermore, these studies demonstrated that low- and high-affinity nAChRs functionally differ in their involvement in nicotine's effects on hippocampus-dependent learning. In the present chapter, we reviewed studies using systemic or local injections of acute or chronic nicotine, nAChR subunit agonists or antagonists; genetically modified mice; and molecular biological techniques to characterize the effects of nicotine on hippocampus-dependent learning.

  11. SCREENING CHEMICALS FOR ESTROGEN RECEPTOR ...

    EPA Pesticide Factsheets

    The U.S. Environmental Protection Agency (EPA) is considering the use high-throughput and computational methods for regulatory applications in the Endocrine Disruptor Screening Program (EDSP). To use these new tools for regulatory decision making, computational methods must be appropriately validated. Traditional validations of toxicity tests are time intensive, evaluate a relatively small number of chemicals, and are not well-suited to high-throughput methods. Here we describe a multi-step, performance-based validation establishing scientific confidence in new computational methods and demonstrating these tools are sufficiently robust to be used in a regulatory context. Results from 18 estrogen receptor (ER) ToxCast high-throughput screening assays, measuring different points along the signaling pathway with different assay technologies, were integrated into a computational model. The resulting ToxCast ER model scores range from 0 (no activity) to 1 (bioactivity of the native ligand, 17β-estradiol) and can discriminate ER bioactivity from assay-specific interference and cytotoxicity. ToxCast ER model performance was evaluated for 40 in vitro and 43 in vivo reference chemicals. ToxCast ER model results were also compared to EDSP Tier 1 screening assays in current regulatory practice for a diverse set of more than 100 chemicals. ToxCast ER model accuracy was 95% when compared to the large set of in vitro and in vivo reference chemicals. In addition, the T

  12. The Cryptochrome Blue Light Receptors.

    PubMed

    Yu, Xuhong; Liu, Hongtao; Klejnot, John; Lin, Chentao

    2010-09-23

    Cryptochromes are photolyase-like blue light receptors originally discovered in Arabidopsis but later found in other plants, microbes, and animals. Arabidopsis has two cryptochromes, CRY1 and CRY2, which mediate primarily blue light inhibition of hypocotyl elongation and photoperiodic control of floral initiation, respectively. In addition, cryptochromes also regulate over a dozen other light responses, including circadian rhythms, tropic growth, stomata opening, guard cell development, root development, bacterial and viral pathogen responses, abiotic stress responses, cell cycles, programmed cell death, apical dominance, fruit and ovule development, seed dormancy, and magnetoreception. Cryptochromes have two domains, the N-terminal PHR (Photolyase-Homologous Region) domain that bind the chromophore FAD (flavin adenine dinucleotide), and the CCE (CRY C-terminal Extension) domain that appears intrinsically unstructured but critical to the function and regulation of cryptochromes. Most cryptochromes accumulate in the nucleus, and they undergo blue light-dependent phosphorylation or ubiquitination. It is hypothesized that photons excite electrons of the flavin molecule, resulting in redox reaction or circular electron shuttle and conformational changes of the photoreceptors. The photoexcited cryptochrome are phosphorylated to adopt an open conformation, which interacts with signaling partner proteins to alter gene expression at both transcriptional and posttranslational levels and consequently the metabolic and developmental programs of plants.

  13. Androgen receptor in prostate cancer.

    PubMed

    Heinlein, Cynthia A; Chang, Chawnshang

    2004-04-01

    The normal development and maintenance of the prostate is dependent on androgen acting through the androgen receptor (AR). AR remains important in the development and progression of prostate cancer. AR expression is maintained throughout prostate cancer progression, and the majority of androgen-independent or hormone refractory prostate cancers express AR. Mutation of AR, especially mutations that result in a relaxation of AR ligand specificity, may contribute to the progression of prostate cancer and the failure of endocrine therapy by allowing AR transcriptional activation in response to antiandrogens or other endogenous hormones. Similarly, alterations in the relative expression of AR coregulators have been found to occur with prostate cancer progression and may contribute to differences in AR ligand specificity or transcriptional activity. Prostate cancer progression is also associated with increased growth factor production and an altered response to growth factors by prostate cancer cells. The kinase signal transduction cascades initiated by mitogenic growth factors modulate the transcriptional activity of AR and the interaction between AR and AR coactivators. The inhibition of AR activity through mechanisms in addition to androgen ablation, such as modulation of signal transduction pathways, may delay prostate cancer progression.

  14. Ryanodine receptors as leak channels.

    PubMed

    Guerrero-Hernández, Agustín; Ávila, Guillermo; Rueda, Angélica

    2014-09-15

    Ryanodine receptors are Ca(2+) release channels of internal stores. This review focuses on those situations and conditions that transform RyRs from a finely regulated ion channel to an unregulated Ca(2+) leak channel and the pathological consequences of this alteration. In skeletal muscle, mutations in either CaV1.1 channel or RyR1 results in a leaky behavior of the latter. In heart cells, RyR2 functions normally as a Ca(2+) leak channel during diastole within certain limits, the enhancement of this activity leads to arrhythmogenic situations that are tackled with different pharmacological strategies. In smooth muscle, RyRs are involved more in reducing excitability than in stimulating contraction so the leak activity of RyRs in the form of Ca(2+) sparks, locally activates Ca(2+)-dependent potassium channels to reduce excitability. In neurons the enhanced activity of RyRs is associated with the development of different neurodegenerative disorders such as Alzheimer and Huntington diseases. It appears then that the activity of RyRs as leak channels can have both physiological and pathological consequences depending on the cell type and the metabolic condition.

  15. Encephalitis and GABAB receptor antibodies

    PubMed Central

    Höftberger, Romana; Titulaer, Maarten J.; Sabater, Lidia; Dome, Balazs; Rózsás, Anita; Hegedus, Balazs; Hoda, Mir Alireza; Laszlo, Viktoria; Ankersmit, Hendrik Jan; Harms, Lutz; Boyero, Sabas; de Felipe, Alicia; Saiz, Albert; Dalmau, Josep

    2013-01-01

    Objective: To report the clinical features of 20 newly diagnosed patients with GABAB receptor (GABABR) antibodies and determine the frequency of associated tumors and concurrent neuronal autoantibodies. Methods: Clinical data were retrospectively obtained and evaluated. Serum and CSF samples were examined for additional antibodies using methods previously reported. Results: Seventeen patients presented with seizures, memory loss, and confusion, compatible with limbic encephalitis (LE), one patient presented with ataxia, one patient presented with status epilepticus, and one patient presented with opsoclonus-myoclonus syndrome (OMS). Nineteen (95%) patients eventually developed LE during the course of the disease. Small-cell lung cancer (SCLC) was identified in 10 (50%) patients, all with LE. Treatment and outcome was available from 19 patients: 15 showed complete (n = 7) or partial (n = 8) neurologic improvement after steroids, IV immunoglobulins, or plasma exchange and oncologic treatment when indicated; 1 patient died of tumor progression shortly after the first cycle of immunotherapy, and 3 were not treated. Five patients with SCLC had additional onconeuronal antibodies (Ri, amphiphysin, or SOX1), and 2 without tumor had GAD65 and NMDAR antibodies, respectively. GABABR antibodies were not detected in serum of 116 patients with SCLC without neurologic symptoms. Conclusion: Our study confirms GABABR as an autoantigen of paraneoplastic and nonparaneoplastic LE and expands the phenotype of GABABR antibodies to ataxia, OMS, and status epilepticus. The long-term prognosis is dictated by the presence of a tumor. Recognition of syndromes associated with GABABR antibodies is important because they usually respond to treatment. PMID:24068784

  16. Metabotropic glutamate receptors in cancer.

    PubMed

    Yu, Lumeng J; Wall, Brian A; Wangari-Talbot, Janet; Chen, Suzie

    2016-02-16

    Metabotropic glutamate receptors (mGluRs) are widely known for their roles in synaptic signaling. However, accumulating evidence suggests roles of mGluRs in human malignancies in addition to synaptic transmission. Somatic cell homeostasis presents intriguing possibilities of mGluRs and glutamate signaling as novel targets for human cancers. More recently, aberrant glutamate signaling has been shown to participate in the transformation and maintenance of various cancer types, including glioma, melanoma skin cancer, breast cancer, and prostate cancer, indicating that genes encoding mGluRs, GRMs, can function as oncogenes. Here, we provide a review on the interactions of mGluRs and their ligand, glutamate, in processes that promote the growth of tumors of neuronal and non-neuronal origins. Further, we discuss the evolution of riluzole, a glutamate release inhibitor approved for amyotrophic lateral sclerosis (ALS), but now fashioned as an mGluR1 inhibitor for melanoma therapy and as a radio-sensitizer for tumors that have metastasized to the brain. With the success of riluzole, it is not far-fetched to believe that other drugs that may act directly or indirectly on other mGluRs can be beneficial for multiple applications.

  17. Palmitoylation of Nicotinic Acetylcholine Receptors

    PubMed Central

    Alexander, J. K.; Govind, A. P.; Drisdel, R. C.; Blanton, M. P.; Vallejo, Y.; Lam, T. T.

    2012-01-01

    It is well established that nicotinic acetylcholine receptors (nAChRs) undergo a number of different post-translational modifications, such as disulfide bond formation, glycosylation, and phosphorylation. Recently, our laboratory has developed more sensitive assays of protein palmitoylation that have allowed us and others to detect the palmitoylation of relatively low abundant proteins such as ligand-gated ion channels. Here, we present evidence that palmitoylation is prevalent on many subunits of different nAChR subtypes, both muscle-type nAChRs and the neuronal “α4β2” and “α7” subtypes most abundant in brain. The loss of ligand binding sites that occurs when palmitoylation is blocked with the inhibitor bromopalmitate suggests that palmitoylation of α4β2 and α7 subtypes occurs during subunit assembly and regulates the formation of ligand binding sites. However, additional experiments are needed to test whether nAChR subunit palmitoylation is involved in other aspects of nAChR trafficking or whether palmitoylation regulates nAChR function. Further investigation would be aided by identifying the sites of palmitoylation on the subunits, and here we propose a mass spectrometry strategy for identification of these sites. PMID:19693711

  18. The Cryptochrome Blue Light Receptors

    PubMed Central

    Yu, Xuhong; Liu, Hongtao; Klejnot, John; Lin, Chentao

    2010-01-01

    Cryptochromes are photolyase-like blue light receptors originally discovered in Arabidopsis but later found in other plants, microbes, and animals. Arabidopsis has two cryptochromes, CRY1 and CRY2, which mediate primarily blue light inhibition of hypocotyl elongation and photoperiodic control of floral initiation, respectively. In addition, cryptochromes also regulate over a dozen other light responses, including circadian rhythms, tropic growth, stomata opening, guard cell development, root development, bacterial and viral pathogen responses, abiotic stress responses, cell cycles, programmed cell death, apical dominance, fruit and ovule development, seed dormancy, and magnetoreception. Cryptochromes have two domains, the N-terminal PHR (Photolyase-Homologous Region) domain that bind the chromophore FAD (flavin adenine dinucleotide), and the CCE (CRY C-terminal Extension) domain that appears intrinsically unstructured but critical to the function and regulation of cryptochromes. Most cryptochromes accumulate in the nucleus, and they undergo blue light-dependent phosphorylation or ubiquitination. It is hypothesized that photons excite electrons of the flavin molecule, resulting in redox reaction or circular electron shuttle and conformational changes of the photoreceptors. The photoexcited cryptochrome are phosphorylated to adopt an open conformation, which interacts with signaling partner proteins to alter gene expression at both transcriptional and posttranslational levels and consequently the metabolic and developmental programs of plants. PMID:21841916

  19. Nicotinic Receptor Fourth Transmembrane Domain

    PubMed Central

    Bouzat, Cecilia; Barrantes, Francisco; Sine, Steven

    2000-01-01

    The fourth transmembrane domain (M4) of the nicotinic acetylcholine receptor (AChR) contributes to the kinetics of activation, yet its close association with the lipid bilayer makes it the outermost of the transmembrane domains. To investigate mechanistic and structural contributions of M4 to AChR activation, we systematically mutated αT422, a conserved residue that has been labeled by hydrophobic probes, and evaluated changes in rate constants underlying ACh binding and channel gating steps. Aromatic and nonpolar mutations of αT422 selectively affect the channel gating step, slowing the rate of opening two- to sevenfold, and speeding the rate of closing four- to ninefold. Additionally, kinetic modeling shows a second doubly liganded open state for aromatic and nonpolar mutations. In contrast, serine and asparagine mutations of αT422 largely preserve the kinetics of the wild-type AChR. Thus, rapid and efficient gating of the AChR channel depends on a hydrogen bond involving the side chain at position 422 of the M4 transmembrane domain. PMID:10779322

  20. Genetic disorders of nuclear receptors.

    PubMed

    Achermann, John C; Schwabe, John; Fairall, Louise; Chatterjee, Krishna

    2017-04-03

    Following the first isolation of nuclear receptor (NR) genes, genetic disorders caused by NR gene mutations were initially discovered by a candidate gene approach based on their known roles in endocrine pathways and physiologic processes. Subsequently, the identification of disorders has been informed by phenotypes associated with gene disruption in animal models or by genetic linkage studies. More recently, whole exome sequencing has associated pathogenic genetic variants with unexpected, often multisystem, human phenotypes. To date, defects in 20 of 48 human NR genes have been associated with human disorders, with different mutations mediating phenotypes of varying severity or several distinct conditions being associated with different changes in the same gene. Studies of individuals with deleterious genetic variants can elucidate novel roles of human NRs, validating them as targets for drug development or providing new insights into structure-function relationships. Importantly, human genetic discoveries enable definitive disease diagnosis and can provide opportunities to therapeutically manage affected individuals. Here we review germline changes in human NR genes associated with "monogenic" conditions, including a discussion of the structural basis of mutations that cause distinctive changes in NR function and the molecular mechanisms mediating pathogenesis.

  1. Length of the TM3-4 loop of the glycine receptor modulates receptor desensitization.

    PubMed

    Langlhofer, G; Janzen, D; Meiselbach, Heike; Villmann, C

    2015-07-23

    Recent studies on the molecular determinants important for glycine receptor biogenesis and function mechanisms indicate an important role of basic residues within the intracellular loop between transmembrane domains (TM) 3 and 4. We investigate the role of loop length and loop exchange in combination with the presence or absence of basic stretches (318)RRKRR and (385)KKIDK of the human glycine receptor α1 using expression in transfected cell lines. Exchanges of the large intracellular loop between members of the Cys-loop receptor family have been shown to keep functionality of the host receptor. Here, constructs were generated with deletion of the intracellular loop of the glycine receptor α1, insertion of the loop from the prokaryotic Cys-loop receptor of Gloeobacter violaceus both with and without leaving the basic stretches at the N-terminal and C-terminal part of the intracellular domain. All receptor constructs were expressed at the cell surface with the significantly lowest expression of the construct with a deletion of the glycine receptor α1 TM3-4 loop, except the two basic stretches adjoined. Functionality of the inhibitory glycine receptor chimeras was demonstrated with whole cell recordings from transfected cells. Chimeras lacking the basic stretches result in non-functionality. An analysis of receptor desensitization demonstrated that close proximity of both basic stretches resulted in large fractions of desensitizing currents. We conclude that the TM3-4 loop length is critical for glycine receptor α1 desensitization and a direct neighborhood of both basic stretches changes receptor properties from non-desensitizing to desensitizing. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  2. 5-HT7 receptor activation promotes an increase in TrkB receptor expression and phosphorylation

    PubMed Central

    Samarajeewa, Anshula; Goldemann, Lolita; Vasefi, Maryam S.; Ahmed, Nawaz; Gondora, Nyasha; Khanderia, Chandni; Mielke, John G.; Beazely, Michael A.

    2014-01-01

    The serotonin (5-HT) type 7 receptor is expressed throughout the CNS including the cortex and hippocampus. We have previously demonstrated that the application of 5-HT7 receptor agonists to primary hippocampal neurons and SH-SY5Y cells increases platelet-derived growth factor (PDGF) receptor expression and promotes neuroprotection against N-methyl-D-aspartate-(NMDA)-induced toxicity. The tropomyosin-related kinase B (TrkB) receptor is one of the receptors for brain-derived neurotrophic factor (BDNF) and is associated with neurodevelopmental and neuroprotective effects. Application of LP 12 to primary cerebral cortical cultures, SH-SY5Y cells, as well as the retinal ganglion cell line, RGC-5, increased both the expression of full length TrkB as well as its basal phosphorylation state at tyrosine 816. The increase in TrkB expression and phosphorylation was observed as early as 30 min after 5-HT7 receptor activation. In addition to full-length TrkB, kinase domain-deficient forms may be expressed and act as dominant-negative proteins toward the full length receptor. We have identified distinct patterns of TrkB isoform expression across our cell lines and cortical cultures. Although TrkB receptor expression is regulated by cyclic AMP and Gαs-coupled GPCRs in several systems, we demonstrate that, depending on the model system, pathways downstream of both Gαs and Gα12 are involved in the regulation of TrkB expression by 5-HT7 receptors. Given the number of psychiatric and degenerative diseases associated with TrkB/BDNF deficiency and the current interest in developing 5-HT7 receptor ligands as pharmaceuticals, identifying signaling relationships between these two receptors will aid in our understanding of the potential therapeutic effects of 5-HT7 receptor ligands. PMID:25426041

  3. 5-HT7 receptor activation promotes an increase in TrkB receptor expression and phosphorylation.

    PubMed

    Samarajeewa, Anshula; Goldemann, Lolita; Vasefi, Maryam S; Ahmed, Nawaz; Gondora, Nyasha; Khanderia, Chandni; Mielke, John G; Beazely, Michael A

    2014-01-01

    The serotonin (5-HT) type 7 receptor is expressed throughout the CNS including the cortex and hippocampus. We have previously demonstrated that the application of 5-HT7 receptor agonists to primary hippocampal neurons and SH-SY5Y cells increases platelet-derived growth factor (PDGF) receptor expression and promotes neuroprotection against N-methyl-D-aspartate-(NMDA)-induced toxicity. The tropomyosin-related kinase B (TrkB) receptor is one of the receptors for brain-derived neurotrophic factor (BDNF) and is associated with neurodevelopmental and neuroprotective effects. Application of LP 12 to primary cerebral cortical cultures, SH-SY5Y cells, as well as the retinal ganglion cell line, RGC-5, increased both the expression of full length TrkB as well as its basal phosphorylation state at tyrosine 816. The increase in TrkB expression and phosphorylation was observed as early as 30 min after 5-HT7 receptor activation. In addition to full-length TrkB, kinase domain-deficient forms may be expressed and act as dominant-negative proteins toward the full length receptor. We have identified distinct patterns of TrkB isoform expression across our cell lines and cortical cultures. Although TrkB receptor expression is regulated by cyclic AMP and Gαs-coupled GPCRs in several systems, we demonstrate that, depending on the model system, pathways downstream of both Gαs and Gα12 are involved in the regulation of TrkB expression by 5-HT7 receptors. Given the number of psychiatric and degenerative diseases associated with TrkB/BDNF deficiency and the current interest in developing 5-HT7 receptor ligands as pharmaceuticals, identifying signaling relationships between these two receptors will aid in our understanding of the potential therapeutic effects of 5-HT7 receptor ligands.

  4. Selectivity of odorant receptors in insects

    USDA-ARS?s Scientific Manuscript database

    Insect olfactory receptors (ORs) detect chemical signals, shape neuronal physiology and regulate behavior. Although ORs have been categorized as generalists and specialists based on their ligand spectrum, both electrophysiological studies and recent pharmacological investigations show that ORs spec...

  5. Presence of Laminin Receptors in Staphylococcus aureus

    NASA Astrophysics Data System (ADS)

    Lopes, J. D.; Dos Reis, M.; Brentani, R. R.

    1985-07-01

    A characteristic feature of infection by Staphylococcus aureus is bloodstream invasion and widespread metastatic abscess formation. The ability to extravasate, which entails crossing the vascular basement membrane, appears to be critical for the organism's pathogenicity. Extravasation by normal and neoplastic mammalian cells has been correlated with the presence of specific cell surface receptors for the basement membrane glycoprotein laminin. Similar laminin receptors were found in Staphylococcus aureus but not in Staphylococcus epidermidis, a noninvasive pathogen. There were about 100 binding sites per cell, with an apparent binding affinity of 2.9 nanomolar. The molecular weight of the receptor was 50,000 and pI was 4.2. Eukaryotic laminin receptors were visualized by means of the binding of S. aureus in the presence of laminin. Prokaryotic and eukaryotic invasive cells might utilize similar, if not identical, mechanisms for invasion.

  6. Genetics Home Reference: leptin receptor deficiency

    MedlinePlus

    ... leptin receptor gene causes obesity and pituitary dysfunction. Nature. 1998 Mar 26;392(6674):398-401. Citation ... and human weight regulation: lessons from experiments of nature. Ann Acad Med Singapore. 2009 Jan;38(1): ...

  7. Brain nuclear receptors and body weight regulation

    USDA-ARS?s Scientific Manuscript database

    Neural pathways, especially those in the hypothalamus, integrate multiple nutritional, hormonal, and neural signals, resulting in the coordinated control of body weight balance and glucose homeostasis. Nuclear receptors (NRs) sense changing levels of nutrients and hormones, and therefore play essent...

  8. Estrogen receptor signaling during vertebrate development

    PubMed Central

    Bondesson, Maria; Hao, Ruixin; Lin, Chin-Yo; Williams, Cecilia; Gustafsson, Jan-Åke

    2014-01-01

    Estrogen receptors are expressed and their cognate ligands produced in all vertebrates, indicative of important and conserved functions. Through evolution estrogen has been involved in controlling reproduction, affecting both the development of reproductive organs and reproductive behavior. This review broadly describes the synthesis of estrogens and the expression patterns of aromatase and the estrogen receptors, in relation to estrogen functions in the developing fetus and child. We focus on the role of estrogens for development of reproductive tissues, as well as non-reproductive effects on the developing brain. We collate data from human, rodent, bird and fish studies and highlight common and species-specific effects of estrogen signaling on fetal development. Morphological malformations originating from perturbed estrogen signaling in estrogen receptor and aromatase knockout mice are discussed, as well as the clinical manifestations of rare estrogen receptor alpha and aromatase gene mutations in humans. PMID:24954179

  9. New technologies for elucidating opioid receptor function

    PubMed Central

    Bruchas, Michael R.; Roth, Bryan L.

    2016-01-01

    Recent advances in technology, including high resolution crystal structures of opioid receptors, novel chemical tools, and new genetic approaches have provided an unparalleled pallette of tools for deconstructing opioid receptor actions in vitro and in vivo. Here we provide a brief description of our understanding of opioid receptor function from both molecular and atomic perspectives, as well as their role in neural circuits in vivo. We then show how insights into the molecular details of opioid actions can facilitate the creation of functionally-selective (biased) and photoswitchable opioid ligands. Finally, we describe how newly engineered opioid receptor-based chemo- and optogenetic tools, and new mouse lines are expanding and transforming our understanding of opioid function and, perhaps, paving the way for new therapeutics. PMID:26833118

  10. Progesterone Modulates a Neuronal Nicotinic Acetylcholine Receptor

    NASA Astrophysics Data System (ADS)

    Valera, S.; Ballivet, M.; Bertrand, D.

    1992-10-01

    The major brain nicotinic acetylcholine receptor is assembled from two subunits termed α 4 and nα 1. When expressed in Xenopus oocytes, these subunits reconstitute a functional acetylcholine receptor that is inhibited by progesterone levels similar to those found in serum. In this report, we show that the steroid interacts with a site located on the extracellular part of the protein, thus confirming that inhibition by progesterone is not due to a nonspecific perturbation of the membrane bilayer or to the activation of second messengers. Because inhibition by progesterone does not require the presence of agonist, is voltage-independent, and does not alter receptor desensitization, we conclude that the steroid is not an open channel blocker. In addition, we show that progesterone is not a competitive inhibitor but may interact with the acetylcholine binding site and that its effect is independent of the ionic permeability of the receptor.

  11. Purification of brain D2 dopamine receptor.

    PubMed Central

    Williamson, R A; Worrall, S; Chazot, P L; Strange, P G

    1988-01-01

    D2 dopamine receptors have been extracted from bovine brain using the detergent cholate and purified approximately 20,000-fold by affinity chromatography on haloperidol-sepharose and wheat germ agglutinin-agarose columns. The purified preparation contains D2 dopamine receptors as judged by the pharmacological specificity of [3H]spiperone binding to the purified material. The sp. act. of [3H]spiperone binding in the purified preparation is 2.5 nmol/mg protein. The purified preparation shows a major diffuse band at Mr 95,000 upon SDS-polyacrylamide gel electrophoresis and there is evidence for microheterogeneity either at the protein or glycosylation level. Photoaffinity labelling of D2 dopamine receptors also shows a species of Mr 95,000. The D2 dopamine receptor therefore is a glycoprotein of Mr 95,000. Images PMID:3243275

  12. G Protein–Coupled Receptor Heteromers

    PubMed Central

    Gomes, Ivone; Ayoub, Mohammed Akli; Fujita, Wakako; Jaeger, Werner C.; Pfleger, Kevin D.G.; Devi, Lakshmi A.

    2016-01-01

    G protein–coupled receptors (GPCRs) compose one of the largest families of membrane proteins involved in intracellular signaling. They are involved in numerous physiological and pathological processes and are prime candidates for drug development. Over the past decade, an increasing number of studies have reported heteromerization between GPCRs. Many investigations in heterologous systems have provided important indications of potential novel pharmacology; however, the physiological relevance of these findings has yet to be established with endogenous receptors in native tissues. In this review, we focus on family A GPCRs and describe the techniques and criteria to assess their heteromerization. We conclude that advances in approaches to study receptor complex functionality in heterologous systems, coupled with techniques that enable specific examination of native receptor heteromers in vivo, are likely to establish GPCR heteromers as novel therapeutic targets. PMID:26514203

  13. Kainate receptors: multiple roles in neuronal plasticity.

    PubMed

    Sihra, Talvinder S; Flores, Gonzalo; Rodríguez-Moreno, Antonio

    2014-02-01

    Ionotropic glutamate receptors of the N-methyl-d-aspartate (NMDA)- and AMPA-type, as well as metabotropic glutamate receptors have been extensively invoked in plasticity. Until relatively recently, however, kainate-type receptors (KARs) had been the most elusive to study because of the lack of appropriate pharmacological tools to specifically address their roles. With the development of selective glutamate receptor antagonists, and knockout mice with specific KAR subunits deleted, the functions of KARs in neuromodulation and synaptic transmission, together with their involvement in some types of plasticity, have been extensively probed in the central nervous system. In this review, we summarize the findings related to the roles of KARs in short- and long-term forms of plasticity, primarily in the hippocampus, where KAR function and synaptic plasticity have received avid attention.

  14. Endothelial glucocorticoid receptor suppresses atherogenesis- Brief Report

    PubMed Central

    Zhang, Xinbo; Rotllan, Noemi; Feng, Yan; Zhou, Han; Fernández-Hernando, Carlos; Yu, Jun; Sessa, William C.

    2015-01-01

    Objective The purpose of this study was to determine the role of the endothelial glucocorticoid receptor in the pathogenesis of atherosclerosis. Approach and Results Control mice and mice lacking the endothelial glucocorticoid receptor were bred onto an Apoe knockout background and subjected to high-fat diet feeding for 12 weeks. Assessment of body weight and total cholesterol and triglycerides before and after the diet revealed no differences between the two groups of mice. However, mice lacking the endothelial glucocorticoid receptor developed more severe atherosclerotic lesions in the aorta, brachiocephalic artery and aortic sinus as well as a heightened inflammatory milieu as evidence by increased macrophage recruitment in the lesions. Conclusions These data suggest the endothelial glucocorticoid receptor is important for tonic inhibition of inflammation and limitation of atherosclerosis progression in this model. PMID:25810297

  15. NMDA receptor and schizophrenia: a brief history.

    PubMed

    Coyle, Joseph T

    2012-09-01

    Although glutamate was first hypothesized to be involved in the pathophysiology of schizophrenia in the 1980s, it was the demonstration that N-methyl-D-aspartate (NMDA) receptor antagonists, the dissociative anesthetics, could replicate the full range of psychotic, negative, cognitive, and physiologic features of schizophrenia in normal subjects that placed the "NMDA receptor hypofunction hypothesis" on firm footing. Additional support came from the demonstration that a variety of agents that enhanced NMDA receptor function at the glycine modulatory site significantly reduced negative symptoms and variably improved cognition in patients with schizophrenia receiving antipsychotic drugs. Finally, persistent blockade of NMDA receptors recreates in experimental animals the critical pathologic features of schizophrenia including downregulation of parvalbumin-positive cortical GABAergic neurons, pyramidal neuron dendritic dysgenesis, and reduced spine density.

  16. Discovery Of An Orexin Receptor Positive Potentiator

    PubMed Central

    Lee, Jiyong; Reddy, M. Muralidhar

    2013-01-01

    The orexin neurohormones control a variety of important physiological processes by signaling through two related G protein-coupled receptors, including appetite and feeding, wakefulness and energy homeostasis. Pharmacological manipulation of orexin signaling is an important goal. Here we describe the isolation of orexin receptor ligands from a library of microarray-displayed peptoids via a novel two-color, cell-based screen. Functional analysis of derivatives of these “hits” resulted in the development of moderate potency, low molecular weight receptor antagonists. Moreover, further optimization efforts resulted in the fortuitous discovery of a compound that positively potentiates the activity of the receptor. This compound is the first small molecule reported to up-regulate orexin signaling. PMID:24409338

  17. Measuring receptor recycling in polarized MDCK cells.

    PubMed

    Gallo, Luciana; Apodaca, Gerard

    2015-01-01

    Recycling of proteins such as channels, pumps, and receptors is critical for epithelial cell function. In this chapter we present a method to measure receptor recycling in polarized Madin-Darby canine kidney cells using an iodinated ligand. We describe a technique to iodinate transferrin (Tf), we discuss how (125)I-Tf can be used to label a cohort of endocytosed Tf receptor, and then we provide methods to measure the rate of recycling of the (125)I-Tf-receptor complex. We also show how this approach, which is easily adaptable to other proteins, can be used to simultaneously measure the normally small amount of (125)I-Tf transcytosis and degradation.

  18. Kainate receptor modulation by sodium and chloride.

    PubMed

    Plested, Andrew J R

    2011-01-01

    The kainate-type glutamate receptor displays strong modulation by monovalent anions and cations. This modulation is independent of permeation of the ion channel. Instead, structural, computational and biophysical evidence shows that receptor activity is controlled by binding of sodium and chloride ions at sites that stabilize active dimers of glutamate binding domains. Modulation by monovalent ions is a surprisingly general property across ion channel families. However, evidence of a physiological role for ion-dependent effects on glutamate receptors is lacking, perhaps reflecting the adventitious use of ions as structural components of the kainate receptor. "ergo, Hercules, vita humanior sine sale non quit degree […]" "Heaven known, a civilized life is impossible without salt" -Pliny the Elder, Natural History XXXI 88.

  19. Ecdysteroid receptors in Drosophila melanogaster adult females

    USDA-ARS?s Scientific Manuscript database

    Ecdysteroid receptors were identified and partially characterized from total cell extracts of whole animals and dissected tissues from Drosophila melanogaster adult females. Binding studies indicated the presence of two ecdysteroid binding components having high affinity and specificity consistent w...

  20. Superactivation of AMPA receptors by auxiliary proteins

    PubMed Central

    Carbone, Anna L.; Plested, Andrew J. R.

    2016-01-01

    Glutamate receptors form complexes in the brain with auxiliary proteins, which control their activity during fast synaptic transmission through a seemingly bewildering array of effects. Here we devise a way to isolate the activation of complexes using polyamines, which enables us to show that transmembrane AMPA receptor regulatory proteins (TARPs) exert their effects principally on the channel opening reaction. A thermodynamic argument suggests that because TARPs promote channel opening, receptor activation promotes AMPAR-TARP complexes into a superactive state with high open probability. A simple model based on this idea predicts all known effects of TARPs on AMPA receptor function. This model also predicts unexpected phenomena including massive potentiation in the absence of desensitization and supramaximal recovery that we subsequently detected in electrophysiological recordings. This transient positive feedback mechanism has implications for information processing in the brain, because it should allow activity-dependent facilitation of excitatory synaptic transmission through a postsynaptic mechanism. PMID:26744192

  1. Receptor binding profile of Otilonium bromide.

    PubMed

    Evangelista, S; Giachetti, A; Chapelain, B; Neliat, G; Maggi, C A

    1998-08-01

    The interaction of Otilonium bromide (OB) with binding sites for 63 different receptors and ion channels in appropriate preparations has been investigated. Experiments were also performed in rat colon, the preferred tissue for OB 'in vivo' uptake after oral administration. Among the receptors investigated OB binds with sub microM affinity to muscarinic M1, M2, M4, M5 and PAF receptors and with microM affinity to the diltiazem binding site on L type Ca2+ channels. In the rat colon OB shows competitive interaction with the verapamil binding site on L type Ca2+ channels and with muscarinic M2 receptors with IC50 of 1020 and 1220 nM, respectively. These findings provide a molecular rationale to explain the spasmolytic action exerted by OB on intestinal smooth muscle. In particular, a combination of antimuscarinic and Ca2+ channel blocker properties seems to best account for the action of this compound.

  2. Muscarinic receptors and ligands in cancer

    PubMed Central

    Shah, Nirish; Khurana, Sandeep; Cheng, Kunrong; Raufman, Jean-Pierre

    2009-01-01

    Emerging evidence indicates that muscarinic receptors and ligands play key roles in regulating cellular proliferation and cancer progression. Both neuronal and nonneuronal acetylcholine production results in neurocrine, paracrine, and autocrine promotion of cell proliferation, apoptosis, migration, and other features critical for cancer cell survival and spread. The present review comprises a focused critical analysis of evidence supporting the role of muscarinic receptors and ligands in cancer. Criteria are proposed to validate the biological importance of muscarinic receptor expression, activation, and postreceptor signaling. Likewise, criteria are proposed to validate the role of nonneuronal acetylcholine production in cancer. Dissecting cellular mechanisms necessary for muscarinic receptor activation as well as those needed for acetylcholine production and release will identify multiple novel targets for cancer therapy. PMID:19036940

  3. Folate-receptor-targeted radionuclide imaging agents.

    PubMed

    Ke, Chun-Yen; Mathias, Carla J; Green, Mark A

    2004-04-29

    The cell-membrane folate receptor is a potential molecular target for tumor-selective drug delivery, including delivery of radiolabeled folate-chelate conjugates for diagnostic imaging. This review surveys the growing literature on tumor imaging with radionuclide agents targeted to the folate receptor. Successful folate-receptor targeting has been reported, both in vitro and in vivo, using a variety of radionuclides that are suitable for clinical diagnostic imaging (67Ga, 111In, 99mTc, 66Ga, and 64Cu). While none of these agents has, to date, been demonstrated to have clinical efficacy as a diagnostic tool, existing data indicates that it is feasible to noninvasively assess (at least qualitatively) tissue folate receptor levels by external radionuclide imaging.

  4. Cholesterol metabolism, LDL, and the LDL receptor

    SciTech Connect

    Myant, N.B. )

    1990-01-01

    This book covers cholesterol and metabolism. Paper include: The LDL Receptor in Perspective, Cholesterol in Animal Tissues, HMG-CoA Reductase. acetyl-CoA: Cholesterol Acyltransferase, and LDL: Physical and Chemical Characteristics.

  5. A taste of the Drosophila gustatory receptors.

    PubMed

    Montell, Craig

    2009-08-01

    Insects such as the fruit fly, Drosophila melanogaster, rely on contact chemosensation to detect nutrient-rich foods, to avoid consuming toxic chemicals, and to select mates and hospitable zones to deposit eggs. Flies sense tastants and nonvolatile pheromones through gustatory bristles and pegs distributed on multiple body parts including the proboscis, wing margins, legs, and ovipositor. The sensilla house gustatory receptor neurons, which express members of the family of 68 gustatory receptors (GRs). In contrast to mammalian chemosensation or Drosophila olfaction, which are initiated by receptors composed of dimers of one or two receptor types, the functional Drosophila GRs may include three or more subunits. Several GRs appear to be expressed in multiple cell types that are not associated with contact chemosensation raising the possibility that these proteins may have roles that extend beyond the detection of tastants and pheromones.

  6. Androgen Receptor Signaling in Bladder Cancer

    PubMed Central

    Li, Peng; Chen, Jinbo; Miyamoto, Hiroshi

    2017-01-01

    Emerging preclinical findings have indicated that steroid hormone receptor signaling plays an important role in bladder cancer outgrowth. In particular, androgen-mediated androgen receptor signals have been shown to correlate with the promotion of tumor development and progression, which may clearly explain some sex-specific differences in bladder cancer. This review summarizes and discusses the available data, suggesting the involvement of androgens and/or the androgen receptor pathways in urothelial carcinogenesis as well as tumor growth. While the precise mechanisms of the functions of the androgen receptor in urothelial cells remain far from being fully understood, current evidence may offer chemopreventive or therapeutic options, using androgen deprivation therapy, in patients with bladder cancer. PMID:28241422

  7. Peptides and receptors controlling root development.

    PubMed

    Stahl, Yvonne; Simon, Rüdiger

    2012-06-05

    The growth of a plant's root system depends on the continued activity of the root meristem, and the generation of new meristems when lateral roots are initiated. Plants have developed intricate signalling systems that employ secreted peptides and plasma membrane-localized receptor kinases for short- and long-range communication. Studies on growth of the vascular system, the generation of lateral roots, the control of cell differentiation in the root meristem and the interaction with invading pathogens or symbionts has unravelled a network of peptides and receptor systems with occasionally shared functions. A common theme is the employment of conserved modules, consisting of a short signalling peptide, a receptor-like kinase and a target transcription factor, that control the fate and proliferation of stem cells during root development. This review intends to give an overview of the recent advances in receptor and peptide ligand-mediated signalling involved in root development.

  8. Endocrine receptors as targets for new drugs.

    PubMed

    Altman, Jennifer

    2006-01-01

    Increasingly detailed knowledge of cellular signalling pathways is providing a sound basis for the development of specific drugs aimed at selected components of the pathways. Many of these targets are receptors and the multitude of hormone receptors makes endocrine functions a rich proving ground for this research. This article reviews a recent meeting (Insights into Receptor Function and New Drug Development Targets; 5th Endocrinology Colloquium of the Fondation Ipsen, Paris, December 5, 2005) where progress in defining suitable targets for drug therapies in the endocrine system and in designing drugs for some of these targets was discussed. Although the family of G-protein-coupled receptors, ubiquitous in the endocrine system, was the central focus, comparisons with other receptor families were made. Many mutations affecting genes coding for receptors or other components of signalling pathways have been found in a wide range of endocrine disorders including obesity, parathyroid malfunction, disorders involving thyroid-stimulating hormone and follicle-stimulating hormone, and tumours in the anterior pituitary, as well as in many types of cancer. These are being used to dissect the normal control mechanisms as well as to provide information for the development of selective drugs. Recently identified mutations that affect the intracellular traffic in newly synthesised receptors open up possibilities of another dimension of cellular regulation of signalling. Both the discovery of hormones such as apelin and its pairing with an 'orphan' receptor, and the unexpected action of a drug against cannabinoid receptors point to further levels of complexity in cardiovascular regulation. Deeper understanding of the evolution of receptor families and of the molecular mechanisms of signal transduction is enabling the design of highly specific agonists and antagonists. Pharmacological intervention is not limited to the ligand-receptor interaction but can extend to inhibition of

  9. Using Nuclear Receptor Activity to Stratify Hepatocarcinogens

    PubMed Central

    Shah, Imran; Houck, Keith; Judson, Richard S.; Kavlock, Robert J.; Martin, Matthew T.; Reif, David M.; Wambaugh, John; Dix, David J.

    2011-01-01

    Background Nuclear receptors (NR) are a superfamily of ligand-activated transcription factors that control a range of cellular processes. Persistent stimulation of some NR is a non-genotoxic mechanism of rodent liver cancer with unclear relevance to humans. Here we report on a systematic analysis of new in vitro human NR activity data on 309 environmental chemicals in relationship to their liver cancer-related chronic outcomes in rodents. Results The effects of 309 environmental chemicals on human constitutive androstane receptors (CAR/NR1I3), pregnane X receptor (PXR/NR1I2), aryl hydrocarbon receptor (AhR), peroxisome proliferator-activated receptors (PPAR/NR1C), liver X receptors (LXR/NR1H), retinoic X receptors (RXR/NR2B) and steroid receptors (SR/NR3) were determined using in vitro data. Hepatic histopathology, observed in rodents after two years of chronic treatment for 171 of the 309 chemicals, was summarized by a cancer lesion progression grade. Chemicals that caused proliferative liver lesions in both rat and mouse were generally more active for the human receptors, relative to the compounds that only affected one rodent species, and these changes were significant for PPAR (p0.001), PXR (p0.01) and CAR (p0.05). Though most chemicals exhibited receptor promiscuity, multivariate analysis clustered them into relatively few NR activity combinations. The human NR activity pattern of chemicals weakly associated with the severity of rodent liver cancer lesion progression (p0.05). Conclusions The rodent carcinogens had higher in vitro potency for human NR relative to non-carcinogens. Structurally diverse chemicals with similar NR promiscuity patterns weakly associated with the severity of rodent liver cancer progression. While these results do not prove the role of NR activation in human liver cancer, they do have implications for nuclear receptor chemical biology and provide insights into putative toxicity pathways. More importantly, these findings suggest the

  10. Mechanism of GABAB receptor-induced BDNF secretion and promotion of GABAA receptor membrane expression.

    PubMed

    Kuczewski, Nicola; Fuchs, Celine; Ferrand, Nadine; Jovanovic, Jasmina N; Gaiarsa, Jean-Luc; Porcher, Christophe

    2011-08-01

    Recent studies have shown that GABA(B) receptors play more than a classical inhibitory role and can function as an important synaptic maturation signal early in life. In a previous study, we reported that GABA(B) receptor activation triggers secretion of brain-derived neurotrophic factor (BDNF) and promotes the functional maturation of GABAergic synapses in the developing rat hippocampus. To identify the signalling pathway linking GABA(B) receptor activation to BDNF secretion in these cells, we have now used the phosphorylated form of the cAMP response element-binding protein as a biological sensor for endogenous BDNF release. In the present study, we show that GABA(B) receptor-induced secretion of BDNF relies on the activation of phospholipase C, followed by the formation of diacylglycerol, activation of protein kinase C, and the opening of L-type voltage-dependent Ca(2+) channels. We further show that once released by GABA(B) receptor activation, BDNF increases the membrane expression of β(2/3) -containing GABA(A) receptors in neuronal cultures. These results reveal a novel function of GABA(B) receptors in regulating the expression of GABA(A) receptor through BDNF-tropomyosin-related kinase B receptor dependent signalling pathway.

  11. Thyroid hormone receptors regulate adipogenesis and carcinogenesis via crosstalk signaling with peroxisome proliferator-activated receptors.

    PubMed

    Lu, Changxue; Cheng, Sheue-Yann

    2010-03-01

    Peroxisome proliferator-activated receptors (PPARs) and thyroid hormone receptors (TRs) are members of the nuclear receptor superfamily. They are ligand-dependent transcription factors that interact with their cognate hormone response elements in the promoters to regulate respective target gene expression to modulate cellular functions. While the transcription activity of each is regulated by their respective ligands, recent studies indicate that via multiple mechanisms PPARs and TRs crosstalk to affect diverse biological functions. Here, we review recent advances in the understanding of the molecular mechanisms and biological impact of crosstalk between these two important nuclear receptors, focusing on their roles in adipogenesis and carcinogenesis.

  12. Interrupting autocrine ligand-receptor binding: comparison between receptor blockers and ligand decoys.

    PubMed Central

    Forsten, K E; Lauffenburger, D A

    1992-01-01

    Stimulation of cell behavioral functions by ligand/receptor binding can be accomplished in autocrine fashion, where cells secrete ligand capable of binding to receptors on their own surfaces. This proximal secretion of autocrine ligands near the surface receptors on the secreting cell suggests that control of these systems by inhibitors of receptor/ligand binding may be more difficult than for systems involving exogenous ligands. Hence, it is of interest to predict the conditions under which successful inhibition of cell receptor binding by the autocrine ligand can be expected. Previous theoretical work using a compartmentalized model for autocrine cells has elucidated the conditions under which addition of solution decoys for the autocrine ligand can interrupt cell receptor/ligand binding via competitive binding of the secreted molecules (Forsten, K. E., and D. A. Lauffenburger. 1992. Biophys. J. 61:1-12.) We now apply a similar modeling approach to examine the addition of solution blockers targeted against the cell receptor. Comparison of the two alternative inhibition strategies reveals that a significantly lower concentration of receptor blockers, compared to ligand decoys, will obtain a high degree of inhibition. The more direct interruption scheme characteristic of the receptor blockers may make them a preferred strategy when feasible. PMID:1330038

  13. Discrimination Between Different Methylation States of Chemotaxis Receptor Tar by Receptor Methyltransferase CheR†

    PubMed Central

    Perez, Eduardo; West, Ann H.; Stock, Ann M.; Djordjevic, Snezana

    2013-01-01

    Bacterial chemotaxis receptors are posttranslationally modified by carboxyl methylation of specific glutamate residues within their cytoplasmic domains. This highly regulated, reversible modification counterbalances the signaling effects of ligand binding and contributes to adaptation. Based on the crystal structure of the γ-glutamyl-methyltransferase CheR, we have postulated that positively charged residues in helix α2 in the N-terminal domain of the enzyme may be complementary to the negatively charged methylation region of the methyltransferase substrates, the bacterial chemotaxis receptors. Several altered CheR proteins, in which positively charged arginine or lysine residues were substituted with alanines, were constructed and assayed for their methylation activities toward wild-type receptor and a series of receptor variants containing different glutamates available for methylation. One of the CheR mutant proteins (Arg53Ala) showed significantly lower activity toward all receptor constructs, suggesting that Arg53 may play a general role in catalysis of methyl transfer. The rest of the mutant proteins exhibited different patterns of relative methylation rates toward different receptor substrates, indicating specificity, probably through interaction of CheR with the receptor at sites distal to the specific site of methylation. The findings imply complementarity between positively charged residues of the α2 helix of CheR and the negatively charged glutamates of the receptor. It is likely that this complementarity is involved in discriminating different methylation states of the receptors. PMID:14744139

  14. Thyroid hormone receptors regulate adipogenesis and carcinogenesis via crosstalk signaling with peroxisome proliferator-activated receptors

    PubMed Central

    Lu, Changxue; Cheng, Sheue-Yann

    2012-01-01

    Peroxisome proliferator-activated receptors (PPARs) and thyroid hormone receptors (TRs) are members of the nuclear receptor superfamily. They are ligand-dependent transcription factors that interact with their cognate hormone response elements in the promoters to regulate respective target gene expression to modulate cellular functions. While the transcription activity of each is regulated by their respective ligands, recent studies indicate that via multiple mechanisms PPARs and TRs crosstalk to affect diverse biological functions. Here, we review recent advances in the understanding of the molecular mechanisms and biological impact of crosstalk between these two important nuclear receptors, focusing on their roles in adipogenesis and carcinogenesis. PMID:19741045

  15. Purification of PRL receptors from toad kidney: Comparisons with rabbit mammary PRL receptors

    SciTech Connect

    Dunand, M.; Kraehenbuhl, J.P.; Rossier, B.C.; Aubert, M.L. Univ. of Lausanne School of Medicine )

    1988-03-01

    The binding characteristics of the prolactin (PRL) receptors present in toad (Bufo marinus) kidneys were investigated and compared to those of PRL receptors present in rabbit mammary glands. The molecular characteristics of the Triton X-100 solubilized renal and mammary PRL receptors were assessed by gel filtration and by migration analysis on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) after affinity labeling of the binding sites with {sup 125}I-human growth hormone. Similar results were obtained for both receptors. Partial purification of the toad PRL receptor could be achieved by affinity chromatography. The molecular weight of this purified receptor could be determined by analysis of SDS-PAGE. With the use of a polyclonal antiserum raised against a purified preparation of rabbit mammary PRL receptor, one or several antigenic epitope(s) could be identified on the core of the toad renal PRL receptor. In conclusion, although the structure and the biological role(s) of PRL have substantially changed during evolution, the receptor for this hormone has retained many of its structural features as could be assessed between an amphibian and a mammalian species on functionally different target tissues.

  16. Activation of 5-HT7 receptors increases neuronal platelet-derived growth factor β receptor expression.

    PubMed

    Vasefi, Maryam S; Kruk, Jeff S; Liu, Hui; Heikkila, John J; Beazely, Michael A

    2012-03-09

    Several antipsychotics have a high affinity for 5-HT7 receptors yet despite intense interest in the 5-HT7 receptor as a potential drug target to treat psychosis, the function and signaling properties of 5-HT7 receptors in neurons remain largely uncharacterized. In primary mouse hippocampal and cortical neurons, as well as in the SH-SY5Y cell line, incubation with 5-HT, 5-carboxamidotryptamine (5-CT), or 5-HT7 receptor-selective agonists increases the expression of platelet-derived growth factor (PDGF)β receptors. The increased PDGFβ receptor expression is cyclic AMP-dependent protein kinase (PKA)-dependent, suggesting that 5-HT7 receptors couple to Gα(s) in primary neurons. Interestingly, up-regulated PDGFβ receptors display an increased basal phosphorylation state at the phospholipase Cγ-activating tyrosine 1021. This novel linkage between the 5-HT7 receptor and the PDGF system may be an important GPCR-neurotrophic factor signaling pathway in neurons.

  17. Pattern recognitions receptors in immunodeficiency disorders.

    PubMed

    Mortaz, Esameil; Adcock, Ian M; Tabarsi, Payam; Darazam, Ilad Alavi; Movassaghi, Masoud; Garssen, Johan; Jamaati, Hamidreza; Velayati, Aliakbar

    2017-01-14

    Pattern recognition receptors (PRRs) recognize common microbial or host-derived macromolecules and have important roles in early activation and response of the immune system. Initiation of the innate immune response starts with the recognition of microbial structures called pathogen associated molecular patterns (PAMPs). Recognition of PAMPs is performed by germline-encoded receptors expressed mainly on immune cells termed pattern recognition receptors (PRRs). Several classes of pattern recognition receptors (PRRs) are involved in the pathogenesis of diseases, including Toll-like receptors (TLRs), C-type lectin receptors (CLRs), and Nod-like receptors (NLRs). Patients with primary immune deficiencies (PIDs) affecting TLR signaling can elucidate the importance of these proteins in the human immune system. Defects in interleukin-1 receptor-associated kinase-4 and myeloid differentiation factor 88 (MyD88) lead to susceptibility to infections with bacteria, while mutations in nuclear factor-κB essential modulator (NEMO) and other downstream mediators generally induce broader susceptibility to bacteria, viruses, and fungi. In contrast, TLR3 signaling defects are associated with susceptibility to herpes simplex virus type 1 encephalitis. Other PIDs induce functional alterations of TLR signaling pathways, such as common variable immunodeficiency in which plasmacytoid dendritic cell defects enhance defective responses of B cells to shared TLR agonists. Altered TLR responses to TLR2 and 4 agonists are seen in chronic granulomatous disease (CGD) and X-linked agammaglobulinemia (XLA). Enhanced TLR responses, meanwhile, are seen for TLRs 5 and 9 in CGD, TLRs 4, 7/8, and 9 in XLA, TLRs 2 and 4 in hyper IgE syndrome (HIES), and for most TLRs in adenosine deaminase deficiency. In this review we provide the reader with an update on the role of TLRs and downstream signaling pathways in PID disorders.

  18. Interactions of Rodent Coronaviruses with Cellular Receptors

    DTIC Science & Technology

    2016-05-08

    Fluorescent-Antibody Staining to Detect Infection of Single Cells .. . ..... .......... . Challenge of BHK and MOCK Cells with MHV...absence of anti-receptor MAb-CCl..... 82 11. Fluorescent-antibody staining of OBT cells protected with anti-receptor MAb-CCl and challenged with MHV...hepatitis virus which share the same appearance in negative stains , recalling a solar corona, should be included in a group which they suggested

  19. Kinin receptors in skin wound healing.

    PubMed

    Soley, Bruna da Silva; Morais, Rafael Leite Tavares de; Pesquero, João Bosco; Bader, Michael; Otuki, Michel Fleith; Cabrini, Daniela Almeida

    2016-05-01

    Wound healing is a complex and dynamic process that includes 3 different phases: inflammation, proliferation, and remodeling. Kinins are vasoactive peptides released after tissue injury, and are directly involved in the development and maintenance of inflammatory processes, and their actions are mediated by the activation of receptors called B1 and B2. We aimed to evaluate the involvement of kinin receptors in the skin healing process. Knockout mice for kinin receptors (KOB1, KOB2 and KOB1B2) and wild type controls (WT) were subjected to a skin excision model, and tissue repair process was evaluated during different phases of wound healing. In knockout animals for kinin receptors differences were observed in the resolution period of injury exceeding 17 days for the total closure of wounds. The absence of kinin receptors promotes a significant reduction in infiltration of polymorphonuclear cells on day 2 of the inflammatory phase. Already at the late stage of this phase (3 days) there was a negative influence on the infiltration of polymorphonuclear and mononuclear cells at the site of injury in comparison to WT. Collagen was significantly diminished in tissue of KOB1, KOB2 and KOB1B2 from day two to the end of the healing process. Moreover, wound tissue from KOB2 and KOB1B2, but not KOB1, presented impaired parameters of re-epitheliazation, reduced proliferation of cells (PCNA immunostaining), and a lower number of myofibroblasts (α-SMA immunostaining). These data reveal the involvement of kinin receptors in processes of skin repair. Both kinin receptors participate especially during the inflammatory phase, while B2 receptors seem to be more relevant in the quality of the wound scar. Thus, a better understanding of the contribution of kinins to skin wound healing may reveal novel options for therapy. Copyright © 2016. Published by Elsevier Ireland Ltd.

  20. Carbamate Insecticides Target Human Melatonin Receptors.

    PubMed

    Popovska-Gorevski, Marina; Dubocovich, Margarita L; Rajnarayanan, Rajendram V

    2017-02-20

    Carbaryl (1-naphthyl methylcarbamate) and carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate) are among the most toxic insecticides, implicated in a variety of diseases including diabetes and cancer among others. Using an integrated pharmacoinformatics based screening approach, we have identified these insecticides to be structural mimics of the neurohormone melatonin and were able to bind to the putative melatonin binding sites in MT1 and MT2 melatonin receptors in silico. Carbaryl and carbofuran then were tested for competition with 2-[(125)I]-iodomelatonin (300 pM) binding to hMT1 or hMT2 receptors stably expressed in CHO cells. Carbaryl and carbofuran showed higher affinity for competition with 2-[(125)I]-iodomelatonin binding to the hMT2 compared to the hMT1 melatonin receptor (33 and 35-fold difference, respectively) as predicted by the molecular modeling. In the presence of GTP (100 μM), which decouples the G-protein linked receptors to modulate signaling, the apparent efficacy of carbaryl and carbofuran for 2-[(125)I]-iodomelatonin binding for the hMT1 melatonin receptor was not affected but significantly decreased for the hMT2 melatonin receptor compatible with receptor antagonist/inverse agonist and agonist efficacy, respectively. Altogether, our data points to a potentially new mechanism through which carbamate insecticides carbaryl and carbofuran could impact human health by altering the homeostatic balance of key regulatory processes by directly binding to melatonin receptors.