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Sample records for receptor signaling implications

  1. TrkB Receptor Signalling: Implications in Neurodegenerative, Psychiatric and Proliferative Disorders

    PubMed Central

    Gupta, Vivek K.; You, Yuyi; Gupta, Veer Bala; Klistorner, Alexander; Graham, Stuart L.

    2013-01-01

    The Trk family of receptors play a wide variety of roles in physiological and disease processes in both neuronal and non-neuronal tissues. Amongst these the TrkB receptor in particular has attracted major attention due to its critical role in signalling for brain derived neurotrophic factor (BDNF), neurotrophin-3 (NT3) and neurotrophin-4 (NT4). TrkB signalling is indispensable for the survival, development and synaptic plasticity of several subtypes of neurons in the nervous system. Substantial evidence has emerged over the last decade about the involvement of aberrant TrkB signalling and its compromise in various neuropsychiatric and degenerative conditions. Unusual changes in TrkB signalling pathway have also been observed and implicated in a range of cancers. Variations in TrkB pathway have been observed in obesity and hyperphagia related disorders as well. Both BDNF and TrkB have been shown to play critical roles in the survival of retinal ganglion cells in the retina. The ability to specifically modulate TrkB signalling can be critical in various pathological scenarios associated with this pathway. In this review, we discuss the mechanisms underlying TrkB signalling, disease implications and explore plausible ameliorative or preventive approaches. PMID:23670594

  2. Lack of glucagon receptor signaling and its implications beyond glucose homeostasis.

    PubMed

    Charron, Maureen J; Vuguin, Patricia M

    2015-03-01

    Glucagon action is transduced by a G protein-coupled receptor located in liver, kidney, intestinal smooth muscle, brain, adipose tissue, heart, pancreatic β-cells, and placenta. Genetically modified animal models have provided important clues about the role of glucagon and its receptor (Gcgr) beyond glucose control. The PubMed database was searched for articles published between 1995 and 2014 using the key terms glucagon, glucagon receptor, signaling, and animal models. Lack of Gcgr signaling has been associated with: i) hypoglycemic pregnancies, altered placentation, poor fetal growth, and increased fetal-neonatal death; ii) pancreatic glucagon cell hyperplasia and hyperglucagonemia; iii) altered body composition, energy state, and protection from diet-induced obesity; iv) impaired hepatocyte survival; v) altered glucose, lipid, and hormonal milieu; vi) altered metabolic response to prolonged fasting and exercise; vii) reduced gastric emptying and increased intestinal length; viii) altered retinal function; and ix) prevention of the development of diabetes in insulin-deficient mice. Similar phenotypic findings were observed in the hepatocyte-specific deletion of Gcgr. Glucagon action has been involved in the modulation of sweet taste responsiveness, inotropic and chronotropic effects in the heart, satiety, glomerular filtration rate, secretion of insulin, cortisol, ghrelin, GH, glucagon, and somatostatin, and hypothalamic signaling to suppress hepatic glucose production. Glucagon (α) cells under certain conditions can transdifferentiate into insulin (β) cells. These findings suggest that glucagon signaling plays an important role in multiple organs. Thus, treatment options designed to block Gcgr activation in diabetics may have implications beyond glucose homeostasis.

  3. An algebra of dimerization and its implications for G-protein coupled receptor signaling.

    PubMed

    Woolf, Peter J; Linderman, Jennifer J

    2004-07-21

    Many species of receptors form dimers, but how can we use this information to make predictions about signal transduction? This problem is particularly difficult when receptors dimerize with many different species, leading to a combinatoric increase in the possible number of dimer pairs. As an example system, we focus on receptors in the G-protein coupled receptor (GPCR) family. GPCRs have been shown to reversibly form dimers, but this dimerization does not directly affect signal transduction. Here we present a new theoretical framework called a dimerization algebra. This algebra provides a systematic and rational way to represent, manipulate, and in some cases simplify large and often complicated networks of dimerization interactions. To compliment this algebra, Monte Carlo simulations are used to predict dimerization's effect on receptor organization on the membrane, signal transduction, and internalization. These simulation results are directly comparable to various experimental measures such as fluorescence resonance energy transfer (FRET), and as such provide a link between the dimerization algebra and experimental data. As an example, we show how the algebra and computational results can be used to predict the effects of dimerization on the dopamine D2 and somatastatin SSTR1 receptors. When these predictions were compared to experimental findings from the literature, good agreement was found, demonstrating the utility of our approach. Applications of this work to the development of a novel class of dimerization-modulating drugs are also discussed.

  4. Structure-function relationships in the IL-17 receptor: Implications for signal transduction and therapy

    PubMed Central

    Shen, Fang; Gaffen, Sarah L.

    2008-01-01

    IL-17 is the defining cytokine of a newly-described “Th17” population that plays critical roles in mediating inflammation and autoimmunity. The IL-17/IL-17 receptor superfamily is the most recent class of cytokines and receptors to be described, and until recently very little was known about its function or molecular biology. However, in the last year important new insights into the composition and dynamics of the receptor complex and mechanisms of downstream signal transduction have been made, which will be reviewed here. PMID:18178098

  5. Role of Gas6 receptors in platelet signaling during thrombus stabilization and implications for antithrombotic therapy

    PubMed Central

    Angelillo-Scherrer, Anne; Burnier, Laurent; Flores, Nathalie; Savi, Pierre; DeMol, Maria; Schaeffer, Paul; Herbert, Jean-Marc; Lemke, Greg; Goff, Stephen P.; Matsushima, Glenn K.; Earp, H. Shelton; Vesin, Christian; Hoylaerts, Marc F.; Plaisance, Stéphane; Collen, Désiré; Conway, Edward M.; Wehrle-Haller, Bernhard; Carmeliet, Peter

    2005-01-01

    Mechanisms regulating thrombus stabilization remain largely unknown. Here, we report that loss of any 1 of the Gas6 receptors (Gas6-Rs), i.e., Tyro3, Axl, or Mer, or delivery of a soluble extracellular domain of Axl that traps Gas6 protects mice against life-threatening thrombosis. Loss of a Gas6-R does not prevent initial platelet aggregation but impairs subsequent stabilization of platelet aggregates, at least in part by reducing “outside-in” signaling and platelet granule secretion. Gas6, through its receptors, activates PI3K and Akt and stimulates tyrosine phosphorylation of the β3 integrin, thereby amplifying outside-in signaling via αIIbβ3. Blocking the Gas6-R–αIIbβ3 integrin cross-talk might be a novel approach to the reduction of thrombosis. PMID:15650770

  6. PPAR-γ Agonists and Their Effects on IGF-I Receptor Signaling: Implications for Cancer

    PubMed Central

    Belfiore, A.; Genua, M.; Malaguarnera, R.

    2009-01-01

    It is now well established that the development and progression of a variety of human malignancies are associated with dysregulated activity of the insulin-like growth factor (IGF) system. In this regard, promising drugs have been developed to target the IGF-I receptor or its ligands. These therapies are limited by the development of insulin resistance and compensatory hyperinsulinemia, which in turn, may stimulate cancer growth. Novel therapeutic approaches are, therefore, required. Synthetic PPAR-γ agonists, such as thiazolidinediones (TZDs), are drugs universally used as antidiabetic agents in patients with type 2 diabetes. In addition of acting as insulin sensitizers, PPAR-γ agonists mediate in vitro and in vivo pleiotropic anticancer effects. At least some of these effects appear to be linked with the downregulation of the IGF system, which is induced by the cross-talk of PPAR-γ agonists with multiple components of the IGF system signaling. As hyperinsulinemia is an emerging cancer risk factor, the insulin lowering action of PPAR-γ agonists may be expected to be also beneficial to reduce cancer development and/or progression. In light of these evidences, TZDs or other PPAR-γ agonists may be exploited in those tumors “addicted” to the IGF signaling and/or in tumors occurring in hyperinsulinemic patients. PMID:19609453

  7. Epigenetic regulation of G protein coupled receptor signaling and its implications in psychiatric disorders.

    PubMed

    Dogra, Shalini; Sona, Chandan; Kumar, Ajeet; Yadav, Prem N

    2016-08-01

    G protein-coupled receptors (GPCRs) act as a relay center through which extracellular signals, in the form of neurotransmitters or therapeutics, are converted into an intracellular response, which ultimately shapes the overall response at the tissue and behavioral level. Remarkably in similar ways, epigenetic mechanisms also modulate the expression pattern of a large number of genes in response to the dynamic environment inside and outside of the body, and consequently overall response. Emerging evidences from the pharmacogenomics and preclinical studies clearly suggest that these two distinct mechanisms criss-cross each other in several neurological disorders. At one hand such cross-talks between two distinct mechanisms make disease etiology more challenging to understand, while on the other hand if dealt appropriately, such situations might provide an opportunity to find novel druggable target and strategy for the treatment of complex diseases. In this review article, we have summarized and highlighted the main findings that tie epigenetic mechanisms to GPCR mediated signaling in the pathophysiology of central nervous system (CNS) disorders, including depression, addiction and pain. PMID:27046448

  8. Signals and Receptors.

    PubMed

    Heldin, Carl-Henrik; Lu, Benson; Evans, Ron; Gutkind, J Silvio

    2016-04-01

    Communication between cells in a multicellular organism occurs by the production of ligands (proteins, peptides, fatty acids, steroids, gases, and other low-molecular-weight compounds) that are either secreted by cells or presented on their surface, and act on receptors on, or in, other target cells. Such signals control cell growth, migration, survival, and differentiation. Signaling receptors can be single-span plasma membrane receptors associated with tyrosine or serine/threonine kinase activities, proteins with seven transmembrane domains, or intracellular receptors. Ligand-activated receptors convey signals into the cell by activating signaling pathways that ultimately affect cytosolic machineries or nuclear transcriptional programs or by directly translocating to the nucleus to regulate transcription. PMID:27037414

  9. 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

  10. 1.9 A crystal structure of interleukin 6: implications for a novel mode of receptor dimerization and signaling.

    PubMed Central

    Somers, W; Stahl, M; Seehra, J S

    1997-01-01

    Interleukin 6 (IL-6) has many biological activities in vivo, and deregulation has been implicated in many disease processes. IL-6, a 185 amino acid polypeptide was refolded, purified and crystallized. The crystals diffracted to beyond 1.9 A and the structure was solved using single isomorphous replacement. The X-ray structure of IL-6 is composed of a four helix bundle linked by loops and an additional mini-helix. 157 out of 185 residues are well defined in the final structure, with 18 N-terminal and 8 A-B loop amino acids displaying no interpretable electron density. The three-dimensional structure has been used to construct a model of IL-6 interacting with the IL-6 receptor (alpha-chain) and gp130 (beta-chain) that gives new insight into the process of molecular recognition and signaling. Based on this model, we predict a fourth binding site on IL-6, a low affinity IL-6-IL-6 interaction, which may be necessary for the sequential assembly of a functional hexameric IL-6 receptor complex. PMID:9118960

  11. Trefoil peptides as proangiogenic factors in vivo and in vitro: implication of cyclooxygenase-2 and EGF receptor signaling.

    PubMed

    Rodrigues, Sylvie; Van Aken, Elisabeth; Van Bocxlaer, Saskia; Attoub, Samir; Nguyen, Quang-Dé; Bruyneel, Erik; Westley, Bruce R; May, Felicity E B; Thim, Lars; Mareel, Marc; Gespach, Christian; Emami, Shahin

    2003-01-01

    We previously established that the trefoil peptides (TFFs) pS2, spasmolytic polypeptide, and intestinal trefoil factor are involved in cellular scattering and invasion in kidney and colonic cancer cells. Using the chorioallantoic membrane (CAM) assay and the formation of tube-like structures by human umbilical vein endothelial cells (HUVEC) plated on the Matrigel matrix substratum, we report here that TFFs are proangiogenic factors. Angiogenic activity of TFFs is comparable to that induced by vascular endothelial growth factor, leptin, and transforming growth factor-alpha. Stimulation of angiogenesis by pS2 in the CAM assay is blocked by pharmacological inhibitors of cyclooxygenase COX-2 (NS-398) and epidermal growth factor receptor (EGF-R) tyrosine kinase (ZD1839), but is independent of KDR/Flk-1 and thromboxane A2 receptors. In contrast, the morphogenic switch induced by pS2 in HUVEC cells could be inhibited by the specific KDR heptapeptide antagonist ATWLPPR and by inhibitors of COX-2 and EGF-R signaling. These results implicate TFFs in the formation of new blood vessels during normal and pathophysiological processes linked to wound healing, inflammation, and cancer progression in the digestive mucosa and other human solid tumors associated with aberrant expression of TFFs.

  12. Insulin receptor substrate-1 involvement in epidermal growth factor receptor and insulin-like growth factor receptor signalling: implication for Gefitinib ('Iressa') response and resistance.

    PubMed

    Knowlden, Janice M; Jones, Helen E; Barrow, Denise; Gee, Julia M W; Nicholson, Robert I; Hutcheson, Iain R

    2008-09-01

    Classically the insulin receptor substrate-1 (IRS-1) is an essential component of insulin-like growth factor type 1 receptor (IGF-IR) signalling, providing an interface between the receptor and key downstream signalling cascades. Here, however, we show that in tamoxifen-resistant MCF-7 (Tam-R) breast cancer cells, that are highly dependent on epidermal growth factor receptor (EGFR) for growth, IRS-1 can interact with EGFR and be preferentially phosphorylated on tyrosine (Y) 896, a Grb2 binding site. Indeed, phosphorylation of this site is greatly enhanced by exposure of these cells, and other EGFR-positive cell lines, to EGF. Importantly, while IGF-II promotes phosphorylation of IRS-1 on Y612, a PI3-K recruitment site, it has limited effect on Y896 phosphorylation in Tam-R cells. Furthermore, EGF and IGF-II co-treatment, reduces the ability of IGF-II to phosphorylate Y612, whilst maintaining Y896 phosphorylation, suggesting that the EGFR is the dominant recruiter of IRS-1 in this cell line. Significantly, challenge of Tam-R cells with the EGFR-selective tyrosine kinase inhibitor gefitinib, for 7 days, reduces IRS-1/EGFR association and IRS-1 Y896 phosphorylation, while promoting IRS-1/IGF-IR association and IRS-1 Y612 phosphorylation. Furthermore, gefitinib significantly enhances IGF-II-mediated phosphorylation of IRS-1 Y612 and AKT in Tam-R cells. Importantly, induction of this pathway by gefitinib can be abrogated by inhibition/downregulation of the IGF-IR. Our data would therefore suggest a novel association exists between the EGFR and IRS-1 in several EGFR-positive cancer cell lines. This association acts to promote phosphorylation of IRS-1 at Y896 and drive MAPK signalling whilst preventing recruitment of IRS-1 by the IGF-IR and inhibiting signalling via this receptor. Treatment with gefitinib alters the dynamics of this system, promoting IGF-IR signalling, the dominant gefitinib-resistant growth regulatory pathway in Tam-R cells, thus, potentially limiting

  13. Inter-domain tagging implicates caveolin-1 in insulin receptor trafficking and Erk signaling bias in pancreatic beta-cells

    PubMed Central

    Boothe, Tobias; Lim, Gareth E.; Cen, Haoning; Skovsø, Søs; Piske, Micah; Li, Shu Nan; Nabi, Ivan R.; Gilon, Patrick; Johnson, James D.

    2016-01-01

    Objective The role and mechanisms of insulin receptor internalization remain incompletely understood. Previous trafficking studies of insulin receptors involved fluorescent protein tagging at their termini, manipulations that may be expected to result in dysfunctional receptors. Our objective was to determine the trafficking route and molecular mechanisms of functional tagged insulin receptors and endogenous insulin receptors in pancreatic beta-cells. Methods We generated functional insulin receptors tagged with pH-resistant fluorescent proteins between domains. Confocal, TIRF and STED imaging revealed a trafficking pattern of inter-domain tagged insulin receptors and endogenous insulin receptors detected with antibodies. Results Surprisingly, interdomain-tagged and endogenous insulin receptors in beta-cells bypassed classical Rab5a- or Rab7-mediated endocytic routes. Instead, we found that removal of insulin receptors from the plasma membrane involved tyrosine-phosphorylated caveolin-1, prior to trafficking within flotillin-1-positive structures to lysosomes. Multiple methods of inhibiting caveolin-1 significantly reduced Erk activation in vitro or in vivo, while leaving Akt signaling mostly intact. Conclusions We conclude that phosphorylated caveolin-1 plays a role in insulin receptor internalization towards lysosomes through flotillin-1-positive structures and that caveolin-1 helps bias physiological beta-cell insulin signaling towards Erk activation. PMID:27110488

  14. IP3 Receptors, Mitochondria, and Ca2+ Signaling: Implications for Aging

    PubMed Central

    Decuypere, Jean-Paul; Monaco, Giovanni; Missiaen, Ludwig; De Smedt, Humbert; Parys, Jan B.; Bultynck, Geert

    2011-01-01

    The tight interplay between endoplasmic-reticulum-(ER-) and mitochondria-mediated Ca2+ signaling is a key determinant of cellular health and cellular fate through the control of apoptosis and autophagy. Proteins that prevent or promote apoptosis and autophagy can affect intracellular Ca2+ dynamics and homeostasis through binding and modulation of the intracellular Ca2+-release and Ca2+-uptake mechanisms. During aging, oxidative stress becomes an additional factor that affects ER and mitochondrial function and thus their role in Ca2+ signaling. Importantly, mitochondrial dysfunction and sustained mitochondrial damage are likely to underlie part of the aging process. In this paper, we will discuss the different mechanisms that control intracellular Ca2+ signaling with respect to apoptosis and autophagy and review how these processes are affected during aging through accumulation of reactive oxygen species. PMID:21423550

  15. The Anticancer Plant Triterpenoid, Avicin D, Regulates Glucocorticoid Receptor Signaling: Implications for Cellular Metabolism

    PubMed Central

    Haridas, Valsala; Xu, Zhi-Xiang; Kitchen, Doug; Jiang, Anna; Michels, Peter; Gutterman, Jordan U.

    2011-01-01

    Avicins, a family of apoptotic triterpene electrophiles, are known to regulate cellular metabolism and energy homeostasis, by targeting the mitochondria. Having evolved from “ancient hopanoids,” avicins bear a structural resemblance with glucocorticoids (GCs), which are the endogenous regulators of metabolism and energy balance. These structural and functional similarities prompted us to compare the mode of action of avicin D with dexamethasone (Dex), a prototypical GC. Using cold competition assay, we show that Avicin D competes with Dex for binding to the GC receptor (GR), leading to its nuclear translocation. In contrast to Dex, avicin-induced nuclear translocation of GR does not result in transcriptional activation of GC-dependent genes. Instead we observe a decrease in the expression of GC-dependent metabolic proteins such as PEPCK and FASN. However, like Dex, avicin D treatment does induce a transrepressive effect on the pro-inflammatory transcription factor NF-κB. While avicin's ability to inhibit NF-κB and its downstream targets appear to be GR-dependent, its pro-apoptotic effects were independent of GR expression. Using various deletion mutants of GR, we demonstrate the requirement of both the DNA and ligand binding domains of GR in mediating avicin D's transrepressive effects. Modeling of avicin-GR interaction revealed that avicin molecule binds only to the antagonist confirmation of GR. These findings suggest that avicin D has properties of being a selective GR modulator that separates transactivation from transrepression. Since the gene-activating properties of GR are mainly linked to its metabolic effects, and the negative interference with the activity of transcription factors to its anti-inflammatory and immune suppressive effects, the identification of such a dissociated GR ligand could have great potential for therapeutic use. PMID:22132201

  16. The anticancer plant triterpenoid, avicin D, regulates glucocorticoid receptor signaling: implications for cellular metabolism.

    PubMed

    Haridas, Valsala; Xu, Zhi-Xiang; Kitchen, Doug; Jiang, Anna; Michels, Peter; Gutterman, Jordan U

    2011-01-01

    Avicins, a family of apoptotic triterpene electrophiles, are known to regulate cellular metabolism and energy homeostasis, by targeting the mitochondria. Having evolved from "ancient hopanoids," avicins bear a structural resemblance with glucocorticoids (GCs), which are the endogenous regulators of metabolism and energy balance. These structural and functional similarities prompted us to compare the mode of action of avicin D with dexamethasone (Dex), a prototypical GC. Using cold competition assay, we show that Avicin D competes with Dex for binding to the GC receptor (GR), leading to its nuclear translocation. In contrast to Dex, avicin-induced nuclear translocation of GR does not result in transcriptional activation of GC-dependent genes. Instead we observe a decrease in the expression of GC-dependent metabolic proteins such as PEPCK and FASN. However, like Dex, avicin D treatment does induce a transrepressive effect on the pro-inflammatory transcription factor NF-κB. While avicin's ability to inhibit NF-κB and its downstream targets appear to be GR-dependent, its pro-apoptotic effects were independent of GR expression. Using various deletion mutants of GR, we demonstrate the requirement of both the DNA and ligand binding domains of GR in mediating avicin D's transrepressive effects. Modeling of avicin-GR interaction revealed that avicin molecule binds only to the antagonist confirmation of GR. These findings suggest that avicin D has properties of being a selective GR modulator that separates transactivation from transrepression. Since the gene-activating properties of GR are mainly linked to its metabolic effects, and the negative interference with the activity of transcription factors to its anti-inflammatory and immune suppressive effects, the identification of such a dissociated GR ligand could have great potential for therapeutic use.

  17. Olfactory receptor signaling.

    PubMed

    Antunes, Gabriela; Simoes de Souza, Fabio Marques

    2016-01-01

    The guanine nucleotide protein (G protein)-coupled receptors (GPCRs) superfamily represents the largest class of membrane protein in the human genome. More than a half of all GPCRs are dedicated to interact with odorants and are termed odorant-receptors (ORs). Linda Buck and Richard Axel, the Nobel Prize laureates in physiology or medicine in 2004, first cloned and characterized the gene family that encode ORs, establishing the foundations to the understanding of the molecular basis for odor recognition. In the last decades, a lot of progress has been done to unravel the functioning of the sense of smell. This chapter gives a general overview of the topic of olfactory receptor signaling and reviews recent advances in this field. PMID:26928542

  18. Progesterone Receptor Signaling Mechanisms.

    PubMed

    Grimm, Sandra L; Hartig, Sean M; Edwards, Dean P

    2016-09-25

    Progesterone receptor (PR) is a master regulator in female reproductive tissues that controls developmental processes and proliferation and differentiation during the reproductive cycle and pregnancy. PR also plays a role in progression of endocrine-dependent breast cancer. As a member of the nuclear receptor family of ligand-dependent transcription factors, the main action of PR is to regulate networks of target gene expression in response to binding its cognate steroid hormone, progesterone. This paper summarizes recent advances in understanding the structure-function properties of the receptor protein and the tissue/cell-type-specific PR signaling pathways that contribute to the biological actions of progesterone in the normal breast and in breast cancer. PMID:27380738

  19. A Novel Nectin-mediated Cell Adhesion Apparatus That Is Implicated in Prolactin Receptor Signaling for Mammary Gland Development.

    PubMed

    Kitayama, Midori; Mizutani, Kiyohito; Maruoka, Masahiro; Mandai, Kenji; Sakakibara, Shotaro; Ueda, Yuki; Komori, Takahide; Shimono, Yohei; Takai, Yoshimi

    2016-03-11

    Mammary gland development is induced by the actions of various hormones to form a structure consisting of collecting ducts and milk-secreting alveoli, which comprise two types of epithelial cells known as luminal and basal cells. These cells adhere to each other by cell adhesion apparatuses whose roles in hormone-dependent mammary gland development remain largely unknown. Here we identified a novel cell adhesion apparatus at the boundary between the luminal and basal cells in addition to desmosomes. This apparatus was formed by the trans-interaction between the cell adhesion molecules nectin-4 and nectin-1, which were expressed in the luminal and basal cells, respectively. Nectin-4 of this apparatus further cis-interacted with the prolactin receptor in the luminal cells to enhance the prolactin-induced prolactin receptor signaling for alveolar development with lactogenic differentiation. Thus, a novel nectin-mediated cell adhesion apparatus regulates the prolactin receptor signaling for mammary gland development. PMID:26757815

  20. A Novel Nectin-mediated Cell Adhesion Apparatus That Is Implicated in Prolactin Receptor Signaling for Mammary Gland Development.

    PubMed

    Kitayama, Midori; Mizutani, Kiyohito; Maruoka, Masahiro; Mandai, Kenji; Sakakibara, Shotaro; Ueda, Yuki; Komori, Takahide; Shimono, Yohei; Takai, Yoshimi

    2016-03-11

    Mammary gland development is induced by the actions of various hormones to form a structure consisting of collecting ducts and milk-secreting alveoli, which comprise two types of epithelial cells known as luminal and basal cells. These cells adhere to each other by cell adhesion apparatuses whose roles in hormone-dependent mammary gland development remain largely unknown. Here we identified a novel cell adhesion apparatus at the boundary between the luminal and basal cells in addition to desmosomes. This apparatus was formed by the trans-interaction between the cell adhesion molecules nectin-4 and nectin-1, which were expressed in the luminal and basal cells, respectively. Nectin-4 of this apparatus further cis-interacted with the prolactin receptor in the luminal cells to enhance the prolactin-induced prolactin receptor signaling for alveolar development with lactogenic differentiation. Thus, a novel nectin-mediated cell adhesion apparatus regulates the prolactin receptor signaling for mammary gland development.

  1. Different intracellular signalling pathways triggered by an anti-prolactin receptor (PRLR) antibody: Implication for a signal-specific PRLR agonist.

    PubMed

    Kan, Quan-E; Su, Yong; Yang, Huihui; Man, Hua

    2016-01-01

    In this work, we prepared a panel of monoclonal antibodies directed against prolactin receptor (PRLR) using the hybridoma technique. Of these monoclonal antibodies (Mabs), the Mab designated B6 was chosen for further characterization based on its biological activity. We first demonstrated that B6 can specifically bind to the prolactin receptor (PRLR) expressed on target cells by immunoprecipitation and Western blotting analysis. Subsequently, epitope mapping studies using a competitive receptor-binding assay indicated that B6 epitopes partially overlapped with those of prolactin (PRL). We then examined the resulting signal transduction pathways activated by this antibody in T-47D and CHO-PRLR cells and found that B6 induced different intracellular signalling compared with prolactin, which activates serine-threonine kinase (AKT), extracellular signal-regulated kinase 1/2 (ERK1/2), signal transducer and activator of transcription1 (STAT1) and STAT3 but not STAT5. The present study suggests that: (a) B6 may be a signal-specific prolactin receptor (PRLR) agonist; (b) B6 may be a biological reagent that can be used to explore the mechanism of PRLR-mediated intracellular signalling. In addition, this work also implies a strategy for preparing signal-specific cytokine agonists.

  2. Functional Selectivity in CB2 Cannabinoid Receptor Signaling and Regulation: Implications for the Therapeutic Potential of CB2 Ligands

    PubMed Central

    Atwood, Brady K.; Wager-Miller, James; Haskins, Christopher; Straiker, Alex

    2012-01-01

    Receptor internalization increases the flexibility and scope of G protein-coupled receptor (GPCR) signaling. CB1 and CB2 cannabinoid receptors undergo internalization after sustained exposure to agonists. However, it is not known whether different agonists internalize CB2 to different extents. Because CB2 is a promising therapeutic target, understanding its trafficking in response to different agonists is necessary for a complete understanding of its biology. Here we profile a number of cannabinoid receptor ligands and provide evidence for marked functional selectivity of cannabinoid receptor internalization. Classic, aminoalkylindole, bicyclic, cannabilactone, iminothiazole cannabinoid, and endocannabinoid ligands varied greatly in their effects on CB1 and CB2 trafficking. Our most striking finding was that (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl) pyrrolo-[1,2,3-d,e]-1,4-benzoxazin-6-yl]-1-naphthalenyl-methanone (WIN55,212-2) (and other aminoalkylindoles) failed to promote CB2 receptor internalization, whereas 5-(1,1-dimethylheptyl)-2-(5-hydroxy-2-(3-hydroxypropyl)cyclohexyl)phenol (CP55,940) robustly internalized CB2 receptors. Furthermore, WIN55,212-2 competitively antagonized CP55,940-induced CB2 internalization. Despite these differences in internalization, both compounds activated CB2 receptors as measured by extracellular signal-regulated kinase 1/2 phosphorylation and recruitment of β-arrestin2 to the membrane. In contrast, whereas CP55,940 inhibited voltage-gated calcium channels via CB2 receptor activation, WIN55,212-2 was ineffective on its own and antagonized the effects of CP55,940. On the basis of the differences we found between these two ligands, we also tested the effects of other cannabinoids on these signaling pathways and found additional evidence for functional selectivity of CB2 ligands. These novel data highlight that WIN55,212-2 and other cannabinoids show strong functional selectivity at CB2 receptors and suggest that

  3. Angiotensin II receptor signalling.

    PubMed

    Daniels, Derek; Yee, Daniel K; Fluharty, Steven J

    2007-05-01

    Angiotensin II plays a key role in the regulation of body fluid homeostasis. To correct body fluid deficits that occur during hypovolaemia, an animal needs to ingest both water and electrolytes. Thus, it is not surprising that angiotensin II, which is synthesized in response to hypovolaemia, acts centrally to increase both water and NaCl intake. Here, we review findings relating to the properties of angiotensin II receptors that give rise to changes in behaviour. Data are described to suggest that divergent signal transduction pathways are responsible for separable behavioural responses to angiotensin II, and a hypothesis is proposed to explain how this divergence may map onto neural circuits in the brain.

  4. Differential actions of orexin receptors in brainstem cholinergic and monoaminergic neurons revealed by receptor knockouts: implications for orexinergic signaling in arousal and narcolepsy

    PubMed Central

    Kohlmeier, Kristi A.; Tyler, Christopher J.; Kalogiannis, Mike; Ishibashi, Masaru; Kristensen, Morten P.; Gumenchuk, Iryna; Chemelli, Richard M.; Kisanuki, Yaz Y.; Yanagisawa, Masashi; Leonard, Christopher S.

    2013-01-01

    Orexin neuropeptides influence multiple homeostatic functions and play an essential role in the expression of normal sleep-wake behavior. While their two known receptors (OX1 and OX2) are targets for novel pharmacotherapeutics, the actions mediated by each receptor remain largely unexplored. Using brain slices from mice constitutively lacking either receptor, we used whole-cell and Ca2+ imaging methods to delineate the cellular actions of each receptor within cholinergic [laterodorsal tegmental nucleus (LDT)] and monoaminergic [dorsal raphe (DR) and locus coeruleus (LC)] brainstem nuclei—where orexins promote arousal and suppress REM sleep. In slices from OX−/−2 mice, orexin-A (300 nM) elicited wild-type responses in LDT, DR, and LC neurons consisting of a depolarizing current and augmented voltage-dependent Ca2+ transients. In slices from OX−/−1 mice, the depolarizing current was absent in LDT and LC neurons and was attenuated in DR neurons, although Ca2+-transients were still augmented. Since orexin-A produced neither of these actions in slices lacking both receptors, our findings suggest that orexin-mediated depolarization is mediated by both receptors in DR, but is exclusively mediated by OX1 in LDT and LC neurons, even though OX2 is present and OX2 mRNA appears elevated in brainstems from OX−/−1 mice. Considering published behavioral data, these findings support a model in which orexin-mediated excitation of mesopontine cholinergic and monoaminergic neurons contributes little to stabilizing spontaneous waking and sleep bouts, but functions in context-dependent arousal and helps restrict muscle atonia to REM sleep. The augmented Ca2+ transients produced by both receptors appeared mediated by influx via L-type Ca2+ channels, which is often linked to transcriptional signaling. This could provide an adaptive signal to compensate for receptor loss or prolonged antagonism and may contribute to the reduced severity of narcolepsy in single receptor

  5. Influence of Berry-Polyphenols on Receptor Signaling and Cell-Death Pathways: Implications for Breast Cancer Prevention

    PubMed Central

    Aiyer, Harini S; Warri, Anni M; Woode, Denzel R; Hilakivi-Clarke, Leena; Clarke, Robert

    2012-01-01

    Breast cancer is the most commonly diagnosed cancer among women worldwide. Many women have become more aware of the benefits of increasing fruit consumption, as part of a healthy lifestyle, for the prevention of cancer. The mechanisms by which fruits, including berries, prevent breast cancer can be partially explained by exploring their interactions with pathways known influence cell-proliferation and evasion of cell-death. Two receptor pathways- estrogen receptor (ER) and tyrosine kinase receptors, especially the epidermal growth factor receptor (EGFR) family- are drivers of cell-proliferation and play a significant role in the development of both primary and recurrent breast cancer. There is strong evidence to show that several phytochemicals present in berries such as cyanidin, delphinidin, quercetin, kaempferol, ellagic acid, resveratrol and pterostilbene, interact with and alter the effects of these pathways. Further, they also induce cell death (apoptosis and autophagy) via their influence on kinase signaling. In this review, we summarize in vitro data regarding the interaction of berry polyphenols with the specific receptors and the mechanisms by which they induce cell death. Further, we also present in vivo data of primary breast cancer prevention by individual compounds and whole berries. Finally, we present a possible role for berries and berry compounds in the prevention of breast cancer and our perspective on the areas that require further research. PMID:22300613

  6. G-protein Coupled Receptor Signaling in Pluripotent Stem Cell-derived Cardiovascular Cells: Implications for Disease Modeling

    PubMed Central

    Dolatshad, Nazanin F.; Hellen, Nicola; Jabbour, Richard J.; Harding, Sian E.; Földes, Gabor

    2015-01-01

    Human pluripotent stem cell derivatives show promise as an in vitro platform to study a range of human cardiovascular diseases. A better understanding of the biology of stem cells and their cardiovascular derivatives will help to understand the strengths and limitations of this new model system. G-protein coupled receptors (GPCRs) are key regulators of stem cell maintenance and differentiation and have an important role in cardiovascular cell signaling. In this review, we will therefore describe the state of knowledge concerning the regulatory role of GPCRs in both the generation and function of pluripotent stem cell derived-cardiomyocytes, -endothelial, and -vascular smooth muscle cells. We will consider how far the in vitro disease models recapitulate authentic GPCR signaling and provide a useful basis for discovery of disease mechanisms or design of therapeutic strategies. PMID:26697426

  7. Structures of the Signal Recognition Particle Receptor From the Archaeon Pyrococcus Furiosus: Implications for the Targeting Step at the Membrane

    SciTech Connect

    Egea, P.F.; Tsuruta, H.; Leon, G.P.de; Napetschnig, J.; Walter, P.; Stroud, R.M.

    2009-05-18

    In all organisms, a ribonucleoprotein called the signal recognition particle (SRP) and its receptor (SR) target nascent proteins from the ribosome to the translocon for secretion or membrane insertion. We present the first X-ray structures of an archeal FtsY, the receptor from the hyper-thermophile Pyrococcus furiosus (Pfu), in its free and GDP {center_dot} magnesium-bound forms. The highly charged N-terminal domain of Pfu-FtsY is distinguished by a long N-terminal helix. The basic charges on the surface of this helix are likely to regulate interactions at the membrane. A peripheral GDP bound near a regulatory motif could indicate a site of interaction between the receptor and ribosomal or SRP RNAs. Small angle X-ray scattering and analytical ultracentrifugation indicate that the crystal structure of Pfu-FtsY correlates well with the average conformation in solution. Based on previous structures of two sub-complexes, we propose a model of the core of archeal and eukaryotic SRP {center_dot} SR targeting complexes.

  8. Structures of the Signal Recognition Particle Receptor from the Archaeon Pyrococcus furiosus: Implications for the Targeting Step at the Membrane

    PubMed Central

    Egea, Pascal F.; Tsuruta, Hiro; de Leon, Gladys P.; Napetschnig, Johanna; Walter, Peter; Stroud, Robert M.

    2008-01-01

    In all organisms, a ribonucleoprotein called the signal recognition particle (SRP) and its receptor (SR) target nascent proteins from the ribosome to the translocon for secretion or membrane insertion. We present the first X-ray structures of an archeal FtsY, the receptor from the hyper-thermophile Pyrococcus furiosus (Pfu), in its free and GDP•magnesium-bound forms. The highly charged N-terminal domain of Pfu-FtsY is distinguished by a long N-terminal helix. The basic charges on the surface of this helix are likely to regulate interactions at the membrane. A peripheral GDP bound near a regulatory motif could indicate a site of interaction between the receptor and ribosomal or SRP RNAs. Small angle X-ray scattering and analytical ultracentrifugation indicate that the crystal structure of Pfu-FtsY correlates well with the average conformation in solution. Based on previous structures of two sub-complexes, we propose a model of the core of archeal and eukaryotic SRP•SR targeting complexes. PMID:18978942

  9. Modeling Transmembrane Domain Dimers/Trimers of Plexin Receptors: Implications for Mechanisms of Signal Transmission across the Membrane

    PubMed Central

    Zhang, Liqun; Polyansky, Anton; Buck, Matthias

    2015-01-01

    Single-pass transmembrane (TM) receptors transmit signals across lipid bilayers by helix association or by configurational changes within preformed dimers. The structure determination for such TM regions is challenging and has mostly been accomplished by NMR spectroscopy. Recently, the computational prediction of TM dimer structures is becoming recognized for providing models, including alternate conformational states, which are important for receptor regulation. Here we pursued a strategy to predict helix oligomers that is based on packing considerations (using the PREDDIMER webserver) and is followed by a refinement of structures, utilizing microsecond all-atom molecular dynamics simulations. We applied this method to plexin TM receptors, a family of 9 human proteins, involved in the regulation of cell guidance and motility. The predicted models show that, overall, the preferences identified by PREDDIMER are preserved in the unrestrained simulations and that TM structures are likely to be diverse across the plexin family. Plexin-B1 and –B3 TM helices are regular and tend to associate, whereas plexin-A1, -A2, –A3, -A4, -C1 and –D1 contain sequence elements, such as poly-Glycine or aromatic residues that distort helix conformation and association. Plexin-B2 does not form stable dimers due to the presence of TM prolines. No experimental structural information on the TM region is available for these proteins, except for plexin-C1 dimeric and plexin-B1 – trimeric structures inferred from X-ray crystal structures of the intracellular regions. Plexin-B1 TM trimers utilize Ser and Thr sidechains for interhelical contacts. We also modeled the juxta-membrane (JM) region of plexin-C1 and plexin-B1 and show that it synergizes with the TM structures. The structure and dynamics of the JM region and TM-JM junction provide determinants for the distance and distribution of the intracellular domains, and for their binding partners relative to the membrane. The structures

  10. Biased signaling at chemokine receptors.

    PubMed

    Corbisier, Jenny; Galès, Céline; Huszagh, Alexandre; Parmentier, Marc; Springael, Jean-Yves

    2015-04-10

    The ability of G protein-coupled receptors (GPCRs) to activate selective signaling pathways according to the conformation stabilized by bound ligands (signaling bias) is a challenging concept in the GPCR field. Signaling bias has been documented for several GPCRs, including chemokine receptors. However, most of these studies examined the global signaling bias between G protein- and arrestin-dependent pathways, leaving unaddressed the potential bias between particular G protein subtypes. Here, we investigated the coupling selectivity of chemokine receptors CCR2, CCR5, and CCR7 in response to various ligands with G protein subtypes by using bioluminescence resonance energy transfer biosensors monitoring directly the activation of G proteins. We also compared data obtained with the G protein biosensors with those obtained with other functional readouts, such as β-arrestin-2 recruitment, cAMP accumulation, and calcium mobilization assays. We showed that the binding of chemokines to CCR2, CCR5, and CCR7 activated the three Gαi subtypes (Gαi1, Gαi2, and Gαi3) and the two Gαo isoforms (Gαoa and Gαob) with potencies that generally correlate to their binding affinities. In addition, we showed that the binding of chemokines to CCR5 and CCR2 also activated Gα12, but not Gα13. For each receptor, we showed that the relative potency of various agonist chemokines was not identical in all assays, supporting the notion that signaling bias exists at chemokine receptors.

  11. GABAB receptors modulate NMDA receptor calcium signals in dendritic spines.

    PubMed

    Chalifoux, Jason R; Carter, Adam G

    2010-04-15

    Metabotropic GABA(B) receptors play a fundamental role in modulating the excitability of neurons and circuits throughout the brain. These receptors influence synaptic transmission by inhibiting presynaptic release or activating postsynaptic potassium channels. However, their ability to directly influence different types of postsynaptic glutamate receptors remains unresolved. Here we examine GABA(B) receptor modulation in layer 2/3 pyramidal neurons from the mouse prefrontal cortex. We use two-photon laser-scanning microscopy to study synaptic modulation at individual dendritic spines. Using two-photon optical quantal analysis, we first demonstrate robust presynaptic modulation of multivesicular release at single synapses. Using two-photon glutamate uncaging, we then reveal that GABA(B) receptors strongly inhibit NMDA receptor calcium signals. This postsynaptic modulation occurs via the PKA pathway and does not affect synaptic currents mediated by AMPA or NMDA receptors. This form of GABA(B) receptor modulation has widespread implications for the control of calcium-dependent neuronal function.

  12. Signaling from Axon Guidance Receptors

    PubMed Central

    Bashaw, Greg J.; Klein, Rüdiger

    2010-01-01

    Determining how axon guidance receptors transmit signals to allow precise pathfinding decisions is fundamental to our understanding of nervous system development and may suggest new strategies to promote axon regeneration after injury or disease. Signaling mechanisms that act downstream of four prominent families of axon guidance cues—netrins, semaphorins, ephrins, and slits—have been extensively studied in both invertebrate and vertebrate model systems. Although details of these signaling mechanisms are still fragmentary and there appears to be considerable diversity in how different guidance receptors regulate the motility of the axonal growth cone, a number of common themes have emerged. Here, we review recent insights into how specific receptors for each of these guidance cues engage downstream regulators of the growth cone cytoskeleton to control axon guidance. PMID:20452961

  13. Signaling from axon guidance receptors.

    PubMed

    Bashaw, Greg J; Klein, Rüdiger

    2010-05-01

    Determining how axon guidance receptors transmit signals to allow precise pathfinding decisions is fundamental to our understanding of nervous system development and may suggest new strategies to promote axon regeneration after injury or disease. Signaling mechanisms that act downstream of four prominent families of axon guidance cues--netrins, semaphorins, ephrins, and slits--have been extensively studied in both invertebrate and vertebrate model systems. Although details of these signaling mechanisms are still fragmentary and there appears to be considerable diversity in how different guidance receptors regulate the motility of the axonal growth cone, a number of common themes have emerged. Here, we review recent insights into how specific receptors for each of these guidance cues engage downstream regulators of the growth cone cytoskeleton to control axon guidance. PMID:20452961

  14. P2Y1 receptor activation elicits its partition out of membrane rafts and its rapid internalization from human blood vessels: implications for receptor signaling.

    PubMed

    Norambuena, Andrés; Poblete, M Inés; Donoso, M Verónica; Espinoza, C Sofía; González, Alfonso; Huidobro-Toro, J Pablo

    2008-12-01

    The nucleotide P2Y(1) receptor (P2Y(1)R) is expressed in both the endothelial and vascular smooth muscle cells; however, its plasma membrane microregionalization and internalization in human tissues remain unknown. We report on the role of membrane rafts in P2Y(1)R signaling by using sodium carbonate or OptiPrep sucrose density gradients, Western blot analysis, reduction of tissue cholesterol content, and vasomotor assays of endothelium-denuded human chorionic arteries. In tissue extracts prepared either in sodium carbonate or OptiPrep, approximately 20 to 30% of the total P2Y(1)R mass consistently partitioned into raft fractions and correlated with vasomotor activity. Vessel treatment with methyl beta-cyclodextrin reduced the raft partitioning of the P2Y(1)R and obliterated the P2Y(1)R-mediated contractions but not the vasomotor responses elicited by either serotonin or KCl. Perfusion of chorionic artery segments with 100 nM 2-methylthio ADP or 10 nM [[(1R,2R,3S,4R,5S)-4-[6-amino-2-(methylthio)-9H-purin-9-yl] 2,3dihydroxybicyclo[3.1.0]hex-1-yl]methyl] diphosphoric acid mono ester trisodium salt (MRS 2365), a selective P2Y(1)R agonist, not only displaced within 4 min the P2Y(1)R localization out of membrane rafts but also induced its subsequent internalization. 2'-Deoxy-N(6)-methyladenosine 3',5'-bisphosphate tetrasodium salt (MRS 2179), a specific P2Y(1)R antagonist, did not cause a similar displacement but blocked the agonist-induced exit from rafts. Neither adenosine nor uridine triphosphate displaced the P2Y(1)R from the membrane raft, further evidencing the pharmacodynamics of the receptor-ligand interaction. Vascular reactivity assays showed fading of the ligand-induced vasoconstrictions, a finding that correlated with the P2Y(1)R exit from raft domains and internalization. These results demonstrate in intact human vascular smooth muscle the association of the P2Y(1)R to membrane rafts, highlighting the role of this microdomain in P2Y(1)R signaling.

  15. Measurement of Receptor Signaling Bias.

    PubMed

    Kenakin, Terry

    2016-01-01

    G protein-coupled receptors (GPCRs) are often pleiotropically linked to numerous cellular signaling mechanisms in cells, and it is now known that many agonists differentially activate some signaling pathways at the expense of others. The mechanism for this effect is the stabilization of different active receptor states by different agonists, and it leads to varying qualities of efficacy for different agonists. Agonist bias is a powerful mechanism to amplify beneficial signals and diminish harmful signals, and thus improve the overall profile of agonist ligands. This unit describes a method to quantify agonist bias with a scale that enables medicinal chemists to amplify or reduce these effects in new molecules. The method is based on the Black/Leff operational model and yields a statistical estimate of the confidence for bias measurements. © 2016 by John Wiley & Sons, Inc. PMID:27636109

  16. 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

  17. Proteomic pathway analysis of the hippocampus in schizophrenia and bipolar affective disorder implicates 14-3-3 signaling, aryl hydrocarbon receptor signaling, and glucose metabolism: potential roles in GABAergic interneuron pathology.

    PubMed

    Schubert, Klaus Oliver; Föcking, Melanie; Cotter, David R

    2015-09-01

    Neuropathological changes of the hippocampus have been associated with psychotic disorders such as schizophrenia and bipolar disorder. Recent work has particularly implicated hippocampal GABAergic interneurons in the pathophysiology of these diseases. However, the molecular mechanisms underlying structural and cellular hippocampal pathology remain poorly understood. We used data from comprehensive difference-in-gel electrophoresis (2-D DIGE) investigations of postmortem human hippocampus of people with schizophrenia and bipolar disorder, covering the acidic (isoelectric point (pI) between pH4 and 7) and, separately, the basic (pI between pH6 and 11) sub-proteome, for Ingenuity Pathway Analysis (IPA) of implicated protein networks and pathways. Comparing disease and control cases, we identified 58 unique differentially expressed proteins in schizophrenia, and 70 differentially expressed proteins in bipolar disorder, using mass spectrometry. IPA implicated, most prominently, 14-3-3 and aryl hydrocarbon receptor signaling in schizophrenia, and gluconeogenesis/glycolysis in bipolar disorder. Both disorders were characterized by alterations of proteins involved in the oxidative stress response, mitochondrial function, and protein-endocytosis, -trafficking, -degradation, and -ubiquitination. These findings are interpreted with a focus on GABAergic interneuron pathology in the hippocampus.

  18. NOD-Like Receptor Signaling in Cholesteatoma

    PubMed Central

    Leichtle, Anke; Klenke, Christin; Ebmeyer, Joerg; Daerr, Markus; Bruchhage, Karl-Ludwig; Hoffmann, Anna Sophie; Ryan, Allen F.; Wollenberg, Barbara; Sudhoff, Holger

    2015-01-01

    Background. Cholesteatoma is a destructive process of the middle ear resulting in erosion of the surrounding bony structures with consequent hearing loss, vestibular dysfunction, facial paralysis, or intracranial complications. The etiopathogenesis of cholesteatoma is controversial but is associated with recurrent ear infections. The role of intracellular innate immune receptors, the NOD-like receptors, and their associated signaling networks was investigated in cholesteatoma, since mutations in NOD-like receptor-related genes have been implicated in other chronic inflammatory disorders. Results. The expression of NOD2 mRNA and protein was significantly induced in cholesteatoma compared to the external auditory canal skin, mainly located in the epithelial layer of cholesteatoma. Microarray analysis showed significant upregulation for NOD2, not for NOD1, TLR2, or TLR4 in cholesteatoma. Moreover, regulation of genes in an interaction network of the NOD-adaptor molecule RIPK2 was detected. In addition to NOD2, NLRC4, and PYCARD, the downstream molecules IRAK1 and antiapoptotic regulator CFLAR showed significant upregulation, whereas SMAD3, a proapoptotic inducer, was significantly downregulated. Finally, altered regulation of inflammatory target genes of NOD signaling was detected. Conclusions. These results indicate that the interaction of innate immune signaling mediated by NLRs and their downstream target molecules is involved in the etiopathogenesis and growth of cholesteatoma. PMID:25922834

  19. NOD-Like Receptor Signaling in Cholesteatoma.

    PubMed

    Leichtle, Anke; Klenke, Christin; Ebmeyer, Joerg; Daerr, Markus; Bruchhage, Karl-Ludwig; Hoffmann, Anna Sophie; Ryan, Allen F; Wollenberg, Barbara; Sudhoff, Holger

    2015-01-01

    Background. Cholesteatoma is a destructive process of the middle ear resulting in erosion of the surrounding bony structures with consequent hearing loss, vestibular dysfunction, facial paralysis, or intracranial complications. The etiopathogenesis of cholesteatoma is controversial but is associated with recurrent ear infections. The role of intracellular innate immune receptors, the NOD-like receptors, and their associated signaling networks was investigated in cholesteatoma, since mutations in NOD-like receptor-related genes have been implicated in other chronic inflammatory disorders. Results. The expression of NOD2 mRNA and protein was significantly induced in cholesteatoma compared to the external auditory canal skin, mainly located in the epithelial layer of cholesteatoma. Microarray analysis showed significant upregulation for NOD2, not for NOD1, TLR2, or TLR4 in cholesteatoma. Moreover, regulation of genes in an interaction network of the NOD-adaptor molecule RIPK2 was detected. In addition to NOD2, NLRC4, and PYCARD, the downstream molecules IRAK1 and antiapoptotic regulator CFLAR showed significant upregulation, whereas SMAD3, a proapoptotic inducer, was significantly downregulated. Finally, altered regulation of inflammatory target genes of NOD signaling was detected. Conclusions. These results indicate that the interaction of innate immune signaling mediated by NLRs and their downstream target molecules is involved in the etiopathogenesis and growth of cholesteatoma. PMID:25922834

  20. Tie2 and Eph Receptor Tyrosine Kinase Activation and Signaling

    PubMed Central

    Barton, William A.; Dalton, Annamarie C.; Seegar, Tom C.M.; Himanen, Juha P.

    2014-01-01

    The Eph and Tie cell surface receptors mediate a variety of signaling events during development and in the adult organism. As other receptor tyrosine kinases, they are activated on binding of extracellular ligands and their catalytic activity is tightly regulated on multiple levels. The Eph and Tie receptors display some unique characteristics, including the requirement of ligand-induced receptor clustering for efficient signaling. Interestingly, both Ephs and Ties can mediate different, even opposite, biological effects depending on the specific ligand eliciting the response and on the cellular context. Here we discuss the structural features of these receptors, their interactions with various ligands, as well as functional implications for downstream signaling initiation. The Eph/ephrin structures are already well reviewed and we only provide a brief overview on the initial binding events. We go into more detail discussing the Tie-angiopoietin structures and recognition. PMID:24478383

  1. Apelin receptors: From signaling to antidiabetic strategy.

    PubMed

    Chaves-Almagro, C; Castan-Laurell, I; Dray, C; Knauf, C; Valet, P; Masri, B

    2015-09-15

    The G protein-coupled receptor APJ and its cognate ligand, apelin, are widely expressed throughout human body. They are implicated in different key physiological processes such as angiogenesis, cardiovascular functions, fluid homeostasis and energy metabolism regulation. On the other hand, this couple ligand-receptor is also involved in the development and progression of different pathologies including diabetes, obesity, cardiovascular disease and cancer. Recently, a new endogenous peptidic ligand of APJ, named Elabela/Toddler, has been identified and shown to play a crucial role in embryonic development. Whereas nothing is yet known regarding Elabela/Toddler functions in adulthood, apelin has been extensively described as a beneficial adipokine regarding to glucose and lipid metabolism and is endowed with anti-diabetic and anti-obesity properties. Indeed, there is a growing body of evidence supporting apelin signaling as a novel promising therapeutic target for metabolic disorders (obesity, type 2 diabetes). In this review, we provide an overview of the pharmacological properties of APJ and its endogenous ligands. We also report the activity of peptidic and non-peptidic agonists and antagonists targeting APJ described in the literature. Finally, we highlight the important role of this signaling pathway in the control of energy metabolism at the peripheral level and in the central nervous system in both physiological conditions and during obesity or diabetes. PMID:26007641

  2. Relaxin-3 receptor (Rxfp3) gene knockout mice display reduced running wheel activity: implications for role of relaxin-3/RXFP3 signalling in sustained arousal.

    PubMed

    Hosken, Ihaia T; Sutton, Steven W; Smith, Craig M; Gundlach, Andrew L

    2015-02-01

    Anatomical and pharmacological evidence suggests the neuropeptide, relaxin-3, is the preferred endogenous ligand for the relaxin family peptide-3 receptor (RXFP3) and suggests a number of putative stress- and arousal-related roles for RXFP3 signalling. However, in vitro and in vivo evidence demonstrates exogenous relaxin-3 can activate other relaxin peptide family receptors, and the role of relaxin-3/RXFP3 signalling in specific brain circuits and associated behaviours in mice is not well described. In this study, we characterised the behaviour of cohorts of male and female Rxfp3 gene knockout (KO) mice (C57/B6J(RXFP3TM1/DGen)), relative to wild-type (WT) littermates to determine if this receptor KO strain has a similar phenotype to its ligand KO equivalent. Rxfp3 KO mice displayed similar performance to WT littermates in several acute behavioural paradigms designed to gauge motor coordination (rotarod test), spatial memory (Y-maze), depressive-like behaviour (repeat forced-swim test) and sensorimotor gating (prepulse inhibition of acoustic startle). Notably however, male and female Rxfp3 KO mice displayed robust and consistent (dark phase) hypoactivity on voluntary home-cage running wheels (∼20-60% less activity/h), and a small but significant decrease in anxiety-like behavioural traits in the elevated plus maze and light/dark box paradigms. Importantly, this phenotype is near identical to that observed in two independent lines of relaxin-3 KO mice, suggesting these phenotypes are due to the elimination of ligand or receptor and RXFP3-linked signalling. Furthermore, this behavioural characterisation of Rxfp3 KO mice identifies them as a useful experimental model for studying RXFP3-linked signalling and assessing the selectivity and/or potential off-target actions of RXFP3 agonists and antagonists, which could lead to an improved understanding of dysfunctional arousal in mental health disorders, including depression, anxiety, insomnia and neurodegenerative

  3. Signaling by the Engulfment Receptor Draper: A Screen in Drosophila melanogaster Implicates Cytoskeletal Regulators, Jun N-Terminal Kinase, and Yorkie

    PubMed Central

    Fullard, John F.; Baker, Nicholas E.

    2015-01-01

    Draper, the Drosophila melanogaster homolog of the Ced-1 protein of Caenorhabditis elegans, is a cell-surface receptor required for the recognition and engulfment of apoptotic cells, glial clearance of axon fragments and dendritic pruning, and salivary gland autophagy. To further elucidate mechanisms of Draper signaling, we screened chromosomal deficiencies to identify loci that dominantly modify the phenotype of overexpression of Draper isoform II (suppressed differentiation of the posterior crossvein in the wing). We found evidence for 43 genetic modifiers of Draper II. Twenty-four of the 37 suppressor loci and 3 of the 6 enhancer loci were identified. An additional 5 suppressors and 2 enhancers were identified among mutations in functionally related genes. These studies reveal positive contributions to Drpr signaling for the Jun N-terminal Kinase pathway, supported by genetic interactions with hemipterous, basket, jun, and puckered, and for cytoskeleton regulation as indicated by genetic interactions with rac1, rac2, RhoA, myoblast city, Wiskcott–Aldrich syndrome protein, and the formin CG32138, and for yorkie and expanded. These findings indicate that Jun N-terminal Kinase activation and cytoskeletal remodeling collaborate in Draper signaling. Relationships between Draper signaling and Decapentaplegic signaling, insulin signaling, Salvador/Warts/Hippo signaling, apical-basal cell polarity, and cellular responses to mechanical forces are also discussed. PMID:25395664

  4. 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.

  5. 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.

  6. 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

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

    PubMed

    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

  8. Absolute Ligand Discrimination by Dimeric Signaling Receptors.

    PubMed

    Fathi, Sepehr; Nayak, Chitra R; Feld, Jordan J; Zilman, Anton G

    2016-09-01

    Many signaling pathways act through shared components, where different ligand molecules bind the same receptors or activate overlapping sets of response regulators downstream. Nevertheless, different ligands acting through cross-wired pathways often lead to different outcomes in terms of the target cell behavior and function. Although a number of mechanisms have been proposed, it still largely remains unclear how cells can reliably discriminate different molecular ligands under such circumstances. Here we show that signaling via ligand-induced receptor dimerization-a very common motif in cellular signaling-naturally incorporates a mechanism for the discrimination of ligands acting through the same receptor. PMID:27602720

  9. Glucocorticoid receptor signaling in health and disease

    PubMed Central

    Kadmiel, Mahita; Cidlowski, John A.

    2013-01-01

    Glucocorticoids are steroid hormones regulated in a circadian and stres-associated manner to maintain various metabolic and homeostatic functions that are necessary for life. Synthetic glucocorticoids are widely prescribed drugs for many conditions including asthma, chronic obstructive pulmonary disease (COPD), and inflammatory disorders of the eye. Research in the last few years has begun to unravel the profound complexity of glucocorticoid signaling and has contributed remarkably to improved therapeutic strategies. Glucocorticoids signal through the glucocorticoid receptor, a member of the superfamily of nuclear receptors, in both genomic and non-genomic ways in almost every tissue in the human body. In this review, we will provide an update on glucocorticoid receptor signaling and highlight the role of GR signaling in physiological and pathophysiological conditions in the major organ systems in the human body. PMID:23953592

  10. Jejunal linoleic acid infusions require GLP-1 receptor signaling to inhibit food intake: implications for the effectiveness of Roux-en-Y gastric bypass

    PubMed Central

    Moghadam, Alexander A.; Moran, Timothy H.

    2011-01-01

    Roux-en-Y gastric bypass surgery results in sustained decreases in food intake and weight loss. A key component is likely the direct delivery of nutrients to the jejunum and resulting changes in levels of gut peptide secretion. Prior work modeling this aspect of the surgery has shown that small-volume, prolonged jejunal infusions of linoleic acid (LA) produce sustained decreases in food intake and weight loss. LA infusions also significantly elevate plasma glucagon-like peptide-1 (GLP-1) levels. To assess a role for the increased circulating GLP-1 in the feeding suppression, we examined the effect of prolonged peripheral minipump administration of the GLP-1 receptor antagonist exendin 9–39 (Ex 9) on the feeding suppression produced by jejunal LA. Using a 2 × 2 design, we infused either saline or LA in the jejunum (7 h/day, 11.4 kcal) for 5 days with a subset of animals from each group receiving either saline or Ex 9 (25 pmol·kg−1·min−1) continuously via a minipump. The antagonist alone had no effect on food intake. LA reduced daily food intake greatly in excess of the kilocalories infused. Ex 9 completely blocked the feeding suppression produced by the jejunal LA infusion. Ex 9 also attenuated the increase in plasma GLP-1 induced by jejunal LA infusions. These data demonstrate that endogenous GLP-1 receptor signaling is necessary for the reduction in food intake produced by jejunal LA infusions. Whether increased secretion of additional gut peptides is also necessary for such suppressions remains to be determined. PMID:21917638

  11. Phosphoinositide 3-kinase mediated signaling in lobster olfactory receptor neurons.

    PubMed

    Corey, Elizabeth A; Bobkov, Yuriy; Pezier, Adeline; Ache, Barry W

    2010-04-01

    In vertebrates and some invertebrates, odorant molecules bind to G protein-coupled receptors on olfactory receptor neurons (ORNs) to initiate signal transduction. Phosphoinositide 3-kinase (PI3K) activity has been implicated physiologically in olfactory signal transduction, suggesting a potential role for a G protein-coupled receptor-activated class I PI3K. Using isoform-specific antibodies, we identified a protein in the olfactory signal transduction compartment of lobster ORNs that is antigenically similar to mammalian PI3Kgamma and cloned a gene for a PI3K with amino acid homology with PI3Kbeta. The lobster olfactory PI3K co-immunoprecipitates with the G protein alpha and beta subunits, and an odorant-evoked increase in phosphatidylinositol (3,4,5)-trisphosphate can be detected in the signal transduction compartment of the ORNs. PI3Kgamma and beta isoform-specific inhibitors reduce the odorant-evoked output of lobster ORNs in vivo. Collectively, these findings provide evidence that PI3K is indeed activated by odorant receptors in lobster ORNs and further support the potential involvement of G protein activated PI3K signaling in olfactory transduction.

  12. Brain human monoclonal autoantibody from sydenham chorea targets dopaminergic neurons in transgenic mice and signals dopamine D2 receptor: implications in human disease.

    PubMed

    Cox, Carol J; Sharma, Meenakshi; Leckman, James F; Zuccolo, Jonathan; Zuccolo, Amir; Kovoor, Abraham; Swedo, Susan E; Cunningham, Madeleine W

    2013-12-01

    How autoantibodies target the brain and lead to disease in disorders such as Sydenham chorea (SC) is not known. SC is characterized by autoantibodies against the brain and is the main neurologic manifestation of streptococcal-induced rheumatic fever. Previously, our novel SC-derived mAb 24.3.1 was found to recognize streptococcal and brain Ags. To investigate in vivo targets of human mAb 24.3.1, VH/VL genes were expressed in B cells of transgenic (Tg) mice as functional chimeric human VH 24.3.1-mouse C-region IgG1(a) autoantibody. Chimeric human-mouse IgG1(a) autoantibody colocalized with tyrosine hydroxylase in the basal ganglia within dopaminergic neurons in vivo in VH 24.3.1 Tg mice. Both human mAb 24.3.1 and IgG1(a) in Tg sera were found to react with human dopamine D2 receptor (D2R). Reactivity of chorea-derived mAb 24.3.1 or SC IgG with D2R was confirmed by dose-dependent inhibitory signaling of D2R as a potential consequence of targeting dopaminergic neurons, reaction with surface-exposed FLAG epitope-tagged D2R, and blocking of Ab reactivity by an extracellular D2R peptide. IgG from SC and a related subset of streptococcal-associated behavioral disorders called "pediatric autoimmune neuropsychiatric disorder associated with streptococci" (PANDAS) with small choreiform movements reacted in ELISA with D2R. Reaction with FLAG-tagged D2R distinguished SC from PANDAS, whereas sera from both SC and PANDAS induced inhibitory signaling of D2R on transfected cells comparably to dopamine. In this study, we define a mechanism by which the brain may be altered by Ab in movement and behavioral disorders. PMID:24184556

  13. 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

  14. P2X and P2Y receptor signaling in red blood cells

    PubMed Central

    Sluyter, Ronald

    2015-01-01

    Purinergic signaling involves the activation of cell surface P1 and P2 receptors by extracellular nucleosides and nucleotides such as adenosine and adenosine triphosphate (ATP), respectively. P2 receptors comprise P2X and P2Y receptors, and have well-established roles in leukocyte and platelet biology. Emerging evidence indicates important roles for these receptors in red blood cells. P2 receptor activation stimulates a number of signaling pathways in progenitor red blood cells resulting in microparticle release, reactive oxygen species formation, and apoptosis. Likewise, activation of P2 receptors in mature red blood cells stimulates signaling pathways mediating volume regulation, eicosanoid release, phosphatidylserine exposure, hemolysis, impaired ATP release, and susceptibility or resistance to infection. This review summarizes the distribution of P2 receptors in red blood cells, and outlines the functions of P2 receptor signaling in these cells and its implications in red blood cell biology. PMID:26579528

  15. Biased Signaling of Protease-Activated Receptors

    PubMed Central

    Zhao, Peishen; Metcalf, Matthew; Bunnett, Nigel W.

    2014-01-01

    In addition to their role in protein degradation and digestion, proteases can also function as hormone-like signaling molecules that regulate vital patho-physiological processes, including inflammation, hemostasis, pain, and repair mechanisms. Certain proteases can signal to cells by cleaving protease-activated receptors (PARs), a family of four G protein-coupled receptors. PARs are expressed by almost all cell types, control important physiological and disease-relevant processes, and are an emerging therapeutic target for major diseases. Most information about PAR activation and function derives from studies of a few proteases, for example thrombin in the case of PAR1, PAR3, and PAR4, and trypsin in the case of PAR2 and PAR4. These proteases cleave PARs at established sites with the extracellular N-terminal domains, and expose tethered ligands that stabilize conformations of the cleaved receptors that activate the canonical pathways of G protein- and/or β-arrestin-dependent signaling. However, a growing number of proteases have been identified that cleave PARs at divergent sites to activate distinct patterns of receptor signaling and trafficking. The capacity of these proteases to trigger distinct signaling pathways is referred to as biased signaling, and can lead to unique patho-physiological outcomes. Given that a different repertoire of proteases are activated in various patho-physiological conditions that may activate PARs by different mechanisms, signaling bias may account for the divergent actions of proteases and PARs. Moreover, therapies that target disease-relevant biased signaling pathways may be more effective and selective approaches for the treatment of protease- and PAR-driven diseases. Thus, rather than mediating the actions of a few proteases, PARs may integrate the biological actions of a wide spectrum of proteases in different patho-physiological conditions. PMID:24860547

  16. Impulsivity, Stimulant Abuse, and Dopamine Receptor Signaling.

    PubMed

    London, E D

    2016-01-01

    The nonmedical use of amphetamine-type stimulants is a worldwide problem, with substantial medical and social consequences. Nonetheless, the identification of a pharmacological treatment for amphetamine use disorder remains elusive. Stimulant users exhibit neurochemical evidence of dopamine-system dysfunction as well as impulsive behaviors that may interfere with the success of treatments for their addiction. This review focuses on the potential role of dopaminergic neurotransmission in impulsivity, both in healthy individuals and chronic stimulant users who meet criteria for methamphetamine dependence. Presented are findings related to the potential contributions of signaling through dopamine D1- and D2-type receptors to self-control impulsivity in methamphetamine- dependent users. The information available points to signaling through striatal D2-type dopamine receptors as a potential therapeutic target for stimulant use disorders, but medications that target D2-type dopamine receptors have not been successful in treating stimulant-use disorders, possibly because D2-type receptors are downregulated. Other means to augment D2-type receptor signaling are therefore under consideration, and one promising approach is the addition of exercise training as an adjunct to behavioral treatment for addiction. PMID:27288074

  17. Opioid-induced central immune signaling: implications for opioid analgesia

    PubMed Central

    Grace, Peter M.; Maier, Steven F.; Watkins, Linda R.

    2015-01-01

    Despite being the mainstay of pain management, opioids are limited in their clinical utility by adverse effects, such as tolerance and paradoxical hyperalgesia. Research of the past 15 years has extended beyond neurons, to implicate central nervous system immune signaling in these adverse effects. This article will provide an overview of these central immune mechanisms in opioid tolerance and paradoxical hyperalgesia, including those mediated by toll like receptor 4, purinergic, ceramide and chemokine signaling. Challenges for the future, as well as new lines of investigation will be highlighted. PMID:25833219

  18. Disease implication of hyper-Hippo signalling

    PubMed Central

    Wang, Shu-Ping

    2016-01-01

    The Hippo signalling pathway regulates cellular proliferation, apoptosis and differentiation, thus exerting profound effects on cellular homeostasis. Inhibition of Hippo signalling has been frequently implicated in human cancers, indicating a well-known tumour suppressor function of the Hippo pathway. However, it is less certain whether and how hyperactivation of the Hippo pathway affects biological outcome in living cells. This review describes current knowledge of the regulatory mechanisms of the Hippo pathway, mainly focusing on hyperactivation of the Hippo signalling nexus. The disease implications of hyperactivated Hippo signalling have also been discussed, including arrhythmogenic cardiomyopathy, Sveinsson's chorioretinal atrophy, Alzheimer's disease, amyotrophic lateral sclerosis and diabetes. By highlighting the significance of disease-relevant Hippo signalling activation, this review can offer exciting prospects to address the onset and potential reversal of Hippo-related disorders. PMID:27805903

  19. T cell Receptor Signal Transduction in T lymphocytes

    PubMed Central

    Gorentla, Balachandra K; Zhong, Xiao-Ping

    2012-01-01

    The T cell receptor (TCR) recognizes self or foreign antigens presented by major histocompatibility complex (MHC) molecules. Engagement of the TCR triggers the formation of multi-molecular signalosomes that lead to the generation of second messengers and subsequent activation of multiple distal signaling cascades, such as the Ca+2-calcineurin-NFAT, RasGRP1-Ras-Erk1/2, PKCθ-IKK-NFκB, and TSC1/2-mTOR pathways. These signaling cascades control many aspects of T cell biology. Mechanisms have been evolved to fine-tune TCR signaling to maintain T cell homeostasis and self-tolerance, and to properly mount effective responses to microbial infection. Defects or deregulation of TCR signaling has been implicated in the pathogenesis of multiple human diseases. PMID:23946894

  20. Complexity of Receptor Tyrosine Kinase Signal Processing

    PubMed Central

    Volinsky, Natalia; Kholodenko, Boris N.

    2013-01-01

    Our knowledge of molecular mechanisms of receptor tyrosine kinase (RTK) signaling advances with ever-increasing pace. Yet our understanding of how the spatiotemporal dynamics of RTK signaling control specific cellular outcomes has lagged behind. Systems-centered experimental and computational approaches can help reveal how overlapping networks of signal transducers downstream of RTKs orchestrate specific cell-fate decisions. We discuss how RTK network regulatory structures, which involve the immediate posttranslational and delayed transcriptional controls by multiple feed forward and feedback loops together with pathway cross talk, adapt cells to the combinatorial variety of external cues and conditions. This intricate network circuitry endows cells with emerging capabilities for RTK signal processing and decoding. We illustrate how mathematical modeling facilitates our understanding of RTK network behaviors by unraveling specific systems properties, including bistability, oscillations, excitable responses, and generation of intricate landscapes of signaling activities. PMID:23906711

  1. Kir3 channel signaling complexes: focus on opioid receptor signaling

    PubMed Central

    Nagi, Karim; Pineyro, Graciela

    2014-01-01

    Opioids are among the most effective drugs to treat severe pain. They produce their analgesic actions by specifically activating opioid receptors located along the pain perception pathway where they inhibit the flow of nociceptive information. This inhibition is partly accomplished by activation of hyperpolarizing G protein-coupled inwardly-rectifying potassium (GIRK or Kir3) channels. Kir3 channels control cellular excitability in the central nervous system and in the heart and, because of their ubiquitous distribution, they mediate the effects of a large range of hormones and neurotransmitters which, upon activation of corresponding G protein-coupled receptors (GPCRs) lead to channel opening. Here we analyze GPCR signaling via these effectors in reference to precoupling and collision models. Existing knowledge on signaling bias is discussed in relation to these models as a means of developing strategies to produce novel opioid analgesics with an improved side effects profile. PMID:25071446

  2. Signaling through G protein coupled receptors

    PubMed Central

    2009-01-01

    Heterotrimeric G proteins (Gα, Gβ/Gγ subunits) constitute one of the most important components of cell signaling cascade. G Protein Coupled Receptors (GPCRs) perceive many extracellular signals and transduce them to heterotrimeric G proteins, which further transduce these signals intracellular to appropriate downstream effectors and thereby play an important role in various signaling pathways. GPCRs exist as a superfamily of integral membrane protein receptors that contain seven transmembrane α-helical regions, which bind to a wide range of ligands. Upon activation by a ligand, the GPCR undergoes a conformational change and then activate the G proteins by promoting the exchange of GDP/GTP associated with the Gα subunit. This leads to the dissociation of Gβ/Gγ dimer from Gα. Both these moieties then become free to act upon their downstream effectors and thereby initiate unique intracellular signaling responses. After the signal propagation, the GTP of Gα-GTP is hydrolyzed to GDP and Gα becomes inactive (Gα-GDP), which leads to its re-association with the Gβ/Gγ dimer to form the inactive heterotrimeric complex. The GPCR can also transduce the signal through G protein independent pathway. GPCRs also regulate cell cycle progression. Till to date thousands of GPCRs are known from animal kingdom with little homology among them, but only single GPCR has been identified in plant system. The Arabidopsis GPCR was reported to be cell cycle regulated and also involved in ABA and in stress signaling. Here I have described a general mechanism of signal transduction through GPCR/G proteins, structure of GPCRs, family of GPCRs and plant GPCR and its role. PMID:19826234

  3. Estradiol signaling via sequestrable surface receptors.

    PubMed

    Benten, W P; Stephan, C; Lieberherr, M; Wunderlich, F

    2001-04-01

    Estradiol (E(2))-signaling is widely considered to be exclusively mediated through the transcription-regulating intracellular estrogen receptor (ER) alpha and ERbeta. The aim of this study was to investigate transcription-independent E(2)-signaling in mouse IC-21 macrophages. E(2) and E(2)-BSA induce a rapid rise in the intracellular free Ca(2+) concentration ([Ca(2+)](i)) of Fura-2 loaded IC-21 cells as examined by spectrofluorometry. These changes in [Ca(2+)](i) can be inhibited by pertussis toxin, but not by the ER-blockers tamoxifen and raloxifene. The E(2)-signaling initiated at the plasma membrane is mediated through neither ERalpha nor ERbeta, but rather through a novel G protein-coupled membrane E(2)-receptor as revealed by RT-PCR, flow cytometry, and confocal laser scanning microscopy. A special feature of this E(2)-receptor is its sequestration upon agonist stimulation. Sequestration depends on energy and temperature, and it proceeds through a clathrin- and caveolin-independent pathway. PMID:11250949

  4. TAM Receptor Signaling in Immune Homeostasis

    PubMed Central

    Rothlin, Carla V.; Carrera-Silva, Eugenio A.; Bosurgi, Lidia; Ghosh, Sourav

    2015-01-01

    The TAM receptor tyrosine kinases (RTKs)—TYRO3, AXL, and MERTK—together with their cognate agonists GAS6 and PROS1 play an essential role in the resolution of inflammation. Deficiencies in TAM signaling have been associated with chronic inflammatory and autoimmune diseases. Three processes regulated by TAM signaling may contribute, either independently or collectively, to immune homeostasis: the negative regulation of the innate immune response, the phagocytosis of apoptotic cells, and the restoration of vascular integrity. Recent studies have also revealed the function of TAMs in infectious diseases and cancer. Here, we review the important milestones in the discovery of these RTKs and their ligands and the studies that underscore the functional importance of this signaling pathway in physiological immune settings and disease. PMID:25594431

  5. Modulation of hematopoiesis through histamine receptor signaling.

    PubMed

    Schneider, Elke; Bertron, Anne-France; Dy, Michel

    2011-01-01

    Histamine is one of the most versatile biogenic amines targeting a variety of cells through extra- and intracellular binding sites and specific receptors, which trigger different signal transduction pathways. It has been associated with cell growth ever since G. Kahlson demonstrated that its synthesis was increased in rapidly growing tissues of plants and animals. He proposed that the newly formed amine, as opposed to its stored counterpart, might play a major role in growth processes. Later on, a number of investigators provided evidence for the contribution of histamine to the expansion of normal and malignant cells, whether of hematopoietic origin or not. These studies have generated conflicting results, revealing growth-promoting as well as inhibitory effects, most likely because the final outcome of exposure to histamine depends on the signaling pathways triggered by distinct receptors and their differential distribution among the target population. The purpose of the present review is to outline our current understanding of the regulatory functions of histamine during growth and differentiation of hematopoietic progenitors, focusing on those mediated through its H4 receptor.

  6. Loss of α1,6-fucosyltransferase suppressed liver regeneration: implication of core fucose in the regulation of growth factor receptor-mediated cellular signaling.

    PubMed

    Wang, Yuqin; Fukuda, Tomohiko; Isaji, Tomoya; Lu, Jishun; Gu, Wei; Lee, Ho-Hsun; Ohkubo, Yasuhito; Kamada, Yoshihiro; Taniguchi, Naoyuki; Miyoshi, Eiji; Gu, Jianguo

    2015-02-05

    Core fucosylation is an important post-translational modification, which is catalyzed by α1,6-fucosyltransferase (Fut8). Increased expression of Fut8 has been shown in diverse carcinomas including hepatocarcinoma. In this study, we investigated the role of Fut8 expression in liver regeneration by using the 70% partial hepatectomy (PH) model, and found that Fut8 is also critical for the regeneration of liver. Interestingly, we show that the Fut8 activities were significantly increased in the beginning of PH (~4d), but returned to the basal level in the late stage of PH. Lacking Fut8 led to delayed liver recovery in mice. This retardation mainly resulted from suppressed hepatocyte proliferation, as supported not only by a decreased phosphorylation level of epidermal growth factor (EGF) receptor and hepatocyte growth factor (HGF) receptor in the liver of Fut8(-/-) mice in vivo, but by the reduced response to exogenous EGF and HGF of the primary hepatocytes isolated from the Fut8(-/-) mice. Furthermore, an administration of L-fucose, which can increase GDP-fucose synthesis through a salvage pathway, significantly rescued the delayed liver regeneration of Fut8(+/-) mice. Overall, our study provides the first direct evidence for the involvement of Fut8 in liver regeneration.

  7. Epidermal growth factor receptor signaling in tissue

    SciTech Connect

    Shvartsman, Stanislav; Wiley, H. S.; Lauffenburger, Douglas A.

    2004-08-01

    Abstract: A peptide purified from the salivary gland of a mouse was shown few years ago to accelerate incisor eruption and eyelid opening in newborn mice, and was named epidermal growth factor (EGF). The members of this family of peptide growth factors had been identified in numerous physiological and pathological contexts. EGF binds to a cell surface EGF receptor, which induces a biochemical modification (phosphorylation) of the receptor's cytoplasmic tail. There is a growing consensus in the research community that, in addition to cellular and molecular studies, the dynamics of the EGFR network and its operation must be examined in tissues. A key challenge is to integrate the existing molecular and cellular information into a system-level description of the EGFR network at the tissue and organism level. In this paper, the two examples of EGFR signaling in tissues are described, and the recent efforts to model EGFR autocrine loops, which is a predominant mode of EGFR activation in vivo, are summarized.

  8. Receptors signaling gravity orientation in an insect

    NASA Technical Reports Server (NTRS)

    Hartman, H. B.

    1982-01-01

    Displacement in any direction from primary orientation is found to evoke tonic activity from at least one of the four interneurons of a certain type of burrowing cockroach; the receptive field for each interneuron is slightly more than a quadrant. The receptive field of each interneuron is found to be the same as the row of receptors providing the input. Displacement about the least stable axis (0-180 deg) or roll, on the one hand, and the most stable axis (90-270 deg) or pitch, on the other, is found to be unambiguously signaled by pairs of interneurons. Indications are obtained that receptors in the lateral row drive a giant interneuron in a contralateral connective and those in the medial row drive one in an ipsilateral connective.

  9. Taste Receptor Signaling-- From Tongues to Lungs

    PubMed Central

    Kinnamon, Sue C.

    2013-01-01

    Taste buds are the transducing endorgans of gustation. Each taste bud comprises 50–100 elongated cells, which extend from the basal lamina to the surface of the tongue, where their apical microvilli encounter taste stimuli in the oral cavity. Salts and acids utilize apically located ion channels for transduction, while bitter, sweet and umami (glutamate) stimuli utilize G protein coupled receptors (GPCRs) and second messenger signaling mechanisms. This review will focus on GPCR signaling mechanisms. Two classes of taste GPCRs have been identified, the T1Rs for sweet and umami (glutamate) stimuli, and the T2Rs for bitter stimuli. These low affinity GPCRs all couple to the same downstream signaling effectors that include Gβγ activation of PLCβ2, IP3-mediated release of Ca2+ from intracellular stores, and Ca2+-dependent activation of the monovalent selective cation channel, TrpM5. These events lead to membrane depolarization, action potentials, and release of ATP as a transmitter to activate gustatory afferents. The Gα subunit, α-gustducin, activates a phosphodiesterase to decrease intracellular cAMP levels, although the precise targets of cAMP have not been identified. With the molecular identification of the taste GPCRs, it has become clear that taste signaling is not limited to taste buds, but occurs in many cell types of the airways. These include solitary chemosensory cells, ciliated epithelial cells, and smooth muscle cells. Bitter receptors are most abundantly expressed in the airways, where they respond to irritating chemicals and promote protective airway reflexes, utilizing the same downstream signaling effectors as taste cells. PMID:21481196

  10. 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

  11. Cell signaling by receptor-tyrosine kinases

    PubMed Central

    Lemmon, Mark A.; Schlessinger, Joseph

    2010-01-01

    Recent structural studies of receptor tyrosine kinases (RTKs) have revealed unexpected diversity in the mechanisms of their activation by growth factor ligands. Strategies for inducing dimerization by ligand binding are surprisingly diverse, as are mechanisms that couple this event to activation of the intracellular tyrosine kinase domains. As our understanding of these details becomes increasingly sophisticated, it provides an important context for therapeutically countering the effects of pathogenic RTK mutations in cancer and other diseases. Much remains to be learned, however, about the complex signaling networks downstream from RTKs and how alterations in these networks are translated into cellular responses. PMID:20602996

  12. Nuclear GPCRs in cardiomyocytes: an insider’s view of β-adrenergic receptor signaling

    PubMed Central

    Vaniotis, George; Allen, Bruce G.; Hébert, Terence E.

    2016-01-01

    In recent years, we have come to appreciate the complexity of G protein-coupled receptor signaling in general and β-adrenergic receptor (β-AR) signaling in particular. Starting originally from three β-AR subtypes expressed in cardiomyocytes with relatively simple, linear signaling cascades, it is now clear that there are large receptor-based networks which provide a rich and diverse set of responses depending on their complement of signaling partners and the physiological state. More recently, it has become clear that subcellular localization of these signaling complexes also enriches the diversity of phenotypic outcomes. Here, we review our understanding of the signaling repertoire controlled by nuclear β-AR subtypes as well our understanding of the novel roles for G proteins themselves in the nucleus, with a special focus, where possible, on their effects in cardiomyocytes. Finally, we discuss the potential pathological implications of alterations in nuclear β-AR signaling. PMID:21890692

  13. High-Resolution Fractionation of Signaling Endosomes Containing Different Receptors

    PubMed Central

    McCaffrey, Gretchen; Welker, Jonathan; Scott, Jessica; van Der Salm, Louise; Grimes, Mark L.

    2010-01-01

    Receptor endocytosis is regulated by ligand binding, and receptors may signal after endocytosis in signaling endosomes. We hypothesized that signaling endosomes containing different types of receptors may be distinct from one another and have different physical characteristics. To test this hypothesis, we developed a high-resolution organelle fractionation method based on mass and density, optimized to resolve endosomes from other organelles. Three different types of receptors undergoing ligand-induced endocytosis were localized predominately in endosomes that were resolved from one another using this method. Endosomes containing activated receptor tyrosine kinases (RTKs), TrkA and EGFR, were similar to one another. Endosomes containing p75NTR (in the tumor necrosis receptor superfamily) and PAC1 (a G-protein-coupled receptor) were distinct from each other and from RTK endosomes. Receptor-specific endosomes may direct the intracellular location and duration of signal transduction pathways to dictate response to signals and determine cell fate. PMID:19416476

  14. In vivo modulation of endothelial polarization by Apelin receptor signalling

    PubMed Central

    Kwon, Hyouk-Bum; Wang, Shengpeng; Helker, Christian S. M.; Rasouli, S. Javad; Maischein, Hans-Martin; Offermanns, Stefan; Herzog, Wiebke; Stainier, Didier Y. R.

    2016-01-01

    Endothelial cells (ECs) respond to shear stress by aligning in the direction of flow. However, how ECs respond to flow in complex in vivo environments is less clear. Here we describe an endothelial-specific transgenic zebrafish line, whereby the Golgi apparatus is labelled to allow for in vivo analysis of endothelial polarization. We find that most ECs polarize within 4.5 h after the onset of vigorous blood flow and, by manipulating cardiac function, observe that flow-induced EC polarization is a dynamic and reversible process. Based on its role in EC migration, we analyse the role of Apelin signalling in EC polarization and find that it is critical for this process. Knocking down Apelin receptor function in human primary ECs also affects their polarization. Our study provides new tools to analyse the mechanisms of EC polarization in vivo and reveals an important role in this process for a signalling pathway implicated in cardiovascular disease. PMID:27248505

  15. An Essential Role for FGF Receptor Signaling in Lens Development

    PubMed Central

    Robinson, Michael L.

    2007-01-01

    Since the days of Hans Spemann, the ocular lens has served as one of the most important developmental systems for elucidating fundamental processes of induction and differentiation. More recently, studies in the lens have contributed significantly to our understanding of cell cycle regulation and apoptosis. Over twenty years of accumulated evidence using several different vertebrate species has suggested that fibroblast growth factors (FGFs) and/or fibroblast growth factor receptors (FGFRs) play a key role in lens development. FGFR signaling has been implicated in lens induction, lens cell proliferation and survival, lens fiber differentiation and lens regeneration. Here we will review and discuss historical and recent evidence suggesting that (FGFR) signaling plays a vital and universal role in multiple aspects of lens development. PMID:17116415

  16. Adaptations in adenosine signaling in drug dependence: therapeutic implications.

    PubMed

    Hack, Stephen P; Christie, Macdonald J

    2003-01-01

    Adenosine is an important endogenous purine neuromodulator in the central nervous system that modulates many important cellular processes in neurons. The physiological effects of adenosine are transduced through four pharmacologically classified receptor types i.e., A1, A2A, A2B and A3. All adenosine receptors are G-protein coupled receptors (GPCR) of the type 1 variety. Adaptations in adenosine signaling have been implicated in a wide range of pathophysiological processes, such as epilepsies, sleep disorders, pain, and drug addictions. Knowledge relating to the etiology of addictive processes is far from complete, and as a result the therapeutic options to deal with drug dependence issues are limited. Drugs of abuse mediate their effects through many distinct cellular effectors, such as neurotransmitter transporters, ion channels, and receptor proteins. However, a unifying feature of the major drugs of abuse-i.e., opiates, cocaine, and alcohol-is that they all directly or indirectly modulate adenosine signaling in neurons. Agents targeting adenosine receptors may therefore offer novel avenues for the development of therapies to manage or treat addictions. A consistent cellular adaptation to long-term drug use is the up- or down-regulation of signaling pathways driven by adenylyl cyclase/cyclic AMP (cAMP) in several brain regions linked to addiction. Withdrawal from mu-opioids or cocaine following their chronic administration leads to an upregulation of adenylyl cyclase-mediated signaling, resulting in high levels of cAMP. Cyclic AMP produced in this way acts as a substrate for the endogenous production of adenosine. Increased levels of endogenous adenosine interact with presynaptic A1 receptors to inhibit the excessive neuronal excitation often seen during morphine/cocaine withdrawal. These pre-clinical findings fit well with other data indicating that drugs which boost endogenous adenosine levels or directly interact with inhibitory A1 receptors can alleviate

  17. Nutritional Signaling via Free Fatty Acid Receptors.

    PubMed

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

    2016-01-01

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

  18. Signal transduction by the growth hormone receptor

    SciTech Connect

    Waters, M.J.; Rowlinson, S.W.; Clarkson, R.W.

    1994-12-31

    It has been proposed that dimerization of identical receptor subunits by growth hormone (GH) is the mechanism of signal transduction across the cell membrane. We present here data with analogs of porcine GH (pGH), with GH receptors (GHR) mutated in the dimerization domain and with monoclonal antibodies to the GHR which indicate that dimerization is necessary but not sufficient for transduction. We also report nuclear uptake of GH both in vivo and in vitro, along with nuclear localization of the receptor and GH-binding protein (GHBP). This suggests that GH acts directly at the nucleus, and one possible target for this action is a rapid increase in transcription of C/EBP delta seen in 3T3-F442A cells in response to GH. This tyrosine kinase-dependent event may be an archetype for induction of other immediate early gene transcription factors which then interact to determine the programming of the subsequent transcriptional response to GH. 29 refs., 1 fig., 1 tab.

  19. Nutritional Signaling via Free Fatty Acid Receptors

    PubMed Central

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

    2016-01-01

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

  20. Estrogen Receptors and Their Implications in Colorectal Carcinogenesis

    PubMed Central

    Caiazza, Francesco; Ryan, Elizabeth J.; Doherty, Glen; Winter, Desmond C.; Sheahan, Kieran

    2015-01-01

    Upon binding their cognate receptors, ERα (ESR1) and ERβ (ESR2), estrogens activate intracellular signaling cascades that have important consequences for cellular behavior. Historically linked to carcinogenesis in reproductive organs, estrogens have also been implicated in the pathogenesis of different cancer types of non-reproductive tissues including the colon. ERβ is the predominant estrogen receptor expressed in both normal and malignant colonic epithelium. However, during colon cancer progression, ERβ expression is lost, suggesting that estrogen signaling may play a role in disease progression. Estrogens may in fact exert an anti-tumor effect through selective activation of pro-apoptotic signaling mediated by ERβ, inhibition of inflammatory signals and modulation of the tumor microenvironment. In this review, we analyze the estrogen pathway as a possible therapeutic avenue in colorectal cancer, we report the most recent experimental evidence to explain the cellular and molecular mechanisms of estrogen-mediated protection against colorectal tumorigenesis, and we discuss future challenges and potential avenues for targeted therapy. PMID:25699240

  1. Molecular Mechanisms of Opioid Receptor-Dependent Signaling and Behavior

    PubMed Central

    Al-Hasani, Ream; Bruchas, Michael R.

    2013-01-01

    Opioid receptors have been targeted for the treatment of pain and related disorders for thousands of years, and remain the most widely used analgesics in the clinic. Mu (μ), kappa (κ), and delta (δ) opioid receptors represent the originally classified receptor subtypes, with opioid receptor like-1 (ORL1) being the least characterized. All four receptors are G-protein coupled, and activate inhibitory G-proteins. These receptors form homo- and hetereodimeric complexes, signal to kinase cascades, and scaffold a variety of proteins. In this review, we discuss classical mechanisms and developments in understanding opioid tolerance, opioid receptor signaling, and highlight advances in opioid molecular pharmacology, behavioral pharmacology, and human genetics. We put into context how opioid receptor signaling leads to the modulation of behavior with the potential for therapeutic intervention. Finally, we conclude that there is a continued need for more translational work on opioid receptors in vivo. PMID:22020140

  2. [Psychiatric implications of PACAP signaling pathway].

    PubMed

    Hashimoto, Hitoshi

    2012-06-01

    Studies on genetically modified mice for investigating the role of pituitary adenylate cyclase-activating polypeptide (PACAP) in the brain have revealed a previously uncharacterized function of this neuropeptidergic signaling in the regulation of psychomotor behaviors. In addition, recent clinical studies investigating single nucleotide polymorphisms and copy number variations in the PACAP and its receptor genes have associated the variations with major psychiatric disorders and stress-dependent mental disorders. Here, I briefly review these recent advances in the field and make this an opportunity to consider future direction of research.

  3. Opioid receptors: Structural and mechanistic insights into pharmacology and signaling.

    PubMed

    Shang, Yi; Filizola, Marta

    2015-09-15

    Opioid receptors are important drug targets for pain management, addiction, and mood disorders. Although substantial research on these important subtypes of G protein-coupled receptors has been conducted over the past two decades to discover ligands with higher specificity and diminished side effects, currently used opioid therapeutics remain suboptimal. Luckily, recent advances in structural biology of opioid receptors provide unprecedented insights into opioid receptor pharmacology and signaling. We review here a few recent studies that have used the crystal structures of opioid receptors as a basis for revealing mechanistic details of signal transduction mediated by these receptors, and for the purpose of drug discovery.

  4. The resurgence of A2B adenosine receptor signaling

    PubMed Central

    Aherne, Carol M.; Kewley, Emily M.; Eltzschig, Holger K.

    2010-01-01

    Since its discovery as a low-affinity adenosine receptor (AR), the A2B receptor (A2BAR), has proven enigmatic in its function. The previous discovery of the A2AAR, which shares many similarities with the A2BAR but demonstrates significantly greater affinity for its endogenous ligand, led to the original perception that the A2BAR was not of substantial physiologic relevance. In addition, lack of specific pharmacological agents targeting the A2BAR made its initial characterization challenging. However, the importance of this receptor was reconsidered when it was observed that the A2BAR is highly transcriptionally regulated by factors implicated in inflammatory hypoxia. Moreover, the notion that during ischemia or inflammation extracellular adenosine is dramatically elevated to levels sufficient for A2BAR activation, indicated that A2BAR signaling may be important to dampen inflammation particularly during tissue hypoxia. In addition, the recent advent of techniques for murine genetic manipulation along with development of pharmacological agents with enhanced A2BAR specificity has provided invaluable tools for focused studies on the explicit role of A2BAR signaling in different disease models. Currently, studies performed with combined genetic and pharmacological approaches have demonstrated that A2BAR signaling plays a tissue protective role in many models of acute diseases e.g. myocardial ischemia, or acute lung injury. These studies indicate that the A2BAR is expressed on a wide variety of cell types and exerts tissue/cell specific effects. This is an important consideration for future studies where tissue or cell type specific targeting of the A2BAR may be used as therapeutic approach. PMID:20546702

  5. Heteromerization of GPR55 and cannabinoid CB2 receptors modulates signalling

    PubMed Central

    Balenga, N A; Martínez-Pinilla, E; Kargl, J; Schröder, R; Peinhaupt, M; Platzer, W; Bálint, Z; Zamarbide, M; Dopeso-Reyes, I G; Ricobaraza, A; Pérez-Ortiz, J M; Kostenis, E; Waldhoer, M; Heinemann, A; Franco, R

    2014-01-01

    Background and Purpose Heteromerization of GPCRs is key to the integration of extracellular signals and the subsequent cell response via several mechanisms including heteromer-selective ligand binding, trafficking and/or downstream signalling. As the lysophosphatidylinositol GPCR 55 (GPR55) has been shown to affect the function of the cannabinoid receptor subtype 2 (CB2 receptor) in human neutrophils, we investigated the possible heteromerization of CB2 receptors with GPR55. Experimental Approach The direct interaction of human GPR55 and CB2 receptors heterologously expressed in HEK293 cells was assessed by co-immunoprecipitation and bioluminescence resonance energy transfer assays. The effect of cross-talk on signalling was investigated at downstream levels by label-free real-time methods (Epic dynamic mass redistribution and CellKey impedance assays), ERK1/2-MAPK activation and gene reporter assays. Key Results GPR55 and CB2 receptors co-localized on the surface of HEK293 cells, co-precipitated in membrane extracts and formed heteromers in living HEK293 cells. Whereas heteromerization led to a reduction in GPR55-mediated activation of transcription factors (nuclear factor of activated T-cells, NF-κB and cAMP response element), ERK1/2-MAPK activation was potentiated in the presence of CB2 receptors. CB2 receptor-mediated signalling was also affected by co-expression with GPR55. Label-free assays confirmed cross-talk between the two receptors. Conclusions and Implications Heteromers, unique signalling units, form in HEK293 cells expressing GPR55 and CB2 receptors. The signalling by agonists of either receptor was governed (i) by the presence or absence of the partner receptors (with the consequent formation of heteromers) and (ii) by the activation state of the partner receptor. PMID:25048571

  6. Regulation of T-cell receptor signalling by membrane microdomains

    PubMed Central

    Razzaq, Tahir M; Ozegbe, Patricia; Jury, Elizabeth C; Sembi, Phupinder; Blackwell, Nathan M; Kabouridis, Panagiotis S

    2004-01-01

    There is now considerable evidence suggesting that the plasma membrane of mammalian cells is compartmentalized by functional lipid raft microdomains. These structures are assemblies of specialized lipids and proteins and have been implicated in diverse biological functions. Analysis of their protein content using proteomics and other methods revealed enrichment of signalling proteins, suggesting a role for these domains in intracellular signalling. In T lymphocytes, structure/function experiments and complementary pharmacological studies have shown that raft microdomains control the localization and function of proteins which are components of signalling pathways regulated by the T-cell antigen receptor (TCR). Based on these studies, a model for TCR phosphorylation in lipid rafts is presented. However, despite substantial progress in the field, critical questions remain. For example, it is unclear if membrane rafts represent a homogeneous population and if their structure is modified upon TCR stimulation. In the future, proteomics and the parallel development of complementary analytical methods will undoubtedly contribute in further delineating the role of lipid rafts in signal transduction mechanisms. PMID:15554919

  7. Retinoid receptor signaling and autophagy in acute promyelocytic leukemia

    SciTech Connect

    Orfali, Nina; McKenna, Sharon L.; Cahill, Mary R.; Gudas, Lorraine J.; Mongan, Nigel P.

    2014-05-15

    Retinoids are a family of signaling molecules derived from vitamin A with well established roles in cellular differentiation. Physiologically active retinoids mediate transcriptional effects on cells through interactions with retinoic acid (RARs) and retinoid-X (RXR) receptors. Chromosomal translocations involving the RARα gene, which lead to impaired retinoid signaling, are implicated in acute promyelocytic leukemia (APL). All-trans-retinoic acid (ATRA), alone and in combination with arsenic trioxide (ATO), restores differentiation in APL cells and promotes degradation of the abnormal oncogenic fusion protein through several proteolytic mechanisms. RARα fusion-protein elimination is emerging as critical to obtaining sustained remission and long-term cure in APL. Autophagy is a degradative cellular pathway involved in protein turnover. Both ATRA and ATO also induce autophagy in APL cells. Enhancing autophagy may therefore be of therapeutic benefit in resistant APL and could broaden the application of differentiation therapy to other cancers. Here we discuss retinoid signaling in hematopoiesis, leukemogenesis, and APL treatment. We highlight autophagy as a potential important regulator in anti-leukemic strategies. - Highlights: • Normal and aberrant retinoid signaling in hematopoiesis and leukemia is reviewed. • We suggest a novel role for RARα in the development of X-RARα gene fusions in APL. • ATRA therapy in APL activates transcription and promotes onco-protein degradation. • Autophagy may be involved in both onco-protein degradation and differentiation. • Pharmacologic autophagy induction may potentiate ATRA's therapeutic effects.

  8. Biased and G Protein-Independent Signaling of Chemokine Receptors

    PubMed Central

    Steen, Anne; Larsen, Olav; Thiele, Stefanie; Rosenkilde, Mette M.

    2014-01-01

    Biased signaling or functional selectivity occurs when a 7TM-receptor preferentially activates one of several available pathways. It can be divided into three distinct forms: ligand bias, receptor bias, and tissue or cell bias, where it is mediated by different ligands (on the same receptor), different receptors (with the same ligand), or different tissues or cells (for the same ligand–receptor pair). Most often biased signaling is differentiated into G protein-dependent and β-arrestin-dependent signaling. Yet, it may also cover signaling differences within these groups. Moreover, it may not be absolute, i.e., full versus no activation. Here we discuss biased signaling in the chemokine system, including the structural basis for biased signaling in chemokine receptors, as well as in class A 7TM receptors in general. This includes overall helical movements and the contributions of micro-switches based on recently published 7TM crystals and molecular dynamics studies. All three forms of biased signaling are abundant in the chemokine system. This challenges our understanding of “classic” redundancy inevitably ascribed to this system, where multiple chemokines bind to the same receptor and where a single chemokine may bind to several receptors – in both cases with the same functional outcome. The ubiquitous biased signaling confers a hitherto unknown specificity to the chemokine system with a complex interaction pattern that is better described as promiscuous with context-defined roles and different functional outcomes in a ligand-, receptor-, or cell/tissue-defined manner. As the low number of successful drug development plans implies, there are great difficulties in targeting chemokine receptors; in particular with regard to receptor antagonists as anti-inflammatory drugs. Un-defined and putative non-selective targeting of the complete cellular signaling system could be the underlying cause of lack of success. Therefore, biased ligands could be the solution

  9. Stress regulates endocannabinoid-CB1 receptor signaling.

    PubMed

    Hillard, Cecilia J

    2014-10-01

    The CB1 cannabinoid receptor is a G protein coupled receptor that is widely expressed throughout the brain. The endogenous ligands for the CB1 receptor (endocannabinoids) are N-arachidonylethanolamine and 2-arachidonoylglycerol; together the endocannabinoids and CB1R subserve activity dependent, retrograde inhibition of neurotransmitter release in the brain. Deficiency of CB1 receptor signaling is associated with anhedonia, anxiety, and persistence of negative memories. CB1 receptor-endocannabinoid signaling is activated by stress and functions to buffer or dampen the behavioral and endocrine effects of acute stress. Its role in regulation of neuronal responses is more complex. Chronic variable stress exposure reduces endocannabinoid-CB1 receptor signaling and it is hypothesized that the resultant deficiency in endocannabinoid signaling contributes to the negative consequences of chronic stress. On the other hand, repeated exposure to the same stress can sensitize CB1 receptor signaling, resulting in dampening of the stress response. Data are reviewed that support the hypothesis that CB1 receptor signaling is stress responsive and that maintaining robust endocannabinoid/CB1 receptor signaling provides resilience against the development of stress-related pathologies.

  10. Structural, signalling and regulatory properties of the group I metabotropic glutamate receptors: prototypic family C G-protein-coupled receptors.

    PubMed Central

    Hermans, E; Challiss, R A

    2001-01-01

    In 1991 a new type of G-protein-coupled receptor (GPCR) was cloned, the type 1a metabotropic glutamate (mGlu) receptor, which, despite possessing the defining seven-transmembrane topology of the GPCR superfamily, bore little resemblance to the growing number of other cloned GPCRs. Subsequent studies have shown that there are eight mammalian mGlu receptors that, together with the calcium-sensing receptor, the GABA(B) receptor (where GABA is gamma-aminobutyric acid) and a subset of pheromone, olfactory and taste receptors, make up GPCR family C. Currently available data suggest that family C GPCRs share a number of structural, biochemical and regulatory characteristics, which differ markedly from those of the other GPCR families, most notably the rhodopsin/family A GPCRs that have been most widely studied to date. This review will focus on the group I mGlu receptors (mGlu1 and mGlu5). This subgroup of receptors is widely and differentially expressed in neuronal and glial cells within the brain, and receptor activation has been implicated in the control of an array of key signalling events, including roles in the adaptative changes needed for long-term depression or potentiation of neuronal synaptic connectivity. In addition to playing critical physiological roles within the brain, the mGlu receptors are also currently the focus of considerable attention because of their potential as drug targets for the treatment of a variety of neurological and psychiatric disorders. PMID:11672421

  11. Nuclear Receptor Signaling Atlas: Opening Access to the Biology of Nuclear Receptor Signaling Pathways

    PubMed Central

    Becnel, Lauren B.; Darlington, Yolanda F.; Ochsner, Scott A.; Easton-Marks, Jeremy R.; Watkins, Christopher M.; McOwiti, Apollo; Kankanamge, Wasula H.; Wise, Michael W.; DeHart, Michael; Margolis, Ronald N.; McKenna, Neil J.

    2015-01-01

    Signaling pathways involving nuclear receptors (NRs), their ligands and coregulators, regulate tissue-specific transcriptomes in diverse processes, including development, metabolism, reproduction, the immune response and neuronal function, as well as in their associated pathologies. The Nuclear Receptor Signaling Atlas (NURSA) is a Consortium focused around a Hub website (www.nursa.org) that annotates and integrates diverse ‘omics datasets originating from the published literature and NURSA-funded Data Source Projects (NDSPs). These datasets are then exposed to the scientific community on an Open Access basis through user-friendly data browsing and search interfaces. Here, we describe the redesign of the Hub, version 3.0, to deploy “Web 2.0” technologies and add richer, more diverse content. The Molecule Pages, which aggregate information relevant to NR signaling pathways from myriad external databases, have been enhanced to include resources for basic scientists, such as post-translational modification sites and targeting miRNAs, and for clinicians, such as clinical trials. A portal to NURSA’s Open Access, PubMed-indexed journal Nuclear Receptor Signaling has been added to facilitate manuscript submissions. Datasets and information on reagents generated by NDSPs are available, as is information concerning periodic new NDSP funding solicitations. Finally, the new website integrates the Transcriptomine analysis tool, which allows for mining of millions of richly annotated public transcriptomic data points in the field, providing an environment for dataset re-use and citation, bench data validation and hypothesis generation. We anticipate that this new release of the NURSA database will have tangible, long term benefits for both basic and clinical research in this field. PMID:26325041

  12. Nuclear Receptor Signaling Atlas: Opening Access to the Biology of Nuclear Receptor Signaling Pathways.

    PubMed

    Becnel, Lauren B; Darlington, Yolanda F; Ochsner, Scott A; Easton-Marks, Jeremy R; Watkins, Christopher M; McOwiti, Apollo; Kankanamge, Wasula H; Wise, Michael W; DeHart, Michael; Margolis, Ronald N; McKenna, Neil J

    2015-01-01

    Signaling pathways involving nuclear receptors (NRs), their ligands and coregulators, regulate tissue-specific transcriptomes in diverse processes, including development, metabolism, reproduction, the immune response and neuronal function, as well as in their associated pathologies. The Nuclear Receptor Signaling Atlas (NURSA) is a Consortium focused around a Hub website (www.nursa.org) that annotates and integrates diverse 'omics datasets originating from the published literature and NURSA-funded Data Source Projects (NDSPs). These datasets are then exposed to the scientific community on an Open Access basis through user-friendly data browsing and search interfaces. Here, we describe the redesign of the Hub, version 3.0, to deploy "Web 2.0" technologies and add richer, more diverse content. The Molecule Pages, which aggregate information relevant to NR signaling pathways from myriad external databases, have been enhanced to include resources for basic scientists, such as post-translational modification sites and targeting miRNAs, and for clinicians, such as clinical trials. A portal to NURSA's Open Access, PubMed-indexed journal Nuclear Receptor Signaling has been added to facilitate manuscript submissions. Datasets and information on reagents generated by NDSPs are available, as is information concerning periodic new NDSP funding solicitations. Finally, the new website integrates the Transcriptomine analysis tool, which allows for mining of millions of richly annotated public transcriptomic data points in the field, providing an environment for dataset re-use and citation, bench data validation and hypothesis generation. We anticipate that this new release of the NURSA database will have tangible, long term benefits for both basic and clinical research in this field.

  13. Nuclear Receptor Signaling Atlas: Opening Access to the Biology of Nuclear Receptor Signaling Pathways.

    PubMed

    Becnel, Lauren B; Darlington, Yolanda F; Ochsner, Scott A; Easton-Marks, Jeremy R; Watkins, Christopher M; McOwiti, Apollo; Kankanamge, Wasula H; Wise, Michael W; DeHart, Michael; Margolis, Ronald N; McKenna, Neil J

    2015-01-01

    Signaling pathways involving nuclear receptors (NRs), their ligands and coregulators, regulate tissue-specific transcriptomes in diverse processes, including development, metabolism, reproduction, the immune response and neuronal function, as well as in their associated pathologies. The Nuclear Receptor Signaling Atlas (NURSA) is a Consortium focused around a Hub website (www.nursa.org) that annotates and integrates diverse 'omics datasets originating from the published literature and NURSA-funded Data Source Projects (NDSPs). These datasets are then exposed to the scientific community on an Open Access basis through user-friendly data browsing and search interfaces. Here, we describe the redesign of the Hub, version 3.0, to deploy "Web 2.0" technologies and add richer, more diverse content. The Molecule Pages, which aggregate information relevant to NR signaling pathways from myriad external databases, have been enhanced to include resources for basic scientists, such as post-translational modification sites and targeting miRNAs, and for clinicians, such as clinical trials. A portal to NURSA's Open Access, PubMed-indexed journal Nuclear Receptor Signaling has been added to facilitate manuscript submissions. Datasets and information on reagents generated by NDSPs are available, as is information concerning periodic new NDSP funding solicitations. Finally, the new website integrates the Transcriptomine analysis tool, which allows for mining of millions of richly annotated public transcriptomic data points in the field, providing an environment for dataset re-use and citation, bench data validation and hypothesis generation. We anticipate that this new release of the NURSA database will have tangible, long term benefits for both basic and clinical research in this field. PMID:26325041

  14. Tyrosine-based signal mediates LRP6 receptor endocytosis and desensitization of Wnt/β-catenin pathway signaling.

    PubMed

    Liu, Chia-Chen; Kanekiyo, Takahisa; Roth, Barbara; Bu, Guojun

    2014-10-01

    Wnt/β-catenin signaling orchestrates a number of critical events including cell growth, differentiation, and cell survival during development. Misregulation of this pathway leads to various human diseases, specifically cancers. Endocytosis and phosphorylation of the LDL receptor-related protein 6 (LRP6), an essential co-receptor for Wnt/β-catenin signaling, play a vital role in mediating Wnt/β-catenin signal transduction. However, its regulatory mechanism is not fully understood. In this study, we define the mechanisms by which LRP6 endocytic trafficking regulates Wnt/β-catenin signaling activation. We show that LRP6 mutant with defective tyrosine-based signal in its cytoplasmic tail has an increased cell surface distribution and decreased endocytosis rate. These changes in LRP6 endocytosis coincide with an increased distribution to caveolae, increased phosphorylation, and enhanced Wnt/β-catenin signaling. We further demonstrate that treatment of Wnt3a ligands or blocking the clathrin-mediated endocytosis of LRP6 leads to a redistribution of wild-type receptor to lipid rafts. The LRP6 tyrosine mutant also exhibited an increase in signaling activation in response to Wnt3a stimulation when compared with wild-type LRP6, and this activation is suppressed when caveolae-mediated endocytosis is blocked. Our results reveal molecular mechanisms by which LRP6 endocytosis routes regulate its phosphorylation and the strength of Wnt/β-catenin signaling, and have implications on how this pathway can be modulated in human diseases.

  15. Ethylene Regulates Levels of Ethylene Receptor/CTR1 Signaling Complexes in Arabidopsis thaliana.

    PubMed

    Shakeel, Samina N; Gao, Zhiyong; Amir, Madiha; Chen, Yi-Feng; Rai, Muneeza Iqbal; Haq, Noor Ul; Schaller, G Eric

    2015-05-01

    The plant hormone ethylene is perceived by a five-member family of receptors in Arabidopsis thaliana. The receptors function in conjunction with the Raf-like kinase CTR1 to negatively regulate ethylene signal transduction. CTR1 interacts with multiple members of the receptor family based on co-purification analysis, interacting more strongly with receptors containing a receiver domain. Levels of membrane-associated CTR1 vary in response to ethylene, doing so in a post-transcriptional manner that correlates with ethylene-mediated changes in levels of the ethylene receptors ERS1, ERS2, EIN4, and ETR2. Interactions between CTR1 and the receptor ETR1 protect ETR1 from ethylene-induced turnover. Kinetic and dose-response analyses support a model in which two opposing factors control levels of the ethylene receptor/CTR1 complexes. Ethylene stimulates the production of new complexes largely through transcriptional induction of the receptors. However, ethylene also induces turnover of receptors, such that levels of ethylene receptor/CTR1 complexes decrease at higher ethylene concentrations. Implications of this model for ethylene signaling are discussed.

  16. Receptor signaling in immune cell development and function

    PubMed Central

    Shin, Jinwook; Gorentla, Balachandra K.; O’Brien, Tommy; Srivatsan, Sruti; Xu, Li; Chen, Yong; Xie, Danli; Pan, Hongjie

    2011-01-01

    Immune cell development and function must be tightly regulated through cell surface receptors to ensure proper responses to pathogen and tolerance to self. In T cells, the signal from the T-cell receptor is essential for T-cell maturation, homeostasis, and activation. In mast cells, the high-affinity receptor for IgE transduces signal that promotes mast cell survival and induces mast cell activation. In dendritic cells and macrophages, the toll-like receptors recognize microbial pathogens and play critical roles for both innate and adaptive immunity against pathogens. Our research explores how signaling from these receptors is transduced and regulated to better understand these immune cells. Our recent studies have revealed diacylglycerol kinases and TSC1/2-mTOR as critical signaling molecules/regulators in T cells, mast cells, dendritic cells, and macrophages. PMID:21128010

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

    PubMed

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

    2015-06-01

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

  18. Inhibition of death receptor signaling by bacterial gut pathogens.

    PubMed

    Giogha, Cristina; Lung, Tania Wong Fok; Pearson, Jaclyn S; Hartland, Elizabeth L

    2014-04-01

    Gastrointestinal bacterial pathogens such as enteropathogenic Escherichia coli, Salmonella and Shigella control inflammatory and apoptotic signaling in human intestinal cells to establish infection, replicate and disseminate to other hosts. These pathogens manipulate host cell signaling through the translocation of virulence effector proteins directly into the host cell cytoplasm, which then target various signaling pathways. Death receptors such as TNFR1, FAS and TRAIL-R induce signaling cascades that are crucial to the clearance of pathogens, and as such are major targets for inhibition by pathogens. This review focuses on what is known about how bacterial gut pathogens inhibit death receptor signaling to suppress inflammation and prevent apoptosis.

  19. Structural mechanism for signal transduction in RXR nuclear receptor heterodimers

    PubMed Central

    Kojetin, Douglas J.; Matta-Camacho, Edna; Hughes, Travis S.; Srinivasan, Sathish; Nwachukwu, Jerome C.; Cavett, Valerie; Nowak, Jason; Chalmers, Michael J.; Marciano, David P.; Kamenecka, Theodore M.; Shulman, Andrew I.; Rance, Mark; Griffin, Patrick R.; Bruning, John B.; Nettles, Kendall W.

    2015-01-01

    A subset of nuclear receptors (NRs) function as obligate heterodimers with retinoid X receptor (RXR), allowing integration of ligand-dependent signals across the dimer interface via an unknown structural mechanism. Using nuclear magnetic resonance (NMR) spectroscopy, x-ray crystallography and hydrogen/deuterium exchange (HDX) mass spectrometry, here we show an allosteric mechanism through which RXR co-operates with a permissive dimer partner, peroxisome proliferator-activated receptor (PPAR)-γ, while rendered generally unresponsive by a non-permissive dimer partner, thyroid hormone (TR) receptor. Amino acid residues that mediate this allosteric mechanism comprise an evolutionarily conserved network discovered by statistical coupling analysis (SCA). This SCA network acts as a signalling rheostat to integrate signals between dimer partners, ligands and coregulator-binding sites, thereby affecting signal transmission in RXR heterodimers. These findings define rules guiding how NRs integrate two ligand-dependent signalling pathways into RXR heterodimer-specific responses. PMID:26289479

  20. Endothelin receptor polymorphisms in the cardiovascular system: potential implications for therapy and screening.

    PubMed

    Holzhauser, Luise; Zolty, Ronald

    2014-11-01

    Since its discovery in 1988, the endothelin system has been employed in multiple physiological and pathological roles. Endothelin-1 (ET-1) is not only a major regulator of vascular tone and cardiac contractility but also exerts mitogenic effects and is involved in inflammatory responses. ET-1 acts via two endothelin receptors located mainly on smooth muscle and endothelial cells through complex intracellular pathways differing between receptors and cell types. Polymorphisms of the endothelin receptor A have been associated not only with the risk in pulmonary arterial hypertension (PAH), systolic heart failure and systemic hypertension but are also of prognostic significance in dilated cardiomyopathy. Polymorphisms of endothelin receptors might lead to altered endothelin signaling and influence the response to endothelin receptor antagonist therapy in PAH in light of pharmacogenetics. This review will summarize the role of ET-1 within major cardiovascular pathologies and discuss endothelin receptor polymorphisms with special emphasis on potential therapeutic and screening implications.

  1. Association between GRB2/Sos and insulin receptor substrate 1 is not sufficient for activation of extracellular signal-regulated kinases by interleukin-4: implications for Ras activation by insulin.

    PubMed

    Pruett, W; Yuan, Y; Rose, E; Batzer, A G; Harada, N; Skolnik, E Y

    1995-03-01

    Insulin receptor substrate 1 (IRS-1) mediates the activation of a variety of signaling pathways by the insulin and insulin-like growth factor 1 receptors by serving as a docking protein for signaling molecules with SH2 domains. We and others have shown that in response to insulin stimulation IRS-1 binds GRB2/Sos and have proposed that this interaction is important in mediating Ras activation by the insulin receptor. Recently, it has been shown that the interleukin (IL)-4 receptor also phosphorylates IRS-1 and an IRS-1-related molecule, 4PS. Unlike insulin, however, IL-4 fails to activate Ras, extracellular signal-regulated kinases (ERKs), or mitogen-activated protein kinases. We have reconstituted the IL-4 receptor into an insulin-responsive L6 myoblast cell line and have shown that IRS-1 is tyrosine phosphorylated to similar degrees in response to insulin and IL-4 stimulation in this cell line. In agreement with previous findings, IL-4 failed to activate the ERKs in this cell line or to stimulate DNA synthesis, whereas the same responses were activated by insulin. Surprisingly, IL-4's failure to activate ERKs was not due to a failure to stimulate the association of tyrosine-phosphorylated IRS-1 with GRB2/Sos; the amounts of GRB2/Sos associated with IRS-1 were similar in insulin- and IL-4-stimulated cells. Moreover, the amounts of phosphatidylinositol 3-kinase activity associated with IRS-1 were similar in insulin- and IL-4-stimulated cells. In contrast to insulin, however, IL-4 failed to induce tyrosine phosphorylation of Shc or association of Shc with GRB2. Thus, ERK activation correlates with Shc tyrosine phosphorylation and formation of an Shc/GRB2 complex. Thus, ERK activation correlates with Shc tyrosine phosphorylation and formation of an Shc/GRB2 complex. Previous studies have indicated that activation of ERks in this cell line is dependent upon Ras since a dominant-negative Ras (Asn-17) blocks ERK activation by insulin. Our findings, taken in the context

  2. Dual-Color Luciferase Complementation for Chemokine Receptor Signaling.

    PubMed

    Luker, Kathryn E; Luker, Gary D

    2016-01-01

    Chemokine receptors may share common ligands, setting up potential competition for ligand binding, and association of activated receptors with downstream signaling molecules such as β-arrestin. Determining the "winner" of competition for shared effector molecules is essential for understanding integrated functions of chemokine receptor signaling in normal physiology, disease, and response to therapy. We describe a dual-color click beetle luciferase complementation assay for cell-based analysis of interactions of two different chemokine receptors, CXCR4 and ACKR3, with the intracellular scaffolding protein β-arrestin 2. This assay provides real-time quantification of receptor activation and signaling in response to chemokine CXCL12. More broadly, this general imaging strategy can be applied to quantify interactions of any set of two proteins that interact with a common binding partner.

  3. Angiotensin Receptors: Structure, Function, Signaling and Clinical Applications

    PubMed Central

    Singh, Khuraijam Dhanachandra; Karnik, Sadashiva S

    2016-01-01

    Angiotensinogen – a serpin family protein predominantly produced by the liver is systematically processed by proteases of the Renin Angiotensin system (RAS) generating hormone peptides. Specific cell surface receptors for at least three distinct angiotensin peptides produce distinct cellular signals that regulate system-wide physiological response to RAS. Two well characterized receptors are angiotensin type 1 receptor (AT1 receptor) and type 2 receptor (AT2 receptor). They respond to the octapeptide hormone angiotensin II. The oncogene product MAS is a putative receptor for Ang (1–7). While these are G-protein coupled receptors (GPCRs), the in vivo angiotensin IV binding sites may be type 2 transmembrane proteins. These four receptors together regulate cardiovascular, hemodynamic, neurological, renal, and endothelial functions; as well as cell proliferation, survival, matrix-cell interactions and inflammation. Angiotensin receptors are important therapeutic targets for several diseases. Thus, researchers and pharmaceutical companies are focusing on drugs targeting AT1 receptor than AT2 receptor, MAS and AngIV binding sites. AT1 receptor blockers are the cornerstone of current treatment for hypertension, heart failure, renal failure and many types of vascular diseases including atherosclerosis, aortic aneurism and Marfan syndrome. PMID:27512731

  4. Orexin/hypocretin receptor signalling: a functional perspective

    PubMed Central

    Leonard, C S; Kukkonen, J P

    2014-01-01

    Multiple homeostatic systems are regulated by orexin (hypocretin) peptides and their two known GPCRs. Activation of orexin receptors promotes waking and is essential for expression of normal sleep and waking behaviour, with the sleep disorder narcolepsy resulting from the absence of orexin signalling. Orexin receptors also influence systems regulating appetite/metabolism, stress and reward, and are found in several peripheral tissues. Nevertheless, much remains unknown about the signalling pathways and targets engaged by native receptors. In this review, we integrate knowledge about the orexin receptor signalling capabilities obtained from studies in expression systems and various native cell types (as presented in Kukkonen and Leonard, this issue of British Journal of Pharmacology) with knowledge of orexin signalling in different tissues. The tissues reviewed include the CNS, the gastrointestinal tract, the pituitary gland, pancreas, adrenal gland, adipose tissue and the male reproductive system. We also summarize the findings in different native and recombinant cell lines, especially focusing on the different cascades in CHO cells, which is the most investigated cell line. This reveals that while a substantial gap exists between what is known about orexin receptor signalling and effectors in recombinant systems and native systems, mounting evidence suggests that orexin receptor signalling is more diverse than originally thought. Moreover, rather than being restricted to orexin receptor ‘overexpressing’ cells, this signalling diversity may be utilized by native receptors in a site-specific manner. 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/10.1111/bph.2014.171.issue-2 PMID:23848055

  5. ERBB receptors in cancer: signaling from the inside.

    PubMed

    Arteaga, Carlos L

    2011-03-16

    ERBB receptor tyrosine kinases are activated by ligand-induced dimerization followed by activation and transphosphorylation of their intracellular kinase domains. A recent study by Bill and colleagues demonstrates that receptor transphosphorylation can be regulated from inside the cell by members of the cytohesin protein family. These data highlight a novel mechanism of amplification of ERBB receptor signaling output that may contribute to embryogenesis and cancer progression.

  6. Perspective: Dynamics of receptor tyrosine kinase signaling complexes.

    PubMed

    Mayer, Bruce J

    2012-08-14

    Textbook descriptions of signal transduction complexes provide a static snapshot view of highly dynamic events. Despite enormous strides in identifying the key components of signaling complexes and the underlying mechanisms of signal transduction, our understanding of the dynamic behavior of these complexes has lagged behind. Using the example of receptor tyrosine kinases, this perspective takes a fresh look at the dynamics of the system and their potential impact on signal processing. PMID:22584051

  7. Dopamine receptor signaling and current and future antipsychotic drugs

    PubMed Central

    Boyd, Kevin N.; Mailman, Richard B.

    2015-01-01

    All currently efficacious antipsychotic drugs have as part of their mechanism the ability to attenuate some or all of their signaling through the dopamine D2 receptor. More recently, the dopamine D1 receptor has been hypothesized to be a promising target for the treatment of negative and/or cognitive aspects of schizophrenia that are not improved by current antipsychotics. Although cAMP has been presumed to be the primary messenger for signaling through the dopamine receptors, the last decade has unveiled a complexity that has provided exciting avenues for the future discovery of antipsychotic drugs (APDs). We review the signaling mechanisms of currently approved APDs at dopamine D2 receptors, and note that aripiprazole is a compound that is clearly differentiated from other approved drugs. Although aripiprazole has been postulated to cause dopamine stabilization due to its partial D2 agonist properties, a body of literature suggests that an alternate mechanism, functional selectivity, is of primary importance. Finally, we review the signaling at dopamine D1 receptors, and the idea that drugs that activate D1 receptors may have use as APDs for improving negative and cognitive symptoms. We address the current state of drug discovery in the D1 area, and its relationship to novel signaling mechanisms. Our conclusion is that although the first APD targeting dopamine receptors was discovered more than a half-century ago, recent research advances offer the possibility that novel and/or improved drugs will emerge in the next decade. PMID:23129328

  8. Casein kinase 1 gamma couples Wnt receptor activation to cytoplasmic signal transduction.

    PubMed

    Davidson, Gary; Wu, Wei; Shen, Jinlong; Bilic, Josipa; Fenger, Ursula; Stannek, Peter; Glinka, Andrei; Niehrs, Christof

    2005-12-01

    Signalling by Wnt proteins (Wingless in Drosophila) has diverse roles during embryonic development and in adults, and is implicated in human diseases, including cancer. LDL-receptor-related proteins 5 and 6 (LRP5 and LRP6; Arrow in Drosophila) are key receptors required for transmission of Wnt/beta-catenin signalling in metazoa. Although the role of these receptors in Wnt signalling is well established, their coupling with the cytoplasmic signalling apparatus remains poorly defined. Using a protein modification screen for regulators of LRP6, we describe the identification of Xenopus Casein kinase 1 gamma (CK1gamma), a membrane-bound member of the CK1 family. Gain-of-function and loss-of-function experiments show that CK1gamma is both necessary and sufficient to transduce LRP6 signalling in vertebrates and Drosophila cells. In Xenopus embryos, CK1gamma is required during anterio-posterior patterning to promote posteriorizing Wnt/beta-catenin signalling. CK1gamma is associated with LRP6, which has multiple, modular CK1 phosphorylation sites. Wnt treatment induces the rapid CK1gamma-mediated phosphorylation of these sites within LRP6, which, in turn, promotes the recruitment of the scaffold protein Axin. Our results reveal an evolutionarily conserved mechanism that couples Wnt receptor activation to the cytoplasmic signal transduction apparatus. PMID:16341016

  9. Investigating G protein signalling bias at the glucagon-like peptide-1 receptor in yeast

    PubMed Central

    Weston, C; Poyner, D; Patel, V; Dowell, S; Ladds, G

    2014-01-01

    BACKGROUND AND PURPOSE The glucagon-like peptide 1 (GLP-1) receptor performs an important role in glycaemic control, stimulating the release of insulin. It is an attractive target for treating type 2 diabetes. Recently, several reports of adverse side effects following prolonged use of GLP-1 receptor therapies have emerged: most likely due to an incomplete understanding of signalling complexities. EXPERIMENTAL APPROACH We describe the expression of the GLP-1 receptor in a panel of modified yeast strains that couple receptor activation to cell growth via single Gα/yeast chimeras. This assay enables the study of individual ligand–receptor G protein coupling preferences and the quantification of the effect of GLP-1 receptor ligands on G protein selectivity. KEY RESULTS The GLP-1 receptor functionally coupled to the chimeras representing the human Gαs, Gαi and Gαq subunits. Calculation of the dissociation constant for a receptor antagonist, exendin-3 revealed no significant difference between the two systems. We obtained previously unobserved differences in G protein signalling bias for clinically relevant therapeutic agents, liraglutide and exenatide; the latter displaying significant bias for the Gαi pathway. We extended the use of the system to investigate small-molecule allosteric compounds and the closely related glucagon receptor. CONCLUSIONS AND IMPLICATIONS These results provide a better understanding of the molecular events involved in GLP-1 receptor pleiotropic signalling and establish the yeast platform as a robust tool to screen for more selective, efficacious compounds acting at this important class of receptors in the future. PMID:24712679

  10. Phagocytosis: receptors, signal integration, and the cytoskeleton.

    PubMed

    Freeman, Spencer A; Grinstein, Sergio

    2014-11-01

    Phagocytosis is a remarkably complex and versatile process: it contributes to innate immunity through the ingestion and elimination of pathogens, while also being central to tissue homeostasis and remodeling by clearing effete cells. The ability of phagocytes to perform such diverse functions rests, in large part, on their vast repertoire of receptors. In this review, we address the various receptor types, their mobility in the plane of the membrane, and two modes of receptor crosstalk: priming and synergy. A major section is devoted to the actin cytoskeleton, which not only governs receptor mobility and clustering but also is instrumental in particle engulfment. Four stages of the actin remodeling process are identified and discussed: (i) the 'resting' stage that precedes receptor engagement, (ii) the disruption of the cortical actin prior to formation of the phagocytic cup, (iii) the actin polymerization that propels pseudopod extension, and (iv) the termination of polymerization and removal of preassembled actin that are required for focal delivery of endomembranes and phagosomal sealing. These topics are viewed in the larger context of the differentiation and polarization of the phagocytic cells.

  11. Translating extranuclear steroid receptor signaling to clinical medicine.

    PubMed

    Levin, Ellis R

    2014-06-01

    The existence and function of extranuclear steroid receptors (SR) to rapidly modulate signal transduction is now acknowledged as present in cells and organs throughout the body. Work over the past 15 years has defined key mechanisms that are required for sex steroid receptors to traffic to the plasma membrane, but mechanisms of localization in other cell organelles such as mitochondria is still unclear. Signaling by membrane-localized SR has now been reported to impact many aspects of adult organ functions, while the roles in organ development are under investigation. In hormone-responsive cancers, both extranuclear and nuclear sex steroid receptors appear to collaborate in the regulation of some key genes that promote malignancy. Here, I review what is understood about the impact of extranuclear steroid receptor signaling to mitigate or promote disease processes. PMID:24752388

  12. MOLECULAR MECHANISMS OF RECEPTOR KINASE ACTION IN BRASSINOSTEROID SIGNAL TRANSDUCTION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Brassinosteroids (BRs) regulate multiple aspects of plant growth and development and require an active BRASSINOSTEROID INSENSITIVE 1 (BRI1) and BRI1-ASSOCIATED RECEPTOR KINASE 1 (BAK1) for hormone perception and signal transduction. To examine early events in BR signaling, we used co-immunoprecipita...

  13. Recognition of Bacterial Signal Peptides by Mammalian Formyl Peptide Receptors

    PubMed Central

    Bufe, Bernd; Schumann, Timo; Kappl, Reinhard; Bogeski, Ivan; Kummerow, Carsten; Podgórska, Marta; Smola, Sigrun; Hoth, Markus; Zufall, Frank

    2015-01-01

    Formyl peptide receptors (FPRs) are G-protein-coupled receptors that function as chemoattractant receptors in innate immune responses. Here we perform systematic structure-function analyses of FPRs from six mammalian species using structurally diverse FPR peptide agonists and identify a common set of conserved agonist properties with typical features of pathogen-associated molecular patterns. Guided by these results, we discover that bacterial signal peptides, normally used to translocate proteins across cytoplasmic membranes, are a vast family of natural FPR agonists. N-terminally formylated signal peptide fragments with variable sequence and length activate human and mouse FPR1 and FPR2 at low nanomolar concentrations, thus establishing FPR1 and FPR2 as sensitive and broad signal peptide receptors. The vomeronasal receptor mFpr-rs1 and its sequence orthologue hFPR3 also react to signal peptides but are much more narrowly tuned in signal peptide recognition. Furthermore, all signal peptides examined here function as potent activators of the innate immune system. They elicit robust, FPR-dependent calcium mobilization in human and mouse leukocytes and trigger a range of classical innate defense mechanisms, such as the production of reactive oxygen species, metalloprotease release, and chemotaxis. Thus, bacterial signal peptides constitute a novel class of immune activators that are likely to contribute to mammalian immune defense against bacteria. This evolutionarily conserved detection mechanism combines structural promiscuity with high specificity and enables discrimination between bacterial and eukaryotic signal sequences. With at least 175,542 predicted sequences, bacterial signal peptides represent the largest and structurally most heterogeneous class of G-protein-coupled receptor agonists currently known for the innate immune system. PMID:25605714

  14. Signal Transduction and Intracellular Trafficking by the Interleukin 36 Receptor*

    PubMed Central

    Saha, Siddhartha S.; Singh, Divyendu; Raymond, Ernest L.; Ganesan, Rajkumar; Caviness, Gary; Grimaldi, Christine; Woska, Joseph R.; Mennerich, Detlev; Brown, Su-Ellen; Mbow, M. Lamine; Kao, C. Cheng

    2015-01-01

    Improper signaling of the IL-36 receptor (IL-36R), a member of the IL-1 receptor family, has been associated with various inflammation-associated diseases. However, the requirements for IL-36R signal transduction remain poorly characterized. This work seeks to define the requirements for IL-36R signaling and intracellular trafficking. In the absence of cognate agonists, IL-36R was endocytosed and recycled to the plasma membrane. In the presence of IL-36, IL-36R increased accumulation in LAMP1+ lysosomes. Endocytosis predominantly used a clathrin-mediated pathway, and the accumulation of the IL-36R in lysosomes did not result in increased receptor turnover. The ubiquitin-binding Tollip protein contributed to IL-36R signaling and increased the accumulation of both subunits of the IL-36R. PMID:26269592

  15. Adenovirus receptors and their implications in gene delivery

    PubMed Central

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

    2010-01-01

    Adenoviruses (Ads) have gained popularity as gene delivery vectors for therapeutic and prophylactic applications. Ad entry into host cells involves specific interactions between cell surface receptors and viral capsid proteins. Several cell surface molecules have been identified as receptors for Ad attachment and entry. Tissue tropism of Ad vectors is greatly influenced by their receptor usage. A variety of strategies have been investigated to modify Ad vector tropism by manipulating the receptor-interacting moieties. Many such strategies are aimed at targeting and/or detargeting of Ad vectors. In this review, we discuss the various cell surface molecules that are implicated as receptors for virus attachment and internalization. Special emphasis is given to Ad types that are utilized as gene delivery vectors. Various strategies to modify Ad tropism using the knowledge of Ad receptors are also discussed. PMID:19647886

  16. Ubiquitylation of Nuclear Receptors: New Linkages and Therapeutic Implications

    PubMed Central

    Helzer, Kyle T.; Hooper, Christopher; Miyamoto, Shigeki; Alarid, Elaine T.

    2015-01-01

    The nuclear receptor superfamily is a group of transcriptional regulators that control multiple aspects of both physiology and pathology, and are broadly recognized as viable therapeutic targets. While receptor-modulating drugs have been successful in many cases, the discovery of new drug targets is still an active area of research, because resistance to nuclear receptor-targeting therapies remains a significant clinical challenge. Many successful targeted therapies have harnessed the control of receptor activity by targeting events within the nuclear receptor signaling pathway. In this review, we explore the role of nuclear receptor ubiquitylation and discuss how the expanding roles of ubiquitin might be leveraged to identify additional entry points to control receptor function for future therapeutic development. PMID:25943391

  17. Biased signalling and proteinase-activated receptors (PARs): targeting inflammatory disease.

    PubMed

    Hollenberg, M D; Mihara, K; Polley, D; Suen, J Y; Han, A; Fairlie, D P; Ramachandran, R

    2014-03-01

    Although it has been known since the 1960s that trypsin and chymotrypsin can mimic hormone action in tissues, it took until the 1990s to discover that serine proteinases can regulate cells by cleaving and activating a unique four-member family of GPCRs known as proteinase-activated receptors (PARs). PAR activation involves the proteolytic exposure of its N-terminal receptor sequence that folds back to function as a 'tethered' receptor-activating ligand (TL). A key N-terminal arginine in each of PARs 1 to 4 has been singled out as a target for cleavage by thrombin (PARs 1, 3 and 4), trypsin (PARs 2 and 4) or other proteases to unmask the TL that activates signalling via Gq , Gi or G12 /13 . Similarly, synthetic receptor-activating peptides, corresponding to the exposed 'TL sequences' (e.g. SFLLRN-, for PAR1 or SLIGRL- for PAR2) can, like proteinase activation, also drive signalling via Gq , Gi and G12 /13 , without requiring receptor cleavage. Recent data show, however, that distinct proteinase-revealed 'non-canonical' PAR tethered-ligand sequences and PAR-activating agonist and antagonist peptide analogues can induce 'biased' PAR signalling, for example, via G12 /13 -MAPKinase instead of Gq -calcium. This overview summarizes implications of this 'biased' signalling by PAR agonists and antagonists for the recognized roles the PARs play in inflammatory settings. PMID:24354792

  18. The protein kinase LKB1 negatively regulates bone morphogenetic protein receptor signaling

    PubMed Central

    Raja, Erna; Edlund, Karolina; Kahata, Kaoru; Zieba, Agata; Morén, Anita; Watanabe, Yukihide; Voytyuk, Iryna; Botling, Johan; Söderberg, Ola; Micke, Patrick; Pyrowolakis, George; Heldin, Carl-Henrik; Moustakas, Aristidis

    2016-01-01

    The protein kinase LKB1 regulates cell metabolism and growth and is implicated in intestinal and lung cancer. Bone morphogenetic protein (BMP) signaling regulates cell differentiation during development and tissue homeostasis. We demonstrate that LKB1 physically interacts with BMP type I receptors and requires Smad7 to promote downregulation of the receptor. Accordingly, LKB1 suppresses BMP-induced osteoblast differentiation and affects BMP signaling in Drosophila wing longitudinal vein morphogenesis. LKB1 protein expression and Smad1 phosphorylation analysis in a cohort of non-small cell lung cancer patients demonstrated a negative correlation predominantly in a subset enriched in adenocarcinomas. Lung cancer patient data analysis indicated strong correlation between LKB1 loss-of-function mutations and high BMP2 expression, and these two events further correlated with expression of a gene subset functionally linked to apoptosis and migration. This new mechanism of BMP receptor regulation by LKB1 has ramifications in physiological organogenesis and disease. PMID:26701726

  19. Signaling, physiological functions and clinical relevance of the G protein-coupled estrogen receptor GPER

    PubMed Central

    Prossnitz, Eric R.; Barton, Matthias

    2009-01-01

    GPR30, now named GPER1 (G protein-coupled estrogen receptor1) or GPER here, was first identified as an orphan 7- transmembrane G protein-coupled receptor by multiple laboratories using either homology cloning or differential expression and subsequently shown to be required for estrogen-mediated signaling in certain cancer cells. The actions of estrogen are extensive in the body and are thought to be mediated predominantly by classical nuclear estrogen receptors that act as transcription factors/regulators. Nevertheless, certain aspects of estrogen function remain incompatible with the generally accepted mechanisms of classical estrogen receptor action. Many recent studies have revealed that GPER contributes to some of the actions of estrogen, including rapid signaling events and rapid transcriptional activation. With the introduction of GPER-selective ligands and GPER knockout mice, the functions of GPER are becoming more clearly defined. In many cases, there appears to be a complex interplay between the two receptor systems, suggesting that estrogen-mediated physiological responses may be mediated by either receptor or a combination of both receptor types, with important medical implications. PMID:19442754

  20. Signal transduction through the IL-4 and insulin receptor families.

    PubMed

    Wang, L M; Keegan, A; Frankel, M; Paul, W E; Pierce, J H

    1995-07-01

    Activation of tyrosine kinase-containing receptors and intracellular tyrosine kinases by ligand stimulation is known to be crucial for mediating initial and subsequent events involved in mitogenic signal transduction. Receptors for insulin and insulin-like growth factor 1 (IGF-1) contain cytoplasmic tyrosine kinase domains that undergo autophosphorylation upon ligand stimulation. Activation of these receptors also leads to pronounced and rapid tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1) in cells of connective tissue origin. A related substrate, designated 4PS, is similarly phosphorylated by insulin and IGF-1 stimulation in many hematopoietic cell types. IRS-1 and 4PS possess a number of tyrosine phosphorylation sites that are within motifs that bind specific SH2-containing molecules known to be involved in mitogenic signaling such as PI-3 kinase, SHPTP-2 (Syp) and Grb-2. Thus, they appear to act as docking substrates for a variety of signaling molecules. The majority of hematopoietic cytokines bind to receptors that do not possess intrinsic kinase activity, and these receptors have been collectively termed as members of the hematopoietin receptor superfamily. Despite their lack of tyrosine kinase domains, stimulation of these receptors has been demonstrated to activate intracellular kinases leading to tyrosine phosphorylation of multiple substrates. Recent evidence has demonstrated that activation of different members of the Janus family of tyrosine kinases is involved in mediating tyrosine phosphorylation events by specific cytokines. Stimulation of the interleukin 4 (IL-4) receptor, a member of the hematopoietin receptor superfamily, is thought to result in activation of Jak1, Jak3, and/or Fes tyrosine kinases.(ABSTRACT TRUNCATED AT 250 WORDS)

  1. Mapping physiological G protein-coupled receptor signaling pathways reveals a role for receptor phosphorylation in airway contraction

    PubMed Central

    Bradley, Sophie J.; Iglesias, Max Maza; Kong, Kok Choi; Butcher, Adrian J.; Plouffe, Bianca; Goupil, Eugénie; Bourgognon, Julie-Myrtille; Macedo-Hatch, Timothy; LeGouill, Christian; Russell, Kirsty; Laporte, Stéphane A.; König, Gabriele M.; Kostenis, Evi; Bouvier, Michel; Chung, Kian Fan; Amrani, Yassine; Tobin, Andrew B.

    2016-01-01

    G protein-coupled receptors (GPCRs) are known to initiate a plethora of signaling pathways in vitro. However, it is unclear which of these pathways are engaged to mediate physiological responses. Here, we examine the distinct roles of Gq/11-dependent signaling and receptor phosphorylation-dependent signaling in bronchial airway contraction and lung function regulated through the M3-muscarinic acetylcholine receptor (M3-mAChR). By using a genetically engineered mouse expressing a G protein-biased M3-mAChR mutant, we reveal the first evidence, to our knowledge, of a role for M3-mAChR phosphorylation in bronchial smooth muscle contraction in health and in a disease state with relevance to human asthma. Furthermore, this mouse model can be used to distinguish the physiological responses that are regulated by M3-mAChR phosphorylation (which include control of lung function) from those responses that are downstream of G protein signaling. In this way, we present an approach by which to predict the physiological/therapeutic outcome of M3-mAChR–biased ligands with important implications for drug discovery. PMID:27071102

  2. GABA-A receptor inhibition of local calcium signaling in spines and dendrites.

    PubMed

    Marlin, Joseph J; Carter, Adam G

    2014-11-26

    Cortical interneurons activate GABA-A receptors to rapidly control electrical and biochemical signaling at pyramidal neurons. Different populations of interneurons are known to uniquely target the soma and dendrites of pyramidal neurons. However, the ability of these interneurons to inhibit Ca(2+) signaling at spines and dendrites is largely unexplored. Here we use whole-cell recordings, two-photon microscopy, GABA uncaging and optogenetics to study dendritic inhibition at layer 5 (L5) pyramidal neurons in slices of mouse PFC. We first show that GABA-A receptors strongly inhibit action potential (AP)-evoked Ca(2+) signals at both spines and dendrites. We find robust inhibition over tens of milliseconds that spreads along the dendritic branch. However, we observe no difference in the amount of inhibition at neighboring spines and dendrites. We then examine the influence of interneurons expressing parvalbumin (PV), somatostatin (SOM), or 5HT3a receptors. We determine that these populations of interneurons make unique contacts onto the apical and basal dendrites of L5 pyramidal neurons. We also show that SOM and 5HT3a but not PV interneurons potently inhibit AP Ca(2+) signals via GABA-A receptors at both spines and dendrites. These findings reveal how multiple interneurons regulate local Ca(2+) signaling in pyramidal neurons, with implications for cortical function and disease.

  3. β1-adrenergic receptor antagonists signal via PDE4 translocation.

    PubMed

    Richter, Wito; Mika, Delphine; Blanchard, Elise; Day, Peter; Conti, Marco

    2013-03-01

    It is generally assumed that antagonists of Gs-coupled receptors do not activate cAMP signalling, because they do not stimulate cAMP production via Gs-protein/adenylyl cyclase activation. Here, we report a new signalling pathway whereby antagonists of β1-adrenergic receptors (β1ARs) increase cAMP levels locally without stimulating cAMP production directly. Binding of antagonists causes dissociation of a preformed complex between β1ARs and Type-4 cyclic nucleotide phosphodiesterases (PDE4s). This reduces the local concentration of cAMP-hydrolytic activity, thereby increasing submembrane cAMP and PKA activity. Our study identifies receptor/PDE4 complex dissociation as a novel mechanism of antagonist action that contributes to the pharmacological properties of β1AR antagonists and might be shared by other receptor subtypes.

  4. COMMENTARY: IL-4 AND IL-13 RECEPTORS AND SIGNALING

    PubMed Central

    McCormick, Sarah M; Heller, Nicola M

    2015-01-01

    Interleukin (IL)-4 and IL-13 were discovered approximately 30 years ago and were immediately linked to allergy and atopic diseases. Since then, new roles for IL-4 and IL-13 and their receptors in normal gestation, fetal development, neurological function and in the pathogenesis of cancer and fibrosis have been appreciated. Studying IL-4/-13 and their receptors has revealed important clues about cytokine biology and lead to the development of numerous experimental therapeutics. Here we aim to highlight new discoveries and consolidate concepts in the field of IL-4 and IL-13 structure, receptor regulation, signaling and experimental therapeutics. PMID:26187331

  5. P2y receptor-mediated angiogenesis via vascular endothelial growth factor receptor 2 signaling.

    PubMed

    Rumjahn, Sharif M; Baldwin, Karla A; Buxton, Iain L O

    2007-01-01

    Pathological as well as physiological angiogenesis is known to be regulated by such factors as nucleotides and Vascular Endothelial Growth Factor (VEGF). Activated P2Y nucleotide receptors have been observed to associate and transactivate VEGF Receptor 2 (VEGFR2), suggesting a cooperation between nucleotide and VEGF signaling in angiogenesis. P2YR mediated VEGFR2 signaling therefore may be important in describing the angiogenic signaling of nucleotides such as ATP. Here, we provide evidence that supports the notion of P2YR-VEGFR2 signaling. The significant angiogenic effect of P2Y1/2 receptor agonists (100 microM ATP and 10 microM 2MS-ATP) on endothelial cell tubulogenesis was suppressed back to near control levels upon addition of 1 microM SU1498 (specific VEGFR2 tyrosine kinase inhibitor). We believe that this P2YR-VEFGR2 signaling is an important component of pathological, as well as physiological angiogenesis.

  6. NMDA Receptor Function During Senescence: Implication on Cognitive Performance

    PubMed Central

    Kumar, Ashok

    2015-01-01

    N-methyl-D-aspartate (NMDA) receptors, a family of L-glutamate receptors, play an important role in learning and memory, and are critical for spatial memory. These receptors are tetrameric ion channels composed of a family of related subunits. One of the hallmarks of the aging human population is a decline in cognitive function; studies in the past couple of years have demonstrated deterioration in NMDA receptor subunit expression and function with advancing age. However, a direct relationship between impaired memory function and a decline in NMDA receptors is still ambiguous. Recent studies indicate a link between an age-associated NMDA receptor hypofunction and memory impairment and provide evidence that age-associated enhanced oxidative stress might be contributing to the alterations associated with senescence. However, clear evidence is still deficient in demonstrating the underlying mechanisms and a relationship between age-associated impaired cognitive faculties and NMDA receptor hypofunction. The current review intends to present an overview of the research findings regarding changes in expression of various NMDA receptor subunits and deficits in NMDA receptor function during senescence and its implication in age-associated impaired hippocampal-dependent memory function. PMID:26732087

  7. Glutamate Signaling in Benign and Malignant Disorders: Current Status, Future Perspectives, and Therapeutic Implications

    PubMed Central

    Willard, Stacey S.; Koochekpour, Shahriar

    2013-01-01

    Glutamate, a nonessential amino acid, is the major excitatory neurotransmitter in the central nervous system. As such, glutamate has been shown to play a role in not only neural processes, such as learning and memory, but also in bioenergetics, biosynthetic and metabolic oncogenic pathways. Glutamate has been the target of intense investigation for its involvement not only in the pathogenesis of benign neurodegenerative diseases (NDDs) such as Parkinson's disease, Alzheimer's disease, schizophrenia, multiple sclerosis, and amyotropic lateral sclerosis (ALS), but also in carcinogenesis and progression of malignant diseases. In addition to its intracellular activities, glutamate in secreted form is a phylogenetically conserved cell signaling molecule. Glutamate binding activates multiple major receptor families including the metabotropic glutamate receptors (mGluRs) and ionotropic glutamate receptors (iGluRs), both of which have been implicated in various signaling pathways in cancer. Inhibition of extracellular glutamate release or glutamate receptor activation via competitive or non-competitive antagonists decreases growth, migration and invasion and induces apoptosis in breast cancer, melanoma, glioma and prostate cancer cells. In this review, we discuss the current state of glutamate signaling research as it relates to benign and malignant diseases. In addition, we provide a synopsis of clinical trials using glutamate antagonists for the treatment of NDD and malignant diseases. We conclude that in addition to its potential role as a metabolic biomarker, glutamate receptors and glutamate-initiated signaling pathways may provide novel therapeutic opportunities for cancer. PMID:23983606

  8. The aryl hydrocarbon receptor agonist benzo(a)pyrene reactivates LINE-1 in HepG2 cells through canonical TGF-β1 signaling: implications in hepatocellular carcinogenesis.

    PubMed

    Reyes-Reyes, Elsa M; Ramos, Irma N; Tavera-Garcia, Marco A; Ramos, Kenneth S

    2016-01-01

    Long interspersed nuclear element-1 (L1) is a genetic element that mobilizes throughout the mammalian genome via retrotransposition and damages host DNA via mutational insertions, chromosomal rearrangements, and reprogramming of gene expression. The cellular mechanisms responsible for aberrant L1 expression during cancer pathogenesis are unclear. Previously, we have shown that L1 reactivation in several human cell lines is dependent upon the activation of aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor member of the PAS superfamily of proteins. We also showed that ectopic expression of L1 reprograms the HepG2 genome leading to epithelial-to-mesenchymal transition (EMT). Here we present evidence that reactivation of L1 and modulation of EMT in HepG2 cells by the AhR ligand benzo(a)pyrene (BaP) is effected through the canonical TGF-β1 signaling pathway. BaP increased TGF-β1 mRNA, SMAD2 phosphorylation and decreased expression of E-Cadherin. The functional relevance of these interactions and the involvement of TGFBR1/ALK5 and SMAD2/3 were confirmed by siRNA interference. Furthermore, expression of L1-encoded ORF1p was positively correlated with the activation of TGF-β1 signaling in human hepatocarcinoma samples at various stages of malignant progression. These results indicate that ligand-mediated AhR activation regulates L1 via canonical TGF-β1 signaling and raise important questions about the molecular etiology of human hepatocarcinomas.

  9. The aryl hydrocarbon receptor agonist benzo(a)pyrene reactivates LINE-1 in HepG2 cells through canonical TGF-β1 signaling: implications in hepatocellular carcinogenesis.

    PubMed

    Reyes-Reyes, Elsa M; Ramos, Irma N; Tavera-Garcia, Marco A; Ramos, Kenneth S

    2016-01-01

    Long interspersed nuclear element-1 (L1) is a genetic element that mobilizes throughout the mammalian genome via retrotransposition and damages host DNA via mutational insertions, chromosomal rearrangements, and reprogramming of gene expression. The cellular mechanisms responsible for aberrant L1 expression during cancer pathogenesis are unclear. Previously, we have shown that L1 reactivation in several human cell lines is dependent upon the activation of aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor member of the PAS superfamily of proteins. We also showed that ectopic expression of L1 reprograms the HepG2 genome leading to epithelial-to-mesenchymal transition (EMT). Here we present evidence that reactivation of L1 and modulation of EMT in HepG2 cells by the AhR ligand benzo(a)pyrene (BaP) is effected through the canonical TGF-β1 signaling pathway. BaP increased TGF-β1 mRNA, SMAD2 phosphorylation and decreased expression of E-Cadherin. The functional relevance of these interactions and the involvement of TGFBR1/ALK5 and SMAD2/3 were confirmed by siRNA interference. Furthermore, expression of L1-encoded ORF1p was positively correlated with the activation of TGF-β1 signaling in human hepatocarcinoma samples at various stages of malignant progression. These results indicate that ligand-mediated AhR activation regulates L1 via canonical TGF-β1 signaling and raise important questions about the molecular etiology of human hepatocarcinomas. PMID:27293999

  10. The aryl hydrocarbon receptor agonist benzo(a)pyrene reactivates LINE-1 in HepG2 cells through canonical TGF-β1 signaling: implications in hepatocellular carcinogenesis

    PubMed Central

    Reyes-Reyes, Elsa M; Ramos, Irma N; Tavera-Garcia, Marco A; Ramos, Kenneth S

    2016-01-01

    Long interspersed nuclear element-1 (L1) is a genetic element that mobilizes throughout the mammalian genome via retrotransposition and damages host DNA via mutational insertions, chromosomal rearrangements, and reprogramming of gene expression. The cellular mechanisms responsible for aberrant L1 expression during cancer pathogenesis are unclear. Previously, we have shown that L1 reactivation in several human cell lines is dependent upon the activation of aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor member of the PAS superfamily of proteins. We also showed that ectopic expression of L1 reprograms the HepG2 genome leading to epithelial-to-mesenchymal transition (EMT). Here we present evidence that reactivation of L1 and modulation of EMT in HepG2 cells by the AhR ligand benzo(a)pyrene (BaP) is effected through the canonical TGF-β1 signaling pathway. BaP increased TGF-β1 mRNA, SMAD2 phosphorylation and decreased expression of E-Cadherin. The functional relevance of these interactions and the involvement of TGFBR1/ALK5 and SMAD2/3 were confirmed by siRNA interference. Furthermore, expression of L1-encoded ORF1p was positively correlated with the activation of TGF-β1 signaling in human hepatocarcinoma samples at various stages of malignant progression. These results indicate that ligand-mediated AhR activation regulates L1 via canonical TGF-β1 signaling and raise important questions about the molecular etiology of human hepatocarcinomas. PMID:27293999

  11. Cannabinoid receptor 1 signaling in embryo neurodevelopment.

    PubMed

    Psychoyos, Delphine; Vinod, K Yaragudri; Cao, Jin; Xie, Shan; Hyson, Richard L; Wlodarczyk, Bogdan; He, Weimin; Cooper, Thomas B; Hungund, Basalingappa L; Finnell, Richard H

    2012-04-01

    In utero exposure to tetrahydrocannabinol, the psychoactive component of marijuana, is associated with an increased risk for neurodevelopmental defects in the offspring by interfering with the functioning of the endocannabinoid (eCB) system. At the present time, it is not clearly known whether the eCB system is present before neurogenesis. Using an array of biochemical techniques, we analyzed the levels of CB1 receptors, eCBs (AEA and 2-AG), and the enzymes (NAPE-PLD, DAGLα, DAGLβ, MAGL, and FAAH) involved in the metabolism of the eCBs in chick and mouse models during development. The findings demonstrate the presence of eCB system in early embryo before neurogenesis. The eCB system might play a critical role in early embryogenesis and there might be adverse developmental consequences of in utero exposure to marijuana and other drugs of abuse during this period.

  12. Immunopathological roles of cytokines, chemokines, signaling molecules, and pattern-recognition receptors in systemic lupus erythematosus.

    PubMed

    Yu, Shui-Lian; Kuan, Woon-Pang; Wong, Chun-Kwok; Li, Edmund K; Tam, Lai-Shan

    2012-01-01

    Systemic lupus erythematosus (SLE) is an autoimmune disease with unknown etiology affecting more than one million individuals each year. It is characterized by B- and T-cell hyperactivity and by defects in the clearance of apoptotic cells and immune complexes. Understanding the complex process involved and the interaction between various cytokines, chemokines, signaling molecules, and pattern-recognition receptors (PRRs) in the immune pathways will provide valuable information on the development of novel therapeutic targets for treating SLE. In this paper, we review the immunopathological roles of novel cytokines, chemokines, signaling molecules, PRRs, and their interactions in immunoregulatory networks and suggest how their disturbances may implicate pathological conditions in SLE.

  13. Effects of Membrane Trafficking on Signaling by Receptor Tyrosine Kinases

    PubMed Central

    Miaczynska, Marta

    2013-01-01

    The intracellular trafficking machinery contributes to the spatial and temporal control of signaling by receptor tyrosine kinases (RTKs). The primary role in this process is played by endocytic trafficking, which regulates the localization of RTKs and their downstream effectors, as well as the duration and the extent of their activity. The key regulatory points along the endocytic pathway are internalization of RTKs from the plasma membrane, their sorting to degradation or recycling, and their residence in various endosomal compartments. Here I will review factors and mechanisms that modulate RTK signaling by (1) affecting receptor internalization, (2) regulating the balance between degradation and recycling of RTK, and (3) compartmentalization of signals in endosomes and other organelles. Cumulatively, these mechanisms illustrate a multilayered control of RTK signaling exerted by the trafficking machinery. PMID:24186066

  14. New Insights into How Trafficking Regulates T Cell Receptor Signaling

    PubMed Central

    Lou, Jieqiong; Rossy, Jérémie; Deng, Qiji; Pageon, Sophie V.; Gaus, Katharina

    2016-01-01

    There is emerging evidence that exocytosis plays an important role in regulating T cell receptor (TCR) signaling. The trafficking molecules involved in lytic granule (LG) secretion in cytotoxic T lymphocytes (CTL) have been well-studied due to the immune disorder known as familial hemophagocytic lymphohistiocytosis (FHLH). However, the knowledge of trafficking machineries regulating the exocytosis of receptors and signaling molecules remains quite limited. In this review, we summarize the reported trafficking molecules involved in the transport of the TCR and downstream signaling molecules to the cell surface. By combining this information with the known knowledge of LG exocytosis and general exocytic trafficking machinery, we attempt to draw a more complete picture of how the TCR signaling network and exocytic trafficking matrix are interconnected to facilitate T cell activation. This also highlights how membrane compartmentalization facilitates the spatiotemporal organization of cellular responses that are essential for immune functions. PMID:27508206

  15. Activating Receptor Signals Drive Receptor Diversity in Developing Natural Killer Cells

    PubMed Central

    Freund, Jacquelyn; May, Rebecca M.; Li, Hongchuan; McCullen, Matthew; Zhang, Bin; Lenvik, Todd; Cichocki, Frank; Anderson, Stephen K.; Kambayashi, Taku

    2016-01-01

    It has recently been appreciated that NK cells exhibit many features reminiscent of adaptive immune cells. Considerable heterogeneity exists with respect to the ligand specificity of individual NK cells and as such, a subset of NK cells can respond, expand, and differentiate into memory-like cells in a ligand-specific manner. MHC I-binding inhibitory receptors, including those belonging to the Ly49 and KIR families, are expressed in a variegated manner, which creates ligand-specific diversity within the NK cell pool. However, how NK cells determine which inhibitory receptors to express on their cell surface during a narrow window of development is largely unknown. In this manuscript, we demonstrate that signals from activating receptors are critical for induction of Ly49 and KIR receptors during NK cell development; activating receptor-derived signals increased the probability of the Ly49 bidirectional Pro1 promoter to transcribe in the forward versus the reverse direction, leading to stable expression of Ly49 receptors in mature NK cells. Our data support a model where the balance of activating and inhibitory receptor signaling in NK cells selects for the induction of appropriate inhibitory receptors during development, which NK cells use to create a diverse pool of ligand-specific NK cells. PMID:27500644

  16. Activating Receptor Signals Drive Receptor Diversity in Developing Natural Killer Cells.

    PubMed

    Freund, Jacquelyn; May, Rebecca M; Yang, Enjun; Li, Hongchuan; McCullen, Matthew; Zhang, Bin; Lenvik, Todd; Cichocki, Frank; Anderson, Stephen K; Kambayashi, Taku

    2016-08-01

    It has recently been appreciated that NK cells exhibit many features reminiscent of adaptive immune cells. Considerable heterogeneity exists with respect to the ligand specificity of individual NK cells and as such, a subset of NK cells can respond, expand, and differentiate into memory-like cells in a ligand-specific manner. MHC I-binding inhibitory receptors, including those belonging to the Ly49 and KIR families, are expressed in a variegated manner, which creates ligand-specific diversity within the NK cell pool. However, how NK cells determine which inhibitory receptors to express on their cell surface during a narrow window of development is largely unknown. In this manuscript, we demonstrate that signals from activating receptors are critical for induction of Ly49 and KIR receptors during NK cell development; activating receptor-derived signals increased the probability of the Ly49 bidirectional Pro1 promoter to transcribe in the forward versus the reverse direction, leading to stable expression of Ly49 receptors in mature NK cells. Our data support a model where the balance of activating and inhibitory receptor signaling in NK cells selects for the induction of appropriate inhibitory receptors during development, which NK cells use to create a diverse pool of ligand-specific NK cells.

  17. Orphan receptor IL-17RD regulates Toll-like receptor signalling via SEFIR/TIR interactions.

    PubMed

    Mellett, Mark; Atzei, Paola; Bergin, Ronan; Horgan, Alan; Floss, Thomas; Wurst, Wolfgang; Callanan, John J; Moynagh, Paul N

    2015-01-01

    Receptor families of the innate immune response engage in 'cross-talk' to tailor optimal immune responses against invading pathogens. However, these responses are subject to multiple levels of regulation to keep in check aberrant inflammatory signals. Here, we describe a role for the orphan receptor interleukin-17 receptor D (IL-17RD) in negatively regulating Toll-like receptor (TLR)-induced responses. Deficiency of IL-17RD expression in cells leads to enhanced pro-inflammatory signalling and gene expression in response to TLR stimulation, and Il17rd(-/-) mice are more susceptible to TLR-induced septic shock. We demonstrate that the intracellular Sef/IL-17R (SEFIR) domain of IL-17RD targets TIR adaptor proteins to inhibit TLR downstream signalling thus revealing a paradigm involving cross-regulation of members of the IL-17R and TLR families.

  18. Steroid signaling activation and intracellular localization of sex steroid receptors.

    PubMed

    Giraldi, Tiziana; Giovannelli, Pia; Di Donato, Marzia; Castoria, Gabriella; Migliaccio, Antimo; Auricchio, Ferdinando

    2010-12-01

    In addition to stimulating gene transcription, sex steroids trigger rapid, non-genomic responses in the extra-nuclear compartment of target cells. These events take place within seconds or minutes after hormone administration and do not require transcriptional activity of sex steroid receptors. Depending on cell systems, activation of extra-nuclear signaling pathways by sex steroids fosters cell cycle progression, prevents apoptosis, leads to epigenetic modifications and increases cell migration through cytoskeleton changes. These findings have raised the question of intracellular localization of sex steroid receptors mediating these responses. During the past years, increasing evidence has shown that classical sex steroid receptors localized in the extra-nuclear compartment or close to membranes of target cells induce these events. The emerging picture is that a process of bidirectional control between signaling activation and sex steroid receptor localization regulates the outcome of hormonal responses in target cells. This mechanism ensures cell cycle progression in estradiol-treated breast cancer cells, and its derangement might occur in progression of human proliferative diseases. These findings will be reviewed here together with unexpected examples of the relationship between sex steroid receptor localization, signaling activation and biological responses in target cells. We apologize to scientists whose reports are not mentioned or extensively discussed owing to space limitations.

  19. Diverse FGF receptor signaling controls astrocyte specification and proliferation

    SciTech Connect

    Kang, Kyungjun; Song, Mi-Ryoung

    2010-05-07

    During CNS development, pluripotency neuronal progenitor cells give rise in succession to neurons and glia. Fibroblast growth factor-2 (FGF-2), a major signal that maintains neural progenitors in the undifferentiated state, is also thought to influence the transition from neurogenesis to gliogenesis. Here we present evidence that FGF receptors and underlying signaling pathways transmit the FGF-2 signals that regulate astrocyte specification aside from its mitogenic activity. Application of FGF-2 to cortical progenitors suppressed neurogenesis whereas treatment with an FGFR antagonist in vitro promoted neurogenesis. Introduction of chimeric FGFRs with mutated tyrosine residues into cortical progenitors and drug treatments to specifically block individual downstream signaling pathways revealed that the overall activity of FGFR rather than individual autophosphorylation sites is important for delivering signals for glial specification. In contrast, a signal for cell proliferation by FGFR was mainly delivered by MAPK pathway. Together our findings indicate that FGFR activity promotes astrocyte specification in the developing CNS.

  20. Autocrine signaling involved in cell volume regulation: the role of released transmitters and plasma membrane receptors.

    PubMed

    Franco, Rodrigo; Panayiotidis, Mihalis I; de la Paz, Lenin D Ochoa

    2008-07-01

    Cell volume regulation is a basic homeostatic mechanism transcendental for the normal physiology and function of cells. It is mediated principally by the activation of osmolyte transport pathways that result in net changes in solute concentration that counteract cell volume challenges in its constancy. This process has been described to be regulated by a complex assortment of intracellular signal transduction cascades. Recently, several studies have demonstrated that alterations in cell volume induce the release of a wide variety of transmitters including hormones, ATP and neurotransmitters, which have been proposed to act as extracellular signals that regulate the activation of cell volume regulatory mechanisms. In addition, changes in cell volume have also been reported to activate plasma membrane receptors (including tyrosine kinase receptors, G-protein coupled receptors and integrins) that have been demonstrated to participate in the regulatory process of cell volume. In this review, we summarize recent studies about the role of changes in cell volume in the regulation of transmitter release as well as in the activation of plasma membrane receptors and their further implications in the regulation of the signaling machinery that regulates the activation of osmolyte flux pathways. We propose that the autocrine regulation of Ca2+-dependent and tyrosine phosphorylation-dependent signaling pathways by the activation of plasma membrane receptors and swelling-induced transmitter release is necessary for the activation/regulation of osmolyte efflux pathways and cell volume recovery. Furthermore, we emphasize the importance of studying these extrinsic signals because of their significance in the understanding of the physiology of cell volume regulation and its role in cell biology in vivo, where the constraint of the extracellular space might enhance the autocrine or even paracrine signaling induced by these released transmitters. PMID:18300263

  1. Signaling Receptors for TGF-β Family Members.

    PubMed

    Heldin, Carl-Henrik; Moustakas, Aristidis

    2016-01-01

    Transforming growth factor β (TGF-β) family members signal via heterotetrameric complexes of type I and type II dual specificity kinase receptors. The activation and stability of the receptors are controlled by posttranslational modifications, such as phosphorylation, ubiquitylation, sumoylation, and neddylation, as well as by interaction with other proteins at the cell surface and in the cytoplasm. Activation of TGF-β receptors induces signaling via formation of Smad complexes that are translocated to the nucleus where they act as transcription factors, as well as via non-Smad pathways, including the Erk1/2, JNK and p38 MAP kinase pathways, and the Src tyrosine kinase, phosphatidylinositol 3'-kinase, and Rho GTPases. PMID:27481709

  2. Ubiquitin-dependent regulation of G protein-coupled receptor trafficking and signaling.

    PubMed

    Marchese, Adriano; Trejo, Joann

    2013-03-01

    G protein-coupled receptors (GPCRs) belong to one of the largest family of signaling receptors in the mammalian genome [1]. GPCRs elicit cellular responses to multiple diverse stimuli and play essential roles in human health and disease. GPCRs have important clinical implications in various diseases and are the targets of approximately 25-50% of all marketed drugs [2,3]. Understanding how GPCRs are regulated is essential to delineating their role in normal physiology and in the pathophysiology of several diseases. Given the vast number and diversity of GPCRs, it is likely that multiple mechanisms exist to regulate GPCR function. While GPCR signaling is typically regulated by desensitization and endocytosis mediated by phosphorylation and β-arrestins, it can also be modulated by ubiquitination. Ubiquitination is emerging an important regulatory process that may have unique roles in governing GPCR trafficking and signaling. Recent studies have revealed a mechanistic link between GPCR phosphorylation, β-arrestins and ubiquitination that may be applicable to some GPCRs but not others. While the function of ubiquitination is generally thought to promote receptor endocytosis and endosomal sorting, recent studies have revealed that ubiquitination also plays an important role in positive regulation of GPCR signaling. Here, we will review recent developments in our understanding of how ubiquitin regulates GPCR endocytic trafficking and how it contributes to signal transduction induced by GPCR activation.

  3. Heteromeric Dopamine Receptor Signaling Complexes: Emerging Neurobiology and Disease Relevance

    PubMed Central

    Perreault, Melissa L; Hasbi, Ahmed; O'Dowd, Brian F; George, Susan R

    2014-01-01

    The pharmacological modification of dopamine transmission has long been employed as a therapeutic tool in the treatment of many mental health disorders. However, as many of the pharmacotherapies today are not without significant side effects, or they alleviate only a particular subset of symptoms, the identification of novel therapeutic targets is imperative. In light of these challenges, the recognition that dopamine receptors can form heteromers has significantly expanded the range of physiologically relevant signaling complexes as well as potential drug targets. Furthermore, as the physiology and disease relevance of these receptor heteromers is further understood, their ability to exhibit pharmacological and functional properties distinct from their constituent receptors, or modulate the function of endogenous homomeric receptor complexes, may allow for the development of alternate therapeutic strategies and provide new avenues for drug design. In this review, we describe the emerging neurobiology of the known dopamine receptor heteromers, their physiological relevance in brain, and discuss the potential role of these receptor complexes in neuropsychiatric disease. We highlight their value as targets for future drug development and discuss innovative research strategies designed to selectively target these dopamine receptor heteromers in the search for novel and clinically efficacious pharmacotherapies. PMID:23774533

  4. Altered B cell receptor signaling in human systemic lupus erythematosus

    PubMed Central

    Jenks, Scott A.; Sanz, Iñaki

    2009-01-01

    Regulation of B cell receptor signaling is essential for the development of specific immunity while retaining tolerance to self. Systemic lupus erythematosus (SLE) is characterized by a loss of B cell tolerance and the production of anti-self antibodies. Accompanying this break down in tolerance are alterations in B cell receptor signal transduction including elevated induced calcium responses and increased protein phosphorylation. Specific pathways that negatively regulate B cell signaling have been shown to be impaired in some SLE patients. These patients have reduced levels of the kinase Lyn in lipid raft microdomains and this reduction is inversely correlated with increased CD45 in lipid rafts. Function and expression of the inhibitory immunoglobulin receptor FcγRIIB is also reduced in Lupus IgM- CD27+ memory cells. Because the relative contribution of different memory and transitional B cell subsets can be abnormal in SLE patients, we believe studies targeted to well defined B cell subsets will be necessary to further our understanding of signaling abnormalities in SLE. Intracellular flow cytometric analysis of signaling is a useful approach to accomplish this goal. PMID:18723129

  5. The Ubiquitous Mineralocorticoid Receptor: Clinical Implications

    PubMed Central

    Hawkins, Urseline A.; Gomez-Sanchez, Elise P.; Gomez-Sanchez, Clara M.; Gomez-Sanchez, Celso E.

    2012-01-01

    Mineralocorticoid receptors (MR) exist in many tissues, in which they mediate diverse functions crucial to normal physiology, including tissue repair and electrolyte and fluid homeostasis. However, inappropriate activation of MR within these tissues, and especially in the brain, causes hypertension and pathological vascular, cardiac, and renal remodeling. MR binds aldosterone, cortisol and corticosterone with equal affinity. In aldosterone-target cells, co-expression with the 11β-hydroxysteroid dehydrogenase 2 (HSD2) allows aldosterone specifically to activate MR. Aldosterone levels are excessive in primary aldosteronism, but in conditions with increased oxidative stress, like CHF, obesity and diabetes, MR may also be inappropriately activated by glucocorticoids. Unlike thiazide diuretics, MR antagonists are diuretics that do not cause insulin resistance. Addition of MR antagonists to standard treatment for hypertension and cardiac or renal disease decreases end-organ pathology and sympathetic nerve activation (SNA), and increases quality of life indices. PMID:22843494

  6. The mechanisms of HAMP-mediated signaling in transmembrane receptors.

    PubMed

    Ferris, Hedda U; Dunin-Horkawicz, Stanislaw; Mondéjar, Laura García; Hulko, Michael; Hantke, Klaus; Martin, Jörg; Schultz, Joachim E; Zeth, Kornelius; Lupas, Andrei N; Coles, Murray

    2011-03-01

    HAMP domains mediate signal transduction in over 7500 enzyme-coupled receptors represented in all kingdoms of life. The HAMP domain of the putative archaeal receptor Af1503 has a parallel, dimeric, four-helical coiled coil structure, but with unusual core packing, related to canonical packing by concerted axial rotation of the helices. This has led to the gearbox model for signal transduction, whereby the alternate packing modes correspond to signaling states. Here we present structures of a series of Af1503 HAMP variants. We show that substitution of a conserved small side chain within the domain core (A291) for larger residues induces a gradual transition in packing mode, involving both changes in helix rotation and bundle shape, which are most prominent at the C-terminal, output end of the domain. These are correlated with activity and ligand response in vitro and in vivo by incorporating Af1503 HAMP into mycobacterial adenylyl cyclase assay systems.

  7. Inflammatory mediators and insulin resistance in obesity: role of nuclear receptor signaling in macrophages.

    PubMed

    Fuentes, Lucía; Roszer, Tamás; Ricote, Mercedes

    2010-01-01

    Visceral obesity is coupled to a general low-grade chronic inflammatory state characterized by macrophage activation and inflammatory cytokine production, leading to insulin resistance (IR). The balance between proinflammatory M1 and antiinflammatory M2 macrophage phenotypes within visceral adipose tissue appears to be crucially involved in the development of obesity-associated IR and consequent metabolic abnormalities. The ligand-dependent transcription factors peroxisome proliferator activated receptors (PPARs) have recently been implicated in the determination of the M1/M2 phenotype. Liver X receptors (LXRs), which form another subgroup of the nuclear receptor superfamily, are also important regulators of proinflammatory cytokine production in macrophages. Disregulation of macrophage-mediated inflammation by PPARs and LXRs therefore underlies the development of IR. This review summarizes the role of PPAR and LXR signaling in macrophages and current knowledge about the impact of these actions in the manifestation of IR and obesity comorbidities such as liver steatosis and diabetic osteopenia.

  8. Effect of Spatial Inhomogeneities on the Membrane Surface on Receptor Dimerization and Signal Initiation

    PubMed Central

    Kerketta, Romica; Halász, Ádám M.; Steinkamp, Mara P.; Wilson, Bridget S.; Edwards, Jeremy S.

    2016-01-01

    Important signal transduction pathways originate on the plasma membrane, where microdomains may transiently entrap diffusing receptors. This results in a non-random distribution of receptors even in the resting state, which can be visualized as “clusters” by high resolution imaging methods. Here, we explore how spatial in-homogeneities in the plasma membrane might influence the dimerization and phosphorylation status of ErbB2 and ErbB3, two receptor tyrosine kinases that preferentially heterodimerize and are often co-expressed in cancer. This theoretical study is based upon spatial stochastic simulations of the two-dimensional membrane landscape, where variables include differential distributions and overlap of transient confinement zones (“domains”) for the two receptor species. The in silico model is parameterized and validated using data from single particle tracking experiments. We report key differences in signaling output based on the degree of overlap between domains and the relative retention of receptors in such domains, expressed as escape probability. Results predict that a high overlap of domains, which favors transient co-confinement of both receptor species, will enhance the rate of hetero-interactions. Where domains do not overlap, simulations confirm expectations that homo-interactions are favored. Since ErbB3 is uniquely dependent on ErbB2 interactions for activation of its catalytic activity, variations in domain overlap or escape probability markedly alter the predicted patterns and time course of ErbB3 and ErbB2 phosphorylation. Taken together, these results implicate membrane domain organization as an important modulator of signal initiation, motivating the design of novel experimental approaches to measure these important parameters across a wider range of receptor systems. PMID:27570763

  9. Effect of Spatial Inhomogeneities on the Membrane Surface on Receptor Dimerization and Signal Initiation.

    PubMed

    Kerketta, Romica; Halász, Ádám M; Steinkamp, Mara P; Wilson, Bridget S; Edwards, Jeremy S

    2016-01-01

    Important signal transduction pathways originate on the plasma membrane, where microdomains may transiently entrap diffusing receptors. This results in a non-random distribution of receptors even in the resting state, which can be visualized as "clusters" by high resolution imaging methods. Here, we explore how spatial in-homogeneities in the plasma membrane might influence the dimerization and phosphorylation status of ErbB2 and ErbB3, two receptor tyrosine kinases that preferentially heterodimerize and are often co-expressed in cancer. This theoretical study is based upon spatial stochastic simulations of the two-dimensional membrane landscape, where variables include differential distributions and overlap of transient confinement zones ("domains") for the two receptor species. The in silico model is parameterized and validated using data from single particle tracking experiments. We report key differences in signaling output based on the degree of overlap between domains and the relative retention of receptors in such domains, expressed as escape probability. Results predict that a high overlap of domains, which favors transient co-confinement of both receptor species, will enhance the rate of hetero-interactions. Where domains do not overlap, simulations confirm expectations that homo-interactions are favored. Since ErbB3 is uniquely dependent on ErbB2 interactions for activation of its catalytic activity, variations in domain overlap or escape probability markedly alter the predicted patterns and time course of ErbB3 and ErbB2 phosphorylation. Taken together, these results implicate membrane domain organization as an important modulator of signal initiation, motivating the design of novel experimental approaches to measure these important parameters across a wider range of receptor systems. PMID:27570763

  10. Activation of signalling by the activin receptor complex.

    PubMed Central

    Attisano, L; Wrana, J L; Montalvo, E; Massagué, J

    1996-01-01

    Activin exerts its effects by simultaneously binding to two types of p rotein serine/threonine kinase receptors, each type existing in various isoforms. Using the ActR-IB and ActR-IIB receptor isoforms, we have investigated the mechanism of activin receptor activation. ActR-IIB are phosphoproteins with demonstrable affinity for each other. However, activin addition strongly promotes an interaction between these two proteins. Activin binds directly to ActR-IIB, and this complex associates with ActR-IB, which does not bind ligand on its own. In the resulting complex, ActR-IB becomes hyperphosphorylated, and this requires the kinase activity of ActR-IIB. Mutation of conserved serines and threonines in the GS domain, a region just upstream of the kinase domain in ActR-IB, abrogates both phosphorylation and signal propagation, suggesting that this domain contains phosphorylation sites required for signalling. ActR-IB activation can be mimicked by mutation of Thr-206 to aspartic acid, which yields a construct, ActR-IB(T206D), that signals in the absence of ligand. Furthermore, the signalling activity of this mutant construct is undisturbed by overexpression of a dominant negative kinase-defective ActR-IIB construct, indicating that ActR-IB(T206D) can signal independently of ActR-IIB. The evidence suggests that ActR-IIB acts as a primary activin receptor and ActR-IB acts as a downstream transducer of activin signals. PMID:8622651

  11. G Protein-Coupled Receptor Signaling in Stem Cells and Cancer

    PubMed Central

    Lynch, Jennifer R.; Wang, Jenny Yingzi

    2016-01-01

    G protein-coupled receptors (GPCRs) are a large superfamily of cell-surface signaling proteins that bind extracellular ligands and transduce signals into cells via heterotrimeric G proteins. GPCRs are highly tractable drug targets. Aberrant expression of GPCRs and G proteins has been observed in various cancers and their importance in cancer stem cells has begun to be appreciated. We have recently reported essential roles for G protein-coupled receptor 84 (GPR84) and G protein subunit Gαq in the maintenance of cancer stem cells in acute myeloid leukemia. This review will discuss how GPCRs and G proteins regulate stem cells with a focus on cancer stem cells, as well as their implications for the development of novel targeted cancer therapies. PMID:27187360

  12. Activity-dependent bidirectional regulation of GABAA receptor channels by the 5-HT4 receptor-mediated signalling in rat prefrontal cortical pyramidal neurons

    PubMed Central

    Cai, Xiang; Flores-Hernandez, Jorge; Feng, Jian; Yan, Zhen

    2002-01-01

    Emerging evidence has implicated a potential role for 5-HT4 receptors in cognition and anxiolysis. One of the main target structures of 5-HT4 receptors on ‘cognitive and emotional’ pathways is the prefrontal cortex (PFC). As GABAergic signalling plays a key role in regulating PFC functions, we examined the effect of 5-HT4 receptors on GABAA receptor channels in PFC pyramidal neurons. Application of 5-HT4 receptor agonists produced either an enhancement or a reduction of GABA-evoked currents in PFC neurons, which are both mediated by anchored protein kinase A (PKA). Although PKA phosphorylation of GABAA receptor β3 or β1 subunits leads to current enhancement or reduction respectively in heterologous expression systems, we found that β3 and β1 subunits are co-expressed in PFC pyramidal neurons. Interestingly, altering PKA activation levels can change the direction of the dual effect, switching enhancement to reduction and vice versa. In addition, increased neuronal activity in PFC slices elevated the PKA activation level, changing the enhancing effect of 5-HT4 receptors on the amplitude of GABAergic inhibitory postsynaptic currents (IPSCs) to a reduction. These results suggest that 5-HT4 receptors can modulate GABAergic signalling bidirectionally, depending on the basal PKA activation levels that are determined by neuronal activity. This modulation provides a unique and flexible mechanism for 5-HT4 receptors to dynamically regulate synaptic transmission and neuronal excitability in the PFC network. PMID:11986365

  13. Benzodiazepines: electron affinity, receptors and cell signaling - a multifaceted approach.

    PubMed

    Kovacic, Peter; Ott, Nadia; Cooksy, Andrew L

    2013-12-01

    This report entails a multifaceted approach to benzodiazepine (BZ) action, involving electron affinity, receptors, cell signaling and other aspects. Computations of the electron affinities (EAs) of different BZs have been carried out to establish the effect of various substituents on their EA. These computations were undertaken to serve as a first step in determining what role electron transfer (ET) plays in BZ activity. The calculations were conducted on the premise that the nature of the substituent will either decrease or increase the electron density of the benzene ring, thus altering the ability of the molecule to accept an electron. Investigations were performed on the effect of drug protonation on EA. Similarities involving substituent effects in prior electrochemical studies are also discussed. As part of the multifaceted approach, EA is linked to ET, which appears to play a role in therapeutic activity and toxicity. There is extensive literature dealing with the role of receptors in BZ activity. Significant information on receptor involvement was reported more than 40 years ago. Gamma-aminobutyric acid (GABA) is known to be importantly involved. GABA is a probable mediator of BZ effects. BZ and GABA receptors, although not identical, are physiologically linked. Cell signaling is known to play a part in the biochemistry of BZ action. Various factors participated, such as gene expression, allosteric influence, toxic effects and therapeutic action. Evidence points to involvement of EA and ET in the mode of action in cell signaling. Oxidative stress and antioxidant effects are also addressed.

  14. Sex-biased stress signaling: the corticotropin-releasing factor receptor as a model.

    PubMed

    Valentino, Rita J; Bangasser, Debra; Van Bockstaele, Elisabeth J

    2013-04-01

    Sex differences in the prevalence or severity of many diseases and in the response to pharmacological agents are well recognized. Elucidating the biologic bases of these differences can advance our understanding of the pathophysiology of disease and facilitate the development of treatments. Despite the importance to medicine, this has been an area of limited research. Here, we review physiologic, cellular, and molecular findings supporting the idea that there are sex differences in receptor signaling and trafficking that can be determinants of pathology. The focus is on the receptor for corticotropin-releasing factor (CRF), the orchestrator of the stress response, which has been implicated in diverse stress-related diseases that show a female prevalence. Data are reviewed that show sex differences in the association of the CRF receptor (CRF1) with the Gs protein and β-arrestin 2 that would render females more responsive to acute stress and less able to adapt to chronic stress as a result of compromised CRF1 internalization. Because β-arrestin 2 serves to link CRF1 to Gs-independent signaling pathways, this sex-biased signaling is proposed to result in distinct cellular responses to stress that are translated to different physiologic and behavioral coping mechanisms and that can have different pathologic consequences. Because stress has been implicated in diverse medical and psychiatric diseases, these sex differences in CRF1 signaling could explain sex differences in a multitude of disorders. The possibility that analogous sex differences may occur with other G-protein-coupled receptors underscores the impact of this effect and is discussed. PMID:23239826

  15. Immune System to Brain Signaling: Neuropsychopharmacological Implications

    PubMed Central

    Capuron, Lucile; Miller, Andrew H.

    2011-01-01

    There has been an explosion in our knowledge of the pathways and mechanisms by which the immune system can influence the brain and behavior. In the context of inflammation, pro-inflammatory cytokines can access the central nervous system and interact with a cytokine network in the brain to influence virtually every aspect of brain function relevant to behavior including neurotransmitter metabolism, neuroendocrine function, synaptic plasticity, and neurocircuits that regulate mood, motor activity, motivation, anxiety and alarm. Behavioral consequences of these effects of the immune system on the brain include depression, anxiety, fatigue, psychomotor slowing, anorexia, cognitive dysfunction and sleep impairment; symptoms that overlap with those which characterize neuropsychiatric disorders, especially depression. Pathways that appear to be especially important in immune system effects on the brain include the cytokine signaling molecules, p38 mitogen activated protein kinase and nuclear factor kappa B; indoleamine 2,3 dioxygenase and its down stream metabolites, kynurenine, quinolinic acid and kynurenic acid; the neurotransmitters, serotonin, dopamine and glutamate; and neurocircuits involving the basal ganglia and anterior cingulate cortex. A series of vulnerability factors including aging and obesity as well as chronic stress also appear to interact with immune to brain signaling to exacerbate immunologic contributions to neuropsychiatric disease. The elucidation of the mechanisms by which the immune system influences behavior yields a host of targets for potential therapeutic development as well as informing strategies for the prevention of neuropsychiatric disease in at risk populations. PMID:21334376

  16. Early signaling dynamics of the epidermal growth factor receptor

    PubMed Central

    Gajadhar, Aaron S.; Swenson, Eric J.; Rothenberg, Daniel A.; Curran, Timothy G.; White, Forest M.

    2016-01-01

    Despite extensive study of the EGF receptor (EGFR) signaling network, the immediate posttranslational changes that occur in response to growth factor stimulation remain poorly characterized; as a result, the biological mechanisms underlying signaling initiation remain obscured. To address this deficiency, we have used a mass spectrometry-based approach to measure system-wide phosphorylation changes throughout the network with 10-s resolution in the 80 s after stimulation in response to a range of eight growth factor concentrations. Significant changes were observed on proteins far downstream in the network as early as 10 s after stimulation, indicating a system capable of transmitting information quickly. Meanwhile, canonical members of the EGFR signaling network fall into clusters with distinct activation patterns. Src homology 2 domain containing transforming protein (Shc) and phosphoinositol 3-kinase (PI3K) phosphorylation levels increase rapidly, but equilibrate within 20 s, whereas proteins such as Grb2-associated binder-1 (Gab1) and SH2-containing tyrosine phosphatase (SHP2) show slower, sustained increases. Proximity ligation assays reveal that Shc and Gab1 phosphorylation patterns are representative of separate timescales for physical association with the receptor. Inhibition of phosphatases with vanadate reveals site-specific regulatory mechanisms and also uncovers primed activating components in the network, including Src family kinases, whose inhibition affects only a subset of proteins within the network. The results presented highlight the complexity of signaling initiation and provide a window into exploring mechanistic hypotheses about receptor tyrosine kinase (RTK) biology. PMID:26929352

  17. Adiponectin Receptor Signaling on Dendritic Cells Blunts Antitumor Immunity

    PubMed Central

    Tan, Peng H.; Tyrrell, Helen E.J.; Gao, Liquan; Xu, Danmei; Quan, Jianchao; Gill, Dipender; Rai, Lena; Ding, Yunchuan; Plant, Gareth; Chen, Yuan; Xue, John Z.; Handa, Ashok I.; Greenall, Michael J.; Walsh, Kenneth; Xue, Shao-An

    2015-01-01

    Immune escape is a fundamental trait of cancer. Dendritic cells (DC) that interact with T cells represent a crucial site for the development of tolerance to tumor antigens, but there remains incomplete knowledge about how DC-tolerizing signals evolve during tumorigenesis. In this study, we show that DCs isolated from patients with metastatic or locally advanced breast cancer express high levels of the adiponectin receptors AdipoR1 and AdipoR2, which are sufficient to blunt antitumor immunity. Mechanistic investigations of ligand–receptor interactions on DCs revealed novel signaling pathways for each receptor. AdipoR1 stimulated IL10 production by activating the AMPK and MAPKp38 pathways, whereas AdipoR2 modified inflammatory processes by activating the COX-2 and PPARγ pathways. Stimulation of these pathways was sufficient to block activation of NF-κB in DC, thereby attenuating their ability to stimulate antigen-specific T-cell responses. Together, our findings reveal novel insights into how DC-tolerizing signals evolve in cancer to promote immune escape. Furthermore, by defining a critical role for adiponectin signaling in this process, our work suggests new and broadly applicable strategies for immunometabolic therapy in patients with cancer. PMID:25261236

  18. Early signaling dynamics of the epidermal growth factor receptor.

    PubMed

    Reddy, Raven J; Gajadhar, Aaron S; Swenson, Eric J; Rothenberg, Daniel A; Curran, Timothy G; White, Forest M

    2016-03-15

    Despite extensive study of the EGF receptor (EGFR) signaling network, the immediate posttranslational changes that occur in response to growth factor stimulation remain poorly characterized; as a result, the biological mechanisms underlying signaling initiation remain obscured. To address this deficiency, we have used a mass spectrometry-based approach to measure system-wide phosphorylation changes throughout the network with 10-s resolution in the 80 s after stimulation in response to a range of eight growth factor concentrations. Significant changes were observed on proteins far downstream in the network as early as 10 s after stimulation, indicating a system capable of transmitting information quickly. Meanwhile, canonical members of the EGFR signaling network fall into clusters with distinct activation patterns. Src homology 2 domain containing transforming protein (Shc) and phosphoinositol 3-kinase (PI3K) phosphorylation levels increase rapidly, but equilibrate within 20 s, whereas proteins such as Grb2-associated binder-1 (Gab1) and SH2-containing tyrosine phosphatase (SHP2) show slower, sustained increases. Proximity ligation assays reveal that Shc and Gab1 phosphorylation patterns are representative of separate timescales for physical association with the receptor. Inhibition of phosphatases with vanadate reveals site-specific regulatory mechanisms and also uncovers primed activating components in the network, including Src family kinases, whose inhibition affects only a subset of proteins within the network. The results presented highlight the complexity of signaling initiation and provide a window into exploring mechanistic hypotheses about receptor tyrosine kinase (RTK) biology. PMID:26929352

  19. Early signaling dynamics of the epidermal growth factor receptor.

    PubMed

    Reddy, Raven J; Gajadhar, Aaron S; Swenson, Eric J; Rothenberg, Daniel A; Curran, Timothy G; White, Forest M

    2016-03-15

    Despite extensive study of the EGF receptor (EGFR) signaling network, the immediate posttranslational changes that occur in response to growth factor stimulation remain poorly characterized; as a result, the biological mechanisms underlying signaling initiation remain obscured. To address this deficiency, we have used a mass spectrometry-based approach to measure system-wide phosphorylation changes throughout the network with 10-s resolution in the 80 s after stimulation in response to a range of eight growth factor concentrations. Significant changes were observed on proteins far downstream in the network as early as 10 s after stimulation, indicating a system capable of transmitting information quickly. Meanwhile, canonical members of the EGFR signaling network fall into clusters with distinct activation patterns. Src homology 2 domain containing transforming protein (Shc) and phosphoinositol 3-kinase (PI3K) phosphorylation levels increase rapidly, but equilibrate within 20 s, whereas proteins such as Grb2-associated binder-1 (Gab1) and SH2-containing tyrosine phosphatase (SHP2) show slower, sustained increases. Proximity ligation assays reveal that Shc and Gab1 phosphorylation patterns are representative of separate timescales for physical association with the receptor. Inhibition of phosphatases with vanadate reveals site-specific regulatory mechanisms and also uncovers primed activating components in the network, including Src family kinases, whose inhibition affects only a subset of proteins within the network. The results presented highlight the complexity of signaling initiation and provide a window into exploring mechanistic hypotheses about receptor tyrosine kinase (RTK) biology.

  20. SORLA facilitates insulin receptor signaling in adipocytes and exacerbates obesity

    PubMed Central

    Schmidt, Vanessa; Schulz, Nadja; Yan, Xin; Schürmann, Annette; Kempa, Stefan; Kern, Matthias; Blüher, Matthias; Poy, Matthew N.

    2016-01-01

    In humans, genetic variation of sortilin-related receptor, L(DLR class) A repeats containing (SORL1), which encodes the intracellular sorting receptor SORLA, is a major genetic risk factor for familial and sporadic forms of Alzheimer’s disease. Recent GWAS analysis has also associated SORL1 with obesity in humans and in mouse models, suggesting that this receptor may play a role in regulating metabolism. Here, using mouse models with genetic loss or tissue-specific overexpression of SORLA as well as data from obese human subjects, we observed a gene-dosage effect that links SORLA expression to obesity and glucose tolerance. Overexpression of human SORLA in murine adipose tissue blocked hydrolysis of triacylglycerides and caused excessive adiposity. In contrast, Sorl1 gene inactivation in mice accelerated breakdown of triacylglycerides in adipocytes and protected animals from diet-induced obesity. We then identified the underlying molecular mechanism whereby SORLA promotes insulin-induced suppression of lipolysis in adipocytes. Specifically, we determined that SORLA acts as a sorting factor for the insulin receptor (IR) that redirects internalized receptor molecules from endosomes to the plasma membrane, thereby enhancing IR surface expression and strengthening insulin signal reception in target cells. Our findings provide a molecular mechanism for the association of SORL1 with human obesity and confirm a genetic link between neurodegeneration and metabolism that converges on the receptor SORLA. PMID:27322061

  1. Dopamine D2 receptor signaling dynamics of dopamine D2-neurotensin 1 receptor heteromers.

    PubMed

    Borroto-Escuela, Dasiel O; Ravani, Annalisa; Tarakanov, Alexander O; Brito, Ismel; Narvaez, Manuel; Romero-Fernandez, Wilber; Corrales, Fidel; Agnati, Luigi F; Tanganelli, Sergio; Ferraro, Luca; Fuxe, Kjell

    2013-05-24

    Biochemical, histochemical and coimmunoprecipitation experiments have indicated the existence of antagonistic dopamine D2 (D2R) and neurotensin 1 (NTS1R) receptor-receptor interactions in the dorsal and ventral striatum indicating a potential role of these receptor-receptor interactions in Parkinson's disease and schizophrenia. By means of Bioluminiscence Resonance energy transfer (BRET(2)) evidence has for the first time been obtained in the current study for the existence of both D2LR/NTS1R and D2SR/NTS1R heteromers in living HEK293T cells. Through confocal laser microscopy the NTS1R(GFP2) and D2R(YFP) were also shown to be colocated in the plasma membrane of these cells. A bioinformatic analysis suggests the existence of a basic set of three homology protriplets (TVM, DLL and/or LRA) in the two participating receptors which may contribute to the formation of the D2R/NTS1R heteromers by participating in guide-clasp interactions in the receptor interface. The CREB reporter gene assay indicated that the neurotensin receptor agonist JMV 449 markedly reduced the potency of the D2R like agonist quinpirole to inhibit the forskolin induced increase of the CREB signal. In contrast, the neurotensin agonist was found to markedly increase the quinpirole potency to activate the MAPK pathway as also studied with luciferase reporter gene assay measuring the degree of SRE activity as well as with ERK1/2 phosphorylation assays. These dynamic changes in D2R signaling produced by the neurotensin receptor agonist may involve antagonistic allosteric receptor-receptor interactions in the D2LR-NTS1R heteromers at the plasma membrane level (CREB pathway) and synergistic interactions in PKC activation at the cytoplasmatic level (MAPK pathway).

  2. Inhibition of insulin/IGF-1 receptor signaling protects from mitochondria-mediated kidney failure.

    PubMed

    Ising, Christina; Koehler, Sybille; Brähler, Sebastian; Merkwirth, Carsten; Höhne, Martin; Baris, Olivier R; Hagmann, Henning; Kann, Martin; Fabretti, Francesca; Dafinger, Claudia; Bloch, Wilhelm; Schermer, Bernhard; Linkermann, Andreas; Brüning, Jens C; Kurschat, Christine E; Müller, Roman-Ulrich; Wiesner, Rudolf J; Langer, Thomas; Benzing, Thomas; Brinkkoetter, Paul Thomas

    2015-02-02

    Mitochondrial dysfunction and alterations in energy metabolism have been implicated in a variety of human diseases. Mitochondrial fusion is essential for maintenance of mitochondrial function and requires the prohibitin ring complex subunit prohibitin-2 (PHB2) at the mitochondrial inner membrane. Here, we provide a link between PHB2 deficiency and hyperactive insulin/IGF-1 signaling. Deletion of PHB2 in podocytes of mice, terminally differentiated cells at the kidney filtration barrier, caused progressive proteinuria, kidney failure, and death of the animals and resulted in hyperphosphorylation of S6 ribosomal protein (S6RP), a known mediator of the mTOR signaling pathway. Inhibition of the insulin/IGF-1 signaling system through genetic deletion of the insulin receptor alone or in combination with the IGF-1 receptor or treatment with rapamycin prevented hyperphosphorylation of S6RP without affecting the mitochondrial structural defect, alleviated renal disease, and delayed the onset of kidney failure in PHB2-deficient animals. Evidently, perturbation of insulin/IGF-1 receptor signaling contributes to tissue damage in mitochondrial disease, which may allow therapeutic intervention against a wide spectrum of diseases.

  3. Reduced 5-HT2A receptor signaling following selective bilateral amygdala damage

    PubMed Central

    Schlaepfer, Thomas E.; Matusch, Andreas; Reich, Harald; Shah, Nadim J.; Zilles, Karl; Maier, Wolfgang; Bauer, Andreas

    2009-01-01

    Neurobiological evidence implicates the amygdala as well as serotonergic (serotonin, 5-HT) signaling via postsynaptic 5-HT2A receptors as essential substrates of anxiety behaviors. Assuming a functional interdependence of these substrates, we hypothesized that a low-fear behavioral phenotype due to bilateral lesion of the amygdala would be associated with significant 5-HT2A receptor changes. Thus, we used [18F]altanserin positron emission tomography (PET) referenced to radioligand plasma levels and corrected for partial volume effects to quantify the spatial distribution of 5-HT2A receptor binding potential (BPP) in a rare patient with Urbach–Wiethe disease and selective bilateral amygdala calcification damage relative to 10 healthy control subjects. Consistent with our a priori hypothesis, we observed a 70% global decrease in 5-HT2A receptor BPP in the Urbach–Wiethe patient relative to controls. Thus, brain abnormalities in this patient are not restricted to the amygdala, but extend to overall 5-HT neurotransmission via 5-HT2A receptors. Our findings provide important insights into the molecular architecture of human anxiety behaviors and suggest the 5-HT2A receptor as a promising pharmacological target to control pathological anxiety. PMID:19015089

  4. Physician Education: The Erythropoietin Receptor and Signal Transduction.

    PubMed

    Yoshimura; Arai

    1996-01-01

    receptor gene was cloned by D'Andrea and coworkers in 1989 from murine erythroleukemia cells [1]. It became clear that the EPO receptor belongs to the cytokine receptor family that comprises receptors for the various interleukins, GM-CSF, granulocyte colony-stimulating factor (G-CSF), growth hormone and prolactin. The special characteristic of this family of receptors is that they are switched on (i.e., the receptor is activated) and transduce signals to the interior of the cell by the formation of homo- or hetero-oligomers (dimers or trimers). Moreover, hetero-oligomers of these receptors share a common receptor subunit. As shown in Figure 2, the IL-3, IL-5 and GM-CSF receptors have a common &bgr; subunit, and their ligand specificity is determined by the &agr; subunit. In the same manner, the IL-6, LIF and oncostatin M (OSM) receptors all share gp130, which is the &bgr; subunit of the IL-6 receptor. The IL-2, IL-4 and IL-7 receptors all share the &ggr; subunit of the IL-2 receptor. All the above receptors are activated by the formation of hetero-oligomers, but the G-CSF receptor, EPO receptor, and growth hormone receptor are activated by the formation of homodimers of the same types of molecules [2]. We can see that groups of cytokines such as the interleukins that affect a relatively wide range of cells and have redundant biological activity create this redundancy through the common use of a single receptor subunit. On the other hand, EPO and G-CSF act with high specificity on a relatively limited range of cells, so it was probably unnecessary for their receptors to share one of the subunits. EPO RECEPTOR AND JAK2 KINASE: The signal for cellular proliferation and differentiation into erythroblasts is thought to originate at the EPO receptor. The cytoplasmic domain of the EPO receptor can be divided into two major regions. Roughly half of the cytoplasmic domain, the part lying nearest the plasma membrane, is required for generating the signals for proliferation and

  5. Emerging principles governing signal transduction by pattern-recognition receptors.

    PubMed

    Kagan, Jonathan C; Barton, Gregory M

    2014-11-13

    The problem of recognizing and disposing of non-self-organisms, whether for nutrients or defense, predates the evolution of multicellularity. Accordingly, the function of the innate immune system is often intimately associated with fundamental aspects of cell biology. Here, we review our current understanding of the links between cell biology and pattern-recognition receptors of the innate immune system. We highlight the importance of receptor localization for the detection of microbes and for the initiation of antimicrobial signaling pathways. We discuss examples that illustrate how pattern-recognition receptors influence, and are influenced by, the general membrane trafficking machinery of mammalian cells. In the future, cell biological analysis likely will rival pure genetic analysis as a tool to uncover fundamental principles that govern host-microbe interactions.

  6. A short form of leptin receptor performs signal transduction.

    PubMed

    Murakami, T; Yamashita, T; Iida, M; Kuwajima, M; Shima, K

    1997-02-01

    The obese (ob) gene product, leptin, a peptide hormone, which is synthesized in adipocytes, is a satiety factor and is involved in the control of body weight via the regulation of energy homeostasis. Several alternate spliced isoforms (a-e, as well as others) of the leptin receptor (OBR) have been cloned, all of which, except for OBRe (soluble form), contain a single transmembrane domain. They share the same extracellular domain, with homology to the class I cytokine receptor family. The OBRb, which has longest cytoplasmic domain, is expressed in high levels in the hypothalamus and is thought to be the only isoform capable of signal transmission. Herein, we report the mRNA expression of immediate early genes, c-fos, c-jun and jun-B, which are induced by leptin addition, not only in CHO cells expressing the OBRb, but also in cells expressing one of the short form receptors, OBRa.

  7. Regulators of G-protein-signaling proteins: negative modulators of G-protein-coupled receptor signaling.

    PubMed

    Woodard, Geoffrey E; Jardín, Isaac; Berna-Erro, A; Salido, Gines M; Rosado, Juan A

    2015-01-01

    Regulators of G-protein-signaling (RGS) proteins are a category of intracellular proteins that have an inhibitory effect on the intracellular signaling produced by G-protein-coupled receptors (GPCRs). RGS along with RGS-like proteins switch on through direct contact G-alpha subunits providing a variety of intracellular functions through intracellular signaling. RGS proteins have a common RGS domain that binds to G alpha. RGS proteins accelerate GTPase and thus enhance guanosine triphosphate hydrolysis through the alpha subunit of heterotrimeric G proteins. As a result, they inactivate the G protein and quickly turn off GPCR signaling thus terminating the resulting downstream signals. Activity and subcellular localization of RGS proteins can be changed through covalent molecular changes to the enzyme, differential gene splicing, and processing of the protein. Other roles of RGS proteins have shown them to not be solely committed to being inhibitors but behave more as modulators and integrators of signaling. RGS proteins modulate the duration and kinetics of slow calcium oscillations and rapid phototransduction and ion signaling events. In other cases, RGS proteins integrate G proteins with signaling pathways linked to such diverse cellular responses as cell growth and differentiation, cell motility, and intracellular trafficking. Human and animal studies have revealed that RGS proteins play a vital role in physiology and can be ideal targets for diseases such as those related to addiction where receptor signaling seems continuously switched on.

  8. Emerging EPO and EPO receptor regulators and signal transducers

    PubMed Central

    Kuhrt, David

    2015-01-01

    As essential mediators of red cell production, erythropoietin (EPO) and its cell surface receptor (EPO receptor [EPOR]) have been intensely studied. Early investigations defined basic mechanisms for hypoxia-inducible factor induction of EPO expression, and within erythroid progenitors EPOR engagement of canonical Janus kinase 2/signal transducer and activator of transcription 5 (JAK2/STAT5), rat sarcoma/mitogen-activated protein kinase/extracellular signal-regulated kinase (RAS/MEK/ERK), and phosphatidylinositol 3-kinase (PI3K) pathways. Contemporary genetic, bioinformatic, and proteomic approaches continue to uncover new clinically relevant modulators of EPO and EPOR expression, and EPO’s biological effects. This Spotlight review highlights such factors and their emerging roles during erythropoiesis and anemia. PMID:25887776

  9. Calcium Channel Signaling Complexes with Receptors and Channels.

    PubMed

    Zamponi, Gerald W

    2015-01-01

    Voltage-gated calcium channels are not only mediators of cell signalling events, but also are recipients of signalling inputs from G protein coupled receptors (GPCRs) and their associated second messenger pathways. The coupling of GPCRs to calcium channels is optimized through the formation of receptor-channel complexes. In addition, this provides a mechanism for receptorchannel co-trafficking to and from the plasma membrane. On the other hand, voltage-gated calcium channel activity affects other types of ion channels such as voltage-and calcium-activated potassium channels. Coupling efficiency between these two families of channels is also enhanced through the formation of channel-channel complexes. This review provides a concise overview of the current state of knowledge on the physical interactions between voltage-gated calcium channels and members of the GPCR family, and with other types of ion channels.

  10. Emerging EPO and EPO receptor regulators and signal transducers.

    PubMed

    Kuhrt, David; Wojchowski, Don M

    2015-06-01

    As essential mediators of red cell production, erythropoietin (EPO) and its cell surface receptor (EPO receptor [EPOR]) have been intensely studied. Early investigations defined basic mechanisms for hypoxia-inducible factor induction of EPO expression, and within erythroid progenitors EPOR engagement of canonical Janus kinase 2/signal transducer and activator of transcription 5 (JAK2/STAT5), rat sarcoma/mitogen-activated protein kinase/extracellular signal-regulated kinase (RAS/MEK/ERK), and phosphatidylinositol 3-kinase (PI3K) pathways. Contemporary genetic, bioinformatic, and proteomic approaches continue to uncover new clinically relevant modulators of EPO and EPOR expression, and EPO's biological effects. This Spotlight review highlights such factors and their emerging roles during erythropoiesis and anemia. PMID:25887776

  11. Biased signalling and proteinase-activated receptors (PARs): targeting inflammatory disease

    PubMed Central

    Hollenberg, M D; Mihara, K; Polley, D; Suen, J Y; Han, A; Fairlie, D P; Ramachandran, R

    2014-01-01

    Although it has been known since the 1960s that trypsin and chymotrypsin can mimic hormone action in tissues, it took until the 1990s to discover that serine proteinases can regulate cells by cleaving and activating a unique four-member family of GPCRs known as proteinase-activated receptors (PARs). PAR activation involves the proteolytic exposure of its N-terminal receptor sequence that folds back to function as a ‘tethered’ receptor-activating ligand (TL). A key N-terminal arginine in each of PARs 1 to 4 has been singled out as a target for cleavage by thrombin (PARs 1, 3 and 4), trypsin (PARs 2 and 4) or other proteases to unmask the TL that activates signalling via Gq, Gi or G12/13. Similarly, synthetic receptor-activating peptides, corresponding to the exposed ‘TL sequences’ (e.g. SFLLRN—, for PAR1 or SLIGRL— for PAR2) can, like proteinase activation, also drive signalling via Gq, Gi and G12/13, without requiring receptor cleavage. Recent data show, however, that distinct proteinase-revealed ‘non-canonical’ PAR tethered-ligand sequences and PAR-activating agonist and antagonist peptide analogues can induce ‘biased’ PAR signalling, for example, via G12/13-MAPKinase instead of Gq-calcium. This overview summarizes implications of this ‘biased’ signalling by PAR agonists and antagonists for the recognized roles the PARs play in inflammatory settings. Linked ArticlesThis article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-5 PMID:24354792

  12. Endogenous GAS6 and Mer receptor signaling regulate prostate cancer stem cells in bone marrow

    PubMed Central

    Jung, Younghun; Decker, Ann M.; Wang, Jingcheng; Lee, Eunsohl; Kana, Lulia A.; Yumoto, Kenji; Cackowski, Frank C.; Rhee, James; Carmeliet, Peter; Buttitta, Laura; Morgan, Todd M.; Taichman, Russell S.

    2016-01-01

    GAS6 and its receptors (Tryo 3, Axl, Mer or “TAM”) are known to play a role in regulating tumor progression in a number of settings. Previously we have demonstrated that GAS6 signaling regulates invasion, proliferation, chemotherapy-induced apoptosis of prostate cancer (PCa) cells. We have also demonstrated that GAS6 secreted from osteoblasts in the bone marrow environment plays a critical role in establishing prostate tumor cell dormancy. Here we investigated the role that endogenous GAS6 and Mer receptor signaling plays in establishing prostate cancer stem cells in the bone marrow microenvironment. We first observed that high levels of endogenous GAS6 are expressed by disseminated tumor cells (DTCs) in the bone marrow, whereas relatively low levels of endogenous GAS6 are expressed in PCa tumors grown in a s.c. setting. Interestingly, elevated levels of endogenous GAS6 were identified in putative cancer stem cells (CSCs, CD133+/CD44+) compared to non-CSCs (CD133–/CD44–) isolated from PCa/osteoblast cocultures in vitro and in DTCs isolated from the bone marrow 24 hours after intracardiac injection. Moreover, we found that endogenous GAS6 expression is associated with Mer receptor expression in growth arrested (G1) PCa cells, which correlates with the increase of the CSC populations. Importantly, we found that overexpression of GAS6 activates phosphorylation of Mer receptor signaling and subsequent induction of the CSC phenotype in vitro and in vivo. Together these data suggest that endogenous GAS6 and Mer receptor signaling contribute to the establishment of PCa CSCs in the bone marrow microenvironment, which may have important implications for targeting metastatic disease. PMID:27028863

  13. Signal Transduction in the Chronic Leukemias: Implications for Targeted Therapies

    PubMed Central

    Ahmed, Wesam; Van Etten, Richard A.

    2013-01-01

    The chronic leukemias, including chronic myeloid leukemia (CML), the Philadelphia-negative myeloproliferative neoplasms (MPNs), and chronic lymphocytic leukemia (CLL), have been characterized extensively for abnormalities of cellular signaling pathways. This effort has led to the elucidation of the central role of dysregulated tyrosine kinase signaling in the chronic myeloid neoplasms and of constitutive B-cell receptor signaling in CLL. This, in turn, has stimulated the development of small molecule inhibitors of these signaling pathways for therapy of chronic leukemia. Although the field is still in its infancy, the clinical results with these agents have ranged from encouraging (CLL) to spectacular (CML). In this review, we summarize recent studies that have helped to define the signaling pathways critical to the pathogenesis of the chronic leukemias. We also discuss correlative studies emerging from clinical trials of drugs targeting these pathways. PMID:23307472

  14. N-glycans of growth factor receptors: their role in receptor function and disease implications.

    PubMed

    Takahashi, Motoko; Hasegawa, Yoshihiro; Gao, Congxiao; Kuroki, Yoshio; Taniguchi, Naoyuki

    2016-10-01

    Numerous signal-transduction-related molecules are secreted proteins or membrane proteins, and the mechanism by which these molecules are regulated by glycan chains is a very important issue for developing an understanding of the cellular events that transpire. This review covers the functional regulation of epidermal growth factor receptor (EGFR), ErbB3 and the transforming growth factor β (TGF-β) receptor by N-glycans. This review shows that the N-glycans play important roles in regulating protein conformation and interactions with carbohydrate recognition molecules. These results point to the possibility of a novel strategy for controlling cell signalling and developing novel glycan-based therapeutics. PMID:27612953

  15. The role of the IAP E3 ubiquitin ligases in regulating pattern-recognition receptor signalling.

    PubMed

    Vandenabeele, Peter; Bertrand, Mathieu J M

    2012-12-01

    An inflammatory response is initiated when innate immune pattern-recognition receptors (PRRs) expressed by different cell types detect constituents of invading microorganisms and endogenous intracellular molecules released by dying cells. The intracellular cascades activated by PRRs induce the expression and maturation of inflammatory molecules that coordinate the removal of the infectious agents and of the infected or damaged cells. In this Review, we discuss the findings implicating members of the inhibitor of apoptosis protein (IAP) family in the ubiquitylation-dependent regulation of PRR signalling. Understanding the role of IAPs in innate immunity may open new therapeutic perspectives for the treatment of PRR-dependent inflammatory diseases.

  16. Cannabinoid receptor 1 signaling in cardiovascular regulating nuclei in the brainstem: A review

    PubMed Central

    Ibrahim, Badr M.; Abdel-Rahman, Abdel A.

    2013-01-01

    Cannabinoids elicit complex hemodynamic responses in experimental animals that involve both peripheral and central sites. Centrally administered cannabinoids have been shown to predominantly cause pressor response. However, very little is known about the mechanism of the cannabinoid receptor 1 (CB1R)-centrally evoked pressor response. In this review, we provided an overview of the contemporary knowledge regarding the cannabinoids centrally elicited cardiovascular responses and the possible underlying signaling mechanisms. The current review focuses on the rostral ventrolateral medulla (RVLM) as the primary brainstem nucleus implicated in CB1R-evoked pressor response. PMID:25685481

  17. Calcium affects OX1 orexin (hypocretin) receptor responses by modifying both orexin binding and the signal transduction machinery

    PubMed Central

    Putula, Jaana; Pihlajamaa, Tero; Kukkonen, Jyrki P

    2014-01-01

    Background and Purpose One of the major responses upon orexin receptor activation is Ca2+ influx, and this influx seems to amplify the other responses mediated by orexin receptors. However, the reduction in Ca2+, often used to assess the importance of Ca2+ influx, might affect other properties, like ligand−receptor interactions, as suggested for some GPCR systems. Hence, we investigated the role of the ligand−receptor interaction and Ca2+ signal cascades in the apparent Ca2+ requirement of orexin-A signalling. Experimental Approach Receptor binding was assessed in CHO cells expressing human OX1 receptors with [125I]-orexin-A by conventional ligand binding as well as scintillation proximity assays. PLC activity was determined by chromatography. Key Results Both orexin receptor binding and PLC activation were strongly dependent on the extracellular Ca2+ concentration. The relationship between Ca2+ concentration and receptor binding was the same as that for PLC activation. However, when Ca2+ entry was reduced by depolarizing the cells or by inhibiting the receptor-operated Ca2+ channels, orexin-A-stimulated PLC activity was much more strongly inhibited than orexin-A binding. Conclusions and Implications Ca2+ plays a dual role in orexin signalling by being a prerequisite for both ligand−receptor interaction and amplifying orexin signals via Ca2+ influx. Some previous results obtained utilizing Ca2+ chelators have to be re-evaluated based on the results of the current study. From a drug discovery perspective, further experiments need to identify the target for Ca2+ in orexin-A−OX1 receptor interaction and its mechanism of action. PMID:25132134

  18. The Role of TAM Family Receptors in Immune Cell Function: Implications for Cancer Therapy

    PubMed Central

    Paolino, Magdalena; Penninger, Josef M.

    2016-01-01

    The TAM receptor protein tyrosine kinases—Tyro3, Axl, and Mer—are essential regulators of immune homeostasis. Guided by their cognate ligands Growth arrest-specific gene 6 (Gas6) and Protein S (Pros1), these receptors ensure the resolution of inflammation by dampening the activation of innate cells as well as by restoring tissue function through promotion of tissue repair and clearance of apoptotic cells. Their central role as negative immune regulators is highlighted by the fact that deregulation of TAM signaling has been linked to the pathogenesis of autoimmune, inflammatory, and infectious diseases. Importantly, TAM receptors have also been associated with cancer development and progression. In a cancer setting, TAM receptors have a dual regulatory role, controlling the initiation and progression of tumor development and, at the same time, the associated anti-tumor responses of diverse immune cells. Thus, modulation of TAM receptors has emerged as a potential novel strategy for cancer treatment. In this review, we discuss our current understanding of how TAM receptors control immunity, with a particular focus on the regulation of anti-tumor responses and its implications for cancer immunotherapy. PMID:27775650

  19. Combinatorial proteomic analysis of intercellular signaling applied to the CD28 T-cell costimulatory receptor

    PubMed Central

    Tian, Ruijun; Wang, Haopeng; Gish, Gerald D.; Petsalaki, Evangelia; Pasculescu, Adrian; Shi, Yu; Mollenauer, Marianne; Bagshaw, Richard D.; Yosef, Nir; Hunter, Tony; Gingras, Anne-Claude; Weiss, Arthur; Pawson, Tony

    2015-01-01

    Systematic characterization of intercellular signaling approximating the physiological conditions of stimulation that involve direct cell–cell contact is challenging. We describe a proteomic strategy to analyze physiological signaling mediated by the T-cell costimulatory receptor CD28. We identified signaling pathways activated by CD28 during direct cell–cell contact by global analysis of protein phosphorylation. To define immediate CD28 targets, we used phosphorylated forms of the CD28 cytoplasmic region to obtain the CD28 interactome. The interaction profiles of selected CD28-interacting proteins were further characterized in vivo for amplifying the CD28 interactome. The combination of the global phosphorylation and interactome analyses revealed broad regulation of CD28 and its interactome by phosphorylation. Among the cellular phosphoproteins influenced by CD28 signaling, CapZ-interacting protein (CapZIP), a regulator of the actin cytoskeleton, was implicated by functional studies. The combinatorial approach applied herein is widely applicable for characterizing signaling networks associated with membrane receptors with short cytoplasmic tails. PMID:25829543

  20. Combinatorial proteomic analysis of intercellular signaling applied to the CD28 T-cell costimulatory receptor.

    PubMed

    Tian, Ruijun; Wang, Haopeng; Gish, Gerald D; Petsalaki, Evangelia; Pasculescu, Adrian; Shi, Yu; Mollenauer, Marianne; Bagshaw, Richard D; Yosef, Nir; Hunter, Tony; Gingras, Anne-Claude; Weiss, Arthur; Pawson, Tony

    2015-03-31

    Systematic characterization of intercellular signaling approximating the physiological conditions of stimulation that involve direct cell-cell contact is challenging. We describe a proteomic strategy to analyze physiological signaling mediated by the T-cell costimulatory receptor CD28. We identified signaling pathways activated by CD28 during direct cell-cell contact by global analysis of protein phosphorylation. To define immediate CD28 targets, we used phosphorylated forms of the CD28 cytoplasmic region to obtain the CD28 interactome. The interaction profiles of selected CD28-interacting proteins were further characterized in vivo for amplifying the CD28 interactome. The combination of the global phosphorylation and interactome analyses revealed broad regulation of CD28 and its interactome by phosphorylation. Among the cellular phosphoproteins influenced by CD28 signaling, CapZ-interacting protein (CapZIP), a regulator of the actin cytoskeleton, was implicated by functional studies. The combinatorial approach applied herein is widely applicable for characterizing signaling networks associated with membrane receptors with short cytoplasmic tails. PMID:25829543

  1. Tonic BCR signaling represses receptor editing via Raf- and calcium-dependent signaling pathways.

    PubMed

    Ramsey, Laura B; Vegoe, Amanda L; Miller, Andrew T; Cooke, Michael P; Farrar, Michael A

    2011-03-30

    Light chain receptor editing is an important mechanism that prevents B cell self-reactivity. We have previously shown that tonic signaling through the BCR represses RAG expression at the immature B cell stage, and that initiation of light chain rearrangements occurs in the absence of these tonic signals in an in vitro model of B cell development. To further test our hypothesis we studied the effect of itpkb deficiency (itpkb(-/-) mice) or Raf hyper-activation (Raf-CAAX transgenic mice), two mutations that enhance BCR signaling, on receptor editing in an in vivo model. This model relies on transferring bone marrow from wild-type or mutant mice into mice expressing an anti-kappa light chain transgene. The anti-kappa transgene induces receptor editing of all kappa light chain expressing B cells, leading to a high frequency of lambda light chain expressing B cells. Anti-κ transgenic recipients of bone marrow from itpkb(-/-) or Raf-CAAX mice showed lower levels of editing to λ light chain than did non-transgenic control recipients. These results provide evidence in an in vivo model that enhanced BCR signaling at the immature B cell stage of development suppresses light chain receptor editing.

  2. Research Resource: A Reference Transcriptome for Constitutive Androstane Receptor and Pregnane X Receptor Xenobiotic Signaling.

    PubMed

    Ochsner, Scott A; Tsimelzon, Anna; Dong, Jianrong; Coarfa, Cristian; McKenna, Neil J

    2016-08-01

    The pregnane X receptor (PXR) (PXR/NR1I3) and constitutive androstane receptor (CAR) (CAR/NR1I2) members of the nuclear receptor (NR) superfamily of ligand-regulated transcription factors are well-characterized mediators of xenobiotic and endocrine-disrupting chemical signaling. The Nuclear Receptor Signaling Atlas maintains a growing library of transcriptomic datasets involving perturbations of NR signaling pathways, many of which involve perturbations relevant to PXR and CAR xenobiotic signaling. Here, we generated a reference transcriptome based on the frequency of differential expression of genes across 159 experiments compiled from 22 datasets involving perturbations of CAR and PXR signaling pathways. In addition to the anticipated overrepresentation in the reference transcriptome of genes encoding components of the xenobiotic stress response, the ranking of genes involved in carbohydrate metabolism and gonadotropin action sheds mechanistic light on the suspected role of xenobiotics in metabolic syndrome and reproductive disorders. Gene Set Enrichment Analysis showed that although acetaminophen, chlorpromazine, and phenobarbital impacted many similar gene sets, differences in direction of regulation were evident in a variety of processes. Strikingly, gene sets representing genes linked to Parkinson's, Huntington's, and Alzheimer's diseases were enriched in all 3 transcriptomes. The reference xenobiotic transcriptome will be supplemented with additional future datasets to provide the community with a continually updated reference transcriptomic dataset for CAR- and PXR-mediated xenobiotic signaling. Our study demonstrates how aggregating and annotating transcriptomic datasets, and making them available for routine data mining, facilitates research into the mechanisms by which xenobiotics and endocrine-disrupting chemicals subvert conventional NR signaling modalities. PMID:27409825

  3. An Update on Adenosine A2A-Dopamine D2 receptor interactions. Implications for the Function of G Protein-Coupled Receptors

    PubMed Central

    Ferré, S.; Quiroz, C.; Woods, A. S.; Cunha, R.; Popoli, P.; Ciruela, F.; Lluis, C.; Franco, R.; Azdad, K.; Schiffmann, S. N.

    2008-01-01

    Adenosine A2A-dopamine D2 receptor interactions play a very important role in striatal function. A2A-D2 receptor interactions provide an example of the capabilities of information processing by just two different G protein-coupled receptors. Thus, there is evidence for the coexistence of two reciprocal antagonistic interactions between A2A and D2 receptors in the same neurons, the GABAergic enkephalinergic nens. An antagonistic A2A-D2 intramembrane receptor interaction, which depends on A2A-D2 receptor heteromerization and Gq/11-PLC signaling, modulates neuronal excitability and neurotransmitter release. On the other hand, an antagonistic A2A-D2 receptor interaction at the adenylyl-cyclase level, which depends on Gs/olf- and Gi/o- type V adenylyl-cyclase signaling, modulates protein phosphorylation and gene expression. Finally, under conditions of upregulation of an activator of G protein signaling (AGS3), such as during chronic treatment with addictive drugs, a synergistic A2A-D2 receptor interaction can also be demonstrated. AGS3 facilitates a synergistic interaction between Gs/olf- and Gi/o- coupled receptors on the activation of types II/IV adenylyl cyclase, leading to a paradoxical increase in protein phosphorylation and gene expression upon co-activation of A2A and D2 receptors. The analysis of A2-D2 receptor interactions will have implications for the pathophysiology and treatment of basal ganglia disorders and drug addiction. PMID:18537670

  4. Exogenous S1P Exposure Potentiates Ischemic Stroke Damage That Is Reduced Possibly by Inhibiting S1P Receptor Signaling

    PubMed Central

    Moon, Eunjung; Han, Jeong Eun; Jeon, Sejin; Ryu, Jong Hoon; Choi, Ji Woong; Chun, Jerold

    2015-01-01

    Initial and recurrent stroke produces central nervous system (CNS) damage, involving neuroinflammation. Receptor-mediated S1P signaling can influence neuroinflammation and has been implicated in cerebral ischemia through effects on the immune system. However, S1P-mediated events also occur within the brain itself where its roles during stroke have been less well studied. Here we investigated the involvement of S1P signaling in initial and recurrent stroke by using a transient middle cerebral artery occlusion/reperfusion (M/R) model combined with analyses of S1P signaling. Gene expression for S1P receptors and involved enzymes was altered during M/R, supporting changes in S1P signaling. Direct S1P microinjection into the normal CNS induced neuroglial activation, implicating S1P-initiated neuroinflammatory responses that resembled CNS changes seen during initial M/R challenge. Moreover, S1P microinjection combined with M/R potentiated brain damage, approximating a model for recurrent stroke dependent on S1P and suggesting that reduction in S1P signaling could ameliorate stroke damage. Delivery of FTY720 that removes S1P signaling with chronic exposure reduced damage in both initial and S1P-potentiated M/R-challenged brain, while reducing stroke markers like TNF-α. These results implicate direct S1P CNS signaling in the etiology of initial and recurrent stroke that can be therapeutically accessed by S1P modulators acting within the brain. PMID:26576074

  5. Reduced signal transduction by 5-HT4 receptors after long-term venlafaxine treatment in rats

    PubMed Central

    Vidal, R; Valdizan, EM; Vilaró, MT; Pazos, A; Castro, E

    2010-01-01

    BACKGROUND AND PURPOSE The 5-HT4 receptor may be a target for antidepressant drugs. Here we have examined the effects of the dual antidepressant, venlafaxine, on 5-HT4 receptor-mediated signalling events. EXPERIMENTAL APPROACH The effects of 21 days treatment (p.o.) with high (40 mg·kg−1) and low (10 mg·kg−1) doses of venlafaxine, were evaluated at different levels of 5-HT4 receptor-mediated neurotransmission by using in situ hybridization, receptor autoradiography, adenylate cyclase assays and electrophysiological recordings in rat brain. The selective noradrenaline reuptake inhibitor, reboxetine (10 mg·kg−1, 21 days) was also evaluated on 5-HT4 receptor density. KEY RESULTS Treatment with a high dose (40 mg·kg−1) of venlafaxine did not alter 5-HT4 mRNA expression, but decreased the density of 5-HT4 receptors in caudate-putamen (% reduction = 26 ± 6), hippocampus (% reduction = 39 ± 7 and 39 ± 8 for CA1 and CA3 respectively) and substantia nigra (% reduction = 49 ± 5). Zacopride-stimulated adenylate cyclase activation was unaltered following low-dose treatment (10 mg·kg−1) while it was attenuated in rats treated with 40 mg·kg−1 of venlafaxine (% reduction = 51 ± 2). Furthermore, the amplitude of population spike in pyramidal cells of CA1 of hippocampus induced by zacopride was significantly attenuated in rats receiving either dose of venlafaxine. Chronic reboxetine did not modify 5-HT4 receptor density. CONCLUSIONS AND IMPLICATIONS Our data indicate a functional desensitization of 5-HT4 receptors after chronic venlafaxine, similar to that observed after treatment with the classical selective inhibitors of 5-HT reuptake. PMID:20880406

  6. P2y Receptor-Mediated Angiogenesis via Vascular Endothelial Growth Factor Receptor 2 Signaling

    PubMed Central

    Rumjahn, Sharif M.; Baldwin, Karla A; Buxton, Iain L. O.

    2011-01-01

    Pathological as well as physiological angiogenesis is known to be regulated by such factors as nucleotides and Vascular Endothelial Growth Factor (VEGF). Activated P2Y nucleotide receptors have been observed to associate and transactivate VEGF Receptor 2 (VEGFR2), suggesting a cooperation between nucleotide and VEGF signaling in angiogenesis. P2YR mediated VEGFR2 signaling therefore may be important in describing the angiogenic signaling of nucleotides such as ATP. Here, we provide evidence that supports the notion of P2YR-VEGFR2 signaling. The significant angiogenic effect of P2Y1/2 receptor agonists (100 μM ATP and 10 μM 2MS-ATP) on endothelial cell tubulogenesis was suppressed back to near control levels upon addition of 1 μM SU1498 (specific VEGFR2 tyrosine kinase inhibitor). We believe that this P2YR-VEFGR2 signaling is an important component of pathological, as well as physiological angiogenesis. PMID:18605230

  7. Vitamin D Receptor Signaling in Renal and Cardiovascular Protection

    PubMed Central

    Li, Yan Chun

    2013-01-01

    The high prevalence of vitamin D-deficiency in patients with chronic kidney disease (CKD) is believed to be an important risk factor for the cardio-renal syndrome commonly seen in this patient population. African Americans suffer disproportionally high incidence of renal and cardiovascular disease with poor disease outcome, which may be partly attributed to their low vitamin D status in part due to low subcutaneous photo-production of vitamin D. Mounting evidence from animal and clinical studies has demonstrated beneficial effects of vitamin D therapy on the renal and cardiovascular systems, and the underlying reno- and cardio-protective mechanisms of vitamin D receptor (VDR)-mediated signaling are under intense investigations. In this article, I will review our most recent understanding of the renal protective mechanism of the podocyte VDR signaling against diabetic nephropathy and the anti-atherosclerotic role of macrophage VDR signaling in the regulation of atherosclerosis. PMID:24119849

  8. Inhibition of the Dopamine D1 Receptor Signaling by PSD-95*◆

    PubMed Central

    Zhang, Jingping; Vinuela, Angel; Neely, Mark H.; Hallett, Penelope J.; Grant, Seth G. N.; Miller, Gregory M.; Isacson, Ole; Caron, Marc G.; Yao, Wei-Dong

    2008-01-01

    Dopamine D1 receptors play an important role in movement, reward, and learning and are implicated in a number of neurological and psychiatric disorders. These receptors are concentrated in dendritic spines of neurons, including the spine head and the postsynaptic density. D1 within spines is thought to modulate the local channels and receptors to control the excitability and synaptic properties of spines. The molecular mechanisms mediating D1 trafficking, anchorage, and function in spines remain elusive. Here we show that the synaptic scaffolding protein PSD-95 thought to play a role in stabilizing gluta-mate receptors in the postsynaptic density, interacts with D1 and regulates its trafficking and function. Interestingly, the D1-PSD-95 interaction does not require the well characterized domains of PSD-95 but is mediated by the carboxyl-terminal tail of D1 and the NH2terminus of PSD-95, a region that is recognized only recently to participate in protein-protein interaction. Co-expression of PSD-95 with D1 in mammalian cells inhibits the D1-mediated cAMP accumulation without altering the total expression level or the agonist binding properties of the receptor. The diminished D1 signaling is mediated by reduced D1 expression at the cell surface as a consequence of an enhanced constitutive, dynamin-dependent endocytosis. In addition, genetically engineered mice lacking PSD-95 show a heightened behavioral response to either a D1 agonist or the psychostimulant amphetamine. These studies demonstrate a role for a glutamatergic scaffold in dopamine receptor signaling and trafficking and identify a new potential target for the modulation of abnormal dopaminergic function. PMID:17369255

  9. Minireview: Evolution of NURSA, the Nuclear Receptor Signaling Atlas.

    PubMed

    McKenna, Neil J; Cooney, Austin J; DeMayo, Francesco J; Downes, Michael; Glass, Christopher K; Lanz, Rainer B; Lazar, Mitchell A; Mangelsdorf, David J; Moore, David D; Qin, Jun; Steffen, David L; Tsai, Ming-Jer; Tsai, Sophia Y; Yu, Ruth; Margolis, Ronald N; Evans, Ronald M; O'Malley, Bert W

    2009-06-01

    Nuclear receptors and coregulators are multifaceted players in normal metabolic and homeostatic processes in addition to a variety of disease states including cancer, inflammation, diabetes, obesity, and atherosclerosis. Over the past 7 yr, the Nuclear Receptor Signaling Atlas (NURSA) research consortium has worked toward establishing a discovery-driven platform designed to address key questions concerning the expression, organization, and function of these molecules in a variety of experimental model systems. By applying powerful technologies such as quantitative PCR, high-throughput mass spectrometry, and embryonic stem cell manipulation, we are pursuing these questions in a series of transcriptomics-, proteomics-, and metabolomics-based research projects and resources. The consortium's web site (www.nursa.org) integrates NURSA datasets and existing public datasets with the ultimate goal of furnishing the bench scientist with a comprehensive framework for hypothesis generation, modeling, and testing. We place a strong emphasis on community input into the development of this resource and to this end have published datasets from academic and industrial laboratories, established strategic alliances with Endocrine Society journals, and are developing tools to allow web site users to act as data curators. With the ongoing support of the nuclear receptor and coregulator signaling communities, we believe that NURSA can make a lasting contribution to research in this dynamic field. PMID:19423650

  10. Disruption of Fas Receptor Signaling by Nitric Oxide in Eosinophils

    PubMed Central

    Hebestreit, Holger; Dibbert, Birgit; Balatti, Ivo; Braun, Doris; Schapowal, Andreas; Blaser, Kurt; Simon, Hans-Uwe

    1998-01-01

    It has been suggested that Fas ligand–Fas receptor interactions are involved in the regulation of eosinophil apoptosis and that dysfunctions in this system could contribute to the accumulation of these cells in allergic and asthmatic diseases. Here, we demonstrate that nitric oxide (NO) specifically prevents Fas receptor–mediated apoptosis in freshly isolated human eosinophils. In contrast, rapid acceleration of eosinophil apoptosis by activation of the Fas receptor occurs in the presence of eosinophil hematopoietins. Analysis of the intracellular mechanisms revealed that NO disrupts Fas receptor–mediated signaling events at the level of, or proximal to, Jun kinase (JNK), but distal to sphingomyelinase (SMase) activation and ceramide generation. In addition, activation of SMase occurs downstream of an interleukin 1 converting enzyme–like (ICE-like) protease(s) that is not blocked by NO. However, NO prevents activation of a protease that targets lamin B1. These findings suggest a role for an additional NO-sensitive apoptotic signaling pathway that amplifies the proteolytic cascade initialized by activation of the Fas receptor. Therefore, NO concentrations within allergic inflammatory sites may be important in determining whether an eosinophil survives or undergoes apoptosis upon Fas ligand stimulation. PMID:9449721

  11. Optodynamic simulation of β-adrenergic receptor signalling

    PubMed Central

    Siuda, Edward R.; McCall, Jordan G.; Al-Hasani, Ream; Shin, Gunchul; Il Park, Sung; Schmidt, Martin J.; Anderson, Sonya L.; Planer, William J.; Rogers, John A.; Bruchas, Michael R.

    2015-01-01

    Optogenetics has provided a revolutionary approach to dissecting biological phenomena. However, the generation and use of optically active GPCRs in these contexts is limited and it is unclear how well an opsin-chimera GPCR might mimic endogenous receptor activity. Here we show that a chimeric rhodopsin/β2 adrenergic receptor (opto-β2AR) is similar in dynamics to endogenous β2AR in terms of: cAMP generation, MAP kinase activation and receptor internalization. In addition, we develop and characterize a novel toolset of optically active, functionally selective GPCRs that can bias intracellular signalling cascades towards either G-protein or arrestin-mediated cAMP and MAP kinase pathways. Finally, we show how photoactivation of opto-β2AR in vivo modulates neuronal activity and induces anxiety-like behavioural states in both fiber-tethered and wireless, freely moving animals when expressed in brain regions known to contain β2ARs. These new GPCR approaches enhance the utility of optogenetics and allow for discrete spatiotemporal control of GPCR signalling in vitro and in vivo. PMID:26412387

  12. Transient Suppression of TGFβ Receptor Signaling Facilitates Human Islet Transplantation.

    PubMed

    Xiao, Xiangwei; Fischbach, Shane; Song, Zewen; Gaffar, Iljana; Zimmerman, Ray; Wiersch, John; Prasadan, Krishna; Shiota, Chiyo; Guo, Ping; Ramachandran, Sabarinathan; Witkowski, Piotr; Gittes, George K

    2016-04-01

    Although islet transplantation is an effective treatment for severe diabetes, its broad application is greatly limited due to a shortage of donor islets. Suppression of TGFβ receptor signaling in β-cells has been shown to increase β-cell proliferation in mice, but has not been rigorously examined in humans. Here, treatment of human islets with a TGFβ receptor I inhibitor, SB-431542 (SB), significantly improved C-peptide secretion by β-cells, and significantly increased β-cell number by increasing β-cell proliferation. In addition, SB increased cell-cycle activators and decreased cell-cycle suppressors in human β-cells. Transplantation of SB-treated human islets into diabetic immune-deficient mice resulted in significant improvement in blood glucose control, significantly higher serum and graft insulin content, and significantly greater increases in β-cell proliferation in the graft, compared with controls. Thus, our data suggest that transient suppression of TGFβ receptor signaling may improve the outcome of human islet transplantation, seemingly through increasing β-cell number and function. PMID:26872091

  13. Nuclear receptor TLX inhibits TGF-β signaling in glioblastoma.

    PubMed

    Johansson, Erik; Zhai, Qiwei; Zeng, Zhao-Jun; Yoshida, Takeshi; Funa, Keiko

    2016-05-01

    TLX (also called NR2E1) is an orphan nuclear receptor that maintains stemness of neuronal stem cells. TLX is highly expressed in the most malignant form of glioma, glioblastoma multiforme (GBM), and is important for the proliferation and maintenance of the stem/progenitor cells of the tumor. Transforming Growth Factor-β (TGF-β) is a cytokine regulating many different cellular processes such as differentiation, migration, adhesion, cell death and proliferation. TGF-β has an important function in cancer where it can work as either a tumor suppressor or oncogene, depending on the cancer type and stage of tumor development. Since glioblastoma often have dysfunctional TGF-β signaling we wanted to find out if there is any interaction between TLX and TGF-β in glioblastoma cells. We demonstrate that knockdown of TLX enhances the canonical TGF-β signaling response in glioblastoma cell lines. TLX physically interacts with and stabilizes Smurf1, which can ubiquitinate and target TGF-β receptor II for degradation, whereas knockdown of TLX leads to stabilization of TGF-β receptor II, increased nuclear translocation of Smad2/3 and enhanced expression of TGF-β target genes. The interaction between TLX and TGF-β may play an important role in the regulation of proliferation and tumor-initiating properties of glioblastoma cells.

  14. Minireview: Evolution of NURSA, the Nuclear Receptor Signaling Atlas.

    PubMed

    McKenna, Neil J; Cooney, Austin J; DeMayo, Francesco J; Downes, Michael; Glass, Christopher K; Lanz, Rainer B; Lazar, Mitchell A; Mangelsdorf, David J; Moore, David D; Qin, Jun; Steffen, David L; Tsai, Ming-Jer; Tsai, Sophia Y; Yu, Ruth; Margolis, Ronald N; Evans, Ronald M; O'Malley, Bert W

    2009-06-01

    Nuclear receptors and coregulators are multifaceted players in normal metabolic and homeostatic processes in addition to a variety of disease states including cancer, inflammation, diabetes, obesity, and atherosclerosis. Over the past 7 yr, the Nuclear Receptor Signaling Atlas (NURSA) research consortium has worked toward establishing a discovery-driven platform designed to address key questions concerning the expression, organization, and function of these molecules in a variety of experimental model systems. By applying powerful technologies such as quantitative PCR, high-throughput mass spectrometry, and embryonic stem cell manipulation, we are pursuing these questions in a series of transcriptomics-, proteomics-, and metabolomics-based research projects and resources. The consortium's web site (www.nursa.org) integrates NURSA datasets and existing public datasets with the ultimate goal of furnishing the bench scientist with a comprehensive framework for hypothesis generation, modeling, and testing. We place a strong emphasis on community input into the development of this resource and to this end have published datasets from academic and industrial laboratories, established strategic alliances with Endocrine Society journals, and are developing tools to allow web site users to act as data curators. With the ongoing support of the nuclear receptor and coregulator signaling communities, we believe that NURSA can make a lasting contribution to research in this dynamic field.

  15. Lymphotoxin β receptor signaling is required for inflammatory lymphangiogenesis in the thyroid

    PubMed Central

    Furtado, Glaucia C.; Marinkovic, Tatjana; Martin, Andrea P.; Garin, Alexandre; Hoch, Benjamin; Hubner, Wolfgang; Chen, Benjamin K.; Genden, Eric; Skobe, Mihaela; Lira, Sergio A.

    2007-01-01

    Infiltration of lymphocytes into the thyroid gland and formation of lymph node-like structures is a hallmark of Hashimoto's thyroiditis. Here we demonstrate that lymphatic vessels are present within these infiltrates. Mice overexpressing the chemokine CCL21 in the thyroid (TGCCL21 mice) developed similar lymphoid infiltrates and lymphatic vessels. TGCCL21 mice lacking mature T and B cells (RAGTGCCL21 mice) did not have cellular infiltrates or increased number of lymphatic vessels compared with controls. Transfer of CD3+CD4+ T cells into RAGTGCCL21 mice promoted the development of LYVE-1+podoplanin+Prox-1+ vessels in the thyroid. Genetic deletion of lymphotoxin β receptor or lymphotoxin α abrogated development of lymphatic vessels in the inflamed areas in the thyroid but did not affect development of neighboring lymphatics. These results define a model for the study of inflammatory lymphangiogenesis in the thyroid and implicate lymphotoxin β receptor signaling in this process. PMID:17360402

  16. Monocyte Signal Transduction Receptors in Active and Latent Tuberculosis

    PubMed Central

    Druszczynska, Magdalena; Wlodarczyk, Marcin; Janiszewska-Drobinska, Beata; Kielnierowski, Grzegorz; Zawadzka, Joanna; Kowalewicz-Kulbat, Magdalena; Fol, Marek; Szpakowski, Piotr; Rudnicka, Karolina; Chmiela, Magdalena; Rudnicka, Wieslawa

    2013-01-01

    The mechanisms that promote either resistance or susceptibility to TB disease remain insufficiently understood. Our aim was to compare the expression of cell signaling transduction receptors, CD14, TLR2, CD206, and β2 integrin LFA-1 on monocytes from patients with active TB or nonmycobacterial lung disease and healthy individuals with M.tb latency and uninfected controls to explain the background of the differences between clinical and subclinical forms of M.tb infection. A simultaneous increase in the expression of the membrane bound mCD14 receptor and LFA-1 integrin in patients with active TB may be considered a prodrome of breaking immune control by M.tb bacilli in subjects with the latent TB and absence of clinical symptoms. PMID:23401703

  17. Engendering biased signalling from the calcium-sensing receptor for the pharmacotherapy of diverse disorders

    PubMed Central

    Leach, K; Sexton, P M; Christopoulos, A; Conigrave, A D

    2014-01-01

    The human calcium-sensing receptor (CaSR) is widely expressed in the body, where its activity is regulated by multiple orthosteric and endogenous allosteric ligands. Each ligand stabilizes a unique subset of conformational states, which enables the CaSR to couple to distinct intracellular signalling pathways depending on the extracellular milieu in which it is bathed. Differential signalling arising from distinct receptor conformations favoured by each ligand is referred to as biased signalling. The outcome of CaSR activation also depends on the cell type in which it is expressed. Thus, the same ligand may activate diverse pathways in distinct cell types. Given that the CaSR is implicated in numerous physiological and pathophysiological processes, it is an ideal target for biased ligands that could be rationally designed to selectively regulate desired signalling pathways in preferred cell types. Linked ArticlesThis article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-5 PMID:24111791

  18. Charged MVB protein 5 is involved in T-cell receptor signaling.

    PubMed

    Wi, Sae Mi; Min, Yoon; Lee, Ki-Young

    2016-01-29

    Charged multivesicular body protein 5 (CHMP5) has a key role in multivesicular body biogenesis and a critical role in the downregulation of signaling pathways through receptor degradation. However, the role of CHMP5 in T-cell receptor (TCR)-mediated signaling has not been previously investigated. In this study, we utilized a short hairpin RNA-based RNA interference approach to investigate the functional role of CHMP5. Upon TCR stimulation, CHMP5-knockdown (CHMP5(KD)) Jurkat T cells exhibited activation of TCR downstream signaling molecules, such as PKCθ and IKKαβ, and resulted in the activation of nuclear factor-κB and the marked upregulation of TCR-induced gene expression. Moreover, we found that activator protein-1 and nuclear factor of activated T-cells transcriptional factors were markedly activated in CHMP5(KD) Jurkat cells in response to TCR stimulation, which led to a significant increase in interleukin-2 secretion. Biochemical studies revealed that CHMP5 endogenously forms high-molecular-weight complexes, including TCR molecules, and specifically interacts with TCRβ. Interestingly, flow cytometry analysis also revealed that CHMP5(KD) Jurkat T cells exhibit upregulation of TCR expression on the cell surface compared with control Jurkat T cells. Taken together, these findings demonstrated that CHMP5 might be involved in the homeostatic regulation of TCR on the cell surface, presumably through TCR recycling or degradation. Thus CHMP5 is implicated in TCR-mediated signaling.

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

    PubMed

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

    2016-03-01

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

  20. Subverting Toll-Like Receptor Signaling by Bacterial Pathogens

    PubMed Central

    McGuire, Victoria A.; Arthur, J. Simon C.

    2015-01-01

    Pathogenic bacteria are detected by pattern-recognition receptors (PRRs) expressed on innate immune cells, which activate intracellular signal transduction pathways to elicit an immune response. Toll-like receptors are, perhaps, the most studied of the PRRs and can activate the mitogen-activated protein kinase (MAPK) and Nuclear Factor-κB (NF-κB) pathways. These pathways are critical for mounting an effective immune response. In order to evade detection and promote virulence, many pathogens subvert the host immune response by targeting components of these signal transduction pathways. This mini-review highlights the diverse mechanisms that bacterial pathogens have evolved to manipulate the innate immune response, with a particular focus on those that target MAPK and NF-κB signaling pathways. Understanding the elaborate strategies that pathogens employ to subvert the immune response not only highlights the importance of these proteins in mounting effective immune responses, but may also identify novel approaches for treatment or prevention of infection. PMID:26648936

  1. Cannabinoid receptor signaling regulates liver development and metabolism.

    PubMed

    Liu, Leah Y; Alexa, Kristen; Cortes, Mauricio; Schatzman-Bone, Stephanie; Kim, Andrew J; Mukhopadhyay, Bani; Cinar, Resat; Kunos, George; North, Trista E; Goessling, Wolfram

    2016-02-15

    Endocannabinoid (EC) signaling mediates psychotropic effects and regulates appetite. By contrast, potential roles in organ development and embryonic energy consumption remain unknown. Here, we demonstrate that genetic or chemical inhibition of cannabinoid receptor (Cnr) activity disrupts liver development and metabolic function in zebrafish (Danio rerio), impacting hepatic differentiation, but not endodermal specification: loss of cannabinoid receptor 1 (cnr1) and cnr2 activity leads to smaller livers with fewer hepatocytes, reduced liver-specific gene expression and proliferation. Functional assays reveal abnormal biliary anatomy and lipid handling. Adult cnr2 mutants are susceptible to hepatic steatosis. Metabolomic analysis reveals reduced methionine content in Cnr mutants. Methionine supplementation rescues developmental and metabolic defects in Cnr mutant livers, suggesting a causal relationship between EC signaling, methionine deficiency and impaired liver development. The effect of Cnr on methionine metabolism is regulated by sterol regulatory element-binding transcription factors (Srebfs), as their overexpression rescues Cnr mutant liver phenotypes in a methionine-dependent manner. Our work describes a novel developmental role for EC signaling, whereby Cnr-mediated regulation of Srebfs and methionine metabolism impacts liver development and function.

  2. Monoterpene (-)-citronellal affects hepatocarcinoma cell signaling via an olfactory receptor.

    PubMed

    Maßberg, Désirée; Simon, Annika; Häussinger, Dieter; Keitel, Verena; Gisselmann, Günter; Conrad, Heike; Hatt, Hanns

    2015-01-15

    Terpenes are the major constituents of essential oils in plants. In recent years, terpenes have become of clinical relevance due to their ability to suppress cancer development. Their effect on cellular proliferation has made them promising agents in the prevention or treatment of many types of cancer. In the present study, a subset of different monoterpenes was investigated for their molecular effects on the hepatocellular carcinoma cell line Huh7. Using fluorometric calcium imaging, acyclic monoterpene (-)-citronellal was found to induce transient Ca(2+) signals in Huh7 cells by activating a cAMP-dependent signaling pathway. Moreover, we detected the (-)-citronellal-activated human olfactory receptor OR1A2 at the mRNA and protein levels and demonstrated its potential involvement in (-)-citronellal-induced calcium signaling in Huh7 cells. Furthermore, activation of OR1A2 results in phosphorylation of p38 MAPK and reduced cell proliferation, indicating an effect on hepatocellular carcinoma progression. Here, we provide for the first time data on the molecular mechanism evoked by (-)-citronellal in human hepatocellular carcinoma cells. The identified olfactory receptor could serve as a potential therapeutic target for cancer diagnosis and treatment.

  3. Beclin 1 regulates growth factor receptor signaling in breast cancer.

    PubMed

    Rohatgi, R A; Janusis, J; Leonard, D; Bellvé, K D; Fogarty, K E; Baehrecke, E H; Corvera, S; Shaw, L M

    2015-10-16

    Beclin 1 is a haploinsufficient tumor suppressor that is decreased in many human tumors. The function of beclin 1 in cancer has been attributed primarily to its role in the degradative process of macroautophagy. However, beclin 1 is a core component of the vacuolar protein sorting 34 (Vps34)/class III phosphatidylinositoI-3 kinase (PI3KC3) and Vps15/p150 complex that regulates multiple membrane-trafficking events. In the current study, we describe an alternative mechanism of action for beclin 1 in breast cancer involving its control of growth factor receptor signaling. We identify a specific stage of early endosome maturation that is regulated by beclin 1, the transition of APPL1-containing phosphatidyIinositol 3-phosphate-negative (PI3P(-)) endosomes to PI3P(+) endosomes. Beclin 1 regulates PI3P production in response to growth factor stimulation to control the residency time of growth factor receptors in the PI3P(-)/APPL(+)-signaling-competent compartment. As a result, suppression of BECN1 sustains growth factor-stimulated AKT and ERK activation resulting in increased breast carcinoma cell invasion. In human breast tumors, beclin 1 expression is inversely correlated with AKT and ERK phosphorylation. Our data identify a novel role for beclin 1 in regulating growth factor signaling and reveal a mechanism by which loss of beclin 1 expression would enhance breast cancer progression.

  4. Prohibitin: A Novel Molecular Player in KDEL Receptor Signalling

    PubMed Central

    Giannotta, Monica; Fragassi, Giorgia; Tamburro, Antonio; Vanessa, Capone; Luini, Alberto; Sallese, Michele

    2015-01-01

    The KDEL receptor (KDELR) is a seven-transmembrane-domain protein involved in retrograde transport of protein chaperones from the Golgi complex to the endoplasmic reticulum. Our recent findings have shown that the Golgi-localised KDELR acts as a functional G-protein-coupled receptor by binding to and activating Gs and Gq. These G proteins induce activation of PKA and Src and regulate retrograde and anterograde Golgi trafficking. Here we used an integrated coimmunoprecipitation and mass spectrometry approach to identify prohibitin-1 (PHB) as a KDELR interactor. PHB is a multifunctional protein that is involved in signal transduction, cell-cycle control, and stabilisation of mitochondrial proteins. We provide evidence that depletion of PHB induces intense membrane-trafficking activity at the ER–Golgi interface, as revealed by formation of GM130-positive Golgi tubules, and recruitment of p115, β-COP, and GBF1 to the Golgi complex. There is also massive recruitment of SEC31 to endoplasmic-reticulum exit sites. Furthermore, absence of PHB decreases the levels of the Golgi-localised KDELR, thus preventing KDELR-dependent activation of Golgi-Src and inhibiting Golgi-to-plasma-membrane transport of VSVG. We propose a model whereby in analogy to previous findings (e.g., the RAS-RAF signalling pathway), PHB can act as a signalling scaffold protein to assist in KDELR-dependent Src activation. PMID:26064897

  5. Effect of a toggle switch mutation in TM6 of the human adenosine A3 receptor on Gi protein-dependent signalling and Gi-independent receptor internalization

    PubMed Central

    Stoddart, Leigh A; Kellam, Barrie; Briddon, Stephen J; Hill, Stephen J

    2014-01-01

    BACKGROUND AND PURPOSE The highly conserved tryptophan (W6.48) in transmembrane domain 6 of GPCRs has been shown to play a central role in forming an active conformation in response to agonist binding. We set out to characterize the effect of this mutation on the efficacy of two agonists at multiple signalling pathways downstream of the adenosine A3 receptor. EXPERIMENTAL APPROACH Residue W6.48 in the human adenosine A3 receptor fused to yellow fluorescent protein was mutated to phenylalanine and expressed in CHO-K1 cells containing a cAMP response element reporter gene. The effects on agonist-mediated receptor internalization were monitored by automated confocal microscopy and image analysis. Further experiments were carried out to investigate agonist-mediated ERK1/2 phosphorylation, inhibition of [3H]-cAMP accumulation and β-arrestin2 binding. KEY RESULTS NECA was able to stimulate agonist-mediated internalization of the W6.48F mutant receptor, while the agonist HEMADO was inactive. Investigation of other downstream signalling pathways indicated that G-protein coupling was impaired for both agonists tested. Mutation of W6.48F therefore resulted in differential effects on agonist efficacy, and introduced signalling pathway bias for HEMADO at the adenosine A3 receptor. CONCLUSIONS AND IMPLICATIONS Investigation of the pharmacology of the W6.48F mutant of the adenosine A3 receptor confirms that this region is important in forming the active conformation of the receptor for stimulating a number of different signalling pathways and that mutations in this residue can lead to changes in agonist efficacy and signalling bias. PMID:24750014

  6. Dopamine D₁-D₂ receptor heteromer regulates signaling cascades involved in addiction: potential relevance to adolescent drug susceptibility.

    PubMed

    Perreault, Melissa L; O'Dowd, Brian F; George, Susan R

    2014-01-01

    Adolescence is a developmental period that has been associated with heightened sensitivity to psychostimulant-induced reward, thus placing adolescents at increased risk to develop drug addiction. Although alterations in dopamine-induced synaptic plasticity are perhaps the most critical factor in mediating addiction processes, developmental differences in the cell signaling mechanisms that contribute to synaptic plasticity, and their contribution to adolescent reward sensitivity, has been grossly understudied. The most abundant dopamine receptors, the D1 and D2 receptors, as well as the dopamine D1-D2 receptor heteromer, exhibit age-dependent and brain region-specific changes in their expression and function and are responsible for regulating cell signaling pathways known to significantly contribute to the neurobiological mechanisms underlying addiction. The D1-D2 receptor heteromer, for instance, has been associated with calcium calmodulin kinase IIα, brain-derived neurotrophic factor and glycogen synthase kinase 3 (GSK-3) signaling, three proteins highly implicated in the regulation of glutamate transmission and synaptic plasticity and which regulate addiction to amphetamine, opioids and cocaine. Therefore, in this review the importance of these signaling proteins as potential mediators of addiction susceptibility in adolescence will be highlighted, and the therapeutic potential of the D1-D2 receptor heteromer in addiction will be discussed. It is the overall goal of this review to draw attention to the research gap in dopamine-induced cell signaling in the adolescent brain--knowledge that would provide much-needed insights into adolescent addiction vulnerability. PMID:24820626

  7. Signaling Pathways in Thyroid Cancer and Their Therapeutic Implications

    PubMed Central

    Jin, Shan; Borkhuu, Oyungerel; Bao, Wuyuntu; Yang, Yun-Tian

    2016-01-01

    Thyroid cancer is a common malignancy of endocrine system, and has now become the fastest increasing cancer among all the malignancies. The development, progression, invasion, and metastasis are closely associated with multiple signaling pathways and the functions of related molecules, such as Src, Janus kinase (JAK)-signal transducers and activators of transcription (STAT), mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K)/Akt, NF-κB, thyroid stimulating hormone receptor (TSHR), Wnt-β-catenin and Notch signaling pathways. Each of the signaling pathways could exert its function singly or through network with other pathways. These pathways could cooperate, promote, antagonize, or interact with each other to form a complex network for the regulation. Dysfunction of this network could increase the development, progression, invasion, and metastasis of thyroid cancer. Inoperable thyroid cancer still has a poor prognosis. However, signaling pathway-related targeted therapies offer the hope of longer quality of meaningful life for this small group of patients. Signaling pathway-related targets provide unprecedented opportunities for further research and clinical development of novel treatment strategies for this cancer. In the present work, the advances in these signaling pathways and targeted treatments of thyroid cancer were reviewed. PMID:26985248

  8. Role of phosphorylation in progesterone receptor signaling and specificity.

    PubMed

    Hagan, Christy R; Daniel, Andrea R; Dressing, Gwen E; Lange, Carol A

    2012-06-24

    Progesterone receptors (PR), in concert with peptide growth factor-initiated signaling pathways, initiate massive expansion of the epithelial cell compartment associated with the process of alveologenesis in the developing mammary gland. PR-dependent signaling events also contribute to inappropriate proliferation observed in breast cancer. Notably, PR-B isoform-specific cross talk with growth factor-driven pathways is required for the proliferative actions of progesterone. Indeed, PRs act as heavily phosphorylated transcription factor "sensors" for mitogenic protein kinases that are often elevated and/or constitutively activated in invasive breast cancers. In addition, phospho-PR-target genes frequently include the components of mitogenic signaling pathways, revealing a mechanism for feed-forward signaling that confers increased responsiveness of, PR +mammary epithelial cells to these same mitogenic stimuli. Understanding the mechanisms and isoform selectivity of PR/kinase interactions may yield further insight into targeting altered signaling networks in breast and other hormonally responsive cancers (i.e. lung, uterine and ovarian) in the clinic. This review focuses on PR phosphorylation by mitogenic protein kinases and mechanisms of PR-target gene selection that lead to increased cell proliferation.

  9. Phosphorylation Site Dynamics of Early T-cell Receptor Signaling

    PubMed Central

    Rigbolt, Kristoffer T. G.; Hu, Bin; Hlavacek, William S.; Blagoev, Blagoy

    2014-01-01

    In adaptive immune responses, T-cell receptor (TCR) signaling impacts multiple cellular processes and results in T-cell differentiation, proliferation, and cytokine production. Although individual protein–protein interactions and phosphorylation events have been studied extensively, we lack a systems-level understanding of how these components cooperate to control signaling dynamics, especially during the crucial first seconds of stimulation. Here, we used quantitative proteomics to characterize reshaping of the T-cell phosphoproteome in response to TCR/CD28 co-stimulation, and found that diverse dynamic patterns emerge within seconds. We detected phosphorylation dynamics as early as 5 s and observed widespread regulation of key TCR signaling proteins by 30 s. Development of a computational model pointed to the presence of novel regulatory mechanisms controlling phosphorylation of sites with central roles in TCR signaling. The model was used to generate predictions suggesting unexpected roles for the phosphatase PTPN6 (SHP-1) and shortcut recruitment of the actin regulator WAS. Predictions were validated experimentally. This integration of proteomics and modeling illustrates a novel, generalizable framework for solidifying quantitative understanding of a signaling network and for elucidating missing links. PMID:25147952

  10. B cell IFN-γ receptor signaling promotes autoimmune germinal centers via cell-intrinsic induction of BCL-6

    PubMed Central

    Jackson, Shaun W.; Jacobs, Holly M.; Arkatkar, Tanvi; Dam, Elizabeth M.; Scharping, Nicole E.; Kolhatkar, Nikita S.; Hou, Baidong; Buckner, Jane H.

    2016-01-01

    Dysregulated germinal center (GC) responses are implicated in the pathogenesis of human autoimmune diseases, including systemic lupus erythematosus (SLE). Although both type 1 and type 2 interferons (IFNs) are involved in lupus pathogenesis, their respective impacts on the establishment of autoimmune GCs has not been addressed. In this study, using a chimeric model of B cell-driven autoimmunity, we demonstrate that B cell type 1 IFN receptor signals accelerate, but are not required for, lupus development. In contrast, B cells functioning as antigen-presenting cells initiate CD4+ T cell activation and IFN-γ production, and strikingly, B cell–intrinsic deletion of the IFN-γ receptor (IFN-γR) abrogates autoimmune GCs, class-switched autoantibodies (auto-Abs), and systemic autoimmunity. Mechanistically, although IFN-γR signals increase B cell T-bet expression, B cell–intrinsic deletion of T-bet exerts an isolated impact on class-switch recombination to pathogenic auto-Ab subclasses without impacting GC development. Rather, in both mouse and human B cells, IFN-γ synergized with B cell receptor, toll-like receptor, and/or CD40 activation signals to promote cell-intrinsic expression of the GC master transcription factor, B cell lymphoma 6 protein. Our combined findings identify a novel B cell–intrinsic mechanism whereby IFN signals promote lupus pathogenesis, implicating this pathway as a potential therapeutic target in SLE. PMID:27069113

  11. Cannabinoid ligand-receptor signaling in the mouse uterus.

    PubMed

    Das, S K; Paria, B C; Chakraborty, I; Dey, S K

    1995-05-01

    Using RNA (Northern) blot hybridization and reverse transcription-PCR, we demonstrate that the brain-type cannabinoid receptor (CB1-R) mRNA, but not the spleen-type cannabinoid receptor (CB2-R) mRNA, is expressed in the mouse uterus and that this organ has the capacity to synthesize the putative endogenous cannabinoid ligand, anandamide (arachidonylethanolamide). The psychoactive cannabinoid component of marijuana--delta 9-tetrahydrocannabinol (THC)--or anandamide, but not the inactive and nonpsychoactive cannabidiol (CBD), inhibited forskolin-stimulated cyclic AMP formation in the mouse uterus, which was prevented by pertussis toxin pretreatment. These results suggest that uterine CB1-R is coupled to inhibitory guanine nucleotide-binding protein and is biologically active. Autoradiographic studies identified ligand binding sites ([3H]anandamide) in the uterine epithelium and stromal cells, suggesting that these cells are perhaps the targets for cannabinoid action. Scatchard analysis of the binding of [3H]WIN 55212-2, another cannabinoid receptor ligand, showed a single class of high-affinity binding sites in the endometrium with an apparent Kd of 2.4 nM and Bmax of 5.4 x 10(9) molecules per mg of protein. The gene encoding lactoferrin is an estrogen-responsive gene in the mouse uterus that was rapidly and transiently up-regulated by THC, but not by CBD, in ovariectomized mice in the absence of ovarian steroids. This effect, unlike that of 17 beta-estradiol (E2), was not influenced by a pure antiestrogen, ICI 182780, suggesting that the THC-induced uterine lactoferrin gene expression does not involve estrogen receptors. We propose that the uterus is a new target for cannabinoid ligand-receptor signaling.

  12. Cannabinoid ligand-receptor signaling in the mouse uterus.

    PubMed Central

    Das, S K; Paria, B C; Chakraborty, I; Dey, S K

    1995-01-01

    Using RNA (Northern) blot hybridization and reverse transcription-PCR, we demonstrate that the brain-type cannabinoid receptor (CB1-R) mRNA, but not the spleen-type cannabinoid receptor (CB2-R) mRNA, is expressed in the mouse uterus and that this organ has the capacity to synthesize the putative endogenous cannabinoid ligand, anandamide (arachidonylethanolamide). The psychoactive cannabinoid component of marijuana--delta 9-tetrahydrocannabinol (THC)--or anandamide, but not the inactive and nonpsychoactive cannabidiol (CBD), inhibited forskolin-stimulated cyclic AMP formation in the mouse uterus, which was prevented by pertussis toxin pretreatment. These results suggest that uterine CB1-R is coupled to inhibitory guanine nucleotide-binding protein and is biologically active. Autoradiographic studies identified ligand binding sites ([3H]anandamide) in the uterine epithelium and stromal cells, suggesting that these cells are perhaps the targets for cannabinoid action. Scatchard analysis of the binding of [3H]WIN 55212-2, another cannabinoid receptor ligand, showed a single class of high-affinity binding sites in the endometrium with an apparent Kd of 2.4 nM and Bmax of 5.4 x 10(9) molecules per mg of protein. The gene encoding lactoferrin is an estrogen-responsive gene in the mouse uterus that was rapidly and transiently up-regulated by THC, but not by CBD, in ovariectomized mice in the absence of ovarian steroids. This effect, unlike that of 17 beta-estradiol (E2), was not influenced by a pure antiestrogen, ICI 182780, suggesting that the THC-induced uterine lactoferrin gene expression does not involve estrogen receptors. We propose that the uterus is a new target for cannabinoid ligand-receptor signaling. Images Fig. 1 Fig. 3 Fig. 4 Fig. 5 PMID:7753807

  13. Receptors, Ion Channels, and Signaling Mechanisms Underlying Microglial Dynamics*

    PubMed Central

    Madry, Christian; Attwell, David

    2015-01-01

    Microglia, the innate immune cells of the CNS, play a pivotal role in brain injury and disease. Microglia are extremely motile; their highly ramified processes constantly survey the brain parenchyma, and they respond promptly to brain damage with targeted process movement toward the injury site. Microglia play a key role in brain development and function by pruning synapses during development, phagocytosing apoptotic newborn neurons, and regulating neuronal activity by direct microglia-neuron or indirect microglia-astrocyte-neuron interactions, which all depend on their process motility. This review highlights recent discoveries about microglial dynamics, focusing on the receptors, ion channels, and signaling pathways involved. PMID:25855789

  14. Chemosensory signals and their receptors in the olfactory neural system.

    PubMed

    Ihara, S; Yoshikawa, K; Touhara, K

    2013-12-19

    Chemical communication is widely used among various organisms to obtain essential information from their environment required for life. Although a large variety of molecules have been shown to act as chemical cues, the molecular and neural basis underlying the behaviors elicited by these molecules has been revealed for only a limited number of molecules. Here, we review the current knowledge regarding the signaling molecules whose flow from receptor to specific behavior has been characterized. Discussing the molecules utilized by mice, insects, and the worm, we focus on how each organism has optimized its reception system to suit its living style. We also highlight how the production of these signaling molecules is regulated, an area in which considerable progress has been recently made.

  15. Interleukin 10 Receptor Signaling: Master Regulator of Intestinal Mucosal Homeostasis in Mice and Humans

    PubMed Central

    Shouval, Dror S.; Ouahed, Jodie; Biswas, Amlan; Goettel, Jeremy A.; Horwitz, Bruce H.; Klein, Christoph; Muise, Aleixo M.; Snapper, Scott B.

    2016-01-01

    Interleukin 10 (IL10) is a key anti-inflammatory cytokine that can inhibit proinflammatory responses of both innate and adaptive immune cells. An association between IL10 and intestinal mucosal homeostasis became clear with the discovery that IL10 and IL10 receptor (IL10R)-deficient mice develop spontaneous intestinal inflammation. Similarly, patients with deleterious mutations in IL10, IL10RA, or IL10RB present with severe enterocolitis within the first months of life. Here, we review recent findings on how IL10- and IL10R-dependent signaling modulates innate and adaptive immune responses in the murine gastrointestinal tract, with implications of their role in the prevention of inflammatory bowel disease (IBD). In addition, we discuss the impact of IL10 and IL10R signaling defects in humans and their relationship to very early-onset IBD (VEO-IBD). PMID:24507158

  16. Interleukin 10 receptor signaling: master regulator of intestinal mucosal homeostasis in mice and humans.

    PubMed

    Shouval, Dror S; Ouahed, Jodie; Biswas, Amlan; Goettel, Jeremy A; Horwitz, Bruce H; Klein, Christoph; Muise, Aleixo M; Snapper, Scott B

    2014-01-01

    Interleukin 10 (IL10) is a key anti-inflammatory cytokine that can inhibit proinflammatory responses of both innate and adaptive immune cells. An association between IL10 and intestinal mucosal homeostasis became clear with the discovery that IL10 and IL10 receptor (IL10R)-deficient mice develop spontaneous intestinal inflammation. Similarly, patients with deleterious mutations in IL10, IL10RA, or IL10RB present with severe enterocolitis within the first months of life. Here, we review recent findings on how IL10- and IL10R-dependent signaling modulates innate and adaptive immune responses in the murine gastrointestinal tract, with implications of their role in the prevention of inflammatory bowel disease (IBD). In addition, we discuss the impact of IL10 and IL10R signaling defects in humans and their relationship to very early-onset IBD (VEO-IBD).

  17. TSH Receptor Signaling Abrogation by a Novel Small Molecule

    PubMed Central

    Latif, Rauf; Realubit, Ronald B.; Karan, Charles; Mezei, Mihaly; Davies, Terry F.

    2016-01-01

    Pathological activation of the thyroid-stimulating hormone receptor (TSHR) is caused by thyroid-stimulating antibodies in patients with Graves’ disease (GD) or by somatic and rare genomic mutations that enhance constitutive activation of the receptor influencing both G protein and non-G protein signaling. Potential selective small molecule antagonists represent novel therapeutic compounds for abrogation of such abnormal TSHR signaling. In this study, we describe the identification and in vitro characterization of a novel small molecule antagonist by high-throughput screening (HTS). The identification of the TSHR antagonist was performed using a transcription-based TSH-inhibition bioassay. TSHR-expressing CHO cells, which also expressed a luciferase-tagged CRE response element, were optimized using bovine TSH as the activator, in a 384 well plate format, which had a Z score of 0.3–0.6. Using this HTS assay, we screened a diverse library of ~80,000 compounds at a final concentration of 16.7 μM. The selection criteria for a positive hit were based on a mean signal threshold of ≥50% inhibition of control TSH stimulation. The screening resulted in 450 positive hits giving a hit ratio of 0.56%. A secondary confirmation screen against TSH and forskolin – a post receptor activator of adenylyl cyclase – confirmed one TSHR-specific candidate antagonist molecule (named VA-K-14). This lead molecule had an IC50 of 12.3 μM and a unique chemical structure. A parallel analysis for cell viability indicated that the lead inhibitor was non-cytotoxic at its effective concentrations. In silico docking studies performed using a TSHR transmembrane model showed the hydrophobic contact locations and the possible mode of inhibition of TSHR signaling. Furthermore, this molecule was capable of inhibiting TSHR stimulation by GD patient sera and monoclonal-stimulating TSHR antibodies. In conclusion, we report the identification of a novel small molecule TSHR inhibitor, which has

  18. Non-ionotropic signaling by the NMDA receptor: controversy and opportunity.

    PubMed

    Gray, John A; Zito, Karen; Hell, Johannes W

    2016-01-01

    Provocative emerging evidence suggests that the N-methyl-d-aspartate (NMDA) receptor can signal in the absence of ion flux through the receptor. This non-ionotropic signaling is thought to be due to agonist-induced conformational changes in the receptor, independently of channel opening. Non-ionotropic NMDA receptor signaling has been proposed to be sufficient to induce synaptic long-term depression (LTD), directly challenging the decades-old model that prolonged low-level calcium influx is required to induce LTD. Here, we briefly review these recent findings, focusing primarily on the potential role of non-ionotropic signaling in NMDA receptor-mediated LTD. Further reports concerning additional roles of non-ionotropic NMDA receptor signaling are also discussed. If validated, this new view of NMDA receptor-mediated signaling will usher in an exciting new era of exploring synapse function and dysfunction. PMID:27303637

  19. Non-ionotropic signaling by the NMDA receptor: controversy and opportunity.

    PubMed

    Gray, John A; Zito, Karen; Hell, Johannes W

    2016-01-01

    Provocative emerging evidence suggests that the N-methyl-d-aspartate (NMDA) receptor can signal in the absence of ion flux through the receptor. This non-ionotropic signaling is thought to be due to agonist-induced conformational changes in the receptor, independently of channel opening. Non-ionotropic NMDA receptor signaling has been proposed to be sufficient to induce synaptic long-term depression (LTD), directly challenging the decades-old model that prolonged low-level calcium influx is required to induce LTD. Here, we briefly review these recent findings, focusing primarily on the potential role of non-ionotropic signaling in NMDA receptor-mediated LTD. Further reports concerning additional roles of non-ionotropic NMDA receptor signaling are also discussed. If validated, this new view of NMDA receptor-mediated signaling will usher in an exciting new era of exploring synapse function and dysfunction.

  20. Non-ionotropic signaling by the NMDA receptor: controversy and opportunity

    PubMed Central

    Gray, John A.; Zito, Karen; Hell, Johannes W.

    2016-01-01

    Provocative emerging evidence suggests that the N-methyl-d-aspartate (NMDA) receptor can signal in the absence of ion flux through the receptor. This non-ionotropic signaling is thought to be due to agonist-induced conformational changes in the receptor, independently of channel opening. Non-ionotropic NMDA receptor signaling has been proposed to be sufficient to induce synaptic long-term depression (LTD), directly challenging the decades-old model that prolonged low-level calcium influx is required to induce LTD. Here, we briefly review these recent findings, focusing primarily on the potential role of non-ionotropic signaling in NMDA receptor-mediated LTD. Further reports concerning additional roles of non-ionotropic NMDA receptor signaling are also discussed. If validated, this new view of NMDA receptor-mediated signaling will usher in an exciting new era of exploring synapse function and dysfunction. PMID:27303637

  1. Insulin receptor substrate 4 couples the leptin receptor to multiple signaling pathways.

    PubMed

    Wauman, Joris; De Smet, Anne-Sophie; Catteeuw, Dominiek; Belsham, Denise; Tavernier, Jan

    2008-04-01

    Leptin is an adipokine that regulates food intake and energy expenditure by activating its hypothalamic leptin receptor (LR). Members of the insulin receptor substrate (IRS) family serve as adaptor proteins in the signaling pathways of several cytokines and hormones and a role for IRS2 in central leptin physiology is well established. Using mammalian protein-protein interaction trap (MAPPIT), a cytokine receptor-based two-hybrid method, in the N38 hypothalamic cell line, we here demonstrate that also IRS4 interacts with the LR. This recruitment is leptin dependent and requires phosphorylation of the Y1077 motif of the LR. Domain mapping of IRS4 revealed the critical role of the pleckstrin homology domain for full interaction. In line with its function as an adaptor protein, IRS4 interacted with the regulatory p85 subunit of the phosphatidylinositol 3-kinase, phospholipase Cgamma, and the suppressor of cytokine signaling (SOCS) family members SOCS2, SOCS6, and SOCS7 and thus can modulate LR signaling. PMID:18165436

  2. SPATA2 links CYLD to the TNF-α receptor signaling complex and modulates the receptor signaling outcomes.

    PubMed

    Wagner, Sebastian A; Satpathy, Shankha; Beli, Petra; Choudhary, Chunaram

    2016-09-01

    TNF-α is a key regulator of innate immune and proinflammatory responses. However, the composition of the TNF-α receptor-associated signaling complexes (TNF-RSC) and the architecture of the downstream signaling networks are incompletely understood. We employed quantitative mass spectrometry to demonstrate that TNF-α stimulation induces widespread protein phosphorylation and that the scope of phosphorylation expands in a temporal manner. TNF-α stimulation also induces rapid ubiquitylation of components of the TNF-RSC Temporal analysis of the TNF-RSC composition identified SPATA2 as a novel component of the TNF-RSC The predicted PUB domain in the N-terminus of SPATA2 interacts with the USP domain of CYLD, whereas the C-terminus of SPATA2 interacts with HOIP SPATA2 is required for recruitment of CYLD to the TNF-RSC Downregulation of SPATA2 augments transcriptional activation of NF-κB and inhibits TNF-α-induced necroptosis, pointing to an important function of SPATA2 in modulating the outcomes of TNF-α signaling. Taken together, our study draws a detailed map of TNF-α signaling, identifies SPATA2 as a novel component of TNF-α signaling, and provides a rich resource for further functional investigations.

  3. Inhibition of Receptor Signaling and of Glioblastoma-derived Tumor Growth by a Novel PDGFRβ Aptamer

    PubMed Central

    Camorani, Simona; Esposito, Carla L; Rienzo, Anna; Catuogno, Silvia; Iaboni, Margherita; Condorelli, Gerolama; de Franciscis, Vittorio; Cerchia, Laura

    2014-01-01

    Platelet-derived growth factor receptor β (PDGFRβ) is a cell-surface tyrosine kinase receptor implicated in several cellular processes including proliferation, migration, and angiogenesis. It represents a compelling therapeutic target in many human tumors, including glioma. A number of tyrosine kinase inhibitors under development as antitumor agents have been found to inhibit PDGFRβ. However, they are not selective as they present multiple tyrosine kinase targets. Here, we report a novel PDGFRβ-specific antagonist represented by a nuclease-resistant RNA-aptamer, named Gint4.T. This aptamer is able to specifically bind to the human PDGFRβ ectodomain (Kd: 9.6 nmol/l) causing a strong inhibition of ligand-dependent receptor activation and of downstream signaling in cell lines and primary cultures of human glioblastoma cells. Moreover, Gint4.T aptamer drastically inhibits cell migration and proliferation, induces differentiation, and blocks tumor growth in vivo. In addition, Gint4.T aptamer prevents PDGFRβ heterodimerization with and resultant transactivation of epidermal growth factor receptor. As a result, the combination of Gint4.T and an epidermal growth factor receptor–targeted aptamer is better at slowing tumor growth than either single aptamer alone. These findings reveal Gint4.T as a PDGFRβ-drug candidate with translational potential. PMID:24566984

  4. Discrete spatial organization of TGFβ receptors couples receptor multimerization and signaling to cellular tension

    PubMed Central

    Rys, Joanna P; DuFort, Christopher C; Monteiro, David A; Baird, Michelle A; Oses-Prieto, Juan A; Chand, Shreya; Burlingame, Alma L; Davidson, Michael W; Alliston, Tamara N

    2015-01-01

    Cell surface receptors are central to the cell's ability to generate coordinated responses to the multitude of biochemical and physical cues in the microenvironment. However, the mechanisms by which receptors enable this concerted cellular response remain unclear. To investigate the effect of cellular tension on cell surface receptors, we combined novel high-resolution imaging and single particle tracking with established biochemical assays to examine TGFβ signaling. We find that TGFβ receptors are discretely organized to segregated spatial domains at the cell surface. Integrin-rich focal adhesions organize TβRII around TβRI, limiting the integration of TβRII while sequestering TβRI at these sites. Disruption of cellular tension leads to a collapse of this spatial organization and drives formation of heteromeric TβRI/TβRII complexes and Smad activation. This work details a novel mechanism by which cellular tension regulates TGFβ receptor organization, multimerization, and function, providing new insight into the mechanisms that integrate biochemical and physical cues. DOI: http://dx.doi.org/10.7554/eLife.09300.001 PMID:26652004

  5. Increased GABAB receptor signaling in a rat model for schizophrenia

    PubMed Central

    Selten, Martijn M.; Meyer, Francisca; Ba, Wei; Vallès, Astrid; Maas, Dorien A.; Negwer, Moritz; Eijsink, Vivian D.; van Vugt, Ruben W. M.; van Hulten, Josephus A.; van Bakel, Nick H. M.; Roosen, Joey; van der Linden, Robert J.; Schubert, Dirk; Verheij, Michel M. M.; Kasri, Nael Nadif; Martens, Gerard J. M.

    2016-01-01

    Schizophrenia is a complex disorder that affects cognitive function and has been linked, both in patients and animal models, to dysfunction of the GABAergic system. However, the pathophysiological consequences of this dysfunction are not well understood. Here, we examined the GABAergic system in an animal model displaying schizophrenia-relevant features, the apomorphine-susceptible (APO-SUS) rat and its phenotypic counterpart, the apomorphine-unsusceptible (APO-UNSUS) rat at postnatal day 20–22. We found changes in the expression of the GABA-synthesizing enzyme GAD67 specifically in the prelimbic- but not the infralimbic region of the medial prefrontal cortex (mPFC), indicative of reduced inhibitory function in this region in APO-SUS rats. While we did not observe changes in basal synaptic transmission onto LII/III pyramidal cells in the mPFC of APO-SUS compared to APO-UNSUS rats, we report reduced paired-pulse ratios at longer inter-stimulus intervals. The GABAB receptor antagonist CGP 55845 abolished this reduction, indicating that the decreased paired-pulse ratio was caused by increased GABAB signaling. Consistently, we find an increased expression of the GABAB1 receptor subunit in APO-SUS rats. Our data provide physiological evidence for increased presynaptic GABAB signaling in the mPFC of APO-SUS rats, further supporting an important role for the GABAergic system in the pathophysiology of schizophrenia. PMID:27687783

  6. Erythropoietin regulates Treg cells in asthma through TGFβ receptor signaling.

    PubMed

    Wan, Guoshi; Wei, Bing

    2015-01-01

    Asthma is a chronic inflammatory disorder of the airways, the development of which is suppressed by regulatory T cells (Treg). Erythropoietin (EPO) is originally defined as a hematopoietic growth factor. Recently, the anti-inflammatory effects of EPO in asthma have been acknowledged. However, the underlying mechanisms remain ill-defined. Here, we showed that EPO treatment significantly reduced the severity of an ovalbumin (OVA)-induced asthma in mice, seemingly through promoting Foxp3-mediated activation of Treg cells in OVA-treated mouse lung. The activation of Treg cells resulted from increases in transforming growth factor β1 (TGFβ1), which were mainly produced by M2 macrophages (M2M). In vitro, Co-culture with M2M increased Foxp3 levels in Treg cells and the Treg cell number, in a TGFβ receptor signaling dependent manner. Moreover, elimination of macrophages abolished the therapeutic effects of EPO in vivo. Together, our data suggest that EPO may increase M2M, which activate Treg cells through TGFβ receptor signaling to mitigate the severity of asthma.

  7. Erythropoietin regulates Treg cells in asthma through TGFβ receptor signaling

    PubMed Central

    Wan, Guoshi; Wei, Bing

    2015-01-01

    Asthma is a chronic inflammatory disorder of the airways, the development of which is suppressed by regulatory T cells (Treg). Erythropoietin (EPO) is originally defined as a hematopoietic growth factor. Recently, the anti-inflammatory effects of EPO in asthma have been acknowledged. However, the underlying mechanisms remain ill-defined. Here, we showed that EPO treatment significantly reduced the severity of an ovalbumin (OVA)-induced asthma in mice, seemingly through promoting Foxp3-mediated activation of Treg cells in OVA-treated mouse lung. The activation of Treg cells resulted from increases in transforming growth factor β1 (TGFβ1), which were mainly produced by M2 macrophages (M2M). In vitro, Co-culture with M2M increased Foxp3 levels in Treg cells and the Treg cell number, in a TGFβ receptor signaling dependent manner. Moreover, elimination of macrophages abolished the therapeutic effects of EPO in vivo. Together, our data suggest that EPO may increase M2M, which activate Treg cells through TGFβ receptor signaling to mitigate the severity of asthma. PMID:26807178

  8. Intestinal farnesoid X receptor signaling promotes nonalcoholic fatty liver disease

    PubMed Central

    Jiang, Changtao; Xie, Cen; Li, Fei; Zhang, Limin; Nichols, Robert G.; Krausz, Kristopher W.; Cai, Jingwei; Qi, Yunpeng; Fang, Zhong-Ze; Takahashi, Shogo; Tanaka, Naoki; Desai, Dhimant; Amin, Shantu G.; Albert, Istvan; Patterson, Andrew D.; Gonzalez, Frank J.

    2014-01-01

    Nonalcoholic fatty liver disease (NAFLD) is a major worldwide health problem. Recent studies suggest that the gut microbiota influences NAFLD pathogenesis. Here, a murine model of high-fat diet–induced (HFD-induced) NAFLD was used, and the effects of alterations in the gut microbiota on NAFLD were determined. Mice treated with antibiotics or tempol exhibited altered bile acid composition, with a notable increase in conjugated bile acid metabolites that inhibited intestinal farnesoid X receptor (FXR) signaling. Compared with control mice, animals with intestine-specific Fxr disruption had reduced hepatic triglyceride accumulation in response to a HFD. The decrease in hepatic triglyceride accumulation was mainly due to fewer circulating ceramides, which was in part the result of lower expression of ceramide synthesis genes. The reduction of ceramide levels in the ileum and serum in tempol- or antibiotic-treated mice fed a HFD resulted in downregulation of hepatic SREBP1C and decreased de novo lipogenesis. Administration of C16:0 ceramide to antibiotic-treated mice fed a HFD reversed hepatic steatosis. These studies demonstrate that inhibition of an intestinal FXR/ceramide axis mediates gut microbiota–associated NAFLD development, linking the microbiome, nuclear receptor signaling, and NAFLD. This work suggests that inhibition of intestinal FXR is a potential therapeutic target for NAFLD treatment. PMID:25500885

  9. Cellular defense processes regulated by pathogen-elicited receptor signaling

    NASA Astrophysics Data System (ADS)

    Wu, Rongcong; Goldsipe, Arthur; Schauer, David B.; Lauffenburger, Douglas A.

    2011-06-01

    Vertebrates are constantly threatened by the invasion of microorganisms and have evolved systems of immunity to eliminate infectious pathogens in the body. Initial sensing of microbial agents is mediated by the recognition of pathogens by means of molecular structures expressed uniquely by microbes of a given type. So-called 'Toll-like receptors' are expressed on host epithelial barrier cells play an essential role in the host defense against microbial pathogens by inducing cell responses (e.g., proliferation, death, cytokine secretion) via activation of intracellular signaling networks. As these networks, comprising multiple interconnecting dynamic pathways, represent highly complex multi-variate "information processing" systems, the signaling activities particularly critical for governing the host cell responses are poorly understood and not easily ascertained by a priori theoretical notions. We have developed over the past half-decade a "data-driven" computational modeling approach, on a 'cue-signal-response' combined experiment/computation paradigm, to elucidate key multi-variate signaling relationships governing the cell responses. In an example presented here, we study how a canonical set of six kinase pathways combine to effect microbial agent-induced apoptotic death of a macrophage cell line. One modeling technique, partial least-squares regression, yielded the following key insights: {a} signal combinations most strongly correlated to apoptotic death are orthogonal to those most strongly correlated with release of inflammatory cytokines; {b} the ratio of two key pathway activities is the most powerful predictor of microbe-induced macrophage apoptotic death; {c} the most influential time-window of this signaling activity ratio is surprisingly fast: less than one hour after microbe stimulation.

  10. Cannabinoids Inhibit Insulin Receptor Signaling in Pancreatic β-Cells

    PubMed Central

    Kim, Wook; Doyle, Máire E.; Liu, Zhuo; Lao, Qizong; Shin, Yu-Kyong; Carlson, Olga D.; Kim, Hee Seung; Thomas, Sam; Napora, Joshua K.; Lee, Eun Kyung; Moaddel, Ruin; Wang, Yan; Maudsley, Stuart; Martin, Bronwen; Kulkarni, Rohit N.; Egan, Josephine M.

    2011-01-01

    OBJECTIVE Optimal glucose homeostasis requires exquisitely precise adaptation of the number of insulin-secreting β-cells in the islets of Langerhans. Insulin itself positively regulates β-cell proliferation in an autocrine manner through the insulin receptor (IR) signaling pathway. It is now coming to light that cannabinoid 1 receptor (CB1R) agonism/antagonism influences insulin action in insulin-sensitive tissues. However, the cells on which the CB1Rs are expressed and their function in islets have not been firmly established. We undertook the current study to investigate if intraislet endogenous cannabinoids (ECs) regulate β-cell proliferation and if they influence insulin action. RESEARCH DESIGN AND METHODS We measured EC production in isolated human and mouse islets and β-cell line in response to glucose and KCl. We evaluated human and mouse islets, several β-cell lines, and CB1R-null (CB1R−/−) mice for the presence of a fully functioning EC system. We investigated if ECs influence β-cell physiology through regulating insulin action and demonstrated the therapeutic potential of manipulation of the EC system in diabetic (db/db) mice. RESULTS ECs are generated within β-cells, which also express CB1Rs that are fully functioning when activated by ligands. Genetic and pharmacologic blockade of CB1R results in enhanced IR signaling through the insulin receptor substrate 2-AKT pathway in β-cells and leads to increased β-cell proliferation and mass. CB1R antagonism in db/db mice results in reduced blood glucose and increased β-cell proliferation and mass, coupled with enhanced IR signaling in β-cells. Furthermore, CB1R activation impedes insulin-stimulated IR autophosphorylation on β-cells in a Gαi-dependent manner. CONCLUSIONS These findings provide direct evidence for a functional interaction between CB1R and IR signaling involved in the regulation of β-cell proliferation and will serve as a basis for developing new therapeutic interventions to

  11. Purified TPC Isoforms Form NAADP Receptors with Distinct Roles for Ca2+ Signaling and Endolysosomal Trafficking

    PubMed Central

    Ruas, Margarida; Rietdorf, Katja; Arredouani, Abdelilah; Davis, Lianne C.; Lloyd-Evans, Emyr; Koegel, Heidi; Funnell, Timothy M.; Morgan, Anthony J.; Ward, John A.; Watanabe, Keiko; Cheng, Xiaotong; Churchill, Grant C.; Zhu, Michael X.; Platt, Frances M.; Wessel, Gary M.; Parrington, John; Galione, Antony

    2010-01-01

    Summary Intracellular Ca2+ signals constitute key elements in signal transduction. Of the three major Ca2+ mobilizing messengers described, the most potent, nicotinic acid adenine dinucleotide phosphate (NAADP) is the least well understood in terms of its molecular targets [1]. Recently, we showed that heterologous expression of two-pore channel (TPC) proteins enhances NAADP-induced Ca2+ release, whereas the NAADP response was abolished in pancreatic beta cells from Tpcn2 gene knockout mice [2]. However, whether TPCs constitute native NAADP receptors is unclear. Here we show that immunopurified endogenous TPC complexes possess the hallmark properties ascribed to NAADP receptors, including nanomolar ligand affinity [3–5]. Our study also reveals important functional differences between the three TPC isoforms. Thus, TPC1 and TPC2 both mediate NAADP-induced Ca2+ release, but the subsequent amplification of this trigger Ca2+ by IP3Rs is more tightly coupled for TPC2. In contrast, TPC3 expression suppressed NAADP-induced Ca2+ release. Finally, increased TPC expression has dramatic and contrasting effects on endolysosomal structures and dynamics, implicating a role for NAADP in the regulation of vesicular trafficking. We propose that NAADP regulates endolysosomal Ca2+ storage and release via TPCs and coordinates endoplasmic reticulum Ca2+ release in a role that impacts on Ca2+ signaling in health and disease [6]. PMID:20346675

  12. The many roles of FAS receptor signaling in the immune system

    PubMed Central

    Strasser, Andreas; Jost, Philipp J; Nagata, Shigekazu

    2010-01-01

    Summary FAS (also known as APO-1 or CD95) belongs to the subgroup of the tumor necrosis factor receptor (TNF-R) family that contain an intra-cellular ‘death domain’ and can trigger apoptosis. Its physiological ligand, FASL (CD95L), is a member of the corresponding TNF cytokine family. Studies with spontaneous mutant mice, gene-targeted mice and cells from human patients have shown that FAS and FASL play critical roles in the immune system, in particular in the killing of pathogen infected target cells and the death of no longer needed, potentially deleterious as well as autoreactive lymphocytes. This ligand-receptor pair thereby functions as a guardian against autoimmunity and tumor development. FASL-FAS signaling triggers apoptosis through FADD (Fas-associated protein with death domain, also called MORT1) adaptor protein-mediated recruitment and activation of the aspartate-specific cysteine protease, caspase-8. In certain cells such as hepatocytes, albeit not in lymphocytes, FAS-induced apoptosis signaling requires amplification through proteolytic activation of the pro-apoptotic BCL-2 family member BID. Curiously, several components of the FAS signaling machinery have been implicated in non-apoptotic processes, including cellular activation, differentiation and proliferation. Here we describe current knowledge of the roles of FASL and FAS in the immune system, discuss important unresolved issues and propose experimental approaches to address them. PMID:19239902

  13. A negative feedback loop controls NMDA receptor function in cortical interneurons via neuregulin 2/ErbB4 signalling

    PubMed Central

    Vullhorst, Detlef; Mitchell, Robert M.; Keating, Carolyn; Roychowdhury, Swagata; Karavanova, Irina; Tao-Cheng, Jung-Hwa; Buonanno, Andres

    2015-01-01

    The neuregulin receptor ErbB4 is an important modulator of GABAergic interneurons and neural network synchronization. However, little is known about the endogenous ligands that engage ErbB4, the neural processes that activate them or their direct downstream targets. Here we demonstrate, in cultured neurons and in acute slices, that the NMDA receptor is both effector and target of neuregulin 2 (NRG2)/ErbB4 signalling in cortical interneurons. Interneurons co-express ErbB4 and NRG2, and pro-NRG2 accumulates on cell bodies atop subsurface cisternae. NMDA receptor activation rapidly triggers shedding of the signalling-competent NRG2 extracellular domain. In turn, NRG2 promotes ErbB4 association with GluN2B-containing NMDA receptors, followed by rapid internalization of surface receptors and potent downregulation of NMDA but not AMPA receptor currents. These effects occur selectively in ErbB4-positive interneurons and not in ErbB4-negative pyramidal neurons. Our findings reveal an intimate reciprocal relationship between ErbB4 and NMDA receptors with possible implications for the modulation of cortical microcircuits associated with cognitive deficits in psychiatric disorders. PMID:26027736

  14. Cocaine decreases expression of neurogranin via alterations in thyroid receptor/retinoid X receptor signaling

    PubMed Central

    Kovalevich, Jane; Corley, Gladys; Yen, William; Kim, Jae; Rawls, Scott M.; Langford, Dianne

    2013-01-01

    Mounting evidence suggests a potential link between cocaine abuse, disruptions in hypothalamic-pituitary-thyroid axis signaling, and neuroplasticity, but molecular mechanisms remain unknown. Neurogranin (Ng) is a gene containing a thyroid hormone-responsive element within its first intron that is involved in synaptic plasticity. Transcriptional activation requires heterodimerization of thyroid hormone receptor (TR) and retinoid X receptor (RXR) bound by their respective ligands, tri-iodothryonine and 9-cis-retinoic acid (9-cis-RA), and subsequent binding of this complex to the thyroid hormone-responsive element of the Ng gene. In this study, the effects of chronic cocaine abuse on Ng expression in euthyroid and hypothyroid mice were assessed. In cocaine-treated mice, decreased Ng expression was observed in the absence of changes in levels of thyroid hormones or other hypothalamic-pituitary-thyroid signaling factors. Therefore, we hypothesized that cocaine decreases Ng expression via alterations in 9-cis-RA availability and TR/RXR signaling. In support of this hypothesis, RXR-γ was significantly decreased in brains of cocaine-treated mice while CYP26A1, the main enzyme responsible for neuronal RA degradation, was significantly increased. Results from this study provide the first evidence for a direct effect of cocaine abuse on TR/RXR signaling, RA metabolism, and transcriptional regulation of Ng, a gene essential for adult neuroplasticity. PMID:22300446

  15. Melanocortin 4 receptor signaling in dopamine 1 receptor neurons is required for procedural memory learning

    PubMed Central

    Cui, Huxing; Mason, Brittany L.; Lee, Charlotte; Nishi, Akinori; Elmquist, Joel K; Lutter, Michael

    2012-01-01

    It is now widely recognized that exposure to palatable foods engages reward circuits that promote over-eating and facilitate the development of obesity. While the melanocortin 4 receptor (MC4R) has previously been shown to regulate food intake and energy expenditure, little is known about its role in food reward. We demonstrate that MC4R is co-expressed with the dopamine 1 receptor (D1R) in the ventral striatum. While MC4R-null mice are hyperphagic and obese, they exhibit impairments in acquisition of operant responding for a high fat reinforcement. Restoration of MC4R signaling in D1R neurons normalizes procedural learning without affecting motivation to obtain high fat diet. MC4R signaling in D1R neurons is also required for learning in a non-food-reinforced version of the cued water maze. Finally, MC4R signaling in neostriatal slices increases phosphorylation of the Thr34 residue of DARPP-32, a protein phosphatase-1 inhibitor that regulates synaptic plasticity. These data identify a novel requirement for MC4R signaling in procedural memory learning. PMID:22342812

  16. Fas death receptor signalling: roles of Bid and XIAP

    PubMed Central

    Kaufmann, T; Strasser, A; Jost, P J

    2012-01-01

    Fas (also called CD95 or APO-1), a member of a subgroup of the tumour necrosis factor receptor superfamily that contain an intracellular death domain, can initiate apoptosis signalling and has a critical role in the regulation of the immune system. Fas-induced apoptosis requires recruitment and activation of the initiator caspase, caspase-8 (in humans also caspase-10), within the death-inducing signalling complex. In so-called type 1 cells, proteolytic activation of effector caspases (-3 and -7) by caspase-8 suffices for efficient apoptosis induction. In so-called type 2 cells, however, killing requires amplification of the caspase cascade. This can be achieved through caspase-8-mediated proteolytic activation of the pro-apoptotic Bcl-2 homology domain (BH)3-only protein BH3-interacting domain death agonist (Bid), which then causes mitochondrial outer membrane permeabilisation. This in turn leads to mitochondrial release of apoptogenic proteins, such as cytochrome c and, pertinent for Fas death receptor (DR)-induced apoptosis, Smac/DIABLO (second mitochondria-derived activator of caspase/direct IAP binding protein with low Pi), an antagonist of X-linked inhibitor of apoptosis (XIAP), which imposes a brake on effector caspases. In this review, written in honour of Juerg Tschopp who contributed so much to research on cell death and immunology, we discuss the functions of Bid and XIAP in the control of Fas DR-induced apoptosis signalling, and we speculate on how this knowledge could be exploited to develop novel regimes for treatment of cancer. PMID:21959933

  17. Dysregulation of cannabinoid CB1 receptor and associated signaling networks in brains of cocaine addicts and cocaine-treated rodents.

    PubMed

    Álvaro-Bartolomé, M; García-Sevilla, J A

    2013-09-01

    The endocannabinoid system is implicated in the neurobiology of cocaine addiction. This study evaluated the status of cannabinoid (CB) CB1 and CB2 receptors, the endocytic cycle of CB1 receptors, G protein-coupled receptor regulatory kinases (GRK), and associated signaling (mammalian target of rapamicin (mTOR) and 70kDa ribosomal protein S6 kinase (p70S6K)) in brain cortices of drug abusers and cocaine- and cannabinoid-treated rodents. The main results indicate that in cocaine adddicts, but not in mixed cocaine/opiate or opiate abusers, CB1 receptor protein in the prefrontal cortex (PFC) was reduced (-44%, total homogenate) with a concomitant receptor redistribution and/or internalization (decreases in membranes and increases in cytosol). In cocaine addicts, the reductions of CB1 receptors and GRK2/3/5 (-26% to -30%) indicated receptor desensitization. CB2 receptor protein was not significantly altered in the PFC of cocacine addicts. Chronic cocaine in mice and rats also reduced CB1 receptor protein (-41% and -80%) in the cerebral cortex inducing receptor redistribution and/or internalization. The CB1 receptor agonist WIN55212-2 caused receptor downregulation (decreases in membranes and cytosol) and the antagonists rimonabant and AM281 induced opposite effects (receptor upregulation in membranes and cytosol). Rimonabant and AM281 also behaved as inverse agonists on the activation of mTOR and its target p70S6K. Chronic cocaine in mice was associated with tolerance to the acute activation of mTOR and p70S6K. In long-term cocaine addicts, mTOR and p70S6K activations were not altered when compared with controls, indicating that CB1 receptor signaling was dampened. The dysregulation of CB1 receptor, GRK2/3/5, and mTOR/p70S6K signaling by cocaine may contribute to alterations of neuroplasticity and/or neurotoxicity in brains of cocaine addicts.

  18. Dysregulation of cannabinoid CB1 receptor and associated signaling networks in brains of cocaine addicts and cocaine-treated rodents.

    PubMed

    Álvaro-Bartolomé, M; García-Sevilla, J A

    2013-09-01

    The endocannabinoid system is implicated in the neurobiology of cocaine addiction. This study evaluated the status of cannabinoid (CB) CB1 and CB2 receptors, the endocytic cycle of CB1 receptors, G protein-coupled receptor regulatory kinases (GRK), and associated signaling (mammalian target of rapamicin (mTOR) and 70kDa ribosomal protein S6 kinase (p70S6K)) in brain cortices of drug abusers and cocaine- and cannabinoid-treated rodents. The main results indicate that in cocaine adddicts, but not in mixed cocaine/opiate or opiate abusers, CB1 receptor protein in the prefrontal cortex (PFC) was reduced (-44%, total homogenate) with a concomitant receptor redistribution and/or internalization (decreases in membranes and increases in cytosol). In cocaine addicts, the reductions of CB1 receptors and GRK2/3/5 (-26% to -30%) indicated receptor desensitization. CB2 receptor protein was not significantly altered in the PFC of cocacine addicts. Chronic cocaine in mice and rats also reduced CB1 receptor protein (-41% and -80%) in the cerebral cortex inducing receptor redistribution and/or internalization. The CB1 receptor agonist WIN55212-2 caused receptor downregulation (decreases in membranes and cytosol) and the antagonists rimonabant and AM281 induced opposite effects (receptor upregulation in membranes and cytosol). Rimonabant and AM281 also behaved as inverse agonists on the activation of mTOR and its target p70S6K. Chronic cocaine in mice was associated with tolerance to the acute activation of mTOR and p70S6K. In long-term cocaine addicts, mTOR and p70S6K activations were not altered when compared with controls, indicating that CB1 receptor signaling was dampened. The dysregulation of CB1 receptor, GRK2/3/5, and mTOR/p70S6K signaling by cocaine may contribute to alterations of neuroplasticity and/or neurotoxicity in brains of cocaine addicts. PMID:23727505

  19. Intestinal epithelial vitamin D receptor signaling inhibits experimental colitis.

    PubMed

    Liu, Weicheng; Chen, Yunzi; Golan, Maya Aharoni; Annunziata, Maria L; Du, Jie; Dougherty, Urszula; Kong, Juan; Musch, Mark; Huang, Yong; Pekow, Joel; Zheng, Changqing; Bissonnette, Marc; Hanauer, Stephen B; Li, Yan Chun

    2013-09-01

    The inhibitory effects of vitamin D on colitis have been previously documented. Global vitamin D receptor (VDR) deletion exaggerates colitis, but the relative anticolitic contribution of epithelial and nonepithelial VDR signaling is unknown. Here, we showed that colonic epithelial VDR expression was substantially reduced in patients with Crohn's disease or ulcerative colitis. Moreover, targeted expression of human VDR (hVDR) in intestinal epithelial cells (IECs) protected mice from developing colitis. In experimental colitis models induced by 2,4,6-trinitrobenzenesulfonic acid, dextran sulfate sodium, or CD4(+)CD45RB(hi) T cell transfer, transgenic mice expressing hVDR in IECs were highly resistant to colitis, as manifested by marked reductions in clinical colitis scores, colonic histological damage, and colonic inflammation compared with WT mice. Reconstitution of Vdr-deficient IECs with the hVDR transgene completely rescued Vdr-null mice from severe colitis and death, even though the mice still maintained a hyperresponsive Vdr-deficient immune system. Mechanistically, VDR signaling attenuated PUMA induction in IECs by blocking NF-κB activation, leading to a reduction in IEC apoptosis. Together, these results demonstrate that gut epithelial VDR signaling inhibits colitis by protecting the mucosal epithelial barrier, and this anticolitic activity is independent of nonepithelial immune VDR actions.

  20. Involvement of p59fynT in interleukin-5 receptor signaling [published erratum appears in J Exp Med 1995 Oct 1;182(4):1179

    PubMed Central

    1995-01-01

    Previous studies implicate the nonreceptor protein tyrosine kinase (PTK) p59fyn in the propagation of signals from the B cell antigen receptor. To elucidate the functions of this kinase, we examined B cell responsiveness in mice engineered to lack the hematopoietic isoform of p59fyn. Remarkably, antigen receptor signaling was only modestly defective in fynTnull B cells. In contrast, signaling from the interleukin (IL)-5 receptor which ordinarily provides a comitogenic stimulus with antiimmunoglobulin, was completely blocked. Our results document the importance of p59fynT in IL-5 responses in B cells, and they support a general model for cytokine receptor signal transduction involving the simultaneous recruitment of at least three families of PTK. PMID:7650487

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

    PubMed Central

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

    2014-01-01

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

  2. The Transcriptomics of Glucocorticoid Receptor Signaling in Developing Zebrafish

    PubMed Central

    Nesan, Dinushan; Vijayan, Mathilakath M.

    2013-01-01

    Cortisol is the primary corticosteroid in teleosts that is released in response to stressor activation of the hypothalamus-pituitary-interrenal axis. The target tissue action of this hormone is primarily mediated by the intracellular glucocorticoid receptor (GR), a ligand-bound transcription factor. In developing zebrafish (Danio rerio) embryos, GR transcripts and cortisol are maternally deposited into the oocyte prior to fertilization and influence early embryogenesis. To better understand of the molecular mechanisms involved, we investigated changes in the developmental transcriptome prior to hatch, in response to morpholino oligonucleotide knockdown of GR using the Agilent zebrafish microarray platform. A total of 1313 and 836 mRNA transcripts were significantly changed at 24 and 36 hours post fertilization (hpf), respectively. Functional analysis revealed numerous developmental processes under GR regulation, including neurogenesis, eye development, skeletal and cardiac muscle formation. Together, this study underscores a critical role for glucocorticoid signaling in programming molecular events essential for zebrafish development. PMID:24348914

  3. Molecular Basis of Signaling Specificity of Insulin and IGF Receptors: Neglected Corners and Recent Advances

    PubMed Central

    Siddle, Kenneth

    2011-01-01

    Insulin and insulin-like growth factor (IGF) receptors utilize common phosphoinositide 3-kinase/Akt and Ras/extracellular signal-regulated kinase signaling pathways to mediate a broad spectrum of “metabolic” and “mitogenic” responses. Specificity of insulin and IGF action in vivo must in part reflect expression of receptors and responsive pathways in different tissues but it is widely assumed that it is also determined by the ligand binding and signaling mechanisms of the receptors. This review focuses on receptor-proximal events in insulin/IGF signaling and examines their contribution to specificity of downstream responses. Insulin and IGF receptors may differ subtly in the efficiency with which they recruit their major substrates (IRS-1 and IRS-2 and Shc) and this could influence effectiveness of signaling to “metabolic” and “mitogenic” responses. Other substrates (Grb2-associated binder, downstream of kinases, SH2Bs, Crk), scaffolds (RACK1, β-arrestins, cytohesins), and pathways (non-receptor tyrosine kinases, phosphoinositide kinases, reactive oxygen species) have been less widely studied. Some of these components appear to be specifically involved in “metabolic” or “mitogenic” signaling but it has not been shown that this reflects receptor-preferential interaction. Very few receptor-specific interactions have been characterized, and their roles in signaling are unclear. Signaling specificity might also be imparted by differences in intracellular trafficking or feedback regulation of receptors, but few studies have directly addressed this possibility. Although published data are not wholly conclusive, no evidence has yet emerged for signaling mechanisms that are specifically engaged by insulin receptors but not IGF receptors or vice versa, and there is only limited evidence for differential activation of signaling mechanisms that are common to both receptors. Cellular context, rather than intrinsic receptor activity, therefore appears

  4. B Cell Antigen Receptor Signaling and Internalization Are Mutually Exclusive Events

    PubMed Central

    Hou, Ping; Araujo, Elizabeth; Zhao, Tong; Zhang, Miao; Massenburg, Don; Veselits, Margaret; Doyle, Colleen; Dinner, Aaron R; Clark, Marcus R

    2006-01-01

    Engagement of the B cell antigen receptor initiates two concurrent processes, signaling and receptor internalization. While both are required for normal humoral immune responses, the relationship between these two processes is unknown. Herein, we demonstrate that following receptor ligation, a small subpopulation of B cell antigen receptors are inductively phosphorylated and selectively retained at the cell surface where they can serve as scaffolds for the assembly of signaling molecules. In contrast, the larger population of non-phosphorylated receptors is rapidly endocytosed. Each receptor can undergo only one of two mutually exclusive fates because the tyrosine-based motifs that mediate signaling when phosphorylated mediate internalization when not phosphorylated. Mathematical modeling indicates that the observed competition between receptor phosphorylation and internalization enhances signaling responses to low avidity ligands. PMID:16719564

  5. Detailed analysis of biased histamine H4 receptor signalling by JNJ 7777120 analogues

    PubMed Central

    Nijmeijer, S; Vischer, H F; Sirci, F; Schultes, S; Engelhardt, H; de Graaf, C; Rosethorne, E M; Charlton, S J; Leurs, R

    2013-01-01

    Background and Purpose The histamine H4 receptor, originally thought to signal merely through Gαi proteins, has recently been shown to also recruit and signal via β-arrestin2. Following the discovery that the reference antagonist indolecarboxamide JNJ 7777120 appears to be a partial agonist in β-arrestin2 recruitment, we have identified additional biased hH4R ligands that preferentially couple to Gαi or β-arrestin2 proteins. In this study, we explored ligand and receptor regions that are important for biased hH4R signalling. Experimental Approach We evaluated a series of 48 indolecarboxamides with subtle structural differences for their ability to induce hH4R-mediated Gαi protein signalling or β-arrestin2 recruitment. Subsequently, a Fingerprints for Ligands and Proteins three-dimensional quantitative structure–activity relationship analysis correlated intrinsic activity values with structural ligand requirements. Moreover, a hH4R homology model was used to identify receptor regions important for biased hH4R signalling. Key Results One indolecarboxamide (75) with a nitro substituent on position R7 of the aromatic ring displayed an equal preference for the Gαi and β-arrestin2 pathway and was classified as unbiased hH4R ligand. The other 47 indolecarboxamides were β-arrestin2-biased agonists. Intrinsic activities of the unbiased as well as β-arrestin2-biased indolecarboxamides to induce β-arrestin2 recruitment could be correlated with different ligand features and hH4R regions. Conclusion and Implications Small structural modifications resulted in diverse intrinsic activities for unbiased (75) and β-arrestin2-biased indolecarboxamides. Analysis of ligand and receptor features revealed efficacy hotspots responsible for biased-β-arrestin2 recruitment. This knowledge is useful for the design of hH4R ligands with biased intrinsic activities and aids our understanding of the mechanism of H4R activation. Linked Articles This article is part of a themed

  6. A mechanism for Src kinase-dependent signaling by non-catalytic receptors

    PubMed Central

    2008-01-01

    A fundamental issue in cell biology is how signals are transmitted across membranes. A variety of transmembrane receptors, including multichain immune recognition receptors, lack catalytic activity and require Src family kinases (SFKs) for signal transduction. However, many receptors only bind and activate SFKs after ligand-induced receptor dimerization. This presents a conundrum: How do SFKs sense the dimerization of receptors to which they are not already bound? Most proposals to resolve this enigma invoke additional players, such as lipid rafts or receptor conformational changes. Here we used simple thermodynamics to show that SFK activation is a natural outcome of clustering of receptors with SFK phosphorylation sites, provided that there is phosphorylation-dependent receptor-SFK association and an SFK bound to one receptor can phosphorylate the second receptor or its associated SFK in a dimer. A simple system of receptor, SFK and an unregulated protein tyrosine phosphatase (PTP) can account for ligand-induced changes in phosphorylation observed in cells. We suggest that a core signaling system comprising a receptor with SFK phosphorylation sites, an SFK and an unregulated PTP provides a robust mechanism for transmembrane signal transduction. Other events that regulate signaling in specific cases may have evolved for fine-tuning of this basic mechanism. PMID:18444664

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

    PubMed

    McGee, Marie A; Abdel-Rahman, Abdel A

    2016-08-01

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

  8. Glycogen synthase kinase 3β in Toll-like receptor signaling

    PubMed Central

    Ko, Ryeojin; Lee, Soo Young

    2016-01-01

    Toll-like receptors (TLRs) play a critical role in the innate immune response against pathogens. Each TLR recognizes specific pathogen-associated molecular patterns, after which they activate the adaptor protein MyD88 or TRIF-assembled signaling complex to produce immune mediators, including inflammatory cytokines and type I IFNs. Although the activation of TLR is important for host defense, its uncontrolled activation can damage the host. During the past decade, numerous studies have demonstrated that GSK3β is a key regulator of inflammatory cytokine production in MyD88-mediated TLR signaling via TLR2 and TLR4. Recently, GSK3β has also been implicated in the TRIF-dependent signaling pathway via TLR3. In this review, we describe current advances on the regulatory role of GSK3β in immune responses associated with various TLRs. A better understanding of the role of GSK3β in TLR signaling might lead to more effective anti-inflammatory interventions. [BMB Reports 2016; 49(6): 305-310] PMID:26996345

  9. P2Y₁ receptor-dependent diacylglycerol signaling microdomains in β cells promote insulin secretion.

    PubMed

    Wuttke, Anne; Idevall-Hagren, Olof; Tengholm, Anders

    2013-04-01

    Diacylglycerol (DAG) controls numerous cell functions by regulating the localization of C1-domain-containing proteins, including protein kinase C (PKC), but little is known about the spatiotemporal dynamics of the lipid. Here, we explored plasma membrane DAG dynamics in pancreatic β cells and determined whether DAG signaling is involved in secretagogue-induced pulsatile release of insulin. Single MIN6 cells, primary mouse β cells, and human β cells within intact islets were transfected with translocation biosensors for DAG, PKC activity, or insulin secretion and imaged with total internal reflection fluorescence microscopy. Muscarinic receptor stimulation triggered stable, homogenous DAG elevations, whereas glucose induced short-lived (7.1 ± 0.4 s) but high-amplitude elevations (up to 109 ± 10% fluorescence increase) in spatially confined membrane regions. The spiking was mimicked by membrane depolarization and suppressed after inhibition of exocytosis or of purinergic P2Y₁, but not P2X receptors, reflecting involvement of autocrine purinoceptor activation after exocytotic release of ATP. Each DAG spike caused local PKC activation with resulting dissociation of its substrate protein MARCKS from the plasma membrane. Inhibition of spiking reduced glucose-induced pulsatile insulin secretion. Thus, stimulus-specific DAG signaling patterns appear in the plasma membrane, including distinct microdomains, which have implications for the kinetic control of exocytosis and other membrane-associated processes.

  10. Comparative studies of Toll-like receptor signalling using zebrafish.

    PubMed

    Kanwal, Zakia; Wiegertjes, Geert F; Veneman, Wouter J; Meijer, Annemarie H; Spaink, Herman P

    2014-09-01

    Zebrafish model systems for infectious disease are increasingly used for the functional analysis of molecular pattern recognition processes. These studies benefit from the high conservation level of all innate immune factors in vertebrates. Zebrafish studies are strategically well positioned for this because of the ease of comparisons with studies in other fish species of which the immune system also has been intensively studied, but that are currently still less amendable to detailed genetic or microscopic studies. In this paper we focus on Toll-like receptor (TLR) signalling factors, which currently are the best characterized in mammalian systems. We review the knowledge on TLR signalling in the context of recent advances in zebrafish studies and discuss possibilities for future approaches that can complement studies in cell cultures and rodent models. A focus in these comparisons is the role of negative control mechanisms in immune responses that appear very important in a whole organism to keep adverse systemic responses in check. We also pay much attention to comparisons with studies in common carp that is highly related to zebrafish and that because of its large body mass can complement immune studies in zebrafish.

  11. Signaling Pathways in Leiomyoma: Understanding Pathobiology and Implications for Therapy

    PubMed Central

    Borahay, Mostafa A; Al-Hendy, Ayman; Kilic, Gokhan S; Boehning, Darren

    2015-01-01

    Uterine leiomyomas are the most common tumors of the female genital tract, affecting 50% to 70% of females by the age of 50. Despite their prevalence and enormous medical and economic impact, no effective medical treatment is currently available. This is, in part, due to the poor understanding of their underlying pathobiology. Although they are thought to start as a clonal proliferation of a single myometrial smooth muscle cell, these early cytogenetic alterations are considered insufficient for tumor development and additional complex signaling pathway alterations are crucial. These include steroids, growth factors, transforming growth factor-beta (TGF-β)/Smad; wingless-type (Wnt)/β-catenin, retinoic acid, vitamin D, and peroxisome proliferator-activated receptor γ (PPARγ). An important finding is that several of these pathways converge in a summative way. For example, mitogen-activated protein kinase (MAPK) and Akt pathways seem to act as signal integrators, incorporating input from several signaling pathways, including growth factors, estrogen and vitamin D. This underlines the multifactorial origin and complex nature of these tumors. In this review, we aim to dissect these pathways and discuss their interconnections, aberrations and role in leiomyoma pathobiology. We also aim to identify potential targets for development of novel therapeutics. PMID:25879625

  12. Acute Overactive Endocannabinoid Signaling Induces Glucose Intolerance, Hepatic Steatosis, and Novel Cannabinoid Receptor 1 Responsive Genes

    PubMed Central

    Ruby, Maxwell A.; Nomura, Daniel K.; Hudak, Carolyn S. S.; Barber, Anne; Casida, John E.; Krauss, Ronald M.

    2011-01-01

    Endocannabinoids regulate energy balance and lipid metabolism by stimulating the cannabinoid receptor type 1 (CB1). Genetic deletion and pharmacological antagonism have shown that CB1 signaling is necessary for the development of obesity and related metabolic disturbances. However, the sufficiency of endogenously produced endocannabinoids to cause hepatic lipid accumulation and insulin resistance, independent of food intake, has not been demonstrated. Here, we show that a single administration of isopropyl dodecylfluorophosphonate (IDFP), perhaps the most potent pharmacological inhibitor of endocannabinoid degradation, increases hepatic triglycerides (TG) and induces insulin resistance in mice. These effects involve increased CB1 signaling, as they are mitigated by pre-administration of a CB1 antagonist (AM251) and in CB1 knockout mice. Despite the strong physiological effects of CB1 on hepatic lipid and glucose metabolism, little is known about the downstream targets responsible for these effects. To elucidate transcriptional targets of CB1 signaling, we performed microarrays on hepatic RNA isolated from DMSO (control), IDFP and AM251/IDFP-treated mice. The gene for the secreted glycoprotein lipocalin 2 (lcn2), which has been implicated in obesity and insulin resistance, was among those most responsive to alterations in CB1 signaling. The expression pattern of IDFP mice segregated from DMSO mice in hierarchal cluster analysis and AM251 pre-administration reduced (>50%) the majority (303 of 533) of the IDFP induced alterations. Pathway analysis revealed that IDFP altered expression of genes involved in lipid, fatty acid and steroid metabolism, the acute phase response, and amino acid metabolism in a CB1-dependent manner. PCR confirmed array results of key target genes in multiple independent experiments. Overall, we show that acute IDFP treatment induces hepatic TG accumulation and insulin resistance, at least in part through the CB1 receptor, and identify novel

  13. Analysis of functional selectivity through G protein-dependent and -independent signaling pathways at the adrenergic α(2C) receptor.

    PubMed

    Kurko, Dalma; Kapui, Zoltán; Nagy, József; Lendvai, Balázs; Kolok, Sándor

    2014-08-01

    Although G protein-coupled receptors (GPCRs) are traditionally categorized as Gs-, Gq-, or Gi/o-coupled, their signaling is regulated by multiple mechanisms. GPCRs can couple to several effector pathways, having the capacity to interact not only with more than one G protein subtype but also with alternative signaling or effector proteins such as arrestins. Moreover, GPCR ligands can have different efficacies for activating these signaling pathways, a characteristic referred to as biased agonism or functional selectivity. In this work our aim was to detect differences in the ability of various agonists acting at the α2C type of adrenergic receptors (α2C-ARs) to modulate cAMP accumulation, cytoplasmic Ca(2+) release, β-arrestin recruitment and receptor internalization. A detailed comparative pharmacological characterization of G protein-dependent and -independent signaling pathways was carried out using adrenergic agonists (norepinephrine, phenylephrine, brimonidine, BHT-920, oxymetazoline, clonidine, moxonidine, guanabenz) and antagonists (MK912, yohimbine). As initial analysis of agonist Emax and EC50 values suggested possible functional selectivity, ligand bias was quantified by applying the relative activity scale and was compared to that of the endogenous agonist norepinephrine. Values significantly different from 0 between pathways indicated an agonist that promoted different level of activation of diverse effector pathways most likely due to the stabilization of a subtly different receptor conformation from that induced by norepinephrine. Our results showed that a series of agonists acting at the α2C-AR displayed different degree of functional selectivity (bias factors ranging from 1.6 to 36.7) through four signaling pathways. As signaling via these pathways seems to have distinct functional and physiological outcomes, studying all these stages of receptor activation could have further implications for the development of more selective therapeutics with

  14. Analysis of functional selectivity through G protein-dependent and -independent signaling pathways at the adrenergic α(2C) receptor.

    PubMed

    Kurko, Dalma; Kapui, Zoltán; Nagy, József; Lendvai, Balázs; Kolok, Sándor

    2014-08-01

    Although G protein-coupled receptors (GPCRs) are traditionally categorized as Gs-, Gq-, or Gi/o-coupled, their signaling is regulated by multiple mechanisms. GPCRs can couple to several effector pathways, having the capacity to interact not only with more than one G protein subtype but also with alternative signaling or effector proteins such as arrestins. Moreover, GPCR ligands can have different efficacies for activating these signaling pathways, a characteristic referred to as biased agonism or functional selectivity. In this work our aim was to detect differences in the ability of various agonists acting at the α2C type of adrenergic receptors (α2C-ARs) to modulate cAMP accumulation, cytoplasmic Ca(2+) release, β-arrestin recruitment and receptor internalization. A detailed comparative pharmacological characterization of G protein-dependent and -independent signaling pathways was carried out using adrenergic agonists (norepinephrine, phenylephrine, brimonidine, BHT-920, oxymetazoline, clonidine, moxonidine, guanabenz) and antagonists (MK912, yohimbine). As initial analysis of agonist Emax and EC50 values suggested possible functional selectivity, ligand bias was quantified by applying the relative activity scale and was compared to that of the endogenous agonist norepinephrine. Values significantly different from 0 between pathways indicated an agonist that promoted different level of activation of diverse effector pathways most likely due to the stabilization of a subtly different receptor conformation from that induced by norepinephrine. Our results showed that a series of agonists acting at the α2C-AR displayed different degree of functional selectivity (bias factors ranging from 1.6 to 36.7) through four signaling pathways. As signaling via these pathways seems to have distinct functional and physiological outcomes, studying all these stages of receptor activation could have further implications for the development of more selective therapeutics with

  15. ZINC-INDUCED EGF RECEPTOR SIGNALING REQUIRES SRC-MEDIATED PHOSPHORYLATION OF THE EGF RECEPTOR ON TYROSINE 845 (Y845)

    EPA Science Inventory

    ZINC-INDUCED EGF RECEPTOR SIGNALING REQUIRES Src-MEDIATED PHOSPHORYLATION OF THE EGF RECEPTOR ON TYROSINE 845 (Y845)
    Weidong Wu1, Lee M. Graves2, Gordon N. Gill3 and James M. Samet4 1Center for Environmental Medicine and Lung Biology; 2Department of Pharmacology, University o...

  16. Nogo Receptor Signaling Restricts Adult Neural Plasticity by Limiting Synaptic AMPA Receptor Delivery

    PubMed Central

    Jitsuki, Susumu; Nakajima, Waki; Takemoto, Kiwamu; Sano, Akane; Tada, Hirobumi; Takahashi-Jitsuki, Aoi; Takahashi, Takuya

    2016-01-01

    Experience-dependent plasticity is limited in the adult brain, and its molecular and cellular mechanisms are poorly understood. Removal of the myelin-inhibiting signaling protein, Nogo receptor (NgR1), restores adult neural plasticity. Here we found that, in NgR1-deficient mice, whisker experience-driven synaptic α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) insertion in the barrel cortex, which is normally complete by 2 weeks after birth, lasts into adulthood. In vivo live imaging by two-photon microscopy revealed more AMPAR on the surface of spines in the adult barrel cortex of NgR1-deficient than on those of wild-type (WT) mice. Furthermore, we observed that whisker stimulation produced new spines in the adult barrel cortex of mutant but not WT mice, and that the newly synthesized spines contained surface AMPAR. These results suggest that Nogo signaling limits plasticity by restricting synaptic AMPAR delivery in coordination with anatomical plasticity. PMID:26472557

  17. Nitric oxide and zinc-mediated protein assemblies involved in mu opioid receptor signaling.

    PubMed

    Rodríguez-Muñoz, María; Garzón, Javier

    2013-12-01

    Opioids are among the most effective analgesics in controlling the perception of intense pain, although their continuous use decreases their potency due to the development of tolerance. The glutamate N-methyl-D-aspartate (NMDA) receptor system is currently considered to be the most relevant functional antagonist of morphine analgesia. In the postsynapse of different brain regions the C terminus of the mu-opioid receptor (MOR) associates with NR1 subunits of NMDARs, as well as with a series of signaling proteins, such as neural nitric oxide synthase (nNOS)/nitric oxide (NO), protein kinase C (PKC), calcium and calmodulin-dependent kinase II (CaMKII) and the mitogen-activated protein kinases (MAPKs). NO is implicated in redox signaling and PKC falls under the regulation of zinc metabolism, suggesting that these signaling elements might participate in the regulation of MOR activity by the NMDAR. In this review, we discuss the influence of redox signaling in the mechanisms whose plasticity triggers opioid tolerance. Thus, the MOR C terminus assembles a series of signaling proteins around the homodimeric histidine triad nucleotide-binding protein 1 (HINT1). The NMDAR NR1 subunit and the regulator of G protein signaling RGSZ2 bind HINT1 in a zinc-independent manner, with RGSZ2 associating with nNOS and regulating MOR-induced production of NO. This NO acts on the RGSZ2 zinc finger, providing the zinc ions that are required for PKC/Raf-1 cysteine-rich domains to simultaneously bind to the histidines present in the HINT1 homodimer. The MOR-induced activation of phospholipase β (PLCβ) regulates PKC, which increases the reactive oxygen species (ROS) by acting on NOX/NADPH, consolidating the long-term PKC activation required to regulate the Raf-1/MAPK cascade and enhancing NMDAR function. Thus, RGSZ2 serves as a Redox Zinc Switch that converts NO signals into Zinc signals, thereby modulating Redox Sensor Proteins like PKCγ and Raf-1. Accordingly, redox-dependent and

  18. Dysregulation of Uterine Signaling Pathways in Progesterone Receptor-Cre Knockout of Dicer

    PubMed Central

    Andreu-Vieyra, Claudia V.; Kim, Tae Hoon; Jeong, Jae-Wook; Hodgson, Myles C.; Chen, Ruihong; Creighton, Chad J.; Lydon, John P.; Gunaratne, Preethi H.; DeMayo, Francesco J.; Matzuk, Martin M.

    2012-01-01

    Epithelial-stromal interactions in the uterus are required for normal uterine functions such as pregnancy, and multiple signaling pathways are essential for this process. Although Dicer and microRNA (miRNA) have been implicated in several reproductive processes, the specific roles of Dicer and miRNA in uterine development are not known. To address the roles of miRNA in the regulation of key uterine pathways, we generated a conditional knockout of Dicer in the postnatal uterine epithelium and stroma using progesterone receptor-Cre. These Dicer conditional knockout females are sterile with small uteri, which demonstrate significant defects, including absence of glandular epithelium and enhanced stromal apoptosis, beginning at approximately postnatal d 15, with coincident expression of Cre and deletion of Dicer. Specific miRNA (miR-181c, −200b, −101, let-7d) were down-regulated and corresponding predicted proapoptotic target genes (Bcl2l11, Aldh1a3) were up-regulated, reflecting the apoptotic phenomenon. Although these mice had normal serum hormone levels, critical uterine signaling pathways, including progesterone-responsive genes, Indian hedgehog signaling, and the Wnt/β-catenin canonical pathway, were dysregulated at the mRNA level. Importantly, uterine stromal cell proliferation in response to progesterone was absent, whereas uterine epithelial cell proliferation in response to estradiol was maintained in adult uteri. These data implicate Dicer and appropriate miRNA expression as essential players in the regulation of multiple uterine signaling pathways required for uterine development and appropriate function. PMID:22798293

  19. Genetic dissection of the signaling domain of a mammalian steroid receptor in yeast.

    PubMed Central

    Garabedian, M J; Yamamoto, K R

    1992-01-01

    The mechanism of signal transduction by steroid receptor proteins is complex and not yet understood. We describe here a facile genetic strategy for dissection of the rat glucocorticoid receptor "signaling domain," a region of the protein that binds and transduces the hormonal signal. We found that the characteristics of signal transduction by the receptor expressed in yeast were similar to those of endogenous receptors in mammalian cells. Interestingly, the rank order of particular ligands differed between species with respect to receptor binding and biological efficacy. This suggests that factors in addition to the receptor alone must determine or influence ligand efficacy in vivo. To obtain a collection of receptors with distinct defects in signal transduction, we screened in yeast an extensive series of random point mutations introduced in that region in vitro. Three phenotypic classes were obtained: one group failed to bind hormone, a second displayed altered ligand specificity, and a third bound hormone but lacked regulatory activity. Our results demonstrate that analysis of glucocorticoid receptor action in yeast provides a general approach for analyzing the mechanism of signaling by the nuclear receptor family and may facilitate identification of non-receptor factors that participate in this process. Images PMID:1457829

  20. MHC Class I Limits Hippocampal Synapse Density by Inhibiting Neuronal Insulin Receptor Signaling

    PubMed Central

    Dixon-Salazar, Tracy J.; Fourgeaud, Lawrence; Tyler, Carolyn M.; Poole, Julianna R.; Park, Joseph J.

    2014-01-01

    Proteins of the major histocompatibility complex class I (MHCI) negatively regulate synapse density in the developing vertebrate brain (Glynn et al., 2011; Elmer et al., 2013; Lee et al., 2014), but the underlying mechanisms remain largely unknown. Here we identify a novel MHCI signaling pathway that involves the inhibition of a known synapse-promoting factor, the insulin receptor. Dominant-negative insulin receptor constructs decrease synapse density in the developing Xenopus visual system (Chiu et al., 2008), and insulin receptor activation increases dendritic spine density in mouse hippocampal neurons in vitro (Lee et al., 2011). We find that genetically reducing cell surface MHCI levels increases synapse density selectively in regions of the hippocampus where insulin receptors are expressed, and occludes the neuronal insulin response by de-repressing insulin receptor signaling. Pharmacologically inhibiting insulin receptor signaling in MHCI-deficient animals rescues synapse density, identifying insulin receptor signaling as a critical mediator of the tonic inhibitory effects of endogenous MHCI on synapse number. Insulin receptors co-immunoprecipitate MHCI from hippocampal lysates, and MHCI unmasks a cytoplasmic epitope of the insulin receptor that mediates downstream signaling. These results identify an important role for an MHCI–insulin receptor signaling pathway in circuit patterning in the developing brain, and suggest that changes in MHCI expression could unexpectedly regulate neuronal insulin sensitivity in the aging and diseased brain. PMID:25164678

  1. Pharmacologic retinoid signaling and physiologic retinoic acid receptor signaling inhibit basal cell carcinoma tumorigenesis.

    PubMed

    So, Po-Lin; Fujimoto, Michele A; Epstein, Ervin H

    2008-05-01

    Basal cell carcinoma (BCC) is the most common human cancer. Patients with basal cell nevus syndrome (Gorlin syndrome) are highly susceptible to developing many BCCs as a result of a constitutive inactivating mutation in one allele of PATCHED 1, which encodes a tumor suppressor that is a major inhibitor of Hedgehog signaling. Dysregulated Hedgehog signaling is a common feature of both hereditary and sporadic BCCs. Recently, we showed remarkable anti-BCC chemopreventive efficacy of tazarotene, a retinoid with retinoic acid receptor (RAR) beta/gamma specificity, in Ptch1+/- mice when treatment was commenced before carcinogenic insults. In this study, we assessed whether the effect of tazarotene against BCC carcinogenesis is sustained after its withdrawal and whether tazarotene is effective against preexisting microscopic BCC lesions. We found that BCCs did not reappear for at least 5 months after topical drug treatment was stopped and that already developed, microscopic BCCs were susceptible to tazarotene inhibition. In vitro, tazarotene inhibited a murine BCC keratinocyte cell line, ASZ001, suggesting that its effect in vivo is by direct action on the actual tumor cells. Down-regulation of Gli1, a target gene of Hedgehog signaling and up-regulation of CRABPII, a target gene of retinoid signaling, were observed with tazarotene treatment. Finally, we investigated the effects of topical applications of other retinoid-related compounds on BCC tumorigenesis in vivo. Tazarotene was the most effective of the preparations studied, and its effect most likely was mediated by RARgamma activation. Furthermore, inhibition of basal RAR signaling in the skin promoted BCC carcinogenesis, suggesting that endogenous RAR signaling restrains BCC growth.

  2. Prolonged signaling at the parathyroid hormone receptor by peptide ligands targeted to a specific receptor conformation

    PubMed Central

    Okazaki, Makoto; Ferrandon, Sebastien; Vilardaga, Jean-Pierre; Bouxsein, Mary L.; Potts, John T.; Gardella, Thomas J.

    2008-01-01

    The parathyroid hormone receptor (PTHR) is a class B G protein-coupled receptor that plays critical roles in bone and mineral ion metabolism. Ligand binding to the PTHR involves interactions to both the amino-terminal extracellular (N) domain, and transmembrane/extracellular loop, or juxtamembrane (J) regions of the receptor. Recently, we found that PTH(1–34), but not PTH-related protein, PTHrP(1–36), or M-PTH(1–14) (M = Ala/Aib1,Aib3,Gln10,Har11,Ala12,Trp14,Arg19), binds to the PTHR in a largely GTPγS-resistant fashion, suggesting selective binding to a novel, high-affinity conformation (R0), distinct from the GTPγS-sensitive conformation (RG). We examined the effects in vitro and in vivo of introducing the M substitutions, which enhance interaction to the J domain, into PTH analogs extended C-terminally to incorporate residues involved in the N domain interaction. As compared with PTH(1–34), M-PTH(1–28) and M-PTH(1–34) bound to R0 with higher affinity, produced more sustained cAMP responses in cells, formed more stable complexes with the PTHR in FRET and subcellular localization assays, and induced more prolonged calcemic and phosphate responses in mice. Moreover, after 2 weeks of daily injection in mice, M-PTH(1–34) induced larger increases in trabecular bone volume and greater increases in cortical bone turnover, than did PTH(1–34). Thus, the putative R0 PTHR conformation can form highly stable complexes with certain PTH ligand analogs and thereby mediate surprisingly prolonged signaling responses in bone and/or kidney PTH target cells. Controlling, via ligand analog design, the selectivity with which a PTH ligand binds to R0, versus RG, may be a strategy for optimizing signaling duration time, and hence therapeutic efficacy, of PTHR agonist ligands. PMID:18946036

  3. Mechanisms of signal transduction by ethylene: overlapping and non-overlapping signalling roles in a receptor family

    PubMed Central

    Shakeel, Samina N.; Wang, Xiaomin; Binder, Brad M.; Schaller, G. Eric

    2013-01-01

    The plant hormone ethylene regulates growth and development as well as responses to biotic and abiotic stresses. Over the last few decades, key elements involved in ethylene signal transduction have been identified through genetic approaches, these elements defining a pathway that extends from initial ethylene perception at the endoplasmic reticulum to changes in transcriptional regulation within the nucleus. Here, we present our current understanding of ethylene signal transduction, focusing on recent developments that support a model with overlapping and non-overlapping roles for members of the ethylene receptor family. We consider the evidence supporting this model for sub-functionalization within the receptor family, and then discuss mechanisms by which such a sub-functionalization may occur. To this end, we consider the importance of receptor interactions in modulating their signal output and how such interactions vary in the receptor family. In addition, we consider evidence indicating that ethylene signal output by the receptors involves both phosphorylation-dependent and phosphorylation-independent mechanisms. We conclude with a current model for signalling by the ethylene receptors placed within the overall context of ethylene signal transduction. PMID:23543258

  4. Application of phosphorylation site-specific antibodies to measure nuclear receptor signaling: characterization of novel phosphoantibodies for estrogen receptor α

    PubMed Central

    Al-Dhaheri, Mariam H.; Rowan, Brian G.

    2006-01-01

    An understanding of posttranslational events in nuclear receptor signaling is crucial for drug design and clinical therapeutic strategies. Phosphorylation is a well-characterized posttranslational modification that regulates subcellular localization and function of nuclear receptors and coregulators. Although the role of single phosphorylation sites in nuclear receptor function has been described, the contribution of combinations of multiple phosphorylation sites to receptor function remains unclear. The development of phosphoantibodies to each phosphorylation site in a nuclear receptor is a powerful tool to address the role of phosphorylation in multiply phosphorylated receptors. However, phosphoantibodies must be rigorously validated prior to use. This review describes the general methodology for design, characterization and validation of phosphoantibodies using the example of eight phosphoantibodies raised against phosphorylation sites in estrogen receptor α (ERα). PMID:16741565

  5. CCR2 chemokine receptor signaling mediates pain in experimental osteoarthritis

    PubMed Central

    Miller, Rachel E.; Tran, Phuong B.; Das, Rosalina; Ghoreishi-Haack, Nayereh; Ren, Dongjun; Miller, Richard J.; Malfait, Anne-Marie

    2012-01-01

    Osteoarthritis is one of the leading causes of chronic pain, but almost nothing is known about the mechanisms and molecules that mediate osteoarthritis-associated joint pain. Consequently, treatment options remain inadequate and joint replacement is often inevitable. Here, we use a surgical mouse model that captures the long-term progression of knee osteoarthritis to longitudinally assess pain-related behaviors and concomitant changes in the innervating dorsal root ganglia (DRG). We demonstrate that monocyte chemoattractant protein (MCP)-1 (CCL2) and its high-affinity receptor, chemokine (C-C motif) receptor 2 (CCR2), are central to the development of pain associated with knee osteoarthritis. After destabilization of the medial meniscus, mice developed early-onset secondary mechanical allodynia that was maintained for 16 wk. MCP-1 and CCR2 mRNA, protein, and signaling activity were temporarily up-regulated in the innervating DRG at 8 wk after surgery. This result correlated with the presentation of movement-provoked pain behaviors, which were maintained up to 16 wk. Mice that lack Ccr2 also developed mechanical allodynia, but this started to resolve from 8 wk onwards. Despite severe allodynia and structural knee joint damage equal to wild-type mice, Ccr2-null mice did not develop movement-provoked pain behaviors at 8 wk. In wild-type mice, macrophages infiltrated the DRG by 8 wk and this was maintained through 16 wk after surgery. In contrast, macrophage infiltration was not observed in Ccr2-null mice. These observations suggest a key role for the MCP-1/CCR2 pathway in establishing osteoarthritis pain. PMID:23185004

  6. Deletion of IGF-I Receptor (IGF-IR) in Primary Osteoblasts Reduces GH-Induced STAT5 Signaling

    PubMed Central

    Gan, Yujun; Zhang, Yue; DiGirolamo, Douglas J.; Jiang, Jing; Wang, Xiangdong; Cao, Xuemei; Zinn, Kurt R.; Carbone, David P.; Clemens, Thomas L.; Frank, Stuart J.

    2010-01-01

    -induced IGF-I gene expression in cells in which endogenous IGF-IR was reduced. These data, in concert with our earlier findings that GH induces a GHR-JAK2-IGF-IR complex, suggest a novel function for IGF-IR. In addition to its role as a key IGF-I signal transducer, this receptor may directly facilitate acute GH signaling. The implications of these findings are discussed. PMID:20133448

  7. Kinase RIP3 is dispensable for normal NF-kappa Bs, signaling by the B-cell and T-cell receptors, tumor necrosis factor receptor 1, and Toll-like receptors 2 and 4.

    PubMed

    Newton, Kim; Sun, Xiaoqing; Dixit, Vishva M

    2004-02-01

    RIP3 is a member of the RIP kinase family. It is expressed in the embryo and in multiple adult tissues, including most hemopoietic cell lineages. Several studies have implicated RIP3 in the regulation of apoptosis and NF-kappa B signaling, but whether RIP3 promotes or attenuates activation of the NF-kappa B family of transcription factors has been controversial. We have generated RIP3-deficient mice by gene targeting and find RIP3 to be dispensable for normal mouse development. RIP3-deficient cells showed normal sensitivity to a variety of apoptotic stimuli and were indistinguishable from wild-type cells in their ability to activate NF-kappa B signaling in response to the following: human tumor necrosis factor (TNF), which selectively engages mouse TNF receptor 1; cross-linking of the B- or T-cell antigen receptors; peptidoglycan, which activates Toll-like receptor 2; and lipopolysaccharide (LPS), which stimulates Toll-like receptor 4. Consistent with these observations, RIP3-deficient mice exhibited normal antibody production after immunization with a T-dependent antigen and normal interleukin-1 beta (IL-1 beta), IL-6, and TNF production after LPS treatment. Thus, we can exclude RIP3 as an essential modulator of NF-kappa B signaling downstream of several receptor systems.

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

    PubMed

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

    2016-05-01

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

  9. Modulation of nociceptive ion channels and receptors via protein-protein interactions: implications for pain relief

    PubMed Central

    Rouwette, Tom; Avenali, Luca; Sondermann, Julia; Narayanan, Pratibha; Gomez-Varela, David; Schmidt, Manuela

    2015-01-01

    In the last 2 decades biomedical research has provided great insights into the molecular signatures underlying painful conditions. However, chronic pain still imposes substantial challenges to researchers, clinicians and patients alike. Under pathological conditions, pain therapeutics often lack efficacy and exhibit only minimal safety profiles, which can be largely attributed to the targeting of molecules with key physiological functions throughout the body. In light of these difficulties, the identification of molecules and associated protein complexes specifically involved in chronic pain states is of paramount importance for designing selective interventions. Ion channels and receptors represent primary targets, as they critically shape nociceptive signaling from the periphery to the brain. Moreover, their function requires tight control, which is usually implemented by protein-protein interactions (PPIs). Indeed, manipulation of such PPIs entails the modulation of ion channel activity with widespread implications for influencing nociceptive signaling in a more specific way. In this review, we highlight recent advances in modulating ion channels and receptors via their PPI networks in the pursuit of relieving chronic pain. Moreover, we critically discuss the potential of targeting PPIs for developing novel pain therapies exhibiting higher efficacy and improved safety profiles. PMID:26039491

  10. Anabolic androgenic steroids and intracellular calcium signaling: a mini review on mechanisms and physiological implications.

    PubMed

    Vicencio, J M; Estrada, M; Galvis, D; Bravo, R; Contreras, A E; Rotter, D; Szabadkai, G; Hill, J A; Rothermel, B A; Jaimovich, E; Lavandero, S

    2011-05-01

    Increasing evidence suggests that nongenomic effects of testosterone and anabolic androgenic steroids (AAS) operate concertedly with genomic effects. Classically, these responses have been viewed as separate and independent processes, primarily because nongenomic responses are faster and appear to be mediated by membrane androgen receptors, whereas long-term genomic effects are mediated through cytosolic androgen receptors regulating transcriptional activity. Numerous studies have demonstrated increases in intracellular Ca2+ in response to AAS. These Ca2+ mediated responses have been seen in a diversity of cell types, including osteoblasts, platelets, skeletal muscle cells, cardiac myocytes and neurons. The versatility of Ca2+ as a second messenger provides these responses with a vast number of pathophysiological implications. In cardiac cells, testosterone elicits voltage-dependent Ca2+ oscillations and IP3R-mediated Ca2+ release from internal stores, leading to activation of MAPK and mTOR signaling that promotes cardiac hypertrophy. In neurons, depending upon concentration, testosterone can provoke either physiological Ca2+ oscillations, essential for synaptic plasticity, or sustained, pathological Ca2+ transients that lead to neuronal apoptosis. We propose therefore, that Ca2+ acts as an important point of crosstalk between nongenomic and genomic AAS signaling, representing a central regulator that bridges these previously thought to be divergent responses.

  11. Cocaine Disrupts Histamine H3 Receptor Modulation of Dopamine D1 Receptor Signaling: σ1-D1-H3 Receptor Complexes as Key Targets for Reducing Cocaine's Effects

    PubMed Central

    Moreno, Estefanía; Moreno-Delgado, David; Navarro, Gemma; Hoffmann, Hanne M.; Fuentes, Silvia; Rosell-Vilar, Santi; Gasperini, Paola; Rodríguez-Ruiz, Mar; Medrano, Mireia; Mallol, Josefa; Cortés, Antoni; Casadó, Vicent; Lluís, Carme; Ferré, Sergi; Ortiz, Jordi; Canela, Enric

    2014-01-01

    The general effects of cocaine are not well understood at the molecular level. What is known is that the dopamine D1 receptor plays an important role. Here we show that a key mechanism may be cocaine's blockade of the histamine H3 receptor-mediated inhibition of D1 receptor function. This blockade requires the σ1 receptor and occurs upon cocaine binding to σ1-D1-H3 receptor complexes. The cocaine-mediated disruption leaves an uninhibited D1 receptor that activates Gs, freely recruits β-arrestin, increases p-ERK 1/2 levels, and induces cell death when over activated. Using in vitro assays with transfected cells and in ex vivo experiments using both rats acutely treated or self-administered with cocaine along with mice depleted of σ1 receptor, we show that blockade of σ1 receptor by an antagonist restores the protective H3 receptor-mediated brake on D1 receptor signaling and prevents the cell death from elevated D1 receptor signaling. These findings suggest that a combination therapy of σ1R antagonists with H3 receptor agonists could serve to reduce some effects of cocaine. PMID:24599455

  12. Downregulation of kinin B1 receptor function by B2 receptor heterodimerization and signaling.

    PubMed

    Zhang, Xianming; Brovkovych, Viktor; Zhang, Yongkang; Tan, Fulong; Skidgel, Randal A

    2015-01-01

    Signaling through the G protein-coupled kinin receptors B1 (kB1R) and B2 (kB2R) plays a critical role in inflammatory responses mediated by activation of the kallikrein-kinin system. The kB2R is constitutively expressed and rapidly desensitized in response to agonist whereas kB1R expression is upregulated by inflammatory stimuli and it is resistant to internalization and desensitization. Here we show that the kB1R heterodimerizes with kB2Rs in co-transfected HEK293 cells and natively expressing endothelial cells, resulting in significant internalization and desensitization of the kB1R response in cells pre-treated with kB2R agonist. However, pre-treatment of cells with kB1R agonist did not affect subsequent kB2R responses. Agonists of other G protein-coupled receptors (thrombin, lysophosphatidic acid) had no effect on a subsequent kB1R response. The loss of kB1R response after pretreatment with kB2R agonist was partially reversed with kB2R mutant Y129S, which blocks kB2R signaling without affecting endocytosis, or T342A, which signals like wild type but is not endocytosed. Co-endocytosis of the kB1R with kB2R was dependent on β-arrestin and clathrin-coated pits but not caveolae. The sorting pathway of kB1R and kB2R after endocytosis differed as recycling of kB1R to the cell surface was much slower than that of kB2R. In cytokine-treated human lung microvascular endothelial cells, pre-treatment with kB2R agonist inhibited kB1R-mediated increase in transendothelial electrical resistance (TER) caused by kB1R stimulation (to generate nitric oxide) and blocked the profound drop in TER caused by kB1R activation in the presence of pyrogallol (a superoxide generator). Thus, kB1R function can be downregulated by kB2R co-endocytosis and signaling, suggesting new approaches to control kB1R signaling in pathological conditions. PMID:25289859

  13. Oviductal estrogen receptor α signaling prevents protease-mediated embryo death

    PubMed Central

    Winuthayanon, Wipawee; Bernhardt, Miranda L; Padilla-Banks, Elizabeth; Myers, Page H; Edin, Matthew L; Lih, Fred B; Hewitt, Sylvia C; Korach, Kenneth S; Williams, Carmen J

    2015-01-01

    Development of uterine endometrial receptivity for implantation is orchestrated by cyclic steroid hormone-mediated signals. It is unknown if these signals are necessary for oviduct function in supporting fertilization and preimplantation development. Here we show that conditional knockout (cKO) mice lacking estrogen receptor α (ERα) in oviduct and uterine epithelial cells have impaired fertilization due to a dramatic reduction in sperm migration. In addition, all successfully fertilized eggs die before the 2-cell stage due to persistence of secreted innate immune mediators including proteases. Elevated protease activity in cKO oviducts causes premature degradation of the zona pellucida and embryo lysis, and wild-type embryos transferred into cKO oviducts fail to develop normally unless rescued by concomitant transfer of protease inhibitors. Thus, suppression of oviductal protease activity mediated by estrogen-epithelial ERα signaling is required for fertilization and preimplantation embryo development. These findings have implications for human infertility and post-coital contraception. DOI: http://dx.doi.org/10.7554/eLife.10453.001 PMID:26623518

  14. Evidence for new homotypic and heterotypic interactions between transmembrane helices of proteins involved in receptor tyrosine kinase and neuropilin signaling.

    PubMed

    Sawma, Paul; Roth, Lise; Blanchard, Cécile; Bagnard, Dominique; Crémel, Gérard; Bouveret, Emmanuelle; Duneau, Jean-Pierre; Sturgis, James N; Hubert, Pierre

    2014-12-12

    Signaling in eukaryotic cells frequently relies on dynamic interactions of single-pass membrane receptors involving their transmembrane (TM) domains. To search for new such interactions, we have developed a bacterial two-hybrid system to screen for both homotypic and heterotypic interactions between TM helices. We have explored the dimerization of TM domains from 16 proteins involved in both receptor tyrosine kinase and neuropilin signaling. This study has revealed several new interactions. We found that the TM domain of Mucin-4, a putative intramembrane ligand for erbB2, dimerizes not only with erbB2 but also with all four members of the erbB family. In the Neuropilin/Plexin family of receptors, we showed that the TM domains of Neuropilins 1 and 2 dimerize with themselves and also with Plexin-A1, Plexin-B1, and L1CAM, but we were unable to observe interactions with several other TM domains notably those of members of the VEGF receptor family. The potentially important Neuropilin 1/Plexin-A1 interaction was confirmed using a surface plasmon resonance assay. This work shows that TM domain interactions can be highly specific. Exploring further the propensities of TM helix-helix association in cell membrane should have important practical implications related to our understanding of the structure-function of bitopic proteins' assembly and subsequent function, especially in the regulation of signal transduction. PMID:25315821

  15. A Coding IRAK2 Protein Variant Compromises Toll-like receptor (TLR) Signaling and Is Associated with Colorectal Cancer Survival*

    PubMed Central

    Wang, Hui; Flannery, Sinead M.; Dickhöfer, Sabine; Huhn, Stefanie; George, Julie; Kubarenko, Andriy V.; Lascorz, Jesus; Bevier, Melanie; Willemsen, Joschka; Pichulik, Tica; Schafmayer, Clemens; Binder, Marco; Manoury, Bénédicte; Paludan, Søren R.; Alarcon-Riquelme, Marta; Bowie, Andrew G.; Försti, Asta; Weber, Alexander N. R.

    2014-01-01

    Within innate immune signaling pathways, interleukin-1 receptor-associated kinases (IRAKs) fulfill key roles downstream of multiple Toll-like receptors and the interleukin-1 receptor. Although human IRAK4 deficiency was shown to lead to severe immunodeficiency in response to pyogenic bacterial infection during childhood, little is known about the role of human IRAK2. We here identified a non-synonymous IRAK2 variant, rs35060588 (coding R214G), as hypofunctional in terms of NF-κB signaling and Toll-like receptor-mediated cytokine induction. This was due to reduced ubiquitination of TRAF6, a key step in signal transduction. IRAK2 rs35060588 occurs in 3–9% of individuals in different ethnic groups, and our studies suggested a genetic association of rs35060588 with colorectal cancer survival. This for the first time implicates human IRAK2 in a human disease and highlights the R214G IRAK2 variant as a potential novel and broadly applicable biomarker for disease or as a therapeutic intervention point. PMID:24973222

  16. Innate immune receptor Toll-like receptor 4 signalling in neuropsychiatric diseases.

    PubMed

    García Bueno, B; Caso, J R; Madrigal, J L M; Leza, J C

    2016-05-01

    The innate immunity is a stereotyped first line of defense against pathogens and unspecified damage signals. One of main actors of innate immunity are the Toll-like receptors (TLRs), and one of the better characterized members of this family is TLR-4, that it is mainly activated by Gram-negative bacteria lipopolysaccharide. In brain, TLR-4 organizes innate immune responses against infections or cellular damage, but also possesses other physiological functions. In the last years, some evidences suggest a role of TLR-4 in stress and stress-related neuropsychiatric diseases. Peripheral and brain TLR-4 activation triggers sickness behavior, and its expression is a risk factor of depression. Some elements of the TLR-4 signaling pathway are up-regulated in peripheral samples and brain post-mortem tissue from depressed and suicidal patients. The "leaky gut" hypothesis of neuropsychiatric diseases is based on the existence of an increase of the intestinal permeability which results in bacterial translocation able to activate TLR-4. Enhanced peripheral TLR-4 expression/activity has been described in subjects diagnosed with schizophrenia, bipolar disorder and in autistic children. A role for TLR-4 in drugs abuse has been also proposed. The therapeutic potential of pharmacological/genetic modulation of TLRs signaling pathways in neuropsychiatry is promising, but a great preclinical/clinical scientific effort is still needed.

  17. Quercetin suppresses insulin receptor signaling through inhibition of the insulin ligand–receptor binding and therefore impairs cancer cell proliferation

    SciTech Connect

    Wang, Feng; Yang, Yong

    2014-10-03

    Graphical abstract: - Highlights: • Quercetin inhibits insulin ligand–receptor interactions. • Quercetin reduces downstream insulin receptor signaling. • Quercetin blocks insulin induced glucose uptake. • Quercetin suppresses insulin stimulated cancer cell proliferation and tumor growth. - Abstract: Although the flavonoid quercetin is known to inhibit activation of insulin receptor signaling, the inhibitory mechanism is largely unknown. In this study, we demonstrate that quercetin suppresses insulin induced dimerization of the insulin receptor (IR) through interfering with ligand–receptor interactions, which reduces the phosphorylation of IR and Akt. This inhibitory effect further inhibits insulin stimulated glucose uptake due to decreased cell membrane translocation of glucose transporter 4 (GLUT4), resulting in impaired cancer cell proliferation. The effect of quercetin in inhibiting tumor growth was also evident in an in vivo model, indicating a potential future application for quercetin in the treatment of cancers.

  18. Ilyanassa Notch signaling implicated in dynamic signaling between all three germ layers.

    PubMed

    Gharbiah, Maey; Nakamoto, Ayaki; Johnson, Adam B; Lambert, J David; Nagy, Lisa M

    2014-01-01

    Two cells (3D and 4d) in the mud snail Ilyanassa obsoleta function to induce proper cell fate. In this study, we provide support for the hypothesis that Notch signaling in Ilyanassa obsoleta functions in inductive signaling at multiple developmental stages. The expression patterns of Notch, Delta and Suppressor of Hairless (SuH) are consistent with a function for Notch signaling in endoderm formation, the function of 3D/4d and the sublineages of 4d. Veligers treated with DAPT show a range of defects that include a loss of endodermal structures, and varying degrees of loss of targets of 4d inductive signaling. Veligers that result from injection of Ilyanassa Delta siRNAi in general mimic the defects observed in the DAPT treated larvae. The most severe DAPT phenotypes mimic early ablations of 4d. However, the early specification of 4d itself appears normal and MAPK activation in both 3D/4d and the micromeres, which are known to activate MAPK as a result of 3D/4d induction, are normal in DAPT treated larvae. Treating larvae at successively later timepoints with DAPT suggests that Notch/Delta signaling is not only required during early 4d inductive signaling, but during subsequent stages of cell fate determination as well. Based on our results, combined with previous reports implicating the endoderm in maintaining induced fate specification in Ilyanassa, we propose a speculative model that Notch signaling is required to specify endoderm fates and 4d sublineages, as well as to maintain cell fates induced by 4d.

  19. Met Receptor Tyrosine Kinase Signaling Induces Secretion of the Angiogenic Chemokine Interleukin-8/CXCL8 in Pancreatic Cancer

    PubMed Central

    Hill, Kristen S.; Gaziova, Ivana; Harrigal, Lindsay; Guerra, Yvette A.; Qiu, Suimin; Sastry, Sarita K.; Arumugam, Thiruvengadam; Logsdon, Craig D.; Elferink, Lisa A.

    2012-01-01

    At diagnosis, the majority of pancreatic cancer patients present with advanced disease when curative resection is no longer feasible and current therapeutic treatments are largely ineffective. An improved understanding of molecular targets for effective intervention of pancreatic cancer is thus urgent. The Met receptor tyrosine kinase is one candidate implicated in pancreatic cancer. Notably, Met is over expressed in up to 80% of invasive pancreatic cancers but not in normal ductal cells correlating with poor overall patient survival and increased recurrence rates following surgical resection. However the functional role of Met signaling in pancreatic cancer remains poorly understood. Here we used RNA interference to directly examine the pathobiological importance of increased Met signaling for pancreatic cancer. We show that Met knockdown in pancreatic tumor cells results in decreased cell survival, cell invasion, and migration on collagen I in vitro. Using an orthotopic model for pancreatic cancer, we provide in vivo evidence that Met knockdown reduced tumor burden correlating with decreased cell survival and tumor angiogenesis, with minimal effect on cell growth. Notably, we report that Met signaling regulates the secretion of the pro-angiogenic chemokine interleukin-8/CXCL8. Our data showing that the interleukin-8 receptors CXCR1 and CXCR2 are not expressed on pancreatic tumor cells, suggests a paracrine mechanism by which Met signaling regulates interleukin-8 secretion to remodel the tumor microenvironment, a novel finding that could have important clinical implications for improving the effectiveness of treatments for pancreatic cancer. PMID:22815748

  20. Biased signaling through G-protein-coupled PROKR2 receptors harboring missense mutations.

    PubMed

    Sbai, Oualid; Monnier, Carine; Dodé, Catherine; Pin, Jean-Philippe; Hardelin, Jean-Pierre; Rondard, Philippe

    2014-08-01

    Various missense mutations in the gene coding for prokineticin receptor 2 (PROKR2), a G-protein-coupled receptor, have been identified in patients with Kallmann syndrome. However, the functional consequences of these mutations on the different signaling pathways of this receptor have not been studied. We first showed that the wild-type PROKR2 can activate different G-protein subtypes (Gq, Gs, and Gi/o) and recruit β-arrestins in transfected HEK-293 cells. We then examined, for each of these signaling pathways, the effects of 9 mutations that did not significantly impair cell surface targeting or ligand binding of the receptor. Four mutant receptors showing defective Gq signaling (R85C, R85H, R164Q, and V331M) could still recruit β-arrestins on ligand activation, which may cause biased signaling in vivo. Conversely, the R80C receptor could activate the 3 types of G proteins but could not recruit β-arrestins. Finally, the R268C receptor could recruit β-arrestins and activate the Gq and Gs signaling pathways but could not activate the Gi/o signaling pathway. Our results validate the concept that mutations in the genes encoding membrane receptors can bias downstream signaling in various ways, possibly leading to pathogenic and, perhaps in some cases, protective (e.g., R268C) effects.

  1. Cochlear progenitor number is controlled through mesenchymal FGF receptor signaling

    PubMed Central

    Huh, Sung-Ho; Warchol, Mark E; Ornitz, David M

    2015-01-01

    The sensory and supporting cells (SCs) of the organ of Corti are derived from a limited number of progenitors. The mechanisms that regulate the number of sensory progenitors are not known. Here, we show that Fibroblast Growth Factors (FGF) 9 and 20, which are expressed in the non-sensory (Fgf9) and sensory (Fgf20) epithelium during otic development, regulate the number of cochlear progenitors. We further demonstrate that Fgf receptor (Fgfr) 1 signaling within the developing sensory epithelium is required for the differentiation of outer hair cells and SCs, while mesenchymal FGFRs regulate the size of the sensory progenitor population and the overall cochlear length. In addition, ectopic FGFR activation in mesenchyme was sufficient to increase sensory progenitor proliferation and cochlear length. These data define a feedback mechanism, originating from epithelial FGF ligands and mediated through periotic mesenchyme that controls the number of sensory progenitors and the length of the cochlea. DOI: http://dx.doi.org/10.7554/eLife.05921.001 PMID:25915623

  2. How complex are intracellular immune receptor signaling complexes?

    PubMed

    Bonardi, Vera; Dangl, Jeffery L

    2012-01-01

    Nucleotide binding leucine-rich repeat proteins (NLRs) are the major class of intracellular immune receptors in plants. NLRs typically function to specifically recognize pathogen effectors and to initiate and control defense responses that severely limit pathogen growth in plants (termed effector-triggered immunity, or ETI). Despite numerous reports supporting a central role in innate immunity, the molecular mechanisms driving NLR activation and downstream signaling remain largely elusive. Recent reports shed light on the pre- and post-activation dynamics of a few NLR-containing protein complexes. Recent technological advances in the use of proteomics may enable high-resolution definition of immune protein complexes and possible activation-relevant post-translational modifications of the components in these complexes. In this review, we focus on research aimed at characterizing pre- and post-activation NLR protein complexes and the molecular events that follow activation. We discuss the use of new or improved technologies as tools to unveil the molecular mechanisms that define NLR-mediated pathogen recognition.

  3. Lipopolysaccharide-Induced CD300b Receptor Binding to Toll-like Receptor 4 Alters Signaling to Drive Cytokine Responses that Enhance Septic Shock.

    PubMed

    Voss, Oliver H; Murakami, Yousuke; Pena, Mirna Y; Lee, Ha-Na; Tian, Linjie; Margulies, David H; Street, Jonathan M; Yuen, Peter S T; Qi, Chen-Feng; Krzewski, Konrad; Coligan, John E

    2016-06-21

    Receptor CD300b is implicated in regulating the immune response to bacterial infection by an unknown mechanism. Here, we identified CD300b as a lipopolysaccharide (LPS)-binding receptor and determined the mechanism underlying CD300b augmentation of septic shock. In vivo depletion and adoptive transfer studies identified CD300b-expressing macrophages as the key cell type augmenting sepsis. We showed that CD300b, and its adaptor DAP12, associated with Toll-like receptor 4 (TLR4) upon LPS binding, thereby enhancing TLR4-adaptor MyD88- and TRIF-dependent signaling that resulted in an elevated pro-inflammatory cytokine storm. LPS engagement of the CD300b-TLR4 complex led to the recruitment and activation of spleen tyrosine kinase (Syk) and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K). This resulted in an inhibition of the ERK1/2 protein kinase- and NF-κB transcription factor-mediated signaling pathways, which subsequently led to a reduced interleukin-10 (IL-10) production. Collectively, our data describe a mechanism of TLR4 signaling regulated by CD300b in myeloid cells in response to LPS. PMID:27261276

  4. A muscle-specific knockout implicates nuclear receptor coactivator MED1 in the regulation of glucose and energy metabolism.

    PubMed

    Chen, Wei; Zhang, Xiaoting; Birsoy, Kivanc; Roeder, Robert G

    2010-06-01

    As conventional transcriptional factors that are activated in diverse signaling pathways, nuclear receptors play important roles in many physiological processes that include energy homeostasis. The MED1 subunit of the Mediator coactivator complex plays a broad role in nuclear receptor-mediated transcription by anchoring the Mediator complex to diverse promoter-bound nuclear receptors. Given the significant role of skeletal muscle, in part through the action of nuclear receptors, in glucose and fatty acid metabolism, we generated skeletal muscle-specific Med1 knockout mice. Importantly, these mice show enhanced insulin sensitivity and improved glucose tolerance as well as resistance to high-fat diet-induced obesity. Furthermore, the white muscle of these mice exhibits increased mitochondrial density and expression of genes specific to type I and type IIA fibers, indicating a fast-to-slow fiber switch, as well as markedly increased expression of the brown adipose tissue-specific UCP-1 and Cidea genes that are involved in respiratory uncoupling. These dramatic results implicate MED1 as a powerful suppressor in skeletal muscle of genetic programs implicated in energy expenditure and raise the significant possibility of therapeutical approaches for metabolic syndromes and muscle diseases through modulation of MED1-nuclear receptor interactions.

  5. Engineered G protein coupled receptors reveal independent regulation of internalization, desensitization and acute signaling

    PubMed Central

    Scearce-Levie, Kimberly; Lieberman, Michael D; Elliott, Heather H; Conklin, Bruce R

    2005-01-01

    Background The physiological regulation of G protein-coupled receptors, through desensitization and internalization, modulates the length of the receptor signal and may influence the development of tolerance and dependence in response to chronic drug treatment. To explore the importance of receptor regulation, we engineered a series of Gi-coupled receptors that differ in signal length, degree of agonist-induced internalization, and ability to induce adenylyl cyclase superactivation. All of these receptors, based on the kappa opioid receptor, were modified to be receptors activated solely by synthetic ligands (RASSLs). This modification allows us to compare receptors that have the same ligands and effectors, but differ only in desensitization and internalization. Results Removal of phosphorylation sites in the C-terminus of the RASSL resulted in a mutant that was resistant to internalization and less prone to desensitization. Replacement of the C-terminus of the RASSL with the corresponding portion of the mu opioid receptor eliminated the induction of AC superactivation, without disrupting agonist-induced desensitization or internalization. Surprisingly, removal of phosphorylation sites from this chimera resulted in a receptor that is constitutively internalized, even in the absence of agonist. However, the receptor still signals and desensitizes in response to agonist, indicating normal G-protein coupling and partial membrane expression. Conclusions These studies reveal that internalization, desensitization and adenylyl cyclase superactivation, all processes that decrease chronic Gi-receptor signals, are independently regulated. Furthermore, specific mutations can radically alter superactivation or internalization without affecting the efficacy of acute Gi signaling. These mutant RASSLs will be useful for further elucidating the temporal dynamics of the signaling of G protein-coupled receptors in vitro and in vivo. PMID:15707483

  6. Nuclear Compartmentalization of α1-Adrenergic Receptor Signaling in Adult Cardiac Myocytes

    PubMed Central

    Wu, Steven C.

    2015-01-01

    Abstract: Although convention dictates that G protein-coupled receptors localize to and signal at the plasma membrane, accumulating evidence suggests that G protein-coupled receptors localize to and signal at intracellular membranes, most notably the nucleus. In fact, there is now significant evidence indicating that endogenous alpha-1 adrenergic receptors (α1-ARs) localize to and signal at the nuclei in adult cardiac myocytes. Cumulatively, the data suggest that α1-ARs localize to the inner nuclear membrane, activate intranuclear signaling, and regulate physiologic function in adult cardiac myocytes. Although α1-ARs signal through Gαq, unlike other Gq-coupled receptors, α1-ARs mediate important cardioprotective functions including adaptive/physiologic hypertrophy, protection from cell death (survival signaling), positive inotropy, and preconditioning. Also unlike other Gq-coupled receptors, most, if not all, functional α1-ARs localize to the nuclei in adult cardiac myocytes, as opposed to the sarcolemma. Together, α1-AR nuclear localization and cardioprotection might suggest a novel model for compartmentalization of Gq-coupled receptor signaling in which nuclear Gq-coupled receptor signaling is cardioprotective. PMID:25264754

  7. Conducting the G-protein Coupled Receptor (GPCR) Signaling Symphony in Cardiovascular Diseases: New Therapeutic Approaches.

    PubMed

    Belmonte, Stephen L; Blaxall, Burns C

    2012-01-01

    G protein-coupled receptors (GPCRs) are a virtually ubiquitous class of membrane-bound receptors, which functionally couple hormone or neurotransmitter signals to physiological responses. Dysregulation of GPCR signaling contributes to the pathophysiology of a host of cardiovascular disorders. Pharmacological agents targeting GPCRs have been established as therapeutic options for decades. Nevertheless, the persistent burden of cardiovascular diseases necessitates improved treatments. To that end, exciting drug development efforts have begun to focus on novel compounds that discriminately activate particular GPCR signaling pathways.

  8. Testosterone signaling through internalizable surface receptors in androgen receptor-free macrophages.

    PubMed

    Benten, W P; Lieberherr, M; Stamm, O; Wrehlke, C; Guo, Z; Wunderlich, F

    1999-10-01

    Testosterone acts on cells through intracellular transcription-regulating androgen receptors (ARs). Here, we show that mouse IC-21 macrophages lack the classical AR yet exhibit specific nongenomic responses to testosterone. These manifest themselves as testosterone-induced rapid increase in intracellular free [Ca(2+)], which is due to release of Ca(2+) from intracellular Ca(2+) stores. This Ca(2+) mobilization is also inducible by plasma membrane-impermeable testosterone-BSA. It is not affected by the AR blockers cyproterone and flutamide, whereas it is completely inhibited by the phospholipase C inhibitor U-73122 and pertussis toxin. Binding sites for testosterone are detectable on the surface of intact IC-21 cells, which become selectively internalized independent on caveolae and clathrin-coated vesicles upon agonist stimulation. Internalization is dependent on temperature, ATP, cytoskeletal elements, phospholipase C, and G-proteins. Collectively, our data provide evidence for the existence of G-protein-coupled, agonist-sequestrable receptors for testosterone in plasma membranes, which initiate a transcription-independent signaling pathway of testosterone. PMID:10512854

  9. Testosterone Signaling through Internalizable Surface Receptors in Androgen Receptor-free Macrophages

    PubMed Central

    Benten, W. Peter M.; Lieberherr, Michèle; Stamm, Olaf; Wrehlke, Christian; Guo, Zhiyong; Wunderlich, Frank

    1999-01-01

    Testosterone acts on cells through intracellular transcription-regulating androgen receptors (ARs). Here, we show that mouse IC-21 macrophages lack the classical AR yet exhibit specific nongenomic responses to testosterone. These manifest themselves as testosterone-induced rapid increase in intracellular free [Ca2+], which is due to release of Ca2+ from intracellular Ca2+ stores. This Ca2+ mobilization is also inducible by plasma membrane-impermeable testosterone-BSA. It is not affected by the AR blockers cyproterone and flutamide, whereas it is completely inhibited by the phospholipase C inhibitor U-73122 and pertussis toxin. Binding sites for testosterone are detectable on the surface of intact IC-21 cells, which become selectively internalized independent on caveolae and clathrin-coated vesicles upon agonist stimulation. Internalization is dependent on temperature, ATP, cytoskeletal elements, phospholipase C, and G-proteins. Collectively, our data provide evidence for the existence of G-protein-coupled, agonist-sequestrable receptors for testosterone in plasma membranes, which initiate a transcription-independent signaling pathway of testosterone. PMID:10512854

  10. Protease-activated receptor 1 (PAR1) signalling desensitization is counteracted via PAR4 signalling in human platelets.

    PubMed

    Fälker, Knut; Haglund, Linda; Gunnarsson, Peter; Nylander, Martina; Lindahl, Tomas L; Grenegård, Magnus

    2011-06-01

    PARs (protease-activated receptors) 1 and 4 belong to the family of G-protein-coupled receptors which induce both G(α12/13) and G(αq) signalling. By applying the specific PAR1- and PAR4-activating hexapeptides, SFLLRN and AYPGKF respectively, we found that aggregation of isolated human platelets mediated via PAR1, but not via PAR4, is abolished upon homologous receptor activation in a concentration- and time-dependent fashion. This effect was not due to receptor internalization, but to a decrease in Ca²⁺ mobilization, PKC (protein kinase C) signalling and α-granule secretion, as well as to a complete lack of dense granule secretion. Interestingly, subthreshold PAR4 activation rapidly abrogated PAR1 signalling desensitization by differentially reconstituting these affected signalling events and functional responses, which was sufficient to re-establish aggregation. The lack of ADP release and P2Y₁₂ receptor-induced G(αi) signalling accounted for the loss of the aggregation response, as mimicking G(αi/z) signalling with 2-MeS-ADP (2-methylthioadenosine-5'-O-diphosphate) or epinephrine (adrenaline) could substitute for intermediate PAR4 activation. Finally, we found that the re-sensitization of PAR1 signalling-induced aggregation via PAR4 relied on PKC-mediated release of both ADP from dense granules and fibrinogen from α-granules. The present study elucidates further differences in human platelet PAR signalling regulation and provides evidence for a cross-talk in which PAR4 signalling counteracts mechanisms involved in PAR1 signalling down-regulation. PMID:21391917

  11. Signaling Properties and Pharmacological Analysis of Two Sulfakinin Receptors from the Red Flour Beetle, Tribolium castaneum

    PubMed Central

    Zels, Sven; Verlinden, Heleen; Dillen, Senne; Vleugels, Rut; Nachman, Ronald J.; Broeck, Jozef Vanden

    2014-01-01

    Sulfakinin is an insect neuropeptide that constitutes an important component of the complex network of hormonal and neural factors that regulate feeding and digestion. The key modulating functions of sulfakinin are mediated by binding and signaling via G-protein coupled receptors. Although a substantial amount of functional data have already been reported on sulfakinins in different insect species, only little information is known regarding the properties of their respective receptors. In this study, we report on the molecular cloning, functional expression and characterization of two sulfakinin receptors in the red flour beetle, Tribolium castaneum. Both receptor open reading frames show extensive sequence similarity with annotated sulfakinin receptors from other insects. Comparison of the sulfakinin receptor sequences with homologous vertebrate cholecystokinin receptors reveals crucial conserved regions for ligand binding and receptor activation. Quantitative reverse transcriptase PCR shows that transcripts of both receptors are primarily expressed in the central nervous system of the beetle. Pharmacological characterization using 29 different peptide ligands clarified the essential requirements for efficient activation of these sulfakinin receptors. Analysis of the signaling pathway in multiple cell lines disclosed that the sulfakinin receptors of T. castaneum can stimulate both the Ca2+ and cyclic AMP second messenger pathways. This in depth characterization of two insect sulfakinin receptors may provide useful leads for the further development of receptor ligands with a potential applicability in pest control and crop protection. PMID:24718573

  12. Crosstalk between RON and androgen receptor signaling in the development of castration resistant prostate cancer

    PubMed Central

    Batth, Izhar; Yun, Huiyoung; Hussain, Suleman; Meng, Peng; Osumulski, Powel; Huang, Tim Hui-Ming; Bedolla, Roble; Profit, Amanda; Reddick, Robert; Kumar, Addanki

    2016-01-01

    Castrate-resistant prostate cancer (CRPC) is the fatal form of prostate cancer. Although reactivation of androgen receptor (AR) occurs following androgen deprivation, the precise mechanism involved is unclear. Here we show that the receptor tyrosine kinase, RON alters mechanical properties of cells to influence epithelial to mesenchymal transition and functions as a transcription factor to differentially regulate AR signaling. RON inhibits AR activation and subset of AR-regulated transcripts in androgen responsive LNCaP cells. However in C4-2B, a castrate-resistant sub-line of LNCaP and AR-negative androgen independent DU145 cells, RON activates subset of AR-regulated transcripts. Expression of AR in PC-3 cells leads to activation of RON under androgen deprivation but not under androgen proficient conditions implicating a role for RON in androgen independence. Consistently, RON expression is significantly elevated in castrate resistant prostate tumors. Taken together our results suggest that RON activation could aid in promoting androgen independence and that inhibition of RON in combination with AR antagonist(s) merits serious consideration as a therapeutic option during hormone deprivation therapy. PMID:26872377

  13. A growth hormone receptor mutation impairs growth hormone autofeedback signaling in pituitary tumors.

    PubMed

    Asa, Sylvia L; Digiovanni, Rebecca; Jiang, Jing; Ward, Megan L; Loesch, Kimberly; Yamada, Shozo; Sano, Toshiaki; Yoshimoto, Katsuhiko; Frank, Stuart J; Ezzat, Shereen

    2007-08-01

    Pituitary tumors are a diverse group of neoplasms that are classified based on clinical manifestations, hormone excess, and histomorphologic features. Those that cause growth hormone (GH) excess and acromegaly are subdivided into morphologic variants that have not yet been shown to have pathogenetic significance or predictive value for therapy and outcome. Here, we identify a selective somatic histidine-to-leucine substitution in codon 49 of the extracellular domain of the GH receptor (GHR) in a morphologic subtype of human GH-producing pituitary tumors that is characterized by the presence of cytoskeletal aggresomes. This GHR mutation significantly impairs glycosylation-mediated receptor processing, maturation, ligand binding, and signaling. Pharmacologic GH antagonism recapitulates the morphologic phenotype of pituitary tumors from which this mutation was identified, inducing the formation of cytoskeletal keratin aggresomes. This novel GHR mutation provides evidence for impaired hormone autofeedback in the pathogenesis of these pituitary tumors. It explains the lack of responsiveness to somatostatin analogue therapy of this tumor type, in contrast to the exquisite sensitivity of tumors that lack aggresomes, and has therapeutic implications for the safety of GH antagonism as a therapeutic modality in acromegaly. PMID:17671221

  14. Regulatory mechanisms that modulate signalling by G-protein-coupled receptors.

    PubMed Central

    Böhm, S K; Grady, E F; Bunnett, N W

    1997-01-01

    The large and functionally diverse group of G-protein-coupled receptors includes receptors for many different signalling molecules, including peptide and non-peptide hormones and neuro-transmitters, chemokines, prostanoids and proteinases. Their principal function is to transmit information about the extracellular environment to the interior of the cell by interacting with the heterotrimeric G-proteins, and they thereby participate in many aspects of regulation. Cellular responses to agonists of these receptors are usually rapidly attenuated. Mechanisms of signal attenuation include removal of agonists from the extracellular fluid, receptor desensitization, endocytosis and down-regulation. Agonists are removed by dilution, uptake by transporters and enzymic degradation. Receptor desensitization is mediated by receptor phosphorylation by G-protein receptor kinases and second-messenger kinases, interaction of phosphorylated receptors with arrestins and receptor uncoupling from G-proteins. Agonist-induced receptor endocytosis also contributes to desensitization by depleting the cell surface of high-affinity receptors, and recycling of internalized receptors contributes to resensitization of cellular responses. Receptor down-regulation is a form of desensitization that occurs during continuous, long-term exposure of cells to receptor agonists. Down-regulation, which may occur during the development of drug tolerance, is characterized by depletion of the cellular receptor content, and is probably mediated by alterations in the rates of receptor degradation and synthesis. These regulatory mechanisms are important, as they govern the ability of cells to respond to agonists. A greater understanding of the mechanisms that modulate signalling may lead to the development of new therapies and may help to explain the mechanism of drug tolerance. PMID:9078236

  15. Leukemia inhibitory factor receptor is structurally related to the IL-6 signal transducer, gp130.

    PubMed Central

    Gearing, D P; Thut, C J; VandeBos, T; Gimpel, S D; Delaney, P B; King, J; Price, V; Cosman, D; Beckmann, M P

    1991-01-01

    Leukemia inhibitory factor (LIF) is a cytokine with a broad range of activities that in many cases parallel those of interleukin-6 (IL-6) although LIF and IL-6 appear to be structurally unrelated. A cDNA clone encoding the human LIF receptor was isolated by expression screening of a human placental cDNA library. The LIF receptor is related to the gp130 'signal-transducing' component of the IL-6 receptor and to the G-CSF receptor, with the transmembrane and cytoplasmic regions of the LIF receptor and gp130 being most closely related. This relationship suggests a common signal transduction pathway for the two receptors and may help to explain similar biological effects of the two ligands. Murine cDNAs encoding soluble LIF receptors were isolated by cross-hybridization and share 70% amino acid sequence identity to the human sequence. Images PMID:1915266

  16. Rab8 modulates metabotropic glutamate receptor subtype 1 intracellular trafficking and signaling in a protein kinase C-dependent manner.

    PubMed

    Esseltine, Jessica L; Ribeiro, Fabiola M; Ferguson, Stephen S G

    2012-11-21

    Metabotropic glutamate receptors (mGluRs) are G protein-coupled receptors (GPCRs) that are activated by glutamate, the primary excitatory neurotransmitter in the CNS. Alterations in glutamate receptor signaling are implicated in neuropathologies such as Alzheimer's disease, ischemia, and Huntington's disease among others. Group 1 mGluRs (mGluR1 and mGluR5) are primarily coupled to Gα(q/11) leading to the activation of phospholipase C and the formation of diacylglycerol and inositol 1,4,5-trisphosphate, which results in the release of intracellular calcium stores and protein kinase C (PKC) activation. Desensitization, endocytosis, and recycling are major mechanisms of GPCR regulation, and the intracellular trafficking of GPCRs is linked to the Rab family of small G proteins. Rab8 is a small GTPase that is specifically involved in the regulation of secretory/recycling vesicles, modulation of the actin cytoskeleton, and cell polarity. Rab8 has been shown to regulate the synaptic delivery of AMPA receptors during long-term potentiation and during constitutive receptor recycling. We show here that Rab8 interacts with the C-terminal tail of mGluR1a in an agonist-dependent manner and plays a role in regulating of mGluR1a signaling and intracellular trafficking in human embryonic kidney 293 cells. Specifically, Rab8 expression attenuates mGluR1a-mediated inositol phosphate formation and calcium release from mouse neurons in a PKC-dependent manner, while increasing cell surface mGluR1a expression via decreased receptor endocytosis. These experiments provide us with an understanding of the role Rabs play in coordinated regulation of mGluR1a and how this impacts mGluR1a signaling.

  17. Structure of FGFR3 transmembrane domain dimer: implications for signaling and human pathologies.

    PubMed

    Bocharov, Eduard V; Lesovoy, Dmitry M; Goncharuk, Sergey A; Goncharuk, Marina V; Hristova, Kalina; Arseniev, Alexander S

    2013-11-01

    Fibroblast growth factor receptor 3 (FGFR3) transduces biochemical signals via lateral dimerization in the plasma membrane, and plays an important role in human development and disease. Eight different pathogenic mutations, implicated in cancers and growth disorders, have been identified in the FGFR3 transmembrane segment. Here, we describe the dimerization of the FGFR3 transmembrane domain in membrane-mimicking DPC/SDS (9/1) micelles. In the solved NMR structure, the two transmembrane helices pack into a symmetric left-handed dimer, with intermolecular stacking interactions occurring in the dimer central region. Some pathogenic mutations fall within the helix-helix interface, whereas others are located within a putative alternative interface. This implies that although the observed dimer structure is important for FGFR3 signaling, the mechanism of FGFR3-mediated transduction across the membrane is complex. We propose an FGFR3 signaling mechanism that is based on the solved structure, available structures of isolated soluble FGFR domains, and published biochemical and biophysical data.

  18. Cell Surface Receptors for Signal Transduction and Ligand Transport: A Design Principles Study

    PubMed Central

    Shankaran, Harish; Resat, Haluk; Wiley, H. Steven

    2007-01-01

    Receptors constitute the interface of cells to their external environment. These molecules bind specific ligands involved in multiple processes, such as signal transduction and nutrient transport. Although a variety of cell surface receptors undergo endocytosis, the systems-level design principles that govern the evolution of receptor trafficking dynamics are far from fully understood. We have constructed a generalized mathematical model of receptor–ligand binding and internalization to understand how receptor internalization dynamics encodes receptor function and regulation. A given signaling or transport receptor system represents a particular implementation of this module with a specific set of kinetic parameters. Parametric analysis of the response of receptor systems to ligand inputs reveals that receptor systems can be characterized as being: i) avidity-controlled where the response control depends primarily on the extracellular ligand capture efficiency, ii) consumption-controlled where the ability to internalize surface-bound ligand is the primary control parameter, and iii) dual-sensitivity where both the avidity and consumption parameters are important. We show that the transferrin and low-density lipoprotein receptors are avidity-controlled, the vitellogenin receptor is consumption-controlled, and the epidermal growth factor receptor is a dual-sensitivity receptor. Significantly, we show that ligand-induced endocytosis is a mechanism to enhance the accuracy of signaling receptors rather than merely serving to attenuate signaling. Our analysis reveals that the location of a receptor system in the avidity-consumption parameter space can be used to understand both its function and its regulation. PMID:17542642

  19. A role for kit receptor signaling in Leydig cell steroidogenesis.

    PubMed

    Rothschild, Gerson; Sottas, Chantal M; Kissel, Holger; Agosti, Valter; Manova, Katia; Hardy, Matthew P; Besmer, Peter

    2003-09-01

    Kit and its ligand, Kitl, function in hematopoiesis, melanogenesis, and gametogenesis. In the testis, Kitl is expressed by Sertoli cells and Kit is expressed by spermatogonia and Leydig cells. Kit functions are mediated by receptor autophosphorylation and subsequent association with signaling molecules, including phosphoinositide (PI) 3-kinase. We previously characterized the reproductive consequences of blocking Kit-mediated PI 3-kinase activation in KitY(719F)/Kit(Y719F) knockin mutant male mice. Only gametogenesis was affected in these mice, and males are sterile because of a block in spermatogenesis during the spermatogonial stages. In the present study, we investigated effects of the Kit(Y719F) mutation on Leydig cell development and steroidogenic function. Although the seminiferous tubules in testes of mutant animals are depleted of germ cells, the testes contain normal numbers of Leydig cells and the Leydig cells in these animals appear to have undergone normal differentiation. Evaluation of steroidogenesis in mutant animals indicates that testosterone levels are not significantly reduced in the periphery but that LH levels are increased 5-fold, implying an impairment of steroidogenesis in the mutant animals. Therefore, a role for Kit signaling in steroidogenesis in Leydig cells was sought in vitro. Purified Leydig cells from C57Bl6/J male mice were incubated with Kitl, and testosterone production was measured. Kitl-stimulated testosterone production was 2-fold higher than that in untreated controls. The Kitl-mediated testosterone biosynthesis in Leydig cells is PI 3-kinase dependent. In vitro, Leydig cells from mutant mice were steroidogenically more competent in response to LH than were normal Leydig cells. In contrast, Kitl-mediated testosterone production in these cells was comparable to that in normal cells. Because LH levels in mutant males are elevated and LH is known to stimulate testosterone biosynthesis, we proposed a model in which serum

  20. Progress toward advanced understanding of metabotropic glutamate receptors: structure, signaling and therapeutic indications

    PubMed Central

    Yin, Shen; Niswender, Colleen M.

    2014-01-01

    The metabotropic glutamate (mGlu) receptors are a group of Class C Seven Transmembrane Spanning/G Protein Coupled Receptors (7TMRs/GPCRs). These receptors are activated by glutamate, one of the standard amino acids and the major excitatory neurotransmitter. By activating G protein-dependent and non G protein-dependent signaling pathways, mGlus modulate glutamatergic transmission in both the periphery and throughout the central nervous system. Since the discovery of the first mGlu receptor, especially the last decade, a great deal of progress has been made in understanding the signaling, structure, pharmacological manipulation and therapeutic indications of the 8 mGlu members. PMID:24793301

  1. Cell surface receptors for signal transduction and ligand transport - a design principles study

    SciTech Connect

    Shankaran, Harish; Resat, Haluk; Wiley, H. S.

    2007-06-01

    Although many different receptors undergo endocytosis, the system-level design principles that govern the evolution of receptor dynamics are far from fully understood. We have constructed a generalized mathematical model to understand how receptor internalization dynamics encodes receptor function and regulation. Parametric analysis of the response of receptor systems to ligand inputs reveals that receptors can be categorized a being: i) avidity-controlled where the response control depends primarily on the extracelluar ligand capture efficiency, ii) consumption-controlled where the ability to internalize surface-bound ligand is the primary control parameter, and iii) dual-sensitivity where both the avidity and consumption parameters are important. We show that the transferrin and low-density lipoprotein receptors are avidity-controlled, the vitellogenin receptor is consumption-controlled and epidermal growth factor receptor is a dual-sensitivity receptor. Significantly, we show that ligand-induced endocytosis is a mechanism to anhance the accuracy of signaling receptors rather than serving to attenuate signaling. Our analysis reveals that the location of a receptor system in the avidity-consumption parameter space can be used to understand both its function and its regulations.

  2. Molecular determinants of agonist and antagonist signaling through the IL-36 receptor.

    PubMed

    Günther, Sebastian; Sundberg, Eric J

    2014-07-15

    The IL-1 family consists of 11 cytokines that control a complex network of proinflammatory signals critical for regulating immune responses to infections. They also play a central role in numerous chronic inflammatory disorders. Accordingly, inhibiting the activities of these cytokines is an important therapeutic strategy for treating autoimmune diseases and lymphomas. Agonist cytokines in the IL-1 family activate signaling by binding their cognate receptor and then recruiting a receptor accessory protein. Conversely, antagonist cytokines bind their cognate receptor but prohibit recruitment of receptor accessory protein, which precludes functional signaling complexes. The IL-36 subfamily of cytokines is the most diverse, including three agonists and at least one antagonist, and is the least well-characterized group within this family. Signaling through the IL-36 receptor directly stimulates dendritic cells and primes naive CD4 T cells for Th1 responses. Appropriately balanced IL-36 signaling is a critical determinant of skin and lung health. IL-36 signaling has been presumed to function analogously to IL-1 signaling. In this study, we have defined molecular determinants of agonist and antagonist signaling through the IL-36 receptor. We present the crystal structure of IL-36γ, which, to our knowledge, is the first reported structure of an IL-36 agonist. Using this structure as a guide, we designed a comprehensive series of IL-36 agonist/antagonist chimeric proteins for which we measured binding to the IL-36 receptor/IL-1 receptor accessory protein complex and functional activation and inhibition of signaling. Our data reveal how the fine specificity of IL-36 signaling is distinct from that of IL-1.

  3. Inflammatory PAF Receptor Signaling Initiates Hedgehog Signaling and Kidney Fibrogenesis During Ethanol Consumption.

    PubMed

    Latchoumycandane, Calivarathan; Hanouneh, Mohamad; Nagy, Laura E; McIntyre, Thomas M

    2015-01-01

    Acute inflammation either resolves or proceeds to fibrotic repair that replaces functional tissue. Pro-fibrotic hedgehog signaling and induction of its Gli transcription factor in pericytes induces fibrosis in kidney, but molecular instructions connecting inflammation to fibrosis are opaque. We show acute kidney inflammation resulting from chronic ingestion of the common xenobiotic ethanol initiates Gli1 transcription and hedgehog synthesis in kidney pericytes, and promotes renal fibrosis. Ethanol ingestion stimulated transcription of TGF-ß, collagens I and IV, and alpha-smooth muscle actin with accumulation of these proteins. This was accompanied by deposition of extracellular fibrils. Ethanol catabolism by CYP2E1 in kidney generates local reactive oxygen species that oxidize cellular phospholipids to phospholipid products that activate the Platelet-activating Factor receptor (PTAFR) for inflammatory phospholipids. Genetically deleting this ptafr locus abolished accumulation of mRNA for TGF-ß, collagen IV, and α-smooth muscle actin. Loss of PTAFR also abolished ethanol-stimulated Sonic (Shh) and Indian hedgehog (Ihh) expression, and abolished transcription and accumulation of Gli1. Shh induced in pericytes and Ihh in tubules escaped to urine of ethanol-fed mice. Neutrophil myeloperoxidase (MPO) is required for ethanol-induced kidney inflammation, and Shh was not present in kidney or urine of mpo-/- mice. Shh also was present in urine of patients with acute kidney injury, but not in normal individuals or those with fibrotic liver cirrhosis We conclude neither endogenous PTAFR signaling nor CYP2E1-generated radicals alone are sufficient to initiate hedgehog signaling, but instead PTAFR-dependent neutrophil infiltration with myeloperoxidase activation is necessary to initiate ethanol-induced fibrosis in kidney. We also show fibrogenic mediators escape to urine, defining a new class of urinary mechanistic biomarkers of fibrogenesis for an organ not commonly

  4. Y2 receptor signalling in NPY neurons controls bone formation and fasting induced feeding but not spontaneous feeding.

    PubMed

    Qi, Yue; Fu, Melissa; Herzog, Herbert

    2016-02-01

    Y2 receptors have been implicated in the development of obesity and are a potential target for obesity treatment due to their known role of inhibiting neuropeptide Y (NPY) induced feeding responses. However, the precise neuronal population on which Y2 receptors act to fulfil this role is less clear. Here we utilise a novel inducible, postnatal onset NPY neurons specific deletion model to investigate the functional consequences of loss of Y2 signalling in this population of neurons on feeding and energy homeostasis regulation. While the consequences of lack of Y2 signalling in NPY neurons are confirmed in terms of the uncoupling of suppression/increasing of NPY and pro-opiomelanocortin (POMC) mRNA expression in the arcuate nuclei (Arc), respectively, this lack of Y2 signalling surprisingly does not have any significant effect on spontaneous food intake. Fasting induced food intake, however, is strongly increased but only in the first 1h after re-feeding. Consequently no significant changes in body weight are being observed although body weight gain is increased in male mice after postnatal onset Y2 deletion. Importantly, another known function of central Y2 receptor signalling, the suppression of bone formation is conserved in this conditional model with whole body bone mineral content being decreased. Taken together this model confirms the critical role of Y2 signalling to control NPY and associated POMC expression in the Arc, but also highlights the possibility that others, non-NPY neuronal Y2 receptors, are also involved in controlling feeding and energy homeostasis regulation.

  5. E3 Ubiquitin Ligases Pellinos as Regulators of Pattern Recognition Receptor Signaling and Immune responses

    PubMed Central

    Medvedev, Andrei E.; Murphy, Michael; Zhou, Hao; Li, Xiaoxia

    2015-01-01

    SUMMARY Pellinos are a family of E3 ubiquitin ligases discovered for their role in catalyzing K63-linked polyubiquitination of Pelle, an IL-1 receptor-associated kinase homologue in the Drosophila Toll pathway. Subsequent studies have revealed the central and non-redundant roles of mammalian Pellino-1, Pellino-2 and Pelino-3 in signaling pathways emanating from IL-1 receptors, Toll-like receptors, NOD-like receptors, T- and B-cell receptors. While Pellinos ability to interact with many signaling intermediates suggested their scaffolding roles, recent findings in mice expressing ligase-inactive Pellinos demonstrated the importance of Pellino ubiquitin ligase activity. Cell-specific functions of Pellinos have emerged, e.g., Pellino-1 being a negative regulator in T-lymphocytes and a positive regulator in myeloid cells, and details of molecular regulation of receptor signaling by various members of the Pellino family have been revealed. In this review, we have summarized current information about Pellino-mediated regulation of signaling by pattern recognition receptors, T-cell and B-cell receptors and TNF receptors, and discuss Pellino’s role in sepsis and infectious diseases, as well as in autoimmune, inflammatory and allergic disorders. We also provide our perspective on the potential of targeting Pellinos with peptide- or small molecule-based drug compounds as a new therapeutic approach for septic shock and autoimmune pathologies. PMID:26085210

  6. Symmetric signaling by an asymmetric 1 erythropoietin: 2 erythropoietin receptor complex.

    PubMed

    Zhang, Yingxin L; Radhakrishnan, Mala L; Lu, Xiaohui; Gross, Alec W; Tidor, Bruce; Lodish, Harvey F

    2009-01-30

    Via sites 1 and 2, erythropoietin binds asymmetrically to two identical receptor monomers, although it is unclear how asymmetry affects receptor activation and signaling. Here we report the design and validation of two mutant erythropoietin receptors that probe the role of individual members of the receptor dimer by selectively binding either site 1 or site 2 on erythropoietin. Ba/F3 cells expressing either mutant receptor do not respond to erythropoietin, but cells co-expressing both receptors respond to erythropoietin by proliferation and activation of the JAK2-Stat5 pathway. A truncated receptor with only one cytosolic tyrosine (Y343) is sufficient for signaling in response to erythropoietin, regardless of the monomer on which it is located. Similarly, only one receptor in the dimer needs a juxtamembrane hydrophobic L253 or W258 residue, essential for JAK2 activation. We conclude that despite asymmetry in the ligand-receptor interaction, both sides are competent for signaling, and appear to signal equally.

  7. E3 ubiquitin ligases Pellinos as regulators of pattern recognition receptor signaling and immune responses.

    PubMed

    Medvedev, Andrei E; Murphy, Michael; Zhou, Hao; Li, Xiaoxia

    2015-07-01

    Pellinos are a family of E3 ubiquitin ligases discovered for their role in catalyzing K63-linked polyubiquitination of Pelle, an interleukin-1 (IL-1) receptor-associated kinase homolog in the Drosophila Toll pathway. Subsequent studies have revealed the central and non-redundant roles of mammalian Pellino-1, Pellino-2, and Pelino-3 in signaling pathways emanating from IL-1 receptors, Toll-like receptors, NOD-like receptors, T- and B-cell receptors. While Pellinos ability to interact with many signaling intermediates suggested their scaffolding roles, recent findings in mice expressing ligase-inactive Pellinos demonstrated the importance of Pellino ubiquitin ligase activity. Cell-specific functions of Pellinos have emerged, e.g. Pellino-1 being a negative regulator in T lymphocytes and a positive regulator in myeloid cells, and details of molecular regulation of receptor signaling by various members of the Pellino family have been revealed. In this review, we summarize current information about Pellino-mediated regulation of signaling by pattern recognition receptors, T-cell and B-cell receptors and tumor necrosis factor receptors, and discuss Pellinos roles in sepsis and infectious diseases, as well as in autoimmune, inflammatory, and allergic disorders. We also provide our perspective on the potential of targeting Pellinos with peptide- or small molecule-based drug compounds as a new therapeutic approach for septic shock and autoimmune pathologies.

  8. Regulation of dopamine D2 receptor-mediated extracellular signal-regulated kinase signaling and spine formation by GABAA receptors in hippocampal neurons.

    PubMed

    Yoon, Dong-Hoon; Yoon, Sehyoun; Kim, Donghoon; Kim, Hyun; Baik, Ja-Hyun

    2015-01-23

    Dopamine (DA) signaling via DA receptors is known to control hippocampal activity that contributes to learning, memory, and synaptic plasticity. In primary hippocampal neuronal culture, we observed that dopamine D2 receptors (D2R) co-localized with certain subtypes of GABAA receptors, namely α1, β3, and γ2 subunits, as revealed by double immunofluorocytochemical analysis. Treatment with the D2R agonist, quinpirole, was shown to elicit an increase in phosphorylation of extracellular signal-regulated kinase (ERK) in hippocampal neurons. This phosphorylation was inhibited by pretreatment with the GABAA receptor agonist, muscimol. Furthermore, treatment of hippocampal neurons with quinpirole increased the dendritic spine density and this regulation was totally blocked by pretreatment with a MAP kinase kinase (MEK) inhibitor (PD98059), D2R antagonist (haloperidol), or by the GABAA receptor agonist, muscimol. These results suggest that D2R-mediated ERK phosphorylation can control spine formation and that the GABAA receptor negatively regulates the D2R-induced spine formation through ERK signaling in hippocampal neurons, thus indicating a potential role of D2R in the control of hippocampal neuronal excitability. PMID:25483619

  9. High Cell Surface Death Receptor Expression Determines Type I Versus Type II Signaling*

    PubMed Central

    Meng, Xue Wei; Peterson, Kevin L.; Dai, Haiming; Schneider, Paula; Lee, Sun-Hee; Zhang, Jin-San; Koenig, Alexander; Bronk, Steve; Billadeau, Daniel D.; Gores, Gregory J.; Kaufmann, Scott H.

    2011-01-01

    Previous studies have suggested that there are two signaling pathways leading from ligation of the Fas receptor to induction of apoptosis. Type I signaling involves Fas ligand-induced recruitment of large amounts of FADD (FAS-associated death domain protein) and procaspase 8, leading to direct activation of caspase 3, whereas type II signaling involves Bid-mediated mitochondrial perturbation to amplify a more modest death receptor-initiated signal. The biochemical basis for this dichotomy has previously been unclear. Here we show that type I cells have a longer half-life for Fas message and express higher amounts of cell surface Fas, explaining the increased recruitment of FADD and subsequent signaling. Moreover, we demonstrate that cells with type II Fas signaling (Jurkat or HCT-15) can signal through a type I pathway upon forced receptor overexpression and that shRNA-mediated Fas down-regulation converts cells with type I signaling (A498) to type II signaling. Importantly, the same cells can exhibit type I signaling for Fas and type II signaling for TRAIL (TNF-α-related apoptosis-inducing ligand), indicating that the choice of signaling pathway is related to the specific receptor, not some other cellular feature. Additional experiments revealed that up-regulation of cell surface death receptor 5 levels by treatment with 7-ethyl-10-hydroxy-camptothecin converted TRAIL signaling in HCT116 cells from type II to type I. Collectively, these results suggest that the type I/type II dichotomy reflects differences in cell surface death receptor expression. PMID:21865165

  10. Signal transduction in light–oxygen–voltage receptors lacking the adduct-forming cysteine residue

    PubMed Central

    Yee, Estella F.; Diensthuber, Ralph P.; Vaidya, Anand T.; Borbat, Peter P.; Engelhard, Christopher; Freed, Jack H.; Bittl, Robert; Möglich, Andreas; Crane, Brian R.

    2015-01-01

    Light–oxygen–voltage (LOV) receptors sense blue light through the photochemical generation of a covalent adduct between a flavin-nucleotide chromophore and a strictly conserved cysteine residue. Here we show that, after cysteine removal, the circadian-clock LOV-protein Vivid still undergoes light-induced dimerization and signalling because of flavin photoreduction to the neutral semiquinone (NSQ). Similarly, photoreduction of the engineered LOV histidine kinase YF1 to the NSQ modulates activity and downstream effects on gene expression. Signal transduction in both proteins hence hinges on flavin protonation, which is common to both the cysteinyl adduct and the NSQ. This general mechanism is also conserved by natural cysteine-less, LOV-like regulators that respond to chemical or photoreduction of their flavin cofactors. As LOV proteins can react to light even when devoid of the adduct-forming cysteine, modern LOV photoreceptors may have arisen from ancestral redox-active flavoproteins. The ability to tune LOV reactivity through photoreduction may have important implications for LOV mechanism and optogenetic applications. PMID:26648256

  11. Signal transduction in light-oxygen-voltage receptors lacking the adduct-forming cysteine residue.

    PubMed

    Yee, Estella F; Diensthuber, Ralph P; Vaidya, Anand T; Borbat, Peter P; Engelhard, Christopher; Freed, Jack H; Bittl, Robert; Möglich, Andreas; Crane, Brian R

    2015-12-09

    Light-oxygen-voltage (LOV) receptors sense blue light through the photochemical generation of a covalent adduct between a flavin-nucleotide chromophore and a strictly conserved cysteine residue. Here we show that, after cysteine removal, the circadian-clock LOV-protein Vivid still undergoes light-induced dimerization and signalling because of flavin photoreduction to the neutral semiquinone (NSQ). Similarly, photoreduction of the engineered LOV histidine kinase YF1 to the NSQ modulates activity and downstream effects on gene expression. Signal transduction in both proteins hence hinges on flavin protonation, which is common to both the cysteinyl adduct and the NSQ. This general mechanism is also conserved by natural cysteine-less, LOV-like regulators that respond to chemical or photoreduction of their flavin cofactors. As LOV proteins can react to light even when devoid of the adduct-forming cysteine, modern LOV photoreceptors may have arisen from ancestral redox-active flavoproteins. The ability to tune LOV reactivity through photoreduction may have important implications for LOV mechanism and optogenetic applications.

  12. Tie1: an orphan receptor provides context for angiopoietin-2/Tie2 signaling.

    PubMed

    Mueller, Sarah B; Kontos, Christopher D

    2016-09-01

    Angiopoietin-1/Tie2 (ANG1/Tie2) signaling is well documented as regulating angiogenesis and vessel maturation. This pathway is complicated by involvement of the orphan receptor Tie1, which has been implicated as both a positive and negative regulator of ANG1/Tie2 signaling, and ANG2, which can serve as both a Tie2 agonist and antagonist, depending on the context. Two papers in this issue of the JCI provide new insight into this complicated pathway. Korhonen et al. reveal that Tie1 acts to modulate the effects of ANG1 and ANG2 on Tie2 in vitro and in vivo. Kim et al. demonstrate that ANG2 acts as a Tie2 agonist in non-pathological conditions, whereas in the setting of inflammation, ANG2 functions as a Tie2 antagonist and promotes vascular dysfunction. Both studies indicate that inflammation promotes cleavage of the ectodomain of Tie1 and that this cleavage event corresponds with the switch of ANG2 from a Tie2 agonist to an antagonist. The results of these studies lay the groundwork for future strategies to therapeutically exploit this pathway in diseases characterized by adverse vascular remodeling and increased permeability. PMID:27548526

  13. Location-Dependent Signaling of the Group 1 Metabotropic Glutamate Receptor mGlu5

    PubMed Central

    Jong, Yuh-Jiin I.; Sergin, Ismail; Purgert, Carolyn A.

    2014-01-01

    Although G protein–coupled receptors are primarily known for converting extracellular signals into intracellular responses, some receptors, such as the group 1 metabotropic glutamate receptor, mGlu5, are also localized on intracellular membranes where they can mediate both overlapping and unique signaling effects. Thus, besides “ligand bias,” whereby a receptor’s signaling modality can shift from G protein dependence to independence, canonical mGlu5 receptor signaling can also be influenced by “location bias” (i.e., the particular membrane and/or cell type from which it signals). Because mGlu5 receptors play important roles in both normal development and in disorders such as Fragile X syndrome, autism, epilepsy, addiction, anxiety, schizophrenia, pain, dyskinesias, and melanoma, a large number of drugs are being developed to allosterically target this receptor. Therefore, it is critical to understand how such drugs might be affecting mGlu5 receptor function on different membranes and in different brain regions. Further elucidation of the site(s) of action of these drugs may determine which signal pathways mediate therapeutic efficacy. PMID:25326002

  14. Tuning cytokine receptor signaling by re-orienting dimer geometry with surrogate ligands.

    PubMed

    Moraga, Ignacio; Wernig, Gerlinde; Wilmes, Stephan; Gryshkova, Vitalina; Richter, Christian P; Hong, Wan-Jen; Sinha, Rahul; Guo, Feng; Fabionar, Hyna; Wehrman, Tom S; Krutzik, Peter; Demharter, Samuel; Plo, Isabelle; Weissman, Irving L; Minary, Peter; Majeti, Ravindra; Constantinescu, Stefan N; Piehler, Jacob; Garcia, K Christopher

    2015-03-12

    Most cell-surface receptors for cytokines and growth factors signal as dimers, but it is unclear whether remodeling receptor dimer topology is a viable strategy to "tune" signaling output. We utilized diabodies (DA) as surrogate ligands in a prototypical dimeric receptor-ligand system, the cytokine Erythropoietin (EPO) and its receptor (EpoR), to dimerize EpoR ectodomains in non-native architectures. Diabody-induced signaling amplitudes varied from full to minimal agonism, and structures of these DA/EpoR complexes differed in EpoR dimer orientation and proximity. Diabodies also elicited biased or differential activation of signaling pathways and gene expression profiles compared to EPO. Non-signaling diabodies inhibited proliferation of erythroid precursors from patients with a myeloproliferative neoplasm due to a constitutively active JAK2V617F mutation. Thus, intracellular oncogenic mutations causing ligand-independent receptor activation can be counteracted by extracellular ligands that re-orient receptors into inactive dimer topologies. This approach has broad applications for tuning signaling output for many dimeric receptor systems. PMID:25728669

  15. Tuning cytokine receptor signaling by re-orienting dimer geometry with surrogate ligands.

    PubMed

    Moraga, Ignacio; Wernig, Gerlinde; Wilmes, Stephan; Gryshkova, Vitalina; Richter, Christian P; Hong, Wan-Jen; Sinha, Rahul; Guo, Feng; Fabionar, Hyna; Wehrman, Tom S; Krutzik, Peter; Demharter, Samuel; Plo, Isabelle; Weissman, Irving L; Minary, Peter; Majeti, Ravindra; Constantinescu, Stefan N; Piehler, Jacob; Garcia, K Christopher

    2015-03-12

    Most cell-surface receptors for cytokines and growth factors signal as dimers, but it is unclear whether remodeling receptor dimer topology is a viable strategy to "tune" signaling output. We utilized diabodies (DA) as surrogate ligands in a prototypical dimeric receptor-ligand system, the cytokine Erythropoietin (EPO) and its receptor (EpoR), to dimerize EpoR ectodomains in non-native architectures. Diabody-induced signaling amplitudes varied from full to minimal agonism, and structures of these DA/EpoR complexes differed in EpoR dimer orientation and proximity. Diabodies also elicited biased or differential activation of signaling pathways and gene expression profiles compared to EPO. Non-signaling diabodies inhibited proliferation of erythroid precursors from patients with a myeloproliferative neoplasm due to a constitutively active JAK2V617F mutation. Thus, intracellular oncogenic mutations causing ligand-independent receptor activation can be counteracted by extracellular ligands that re-orient receptors into inactive dimer topologies. This approach has broad applications for tuning signaling output for many dimeric receptor systems.

  16. Testin, a novel binding partner of the calcium-sensing receptor, enhances receptor-mediated Rho-kinase signalling

    SciTech Connect

    Magno, Aaron L.; Ingley, Evan; Brown, Suzanne J.; Conigrave, Arthur D.; Ratajczak, Thomas; Ward, Bryan K.

    2011-09-09

    Highlights: {yields} A yeast two-hybrid screen revealed testin bound to the calcium-sensing receptor. {yields} The second zinc finger of LIM domain 1 of testin is critical for interaction. {yields} Testin bound to a region of the receptor tail important for cell signalling. {yields} Testin and receptor interaction was confirmed in mammalian (HEK293) cells. {yields} Overexpression of testin enhanced receptor-mediated Rho signalling in HEK293 cells. -- Abstract: The calcium-sensing receptor (CaR) plays an integral role in calcium homeostasis and the regulation of other cellular functions including cell proliferation and cytoskeletal organisation. The multifunctional nature of the CaR is manifested through ligand-dependent stimulation of different signalling pathways that are also regulated by partner binding proteins. Following a yeast two-hybrid library screen using the intracellular tail of the CaR as bait, we identified several novel binding partners including the focal adhesion protein, testin. Testin has not previously been shown to interact with cell surface receptors. The sites of interaction between the CaR and testin were mapped to the membrane proximal region of the receptor tail and the second zinc-finger of LIM domain 1 of testin, the integrity of which was found to be critical for the CaR-testin interaction. The CaR-testin association was confirmed in HEK293 cells by coimmunoprecipitation and confocal microscopy studies. Ectopic expression of testin in HEK293 cells stably expressing the CaR enhanced CaR-stimulated Rho activity but had no effect on CaR-stimulated ERK signalling. These results suggest an interplay between the CaR and testin in the regulation of CaR-mediated Rho signalling with possible effects on the cytoskeleton.

  17. Conformational Changes in the GM-CSF Receptor Suggest a Molecular Mechanism for Affinity Conversion and Receptor Signaling.

    PubMed

    Broughton, Sophie E; Hercus, Timothy R; Nero, Tracy L; Dottore, Mara; McClure, Barbara J; Dhagat, Urmi; Taing, Houng; Gorman, Michael A; King-Scott, Jack; Lopez, Angel F; Parker, Michael W

    2016-08-01

    The GM-CSF, IL-3, and IL-5 receptors constitute the βc family, playing important roles in inflammation, autoimmunity, and cancer. Typical of heterodimeric type I cytokine receptors, signaling requires recruitment of the shared subunit to the initial cytokine:α subunit binary complex through an affinity conversion mechanism. This critical process is poorly understood due to the paucity of crystal structures of both binary and ternary receptor complexes for the same cytokine. We have now solved the structure of the binary GM-CSF:GMRα complex at 2.8-Å resolution and compared it with the structure of the ternary complex, revealing distinct conformational changes. Guided by these differences we performed mutational and functional studies that, importantly, show GMRα interactions playing a major role in receptor signaling while βc interactions control high-affinity binding. These results support the notion that conformational changes underlie the mechanism of GM-CSF receptor activation and also suggest how related type I cytokine receptors signal. PMID:27396825

  18. G protein-coupled receptor signalling in astrocytes in health and disease: a focus on metabotropic glutamate receptors.

    PubMed

    Bradley, Sophie J; Challiss, R A John

    2012-08-01

    Work published over the past 10-15 years has caused the neuroscience community to engage in a process of constant re-evaluation of the roles of glial cells in the mammalian central nervous system. Recent emerging evidence suggests that, in addition to carrying out various homeostatic functions within the CNS, astrocytes can also engage in a two-way dialogue with neurons. Astrocytes possess many of the receptors, and some of the ion channels, present in neurons endowing them with an ability to sense and respond to an array of neuronal signals. In addition, an expanding number of small molecules and proteins have been shown to be released by astrocytes in both health and disease. In this commentary we will highlight advances in our understanding of G protein-coupled receptor signalling in astrocytes, with a particular emphasis on metabotropic glutamate (mGlu) receptors. Discussion will focus on the major mGlu receptors expressed in astrocytes, mGlu3 and mGlu5, how these receptors can influence different aspects of astrocyte physiology, and how signalling by these G protein-coupled receptors might change under pathophysiological circumstances. PMID:22531220

  19. Angiotensin II type 1a receptor signalling directly contributes to the increased arrhythmogenicity in cardiac hypertrophy

    PubMed Central

    Yasuno, Shinji; Kuwahara, Koichiro; Kinoshita, Hideyuki; Yamada, Chinatsu; Nakagawa, Yasuaki; Usami, Satoru; Kuwabara, Yoshihiro; Ueshima, Kenji; Harada, Masaki; Nishikimi, Toshio; Nakao, Kazuwa

    2013-01-01

    BACKGROUND AND PURPOSE Angiotensin II has been implicated in the development of various cardiovascular ailments, including cardiac hypertrophy and heart failure. The fact that inhibiting its signalling reduced the incidences of both sudden cardiac death and heart failure in several large-scale clinical trials suggests that angiotensin II is involved in increased cardiac arrhythmogenicity during the development of heart failure. However, because angiotensin II also promotes structural remodelling, including cardiomyocyte hypertrophy and cardiac fibrosis, it has been difficult to assess its direct contribution to cardiac arrhythmogenicity independently of the structural effects. EXPERIMENTAL APPROACH We induced cardiac hypertrophy in wild-type (WT) and angiotensin II type 1a receptor knockout (AT1aR-KO) mice by transverse aortic constriction (TAC). The susceptibility to ventricular tachycardia (VT) assessed in an in vivo electrophysiological study was compared in the two genotypes. The effect of acute pharmacological blockade of AT1R on the incidences of arrhythmias was also assessed. KEY RESULTS As described previously, WT and AT1aR-KO mice with TAC developed cardiac hypertrophy to the same degree, but the incidence of VT was much lower in the latter. Moreover, although TAC induced an increase in tyrosine phosphorylation of connexin 43, a critical component of gap junctional channels, and a reduction in ventricular levels of connexin 43 protein in both genotypes, the effect was significantly ameliorated in AT1aR-KO mice. Acute pharmacological blockade of AT1R also reduced the incidence of arrhythmias. CONCLUSIONS AND IMPLICATIONS Our findings demonstrate that AT1aR-mediated signalling makes a direct contribution to the increase in arrhythmogenicity in hypertrophied hearts independently of structural remodelling. PMID:23937445

  20. Signaling Modification by GPCR Heteromer and Its Implication on X-Linked Nephrogenic Diabetes Insipidus.

    PubMed

    Ng, Hans K H; Harikumar, Kaleeckal G; Miller, Laurence J; Chow, Billy K C

    2016-01-01

    The involvement of secretin (SCT) and secretin receptor (SCTR) in regulating body water homeostasis is well established. Identified as one of the vasopressin (Vp)-independent mechanisms in fluid balance, SCT regulates aquaporin 2 (AQP2) in the kidney distal collecting duct cells through activating intracellular cAMP production. This ability to bypass Vp-mediated water reabsorption in kidney implicates SCT's potential to treat nephrogenic diabetes insipidus (NDI). Research on NDI in the past has largely been focused on the searching for mutations in vasopressin receptor 2 (AVPR2), while the functional relationship between SCTR, AVPR2 and NDI remains unclear. Here, we demonstrate the interaction between SCTR and AVPR2 to modulate cellular signaling in vitro. Interestingly, we show in this report that upon heteromer formation with SCTR, R137H, a NDI-causing AVPR2 mutant that is defective in trafficking to cell surface, can functionally be rescued. Our data may provide an explanation for this clinically mild case of NDI, and insights into the pathological development of NDI in the future. PMID:27649563

  1. Signaling Modification by GPCR Heteromer and Its Implication on X-Linked Nephrogenic Diabetes Insipidus.

    PubMed

    Ng, Hans K H; Harikumar, Kaleeckal G; Miller, Laurence J; Chow, Billy K C

    2016-01-01

    The involvement of secretin (SCT) and secretin receptor (SCTR) in regulating body water homeostasis is well established. Identified as one of the vasopressin (Vp)-independent mechanisms in fluid balance, SCT regulates aquaporin 2 (AQP2) in the kidney distal collecting duct cells through activating intracellular cAMP production. This ability to bypass Vp-mediated water reabsorption in kidney implicates SCT's potential to treat nephrogenic diabetes insipidus (NDI). Research on NDI in the past has largely been focused on the searching for mutations in vasopressin receptor 2 (AVPR2), while the functional relationship between SCTR, AVPR2 and NDI remains unclear. Here, we demonstrate the interaction between SCTR and AVPR2 to modulate cellular signaling in vitro. Interestingly, we show in this report that upon heteromer formation with SCTR, R137H, a NDI-causing AVPR2 mutant that is defective in trafficking to cell surface, can functionally be rescued. Our data may provide an explanation for this clinically mild case of NDI, and insights into the pathological development of NDI in the future.

  2. Signaling Modification by GPCR Heteromer and Its Implication on X-Linked Nephrogenic Diabetes Insipidus

    PubMed Central

    Harikumar, Kaleeckal G.; Miller, Laurence J.; Chow, Billy K. C.

    2016-01-01

    The involvement of secretin (SCT) and secretin receptor (SCTR) in regulating body water homeostasis is well established. Identified as one of the vasopressin (Vp)-independent mechanisms in fluid balance, SCT regulates aquaporin 2 (AQP2) in the kidney distal collecting duct cells through activating intracellular cAMP production. This ability to bypass Vp-mediated water reabsorption in kidney implicates SCT’s potential to treat nephrogenic diabetes insipidus (NDI). Research on NDI in the past has largely been focused on the searching for mutations in vasopressin receptor 2 (AVPR2), while the functional relationship between SCTR, AVPR2 and NDI remains unclear. Here, we demonstrate the interaction between SCTR and AVPR2 to modulate cellular signaling in vitro. Interestingly, we show in this report that upon heteromer formation with SCTR, R137H, a NDI-causing AVPR2 mutant that is defective in trafficking to cell surface, can functionally be rescued. Our data may provide an explanation for this clinically mild case of NDI, and insights into the pathological development of NDI in the future. PMID:27649563

  3. Signalling properties and pharmacology of a 5-HT7 -type serotonin receptor from Tribolium castaneum.

    PubMed

    Vleugels, R; Lenaerts, C; Vanden Broeck, J; Verlinden, H

    2014-04-01

    In the last decade, genome sequence data and gene structure information on invertebrate receptors has been greatly expanded by large sequencing projects and cloning studies. This information is of great value for the identification of receptors; however, functional and pharmacological data are necessary for an accurate receptor classification and for practical applications. In insects, an important group of neurotransmitter and neurohormone receptors, for which ample sequence information is available but pharmacological information is missing, are the biogenic amine G protein-coupled receptors (GPCRs). In the present study, we investigated the sequence information, pharmacology and signalling properties of a 5-HT7 -type serotonin receptor from the red flour beetle, Tribolium castaneum (Trica5-HT7 ). The receptor encoding cDNA shows considerable sequence similarity with cognate 5-HT7 receptors and phylogenetic analysis also clusters the receptor within this 5-HT receptor group. Real-time reverse transcription PCR demonstrated high expression levels in the brain, indicating the possible importance of this receptor in neural processes. Trica5-HT7 was dose-dependently activated by 5-HT, which induced elevated intracellular cyclic AMP levels but had no effect on calcium signalling. The synthetic agonists, α-methyl 5-HT, 5-methoxytryptamine, 5-carboxamidotryptamine and 8-hydroxy-2-(dipropylamino)tetralin hydrobromide, showed a response, although with a much lower potency and efficacy than 5-HT. Ketanserin and methiothepin were the most potent antagonists. Both showed characteristics of competitive inhibition on Trica5-HT7 . The signalling pathway and pharmacological profile offer important information that will facilitate functional and comparative studies of 5-HT receptors in insects and other invertebrates. The pharmacology of invertebrate 5-HT receptors differs considerably from that of vertebrates. The present study may therefore contribute to establishing a more

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

    PubMed

    Copple, Bryan L; Li, Tiangang

    2016-02-01

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

  5. Molecular and functional profiling of histamine receptor-mediated calcium ion signals in different cell lines.

    PubMed

    Meisenberg, Annika; Kaschuba, Dagmar; Balfanz, Sabine; Jordan, Nadine; Baumann, Arnd

    2015-10-01

    Calcium ions (Ca(2+)) play a pivotal role in cellular physiology. Often Ca(2+)-dependent processes are studied in commonly available cell lines. To induce Ca(2+) signals on demand, cells may need to be equipped with additional proteins. A prominent group of membrane proteins evoking Ca(2+) signals are G-protein coupled receptors (GPCRs). These proteins register external signals such as photons, odorants, and neurotransmitters and convey ligand recognition into cellular responses, one of which is Ca(2+) signaling. To avoid receptor cross-talk or cross-activation with introduced proteins, the repertoire of cell-endogenous receptors must be known. Here we examined the presence of histamine receptors in six cell lines frequently used as hosts to study cellular signaling processes. In a concentration-dependent manner, histamine caused a rise in intracellular Ca(2+) in HeLa, HEK 293, and COS-1 cells. The concentration for half-maximal activation (EC50) was in the low micromolar range. In individual cells, transient Ca(2+) signals and Ca(2+) oscillations were uncovered. The results show that (i) HeLa, HEK 293, and COS-1 cells express sufficient amounts of endogenous receptors to study cellular Ca(2+) signaling processes directly and (ii) these cell lines are suitable for calibrating Ca(2+) biosensors in situ based on histamine receptor evoked responses.

  6. Multiple GPCR conformations and signalling pathways: implications for antagonist affinity estimates

    PubMed Central

    Baker, Jillian G.; Hill, Stephen J.

    2007-01-01

    Antagonist affinity measurements have traditionally been considered important in characterizing the cell-surface receptors present in a particular cell or tissue. A central assumption has been that antagonist affinity is constant for a given receptor–antagonist interaction, regardless of the agonist used to stimulate that receptor or the downstream response that is measured. As a consequence, changes in antagonist affinity values have been taken as initial evidence for the presence of novel receptor subtypes. Emerging evidence suggests, however, that receptors can possess multiple binding sites and the same receptor can show different antagonist affinity measurements under distinct experimental conditions. Here, we discuss several mechanisms by which antagonists have different affinities for the same receptor as a consequence of allosterism, coupling to different G proteins, multiple (but non-interacting) receptor sites, and signal-pathway-dependent pharmacology (where the pharmacology observed varies depending on the signalling pathway measured). PMID:17629959

  7. Liver X Receptors Regulate the Transcriptional Activity of the Glucocorticoid Receptor: Implications for the Carbohydrate Metabolism

    PubMed Central

    Nader, Nancy; Ng, Sinnie Sin Man; Wang, Yonghong; Abel, Brent S.; Chrousos, George P.; Kino, Tomoshige

    2012-01-01

    GLUCOCORTICOIDS are steroid hormones that strongly influence intermediary carbohydrate metabolism by increasing the transcription rate of glucose-6-phosphatase (G6Pase), a key enzyme of gluconeogenesis, and suppress the immune system through the glucocorticoid receptor (GR). The liver X receptors (LXRs), on the other hand, bind to cholesterol metabolites, heterodimerize with the retinoid X receptor (RXR), and regulate the cholesterol turnover, the hepatic glucose metabolism by decreasing the expression of G6Pase, and repress a set of inflammatory genes in immune cells. Since the actions of these receptors overlap with each other, we evaluated the crosstalk between the GR- and LXR-mediated signaling systems. Transient transfection-based reporter assays and gene silencing methods using siRNAs for LXRs showed that overexpression/ligand (GW3965) activation of LXRs/RXRs repressed GR-stimulated transactivation of certain glucocorticoid response element (GRE)-driven promoters in a gene-specific fashion. Activation of LXRs by GW3965 attenuated dexamethasone-stimulated elevation of circulating glucose in rats. It also suppressed dexamethasone-induced mRNA expression of hepatic glucose-6-phosphatase (G6Pase) in rats, mice and human hepatoma HepG2 cells, whereas endogenous, unliganded LXRs were required for dexamethasone-induced mRNA expression of phosphoenolpyruvate carboxylase. In microarray transcriptomic analysis of rat liver, GW3965 differentially regulated glucocorticoid-induced transcriptional activity of about 15% of endogenous glucocorticoid-responsive genes. To examine the mechanism through which activated LXRs attenuated GR transcriptional activity, we examined LXRα/RXRα binding to GREs. Endogenous LXRα/RXRα bound GREs and inhibited GR binding to these DNA sequences both in in vitro and in vivo chromatin immunoprecipitation assays, while their recombinant proteins did so on classic or G6Pase GREs in gel mobility shift assays. We propose that administration of

  8. Heterotrimeric G Protein-coupled Receptor Signaling in Yeast Mating Pheromone Response*

    PubMed Central

    Alvaro, Christopher G.; Thorner, Jeremy

    2016-01-01

    The DNAs encoding the receptors that respond to the peptide mating pheromones of the budding yeast Saccharomyces cerevisiae were isolated in 1985, and were the very first genes for agonist-binding heterotrimeric G protein-coupled receptors (GPCRs) to be cloned in any organism. Now, over 30 years later, this yeast and its receptors continue to provide a pathfinding experimental paradigm for investigating GPCR-initiated signaling and its regulation, as described in this retrospective overview. PMID:26907689

  9. Mechanisms of Biased β-Arrestin-Mediated Signaling Downstream from the Cannabinoid 1 Receptor

    PubMed Central

    Delgado-Peraza, Francheska; Ahn, Kwang H.; Nogueras-Ortiz, Carlos; Mungrue, Imran N.; Mackie, Ken; Kendall, Debra A.

    2016-01-01

    Activation of G protein-coupled receptors results in multiple waves of signaling that are mediated by heterotrimeric G proteins and the scaffolding proteins β-arrestin 1/2. Ligands can elicit full or subsets of cellular responses, a concept defined as ligand bias or functional selectivity. However, our current understanding of β-arrestin-mediated signaling is still very limited. Here we provide a comprehensive view of β-arrestin-mediated signaling from the cannabinoid 1 receptor (CB1R). By using a signaling biased receptor, we define the cascades, specific receptor kinases, and molecular mechanism underlying β-arrestin-mediated signaling: We identify the interaction kinetics of CB1R and β-arrestin 1 during their endocytic trafficking as directly proportional to its efficacy. Finally, we demonstrate that signaling results in the control of genes clustered around prosurvival and proapoptotic functions among others. Together, these studies constitute a comprehensive description of β-arrestin-mediated signaling from CB1Rs and suggest modulation of receptor endocytic trafficking as a therapeutic approach to control β-arrestin-mediated signaling. PMID:27009233

  10. An integrated model of epidermal growth factor receptor trafficking and signal transduction.

    PubMed

    Resat, Haluk; Ewald, Jonathan A; Dixon, David A; Wiley, H Steven

    2003-08-01

    Endocytic trafficking of many types of receptors can have profound effects on subsequent signaling events. Quantitative models of these processes, however, have usually considered trafficking and signaling independently. Here, we present an integrated model of both the trafficking and signaling pathway of the epidermal growth factor receptor (EGFR) using a probability weighted-dynamic Monte Carlo simulation. Our model consists of hundreds of distinct endocytic compartments and approximately 13,000 reactions/events that occur over a broad spatio-temporal range. By using a realistic multicompartment model, we can investigate the distribution of the receptors among cellular compartments as well as their potential signal transduction characteristics. Our new model also allows the incorporation of physiochemical aspects of ligand-receptor interactions, such as pH-dependent binding in different endosomal compartments. To determine the utility of this approach, we simulated the differential activation of the EGFR by two of its ligands, epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha). Our simulations predict that when EGFR is activated with TGF-alpha, receptor activation is biased toward the cell surface whereas EGF produces a signaling bias toward the endosomal compartment. Experiments confirm these predictions from our model and simulations. Our model accurately predicts the kinetics and extent of receptor downregulation induced by either EGF or TGF-alpha. Our results suggest that receptor trafficking controls the compartmental bias of signal transduction, rather than simply modulating signal magnitude. Our model provides a new approach to evaluating the complex effect of receptor trafficking on signal transduction. Importantly, the stochastic and compartmental nature of the simulation allows these models to be directly tested by high-throughput approaches, such as quantitative image analysis. PMID:12885624

  11. Visualization of BRI1 and BAK1(SERK3) membrane receptor heterooligomers during brassinosteroid signaling.

    PubMed

    Bücherl, Christoph A; van Esse, G Wilma; Kruis, Alex; Luchtenberg, Jeroen; Westphal, Adrie H; Aker, José; van Hoek, Arie; Albrecht, Catherine; Borst, Jan Willem; de Vries, Sacco C

    2013-08-01

    The leucine-rich repeat receptor-like kinase BRASSINOSTEROID-INSENSITIVE1 (BRI1) is the main ligand-perceiving receptor for brassinosteroids (BRs) in Arabidopsis (Arabidopsis thaliana). Binding of BRs to the ectodomain of plasma membrane (PM)-located BRI1 receptors initiates an intracellular signal transduction cascade that influences various aspects of plant growth and development. Even though the major components of BR signaling have been revealed and the PM was identified as the main site of BRI1 signaling activity, the very first steps of signal transmission are still elusive. Recently, it was shown that the initiation of BR signal transduction requires the interaction of BRI1 with its SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) coreceptors. In addition, the resolved structure of the BRI1 ectodomain suggested that BRI1-ASSOCIATED KINASE1 [BAK1](SERK3) may constitute a component of the ligand-perceiving receptor complex. Therefore, we investigated the spatial correlation between BRI1 and BAK1(SERK3) in the natural habitat of both leucine-rich repeat receptor-like kinases using comparative colocalization analysis and fluorescence lifetime imaging microscopy. We show that activation of BR signaling by exogenous ligand application resulted in both elevated colocalization between BRI1 and BAK1(SERK3) and an about 50% increase of receptor heterooligomerization in the PM of live Arabidopsis root epidermal cells. However, large populations of BRI1 and BAK1(SERK3) colocalized independently of BRs. Moreover, we could visualize that approximately 7% of the BRI1 PM pool constitutively heterooligomerizes with BAK1(SERK3) in live root cells. We propose that only small populations of PM-located BRI1 and BAK1(SERK3) receptors participate in active BR signaling and that the initiation of downstream signal transduction involves preassembled BRI1-BAK1(SERK3) heterooligomers.

  12. An Integrated Model of Epidermal Growth Factor Receptor Trafficking and Signal Transduction

    SciTech Connect

    Resat, Haluk; Ewald, Jonathan A.; Dixon, David A.; Wiley, H. S.

    2003-08-01

    Endocytic trafficking of many types of receptors can have profound effects on subsequent signaling events. Quantitative models of these processes, however, have usually considered trafficking and signaling independently. Here, we present an integrated model of both the trafficking and signaling pathway of the epidermal growth factor receptor (EGFR) using a probability weighted-dynamic Monte Carlo simulation. Our model consists of hundreds of distinct endocytic compartments and about 13,000 reactions/events that occur over a broad spatio-temporal range. By using a realistic multi-compartment model, we can investigate the distribution of the receptors among cellular compartments as well as their potential signal transduction characteristics. Our new model also allows the incorporation of physio-chemical aspects of ligand-receptor interactions, such as pH-dependent binding in different endosomal compartments. To determine the utility of this approach, we simulated the differential activation of the EGFR by two of its ligands, epidermal growth factor (EGF) and transforming growth factor- alpha (TGF-a). Our simulations predict that when EGFR is activated with TGF-a, receptor activation is biased toward the cell surface whereas EGF produces a signaling bias towards the endosomal compartment. Experiments confirm these predictions from our model and simulations. Our model accurately predicts the kinetics and extent of receptor down-regulation induced by either EGF or TGF-a. Our results suggest that receptor trafficking controls the compartmental bias of signal transduction, rather than simply modulating signal magnitude. Our model provides a new approach to evaluating the complex effect of receptor trafficking on signal transduction. Importantly, the stochastic and compartmental nature of the simulation allows these models to be directly tested by high-throughput approaches, such as quantitative image analysis.

  13. The growth hormone receptor: mechanism of activation and clinical implications.

    PubMed

    Brooks, Andrew J; Waters, Michael J

    2010-09-01

    Growth hormone is widely used clinically to promote growth and anabolism and for other purposes. Its actions are mediated via the growth hormone receptor, both directly by tyrosine kinase activation and indirectly by induction of insulin-like growth factor 1 (IGF-1). Insensitivity to growth hormone (Laron syndrome) can result from mutations in the growth hormone receptor and can be treated with IGF-1. This treatment is, however, not fully effective owing to the loss of the direct actions of growth hormone and altered availability of exogenous IGF-1. Excessive activation of the growth hormone receptor by circulating growth hormone results in gigantism and acromegaly, whereas cell transformation and cancer can occur in response to autocrine activation of the receptor. Advances in understanding the mechanism of receptor activation have led to a model in which the growth hormone receptor exists as a constitutive dimer. Binding of the hormone realigns the subunits by rotation and closer apposition, resulting in juxtaposition of the catalytic domains of the associated tyrosine-protein kinase JAK2 below the cell membrane. This change results in activation of JAK2 by transphosphorylation, then phosphorylation of receptor tyrosines in the cytoplasmic domain, which enables binding of adaptor proteins, as well as direct phosphorylation of target proteins. This model is discussed in the light of salient information from closely related class 1 cytokine receptors, such as the erythropoietin, prolactin and thrombopoietin receptors. PMID:20664532

  14. Phospholipase C-delta1 and oxytocin receptor signalling: evidence of its role as an effector.

    PubMed Central

    Park, E S; Won, J H; Han, K J; Suh, P G; Ryu, S H; Lee, H S; Yun, H Y; Kwon, N S; Baek, K J

    1998-01-01

    Although the oxytocin receptor modulates intracellular Ca2+ ion levels in myometrium, the identities of signal molecules have not been clearly clarified. Our previous studies on oxytocin receptor signalling demonstrated that 80 kDa Ghalpha is a signal mediator [Baek, Kwon, Lee, Kim, Muralidhar and Im (1996) Biochem. J. 315, 739-744]. To elucidate the effector in the oxytocin receptor signalling pathway, we evaluated the oxytocin-mediated activation of phospholipase C (PLC) by using solubilized membranes from human myometrium and a three-component preparation containing the oxytocin receptor-Ghalpha-PLC-delta1 complex. PLC-delta1 activity in the three-component preparation, as well as PLC activity in solubilized membranes, was increased by oxytocin in the presence of Ca2+ and activated Ghalpha (GTP-bound Ghalpha). Furthermore the stimulated PLC-delta1 activity resulting from activation of Ghalpha via the oxytocin receptor was significantly attenuated by the selective oxytocin antagonist desGly-NH2d(CH2)5[Tyr(Me)2,Thr4]ornithine vasotocin or GDP. Consistent with these observations, co-immunoprecipitation and co-immunoadsorption of PLC-delta1 in the three-component preparation by anti-Gh7alpha antibody resulted in the PLC-delta1 being tightly coupled to activated Ghalpha on stimulation of the oxytocin receptor. These results indicate that PLC-delta1 is the effector for Ghalpha-mediated oxytocin receptor signalling. PMID:9512491

  15. Steroid Receptor-Associated Immunophilins: A Gateway to Steroid Signalling

    PubMed Central

    Ratajczak, Thomas; Cluning, Carmel; Ward, Bryan K

    2015-01-01

    The steroid receptor-associated immunophilins FKBP51, FKBP52, CyP40 and PP5 have specific roles in steroid receptor function that impact steroid hormone-binding affinity, nucleocytoplasmic shuttling and transcriptional activation of target genes in a tissue-specific manner. Aberrant expression of these functionally unique immunophilins has the potential to cause steroid-based diseases, including breast and prostate cancer, diabetes and related metabolic disorders, male and female infertility and major depressive disorders. This review addresses the function of these proteins as co-chaperones in steroid receptor-Hsp90 complexes and extensively covers current knowledge of the link between the steroid receptor-associated immunophilins and human disease. An improved understanding of their mechanisms of action has revealed opportunities for molecular therapies to enhance or inhibit cellular processes under immunophilin control that contribute both to human health and disease. PMID:26224894

  16. Neutrophil Elastase and Proteinase-3 Trigger G Protein-biased Signaling through Proteinase-activated Receptor-1 (PAR1)*

    PubMed Central

    Mihara, Koichiro; Ramachandran, Rithwik; Renaux, Bernard; Saifeddine, Mahmoud; Hollenberg, Morley D.

    2013-01-01

    Neutrophil proteinases released at sites of inflammation can affect tissue function by either activating or disarming signal transduction mediated by proteinase-activated receptors (PARs). Because PAR1 is expressed at sites where abundant neutrophil infiltration occurs, we hypothesized that neutrophil-derived enzymes might also regulate PAR1 signaling. We report here that both neutrophil elastase and proteinase-3 cleave the human PAR1 N terminus at sites distinct from the thrombin cleavage site. This cleavage results in a disarming of thrombin-activated calcium signaling through PAR1. However, the distinct non-canonical tethered ligands unmasked by neutrophil elastase and proteinase-3, as well as synthetic peptides with sequences derived from these novel exposed tethered ligands, selectively stimulated PAR1-mediated mitogen-activated protein kinase activation. This signaling was blocked by pertussis toxin, implicating a Gαi-triggered signal pathway. We conclude that neutrophil proteinases trigger biased PAR1 signaling and we describe a novel set of tethered ligands that are distinct from the classical tethered ligand revealed by thrombin. We further demonstrate the function of this biased signaling in regulating endothelial cell barrier integrity. PMID:24052258

  17. CSF-1 receptor signalling is governed by pre-requisite EHD1 mediated receptor display on the macrophage cell surface.

    PubMed

    Cypher, Luke R; Bielecki, Timothy Alan; Huang, Lu; An, Wei; Iseka, Fany; Tom, Eric; Storck, Matthew D; Hoppe, Adam D; Band, Vimla; Band, Hamid

    2016-09-01

    Colony stimulating factor-1 receptor (CSF-1R), a receptor tyrosine kinase (RTK), is the master regulator of macrophage biology. CSF-1 can bind CSF-1R resulting in receptor activation and signalling essential for macrophage functions such as proliferation, differentiation, survival, polarization, phagocytosis, cytokine secretion, and motility. CSF-1R activation can only occur after the receptor is presented on the macrophage cell surface. This process is reliant upon the underlying macrophage receptor trafficking machinery. However, the mechanistic details governing this process are incompletely understood. C-terminal Eps15 Homology Domain-containing (EHD) proteins have recently emerged as key regulators of receptor trafficking but have not yet been studied in the context of macrophage CSF-1R signalling. In this manuscript, we utilize primary bone-marrow derived macrophages (BMDMs) to reveal a novel function of EHD1 as a regulator of CSF-1R abundance on the cell surface. We report that EHD1-knockout (EHD1-KO) macrophages cell surface and total CSF-1R levels are significantly decreased. The decline in CSF-1R levels corresponds with reduced downstream macrophage functions such as cell proliferation, migration, and spreading. In EHD1-KO macrophages, transport of newly synthesized CSF-1R to the macrophage cell surface was reduced and was associated with the shunting of the receptor to the lysosome, which resulted in receptor degradation. These findings reveal a novel and functionally important role for EHD1 in governing CSF-1R signalling via regulation of anterograde transport of CSF-1R to the macrophage cell surface. PMID:27224507

  18. GABAA receptor signaling in the lateral septum regulates maternal aggression in mice

    PubMed Central

    Lee, Grace; Gammie, Stephen C.

    2010-01-01

    Maternal aggression (maternal defense) is a fierce aggression produced by lactating females towards intruders that plays an important role in protection of vulnerable offspring. Enhancement of GABAA receptor signaling by benzodiazepines increases maternal aggression and we recently found indirect evidence that lateral septum (LS) could be a key site where benzodiazepines elevate aggression. In this study, we directly tested the hypothesis that activation of GABAA receptors in LS would promote maternal aggression while inhibition of this receptor would decrease aggression. Site-directed injections to LS were made using the GABAA receptor antagonist, bicuculline (3-30 ng), or the GABAA receptor agonists, chlordiazepoxide, a benzodiazepine (2.5-5 μg), and muscimol (0.05–5 ng). Maternal aggression and other behavioral measures were then evaluated in lactating mice. Neither GABAA receptor agonist elevated aggression, which could reflect a ceiling effect. However, 7 ng of the GABAA receptor antagonist, bicuculline, in LS significantly decreased maternal aggression without altering other maternal behaviors or light-dark box performance, suggesting some GABAA receptor signaling in LS is required for full maternal aggression expression. Together these results confirm a role for GABAA receptor signaling in LS in the regulation of maternal aggression. PMID:20001101

  19. Trace Amines and the Trace Amine-Associated Receptor 1: Pharmacology, Neurochemistry, and Clinical Implications.

    PubMed

    Pei, Yue; Asif-Malik, Aman; Canales, Juan J

    2016-01-01

    Biogenic amines are a collection of endogenous molecules that play pivotal roles as neurotransmitters and hormones. In addition to the "classical" biogenic amines resulting from decarboxylation of aromatic acids, including dopamine (DA), norepinephrine, epinephrine, serotonin (5-HT), and histamine, other biogenic amines, present at much lower concentrations in the central nervous system (CNS), and hence referred to as "trace" amines (TAs), are now recognized to play significant neurophysiological and behavioral functions. At the turn of the century, the discovery of the trace amine-associated receptor 1 (TAAR1), a phylogenetically conserved G protein-coupled receptor that is responsive to both TAs, such as β-phenylethylamine, octopamine, and tyramine, and structurally-related amphetamines, unveiled mechanisms of action for TAs other than interference with aminergic pathways, laying the foundations for deciphering the functional significance of TAs and its mammalian CNS receptor, TAAR1. Although, its molecular interactions and downstream targets have not been fully elucidated, TAAR1 activation triggers accumulation of intracellular cAMP, modulates PKA and PKC signaling and interferes with the β-arrestin2-dependent pathway via G protein-independent mechanisms. TAAR1 is uniquely positioned to exert direct control over DA and 5-HT neuronal firing and release, which has profound implications for understanding the pathophysiology of, and therefore designing more efficacious therapeutic interventions for, a range of neuropsychiatric disorders that involve aminergic dysregulation, including Parkinson's disease, schizophrenia, mood disorders, and addiction. Indeed, the recent development of novel pharmacological tools targeting TAAR1 has uncovered the remarkable potential of TAAR1-based medications as new generation pharmacotherapies in neuropsychiatry. This review summarizes recent developments in the study of TAs and TAAR1, their intricate neurochemistry and

  20. Trace Amines and the Trace Amine-Associated Receptor 1: Pharmacology, Neurochemistry, and Clinical Implications

    PubMed Central

    Pei, Yue; Asif-Malik, Aman; Canales, Juan J.

    2016-01-01

    Biogenic amines are a collection of endogenous molecules that play pivotal roles as neurotransmitters and hormones. In addition to the “classical” biogenic amines resulting from decarboxylation of aromatic acids, including dopamine (DA), norepinephrine, epinephrine, serotonin (5-HT), and histamine, other biogenic amines, present at much lower concentrations in the central nervous system (CNS), and hence referred to as “trace” amines (TAs), are now recognized to play significant neurophysiological and behavioral functions. At the turn of the century, the discovery of the trace amine-associated receptor 1 (TAAR1), a phylogenetically conserved G protein-coupled receptor that is responsive to both TAs, such as β-phenylethylamine, octopamine, and tyramine, and structurally-related amphetamines, unveiled mechanisms of action for TAs other than interference with aminergic pathways, laying the foundations for deciphering the functional significance of TAs and its mammalian CNS receptor, TAAR1. Although, its molecular interactions and downstream targets have not been fully elucidated, TAAR1 activation triggers accumulation of intracellular cAMP, modulates PKA and PKC signaling and interferes with the β-arrestin2-dependent pathway via G protein-independent mechanisms. TAAR1 is uniquely positioned to exert direct control over DA and 5-HT neuronal firing and release, which has profound implications for understanding the pathophysiology of, and therefore designing more efficacious therapeutic interventions for, a range of neuropsychiatric disorders that involve aminergic dysregulation, including Parkinson's disease, schizophrenia, mood disorders, and addiction. Indeed, the recent development of novel pharmacological tools targeting TAAR1 has uncovered the remarkable potential of TAAR1-based medications as new generation pharmacotherapies in neuropsychiatry. This review summarizes recent developments in the study of TAs and TAAR1, their intricate neurochemistry and

  1. Trace Amines and the Trace Amine-Associated Receptor 1: Pharmacology, Neurochemistry, and Clinical Implications.

    PubMed

    Pei, Yue; Asif-Malik, Aman; Canales, Juan J

    2016-01-01

    Biogenic amines are a collection of endogenous molecules that play pivotal roles as neurotransmitters and hormones. In addition to the "classical" biogenic amines resulting from decarboxylation of aromatic acids, including dopamine (DA), norepinephrine, epinephrine, serotonin (5-HT), and histamine, other biogenic amines, present at much lower concentrations in the central nervous system (CNS), and hence referred to as "trace" amines (TAs), are now recognized to play significant neurophysiological and behavioral functions. At the turn of the century, the discovery of the trace amine-associated receptor 1 (TAAR1), a phylogenetically conserved G protein-coupled receptor that is responsive to both TAs, such as β-phenylethylamine, octopamine, and tyramine, and structurally-related amphetamines, unveiled mechanisms of action for TAs other than interference with aminergic pathways, laying the foundations for deciphering the functional significance of TAs and its mammalian CNS receptor, TAAR1. Although, its molecular interactions and downstream targets have not been fully elucidated, TAAR1 activation triggers accumulation of intracellular cAMP, modulates PKA and PKC signaling and interferes with the β-arrestin2-dependent pathway via G protein-independent mechanisms. TAAR1 is uniquely positioned to exert direct control over DA and 5-HT neuronal firing and release, which has profound implications for understanding the pathophysiology of, and therefore designing more efficacious therapeutic interventions for, a range of neuropsychiatric disorders that involve aminergic dysregulation, including Parkinson's disease, schizophrenia, mood disorders, and addiction. Indeed, the recent development of novel pharmacological tools targeting TAAR1 has uncovered the remarkable potential of TAAR1-based medications as new generation pharmacotherapies in neuropsychiatry. This review summarizes recent developments in the study of TAs and TAAR1, their intricate neurochemistry and

  2. International law implications of the detection of extraterrestrial intelligent signals

    NASA Astrophysics Data System (ADS)

    Kopal, Vladimir

    This paper first considers whether the present law of outer space, as it has been enshrined in five United Nations treaties and other legal documents concerning outer space, provides a satisfactory basis for SETI/CETI activities. In the author's opinion, these activities may serve "the common interest of all mankind in the progress of the exploration and use of outer space for peaceful purposes," as recognized in the 1967 Outer Space Treaty. The use of the radio frequency spectrum for SETI/CETI purposes should be in conformity with the legal principles governing this valuable natural resource, as expressed in the International Telecommunication Convention and related documents, and with allocations of the relevant segments of the spectrum by the competent bodies of the International Telecommunication Union. In the second part the author examines the impact that the detection of extraterrestrial intelligent signals may have on the present body of space law. A possible role for the United Nations in this respect is also explored and a timely interest of the world body in discussing questions relating to this subject is recommended. Consideration of these questions could become a tool helping to concentrate the attention of the world community on problems of common concern and thus to strengthen international cooperation. However, the author believes that a law-making process that would aim at elaborating a special regulation of activities in this field would be premature at this stage. It should be initiated only when the boundary between possibilities and realities is crossed. Finally, the paper outlines some likely transformation in our space law thinking that would be the consequence of the detection of extraterrestrial intelligent signals. Elaboration of the principles and norms to govern relations between the international community of our own planet and other intelligent communities in the universe would add a new dimension to the present body of outer space

  3. Implications of scavenger receptors in the safe development of nanotherapeutics

    PubMed Central

    Shannahan, Jonathan H.; Bai, Wei; Brown, Jared M.

    2015-01-01

    Nanomaterials (NMs) are being utilized in a variety of biomedical applications including drug delivery, diagnostics, and therapeutic targeting. These applications are made possible due to the unique physicochemical properties that are exhibited at the nanoscale. To ensure safe development of NMs for clinical use, it is necessary to understand their interactions with cells and specifically cell surface receptors, which will facilitate either their toxicity and/or clinical function. Recently our research and others have investigated the role of scavenger receptors in mediating NM-cell interactions and responses. Scavenger receptors are expressed by a variety of cell types that are first to encounter NMs during clinical use such as macrophages and endothelial cells. Scavenger receptors are recognized to facilitate uptake of a wide variety of ligands ranging from foreign substances to endogenous lipids/proteins. While interaction of NMs with scavenger receptors may allow therapeutic targeting in some instances, it also presents a challenge for the stealth delivery of NMs and avoidance of the scavenging capability of this class of receptors. Due to their role in facilitating immune responses, scavenger receptor-mediated inflammation is also of concern following NM delivery. The research highlighted in this brief review intends to summarize our current understanding regarding the consequences of NM-scavenger receptor interactions. PMID:26005702

  4. Smad2 transduces common signals from receptor serine-threonine and tyrosine kinases.

    PubMed

    de Caestecker, M P; Parks, W T; Frank, C J; Castagnino, P; Bottaro, D P; Roberts, A B; Lechleider, R J

    1998-06-01

    SMAD proteins mediate signals from receptor serine-threonine kinases (RSKs) of the TGF-beta superfamily. We demonstrate here that HGF and EGF, which signal through RTKs, can also mediate SMAD-dependent reporter gene activation and induce rapid phosphorylation of endogenous SMAD proteins by kinase(s) downstream of MEK1. HGF induces phosphorylation and nuclear translocation of epitope-tagged Smad2 and a mutation that blocks TGF-beta signaling also blocks HGF signal transduction. Smad2 may thus act as a common positive effector of TGF-beta- and HGF-induced signals and serve to modulate cross talk between RTK and RSK signaling pathways.

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

    PubMed

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

    2015-02-01

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

  6. Cannabinoid receptor-interacting protein 1a modulates CB1 receptor signaling and regulation.

    PubMed

    Smith, Tricia H; Blume, Lawrence C; Straiker, Alex; Cox, Jordan O; David, Bethany G; McVoy, Julie R Secor; Sayers, Katherine W; Poklis, Justin L; Abdullah, Rehab A; Egertová, Michaela; Chen, Ching-Kang; Mackie, Ken; Elphick, Maurice R; Howlett, Allyn C; Selley, Dana E

    2015-04-01

    Cannabinoid CB1 receptors (CB1Rs) mediate the presynaptic effects of endocannabinoids in the central nervous system (CNS) and most behavioral effects of exogenous cannabinoids. Cannabinoid receptor-interacting protein 1a (CRIP1a) binds to the CB1R C-terminus and can attenuate constitutive CB1R-mediated inhibition of Ca(2+) channel activity. We now demonstrate cellular colocalization of CRIP1a at neuronal elements in the CNS and show that CRIP1a inhibits both constitutive and agonist-stimulated CB1R-mediated guanine nucleotide-binding regulatory protein (G-protein) activity. Stable overexpression of CRIP1a in human embryonic kidney (HEK)-293 cells stably expressing CB1Rs (CB1-HEK), or in N18TG2 cells endogenously expressing CB1Rs, decreased CB1R-mediated G-protein activation (measured by agonist-stimulated [(35)S]GTPγS (guanylyl-5'-[O-thio]-triphosphate) binding) in both cell lines and attenuated inverse agonism by rimonabant in CB1-HEK cells. Conversely, small-interfering RNA-mediated knockdown of CRIP1a in N18TG2 cells enhanced CB1R-mediated G-protein activation. These effects were not attributable to differences in CB1R expression or endocannabinoid tone because CB1R levels did not differ between cell lines varying in CRIP1a expression, and endocannabinoid levels were undetectable (CB1-HEK) or unchanged (N18TG2) by CRIP1a overexpression. In CB1-HEK cells, 4-hour pretreatment with cannabinoid agonists downregulated CB1Rs and desensitized agonist-stimulated [(35)S]GTPγS binding. CRIP1a overexpression attenuated CB1R downregulation without altering CB1R desensitization. Finally, in cultured autaptic hippocampal neurons, CRIP1a overexpression attenuated both depolarization-induced suppression of excitation and inhibition of excitatory synaptic activity induced by exogenous application of cannabinoid but not by adenosine A1 agonists. These results confirm that CRIP1a inhibits constitutive CB1R activity and demonstrate that CRIP1a can also inhibit agonist

  7. Inositol triphosphate-mediated Ca2+ signals direct purinergic P2Y receptor regulation of neuronal ion channels.

    PubMed

    Zaika, Oleg; Tolstykh, Gleb P; Jaffe, David B; Shapiro, Mark S

    2007-08-15

    Purinergic P2Y receptors are one of four types of G(q/11)-coupled receptors in rat superior cervical ganglia (SCG) sympathetic neurons. In cultured SCG neurons, purinergic and bradykinin suppression of I(M) were similar in magnitude and somewhat less than that by muscarinic agonists. The effects of the P2Y receptor agonist UTP on neuronal excitability and discharge properties were studied. Under current clamp, UTP increased action potential (AP) firing in response to depolarizing current steps, depolarized the resting potential, decreased the threshold current required to fire an AP, and decreased spike-frequency adaptation. These effects were very similar to those resulting from bradykinin stimulation and not as profound as from muscarinic stimulation or full M-current blockade. We then examined the P2Y mechanism of action. Like bradykinin, but unlike muscarinic, purinergic stimulation induced rises in intracellular [Ca(2+)](i). Tests using expression of IP(3)"sponge" or IP(3) phosphatase constructs implicated IP(3) accumulation as necessary for purinergic suppression of I(M). Overexpression of wild-type or dominant-negative calmodulin (CaM) implicated Ca(2+)/CaM in the purinergic action. Both sets of results were similar to bradykinin, and opposite to muscarinic, suppression. We also examined modulation of Ca(2+) channels. As for bradykinin, purinergic stimulation did not suppress I(Ca), unless neuronal calcium sensor-1 (NCS-1) activity was blocked by a dominant-negative NCS-1 construct. Our results indicate that P2Y receptors modulate M-type channels in SCG cells via IP(3)-mediated [Ca(2+)](i) signals in concert with CaM and not by depletion of phosphatidylinositol-4, 5-biphosphate. We group purinergic P2Y and bradykinin B(2) receptors together as having a common mode of action.

  8. Adrenergic DNA damage of embryonic pluripotent cells via β2 receptor signalling.

    PubMed

    Sun, Fan; Ding, Xu-Ping; An, Shi-Min; Tang, Ya-Bin; Yang, Xin-Jie; Teng, Lin; Zhang, Chun; Shen, Ying; Chen, Hong-Zhuan; Zhu, Liang

    2015-01-01

    Embryonic pluripotent cells are sensitive to genotoxicity though they need more stringent genome integrity to avoid compromising multiple cell lineages and subsequent generations. However it remains unknown whether the cells are susceptible to adrenergic stress which can induce somatic cell genome lesion. We have revealed that adrenergic stress mediators cause DNA damage of the cells through the β2 adrenergic receptor/adenylate cyclase/cAMP/PKA signalling pathway involving an induction of intracellular reactive oxygen species (ROS) accumulation. The adrenergic stress agonists adrenaline, noradrenaline, and isoprenaline caused DNA damage and apoptosis of embryonic stem (ES) cells and embryonal carcinoma stem cells. The effects were mimicked by β2 receptor-coupled signalling molecules and abrogated by selective blockade of β2 receptors and inhibition of the receptor signalling pathway. RNA interference targeting β2 receptors of ES cells conferred the cells the ability to resist the DNA damage and apoptosis. In addition, adrenergic stimulation caused a consistent accumulation of ROS in the cells and the effect was abrogated by β2 receptor blockade; quenching of ROS reversed the induced DNA damage. This finding will improve the understanding of the stem cell regulatory physiology/pathophysiology in an adrenergic receptor subtype signalling mechanism. PMID:26516061

  9. Mutational analysis of a critical signaling domain of the human interleukin 4 receptor.

    PubMed Central

    Seldin, D C; Leder, P

    1994-01-01

    The human interleukin 4 receptor (hIL-4R) is a member of a superfamily of cytokine receptors defined by conserved features of their extracellular domains. The intracellular domains of the hIL-4R and of other members of this family lack any recognizable enzymatic motifs, though ligand-dependent tyrosine phosphorylation of these receptors has been observed. Recent studies have suggested that serine-rich and acidic domains within the cytoplasmic portions of cytokine receptors might be required for signal transduction. Using deletion and truncation mutants of the hIL-4R, we have explored an essential 39-amino acid signaling domain that is rich in acidic amino acid residues and in serine residues that form consensus phosphorylation sites for known serine/threonine kinases. To assess the contribution of these motifs to signaling, we engineered site-directed mutants of these residues. Surprisingly, cells expressing mutant hIL-4R lacking either the serine or the acidic amino acids retain the ability of cells expressing the wild-type receptor to proliferate in hIL-4. Furthermore, receptors in which all six cytoplasmic tyrosines are absent can function, suggesting that tyrosine phosphorylation of the receptor may be an epiphenomenon rather than a requisite event in signaling. Images PMID:8134361

  10. Adrenergic DNA damage of embryonic pluripotent cells via β2 receptor signalling

    PubMed Central

    Sun, Fan; Ding, Xu-Ping; An, Shi-Min; Tang, Ya-Bin; Yang, Xin-Jie; Teng, Lin; Zhang, Chun; Shen, Ying; Chen, Hong-Zhuan; Zhu, Liang

    2015-01-01

    Embryonic pluripotent cells are sensitive to genotoxicity though they need more stringent genome integrity to avoid compromising multiple cell lineages and subsequent generations. However it remains unknown whether the cells are susceptible to adrenergic stress which can induce somatic cell genome lesion. We have revealed that adrenergic stress mediators cause DNA damage of the cells through the β2 adrenergic receptor/adenylate cyclase/cAMP/PKA signalling pathway involving an induction of intracellular reactive oxygen species (ROS) accumulation. The adrenergic stress agonists adrenaline, noradrenaline, and isoprenaline caused DNA damage and apoptosis of embryonic stem (ES) cells and embryonal carcinoma stem cells. The effects were mimicked by β2 receptor-coupled signalling molecules and abrogated by selective blockade of β2 receptors and inhibition of the receptor signalling pathway. RNA interference targeting β2 receptors of ES cells conferred the cells the ability to resist the DNA damage and apoptosis. In addition, adrenergic stimulation caused a consistent accumulation of ROS in the cells and the effect was abrogated by β2 receptor blockade; quenching of ROS reversed the induced DNA damage. This finding will improve the understanding of the stem cell regulatory physiology/pathophysiology in an adrenergic receptor subtype signalling mechanism. PMID:26516061

  11. Noncanonical GPCR signaling arising from a PTH receptor-arrestin-Gβγ complex.

    PubMed

    Wehbi, Vanessa L; Stevenson, Hilary P; Feinstein, Timothy N; Calero, Guillermo; Romero, Guillermo; Vilardaga, Jean-Pierre

    2013-01-22

    G protein-coupled receptors (GPCRs) participate in ubiquitous transmembrane signal transduction processes by activating heterotrimeric G proteins. In the current "canonical" model of GPCR signaling, arrestins terminate receptor signaling by impairing receptor-G-protein coupling and promoting receptor internalization. However, parathyroid hormone receptor type 1 (PTHR), an essential GPCR involved in bone and mineral metabolism, does not follow this conventional desensitization paradigm. β-Arrestins prolong G protein (G(S))-mediated cAMP generation triggered by PTH, a process that correlates with the persistence of arrestin-PTHR complexes on endosomes and which is thought to be associated with prolonged physiological calcemic and phosphate responses. This presents an inescapable paradox for the current model of arrestin-mediated receptor-G-protein decoupling. Here we show that PTHR forms a ternary complex that includes arrestin and the Gβγ dimer in response to PTH stimulation, which in turn causes an accelerated rate of G(S) activation and increases the steady-state levels of activated G(S), leading to prolonged generation of cAMP. This work provides the mechanistic basis for an alternative model of GPCR signaling in which arrestins contribute to sustaining the effect of an agonist hormone on the receptor.

  12. Structural features of the Nogo receptor signaling complexes at the neuron/myelin interface.

    PubMed

    Saha, Nayanendu; Kolev, Momchil; Nikolov, Dimitar B

    2014-10-01

    Upon spinal cord injury, the central nervous system axons are unable to regenerate, partially due to the repulsive action of myelin inhibitors, such as the myelin-associated glycoprotein (MAG), Nogo-A and the oligodendrocyte myelin glycoprotein (OMgp). These inhibitors bind and signal through a single receptor/co-receptor complex that comprises of NgR1/LINGO-1 and either p75 or TROY, triggering intracellular downstream signaling that impedes the re-growth of axons. Structure-function analysis of myelin inhibitors and their neuronal receptors, particularly the NgRs, have provided novel information regarding the molecular details of the inhibitor/receptor/co-receptor interactions. Structural and biochemical studies have revealed the architecture of many of these proteins and identified the molecular regions important for assembly of the inhibitory signaling complexes. It was also recently shown that gangliosides, such as GT1b, mediate receptor/co-receptor binding. In this review, we highlight these studies and summarize our current understanding of the multi-protein cell-surface complexes mediating inhibitory signaling events at the neuron/myelin interface.

  13. Dopamine D2-receptor blockade enhances decoding of prefrontal signals in humans.

    PubMed

    Kahnt, Thorsten; Weber, Susanna C; Haker, Helene; Robbins, Trevor W; Tobler, Philippe N

    2015-03-01

    The prefrontal cortex houses representations critical for ongoing and future behavior expressed in the form of patterns of neural activity. Dopamine has long been suggested to play a key role in the integrity of such representations, with D2-receptor activation rendering them flexible but weak. However, it is currently unknown whether and how D2-receptor activation affects prefrontal representations in humans. In the current study, we use dopamine receptor-specific pharmacology and multivoxel pattern-based functional magnetic resonance imaging to test the hypothesis that blocking D2-receptor activation enhances prefrontal representations. Human subjects performed a simple reward prediction task after double-blind and placebo controlled administration of the D2-receptor antagonist amisulpride. Using a whole-brain searchlight decoding approach we show that D2-receptor blockade enhances decoding of reward signals in the medial orbitofrontal cortex. Examination of activity patterns suggests that amisulpride increases the separation of activity patterns related to reward versus no reward. Moreover, consistent with the cortical distribution of D2 receptors, post hoc analyses showed enhanced decoding of motor signals in motor cortex, but not of visual signals in visual cortex. These results suggest that D2-receptor blockade enhances content-specific representations in frontal cortex, presumably by a dopamine-mediated increase in pattern separation. These findings are in line with a dual-state model of prefrontal dopamine, and provide new insights into the potential mechanism of action of dopaminergic drugs.

  14. Peptide YY signaling in the lateral parabrachial nucleus increases food intake through the Y1 receptor.

    PubMed

    Alhadeff, Amber L; Golub, Danielle; Hayes, Matthew R; Grill, Harvey J

    2015-10-15

    Although central PYY delivery potently increases food intake, the sites of action and mechanisms mediating these hyperphagic effects are not fully understood. The present studies investigate the contribution of lateral parabrachial nucleus (lPBN) PYY-Y receptor signaling to food intake control, as lPBN neurons express Y receptors and receive PYY fibers and are known to integrate circulating and visceral sensory signals to regulate energy balance. Immunohistochemical results identified a subpopulation of gigantocellular reticular nucleus PYY-producing neurons that project monosynaptically to the lPBN, providing an endogenous source of PYY to the lPBN. lPBN microinjection of PYY-(1-36) or PYY-(3-36) markedly increased food intake by increasing meal size. To determine which receptors mediate these behavioral results, we first performed quantitative real-time PCR to examine the relative levels of Y receptor expression in lPBN tissue. Gene expression analyses revealed that, while Y1, Y2, and Y5 receptors are each expressed in lPBN tissue, Y1 receptor mRNA is expressed at fivefold higher levels than the others. Furthermore, behavioral/pharmacological results demonstrated that the hyperphagic effects of PYY-(3-36) were eliminated by lPBN pretreatment with a selective Y1 receptor antagonist. Together, these results highlight the lPBN as a novel site of action for the intake-stimulatory effects of central PYY-Y1 receptor signaling.

  15. Dopamine D2-receptor blockade enhances decoding of prefrontal signals in humans.

    PubMed

    Kahnt, Thorsten; Weber, Susanna C; Haker, Helene; Robbins, Trevor W; Tobler, Philippe N

    2015-03-01

    The prefrontal cortex houses representations critical for ongoing and future behavior expressed in the form of patterns of neural activity. Dopamine has long been suggested to play a key role in the integrity of such representations, with D2-receptor activation rendering them flexible but weak. However, it is currently unknown whether and how D2-receptor activation affects prefrontal representations in humans. In the current study, we use dopamine receptor-specific pharmacology and multivoxel pattern-based functional magnetic resonance imaging to test the hypothesis that blocking D2-receptor activation enhances prefrontal representations. Human subjects performed a simple reward prediction task after double-blind and placebo controlled administration of the D2-receptor antagonist amisulpride. Using a whole-brain searchlight decoding approach we show that D2-receptor blockade enhances decoding of reward signals in the medial orbitofrontal cortex. Examination of activity patterns suggests that amisulpride increases the separation of activity patterns related to reward versus no reward. Moreover, consistent with the cortical distribution of D2 receptors, post hoc analyses showed enhanced decoding of motor signals in motor cortex, but not of visual signals in visual cortex. These results suggest that D2-receptor blockade enhances content-specific representations in frontal cortex, presumably by a dopamine-mediated increase in pattern separation. These findings are in line with a dual-state model of prefrontal dopamine, and provide new insights into the potential mechanism of action of dopaminergic drugs. PMID:25740537

  16. Receptor clustering affects signal transduction at the membrane level in the reaction-limited regime

    NASA Astrophysics Data System (ADS)

    Caré, Bertrand R.; Soula, Hédi A.

    2013-01-01

    Many types of membrane receptors are found to be organized as clusters on the cell surface. We investigate the potential effect of such receptor clustering on the intracellular signal transduction stage. We consider a canonical pathway with a membrane receptor (R) activating a membrane-bound intracellular relay protein (G). We use Monte Carlo simulations to recreate biochemical reactions using different receptor spatial distributions and explore the dynamics of the signal transduction. Results show that activation of G by R is severely impaired by R clustering, leading to an apparent blunted biological effect compared to control. Paradoxically, this clustering decreases the half maximal effective dose (ED50) of the transduction stage, increasing the apparent affinity. We study an example of inter-receptor interaction in order to account for possible compensatory effects of clustering and observe the parameter range in which such interactions slightly counterbalance the loss of activation of G. The membrane receptors’ spatial distribution affects the internal stages of signal amplification, suggesting a functional role for membrane domains and receptor clustering independently of proximity-induced receptor-receptor interactions.

  17. G-Protein–Coupled Receptors Signaling Pathways in New Antiplatelet Drug Development

    PubMed Central

    Gurbel, Paul A.; Kuliopulos, Athan; Tantry, Udaya S.

    2016-01-01

    Platelet G-protein–coupled receptors influence platelet function by mediating the response to various agonists, including ADP, thromboxane A2, and thrombin. Blockade of the ADP receptor, P2Y12, in combination with cyclooxygenase-1 inhibition by aspirin has been among the most widely used pharmacological strategies to reduce cardiovascular event occurrence in high-risk patients. The latter dual pathway blockade strategy is one of the greatest advances in the field of cardiovascular medicine. In addition to P2Y12, the platelet thrombin receptor, protease activated receptor-1, has also been recently targeted for inhibition. Blockade of protease activated receptor-1 has been associated with reduced thrombotic event occurrence when added to a strategy using P2Y12 and cyclooxygenase-1 inhibition. At this time, the relative contributions of these G-protein–coupled receptor signaling pathways to in vivo thrombosis remain incompletely defined. The observation of treatment failure in ≈10% of high-risk patients treated with aspirin and potent P2Y12 inhibitors provides the rationale for targeting novel pathways mediating platelet function. Targeting intracellular signaling downstream from G-protein–coupled receptor receptors with phosphotidylionisitol 3-kinase and Gq inhibitors are among the novel strategies under investigation to prevent arterial ischemic event occurrence. Greater understanding of the mechanisms of G-protein–coupled receptor–mediated signaling may allow the tailoring of antiplatelet therapy. PMID:25633316

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

    PubMed

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

    2016-01-01

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

  19. β-Adrenergic receptor signaling and modulation of long-term potentiation in the mammalian hippocampus

    PubMed Central

    O'Dell, Thomas J.; Connor, Steven A.; Guglietta, Ryan

    2015-01-01

    Encoding new information in the brain requires changes in synaptic strength. Neuromodulatory transmitters can facilitate synaptic plasticity by modifying the actions and expression of specific signaling cascades, transmitter receptors and their associated signaling complexes, genes, and effector proteins. One critical neuromodulator in the mammalian brain is norepinephrine (NE), which regulates multiple brain functions such as attention, perception, arousal, sleep, learning, and memory. The mammalian hippocampus receives noradrenergic innervation and hippocampal neurons express β-adrenergic receptors, which are known to play important roles in gating the induction of long-lasting forms of synaptic potentiation. These forms of long-term potentiation (LTP) are believed to importantly contribute to long-term storage of spatial and contextual memories in the brain. In this review, we highlight the contributions of noradrenergic signaling in general and β-adrenergic receptors in particular, toward modulating hippocampal LTP. We focus on the roles of NE and β-adrenergic receptors in altering the efficacies of specific signaling molecules such as NMDA and AMPA receptors, protein phosphatases, and translation initiation factors. Also, the roles of β-adrenergic receptors in regulating synaptic “tagging” and “capture” of LTP within synaptic networks of the hippocampus are reviewed. Understanding the molecular and cellular bases of noradrenergic signaling will enrich our grasp of how the brain makes new, enduring memories, and may shed light on credible strategies for improving mental health through treatment of specific disorders linked to perturbed memory processing and dysfunctional noradrenergic synaptic transmission. PMID:26286656

  20. Mannose Phosphate Isomerase Regulates Fibroblast Growth Factor Receptor Family Signaling and Glioma Radiosensitivity

    PubMed Central

    Cazet, Aurélie; Charest, Jonathan; Bennett, Daniel C.; Sambrooks, Cecilia Lopez; Contessa, Joseph N.

    2014-01-01

    Asparagine-linked glycosylation is an endoplasmic reticulum co- and post- translational modification that enables the transit and function of receptor tyrosine kinase (RTK) glycoproteins. To gain insight into the regulatory role of glycosylation enzymes on RTK function, we investigated shRNA and siRNA knockdown of mannose phosphate isomerase (MPI), an enzyme required for mature glycan precursor biosynthesis. Loss of MPI activity reduced phosphorylation of FGFR family receptors in U-251 and SKMG-3 malignant glioma cell lines and also resulted in significant decreases in FRS2, Akt, and MAPK signaling. However, MPI knockdown did not affect ligand-induced activation or signaling of EGFR or MET RTKs, suggesting that FGFRs are more susceptible to MPI inhibition. The reductions in FGFR signaling were not caused by loss of FGF ligands or receptors, but instead were caused by interference with receptor dimerization. Investigations into the cellular consequences of MPI knockdown showed that cellular programs driven by FGFR signaling, and integral to the clinical progression of malignant glioma, were impaired. In addition to a blockade of cellular migration, MPI knockdown also significantly reduced glioma cell clonogenic survival following ionizing radiation. Therefore our results suggest that targeted inhibition of enzymes required for cell surface receptor glycosylation can be manipulated to produce discrete and limited consequences for critical client glycoproteins expressed by tumor cells. Furthermore, this work identifies MPI as a potential enzymatic target for disrupting cell surface receptor-dependent survival signaling and as a novel approach for therapeutic radiosensitization. PMID:25314669

  1. ß-Adrenergic Receptor Signaling and Modulation of Long-Term Potentiation in the Mammalian Hippocampus

    ERIC Educational Resources Information Center

    O'Dell, Thomas J.; Connor, Steven A.; Guglietta, Ryan; Nguyen, Peter V.

    2015-01-01

    Encoding new information in the brain requires changes in synaptic strength. Neuromodulatory transmitters can facilitate synaptic plasticity by modifying the actions and expression of specific signaling cascades, transmitter receptors and their associated signaling complexes, genes, and effector proteins. One critical neuromodulator in the…

  2. Mechanistic pathways and biological roles for receptor-independent activators of G-protein signaling.

    PubMed

    Blumer, Joe B; Smrcka, Alan V; Lanier, Stephen M

    2007-03-01

    Signal processing via heterotrimeric G-proteins in response to cell surface receptors is a central and much investigated aspect of how cells integrate cellular stimuli to produce coordinated biological responses. The system is a target of numerous therapeutic agents and plays an important role in adaptive processes of organs; aberrant processing of signals through these transducing systems is a component of various disease states. In addition to G-protein coupled receptor (GPCR)-mediated activation of G-protein signaling, nature has evolved creative ways to manipulate and utilize the Galphabetagamma heterotrimer or Galpha and Gbetagamma subunits independent of the cell surface receptor stimuli. In such situations, the G-protein subunits (Galpha and Gbetagamma) may actually be complexed with alternative binding partners independent of the typical heterotrimeric Galphabetagamma. Such regulatory accessory proteins include the family of regulator of G-protein signaling (RGS) proteins that accelerate the GTPase activity of Galpha and various entities that influence nucleotide binding properties and/or subunit interaction. The latter group of proteins includes receptor-independent activators of G-protein signaling (AGS) proteins that play surprising roles in signal processing. This review provides an overview of our current knowledge regarding AGS proteins. AGS proteins are indicative of a growing number of accessory proteins that influence signal propagation, facilitate cross talk between various types of signaling pathways, and provide a platform for diverse functions of both the heterotrimeric Galphabetagamma and the individual Galpha and Gbetagamma subunits.

  3. PDZ Protein Regulation of G Protein-Coupled Receptor Trafficking and Signaling Pathways.

    PubMed

    Dunn, Henry A; Ferguson, Stephen S G

    2015-10-01

    G protein-coupled receptors (GPCRs) contribute to the regulation of every aspect of human physiology and are therapeutic targets for the treatment of numerous diseases. As a consequence, understanding the myriad of mechanisms controlling GPCR signaling and trafficking is essential for the development of new pharmacological strategies for the treatment of human pathologies. Of the many GPCR-interacting proteins, postsynaptic density protein of 95 kilodaltons, disc large, zona occludens-1 (PDZ) domain-containing proteins appear most abundant and have similarly been implicated in disease mechanisms. PDZ proteins play an important role in regulating receptor and channel protein localization within synapses and tight junctions and function to scaffold intracellular signaling protein complexes. In the current study, we review the known functional interactions between PDZ domain-containing proteins and GPCRs and provide insight into the potential mechanisms of action. These PDZ domain-containing proteins include the membrane-associated guanylate-like kinases [postsynaptic density protein of 95 kilodaltons; synapse-associated protein of 97 kilodaltons; postsynaptic density protein of 93 kilodaltons; synapse-associated protein of 102 kilodaltons; discs, large homolog 5; caspase activation and recruitment domain and membrane-associated guanylate-like kinase domain-containing protein 3; membrane protein, palmitoylated 3; calcium/calmodulin-dependent serine protein kinase; membrane-associated guanylate kinase protein (MAGI)-1, MAGI-2, and MAGI-3], Na(+)/H(+) exchanger regulatory factor proteins (NHERFs) (NHERF1, NHERF2, PDZ domain-containing kidney protein 1, and PDZ domain-containing kidney protein 2), Golgi-associated PDZ proteins (Gα-binding protein interacting protein, C-terminus and CFTR-associated ligand), PDZ domain-containing guanine nucleotide exchange factors (GEFs) 1 and 2, regulator of G protein signaling (RGS)-homology-RhoGEFs (PDZ domain-containing RhoGEF and

  4. An In Vivo EGF Receptor Localization Screen in C. elegans Identifies the Ezrin Homolog ERM-1 as a Temporal Regulator of Signaling

    PubMed Central

    Walser, Michael; Yang, Qiutan; Langouët, Maeva; Kradolfer, David; Fröhli, Erika; Herrmann, Christina J.; Hajnal, Alex; Escobar-Restrepo, Juan M.

    2014-01-01

    The subcellular localization of the epidermal growth factor receptor (EGFR) in polarized epithelial cells profoundly affects the activity of the intracellular signaling pathways activated after EGF ligand binding. Therefore, changes in EGFR localization and signaling are implicated in various human diseases, including different types of cancer. We have performed the first in vivo EGFR localization screen in an animal model by observing the expression of the EGFR ortholog LET-23 in the vulval epithelium of live C. elegans larvae. After systematically testing all genes known to produce an aberrant vulval phenotype, we have identified 81 genes regulating various aspects of EGFR localization and expression. In particular, we have found that ERM-1, the sole C. elegans Ezrin/Radixin/Moesin homolog, regulates EGFR localization and signaling in the vulval cells. ERM-1 interacts with the EGFR at the basolateral plasma membrane in a complex distinct from the previously identified LIN-2/LIN-7/LIN-10 receptor localization complex. We propose that ERM-1 binds to and sequesters basolateral LET-23 EGFR in an actin-rich inactive membrane compartment to restrict receptor mobility and signaling. In this manner, ERM-1 prevents the immediate activation of the entire pool of LET-23 EGFR and permits the generation of a long-lasting inductive signal. The regulation of receptor localization thus serves to fine-tune the temporal activation of intracellular signaling pathways. PMID:24785082

  5. FRS2 proteins recruit intracellular signaling pathways by binding to diverse targets on fibroblast growth factor and nerve growth factor receptors.

    PubMed

    Ong, S H; Guy, G R; Hadari, Y R; Laks, S; Gotoh, N; Schlessinger, J; Lax, I

    2000-02-01

    The docking protein FRS2 was implicated in the transmission of extracellular signals from the fibroblast growth factor (FGF) or nerve growth factor (NGF) receptors to the Ras/mitogen-activated protein kinase signaling cascade. The two members of the FRS2 family, FRS2alpha and FRS2beta, are structurally very similar. Each is composed of an N-terminal myristylation signal, a phosphotyrosine-binding (PTB) domain, and a C-terminal tail containing multiple binding sites for the SH2 domains of the adapter protein Grb2 and the protein tyrosine phosphatase Shp2. Here we show that the PTB domains of both the alpha and beta isoforms of FRS2 bind directly to the FGF or NGF receptors. The PTB domains of the FRS2 proteins bind to a highly conserved sequence in the juxtamembrane region of FGFR1. While FGFR1 interacts with FRS2 constitutively, independent of ligand stimulation and tyrosine phosphorylation, NGF receptor (TrkA) binding to FRS2 is strongly dependent on receptor activation. Complex formation with TrkA is dependent on phosphorylation of Y490, a canonical PTB domain binding site that also functions as a binding site for Shc (NPXpY). Using deletion and alanine scanning mutagenesis as well as peptide competition assays, we demonstrate that the PTB domains of the FRS2 proteins specifically recognize two different primary structures in two different receptors in a phosphorylation-dependent or -independent manner. In addition, NGF-induced tyrosine phosphorylation of FRS2alpha is diminished in cells that overexpress a kinase-inactive mutant of FGFR1. This experiment suggests that FGFR1 may regulate signaling via NGF receptors by sequestering a common key element which both receptors utilize for transmitting their signals. The multiple interactions mediated by FRS2 appear to play an important role in target selection and in defining the specificity of several families of receptor tyrosine kinases. PMID:10629055

  6. Spinal 5-HT7 receptors induce phrenic motor facilitation via EPAC-mTORC1 signaling.

    PubMed

    Fields, D P; Springborn, S R; Mitchell, G S

    2015-09-01

    Spinal serotonin type 7 (5-HT7) receptors elicit complex effects on motor activity. Whereas 5-HT7 receptor activation gives rise to long-lasting phrenic motor facilitation (pMF), it also constrains 5-HT2 receptor-induced pMF via "cross-talk inhibition." We hypothesized that divergent cAMP-dependent signaling pathways give rise to these distinct 5-HT7 receptor actions. Specifically, we hypothesized that protein kinase A (PKA) mediates cross-talk inhibition of 5-HT2 receptor-induced pMF whereas 5-HT7 receptor-induced pMF results from exchange protein activated by cAMP (EPAC) signaling. Anesthetized, paralyzed, and ventilated rats receiving intrathecal (C4) 5-HT7 receptor agonist (AS-19) injections expressed pMF for >90 min, an effect abolished by pretreatment with a selective EPAC inhibitor (ESI-05) but not a selective PKA inhibitor (KT-5720). Furthermore, intrathecal injections of a selective EPAC activator (8-pCPT-2'-Me-cAMP) were sufficient to elicit pMF. Finally, spinal mammalian target of rapamycin complex-1 (mTORC1) inhibition via intrathecal rapamycin abolished 5-HT7 receptor- and EPAC-induced pMF, demonstrating that spinal 5-HT7 receptors elicit pMF by an EPAC-mTORC1 signaling pathway. Thus 5-HT7 receptors elicit and constrain spinal phrenic motor plasticity via distinct signaling mechanisms that diverge at cAMP (EPAC vs. PKA). Selective manipulation of these molecules may enable refined regulation of serotonin-dependent spinal motor plasticity for therapeutic advantage. PMID:26269554

  7. Spinal 5-HT7 receptors induce phrenic motor facilitation via EPAC-mTORC1 signaling

    PubMed Central

    Fields, D. P.; Springborn, S. R.

    2015-01-01

    Spinal serotonin type 7 (5-HT7) receptors elicit complex effects on motor activity. Whereas 5-HT7 receptor activation gives rise to long-lasting phrenic motor facilitation (pMF), it also constrains 5-HT2 receptor-induced pMF via “cross-talk inhibition.” We hypothesized that divergent cAMP-dependent signaling pathways give rise to these distinct 5-HT7 receptor actions. Specifically, we hypothesized that protein kinase A (PKA) mediates cross-talk inhibition of 5-HT2 receptor-induced pMF whereas 5-HT7 receptor-induced pMF results from exchange protein activated by cAMP (EPAC) signaling. Anesthetized, paralyzed, and ventilated rats receiving intrathecal (C4) 5-HT7 receptor agonist (AS-19) injections expressed pMF for >90 min, an effect abolished by pretreatment with a selective EPAC inhibitor (ESI-05) but not a selective PKA inhibitor (KT-5720). Furthermore, intrathecal injections of a selective EPAC activator (8-pCPT-2′-Me-cAMP) were sufficient to elicit pMF. Finally, spinal mammalian target of rapamycin complex-1 (mTORC1) inhibition via intrathecal rapamycin abolished 5-HT7 receptor- and EPAC-induced pMF, demonstrating that spinal 5-HT7 receptors elicit pMF by an EPAC-mTORC1 signaling pathway. Thus 5-HT7 receptors elicit and constrain spinal phrenic motor plasticity via distinct signaling mechanisms that diverge at cAMP (EPAC vs. PKA). Selective manipulation of these molecules may enable refined regulation of serotonin-dependent spinal motor plasticity for therapeutic advantage. PMID:26269554

  8. Frequency of alcohol consumption in humans; the role of metabotropic glutamate receptors and downstream signaling pathways.

    PubMed

    Meyers, J L; Salling, M C; Almli, L M; Ratanatharathorn, A; Uddin, M; Galea, S; Wildman, D E; Aiello, A E; Bradley, B; Ressler, K; Koenen, K C

    2015-01-01

    Rodent models implicate metabotropic glutamate receptors (mGluRs) and downstream signaling pathways in addictive behaviors through metaplasticity. One way mGluRs can influence synaptic plasticity is by regulating the local translation of AMPA receptor trafficking proteins via eukaryotic elongation factor 2 (eEF2). However, genetic variation in this pathway has not been examined with human alcohol use phenotypes. Among a sample of adults living in Detroit, Michigan (Detroit Neighborhood Health Study; n = 788; 83% African American), 206 genetic variants across the mGluR-eEF2-AMPAR pathway (including GRM1, GRM5, HOMER1, HOMER2, EEF2K, MTOR, EIF4E, EEF2, CAMK2A, ARC, GRIA1 and GRIA4) were found to predict number of drinking days per month (corrected P-value < 0.01) when considered as a set (set-based linear regression conducted in PLINK). In addition, a CpG site located in the 3'-untranslated region on the north shore of EEF2 (cg12255298) was hypermethylated in those who drank more frequently (P < 0.05). Importantly, the association between several genetic variants within the mGluR-eEF2-AMPAR pathway and alcohol use behavior (i.e., consumption and alcohol-related problems) replicated in the Grady Trauma Project (GTP), an independent sample of adults living in Atlanta, Georgia (n = 1034; 95% African American), including individual variants in GRM1, GRM5, EEF2, MTOR, GRIA1, GRIA4 and HOMER2 (P < 0.05). Gene-based analyses conducted in the GTP indicated that GRM1 (empirical P < 0.05) and EEF2 (empirical P < 0.01) withstood multiple test corrections and predicted increased alcohol consumption and related problems. In conclusion, insights from rodent studies enabled the identification of novel human alcohol candidate genes within the mGluR-eEF2-AMPAR pathway. PMID:26101849

  9. Frequency of alcohol consumption in humans; the role of metabotropic glutamate receptors and downstream signaling pathways

    PubMed Central

    Meyers, J L; Salling, M C; Almli, L M; Ratanatharathorn, A; Uddin, M; Galea, S; Wildman, D E; Aiello, A E; Bradley, B; Ressler, K; Koenen, K C

    2015-01-01

    Rodent models implicate metabotropic glutamate receptors (mGluRs) and downstream signaling pathways in addictive behaviors through metaplasticity. One way mGluRs can influence synaptic plasticity is by regulating the local translation of AMPA receptor trafficking proteins via eukaryotic elongation factor 2 (eEF2). However, genetic variation in this pathway has not been examined with human alcohol use phenotypes. Among a sample of adults living in Detroit, Michigan (Detroit Neighborhood Health Study; n=788; 83% African American), 206 genetic variants across the mGluR–eEF2–AMPAR pathway (including GRM1, GRM5, HOMER1, HOMER2, EEF2K, MTOR, EIF4E, EEF2, CAMK2A, ARC, GRIA1 and GRIA4) were found to predict number of drinking days per month (corrected P-value <0.01) when considered as a set (set-based linear regression conducted in PLINK). In addition, a CpG site located in the 3′-untranslated region on the north shore of EEF2 (cg12255298) was hypermethylated in those who drank more frequently (P<0.05). Importantly, the association between several genetic variants within the mGluR–eEF2–AMPAR pathway and alcohol use behavior (i.e., consumption and alcohol-related problems) replicated in the Grady Trauma Project (GTP), an independent sample of adults living in Atlanta, Georgia (n=1034; 95% African American), including individual variants in GRM1, GRM5, EEF2, MTOR, GRIA1, GRIA4 and HOMER2 (P<0.05). Gene-based analyses conducted in the GTP indicated that GRM1 (empirical P<0.05) and EEF2 (empirical P<0.01) withstood multiple test corrections and predicted increased alcohol consumption and related problems. In conclusion, insights from rodent studies enabled the identification of novel human alcohol candidate genes within the mGluR–eEF2–AMPAR pathway. PMID:26101849

  10. Pharmacological and signalling properties of a D2-like dopamine receptor (Dop3) in Tribolium castaneum.

    PubMed

    Verlinden, Heleen; Vleugels, Rut; Verdonck, Rik; Urlacher, Elodie; Vanden Broeck, Jozef; Mercer, Alison

    2015-01-01

    Dopamine is an important neurotransmitter in the central nervous system of vertebrates and invertebrates. Despite their evolutionary distance, striking parallels exist between deuterostomian and protostomian dopaminergic systems. In both, signalling is achieved via a complement of functionally distinct dopamine receptors. In this study, we investigated the sequence, pharmacology and tissue distribution of a D2-like dopamine receptor from the red flour beetle Tribolium castaneum (TricaDop3) and compared it with related G protein-coupled receptors in other invertebrate species. The TricaDop3 receptor-encoding cDNA shows considerable sequence similarity with members of the Dop3 receptor class. Real time qRT-PCR showed high expression in both the central brain and the optic lobes, consistent with the role of dopamine as neurotransmitter. Activation of TricaDop3 expressed in mammalian cells increased intracellular Ca(2+) signalling and decreased NKH-477 (a forskolin analogue)-stimulated cyclic AMP levels in a dose-dependent manner. We studied the pharmacological profile of the TricaDop3 receptor and demonstrated that the synthetic vertebrate dopamine receptor agonists, 2 - amino- 6,7 - dihydroxy - 1,2,3,4 - tetrahydronaphthalene hydrobromide (6,7-ADTN) and bromocriptine acted as agonists. Methysergide was the most potent of the antagonists tested and showed competitive inhibition in the presence of dopamine. This study offers important information on the Dop3 receptor from Tribolium castaneum that will facilitate functional analyses of dopamine receptors in insects and other invertebrates.

  11. Metabotropic glutamate receptor signaling is required for NMDA receptor-dependent ocular dominance plasticity and LTD in visual cortex.

    PubMed

    Sidorov, Michael S; Kaplan, Eitan S; Osterweil, Emily K; Lindemann, Lothar; Bear, Mark F

    2015-10-13

    A feature of early postnatal neocortical development is a transient peak in signaling via metabotropic glutamate receptor 5 (mGluR5). In visual cortex, this change coincides with increased sensitivity of excitatory synapses to monocular deprivation (MD). However, loss of visual responsiveness after MD occurs via mechanisms revealed by the study of long-term depression (LTD) of synaptic transmission, which in layer 4 is induced by acute activation of NMDA receptors (NMDARs) rather than mGluR5. Here we report that chronic postnatal down-regulation of mGluR5 signaling produces coordinated impairments in both NMDAR-dependent LTD in vitro and ocular dominance plasticity in vivo. The data suggest that ongoing mGluR5 signaling during a critical period of postnatal development establishes the biochemical conditions that are permissive for activity-dependent sculpting of excitatory synapses via the mechanism of NMDAR-dependent LTD.

  12. Metabotropic glutamate receptor signaling is required for NMDA receptor-dependent ocular dominance plasticity and LTD in visual cortex.

    PubMed

    Sidorov, Michael S; Kaplan, Eitan S; Osterweil, Emily K; Lindemann, Lothar; Bear, Mark F

    2015-10-13

    A feature of early postnatal neocortical development is a transient peak in signaling via metabotropic glutamate receptor 5 (mGluR5). In visual cortex, this change coincides with increased sensitivity of excitatory synapses to monocular deprivation (MD). However, loss of visual responsiveness after MD occurs via mechanisms revealed by the study of long-term depression (LTD) of synaptic transmission, which in layer 4 is induced by acute activation of NMDA receptors (NMDARs) rather than mGluR5. Here we report that chronic postnatal down-regulation of mGluR5 signaling produces coordinated impairments in both NMDAR-dependent LTD in vitro and ocular dominance plasticity in vivo. The data suggest that ongoing mGluR5 signaling during a critical period of postnatal development establishes the biochemical conditions that are permissive for activity-dependent sculpting of excitatory synapses via the mechanism of NMDAR-dependent LTD. PMID:26417096

  13. Altered CB receptor-signaling in prefrontal cortex from an animal model of depression is reversed by chronic fluoxetine.

    PubMed

    Rodríguez-Gaztelumendi, Antonio; Rojo, M Luisa; Pazos, Angel; Díaz, Alvaro

    2009-03-01

    Bilateral olfactory bulbectomy in the rat (OBX) induces behavioral, neurochemical, and structural abnormalities similar to those observed in human depression that are normalized after chronic, but not acute, treatment with antidepressants. In our study, OBX animals exhibited significant increases in both CB(1) receptor density ([(3)H]CP55490 binding) and functionality (stimulation of [(35)S]GTPgammaS binding by the cannabinoid (CB) agonist WIN 55212-2) at the prefrontal cortex (PFC). After chronic treatment with fluoxetine (10 mg/kg/day, 14 days, s.c.), OBX-induced hyperactivity in the open-field test was fully abolished. Interestingly, chronic fluoxetine fully reversed the enhanced CB(1)-receptor signaling in PFC observed following OBX. The CB agonist Delta(9)-tetrahydrocannabinol (5 mg/kg, i.p., 1 day) did not produce any behavioral effect in sham-operated animals but returned locomotor activity to control values in OBX rats. As both acute administration of Delta(9)-tetrahydrocannabinol and chronic fluoxetine elicited a similar behavioral effect in the OBX rat, it is not unlikely that the regionally selective enhancement of CB(1) receptor-signaling in the PFC could be related with the altered OBX behavior. Our findings reinforce the utility of this animal model to further investigating the implication of the endocannabinoid system in the modulation of emotional processes and its potential role in the adaptive responses to chronic antidepressants.

  14. Heat Avoidance Is Regulated by Transient Receptor Potential (TRP) Channels and a Neuropeptide Signaling Pathway in Caenorhabditis elegans

    PubMed Central

    Glauser, Dominique A.; Chen, Will C.; Agin, Rebecca; MacInnis, Bronwyn L.; Hellman, Andrew B.; Garrity, Paul A.; Tan, Man-Wah; Goodman, Miriam B.

    2011-01-01

    The ability to avoid noxious extremes of hot and cold is critical for survival and depends on thermal nociception. The TRPV subset of transient receptor potential (TRP) channels is heat activated and proposed to be responsible for heat detection in vertebrates and fruit flies. To gain insight into the genetic and neural basis of thermal nociception, we developed assays that quantify noxious heat avoidance in the nematode Caenorhabditis elegans and used them to investigate the genetic basis of this behavior. First, we screened mutants for 18 TRP channel genes (including all TRPV orthologs) and found only minor defects in heat avoidance in single and selected double and triple mutants, indicating that other genes are involved. Next, we compared two wild isolates of C. elegans that diverge in their threshold for heat avoidance and linked this phenotypic variation to a polymorphism in the neuropeptide receptor gene npr-1. Further analysis revealed that loss of either the NPR-1 receptor or its ligand, FLP-21, increases the threshold for heat avoidance. Cell-specific rescue of npr-1 implicates the interneuron RMG in the circuit regulating heat avoidance. This neuropeptide signaling pathway operates independently of the TRPV genes, osm-9 and ocr-2, since mutants lacking npr-1 and both TRPV channels had more severe defects in heat avoidance than mutants lacking only npr-1 or both osm-9 and ocr-2. Our results show that TRPV channels and the FLP-21/NPR-1 neuropeptide signaling pathway determine the threshold for heat avoidance in C. elegans. PMID:21368276

  15. The apelin receptor: physiology, pathology, cell signalling, and ligand modulation of a peptide-activated class A GPCR.

    PubMed

    Chapman, Nigel A; Dupré, Denis J; Rainey, Jan K

    2014-12-01

    The apelin receptor (AR or APJ) is a class A (rhodopsin-like) G-protein-coupled receptor with wide distribution throughout the human body. Activation of the AR by its cognate peptide ligand, apelin, induces diverse physiological effects including vasoconstriction and dilation, strengthening of heart muscle contractility, angiogenesis, and regulation of energy metabolism and fluid homeostasis. Recently, another endogenous peptidic activator of the AR, Toddler/ELABELA, was identified as having a crucial role in zebrafish (Danio rerio) embryonic development. The AR is also implicated in pathologies including cardiovascular disease, diabetes, obesity, and cancer, making it a promising therapeutic target. Despite its established importance, the precise roles of AR signalling remain poorly understood. Moreover, little is known about the mechanisms of peptide-AR activation. Additional complexity arises from modulation of the AR by 2 endogenous peptide ligands, both with multiple bioactive isoforms of variable length and distribution. The various apelin and Toddler/ELABELA isoforms may also produce distinct cellular effects. Further complexity arises through formation of functionally distinct heterodimers between the AR and other G-protein-coupled receptors. This minireview outlines key (patho)physiological actions of the AR, addresses what is known about signal transduction downstream of AR activation, and concludes by discussing unique properties of the endogenous peptidic ligands of the AR. PMID:25275559

  16. The receptor kinase CERK1 has dual functions in symbiosis and immunity signalling.

    PubMed

    Zhang, Xiaowei; Dong, Wentao; Sun, Jongho; Feng, Feng; Deng, Yiwen; He, Zuhua; Oldroyd, Giles E D; Wang, Ertao

    2015-01-01

    The establishment of symbiotic interactions between mycorrhizal fungi, rhizobial bacteria and their legume hosts involves a common symbiosis signalling pathway. This signalling pathway is activated by Nod factors produced by rhizobia and these are recognised by the Nod factor receptors NFR1/LYK3 and NFR5/NFP. Mycorrhizal fungi produce lipochitooligosaccharides (LCOs) similar to Nod factors, as well as short-chain chitin oligomers (CO4/5), implying commonalities in signalling during mycorrhizal and rhizobial associations. Here we show that NFR1/LYK3, but not NFR5/NFP, is required for the establishment of the mycorrhizal interaction in legumes. NFR1/LYK3 is necessary for the recognition of mycorrhizal fungi and the activation of the symbiosis signalling pathway leading to induction of calcium oscillations and gene expression. Chitin oligosaccharides also act as microbe associated molecular patterns that promote plant immunity via similar LysM receptor-like kinases. CERK1 in rice has the highest homology to NFR1 and we show that this gene is also necessary for the establishment of the mycorrhizal interaction as well as for resistance to the rice blast fungus. Our results demonstrate that NFR1/LYK3/OsCERK1 represents a common receptor for chitooligosaccharide-based signals produced by mycorrhizal fungi, rhizobial bacteria (in legumes) and fungal pathogens. It would appear that mycorrhizal recognition has been conserved in multiple receptors across plant species, but additional diversification in certain plant species has defined other signals that this class of receptors can perceive.

  17. Quantitative impedimetric NPY-receptor activation monitoring and signal pathway profiling in living cells.

    PubMed

    te Kamp, Verena; Lindner, Ricco; Jahnke, Heinz-Georg; Krinke, Dana; Kostelnik, Katja B; Beck-Sickinger, Annette G; Robitzki, Andrea A

    2015-05-15

    Label-free and non-invasive monitoring of receptor activation and identification of the involved signal pathways in living cells is an ongoing analytic challenge and a great opportunity for biosensoric systems. In this context, we developed an impedance spectroscopy-based system for the activation monitoring of NPY-receptors in living cells. Using an optimized interdigital electrode array for sensitive detection of cellular alterations, we were able for the first time to quantitatively detect the NPY-receptor activation directly without a secondary or enhancer reaction like cAMP-stimulation by forskolin. More strikingly, we could show that the impedimetric based NPY-receptor activation monitoring is not restricted to the Y1-receptor but also possible for the Y2- and Y5-receptor. Furthermore, we could monitor the NPY-receptor activation in different cell lines that natively express NPY-receptors and proof the specificity of the observed impedimetric effect by agonist/antagonist studies in recombinant NPY-receptor expressing cell lines. To clarify the nature of the observed impedimetric effect we performed an equivalent circuit analysis as well as analyzed the role of cell morphology and receptor internalization. Finally, an antagonist based extensive molecular signal pathway analysis revealed small alterations of the actin cytoskeleton as well as the inhibition of at least L-type calcium channels as major reasons for the observed NPY-induced impedance increase. Taken together, our novel impedance spectroscopy based NPY-receptor activation monitoring system offers the opportunity to identify signal pathways as well as for novel versatile agonist/antagonist screening systems for identification of novel therapeutics in the field of obesity and cancer.

  18. Natriuretic peptide C receptor signalling in the heart and vasculature.

    PubMed

    Rose, Robert A; Giles, Wayne R

    2008-01-15

    Natriuretic peptides (NPs), including atrial, brain and C-type natriuretic peptides (ANP, BNP and CNP), bind two classes of cell surface receptors: the guanylyl cyclase-linked A and B receptors (NPR-A and NPR-B) and the C receptor (NPR-C). The biological effects of NPs have been mainly attributed to changes in intracellular cGMP following their binding to NPR-A and NPR-B. NPR-C does not include a guanylyl cyclase domain. It has been denoted as a clearance receptor and is thought to bind and internalize NPs for ultimate degradation. However, a substantial body of biochemical work has demonstrated the ability of NPR-C to couple to inhibitory G proteins (Gi) and cause inhibition of adenylyl cyclase and activation of phospholipase-C. Recently, novel physiological effects of NPs, mediated specifically by NPR-C, have been discovered in the heart and vasculature. We have described the ability of CNP, acting via NPR-C, to selectively inhibit L-type calcium currents in atrial and ventricular myocytes, as well as in pacemaker cells (sinoatrial node myocytes). In contrast, our studies of the electrophysiological effects of CNP on cardiac fibroblasts demonstrated an NPR-C-Gi-phospholipase-C-dependent activation of a non-selective cation current mediated by transient receptor potential (TRP) channels. It is also known that CNP and BNP have important anti-proliferative effects in cardiac fibroblasts that appear to involve NPR-C. In the mammalian resistance vessels, including mesenteric and coronary arteries, CNP has been found to function as an NPR-C-dependent endothelium-derived hyperpolarizing factor that regulates local blood flow and systemic blood pressure by hyperpolarizing smooth muscle cells. In this review we highlight the role of NPR-C in mediating these NP effects in myocytes and fibroblasts from the heart as well as in vascular smooth muscle cells.

  19. Natriuretic peptide C receptor signalling in the heart and vasculature

    PubMed Central

    Rose, Robert A; Giles, Wayne R

    2008-01-01

    Natriuretic peptides (NPs), including atrial, brain and C-type natriuretic peptides (ANP, BNP and CNP), bind two classes of cell surface receptors: the guanylyl cyclase-linked A and B receptors (NPR-A and NPR-B) and the C receptor (NPR-C). The biological effects of NPs have been mainly attributed to changes in intracellular cGMP following their binding to NPR-A and NPR-B. NPR-C does not include a guanylyl cyclase domain. It has been denoted as a clearance receptor and is thought to bind and internalize NPs for ultimate degradation. However, a substantial body of biochemical work has demonstrated the ability of NPR-C to couple to inhibitory G proteins (Gi) and cause inhibition of adenylyl cyclase and activation of phospholipase-C. Recently, novel physiological effects of NPs, mediated specifically by NPR-C, have been discovered in the heart and vasculature. We have described the ability of CNP, acting via NPR-C, to selectively inhibit L-type calcium currents in atrial and ventricular myocytes, as well as in pacemaker cells (sinoatrial node myocytes). In contrast, our studies of the electrophysiological effects of CNP on cardiac fibroblasts demonstrated an NPR-C–Gi–phospholipase-C-dependent activation of a non-selective cation current mediated by transient receptor potential (TRP) channels. It is also known that CNP and BNP have important anti-proliferative effects in cardiac fibroblasts that appear to involve NPR-C. In the mammalian resistance vessels, including mesenteric and coronary arteries, CNP has been found to function as an NPR-C-dependent endothelium-derived hyperpolarizing factor that regulates local blood flow and systemic blood pressure by hyperpolarizing smooth muscle cells. In this review we highlight the role of NPR-C in mediating these NP effects in myocytes and fibroblasts from the heart as well as in vascular smooth muscle cells. PMID:18006579

  20. The endocannabinoid system in renal cells: regulation of Na+ transport by CB1 receptors through distinct cell signalling pathways

    PubMed Central

    Sampaio, L S; Taveira Da Silva, R; Lima, D; Sampaio, C L C; Iannotti, F A; Mazzarella, E; Di Marzo, V; Vieyra, A; Reis, R A M; Einicker-Lamas, M

    2015-01-01

    Background and Purpose The function of the endocannabinoid system (ECS) in renal tissue is not completely understood. Kidney function is closely related to ion reabsorption in the proximal tubule, the nephron segment responsible for the re-absorption of 70–80% of the filtrate. We studied the effect of compounds modulating the activity of cannabinoid (CB) receptors on the active re-absorption of Na+ in LLC-PK1 cells. Experimental Approach Changes in Na+/K+-ATPase activity were assessed after treatment with WIN55,212-2 (WIN), a non-selective lipid agonist, and haemopressin (HP), an inverse peptide agonist at CB1 receptors. Pharmacological tools were used to investigate the signalling pathways involved in the modulation of Na+ transport. Key Results In addition to CB1 and CB2 receptors and TRPV1 channels, the mRNAs encoding for enzymes of the ECS were also expressed in LLC-PK1. WIN (10−7 M) and HP (10−6 M) altered Na+ re-absorption in LLC-PK1 in a dual manner. They both acutely (after 1 min) increased Na+/K+-ATPase activity in a TRPV1 antagonist-sensitive way. WIN's stimulating effect persisted for 30 min, and this effect was partially blocked by a CB1 antagonist or a PKC inhibitor. In contrast, HP inhibited Na+/K+-ATPase after 30 min incubation, and this effect was attenuated by a CB1 antagonist or a PKA inhibitor. Conclusion and Implications The ECS is expressed in LLC-PK1 cells. Both CB1 receptors and TRPV1 channels regulate Na+/K+-ATPase activity in these cells, and are modulated by lipid and peptide CB1 receptor ligands, which act via different signalling pathways. PMID:25537261

  1. Network Analysis of Neurodegenerative Disease Highlights a Role of Toll-Like Receptor Signaling

    PubMed Central

    Nguyen, Thanh-Phuong; Morine, Melissa J.

    2014-01-01

    Despite significant advances in the study of the molecular mechanisms altered in the development and progression of neurodegenerative diseases (NDs), the etiology is still enigmatic and the distinctions between diseases are not always entirely clear. We present an efficient computational method based on protein-protein interaction network (PPI) to model the functional network of NDs. The aim of this work is fourfold: (i) reconstruction of a PPI network relating to the NDs, (ii) construction of an association network between diseases based on proximity in the disease PPI network, (iii) quantification of disease associations, and (iv) inference of potential molecular mechanism involved in the diseases. The functional links of diseases not only showed overlap with the traditional classification in clinical settings, but also offered new insight into connections between diseases with limited clinical overlap. To gain an expanded view of the molecular mechanisms involved in NDs, both direct and indirect connector proteins were investigated. The method uncovered molecular relationships that are in common apparently distinct diseases and provided important insight into the molecular networks implicated in disease pathogenesis. In particular, the current analysis highlighted the Toll-like receptor signaling pathway as a potential candidate pathway to be targeted by therapy in neurodegeneration. PMID:24551850

  2. Sustained N-methyl-D-aspartate receptor hypofunction remodels the dopamine system and impairs phasic signaling

    PubMed Central

    Ferris, Mark J.; Milenkovic, Marija; Liu, Shuai; Mielnik, Catharine A.; Beerepoot, Pieter; John, Carrie E.; España, Rodrigo A.; Sotnikova, Tatyana D.; Gainetdinov, Raul R.; Borgland, Stephanie L.; Jones, Sara R.; Ramsey, Amy J.

    2014-01-01

    Chronic N-methyl-D-aspartate receptor (NMDAR) hypofunction has been proposed as a contributing factor to symptoms of schizophrenia. However, it is unclear how sustained NMDAR hypofunction throughout development affects other neurotransmitter systems that have been implicated in the disease. Dopamine neuron biochemistry and activity were examined to determine whether sustained NMDAR hypofunction causes a state of hyperdopaminergia. We report that a global, genetic reduction in NMDARs led to a remodeling of dopamine neurons, substantially affecting two key regulators of dopamine homeostasis, i.e. tyrosine hydroxylase and the dopamine transporter. In NR1 knockdown mice, dopamine synthesis and release were attenuated, and dopamine clearance was increased. Although these changes would have the effect of reducing dopamine transmission, we demonstrated that a state of hyperdopaminergia existed in these mice because dopamine D2 autoreceptors were desensitized. In support of this conclusion, NR1 knockdown dopamine neurons have higher tonic firing rates. Although the tonic firing rates are higher, phasic signaling is impaired, and dopamine overflow cannot be achieved with exogenous high-frequency stimulation that models phasic firing. Through the examination of several parameters of dopamine neurotransmission, we provide evidence that chronic NMDAR hypofunction leads to a state of elevated synaptic dopamine. Compensatory mechanisms to attenuate hyperdopaminergia also impact the ability to generate dopamine surges through phasic firing. PMID:24754704

  3. Regulation of T cell receptor complex-mediated signaling by ubiquitin and ubiquitin-like modifications

    PubMed Central

    Friend, Samantha F; Deason-Towne, Francina; Peterson, Lisa K; Berger, Allison J; Dragone, Leonard L

    2014-01-01

    Post-translational protein modifications are a dynamic method of regulating protein function in response to environmental signals. As with any cellular process, T cell receptor (TCR) complex-mediated signaling is highly regulated, since the strength and duration of TCR-generated signals governs T cell development and activation. While regulation of TCR complex-mediated signaling by phosphorylation has been well studied, regulation by ubiquitin and ubiquitin-like modifiers is still an emerging area of investigation. This review will examine how ubiquitin, E3 ubiquitin ligases, and other ubiquitin-like modifications such as SUMO and NEDD8 regulate TCR complex-mediated signaling. PMID:25628960

  4. Regulation of T cell receptor complex-mediated signaling by ubiquitin and ubiquitin-like modifications.

    PubMed

    Friend, Samantha F; Deason-Towne, Francina; Peterson, Lisa K; Berger, Allison J; Dragone, Leonard L

    2014-01-01

    Post-translational protein modifications are a dynamic method of regulating protein function in response to environmental signals. As with any cellular process, T cell receptor (TCR) complex-mediated signaling is highly regulated, since the strength and duration of TCR-generated signals governs T cell development and activation. While regulation of TCR complex-mediated signaling by phosphorylation has been well studied, regulation by ubiquitin and ubiquitin-like modifiers is still an emerging area of investigation. This review will examine how ubiquitin, E3 ubiquitin ligases, and other ubiquitin-like modifications such as SUMO and NEDD8 regulate TCR complex-mediated signaling.

  5. Regulation of T cell receptor complex-mediated signaling by ubiquitin and ubiquitin-like modifications.

    PubMed

    Friend, Samantha F; Deason-Towne, Francina; Peterson, Lisa K; Berger, Allison J; Dragone, Leonard L

    2014-01-01

    Post-translational protein modifications are a dynamic method of regulating protein function in response to environmental signals. As with any cellular process, T cell receptor (TCR) complex-mediated signaling is highly regulated, since the strength and duration of TCR-generated signals governs T cell development and activation. While regulation of TCR complex-mediated signaling by phosphorylation has been well studied, regulation by ubiquitin and ubiquitin-like modifiers is still an emerging area of investigation. This review will examine how ubiquitin, E3 ubiquitin ligases, and other ubiquitin-like modifications such as SUMO and NEDD8 regulate TCR complex-mediated signaling. PMID:25628960

  6. Identification of intracellular domains in the growth hormone receptor involved in signal transduction

    SciTech Connect

    Billestrup, N.; Allevato, G.; Moldrup, A.

    1994-12-31

    The growth hormone (GH) receptor belongs to the GH/prolactin/cytokine super-family of receptors. The signal transduction mechanism utilized by this class of receptors remains largely unknown. In order to identify functional domains in the intracellular region of the GH receptor we generated a number of GH receptor mutants and analyzed their function after transfection into various cell lines. A truncated GH receptor missing 184 amino acids at the C-terminus was unable to medite GH effects on transcription of the Spi 2.1 and insulin genes. However, this mutant was fully active in mediating GH-stimulated metabolic effects such as protein synthesis and lipolysis. Furthermore, this mutant GH receptor internalized rapidly following GH binding. Another truncated GH receptor lacking all but five amino acids of the cytoplasmic domain could not mediate any effects of GH nor did it internalize. Deletion of the proline-rich region or changing the four prolines to alanines also resulted in a GH receptor deficient in signaling. Mutation of phenylalanine 346 to alanine resulted in a GH receptor which did not internalize rapidly; however, this mutant GH receptor was capable of mediating GH-stimulated transcription as well as metabolic effects. These results indicate that the intracellular part of the GH receptor can be divided into at least three functional domains: (1) for transcriptional activity, two domains are involved, one located in the C-terminal 184 amino acids and the other in the proline-rich domain; (2) for metabolic effects, a domain located in or near the proline-rich region is of importance; and (3) for internalization, phenylalanine 346 is necessary. 28 refs., 1 fig.

  7. SIGNALLING THROUGH RETINOIC ACID RECEPTORS IN CARDIAC DEVELOPMENT: DOING THE RIGHT THINGS AT THE RIGHT TIMES

    PubMed Central

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

    2015-01-01

    Retinoic acid (RA) is a terpenoid that is synthesized from Vitamin A/retinol (ROL) and binds to the nuclear receptors retinoic acid receptor (RAR)/retinoid X receptor (RXR) to control multiple developmental processes in vertebrates. The available clinic and experimental data provide uncontested evidence for the pleiotropic roles of RA signalling in development of multiple embryonic structures and organs such eyes, central nervous system, gonads, lungs and heart. The development of any of these above-mentioned embryonic organ systems can be effectively utilized to showcase the many strategies utilized by RA signalling. However, it is very likely that the strategies employed to transfer RA signals during cardiac development comprise the majority of the relevant and sophisticated ways through which retinoid signals can be conveyed in a complex biological system. Here, we provide the reader with arguments indicating that RA signalling is exquisitely regulated according to specific phases of cardiac development and that RA signalling itself is one of the major regulators of the timing of cardiac morphogenesis and differentiation. We will focus on the role of signalling by RA receptors (RARs) in early phases of heart development. PMID:25134739

  8. Signal transmission through the CXC chemokine receptor 4 (CXCR4) transmembrane helices.

    PubMed

    Wescott, Melanie P; Kufareva, Irina; Paes, Cheryl; Goodman, Jason R; Thaker, Yana; Puffer, Bridget A; Berdougo, Eli; Rucker, Joseph B; Handel, Tracy M; Doranz, Benjamin J

    2016-08-30

    The atomic-level mechanisms by which G protein-coupled receptors (GPCRs) transmit extracellular ligand binding events through their transmembrane helices to activate intracellular G proteins remain unclear. Using a comprehensive library of mutations covering all 352 residues of the GPCR CXC chemokine receptor 4 (CXCR4), we identified 41 amino acids that are required for signaling induced by the chemokine ligand CXCL12 (stromal cell-derived factor 1). CXCR4 variants with each of these mutations do not signal properly but remain folded, based on receptor surface trafficking, reactivity to conformationally sensitive monoclonal antibodies, and ligand binding. When visualized on the structure of CXCR4, the majority of these residues form a continuous intramolecular signaling chain through the transmembrane helices; this chain connects chemokine binding residues on the extracellular side of CXCR4 to G protein-coupling residues on its intracellular side. Integrated into a cohesive model of signal transmission, these CXCR4 residues cluster into five functional groups that mediate (i) chemokine engagement, (ii) signal initiation, (iii) signal propagation, (iv) microswitch activation, and (v) G protein coupling. Propagation of the signal passes through a "hydrophobic bridge" on helix VI that coordinates with nearly every known GPCR signaling motif. Our results agree with known conserved mechanisms of GPCR activation and significantly expand on understanding the structural principles of CXCR4 signaling. PMID:27543332

  9. Evaluation of Intracellular Signaling Downstream Chimeric Antigen Receptors

    PubMed Central

    Karlsson, Hannah; Svensson, Emma; Gigg, Camilla; Jarvius, Malin; Olsson-Strömberg, Ulla; Savoldo, Barbara; Dotti, Gianpietro; Loskog, Angelica

    2015-01-01

    CD19-targeting CAR T cells have shown potency in clinical trials targeting B cell leukemia. Although mainly second generation (2G) CARs carrying CD28 or 4-1BB have been investigated in patients, preclinical studies suggest that third generation (3G) CARs with both CD28 and 4-1BB have enhanced capacity. However, little is known about the intracellular signaling pathways downstream of CARs. In the present work, we have analyzed the signaling capacity post antigen stimulation in both 2G and 3G CARs. 3G CAR T cells expanded better than 2G CAR T cells upon repeated stimulation with IL-2 and autologous B cells. An antigen-driven accumulation of CAR+ cells was evident post antigen stimulation. The cytotoxicity of both 2G and 3G CAR T cells was maintained by repeated stimulation. The phosphorylation status of intracellular signaling proteins post antigen stimulation showed that 3G CAR T cells had a higher activation status than 2G. Several proteins involved in signaling downstream the TCR were activated, as were proteins involved in the cell cycle, cell adhesion and exocytosis. In conclusion, 3G CAR T cells had a higher degree of intracellular signaling activity than 2G CARs which may explain the increased proliferative capacity seen in 3G CAR T cells. The study also indicates that there may be other signaling pathways to consider when designing or evaluating new generations of CARs. PMID:26700307

  10. Examining the critical roles of human CB2 receptor residues Valine 3.32 (113) and Leucine 5.41 (192) in ligand recognition and downstream signaling activities.

    PubMed

    Alqarni, Mohammed; Myint, Kyaw Zeyar; Tong, Qin; Yang, Peng; Bartlow, Patrick; Wang, Lirong; Feng, Rentian; Xie, Xiang-Qun

    2014-09-26

    We performed molecular modeling and docking to predict a putative binding pocket and associated ligand-receptor interactions for human cannabinoid receptor 2 (CB2). Our data showed that two hydrophobic residues came in close contact with three structurally distinct CB2 ligands: CP-55,940, SR144528 and XIE95-26. Site-directed mutagenesis experiments and subsequent functional assays implicated the roles of Valine residue at position 3.32 (V113) and Leucine residue at position 5.41 (L192) in the ligand binding function and downstream signaling activities of the CB2 receptor. Four different point mutations were introduced to the wild type CB2 receptor: V113E, V113L, L192S and L192A. Our results showed that mutation of Val113 with a Glutamic acid and Leu192 with a Serine led to the complete loss of CB2 ligand binding as well as downstream signaling activities. Substitution of these residues with those that have similar hydrophobic side chains such as Leucine (V113L) and Alanine (L192A), however, allowed CB2 to retain both its ligand binding and signaling functions. Our modeling results validated by competition binding and site-directed mutagenesis experiments suggest that residues V113 and L192 play important roles in ligand binding and downstream signaling transduction of the CB2 receptor.

  11. Essential role of endocytosis for interleukin-4-receptor-mediated JAK/STAT signalling.

    PubMed

    Kurgonaite, Kristina; Gandhi, Hetvi; Kurth, Thomas; Pautot, Sophie; Schwille, Petra; Weidemann, Thomas; Bökel, Christian

    2015-10-15

    Many important signalling cascades operate through specialized signalling endosomes, but a corresponding mechanism has as yet not been described for hematopoietic cytokine receptors. Based on live-cell affinity measurements, we recently proposed that ligand-induced interleukin-4 receptor (IL-4R) complex formation and thus JAK/STAT pathway activation requires a local subcellular increase in receptor density. Here, we show that this concentration step is provided by the internalization of IL-4R subunits through a constitutive, Rac1-, Pak- and actin-mediated endocytosis route that causes IL-4R subunits to become enriched by about two orders of magnitude within a population of cortical endosomes. Consistently, ligand-induced receptor dimers are preferentially detected within these endosomes. IL-4 signalling can be blocked by pharmacological inhibitors targeting the actin polymerization machinery driving receptor internalization, placing endocytosis unambigously upstream of receptor activation. Taken together, these observations demonstrate a role for endocytosis that is mechanistically distinct from the scaffolding function of signalling endosomes in other pathways.

  12. Metabotropic glutamate receptor-mediated signaling dampens the HPA axis response to restraint stress.

    PubMed

    Evanson, Nathan K; Herman, James P

    2015-10-15

    Glutamate is an important neurotransmitter in the regulation of the neural portion of hypothalamus-pituitary-adrenal (HPA) axis activity, and signals through ionotropic and metabotropic receptors. In the current studies we investigated the role of hypothalamic paraventricular group I metabotropic glutamate receptors in the regulation of the HPA axis response to restraint stress in rats. Direct injection of the group I metabotropic glutamate receptor agonist 3,5-dihydroxyphenylglycine (DHPG) into the PVN prior to restraint leads to blunting of the HPA axis response in awake animals. Consistent with this result, infusion of the group I receptor antagonist hexyl-homoibotenic acid (HIBO) potentiates the HPA axis response to restraint. The excitatory effect of blocking paraventricular group I metabotropic glutamate signaling is blocked by co-administration of dexamethasone into the PVN. However, the inhibitory effect of DHPG is not affected by co-administration of the cannabinoid CB1 receptor antagonist AM-251 into the PVN. Together, these results suggest that paraventricular group I metabotropic glutamate receptor signaling acts to dampen HPA axis reactivity. This effect appears to be similar to the rapid inhibitory effect of glucocorticoids at the PVN, but is not mediated by endocannabinoid signaling.

  13. Receptors for bitter, sweet and umami taste couple to inhibitory G protein signaling pathways.

    PubMed

    Ozeck, Mark; Brust, Paul; Xu, Hong; Servant, Guy

    2004-04-12

    Taste receptors are thought to couple to the G protein Galpha-gustducin to initiate signal transduction cascades leading to taste perception. To further characterize the G protein-coupling selectivity of these receptors, we expressed them in HEK293 cells and monitored the modulation of different signaling pathways upon stimulation. We found that the bitter compound cycloheximide induces phosphorylation of extracellular signal-regulated kinases1 and 2 (ERK 1/2) and inhibits cAMP accumulation in HEK293 cells expressing the mouse bitter T2R(5) receptor. These effects are totally abolished upon treatment with pertussis toxin. On the other hand, sweeteners and monosodium glutamate induce phosphorylation of ERK1/2 and inhibit cAMP accumulation in HEK293 cells expressing the human sweet T1R(2)/T1R(3) receptor and the human umami T1R(1)/T1R(3) receptor, respectively. The effects of these taste modalities are also prevented by treatment with pertussis toxin. Collectively, our results show that taste receptors can functionally couple to Galpha(i/o) proteins to transmit intracellular signals.

  14. Signaling pathways engaged by NK cell receptors: double concerto for activating receptors, inhibitory receptors and NK cells.

    PubMed

    Tomasello, E; Bléry, M; Vély, F; Vivier, E

    2000-04-01

    Despite the absence of antigen-specific receptors at their surface, NK cells can selectively eliminate virus-infected cells, tumor cells and allogenic cells. A dynamic and precisely coordinated balance between activating and inhibitory receptors governs NK cell activation programs. Multiple activating and inhibitory NK cell surface molecules have been described, a group of them acting as receptors for MHC class I molecules. In spite of their heterogeneity, activating NK cell receptors present remarkable structural and functional homologies with T cell- and B cell-antigen receptors. Inhibitory NK cell receptors operate at early stages of activating cascades by recruiting protein tyrosine phosphatases via intra- cytoplasmic motifs (ITIM), a strategy which is widely conserved in hematopoietic and non-hematopoietic cells.

  15. Dynamic mass redistribution as a means to measure and differentiate signaling via opioid and cannabinoid receptors.

    PubMed

    Codd, Ellen E; Mabus, John R; Murray, Brian S; Zhang, Sui-Po; Flores, Christopher M

    2011-08-01

    Classically, G protein-coupled receptor activation by a ligand has been viewed as producing a defined response such as activation of a G protein, activation or inhibition of adenylyl cyclase, or stimulation of phospholipase C and/or alteration in calcium flux. Newer concepts of ligand-directed signaling recognize that different ligands, ostensibly acting at the same receptors, may induce different downstream effects, complicating the selection of a screening assay. Dynamic mass redistribution (DMR), a label-free technology that uses light to measure ligand-induced changes in the mass of cells proximate to the biosensor, provides an integrated cellular response comprising multiple pathways and cellular events. Using DMR, signals induced by opioid or cannabinoid agonists in cells transfected with these receptors were blocked by pharmacologically appropriate receptor antagonists as well as by pertussis toxin. Differences among compounds in relative potencies at DMR versus ligand-stimulated GTPγS or receptor binding endpoints, suggesting functional selectivity, were observed. Preliminary evidence indicates that inhibitors of intermediate steps in the cell signaling cascade, such as receptor recycling inhibitors, mitogen-activated protein kinase kinase/p38 mitogen-activated protein kinase inhibitors, or cytoskeletal disruptors, altered or attenuated the cannabinoid-induced response. Notable is the finding that mitogen-activated protein kinase kinase 1/2 inhibitors attenuated signaling induced by the cannabinoid type 2 receptor inverse agonist AM630 but not that stimulated by the agonist CP 55,940. Thus, DMR has the potential to not only identify ligands that activate a given G protein-coupled receptor, but also ascertain the signaling pathways engaged by a specific ligand, making DMR a useful tool in the identification of biased ligands, which may ultimately exhibit improved therapeutic profiles. PMID:21323580

  16. kappa-Opioid receptor signaling and brain reward function.

    PubMed

    Bruijnzeel, Adrie W

    2009-12-11

    The dynorphin-like peptides have profound effects on the state of the brain reward system and human and animal behavior. The dynorphin-like peptides affect locomotor activity, food intake, sexual behavior, anxiety-like behavior, and drug intake. Stimulation of kappa-opioid receptors, the endogenous receptor for the dynorphin-like peptides, inhibits dopamine release in the striatum (nucleus accumbens and caudate putamen) and induces a negative mood state in humans and animals. The administration of drugs of abuse increases the release of dopamine in the striatum and mediates the concomitant release of dynorphin-like peptides in this brain region. The reviewed studies suggest that chronic drug intake leads to an upregulation of the brain dynorphin system in the striatum and in particular in the dorsal part of the striatum/caudate putamen. This might inhibit drug-induced dopamine release and provide protection against the neurotoxic effects of high dopamine levels. After the discontinuation of chronic drug intake these neuroadaptations remain unopposed which has been suggested to contribute to the negative emotional state associated with drug withdrawal and increased drug intake. kappa-Opioid receptor agonists have also been shown to inhibit calcium channels. Calcium channel inhibitors have antidepressant-like effects and inhibit the release of norepinephrine. This might explain that in some studies kappa-opioid receptor agonists attenuate nicotine and opioid withdrawal symptomatology. A better understanding of the role of dynorphins in the regulation of brain reward function might contribute to the development of novel treatments for mood disorders and other disorders that stem from a dysregulation of the brain reward system.

  17. Small molecule modulation of nuclear receptor conformational dynamics: implications for function and drug discovery.

    PubMed

    Kojetin, Douglas J; Burris, Thomas P

    2013-01-01

    Nuclear receptors are targets for a wide range of ligands, both natural and synthetic, that regulate their activity and provide a means to pharmacologically modulate the receptor. Recent emphasis in the nuclear receptor field has focused on selective nuclear receptor modulators, which can display graded transcriptional responses and tissue selective pharmacological responses that deviate from the prototypical agonist or antagonist. Understanding the molecular mechanism of action of these selective modulators will provide significant insight toward the development of the next generation of modulators. Although most nuclear receptor structural studies have primarily focused on obtaining ligand-receptor cocrystal structures, recent studies implicate an important role for protein dynamics in the mechanism of action of nuclear receptor ligands. Here we review nuclear receptor studies reporting how ligands modulate the conformational dynamics of the nuclear receptor ligand-binding domain (LBD). A particular emphasis is placed on protein NMR and hydrogen/deuterium exchange (HDX) techniques and how they provide complementary information that, when combined with crystallography, provide detailed insight into the function of nuclear receptors.

  18. The cannabinoid CB1 receptor and mTORC1 signalling pathways interact to modulate glucose homeostasis in mice

    PubMed Central

    Bermudez-Silva, Francisco J.; Romero-Zerbo, Silvana Y.; Haissaguerre, Magalie; Ruz-Maldonado, Inmaculada; Lhamyani, Said; El Bekay, Rajaa; Tabarin, Antoine; Marsicano, Giovanni; Cota, Daniela

    2016-01-01

    ABSTRACT The endocannabinoid system (ECS) is an intercellular signalling mechanism that is present in the islets of Langerhans and plays a role in the modulation of insulin secretion and expansion of the β-cell mass. The downstream signalling pathways mediating these effects are poorly understood. Mammalian target of rapamycin complex 1 (mTORC1) signalling is a key intracellular pathway involved in energy homeostasis and is known to importantly affect the physiology of pancreatic islets. We investigated the possible relationship between cannabinoid type 1 (CB1) receptor signalling and the mTORC1 pathway in the endocrine pancreas of mice by using pharmacological analysis as well as mice genetically lacking the CB1 receptor or the downstream target of mTORC1, the kinase p70S6K1. In vitro static secretion experiments on islets, western blotting, and in vivo glucose and insulin tolerance tests were performed. The CB1 receptor antagonist rimonabant decreased glucose-stimulated insulin secretion (GSIS) at 0.1 µM while increasing phosphorylation of p70S6K1 and ribosomal protein S6 (rpS6) within the islets. Specific pharmacological blockade of mTORC1 by 3 nM rapamycin, as well as genetic deletion of p70S6K1, impaired the CB1-antagonist-mediated decrease in GSIS. In vivo experiments showed that 3 mg/kg body weight rimonabant decreased insulin levels and induced glucose intolerance in lean mice without altering peripheral insulin sensitivity; this effect was prevented by peripheral administration of low doses of rapamycin (0.1 mg/kg body weight), which increased insulin sensitivity. These findings suggest a functional interaction between the ECS and the mTORC1 pathway within the endocrine pancreas and at the whole-organism level, which could have implications for the development of new therapeutic approaches for pancreatic β-cell diseases. PMID:26563389

  19. The cannabinoid CB1 receptor and mTORC1 signalling pathways interact to modulate glucose homeostasis in mice.

    PubMed

    Bermudez-Silva, Francisco J; Romero-Zerbo, Silvana Y; Haissaguerre, Magalie; Ruz-Maldonado, Inmaculada; Lhamyani, Said; El Bekay, Rajaa; Tabarin, Antoine; Marsicano, Giovanni; Cota, Daniela

    2016-01-01

    The endocannabinoid system (ECS) is an intercellular signalling mechanism that is present in the islets of Langerhans and plays a role in the modulation of insulin secretion and expansion of the β-cell mass. The downstream signalling pathways mediating these effects are poorly understood. Mammalian target of rapamycin complex 1 (mTORC1) signalling is a key intracellular pathway involved in energy homeostasis and is known to importantly affect the physiology of pancreatic islets. We investigated the possible relationship between cannabinoid type 1 (CB1) receptor signalling and the mTORC1 pathway in the endocrine pancreas of mice by using pharmacological analysis as well as mice genetically lacking the CB1 receptor or the downstream target of mTORC1, the kinase p70S6K1. In vitro static secretion experiments on islets, western blotting, and in vivo glucose and insulin tolerance tests were performed. The CB1 receptor antagonist rimonabant decreased glucose-stimulated insulin secretion (GSIS) at 0.1 µM while increasing phosphorylation of p70S6K1 and ribosomal protein S6 (rpS6) within the islets. Specific pharmacological blockade of mTORC1 by 3 nM rapamycin, as well as genetic deletion of p70S6K1, impaired the CB1-antagonist-mediated decrease in GSIS. In vivo experiments showed that 3 mg/kg body weight rimonabant decreased insulin levels and induced glucose intolerance in lean mice without altering peripheral insulin sensitivity; this effect was prevented by peripheral administration of low doses of rapamycin (0.1 mg/kg body weight), which increased insulin sensitivity. These findings suggest a functional interaction between the ECS and the mTORC1 pathway within the endocrine pancreas and at the whole-organism level, which could have implications for the development of new therapeutic approaches for pancreatic β-cell diseases.

  20. Signaling of human frizzled receptors to the mating pathway in yeast.

    PubMed

    Dirnberger, Dietmar; Seuwen, Klaus

    2007-09-26

    Frizzled receptors have seven membrane-spanning helices and are considered as atypical G protein-coupled receptors (GPCRs). The mating response of the yeast Saccharomyces cerevisiae is mediated by a GPCR signaling system and this model organism has been used extensively in the past to study mammalian GPCR function. We show here that human Frizzled receptors (Fz1 and Fz2) can be properly targeted to the yeast plasma membrane, and that they stimulate the yeast mating pathway in the absence of added Wnt ligands, as evidenced by cell cycle arrest in G1 and reporter gene expression dependent on the mating pathway-activated FUS1 gene. Introducing intracellular portions of Frizzled receptors into the Ste2p backbone resulted in the generation of constitutively active receptor chimeras that retained mating factor responsiveness. Introducing intracellular portions of Ste2p into the Frizzled receptor backbone was found to strongly enhance mating pathway activation as compared to the native Frizzleds, likely by facilitating interaction with the yeast Galpha protein Gpa1p. Furthermore, we show reversibility of the highly penetrant G1-phase arrests exerted by the receptor chimeras by deletion of the mating pathway effector FAR1. Our data demonstrate that Frizzled receptors can functionally replace mating factor receptors in yeast and offer an experimental system to study modulators of Frizzled receptors.

  1. The βc receptor family - Structural insights and their functional implications.

    PubMed

    Broughton, Sophie E; Nero, Tracy L; Dhagat, Urmi; Kan, Winnie L; Hercus, Timothy R; Tvorogov, Denis; Lopez, Angel F; Parker, Michael W

    2015-08-01

    Granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3) and IL-5 are members of a small family of cytokines that share a beta receptor subunit (βc). These cytokines regulate the growth, differentiation, migration and effector function activities of many hematopoietic cells in bone marrow, blood and sites of inflammation. Excessive or aberrant signaling can result in chronic inflammatory conditions and myeloid leukemias. The crystal structures of the GM-CSF ternary complex, the IL-5 binary complex and the very recent IL-3 receptor alpha subunit build upon decades of structure-function studies, giving new insights into cytokine-receptor specificity and signal transduction. Selective modulation of receptor function is now a real possibility and the structures of the βc receptor family are being used to discover novel and disease-specific therapeutics. PMID:25982846

  2. Respiratory burst in human B lymphocytes. Triggering of surface Ig receptors induces modulation of chemiluminescence signal.

    PubMed

    Leca, G; Benichou, G; Bensussan, A; Mitenne, F; Galanaud, P; Vazquez, A

    1991-05-15

    B lymphocytes have been shown to proliferate and release oxygen metabolites when surface Ig is cross-linked and when stimulated with phorbol ester. Biochemical evidence has been provided for the presence of a superoxide generating system in B cells, which seems to be identical to the well-characterized NADPH-oxidase of phagocytes. In this report, we show that normal and EBV-transformed B cells produce superoxide anions after stimulation with phorbol ester and when surface Ig was cross-linked, as detected by lucigenin-dependent chemiluminescence. Anti-surface IgG antibodies induced a significant respiratory burst whereas those directed against surface IgM had no effect on B cell oxidative metabolism. Prestimulated B lymphocytes responded to further triggering by the same or another ligand. Pretreatment with Staphlococcus aureus Cowan I strain (SAC) or anti-IgM antibodies resulted in complete unresponsiveness to subsequent SAC or anti-IgG stimulation, but it did not affect PMA- and ionomycin-mediated B cell chemiluminescence. In contrast to preincubation with anti-IgM antibodies, the pretreatment of B cells with SAC induced a transient inhibitory effect on B cell signaling. In fact, SAC-pretreated B lymphocytes could be restimulated with the same ligand when blast cells were isolated. Furthermore, a 24-h incubation of the pretreated B cells in the absence of SAC completely restored the SAC-mediated respiratory burst. These results suggest that two distinct mechanisms may account for SAC- and anti-IgM-induced inhibition: a transient and reversible modulation of surface Ig, induced by SAC, and a long-lasting desensitization of the surface Ig receptors, respectively. These findings may have interesting implications for understanding the transduction of negative signals in B lymphocytes.

  3. Trichostatin A Protects Liver against Septic Injury through Inhibiting Toll-Like Receptor Signaling

    PubMed Central

    Kim, So-Jin; Park, Jin-Sook; Lee, Do-Won; Lee, Sun-Mee

    2016-01-01

    Sepsis, a serious clinical problem, is characterized by a systemic inflammatory response to infection and leads to organ failure. Toll-like receptor (TLR) signaling is intimately implicated in hyper-inflammatory responses and tissue injury during sepsis. Histone deacetylase (HDAC) inhibitors have been reported to exhibit anti-inflammatory properties. The aim of this study was to investigate the hepatoprotective mechanisms of trichostatin A (TSA), a HDAC inhibitor, associated with TLR signaling pathway during sepsis. The anti-inflammatory properties of TSA were assayed in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Polymicrobial sepsis was induced in mice by cecal ligation and puncture (CLP), a clinically relevant model of sepsis. The mice were intraperitoneally received TSA (1, 2 or 5 mg/kg) 30 min before CLP. The serum and liver samples were collected 6 and 24-h after CLP. TSA inhibited the increased production of tumor necrosis factor (TNF)-α and interleukin (IL)-6 in LPS-stimulated RAW264.7 cells. TSA improved sepsis-induced mortality, attenuated liver injury and decreased serum TNF-α and IL-6 levels. CLP increased the levels of TLR4, TLR2 and myeloid differentiation primary response protein 88 (MyD88) protein expression and association of MyD88 with TLR4 and TLR2, which were attenuated by TSA. CLP increased nuclear translocation of nuclear factor kappa B and decreased cytosolic inhibitor of kappa B (IκB) protein expression, which were attenuated by TSA. Moreover, CLP decreased acetylation of IκB kinase (IKK) and increased association of IKK with IκB and TSA attenuated these alterations. Our findings suggest that TSA attenuates liver injury by inhibiting TLR-mediated inflammatory response during sepsis. PMID:27068262

  4. Ring Finger Protein 11 Inhibits Melanocortin 3 and 4 Receptor Signaling.

    PubMed

    Müller, Anne; Niederstadt, Lars; Jonas, Wenke; Yi, Chun-Xia; Meyer, Franziska; Wiedmer, Petra; Fischer, Jana; Grötzinger, Carsten; Schürmann, Annette; Tschöp, Matthias; Kleinau, Gunnar; Grüters, Annette; Krude, Heiko; Biebermann, Heike

    2016-01-01

    Intact melanocortin signaling via the G protein-coupled receptors (GPCRs), melanocortin receptor 4 (MC4R), and melanocortin receptor 3 (MC3R) is crucial for body weight maintenance. So far, no connection between melanocortin signaling and hypothalamic inflammation has been reported. Using a bimolecular fluorescence complementation library screen, we identified a new interaction partner for these receptors, ring finger protein 11 (RNF11). RNF11 participates in the constitution of the A20 complex that is involved in reduction of tumor necrosis factor α (TNFα)-induced NFκB signaling, an important pathway in hypothalamic inflammation. Mice treated with high-fat diet (HFD) for 3 days demonstrated a trend toward an increase in hypothalamic Rnf11 expression, as shown for other inflammatory markers under HFD. Furthermore, Gs-mediated signaling of MC3/4R was demonstrated to be strongly reduced to 20-40% by co-expression of RNF11 despite unchanged total receptor expression. Cell surface expression was not affected for MC3R but resulted in a significant reduction of MC4R to 61% by co-expression with RNF11. Mechanisms linking HFD, inflammation, and metabolism remain partially understood. In this study, a new axis between signaling of specific body weight regulating GPCRs and factors involved in hypothalamic inflammation is suggested. PMID:27551276

  5. Ring Finger Protein 11 Inhibits Melanocortin 3 and 4 Receptor Signaling

    PubMed Central

    Müller, Anne; Niederstadt, Lars; Jonas, Wenke; Yi, Chun-Xia; Meyer, Franziska; Wiedmer, Petra; Fischer, Jana; Grötzinger, Carsten; Schürmann, Annette; Tschöp, Matthias; Kleinau, Gunnar; Grüters, Annette; Krude, Heiko; Biebermann, Heike

    2016-01-01

    Intact melanocortin signaling via the G protein-coupled receptors (GPCRs), melanocortin receptor 4 (MC4R), and melanocortin receptor 3 (MC3R) is crucial for body weight maintenance. So far, no connection between melanocortin signaling and hypothalamic inflammation has been reported. Using a bimolecular fluorescence complementation library screen, we identified a new interaction partner for these receptors, ring finger protein 11 (RNF11). RNF11 participates in the constitution of the A20 complex that is involved in reduction of tumor necrosis factor α (TNFα)-induced NFκB signaling, an important pathway in hypothalamic inflammation. Mice treated with high-fat diet (HFD) for 3 days demonstrated a trend toward an increase in hypothalamic Rnf11 expression, as shown for other inflammatory markers under HFD. Furthermore, Gs-mediated signaling of MC3/4R was demonstrated to be strongly reduced to 20–40% by co-expression of RNF11 despite unchanged total receptor expression. Cell surface expression was not affected for MC3R but resulted in a significant reduction of MC4R to 61% by co-expression with RNF11. Mechanisms linking HFD, inflammation, and metabolism remain partially understood. In this study, a new axis between signaling of specific body weight regulating GPCRs and factors involved in hypothalamic inflammation is suggested. PMID:27551276

  6. Nanoconjugation prolongs endosomal signaling of the epidermal growth factor receptor and enhances apoptosis

    NASA Astrophysics Data System (ADS)

    Wu, L.; Xu, F.; Reinhard, B. M.

    2016-07-01

    It is becoming increasingly clear that intracellular signaling can be subject to strict spatial control. As the covalent attachment of a signaling ligand to a nanoparticle (NP) impacts ligand-receptor binding, uptake, and trafficking, nanoconjugation provides new opportunities for manipulating intracellular signaling in a controlled fashion. To establish the effect of nanoconjugation on epidermal growth factor (EGF) mediated signaling, we investigate here the intracellular fate of nanoconjugated EGF (NP-EGF) and its bound receptor (EGFR) by quantitative correlated darkfield/fluorescence microscopy and density-based endosomal fractionation. We demonstrate that nanoconjugation prolongs the dwell time of phosphorylated receptors in the early endosomes and that the retention of activated EGFR in the early endosomes is accompanied by an EGF mediated apoptosis at effective concentrations that do not induce apoptosis in the case of free EGF. Overall, these findings indicate nanoconjugation as a rational strategy for modifying signaling that acts by modulating the temporo-spatial distribution of the activated EGF-EGFR ligand-receptor complex.It is becoming increasingly clear that intracellular signaling can be subject to strict spatial control. As the covalent attachment of a signaling ligand to a nanoparticle (NP) impacts ligand-receptor binding, uptake, and trafficking, nanoconjugation provides new opportunities for manipulating intracellular signaling in a controlled fashion. To establish the effect of nanoconjugation on epidermal growth factor (EGF) mediated signaling, we investigate here the intracellular fate of nanoconjugated EGF (NP-EGF) and its bound receptor (EGFR) by quantitative correlated darkfield/fluorescence microscopy and density-based endosomal fractionation. We demonstrate that nanoconjugation prolongs the dwell time of phosphorylated receptors in the early endosomes and that the retention of activated EGFR in the early endosomes is accompanied by an EGF

  7. Restless AMPA receptors: implications for synaptic transmission and plasticity

    PubMed Central

    Lüscher, Christian; Frerking, Matthew

    2010-01-01

    A central assumption in neurobiology holds that changes in the strength of individual synapses underlie changes in behavior. This concept is widely accepted in the case of learning and memory where LTP and LTD are the most compelling cellular models. It is therefore of great interest to understand, on a molecular level, how the brain regulates the strength of neuronal connections. We review a large body of evidence in support of the very straightforward regulation of synaptic strength by changing the number of postsynaptic receptors, and discuss the molecular machinery required for insertion and removal of AMPA receptors. PMID:11672812

  8. Chronic Cocaine Dampens Dopamine Signaling during Cocaine Intoxication and Unbalances D1 over D2 Receptor Signaling

    PubMed Central

    Park, Kicheon; Pan, Yingtian

    2013-01-01

    Dopamine increases triggered by cocaine and consequent stimulation of dopamine receptors (including D1 and D2) are associated with its rewarding effects. However, while facilitation of D1 receptor (D1R) signaling enhances the rewarding effects of cocaine, facilitation of D2R signaling decreases it, which indicates that for cocaine to be rewarding it must result in a predominance of D1R over D2R signaling. Moreover, the transition to compulsive cocaine intake might result from an imbalance between D1R and D2R signaling. To test the hypothesis that chronic cocaine use unbalances D1R over D2R signaling during cocaine intoxication, we used microprobe optical imaging to compare dynamic changes in intracellular calcium ([Ca2+]i, marker of neuronal activation) to acute cocaine in striatal D1R-EGFP and D2R-EGFP-expressing neurons between control and chronically treated mice. Chronic cocaine attenuated responses to acute cocaine in D1R (blunting Ca2+ increases by 67 ± 16%) and D2R (blunting Ca2+ decrease by 72 ± 17%) neurons in most D1R and D2R neurons (∼75%). However, the dynamics of this attenuation during cocaine intoxication was longer lasting for D2R than for D1R. Thus, whereas control mice showed a fast but short-lasting predominance of D1R over D2R signaling (peaking at ∼8 min) during acute cocaine intoxication, in chronically treated mice D1R predominance was sustained for >30 min (throughout the measurement period). Thus, chronic cocaine use dramatically reduced cocaine-induced DA signaling, shifting the balance between D1R and D2R signaling during intoxication to a predominance of D1R (stimulatory) over D2R (inhibitory) signaling, which might facilitate compulsive intake in addiction. PMID:24089490

  9. CB2 cannabinoid receptors promote neural progenitor cell proliferation via mTORC1 signaling.

    PubMed

    Palazuelos, Javier; Ortega, Zaira; Díaz-Alonso, Javier; Guzmán, Manuel; Galve-Roperh, Ismael

    2012-01-01

    The endocannabinoid system is known to regulate neural progenitor (NP) cell proliferation and neurogenesis. In particular, CB(2) cannabinoid receptors have been shown to promote NP proliferation. As CB(2) receptors are not expressed in differentiated neurons, CB(2)-selective agonists are promising candidates to manipulate NP proliferation and indirectly neurogenesis by overcoming the undesired psychoactive effects of neuronal CB(1) cannabinoid receptor activation. Here, by using NP cells, brain organotypic cultures, and in vivo animal models, we investigated the signal transduction mechanism involved in CB(2) receptor-induced NP cell proliferation and neurogenesis. Exposure of hippocampal HiB5 NP cells to the CB(2) receptor-selective agonist HU-308 led to the activation of the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin complex 1 (mTORC1) pathway, which, by inhibiting its downstream target p27Kip1, induced NP proliferation. Experiments conducted with the CB(2) receptor-selective antagonist SR144528, inhibitors of the PI3K/Akt/mTORC1 axis, and CB(2) receptor transient-transfection vector further supported that CB(2) receptors control NP cell proliferation via activation of mTORC1 signaling. Likewise, CB(2) receptor engagement induced cell proliferation in an mTORC1-dependent manner both in embryonic cortical slices and in adult hippocampal NPs. Thus, HU-308 increased ribosomal protein S6 phosphorylation and 5-bromo-2'-deoxyuridine incorporation in wild-type but not CB(2) receptor-deficient NPs of the mouse subgranular zone. Moreover, adult hippocampal NP proliferation induced by HU-308 and excitotoxicity was blocked by the mTORC1 inhibitor rapamycin. Altogether, these findings provide a mechanism of action and a rationale for the use of nonpsychotomimetic CB(2) receptor-selective ligands as a novel strategy for the control of NP cell proliferation and neurogenesis.

  10. CB2 Cannabinoid Receptors Promote Neural Progenitor Cell Proliferation via mTORC1 Signaling*

    PubMed Central

    Palazuelos, Javier; Ortega, Zaira; Díaz-Alonso, Javier; Guzmán, Manuel; Galve-Roperh, Ismael

    2012-01-01

    The endocannabinoid system is known to regulate neural progenitor (NP) cell proliferation and neurogenesis. In particular, CB2 cannabinoid receptors have been shown to promote NP proliferation. As CB2 receptors are not expressed in differentiated neurons, CB2-selective agonists are promising candidates to manipulate NP proliferation and indirectly neurogenesis by overcoming the undesired psychoactive effects of neuronal CB1 cannabinoid receptor activation. Here, by using NP cells, brain organotypic cultures, and in vivo animal models, we investigated the signal transduction mechanism involved in CB2 receptor-induced NP cell proliferation and neurogenesis. Exposure of hippocampal HiB5 NP cells to the CB2 receptor-selective agonist HU-308 led to the activation of the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin complex 1 (mTORC1) pathway, which, by inhibiting its downstream target p27Kip1, induced NP proliferation. Experiments conducted with the CB2 receptor-selective antagonist SR144528, inhibitors of the PI3K/Akt/mTORC1 axis, and CB2 receptor transient-transfection vector further supported that CB2 receptors control NP cell proliferation via activation of mTORC1 signaling. Likewise, CB2 receptor engagement induced cell proliferation in an mTORC1-dependent manner both in embryonic cortical slices and in adult hippocampal NPs. Thus, HU-308 increased ribosomal protein S6 phosphorylation and 5-bromo-2′-deoxyuridine incorporation in wild-type but not CB2 receptor-deficient NPs of the mouse subgranular zone. Moreover, adult hippocampal NP proliferation induced by HU-308 and excitotoxicity was blocked by the mTORC1 inhibitor rapamycin. Altogether, these findings provide a mechanism of action and a rationale for the use of nonpsychotomimetic CB2 receptor-selective ligands as a novel strategy for the control of NP cell proliferation and neurogenesis. PMID:22102284

  11. Serotonergic innervation of the amygdala: targets, receptors, and implications for stress and anxiety.

    PubMed

    Asan, Esther; Steinke, Maria; Lesch, Klaus-Peter

    2013-06-01

    The amygdala is a core component of neural circuits that mediate processing of emotional, particularly anxiety and fear-related stimuli across species. In addition, the nuclear complex plays a key role in the central nervous system stress response, and alterations in amygdala responsivity are found in neuropsychiatric disorders, especially those precipitated or sustained by stressors. Serotonin has been shown to shape and fine-tune neural plasticity in development and adulthood, thereby allowing for network flexibility and adaptive capacity in response to environmental challenges, and is implicated in the modulation of stimulus processing and stress sensitivity in the amygdala. The fact that altered amygdala activity patterns are observed upon pharmacological manipulations of serotonergic transmission, as well as in carriers of genetic variations in serotonin pathway-associated signaling molecules representing risk factors for neuropsychiatric disorders, underlines the importance of understanding the role and mode of action of serotonergic transmission in the amygdala for human psychopathology. Here, we present a short overview over organizational principles of the amygdala in rodents, non-human primates and humans, and review findings on the origin, morphology, and targets of serotonergic innervation, the distribution patterns and cellular expression of serotonin receptors, and the consequences of stress and pharmacological manipulations of serotonergic transmission in the amygdala, focusing particularly on the extensively studied basolateral complex and central nucleus.

  12. An engineered Axl 'decoy receptor' effectively silences the Gas6-Axl signaling axis

    SciTech Connect

    Kariolis, Mihalis S.; Miao, Yu Rebecca; Jones, Douglas S.; Kapur, Shiven; Mathews, Irimpan I.; Giaccia, Amato J.; Cochran, Jennifer R.

    2014-09-21

    Aberrant signaling through the Axl receptor tyrosine kinase has been associated with a myriad of human diseases, most notably metastatic cancer, identifying Axl and its ligand Gas6 as important therapeutic targets. Using rational and combinatorial approaches, we engineered an Axl ‘decoy receptor’ that binds Gas6 with high affinity and inhibits its function, offering an alternative approach from drug discovery efforts that directly target Axl. Four mutations within this high affinity Axl variant caused structural alterations in side chains across the Gas6/Axl binding interface, stabilizing a conformational change on Gas6. When reformatted as an Fc-fusion, the engineered decoy receptor bound to Gas6 with femtomolar affinity, an 80-fold improvement compared to the wild-type Axl receptor, allowing effective sequestration of Gas6 and specific abrogation of Axl signaling. Additionally, increased Gas6 binding affinity was critical and correlative with the ability of decoy receptors to potently inhibit metastasis and disease progression in vivo.

  13. Dynamics of Virus-Receptor Interactions in Virus Binding, Signaling, and Endocytosis

    PubMed Central

    Boulant, Steeve; Stanifer, Megan; Lozach, Pierre-Yves

    2015-01-01

    During viral infection the first challenge that viruses have to overcome is gaining access to the intracellular compartment. The infection process starts when the virus contacts the surface of the host cell. A complex series of events ensues, including diffusion at the host cell membrane surface, binding to receptors, signaling, internalization, and delivery of the genetic information. The focus of this review is on the very initial steps of virus entry, from receptor binding to particle uptake into the host cell. We will discuss how viruses find their receptor, move to sub-membranous regions permissive for entry, and how they hijack the receptor-mediated signaling pathway to promote their internalization. PMID:26043381

  14. New paradigms in chemokine receptor signal transduction: Moving beyond the two-site model.

    PubMed

    Kleist, Andrew B; Getschman, Anthony E; Ziarek, Joshua J; Nevins, Amanda M; Gauthier, Pierre-Arnaud; Chevigné, Andy; Szpakowska, Martyna; Volkman, Brian F

    2016-08-15

    Chemokine receptor (CKR) signaling forms the basis of essential immune cellular functions, and dysregulated CKR signaling underpins numerous disease processes of the immune system and beyond. CKRs, which belong to the seven transmembrane domain receptor (7TMR) superfamily, initiate signaling upon binding of endogenous, secreted chemokine ligands. Chemokine-CKR interactions are traditionally described by a two-step/two-site mechanism, in which the CKR N-terminus recognizes the chemokine globular core (i.e. site 1 interaction), followed by activation when the unstructured chemokine N-terminus is inserted into the receptor TM bundle (i.e. site 2 interaction). Several recent studies challenge the structural independence of sites 1 and 2 by demonstrating physical and allosteric links between these supposedly separate sites. Others contest the functional independence of these sites, identifying nuanced roles for site 1 and other interactions in CKR activation. These developments emerge within a rapidly changing landscape in which CKR signaling is influenced by receptor PTMs, chemokine and CKR dimerization, and endogenous non-chemokine ligands. Simultaneous advances in the structural and functional characterization of 7TMR biased signaling have altered how we understand promiscuous chemokine-CKR interactions. In this review, we explore new paradigms in CKR signal transduction by considering studies that depict a more intricate architecture governing the consequences of chemokine-CKR interactions. PMID:27106080

  15. Endocrine disrupting chemicals targeting estrogen receptor signaling: Identification and mechanisms of action

    PubMed Central

    Shanle, Erin K.; Xu, Wei

    2011-01-01

    Many endocrine disrupting chemicals (EDCs) adversely impact estrogen signaling by interacting with two estrogen receptors (ERs): ERα and ERβ. Though the receptors have similar ligand binding and DNA binding domains, ERα and ERβ have some unique properties in terms of ligand selectivity and target gene regulation. EDCs that target ER signaling can modify genomic and non-genomic ER activity through direct interactions with ERs, indirectly through transcription factors like the aryl hydrocarbon receptor (AhR), or through modulation of metabolic enzymes that are critical for normal estrogen synthesis and metabolism. Many EDCs act through multiple mechanisms as exemplified by chemicals that bind both AhR and ER, such as 3-methylcholanthrene. Other EDCs that target ER signaling include phytoestrogens, bisphenolics, and organochlorine pesticides and many alter normal ER signaling through multiple mechanisms. EDCs can also display tissue-selective ER agonist and antagonist activities similar to selective estrogen receptor modulators (SERMs) designed for pharmaceutical use. Thus, biological effects of EDCs need to be carefully interpreted because EDCs can act through complex tissue-selective modulation of ERs and other signaling pathways in vivo. Current requirements by the U.S. Environmental Protection Agency require some in vitro and cell-based assays to identify EDCs that target ER signaling through direct and metabolic mechanisms. Additional assays may be useful screens for identifying EDCs that act through alternative mechanisms prior to further in vivo study. PMID:21053929

  16. New paradigms in chemokine receptor signal transduction: Moving beyond the two-site model.

    PubMed

    Kleist, Andrew B; Getschman, Anthony E; Ziarek, Joshua J; Nevins, Amanda M; Gauthier, Pierre-Arnaud; Chevigné, Andy; Szpakowska, Martyna; Volkman, Brian F

    2016-08-15

    Chemokine receptor (CKR) signaling forms the basis of essential immune cellular functions, and dysregulated CKR signaling underpins numerous disease processes of the immune system and beyond. CKRs, which belong to the seven transmembrane domain receptor (7TMR) superfamily, initiate signaling upon binding of endogenous, secreted chemokine ligands. Chemokine-CKR interactions are traditionally described by a two-step/two-site mechanism, in which the CKR N-terminus recognizes the chemokine globular core (i.e. site 1 interaction), followed by activation when the unstructured chemokine N-terminus is inserted into the receptor TM bundle (i.e. site 2 interaction). Several recent studies challenge the structural independence of sites 1 and 2 by demonstrating physical and allosteric links between these supposedly separate sites. Others contest the functional independence of these sites, identifying nuanced roles for site 1 and other interactions in CKR activation. These developments emerge within a rapidly changing landscape in which CKR signaling is influenced by receptor PTMs, chemokine and CKR dimerization, and endogenous non-chemokine ligands. Simultaneous advances in the structural and functional characterization of 7TMR biased signaling have altered how we understand promiscuous chemokine-CKR interactions. In this review, we explore new paradigms in CKR signal transduction by considering studies that depict a more intricate architecture governing the consequences of chemokine-CKR interactions.

  17. Sensory habituation of auditory receptor neurons: implications for sound localization.

    PubMed

    Givois, V; Pollack, G S

    2000-09-01

    Auditory receptor neurons exhibit sensory habituation; their responses decline with repeated stimulation. We studied the effects of sensory habituation on the neural encoding of sound localization cues using crickets as a model system. In crickets, Teleogryllus oceanicus, sound localization is based on binaural comparison of stimulus intensity. There are two potential codes at the receptor-neuron level for interaural intensity difference: interaural difference in response strength, i.e. spike rate and/or count, and interaural difference in response latency. These are affected differently by sensory habituation. When crickets are stimulated with cricket-song-like trains of sound pulses, response strength declines for successive pulses in the train, and the decrease becomes more pronounced as the stimulus intensity increases. Response decrement is thus greater for receptors serving the ear ipsilateral to the sound source, where intensity is higher, resulting in a decrease in the interaural difference in response strength. Sensory habituation also affects response latency, which increases for responses to successive sound pulses in the stimulus train. The change in latency is independent of intensity, and thus is similar for receptors serving both ears. As a result, interaural latency difference is unaffected by sensory habituation and may be a more reliable cue for sound localization.

  18. Signal Transduction Pathway Analysis in Desmoid-type Fibromatosis: TGFβ, COX2 and Sex Steroid Receptors

    PubMed Central

    Mignemi, Nicholas A.; Itani, Doha M.; Fasig, John H.; Keedy, Vicki L.; Hande, Kenneth R.; Whited, Brent W.; Homlar, Kelly C.; Correa, Hernan; Coffin, Cheryl M.; Black, Jennifer O.; Yi, Yajun; Halpern, Jennifer L.; Holt, Ginger E.; Schwartz, Herbert S.; Schoenecker, Jonathan G.; Cates, Justin M. M.

    2014-01-01

    Summary Despite reports of sex steroid receptor and COX2 expression in desmoid-type fibromatosis, responses to single agent therapy with anti-estrogens and nonsteroidal anti-inflammatory drugs are unpredictable. Perhaps combination pharmacotherapy might be more effective in desmoid tumors that co-express these targets. Clearly, a further understanding of the signaling pathways deregulated in desmoid tumors is essential for development of targeted molecular therapy. Transforming growth factor-β (TGFβ) and bone morphogenetic proteins (BMPs) are important regulators of fibroblast proliferation and matrix deposition, but little is known about the TGFβ superfamily in fibromatosis. A tissue microarray representing 27 desmoid tumors was constructed; 14 samples of healing scar and 6 samples of normal fibrous tissue were included for comparison. Expression of selected receptors and activated downstream transcription factors of TGFβ family signaling pathways, β-catenin, sex steroid hormone receptors and COX2 were assessed by immunohistochemistry; patterns of co-expression were explored via correlational statistical analyses. In addition to β-catenin, immunoreactivity for phosphorylated SMAD2/3 (indicative of active TGFβ signaling) and COX2 was significantly increased in desmoid tumors compared to healing scar and quiescent fibrous tissue. Low levels of phosphorylated SMAD1/5/8 were detected in only a minority of cases. TGFβ receptor type 1 and androgen receptor were expressed in both desmoid tumors and scar, but not in fibrous tissue. Estrogen receptor-β was present in all cases studied. TGFβ signaling appears to be activated in desmoid-type fibromatosis and phosphorylated SMAD2/3 and COX2 immunoreactivity may be of diagnostic utility in these tumors. Given the frequency of androgen receptor, estrogen receptor-β and COX2 co-expression in desmoid tumors, further assessment of the efficacy of combination pharmacotherapy using hormonal agonists/antagonists together

  19. GABAA receptor signaling in caudal periaqueductal gray regulates maternal aggression and maternal care in mice

    PubMed Central

    Lee, Grace; Gammie, Stephen C.

    2010-01-01

    Maternal aggression (maternal defense) is exhibited by lactating females towards intruders and contributes to the protection of offspring. Enhancement of GABAA receptor signaling by benzodiazepines elevates maternal aggression, and we previously found indirect evidence (via c-Fos immunhistochemistry) that caudal periaqueductal gray (cPAG) and lateral septum (LS) could be sites where benzodiazepines increase aggression. We recently found that GABAA receptor signaling in LS modulates maternal aggression, and in this study, we tested the hypothesis that GABAA receptor signaling in cPAG also regulates this behavior. Site-directed injections to cPAG were made in lactating mice using the GABAA receptor antagonist, bicuculline (3–9 ng) or the GABAA receptor positive modulator, chlordiazepoxide (CDP), a benzodiazepine (2.5–20 µg). Maternal aggression, other maternal behaviors, and anxiety-like measures (using the light-dark box) were then examined. GABAA receptor positive modulator did not increase aggression, which could have resulted from a ceiling effect. However, 8 ng and 9 ng of bicuculline in cPAG significantly decreased maternal aggression without altering other maternal behaviors or light-dark box performance, suggesting some GABAA receptor signaling in cPAG is required for full maternal aggression expression. Additionally, 7 ng of bicuculline significantly increased licking/grooming of pups, and decreased the number of transitions between the light and dark compartments of the light-dark box without affecting aggression. Given these results indicating that antagonizing GABAA-receptor in cPAG dose-dependently promotes offspring grooming behavior while impairing aggression, it is possible that the cPAG represents a key site for decision making (aggression versus other behaviors) in the lactating female. PMID:20457185

  20. Disruption of Androgen Receptor Signaling in Males by Environmental Chemicals

    PubMed Central

    Luccio-Camelo, Doug C.; Prins, Gail S

    2011-01-01

    Androgen-disruptors are environmental chemicals in that interfere with the biosynthesis, metabolism or action of endogenous androgens resulting in a deflection from normal male developmental programming and reproductive tract growth and function. Since male sexual differentiation is entirely androgen-dependent, it is highly susceptible to androgen-disruptors. Animal models and epidemiological evidence link exposure to androgen disrupting chemicals with reduced sperm counts, increased infertility, testicular dysgenesis syndrome, and testicular and prostate cancers. Further, there appears to be increased sensitivity to these agents during critical developmental windows when male differentiation is at its peak. A variety of in vitro and in silico approaches have been used to identify broad classes of androgen disrupting molecules that include organochlorinated pesticides, industrial chemicals, and plasticizers with capacity to ligand the androgen receptor. The vast majority of these synthetic molecules act as anti-androgens. This review will highlight the evidence for androgen disrupting chemicals that act through interference with the androgen receptor, discussing specific compounds for which there is documented in vivo evidence for male reproductive tract perturbations. PMID:21515368

  1. Endosomal receptor kinetics determine the stability of intracellular growth factor signalling complexes

    PubMed Central

    Tzafriri, A. Rami; Edelman, Elazer R.

    2006-01-01

    There is an emerging paradigm that growth factor signalling continues in the endosome and that cell response to a growth factor is defined by the integration of cell surface and endosomal events. As activated receptors in the endosome are exposed to a different set of binding partners, they probably elicit differential signals compared with when they are at the cell surface. As such, complete appreciation of growth factor signalling requires understanding of growth factor–receptor binding and trafficking kinetics both at the cell surface and in endosomes. Growth factor binding to surface receptors is well characterized, and endosomal binding is assumed to follow surface kinetics if one accounts for changes in pH. Yet, specific binding kinetics within the endosome has not been examined in detail. To parse the factors governing the binding state of endosomal receptors we analysed a whole-cell mathematical model of epidermal growth factor receptor trafficking and binding. We discovered that the stability of growth factor–receptor complexes within endosomes is governed by three primary independent factors: the endosomal dissociation constant, total endosomal volume and the number of endosomal receptors. These factors were combined into a single dimensionless parameter that determines the endosomal binding state of the growth factor–receptor complex and can distinguish different growth factors from each other and different cell states. Our findings indicate that growth factor binding within endosomal compartments cannot be appreciated solely on the basis of the pH-dependence of the dissociation constant and that the concentration of receptors in the endosomal compartment must also be considered. PMID:17117924

  2. Endothelin receptors and their cellular signal transduction mechanism in human cultured prostatic smooth muscle cells.

    PubMed

    Saita, Y; Koizumi, T; Yazawa, H; Morita, T; Takenaka, T; Honda, K

    1997-06-01

    1. Endothelin (ET) receptors, and their cellular signal transduction mechanism, were characterized in a primary culture of human prostatic smooth muscle cells (HP cell). 2. [125I]-ET-1 and [125I]-ET-3 binding studies revealed that both ETA and ETB receptors were present in the HP cells, and the ratio of ETA to ETB receptors was 1.4:1. 3. Analysis of ET receptor mRNA by reverse transcription-polymerase chain reaction also demonstrated that HP cells express both ETA and ETB receptors. 4. ET-1 and ET-3 increased intracellular free Ca2+ concentration ([Ca2+]i) in the HP cells in a concentration-dependent manner. Use of subtype selective antagonists BQ-123 and BQ-788, indicated that both ETA and ETB receptors were coupled to an increase in [Ca2+]i. 5. Pretreatment of the cells with pertussis toxin resulted in a significant but partial attenuation of the [Ca2+]i increase mediated through the ETA and ETB receptors. However, sensitivity to pertussis toxin (PTX) was significantly different between them. 6. In conclusion, HP cells possess ETA and ETB receptors. Further, these two endothelin receptor subtypes evoke an increase in [Ca2+]i possibly via the action of different GTP-binding proteins. PMID:9208135

  3. Endothelin receptors and their cellular signal transduction mechanism in human cultured prostatic smooth muscle cells

    PubMed Central

    Saita, Yuji; Koizumi, Tomonobu; Yazawa, Hidenori; Morita, Takashi; Takenaka, Toichi; Honda, Kazuo

    1997-01-01

    Endothelin (ET) receptors, and their cellular signal transduction mechanism, were characterized in a primary culture of human prostatic smooth muscle cells (HP cell). [125I]-ET-1 and [125I]-ET-3 binding studies revealed that both ETA and ETB receptors were present in the HP cells, and the ratio of ETA to ETB receptors was 1.4:1. Analysis of ET receptor mRNA by reverse transcription-polymerase chain reaction also demonstrated that HP cells express both ETA and ETB receptors. ET-1 and ET-3 increased intracellular free Ca2+ concentration ([Ca2+]i) in the HP cells in a concentration-dependent manner. Use of subtype selective antagonists BQ-123 and BQ-788, indicated that both ETA and ETB receptors were coupled to an increase in [Ca2+]i. Pretreatment of the cells with pertussis toxin resulted in a significant but partial attenuation of the [Ca2+]i increase mediated through the ETA and ETB receptors. However, sensitivity to pertussis toxin (PTX) was significantly different between them. In conclusion, HP cells possess ETA and ETB receptors. Further, these two endothelin receptor subtypes evoke an increase in [Ca2+]i possibly via the action of different GTP-binding proteins. PMID:9208135

  4. Mechanisms of progesterone receptor export from nuclei: role of nuclear localization signal, nuclear export signal, and ran guanosine triphosphate.

    PubMed

    Tyagi, R K; Amazit, L; Lescop, P; Milgrom, E; Guiochon-Mantel, A

    1998-11-01

    Steroid hormone receptors are, in most cases, mainly nuclear proteins that undergo a continuous nucleocytoplasmic shuttling. The mechanism of the nuclear export of these proteins remains largely unknown. To approach this problem experimentally in vivo, we have prepared cell lines permanently coexpressing the wild-type nuclear progesterone receptor (PR) and a cytoplasmic receptor mutant deleted of its nuclear localization signal (NLS) [(deltaNLS)PR]. Each receptor species was deleted from the epitope recognized by a specific monoclonal antibody, thus allowing separated observation of the two receptor forms in the same cells. Administration of hormone provoked formation of heterodimers during nucleocytoplasmic shuttling and import of (deltaNLS)PR into the nucleus. Washing out of the hormone allowed us to follow the export of (deltaNLS)PR into the cytoplasm. Microinjection of BSA coupled to a NLS inhibited the export of (deltaNLS)PR. On the contrary, microinjection of BSA coupled to a nuclear export signal (NES) was without effect. Moreover, leptomycin B, which inhibits NES-mediated export, was also without effect. tsBN2 cells contain a thermosensitive RCC1 protein (Ran GTP exchange protein). At the nonpermissive temperature, the nuclear export of (deltaNLS)PR could be observed, whereas the export of NES-BSA was suppressed. Microinjection of GTPgammaS confirmed that the export of (deltaNLS)PR was not dependent on GTP hydrolysis. These experiments show that the nuclear export of PR is not NES mediated but probably involves the NLS. It does not involve Ran GTP, and it is not dependent on the hydrolysis of GTP. The nucleocytoplasmic shuttling of steroid hormone receptors thus appears to utilize mechanisms different from those previously described for some viral, regulatory, and heterogeneous ribonuclear proteins. PMID:9817595

  5. beta-Arrestin mediates beta1-adrenergic receptor-epidermal growth factor receptor interaction and downstream signaling.

    PubMed

    Tilley, Douglas G; Kim, Il-Man; Patel, Priyesh A; Violin, Jonathan D; Rockman, Howard A

    2009-07-24

    beta1-Adrenergic receptor (beta1AR) stimulation confers cardioprotection via beta-arrestin-de pend ent transactivation of epidermal growth factor receptors (EGFRs), however, the precise mechanism for this salutary process is unknown. We tested the hypothesis that the beta1AR and EGFR form a complex that differentially directs intracellular signaling pathways. beta1AR stimulation and EGF ligand can each induce equivalent EGFR phosphorylation, internalization, and downstream activation of ERK1/2, but only EGF ligand causes translocation of activated ERK to the nucleus, whereas beta1AR-stimulated/EGFR-transactivated ERK is restricted to the cytoplasm. beta1AR and EGFR are shown to interact as a receptor complex both in cell culture and endogenously in human heart, an interaction that is selective and undergoes dynamic regulation by ligand stimulation. Although catecholamine stimulation mediates the retention of beta1AR-EGFR interaction throughout receptor internalization, direct EGF ligand stimulation initiates the internalization of EGFR alone. Continued interaction of beta1AR with EGFR following activation is dependent upon C-terminal tail GRK phosphorylation sites of the beta1AR and recruitment of beta-arrestin. These data reveal a new signaling paradigm in which beta-arrestin is required for the maintenance of a beta1AR-EGFR interaction that can direct cytosolic targeting of ERK in response to catecholamine stimulation.

  6. Chromatin Modulatory Proteins and Olfactory Receptor Signaling in the Refinement and Maintenance of Fruitless Expression in Olfactory Receptor Neurons

    PubMed Central

    Li, Qingyun; Okuwa, Sumie; Peng, Bo; Wu, Jianni; Volkan, Pelin Cayirlioglu

    2016-01-01

    During development, sensory neurons must choose identities that allow them to detect specific signals and connect with appropriate target neurons. Ultimately, these sensory neurons will successfully integrate into appropriate neural circuits to generate defined motor outputs, or behavior. This integration requires a developmental coordination between the identity of the neuron and the identity of the circuit. The mechanisms that underlie this coordination are currently unknown. Here, we describe two modes of regulation that coordinate the sensory identities of Drosophila melanogaster olfactory receptor neurons (ORNs) involved in sex-specific behaviors with the sex-specific behavioral circuit identity marker fruitless (fru). The first mode involves a developmental program that coordinately restricts to appropriate ORNs the expression of fru and two olfactory receptors (Or47b and Ir84a) involved in sex-specific behaviors. This regulation requires the chromatin modulatory protein Alhambra (Alh). The second mode relies on the signaling from the olfactory receptors through CamK and histone acetyl transferase p300/CBP to maintain ORN-specific fru expression. Our results highlight two feed-forward regulatory mechanisms with both developmentally hardwired and olfactory receptor activity-dependent components that establish and maintain fru expression in ORNs. Such a dual mechanism of fru regulation in ORNs might be a trait of neurons driving plastic aspects of sex-specific behaviors. PMID:27093619

  7. Distinct CCR7 glycosylation pattern shapes receptor signaling and endocytosis to modulate chemotactic responses.

    PubMed

    Hauser, Mark A; Kindinger, Ilona; Laufer, Julia M; Späte, Anne-Katrin; Bucher, Delia; Vanes, Sarah L; Krueger, Wolfgang A; Wittmann, Valentin; Legler, Daniel F

    2016-06-01

    The homeostatic chemokines CCL19 and CCL21 and their common cognate chemokine receptor CCR7 orchestrate immune cell trafficking by eliciting distinct signaling pathways. Here, we demonstrate that human CCR7 is N-glycosylated on 2 specific residues in the N terminus and the third extracellular loop. Conceptually, CCR7 glycosylation adds steric hindrance to the receptor N terminus and extracellular loop 3, acting as a "swinging door" to regulate receptor sensitivity and cell migration. We found that freshly isolated human B cells, as well as expanded T cells, but not naïve T cells, express highly sialylated CCR7. Moreover, we identified that human dendritic cells imprint T cell migration toward CCR7 ligands by secreting enzymes that deglycosylate CCR7, thereby boosting CCR7 signaling on T cells, permitting enhanced T cell locomotion, while simultaneously decreasing receptor endocytosis. In addition, dendritic cells proteolytically convert immobilized CCL21 to a soluble form that is more potent in triggering chemotactic movement and does not desensitize the receptor. Furthermore, we demonstrate that soluble CCL21 functionally resembles neither the CCL19 nor the CCL21 phenotype but acts as a chemokine with unique features. Thus, we advance the concept of dendritic cell-dependent generation of micromilieus and lymph node conditioning by demonstrating a novel layer of CCR7 regulation through CCR7 sialylation. In summary, we demonstrate that leukocyte subsets express distinct patterns of CCR7 sialylation that contribute to receptor signaling and fine-tuning chemotactic responses. PMID:26819318

  8. The Rac1 inhibitor NSC23766 suppresses CREB signaling by targeting NMDA receptor function.

    PubMed

    Hou, Hailong; Chávez, Andrés E; Wang, Chih-Chieh; Yang, Hongtian; Gu, Hua; Siddoway, Benjamin A; Hall, Benjamin J; Castillo, Pablo E; Xia, Houhui

    2014-10-15

    NMDA receptor signaling plays a complex role in CREB activation and CREB-mediated gene transcription, depending on the subcellular location of NMDA receptors, as well as how strongly they are activated. However, it is not known whether Rac1, the prototype of Rac GTPase, plays a role in neuronal CREB activation induced by NMDA receptor signaling. Here, we report that NSC23766, a widely used specific Rac1 inhibitor, inhibits basal CREB phosphorylation at S133 (pCREB) and antagonizes changes in pCREB levels induced by NMDA bath application in rat cortical neurons. Unexpectedly, we found that NSC23766 affects the levels of neuronal pCREB in a Rac1-independent manner. Instead, our results indicate that NSC23766 can directly regulate NMDA receptors as indicated by their strong effects on both exogenous and synaptically evoked NMDA receptor-mediated currents in mouse and rat neurons, respectively. Our findings strongly suggest that Rac1 does not affect pCREB signaling in cortical neurons and reveal that NSC23766 could be a novel NMDA receptor antagonist.

  9. Activation of GABA(B) receptors inhibits protein kinase B/glycogen synthase kinase 3 signaling.

    PubMed

    Lu, Frances Fangjia; Su, Ping; Liu, Fang; Daskalakis, Zafiris J

    2012-11-28

    Accumulated evidence has suggested that potentiation of cortical GABAergic inhibitory neurotransmission may be a key mechanism in the treatment of schizophrenia. However, the downstream molecular mechanisms related to GABA potentiation remain unexplored. Recent studies have suggested that dopamine D2 receptor antagonists, which are used in the clinical treatment of schizophrenia, modulate protein kinase B (Akt)/glycogen synthase kinase (GSK)-3 signaling. Here we report that activation of GABA(B) receptors significantly inhibits Akt/GSK-3 signaling in a β-arrestin-dependent pathway. Agonist stimulation of GABA(B) receptors enhances the phosphorylation of Akt (Thr-308) and enhances the phosphorylation of GSK-3α (Ser-21)/β (Ser-9) in both HEK-293T cells expressing GABA(B) receptors and rat hippocampal slices. Furthermore, knocking down the expression of β-arrestin2 using siRNA abolishes the GABA(B) receptor-mediated modulation of GSK-3 signaling. Our data may help to identify potentially novel targets through which GABA(B) receptor agents may exert therapeutic effects in the treatment of schizophrenia.

  10. Molecular mechanisms of corticotropin-releasing factor receptor-induced calcium signaling.

    PubMed

    Gutknecht, Eric; Van der Linden, Ilse; Van Kolen, Kristof; Verhoeven, Kim F C; Vauquelin, Georges; Dautzenberg, Frank M

    2009-03-01

    The molecular mechanisms governing calcium signal transduction of corticotropin-releasing factor (CRF) receptors CRF(1) and CRF(2(a)) stably expressed in human embryonic kidney (HEK) 293 cells were investigated. Calcium signaling strictly depended on intracellular calcium sources, and this is the first study to establish a prominent contribution of the three major G-protein families to CRF receptor-mediated calcium signaling. Overexpression of Galpha(q/11) and Galpha(16) led to leftward shifts of the agonist concentration-response curves. Blockade of Galpha(q/11) proteins by the small interfering RNA (siRNA) technology partially reduced agonist-mediated calcium responses in CRF(1)- and CRF(2(a))-expressing HEK293 cells, thereby proving a contribution of the G(q) protein family. A small but significant inhibition of calcium signaling was recorded by pharmacological inhibition of G(i/o) proteins with pertussis toxin treatment. This effect was mediated by direct binding of Gbetagamma subunits to phospholipase C. G(i/o) inhibition also elevated cAMP responses in CRF receptor-overexpressing HEK293 cells and in Y79 retinoblastoma cells endogenously expressing human CRF(1) and CRF(2(a)) receptors, thereby demonstrating natural coupling of G(i) proteins to both CRF receptors. The strongest reduction of CRF receptor-mediated calcium mobilization was noted when blocking the G(s) signaling protein either by cholera toxin or by siRNA. It is noteworthy that simultaneous inhibition of two G-proteins shed light on the additive effects of G(s) and G(q) on the calcium signaling and, hence, that they act in parallel. On the other hand, G(i) coupling required prior G(s) activation. PMID:19098121

  11. Astroglial CB1 cannabinoid receptors regulate leptin signaling in mouse brain astrocytes.

    PubMed

    Bosier, Barbara; Bellocchio, Luigi; Metna-Laurent, Mathilde; Soria-Gomez, Edgar; Matias, Isabelle; Hebert-Chatelain, Etienne; Cannich, Astrid; Maitre, Marlène; Leste-Lasserre, Thierry; Cardinal, Pierre; Mendizabal-Zubiaga, Juan; Canduela, Miren Josune; Reguero, Leire; Hermans, Emmanuel; Grandes, Pedro; Cota, Daniela; Marsicano, Giovanni

    2013-01-01

    Type-1 cannabinoid (CB1) and leptin (ObR) receptors regulate metabolic and astroglial functions, but the potential links between the two systems in astrocytes were not investigated so far. Genetic and pharmacological manipulations of CB1 receptor expression and activity in cultured cortical and hypothalamic astrocytes demonstrated that cannabinoid signaling controls the levels of ObR expression. Lack of CB1 receptors also markedly impaired leptin-mediated activation of signal transducers and activators of transcription 3 and 5 (STAT3 and STAT5) in astrocytes. In particular, CB1 deletion determined a basal overactivation of STAT5, thereby leading to the downregulation of ObR expression, and leptin failed to regulate STAT5-dependent glycogen storage in the absence of CB1 receptors. These results show that CB1 receptors directly interfere with leptin signaling and its ability to regulate glycogen storage, thereby representing a novel mechanism linking endocannabinoid and leptin signaling in the regulation of brain energy storage and neuronal functions.

  12. Regulation of Epidermal Growth Factor Receptor Signaling by Endocytosis and Intracellular Trafficking

    SciTech Connect

    Burke, Patrick; Schooler, Kevin; Wiley, H S.

    2001-06-01

    Ligand activation of the epidermal growth factor receptor (EGFR) leads to its rapid internalization and eventual delivery to lysosomes. This process is thought to be a mechanism to attenuate signaling, but signals could potentially be generated following endocytosis. To directly evaluate EGFR signaling during receptor trafficking, we developed a technique to rapidly and selectively isolate internalized EGFR and associated molecules using reversibly-biotinylated anti-EGFR antibodies. In addition, we developed antibodies specific to tyrosine-phosphorylated EGFR. Using a combination of fluorescence imaging and affinity precipitation approaches, we evaluated the state of EGFR activation and substrate association during trafficking in epithelial cells. We found that following internalization, EGFR remained active in the early endosomes. However, receptors were inactivated prior to degradation, apparently due to ligand removal from endosomes. Adapter molecules, such as Shc, were associated with EGFR both at the cell surface and within endosomes. Some molecules, such as Grb2, were primarily found associated with surface EGFR, while others, such as Eps8, were only found with intracellular receptors. During the inactivation phase, c-Cbl became EGFR-associated, consistent with its postulated role in receptor attenuation. We conclude that the association of the EGFR with different proteins is compartment-specific . In addition, ligand loss is the proximal cause of EGFR inactivation. Thus, regulated trafficking could potentially influence the pattern as well as the duration of signal transduction.

  13. Signaling and regulation of G protein-coupled receptors in airway smooth muscle

    PubMed Central

    Billington, Charlotte K; Penn, Raymond B

    2003-01-01

    Signaling through G protein-coupled receptors (GPCRs) mediates numerous airway smooth muscle (ASM) functions including contraction, growth, and "synthetic" functions that orchestrate airway inflammation and promote remodeling of airway architecture. In this review we provide a comprehensive overview of the GPCRs that have been identified in ASM cells, and discuss the extent to which signaling via these GPCRs has been characterized and linked to distinct ASM functions. In addition, we examine the role of GPCR signaling and its regulation in asthma and asthma treatment, and suggest an integrative model whereby an imbalance of GPCR-derived signals in ASM cells contributes to the asthmatic state. PMID:12648290

  14. Glycosylphosphatidylinositol-anchored proteins as chaperones and co-receptors for FERONIA receptor kinase signaling in Arabidopsis

    PubMed Central

    Li, Chao; Yeh, Fang-Ling; Cheung, Alice Y; Duan, Qiaohong; Kita, Daniel; Liu, Ming-Che; Maman, Jacob; Luu, Emily J; Wu, Brendan W; Gates, Laura; Jalal, Methun; Kwong, Amy; Carpenter, Hunter; Wu, Hen-Ming

    2015-01-01

    The Arabidopsis receptor kinase FERONIA (FER) is a multifunctional regulator for plant growth and reproduction. Here we report that the female gametophyte-expressed glycosylphosphatidylinositol-anchored protein (GPI-AP) LORELEI and the seedling-expressed LRE-like GPI-AP1 (LLG1) bind to the extracellular juxtamembrane region of FER and show that this interaction is pivotal for FER function. LLG1 interacts with FER in the endoplasmic reticulum and on the cell surface, and loss of LLG1 function induces cytoplasmic retention of FER, consistent with transport of FER from the endoplasmic reticulum to the plasma membrane in a complex with LLG1. We further demonstrate that LLG1 is a component of the FER-regulated RHO GTPase signaling complex and that fer and llg1 mutants display indistinguishable growth, developmental and signaling phenotypes, analogous to how lre and fer share similar reproductive defects. Together our results support LLG1/LRE acting as a chaperone and co-receptor for FER and elucidate a mechanism by which GPI-APs enable the signaling capacity of a cell surface receptor. DOI: http://dx.doi.org/10.7554/eLife.06587.001 PMID:26052747

  15. Glycosylphosphatidylinositol-anchored proteins as chaperones and co-receptors for FERONIA receptor kinase signaling in Arabidopsis.

    PubMed

    Li, Chao; Yeh, Fang-Ling; Cheung, Alice Y; Duan, Qiaohong; Kita, Daniel; Liu, Ming-Che; Maman, Jacob; Luu, Emily J; Wu, Brendan W; Gates, Laura; Jalal, Methun; Kwong, Amy; Carpenter, Hunter; Wu, Hen-Ming

    2015-01-01

    The Arabidopsis receptor kinase FERONIA (FER) is a multifunctional regulator for plant growth and reproduction. Here we report that the female gametophyte-expressed glycosylphosphatidylinositol-anchored protein (GPI-AP) LORELEI and the seedling-expressed LRE-like GPI-AP1 (LLG1) bind to the extracellular juxtamembrane region of FER and show that this interaction is pivotal for FER function. LLG1 interacts with FER in the endoplasmic reticulum and on the cell surface, and loss of LLG1 function induces cytoplasmic retention of FER, consistent with transport of FER from the endoplasmic reticulum to the plasma membrane in a complex with LLG1. We further demonstrate that LLG1 is a component of the FER-regulated RHO GTPase signaling complex and that fer and llg1 mutants display indistinguishable growth, developmental and signaling phenotypes, analogous to how lre and fer share similar reproductive defects. Together our results support LLG1/LRE acting as a chaperone and co-receptor for FER and elucidate a mechanism by which GPI-APs enable the signaling capacity of a cell surface receptor. PMID:26052747

  16. Glycosylphosphatidylinositol-anchored proteins as chaperones and co-receptors for FERONIA receptor kinase signaling in Arabidopsis.

    PubMed

    Li, Chao; Yeh, Fang-Ling; Cheung, Alice Y; Duan, Qiaohong; Kita, Daniel; Liu, Ming-Che; Maman, Jacob; Luu, Emily J; Wu, Brendan W; Gates, Laura; Jalal, Methun; Kwong, Amy; Carpenter, Hunter; Wu, Hen-Ming

    2015-06-08

    The Arabidopsis receptor kinase FERONIA (FER) is a multifunctional regulator for plant growth and reproduction. Here we report that the female gametophyte-expressed glycosylphosphatidylinositol-anchored protein (GPI-AP) LORELEI and the seedling-expressed LRE-like GPI-AP1 (LLG1) bind to the extracellular juxtamembrane region of FER and show that this interaction is pivotal for FER function. LLG1 interacts with FER in the endoplasmic reticulum and on the cell surface, and loss of LLG1 function induces cytoplasmic retention of FER, consistent with transport of FER from the endoplasmic reticulum to the plasma membrane in a complex with LLG1. We further demonstrate that LLG1 is a component of the FER-regulated RHO GTPase signaling complex and that fer and llg1 mutants display indistinguishable growth, developmental and signaling phenotypes, analogous to how lre and fer share similar reproductive defects. Together our results support LLG1/LRE acting as a chaperone and co-receptor for FER and elucidate a mechanism by which GPI-APs enable the signaling capacity of a cell surface receptor.

  17. Expression of a glycosylphosphatidylinositol-anchored ligand, growth hormone, blocks receptor signalling

    PubMed Central

    Guesdon, François; Kaabi, Yahia; Riley, Aiden H.; Wilkinson, Ian R.; Gray, Colin; James, David C.; Artymiuk, Peter J.; Sayers, Jon R.; Ross, Richard J.

    2012-01-01

    We have investigated the interaction between GH (growth hormone) and GHR (GH receptor). We previously demonstrated that a truncated GHR that possesses a transmembrane domain but no cytoplasmic domain blocks receptor signalling. Based on this observation we investigated the impact of tethering the receptor's extracellular domain to the cell surface using a native lipid GPI (glycosylphosphatidylinositol) anchor. We also investigated the effect of tethering GH, the ligand itself, to the cell surface and demonstrated that tethering either the ecGHR (extracellular domain of GHR) or the ligand itself to the cell membrane via a GPI anchor greatly attenuates signalling. To elucidate the mechanism for this antagonist activity, we used confocal microscopy to examine the fluorescently modified ligand and receptor. GH–GPI was expressed on the cell surface and formed inactive receptor complexes that failed to internalize and blocked receptor activation. In conclusion, contrary to expectation, tethering an agonist to the cell surface can generate an inactive hormone receptor complex that fails to internalize. PMID:23013472

  18. Targeting CB2-GPR55 Receptor Heteromers Modulates Cancer Cell Signaling*

    PubMed Central

    Moreno, Estefanía; Andradas, Clara; Medrano, Mireia; Caffarel, María M.; Pérez-Gómez, Eduardo; Blasco-Benito, Sandra; Gómez-Cañas, María; Pazos, M. Ruth; Irving, Andrew J.; Lluís, Carme; Canela, Enric I.; Fernández-Ruiz, Javier; Guzmán, Manuel; McCormick, Peter J.; Sánchez, Cristina

    2014-01-01

    The G protein-coupled receptors CB2 (CB2R) and GPR55 are overexpressed in cancer cells and human tumors. Because a modulation of GPR55 activity by cannabinoids has been suggested, we analyzed whether this receptor participates in cannabinoid effects on cancer cells. Here we show that CB2R and GPR55 form heteromers in cancer cells, that these structures possess unique signaling properties, and that modulation of these heteromers can modify the antitumoral activity of cannabinoids in vivo. These findings unveil the existence of previously unknown signaling platforms that help explain the complex behavior of cannabinoids and may constitute new targets for therapeutic intervention in oncology. PMID:24942731

  19. Unifying electrostatic mechanism for metal cations in receptors and cell signaling.

    PubMed

    Kovacic, Peter

    2008-01-01

    Previously, an electrostatic mechanism was proposed for receptor-ligand action and for cell signaling by phosphate and sulfate. The hypothesis is further elaborated by application to metal ions, mainly calcium, magnesium, zinc, iron, and copper, in receptors and cell signaling. Evidence is provided for involvement of electrostatics in various reaction modes in biosystems. Calcium plays an important role electrochemically in neurotransmission. In some cases, electron transfer and redox processes are also involved. Electrostatics are known to participate in plant biochemistry. Mechanistically, the electrostatic field may act as a conduit for electrons and radicals and in involvement with energetics.

  20. Medial nucleus tractus solitarius oxytocin receptor signaling and food intake control: the role of gastrointestinal satiation signal processing

    PubMed Central

    Alhadeff, Amber L.; Grill, Harvey J.

    2015-01-01

    Central oxytocin (OT) administration reduces food intake and its effects are mediated, in part, by hindbrain oxytocin receptor (OT-R) signaling. The neural substrate and mechanisms mediating the intake inhibitory effects of hindbrain OT-R signaling are undefined. We examined the hypothesis that hindbrain OT-R-mediated feeding inhibition results from an interaction between medial nucleus tractus solitarius (mNTS) OT-R signaling and the processing of gastrointestinal (GI) satiation signals by neurons of the mNTS. Here, we demonstrated that mNTS or fourth ventricle (4V) microinjections of OT in rats reduced chow intake in a dose-dependent manner. To examine whether the intake suppressive effects of mNTS OT-R signaling is mediated by GI signal processing, rats were injected with OT to the 4V (1 μg) or mNTS (0.3 μg), followed by self-ingestion of a nutrient preload, where either treatment was designed to be without effect on chow intake. Results showed that the combination of mNTS OT-R signaling and GI signaling processing by preload ingestion reduced chow intake significantly and to a greater extent than either stimulus alone. Using enzyme immunoassay, endogenous OT content in mNTS-enriched dorsal vagal complex (DVC) in response to ingestion of nutrient preload was measured. Results revealed that preload ingestion significantly elevated endogenous DVC OT content. Taken together, these findings provide evidence that mNTS neurons are a site of action for hindbrain OT-R signaling in food intake control and that the intake inhibitory effects of hindbrain mNTS OT-R signaling are mediated by interactions with GI satiation signal processing by mNTS neurons. PMID:25740340

  1. Medial nucleus tractus solitarius oxytocin receptor signaling and food intake control: the role of gastrointestinal satiation signal processing.

    PubMed

    Ong, Zhi Yi; Alhadeff, Amber L; Grill, Harvey J

    2015-05-01

    Central oxytocin (OT) administration reduces food intake and its effects are mediated, in part, by hindbrain oxytocin receptor (OT-R) signaling. The neural substrate and mechanisms mediating the intake inhibitory effects of hindbrain OT-R signaling are undefined. We examined the hypothesis that hindbrain OT-R-mediated feeding inhibition results from an interaction between medial nucleus tractus solitarius (mNTS) OT-R signaling and the processing of gastrointestinal (GI) satiation signals by neurons of the mNTS. Here, we demonstrated that mNTS or fourth ventricle (4V) microinjections of OT in rats reduced chow intake in a dose-dependent manner. To examine whether the intake suppressive effects of mNTS OT-R signaling is mediated by GI signal processing, rats were injected with OT to the 4V (1 μg) or mNTS (0.3 μg), followed by self-ingestion of a nutrient preload, where either treatment was designed to be without effect on chow intake. Results showed that the combination of mNTS OT-R signaling and GI signaling processing by preload ingestion reduced chow intake significantly and to a greater extent than either stimulus alone. Using enzyme immunoassay, endogenous OT content in mNTS-enriched dorsal vagal complex (DVC) in response to ingestion of nutrient preload was measured. Results revealed that preload ingestion significantly elevated endogenous DVC OT content. Taken together, these findings provide evidence that mNTS neurons are a site of action for hindbrain OT-R signaling in food intake control and that the intake inhibitory effects of hindbrain mNTS OT-R signaling are mediated by interactions with GI satiation signal processing by mNTS neurons.

  2. Glycine and Glycine Receptor Signalling in Non-Neuronal Cells

    PubMed Central

    den Eynden, Jimmy Van; Ali, Sheen Saheb; Horwood, Nikki; Carmans, Sofie; Brône, Bert; Hellings, Niels; Steels, Paul; Harvey, Robert J.; Rigo, Jean-Michel

    2009-01-01

    Glycine is an inhibitory neurotransmitter acting mainly in the caudal part of the central nervous system. Besides this neurotransmitter function, glycine has cytoprotective and modulatory effects in different non-neuronal cell types. Modulatory effects were mainly described in immune cells, endothelial cells and macroglial cells, where glycine modulates proliferation, differentiation, migration and cytokine production. Activation of glycine receptors (GlyRs) causes membrane potential changes that in turn modulate calcium flux and downstream effects in these cells. Cytoprotective effects were mainly described in renal cells, hepatocytes and endothelial cells, where glycine protects cells from ischemic cell death. In these cell types, glycine has been suggested to stabilize porous defects that develop in the plasma membranes of ischemic cells, leading to leakage of macromolecules and subsequent cell death. Although there is some evidence linking these effects to the activation of GlyRs, they seem to operate in an entirely different mode from classical neuronal subtypes. PMID:19738917

  3. CXC Chemokine Receptor 3 Alternative Splice Variants Selectively Activate Different Signaling Pathways.

    PubMed

    Berchiche, Yamina A; Sakmar, Thomas P

    2016-10-01

    The G protein-coupled receptor (GPCR) C-X-C chemokine receptor 3 (CXCR3) is a potential drug target that mediates signaling involved in cancer metastasis and inflammatory diseases. The CXCR3 primary transcript has three potential alternative splice variants and cell-type specific expression results in receptor variants that are believed to have different functional characteristics. However, the molecular pharmacology of ligand binding to CXCR3 alternative splice variants and their downstream signaling pathways remain poorly explored. To better understand the role of the functional consequences of alternative splicing of CXCR3, we measured signaling in response to four different chemokine ligands (CXCL4, CXCL9, CXCL10, and CXCL11) with agonist activity at CXCR3. Both CXCL10 and CXCL11 activated splice variant CXCR3A. Whereas CXCL10 displayed full agonistic activity for Gαi activation and extracellular signal regulated kinase (ERK) 1/2 phosphorylation and partial agonist activity for β-arrestin recruitment, CXCL9 triggered only modest ERK1/2 phosphorylation. CXCL11 induced CXCR3B-mediated β-arrestin recruitment and little ERK phosphorylation. CXCR3Alt signaling was limited to modest ligand-induced receptor internalization and ERK1/2 phosphorylation in response to chemokines CXCL11, CXCL10, and CXCL9. These results show that CXCR3 splice variants activate different signaling pathways and that CXCR3 variant function is not redundant, suggesting a mechanism for tissue specific biased agonism. Our data show an additional layer of complexity for chemokine receptor signaling that might be exploited to target specific CXCR3 splice variants. PMID:27512119

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

    PubMed Central

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

    2016-01-01

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

  5. A dual receptor crosstalk model of G-protein-coupled signal transduction.

    PubMed

    Flaherty, Patrick; Radhakrishnan, Mala L; Dinh, Tuan; Rebres, Robert A; Roach, Tamara I; Jordan, Michael I; Arkin, Adam P

    2008-09-26

    Macrophage cells that are stimulated by two different ligands that bind to G-protein-coupled receptors (GPCRs) usually respond as if the stimulus effects are additive, but for a minority of ligand combinations the response is synergistic. The G-protein-coupled receptor system integrates signaling cues from the environment to actuate cell morphology, gene expression, ion homeostasis, and other physiological states. We analyze the effects of the two signaling molecules complement factors 5a (C5a) and uridine diphosphate (UDP) on the intracellular second messenger calcium to elucidate the principles that govern the processing of multiple signals by GPCRs. We have developed a formal hypothesis, in the form of a kinetic model, for the mechanism of action of this GPCR signal transduction system using data obtained from RAW264.7 macrophage cells. Bayesian statistical methods are employed to represent uncertainty in both data and model parameters and formally tie the model to experimental data. When the model is also used as a tool in the design of experiments, it predicts a synergistic region in the calcium peak height dose response that results when cells are simultaneously stimulated by C5a and UDP. An analysis of the model reveals a potential mechanism for crosstalk between the Galphai-coupled C5a receptor and the Galphaq-coupled UDP receptor signaling systems that results in synergistic calcium release.

  6. Vestibular receptor cells and signal detection: bioaccelerometers and the hexagonal sampling of two-dimensional signals

    NASA Technical Reports Server (NTRS)

    Mugler, D. H.; Ross, M. D.

    1990-01-01

    The inner ear contains sensory organs which signal changes in head movement. The vestibular sacs, in particular, are sensitive to linear accelerations. Electron microscopic images have revealed the structure of tiny sensory hair bundles, whose mechanical deformation results in the initiation of neuronal activity and the transmission of electrical signals to the brain. The structure of the hair bundles is shown in this paper to be that of the most efficient two-dimensional phased-array signal processors.

  7. A receptor-like protein mediates the response to pectin modification by activating brassinosteroid signaling.

    PubMed

    Wolf, Sebastian; van der Does, Dieuwertje; Ladwig, Friederike; Sticht, Carsten; Kolbeck, Andreas; Schürholz, Ann-Kathrin; Augustin, Sebastian; Keinath, Nana; Rausch, Thomas; Greiner, Steffen; Schumacher, Karin; Harter, Klaus; Zipfel, Cyril; Höfte, Herman

    2014-10-21

    The brassinosteroid (BR) signaling module is a central regulator of plant morphogenesis, as indicated by the large number of BR-responsive cell wall-related genes and the severe growth defects of BR mutants. Despite a detailed knowledge of the signaling components, the logic of this auto-/paracrine signaling module in growth control remains poorly understood. Recently, extensive cross-talk with other signaling pathways has been shown, suggesting that the outputs of BR signaling, such as gene-expression changes, are subject to complex control mechanisms. We previously provided evidence for a role of BR signaling in a feedback loop controlling the integrity of the cell wall. Here, we identify the first dedicated component of this feedback loop: a receptor-like protein (RLP44), which is essential for the compensatory triggering of BR signaling upon inhibition of pectin de-methylesterification in the cell wall. RLP44 is required for normal growth and stress responses and connects with the BR signaling pathway, presumably through a direct interaction with the regulatory receptor-like kinase BAK1. These findings corroborate a role for BR in controlling the sensitivity of a feedback signaling module involved in maintaining the physico-chemical homeostasis of the cell wall during cell expansion.

  8. Hedgehog Signaling Regulates the Ciliary Transport of Odorant Receptors in Drosophila.

    PubMed

    Sanchez, Gonzalo M; Alkhori, Liza; Hatano, Eduardo; Schultz, Sebastian W; Kuzhandaivel, Anujaianthi; Jafari, Shadi; Granseth, Björn; Alenius, Mattias

    2016-01-26

    Hedgehog (Hh) signaling is a key regulatory pathway during development and also has a functional role in mature neurons. Here, we show that Hh signaling regulates the odor response in adult Drosophila olfactory sensory neurons (OSNs). We demonstrate that this is achieved by regulating odorant receptor (OR) transport to and within the primary cilium in OSN neurons. Regulation relies on ciliary localization of the Hh signal transducer Smoothened (Smo). We further demonstrate that the Hh- and Smo-dependent regulation of the kinesin-like protein Cos2 acts in parallel to the intraflagellar transport system (IFT) to localize ORs within the cilium compartment. These findings expand our knowledge of Hh signaling to encompass chemosensory modulation and receptor trafficking.

  9. Neuroendocrine function and response to stress in mice with complete disruption of glucagon-like peptide-1 receptor signaling.

    PubMed

    MacLusky, N J; Cook, S; Scrocchi, L; Shin, J; Kim, J; Vaccarino, F; Asa, S L; Drucker, D J

    2000-02-01

    Glucagon-like peptide-1 (GLP-1), a potent regulator of glucose homeostasis, is also produced in the central nervous system, where GLP-1 has been implicated in the neuroendocrine control of hypothalamic-pituitary function, food intake, and the response to stress. The finding that intracerebroventricular GLP-1 stimulates LH, TSH, corticosterone, and vasopressin secretion in rats prompted us to assess the neuroendocrine consequences of disrupting GLP-1 signaling in mice in vivo. Male GLP-1 receptor knockout (GLP-1R-/-) mice exhibit reduced gonadal weights, and females exhibit a slight delay in the onset of puberty; however, male and female GLP-1R-/- animals reproduce successfully and respond appropriately to fluid restriction. Although adrenal weights are reduced in GLP-1R-/- mice, hypothalamic CRH gene expression and circulating levels of corticosterone, thyroid hormone, testosterone, estradiol, and progesterone are normal in the absence of GLP-1R-/- signaling. Intriguingly, GLP-1R-/- mice exhibit paradoxically increased corticosterone responses to stress as well as abnormal responses to acoustic startle that are corrected by glucocorticoid treatment. These findings suggest that although GLP-1R signaling is not essential for development and basal function of the murine hypothalamic-pituitary-adrenal axis, abrogation of GLP-1 signaling is associated with impairment of the behavioral and neuroendocrine responses to stress.

  10. Distinct structural specificities for functional coupling of the epidermal growth factor receptor to calcium-signalling versus phospholipase A2 responses.

    PubMed

    Hack, N; Margolis, B L; Ullrich, A; Schlessinger, J; Skorecki, K L

    1991-05-01

    Activation of phospholipase C (PLC), leading to a rise in cytosolic Ca2+, and of phospholipase A2 (PLA2) leading to a release of arachidonic acid, are among the early transmembrane signalling events that have been demonstrated in response to occupancy of the epidermal growth factor (EGF) receptor. The tyrosine kinase activity of the receptor has been shown to be necessary for both of these responses. This requirement for the tyrosine kinase activity could conceivably implicate a role for receptor autophosphorylation in the activation of PLA2. We now demonstrate that coupling of the EGF receptor to PLA2 was not impaired in a deletion mutant (CD126) devoid of the 126 amino acids from the C-terminus which include four major autophosphorylation sites. Functional coupling of the EGF receptor to PLA2 was demonstrated using three different experimental designs: (1) release of [14C]arachidonic acid from prelabelled intact cells. (2) release of [3H]arachidonic acid from prelabelled cells permeabilized with glass beads, and (3) direct measurement of PLA2 enzymic activity in cell-free extracts using an 'in vitro' assay employing exogenous phospholipid substrate. Functional coupling of the EGF receptor to PLA2 occurred despite the absence of a demonstrable Ca(2+)-signalling response and the detection of diminished but persistent PLC-gamma phosphorylation on tyrosine residues in the CD126 deletion mutants. These results point to a clear distinction in the biochemical mechanism and role for receptor autophosphorylation in functional coupling of the EGF receptor to PLA2 activation versus Ca2+ signalling.

  11. Activation of sigma-1 receptor chaperone in the treatment of neuropsychiatric diseases and its clinical implication.

    PubMed

    Hashimoto, Kenji

    2015-01-01

    Endoplasmic reticulum (ER) protein sigma-1 receptor represents unique chaperone activity in the central nervous system, and it exerts a potent influence on a number of neurotransmitter systems. Several lines of evidence suggest that activation of sigma-1 receptor plays a role in the pathophysiology of neuropsychiatric diseases, as well as in the mechanisms of some therapeutic drugs and neurosteroids. Preclinical studies showed that some selective serotonin reuptake inhibitors (SSRIs; fluvoxamine, fluoxetine, excitalopram), donepezil, and ifenprodil act as sigma-1 receptor agonists. Furthermore, sigma-1 receptor agonists could improve the N-methyl-D-aspartate (NMDA) antagonist phencyclidine (PCP)-induced cognitive deficits in mice. A study using positron emission tomography have demonstrated that an oral administration of fluvoxamine or donepezil could bind to sigma-1 receptor in the healthy human brain, suggesting that sigma-1 receptor might be involved in the therapeutic mechanisms of these drugs. Moreover, case reports suggest that sigma-1 receptor agonists, including fluvoxamine, and ifenprodil, may be effective in the treatment of cognitive impairment in schizophrenia, delirium in elderly people, and flashbacks in post-traumatic stress disorder. In this review article, the author would like to discuss the clinical implication of sigma-1 receptor agonists, including endogenous neurosteroids, in the neuropsychiatric diseases.

  12. Astrocytic adenosine receptor A2A and Gs-coupled signaling regulate memory

    PubMed Central

    Orr, Anna G.; Hsiao, Edward C.; Wang, Max M.; Ho, Kaitlyn; Kim, Daniel H.; Wang, Xin; Guo, Weikun; Kang, Jing; Yu, Gui-Qiu; Adame, Anthony; Devidze, Nino; Dubal, Dena B.; Masliah, Eliezer; Conklin, Bruce R.; Mucke, Lennart

    2014-01-01

    Astrocytes express a variety of G protein-coupled receptors and might influence cognitive functions, such as learning and memory. However, the roles of astrocytic Gs-coupled receptors in cognitive function are not known. We found that humans with Alzheimer’s disease (AD) had increased levels of the Gs-coupled adenosine receptor A2A in astrocytes. Conditional genetic removal of these receptors enhanced long-term memory in young and aging mice, and increased the levels of Arc/Arg3.1, an immediate-early gene required for long-term memory. Chemogenetic activation of astrocytic Gs-coupled signaling reduced long-term memory in mice without affecting learning. Similar to humans with AD, aging mice expressing human amyloid precursor protein (hAPP) showed increased levels of astrocytic A2A receptors. Con