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Sample records for receptor signaling implications

  1. Sweet Taste Receptor Signaling Network: Possible Implication for Cognitive Functioning

    PubMed Central

    Welcome, Menizibeya O.; Mastorakis, Nikos E.; Pereverzev, Vladimir A.

    2015-01-01

    Sweet taste receptors are transmembrane protein network specialized in the transmission of information from special “sweet” molecules into the intracellular domain. These receptors can sense the taste of a range of molecules and transmit the information downstream to several acceptors, modulate cell specific functions and metabolism, and mediate cell-to-cell coupling through paracrine mechanism. Recent reports indicate that sweet taste receptors are widely distributed in the body and serves specific function relative to their localization. Due to their pleiotropic signaling properties and multisubstrate ligand affinity, sweet taste receptors are able to cooperatively bind multiple substances and mediate signaling by other receptors. Based on increasing evidence about the role of these receptors in the initiation and control of absorption and metabolism, and the pivotal role of metabolic (glucose) regulation in the central nervous system functioning, we propose a possible implication of sweet taste receptor signaling in modulating cognitive functioning. PMID:25653876

  2. Sweet taste receptor signaling network: possible implication for cognitive functioning.

    PubMed

    Welcome, Menizibeya O; Mastorakis, Nikos E; Pereverzev, Vladimir A

    2015-01-01

    Sweet taste receptors are transmembrane protein network specialized in the transmission of information from special "sweet" molecules into the intracellular domain. These receptors can sense the taste of a range of molecules and transmit the information downstream to several acceptors, modulate cell specific functions and metabolism, and mediate cell-to-cell coupling through paracrine mechanism. Recent reports indicate that sweet taste receptors are widely distributed in the body and serves specific function relative to their localization. Due to their pleiotropic signaling properties and multisubstrate ligand affinity, sweet taste receptors are able to cooperatively bind multiple substances and mediate signaling by other receptors. Based on increasing evidence about the role of these receptors in the initiation and control of absorption and metabolism, and the pivotal role of metabolic (glucose) regulation in the central nervous system functioning, we propose a possible implication of sweet taste receptor signaling in modulating cognitive functioning.

  3. TAM Receptors in Leukemia: Expression, Signaling, and Therapeutic Implications

    PubMed Central

    Brandão, Luis; Migdall-Wilson, Justine; Eisenman, Kristen; Graham, Douglas K.

    2016-01-01

    In the past 30 years there has been remarkable progress in the treatment of leukemia and lymphoma. However, current treatments are largely ineffective against relapsed leukemia and, in the case of pediatric patients, are often associated with severe long-term toxicities. Thus, there continues to be a critical need for the development of effective biologically targeted therapies. The TAM family of receptor tyrosine kinases—Tyro3, Axl, and Mer—plays an important role in normal hematopoiesis, including natural killer cell maturation, macrophage function, and platelet activation and signaling. Furthermore, TAM receptor activation leads to upregulation of pro-survival and proliferation signaling pathways, and aberrant TAM receptor expression contributes to cancer development, including myeloid and lymphoid leukemia. This review summarizes the role of TAM receptors in leukemia. We outline TAM receptor expression patterns in different forms of leukemia, describe potential mechanisms leading to their overexpression, and delineate the signaling pathways downstream of receptor activation that have been implicated in leukemogenesis. Finally, we discuss the current research focused on inhibitors against these receptors in an effort to develop new therapeutic strategies for leukemia. PMID:22150307

  4. 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

  5. TrkB receptor signalling: implications in neurodegenerative, psychiatric and proliferative disorders.

    PubMed

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

    2013-05-13

    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.

  6. The alpha1-adrenergic receptors in cardiac hypertrophy: signaling mechanisms and functional implications.

    PubMed

    Cotecchia, Susanna; Del Vescovo, Cosmo Damiano; Colella, Matilde; Caso, Stefania; Diviani, Dario

    2015-10-01

    Cardiac hypertrophy is a complex remodeling process of the heart induced by physiological or pathological stimuli resulting in increased cardiomyocyte size and myocardial mass. Whereas cardiac hypertrophy can be an adaptive mechanism to stressful conditions of the heart, prolonged hypertrophy can lead to heart failure which represents the primary cause of human morbidity and mortality. Among G protein-coupled receptors, the α1-adrenergic receptors (α1-ARs) play an important role in the development of cardiac hypertrophy as demonstrated by numerous studies in the past decades, both in primary cardiomyocyte cultures and genetically modified mice. The results of these studies have provided evidence of a large variety of α1-AR-induced signaling events contributing to the defining molecular and cellular features of cardiac hypertrophy. Recently, novel signaling mechanisms have been identified and new hypotheses have emerged concerning the functional role of the α1-adrenergic receptors in the heart. This review will summarize the main signaling pathways activated by the α1-AR in the heart and their functional implications in cardiac hypertrophy. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. 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. © 2015 Society for Endocrinology.

  8. Vitamin D receptor signaling and its therapeutic implications: Genome-wide and structural view.

    PubMed

    Carlberg, Carsten; Molnár, Ferdinand

    2015-05-01

    Vitamin D3 is one of the few natural compounds that has, via its metabolite 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) and the transcription factor vitamin D receptor (VDR), a direct effect on gene regulation. For efficiently applying the therapeutic and disease-preventing potential of 1,25(OH)2D3 and its synthetic analogs, the key steps in vitamin D signaling need to be understood. These are the different types of molecular interactions with the VDR, such as (i) the complex formation of VDR with genomic DNA, (ii) the interaction of VDR with its partner transcription factors, (iii) the binding of 1,25(OH)2D3 or its synthetic analogs within the ligand-binding pocket of the VDR, and (iv) the resulting conformational change on the surface of the VDR leading to a change of the protein-protein interaction profile of the receptor with other proteins. This review will present the latest genome-wide insight into vitamin D signaling, and will discuss its therapeutic implications.

  9. 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.

  10. 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

  11. 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

  12. Blueprints of signaling interactions between pattern recognition receptors: implications for the design of vaccine adjuvants.

    PubMed

    Timmermans, Kim; Plantinga, Theo S; Kox, Matthijs; Vaneker, Michiel; Scheffer, Gert Jan; Adema, Gosse J; Joosten, Leo A B; Netea, Mihai G

    2013-03-01

    Innate immunity activation largely depends on recognition of microorganism structures by Pattern Recognition Receptors (PRRs). PRR downstream signaling results in production of pro- and anti-inflammatory cytokines and other mediators. Moreover, PRR engagement in antigen-presenting cells initiates the activation of adaptive immunity. Recent reports suggest that for the activation of innate immune responses and initiation of adaptive immunity, synergistic effects between two or more PRRs are necessary. No systematic analysis of the interaction between the major PRR pathways were performed to date. In this study, a systematical analysis of the interactions between PRR signaling pathways was performed. PBMCs derived from 10 healthy volunteers were stimulated with either a single PRR ligand or a combination of two PRR ligands. Known ligands for the major PRR families were used: Toll-like receptors (TLRs), C-type lectin receptors (CLRs), NOD-like receptors (NLRs), and RigI-helicases. After 24 h of incubation, production of tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, and IL-10 was measured in supernatants by enzyme-linked immunosorbent assay (ELISA). The consistency of the PRR interactions (both inhibitory and synergistic) between the various individuals was assessed. A number of PRR-dependent signaling interactions were found to be consistent, both between individuals and with regard to multiple cytokines. The combinations of TLR2 and NOD2, TLR5 and NOD2, TLR5 and TLR3, and TLR5 and TLR9 acted as synergistic combinations. Surprisingly, inhibitory interactions between TLR4 and TLR2, TLR4 and Dectin-1, and TLR2 and TLR9 as well as TLR3 and TLR2 were observed. These consistent signaling interactions between PRR combinations may represent promising targets for immunomodulation and vaccine adjuvant development.

  13. 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

  14. Molecular Tuning of Odorant Receptors and Its Implication for Odor Signal Processing

    PubMed Central

    Reisert, Johannes

    2009-01-01

    The discovery of the odorant receptor (OR) family by Buck and Axel in 1991 provided a quantum jump in our understanding of olfactory function. However, the study of the responsiveness of ORs to odor ligands was challenging due to the difficulties in deorphanizing the receptors. In this manuscript, we review recent findings of OR responsiveness that have come about through improved OR deorphanization methods, site-directed mutagenesis, structural modeling studies, and studies of OR responses in situ in olfactory sensory neurons. Although there has been a major leap in our understanding of receptor–ligand interactions and how these contribute to the input to the olfactory system, an improvement of our understanding of receptor structure and dynamics and interactions with intracellular and extracellular proteins is necessary. PMID:19525317

  15. Pituitary Somatostatin Receptor Signaling

    PubMed Central

    Ben-Shlomo, Anat; Melmed, Shlomo

    2010-01-01

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

  16. 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

  17. 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.

  18. The evolving role of lipid rafts and caveolae in G protein-coupled receptor signaling: implications for molecular pharmacology.

    PubMed

    Ostrom, Rennolds S; Insel, Paul A

    2004-09-01

    The many components of G-protein-coupled receptor (GPCR) signal transduction provide cells with numerous combinations with which to customize their responses to hormones, neurotransmitters, and pharmacologic agonists. GPCRs function as guanine nucleotide exchange factors for heterotrimeric (alpha, beta, gamma) G proteins, thereby promoting exchange of GTP for GDP and, in turn, the activation of 'downstream' signaling components. Recent data indicate that individual cells express mRNA for perhaps over 100 different GPCRs (out of a total of nearly a thousand GPCR genes), several different combinations of G-protein subunits, multiple regulators of G-protein signaling proteins (which function as GTPase activating proteins), and various isoforms of downstream effector molecules. The differential expression of such protein combinations allows for modulation of signals that are customized for a specific cell type, perhaps at different states of maturation or differentiation. In addition, in the linear arrangement of molecular interactions involved in a given GPCR-G-protein-effector pathway, one needs to consider the localization of receptors and post-receptor components in subcellular compartments, microdomains, and molecular complexes, and to understand the movement of proteins between these compartments. Co-localization of signaling components, many of which are expressed at low overall concentrations, allows cells to tailor their responses by arranging, or spatially organizing in unique and kinetically favorable ways, the molecules involved in GPCR signal transduction. This review focuses on the role of lipid rafts and a subpopulation of such rafts, caveolae, as a key spatial compartment enriched in components of GPCR signal transduction. Recent data suggest cell-specific patterns for expression of those components in lipid rafts and caveolae. Such domains likely define functionally important, cell-specific regions of signaling by GPCRs and drugs active at those GPCRs.

  19. Functional selectivity in CB(2) cannabinoid receptor signaling and regulation: implications for the therapeutic potential of CB(2) ligands.

    PubMed

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

    2012-02-01

    Receptor internalization increases the flexibility and scope of G protein-coupled receptor (GPCR) signaling. CB(1) and CB(2) cannabinoid receptors undergo internalization after sustained exposure to agonists. However, it is not known whether different agonists internalize CB(2) to different extents. Because CB(2) 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 CB(1) and CB(2) 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 CB(2) receptor internalization, whereas 5-(1,1-dimethylheptyl)-2-(5-hydroxy-2-(3-hydroxypropyl)cyclohexyl)phenol (CP55,940) robustly internalized CB(2) receptors. Furthermore, WIN55,212-2 competitively antagonized CP55,940-induced CB(2) internalization. Despite these differences in internalization, both compounds activated CB(2) receptors as measured by extracellular signal-regulated kinase 1/2 phosphorylation and recruitment of β-arrestin(2) to the membrane. In contrast, whereas CP55,940 inhibited voltage-gated calcium channels via CB(2) 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 CB(2) ligands. These novel data highlight that WIN55,212-2 and other cannabinoids show strong functional selectivity at CB(2

  20. Potential Signal Transduction Regulation by HDL of the β2-Adrenergic Receptor Pathway. Implications in Selected Pathological Situations.

    PubMed

    Niesor, Eric J; Benghozi, Renée

    2015-07-01

    The main atheroprotective mechanism of high-density lipoprotein (HDL) has been regarded as reverse cholesterol transport, whereby cholesterol from peripheral tissues is removed and transported to the liver for elimination. Although numerous additional atheroprotective mechanisms have been suggested, the role of HDL in modulating signal transduction of cell membrane-bound receptors has received little attention to date. This potential was recently highlighted following the identification of a polymorphism in the adenylyl cyclase 9 gene (ADCY9) that was shown to be a determining factor in the risk of cardiovascular (CV) events in patients treated with the HDL-raising compound dalcetrapib. Indeed, ADCY9 is part of the signaling pathway of the β2-adrenergic receptor (β2-AR) and both are membrane-bound proteins affected by changes in membrane-rich cholesterol plasma membrane domains (caveolae). Numerous G-protein-coupled receptors (GPCRs) and ion channels are affected by caveolae, with caveolae composition acting as a 'signalosome'. Polymorphisms in the genes encoding ADCY9 and β2-AR are associated with response to β2-agonist drugs in patients with asthma, malaria and with sickle cell disease. Crystallization of the β2-AR has found cholesterol tightly bound to transmembrane structures of the receptor. Cholesterol has also been shown to modulate the activity of this receptor. Apolipoprotein A1 (ApoA1), the major protein component of HDL, destabilizes and removes cholesterol from caveolae with high affinity through interaction with ATP-binding cassette transporter. Furthermore, β2-AR activity may be affected by ApoA1/HDL-targeted therapies. Taken together, these observations suggest a common pathway that potentially links a primary HDL function to the regulation of signal transduction. Copyright © 2015 IMSS. Published by Elsevier Inc. All rights reserved.

  1. Minireview: the intimate link between calcium sensing receptor trafficking and signaling: implications for disorders of calcium homeostasis.

    PubMed

    Breitwieser, Gerda E

    2012-09-01

    The calcium-sensing receptor (CaSR) regulates organismal Ca(2+) homeostasis. Dysregulation of CaSR expression or mutations in the CASR gene cause disorders of Ca(2+) homeostasis and contribute to the progression or severity of cancers and cardiovascular disease. This brief review highlights recent findings that define the CaSR life cycle, which controls the cellular abundance of CaSR and CaSR signaling. A novel mechanism, termed agonist-driven insertional signaling (ADIS), contributes to the unique hallmarks of CaSR signaling, including the high degree of cooperativity and the lack of functional desensitization. Agonist-mediated activation of plasma membrane-localized CaSR increases the rate of insertion of CaSR at the plasma membrane without altering the constitutive endocytosis rate, thereby acutely increasing the maximum signaling response. Prolonged CaSR signaling requires a large intracellular ADIS-mobilizable pool of CaSR, which is maintained by signaling-mediated increases in biosynthesis. This model provides a rational framework for characterizing the defects caused by CaSR mutations and the altered functional expression of wild-type CaSR in disease states. Mechanistic dissection of ADIS of CaSR should lead to optimized pharmacological approaches to normalize CaSR signaling in disorders of Ca(2+) homeostasis.

  2. Minireview: The Intimate Link Between Calcium Sensing Receptor Trafficking and Signaling: Implications for Disorders of Calcium Homeostasis

    PubMed Central

    2012-01-01

    The calcium-sensing receptor (CaSR) regulates organismal Ca2+ homeostasis. Dysregulation of CaSR expression or mutations in the CASR gene cause disorders of Ca2+ homeostasis and contribute to the progression or severity of cancers and cardiovascular disease. This brief review highlights recent findings that define the CaSR life cycle, which controls the cellular abundance of CaSR and CaSR signaling. A novel mechanism, termed agonist-driven insertional signaling (ADIS), contributes to the unique hallmarks of CaSR signaling, including the high degree of cooperativity and the lack of functional desensitization. Agonist-mediated activation of plasma membrane-localized CaSR increases the rate of insertion of CaSR at the plasma membrane without altering the constitutive endocytosis rate, thereby acutely increasing the maximum signaling response. Prolonged CaSR signaling requires a large intracellular ADIS-mobilizable pool of CaSR, which is maintained by signaling-mediated increases in biosynthesis. This model provides a rational framework for characterizing the defects caused by CaSR mutations and the altered functional expression of wild-type CaSR in disease states. Mechanistic dissection of ADIS of CaSR should lead to optimized pharmacological approaches to normalize CaSR signaling in disorders of Ca2+ homeostasis. PMID:22745192

  3. 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

  4. A Fluorescent Live Imaging Screening Assay Based on Translocation Criteria Identifies Novel Cytoplasmic Proteins Implicated in G Protein-coupled Receptor Signaling Pathways.

    PubMed

    Lecat, Sandra; Matthes, Hans W D; Pepperkok, Rainer; Simpson, Jeremy C; Galzi, Jean-Luc

    2015-05-01

    Several cytoplasmic proteins that are involved in G protein-coupled receptor signaling cascades are known to translocate to the plasma membrane upon receptor activation, such as beta-arrestin2. Based on this example and in order to identify new cytoplasmic proteins implicated in the ON-and-OFF cycle of G protein-coupled receptor, a live-imaging screen of fluorescently labeled cytoplasmic proteins was performed using translocation criteria. The screening of 193 fluorescently tagged human proteins identified eight proteins that responded to activation of the tachykinin NK2 receptor by a change in their intracellular localization. Previously we have presented the functional characterization of one of these proteins, REDD1, that translocates to the plasma membrane. Here we report the results of the entire screening. The process of cell activation was recorded on videos at different time points and all the videos can be visualized on a dedicated website. The proteins BAIAP3 and BIN1, partially translocated to the plasma membrane upon activation of NK2 receptors. Proteins ARHGAP12 and PKM2 translocated toward membrane blebs. Three proteins that associate with the cytoskeleton were of particular interest : PLEKHH2 rearranged from individual dots located near the cell-substrate adhesion surface into lines of dots. The speriolin-like protein, SPATC1L, redistributed to cell-cell junctions. The Chloride intracellular Channel protein, CLIC2, translocated from actin-enriched plasma membrane bundles to cell-cell junctions upon activation of NK2 receptors. CLIC2, and one of its close paralogs, CLIC4, were further shown to respond with the same translocation pattern to muscarinic M3 and lysophosphatidic LPA receptors. This screen allowed us to identify potential actors in signaling pathways downstream of G protein-coupled receptors and could be scaled-up for high-content screening.

  5. A Fluorescent Live Imaging Screening Assay Based on Translocation Criteria Identifies Novel Cytoplasmic Proteins Implicated in G Protein-coupled Receptor Signaling Pathways*

    PubMed Central

    Lecat, Sandra; Matthes, Hans W.D.; Pepperkok, Rainer; Simpson, Jeremy C.; Galzi, Jean-Luc

    2015-01-01

    Several cytoplasmic proteins that are involved in G protein-coupled receptor signaling cascades are known to translocate to the plasma membrane upon receptor activation, such as beta-arrestin2. Based on this example and in order to identify new cytoplasmic proteins implicated in the ON-and-OFF cycle of G protein-coupled receptor, a live-imaging screen of fluorescently labeled cytoplasmic proteins was performed using translocation criteria. The screening of 193 fluorescently tagged human proteins identified eight proteins that responded to activation of the tachykinin NK2 receptor by a change in their intracellular localization. Previously we have presented the functional characterization of one of these proteins, REDD1, that translocates to the plasma membrane. Here we report the results of the entire screening. The process of cell activation was recorded on videos at different time points and all the videos can be visualized on a dedicated website. The proteins BAIAP3 and BIN1, partially translocated to the plasma membrane upon activation of NK2 receptors. Proteins ARHGAP12 and PKM2 translocated toward membrane blebs. Three proteins that associate with the cytoskeleton were of particular interest : PLEKHH2 rearranged from individual dots located near the cell-substrate adhesion surface into lines of dots. The speriolin-like protein, SPATC1L, redistributed to cell-cell junctions. The Chloride intracellular Channel protein, CLIC2, translocated from actin-enriched plasma membrane bundles to cell-cell junctions upon activation of NK2 receptors. CLIC2, and one of its close paralogs, CLIC4, were further shown to respond with the same translocation pattern to muscarinic M3 and lysophosphatidic LPA receptors. This screen allowed us to identify potential actors in signaling pathways downstream of G protein-coupled receptors and could be scaled-up for high-content screening. PMID:25759509

  6. Microenvironment interactions and B-cell receptor signaling in Chronic Lymphocytic Leukemia: implications for disease pathogenesis and treatment

    PubMed Central

    ten Hacken, Elisa; Burger, Jan A.

    2015-01-01

    Chronic Lymphocytic Leukemia (CLL) is a malignancy of mature B lymphocytes which are highly dependent on interactions with the tissue microenvironment for their survival and proliferation. Critical components of the microenvironment are monocyte-derived nurselike cells (NLCs), mesenchymal stromal cells, T cells and NK cells, which communicate with CLL cells through a complex network of adhesion molecules, chemokine receptors, tumor necrosis factor (TNF) family members, and soluble factors. (Auto-) antigens and/or autonomous mechanisms activate the B-cell receptor (BCR) and its downstream signaling cascade in secondary lymphatic tissues, playing a central pathogenetic role in CLL. Novel small molecule inhibitors, including the Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib and the phosphoinositide-3-kinase delta (PI3Kδ) inhibitor idelalisib, target BCR signaling and have become the most successful new therapeutics in this disease. We here review the cellular and molecular characteristics of CLL cells, and discuss the cellular components and key pathways involved in the cross-talk with their microenvironment. We also highlight the relevant novel treatment strategies, focusing on immunomodulatory agents and BCR signaling inhibitors and how these treatments disrupt CLL-microenvironment interactions. PMID:26193078

  7. 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

  8. 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.

  9. Estrogen receptor and aryl hydrocarbon receptor signaling pathways

    PubMed Central

    Matthews, Jason; Gustafsson, Jan-Åke

    2006-01-01

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

  10. Oxytocin receptor signalling.

    PubMed

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

    2008-01-01

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

  11. JAK/STAT signaling by cytokine receptors.

    PubMed

    Liu, K D; Gaffen, S L; Goldsmith, M A

    1998-06-01

    The JAK/STAT pathway is recognized as one of the major mechanisms by which cytokine receptors transduce intracellular signals. This system is regulated at multiple levels, including JAK activation, nuclear trafficking of STAT factors, and negative feedback loops. Gene deletion studies have implicated selected STAT factors as predominant mediators for a limited number of lymphokines. This signaling pathway influences normal cell survival and growth mechanisms and may contribute to oncogenic transformation.

  12. Implicating Receptor Activator of NF-κB (RANK)/RANK Ligand Signalling in Microglial Responses to Toll-Like Receptor Stimuli.

    PubMed

    Kichev, Anton; Eede, Pascale; Gressens, Pierre; Thornton, Claire; Hagberg, Henrik

    2017-01-01

    Inflammation in the perinatal brain caused by maternal or intrauterine fetal infection is now well established as an important contributor to the development of perinatal brain injury. Exposure to inflammatory products can impair perinatal brain development and act as a risk factor for neurological dysfunction, cognitive disorders, cerebral palsy, or preterm birth. Pre-exposure to inflammation significantly exacerbates brain injury caused by hypoxic/ischaemic insult. Tumour necrosis factor (TNF) is a family of cytokines largely involved in inflammation signalling. In our previous study, we identified the importance of TNF-related apoptosis-inducing ligand (TRAIL) signalling in the development of perinatal brain injury. We observed a significant increase in the expression levels of a soluble decoy receptor for TRAIL, osteoprotegerin (OPG). Besides TRAIL, OPG is able to bind the receptor activator of the NF-κB (RANK) ligand (RANKL) and inhibit its signalling. The function of the RANK/RANKL/OPG system in the brain has not come under much scrutiny. The aim of this research study was to elucidate the role of RANK, RANKL, and OPG in microglial responses to the proinflammatory stimuli lipopolysaccharide (LPS) and polyinosinic-polycytidylic acid (Poly I:C). Here, we show that RANK signalling is important for regulating the activation of the BV2 microglial cell line. We found that LPS treatment causes a significant decrease in the expression of RANK in the BV2 cell line while significantly increasing the expression of OPG, Toll-like receptor (TLR)3, and the adaptor proteins MyD88 and TRIF. We found that pretreatment of BV2 cells with RANKL for 24 h before the LPS or Poly I:C exposure decreases the expression of inflammatory markers such as inducible nitric oxide synthase and cyclooxygenase. This is accompanied by a decreased expression of the TLR adaptor proteins MyD88 and TRIF, which we observed after RANKL treatment. Similar results were obtained in our experiments with

  13. Stilbene Induced Inhibition of Androgen Receptor Dimerization: Implications for AR and ARΔLBD-Signalling in Human Prostate Cancer Cells

    PubMed Central

    Streicher, Wolfgang; Luedeke, Manuel; Azoitei, Anca; Zengerling, Friedemann; Herweg, Alexander; Genze, Felicitas; Schrader, Mark G.; Schrader, Andres J.; Cronauer, Marcus V.

    2014-01-01

    Background Advanced castration resistant prostate cancer (CRPC) is often characterized by an increase of C-terminally truncated, constitutively active androgen receptor (AR) variants. Due to the absence of a ligand binding domain located in the AR-C-terminus, these receptor variants (also termed ARΔLBD) are unable to respond to all classical forms of endocrine treatments like surgical/chemical castration and/or application of anti-androgens. Methodology In this study we tested the effects of the naturally occurring stilbene resveratrol (RSV) and (E)-4-(2, 6-Difluorostyryl)-N, N-dimethylaniline, a fluorinated dialkylaminostilbene (FIDAS) on AR- and ARΔLBD in prostate cancer cells. The ability of the compounds to modulate transcriptional activity of AR and the ARΔLBD-variant Q640X was shown by reporter gene assays. Expression of endogenous AR and ARΔLBD mRNA and protein levels were determined by qRT-PCR and Western Blot. Nuclear translocation of AR-molecules was analyzed by fluorescence microscopy. AR and ARΔLBD/Q640X homo-/heterodimer formation was assessed by mammalian two hybrid assays. Biological activity of both compounds in vivo was demonstrated using a chick chorioallantoic membrane xenograft assay. Results The stilbenes RSV and FIDAS were able to significantly diminish AR and Q640X-signalling. Successful inhibition of the Q640X suggests that RSV and FIDAS are not interfering with the AR-ligand binding domain like all currently available anti-hormonal drugs. Repression of AR and Q640X-signalling by RSV and FIDAS in prostate cancer cells was caused by an inhibition of the AR and/or Q640X-dimerization. Although systemic bioavailability of both stilbenes is very low, both compounds were also able to downregulate tumor growth and AR-signalling in vivo. Conclusion RSV and FIDAS are able to inhibit the dimerization of AR and ARΔLBD molecules suggesting that stilbenes might serve as lead compounds for a novel generation of AR-inhibitors. PMID:24887556

  14. Lymphotropic Virions Affect Chemokine Receptor-Mediated Neural Signaling and Apoptosis: Implications for Human Immunodeficiency Virus Type 1-Associated Dementia

    PubMed Central

    Zheng, Jialin; Ghorpade, Anuja; Niemann, Douglas; Cotter, Robin L.; Thylin, Michael R.; Epstein, Leon; Swartz, Jennifer M.; Shepard, Robin B.; Liu, Xiaojuan; Nukuna, Adeline; Gendelman, Howard E.

    1999-01-01

    Chemokine receptors pivotal for human immunodeficiency virus type 1 (HIV-1) infection in lymphocytes and macrophages (CCR3, CCR5, and CXCR4) are expressed on neural cells (microglia, astrocytes, and/or neurons). It is these cells which are damaged during progressive HIV-1 infection of the central nervous system. We theorize that viral coreceptors could effect neural cell damage during HIV-1-associated dementia (HAD) without simultaneously affecting viral replication. To these ends, we studied the ability of diverse viral strains to affect intracellular signaling and apoptosis of neurons, astrocytes, and monocyte-derived macrophages. Inhibition of cyclic AMP, activation of inositol 1,4,5-trisphosphate, and apoptosis were induced by diverse HIV-1 strains, principally in neurons. Virions from T-cell-tropic (T-tropic) strains (MN, IIIB, and Lai) produced the most significant alterations in signaling of neurons and astrocytes. The HIV-1 envelope glycoprotein, gp120, induced markedly less neural damage than purified virions. Macrophage-tropic (M-tropic) strains (ADA, JR-FL, Bal, MS-CSF, and DJV) produced the least neural damage, while 89.6, a dual-tropic HIV-1 strain, elicited intermediate neural cell damage. All T-tropic strain-mediated neuronal impairments were blocked by the CXCR4 antibody, 12G5. In contrast, the M-tropic strains were only partially blocked by 12G5. CXCR4-mediated neuronal apoptosis was confirmed in pure populations of rat cerebellar granule neurons and was blocked by HA1004, an inhibitor of calcium/calmodulin-dependent protein kinase II, protein kinase A, and protein kinase C. Taken together, these results suggest that progeny HIV-1 virions can influence neuronal signal transduction and apoptosis. This process occurs, in part, through CXCR4 and is independent of CD4 binding. T-tropic viruses that traffic in and out of the brain during progressive HIV-1 disease may play an important role in HAD neuropathogenesis. PMID:10482576

  15. Template-based docking of a prolactin receptor proline-rich motif octapeptide to FKBP12: implications for cytokine receptor signaling.

    PubMed

    Soman, K V; Hanks, B A; Tien, H; Chari, M V; O'Neal, K D; Morrisett, J D

    1997-05-01

    A conserved proline-rich motif (PRM) in the cytoplasmic domain of cytokine receptors has been suggested to be a signaling switch regulated by the action of the FK506 binding protein (FKBP) family of peptidylprolyl isomerases (O'Neal KD, Yu-Lee LY, Shearer WT, 1995, Ann NY Acad Sci 766:282-284). We have docked the prolactin receptor PRM (Ile1-Phe2-Pro3-Pro4-Val5-Pro6-Gly7-Pro8) to the ligand binding site of FKBP12. The procedure involved conformational search restricted by NMR restraints (O'Neal KD et al., 1996, Biochem J 315:833-844), energy minimization of the octapeptide conformers so obtained, template-based docking of a selected conformer to FKBP12, and energy refinement of the resulting complex. The template used was the crystal structure of a cyclic FK506-peptide hybrid bound to FKBP12. Val5-Pro6 of the PRM was taken to be the biologically relevant Xaa-Pro bond. The docked conformer is stabilized by two intramolecular hydrogen bonds, N7H7-->O4 and N2H2-->O8, and two intermolecular ones, Ile56; N-H-->O = C:Pro6 and Tyr82:O-H-->O = C:Gly7. This conformer features a Type I beta-turn and has extensive hydrophobic contacts with the FKBP12 binding surface. The observed interactions support the hypothesis that FKBP12 catalyzes cis-trans isomerization in the PRM when it is part of the longer cytoplasmic domain of a cytokine receptor, and suggest a significant role for the PRM in signal transduction.

  16. Receptor-mediated signaling at plasmodesmata.

    PubMed

    Faulkner, Christine

    2013-01-01

    Plasmodesmata (PD) generate continuity between plant cells via the cytoplasm, endoplasmic reticulum (ER) and plasma membrane (PM), allowing movement of different classes of molecules between cells. Proteomic data indicates that the PD PM hosts many receptors and receptor kinases, as well as lipid raft and tetraspanin enriched microdomain associated proteins, suggesting the hypothesis that the PD PM is specialized with respect to both composition and function. PD-located receptor proteins and receptor kinases are responsible for perception of microbe associated molecular patterns at PD and initiate signaling that mediates changes to PD flux. In addition, developmentally relevant receptor kinases have different interactions dependent upon whether located at the PD PM or the cellular PM. The implications of these findings are that receptor-mediated signaling in PD membranes differs from that in the cellular PM and, in light the identification of PD-located proteins associated with membrane microdomains and the role of membrane microdomains in analogous signaling processes in animals, suggests that the PD PM contains specialized signaling platforms.

  17. Concomitant high expression of Toll-like receptor (TLR) and B-cell receptor (BCR) signalling molecules has clinical implications in mantle cell lymphoma.

    PubMed

    Akhter, Ariz; Street, Lesley; Ghosh, Sunita; Burns, Bruce F; Elyamany, Ghaleb; Shabani-Rad, Meer-Taher; Stewart, Douglas A; Mansoor, Adnan

    2017-03-01

    Mantle cell lymphoma (MCL) is an aggressive disease with frequent relapse. Targeted therapies against B-cell receptor (BCR) molecules have demonstrated improved outcomes in relapsed cases. However, clinical responses are slow and selective, with failure to attain complete remission in a significant subset of patients. Complex interaction of BCR signal transduction with toll-like receptor (TLR) and other pathways in MCL remains unknown, thus averting progress in development of targeted therapies. We have performed detailed digital quantification of BCR/TLR signalling molecules and their effector pathways in a cohort (n = 81) of MCL patients and correlated these data with overall survival. Hierarchical clustering model based on BCR/TLR genes revealed two distinct (BCR(high) and BCR(low) ) subsets of patients (n = 32; 40%) with significant differences in expression (>1.5-fold change; p < 0.05). Higher levels of BTK/SYK/BLNK/CARD11/PLCG signalosome and lower expression of MALT1/BCL10 genes suggested tonic pattern of BCR activation. Amplified expression of TLR6/TLR7/TLR9 was noted in concert with hyper-responsiveness of BCR machinery. MYD88, a key TLR adaptor molecule, was not upregulated in any of these clusters, which may suggest a 'cross-talk' between BCR and TLR pathways. In sync with BCR/TLR signalling, we recorded significantly enhanced expression of genes associated with NF-kB pathway in BCR(high) subset of MCL patients. On univariate analysis, the BCR(high) patients showed a trend towards inferior clinical response to a standardized treatment protocol, compared with the BCR(low) group (log rank, p = 0.043). In conclusion, we have identified hyperactive BCR/TLR signalling pathways and their effector downstream targets in a subset of MCL patients and associated it with poor clinical outcomes. Our study provides quantitative evidence at RNA expression level of possible concomitant collaboration between TLR and BCR signalling molecules in MCL. These

  18. Androgen Receptor Signaling in Salivary Gland Cancer

    PubMed Central

    Dalin, Martin G.; Watson, Philip A.; Ho, Alan L.; Morris, Luc G. T.

    2017-01-01

    Salivary gland cancers comprise a small subset of human malignancies, and are classified into multiple subtypes that exhibit diverse histology, molecular biology and clinical presentation. Local disease is potentially curable with surgery, which may be combined with adjuvant radiotherapy. However, metastatic or unresectable tumors rarely respond to chemotherapy and carry a poorer prognosis. Recent molecular studies have shown evidence of androgen receptor signaling in several types of salivary gland cancer, mainly salivary duct carcinoma. Successful treatment with anti-androgen therapy in other androgen receptor-positive malignancies such as prostate and breast cancer has inspired researchers to investigate this treatment in salivary gland cancer as well. In this review, we describe the prevalence, biology, and therapeutic implications of androgen receptor signaling in salivary gland cancer. PMID:28208703

  19. Dynamics of the actin cytoskeleton mediates receptor cross talk: An emerging concept in tuning receptor signaling.

    PubMed

    Mattila, Pieta K; Batista, Facundo D; Treanor, Bebhinn

    2016-02-01

    Recent evidence implicates the actin cytoskeleton in the control of receptor signaling. This may be of particular importance in the context of immune receptors, such as the B cell receptor, where dysregulated signaling can result in autoimmunity and malignancy. Here, we discuss the role of the actin cytoskeleton in controlling receptor compartmentalization, dynamics, and clustering as a means to regulate receptor signaling through controlling the interactions with protein partners. We propose that the actin cytoskeleton is a point of integration for receptor cross talk through modulation of protein dynamics and clustering. We discuss the implication of this cross talk via the cytoskeleton for both ligand-induced and low-level constitutive (tonic) signaling necessary for immune cell survival.

  20. 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

  1. 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.

  2. Synergy of interleukin 10 and toll-like receptor 9 signalling in B cell proliferation: Implications for lymphoma pathogenesis.

    PubMed

    Feist, Maren; Kemper, Judith; Taruttis, Franziska; Rehberg, Thorsten; Engelmann, Julia C; Gronwald, Wolfram; Hummel, Michael; Spang, Rainer; Kube, Dieter

    2017-03-01

    A network of autocrine and paracrine signals defines B cell homeostasis and is thought to be involved in transformation processes. Investigating interactions of these microenvironmental factors and their relation to proto-oncogenes as c-Myc (MYC) is fundamental to understand the biology of B cell lymphoma. Therefore, B cells with conditional MYC expression were stimulated with CD40L, insulin-like growth factor 1, α-IgM, Interleukin-10 (IL10) and CpG alone or in combination. The impact of forty different interventions on cell proliferation was investigated in MYC deprived cells and calculated by linear regression. Combination of CpG and IL10 led to a strong synergistic activation of cell proliferation (S-phase/doubling of total cell number) comparable to cells with high MYC expression. A synergistic up-regulation of CDK4, CDK6 and CCND3 expression by IL10 and CpG treatment was causal for this proliferative effect as shown by qRT-PCR analysis and inhibition of the CDK4/6 complex by PD0332991. Furthermore, treatment of stimulated MYC deprived cells with MLN120b, ACHP, Pyridone 6 or Ruxolitinib showed that IL10/CpG induced proliferation and CDK4 expression were JAK/STAT3 and IKK/NF-κB dependent. This was further supported by STAT3 and p65/RELA knockdown experiments, showing strongest effects on cell proliferation and CDK4 expression after double knockdown. Additionally, chromatin immunoprecipitation revealed a dual binding of STAT3 and p65 to the proximal promotor of CDK4 after IL10/CpG treatment. Therefore, the observed synergism of IL10R and TLR9 signalling was able to induce proliferation in a comparable way as aberrant MYC and might play a role in B cell homeostasis or transformation. © 2016 UICC.

  3. Cytokines: sources, receptors and signalling.

    PubMed

    Barrett, K E

    1996-03-01

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

  4. MyD88-dependent signaling contributes to protection following Bacillus anthracis spore challenge of mice: implications for Toll-like receptor signaling.

    PubMed

    Hughes, Molly A; Green, Candace S; Lowchyj, Lisa; Lee, Gloria M; Grippe, Vanessa K; Smith, Michael F; Huang, Li-Yun; Harvill, Eric T; Merkel, Tod J

    2005-11-01

    Bacillus anthracis is a spore-forming, gram-positive organism that is the causative agent of the disease anthrax. Recognition of Bacillus anthracis by the host innate immune system likely plays a key protective role following infection. In the present study, we examined the role of TLR2, TLR4, and MyD88 in the response to B. anthracis. Heat-killed Bacillus anthracis stimulated TLR2, but not TLR4, signaling in HEK293 cells and stimulated tumor necrosis factor alpha (TNF-alpha) production in C3H/HeN, C3H/HeJ, and C57BL/6J bone marrow-derived macrophages. The ability of heat-killed B. anthracis to induce a TNF-alpha response was preserved in TLR2-/- but not in MyD88-/- macrophages. In vivo studies revealed that TLR2-/- mice and TLR4-deficient mice were resistant to challenge with aerosolized Sterne strain spores but MyD88-/- mice were as susceptible as A/J mice. We conclude that, although recognition of B. anthracis occurs via TLR2, additional MyD88-dependent pathways contribute to the host innate immune response to anthrax infection.

  5. Insulin Receptor Signaling in Cones*

    PubMed Central

    Rajala, Ammaji; Dighe, Radhika; Agbaga, Martin-Paul; Anderson, Robert E.; Rajala, Raju V.S.

    2013-01-01

    In humans, age-related macular degeneration and diabetic retinopathy are the most common disorders affecting cones. In retinitis pigmentosa (RP), cone cell death precedes rod cell death. Systemic administration of insulin delays the death of cones in RP mouse models lacking rods. To date there are no studies on the insulin receptor signaling in cones; however, mRNA levels of IR signaling proteins are significantly higher in cone-dominant neural retina leucine zipper (Nrl) knock-out mouse retinas compared with wild type rod-dominant retinas. We previously reported that conditional deletion of the p85α subunit of phosphoinositide 3-kinase (PI3K) in cones resulted in age-related cone degeneration, and the phenotype was not rescued by healthy rods, raising the question of why cones are not protected by the rod-derived cone survival factors. Interestingly, systemic administration of insulin has been shown to delay the death of cones in mouse models of RP lacking rods. These observations led to the hypothesis that cones may have their own endogenous neuroprotective pathway, or rod-derived cone survival factors may be signaled through cone PI3K. To test this hypothesis we generated p85α−/−/Nrl−/− double knock-out mice and also rhodopsin mutant mice lacking p85α and examined the effect of the p85α subunit of PI3K on cone survival. We found that the rate of cone degeneration is significantly faster in both of these models compared with respective mice with competent p85α. These studies suggest that cones may have their own endogenous PI3K-mediated neuroprotective pathway in addition to the cone viability survival signals derived from rods. PMID:23673657

  6. 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

  7. 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

  8. CD3ζ-based chimeric antigen receptors mediate T cell activation via cis- and trans-signalling mechanisms: implications for optimization of receptor structure for adoptive cell therapy.

    PubMed

    Bridgeman, J S; Ladell, K; Sheard, V E; Miners, K; Hawkins, R E; Price, D A; Gilham, D E

    2014-02-01

    Chimeric antigen receptors (CARs) can mediate redirected lysis of tumour cells in a major histocompatibility complex (MHC)-independent manner, thereby enabling autologous adoptive T cell therapy for a variety of malignant neoplasms. Currently, most CARs incorporate the T cell receptor (TCR) CD3ζ signalling chain; however, the precise mechanisms responsible for CAR-mediated T cell activation are unclear. In this study, we used a series of immunoreceptor tyrosine-based activation motif (ITAM)-mutant and transmembrane-modified receptors to demonstrate that CARs activate T cells both directly via the antigen-ligated signalling chain and indirectly via associated chains within the TCR complex. These observations allowed us to generate new receptors capable of eliciting polyfunctional responses in primary human T cells. This work increases our understanding of CAR function and identifies new avenues for the optimization of CAR-based therapeutic interventions.

  9. 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.

  10. 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.

  11. Transferrin receptor 2 and HFE regulate furin expression via mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/Erk) signaling. Implications for transferrin-dependent hepcidin regulation

    PubMed Central

    Poli, Maura; Luscieti, Sara; Gandini, Valentina; Maccarinelli, Federica; Finazzi, Dario; Silvestri, Laura; Roetto, Antonella; Arosio, Paolo

    2010-01-01

    Background Impaired regulation of hepcidin in response to iron is the cause of genetic hemochromatosis associated with defects of HFE and transferrin receptor 2. However, the role of these proteins in the regulation of hepcidin expression is unclear. Design and Methods Hepcidin expression, SMAD and extracellular signal-regulated kinase (Erk) phosphorylation and furin expression were analyzed in hepatic HepG2 cells in which HFE and transferrin receptor 2 were down-regulated or expressed, or furin activity specifically inhibited. Furin expression was also analyzed in the liver of transferrin receptor 2 null mice. Results We showed that the silencing of HFE and transferrin receptor 2 reduced both Erk phosphorylation and furin expression, that the exogenous expression of the two enhanced the induction of phosphoErk1/2 and furin by holotransferrin, but that this did not occur when the pathogenic HFE mutant C282Y was expressed. Furin, phosphoErk1/2 and phosphoSMAD1/5/8 were down-regulated also in transferrin receptor 2-null mice. Treatment of HepG2 cells with an inhibitor of furin activity caused a strong suppression of hepcidin mRNA, probably due to the inhibition of bone morphogenic protein maturation. Conclusions The data indicate that transferrin receptor 2 and HFE are involved in holotransferrin-dependent signaling for the regulation of furin which involved Erk phosphorylation. Furin in turn may control hepcidin expression. PMID:20634490

  12. 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

  13. Differential Regulation of Smad3 and of the Type II Transforming Growth Factor-β Receptor in Mitosis: Implications for Signaling

    PubMed Central

    Hirschhorn, Tal; Barizilay, Lior; Smorodinsky, Nechama I.; Ehrlich, Marcelo

    2012-01-01

    The response to transforming growth factor-β (TGF-β) depends on cellular context. This context is changed in mitosis through selective inhibition of vesicle trafficking, reduction in cell volume and the activation of mitotic kinases. We hypothesized that these alterations in cell context may induce a differential regulation of Smads and TGF-β receptors. We tested this hypothesis in mesenchymal-like ovarian cancer cells, arrested (or not) in mitosis with 2-methoxyestradiol (2ME2). In mitosis, without TGF-β stimulation, Smad3 was phosphorylated at the C-terminus and linker regions and localized to the mitotic spindle. Phosphorylated Smad3 interacted with the negative regulators of Smad signaling, Smurf2 and Ski, and failed to induce a transcriptional response. Moreover, in cells arrested in mitosis, Smad3 levels were progressively reduced. These phosphorylations and reduction in the levels of Smad3 depended on ERK activation and Mps1 kinase activity, and were abrogated by increasing the volume of cells arrested in mitosis with hypotonic medium. Furthermore, an Mps1-dependent phosphorylation of GFP-Smad3 was also observed upon its over-expression in interphase cells, suggesting a mechanism of negative regulation which counters increases in Smad3 concentration. Arrest in mitosis also induced a block in the clathrin-mediated endocytosis of the type II TGF-β receptor (TβRII). Moreover, following the stimulation of mitotic cells with TGF-β, the proteasome-mediated attenuation of TGF-β receptor activity, the degradation and clearance of TβRII from the plasma membrane, and the clearance of the TGF-β ligand from the medium were compromised, and the C-terminus phosphorylation of Smad3 was prolonged. We propose that the reduction in Smad3 levels, its linker phosphorylation, and its association with negative regulators (observed in mitosis prior to ligand stimulation) represent a signal attenuating mechanism. This mechanism is balanced by the retention of active TGF

  14. Differential regulation of Smad3 and of the type II transforming growth factor-β receptor in mitosis: implications for signaling.

    PubMed

    Hirschhorn, Tal; Barizilay, Lior; Smorodinsky, Nechama I; Ehrlich, Marcelo

    2012-01-01

    The response to transforming growth factor-β (TGF-β) depends on cellular context. This context is changed in mitosis through selective inhibition of vesicle trafficking, reduction in cell volume and the activation of mitotic kinases. We hypothesized that these alterations in cell context may induce a differential regulation of Smads and TGF-β receptors. We tested this hypothesis in mesenchymal-like ovarian cancer cells, arrested (or not) in mitosis with 2-methoxyestradiol (2ME2). In mitosis, without TGF-β stimulation, Smad3 was phosphorylated at the C-terminus and linker regions and localized to the mitotic spindle. Phosphorylated Smad3 interacted with the negative regulators of Smad signaling, Smurf2 and Ski, and failed to induce a transcriptional response. Moreover, in cells arrested in mitosis, Smad3 levels were progressively reduced. These phosphorylations and reduction in the levels of Smad3 depended on ERK activation and Mps1 kinase activity, and were abrogated by increasing the volume of cells arrested in mitosis with hypotonic medium. Furthermore, an Mps1-dependent phosphorylation of GFP-Smad3 was also observed upon its over-expression in interphase cells, suggesting a mechanism of negative regulation which counters increases in Smad3 concentration. Arrest in mitosis also induced a block in the clathrin-mediated endocytosis of the type II TGF-β receptor (TβRII). Moreover, following the stimulation of mitotic cells with TGF-β, the proteasome-mediated attenuation of TGF-β receptor activity, the degradation and clearance of TβRII from the plasma membrane, and the clearance of the TGF-β ligand from the medium were compromised, and the C-terminus phosphorylation of Smad3 was prolonged. We propose that the reduction in Smad3 levels, its linker phosphorylation, and its association with negative regulators (observed in mitosis prior to ligand stimulation) represent a signal attenuating mechanism. This mechanism is balanced by the retention of active TGF

  15. Changes in interleukin-1 signal modulators induced by 3,4-methylenedioxymethamphetamine (MDMA): regulation by CB2 receptors and implications for neurotoxicity

    PubMed Central

    2011-01-01

    Background 3,4-Methylenedioxymethamphetamine (MDMA) produces a neuroinflammatory reaction in rat brain characterized by an increase in interleukin-1 beta (IL-1β) and microglial activation. The CB2 receptor agonist JWH-015 reduces both these changes and partially protects against MDMA-induced neurotoxicity. We have examined MDMA-induced changes in IL-1 receptor antagonist (IL-1ra) levels and IL-1 receptor type I (IL-1RI) expression and the effects of JWH-015. The cellular location of IL-1β and IL-1RI was also examined. MDMA-treated animals were given the soluble form of IL-1RI (sIL-1RI) and neurotoxic effects examined. Methods Dark Agouti rats received MDMA (12.5 mg/kg, i.p.) and levels of IL-1ra and expression of IL-1RI measured 1 h, 3 h or 6 h later. JWH-015 (2.4 mg/kg, i.p.) was injected 48 h, 24 h and 0.5 h before MDMA and IL-1ra and IL-1RI measured. For localization studies, animals were sacrificed 1 h or 3 h following MDMA and stained for IL-1β or IL-1RI in combination with neuronal and microglial markers. sIL-1RI (3 μg/animal; i.c.v.) was administered 5 min before MDMA and 3 h later. 5-HT transporter density was determined 7 days after MDMA injection. Results MDMA produced an increase in IL-ra levels and a decrease in IL-1RI expression in hypothalamus which was prevented by CB2 receptor activation. IL-1RI expression was localized on neuronal cell bodies while IL-1β expression was observed in microglial cells following MDMA. sIL-1RI potentiated MDMA-induced neurotoxicity. MDMA also increased IgG immunostaining indicating that blood brain-barrier permeability was compromised. Conclusions In summary, MDMA produces changes in IL-1 signal modulators which are modified by CB2 receptor activation. These results indicate that IL-1β may play a partial role in MDMA-induced neurotoxicity. PMID:21595923

  16. Orexin/hypocretin receptor signalling cascades

    PubMed Central

    Kukkonen, JP; Leonard, CS

    2014-01-01

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

  17. Signal-dependent hydrolysis of phosphatidylinositol 4,5-bisphosphate without activation of phospholipase C: implications on gating of Drosophila TRPL (transient receptor potential-like) channel.

    PubMed

    Lev, Shaya; Katz, Ben; Tzarfaty, Vered; Minke, Baruch

    2012-01-06

    In Drosophila, a phospholipase C (PLC)-mediated signaling cascade, couples photo-excitation of rhodopsin to the opening of the transient receptor potential (TRP) and TRP-like (TRPL) channels. A lipid product of PLC, diacylglycerol (DAG), and its metabolites, polyunsaturated fatty acids (PUFAs) may function as second messengers of channel activation. However, how can one separate between the increase in putative second messengers, change in pH, and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) depletion when exploring the TRPL gating mechanism? To answer this question we co-expressed the TRPL channels together with the muscarinic (M1) receptor, enabling the openings of TRPL channels via G-protein activation of PLC. To dissect PLC activation of TRPL into its molecular components, we used a powerful method that reduced plasma membrane-associated PI(4,5)P(2) in HEK cells within seconds without activating PLC. Upon the addition of a dimerizing drug, PI(4,5)P(2) was selectively hydrolyzed in the cell membrane without producing DAG, inositol trisphosphate, or calcium signals. We show that PI(4,5)P(2) is not an inhibitor of TRPL channel activation. PI(4,5)P(2) hydrolysis combined with either acidification or application of DAG analogs failed to activate the channels, whereas PUFA did activate the channels. Moreover, a reduction in PI(4,5)P(2) levels or inhibition of DAG lipase during PLC activity suppressed the PLC-activated TRPL current. This suggests that PI(4,5)P(2) is a crucial substrate for PLC-mediated activation of the channels, whereas PUFA may function as the channel activator. Together, this study defines a narrow range of possible mechanisms for TRPL gating.

  18. Toll-like receptor ligands sensitize B-cell receptor signalling by reducing actin-dependent spatial confinement of the receptor.

    PubMed

    Freeman, Spencer A; Jaumouillé, Valentin; Choi, Kate; Hsu, Brian E; Wong, Harikesh S; Abraham, Libin; Graves, Marcia L; Coombs, Daniel; Roskelley, Calvin D; Das, Raibatak; Grinstein, Sergio; Gold, Michael R

    2015-02-03

    Integrating signals from multiple receptors allows cells to interpret the physiological context in which a signal is received. Here we describe a mechanism for receptor crosstalk in which receptor-induced increases in actin dynamics lower the threshold for signalling by another receptor. We show that the Toll-like receptor ligands lipopolysaccharide and CpG DNA, which are conserved microbial molecules, enhance signalling by the B-cell antigen receptor (BCR) by activating the actin-severing protein cofilin. Single-particle tracking reveals that increased severing of actin filaments reduces the spatial confinement of the BCR within the plasma membrane and increases BCR mobility. This allows more frequent collisions between BCRs and greater signalling in response to low densities of membrane-bound antigen. These findings implicate actin dynamics as a means of tuning receptor signalling and as a mechanism by which B cells distinguish inert antigens from those that are accompanied by indicators of microbial infection.

  19. Toll-like receptor ligands sensitize B-cell receptor signalling by reducing actin-dependent spatial confinement of the receptor

    PubMed Central

    Freeman, Spencer A.; Jaumouillé, Valentin; Choi, Kate; Hsu, Brian E.; Wong, Harikesh S.; Abraham, Libin; Graves, Marcia L.; Coombs, Daniel; Roskelley, Calvin D.; Das, Raibatak; Grinstein, Sergio; Gold, Michael R.

    2015-01-01

    Integrating signals from multiple receptors allows cells to interpret the physiological context in which a signal is received. Here we describe a mechanism for receptor crosstalk in which receptor-induced increases in actin dynamics lower the threshold for signalling by another receptor. We show that the Toll-like receptor ligands lipopolysaccharide and CpG DNA, which are conserved microbial molecules, enhance signalling by the B-cell antigen receptor (BCR) by activating the actin-severing protein cofilin. Single-particle tracking reveals that increased severing of actin filaments reduces the spatial confinement of the BCR within the plasma membrane and increases BCR mobility. This allows more frequent collisions between BCRs and greater signalling in response to low densities of membrane-bound antigen. These findings implicate actin dynamics as a means of tuning receptor signalling and as a mechanism by which B cells distinguish inert antigens from those that are accompanied by indicators of microbial infection. PMID:25644899

  20. Regulation of protein kinase C-related kinase (PRK) signalling by the TPα and TPβ isoforms of the human thromboxane A2 receptor: Implications for thromboxane- and androgen- dependent neoplastic and epigenetic responses in prostate cancer.

    PubMed

    O'Sullivan, Aine G; Mulvaney, Eamon P; Kinsella, B Therese

    2017-04-01

    The prostanoid thromboxane (TX) A2 and its T Prostanoid receptor (the TP) are increasingly implicated in prostate cancer (PCa). Mechanistically, we recently discovered that both TPα and TPβ form functional signalling complexes with members of the protein kinase C-related kinase (PRK) family, AGC- kinases essential for the epigenetic regulation of androgen receptor (AR)-dependent transcription and promising therapeutic targets for treatment of castrate-resistant prostate cancer (CRPC). Critically, similar to androgens, activation of the PRKs through the TXA2/TP signalling axis induces phosphorylation of histone H3 at Thr11 (H3Thr11), a marker of androgen-induced chromatin remodelling and transcriptional activation, raising the possibility that TXA2-TP signalling can mimic and/or enhance AR-induced cellular changes even in the absence of circulating androgens such as in CRPC. Hence the aim of the current study was to investigate whether TXA2/TP-induced PRK activation can mimic and/or enhance AR-mediated cellular responses in the model androgen-responsive prostate adenocarcinoma LNCaP cell line. We reveal that TXA2/TP signalling can act as a neoplastic- and epigenetic-regulator, promoting and enhancing both AR-associated chromatin remodelling (H3Thr11 phosphorylation, WDR5 recruitment and acetylation of histone H4 at lysine 16) and AR-mediated transcriptional activation (e.g of the KLK3/prostate-specific antigen and TMPRSS2 genes) through mechanisms involving TPα/TPβ mediated-PRK1 and PRK2, but not PRK3, signalling complexes. Overall, these data demonstrate that TPα/TPβ can act as neoplastic and epigenetic regulators by mimicking and/or enhancing the actions of androgens within the prostate and provides further mechanistic insights into the role of the TXA2/TP signalling axis in PCa, including potentially in CRPC.

  1. Loss of α1,6-Fucosyltransferase Decreases Hippocampal Long Term Potentiation: IMPLICATIONS FOR CORE FUCOSYLATION IN THE REGULATION OF AMPA RECEPTOR HETEROMERIZATION AND CELLULAR SIGNALING.

    PubMed

    Gu, Wei; Fukuda, Tomohiko; Isaji, Tomoya; Hang, Qinglei; Lee, Ho-hsun; Sakai, Seiichiro; Morise, Jyoji; Mitoma, Junya; Higashi, Hideyoshi; Taniguchi, Naoyuki; Yawo, Hiromu; Oka, Shogo; Gu, Jianguo

    2015-07-10

    Core fucosylation is catalyzed by α1,6-fucosyltransferase (FUT8), which transfers a fucose residue to the innermost GlcNAc residue via α1,6-linkage on N-glycans in mammals. We previously reported that Fut8-knock-out (Fut8(-/-)) mice showed a schizophrenia-like phenotype and a decrease in working memory. To understand the underlying molecular mechanism, we analyzed early form long term potentiation (E-LTP), which is closely related to learning and memory in the hippocampus. The scale of E-LTP induced by high frequency stimulation was significantly decreased in Fut8(-/-) mice. Tetraethylammonium-induced LTP showed no significant differences, suggesting that the decline in E-LTP was caused by postsynaptic events. Unexpectedly, the phosphorylation levels of calcium/calmodulin-dependent protein kinase II (CaMKII), an important mediator of learning and memory in postsynapses, were greatly increased in Fut8(-/-) mice. The expression levels of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPARs) in the postsynaptic density were enhanced in Fut8(-/-) mice, although there were no significant differences in the total expression levels, implicating that AMPARs without core fucosylation might exist in an active state. The activation of AMPARs was further confirmed by Fura-2 calcium imaging using primary cultured neurons. Taken together, loss of core fucosylation on AMPARs enhanced their heteromerization, which increase sensitivity for postsynaptic depolarization and persistently activate N-methyl-d-aspartate receptors as well as Ca(2+) influx and CaMKII and then impair LTP.

  2. Orexin/hypocretin receptor signalling cascades.

    PubMed

    Kukkonen, J P; Leonard, C S

    2014-01-01

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

  3. Ethanol induced adaptations in 5-HT2c receptor signaling in the bed nucleus of the stria terminalis: implications for anxiety during ethanol withdrawal.

    PubMed

    Marcinkiewcz, Catherine A; Dorrier, Cayce E; Lopez, Alberto J; Kash, Thomas L

    2015-02-01

    One of the hallmarks of alcohol dependence is the presence of a withdrawal syndrome during abstinence, which manifests as physical craving for alcohol accompanied by subjective feelings of anxiety. Using a model of chronic intermittent ethanol (CIE) vapor in mice, we investigated the role of serotonin2c receptor (5HT2c-R) signaling in the BNST as a neural substrate underlying ethanol-induced anxiety during withdrawal. Mice were subjected to a 5-day CIE regimen of 16 h of ethanol vapor exposure followed by an 8 h "withdrawal" period between exposures. After the 5th and final exposure, mice were withdrawn for 24 h or 1 week before experiments began. Anxiety-like behavior was assessed in the social approach, light dark, and open field tests with mice showing deficits in social, but not general anxiety-like behavior that was alleviated by pretreatment with the 5HT2c-R antagonist SB 242,084 (3 mg/kg, i.p.) 24 h and 1 week post-CIE. Using immunohistochemistry and whole cell patch clamp electrophysiology, we also found that CIE increased FOS-IR and enhanced neuronal excitability in the ventral BNST (vBNST) 24 h into withdrawal in a 5HT2c-R dependent manner. This enhanced excitability persisted for 1 week post-CIE. We also found that mCPP, a 5HT2c/b agonist, induced a more robust depolarization in cells of the vBNST in CIE mice, confirming that 5HT2c-R signaling is upregulated in the vBNST following CIE. Taken together, these results suggest that CIE upregulates 5HT2c-R signaling in the vBNST, leading to increased excitability. This enhanced excitability of the vBNST may drive increased anxiety-like behavior during ethanol withdrawal. Published by Elsevier Ltd.

  4. 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

  5. Brain Human Monoclonal Autoantibody from Sydenham Chorea Targets Dopaminergic Neurons in Transgenic Mice and Signals Dopamine D2 Receptor: Implications in Human Disease1

    PubMed Central

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

    2013-01-01

    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 antigens. 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 constant region IgG1a autoantibody. Chimeric human-mouse IgG1a autoantibody co-localized 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 IgG1a 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 1) dose dependent inhibitory signaling of D2R as a potential consequence of targeting dopaminergic neurons, 2) reaction with surface-exposed FLAG epitope-tagged D2R, and 3) 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 while sera from both SC and PANDAS induced inhibitory signaling of D2R on transfected cells comparable to dopamine. Here we define a mechanism by which the brain may be altered by antibody in movement and behavioral disorders. PMID:24184556

  6. Mycobacterial signaling through toll-like receptors

    PubMed Central

    Basu, Joyoti; Shin, Dong-Min; Jo, Eun-Kyeong

    2012-01-01

    Studies over the past decade have helped to decipher molecular networks dependent on Toll-like receptor (TLR) signaling, in mycobacteria-infected macrophages. Stimulation of TLRs by mycobacteria and their antigenic components rapidly induces intracellular signaling cascades involved in the activation of nuclear factor-κB and mitogen-activated protein kinase pathways, which play important roles in orchestrating proinflammatory responses and innate defense through generation of a variety of antimicrobial effector molecules. Recent studies have provided evidence that mycobacterial TLR-signaling cross talks with other intracellular antimicrobial innate pathways, the autophagy process and functional vitamin D receptor (VDR) signaling. In this article we describe recent advances in the recognition, responses, and regulation of mycobacterial signaling through TLRs. PMID:23189273

  7. 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

  8. Androgen Receptor Signaling in Bladder Cancer

    PubMed Central

    Li, Peng; Chen, Jinbo; Miyamoto, Hiroshi

    2017-01-01

    Emerging preclinical findings have indicated that steroid hormone receptor signaling plays an important role in bladder cancer outgrowth. In particular, androgen-mediated androgen receptor signals have been shown to correlate with the promotion of tumor development and progression, which may clearly explain some sex-specific differences in bladder cancer. This review summarizes and discusses the available data, suggesting the involvement of androgens and/or the androgen receptor pathways in urothelial carcinogenesis as well as tumor growth. While the precise mechanisms of the functions of the androgen receptor in urothelial cells remain far from being fully understood, current evidence may offer chemopreventive or therapeutic options, using androgen deprivation therapy, in patients with bladder cancer. PMID:28241422

  9. Receptor signaling clusters in the immune synapse

    SciTech Connect

    Dustin, Michael L.; Groves, Jay T.

    2012-02-23

    Signaling processes between various immune cells involve large-scale spatial reorganization of receptors and signaling molecules within the cell-cell junction. These structures, now collectively referred to as immune synapses, interleave physical and mechanical processes with the cascades of chemical reactions that constitute signal transduction systems. Molecular level clustering, spatial exclusion, and long-range directed transport are all emerging as key regulatory mechanisms. The study of these processes is drawing researchers from physical sciences to join the effort and represents a rapidly growing branch of biophysical chemistry. Furthermore, recent advances in physical and quantitative analyses of signaling within the immune synapses are reviewed here.

  10. 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

  11. P2X and P2Y receptor signaling in red blood cells.

    PubMed

    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.

  12. ATP Receptors Gate Microglia Signaling in Neuropathic Pain

    PubMed Central

    Trang, Tuan; Beggs, Simon; Salter, Michael W.

    2013-01-01

    Microglia were described by Pio del Rio-Hortega (1932) as being the ‘third element’ distinct from neurons and astrocytes. Decades after this observation, the function and even the very existence of microglia as a distinct cell type was a topic of intense debate and conjecture. However, considerable advances have been made towards understanding the neurobiology of microglia resulting in a radical shift in our view of them as being passive bystanders that have solely immune and supportive roles, to being active principal players that contribute to central nervous system pathologies caused by disease or following injury. Converging lines of evidence implicate microglia as being essential in the pathogenesis of neuropathic pain, a debilitating chronic pain condition that can occur after peripheral nerve damage caused by disease, infection, or physical injury. A key molecule that modulates microglial activity is ATP, an endogenous ligand of the P2-purinoceptor family consisting of P2X ionotropic and P2Y metabotropic receptors. Microglia express several P2 receptor subtypes, and of these the P2X4, P2X7, and P2Y12 receptor subtypes have been implicated in neuropathic pain. The P2X4 receptor has emerged as the core microglia-neuron signaling pathway: activation of this receptor causes release of brain-derived neurotrophic factor (BDNF) which causes disinhibition of pain-transmission neurons in spinal lamina I. The present review highlights recent advances in understanding the signaling and regulation of P2 receptors expressed in microglia and the implications for microglia-neuron interactions for the management of neuropathic pain. PMID:22116040

  13. Metabolic labelling of membrane microdomains/rafts in Jurkat cells indicates the presence of glycerophospholipids implicated in signal transduction by the CD3 T-cell receptor.

    PubMed Central

    Rouquette-Jazdanian, Alexandre K; Pelassy, Claudette; Breittmayer, Jean-Philippe; Cousin, Jean-Louis; Aussel, Claude

    2002-01-01

    Cell membranes contain sphingolipids and cholesterol, which cluster together in distinct domains called rafts. The outer-membrane leaflet of these peculiar membrane domains contains glycosylphosphatidylinositol-anchored proteins, while the inner leaflet contains proteins implicated in signalling, such as the acylated protein kinase p56(lck) and the palmitoylated adaptator LAT (linker for activation of T-cells). We present here an approach to study the lipid composition of rafts and its change upon T-cell activation. Our method is based on metabolic labelling of Jurkat T-cells with different precursors of glycerophospholipid synthesis, including glycerol and fatty acids with different lengths and degrees of saturation as well as phospholipid polar head groups. The results obtained indicate that lipid rafts isolated by the use of sucrose density-gradient centrifugation after Triton X-100 extraction in the cold, besides sphingolipids and cholesterol, contain unambiguously all classes of glycerophospholipids: phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine and phosphatidylcholine. Fatty acid labelling shows that lipid rafts are labelled preferentially with saturated fatty acids while the rest of the plasma membrane incorporates mostly long-chained polyunsaturated fatty acids. To see whether the raft composition as measured by metabolic labelling of phospholipids is involved in T-cell activation, we investigated the production of sn-1,2-diacylglycerol (DAG) in CD3-activated cells. DAG production occurs within rafts, confirming previous demonstration of protein kinase C translocation into membrane microdomains. Our data demonstrate that raft disorganization by methyl-beta-cyclodextrin impairs both CD3-induced DAG production and changes in cytosolic Ca(2+) concentration. These lines of evidence support the conclusion that the major events in T-cell activation occur within or due to lipid rafts. PMID:11964165

  14. Sustained Extracellular Signal-Regulated Kinase 1/2 Phosphorylation in Neonate 6-Hydroxydopamine-Lesioned Rats after Repeated D1-Dopamine Receptor Agonist Administration: Implications for NMDA Receptor Involvement

    PubMed Central

    Papadeas, Sophia T.; Blake, Bonita L.; Knapp, Darin J.; Breese, George R.

    2010-01-01

    Extracellular signal-regulated kinase (ERK) 1/2, a well known regulator of gene expression, is likely to contribute to signaling events underlying enduring neural adaptations. Phosphorylated (phospho)-ERK was examined immunohistochemically after both single and repeated (i.e., sensitizing) doses of the partial D1-dopamine (DA) receptor agonist SKF-38393 (2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benazepine HCl) to adult rats lesioned as neonates (neonate lesioned) with 6-hydroxydopamine. Remarkably, prolonged phospho-ERK accumulated primarily in layers II–III of medial prefrontal cortex (MPC), where it declined gradually yet remained significantly elevated for at least 36 d after repeated doses of SKF-38393. Sustained (≥7 d) phospho-ERK was observed for shorter periods in various other cortical regions but was not detectable in striatum or nucleus accumbens. At 36 d, an additional injection of SKF-38393 to sensitized rats restored phospho-ERK to maximal levels only in MPC when examined 7 d later. Phosphorylated cAMP response element-binding protein (CREB), examined 7 d after the sensitizing regimen, was observed exclusively in MPC, where it was abundant throughout all layers. Systemic injections of SL327 (α-[amino[(4-aminophenyl)thio]methylene]-2-(trifluoromethyl)benzeneacetonitrile), an inhibitor of the upstream ERK activator mitogen ERK kinase, attenuated both ERK and CREB phosphorylation in layers II–III of MPC. Pretreatment with the D1 antagonist SCH-23390 ((R)-(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepine-7-OL maleate) inhibited the prolonged increase in MPC phospho-ERK, whereas the 5-HT2 receptor antagonist ketanserin (3-[2-[4-(4-fluorobenzoyl)-1-piperidinyl]ethyl]-2,4(1H,3H)-quinazolinedione tartrate) was ineffective. Competitive and noncompetitive NMDA receptor antagonists also blocked sustained ERK phosphorylation. Collectively, the present results demonstrate coupling of D1 and NMDA receptor function reflected in sustained

  15. Receptor-mediated signaling in Aspergillus fumigatus

    PubMed Central

    Grice, C. M.; Bertuzzi, M.; Bignell, E. M.

    2013-01-01

    Aspergillus fumigatus is the most pathogenic species among the Aspergilli, and the major fungal agent of human pulmonary infection. To prosper in diverse ecological niches, Aspergilli have evolved numerous mechanisms for adaptive gene regulation, some of which are also crucial for mammalian infection. Among the molecules which govern such responses, integral membrane receptors are thought to be the most amenable to therapeutic modulation. This is due to the localization of these molecular sensors at the periphery of the fungal cell, and to the prevalence of small molecules and licensed drugs which target receptor-mediated signaling in higher eukaryotic cells. In this review we highlight the progress made in characterizing receptor-mediated environmental adaptation in A. fumigatus and its relevance for pathogenicity in mammals. By presenting a first genomic survey of integral membrane proteins in this organism, we highlight an abundance of putative seven transmembrane domain (7TMD) receptors, the majority of which remain uncharacterized. Given the dependency of A. fumigatus upon stress adaptation for colonization and infection of mammalian hosts, and the merits of targeting receptor-mediated signaling as an antifungal strategy, a closer scrutiny of sensory perception and signal transduction in this organism is warranted. PMID:23430083

  16. LPA receptor signaling: pharmacology, physiology, and pathophysiology

    PubMed Central

    Yung, Yun C.; Stoddard, Nicole C.; Chun, Jerold

    2014-01-01

    Lysophosphatidic acid (LPA) is a small ubiquitous lipid found in vertebrate and nonvertebrate organisms that mediates diverse biological actions and demonstrates medicinal relevance. LPA’s functional roles are driven by extracellular signaling through at least six 7-transmembrane G protein-coupled receptors. These receptors are named LPA1–6 and signal through numerous effector pathways activated by heterotrimeric G proteins, including Gi/o, G12/13, Gq, and Gs. LPA receptor-mediated effects have been described in numerous cell types and model systems, both in vitro and in vivo, through gain- and loss-of-function studies. These studies have revealed physiological and pathophysiological influences on virtually every organ system and developmental stage of an organism. These include the nervous, cardiovascular, reproductive, and pulmonary systems. Disturbances in normal LPA signaling may contribute to a range of diseases, including neurodevelopmental and neuropsychiatric disorders, pain, cardiovascular disease, bone disorders, fibrosis, cancer, infertility, and obesity. These studies underscore the potential of LPA receptor subtypes and related signaling mechanisms to provide novel therapeutic targets. PMID:24643338

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

    PubMed Central

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

    2010-01-01

    In vertebrates and some invertebrates, odorant molecules bind to G protein-coupled receptors (GPCRs) 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 GPCR-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 PI3Kγ and cloned a gene for a PI3K with amino acid homology with PI3Kβ. The lobster olfactory PI3K co-immunoprecipitates with the G protein α and β subunits, and an odorant-evoked increase in phosphatidylinositol (3,4,5)-trisphosphate can be detected in the signal transduction compartment of the ORNs. PI3Kγ and β 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. PMID:20132480

  18. Crosstalk between integrin and receptor tyrosine kinase signaling in breast carcinoma progression.

    PubMed

    Soung, Young Hwa; Clifford, John L; Chung, Jun

    2010-05-01

    This review explored the mechanism of breast carcinoma progression by focusing on integrins and receptor tyrosine kinases (or growth factor receptors). While the primary role of integrins was previously thought to be solely as mediators of adhesive interactions between cells and extracellular matrices, it is now believed that integrins also regulate signaling pathways that control cancer cell growth, survival, and invasion. A large body of evidence suggests that the cooperation between integrin and receptor tyrosine kinase signaling regulates certain signaling functions that are important for cancer progression. Recent developments on the crosstalk between integrins and receptor tyrosine kinases, and its implication in mammary tumor progression, are discussed.

  19. Multiple roles and therapeutic implications of Akt signaling in cancer

    PubMed Central

    Calvo, Emiliano; Bolós, Victoria; Grande, Enrique

    2009-01-01

    The prominence of the PI3K-Akt signaling pathway in several tumors indicates a relationship with tumor grade and proliferation. Critical cellular processes are driven through this pathway. More detailed knowledge of the pathogenesis of tumors would enable us to design targeted drugs to block both membrane tyrosine kinase receptors and the intracellular kinases involved in the transmission of the signal. The newly approved molecular inhibitors sunitinib (an inhibitor of vascular endothelial growth factor receptor, platelet-derived growth factor receptor, and other tyrosine kinase receptors), sorafenib (a serine–threonine kinase inhibitor that acts against B-Raf) and temsirolimus (an mTOR inhibitor) shown clinical activity in advanced kidney cancer. Chronic myeloid leukemia has changed its natural history thanks to imatinib and dasatinib, both of which inhibit the intracellular bcr/abl protein derived from the alteration in the Philadelphia chromosome. Intracellular pathways are still important in cancer development and their blockade directly affects outcome. Cross-talk has been observed but is not well understood. Vertical and horizontal pathway blockade are promising anticancer strategies. Indeed, preclinical and early clinical data suggest that combining superficial and intracellular blocking agents can synergize and leverage single-agent activity. The implication of the Akt signaling pathway in cancer is well established and has led to the development of new anticancer agents that block its activation. PMID:20616901

  20. Phosphoinositide turnover in Toll-like receptor signaling and trafficking

    PubMed Central

    Tu Le, Oanh Thi; Ngoc Nguyen, Tu Thi; Lee, Sang Yoon

    2014-01-01

    Lipid components in biological membranes are essential for maintaining cellular function. Phosphoinositides, the phosphorylated derivatives of phosphatidylinositol (PI), regulate many critical cell processes involving membrane signaling, trafficking, and reorganization. Multiple metabolic pathways including phosphoinositide kinases and phosphatases and phospholipases tightly control spatio-temporal concentration of membrane phosphoinositides. Metabolizing enzymes responsible for PI 4,5-bisphosphate (PI(4,5)P2) production or degradation play a regulatory role in Toll-like receptor (TLR) signaling and trafficking. These enzymes include PI 4-phosphate 5-kinase, phosphatase and tensin homolog, PI 3-kinase, and phospholipase C. PI(4,5)P2 mediates the interaction with target cytosolic proteins to induce their membrane translocation, regulate vesicular trafficking, and serve as a precursor for other signaling lipids. TLR activation is important for the innate immune response and is implicated in diverse pathophysiological disorders. TLR signaling is controlled by specific interactions with distinct signaling and sorting adaptors. Importantly, TLR signaling machinery is differentially formed depending on a specific membrane compartment during signaling cascades. Although detailed mechanisms remain to be fully clarified, phosphoinositide metabolism is promising for a better understanding of such spatio-temporal regulation of TLR signaling and trafficking. [BMB Reports 2014; 47(7): 361-368] PMID:24856829

  1. A kinase-independent biological activity for insulin growth factor-1 receptor (IGF-1R) : implications for inhibition of the IGF-1R signal.

    PubMed

    Janku, Filip; Huang, Helen J; Angelo, Laura S; Kurzrock, Razelle

    2013-03-01

    It has been demonstrated that epidermal growth factor receptor (EGFR) can have kinase independent activity. EGFR kinase-independent function maintains intracellular glucose levels via sodium glucose transporter protein 1 (SGLT1) and supports cell survival. It is plausible that this phenomenon can apply to other receptor tyrosine kinases. We found that transfection of insulin-like growth factor receptor (IGF-1R) siRNA into HEK293 (human embryonic kidney) and MCF7 (metastatic breast cancer) cells result in decreased intracellular glucose levels, whereas treatment with an IGF-1R tyrosine kinase inhibitor OSI-906 did not affect intracellular glucose levels. In addition, IGF-1R interacted with SGLT1 in a manner similar to that previously reported with EGFR. The combination of IGF-1R siRNA and OSI-906 resulted in decreased viability of HEK293 and MCF7 cell lines compared to either agent alone. Collectively, these experiments suggest that IGF-1R, has kinase-independent biologic functions and provide a rationale for combining anti-IGF-1R antibodies or siRNA and IGF-1R small molecule inhibitors.

  2. Epidermal Growth Factor Receptor Cell Survival Signaling Requires Phosphatidylcholine Biosynthesis

    PubMed Central

    Crook, Matt; Upadhyay, Awani; Ido, Liyana J.; Hanna-Rose, Wendy

    2016-01-01

    Identification of pro-cell survival signaling pathways has implications for cancer, cardiovascular, and neurodegenerative disease. We show that the Caenorhabditis elegans epidermal growth factor receptor LET-23 (LET-23 EGFR) has a prosurvival function in counteracting excitotoxicity, and we identify novel molecular players required for this prosurvival signaling. uv1 sensory cells in the C. elegans uterus undergo excitotoxic death in response to activation of the OSM-9/OCR-4 TRPV channel by the endogenous agonist nicotinamide. Activation of LET-23 EGFR can effectively prevent this excitotoxic death. We investigate the roles of signaling pathways known to act downstream of LET-23 EGFR in C. elegans and find that the LET-60 Ras/MAPK pathway, but not the IP3 receptor pathway, is required for efficient LET-23 EGFR activity in its prosurvival function. However, activation of LET-60 Ras/MAPK pathway does not appear to be sufficient to fully mimic LET-23 EGFR activity. We screen for genes that are required for EGFR prosurvival function and uncover a role for phosphatidylcholine biosynthetic enzymes in EGFR prosurvival function. Finally, we show that exogenous application of phosphatidylcholine is sufficient to prevent some deaths in this excitotoxicity model. Our work implicates regulation of lipid synthesis downstream of EGFR in cell survival and death decisions. PMID:27605519

  3. Science Signaling Podcast for 29 November 2016: Pre-B cell receptor signaling in leukemia.

    PubMed

    Wilson, Bridget S; VanHook, Annalisa M

    2016-11-29

    This Podcast features an interview with Bridget Wilson, author of a Research Article that appears in the 29 November 2016 issue of Science Signaling, about pre-B cell receptor (pre-BCR) signaling in B cell precursor acute lymphoblastic leukemia (BCP-ALL). Signaling through the pre-BCR, an immature form of the BCR, promotes the survival of B cell progenitors and has been implicated in the pathology of BCP-ALL. Erasmus et al found that pre-BCRs formed transient homomeric complexes that correlated with pro-survival signaling. Preventing homotypic interactions between pre-BCRs sensitized B cells to chemotherapeutic agents, suggesting that interfering with such interactions may improve the efficacy of existing chemotherapies for BCP-ALL.Listen to Podcast. Copyright © 2016, American Association for the Advancement of Science.

  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. 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.

  6. A Genetic Approach to Identifying Signal Transduction Mechanisms Initiated by Receptors for TGF-B-Related Factors.

    DTIC Science & Technology

    1998-10-01

    resistant to TGF-ß-induced growth arrest suggest that both types of receptors are required for signaling (Boyd and Massague, 1989; Laiho et ah, 1990...II in TGF-ß- resistant cell mutants implicates both receptor types in signal transduction. J. Biol. Chem. 265, 18518-18524. Lechleider, R. J., de...I-1 « -J AD GRANT NUMBER DAMD17-94-J-4339 TITLE: A Genetic Approach to Identifying Signal Transduction Mechanisms Initiated by Receptors

  7. Ethanol induced adaptations in 5-HT2c receptor signaling in the bed nucleus of stria terminalis: Implications for anxiety during ethanol withdrawal

    PubMed Central

    Marcinkiewcz, Catherine A.; Dorrier, Cayce E.; Lopez, Alberto J.; Kash, Thomas L.

    2015-01-01

    One of the hallmarks of alcohol dependence is the presence of a withdrawal syndrome during abstinence, which manifests as physical craving for alcohol accompanied by subjective feelings of anxiety. Using a model of chronic intermittent ethanol (CIE) vapor in mice, we investigated the role of serotonin2c signaling in the BNST as a neural substrate underlying ethanol-induced anxiety during withdrawal. Mice were subjected to a 5-day CIE regimen of 16 hours of ethanol vapor exposure followed by an 8 hour “withdrawal” period between exposures. After the 5th and final exposure, mice were withdrawn for 24 hours or 1 week before experiments began. Anxiety-like behavior was assessed in the social approach, light dark, and open field test with mice showing deficits in social, but not general anxiety-like behavior that was alleviated by pretreatment with the 5HT2c-R antagonist SB 242,084 (3 mg/kg, i.p.) 24 hours and 1 week post-CIE. Using immunohistochemistry and whole cell patch clamp electrophysiology, we also found that CIE increased FOS-IR and enhanced neuronal excitability in the ventral BNST (vBNST) 24 hrs into withdrawal in a 5HT2c-R dependent manner. This enhanced excitability persisted for 1 week post-CIE. We also found that mCPP, a 5HT2c/b agonist, induced a more robust depolarization in cells of the vBNST in CIE mice, confirming that 5HT2c-R signaling is upregulated in the vBNST following CIE. Taken together, these results suggest that CIE upregulates 5HT2c-R signaling in the vBNST, leading to increased excitability. This enhanced excitability of the vBNST may drive increased anxiety-like behavior during ethanol withdrawal. PMID:25229718

  8. Nuclear Receptor Signaling: a home for nuclear receptor and coregulator signaling research.

    PubMed

    McKenna, Neil J; Evans, Ronald M; O'Malley, Bert W

    2014-01-01

    The field of nuclear receptor and coregulator signaling has grown into one of the most active and interdisciplinary in eukaryotic biology. Papers in this field are spread widely across a vast number of journals, which complicates the task of investigators in keeping current with the literature in the field. In 2003, we launched Nuclear Receptor Signaling as an Open Access reviews, perspectives and methods journal for the nuclear receptor signaling field. Building on its success and impact on the community, we have added primary research and dataset articles to this list of article categories, and we now announce the re-launch of the journal this month. Here we will summarize the rationale that informed the creation and expansion of the journal, and discuss the possibilities for its future development.

  9. CXCR4 chemokine receptor signaling mediates pain in diabetic neuropathy

    PubMed Central

    2014-01-01

    Background Painful Diabetic Neuropathy (PDN) is a debilitating syndrome present in a quarter of diabetic patients that has a substantial impact on their quality of life. Despite this significant prevalence and impact, current therapies for PDN are only partially effective. Moreover, the cellular mechanisms underlying PDN are not well understood. Neuropathic pain is caused by a variety of phenomena including sustained excitability in sensory neurons that reduces the pain threshold so that pain is produced in the absence of appropriate stimuli. Chemokine signaling has been implicated in the pathogenesis of neuropathic pain in a variety of animal models. We therefore tested the hypothesis that chemokine signaling mediates DRG neuronal hyperexcitability in association with PDN. Results We demonstrated that intraperitoneal administration of the specific CXCR4 antagonist AMD3100 reversed PDN in two animal models of type II diabetes. Furthermore DRG sensory neurons acutely isolated from diabetic mice displayed enhanced SDF-1 induced calcium responses. Moreover, we demonstrated that CXCR4 receptors are expressed by a subset of DRG sensory neurons. Finally, we observed numerous CXCR4 expressing inflammatory cells infiltrating into the DRG of diabetic mice. Conclusions These data suggest that CXCR4/SDF-1 signaling mediates enhanced calcium influx and excitability in DRG neurons responsible for PDN. Simultaneously, CXCR4/SDF-1 signaling may coordinate inflammation in diabetic DRG that could contribute to the development of pain in diabetes. Therefore, targeting CXCR4 chemokine receptors may represent a novel intervention for treating PDN. PMID:24961298

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. Oxidation inhibits PTH receptor signaling and trafficking.

    PubMed

    Ardura, Juan A; Alonso, Verónica; Esbrit, Pedro; Friedman, Peter A

    2017-01-22

    Reactive Oxygen Species (ROS) increase during aging, potentially affecting many tissues including brain, heart, and bone. ROS alter signaling pathways and constitute potential therapeutic targets to limit oxidative damaging effects in aging-associated diseases. Parathyroid hormone receptors (PTHR) are widely expressed and PTH is the only anabolic therapy for osteoporosis. The effects of oxidative stress on PTHR signaling and trafficking have not been elucidated. Here, we used Fluorescence Resonance Energy Transfer (FRET)-based cAMP, ERK, and calcium fluorescent biosensors to analyze the effects of ROS on PTHR signaling and trafficking by live-cell imaging. PTHR internalization and recycling were measured in HEK-293 cells stably transfected with HA-PTHR. PTH increased cAMP production, ERK phosphorylation, and elevated intracellular calcium. Pre-incubation with H2O2 reduced all PTH-dependent signaling pathways. These inhibitory effects were not a result of PTH oxidation since PTH incubated with H2O2 triggered similar responses. PTH promoted internalization and recycling of the PTHR. Both events were significantly reduced by H2O2 pre-incubation. These findings highlight the role of oxidation on PTHR signaling and trafficking, and suggest the relevance of ROS as a putative target in diseases associated with oxidative stress such as age-related osteoporosis. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Bisacodyl and its cytotoxic activity on human glioblastoma stem-like cells. Implication of inositol 1,4,5-triphosphate receptor dependent calcium signaling.

    PubMed

    Dong, Jihu; Aulestia, Francisco J; Assad Kahn, Suzana; Zeniou, Maria; Dubois, Luiz Gustavo; El-Habr, Elias A; Daubeuf, François; Tounsi, Nassera; Cheshier, Samuel H; Frossard, Nelly; Junier, Marie-Pierre; Chneiweiss, Hervé; Néant, Isabelle; Moreau, Marc; Leclerc, Catherine; Haiech, Jacques; Kilhoffer, Marie-Claude

    2017-06-01

    Glioblastoma is the most common malignant brain tumor. The heterogeneity at the cellular level, metabolic specificities and plasticity of the cancer cells are a challenge for glioblastoma treatment. Identification of cancer cells endowed with stem properties and able to propagate the tumor in animal xenografts has opened a new paradigm in cancer therapy. Thus, to increase efficacy and avoid tumor recurrence, therapies need to target not only the differentiated cells of the tumor mass, but also the cancer stem-like cells. These therapies need to be effective on cells present in the hypoxic, slightly acidic microenvironment found within tumors. Such a microenvironment is known to favor more aggressive undifferentiated phenotypes and a slow-growing "quiescent state" that preserves the cells from chemotherapeutic agents, which mostly target proliferating cells. Based on these considerations, we performed a differential screening of the Prestwick Chemical Library of approved drugs on both proliferating and quiescent glioblastoma stem-like cells and identified bisacodyl as a cytotoxic agent with selectivity for quiescent glioblastoma stem-like cells. In the present study we further characterize bisacodyl activity and show its efficacy in vitro on clonal macro-tumorospheres, as well as in vivo in glioblastoma mouse models. Our work further suggests that bisacodyl acts through inhibition of Ca(2+) release from the InsP3 receptors. Copyright © 2017. Published by Elsevier B.V.

  16. Research Resources for Nuclear Receptor Signaling Pathways.

    PubMed

    McKenna, Neil J

    2016-08-01

    Nuclear receptor (NR) signaling pathways impact cellular function in a broad variety of tissues in both normal physiology and disease states. The complex tissue-specific biology of these pathways is an enduring impediment to the development of clinical NR small-molecule modulators that combine therapeutically desirable effects in specific target tissues with suppression of off-target effects in other tissues. Supporting the important primary research in this area is a variety of web-based resources that assist researchers in gaining an appreciation of the molecular determinants of the pharmacology of a NR pathway in a given tissue. In this study, selected representative examples of these tools are reviewed, along with discussions on how current and future generations of tools might optimally adapt to the future of NR signaling research. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

  17. Research Resources for Nuclear Receptor Signaling Pathways

    PubMed Central

    2016-01-01

    Nuclear receptor (NR) signaling pathways impact cellular function in a broad variety of tissues in both normal physiology and disease states. The complex tissue-specific biology of these pathways is an enduring impediment to the development of clinical NR small-molecule modulators that combine therapeutically desirable effects in specific target tissues with suppression of off-target effects in other tissues. Supporting the important primary research in this area is a variety of web-based resources that assist researchers in gaining an appreciation of the molecular determinants of the pharmacology of a NR pathway in a given tissue. In this study, selected representative examples of these tools are reviewed, along with discussions on how current and future generations of tools might optimally adapt to the future of NR signaling research. PMID:27216565

  18. 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

  19. Adiponectin receptor signalling in the brain

    PubMed Central

    Thundyil, John; Pavlovski, Dale; Sobey, Christopher G; Arumugam, Thiruma V

    2012-01-01

    Adiponectin is an important adipocyte-derived hormone that regulates metabolism of lipids and glucose, and its receptors (AdipoR1, AdipoR2, T-cadherin) appear to exert actions in peripheral tissues by activating the AMP-activated protein kinase, p38-MAPK, PPARα and NF-kappa B. Adiponectin has been shown to exert a wide range of biological functions that could elicit different effects, depending on the target organ and the biological milieu. There is substantial evidence to suggest that adiponectin receptors are expressed widely in the brain. Their expression has been detected in regions of the mouse hypothalamus, brainstem, cortical neurons and endothelial cells, as well as in whole brain and pituitary extracts. While there is now considerable evidence for the presence of adiponectin and its receptors in the brain, their precise roles in brain diseases still remain unclear. Only a few research studies have looked at this facet of adiponectins in brain disorders. This brief review will describe the evidence for important functions by adiponectin, its structure and known actions, evidence for expression of AdipoRs in the brain, their involvement in brain disorders and the therapeutic potential of agents that could modify AdipoR signalling. PMID:21718299

  20. 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

  1. IL-17 family: cytokines, receptors and signaling

    PubMed Central

    Gu, Chunfang; Wu, Ling; Li, Xiaoxia

    2013-01-01

    The interleukin 17 (IL-17) family, a subset of cytokines consisting of IL-17A-F, plays crucial roles in host defense against microbial organisms and in the development of inflammatory diseases. Although IL-17A is the signature cytokine produced by T helper 17 (Th17) cells, IL-17A and other IL-17 family cytokines have multiple sources ranging from immune cells to non-immune cells. The IL-17 family signals via their correspondent receptors and activates downstream pathways that include NFκB, MAPKs and C/EBPs to induce the expression of anti-microbial peptides, cytokines and chemokines. The proximal adaptor Act1 is a common mediator during the signaling of all IL-17 cytokines so far and is thus involved in IL-17 mediated host defense and IL-17-driven autoimmune conditions. This review will give an overview and recent updates on the IL-17family, the activation and regulation of IL-17 signaling as well as diseases associated with this cytokine family PMID:24011563

  2. 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

  3. Nuclear hormone receptor signals as new therapeutic targets for urothelial carcinoma.

    PubMed

    Miyamoto, H; Zheng, Y; Izumi, K

    2012-01-01

    Unlike prostate and breast cancers, urothelial carcinoma of the urinary bladder is not yet considered as an endocrine-related neoplasm, and hormonal therapy for bladder cancer remains experimental. Nonetheless, there is increasing evidence indicating that nuclear hormone receptor signals are implicated in the development and progression of bladder cancer. Androgen-mediated androgen receptor (AR) signals have been convincingly shown to induce bladder tumorigenesis. Androgens also promote the growth of AR-positive bladder cancer cells, although it is controversial whether AR plays a dominant role in bladder cancer progression. Both stimulatory and inhibitory functions of estrogen receptor signals in bladder cancer have been reported. Various studies have also demonstrated the involvement of other nuclear receptors, including progesterone receptor, glucocorticoid receptor, vitamin D receptor, and retinoid receptors, as well as some orphan receptors, in bladder cancer. This review summarizes and discusses available data suggesting the modulation of bladder carcinogenesis and cancer progression via nuclear hormone receptor signaling pathways. These pathways have the potential to be an extremely important area of bladder cancer research, leading to the development of effective chemopreventive/therapeutic approaches, using hormonal manipulation. Considerable uncertainty remains regarding the selection of patients who are likely to benefit from hormonal therapy and optimal options for the treatment.

  4. Toll-like receptor signaling in transplantation

    PubMed Central

    Alegre, Maria-Luisa; Goldstein, Daniel R.; Chong, Anita S.

    2008-01-01

    Purpose of the review This review summarizes recent advances on the role of endogenous and exogenous Toll-like receptor (TLR) ligands in the activation and inhibition of immune responses in transplantation. Recent findings During an alloresponse, TLRs can be engaged by both damage-induced endogenous ligands or microbial-associated molecular patterns. The damage-induced molecule high mobility group box 1 protein (HGMB1) and its binding to TLR4 have been identified as major initiators of anti-tumor and anti-transplant immune responses. Type I interferon (IFN) signaling plays an important role in the pro-rejection effect mediated by TLR agonists and some bacteria. However, similar pathways in neonates can result in inhibition rather than activation of alloimmune responses. Summary The consequences of TLR engagement by endogenous and exogenous ligands in transplantation may depend on the relative induction of inflammatory and regulatory pathways and the stage of development of the immune system. PMID:18685330

  5. Molecular mechanisms of glucocorticoid receptor signaling.

    PubMed

    Labeur, Marta; Holsboer, Florian

    2010-01-01

    This review highlights the most recent findings on the molecular mechanisms of the glucocorticoid receptor (GR). Most effects of glucocorticoids are mediated by the intracellular GR which is present in almost every tissue and controls transcriptional activation via direct and indirect mechanisms. Nevertheless the glu-cocorticoid responses are tissue -and gene- specific. GR associates selectively with corticosteroid ligands produced in the adrenal gland in response to changes of humoral homeostasis. Ligand interaction with GR promotes either GR binding to genomic glucocorticoid response elements, in turn modulating gene transcription, or interaction of GR monomers with other transcription factors activated by other signalling pathways leading to transrepression. The GR regulates a broad spectrum of physiological functions, including cell differentiation, metabolism and inflammatory responses. Thus, disruption or dysregulation of GR function will result in severe impairments in the maintenance of homeostasis and the control of adaptation to stress.

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

    PubMed Central

    Shang, Yi; Filizola, Marta

    2015-01-01

    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. PMID:25981301

  7. 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.

  8. 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.

  9. Toll-like receptor signaling in cell proliferation and survival

    PubMed Central

    Li, Xinyan; Jiang, Song; Tapping, Richard I.

    2009-01-01

    Toll-like receptors (TLRs) are important sensors of foreign microbial components as well as products of damaged or inflamed self tissues. Upon sensing these molecules, TLRs initiate a series of downstream signaling events that drive cellular responses including the production of cytokines, chemokines and other inflammatory mediators. This outcome results from the intracellular assembly of protein complexes that drive phosphorylation and other signaling cascades ultimately leading to chromatin remodeling and transcription factor activation. In addition to driving inflammatory responses, TLRs also regulate cell proliferation and survival which serves to expand useful immune cells and integrate inflammatory responses and tissue repair processes. In this context, central TLR signaling molecules, such as the mitogen-activated protein kinases (MAPK) and phosphoinositide 3-kinase (PI3K), play key roles. In addition, four major groups of transcription factors which are targets of TLR activation also control cell fate. This review focuses on the role of TLR signaling as it relates to cell proliferation and survival. This topic not only has important implications for understanding host defense and tissue repair, but also cancer which is often associated with conditions of chronic inflammation. PMID:19775907

  10. Targeting fibroblast growth factor receptor signaling in hepatocellular carcinoma.

    PubMed

    Cheng, Ann-Lii; Shen, Ying-Chun; Zhu, Andrew X

    2011-01-01

    Hepatocellular carcinoma (HCC) is the primary type of liver cancer, and both the age-adjusted incidence and mortality of HCC have steadily increased in recent years. Advanced HCC is associated with a very poor survival rate. Despite accumulating data regarding the risk factors for HCC, the mechanisms that contribute to HCC tumorigenesis remain poorly understood. Signaling through the fibroblast growth factor (FGF) family is involved in fibrosis and its progression to cirrhosis of the liver, which is a risk factor for the development of HCC. Furthermore, several alterations in FGF/FGF receptor (FGFR) signaling correlate with the outcomes of HCC patients, suggesting that signaling through this family of proteins contributes to the development or progression of HCC tumors. Currently, there are no established systemic treatments for patients with advanced HCC in whom sorafenib treatment has failed or who were unable to tolerate it. Recently, several multikinase inhibitors that target FGFRs have demonstrated some early evidence of antitumor activity in phase I/II trials. Therefore, this review discusses the molecular implications of FGFR-mediated signaling in HCC and summarizes the clinical evidence for novel FGFR-targeted therapies for HCC currently being studied in clinical trials.

  11. New Developments in Platelet Cyclic Nucleotide Signalling: Therapeutic Implications.

    PubMed

    Procter, Nathan E K; Hurst, Nicola L; Nooney, Vivek B; Imam, Hasan; De Caterina, Raffaele; Chirkov, Yuliy Y; Horowitz, John D

    2016-10-01

    Altered platelet physiology may contribute to the emergence of thrombosis in patients with many forms of cardiovascular disease. Excess platelet activation may reflect increased stimulation of pro-aggregatory pathways. There is, however, increasing evidence that excessive platelet response, due to impaired efficacy of anti-aggregatory autacoids such as nitric oxide (NO) and prostacyclin (PGI2), may be just as important. For example, diminished platelet response to NO has been documented in acute and chronic myocardial ischaemia, heart failure, aortic valve disease and in the presence of hyperglycaemia. This "NO resistance" has been shown to reflect both the scavenging of NO by reactive oxygen species and dysfunction of its intracellular "receptor", soluble guanylate cyclase. Importantly, these abnormalities of NO signalling are potentially reversible through judicious application of pharmacotherapy. The analogous condition of impaired PGI2/adenylate cyclase (AC) signalling has received comparatively less attention to date. We have shown that platelet response to prostaglandin E1 (PGE1) is frequently impaired in patients with symptomatic myocardial ischaemia. Because the effects of ADP receptor antagonists such as clopidogrel and ticagrelor at the level of the P2Y12 receptor are coupled with changes in activity of AC, impaired response to PGE1 might imply both increased thrombotic risk and a reduced efficacy of anti-aggregatory drugs. Accordingly, patient response to treatment with clopidogrel is determined not only by variability of clopidogrel bio-activation, but also extensively by the integrity of platelet AC signalling. We here review these recent developments and their emerging therapeutic implications for thrombotic disorders.

  12. Biased signaling at neural melanocortin receptors in regulation of energy homeostasis.

    PubMed

    Yang, Li-Kun; Tao, Ya-Xiong

    2017-10-01

    The global prevalence of obesity highlights the importance of understanding on regulation of energy homeostasis. The central melanocortin system is an important intersection connecting the neural pathways controlling satiety and energy expenditure to regulate energy homeostasis by sensing and integrating the signals of external stimuli. In this system, neural melanocortin receptors (MCRs), melanocortin-3 and -4 receptors (MC3R and MC4R), play crucial roles in the regulation of energy homeostasis. Recently, multiple intracellular signaling pathways and biased signaling at neural MCRs have been discovered, providing new insights into neural MCR signaling. This review attempts to summarize biased signaling including biased receptor mutants (both naturally occurring and lab-generated) and biased ligands at neural MCRs, and to provide a better understanding of obesity pathogenesis and new therapeutic implications for obesity treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. A tail of two signals: the C terminus of the A(2A)-adenosine receptor recruits alternative signaling pathways.

    PubMed

    Gsandtner, Ingrid; Freissmuth, Michael

    2006-08-01

    G protein-coupled receptors are endowed with carboxyl termini that vary greatly in length and sequence. In most instances, the distal portion of the C terminus is dispensable for G protein coupling. This is also true for the A(2A)-adenosine receptor, where the last 100 amino acids are of very modest relevance to G(s) coupling. The C terminus was originally viewed mainly as the docking site for regulatory proteins of the beta-arrestin family. These beta-arrestins bind to residues that have been phosphorylated by specialized kinases (G protein-coupled receptor kinases) and thereby initiate receptor desensitization and endocytosis. More recently, it has become clear that many additional "accessory" proteins bind to C termini of G protein-coupled receptors. The article by Sun et al. in the current issue of Molecular Pharmacology identifies translin-associated protein-X as yet another interaction partner of the A(2A) receptor; translin-associated protein allows the A(2A) receptor to impinge on the signaling mechanisms by which p53 regulates neuronal differentiation, but the underlying signaling pathways are uncharted territory. With a list of five known interaction partners, the C terminus of the A(2A) receptor becomes a crowded place. Hence, there must be rules that regulate the interaction. This allows the C terminus to act as coincidence detector and as signal integrator. Despite our ignorance about the precise mechanisms, the article has exciting implications: the gene encoding for translin-associated protein-X maps to a locus implicated in some forms of schizophrenia; A(2A) receptor agonists are candidate drugs for the treatment of schizophrenic symptoms. It is of obvious interest to explore a possible link.

  14. 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

  15. NPY signalling pathway in bone homeostasis: Y1 receptor as a potential drug target.

    PubMed

    Sousa, D M; Herzog, H; Lamghari, M

    2009-01-01

    Neuropeptide (NPY) is a neurotransmitter widely distributed in central and peripheral nervous system that has been implicated in several physiological processes through activation of five different Y receptors: Y1, Y2, Y4, Y5, and y6. NPY system has been extensively studied for the last decades due to its implications in a wide variety of physiological processes. For this purpose a diversity of sophisticated animal models and receptors agonists and antagonists has been developed to better understand its actions throughout body homeostasis. Consequently, NPY and its receptors have recently emerged as a potential regulator of bone homeostasis. This is supported by the demonstration of an increase of bone mass in mice lacking Y1 or Y2 receptor genes. Recent findings revealed Y1 receptor as a potential drug target candidate for prevention and treatment of bone loss. Indeed, it has been demonstrated that osteoblasts express Y1 receptor while no other Y receptor was detected in these cells, implicating Y1 receptor signalling in the local control of bone turnover. In this review, we have summarized the findings obtained from studies on NPY system in skeletogenesis focusing on Y1 receptor.

  16. Deficiency of polycystic kidney disease-1 gene (PKD1) expression increases A(3) adenosine receptors in human renal cells: implications for cAMP-dependent signalling and proliferation of PKD1-mutated cystic cells.

    PubMed

    Aguiari, Gianluca; Varani, Katia; Bogo, Marco; Mangolini, Alessandra; Vincenzi, Fabrizio; Durante, Chiara; Gessi, Stefania; Sacchetto, Valeria; Catizone, Luigi; Harris, Peter; Rizzuto, Rosario; Borea, Pier Andrea; Del Senno, Laura

    2009-06-01

    Cyst growth and expansion in autosomal dominant polycystic kidney disease (ADPKD) has been attributed to numerous factors, including ATP, cAMP and adenosine signalling. Although the role of ATP and cAMP has been widely investigated in PKD1-deficient cells, no information is currently available on adenosine-mediated signalling. Here we investigate for the first time the impact of abnormalities of polycystin-1 (PC1) on the expression and functional activity of adenosine receptors, members of the G-protein-coupled receptor superfamily. Pharmacological, molecular and biochemical findings show that a siRNA-dependent PC1-depletion in HEK293 cells and a PKD1-nonsense mutation in cyst-derived cell lines result in increased expression of the A(3) adenosine receptor via an NFkB-dependent mechanism. Interestingly, A(3) adenosine receptor levels result higher in ADPKD than in normal renal tissues. Furthermore, the stimulation of this receptor subtype with the selective agonist Cl-IB-MECA causes a reduction in both cytosolic cAMP and cell proliferation in both PC1-deficient HEK293 cells and cystic cells. This reduction is associated with increased expression of p21(waf) and reduced activation not only of ERK1/2, but also of S6 kinase, the main target of mTOR signalling. In the light of these findings, the ability of Cl-IB-MECA to reduce disease progression in ADPKD should be further investigated. Moreover, our results suggest that NFkB, which is markedly activated in PC1-deficient and cystic cells, plays an important role in modulating A(3)AR expression in cystic cells.

  17. Vascular cell signaling by membrane estrogen receptors.

    PubMed

    Kim, Kyung Hee; Moriarty, Katie; Bender, Jeffrey R

    2008-10-01

    The definition of estrogen's actions has expanded from transcriptional regulation to the rapid, membrane-initiated activation of numerous signal transduction cascades. Multiple biological effects of estrogen have been shown in numerous animals, cellular and molecular studies, which support the favorable effects of estrogen on vascular structure, function, and cell signaling. Work from several laboratories has shown that these effects are mediated by distinct forms of estrogen receptor (ER) alpha. This includes estrogen-stimulated rapid activation of endothelial nitric oxide synthase (eNOS), resulting in the elaboration of the athero-protective, angiogenesis-promoting product nitric oxide (NO). We have described the expression of ER46, an N-terminus truncated isoform of the ERalpha, in human endothelial cells (EC), and its critical role in membrane-initiated, rapid responses to 17beta-estradiol (E2). We have proposed an ER46-centered, eNOS activating molecular complex in human EC caveolar membranes, containing c-Src, phosphatidylinositol 3-kinase (PI3K), Akt and eNOS. Our previous studies support estrogen-induced rapid eNOS activation via a sequential c-Src/PI3K/Akt cascade in EC. In this review, we describe estrogen-induced, rapid, non-genomic actions in endothelium, driven by c-Src-ER46-caveolin-1 interactions, with consequent activation of eNOS. Amidst ongoing controversies in hormone replacement therapy, these molecular and cellular data, defining favorable estrogenic effects on the endothelium, provide a strong impetus to resolve these clinical questions.

  18. 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

    2014-10-03

    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.

  19. 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

  20. 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.

  1. 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

  2. [FGF/FGFR signalling: Implication in oncogenesis and perspectives].

    PubMed

    Flippot, Ronan; Kone, Moumini; Magné, Nicolas; Vignot, Stéphane

    2015-06-01

    Deregulation of FGF (fibroblast growth factor)/FGFR (fibroblast growth factor receptor) signalling leads to the promotion of several oncogenic mechanisms: proliferation, epithelial-mesenchymal transition, cytoskeleton modifications, migration and angiogenesis. Deregulation of this pathway is reported in various cancers at early stages, and can therefore be responsible for the emergence of the hallmarks of cancer. It is necessary to precise downstream pathways of FGFR signalling to understand its oncogenic potential. We will then describe its implications in different cancer types. Oncogenic mechanisms will be studied through the example of melanoma, in which deregulation of FGF/FGFR pathway is considered as a driver event and occurs in nearly 90% of cases. The FGF/FGFR signalling pathway is a putative therapeutic target. Numerous agents are in active development, operating through a selective or multi-targeted approach. Recent studies have shown rather disappointing results in non-selected patients, but promising results in patients with FGF/FGFR pathway alterations. A careful screening of patients is the key to a valuable evaluation of these new targeted molecular therapies.

  3. Strontium signaling: molecular mechanisms and therapeutic implications in osteoporosis.

    PubMed

    Saidak, Zuzana; Marie, Pierre J

    2012-11-01

    Osteoporosis is an important age-related bone disease characterized by increased bone turnover with insufficient bone formation relative to bone resorption. According to the current understanding of this disorder, anti-resorptive and anabolic drugs have been developed for therapeutic intervention. Another therapeutic approach consists of dissociating bone resorption and formation. Preclinical and clinical studies provided evidence that strontium (in the form of ranelate) induces beneficial effects on bone mass and resistance in animal models of bone loss and in osteoporotic patients. These effects are mediated in part by the pharmacological actions of strontium on bone metabolism, by reducing bone resorption and maintaining or increasing bone formation. Current pharmacological studies showed that strontium activates multiple signaling pathways in bone cells to achieve its pharmacological actions. Notably, activation of the calcium-sensing receptor by strontium in osteoclasts or osteoblasts leads to activation of phospholipase Cβ, inositol 1,4,5-triphosphate, release of intracellular Ca²⁺, and activation of MAPK ERK1/2 and Wnt/NFATc signaling. Strontium-mediated activation of these pathways results in the modulation of key molecules such as RANKL and OPG that control bone resorption, and to the regulation of genes promoting osteoblastic cell replication, differentiation and survival. This review focuses on the more recent knowledge of strontium signaling in bone cells and describes how the resulting pharmacological actions on bone metabolism have important therapeutic implications in the treatment of age-related bone loss and possibly other disorders.

  4. Pharmacology of Signaling Induced by Dopamine D1-Like Receptor Activation

    PubMed Central

    Undieh, Ashiwel S.

    2010-01-01

    Dopamine D1-like receptors consisting of D1 and D5 subtypes are intimately implicated in dopaminergic regulation of fundamental neurophysiologic processes such as mood, motivation, cognitive function, and motor activity. Upon stimulation, D1-like receptors initiate signal transduction cascades that are mediated through adenylyl cyclase or phosphoinositide metabolism, with subsequent enhancement of multiple downstream kinase cascades. The latter actions propagate and further amplify the receptor signals, thus predisposing D1-like receptors to multifaceted interactions with various other mediators and receptor systems. The adenylyl cyclase response to dopamine or selective D1-like receptor agonists is reliably associated with the D1 subtype, while emerging evidence indicates that the phosphoinositide responses in native brain tissues may be preferentially mediated through stimulation of the D5 receptor. Besides classic coupling of each receptor subtype to specific G proteins, additional biophysical models are advanced in attempts to account for differential subcellular distribution, heteromolecular oligomerization, and activity-dependent selectivity of the receptors. It is expected that significant advances in understanding of dopamine neurobiology will emerge from current and anticipated studies directed at uncovering the molecular mechanisms of D5 coupling to phosphoinositide signaling, the structural features that might enhance pharmacological selectivity for D5 versus D1 subtypes, the mechanism by which dopamine may modulate phosphoinositide synthesis, the contributions of the various responsive signal mediators to D1 or D5 interactions with D2-like receptors, and the spectrum of dopaminergic functions that may be attributed to each receptor subtype and signaling pathway. PMID:20547182

  5. Structural basis for cytokinin receptor signaling: an evolutionary approach.

    PubMed

    Steklov, Mikhail Yu; Lomin, Sergey N; Osolodkin, Dmitry I; Romanov, Georgy A

    2013-06-01

    Cytokinins are ubiquitous plant hormones; their signal is perceived by sensor histidine kinases-cytokinin receptors. This review focuses on recent advances on cytokinin receptor structure, in particular sensing module and adjacent domains which play an important role in hormone recognition, signal transduction and receptor subcellular localization. Principles of cytokinin binding site organization and point mutations affecting signaling are discussed. To date, more than 100 putative cytokinin receptor genes from different plant species were revealed due to the total genome sequencing. This allowed us to employ an evolutionary and bioinformatics approaches to clarify some new aspects of receptor structure and function. Non-transmembrane areas adjacent to the ligand-binding CHASE domain were characterized in detail and new conserved protein motifs were recovered. Putative mechanisms for cytokinin-triggered receptor activation were suggested.

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

    DOE PAGES

    Shakeel, Samina N.; Gao, Zhiyong; Amir, Madiha; ...

    2015-03-26

    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 analysesmore » 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. Lastly, we discuss implications of this model for ethylene signaling.« less

  7. 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

    2015-05-08

    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.

  8. Receptor tyrosine kinase signaling: a view from quantitative proteomics.

    PubMed

    Dengjel, Joern; Kratchmarova, Irina; Blagoev, Blagoy

    2009-10-01

    Growth factor receptor signaling via receptor tyrosine kinases (RTKs) is one of the basic cellular communication principals found in all metazoans. Extracellular signals are transferred via membrane spanning receptors into the cytoplasm, reversible tyrosine phosphorylation being the hallmark of all RTKs. In recent years proteomic approaches have yielded detailed descriptions of cellular signaling events. Quantitative proteomics is able to characterize the exact position and strength of post-translational modifications (PTMs) providing essential information for understanding the molecular basis of signal transduction. Numerous new post-translational modification sites have been identified by quantitative mass spectrometry-based proteomics. In addition, plentiful new players in signal transduction have been identified underlining the complexity and the modular architecture of most signaling networks. In this review, we outline the principles of signal transduction via RTKs and highlight some of the new insights obtained from proteomic approaches such as protein microarrays and quantitative mass spectrometry.

  9. G protein βγ subunits: Central mediators of G protein-coupled receptor signaling

    PubMed Central

    Smrcka, A. V.

    2008-01-01

    G protein βγ subunits are central participants in G protein-coupled receptor signaling pathways. They interact with receptors, G protein α subunits and downstream targets to coordinate multiple, different GPCR functions. Much is known about the biology of Gβγ subunits but mysteries remain. Here, we will review what is known about general aspects of structure and function of Gβγ as well as discuss emerging mechanisms for regulation of Gβγ signaling. Recent data suggest that Gβγ is a potential therapeutic drug target. Thus, a thorough understanding of the molecular and physiological functions of Gβγ has significant implications. PMID:18488142

  10. Platelet-activating factor: receptors and signal transduction.

    PubMed

    Chao, W; Olson, M S

    1993-06-15

    During the past two decades, studies describing the chemistry and biology of PAF have been extensive. This potent phosphoacylglycerol exhibits a wide variety of physiological and pathophysiological effects in various cells and tissues. PAF acts, through specific receptors and a variety of signal transduction systems, to elicit diverse biochemical responses. Several important future directions can be enumerated for the characterization of PAF receptors and their attendant signalling mechanisms. The recent cloning and sequence analysis of the gene for the PAF receptor will allow a number of important experimental approaches for characterizing the structure and analysing the function of the various domains of the receptor. Using molecular genetic and immunological technologies, questions relating to whether there is receptor heterogeneity, the precise mechanism(s) for the regulation of the PAF receptor, and the molecular details of the signalling mechanisms in which the PAF receptor is involved can be explored. Another area of major significance is the examination of the relationship between the signalling response(s) evoked by PAF binding to its receptor and signalling mechanisms activated by a myriad of other mediators, cytokines and growth factors. A very exciting recent development in which PAF receptors undoubtedly play a role is in the regulation of the function of various cellular adhesion molecules. Finally, there remain many incompletely characterized physiological and pathophysiological situations in which PAF and its receptor play a crucial signalling role. Our laboratory has been active in the elucidation of several tissue responses in which PAF exhibits major autocoid signalling responses, e.g. hepatic injury and inflammation, acute and chronic pancreatitis, and cerebral stimulation and/or trauma. As new experimental strategies are developed for characterizing the fine structure of the molecular mechanisms involved in tissue injury and inflammation, the

  11. 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.

  12. Brain CB₂ Receptors: Implications for Neuropsychiatric Disorders.

    PubMed

    Roche, Michelle; Finn, David P

    2010-08-10

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

  13. 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

  14. Toll-like receptor signalling through macromolecular protein complexes.

    PubMed

    Bryant, Clare E; Symmons, Martyn; Gay, Nicholas J

    2015-02-01

    The molecular mechanisms by which pattern recognition receptors (PRRs) signal are increasingly well understood. Toll-like receptor 4 (TLR4) signals through two separate pairs of adaptor proteins Mal/MyD88 and Tram/Trif. Structural studies have revealed a common theme for PRR signalling in that their signalling proteins form large macromolecular complexes which are thought to form the active signalling complex. The first of these to be characterised was the MyD88 signalling complex Myddosome. Many questions remain unanswered however. In particular it is unclear whether these signalling complexes form within the living cell, how many of each signalling protein is within the intracellular Myddosome and whether the stoichiometry can vary in a ligand-dependent manner. In this review we will discuss what is known about the macromolecular complexes thought to be important for TLR4 signalling. Copyright © 2014 Elsevier Ltd. All rights reserved.

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

    PubMed

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

    2001-11-01

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

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

    PubMed

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

    2005-07-01

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

  17. Histamine H3 Receptor Regulates Sensorimotor Gating and Dopaminergic Signaling in the Striatum.

    PubMed

    Kononoff Vanhanen, Jenni; Nuutinen, Saara; Tuominen, Mervi; Panula, Pertti

    2016-05-01

    The brain histamine system has been implicated in regulation of sensorimotor gating deficits and in Gilles de la Tourette syndrome. Histamine also regulates alcohol reward and consumption via H3 receptor (H3R), possibly through an interaction with the brain dopaminergic system. Here, we identified the histaminergic mechanism of sensorimotor gating and the role of histamine H3R in the regulation of dopaminergic signaling. We found that H3R knockout mice displayed impaired prepulse inhibition (PPI), indicating deficiency in sensorimotor gating. Histamine H1 receptor knockout and histidine decarboxylase knockout mice had similar PPI as their controls. Dopaminergic drugs increased PPI of H3R knockout mice to the same level as in control mice, suggesting that changes in dopamine receptors might underlie deficient PPI response when H3R is lacking. Striatal dopamine D1 receptor mRNA level was lower, and D1 and D2 receptor-mediated activation of extracellular signal-regulated kinase 1/2 was absent in the striatum of H3R knockout mice, suggesting that H3R is essential for the dopamine receptor-mediated signaling. In conclusion, these findings demonstrate that H3R is an important regulator of sensorimotor gating, and the lack of H3R significantly modifies striatal dopaminergic signaling. These data support the usefulness of H3R ligands in neuropsychiatric disorders with preattentional deficits and disturbances in dopaminergic signaling.

  18. CD23 can negatively regulate B-cell receptor signaling

    PubMed Central

    Liu, Chaohong; Richard, Katharina; Wiggins, Melvin; Zhu, Xiaoping; Conrad, Daniel H.; Song, Wenxia

    2016-01-01

    CD23 has been implicated as a negative regulator of IgE and IgG antibody responses. However, whether CD23 has any role in B-cell activation remains unclear. We examined the expression of CD23 in different subsets of peripheral B cells and the impact of CD23 expression on the early events of B-cell receptor (BCR) activation using CD23 knockout (KO) mice. We found that in addition to marginal zone B cells, mature follicular B cells significantly down regulate the surface expression level of CD23 after undergoing isotype switch and memory B-cell differentiation. Upon stimulation with membrane-associated antigen, CD23 KO causes significant increases in the area of B cells contacting the antigen-presenting membrane and the magnitude of BCR clustering. This enhanced cell spreading and BCR clustering is concurrent with increases in the levels of phosphorylation of tyrosine and Btk, as well as the levels of F-actin and phosphorylated Wiskott Aldrich syndrome protein, an actin nucleation promoting factor, in the contract zone of CD23 KO B cells. These results reveal a role of CD23 in the negative regulation of BCR signaling in the absence of IgE immune complex and suggest that CD23 down-regulates BCR signaling by influencing actin-mediated BCR clustering and B-cell morphological changes. PMID:27181049

  19. Central IL-1 receptor signaling regulates bone growth and mass

    PubMed Central

    Bajayo, Alon; Goshen, Inbal; Feldman, Sharon; Csernus, Valer; Iverfeldt, Kerstin; Shohami, Esther; Yirmiya, Raz; Bab, Itai

    2005-01-01

    The proinflammatory cytokine IL-1, acting via the hypothalamic IL-1 receptor type 1 (IL-1RI), activates pathways known to suppress bone formation such as the hypothalamo pituitary-adrenocortical axis and the sympathetic nervous system. In addition, peripheral IL-1 has been implicated as a mediator of the bone loss induced by sex hormone depletion and TNF. Here, we report an unexpected low bone mass (LBM) phenotype, including impairment of bone growth, in IL-1RI-deficient mice (IL-1rKO mice). Targeted overexpression of human IL-1 receptor antagonist to the central nervous system using the murine glial fibrillary acidic protein promoter (IL-1raTG mice) resulted in a similar phenotype, implying that central IL-1RI silencing is the causative process in the LBM induction. Analysis of bone remodeling indicates that the process leading to the LBM in both IL-1rKO and IL-1raTG is characterized mainly by doubling the osteoclast number. Either genetic modification does not decrease testosterone or increase corticosterone serum levels, suggesting that systems other than the gonads and hypothalamo pituitary-adrenocortical axis mediate the central IL-1RI effect on bone. We further demonstrate that WT mice express mouse IL-1ra in bone but not in the hypothalamus. Because low levels of IL-1 are present in both tissues, it is suggested that skeletal IL-1 activity is normally suppressed, whereas central IL-1 produces a constant physiologic stimulation of IL-1RI signaling. Although the pathway connecting the central IL-1RI signaling to bone remodeling remains unknown, the outburst of osteoclastogenesis in its absence suggests that normally it controls bone growth and mass by tonically restraining bone resorption. PMID:16126903

  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. Neutrophil cell surface receptors and their intracellular signal transduction pathways☆

    PubMed Central

    Futosi, Krisztina; Fodor, Szabina; Mócsai, Attila

    2013-01-01

    Neutrophils play a critical role in the host defense against bacterial and fungal infections, but their inappropriate activation also contributes to tissue damage during autoimmune and inflammatory diseases. Neutrophils express a large number of cell surface receptors for the recognition of pathogen invasion and the inflammatory environment. Those include G-protein-coupled chemokine and chemoattractant receptors, Fc-receptors, adhesion receptors such as selectins/selectin ligands and integrins, various cytokine receptors, as well as innate immune receptors such as Toll-like receptors and C-type lectins. The various cell surface receptors trigger very diverse signal transduction pathways including activation of heterotrimeric and monomeric G-proteins, receptor-induced and store-operated Ca2 + signals, protein and lipid kinases, adapter proteins and cytoskeletal rearrangement. Here we provide an overview of the receptors involved in neutrophil activation and the intracellular signal transduction processes they trigger. This knowledge is crucial for understanding how neutrophils participate in antimicrobial host defense and inflammatory tissue damage and may also point to possible future targets of the pharmacological therapy of neutrophil-mediated autoimmune or inflammatory diseases. PMID:23994464

  2. Purinergic signaling in inflammatory cells: P2 receptor expression, functional effects, and modulation of inflammatory responses.

    PubMed

    Jacob, Fenila; Pérez Novo, Claudina; Bachert, Claus; Van Crombruggen, Koen

    2013-09-01

    Extracellular ATP and related nucleotides promote a wide range of pathophysiological responses via activation of cell surface purinergic P2 receptors. Almost every cell type expresses P2 receptors and/or exhibit regulated release of ATP. In this review, we focus on the purinergic receptor distribution in inflammatory cells and their implication in diverse immune responses by providing an overview of the current knowledge in the literature related to purinergic signaling in neutrophils, macrophages, dendritic cells, lymphocytes, eosinophils, and mast cells. The pathophysiological role of purinergic signaling in these cells include among others calcium mobilization, actin polymerization, chemotaxis, release of mediators, cell maturation, cytotoxicity, and cell death. We finally discuss the therapeutic potential of P2 receptor subtype selective drugs in inflammatory conditions.

  3. Legume LysM receptors mediate symbiotic and pathogenic signalling.

    PubMed

    Kelly, Simon; Radutoiu, Simona; Stougaard, Jens

    2017-10-01

    Legume-rhizobia symbiosis is coordinated through the production and perception of signal molecules by both partners with legume LysM receptor kinases performing a central role in this process. Receptor complex formation and signalling outputs derived from these are regulated through ligand binding and further modulated by a diverse variety of interactors. The challenge now is to understand the molecular mechanisms of these reported interactors. Recently attributed roles of LysM receptors in the perception of rhizobial exopolysaccharide, distinguishing between pathogens and symbionts, and assembly of root and rhizosphere communities expand on the importance of these receptors. These studies also highlight challenges, such as identification of cognate ligands, formation of responsive receptor complexes and separation of downstream signal transduction pathways. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. 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.

  5. Progesterone Receptor Signaling in Uterine Myometrial Physiology and Preterm Birth

    PubMed Central

    Wu, San-Pin; DeMayo, Francesco J.

    2017-01-01

    Myometrium holds the structural integrity for the uterus and generates force for parturition with its primary component, the smooth muscle cells. The progesterone receptor mediates progesterone dependent signaling and connects to a network of pathways for regulation of contractility and inflammatory responses in myometrium. Dysfunctional progesterone signaling has been linked to pregnancy complications including preterm birth. In the present review, we summarize recent findings on modifiers and effectors of the progesterone receptor signaling. Discussions include novel conceptual discoveries and new development in legacy pathways such as the signal transducers NF-κB, ZEB, micro RNA and the unfolded protein response pathways. We also discuss the impact of progesterone receptor isoform composition and ligand accessibility in modification of the progesterone receptor genomic actions. PMID:28527571

  6. Orchestration of membrane receptor signaling by membrane lipids.

    PubMed

    Arish, Mohd; Husein, Atahar; Kashif, Mohammad; Sandhu, Padmani; Hasnain, Seyed E; Akhter, Yusuf; Rub, Abdur

    2015-06-01

    Receptors on cell membrane bind to their respective ligands and transduce intracellular signals resulting in variety of effector functions. Membrane lipid composition determines the receptor signaling behavior, as the receptors assume different conformation to suit the biochemical milieu in its immediate vicinity in the membrane. Accordingly, these accommodate different signaling intermediates that dictate the course of intracellular signaling and the resulting effectors functions. In this review we provide an overview of how membrane lipids modulate membrane-properties, membrane-receptor functions and their significance in the host-pathogen interaction. Copyright © 2015 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

  7. Cannabinoid CB1 and CB2 Receptor Signaling and Bias

    PubMed Central

    Ibsen, Mikkel Søes; Connor, Mark; Glass, Michelle

    2017-01-01

    Abstract An agonist that acts through a single receptor can activate numerous signaling pathways. Recent studies have suggested that different ligands can differentially activate these pathways by stabilizing a limited range of receptor conformations, which in turn preferentially drive different downstream signaling cascades. This concept, termed “biased signaling” represents an exciting therapeutic opportunity to target specific pathways that elicit only desired effects, while avoiding undesired effects mediated by different signaling cascades. The cannabinoid receptors CB1 and CB2 each activate multiple pathways, and evidence is emerging for bias within these pathways. This review will summarize the current evidence for biased signaling through cannabinoid receptor subtypes CB1 and CB2. PMID:28861504

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

    PubMed Central

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

    1989-01-01

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

  9. 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

    2005-12-08

    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.

  10. 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

  11. 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.

  12. Ubiquitination and de-ubiquitination: role in regulation of signaling by Toll-like receptors.

    PubMed

    Lowe, Emily L; Doherty, Terence M; Karahashi, Hisae; Arditi, Moshe

    2006-01-01

    Signaling by Toll-like receptors (TLRs) has attracted accelerating attention over the past decade because of the central role of TLR signaling in both innate and adaptive immunity. In addition, TLR signaling is now increasingly implicated in a remarkably wide range of diseases that are either caused, or accompanied, by dysregulated inflammation. Much has been learned about the basic signaling framework and participants, as well as how signaling is turned off and fine-tuned. Here, we summarize key aspects of TLR signaling, focusing on interaction with the anti-inflammatory TGF-beta signaling network. We propose that ubiquitination and de-ubiquitination of TLR pathway components may be a mechanism by which predominantly anti-inflammatory input is integrated into the host response to fine-tune inflammation in accordance with the needs of host defenses.

  13. Receptor kinase signaling pathways in plant-microbe interactions.

    PubMed

    Antolín-Llovera, Meritxell; Ried, Martina K; Binder, Andreas; Parniske, Martin

    2012-01-01

    Plant receptor-like kinases (RLKs) function in diverse signaling pathways, including the responses to microbial signals in symbiosis and defense. This versatility is achieved with a common overall structure: an extracytoplasmic domain (ectodomain) and an intracellular protein kinase domain involved in downstream signal transduction. Various surfaces of the leucine-rich repeat (LRR) ectodomain superstructure are utilized for interaction with the cognate ligand in both plant and animal receptors. RLKs with lysin-motif (LysM) ectodomains confer recognitional specificity toward N-acetylglucosamine-containing signaling molecules, such as chitin, peptidoglycan (PGN), and rhizobial nodulation factor (NF), that induce immune or symbiotic responses. Signaling downstream of RLKs does not follow a single pattern; instead, the detailed analysis of brassinosteroid (BR) signaling, innate immunity, and symbiosis revealed at least three largely nonoverlapping pathways. In this review, we focus on RLKs involved in plant-microbe interactions and contrast the signaling pathways leading to symbiosis and defense.

  14. Receptor tyrosine kinases: mechanisms of activation and signaling

    PubMed Central

    Hubbard, Stevan R.; Miller, W. Todd

    2008-01-01

    Receptor tyrosine kinases (RTKs) are essential components of signal transduction pathways that mediate cell-to-cell communication. These single-pass transmembrane receptors, which bind polypeptide ligands — mainly growth factors — play key roles in processes such as cellular growth, differentiation, metabolism and motility. Recent progress has been achieved towards an understanding of the precise (and varied) mechanisms by which RTKs are activated by ligand binding and by which signals are propagated from the activated receptors to downstream targets in the cell. PMID:17306972

  15. Eph receptors and ephrins in cancer: bidirectional signaling and beyond

    PubMed Central

    Pasquale, Elena B.

    2010-01-01

    The Eph receptor tyrosine kinases and their ephrin ligands have intriguing expression patterns in cancer cells and tumor blood vessels, which suggest important roles for their bidirectional signals in multiple aspects of cancer development and progression. Eph gene mutations likely also contribute to cancer pathogenesis. Eph receptors and ephrins have been shown to affect the growth and migration/invasion of cancer cells in culture as well as tumor growth, invasiveness, angiogenesis, and metastasis in vivo. However, Eph signaling activities in cancer appear to be complex, and are characterized by puzzling dichotomies. The Eph receptors nevertheless represent promising new therapeutic targets in cancer. PMID:20179713

  16. Receptor-mediated signalling in plants: molecular patterns and programmes

    PubMed Central

    Tör, Mahmut; Lotze, Michael T.; Holton, Nicholas

    2009-01-01

    A highly evolved surveillance system in plants is able to detect a broad range of signals originating from pathogens, damaged tissues, or altered developmental processes, initiating sophisticated molecular mechanisms that result in defence, wound healing, and development. Microbe-associated molecular pattern molecules (MAMPs), damage-associated molecular pattern molecules (DAMPs), virulence factors, secreted proteins, and processed peptides can be recognized directly or indirectly by this surveillance system. Nucleotide binding-leucine rich repeat proteins (NB-LRR) are intracellular receptors and have been targeted by breeders for decades to elicit resistance to crop pathogens in the field. Receptor-like kinases (RLKs) or receptor like proteins (RLPs) are membrane bound signalling molecules with an extracellular receptor domain. They provide an early warning system for the presence of potential pathogens and activate protective immune signalling in plants. In addition, they act as a signal amplifier in the case of tissue damage, establishing symbiotic relationships and effecting developmental processes. The identification of several important ligands for the RLK-type receptors provided an opportunity to understand how plants differentiate, how they distinguish beneficial and detrimental stimuli, and how they co-ordinate the role of various types of receptors under varying environmental conditions. The diverse roles of extra-and intracellular plant receptors are examined here and the recent findings on how they promote defence and development is reviewed. PMID:19628572

  17. Axon Growth and Guidance: Receptor Regulation and Signal Transduction

    PubMed Central

    O’Donnell, Michael; Chance, Rebecca K.; Bashaw, Greg J.

    2016-01-01

    The development of precise connectivity patterns during the establishment of the nervous system depends on the regulated action of diverse, conserved families of guidance cues and their neuronal receptors. Determining how these signaling pathways function to regulate axon growth and guidance is fundamentally important to understanding wiring specificity in the nervous system and will undoubtedly shed light on many neural developmental disorders. Considerable progress has been made in defining the mechanisms that regulate the correct spatial and temporal distribution of guidance receptors and how these receptors in turn signal to the growth cone cytoskeleton to control steering decisions. This review focuses on recent advances in our understanding of the mechanisms mediating growth cone guidance with a particular emphasis on the control of guidance receptor regulation and signaling. PMID:19400716

  18. Axon growth and guidance: receptor regulation and signal transduction.

    PubMed

    O'Donnell, Michael; Chance, Rebecca K; Bashaw, Greg J

    2009-01-01

    The development of precise connectivity patterns during the establishment of the nervous system depends on the regulated action of diverse, conserved families of guidance cues and their neuronal receptors. Determining how these signaling pathways function to regulate axon growth and guidance is fundamentally important to understanding wiring specificity in the nervous system and will undoubtedly shed light on many neural developmental disorders. Considerable progress has been made in defining the mechanisms that regulate the correct spatial and temporal distribution of guidance receptors and how these receptors in turn signal to the growth cone cytoskeleton to control steering decisions. This review focuses on recent advances in our understanding of the mechanisms mediating growth cone guidance with a particular emphasis on the control of guidance receptor regulation and signaling.

  19. 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

  20. 5-HT1A receptor-mediated phosphorylation of extracellular signal-regulated kinases (ERK1/2) is modulated by regulator of G protein signaling protein 19.

    PubMed

    Wang, Qin; Terauchi, Akiko; Yee, Christopher H; Umemori, Hisashi; Traynor, John R

    2014-09-01

    The 5-HT1A receptor is a G protein coupled receptor (GPCR) that activates G proteins of the Gαi/o family. 5-HT1A receptors expressed in the raphe, hippocampus and prefrontal cortex are implicated in the control of mood and are targets for anti-depressant drugs. Regulators of G protein signaling (RGS) proteins are members of a large family that play important roles in signal transduction downstream of G protein coupled receptors (GPCRs). The main role of RGS proteins is to act as GTPase accelerating proteins (GAPs) to dampen or negatively regulate GPCR-mediated signaling. We have shown that a mouse expressing Gαi2 that is insensitive to all RGS protein GAP activity has an anti-depressant-like phenotype due to increased signaling of postsynaptic 5-HT1A receptors, thus implicating the 5-HT1A receptor-Gαi2 complex as an important target. Here we confirm that RGS proteins act as GAPs to regulate signaling to adenylate cyclase and the mitogen-activated protein kinase (MAPK) pathway downstream of the 5-HT1A receptor, using RGS-insensitive Gαi2 protein expressed in C6 cells. We go on to use short hairpin RNA (shRNA) to show that RGS19 is responsible for the GAP activity in C6 cells and also that RGS19 acts as a GAP for 5-HT1A receptor signaling in human neuroblastoma SH-SY5Y cells and primary hippocampal neurons. In addition, in both cell types the synergy between 5-HT1A receptor and the fibroblast growth factor receptor 1 in stimulating the MAPK pathway is enhanced following shRNA reduction of RGS19 expression. Thus RGS19 may be a viable new target for anti-depressant medications.

  1. Recruiting extrasynaptic NMDA receptors augments synaptic signaling.

    PubMed

    Harris, Alexander Z; Pettit, Diana L

    2008-02-01

    N-Methyl-d-aspartate receptor (NMDAR) activation may promote cell survival or initiate cell death, with the outcome dependent on whether synaptic or extrasynaptic receptors are activated. Similarly, this differential activation has been proposed to govern the direction of plasticity. However, the physiological parameters necessary to activate extrasynaptic NMDARs in brain slices remain unknown. Using the irreversible use-dependent NMDAR antagonist MK-801 to isolate extrasynaptic NMDARs, we have tested the ability of short-stimulation trains from 5 to 400 Hz to activate these receptors on CA1 hippocampal slice pyramidal neurons. Frequencies as low as 25 Hz engage extrasynaptic NMDARs, with maximal activation at frequencies between 100 and 200 Hz. Since similar bursts of synaptic input occur during exploratory behavior in rats, our results demonstrate that "extrasynaptic" NMDARs regularly participate in synaptic transmission. Further, 175-Hz-stimulation trains activate all available synaptic and extrasynaptic dendritic NMDARs, suggesting these NMDARs act as synaptic receptors as needed, transiently increasing synaptic strength. Thus extrasynaptic NMDARs play a vital role in synaptic physiology, calling into question their status as "extrasynaptic."

  2. Bioinformatic approaches to interrogating vitamin D receptor signaling.

    PubMed

    Campbell, Moray J

    2017-09-15

    Bioinformatics applies unbiased approaches to develop statistically-robust insight into health and disease. At the global, or "20,000 foot" view bioinformatic analyses of vitamin D receptor (NR1I1/VDR) signaling can measure where the VDR gene or protein exerts a genome-wide significant impact on biology; VDR is significantly implicated in bone biology and immune systems, but not in cancer. With a more VDR-centric, or "2000 foot" view, bioinformatic approaches can interrogate events downstream of VDR activity. Integrative approaches can combine VDR ChIP-Seq in cell systems where significant volumes of publically available data are available. For example, VDR ChIP-Seq studies can be combined with genome-wide association studies to reveal significant associations to immune phenotypes. Similarly, VDR ChIP-Seq can be combined with data from Cancer Genome Atlas (TCGA) to infer the impact of VDR target genes in cancer progression. Therefore, bioinformatic approaches can reveal what aspects of VDR downstream networks are significantly related to disease or phenotype. Copyright © 2017 The Author. Published by Elsevier B.V. All rights reserved.

  3. Revolution in GPCR signalling: opioid receptor heteromers as novel therapeutic targets: IUPHAR review 10.

    PubMed

    Fujita, Wakako; Gomes, Ivone; Devi, Lakshmi A

    2014-09-01

    GPCRs can interact with each other to form homomers or heteromers. Homomers involve interactions with the same receptor type while heteromers involve interactions between two different GPCRs. These receptor-receptor interactions modulate not only the binding but also the signalling and trafficking properties of individual receptors. Opioid receptor heteromerization has been extensively investigated with the objective of identifying novel therapeutic targets that are as potent as morphine but without the side effects associated with chronic morphine use. In this context, studies have described heteromerization between the different types of opioid receptors and between opioid receptors and a wide range of GPCRs including adrenoceptors, cannabinoid, 5-HT, metabotropic glutamate and sensory neuron-specific receptors. Recent advances in the field involving the generation of heteromer-specific reagents (antibodies or ligands) or of membrane-permeable peptides that disrupt the heteromer interaction are helping to elucidate the physiological role of opioid receptor heteromers and the contribution of the partner receptor to the side effects associated with opioid use. For example, studies using membrane-permeable peptides targeting the heteromer interface have implicated μ and δ receptor heteromers in the development of tolerance to morphine, and heteromers of μ and gastrin-releasing peptide receptors in morphine-induced itch. In addition, a number of ligands that selectively target opioid receptor heteromers exhibit potent antinociception with a decrease in the side effects commonly associated with morphine use. In this review, we summarize the latest findings regarding the biological and functional characteristics of opioid receptor heteromers both in vitro and in vivo.

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

    PubMed Central

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

    2013-01-01

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

  5. Novel Insights on Thyroid-Stimulating Hormone Receptor Signal Transduction

    PubMed Central

    Neumann, Susanne; Grüters, Annette; Krude, Heiko

    2013-01-01

    The TSH receptor (TSHR) is a member of the glycoprotein hormone receptors, a subfamily of family A G protein-coupled receptors. The TSHR is of great importance for the growth and function of the thyroid gland. The TSHR and its endogenous ligand TSH are pivotal proteins with respect to a variety of physiological functions and malfunctions. The molecular events of TSHR regulation can be summarized as a process of signal transduction, including signal reception, conversion, and amplification. The steps during signal transduction from the extra- to the intracellular sites of the cell are not yet comprehensively understood. However, essential new insights have been achieved in recent years on the interrelated mechanisms at the extracellular region, the transmembrane domain, and intracellular components. This review contains a critical summary of available knowledge of the molecular mechanisms of signal transduction at the TSHR, for example, the key amino acids involved in hormone binding or in the structural conformational changes that lead to G protein activation or signaling regulation. Aspects of TSHR oligomerization, signaling promiscuity, signaling selectivity, phenotypes of genetic variations, and potential extrathyroidal receptor activity are also considered, because these are relevant to an understanding of the overall function of the TSHR, including physiological, pathophysiological, and pharmacological perspectives. Directions for future research are discussed. PMID:23645907

  6. β2-adrenergic receptor control of endosomal PTH receptor signaling via Gβγ

    PubMed Central

    Jean-Alphonse, Frédéric G; Wehbi, Vanessa L; Chen, Jingming; Noda, Masaki; Taboas, Juan M; Xiao, Kunhong; Vilardaga, Jean-Pierre

    2017-01-01

    Cells express several G-protein-coupled receptors (GPCRs) at their surfaces, transmitting simultaneous extracellular hormonal and chemical signals into cells. A comprehensive understanding of mechanisms underlying the integrated signaling response induced by distinct GPCRs is thus required. Here we found that the β2-adrenergic receptor, which induces a short cAMP response, prolongs nuclear cAMP and protein kinase A (PKA) activation by promoting endosomal cAMP production in parathyroid hormone (PTH) receptor signaling through the stimulatory action of G protein Gβγ subunits on adenylate cyclase type 2. PMID:28024151

  7. Gd compounds signaling through Toll-like receptors 4 and 7 in normal human macrophages: establishment of a proinflammatory phenotype and implications for the pathogenesis of Nephrogenic Systemic Fibrosis

    PubMed Central

    Wermuth, Peter J.; Jimenez, Sergio A.

    2012-01-01

    Nephrogenic Systemic Fibrosis (NSF) is a progressive disorder occurring in some renal insufficiency patients exposed to Gd based contrast agents (GdBCA). Previous studies demonstrated that the GdBCA Omniscan® upregulated several innate immunity pathways in normal differentiated human macrophages, induced rapid nuclear localization of the transcription factor NFκB, and increased the expression and production of numerous profibrotic/proinflammatory cytokines, chemokines and growth factors. To further examine GdBCA stimulation of the innate immune system, cultured human embryonic kidney 293 (HEK293) cells expressing one of seven different human TLRs or one of two human Nucleotide Oligomerization Domain (NOD)-like receptors (NLRs) were exposed in vitro for 24 h to various GdBCA. The signaling activity of each compound was evaluated by its ability to activate an NFκB-inducible reporter gene. Omniscan® and gadodiamide induced strong TLR 4 and 7 mediated reporter gene activation. The other Gd compounds examined failed to induce reporter gene activation. TLR pathway inhibition using chloroquine or an inhibitor of IL-1 receptor associated kinase 1 (IRAK1) and IRAK4 in normal differentiated human macrophages abrogated Omniscan®-induced gene expression. Omniscan® and gadodiamide signaling via TLR 4 and 7 resulted in increased production and expression of numerous proinflammatory/profibrotic cytokines, chemokines, and growth factors including CXCL10, CCL2, CCL8, CXCL12, IL-4, IL-6, TGF-β and VEGF. These observations suggest that TLR activation by environmental stimuli may participate in the pathogenesis of NSF and of other fibrotic disorders including systemic sclerosis. PMID:22649203

  8. AdipoRon, an adiponectin receptor agonist, attenuates PDGF-induced VSMC proliferation through inhibition of mTOR signaling independent of AMPK: Implications toward suppression of neointimal hyperplasia.

    PubMed

    Fairaq, Arwa; Shawky, Noha M; Osman, Islam; Pichavaram, Prahalathan; Segar, Lakshman

    2017-02-22

    Hypoadiponectinemia is associated with an increased risk of coronary artery disease. Although adiponectin replenishment mitigates neointimal hyperplasia and atherosclerosis in mouse models, adiponectin therapy has been hampered in a clinical setting due to its large molecular size. Recent studies demonstrate that AdipoRon (a small-molecule adiponectin receptor agonist) improves glycemic control in type 2 diabetic mice and attenuates postischemic cardiac injury in adiponectin-deficient mice, in part, through activation of AMP-activated protein kinase (AMPK). To date, it remains unknown as to whether AdipoRon regulates vascular smooth muscle cell (VSMC) proliferation, which plays a major role in neointima formation. In the present study, oral administration of AdipoRon (50mg/kg) in C57BL/6J mice significantly diminished arterial injury-induced neointima formation by ∼57%. Under in vitro conditions, AdipoRon treatment led to significant inhibition of platelet-derived growth factor (PDGF)-induced VSMC proliferation, DNA synthesis, and cyclin D1 expression. While AdipoRon induced a rapid and sustained activation of AMPK, it also diminished basal and PDGF-induced phosphorylation of mTOR and its downstream targets, including p70S6K/S6 and 4E-BP1. However, siRNA-mediated AMPK downregulation showed persistent inhibition of p70S6K/S6 and 4E-BP1 phosphorylation, indicating AMPK-independent effects for AdipoRon inhibition of mTOR signaling. In addition, AdipoRon treatment resulted in a sustained and transient decrease in PDGF-induced phosphorylation of Akt and ERK, respectively. Furthermore, PDGF receptor-β tyrosine phosphorylation, which controls the phosphorylation state of Akt and ERK, was diminished upon AdipoRon treatment. Together, the present findings suggest that orally-administered AdipoRon has the potential to limit restenosis after angioplasty by targeting mTOR signaling independent of AMPK activation.

  9. 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

  10. The Janus Face of Death Receptor Signaling during Tumor Immunoediting

    PubMed Central

    O’ Reilly, Eimear; Tirincsi, Andrea; Logue, Susan E.; Szegezdi, Eva

    2016-01-01

    Cancer immune surveillance is essential for the inhibition of carcinogenesis. Malignantly transformed cells can be recognized by both the innate and adaptive immune systems through different mechanisms. Immune effector cells induce extrinsic cell death in the identified tumor cells by expressing death ligand cytokines of the tumor necrosis factor ligand family. However, some tumor cells can escape immune elimination and progress. Acquisition of resistance to the death ligand-induced apoptotic pathway can be obtained through cleavage of effector cell expressed death ligands into a poorly active form, mutations or silencing of the death receptors, or overexpression of decoy receptors and pro-survival proteins. Although the immune system is highly effective in the elimination of malignantly transformed cells, abnormal/dysfunctional death ligand signaling curbs its cytotoxicity. Moreover, DRs can also transmit pro-survival and pro-migratory signals. Consequently, dysfunctional death receptor-mediated apoptosis/necroptosis signaling does not only give a passive resistance against cell death but actively drives tumor cell motility, invasion, and contributes to consequent metastasis. This dual contribution of the death receptor signaling in both the early, elimination phase, and then in the late, escape phase of the tumor immunoediting process is discussed in this review. Death receptor agonists still hold potential for cancer therapy since they can execute the tumor-eliminating immune effector function even in the absence of activation of the immune system against the tumor. The opportunities and challenges of developing death receptor agonists into effective cancer therapeutics are also discussed. PMID:27843441

  11. Signaling within Allosteric Machines: Signal Transmission Pathways Inside G Protein-Coupled Receptors.

    PubMed

    Bartuzi, Damian; Kaczor, Agnieszka A; Matosiuk, Dariusz

    2017-07-15

    In recent years, our understanding of function of G protein-coupled receptors (GPCRs) has changed from a picture of simple signal relays, transmitting only a particular signal to a particular G protein heterotrimer, to versatile machines, capable of various responses to different stimuli and being modulated by various factors. Some recent reports provide not only the data on ligands/modulators and resultant signals induced by them, but also deeper insights into exact pathways of signal migration and mechanisms of signal transmission through receptor structure. Combination of these computational and experimental data sheds more light on underlying mechanisms of signal transmission and signaling bias in GPCRs. In this review we focus on available clues on allosteric pathways responsible for complex signal processing within GPCRs structures, with particular emphasis on linking compatible in silico- and in vitro-derived data on the most probable allosteric connections.

  12. Systems Pharmacology of the NGF Signaling Through p75 and TrkA Receptors

    PubMed Central

    Toni, T; Dua, P; van der Graaf, P H

    2014-01-01

    The nerve growth factor (NGF) pathway has been shown to play a key role in pain treatment. Recently, a systems pharmacology model has been proposed that can aid in the identification and validation of drug targets in the NGF pathway. However, this model did not include the role of the p75 receptor, which modulates the signaling of NGF through the tropomyosin receptor kinase A (TrkA). The precise mechanism of the interaction between these two receptors has not been completely elucidated, and we therefore adopted a systems pharmacology modeling approach to gain understanding of the effect of p75 on the dynamics of NGF signal transduction. Specifically, models were developed for the so-called heterodimer and for the ligand-passing hypotheses. We used the model to compare the effect of inhibition of NGF and TrkA and its implication for drug discovery and development for pain treatment. PMID:25470184

  13. 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

  14. Nuclear receptor signaling and cardiac energetics.

    PubMed

    Huss, Janice M; Kelly, Daniel P

    2004-09-17

    The heart has a tremendous capacity for ATP generation, allowing it to function as an efficient pump throughout the life of the organism. The adult myocardium uses either fatty acid or glucose oxidation as its main energy source. Under normal conditions, the adult heart derives most of its energy through oxidation of fatty acids in mitochondria. However, the myocardium has a remarkable ability to switch between carbohydrate and fat fuel sources so that ATP production is maintained at a constant rate in diverse physiological and dietary conditions. This fuel selection flexibility is important for normal cardiac function. Although cardiac energy conversion capacity and metabolic flux is modulated at many levels, an important mechanism of regulation occurs at the level of gene expression. The expression of genes involved in multiple energy transduction pathways is dynamically regulated in response to developmental, physiological, and pathophysiological cues. This review is focused on gene transcription pathways involved in short- and long-term regulation of myocardial energy metabolism. Much of our knowledge about cardiac metabolic regulation comes from studies focused on mitochondrial fatty acid oxidation. The genes involved in this key energy metabolic pathway are transcriptionally regulated by members of the nuclear receptor superfamily, specifically the fatty acid-activated peroxisome proliferator-activated receptors (PPARs) and the nuclear receptor coactivator, PPARgamma coactivator-1alpha (PGC-1alpha). The dynamic regulation of the cardiac PPAR/PGC-1 complex in accordance with physiological and pathophysiological states will be described.

  15. Lysophospholipid receptors: signalling, pharmacology and regulation by lysophospholipid metabolism.

    PubMed

    Meyer zu Heringdorf, Dagmar; Jakobs, Karl H

    2007-04-01

    The lysophospholipids, sphingosine-1-phosphate (S1P), lysophosphatidic acid (LPA), sphingosylphosphorylcholine (SPC) and lysophosphatidylcholine (LPC), activate diverse groups of G-protein-coupled receptors that are widely expressed and regulate decisive cellular functions. Receptors of the endothelial differentiation gene family are activated by S1P (S1P(1-5)) or LPA (LPA(1-3)); two more distantly related receptors are activated by LPA (LPA(4/5)); the GPR(3/6/12) receptors have a high constitutive activity but are further activated by S1P and/or SPC; and receptors of the OGR1 cluster (OGR1, GPR4, G2A, TDAG8) appear to be activated by SPC, LPC, psychosine and/or protons. G-protein-coupled lysophospholipid receptors regulate cellular Ca(2+) homoeostasis and the cytoskeleton, proliferation and survival, migration and adhesion. They have been implicated in development, regulation of the cardiovascular, immune and nervous systems, inflammation, arteriosclerosis and cancer. The availability of S1P and LPA at their G-protein-coupled receptors is regulated by enzymes that generate or metabolize these lysophospholipids, and localization plays an important role in this process. Besides FTY720, which is phosphorylated by sphingosine kinase-2 and then acts on four of the five S1P receptors of the endothelial differentiation gene family, other compounds have been identified that interact with more ore less selectivity with lysophospholipid receptors.

  16. Substitution of 5-HT1A receptor signaling by a light-activated G protein-coupled receptor.

    PubMed

    Oh, Eugene; Maejima, Takashi; Liu, Chen; Deneris, Evan; Herlitze, Stefan

    2010-10-01

    Understanding serotonergic (5-HT) signaling is critical for understanding human physiology, behavior, and neuropsychiatric disease. 5-HT mediates its actions via ionotropic and metabotropic 5-HT receptors. The 5-HT(1A) receptor is a metabotropic G protein-coupled receptor linked to the G(i/o) signaling pathway and has been specifically implicated in the pathogenesis of depression and anxiety. To understand and precisely control 5-HT(1A) signaling, we created a light-activated G protein-coupled receptor that targets into 5-HT(1A) receptor domains and substitutes for endogenous 5-HT(1A) receptors. To induce 5-HT(1A)-like targeting, vertebrate rhodopsin was tagged with the C-terminal domain (CT) of 5-HT(1A) (Rh-CT(5-HT1A)). Rh-CT(5-HT1A) activates G protein-coupled inward rectifying K(+) channels in response to light and causes membrane hyperpolarization in hippocampal neurons, similar to the agonist-induced responses of the 5-HT(1A) receptor. The intracellular distribution of Rh-CT(5-HT1A) resembles that of the 5-HT(1A) receptor; Rh-CT(5-HT1A) localizes to somatodendritic sites and is efficiently trafficked to distal dendritic processes. Additionally, neuronal expression of Rh-CT(5-HT1A), but not Rh, decreases 5-HT(1A) agonist sensitivity, suggesting that Rh-CT(5-HT1A) and 5-HT(1A) receptors compete to interact with the same trafficking machinery. Finally, Rh-CT(5-HT1A) is able to rescue 5-HT(1A) signaling of 5-HT(1A) KO mice in cultured neurons and in slices of the dorsal raphe showing that Rh-CT(5-HT1A) is able to functionally compensate for native 5-HT(1A). Thus, as an optogenetic tool, Rh-CT(5-HT1A) has the potential to directly correlate in vivo 5-HT(1A) signaling with 5-HT neuron activity and behavior in both normal animals and animal models of neuropsychiatric disease.

  17. Dynamical modelling of prostaglandin signalling in platelets reveals individual receptor contributions and feedback properties.

    PubMed

    Mischnik, Marcel; Hubertus, Katharina; Geiger, Jörg; Dandekar, Thomas; Timmer, Jens

    2013-10-01

    Prostaglandins are the key-players in diminishing platelet function. They exert their effects via a variety of surface receptors that are linked to the cAMP/PKA-signalling cascade. However, less is known about the quantitative impact of the individual receptors on the underlying pathway. We present here a comprehensive ordinary differential equation-based model of the platelet cAMP pathway, including the four prostaglandin receptors IP, DP1, EP3 and EP4, the ADP receptor P2Y12, a detailed PKA-module as well as downstream-targets. Parameter estimation along with a comprehensive combination of time-course and dose-response measurements revealed the individual quantitative role of each receptor in elevating or decreasing pathway activity. A comparison of the two inhibiting receptors EP3 and P2Y12 exhibited a greater signalling strength of the EP3 receptor with implications for antithrombotic treatment. Furthermore, analysis of different model topologies revealed a direct influence of PKA on adenylate cyclase, reducing its maximum catalytic speed. Finally, we show here for the first time the dynamic behaviour of VASP-phosphorylation, which is commonly used as a marker for platelet-inhibition. We validate our model by comparing it to further experimental data.

  18. Manipulation of receptor oligomerization as a strategy to inhibit signaling by TNF superfamily members.

    PubMed

    Warren, Julia T; Nelson, Christopher A; Decker, Corinne E; Zou, Wei; Fremont, Daved H; Teitelbaum, Steven L

    2014-08-19

    Signaling by receptor activator of nuclear factor κB (RANK) in response to its ligand RANKL, which is a member of the tumor necrosis factor (TNF) superfamily of cytokines, stimulates osteoclast formation and bone resorption. Thus, this ligand-receptor pair is a therapeutic target for various disorders, such as osteoporosis and metastasis of cancer to bone. RANKL exists as a physiological homotrimer, with each monomer recognizing a single molecule of RANK or the decoy receptor osteoprotegerin (OPG), which inhibits osteoclastogenesis. We engineered a RANKL protein in which all three monomers of RANKL were encoded as a single polypeptide chain, which enabled us to independently control receptor binding at each binding interface. To generate an effective RANK inhibitor, we used an unbiased forward genetic approach to identify mutations in RANKL that had a 500-fold increased affinity for RANK but had decreased affinity for the decoy receptor OPG. Incorporating mutations that blocked receptor binding into this high-affinity RANKL variant generated a mutant RANKL that completely inhibited wild-type RANKL-induced osteoclastogenesis in vitro and bone resorption in mice. Our approach may be generalized to enable the inhibition of other TNF receptor signaling systems, which are implicated in a wide range of pathological conditions.

  19. 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)

  20. Androgen receptor signaling regulates growth of glioblastoma multiforme in men.

    PubMed

    Yu, Xiaoming; Jiang, Yuhua; Wei, Wei; Cong, Ping; Ding, Yinlu; Xiang, Lei; Wu, Kang

    2015-02-01

    Although glioblastoma multiforme (GBM) is the most malignant primary human brain cancer with surprisingly high incidence rate in adult men than in women, the exact mechanism underlying this pronounced epidemiology is unclear. Here, we showed significant upregulated androgen receptor (AR) expression in the GBM tissue compared to the periphery normal brain tissue in patients. An expression of AR was further detected in all eight examined human GBM cell lines. To figure out whether AR signaling may play a role in GBM, we used high AR-expressing U87-MG GBM line for further study. We found that activation of transforming growth factor β (TGFβ) receptor signaling by TGFβ1 in GBM significantly inhibited cell growth and increased apoptosis. Moreover, application of active AR ligand 5α-dihydrotestosterone (DHT) significantly decreased the effect of TGFβ1 on GBM growth and apoptosis, suggesting that AR signaling pathway may contradict the effect of TGFβ receptor signaling in GBM. However, neither total protein nor the phosphorylated protein of SMAD3, a major TGFβ receptor signaling downstream effector in GBM, was affected by DHT, suggesting that AR activation may not affect the SMAD3 protein production or phosphorylation of TGFβ receptor and SMAD3. Finally, immunoprecipitation followed by immunoblot confirmed binding of pAR to pSMAD3, which may prevent the DNA binding of pSMAD3 and subsequently prevent its effect on cell growth in GBM. Taken together, our study suggests that AR signaling may promote tumorigenesis of GBM in adult men by inhibiting TGFβ receptor signaling.

  1. Cannabinoid Receptors in the Central Nervous System: Their Signaling and Roles in Disease

    PubMed Central

    Kendall, Debra A.; Yudowski, Guillermo A.

    2017-01-01

    The identification and cloning of the two major cannabinoid (CB1 and CB2) receptors together with the discovery of their endogenous ligands in the late 80s and early 90s, resulted in a major effort aimed at understanding the mechanisms and physiological roles of the endocannabinoid system (ECS). Due to its expression and localization in the central nervous system (CNS), the CB1 receptor together with its endogenous ligands (endocannabinoids (eCB)) and the enzymes involved in their synthesis and degradation, has been implicated in multiple pathophysiological events ranging from memory deficits to neurodegenerative disorders among others. In this review, we will provide a general overview of the ECS with emphasis on the CB1 receptor in health and disease. We will describe our current understanding of the complex aspects of receptor signaling and trafficking, including the non-canonical signaling pathways such as those mediated by β-arrestins within the context of functional selectivity and ligand bias. Finally, we will highlight some of the disorders in which CB1 receptors have been implicated. Significant knowledge has been achieved over the last 30 years. However, much more research is still needed to fully understand the complex roles of the ECS, particularly in vivo and to unlock its true potential as a source of therapeutic targets. PMID:28101004

  2. Brassinosteroid signal transduction from receptor kinases to transcription factors.

    PubMed

    Kim, Tae-Wuk; Wang, Zhi-Yong

    2010-01-01

    Brassinosteroids (BRs) are growth-promoting steroid hormones in plants. Genetic studies in Arabidopsis illustrated the essential roles of BRs in a wide range of developmental processes and helped identify many genes involved in BR biosynthesis and signal transduction. Recently, proteomic studies identified missing links. Together, these approaches established the BR signal transduction cascade, which includes BR perception by the BRI1 receptor kinase at the cell surface, activation of BRI1/BAK1 kinase complex by transphosphorylation, subsequent phosphorylation of the BSK kinases, activation of the BSU1 phosphatase, dephosphorylation and inactivation of the BIN2 kinase, and accumulation of unphosphorylated BZR transcription factors in the nucleus. Mass spectrometric analyses are providing detailed information on the phosphorylation events involved in each step of signal relay. Thus, the BR signaling pathway provides a paradigm for understanding receptor kinase-mediated signal transduction as well as tools for the genetic improvement of the productivity of crop plants.

  3. 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

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

    PubMed

    Bradley, Sophie J; Wiegman, Coen H; 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

    2016-04-19

    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.

  5. Revolution in GPCR signalling: opioid receptor heteromers as novel therapeutic targets: IUPHAR Review 10

    PubMed Central

    Fujita, Wakako; Gomes, Ivone; Devi, Lakshmi A

    2014-01-01

    GPCRs can interact with each other to form homomers or heteromers. Homomers involve interactions with the same receptor type while heteromers involve interactions between two different GPCRs. These receptor–receptor interactions modulate not only the binding but also the signalling and trafficking properties of individual receptors. Opioid receptor heteromerization has been extensively investigated with the objective of identifying novel therapeutic targets that are as potent as morphine but without the side effects associated with chronic morphine use. In this context, studies have described heteromerization between the different types of opioid receptors and between opioid receptors and a wide range of GPCRs including adrenoceptors, cannabinoid, 5-HT, metabotropic glutamate and sensory neuron-specific receptors. Recent advances in the field involving the generation of heteromer-specific reagents (antibodies or ligands) or of membrane-permeable peptides that disrupt the heteromer interaction are helping to elucidate the physiological role of opioid receptor heteromers and the contribution of the partner receptor to the side effects associated with opioid use. For example, studies using membrane-permeable peptides targeting the heteromer interface have implicated μ and δ receptor heteromers in the development of tolerance to morphine, and heteromers of μ and gastrin-releasing peptide receptors in morphine-induced itch. In addition, a number of ligands that selectively target opioid receptor heteromers exhibit potent antinociception with a decrease in the side effects commonly associated with morphine use. In this review, we summarize the latest findings regarding the biological and functional characteristics of opioid receptor heteromers both in vitro and in vivo. PMID:24916280

  6. Evolution of retinoic acid receptors and retinoic acid signaling.

    PubMed

    Gutierrez-Mazariegos, Juliana; Schubert, Michael; Laudet, Vincent

    2014-01-01

    Retinoic acid (RA) is a vitamin A-derived morphogen controlling important developmental processes in vertebrates, and more generally in chordates, including axial patterning and tissue formation and differentiation. In the embryo, endogenous RA levels are controlled by RA synthesizing and degrading enzymes and the RA signal is transduced by two retinoid receptors: the retinoic acid receptor (RAR) and the retinoid X receptor (RXR). Both RAR and RXR are members of the nuclear receptor superfamily of ligand-activated transcription factors and mainly act as heterodimers to activate the transcription of target genes in the presence of their ligand, all-trans RA. This signaling pathway was long thought to be a chordate innovation, however, recent findings of gene homologs involved in RA signaling in the genomes of a wide variety of non-chordate animals, including ambulacrarians (sea urchins and acorn worms) and lophotrochozoans (annelids and mollusks), challenged this traditional view and suggested that the RA signaling pathway might have a more ancient evolutionary origin than previously thought. In this chapter, we discuss the evolutionary history of the RA signaling pathway, and more particularly of the RARs, which might have experienced independent gene losses and duplications in different animal lineages. In sum, the available data reveal novel insights into the origin of the RA signaling pathway as well as into the evolutionary history of the RARs.

  7. Opposite function of dopamine D1 and NMDA receptors in striatal cannabinoid-mediated signaling

    PubMed Central

    Daigle, Tanya L.; Wetsel, William C.; Caron, Marc G.

    2011-01-01

    It is well established that the cannabinoid and dopamine systems interact at various levels to regulate basal ganglia function. While it is well known that acute administration of cannabinoids to mice can modify dopamine-dependent behaviors, an understanding of the intraneuronal signaling pathways employed by these agents in the striatum is not well understood. Here we use knockout (KO) mouse models to examine the regulation of striatal ERK1/2 signaling by behaviorally relevant doses of cannabinoids. This cellular pathway has been implicated as a central mediator of drug reward and synaptic plasticity. In C57BL/6J mice, acute administration of cannabinoid agonists, HU-210 and Δ9-THC, promotes a dose- and time-dependent decrease in the phosphorylation of ERK1/2 in dorsal striatum. Co-administration of the CB1 cannabinoid receptor (CB1R) antagonist AM251 with HU-210 prevents ERK1/2 inactivation, indicating a requirement for activation of this receptor. In dopamine D1 receptor (D1R) KO animals treated with HU-210, the magnitude of the HU-210-dependent decrease in striatal ERK1/2 signaling is greater than in wild-type controls. In contrast, the HU-210 administration to NMDA receptor knockdown mice (NR1-Kd) was ineffective at promoting striatal ERK1/2 inactivation. Genetic deletion of other potential ERK1/2 mediators, the dopamine D2 receptors (D2R)s or βarrestin-1 or -2, did not affect HU-210-induced modulation of ERK1/2 signaling in the striatum. These results support the hypothesis that dopamine D1 receptors and NMDA receptors act in an opposite manner to regulate striatal CB1R signal transduction. PMID:22034973

  8. Kalirin Signaling: Implications for Synaptic Pathology

    PubMed Central

    Remmers, Christine

    2012-01-01

    Spine morphogenesis and plasticity are intimately linked to cognition, and there is strong evidence that aberrant regulation of spine plasticity is associated with physiological, behavioral, and pathological conditions. The neuronal guanine nucleotide exchange factor (GEF) kalirin is emerging as a key regulator of structural and functional plasticity at dendritic spines. Here, we review recent studies that have genetically and functionally linked kalirin signaling to a number of human disorders. Kalirin signaling may thus represent a disease mechanism and provide a novel therapeutic target. PMID:22194219

  9. Prolactin receptor and signal transduction to milk protein genes

    SciTech Connect

    Djiane, J.; Daniel, N.; Bignon, C.

    1994-06-01

    After cloning of the mammary gland prolactin (PRL) receptor cDNA, a functional assay was established using co-transfection of PRL receptor cDNA together with a milk protein promoter/chloramphenicol acetyl transferase (CAT) construct in Chinese hamster ovary (CHO) cells. Different mutants of the PRL receptor were tested in this CAT assay to delimit the domains in the receptor necessary for signal transduction to milk protein genes. In CHO cells stably transfected with PRL receptor cDNA, high numbers of PRL receptor are expressed. By metabolic labeling and immunoprecipitation, expressed PRL receptor was identified as a single species of 100 kDa. Using these cells, we analyzed the effects of PRL on intracellular free Ca{sup ++} concentration. PRL stimulates Ca{sup ++} entry and induces secondary Ca{sup ++} mobilization. The entry of Ca{sup ++} is a result of an increase in K{sup +} conductance that hyperpolarizes the membranes. We have also analyzed tyrosine phosphorylation induced by PRL. In CHO cells stably transfected with PRL receptor cDNA, PRL induced a very rapid and transient tyrosine phosphorylation of a 100-kDa protein which is most probably the PRL receptor. The same finding was obtained in mammary membranes after PRL injection to lactating rabbits. Whereas tyrosine kinase inhibitors genistein and lavendustin were without effect, PRL stimulation of milk protein gene promoters was partially inhibited by 2 {mu}M herbimycin in CHO cells co-transfected with PRL receptor cDNA and the {Beta} lactoglobulin CAT construct. Taken together these observations indicate that the cytoplasmic domain of the PRL receptor interacts with one or several tyrosine kinases, which may represent early postreceptor events necessary for PRL signal transduction to milk protein genes. 14 refs., 4 figs.

  10. Multiple roles of the PGE2-EP receptor signal in vascular permeability

    PubMed Central

    Omori, K; Kida, T; Hori, M; Ozaki, H; Murata, T

    2014-01-01

    Background and Purpose PGE2 is a major prostanoid that regulates inflammation by stimulating EP1–4 receptors. However, how PGE2 induces an initial inflammatory response to vascular hyper-permeability remains unknown. Here we investigated the role of the PGE2-EP receptor signal in modulating vascular permeability both in vivo and in vitro. Experimental Approach We used a modified Miles assay and intravital microscopy to examine vascular permeability in vivo. Endothelial barrier property was assessed by measuring transendothelial electrical resistance (TER) in vitro. Key Results Local administration of PGE2, an EP2 or EP4 receptor agonist into FVB/NJcl mouse ear skin caused vascular leakage, indicated by dye extravasation. Intravital microscopy and laser Doppler blood-flow imaging revealed that these treatments dilated peripheral vessels and increased local blood flow. Pretreatment with the vasoconstrictor phenylephrine inhibited the PGE2-induced blood flow increase and vascular leakage. In contrast to the EP2 and EP4 receptor agonists, administration of an EP3 receptor agonist suppressed vascular leakage without altering vascular diameter or blood flow. In isolated HUVECs, the EP3 receptor agonist elevated TER and blocked thrombin-induced dextran passage. Inhibiting PKA restored the hypo-permeability induced by the EP3 receptor agonist. Conclusions and Implications Activation of the PGE2-EP2 or -EP4 receptor signal induces vasodilatation in mural cells, resulting in increased local blood flow and hyper-permeability. In contrast, activation of the PGE2-EP3 receptor signal induces a cAMP-dependent enhancement of the endothelial barrier, leading to hypo-permeability. We provide the first evidence that endothelial cells and mural cells cooperate to modulate vascular permeability. PMID:24923772

  11. Of ITIMs, ITAMs, and ITAMis: revisiting immunoglobulin Fc receptor signaling.

    PubMed

    Getahun, Andrew; Cambier, John C

    2015-11-01

    Receptors for immunoglobulin Fc regions play multiple critical roles in the immune system, mediating functions as diverse as phagocytosis, triggering degranulation of basophils and mast cells, promoting immunoglobulin class switching, and preventing excessive activation. Transmembrane signaling associated with these functions is mediated primarily by two amino acid sequence motifs, ITAMs (immunoreceptor tyrosine-based activation motifs) and ITIMs (immunoreceptor tyrosine-based inhibition motifs) that act as the receptors' interface with activating and inhibitory signaling pathways, respectively. While ITAMs mobilize activating tyrosine kinases and their consorts, ITIMs mobilize opposing tyrosine and inositol-lipid phosphatases. In this review, we will discuss our current understanding of signaling by these receptors/motifs and their sometimes blurred lines of function.

  12. The Growth Hormone Secretagogue Receptor: Its Intracellular Signaling and Regulation

    PubMed Central

    Yin, Yue; Li, Yin; Zhang, Weizhen

    2014-01-01

    The growth hormone secretagogue receptor (GHSR), also known as the ghrelin receptor, is involved in mediating a wide variety of biological effects of ghrelin, including: stimulation of growth hormone release, increase of food intake and body weight, modulation of glucose and lipid metabolism, regulation of gastrointestinal motility and secretion, protection of neuronal and cardiovascular cells, and regulation of immune function. Dependent on the tissues and cells, activation of GHSR may trigger a diversity of signaling mechanisms and subsequent distinct physiological responses. Distinct regulation of GHSR occurs at levels of transcription, receptor interaction and internalization. Here we review the current understanding on the intracellular signaling pathways of GHSR and its modulation. An overview of the molecular structure of GHSR is presented first, followed by the discussion on its signaling mechanisms. Finally, potential mechanisms regulating GHSR are reviewed. PMID:24651458

  13. Proteoglycan Signaling Co–receptors: Roles in Cell Adhesion, Migration and Invasion

    PubMed Central

    Mythreye, Karthikeyan; Blobe, Gerard C.

    2009-01-01

    Signaling co-receptors are diverse, multifunctional components of most major signaling pathways, with roles in mediating and regulating signaling in both physiological and pathophysiological circumstances. Many of these signaling co-receptors, including CD44, glypicans, neuropilins, syndecans and TβRIII/betaglycan are also proteoglycans. Like other co-receptors, these proteoglycan signaling co–receptors can bind multiple ligands, promoting the formation of receptor signaling complexes and regulating signaling at the cell surface. The proteoglycan signaling co-receptors can also function as structural molecules to regulate adhesion, cell migration, morphogenesis and differentiation. Through a balance of these signaling and structural roles, proteoglycan signaling co-receptors can have either tumor promoting or tumor suppressing functions. Defining the role and mechanism of action of these proteoglycan signaling co-receptors should enable more effective targeting of these co-receptors and their respective pathways for the treatment of human disease. PMID:19427900

  14. CSF-1 Receptor Signaling in Myeloid Cells

    PubMed Central

    Stanley, E. Richard; Chitu, Violeta

    2014-01-01

    The CSF-1 receptor (CSF-1R) is activated by the homodimeric growth factors colony-stimulating factor-1 (CSF-1) and interleukin-34 (IL-34). It plays important roles in development and in innate immunity by regulating the development of most tissue macrophages and osteoclasts, of Langerhans cells of the skin, of Paneth cells of the small intestine, and of brain microglia. It also regulates the differentiation of neural progenitor cells and controls functions of oocytes and trophoblastic cells in the female reproductive tract. Owing to this broad tissue expression pattern, it plays a central role in neoplastic, inflammatory, and neurological diseases. In this review we summarize the evolution, structure, and regulation of expression of the CSF-1R gene. We review, the structures of CSF-1, IL-34, and the CSF-1R and the mechanism of ligand binding to and activation of the receptor. We further describe the pathways regulating macrophage survival, proliferation, differentiation, and chemotaxis downstream from the CSF-1R. PMID:24890514

  15. Primary cilia and coordination of receptor tyrosine kinase (RTK) signalling

    PubMed Central

    Christensen, Søren T; Clement, Christian A; Satir, Peter; Pedersen, Lotte B

    2015-01-01

    Primary cilia are microtubule-based sensory organelles that coordinate signalling pathways in cell-cycle control, migration, differentiation and other cellular processes critical during development and for tissue homeostasis. Accordingly, defects in assembly or function of primary cilia lead to a plethora of developmental disorders and pathological conditions now known as ciliopathies. In this review, we summarize the current status of the role of primary cilia in coordinating receptor tyrosine kinase (RTK) signalling pathways. Further, we present potential mechanisms of signalling crosstalk and networking in the primary cilium and discuss how defects in ciliary RTK signalling are linked to human diseases and disorders. PMID:21956154

  16. Assembly and localization of Toll-like receptor signalling complexes.

    PubMed

    Gay, Nicholas J; Symmons, Martyn F; Gangloff, Monique; Bryant, Clare E

    2014-08-01

    Signal transduction by the Toll-like receptors (TLRs) is central to host defence against many pathogenic microorganisms and also underlies a large burden of human disease. Thus, the mechanisms and regulation of signalling by TLRs are of considerable interest. In this Review, we discuss the molecular basis for the recognition of pathogen-associated molecular patterns, the nature of the protein complexes that mediate signalling, and the way in which signals are regulated and integrated at the level of allosteric assembly, post-translational modification and subcellular trafficking of the components of the signalling complexes. These fundamental molecular mechanisms determine whether the signalling output leads to a protective immune response or to serious pathologies such as sepsis. A detailed understanding of these processes at the molecular level provides a rational framework for the development of new drugs that can specifically target pathological rather than protective signalling in inflammatory and autoimmune disease.

  17. Hindbrain ghrelin receptor signaling is sufficient to maintain fasting glucose.

    PubMed

    Scott, Michael M; Perello, Mario; Chuang, Jen-Chieh; Sakata, Ichiro; Gautron, Laurent; Lee, Charlotte E; Lauzon, Danielle; Elmquist, Joel K; Zigman, Jeffrey M

    2012-01-01

    The neuronal coordination of metabolic homeostasis requires the integration of hormonal signals with multiple interrelated central neuronal circuits to produce appropriate levels of food intake, energy expenditure and fuel availability. Ghrelin, a peripherally produced peptide hormone, circulates at high concentrations during nutrient scarcity. Ghrelin promotes food intake, an action lost in ghrelin receptor null mice and also helps maintain fasting blood glucose levels, ensuring an adequate supply of nutrients to the central nervous system. To better understand mechanisms of ghrelin action, we have examined the roles of ghrelin receptor (GHSR) expression in the mouse hindbrain. Notably, selective hindbrain ghrelin receptor expression was not sufficient to restore ghrelin-stimulated food intake. In contrast, the lowered fasting blood glucose levels observed in ghrelin receptor-deficient mice were returned to wild-type levels by selective re-expression of the ghrelin receptor in the hindbrain. Our results demonstrate the distributed nature of the neurons mediating ghrelin action.

  18. Transit of hormonal and EGF receptor-dependent signals through cholesterol-rich membranes.

    PubMed

    Freeman, Michael R; Cinar, Bekir; Kim, Jayoung; Mukhopadhyay, Nishit K; Di Vizio, Dolores; Adam, Rosalyn M; Solomon, Keith R

    2007-02-01

    The functional consequences of changes in membrane lipid composition that coincide with malignant growth are poorly understood. Sufficient data have been acquired from studies of lipid binding proteins, post-translational modifications of signaling proteins, and biochemical inhibition of lipidogenic pathways to indicate that growth and survival pathways might be substantially re-directed by alterations in the lipid content of membranes. Cholesterol and glycosphingolipids segregate into membrane patches that exhibit a liquid-ordered state in comparison to membrane domains containing relatively lower amounts of these classes of lipids. These "lipid raft" structures, which may vary in size and stability in different cell types, both accumulate and exclude signaling proteins and have been implicated in signal transduction through a number of cancer-relevant pathways. In prostate cancer cells, signaling from epidermal growth factor receptor (EGFR) to the serine-threonine kinase Akt1, as well as from IL-6 to STAT3, have been demonstrated to be influenced by experimental interventions that target cholesterol homeostasis. The recent finding that classical steroid hormone receptors also reside in these microdomains, and thus may function within these structures in a signaling capacity independent of their role as nuclear factors, suggests a novel means of cross-talk between receptor tyrosine kinase-derived and steroidogenic signals. Potential points of intersection between components of the EGFR family of receptor tyrosine kinases and androgen receptor signaling pathways, which may be sensitive to disruptions in cholesterol metabolism, are discussed. Understanding the manner in which these pathways converge within cholesterol-rich membranes may present new avenues for therapeutic intervention in hormone-dependent cancers.

  19. Immunopathological Roles of Cytokines, Chemokines, Signaling Molecules, and Pattern-Recognition Receptors in Systemic Lupus Erythematosus

    PubMed Central

    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. PMID:22312407

  20. Modulation of Toll-interleukin 1 receptor mediated signaling.

    PubMed

    Li, Xiaoxia; Qin, Jinzhong

    2005-04-01

    Toll-like receptors (TLRs) belong to the Toll-interleukin 1 receptor superfamily, which is defined by a common intracellular Toll-IL-1 receptor (TIR) domain. A group of TIR domain containing adaptors (MyD88, TIRAP, TRIF and TRAM), are differentially recruited to the Toll-IL-1 receptors, contributing to the specificity of signaling. The IL-1 mediated signaling pathway serves as a "prototype" for other family members. Genetic and biochemical studies reveal that IL-1R uses adaptor molecule MyD88 to mediate a very complex pathway, involving a cascade of kinases organized by multiple adapter molecules into signaling complexes, leading to activation of the transcription factor NFkappaB. Several Toll-like receptors utilize variations of the "prototype" pathway by employing different adaptor molecules. Double-stranded RNA triggered, TLR3-mediated signaling is independent of MyD88, IRAK4, and IRAK. The adapter molecule TRIF is utilized by TLR3 to mediate the activation of NFkappaB and IRF3. LPS-induced, TLR4-mediated signaling employs multiple TIR-domain containing adaptors, MyD88/TIRAP to mediate NFkappaB activation, TRIF/TRAM for IRF3 activation. Recent studies have also begun to unravel how these pathways are negatively regulated. SIGIRR (also known as TIR8), a member of TIR superfamily that does not activate the transcription factors NFkappaB and IRF3, instead negatively modulates responses. Cells from SIGIRR-null mice show enhanced activation in response to either IL-1 or certain Toll ligands. In addition to SIGIRR, several other negative regulators have been shown to inhibit the TIR signaling, including ST2, IRAKM, MyD88s, SOCS1, and Triad3A. The coordinated positive and negative regulation of the TIR signaling ensures the appropriate modulation of the innate and inflammatory responses.

  1. Sex steroid signaling: implications for lung diseases.

    PubMed

    Sathish, Venkatachalem; Martin, Yvette N; Prakash, Y S

    2015-06-01

    There is increasing recognition that sex hormones (estrogen, progesterone, and testosterone) have biological and pathophysiological actions in peripheral, non-reproductive organs, including the lung. Clinically, sex differences in the incidence, morbidity and mortality of lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, lung cancer and pulmonary hypertension have been noted, although intrinsic sex differences vs. the roles of sex steroids are still not well-understood. Accordingly, it becomes important to ask the following questions: 1) Which sex steroids are involved? 2) How do they affect different components of the lung under normal circumstances? 3) How does sex steroid signaling change in or contribute to lung disease, and in this regard, are sex steroids detrimental or beneficial? As our understanding of sex steroid signaling in the lung improves, it is important to consider whether such information can be used to develop new therapeutic strategies to target lung diseases, perhaps in both sexes or in a sex-specific manner. In this review, we focus on the basics of sex steroid signaling, and the current state of knowledge regarding how they influence structure and function of specific lung components across the life span and in the context of some important lung diseases. We then summarize the potential for sex steroids as useful biomarkers and therapeutic targets in these lung diseases as a basis for future translational research in the area of gender and individualized medicine. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Sex Steroid Signaling: Implications for Lung Diseases

    PubMed Central

    Sathish, Venkatachalem; Martin, Yvette N.; Prakash, Y.S.

    2015-01-01

    There is increasing recognition that the sex hormones (estrogen, progesterone, and testosterone) have biological and pathophysiological actions in peripheral, non-reproductive organs, including the lung. Clinically, sex differences in the incidence, morbidity and mortality of lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, lung cancer and pulmonary hypertension have been noted, although intrinsic sex differences vs. the roles of sex steroids are still not well-understood. Accordingly, it becomes important to ask the following questions: 1) Which sex steroids are involved? 2) How do they affect different components of the lung under normal circumstances? 3) How does sex steroid signaling change in or contribute to lung disease, and in this regard, are sex steroids detrimental or beneficial? As our understanding of sex steroid signaling in the lung improves, it is important to consider whether such information can be used to develop new therapeutic strategies to target lung diseases, perhaps in both sexes or in a sex-specific manner. In this review, we focus on the basics of sex steroid signaling, and the current state of knowledge regarding how they influence structure and function of specific lung components across the life span and in the context of some important lung diseases. We then summarize the potential for sex steroids as useful biomarkers and therapeutic targets in these lung diseases as a basis for future translational research in the area of gender and individualized medicine. PMID:25595323

  3. 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

  4. 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

  5. Receptor for Advanced Glycation End Products Regulates Leukotriene B4 Receptor 1 Signaling.

    PubMed

    Ichiki, Takako; Koga, Tomoaki; Yokomizo, Takehiko

    2016-12-01

    Leukotriene B4 receptor 1 (BLT1), a high-affinity G protein-coupled receptor (GPCR) for leukotriene B4 (LTB4), plays important roles in inflammatory and immune reactions. Although the LTB4-BLT1 axis is known to promote inflammation, the binding proteins that modulate LTB4-BLT1 signaling have not been identified. Recently, we discovered that receptor for advanced glycation end products (RAGE) interacts with BLT1 and modulates LTB4-BLT1 signaling. We propose RAGE as a new class of GPCR modulator and a new target of future GPCR studies.

  6. Analysis of insulin receptor substrate signaling dynamics on microstructured surfaces.

    PubMed

    Lanzerstorfer, Peter; Yoneyama, Yosuke; Hakuno, Fumihiko; Müller, Ulrike; Höglinger, Otmar; Takahashi, Shin-Ichiro; Weghuber, Julian

    2015-03-01

    Insulin receptor substrates (IRS) are phosphorylated by activated insulin/insulin-like growth factor I receptor tyrosine kinases, with this comprising an initial key event for downstream signaling and bioactivities. Despite the structural similarities, increasing evidence shows that IRS family proteins have nonredundant functions. Although the specificity of insulin/insulin-like growth factor signaling and biological responses partly reflects which IRS proteins are dominantly phosphorylated by the receptors, the precise properties of the respective IRS interaction with the receptors remain elusive. In the present study, we utilized a technique that combines micropatterned surfaces and total internal reflection fluorescence microscopy for the quantitative analysis of the interaction between IRS proteins and insulin/insulin-like growth factor in living cells. Our experimental set-up enabled the measurement of equilibrium associations and interaction dynamics of these molecules with high specificity. We revealed that several domains of IRS including pleckstrin homology and phosphotyrosine binding domains critically determine the turnover rate of the receptors. Furthermore, we found significant differences among IRS proteins in the strength and kinetic stability of the interaction with the receptors, suggesting that these interaction properties could account for the diverse functions of IRS. In addition, our analyses using fluorescent recovery after photobleaching revealed that kinases such as c-Jun N-terminal kinase and IκB kinase β, which phosphorylate serine/threonine residues of IRS and contribute to insulin resistance, altered the interaction kinetics of IRS with insulin receptor. Collectively, our experimental set-up is a valuable system for quantitifying the physiological interaction of IRS with the receptors in insulin/insulin-like growth factor signaling. © 2015 FEBS.

  7. Receptor domains of two-component signal transduction systems.

    PubMed

    Perry, Julie; Koteva, Kalinka; Wright, Gerard

    2011-05-01

    Two-component signal transduction systems are found ubiquitously in prokaryotes, and in archaea, fungi, yeast and some plants, where they regulate physiologic and molecular processes at both transcriptional and post-transcriptional levels. Two-component systems sense changes in environmental conditions when a specific ligand binds to the receptor domain of the histidine kinase sensory component. The structures of many histidine kinase receptors are known, including those which sense extracellular and cytoplasmic signals. In this review, we discuss the basic architecture of two-component signalling circuits, including known system ligands, structure and function of both receptor and signalling domains, the chemistry of phosphotransfer, and cross-talk between different two-component pathways. Given the importance of these systems in regulating cellular responses, many biochemical techniques have been developed for their study and analysis. We therefore also review current methods used to study two-component signalling, including a new affinity-based proteomics approach used to study inducible resistance to the antibiotic vancomycin through the VanSR two-component signal transduction system.

  8. Commensal-Epithelial Signaling Mediated via Formyl Peptide Receptors

    PubMed Central

    Wentworth, Christy C.; Jones, Rheinallt M.; Kwon, Young Man; Nusrat, Asma; Neish, Andrew S.

    2010-01-01

    Commensal bacteria and/or their products engender beneficial effects to the mammalian gut, including stimulating physiological cellular turnover and enhancing wound healing, without activating overt inflammation. In the present study, we observed commensal bacteria-mediated activation of the noninflammatory extracellular signal-regulated kinase[ERK]/mitogen-activated protein kinase and Akt signaling pathways in gut epithelial cells and delineated a mechanism for this bacterially activated signaling. All tested strains of commensal bacteria induced ERK phosphorylation without stimulating pro-inflammatory phospho-IκB or pro-apoptotic phospho-c-Jun NH2-terminal kinase, with Lactobacillus species being most potent. This pattern of signaling activation was recapitulated using the peptide N-formyl-Met-Leu-Phe, a bacterial product known to stimulate signaling events in mammalian phagocytes. Sensing of N-formyl-Met-Leu-Phe by gut epithelial cells occurs via recently characterized formyl peptide receptors located in the plasma membrane. Both commensal bacteria and N-formyl-Met-Leu-Phe application to the apical surface of polarized gut epithelial cells resulted in specific formyl peptide receptor activation. In addition, pretreatment of model epithelia and murine colon with Boc2 (a specific peptide antagonist) or pertussis toxin (a Gi-protein inhibitor) abolished commensal-mediated ERK phosphorylation. Taken together, these data show that commensal bacteria specifically activate the ERK/mitogen-activated protein kinase pathway in an formyl peptide receptor-dependent manner, delineating a mechanism by which commensal bacteria contribute to cellular signaling in gut epithelia. PMID:21037077

  9. Commensal-epithelial signaling mediated via formyl peptide receptors.

    PubMed

    Wentworth, Christy C; Jones, Rheinallt M; Kwon, Young Man; Nusrat, Asma; Neish, Andrew S

    2010-12-01

    Commensal bacteria and/or their products engender beneficial effects to the mammalian gut, including stimulating physiological cellular turnover and enhancing wound healing, without activating overt inflammation. In the present study, we observed commensal bacteria-mediated activation of the noninflammatory extracellular signal-regulated kinase[ERK]/mitogen-activated protein kinase and Akt signaling pathways in gut epithelial cells and delineated a mechanism for this bacterially activated signaling. All tested strains of commensal bacteria induced ERK phosphorylation without stimulating pro-inflammatory phospho-IκB or pro-apoptotic phospho-c-Jun NH(2)-terminal kinase, with Lactobacillus species being most potent. This pattern of signaling activation was recapitulated using the peptide N-formyl-Met-Leu-Phe, a bacterial product known to stimulate signaling events in mammalian phagocytes. Sensing of N-formyl-Met-Leu-Phe by gut epithelial cells occurs via recently characterized formyl peptide receptors located in the plasma membrane. Both commensal bacteria and N-formyl-Met-Leu-Phe application to the apical surface of polarized gut epithelial cells resulted in specific formyl peptide receptor activation. In addition, pretreatment of model epithelia and murine colon with Boc2 (a specific peptide antagonist) or pertussis toxin (a G(i)-protein inhibitor) abolished commensal-mediated ERK phosphorylation. Taken together, these data show that commensal bacteria specifically activate the ERK/mitogen-activated protein kinase pathway in an formyl peptide receptor-dependent manner, delineating a mechanism by which commensal bacteria contribute to cellular signaling in gut epithelia.

  10. Alternate transcription of the Toll-like receptor signaling cascade

    PubMed Central

    Wells, Christine A; Chalk, Alistair M; Forrest, Alistair; Taylor, Darrin; Waddell, Nic; Schroder, Kate; Himes, S Roy; Faulkner, Geoffrey; Lo, Sandra; Kasukawa, Takeya; Kawaji, Hideya; Kai, Chikatoshi; Kawai, Jun; Katayama, Shintaro; Carninci, Piero; Hayashizaki, Yoshihide; Hume, David A; Grimmond, Sean M

    2006-01-01

    Background Alternate splicing of key signaling molecules in the Toll-like receptor (Tlr) cascade has been shown to dramatically alter the signaling capacity of inflammatory cells, but it is not known how common this mechanism is. We provide transcriptional evidence of widespread alternate splicing in the Toll-like receptor signaling pathway, derived from a systematic analysis of the FANTOM3 mouse data set. Functional annotation of variant proteins was assessed in light of inflammatory signaling in mouse primary macrophages, and the expression of each variant transcript was assessed by splicing arrays. Results A total of 256 variant transcripts were identified, including novel variants of Tlr4, Ticam1, Tollip, Rac1, Irak1, 2 and 4, Mapk14/p38, Atf2 and Stat1. The expression of variant transcripts was assessed using custom-designed splicing arrays. We functionally tested the expression of Tlr4 transcripts under a range of cytokine conditions via northern and quantitative real-time polymerase chain reaction. The effects of variant Mapk14/p38 protein expression on macrophage survival were demonstrated. Conclusion Members of the Toll-like receptor signaling pathway are highly alternatively spliced, producing a large number of novel proteins with the potential to functionally alter inflammatory outcomes. These variants are expressed in primary mouse macrophages in response to inflammatory mediators such as interferon-γ and lipopolysaccharide. Our data suggest a surprisingly common role for variant proteins in diversification/repression of inflammatory signaling. PMID:16507160

  11. 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.

  12. 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

    2015-03-26

    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.

  13. SIGIRR, a negative regulator of Toll-like receptor-interleukin 1 receptor signaling.

    PubMed

    Wald, David; Qin, Jinzhong; Zhao, Zhendong; Qian, Youcun; Naramura, Mayumi; Tian, Liping; Towne, Jennifer; Sims, John E; Stark, George R; Li, Xiaoxia

    2003-09-01

    The Toll-like receptor-interleukin 1 receptor signaling (TLR-IL-1R) receptor superfamily is important in differentially recognizing pathogen products and eliciting appropriate immune responses. These receptors alter gene expression, mainly through the activation of nuclear factor-kappaB and activating protein 1. SIGIRR (single immunoglobulin IL-1R-related molecule), a member of this family that does not activate these factors, instead negatively modulates immune responses. Inflammation is enhanced in SIGIRR-deficient mice, as shown by their enhanced chemokine induction after IL-1 injection and reduced threshold for lethal endotoxin challenge. Cells from SIGIRR-deficient mice showed enhanced activation in response to either IL-1 or certain Toll ligands. Finally, biochemical analysis indicated that SIGIRR binds to the TLR-IL-1R signaling components in a ligand-dependent way. Our data show that SIGIRR functions as a biologically important modulator of TLR-IL-1R signaling.

  14. 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

  15. Oxytocin receptors: ligand binding, signalling and cholesterol dependence.

    PubMed

    Gimpl, Gerald; Reitz, Julian; Brauer, Sabine; Trossen, Conny

    2008-01-01

    The G protein coupled oxytocin receptor (OTR) reveals some specific molecular and physiological characteristics. Ligand-receptor interaction has been analysed by photoaffinity labelling, site-directed mutagenesis, the construction of receptor chimeras and molecular modelling. Major results of these studies will be summarized. The N-terminus of the OTR is mainly involved in agonist binding. Notably, antagonists that are derived from the ground structure of oxytocin, bind the receptor at distinct sites partly non-overlapping with the agonist binding site. OTRs are able to couple to different G proteins, with a subsequent stimulation of phospholipase C-beta isoforms. In dependence on G protein coupling, OTRs can transduce growth-inhibitory or proliferatory signals. Some evidence is provided that OTRs are also present in form of dimeric or oligomeric complexes at the cell surface. The affinity of the receptor for ligands is strongly dependent on the presence of divalent cations (Mg(2+)) and cholesterol that both act like positive allosteric modulators. While the high-affinity state of the receptor for agonists requires divalent cations and cholesterol, the high-affinity state for antagonists is only dependent on a sufficient amount of cholesterol. Cholesterol affects ligand-binding affinity, receptor signalling and stability. Since the purification of the OTR has never been achieved, alternative methods to study the receptor in its native environment are necessary. Promising strategies for the site-specific labelling of the OTR will be presented. The employment of diverse reporter molecules introduced at different positions within the OTR might allow us in the near future to measure conformational changes of the receptor in its native lipid environment.

  16. Modulation of FGF receptor signaling as an intervention and potential therapy for myelin breakdown in Alzheimer's disease.

    PubMed

    Li, Jia-Su; Yao, Zhong-Xiang

    2013-04-01

    Alzheimer's disease (AD) is the most common neurodegenerative disease and oligodendrocyte degeneration and white matter damage play a critical role in the pathogenesis of AD. FGF/FGF receptor signaling have been implicated in diverse cellular processes including cell apoptosis, survival, adhesion, migration, differentiation, and proliferation, as well as key regulators of the development of the central nervous system (including in axon guidance and synaptogenesis) via multiple signal pathways. It has been demonstrated that FGF infusion or gene transfer restores neurogenesis in subventricular zone and hippocampal functions in aged mice and mouse models of AD and has therapeutic implications for neurocognitive disorders. Besides, FGF receptor signaling in oligodendrocytes regulates myelin sheath thickness via Erk1/2 MAPK and PI3K/Akt/mTOR signaling, which sequentially regulates progression through distinct stages of oligodendrocyte differentiation. The effect could be effectively antagonized by the potent, selective tyrosine kinase inhibitor of FGF receptor activity. We therefore propose that modulation of FGF receptor signaling will suppress the development of oligodendrocyte degeneration and myelin breakdown or white matter damage in mouse models or patients of AD and improve or restore the pathological and clinical symptoms of cognitive decline, and FGF receptor signaling with its inhibitors and/or gene transfer would serve as an intervention and potential therapy for myelin breakdown and cognitive decline in AD.

  17. EP2 Receptor Signaling Regulates Microglia Death

    PubMed Central

    Yang, Myung-Soon; Jiang, Jianxiong; Ganesh, Thota; Joe, Eunhye; Dingledine, Raymond

    2015-01-01

    The timely resolution of inflammation prevents continued tissue damage after an initial insult. In the brain, the death of activated microglia by apoptosis has been proposed as one mechanism to resolve brain inflammation. How microglial death is regulated after activation is still unclear. We reported that exposure to lipopolysaccharide (LPS) and interleukin (IL)-13 together initially activates and then kills rat microglia in culture by a mechanism dependent on cyclooxygenase-2 (COX-2). We show here that activation of the E prostanoid receptor 2 (EP2, PTGER2) for prostaglandin E2 mediates microglial death induced by LPS/IL-13, and that EP2 activation by agonist alone kills microglia. Both EP2 antagonists and reactive oxygen scavengers block microglial death induced by either LPS/IL-13 or EP2 activation. By contrast, the homeostatic induction of heme oxygenase 1 (Hmox1) by LPS/IL-13 or EP2 activation protects microglia. Both the Hmox1 inducer cobalt protoporphyrin and a compound that releases the Hmox1 product carbon monoxide (CO) attenuated microglial death produced by LPS/IL-13. Whereas CO reduced COX-2 protein expression, EP2 activation increased Hmox1 and COX-2 expression at both the mRNA and protein level. Interestingly, caspase-1 inhibition prevented microglial death induced by either LPS/IL-13 or low (but not high) concentrations of butaprost, suggestive of a predominantly pyroptotic mode of death. Butaprost also caused the expression of activated caspase-3 in microglia, pointing to apoptosis. These results indicate that EP2 activation, which initially promotes microglial activation, later causes delayed death of activated microglia, potentially contributing to the resolution phase of neuroinflammation. PMID:25715797

  18. Intracellular LINGO-1 negatively regulates Trk neurotrophin receptor signaling.

    PubMed

    Meabon, James S; de Laat, Rian; Ieguchi, Katsuaki; Serbzhinsky, Dmitry; Hudson, Mark P; Huber, B Russel; Wiley, Jesse C; Bothwell, Mark

    2016-01-01

    Neurotrophins, essential regulators of many aspects of neuronal differentiation and function, signal via four receptors, p75, TrkA, TrkB and TrkC. The three Trk paralogs are members of the LIG superfamily of membrane proteins, which share extracellular domains consisting of leucine-rich repeat and C2 Ig domains. Another LIG protein, LINGO-1 has been reported to bind and influence signaling of p75 as well as TrkA, TrkB and TrkC. Here we examine the manner in which LINGO-1 influences the function of TrkA, TrkB and TrkC. We report that Trk activation promotes Trk association with LINGO-1, and that this association promotes Trk degradation by a lysosomal mechanism. This mechanism resembles the mechanism by which another LIG protein, LRIG1, promotes lysosomal degradation of receptor tyrosine kinases such as the EGF receptor. We present evidence indicating that the Trk/LINGO-1 interaction occurs, in part, within recycling endosomes. We show that a mutant form of LINGO-1, with much of the extracellular domain deleted, has the capacity to enhance TrkA signaling in PC12 cells, possibly by acting as an inhibitor of Trk down-regulation by full length LINGO-1. We propose that LINGO-1 functions as a negative feedback regulator of signaling by cognate receptor tyrosine kinases including TrkA, TrkB and TrkC.

  19. Regulation of cell differentiation by Eph receptor and ephrin signaling

    PubMed Central

    Wilkinson, David G

    2014-01-01

    There is increasing evidence that in addition to having major roles in morphogenesis, in some tissues Eph receptor and ephrin signaling regulates the differentiation of cells. In one mode of deployment, cell contact dependent Eph-ephrin activation induces a distinct fate of cells at the interface of their expression domains, for example in early ascidian embryos and in the vertebrate hindbrain. In another mode, overlapping Eph receptor and ephrin expression underlies activation within a cell population, which promotes or inhibits cell differentiation in bone remodelling, neural progenitors and keratinocytes. Eph-ephrin activation also contributes to formation of the appropriate number of progenitor cells by increasing or decreasing cell proliferation. These multiple roles of Eph receptor and ephrin signaling may enable a coupling between morphogenesis and the differentiation and proliferation of cells. PMID:25482623

  20. Regulation of Golgi signaling and trafficking by the KDEL receptor.

    PubMed

    Cancino, Jorge; Jung, Juan E; Luini, Alberto

    2013-10-01

    Intracellular membrane transport involves the well-coordinated engagement of a series of organelles and molecular machineries that ensure that proteins are delivered to their correct cellular locations according to their function. To maintain the homeostasis of the secretory system, the fluxes of membranes and protein across the transport compartments must be precisely balanced. This control should rely on a mechanism that senses the movement of the traffic and generates the required homeostatic response. Due to its central position in the secretory pathway and to the large amounts of signaling molecules associated with it, the Golgi complex represents the ideal candidate for this regulation. The generation of autonomous signaling by the Golgi complex in response to the arrival of cargo from the endoplasmic reticulum (ER) has been experimentally addressed only in recent years. These studies have revealed that cargo moving from the ER to the Golgi activates a series of signaling pathways, the functional significance of which appears to be to maintain the homeostasis of the Golgi complex and to activate Golgi trafficking according to internal demand. We have termed this regulatory mechanism the Golgi control system. A key player in this Golgi control system is the KDEL receptor, which has previously been shown to retrieve chaperones back to the endoplasmic reticulum and more recently to behave as a signaling receptor. Here, we discuss the particular role of KDEL receptor signaling in the regulation of important pathways involved in the maintenance of the homeostasis of the transport apparatus, and in particular, of the Golgi complex.

  1. Structure of an extracellular gp130 cytokine receptor signaling complex.

    PubMed

    Chow, D; He, X; Snow, A L; Rose-John, S; Garcia, K C

    2001-03-16

    The activation of gp130, a shared signal-transducing receptor for a family of cytokines, is initiated by recognition of ligand followed by oligomerization into a higher order signaling complex. Kaposi's sarcoma-associated herpesvirus encodes a functional homolog of human interleukin-6 (IL-6) that activates human gp130. In the 2.4 angstrom crystal structure of the extracellular signaling assembly between viral IL-6 and human gp130, two complexes are cross-linked into a tetramer through direct interactions between the immunoglobulin domain of gp130 and site III of viral IL-6, which is necessary for receptor activation. Unlike human IL-6 (which uses many hydrophilic residues), the viral cytokine largely uses hydrophobic amino acids to contact gp130, which enhances the complementarity of the viral IL-6-gp130 binding interfaces. The cross-reactivity of gp130 is apparently due to a chemical plasticity evident in the amphipathic gp130 cytokine-binding sites.

  2. Signal Transduction by Vascular Endothelial Growth Factor Receptors

    PubMed Central

    Koch, Sina; Claesson-Welsh, Lena

    2012-01-01

    Vascular endothelial growth factors (VEGFs) are master regulators of vascular development and of blood and lymphatic vessel function during health and disease in the adult. It is therefore important to understand the mechanism of action of this family of five mammalian ligands, which act through three receptor tyrosine kinases (RTKs). In addition, coreceptors like neuropilins (NRPs) and integrins associate with the ligand/receptor signaling complex and modulate the output. Therapeutics to block several of the VEGF signaling components have been developed with the aim to halt blood vessel formation, angiogenesis, in diseases that involve tissue growth and inflammation, such as cancer. In this review, we outline the current information on VEGF signal transduction in relation to blood and lymphatic vessel biology. PMID:22762016

  3. Metabotropic glutamate receptor-mediated signaling in neuroglia

    PubMed Central

    Loane, David J.; Stoica, Bogdan A.; Faden, Alan I.

    2011-01-01

    Metabotropic glutamate (mGlu) receptors are G-protein-coupled receptors, which include eight subtypes that have been classified into three groups (I–III) based upon sequence homology, signal transduction mechanism and pharmacological profile. Although most studied with regard to neuronal function and modulation, mGlu receptors are also expressed by neuroglia-including astrocytes, microglia and oligodendrocytes. Activation of mGlu receptors on neuroglia under both physiologic and pathophysiologic conditions mediates numerous actions that are essential for intrinsic glial cell function, as well as for glial–neuronal interactions. Astrocyte mGlu receptors play important physiological roles in regulating neurotransmission and maintaining neuronal homeostasis. However, mGlu receptors on astrocytes and microglia also serve to modulate cell death and neurological function in a variety of pathophysiological conditions such as acute and chronic neurodegenerative disorders. The latter effects are complex and bi-directional, depending on which mGlu receptor sub-types are activated. PMID:22662309

  4. Inhibition of the regulator of G protein signalling RGS4 in the spinal cord decreases neuropathic hyperalgesia and restores cannabinoid CB1 receptor signalling

    PubMed Central

    Bosier, Barbara; Doyen, Pierre J.; Brolet, Amandine; Muccioli, Giulio G.; Ahmed, Eman; Desmet, Nathalie; Hermans, Emmanuel

    2015-01-01

    Background and Purpose Regulators of G protein signalling (RGS) are major determinants of metabotropic receptor activity, reducing the lifespan of the GTP‐bound state of G proteins. Because the reduced potency of analgesic agents in neuropathic pain may reflect alterations in RGS, we assessed the effects of CCG 63802, a specific RGS4 inhibitor, on pain hypersensitivity and signalling through cannabinoid receptors, in a model of neuropathic pain. Experimental Approach The partial sciatic nerve ligation (PSNL) model in male Sprague Dawley rats was used to measure paw withdrawal thresholds to mechanical (von Frey hairs) or thermal (Hargreaves method) stimuli, during and after intrathecal injection of CCG 63802. HEK293 cells expressing CB1 receptors and conditional expression of RGS4 were used to correlate cAMP production and ERK phosphorylation with receptor activation and RGS4 action. Key Results Treatment of PSNL rats with CCG 63802, twice daily for 7 days after nerve injury, attenuated thermal hyperalgesia during treatment. Spinal levels of anandamide were higher in PSNL animals, irrespective of the treatment. Although expression of CB1 receptors was unaffected, HU210‐induced CB1 receptor signalling was inhibited in PSNL rats and restored after intrathecal CCG 63802. In transfected HEK cells expressing CB1 receptors and RGS4, inhibition of cAMP production, a downstream effect of CB1 receptor signalling, was blunted after RGS4 overexpression. RGS4 expression also attenuated the CB1 receptor‐controlled activation of ERK1/2. Conclusions and Implications Inhibition of spinal RGS4 restored endogenous analgesic signalling pathways and mitigated neuropathic pain. Signalling through CB1 receptors may be involved in this beneficial effect PMID:26478461

  5. Inflammatory Mediators and Insulin Resistance in Obesity: Role of Nuclear Receptor Signaling in Macrophages

    PubMed Central

    Fuentes, Lucía; Rőszer, 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. PMID:20508742

  6. 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.

  7. Constitutively active Lck kinase in T cells drives antigen receptor signal transduction.

    PubMed

    Nika, Konstantina; Soldani, Cristiana; Salek, Mogjiborahman; Paster, Wolfgang; Gray, Adrian; Etzensperger, Ruth; Fugger, Lars; Polzella, Paolo; Cerundolo, Vincenzo; Dushek, Omer; Höfer, Thomas; Viola, Antonella; Acuto, Oreste

    2010-06-25

    T cell antigen receptor (TCR) and coreceptor ligation is thought to initiate signal transduction by inducing activation of the kinase Lck. Here we showed that catalytically active Lck was present in unstimulated naive T cells and thymocytes and was readily detectable in these cells in lymphoid organs. In naive T cells up to approximately 40% of total Lck was constitutively activated, part of which was also phosphorylated on the C-terminal inhibitory site. Formation of activated Lck was independent of TCR and coreceptors but required Lck catalytic activity and its maintenance relied on monitoring by the HSP90-CDC37 chaperone complex to avoid degradation. The amount of activated Lck did not change after TCR and coreceptor engagement; however it determined the extent of TCR-zeta phosphorylation. Our findings suggest a dynamic regulation of Lck activity that can be promptly utilized to initiate T cell activation and have implications for signaling by other immune receptors.

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

    PubMed

    Lynch, Jennifer R; Wang, Jenny Yingzi

    2016-05-11

    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.

  9. 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

  10. 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

  11. 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.

  12. NOTCH, a new signaling pathway implicated in holoprosencephaly

    PubMed Central

    Dupé, Valérie; Rochard, Lucie; Mercier, Sandra; Le Pétillon, Yann; Gicquel, Isabelle; Bendavid, Claude; Bourrouillou, Georges; Kini, Usha; Thauvin-Robinet, Christel; Bohan, Timothy P.; Odent, Sylvie; Dubourg, Christèle; David, Véronique

    2011-01-01

    Genetics of Holoprosencephaly (HPE), a congenital malformation of the developing human forebrain, is due to multiple genetic defects. Most genes that have been implicated in HPE belong to the Sonic Hedgehog (SHH) signaling pathway. Here we describe a new candidate gene isolated from array CGH redundant 6qter deletions, DELTA Like 1 (DLL1), which is a ligand of NOTCH. We show that DLL1 is co-expressed in the developing chick forebrain with Fgf8. By treating chick embryos with a pharmacological inhibitor, we demonstrate that DLL1 interacts with FGF signaling pathway. Moreover, a mutation analysis of DLL1 in HPE patients, revealed a three-nucleotide deletion. These various findings implicate DLL1 in early patterning of the forebrain and identify NOTCH as a new signaling pathway involved in HPE. PMID:21196490

  13. Roles of CLR/RAMP Receptor Signaling in Reproduction and Development

    PubMed Central

    Chang, Chia Lin; Hsu, Sheau Yu Teddy

    2016-01-01

    Adrenomedullin (ADM), calcitonin gene-related peptides (α- and β-CGRPs), and intermedin/adrenomedullin 2 (IMD/ADM2) are major regulators of vascular tone and cardiovascular development in vertebrates. Recent research into their functions in reproduction has illuminated the role of these peptides and their cognate receptors (calcitonin receptor-like receptor/receptor activity-modifying protein (CLR/RAMP) receptors) in fetal–maternal blood circulation, feto-placental development, female gamete development, and gamete movement in the oviduct. Although ADM family peptides function in a temporally and spatially specific manner in various reproductive processes, they appear to act via a similar set of second messengers, including nitric oxide, cyclic GMP, cyclic AMP, and calcium-activated potassium channels in different tissues. These discoveries supported the view that CLR/RAMP receptors were recruited to perform a variety of newly evolved reproductive functions during the evolution of internal reproduction in mammals. These advances also provided insight into how CLR/RAMP receptor signaling pathways coordinate with other physiological adaptions to accommodate the extra metabolic needs during pregnancy, and captured some important details as to how fetal–maternal vascular communications are generated in the first place. Furthermore, these findings have revealed novel, promising opportunities for the prevention and treatment of aberrant pregnancies such as pregnancy-induced hypertension, preeclampsia, and tubal ectopic pregnancy. However, significant efforts are still needed to clarify the relationships between certain components of the CLR/RAMP signaling pathway and aberrant pregnancies before CLR/RAMP receptors can become targets for clinical management. With this understanding, this review summarizes recent progresses with particular focus on clinical implications. PMID:23745703

  14. 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

  15. 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

  16. Regulator of G protein signaling proteins differentially modulate signaling of μ and δ opioid receptors

    PubMed Central

    Xie, Zhihua; Li, Zhisong; Guo, Lei; Ye, Caiying; Li, Juan; Yu, Xiaoli; Yang, Huifen; Wang, Yulin; Chen, Chongguang; Zhang, Dechang; Liu-Chen, Lee-Yuan

    2009-01-01

    Effects of regulator of G protein signaling (RGS) proteins on μ and δ opioid receptors were investigated in HEK293 cells. Co-expression of RGS1, RGS2, RGS4, RGS9, RGS10 or RGS19 (Gα-interacting protein (GAIP)) significantly reduced [Tyr-D-Ala-Gly-N-methyl-Phe-Gly-ol]-Enkephalin (DAMGO)-induced inhibition of adenylyl cyclase (AC) mediated by μ opioid receptor, but only RGS9 decreased the effects of [Tyr-D-Pen-Gly-p-Chloro-Phe-D-Pen]-Enkephalin (DPDPE) mediated by δ opioid receptor. When C-tails of the receptors were exchanged (μ/δC and δ/μC chimeras), RGS proteins decreased δ/μC-mediated AC inhibition, but none had significant effects on that via μ/δC receptor. Thus, the C-terminal domains of the receptors are critical for the differential effects of RGS proteins, which may be due to differences in receptor - G protein - RGS protein interactions in signaling complexes. PMID:17433292

  17. 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

    2015-03-01

    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. © 2015 The Authors. Published under the terms of the CC BY 4.0 license.

  18. 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

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

    PubMed

    Schmidt, Vanessa; Schulz, Nadja; Yan, Xin; Schürmann, Annette; Kempa, Stefan; Kern, Matthias; Blüher, Matthias; Poy, Matthew N; Olivecrona, Gunilla; Willnow, Thomas E

    2016-07-01

    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.

  20. Biological Signaling: the Role of ``Electrostatic Epicenter'' in ``Protein Quake'' and Receptor Activation

    NASA Astrophysics Data System (ADS)

    Xie, Aihua; Kaledhonkar, Sandip; Kang, Zhouyang; Hendriks, Johnny; Hellingwerf, Klaas

    2013-03-01

    Activation of a receptor protein during biological signaling is often characterized by a two state model: a receptor state (also called ``off state'') for detection of a stimuli, and a signaling state (``on state'') for signal relay. Receptor activation is a process that a receptor protein is structurally transformed from its receptor state to its signaling state through substantial conformational changes that are recognizable by its downstream signal relay partner. What are the structural and energetic origins for receptor activation in biological signaling? We report extensive evidence that further support the role of ``electrostatic epicenter'' in driving ``protein quake'' and receptor activation. Photoactive yellow protein (PYP), a bacterial blue light photoreceptor protein for the negative phototaxis of a salt loving Halorhodospira halophia, is employed as a model system in this study. We will discuss potential applications of this receptor activation mechanism to other receptor proteins, including B-RAF receptor protein that is associated with many cancers.

  1. G-protein-coupled receptors, Hedgehog signaling and primary cilia.

    PubMed

    Mukhopadhyay, Saikat; Rohatgi, Rajat

    2014-09-01

    The Hedgehog (Hh) pathway has become an important model to study the cell biology of primary cilia, and reciprocally, the study of ciliary processes provides an opportunity to solve longstanding mysteries in the mechanism of vertebrate Hh signal transduction. The cilium is emerging as an unique compartment for G-protein-coupled receptor (GPCR) signaling in many systems. Two members of the GPCR family, Smoothened and Gpr161, play important roles in the Hh pathway. We review the current understanding of how these proteins may function to regulate Hh signaling and also highlight some of the critical unanswered questions being tackled by the field. Uncovering GPCR-regulated mechanisms important in Hh signaling may provide therapeutic strategies against the Hh pathway that plays important roles in development, regeneration and cancer.

  2. Receptor signaling clusters in the immune synapse(in eng)

    DOE PAGES

    Dustin, Michael L.; Groves, Jay T.

    2012-02-23

    Signaling processes between various immune cells involve large-scale spatial reorganization of receptors and signaling molecules within the cell-cell junction. These structures, now collectively referred to as immune synapses, interleave physical and mechanical processes with the cascades of chemical reactions that constitute signal transduction systems. Molecular level clustering, spatial exclusion, and long-range directed transport are all emerging as key regulatory mechanisms. The study of these processes is drawing researchers from physical sciences to join the effort and represents a rapidly growing branch of biophysical chemistry. Furthermore, recent advances in physical and quantitative analyses of signaling within the immune synapses are reviewedmore » here.« less

  3. A comprehensive pathway map of epidermal growth factor receptor signaling

    PubMed Central

    Oda, Kanae; Matsuoka, Yukiko; Funahashi, Akira; Kitano, Hiroaki

    2005-01-01

    The epidermal growth factor receptor (EGFR) signaling pathway is one of the most important pathways that regulate growth, survival, proliferation, and differentiation in mammalian cells. Reflecting this importance, it is one of the best-investigated signaling systems, both experimentally and computationally, and several computational models have been developed for dynamic analysis. A map of molecular interactions of the EGFR signaling system is a valuable resource for research in this area. In this paper, we present a comprehensive pathway map of EGFR signaling and other related pathways. The map reveals that the overall architecture of the pathway is a bow-tie (or hourglass) structure with several feedback loops. The map is created using CellDesigner software that enables us to graphically represent interactions using a well-defined and consistent graphical notation, and to store it in Systems Biology Markup Language (SBML). PMID:16729045

  4. G-protein—coupled receptors, hedgehog signaling and primary cilia

    PubMed Central

    Mukhopadhyay, Saikat; Rohatgi, Rajat

    2014-01-01

    The Hedgehog (Hh) pathway has become an important model to study diverse aspects of cell biology of the primary cilium, and reciprocally, the study of ciliary processes provides an opportunity to solve longstanding mysteries in the mechanism of vertebrate Hh signal transduction. The cilium is emerging as an unique compartment for G-protein—coupled receptor (GPCR) signaling in many systems. Two members of the GPCR family, Smoothened and Gpr161, play important roles in the Hh pathway. We review the current understanding of how these proteins may function to regulate Hh signaling and also highlight some of the critical unanswered questions being tackled by the field. Uncovering GPCR-regulated mechanisms important in Hh signaling may provide therapeutic strategies against the Hh pathway that plays important roles in development, regeneration and cancer. PMID:24845016

  5. Primary cilia and coordination of receptor tyrosine kinase (RTK) signalling.

    PubMed

    Christensen, Søren T; Clement, Christian A; Satir, Peter; Pedersen, Lotte B

    2012-01-01

    Primary cilia are microtubule-based sensory organelles that coordinate signalling pathways in cell-cycle control, migration, differentiation and other cellular processes critical during development and for tissue homeostasis. Accordingly, defects in assembly or function of primary cilia lead to a plethora of developmental disorders and pathological conditions now known as ciliopathies. In this review, we summarize the current status of the role of primary cilia in coordinating receptor tyrosine kinase (RTK) signalling pathways. Further, we present potential mechanisms of signalling crosstalk and networking in the primary cilium and discuss how defects in ciliary RTK signalling are linked to human diseases and disorders. Copyright © 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

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

    SciTech Connect

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

    2015-03-26

    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. Lastly, we discuss implications of this model for ethylene signaling.

  7. Signaling control of the constitutive androstane receptor (CAR).

    PubMed

    Yang, Hui; Wang, Hongbing

    2014-02-01

    The constitutive androstane receptor (CAR, NR1I3) plays a crucial role in the regulation of drug metabolism, energy homeostasis, and cancer development through modulating the transcription of its numerous target genes. Different from prototypical nuclear receptors, CAR can be activated by either direct ligand binding or ligand-independent (indirect) mechanisms both initiated with nuclear translocation of CAR from the cytoplasm. In comparison to the well-defined ligand-based activation, indirect activation of CAR appears to be exclusively involved in the nuclear translocation through mechanisms yet to be fully understood. Accumulating evidence reveals that without activation, CAR forms a protein complex in the cytoplasm where it can be functionally affected by multiple signaling pathways. In this review, we discuss recent progresses in our understanding of the signaling regulation of CAR nuclear accumulation and activation. We expect that this review will also provide greater insight into the similarity and difference between the mechanisms of direct vs. indirect human CAR activation.

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

    PubMed

    Kuhrt, David; Wojchowski, Don M

    2015-06-04

    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.

  9. Alternate signalling pathways from the interleukin-2 receptor.

    PubMed

    Ellery, Jonathan M; Nicholls, Peter J

    2002-02-01

    Interleukin-2 (IL-2) plays a major role in the proliferation of cell populations during an immune reaction. The beta(c) and gamma(c) subunits of the IL-2 receptor (IL-2R) are sufficient and necessary for signal transduction. Despite lacking known catalytic domains, receptor engagement leads to the activation of a diverse array protein tyrosine kinases (PTKs). In resting or anergised T cells, Jak3 is not activated. Signals arising from the PROX domain of the gamma(c) subunit activate p56(lck) (lck) leading to the induction of anti-apoptotic mechanisms. When Jak3 is activated, in primed T cells, other PTKs predominantly mediate the induction of anti-apoptotic mechanisms and drive cellular proliferation. This review intends to suggest a role for these differences within the context of the immune system.

  10. Cannabinoid-receptor-independent cell signalling by N-acylethanolamines.

    PubMed Central

    Berdyshev, E V; Schmid, P C; Krebsbach, R J; Hillard, C J; Huang, C; Chen, N; Dong, Z; Schmid, H H

    2001-01-01

    Anandamide and other polyunsaturated N-acylethanolamines (NAEs) exert biological activity by binding to cannabinoid receptors. These receptors are linked to G(i/o) proteins and their activation leads to extracellular-signal-regulated protein kinase (ERK) and c-Jun N-terminal kinase (JNK) mitogen-activated protein kinase (MAP kinase) activation, inhibition of cAMP-dependent signalling and complex changes in the expression of various genes. Saturated and monounsaturated NAEs cannot bind to cannabinoid receptors and may thus mediate cell signalling through other targets. Here we report that both saturated/monounsaturated NAEs and anandamide (20:4(n-6) NAE) stimulate cannabinoid-receptor-independent ERK phosphorylation and activator protein-1 (AP-1)-dependent transcriptional activity in mouse epidermal JB6 cells. Using a clone of JB6 P(+) cells with an AP-1 collagen-luciferase reporter construct, we found that 16:0, 18:1(n-9), 18:1(n-7), 18:2(n-6) and 20:4(n-6) NAEs stimulated AP-1-dependent transcriptional activity up to 2-fold, with maximal stimulation at approx. 10-15 microM. Higher NAE concentrations had toxic effects mediated by alterations in mitochondrial energy metabolism. The AP-1 stimulation appeared to be mediated by ERK but not JNK or p38 signalling pathways, because all NAEs stimulated ERK1/ERK2 phosphorylation without having any effect on JNK or p38 kinases. Also, overexpression of dominant negative ERK1/ERK2 kinases completely abolished NAE-induced AP-1 activation. In contrast with 18:1(n-9) NAE and anandamide, the cannabinoid receptor agonist WIN 55,212-2 did not stimulate AP-1 activity and inhibited ERK phosphorylation. The NAE-mediated effects were not attenuated by pertussis toxin and appeared to be NAE-specific, as a close structural analogue, oleyl alcohol, failed to induce ERK phosphorylation. The data support our hypothesis that the major saturated and monounsaturated NAEs are signalling molecules acting through intracellular targets without

  11. 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

  12. Efficient T-cell priming and activation requires signaling through prostaglandin E2 (EP) receptors.

    PubMed

    Sreeramkumar, Vinatha; Hons, Miroslav; Punzón, Carmen; Stein, Jens V; Sancho, David; Fresno, Manuel; Cuesta, Natalia

    2016-01-01

    Understanding the regulation of T-cell responses during inflammation and auto-immunity is fundamental for designing efficient therapeutic strategies against immune diseases. In this regard, prostaglandin E2 (PGE2) is mostly considered a myeloid-derived immunosuppressive molecule. We describe for the first time that T cells secrete PGE2 during T-cell receptor stimulation. In addition, we show that autocrine PGE2 signaling through EP receptors is essential for optimal CD4(+) T-cell activation in vitro and in vivo, and for T helper 1 (Th1) and regulatory T cell differentiation. PGE2 was found to provide additive co-stimulatory signaling through AKT activation. Intravital multiphoton microscopy showed that triggering EP receptors in T cells is also essential for the stability of T cell-dendritic cell (DC) interactions and Th-cell accumulation in draining lymph nodes (LNs) during inflammation. We further demonstrated that blocking EP receptors in T cells during the initial phase of collagen-induced arthritis in mice resulted in a reduction of clinical arthritis. This could be attributable to defective T-cell activation, accompanied by a decline in activated and interferon-γ-producing CD4(+) Th1 cells in draining LNs. In conclusion, we prove that T lymphocytes secret picomolar concentrations of PGE2, which in turn provide additive co-stimulatory signaling, enabling T cells to attain a favorable activation threshold. PGE2 signaling in T cells is also required for maintaining long and stable interactions with DCs within LNs. Blockade of EP receptors in vivo impairs T-cell activation and development of T cell-mediated inflammatory responses. This may have implications in various pathophysiological settings.

  13. Conformational suppression of inter-receptor signaling defects

    PubMed Central

    Ames, Peter; Parkinson, John S.

    2006-01-01

    Motile bacteria follow gradients of attractant and repellent chemicals with high sensitivity. Their chemoreceptors are physically clustered, which may enable them to function as a cooperative array. Although native chemoreceptor molecules are typically transmembrane homodimers, they appear to associate through their cytoplasmic tips to form trimers of dimers, which may be an important architectural element in the assembly and operation of receptor clusters. The five receptors of Escherichia coli that mediate most of its chemotactic and aerotactic behaviors have identical trimer contact residues and have been shown by in vivo crosslinking methods to form mixed trimers of dimers. Mutations at the trimer contact sites of Tsr, the serine chemoreceptor, invariably abrogate Tsr function, but some of those lesions (designated Tsr*) are epistatic and block the function of heterologous chemoreceptors. We isolated and characterized mutations (designated Tar⋀) in the aspartate chemoreceptor that restored function to Tsr* receptors. The suppressors arose at or near the Tar trimer contact sites and acted in an allele-specific fashion on Tsr* partners. Alone, many Tar⋀ receptors were unable to mediate chemotactic responses to aspartate, but all formed clusters with varying efficiencies. Most of those Tar⋀ receptors were epistatic to WT Tsr, but some regained Tar function in combination with a suppressible Tsr* partner. Tar⋀–Tsr* suppression most likely occurs through compensatory changes in the conformation or dynamics of a mixed receptor signaling complex, presumably based on trimer-of-dimer interactions. These collaborative teams may be responsible for the high-gain signaling properties of bacterial chemoreceptors. PMID:16751275

  14. Nicotinic Acetylcholine Receptor Signaling in Tumor Growth and Metastasis

    PubMed Central

    Singh, Sandeep; Pillai, Smitha; Chellappan, Srikumar

    2011-01-01

    Cigarette smoking is highly correlated with the onset of a variety of human cancers, and continued smoking is known to abrogate the beneficial effects of cancer therapy. While tobacco smoke contains hundreds of molecules that are known carcinogens, nicotine, the main addictive component of tobacco smoke, is not carcinogenic. At the same time, nicotine has been shown to promote cell proliferation, angiogenesis, and epithelial-mesenchymal transition, leading to enhanced tumor growth and metastasis. These effects of nicotine are mediated through the nicotinic acetylcholine receptors that are expressed on a variety of neuronal and nonneuronal cells. Specific signal transduction cascades that emanate from different nAChR subunits or subunit combinations facilitate the proliferative and prosurvival functions of nicotine. Nicotinic acetylcholine receptors appear to stimulate many downstream signaling cascades induced by growth factors and mitogens. It has been suggested that antagonists of nAChR signaling might have antitumor effects and might open new avenues for combating tobacco-related cancer. This paper examines the historical data connecting nicotine tumor progression and the recent efforts to target the nicotinic acetylcholine receptors to combat cancer. PMID:21541211

  15. Role of fibroblast growth factor receptor signaling in kidney development.

    PubMed

    Bates, Carlton M

    2011-09-01

    Fibroblast growth factor receptors (Fgfrs) are expressed throughout the developing kidney. Several early studies have shown that exogenous fibroblast growth factors (Fgfs) affect growth and maturation of the metanephric mesenchyme (MM) and ureteric bud (UB). Transgenic mice that over-express a dominant negative receptor isoform develop renal aplasia/severe dysplasia, confirming the importance of Fgfrs in renal development. Furthermore, global deletion of Fgf7, Fgf10, and Fgfr2IIIb (isoform that binds Fgf7 and Fgf10) in mice leads to small kidneys with fewer collecting ducts and nephrons. Deletion of Fgfrl1, a receptor lacking intracellular signaling domains, causes severe renal dysgenesis. Conditional targeting of Fgf8 from the MM interrupts nephron formation. Deletion of Fgfr2 from the UB results in severe ureteric branching and stromal mesenchymal defects, although loss of Frs2α (major signaling adapter for Fgfrs) in the UB causes only mild renal hypoplasia. Deletion of both Fgfr1 and Fgfr2 in the MM results in renal aplasia with defects in MM formation and initial UB elongation and branching. Loss of Fgfr2 in the MM leads to many renal and urinary tract anomalies as well as vesicoureteral reflux. Thus, Fgfr signaling is critical for patterning of virtually all renal lineages at early and later stages of development.

  16. Voltage-gated calcium channels function as Ca2+-activated signaling receptors.

    PubMed

    Atlas, Daphne

    2014-02-01

    Voltage-gated calcium channels (VGCCs) are transmembrane cell surface proteins responsible for multifunctional signals. In response to voltage, VGCCs trigger synaptic transmission, drive muscle contraction, and regulate gene expression. Voltage perturbations open VGCCs enabling Ca(2+) binding to the low affinity Ca(2+) binding site of the channel pore. Subsequent to permeation, Ca(2+) targets selective proteins to activate diverse signaling pathways. It is becoming apparent that the Ca(2+)-bound channel triggers secretion in excitable cells and drives contraction in cardiomyocytes prior to Ca(2+) permeation. Here, I highlight recent data implicating receptor-like function of the Ca(2+)-bound channel in converting external Ca(2+) into an intracellular signal. The two sequential mechanistic perspectives of VGCC function are discussed in the context of the prevailing and long-standing current models of depolarization-evoked secretion and cardiac contraction. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Novel insights into G protein and G protein-coupled receptor signaling in cancer.

    PubMed

    O'Hayre, Morgan; Degese, Maria S; Gutkind, J Silvio

    2014-04-01

    G protein-coupled receptors (GPCRs) play a central role in signal transmission, thereby controlling many facets of cellular function. Overwhelming evidence now implicates GPCRs, G proteins and their downstream signaling targets in cancer initiation and progression, where they can influence aberrant cell growth and survival, largely through activation of AKT/mTOR, MAPKs, and Hippo signaling pathways. GPCRs also play critical roles in the invasion and metastasis of cancer cells via activation of Rho GTPases and cytoskeletal changes, and angiogenesis to supply the tumor with nutrients and provide routes for metastasis. Lastly, GPCRs contribute to the establishment and maintenance of a permissive tumor microenvironment. Understanding GPCR involvement in cancer malignancy may help identify novel therapeutic opportunities for cancer prevention and treatment.

  18. Design principles of nuclear receptor signaling: how complex networking improves signal transduction

    PubMed Central

    Kolodkin, Alexey N; Bruggeman, Frank J; Plant, Nick; Moné, Martijn J; Bakker, Barbara M; Campbell, Moray J; van Leeuwen, Johannes P T M; Carlberg, Carsten; Snoep, Jacky L; Westerhoff, Hans V

    2010-01-01

    The topology of nuclear receptor (NR) signaling is captured in a systems biological graphical notation. This enables us to identify a number of ‘design' aspects of the topology of these networks that might appear unnecessarily complex or even functionally paradoxical. In realistic kinetic models of increasing complexity, calculations show how these features correspond to potentially important design principles, e.g.: (i) cytosolic ‘nuclear' receptor may shuttle signal molecules to the nucleus, (ii) the active export of NRs may ensure that there is sufficient receptor protein to capture ligand at the cytoplasmic membrane, (iii) a three conveyor belts design dissipating GTP-free energy, greatly aids response, (iv) the active export of importins may prevent sequestration of NRs by importins in the nucleus and (v) the unspecific nature of the nuclear pore may ensure signal-flux robustness. In addition, the models developed are suitable for implementation in specific cases of NR-mediated signaling, to predict individual receptor functions and differential sensitivity toward physiological and pharmacological ligands. PMID:21179018

  19. Brain-derived neurotrophic factor signaling rewrites the glucocorticoid transcriptome via glucocorticoid receptor phosphorylation.

    PubMed

    Lambert, W Marcus; Xu, Chong-Feng; Neubert, Thomas A; Chao, Moses V; Garabedian, Michael J; Jeanneteau, Freddy D

    2013-09-01

    Abnormal glucocorticoid and neurotrophin signaling has been implicated in numerous psychiatric disorders. However, the impact of neurotrophic signaling on glucocorticoid receptor (GR)-dependent gene expression is not understood. We therefore examined the impact of brain-derived neurotrophic factor (BDNF) signaling on GR transcriptional regulatory function by gene expression profiling in primary rat cortical neurons stimulated with the selective GR agonist dexamethasone (Dex) and BDNF, alone or in combination. Simultaneous treatment with BDNF and Dex elicited a unique set of GR-responsive genes associated with neuronal growth and differentiation and also enhanced the induction of a large number of Dex-sensitive genes. BDNF via its receptor TrkB enhanced the transcriptional activity of a synthetic GR reporter, suggesting a direct effect of BDNF signaling on GR function. Indeed, BDNF treatment induces the phosphorylation of GR at serine 155 (S155) and serine 287 (S287). Expression of a nonphosphorylatable mutant (GR S155A/S287A) impaired the induction of a subset of BDNF- and Dex-regulated genes. Mechanistically, BDNF-induced GR phosphorylation increased GR occupancy and cofactor recruitment at the promoter of a BDNF-enhanced gene. GR phosphorylation in vivo is sensitive to changes in the levels of BDNF and TrkB as well as stress. Therefore, BDNF signaling specifies and amplifies the GR transcriptome through a coordinated GR phosphorylation-dependent detection mechanism.

  20. Harnessing Novel Secreted Inhibitors of EGF Receptor Signaling for Breast Cancer Treatment

    DTIC Science & Technology

    2006-04-01

    of EGF Receptor Signaling for Breast Cancer Treatment PRINCIPAL INVESTIGATOR: Mark A. Lemmon, Ph.D. CONTRACTING...Receptor Signaling for Breast Cancer Treatment INTRODUCTION The aim of this research project is to develop novel inhibitors of signaling through receptors...related proteins), thus providing the essential groundwork for developing an innovative approach for breast cancer treatment that will attack the

  1. Implication of PDGF signaling in cigarette smoke-induced pulmonary arterial hypertension in rat.

    PubMed

    Xing, Ai-ping; Hu, Xiao-yun; Shi, Yi-wei; Du, Yong-cheng

    2012-07-01

    Pulmonary artery hypertension (PAH) is a severe disease characterized with progressive increase of pulmonary vascular resistance that finally causes right ventricular failure and premature death. Cigarette smoke (CS) is a major factor of Chronic Obstructive Pulmonary Disease (COPD) that can lead to PAH. However, the mechanism of CS-induced PAH is poorly understood. Mounting evidence supports that pulmonary vascular remodeling play an important role in the development of PAH. PDGF signaling has been demonstrated to be a major mediator of vascular remodeling implicated in PAH. However, the association of PDGF signaling with CS-induced PAH has not been documented. In this study, we investigated CS-induced PAH in rats and the expression of platelet derived growth factor (PDGF) and PDGF receptor (PDGFR) in pulmonary artery. Forty male rats were randomly divided into control group and three experimental groups that were exposed to CS for 1, 2, and 3 months, respectively. CS significantly increased right ventricular systolic pressure (RVSP) and right ventricular hypertrophy index (RVHI). Histology staining demonstrated that CS significantly increased the thickness of pulmonary artery wall and collagen deposition. The expression of PDGF isoform B (PDGF-B) and PDGF receptor beta (PDGFRβ) were significantly increased at both protein and mRNA levels in pulmonary artery of rats with CS exposure. Furthermore, Cigarette smoke extract (CSE) significantly increased rat pulmonary artery smooth muscle cell (PASMC) proliferation, which was inhibited by PDGFR inhibitor Imatinib. Thus, our data suggest PDGF signaling is implicated in CS-induced PAH.

  2. Ca2+ signals evoked by histamine H1 receptors are attenuated by activation of prostaglandin EP2 and EP4 receptors in human aortic smooth muscle cells

    PubMed Central

    Pantazaka, Evangelia; Taylor, Emily J A; Bernard, William G; Taylor, Colin W

    2013-01-01

    Background and Purpose Histamine and prostaglandin E2 (PGE2), directly and via their effects on other cells, regulate the behaviour of vascular smooth muscle (VSM), but their effects on human VSM are incompletely resolved. Experimental Approach The effects of PGE2 on histamine-evoked changes in intracellular free Ca2+ concentration ([Ca2+]i) and adenylyl cyclase activity were measured in populations of cultured human aortic smooth muscle cells (ASMCs). Selective ligands of histamine and EP receptors were used to identify the receptors that mediate the responses. Key Results Histamine, via H1 receptors, stimulates an increase in [Ca2+]i that is entirely mediated by activation of inositol 1,4,5-trisphosphate receptors. Selective stimulation of EP2 or EP4 receptors attenuates histamine-evoked Ca2+ signals, but the effects of PGE2 on both Ca2+ signals and AC activity are largely mediated by EP2 receptors. Conclusions and Implications Two important inflammatory mediators, histamine via H1 receptors and PGE2 acting largely via EP2 receptors, exert opposing effects on [Ca2+]i in human ASMCs. PMID:23638853

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

    PubMed

    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.

  4. 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

  5. Kinase Cascades and Ligand-Directed Signaling at the Kappa Opioid Receptor

    PubMed Central

    Bruchas, Michael R.; Chavkin, Charles

    2013-01-01

    Background and Rationale The dynorphin / kappa-opioid receptor (KOR) system has been implicated as a critical component of the stress response. Stress-induced activation of dynorphin-KOR is well-known to produce analgesia, and more recently it has been implicated as a mediator of stress-induced responses including anxiety, depression, and reinstatement of drug seeking. Objective Drugs selectively targeting specific KOR signaling pathways may prove potentially useful as therapeutic treatments for mood and addiction disorders. Results KOR is a member of the seven transmembrane spanning (7TM) G-protein coupled receptor (GPCR) superfamily. KOR activation of pertussis toxin-sensitive G proteins leads to Gαi/o inhibition of adenylyl cyclase production of cAMP and releases Gβγ, which modulates the conductances of Ca+2 and K+ channels. In addition, KOR agonists activate kinase cascades including G-protein coupled Receptor Kinases (GRK) and members of the mitogen-activated protein kinase (MAPK) family: ERK1/2, p38 and JNK. Recent pharmacological data suggests that GPCRs exist as dynamic, multi-conformational protein complexes that can be directed by specific ligands towards distinct signaling pathways. Ligand-induced conformations of KOR that evoke β–arrestin-dependent p38 MAPK activation result in aversion; whereas ligand-induced conformations that activate JNK without activating arrestin produce long-lasting inactivation of KOR signaling. Conclusions In this review, we discuss the current status of KOR signal transduction research and the data that support two novel hypotheses: 1) KOR selective partial agonists that do not efficiently activate p38 MAPK may be useful analgesics without producing the dysphoric or hallucinogenic effects of selective, highly efficacious KOR agonists and 2) KOR antagonists that do not activate JNK may be effective short-acting drugs that may promote stress-resilience. PMID:20401607

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

    PubMed Central

    Ochsner, Scott A.; Tsimelzon, Anna; Dong, Jianrong; Coarfa, Cristian

    2016-01-01

    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

  7. Vitamin D receptor-retinoid X receptor heterodimer signaling regulates oligodendrocyte progenitor cell differentiation.

    PubMed

    de la Fuente, Alerie Guzman; Errea, Oihana; van Wijngaarden, Peter; Gonzalez, Ginez A; Kerninon, Christophe; Jarjour, Andrew A; Lewis, Hilary J; Jones, Clare A; Nait-Oumesmar, Brahim; Zhao, Chao; Huang, Jeffrey K; ffrench-Constant, Charles; Franklin, Robin J M

    2015-12-07

    The mechanisms regulating differentiation of oligodendrocyte (OLG) progenitor cells (OPCs) into mature OLGs are key to understanding myelination and remyelination. Signaling via the retinoid X receptor γ (RXR-γ) has been shown to be a positive regulator of OPC differentiation. However, the nuclear receptor (NR) binding partner of RXR-γ has not been established. In this study we show that RXR-γ binds to several NRs in OPCs and OLGs, one of which is vitamin D receptor (VDR). Using pharmacological and knockdown approaches we show that RXR-VDR signaling induces OPC differentiation and that VDR agonist vitamin D enhances OPC differentiation. We also show expression of VDR in OLG lineage cells in multiple sclerosis. Our data reveal a role for vitamin D in the regenerative component of demyelinating disease and identify a new target for remyelination medicines. © 2015 de la Fuente et al.

  8. Kappa opioid receptor signaling protects cartilage tissue against posttraumatic degeneration

    PubMed Central

    Zhang, Shu; Shkhyan, Ruzanna; Lee, Siyoung; Gullo, Francesca; Petrigliano, Frank A.; Ba, Kai; Wang, Jing

    2017-01-01

    Osteoarthritis is the most common form of arthritis, and pain relief with opioid-like drugs is a commonly used therapeutic for osteoarthritic patients. Recent studies published by our group showed that the kappa opioid receptor (KOR) is highly expressed during human development in joint-forming cells. However, the precise role of this receptor in the skeletal system remains elusive. The main aim of the current study was to investigate the role of KOR signaling in synovial and cartilaginous tissues in pathological conditions. Our data demonstrate that KOR null mice exhibit accelerated cartilage degeneration after injury when compared with WT mice. Activation of KOR signaling increased the expression of anabolic enzymes and inhibited cartilage catabolism and degeneration in response to proinflammatory cytokines such as TNF-α. In addition, selective KOR agonists increased joint lubrication via the activation of cAMP/CREB signaling in chondrocytes and synovial cells. Taken together, these results demonstrate direct effects of KOR agonists on cartilage and synovial cells and reveals a protective effect of KOR signaling against cartilage degeneration after injury. In addition to pain control, local administration of dynorphin or other KOR agonist represents an attractive therapeutic approach in patients with early stages of osteoarthritis. PMID:28097228

  9. Role of fibroblast growth factor receptor signaling in kidney development.

    PubMed

    Bates, Carlton M

    2011-08-01

    Fibroblast growth factor receptors (Fgfrs) consist of four signaling family members and one nonsignaling "decoy" receptor, Fgfr-like 1 (Fgfrl1), all of which are expressed in the developing kidney. Several studies have shown that exogenous fibroblast growth factors (Fgfs) affect growth and maturation of the metanephric mesenchyme (MM) and ureteric bud (UB) in cultured tissues. Transgenic and conditional knockout approaches in whole animals have shown that Fgfr1 and Fgfr2 (predominantly the IIIc isoform) in kidney mesenchyme are critical for early MM and UB formation. Conditional deletion of the ligand, Fgf8, in nephron precursors or global deletion of Fgfrl1 interrupts nephron formation. Fgfr2 (likely the IIIb isoform signaling downstream of Fgf7 and Fgf10) is critical for ureteric morphogenesis. Moreover, Fgfr2 appears to act independently of Frs2α (the major signaling adapter for Fgfrs) in regulating UB branching. Loss of Fgfr2 in the MM leads to many kidney and urinary tract anomalies, including vesicoureteral reflux. Thus Fgfr signaling is critical for patterning of virtually all renal lineages at early and later stages of development.

  10. Odorant-stimulated phosphoinositide signaling in mammalian olfactory receptor neurons

    PubMed Central

    Klasen, K.; Corey, E.A.; Kuck, F.; Wetzel, C.H.; Hatt, H.; Ache, B.W.

    2009-01-01

    Recent evidence has revived interest in the idea that phosphoinositides (PIs) may play a role in signal transduction in mammalian olfactory receptor neurons (ORNs). To provide direct evidence that odorants indeed activate PI signaling in ORNs, we used adenoviral vectors carrying two different fluorescently tagged probes, the pleckstrin homology (PH) domains of phospholipase Cδ1 (PLCδ1) and the general receptor of phosphoinositides (GRP1), to monitor PI activity in the dendritic knobs of ORNs in vivo. Odorants mobilized PI(4,5)P2/IP3 and PI(3,4,5)P3, the substrates and products of PLC and PI3K. We then measured odorant activation of PLC and PI3K in olfactory ciliary-enriched membranes in vitro using a phospholipid overlay assay and ELISAs. Odorants activated both PLC and PI3K in the olfactory cilia within 2 sec of odorant stimulation. Odorant-dependent activation of PLC and PI3K in the olfactory epithelium could be blocked by enzyme-specific inhibitors. Odorants activated PLC and PI3K with partially overlapping specificity. These results provide direct evidence that odorants indeed activate PI signaling in mammalian ORNs in a manner that is consistent with the idea that PI signaling plays a role in olfactory transduction. PMID:19781634

  11. Epidermal Growth Factor Receptor Cell Proliferation Signaling Pathways

    PubMed Central

    Wee, Ping; Wang, Zhixiang

    2017-01-01

    The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that is commonly upregulated in cancers such as in non-small-cell lung cancer, metastatic colorectal cancer, glioblastoma, head and neck cancer, pancreatic cancer, and breast cancer. Various mechanisms mediate the upregulation of EGFR activity, including common mutations and truncations to its extracellular domain, such as in the EGFRvIII truncations, as well as to its kinase domain, such as the L858R and T790M mutations, or the exon 19 truncation. These EGFR aberrations over-activate downstream pro-oncogenic signaling pathways, including the RAS-RAF-MEK-ERK MAPK and AKT-PI3K-mTOR pathways. These pathways then activate many biological outputs that are beneficial to cancer cell proliferation, including their chronic initiation and progression through the cell cycle. Here, we review the molecular mechanisms that regulate EGFR signal transduction, including the EGFR structure and its mutations, ligand binding and EGFR dimerization, as well as the signaling pathways that lead to G1 cell cycle progression. We focus on the induction of CYCLIN D expression, CDK4/6 activation, and the repression of cyclin-dependent kinase inhibitor proteins (CDKi) by EGFR signaling pathways. We also discuss the successes and challenges of EGFR-targeted therapies, and the potential for their use in combination with CDK4/6 inhibitors. PMID:28513565

  12. Structural Dynamics of Insulin Receptor and Transmembrane Signaling.

    PubMed

    Tatulian, Suren A

    2015-09-15

    The insulin receptor (IR) is a (αβ)2-type transmembrane tyrosine kinase that plays a central role in cell metabolism. Each αβ heterodimer consists of an extracellular ligand-binding α-subunit and a membrane-spanning β-subunit that comprises the cytoplasmic tyrosine kinase (TK) domain and the phosphorylation sites. The α- and β-subunits are linked via a single disulfide bridge, and the (αβ)2 tetramer is formed by disulfide bonds between the α-chains. Insulin binding induces conformational changes in IR that reach the intracellular β-subunit followed by a protein phosphorylation and activation cascade. Defects in this signaling process, including IR dysfunction caused by mutations, result in type 2 diabetes. Rational drug design aimed at treatment of diabetes relies on knowledge of the detailed structure of IR and the dynamic structural transformations during transmembrane signaling. Recent X-ray crystallographic studies have provided important clues about the mode of binding of insulin to IR, the resulting structural changes and their transmission to the TK domain, but a complete understanding of the structural basis underlying insulin signaling has not been achieved. This review presents a critical analysis of the current status of the structure-function relationship of IR, with a comparative assessment of the other IR family receptors, and discusses potential advancements that may provide insight into the molecular mechanism of insulin signaling.

  13. 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

  14. Endosomal Signaling of Epidermal Growth Factor Receptor Stimulates Signal Transduction Pathways Leading to Cell Survival

    PubMed Central

    Wang, Yi; Pennock, Steven; Chen, Xinmei; Wang, Zhixiang

    2002-01-01

    In spite of intensified efforts to understand cell signaling from endosomes, there is no direct evidence demonstrating that endosomal signaling is sufficient to activate signal transduction pathways and no evidence to demonstrate that endosomal signaling is able to produce a biological outcome. The lack of breakthrough is due in part to the lack of means to generate endosomal signals without plasma membrane signaling. In this paper, we report the establishment of a system to specifically activate epidermal growth factor (EGF) receptor (EGFR) when it endocytoses into endosomes. We treated cells with EGF in the presence of AG-1478, a specific EGFR tyrosine kinase inhibitor, and monensin, which blocks the recycling of EGFR. This treatment led to the internalization of nonactivated EGF-EGFR complexes into endosomes. The endosome-associated EGFR was then activated by removing AG-1478 and monensin. During this procedure we did not observe any surface EGFR phosphorylation. We also achieved specific activation of endosome-associated EGFR without using monensin. By using this system, we provided original evidence demonstrating that (i) the endosome can serve as a nucleation site for the formation of signaling complexes, (ii) endosomal EGFR signaling is sufficient to activate the major signaling pathways leading to cell proliferation and survival, and (iii) endosomal EGFR signaling is sufficient to suppress apoptosis induced by serum withdrawal. PMID:12242303

  15. G-protein-coupled receptor signaling and neural tube closure defects.

    PubMed

    Shimada, Issei S; Mukhopadhyay, Saikat

    2017-01-30

    Disruption of the normal mechanisms that mediate neural tube closure can result in neural tube defects (NTDs) with devastating consequences in affected patients. With the advent of next-generation sequencing, we are increasingly detecting mutations in multiple genes in NTD cases. However, our ability to determine which of these genes contribute to the malformation is limited by our understanding of the pathways controlling neural tube closure. G-protein-coupled receptors (GPCRs) comprise the largest family of transmembrane receptors in humans and have been historically favored as drug targets. Recent studies implicate several GPCRs and downstream signaling pathways in neural tube development and closure. In this review, we will discuss our current understanding of GPCR signaling pathways in pathogenesis of NTDs. Notable examples include the orphan primary cilia-localized GPCR, Gpr161 that regulates the basal suppression machinery of sonic hedgehog pathway by means of activation of cAMP-protein kinase A signaling in the neural tube, and protease-activated receptors that are activated by a local network of membrane-tethered proteases during neural tube closure involving the surface ectoderm. Understanding the role of these GPCR-regulated pathways in neural tube development and closure is essential toward identification of underlying genetic causes to prevent NTDs. Birth Defects Research 109:129-139, 2017. © 2016 Wiley Periodicals, Inc.

  16. KDM4B is a master regulator of the estrogen receptor signalling cascade.

    PubMed

    Gaughan, Luke; Stockley, Jacqueline; Coffey, Kelly; O'Neill, Daniel; Jones, Dominic L; Wade, Mark; Wright, Jamie; Moore, Madeleine; Tse, Sandy; Rogerson, Lynsey; Robson, Craig N

    2013-08-01

    The importance of the estrogen receptor (ER) in breast cancer (BCa) development makes it a prominent target for therapy. Current treatments, however, have limited effectiveness, and hence the definition of new therapeutic targets is vital. The ER is a member of the nuclear hormone receptor superfamily of transcription factors that requires co-regulator proteins for complete regulation. Emerging evidence has implicated a small number of histone methyltransferase (HMT) and histone demethylase (HDM) enzymes as regulators of ER signalling, including the histone H3 lysine 9 tri-/di-methyl HDM enzyme KDM4B. Two recent independent reports have demonstrated that KDM4B is required for ER-mediated transcription and depletion of the enzyme attenuates BCa growth in vitro and in vivo. Here we show that KDM4B has an overarching regulatory role in the ER signalling cascade by controlling expression of the ER and FOXA1 genes, two critical components for maintenance of the estrogen-dependent phenotype. KDM4B interacts with the transcription factor GATA-3 in BCa cell lines and directly co-activates GATA-3 activity in reporter-based experiments. Moreover, we reveal that KDM4B recruitment and demethylation of repressive H3K9me3 marks within upstream regulatory regions of the ER gene permits binding of GATA-3 to drive receptor expression. Ultimately, our findings confirm the importance of KDM4B within the ER signalling cascade and as a potential therapeutic target for BCa treatment.

  17. Vitamin D receptor signaling in renal and cardiovascular protection.

    PubMed

    Li, Yan Chun

    2013-09-01

    The high prevalence of vitamin D deficiency in patients with chronic kidney disease is believed to be an important risk factor for the cardiorenal syndrome commonly seen in this patient population. African Americans suffer a 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 owing to low subcutaneous photoproduction of vitamin D. Mounting evidence from animal and clinical studies has shown beneficial effects of vitamin D therapy on the renal and cardiovascular systems, and the underlying renoprotective and cardioprotective mechanisms of vitamin D receptor (VDR)-mediated signaling are under intense investigation. In this article, 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 is reviewed.

  18. The role of SLAM family receptors in immune cell signaling.

    PubMed

    Ostrakhovitch, Elena A; Li, Shawn S-C

    2006-12-01

    The signaling lymphocyte-activating molecule (SLAM) family immunoreceptors are expressed in a wide array of immune cells, including both T and B lymphocytes. By virtue of their ability to transduce tyrosine phosphorylation signals through the so-called ITSM (immunoreceptor tyrosine-based switch motif) sequences, they play an important part in regulating both innate and adaptive immune responses. The critical role of the SLAM immunoreceptors in mediating normal immune reactions was highlighted in recent findings that SAP, a SLAM-associated protein, modulates the activities of various immune cells through interactions with different members of the SLAM family expressed in these cells. Importantly, mutations or deletions of the sap gene in humans result in the X-linked lymphoproliferative syndrome. In this review, we summarize current knowledge and survey the latest developments in signal transduction events triggered by the activation of SLAM family receptors in different cell types.

  19. 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

  20. A sharp T-cell antigen receptor signaling threshold for T-cell proliferation

    PubMed Central

    Au-Yeung, Byron B.; Zikherman, Julie; Mueller, James L.; Ashouri, Judith F.; Matloubian, Mehrdad; Cheng, Debra A.; Chen, Yiling; Shokat, Kevan M.; Weiss, Arthur

    2014-01-01

    T-cell antigen receptor (TCR) signaling is essential for activation, proliferation, and effector function of T cells. Modulation of both intensity and duration of TCR signaling can regulate these events. However, it remains unclear how individual T cells integrate such signals over time to make critical cell-fate decisions. We have previously developed an engineered mutant allele of the critical T-cell kinase zeta-chain-associated protein kinase 70 kDa (Zap70) that is catalytically inhibited by a small molecule inhibitor, thereby blocking TCR signaling specifically and efficiently. We have also characterized a fluorescent reporter Nur77–eGFP transgenic mouse line in which T cells up-regulate GFP uniquely in response to TCR stimulation. The combination of these technologies unmasked a sharp TCR signaling threshold for commitment to cell division both in vitro and in vivo. Further, we demonstrate that this threshold is independent of both the magnitude of the TCR stimulus and Interleukin 2. Similarly, we identify a temporal threshold of TCR signaling that is required for commitment to proliferation, after which T cells are able to proliferate in a Zap70 kinase-independent manner. Taken together, our studies reveal a sharp threshold for the magnitude and duration of TCR signaling required for commitment of T cells to proliferation. These results have important implications for understanding T-cell responses to infection and optimizing strategies for immunomodulatory drug delivery. PMID:25136127

  1. 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

  2. Direct interactions between calcitonin-like receptor (CLR) and CGRP-receptor component protein (RCP) regulate CGRP receptor signaling.

    PubMed

    Egea, Sophie C; Dickerson, Ian M

    2012-04-01

    Calcitonin gene-related peptide (CGRP) is a neuropeptide with multiple neuroendocrine roles, including vasodilation, migraine, and pain. The receptor for CGRP is a G protein-coupled receptor (GPCR) that requires three proteins for function. CGRP binds to a heterodimer composed of the GPCR calcitonin-like receptor (CLR) and receptor activity-modifying protein (RAMP1), a single transmembrane protein required for pharmacological specificity and trafficking of the CLR/RAMP1 complex to the cell surface. In addition, the CLR/RAMP1 complex requires a third protein named CGRP-receptor component protein (RCP) for signaling. Previous studies have demonstrated that depletion of RCP from cells inhibits CLR signaling, and in vivo studies have demonstrated that expression of RCP correlates with CLR signaling and CGRP efficacy. It is not known whether RCP interacts directly with CLR to exert its effect. The current studies identified a direct interaction between RCP and an intracellular domain of CLR using yeast two-hybrid analysis and coimmunoprecipitation. When this interacting domain of CLR was expressed as a soluble fusion protein, it coimmunoprecipitated with RCP and inhibited signaling from endogenous CLR. Expression of this dominant-negative domain of CLR did not significantly inhibit trafficking of CLR to the cell surface, and thus RCP may not have a chaperone function for CLR. Instead, RCP may regulate CLR signaling in the cell membrane, and direct interaction between RCP and CLR is required for CLR activation. To date, RCP has been found to interact only with CLR and represents a novel neuroendocrine regulatory step in GPCR signaling.

  3. Direct Interactions between Calcitonin-Like Receptor (CLR) and CGRP-Receptor Component Protein (RCP) Regulate CGRP Receptor Signaling

    PubMed Central

    Egea, Sophie C.

    2012-01-01

    Calcitonin gene-related peptide (CGRP) is a neuropeptide with multiple neuroendocrine roles, including vasodilation, migraine, and pain. The receptor for CGRP is a G protein-coupled receptor (GPCR) that requires three proteins for function. CGRP binds to a heterodimer composed of the GPCR calcitonin-like receptor (CLR) and receptor activity-modifying protein (RAMP1), a single transmembrane protein required for pharmacological specificity and trafficking of the CLR/RAMP1 complex to the cell surface. In addition, the CLR/RAMP1 complex requires a third protein named CGRP-receptor component protein (RCP) for signaling. Previous studies have demonstrated that depletion of RCP from cells inhibits CLR signaling, and in vivo studies have demonstrated that expression of RCP correlates with CLR signaling and CGRP efficacy. It is not known whether RCP interacts directly with CLR to exert its effect. The current studies identified a direct interaction between RCP and an intracellular domain of CLR using yeast two-hybrid analysis and coimmunoprecipitation. When this interacting domain of CLR was expressed as a soluble fusion protein, it coimmunoprecipitated with RCP and inhibited signaling from endogenous CLR. Expression of this dominant-negative domain of CLR did not significantly inhibit trafficking of CLR to the cell surface, and thus RCP may not have a chaperone function for CLR. Instead, RCP may regulate CLR signaling in the cell membrane, and direct interaction between RCP and CLR is required for CLR activation. To date, RCP has been found to interact only with CLR and represents a novel neuroendocrine regulatory step in GPCR signaling. PMID:22315449

  4. Apo-Ghrelin Receptor (apo-GHSR1a) Regulates Dopamine Signaling in the Brain

    PubMed Central

    Kern, Andras; Grande, Cristina; Smith, Roy G.

    2014-01-01

    The orexigenic peptide hormone ghrelin is synthesized in the stomach and its receptor growth hormone secretagogue receptor (GHSR1a) is expressed mainly in the central nervous system (CNS). In this review, we confine our discussion to the physiological role of GHSR1a in the brain. Paradoxically, despite broad expression of GHSR1a in the CNS, other than trace amounts in the hypothalamus, ghrelin is undetectable in the brain. In our efforts to elucidate the function of the ligand-free ghrelin receptor (apo-GHSR1a), we identified subsets of neurons that co-express GHSR1a and dopamine receptors. In this review, we focus on interactions between apo-GHSR1a and dopamine-2 receptor (DRD2) and formation of GHSR1a:DRD2 heteromers in hypothalamic neurons that regulate appetite, and discuss implications for the treatment of Prader–Willi syndrome (PWS). GHSR1a antagonists of distinct chemical structures, a quinazolinone and a triazole, respectively, enhance and inhibit dopamine signaling through GHSR1a:DRD2 heteromers by an allosteric mechanism. This finding illustrates a potential strategy for designing the next generation of drugs for treating eating disorders as well as psychiatric disorders caused by abnormal dopamine signaling. Treatment with a GHSR1a antagonist that enhances dopamine/DRD2 activity in GHSR1a:DRD2 expressing hypothalamic neurons has the potential to inhibit the uncontrollable hyperphagia associated with PWS. DRD2 antagonists are prescribed for treating schizophrenia, but these block dopamine signaling in all DRD2 expressing neurons and are associated with adverse side effects, including enhanced appetite and excessive weight gain. A GHSR1a antagonist of structural class that allosterically blocks dopamine/DRD2 action in GHSR1a:DRD2 expressing neurons would have no effect on neurons expressing DRD2 alone; therefore, the side effects of DRD2 antagonists would potentially be reduced thereby enhancing patient compliance. PMID:25183960

  5. Cannabinoid receptor signaling in progenitor/stem cell proliferation and differentiation.

    PubMed

    Galve-Roperh, Ismael; Chiurchiù, Valerio; Díaz-Alonso, Javier; Bari, Monica; Guzmán, Manuel; Maccarrone, Mauro

    2013-10-01

    Cannabinoids, the active components of cannabis (Cannabis sativa) extracts, have attracted the attention of human civilizations for centuries, much earlier than the discovery and characterization of their substrate of action, the endocannabinoid system (ECS). The latter is an ensemble of endogenous lipids, their receptors [in particular type-1 (CB1) and type-2 (CB2) cannabinoid receptors] and metabolic enzymes. Cannabinoid signaling regulates cell proliferation, differentiation and survival, with different outcomes depending on the molecular targets and cellular context involved. Cannabinoid receptors are expressed and functional from the very early developmental stages, when they regulate embryonic and trophoblast stem cell survival and differentiation, and thus may affect the formation of manifold adult specialized tissues derived from the three different germ layers (ectoderm, mesoderm and endoderm). In the ectoderm-derived nervous system, both CB1 and CB2 receptors are present in neural progenitor/stem cells and control their self-renewal, proliferation and differentiation. CB1 and CB2 show opposite patterns of expression, the former increasing and the latter decreasing along neuronal differentiation. Recently, endocannabinoid (eCB) signaling has also been shown to regulate proliferation and differentiation of mesoderm-derived hematopoietic and mesenchymal stem cells, with a key role in determining the formation of several cell types in peripheral tissues, including blood cells, adipocytes, osteoblasts/osteoclasts and epithelial cells. Here, we will review these new findings, which unveil the involvement of eCB signaling in the regulation of progenitor/stem cell fate in the nervous system and in the periphery. The developmental regulation of cannabinoid receptor expression and cellular/subcellular localization, together with their role in progenitor/stem cell biology, may have important implications in human health and disease. Copyright © 2013 Elsevier Ltd

  6. Postoperative ileus involves interleukin-1 receptor signaling in enteric glia.

    PubMed

    Stoffels, Burkhard; Hupa, Kristof Johannes; Snoek, Susanne A; van Bree, Sjoerd; Stein, Kathy; Schwandt, Timo; Vilz, Tim O; Lysson, Mariola; Veer, Cornelis Van't; Kummer, Markus P; Hornung, Veit; Kalff, Joerg C; de Jonge, Wouter J; Wehner, Sven

    2014-01-01

    Postoperative ileus (POI) is a common consequence of abdominal surgery that increases the risk of postoperative complications and morbidity. We investigated the cellular mechanisms and immune responses involved in the pathogenesis of POI. We studied a mouse model of POI in which intestinal manipulation leads to inflammation of the muscularis externa and disrupts motility. We used C57BL/6 (control) mice as well as mice deficient in Toll-like receptors (TLRs) and cytokine signaling components (TLR-2(-/-), TLR-4(-/-), TLR-2/4(-/-), MyD88(-/-), MyD88/TLR adaptor molecule 1(-/-), interleukin-1 receptor [IL-1R1](-/-), and interleukin (IL)-18(-/-) mice). Bone marrow transplantation experiments were performed to determine which cytokine receptors and cell types are involved in the pathogenesis of POI. Development of POI did not require TLRs 2, 4, or 9 or MyD88/TLR adaptor molecule 2 but did require MyD88, indicating a role for IL-1R1. IL-1R1(-/-) mice did not develop POI; however, mice deficient in IL-18, which also signals via MyD88, developed POI. Mice given injections of an IL-1 receptor antagonist (anakinra) or antibodies to deplete IL-1α and IL-1β before intestinal manipulation were protected from POI. Induction of POI activated the inflammasome in muscularis externa tissues of C57BL6 mice, and IL-1α and IL-1β were released in ex vivo organ bath cultures. In bone marrow transplantation experiments, the development of POI required activation of IL-1 receptor in nonhematopoietic cells. IL-1R1 was expressed by enteric glial cells in the myenteric plexus layer, and cultured primary enteric glia cells expressed IL-6 and the chemokine monocyte chemotactic protein 1 in response to IL-1β stimulation. Immunohistochemical analysis of human small bowel tissue samples confirmed expression of IL-1R1 in the ganglia of the myenteric plexus. IL-1 signaling, via IL-1R1 and MyD88, is required for development of POI after intestinal manipulation in mice. Agents that interfere with

  7. Sphingosine kinase-mediated calcium signaling by muscarinic acetylcholine receptors.

    PubMed

    van Koppen, C J; Meyer zu Heringdorf, D; Alemany, R; Jakobs, K H

    2001-04-27

    Based on the finding that G protein-coupled receptors (GPCRs) can induce Ca2+ mobilization, apparently independent of the phospholipase C (PLC)/inositol-1,4,5-trisphosphate (IP3) pathway, we investigated whether sphingosine kinase, which generates sphingosine-1-phosphate (SPP), is involved in calcium signaling by mAChR and other GPCRs. Inhibition of sphingosine kinase by DL-threo-dihydrosphingosine and N,/N-dimethylsphingosine markedly inhibited [Ca2+]i increases elicited by M2 and M3 mAChRs in HEK-293 cells without affecting PLC activation. Activation of M2 and M3 mAChR rapidly and transiently stimulated production of SPP. Furthermore, microinjection of SPP into HEK-293 cells induced rapid and transient Ca2+ mobilization. Pretreatment of HEK-293 cells with the calcium chelator BAPTA/AM fully blocked mAChR-induced SPP production. On the other hand, incubation of HEK-293 cells with calcium ionophores activated SPP production. Similar findings were obtained for formyl peptide and P2Y2 purinergic receptors in HL-60 cells. On the basis of these studies we propose, that following initial IP3 production by receptor-mediated PLC activation, a local discrete increase in [Ca2+]i induces sphingosine kinase stimulation, which ultimately leads to full calcium mobilization. Thus, sphingosine kinase activation most likely represents an amplification system for calcium signaling by mAChRs and other GPCRs.

  8. 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

  9. 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. Copyright © 2016. Published by Elsevier Inc.

  10. The glucocorticoid receptor dimer interface allosterically transmits sequence-specific DNA signals.

    PubMed

    Watson, Lisa C; Kuchenbecker, Kristopher M; Schiller, Benjamin J; Gross, John D; Pufall, Miles A; Yamamoto, Keith R

    2013-07-01

    Glucocorticoid receptor (GR) binds to genomic response elements and regulates gene transcription with cell and gene specificity. Within a response element, the precise sequence to which the receptor binds has been implicated in directing its structure and activity. Here, we use NMR chemical-shift difference mapping to show that nonspecific interactions with bases at particular positions in the binding sequence, such as those of the 'spacer', affect the conformation of distinct regions of the rat GR DNA-binding domain. These regions include the DNA-binding surface, the 'lever arm' and the dimerization interface, suggesting an allosteric pathway that signals between the DNA-binding sequence and the associated dimer partner. Disrupting this pathway by mutating the dimer interface alters sequence-specific conformations, DNA-binding kinetics and transcriptional activity. Our study demonstrates that GR dimer partners collaborate to read DNA shape and to direct sequence-specific gene activity.

  11. Novel Role for the Innate Immune Receptor Toll-Like Receptor 4 (TLR4) in the Regulation of the Wnt Signaling Pathway and Photoreceptor Apoptosis

    PubMed Central

    Yi, Hyun; Patel, Amit K.; Sodhi, Chhinder P.; Hackam, David J.; Hackam, Abigail S.

    2012-01-01

    Recent evidence has implicated innate immunity in regulating neuronal survival in the brain during stroke and other neurodegenerations. Photoreceptors are specialized light-detecting neurons in the retina that are essential for vision. In this study, we investigated the role of the innate immunity receptor TLR4 in photoreceptors. TLR4 activation by lipopolysaccharide (LPS) significantly reduced the survival of cultured mouse photoreceptors exposed to oxidative stress. With respect to mechanism, TLR4 suppressed Wnt signaling, decreased phosphorylation and activation of the Wnt receptor LRP6, and blocked the protective effect of the Wnt3a ligand. Paradoxically, TLR4 activation prior to oxidative injury protected photoreceptors, in a phenomenon known as preconditioning. Expression of TNFα and its receptors TNFR1 and TNFR2 decreased during preconditioning, and preconditioning was mimicked by TNFα antagonists, but was independent of Wnt signaling. Therefore, TLR4 is a novel regulator of photoreceptor survival that acts through the Wnt and TNFα pathways. PMID:22615780

  12. [Negative regulation of Toll-like receptor signalling].

    PubMed

    Antosz, Halina; Choroszyńska, Dorota

    2013-04-25

    The mechanism of innate immunity is based on the pattern recognition receptors (PRR) that recognize molecular patterns associated with pathogens (PAMPs). Among PRR receptors Toll-like receptors (TLR) are distinguished. As a result of contact with pathogens, TLRs activate specific intracellular signaling pathways. It happens through proteins such as adaptor molecules, e.g. MyD88, TIRAP, TRIF, TRAM, and IPS-1, which participate in the cascade activation of kinases (IKK, MAP, RIP-1, TBK-1) as well as transcription factors (NF-κB, AP-1) and regulatory factor (IRF3). The result of this activation is the production of active proinflammatory cytokines, chemokines, interferons and enzymes. The PRR pathways are controlled by extra- and intracellular molecules to prevent overexpression of PRR. They include soluble receptors (sTLR), transmembrane proteins (ST2, SIGIRR, RP105, TRAIL-R) and intracellular inhibitors (SOCS-1, SOCS-3, sMyD88, TOLLIP, IRAK-M, SARM, A20, β-arrestin, CYLD, SHP). These molecules maintain the balance between activation and inhibition and ensure balancing of the beneficial and adverse effects of antigen recognition.

  13. Role of fibroblast growth factor receptor signaling in kidney development.

    PubMed

    Bates, Carlton M

    2007-03-01

    Fibroblast growth factor receptors (Fgfrs) are expressed in the ureteric bud and metanephric mesenchyme of the developing kidney. Furthermore, in vitro and in vivo studies have shown that exogenous fibroblast growth factors (Fgfs) increase growth and maturation of the metanephric mesenchyme and ureteric bud. Deletion of fgf7, fgf10, and fgfr2IIIb (the receptor isoform that binds Fgf7 and Fgf10) in mice lead to smaller kidneys with fewer collecting ducts and nephrons. Overexpression of a dominant negative receptor isoform in transgenic mice has revealed more striking defects including renal aplasia or severe dysplasia. Moreover, deletion of many fgf ligands and receptors in mice results in early embryonic lethality, making it difficult to determine their roles in kidney development. Recently, conditional targeting approaches revealed that deletion of fgf8 from the metanephric mesenchyme interrupts nephron formation. Furthermore, deletion of fgfr2 from the ureteric bud resulted in both ureteric bud branching and stromal mesenchymal patterning defects. Deletion of both fgfr1 and fgfr2 in the metanephric mesenchyme resulted in renal aplasia, characterized by defects in metanephric mesenchyme formation and initial ureteric bud elongation and branching. Thus, Fgfr signaling is critical for growth and patterning of all renal lineages at early and later stages of kidney development.

  14. 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

  15. Structure–Function Analysis of Delta Trafficking, Receptor Binding and Signaling in Drosophila

    PubMed Central

    Parks, Annette L.; Stout, Jane R.; Shepard, Scott B.; Klueg, Kristin M.; Dos Santos, Ana A.; Parody, Todd R.; Vaskova, Martina; Muskavitch, Marc A. T.

    2006-01-01

    The transmembrane proteins Delta and Notch act as ligand and receptor in a conserved signaling pathway required for a variety of cell fate specification events in many organisms. Binding of Delta to Notch results in a proteolytic cascade that releases the Notch intracellular domain, allowing it to participate in transcriptional activation in the nucleus. Recent research has implicated the endocytic and ubiquitylation machinery as essential components of Delta–Notch signaling. Our analysis of chimeric and missense Delta variants has delineated a number of structural requirements for Delta trafficking, receptor binding, and signaling. We find that while the Delta N-terminal domain is necessary and sufficient for binding to Notch, the integrity of the epidermal-growth-factor-like repeat (ELR) 2 is also required for Notch binding. Screening of 117 Delta mutant lines for proteins that exhibit aberrant subcellular trafficking has led to the identification of 18 Delta alleles (DlTD alleles) that encode “trafficking-defective” Delta proteins. We find, unexpectedly, that many DlTD alleles contain missense mutations in ELRs within the Delta extracellular domain. Finally, we find that two DlTD alleles contain lysine missense mutations within the Delta intracellular domain (DeltaICD) that may identify residues important for DeltaICD mono-ubiquitylation and subsequent Delta endocytosis and signaling. PMID:17028337

  16. Toll-like receptor signaling in primary immune deficiencies

    PubMed Central

    Maglione, Paul J.; Simchoni, Noa; Cunningham-Rundles, Charlotte

    2015-01-01

    Toll-like receptors (TLRs) recognize common microbial or host-derived macromolecules and have important roles in early activation of the immune system. Patients with primary immune deficiencies (PIDs) affecting TLR signaling can elucidate the importance of these proteins to the human immune system. Defects in interleukin-1 receptor-associated kinase (IRAK)-4 and myeloid differentiation factor 88 (MyD88) lead to susceptibility to infections with bacteria, while mutations in nuclear factor-κB essential modulator (NEMO) and other downstream mediators generally induce broader susceptibility to bacteria, viruses, and fungi. In contrast, TLR3 signaling defects are specific for susceptibility to herpes simplex virus type 1 (HSV-1) encephalitis. Other PIDs induce functional alterations of TLR signaling pathways, such as common variable immunodeficiency in which plasmacytoid dendritic cell (pDC) defects enhance defective responses of B cells to shared TLR agonists. Dampening of TLR responses is seen for TLRs 2 and 4 in chronic granulomatous disease (CGD) and X-linked agammaglobulinemia (XLA). Enhanced TLR responses, meanwhile, are seen for TLRs 5 and 9 in CGD, TLRs 4, 7/8, and 9 in XLA, TLRs 2 and 4 in hyper IgE syndrome, and for most TLRs in adenosine deaminase deficiency. PMID:25930993

  17. Cannabinoid receptor signaling regulates liver development and metabolism

    PubMed Central

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

    2016-01-01

    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. PMID:26884397

  18. Argos inhibits epidermal growth factor receptor signalling by ligand sequestration.

    PubMed

    Klein, Daryl E; Nappi, Valerie M; Reeves, Gregory T; Shvartsman, Stanislav Y; Lemmon, Mark A

    2004-08-26

    The epidermal growth factor receptor (EGFR) has critical functions in development and in many human cancers. During development, the spatial extent of EGFR signalling is regulated by feedback loops comprising both well-understood activators and less well-characterized inhibitors. In Drosophila melanogaster the secreted protein Argos functions as the only known extracellular inhibitor of EGFR, with clearly identified roles in multiple stages of development. Argos is only expressed when the Drosophila EGFR (DER) is activated at high levels, and downregulates further DER signalling. Although there is ample genetic evidence that Argos inhibits DER activation, the biochemical mechanism has not been established. Here we show that Argos inhibits DER signalling without interacting directly with the receptor, but instead by sequestering the DER-activating ligand Spitz. Argos binds tightly to the EGF motif of Spitz and forms a 1:1 (Spitz:Argos) complex that does not bind DER in vitro or at the cell surface. Our results provide an insight into the mechanism of Argos function, and suggest new strategies for EGFR inhibitor design.

  19. 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.

  20. Receptor Tyrosine Kinase Signaling – A Proteomic Perspective

    PubMed Central

    Biarc, Jordane; Chalkley, Robert J.; Burlingame, A. L.; Bradshaw, Ralph A.

    2011-01-01

    The stimulation of various cellular processes through extracellular signals is of paramount importance in biological systems and is a central focus in the diagnosis, treatment and prevention of disease. The information transfer is accomplished in a variety of ways by the interaction of soluble, matrix-associated and cell bound ligands that either bind specifically to plasma membrane-associated proteins that act as receptors, or penetrate to the cytoplasmic/nuclear compartments to bind and activate receptors located there. The former class of entities generates intracellular signals that are transmitted and amplified by chemical modifications that are manifested as protein post-translational modifications (PTMs). These are both reversible and irreversible and range from phosphorylation of tyrosine, threonine and serine residues to endoproteolytic cleavages. Although the PTMs alter the activity and functions of many of the proteins in these cascades, the major outcomes of most of the signaling pathways are the activation/deactivation of transcriptional regulators with the concomitant changes in gene expression that generally underlie biological responses. PMID:21056590

  1. Cross-talk of opioid peptide receptor and beta-adrenergic receptor signalling in the heart.

    PubMed

    Pepe, Salvatore; van den Brink, Olivier W V; Lakatta, Edward G; Xiao, Rui-Ping

    2004-08-15

    Opioid peptide receptor (OPR) and beta-adrenergic receptor (beta-AR) are well-established members of G-protein-coupled receptor (GPCR) superfamily and are involved in regulating cardiac contractility, energy metabolism, myocyte survival or death. OPRs are typical Gi/Go-coupled receptors and activated by opioid peptides derived from the endorphin, dynorphin and enkephalin families, whereas beta-AR stimulated by catecholamines is the model system for Gs-coupled receptors. While it is widely accepted that beta-AR stimulation serves as the most powerful means to increase cardiac output in response to stress or exercise, we have only begun to appreciate functional roles of OPR stimulation in regulating cardiovascular performance. Cardiovascular regulatory effects of endogenous opioids were initially considered to originate from the central nervous system and involved the pre-synaptic co-release of norepinephrine with enkephalin from sympathetic neuronal terminals in the heart. However, opioid peptides of myocardial origin have been shown to play important roles in local regulation of the heart. Notably, OPR stimulation not only inhibits cardiac excitation-contraction coupling, but also protects the heart against hypoxic and ischemic injury via activation of Gi-mediated signalling pathways. Further, OPRs functionally and physically cross-talk with beta-ARs via multiple hierarchical mechanisms, including heterodimerization of these receptors, counterbalance of functional opposing G protein signalling, and interface at downstream signalling events. As a result, the beta-AR-mediated positive inotropic effect and increase in cAMP are markedly attenuated by OPR activation in isolated cardiomyocytes as well as sympathectomized intact rat hearts. This brief review will focus on the interaction between beta-AR and OPR and its potential physiological and pathophysiological relevance in the heart. Copryright 2004 European Society of Cardiology

  2. Adenosine receptor modulation: potential implications in veterinary medicine.

    PubMed

    Dip, Ramiro G

    2009-01-01

    Adenosine is a purine nucleoside whose concentration increases during inflammation and hypoxia and the many roles of this molecule are becoming better understood. Increased reactivity to adenosine of the airways of asthmatic but not of normal subjects underlines the role of adenosine in airway inflammation. The identification and pharmacological characterisation of different adenosine receptors have stimulated the search for subtype-specific ligands able to modulate the effects of this molecule in a directed way. Several compounds of different chemical classes have been identified as having potential drawbacks, including side effects resulting from the broad distribution of the receptors across the organism, have prevented clinical application. In this article, the effects of adenosine's different receptors and the intracellular signalling pathways are reviewed. The potential of adenosine receptor modulation as a therapeutic target for chronic airway inflammation is considered, taking equine recurrent airway disease and feline asthma as examples of naturally occurring airway obstructive diseases. Other potential applications for adenosine receptor modulation are also discussed. As the intrinsic molecular events of adenosine's mechanism of action become uncovered, new concrete therapeutic approaches will become available for the treatment of various conditions in veterinary medicine.

  3. P2 receptor-mediated signaling in mast cell biology.

    PubMed

    Bulanova, Elena; Bulfone-Paus, Silvia

    2010-03-01

    Mast cells are widely recognized as effector cells of allergic inflammatory reactions. They contribute to the pathogenesis of different chronic inflammatory diseases, wound healing, fibrosis, thrombosis/fibrinolysis, and anti-tumor immune responses. In this paper, we summarized the role of P2X and P2Y receptors in mast cell activation and effector functions. Mast cells are an abundant source of ATP which is stored in their granules and secreted upon activation. We discuss the contribution of mast cells to the extracellular ATP release and to the maintenance of extracellular nucleotides pool. Recent publications highlight the importance of purinergic signaling for the pathogenesis of chronic airway inflammation. Therefore, the role of ATP and P2 receptors in allergic inflammation with focus on mast cells was analyzed. Finally, ATP functions as mast cell autocrine/paracrine factor and as messenger in intercellular communication between mast cells, nerves, and glia in the central nervous system.

  4. Insulin receptor substrate signaling suppresses neonatal autophagy in the heart

    PubMed Central

    Riehle, Christian; Wende, Adam R.; Sena, Sandra; Pires, Karla Maria; Pereira, Renata Oliveira; Zhu, Yi; Bugger, Heiko; Frank, Deborah; Bevins, Jack; Chen, Dong; Perry, Cynthia N.; Dong, Xiaocheng C.; Valdez, Steven; Rech, Monika; Sheng, Xiaoming; Weimer, Bart C.; Gottlieb, Roberta A.; White, Morris F.; Abel, E. Dale

    2013-01-01

    The induction of autophagy in the mammalian heart during the perinatal period is an essential adaptation required to survive early neonatal starvation; however, the mechanisms that mediate autophagy suppression once feeding is established are not known. Insulin signaling in the heart is transduced via insulin and IGF-1 receptors (IGF-1Rs). We disrupted insulin and IGF-1R signaling by generating mice with combined cardiomyocyte-specific deletion of Irs1 and Irs2. Here we show that loss of IRS signaling prevented the physiological suppression of autophagy that normally parallels the postnatal increase in circulating insulin. This resulted in unrestrained autophagy in cardiomyocytes, which contributed to myocyte loss, heart failure, and premature death. This process was ameliorated either by activation of mTOR with aa supplementation or by genetic suppression of autophagic activation. Loss of IRS1 and IRS2 signaling also increased apoptosis and precipitated mitochondrial dysfunction, which were not reduced when autophagic flux was normalized. Together, these data indicate that in addition to prosurvival signaling, insulin action in early life mediates the physiological postnatal suppression of autophagy, thereby linking nutrient sensing to postnatal cardiac development. PMID:24177427

  5. Crammed signaling motifs in the T-cell receptor.

    PubMed

    Borroto, Aldo; Abia, David; Alarcón, Balbino

    2014-09-01

    Although the T cell antigen receptor (TCR) is long known to contain multiple signaling subunits (CD3γ, CD3δ, CD3ɛ and CD3ζ), their role in signal transduction is still not well understood. The presence of at least one immunoreceptor tyrosine-based activation motif (ITAM) in each CD3 subunit has led to the idea that the multiplication of such elements essentially serves to amplify signals. However, the evolutionary conservation of non-ITAM sequences suggests that each CD3 subunit is likely to have specific non-redundant roles at some stage of development or in mature T cell function. The CD3ɛ subunit is paradigmatic because in a relatively short cytoplasmic sequence (∼55 amino acids) it contains several docking sites for proteins involved in intracellular trafficking and signaling, proteins whose relevance in T cell activation is slowly starting to be revealed. In this review we will summarize our current knowledge on the signaling effectors that bind directly to the TCR and we will propose a hierarchy in their response to TCR triggering.

  6. Signal transduction in podocytes—spotlight on receptor tyrosine kinases

    PubMed Central

    Reiser, Jochen; Sever, Sanja; Faul, Christian

    2014-01-01

    The mammalian kidney filtration barrier is a complex multicellular, multicomponent structure that maintains homeostasis by regulating electrolytes, acid–base balance, and blood pressure (via maintenance of salt and water balance). To perform these multiple functions, podocytes—an important component of the filtration apparatus—must process a series of intercellular signals. Integrating these signals with diverse cellular responses enables a coordinated response to various conditions. Although mature podocytes are terminally differentiated and cannot proliferate, they are able to respond to growth factors. It is possible that the initial response of podocytes to growth factors is beneficial and protective, and might include the induction of hypertrophic cell growth. However, extended and/or uncontrolled growth factor signalling might be maladaptive and could result in the induction of apoptosis and podocyte loss. Growth factors signal via the activation of receptor tyrosine kinases (RTKs) on their target cells and around a quarter of the 58 RTK family members that are encoded in the human genome have been identified in podocytes. Pharmacological inhibitors of many RTKs exist and are currently used in experimental and clinical cancer therapy. The identification of pathological RTK-mediated signal transduction pathways in podocytes could provide a starting point for the development of novel therapies for glomerular disorders. PMID:24394191

  7. Dynamic kisspeptin receptor trafficking modulates kisspeptin-mediated calcium signaling.

    PubMed

    Min, Le; Soltis, Kathleen; Reis, Ana Claudia S; Xu, Shuyun; Kuohung, Wendy; Jain, Manisha; Carroll, Rona S; Kaiser, Ursula B

    2014-01-01

    Kisspeptin receptor (KISS1R) signaling plays a critical role in the regulation of reproduction. We investigated the role of kisspeptin-stimulated KISS1R internalization, recycling, and degradation in the modulation of KISS1R signaling. Kisspeptin stimulation of Chinese hamster ovary or GT1-7 cells expressing KISS1R resulted in a biphasic increase in intracellular Ca(2+) ([Ca(2+)]i), with a rapid acute increase followed by a more sustained second phase. In contrast, stimulation of the TRH receptor, another Gq/11-coupled receptor, resulted in a much smaller second-phase [Ca(2+)]i response. The KISS1R-mediated second-phase [Ca(2+)]i response was abolished by removal of kisspeptin from cell culture medium. Notably, the second-phase [Ca(2+)]i response was also inhibited by dynasore, brefeldin A, and phenylarsine oxide, which inhibit receptor internalization and recycling, suggesting that KISS1R trafficking contributes to the sustained [Ca(2+)]i response. We further demonstrated that KISS1R undergoes dynamic ligand-dependent and -independent recycling. We next investigated the fate of the internalized kisspeptin-KISS1R complex. Most internalized kisspeptin was released extracellularly in degraded form within 1 hour, suggesting rapid processing of the internalized kisspeptin-KISS1R complex. Using a biotinylation assay, we demonstrated that degradation of cell surface KISS1R was much slower than that of the internalized ligand, suggesting dissociated processing of the internalized kisspeptin-KISS1R complex. Taken together, our results suggest that the sustained calcium response to kisspeptin is dependent on the continued presence of extracellular ligand and is the result of dynamic KISS1R trafficking.

  8. 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

  9. 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

  10. Plant cell wall signalling and receptor-like kinases.

    PubMed

    Wolf, Sebastian

    2017-02-15

    Communication between the extracellular matrix and the cell interior is essential for all organisms as intrinsic and extrinsic cues have to be integrated to co-ordinate development, growth, and behaviour. This applies in particular to plants, the growth and shape of which is governed by deposition and remodelling of the cell wall, a rigid, yet dynamic, extracellular network. It is thus generally assumed that cell wall surveillance pathways exist to monitor the state of the wall and, if needed, elicit compensatory responses such as altered expression of cell wall remodelling and biosynthesis genes. Here, I highlight recent advances in the field of cell wall signalling in plants, with emphasis on the role of plasma membrane receptor-like kinase complexes. In addition, possible roles for cell wall-mediated signalling beyond the maintenance of cell wall integrity are discussed. © 2017 The Author(s); published by Portland Press Limited on behalf of the Biochemical Society.

  11. Vitamin D Receptor Signaling and Pancreatic Cancer Cell EMT

    PubMed Central

    Li, Zhiwei; Guo, Junli; Xie, Keping; Zheng, Shaojiang

    2016-01-01

    Pancreatic ductal adenocarcinoma remains one of the most lethal of human malignancies. Even in patients who undergo resection, long-term survival rates remain extremely low. A major contributor to the aggressiveness of pancreatic ductal adenocarcinoma is epithelial-to-mesenchymal transition (EMT), a physiologic process of morphological and genetic changes in carcinoma cells from an epithelial phenotype to a mesenchymal phenotype, which is the basis of the high metastatic potential of pancreatic cancer cells. EMT is triggered by various tumor microenvironmental factors, including cytokines, growth factors, and chemotherapeutic agents. This review highlights the growing evidence of the effect of EMT on pancreatic cancer progression, focusing on the interaction of EMT with other pathways central to cancer progression, especially vitamin D receptor signaling. Studies of the signaling pathways that lead to the inactivation of EMT programs during these disease processes are providing new insights into the plasticity of cellular phenotypes and possible therapeutic interventions. PMID:25506892

  12. 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

  13. 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

  14. Understanding EGFR Signaling in Breast Cancer and Breast Cancer Stem Cells: Overexpression and Therapeutic Implications.

    PubMed

    Alanazi, Ibrahim O; Khan, Zahid

    2016-01-01

    Epidermal growth factor receptors (EGFRs/HERs) and downstream signaling pathways have been implicated in the pathogenesis of several malignancies including breast cancer and its resistance to treatment with chemotherapeutic drugs. Consequently, several monoclonal antibodies as well as small molecule inhibitors targeting these pathways have emerged as therapeutic tools in the recent past. However, studies have shown that utilizing these molecules in combination with chemotherapy has yielded only limited success. This review describes the current understanding of EGFRs/HERs and associated signaling pathways in relation to development of breast cancer and responses to various cancer treatments in the hope of pointing to improved prevention, diagnosis and treatment. Also, we review the role of breast cancer stem cells (BCSCs) in disease and the potential to target these cells.

  15. Activation of NR2A receptors induces ischemic tolerance through CREB signaling.

    PubMed

    Terasaki, Yasukazu; Sasaki, Tsutomu; Yagita, Yoshiki; Okazaki, Shuhei; Sugiyama, Yukio; Oyama, Naoki; Omura-Matsuoka, Emi; Sakoda, Saburo; Kitagawa, Kazuo

    2010-08-01

    Previous exposure to a nonlethal ischemic insult protects the brain against subsequent harmful ischemia. N-methyl-D-aspartate (NMDA) receptors are a highly studied target of neuroprotection after ischemia. Recently, NMDA receptor subtypes were implicated in neuronal survival and death. We focused on the contribution of NR2A and cyclic-AMP response element (CRE)-binding protein (CREB) signaling to ischemic tolerance using primary cortical neurons. Ischemia in vitro was modeled by oxygen-glucose deprivation (OGD). Ischemic tolerance was induced by applying 45-mins OGD 24 h before 180-mins OGD. Sublethal OGD also induced cross-tolerance against lethal glutamate and hydrogen peroxide. After sublethal OGD, expression of phosphorylated CREB and CRE transcriptional activity were significantly increased. When CRE activity was inhibited by CREB-S133A, a mutant CREB, ischemic tolerance was abolished. Inhibiting NR2A using NVP-AAM077 attenuated preconditioning-induced neuroprotection and correlated with decreased CRE activity levels. Activating NR2A using bicuculline and 4-aminopiridine induced resistance to lethal ischemia accompanied by elevated CRE activity levels, and this effect was abolished by NVP-AAM077. Elevated brain-derived neurotrophic factor (BDNF) transcriptional activities were observed after sublethal OGD and administration of bicuculline and 4-aminopiridine. NR2A-containing NMDA receptors and CREB signaling have important functions in the induction of ischemic tolerance. This may provide potential novel therapeutic strategies to treat ischemic stroke.

  16. 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.

  17. Feed-forward transcriptional programming by nuclear receptors: regulatory principles and therapeutic implications.

    PubMed

    Sasse, Sarah K; Gerber, Anthony N

    2015-01-01

    Nuclear receptors (NRs) are widely targeted to treat a range of human diseases. Feed-forward loops are an ancient mechanism through which single cell organisms organize transcriptional programming and modulate gene expression dynamics, but they have not been systematically studied as a regulatory paradigm for NR-mediated transcriptional responses. Here, we provide an overview of the basic properties of feed-forward loops as predicted by mathematical models and validated experimentally in single cell organisms. We review existing evidence implicating feed-forward loops as important in controlling clinically relevant transcriptional responses to estrogens, progestins, and glucocorticoids, among other NR ligands. We propose that feed-forward transcriptional circuits are a major mechanism through which NRs integrate signals, exert temporal control over gene regulation, and compartmentalize client transcriptomes into discrete subunits. Implications for the design and function of novel selective NR ligands are discussed.

  18. Aripiprazole Increases the PKA Signalling and Expression of the GABAA Receptor and CREB1 in the Nucleus Accumbens of Rats.

    PubMed

    Pan, Bo; Lian, Jiamei; Huang, Xu-Feng; Deng, Chao

    2016-05-01

    The GABAA receptor is implicated in the pathophysiology of schizophrenia and regulated by PKA signalling. Current antipsychotics bind with D2-like receptors, but not the GABAA receptor. The cAMP-responsive element-binding protein 1 (CREB1) is also associated with PKA signalling and may be related to the positive symptoms of schizophrenia. This study investigated the effects of antipsychotics in modulating D2-mediated PKA signalling and its downstream GABAA receptors and CREB1. Rats were treated orally with aripiprazole (0.75 mg/kg, ter in die (t.i.d.)), bifeprunox (0.8 mg/kg, t.i.d.), haloperidol (0.1 mg/kg, t.i.d.) or vehicle for 1 week. The levels of PKA-Cα and p-PKA in the prefrontal cortex (PFC), nucleus accumbens (NAc) and caudate putamen (CPu) were detected by Western blots. The mRNA levels of Gabrb1, Gabrb2, Gabrb3 and Creb1, and their protein expression were measured by qRT-PCR and Western blots, respectively. Aripiprazole elevated the levels of p-PKA and the ratio of p-PKA/PKA in the NAc, but not the PFC and CPu. Correlated with this elevated PKA signalling, aripiprazole elevated the mRNA and protein expression of the GABAA (β-1) receptor and CREB1 in the NAc. While haloperidol elevated the levels of p-PKA and the ratio of p-PKA/PKA in both NAc and CPu, it only tended to increase the expression of the GABAA (β-1) receptor and CREB1 in the NAc, but not the CPu. Bifeprunox had no effects on PKA signalling in these brain regions. These results suggest that aripiprazole has selective effects on upregulating the GABAA (β-1) receptor and CREB1 in the NAc, probably via activating PKA signalling.

  19. Cocaine-induced changes in NMDA receptor signaling

    PubMed Central

    Ortinski, Pavel I.

    2014-01-01

    Addictive states are often thought to rely on lasting modification of signaling at relevant synapses. A long-standing theory posits that activity at N-methyl-D-aspartate receptors (NMDARs) is a critical component of long-term synaptic plasticity in many brain areas. Indeed, NMDAR signaling has been found to play a role in the etiology of addictive states, in particular following cocaine exposure. However, no consensus is apparent with respect to the specific effects of cocaine exposure on NMDARs. Part of the difficulty lies in the fact that NMDARs interact extensively with multiple membrane proteins and intracellular signaling cascades. This allows for highly heterogeneous patterns of NMDAR regulation by cocaine in distinct brain regions and at distinct synapses. The picture is further complicated by findings that cocaine effects on NMDARs are sensitive to the behavioral history of cocaine exposure, such as the mode of cocaine administration. This review provides a summary of evidence for cocaine-induced changes in NMDAR expression, cocaine-induced alterations in NMDAR function and cocaine effects on NMDAR control of intracellular signaling cascades. PMID:24445951

  20. Signal transduction by the lipopolysaccharide receptor, Toll-like receptor-4

    PubMed Central

    Pålsson-McDermott, Eva M; O'Neill, Luke A J

    2004-01-01

    An understanding of lipopolysaccharide (LPS) signal transduction is a key goal in the effort to provide a molecular basis for the lethal effect of LPS during septic shock and point the way to novel therapies. Rapid progress in this field during the last 6 years has resulted in the discovery of not only the receptor for LPS – Toll-like receptor 4 (TLR4) – but also in a better appreciation of the complexity of the signalling pathways activated by LPS. Soon after the discovery of TLR4, the formation of a receptor complex in response to LPS, consisting of dimerized TLR4 and MD-2, was described. Intracellular events following the formation of this receptor complex depend on different sets of adapters. An early response, which is dependent on MyD88 and MyD88-like adapter (Mal), leads to the activation of nuclear factor-κB (NF-κB). A later response to LPS makes use of TIR-domain-containing adapter-inducing interferon-β (TRIF) and TRIF-related adapter molecule (TRAM), and leads to the late activation of NF-κB and IRF3, and to the induction of cytokines, chemokines, and other transcription factors. As LPS signal transduction is an area of intense research and rapid progress, this review is intended to sum up our present understanding of the events following LPS binding to TLR4, and we also attempt to create a model of the signalling pathways activated by LPS. PMID:15379975

  1. Biased signaling by peptide agonists of protease activated receptor 2.

    PubMed

    Jiang, Yuhong; Yau, Mei-Kwan; Kok, W Mei; Lim, Junxian; Wu, Kai-Chen; Liu, Ligong; Hill, Timothy A; Suen, Jacky Y; Fairlie, David P

    2017-02-07

    Protease activated receptor 2 (PAR2) is associated with metabolism, obesity, inflammatory, respiratory and gastrointestinal disorders, pain, cancer and other diseases. The extracellular N-terminus of PAR2 is a common target for multiple proteases, which cleave it at different sites to generate different N-termini that activate different PAR2-mediated intracellular signaling pathways. There are no synthetic PAR2 ligands that reproduce the same signaling profiles and potencies as proteases. Structure-activity relationships here for 26 compounds spanned a signaling bias over 3 log units, culminating in three small ligands as biased agonist tools for interrogating PAR2 functions. DF253 (2f-LAAAAI-NH2) triggered PAR2-mediated calcium release (EC50 2 μM) but not ERK1/2 phosphorylation (EC50 > 100 μM) in CHO cells transfected with hPAR2. AY77 (Isox-Cha-Chg-NH2) was a more potent calcium-biased agonist (EC50 40 nM, Ca2+; EC50 2 μM, ERK1/2), while its analogue AY254 (Isox-Cha-Chg-A-R-NH2) was an ERK-biased agonist (EC50 2 nM, ERK1/2; EC50 80 nM, Ca2+). Signaling bias led to different functional responses in human colorectal carcinoma cells (HT29). AY254, but not AY77 or DF253, attenuated cytokine-induced caspase 3/8 activation, promoted scratch-wound healing and induced IL-8 secretion, all via PAR2-ERK1/2 signaling. Different ligand components were responsible for different PAR2 signaling and functions, clues that can potentially lead to drugs that modulate different pathway-selective cellular and physiological responses.

  2. 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.

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

    PubMed

    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

    2016-09-30

    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.

  4. New concepts in calcium-sensing receptor pharmacology and signalling.

    PubMed

    Ward, Donald T; Riccardi, Daniela

    2012-01-01

    The calcium-sensing receptor (CaR) is the key controller of extracellular calcium (Ca(2+)(o)) homeostasis via its regulation of parathyroid hormone (PTH) secretion and renal Ca(2+) reabsorption. The CaR-selective calcimimetic drug Cinacalcet stimulates the CaR to suppress PTH secretion in chronic kidney disease and represents the world's first clinically available receptor positive allosteric modulator (PAM). Negative CaR allosteric modulators (NAMs), known as calcilytics, can increase PTH secretion and are being investigated as possible bone anabolic treatments against age-related osteoporosis. Here we address the current state of development and clinical use of a series of positive and negative CaR modulators. In addition, clinical CaR mutations and transgenic mice carrying tissue-specific CaR deletions have provided a novel understanding of the relative functional importance of CaR in both calciotropic tissues and those elsewhere in the body. The development of CaR-selective modulators and signalling reagents have provided us with a more detailed appreciation of how the CaR signals in vivo. Thus, both of these areas of CaR research will be reviewed. © 2011 The Authors. British Journal of Pharmacology © 2011 The British Pharmacological Society.

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

    PubMed

    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

    2015-01-01

    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.

  6. 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

  7. Polychlorinated Biphenyls Disrupt Hepatic Epidermal Growth Factor Receptor Signaling.

    PubMed

    Hardesty, Josiah E; Wahlang, Banrida; Falkner, K Cameron; Clair, Heather B; Clark, Barbara J; Ceresa, Brian P; Prough, Russell A; Cave, Matthew C

    2016-07-26

    1. Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that disrupt hepatic xenobiotic and intermediary metabolism, leading to metabolic syndrome and nonalcoholic steatohepatitis (NASH). 2. Since phenobarbital indirectly activates Constitutive Androstane Receptor (CAR) by antagonizing growth factor binding to the epidermal growth factor receptor (EGFR), we hypothesised that PCBs may also diminish EGFR signaling. 3. The effects of the PCB mixture Aroclor 1260 on the protein phosphorylation cascade triggered by EGFR activation were determined in murine (in vitro and in vivo) and human models (in vitro). EGFR tyrosine residue phosphorylation was decreased by PCBs in all models tested. 4. The IC50 values for Aroclor 1260 concentrations that decreased Y1173 phosphorylation of EGFR were similar in murine AML-12 and human HepG2 cells (∼2-4 μg/mL). Both dioxin and non-dioxin-like PCB congeners decreased EGFR phosphorylation in cell culture. 5. PCB treatment reduced phosphorylation of downstream EGFR effectors including Akt and mTOR, as well as other phosphoprotein targets including STAT3 and c-RAF in vivo. 6. PCBs diminish EGFR signaling in human and murine hepatocyte models and may dysregulate critical phosphoprotein regulators of energy metabolism and nutrition, providing a new mechanism of action in environmental diseases.

  8. 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.

  9. The receptor tyrosine kinase c-Kit controls IL-33 receptor signaling in mast cells.

    PubMed

    Drube, Sebastian; Heink, Sylvia; Walter, Sabine; Löhn, Tobias; Grusser, Mandy; Gerbaulet, Alexander; Berod, Luciana; Schons, Julia; Dudeck, Anne; Freitag, Jenny; Grotha, Stefan; Reich, Daniela; Rudeschko, Olga; Norgauer, Johannes; Hartmann, Karin; Roers, Axel; Kamradt, Thomas

    2010-05-13

    Members of the Toll/interleukin-1 receptor (TIR) family are of importance for host defense and inflammation. Here we report that the TIR-family member interleukin-33R (IL-33R) cross-activates the receptor tyrosine kinase c-Kit in human and murine mast cells. The IL-33R-induced activation of signal transducer and activator of transcription 3 (STAT3), extracellular signal-regulated kinase 1/2 (Erk1/2), protein kinase B (PKB), and Jun NH(2)-terminal kinase 1 (JNK1) depends on c-Kit and is required to elicit optimal effector functions. Costimulation with the c-Kit ligand stem cell factor (SCF) is necessary for IL-33-induced cytokine production in primary mast cells. The structural basis for this cross-activation is the complex formation between c-Kit, IL-33R, and IL-1R accessory protein (IL-1RAcP). We found that c-Kit and IL-1RAcP interact constitutively and that IL-33R joins this complex upon ligand binding. Our findings support a model in which signals from seemingly disparate receptors are integrated for full cellular responses.

  10. Modeling the epidermal growth factor -- epidermal growth factor receptor l2 domain interaction: implications for the ligand binding process.

    PubMed

    Jorissen, Robert N; Treutlein, Herbert R; Epa, V Chandana; Burgess, Antony W

    2002-06-01

    Signaling from the epidermal growth factor (EGF) receptor is triggered by the binding of ligands such as EGF or transforming growth factor alpha (TGF-alpha) and subsequent receptor dimerization. An understanding of these processes has been hindered by the lack of structural information about the ligand-bound, dimerized EGF receptor. Using an NMR-derived structure of EGF and a homology model of the major ligand binding domain of the EGF receptor and experimental data, we modeled the binding of EGF to this EGF receptor fragment. In this low resolution model of the complex, EGF sits across the second face of the EGF receptor L2 domain and EGF residues 10-16, 36-37, 40-47 bind to this face. The structural model is largely consistent with previously published NMR data describing the residues of TGF-alpha which interact strongly with the EGF receptor. Other EGF residues implicated in receptor binding are accounted by our proposal that the ligand binding is a two-step process with the EGF binding to at least one other site of the receptor. This three-dimensional model is expected to be useful in the design of ligand-based antagonists of the receptor.

  11. TAM Receptor Tyrosine Kinases: Biologic Functions, Signaling, and Potential Therapeutic Targeting in Human Cancer

    PubMed Central

    Linger, Rachel M. A.; Keating, Amy K.; Earp, H. Shelton; Graham, Douglas K.

    2011-01-01

    Tyro-3, Axl, and Mer constitute the TAM family of receptor tyrosine kinases (RTKs) characterized by a conserved sequence within the kinase domain and adhesion molecule-like extracellular domains. This small family of RTKs regulates an intriguing mix of processes, including cell proliferation/survival, cell adhesion and migration, blood clot stabilization, and regulation of inflammatory cytokine release. Genetic or experimental alteration of TAM receptor function can contribute to a number of disease states, including coagulopathy, autoimmune disease, retinitis pigmentosa, and cancer. In this chapter, we first provide a comprehensive review of the structure, regulation, biologic functions, and down-stream signaling pathways of these receptors. In addition, we discuss recent evidence which suggests a role for TAM receptors in oncogenic mechanisms as family members are over-expressed in a spectrum of human cancers and have prognostic significance in some. Possible strategies for targeted inhibition of the TAM family in the treatment of human cancer are described. Further research will be necessary to evaluate the full clinical implications of TAM family expression and activation in cancer. PMID:18620092

  12. Characterization of signaling pathways coupled to melatonin receptors in gastrointestinal smooth muscle.

    PubMed

    Ahmed, Rashad; Mahavadi, Sunila; Al-Shboul, Othman; Bhattacharya, Sayak; Grider, John R; Murthy, Karnam S

    2013-06-10

    Melatonin, a close derivative of serotonin, is involved in physiological regulation of circadian rhythms. In the gastrointestinal (GI) system, melatonin exhibits endocrine, paracrine and autocrine actions and is implicated in the regulation of GI motility. However, it is not known whether melatonin can also act directly on GI smooth muscle cells. The aim of the present study was to determine the expression of melatonin receptors in smooth muscle and identify their signaling pathways. MT1, but not MT2 receptors are expressed in freshly dispersed and cultured gastric smooth muscle cells. Melatonin selectively activated Gq and stimulated phosphoinositide (PI) hydrolysis in freshly dispersed and cultured muscle cells. PI hydrolysis was blocked by the expression of Gq, but not Gi minigene in cultured muscle cells. Melatonin also caused rapid increase in cytosolic Ca(2+) as determined by epifluorescence microscopy in fura-2 loaded single smooth muscle cells, and induced rapid contraction. Melatonin-induced PI hydrolysis and contraction were blocked by a non-selective MT1/MT2 antagonist luzindole (1 μM), but not by a selective MT2 antagonist 4P-PDOT (100 nM), and by the PLC inhibitor U73122. MT2 selective agonist IIK7 (100 nM) had no effect on PI hydrolysis and contraction. We conclude that rabbit gastric smooth muscle cells express melatonin MT1 receptors coupled to Gq. Activation of these receptors causes stimulation of PI hydrolysis and increase in cytosolic Ca(2+), and elicits muscle contraction.

  13. MC1R signaling. Intracellular partners and pathophysiological implications.

    PubMed

    Herraiz, Cecilia; Garcia-Borron, Jose C; Jiménez-Cervantes, Celia; Olivares, Conchi

    2017-03-01

    The melanocortin-1 receptor (MC1R) preferentially expressed in melanocytes is best known as a key regulator of the synthesis of epidermal melanin pigments. Its paracrine stimulation by keratinocyte-derived melanocortins also activates DNA repair pathways and antioxidant defenses to build a complex, multifaceted photoprotective response. Many MC1R actions rely on cAMP-dependent activation of two transcription factors, MITF and PGC1α, but pleiotropic MC1R signaling also involves activation of mitogen-activated kinases and AKT. MC1R partners such as β-arrestins, PTEN and the E3 ubiquitin ligase MGRN1 differentially regulate these pathways. The MC1R gene is complex and polymorphic, with frequent variants associated with skin phenotypes and increased cancer risk. We review current knowledge of signaling from canonical MC1R, its splice isoforms and natural polymorphic variants. Recently discovered intracellular targets and partners are also discussed, to highlight the diversity of mechanisms that may contribute to normal and pathological variation of pigmentation and sensitivity to solar radiation-induced damage. This article is part of a Special Issue entitled: Melanocortin Receptors - edited by Ya-Xiong Tao.

  14. 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

  15. Human glucocorticoid-induced TNF receptor ligand regulates its signaling activity through multiple oligomerization states

    PubMed Central

    Zhou, Zhaocai; Song, Xiaomin; Berezov, Alan; Zhang, Geng; Li, Yanjing; Zhang, Hongtao; Murali, Ramachandran; Li, Bin; Greene, Mark I.

    2008-01-01

    Ligation between glucocorticoid-induced tumor necrosis factor receptor (GITR) and its ligand (GITRL) provides an undefined signal that renders CD4+CD25− effector T cells resistant to the inhibitory effects of CD4+CD25+ regulatory T cells. To understand the structural basis of GITRL function, we have expressed and purified the extracellular domain of human GITR ligand in Escherichia coli. Chromotography and cross-linking studies indicate that human GITRL (hGITRL) exists as dimers and trimers in solution and also can form a supercluster. To gain insight into the nature of GITRL oligomerization, we determined the crystallographic structures of hGITRL, which revealed a loosely associated open trimer with a deep cavity at the molecular center and a flexible C-terminal tail bent for trimerization. Moreover, a tetramer of trimers (i.e., supercluster) has also been observed in the crystal, consistent with the cross-linking analysis. Deletion of the C-terminal distal three residues disrupts the loosely assembled trimer and favors the formation of a dimer that has compromised receptor binding and signaling activity. Collectively, our studies identify multiple oligomeric species of hGITRL that possess distinct kinetics of ERK activation. The studies address the functional implications and structural models for a process by which hGITRL utilizes multiple oligomerization states to regulate GITR-mediated signaling during T cell costimulation. PMID:18378892

  16. Prolonged calcitonin receptor signaling by salmon, but not human calcitonin, reveals ligand bias.

    PubMed

    Andreassen, Kim Vietz; Hjuler, Sara Toftegaard; Furness, Sebastian G; Sexton, Patrick M; Christopoulos, Arthur; Nosjean, Olivier; Karsdal, Morten Asser; Henriksen, Kim

    2014-01-01

    Salmon calcitonin (sCT) and human calcitonin (hCT) are pharmacologically distinct. However, the reason for the differences is unclear. Here we analyze the differences between sCT and hCT on the human calcitonin receptor (CT(a)R) with respect to activation of cAMP signaling, β-arrestin recruitment, ligand binding kinetics and internalization. The study was conducted using mammalian cell lines heterologously expressing the human CT(a) receptor. CT(a)R downstream signaling was investigated with dose response profiles for cAMP production and β-arrestin recruitment for sCT and hCT during short term (<2 hours) and prolonged (up to 72 hours) stimulation. CT(a)R kinetics and internalization was investigated with radio-labeled sCT and hCT ligands on cultured cells and isolated membrane preparations from the same cell line. We found that sCT and hCT are equipotent during short-term stimulations with differences manifesting themselves only during long-term stimulation with sCT inducing a prolonged activation up to 72 hours, while hCT loses activity markedly earlier. The prolonged sCT stimulation of both cAMP accumulation and β-arrestin recruitment was attenuated, but not abrogated by acid wash, suggesting a role for sCT activated internalized receptors. We have demonstrated a novel phenomenon, namely that two distinct CT(a)R downstream signaling activation patterns are activated by two related ligands, thereby highlighting qualitatively different signaling responses in vitro that could have implications for sCT use in vivo.

  17. Autocrine endothelin-3/endothelin receptor B signaling maintains cellular and molecular properties of glioblastoma stem cells.

    PubMed

    Liu, Yue; Ye, Fei; Yamada, Kazunari; Tso, Jonathan L; Zhang, Yibei; Nguyen, David H; Dong, Qinghua; Soto, Horacio; Choe, Jinny; Dembo, Anna; Wheeler, Hayley; Eskin, Ascia; Schmid, Ingrid; Yong, William H; Mischel, Paul S; Cloughesy, Timothy F; Kornblum, Harley I; Nelson, Stanley F; Liau, Linda M; Tso, Cho-Lea

    2011-12-01

    Glioblastoma stem cells (GSC) express both radial glial cell and neural crest cell (NCC)-associated genes. We report that endothelin 3 (EDN3), an essential mitogen for NCC development and migration, is highly produced by GSCs. Serum-induced proliferative differentiation rapidly decreased EDN3 production and downregulated the expression of stemness-associated genes, and reciprocally, two glioblastoma markers, EDN1 and YKL-40 transcripts, were induced. Correspondingly, patient glioblastoma tissues express low levels of EDN3 mRNA and high levels of EDN1 and YKL-40 mRNA. Blocking EDN3/EDN receptor B (EDNRB) signaling by an EDNRB antagonist (BQ788), or EDN3 RNA interference (siRNA), leads to cell apoptosis and functional impairment of tumor sphere formation and cell spreading/migration in culture and loss of tumorigenic capacity in animals. Using exogenous EDN3 as the sole mitogen in culture does not support GSC propagation, but it can rescue GSCs from undergoing cell apoptosis. Molecular analysis by gene expression profiling revealed that most genes downregulated by EDN3/EDNRB blockade were those involved in cytoskeleton organization, pause of growth and differentiation, and DNA damage response, implicating the involvement of EDN3/EDNRB signaling in maintaining GSC migration, undifferentiation, and survival. These data suggest that autocrine EDN3/EDNRB signaling is essential for maintaining GSCs. Incorporating END3/EDNRB-targeted therapies into conventional cancer treatments may have clinical implication for the prevention of tumor recurrence.

  18. 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

  19. Metabotropic glutamate receptor 1 and glutamate signaling in human melanoma.

    PubMed

    Namkoong, Jin; Shin, Seung-Shick; Lee, Hwa Jin; Marín, Yarí E; Wall, Brian A; Goydos, James S; Chen, Suzie

    2007-03-01

    Recently, several laboratories have started to investigate the involvement of glutamate signaling in cancer. In previous studies, we reported on a transgenic mouse model that develops melanoma spontaneously. Subsequent studies in these mice identified that the aberrant expression of metabotropic glutamate receptor 1 (GRM1) in melanocytes played a critical role in the onset of melanoma. Confirmation of the etiologic role of GRM1 in melanoma development was shown in a second transgenic line with GRM1 expression under the regulation of a melanocyte-specific dopachrome tautomerase promoter. Ectopic expression of GRM1 was also detected in a subset of human melanoma cell lines and biopsies, suggesting that aberrant expression of GRM1 in melanocytes may contribute to the development of human melanoma. GRM1, a seven-transmembrane domain G protein-coupled receptor, is normally expressed and functional in neuronal cells, and its ligand, glutamate, is the major excitatory neurotransmitter. Human melanoma cells are shown here to release elevated levels of glutamate, implying a possible autocrine loop. Treatment of GRM1-expressing human melanoma cells with a GRM1 antagonist (LY367385 or BAY36-7620) or a glutamate release inhibitor (riluzole) leads to a suppression of cell proliferation as well as a decrease in levels of extracellular glutamate. Treatment of human melanoma cell xenografts with riluzole for 18 days via p.o. gavage or i.v. injection leads to inhibition of tumor growth by 50% in comparison with controls. These data suggest the importance of glutamate signaling in human melanoma and imply that the suppression of glutamate signaling may be a new target for melanoma therapy.

  20. A novel calmodulin-β-PIX interaction and its implication in receptor tyrosine kinase regulation.

    PubMed

    Singh, Vinay K; Munro, Kim; Jia, Zongchao

    2012-09-01

    Calmodulin (CaM), a ubiquitous calcium-binding protein, regulates numerous cellular processes, primarily in response to calcium flux. We have identified and characterized a novel interaction between CaM and β-p21-activated kinase interacting exchange factor (β-PIX), a putative guanine exchange factor implicated in cell signaling, using affinity pull-down assays, co-immunoprecipitation, co-localization and circular dichroism studies. Fluorescence-based titration and isothermal titration calorimetry experiments revealed a Ca(2+)-dependent binding mechanism (K(D)≤10μM). Further, we show that CaM participates in a multi-protein complex involving β-PIX and E3 ubiquitin ligase c-Cbl (casitas B-cell lymphoma), which may play a critical role in receptor tyrosine kinase regulation and downstream signaling. Copyright © 2012 Elsevier Inc. All rights reserved.

  1. Biased agonism as a mechanism for differential signaling by chemokine receptors.

    PubMed

    Rajagopal, Sudarshan; Bassoni, Daniel L; Campbell, James J; Gerard, Norma P; Gerard, Craig; Wehrman, Tom S

    2013-12-06

    Chemokines display considerable promiscuity with multiple ligands and receptors shared in common, a phenomenon that is thought to underlie their biochemical "redundancy." Their receptors are part of a larger seven-transmembrane receptor superfamily, commonly referred to as G protein-coupled receptors, which have been demonstrated to be able to signal with different efficacies to their multiple downstream signaling pathways, a phenomenon referred to as biased agonism. Biased agonism has been primarily reported as a phenomenon of synthetic ligands, and the biologic prevalence and importance of such signaling are unclear. Here, to assess the presence of biased agonism that may underlie differential signaling by chemokines targeting the same receptor, we performed a detailed pharmacologic analysis of a set of chemokine receptors with multiple endogenous ligands using assays for G protein signaling, β-arrestin recruitment, and receptor internalization. We found that chemokines targeting the same receptor can display marked differences in their efficacies for G protein- or β-arrestin-mediated signaling or receptor internalization. This ligand bias correlates with changes in leukocyte migration, consistent with different mechanisms underlying the signaling downstream of these receptors induced by their ligands. These findings demonstrate that biased agonism is a common and likely evolutionarily conserved biological mechanism for generating qualitatively distinct patterns of signaling via the same receptor in response to different endogenous ligands.

  2. 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

  3. Targeting fibroblast growth factor receptor signaling inhibits prostate cancer progression

    PubMed Central

    Feng, Shu; Shao, Longjiang; Yu, Wendong; Gavine, Paul; Ittmann, Michael

    2015-01-01

    Purpose Extensive correlative studies in human prostate cancer (PCa) as well as studies in vitro and in mouse models indicate that FGF receptor (FGFR) signaling plays an important role in PCa progression. In this study, we employed a probe compound for an FGFR inhibitor which potently inhibits FGFR1-3 and significantly inhibits FGFR-4. The purpose of this study is to determine if targeting FGFR signaling from all four FGFRs will have in vitro activities consistent with inhibition of tumor progression and will inhibit tumor progression in vivo. Experimental Design Effects of AZ8010 on FGFR signaling and invasion were analyzed using immortalized normal prostate epithelial (PNT1a) cells and PNT1a overexpressing FGFR-1 or FGFR-4. The effect of AZ8010 on invasion and proliferation in vitro was also evaluated in PCa cell lines. Finally, the impact of AZ8010 on tumor progression in vivo was evaluated using a VCaP xenograft model. Results AZ8010 completely inhibits FGFR-1 and significantly inhibits FGFR-4 signaling at 100 nM, which is an achievable in vivo concentration. These results in marked inhibition of ERK phosphorylation and invasion in PNT1a cells expressing FGFR-1 and FGFR-4 and all PCa cell lines tested. Treatment in vivo completely inhibited VCaP tumor growth and significantly inhibited angiogenesis and proliferation and increased cell death in treated tumors. This was associated with marked inhibition of ERK phosphorylation in treated tumors. Conclusions Targeting FGFR signaling is a promising new approach to treating aggressive PCa. PMID:22573348

  4. Regulation of Clock Genes by Adrenergic Receptor Signaling in Osteoblasts.

    PubMed

    Hirai, Takao

    2017-07-27

    The clock system has been identified as one of the major mechanisms controlling cellular functions. Circadian clock gene oscillations also actively participate in the functions of various cell types including bone-related cells. Previous studies demonstrated that clock genes were expressed in bone tissue and also that their expression exhibited circadian rhythmicity. Recent findings have shown that sympathetic tone plays a central role in biological oscillations in bone. Adrenergic receptor (AR) signaling regulates the expression of clock genes in cancellous bone. Furthermore, α1-AR signaling in osteoblasts is known to negatively regulate the expression of bone morphogenetic protein-4 (Bmp4) by up-regulating nuclear factor IL-3 (Nfil3)/e4 promoter-binding protein 4 (E4BP4). The ablation of α1B-AR signaling also increases the expression of the Bmp4 gene in bone. The findings of transient overexpression and siRNA experiments have supported the involvement of the transcription factor CCAAT/enhancer-binding protein delta (C/EBPδ, Cebpd) in Nfil3 and Bmp4 expression in MC3T3-E1 cells. These findings suggest that the effects of Cebpd are due to the circadian regulation of Bmp4 expression, at least in part, by the up-regulated expression of the clock gene Nfil3 in response to α1B-AR signaling in osteoblasts. Therefore, AR signaling appears to modulate cellular functionality through the expression of clock genes that are circadian rhythm regulators in osteoblasts. The expression of clock genes regulated by the sympathetic nervous system and clock-controlled genes that affect bone metabolism are described herein.

  5. Membrane-Mediated Oligomerization of G Protein Coupled Receptors and Its Implications for GPCR Function

    PubMed Central

    Gahbauer, Stefan; Böckmann, Rainer A.

    2016-01-01

    The dimerization or even oligomerization of G protein coupled receptors (GPCRs) causes ongoing, controversial debates about its functional role and the coupled biophysical, biochemical or biomedical implications. A continously growing number of studies hints to a relation between oligomerization and function of GPCRs and strengthens the assumption that receptor assembly plays a key role in the regulation of protein function. Additionally, progress in the structural analysis of GPCR-G protein and GPCR-ligand interactions allows to distinguish between actively functional and non-signaling complexes. Recent findings further suggest that the surrounding membrane, i.e., its lipid composition may modulate the preferred dimerization interface and as a result the abundance of distinct dimeric conformations. In this review, the association of GPCRs and the role of the membrane in oligomerization will be discussed. An overview of the different reported oligomeric interfaces is provided and their capability for signaling discussed. The currently available data is summarized with regard to the formation of GPCR oligomers, their structures and dependency on the membrane microenvironment as well as the coupling of oligomerization to receptor function. PMID:27826255

  6. Signal transduction induced in endothelial cells by growth factor receptors involved in angiogenesis

    PubMed Central

    Hofer, Erhard; Schweighofer, Bernhard

    2010-01-01

    Summary New vessel formation during development and in the adult is triggered by concerted signals of largely endothelial-specific receptors for ligands of the VEGF, angiopoietin and ephrin families. The signals and genes induced by these receptors operate in the context of additional signals transduced by non-endothelial specific growth factor receptors, inflammatory cytokine receptors as well as adhesion molecules. We summarize here available data on characteristic signaling of the VEGF receptor-2 and the current state of knowledge regarding the additional different receptor tyrosine kinases of the VEGF, Tie and Ephrin receptor families. Furthermore, the potential cross-talk with signals induced by other growth factors and inflammatory cytokines as well as the modulation by VE-cadherin is discussed. PMID:17334501

  7. Quantitative Phosphoproteomic Analysis of T-Cell Receptor Signaling.

    PubMed

    Ahsan, Nagib; Salomon, Arthur R

    2017-01-01

    TCR signaling critically depends on protein phosphorylation across many proteins. Localization of each phosphorylation event relative to the T-cell receptor (TCR) and canonical T-cell signaling proteins will provide clues about the structure of TCR signaling networks. Quantitative phosphoproteomic analysis by mass spectrometry provides a wide-scale view of cellular phosphorylation networks. However, analysis of phosphorylation by mass spectrometry is still challenging due to the relative low abundance of phosphorylated proteins relative to all proteins and the extraordinary diversity of phosphorylation sites across the proteome. Highly selective enrichment of phosphorylated peptides is essential to provide the most comprehensive view of the phosphoproteome. Optimization of phosphopeptide enrichment methods coupled with highly sensitive mass spectrometry workflows significantly improves the sequencing depth of the phosphoproteome to over 10,000 unique phosphorylation sites from complex cell lysates. Here we describe a step-by-step method for phosphoproteomic analysis that has achieved widespread success for identification of serine, threonine, and tyrosine phosphorylation. Reproducible quantification of relative phosphopeptide abundance is provided by intensity-based label-free quantitation. An ideal set of mass spectrometry analysis parameters is also provided that optimize the yield of identified sites. We also provide guidelines for the bioinformatic analysis of this type of data to assess the quality of the data and to comply with proteomic data reporting requirements.

  8. Estrogen receptors regulate innate immune cells and signaling pathways.

    PubMed

    Kovats, Susan

    2015-04-01

    Humans show strong sex differences in immunity to infection and autoimmunity, suggesting sex hormones modulate immune responses. Indeed, receptors for estrogens (ERs) regulate cells and pathways in the innate and adaptive immune system, as well as immune cell development. ERs are ligand-dependent transcription factors that mediate long-range chromatin interactions and form complexes at gene regulatory elements, thus promoting epigenetic changes and transcription. ERs also participate in membrane-initiated steroid signaling to generate rapid responses. Estradiol and ER activity show profound dose- and context-dependent effects on innate immune signaling pathways and myeloid cell development. While estradiol most often promotes the production of type I interferon, innate pathways leading to pro-inflammatory cytokine production may be enhanced or dampened by ER activity. Regulation of innate immune cells and signaling by ERs may contribute to the reported sex differences in innate immune pathways. Here we review the recent literature and highlight several molecular mechanisms by which ERs regulate the development or functional responses of innate immune cells. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Vitamin D receptor signaling enhances locomotive ability in mice.

    PubMed

    Sakai, Sadaoki; Suzuki, Miho; Tashiro, Yoshihito; Tanaka, Keisuke; Takeda, Satoshi; Aizawa, Ken; Hirata, Michinori; Yogo, Kenji; Endo, Koichi

    2015-01-01

    Bone fractures markedly reduce quality of life and life expectancy in elderly people. Although osteoporosis increases bone fragility, fractures frequently occur in patients with normal bone mineral density. Because most fractures occur on falling, preventing falls is another focus for reducing bone fractures. In this study, we investigated the role of vitamin D receptor (VDR) signaling in locomotive ability. In the rotarod test, physical exercise enhanced locomotive ability of wild-type (WT) mice by 1.6-fold, whereas exercise did not enhance locomotive ability of VDR knockout (KO) mice. Compared with WT mice, VDR KO mice had smaller peripheral nerve axonal diameter and disordered AChR morphology on the extensor digitorum longus muscle. Eldecalcitol (ED-71, ELD), an analog of 1,25(OH)2 D3 , administered to rotarod-trained C57BL/6 mice enhanced locomotor performance compared with vehicle-treated nontrained mice. The area of AChR cluster on the extensor digitorum longus was greater in ELD-treated mice than in vehicle-treated mice. ELD and 1,25(OH)2 D3 enhanced expression of IGF-1, myelin basic protein, and VDR in rat primary Schwann cells. VDR signaling regulates neuromuscular maintenance and enhances locomotive ability after physical exercise. Further investigation is required, but Schwann cells and the neuromuscular junction are targets of vitamin D3 signaling in locomotive ability.

  10. Neuropilin-1-dependent regulation of EGF-receptor signaling.

    PubMed

    Rizzolio, Sabrina; Rabinowicz, Noa; Rainero, Elena; Lanzetti, Letizia; Serini, Guido; Norman, Jim; Neufeld, Gera; Tamagnone, Luca

    2012-11-15

    Neuropilin-1 (NRP1) is a coreceptor for multiple extracellular ligands. NRP1 is widely expressed in cancer cells and in advanced human tumors; however, its functional relevance and signaling mechanisms are unclear. Here, we show that NRP1 expression controls viability and proliferation of different cancer cells, independent of its short intracellular tail. We found that the extracellular domain of NRP1 interacts with the EGF receptor (EGFR) and promotes its signaling cascade elicited upon EGF or TGF-α stimulation. Upon NRP1 silencing, the ability of ligand-bound EGFR to cluster on the cell surface, internalize, and activate the downstream AKT pathway is severely impaired. EGFR is frequently activated in human tumors due to overexpression, mutation, or sustained autocrine/paracrine stimulation. Here we show that NRP1-blocking antibodies and NRP1 silencing can counteract ligand-induced EGFR activation in cancer cells. Thus our findings unveil a novel molecular mechanism by which NRP1 can control EGFR signaling and tumor growth.

  11. Fine specificity and molecular competition in SLAM family receptor signalling.

    PubMed

    Wilson, Timothy J; Garner, Lee I; Metcalfe, Clive; King, Elliott; Margraf, Stefanie; Brown, Marion H

    2014-01-01

    SLAM family receptors regulate activation and inhibition in immunity through recruitment of activating and inhibitory SH2 domain containing proteins to immunoreceptor tyrosine based switch motifs (ITSMs). Binding of the adaptors, SAP and EAT-2 to ITSMs in the cytoplasmic regions of SLAM family receptors is important for activation. We analysed the fine specificity of SLAM family receptor phosphorylated ITSMs and the conserved tyrosine motif in EAT-2 for SH2 domain containing signalling proteins. Consistent with the literature describing dependence of CRACC (SLAMF7) on EAT-2, CRACC bound EAT-2 (KD = 0.003 μM) with approximately 2 orders of magnitude greater affinity than SAP (KD = 0.44 μM). RNA interference in cytotoxicity assays in NK92 cells showed dependence of CRACC on SAP in addition to EAT-2, indicating selectivity of SAP and EAT-2 may depend on the relative concentrations of the two adaptors. The concentration of SAP was four fold higher than EAT-2 in NK92 cells. Compared with SAP, the significance of EAT-2 recruitment and its downstream effectors are not well characterised. We identified PLCγ1 and PLCγ2 as principal binding partners for the EAT-2 tail. Both PLCγ1 and PLCγ2 are functionally important for cytotoxicity in NK92 cells through CD244 (SLAMF4), NTB-A (SLAMF6) and CRACC. Comparison of the specificity of SH2 domains from activating and inhibitory signalling mediators revealed a hierarchy of affinities for CD244 (SLAMF4) ITSMs. While binding of phosphatase SH2 domains to individual ITSMs of CD244 was weak compared with SAP or EAT-2, binding of tandem SH2 domains of SHP-2 to longer peptides containing tandem phosphorylated ITSMs in human CD244 increased the affinity ten fold. The concentration of the tyrosine phosphatase, SHP-2 was in the order of a magnitude higher than the adaptors, SAP and EAT-2. These data demonstrate a mechanism for direct recruitment of phosphatases in inhibitory signalling by ITSMs, while explaining competitive

  12. Fine Specificity and Molecular Competition in SLAM Family Receptor Signalling

    PubMed Central

    Wilson, Timothy J.; Garner, Lee I.; Metcalfe, Clive; King, Elliott; Margraf, Stefanie; Brown, Marion H.

    2014-01-01

    SLAM family receptors regulate activation and inhibition in immunity through recruitment of activating and inhibitory SH2 domain containing proteins to immunoreceptor tyrosine based switch motifs (ITSMs). Binding of the adaptors, SAP and EAT-2 to ITSMs in the cytoplasmic regions of SLAM family receptors is important for activation. We analysed the fine specificity of SLAM family receptor phosphorylated ITSMs and the conserved tyrosine motif in EAT-2 for SH2 domain containing signalling proteins. Consistent with the literature describing dependence of CRACC (SLAMF7) on EAT-2, CRACC bound EAT-2 (KD = 0.003 μM) with approximately 2 orders of magnitude greater affinity than SAP (KD = 0.44 μM). RNA interference in cytotoxicity assays in NK92 cells showed dependence of CRACC on SAP in addition to EAT-2, indicating selectivity of SAP and EAT-2 may depend on the relative concentrations of the two adaptors. The concentration of SAP was four fold higher than EAT-2 in NK92 cells. Compared with SAP, the significance of EAT-2 recruitment and its downstream effectors are not well characterised. We identified PLCγ1 and PLCγ2 as principal binding partners for the EAT-2 tail. Both PLCγ1 and PLCγ2 are functionally important for cytotoxicity in NK92 cells through CD244 (SLAMF4), NTB-A (SLAMF6) and CRACC. Comparison of the specificity of SH2 domains from activating and inhibitory signalling mediators revealed a hierarchy of affinities for CD244 (SLAMF4) ITSMs. While binding of phosphatase SH2 domains to individual ITSMs of CD244 was weak compared with SAP or EAT-2, binding of tandem SH2 domains of SHP-2 to longer peptides containing tandem phosphorylated ITSMs in human CD244 increased the affinity ten fold. The concentration of the tyrosine phosphatase, SHP-2 was in the order of a magnitude higher than the adaptors, SAP and EAT-2. These data demonstrate a mechanism for direct recruitment of phosphatases in inhibitory signalling by ITSMs, while explaining competitive

  13. 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

  14. Implications of mitogen-activated protein kinase signaling in glioma.

    PubMed

    Pandey, Vimal; Bhaskara, Vasantha Kumar; Babu, Phanithi Prakash

    2016-02-01

    Gliomas are the most common primary central nervous system tumors. Gliomas originate from astrocytes, oligodendrocytes, and neural stem cells or their precursors. According to WHO classification, gliomas are classified into four different malignant grades ranging from grade I to grade IV based on histopathological features and related molecular aberrations. The induction and maintenance of these tumors can be attributed largely to aberrant signaling networks. In this regard, the mitogen-activated protein kinase (MAPK) network has been widely studied and is reported to be severely altered in glial tumors. Mutations in MAPK pathways most frequently affect RAS and B-RAF in the ERK, c-Jun N-terminal kinase (JNK), and p38 pathways leading to malignant transformation. Also, it is linked to both inherited and sequential accumulations of mutations that control receptor tyrosine kinase (RTK)-activated signal transduction pathways, cell cycle growth arrest pathways, and nonresponsive cell death pathways. Genetic alterations that modulate RTK signaling can also alter several downstream pathways, including RAS-mediated MAP kinases along with JNK pathways, which ultimately regulate cell proliferation and cell death. The present review focuses on recent literature regarding important deregulations in the RTK-activated MAPK pathway during gliomagenesis and progression.

  15. Interactions between PTEN and receptor tyrosine kinase pathways and their implications for glioma therapy

    PubMed Central

    Abounader, Roger

    2009-01-01

    Gliomas are the most common and deadly form of malignant primary brain tumors. Loss of the tumor-suppressor PTEN and activation of the receptor tyrosine kinases (RTKs) EGF receptor, c-Met, PDGF receptor and VEGF receptor are among the most common molecular dysfunctions associated with glioma malignancy. PTEN interacts with RTK-dependent signaling at multiple levels. These include the ability of PTEN to counteract PI3K activation by RTKs, as well as possible effects of PTEN on RTK activation of the MAPK pathway and RTK-dependent gene-expression regulation. Consequently, PTEN expression affects RTK-induced malignancy. Importantly, the PTEN status was recently found to be critical for the outcome of RTK-targeted clinical therapies that have been developed recently. Combining RTK-targeted therapies with therapies aimed at counteracting the effects of PTEN loss, such as mTOR inhibition, might also have therapeutic advantage. This article reviews the known molecular and functional interactions between PTEN and RTK pathways and their implications for glioma therapy. PMID:19192961

  16. Neutralizing antibodies against epidermal growth factor and ErbB-2/neu receptor tyrosine kinases down-regulate vascular endothelial growth factor production by tumor cells in vitro and in vivo: angiogenic implications for signal transduction therapy of solid tumors.

    PubMed Central

    Petit, A. M.; Rak, J.; Hung, M. C.; Rockwell, P.; Goldstein, N.; Fendly, B.; Kerbel, R. S.

    1997-01-01

    The overexpression in tumor cells of (proto)-oncogenic receptor tyrosine kinases such as epidermal growth factor receptor (EGFR) or ErbB2/neu (also known as HER-2) is generally thought to contribute to the development of solid tumors primarily through their effects on promoting uncontrolled cell proliferation. However, agents that antagonize the function of the protein products encoded by these (proto)-oncogenes are known to behave in vivo in a cytotoxic-like manner. This implies that such oncogenes may regulate critical cell survival functions, including angiogenesis. The latter could occur as a consequence of regulation of relevant growth factors by such oncogenes. We therefore sought to determine whether EGFR or ErbB2/neu may contribute to tumor angiogenesis by examining their effects on the expression of vascular endothelial cell growth factor (VEGF)/vascular permeability factor (VPF), one of the most important of all known inducers of tumor angiogenesis. We found that in vitro treatment of EGFR-positive A431 human epidermoid carcinoma cells, which are known to be heavily dependent on VEGF/VPF in vivo as an angiogenesis growth factor, with the C225 anti-EGFR neutralizing antibody caused a dose-dependent inhibition of VEGF protein expression. Prominent suppression of VEGF/VPF expression in vivo, as well as a significant reduction in tumor blood vessel counts, were also observed in established A431 tumors shortly after injection of the antibody as few as four times into nude mice. Transformation of NIH 3T3 fibroblasts with mutant ErbB2/neu, another EGFR-like oncogenic tyrosine kinase, resulted in a significant induction of VEGF/VPF, and the magnitude of this effect was further elevated by hypoxia. Moreover, treatment of ErbB2/neu-positive SKBR-3 human breast cancer cells in vitro with a specific neutralizing anti-ErbB2/neu monoclonal antibody (4D5) resulted in a dose-dependent reduction of VEGF/VPF protein expression. Taken together, the results suggest that

  17. Direct Interaction of GABAB Receptors with M2 Muscarinic Receptors Enhances Muscarinic Signaling

    PubMed Central

    Boyer, Stephanie B.; Clancy, Sinead M.; Terunuma, Miho; Revilla-Sanchez, Raquel; Thomas, Steven M.; Moss, Stephen J.; Slesinger, Paul A.

    2009-01-01

    Down-regulation of G protein coupled receptors (GPCR) provides an important mechanism for reducing neurotransmitter signaling during sustained stimulation. Chronic stimulation of M2 muscarinic receptors (M2R) causes internalization of M2R and G protein-activated inwardly rectifying potassium (GIRK) channels in neuronal PC12 cells, resulting in loss of function. Here, we show that co-expression of GABAB R2 receptors (GBR2) rescues both surface expression and function of M2R, including M2R-induced activation of GIRKs and inhibition of cAMP production. GBR2 showed significant association with M2R at the plasma membrane but not other GPCRs (M1R, μOR), as detected by FRET measured with TIRF microscopy. Unique regions of the proximal C-terminal domains of GBR2 and M2R mediate specific binding between M2R and GBR2. In the brain, GBR2, but not GBR1, biochemically coprecipitates with M2R and overlaps with M2R expression in cortical neurons. This novel heteromeric association between M2R and GBR2 provides a possible mechanism for altering muscarinic signaling in the brain and represents a previously unrecognized role for GBR2. PMID:20016095

  18. Hedgehog Signaling in Prostate Cancer and Its Therapeutic Implication

    PubMed Central

    Gonnissen, Annelies; Isebaert, Sofie; Haustermans, Karin

    2013-01-01

    Activation of Hedgehog (Hh) signaling is implicated in the development and progression of several tumor types, including prostate cancer, which is still the most common non-skin malignancy and the third leading cause of cancer-related mortality in men in industrialized countries worldwide. Several studies have indicated that the Hh pathway plays a crucial role in the development as well as in the progression of this disease to more aggressive and even therapy-resistant disease states. Moreover, preclinical data have shown that inhibition of Hh signaling has the potential to reduce prostate cancer invasiveness and metastatic potential. Clinical trials investigating the benefit of Hh inhibitors in patients with prostate cancer have recently been initiated. However, acquired drug resistance has already been observed in other tumor types after long-term Hh inhibition. Therefore, combining Hh inhibitors with ionizing radiation, chemotherapy or other molecular targeted agents could represent an alternative therapeutic strategy. In this review, we will highlight the role of Hh signaling in the development and progression of prostate cancer and summarize the different therapeutic applications of Hedgehog inhibition. PMID:23880852

  19. Identification of a negative regulatory cis-element in the enhancer core region of the prostate-specific antigen promoter: implications for intersection of androgen receptor and nuclear factor-kappaB signalling in prostate cancer cells.

    PubMed Central

    Cinar, Bekir; Yeung, Fan; Konaka, Hiroyuki; Mayo, Marty W; Freeman, Michael R; Zhau, Haiyen E; Chung, Leland W K

    2004-01-01

    The NF-kappaB (nuclear factor-kappaB) transcription factors mediate activation of a large number of gene promoters containing diverse kappaB-site sequences. Here, PSA (prostate-specific antigen) was used as an AR (androgen receptor)-responsive gene to examine the underlying mechanism by which the NF-kappaB p65 transcription factor down-regulates the transcriptional activity of AR in cells. We observed that activation of NF-kappaB by TNFalpha (tumour necrosis factor alpha) inhibited both basal and androgen-stimulated PSA expression, and that this down-regulation occurred at the promoter level, as confirmed by the super-repressor IkappaBalpha (S32A/S36A), a dominant negative inhibitor of NF-kappaB. Using a linker-scanning mutagenesis approach, we identified a cis -element, designated XBE (X-factor-binding element), in the AREc (androgen response element enhancer core) of the PSA promoter, which negatively regulated several AR-responsive promoters, including that of PSA. When three copies of XBE in tandem were juxtaposed to GRE4 (glucocorticoid response element 4), a 4-6-fold reduction of inducible GRE4 activity was detected in three different cell lines, LNCaP, ARCaP-AR and PC3-AR. Bioinformatics and molecular biochemical studies indicated that XBE is a kappaB-like element that binds specifically to the NF-kappaB p65 subunit; consistent with these observations, only NF-kappaB p65, but not the NF-kappaB p50 subunit, was capable of inhibiting AR-mediated PSA promoter transactivation in LNCaP cells. In addition, our data also showed that AR binds to XBE, as well as to the kappaB consensus site, and that the transfection of AR inhibits the kappaB-responsive promoter in transient co-transfection assays. Collectively, these data indicate that cross-modulation between AR and NF-kappaB p65 transcription factors may occur by a novel mechanism involving binding to a common cis -DNA element. PMID:14715080

  20. PSM/SH2-B distributes selected mitogenic receptor signals to distinct components in the PI3-kinase and MAP kinase signaling pathways.

    PubMed

    Deng, Youping; Xu, Hu; Riedel, Heimo

    2007-02-15

    The Pro-rich, PH, and SH2 domain containing mitogenic signaling adapter PSM/SH2-B has been implicated as a cellular partner of various mitogenic receptor tyrosine kinases and related signaling mechanisms. Here, we report in a direct comparison of three peptide hormones, that PSM participates in the assembly of distinct mitogenic signaling complexes in response to insulin or IGF-I when compared to PDGF in cultured normal fibroblasts. The complex formed in response to insulin or IGF-I involves the respective peptide hormone receptor and presumably the established components leading to MAP kinase activation. However, our data suggest an alternative link from the PDGF receptor via PSM directly to MEK1/2 and consequently also to p44/42 activation, possibly through a scaffold protein. At least two PSM domains participate, the SH2 domain anticipated to link PSM to the respective receptor and the Pro-rich region in an association with an unidentified downstream component resulting in direct MEK1/2 and p44/42 regulation. The PDGF receptor signaling complex formed in response to PDGF involves PI 3-kinase in addition to the same components and interactions as described for insulin or IGF-I. PSM associates with PI 3-kinase via p85 and in addition the PSM PH domain participates in the regulation of PI 3-kinase activity, presumably through membrane interaction. In contrast, the PSM Pro-rich region appears to participate only in the MAP kinase signal. Both pathways contribute to the mitogenic response as shown by cell proliferation, survival, and focus formation. PSM regulates p38 MAP kinase activity in a pathway unrelated to the mitogenic response.

  1. Peroxisome proliferator-activated receptorsignaling in hepatocarcinogenesis.

    PubMed

    Misra, Parimal; Viswakarma, Navin; Reddy, Janardan K

    2013-01-01

    Peroxisomes are subcellular organelles that are found in the cytoplasm of most animal cells. They perform diverse metabolic functions, including H2O2-derived respiration, β-oxidation of fatty acids, and cholesterol metabolism. Peroxisome proliferators are a large class of structurally dissimilar industrial and pharmaceutical chemicals that were originally identified as inducers of both the size and the number of peroxisomes in rat and mouse livers or hepatocytes in vitro. Exposure to peroxisome proliferators leads to a stereotypical orchestration of adaptations consisting of hepatocellular hypertrophy and hyperplasia, and transcriptional induction of fatty acid metabolizing enzymes regulated in parallel with peroxisome proliferation. Chronic exposure to peroxisome proliferators causes liver tumors in both male and female mice and rats. Evidence indicates a pivotal role for a subset of nuclear receptor superfamily members, called peroxisome proliferator-activated receptors (PPARs), in mediating energy metabolism. Upon activation, PPARs regulate the expression of genes involved in lipid metabolism and peroxisome proliferation, as well as genes involved in cell growth. In this review, we describe the molecular mode of action of PPAR transcription factors, including ligand binding, interaction with specific DNA response elements, transcriptional activation, and cross talk with other signaling pathways. We discuss the evidence that suggests that PPARα and transcriptional coactivator Med1/PBP, a key subunit of the Mediator complex play a central role in mediating hepatic steatosis to hepatocarcinogenesis. Disproportionate increases in H2O2-generating enzymes generates excess reactive oxygen species resulting in sustained oxidative stress and progressive endoplasmic reticulum (ER) stress with activation of unfolded protein response signaling. Thus, these major contributors coupled with hepatocellular proliferation are the key players of peroxisome proliferators

  2. Potential Clinical Implications of the Urotensin II Receptor Antagonists.

    PubMed

    Tsoukas, Philip; Kane, Emilie; Giaid, Adel

    2011-01-01

    Urotensin II (UII) binds to its receptor, UT, playing an important role in the heart, kidneys, pancreas, adrenal gland, and central nervous system. In the vasculature, it acts as a potent endothelium-independent vasoconstrictor and endothelium-dependent vasodilator. In disease states, however, this constriction-dilation equilibrium is disrupted. There is an upregulation of the UII system in heart disease, metabolic syndrome, and kidney failure. The increase in UII release and UT expression suggest that UII system may be implicated in the pathology and pathogenesis of these diseases by causing an increase in acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT-1) activity leading to smooth muscle cell proliferation and foam cell infiltration, insulin resistance (DMII), as well as inflammation, high blood pressure, and plaque formation. Recently, UT antagonists such as SB-611812, palosuran, and most recently a piperazino-isoindolinone based antagonist have been developed in the hope of better understanding the UII system and treating its associated diseases.

  3. The Pseudo Signal Peptide of the Corticotropin-releasing Factor Receptor Type 2A Prevents Receptor Oligomerization*

    PubMed Central

    Teichmann, Anke; Rutz, Claudia; Kreuchwig, Annika; Krause, Gerd; Wiesner, Burkhard; Schülein, Ralf

    2012-01-01

    N-terminal signal peptides mediate the interaction of native proteins with the translocon complex of the endoplasmic reticulum membrane and are cleaved off during early protein biogenesis. The corticotropin-releasing factor receptor type 2a (CRF2(a)R) possesses an N-terminal pseudo signal peptide, which represents a so far unique domain within the large protein family of G protein-coupled receptors (GPCRs). In contrast to a conventional signal peptide, the pseudo signal peptide remains uncleaved and consequently forms a hydrophobic extension at the N terminus of the receptor. The functional consequence of the presence of the pseudo signal peptide is not understood. Here, we have analyzed the significance of this domain for receptor dimerization/oligomerization in detail. To this end, we took the CRF2(a)R and the homologous corticotropin-releasing factor receptor type 1 (CRF1R) possessing a conventional cleaved signal peptide and conducted signal peptide exchange experiments. Using single cell and single molecule imaging methods (fluorescence resonance energy transfer and fluorescence cross-correlation spectroscopy, respectively) as well as biochemical experiments, we obtained two novel findings; we could show that (i) the CRF2(a)R is expressed exclusively as a monomer, and (ii) the presence of the pseudo signal peptide prevents its oligomerization. Thus, we have identified a novel functional domain within the GPCR protein family, which plays a role in receptor oligomerization and which may be useful to study the functional significance of this process in general. PMID:22689579

  4. 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

  5. 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

  6. R3 receptor tyrosine phosphatases: conserved regulators of receptor tyrosine kinase signaling and tubular organ development.

    PubMed

    Jeon, Mili; Zinn, Kai

    2015-01-01

    R3 receptor tyrosine phosphatases (RPTPs) are characterized by extracellular domains composed solely of long chains of fibronectin type III repeats, and by the presence of a single phosphatase domain. There are five proteins in mammals with this structure, two in Drosophila and one in Caenorhabditis elegans. R3 RPTPs are selective regulators of receptor tyrosine kinase (RTK) signaling, and a number of different RTKs have been shown to be direct targets for their phosphatase activities. Genetic studies in both invertebrate model systems and in mammals have shown that R3 RPTPs are essential for tubular organ development. They also have important functions during nervous system development. R3 RPTPs are likely to be tumor suppressors in a number of types of cancer.

  7. R3 receptor tyrosine phosphatases: conserved regulators of receptor tyrosine kinase signaling and tubular organ development

    PubMed Central

    Jeon, Mili; Zinn, Kai

    2014-01-01

    Summary R3 receptor tyrosine phosphatases (RPTPs) are characterized by extracellular domains composed solely of long chains of fibronectin type III repeats, and by the presence of a single phosphatase domain. There are five proteins in mammals with this structure, two in Drosophila, and one in Caenorhabditis elegans. R3 RPTPs are selective regulators of receptor tyrosine kinase (RTK) signaling, and a number of different RTKs have been shown to be direct targets for their phosphatase activities. Genetic studies in both invertebrate model systems and in mammals have shown that R3 RPTPs are essential for tubular organ development. They also have important functions during nervous system development. R3 RPTPs are likely to be tumor suppressors in a number of types of cancer. PMID:25242281

  8. MERIT40 deficiency expands hematopoietic stem cell pools by regulating thrombopoietin receptor signaling

    PubMed Central

    Rozenova, Krasimira; Jiang, Jing; Donaghy, Ryan; Aressy, Bernadette; Greenberg, Roger A.

    2015-01-01

    Hematopoietic stem cell (HSC) self-renewal and multilineage reconstitution are controlled by positive and negative signaling cues with perturbations leading to disease. Lnk is an essential signaling adaptor protein that dampens signaling by the cytokine thrombopoietin (Tpo) to limit HSC expansion. Here, we show that MERIT40 (Mediator of RAP80 Interactions and Targeting 40 kDa [M40]), a core subunit of an Lnk-associated Lys63 deubiquitinating (DUB) complex, attenuates HSC expansion. M40 deficiency increases the size of phenotypic and functional HSC pools. M40−/− HSCs are more resistant to cytoablative stress, and exhibit superior repopulating ability and self-renewal upon serial transplantation. M40−/− HSCs display increased quiescence and decelerated cell cycle kinetics accompanied by downregulation of gene sets associated with cell division. Mechanistically, M40 deficiency triggers hypersensitivity to Tpo stimulation and the stem cell phenotypes are abrogated on a background null for the Tpo receptor Mpl. These results establish M40-containing DUB complexes as novel HSC regulators of HSC expansion, implicate Lys63 ubiquitination in HSC signaling, and point to DUB-specific inhibitors as reagents to expand stem cell populations. PMID:25636339

  9. CXCR3 chemokine receptor signaling mediates itch in experimental allergic contact dermatitis.

    PubMed

    Qu, Lintao; Fu, Kai; Yang, Jennifer; Shimada, Steven G; LaMotte, Robert H

    2015-09-01

    Persistent itch is a common symptom of allergic contact dermatitis (ACD) and represents a significant health burden. The chemokine CXCL10 is predominantly produced by epithelial cells during ACD. Although the chemokine CXCL10 and its receptor CXCR3 are implicated in the pathophysiology of ACD, it is largely unexplored for itch and pain accompanying this disorder. Here, we showed that CXCL10 and CXCR3 mRNA, protein, and signaling activity were upregulated in the dorsal root ganglion after contact hypersensitivity (CHS), a murine model of ACD, induced by squaric acid dibutylester. CXCL10 directly activated a subset of cutaneous dorsal root ganglion neurons innervating the area of CHS through neuronal CXCR3. In behavioral tests, a CXCR3 antagonist attenuated spontaneous itch- but not pain-like behaviors directed to the site of CHS. Injection of CXCL10 into the site of CHS elicited site-directed itch- but not pain-like behaviors, but neither type of CXCL10-evoked behaviors was observed in control mice. These results suggest that CXCL10/CXCR3 signaling mediates allergic itch but not inflammatory pain in the context of skin inflammation. Thus, upregulation of CXCL10/CXCR3 signaling in sensory neurons may contribute to itch associated with ACD. Targeting the CXCL10/CXCR3 signaling might be beneficial for the treatment of allergic itch.

  10. Principal function of mineralocorticoid signaling suggested by constitutive knockout of the mineralocorticoid receptor in medaka fish

    PubMed Central

    Sakamoto, Tatsuya; Yoshiki, Madoka; Takahashi, Hideya; Yoshida, Masayuki; Ogino, Yukiko; Ikeuchi, Toshitaka; Nakamachi, Tomoya; Konno, Norifumi; Matsuda, Kouhei; Sakamoto, Hirotaka

    2016-01-01

    As in osmoregulation, mineralocorticoid signaling is implicated in the control of brain-behavior actions. Nevertheless, the understanding of this role is limited, partly due to the mortality of mineralocorticoid receptor (MR)-knockout (KO) mice due to impaired Na+ reabsorption. In teleost fish, a distinct mineralocorticoid system has only been identified recently. Here, we generated a constitutive MR-KO medaka as the first adult-viable MR-KO animal, since MR expression is modest in osmoregulatory organs but high in the brain of adult medaka as for most teleosts. Hyper- and hypo-osmoregulation were normal in MR-KO medaka. When we studied the behavioral phenotypes based on the central MR localization, however, MR-KO medaka failed to track moving dots despite having an increase in acceleration of swimming. These findings reinforce previous results showing a minor role for mineralocorticoid signaling in fish osmoregulation, and provide the first convincing evidence that MR is required for normal locomotor activity in response to visual motion stimuli, but not for the recognition of these stimuli per se. We suggest that MR potentially integrates brain-behavioral and visual responses, which might be a conserved function of mineralocorticoid signaling through vertebrates. Importantly, this fish model allows for the possible identification of novel aspects of mineralocorticoid signaling. PMID:27897263

  11. Agonist-dependent cannabinoid receptor signalling in human trabecular meshwork cells

    PubMed Central

    McIntosh, B T; Hudson, B; Yegorova, S; Jollimore, C A B; Kelly, M E M

    2007-01-01

    Background and purpose: Trabecular meshwork (TM) is an ocular tissue involved in the regulation of aqueous humour outflow and intraocular pressure (IOP). CB1 receptors (CB1) are present in TM and cannabinoid administration decreases IOP. CB1 signalling was investigated in a cell line derived from human TM (hTM). Experimental approach: CB1 signalling was investigated using ratiometric Ca2+ imaging, western blotting and infrared In-Cell Western analysis. Key results: WIN55212-2, a synthetic aminoalkylindole cannabinoid receptor agonist (10–100 μM) increased intracellular Ca2+ in hTM cells. WIN55,212-2-mediated Ca2+ increases were blocked by AM251, a CB1 antagonist, but were unaffected by the CB2 antagonist, AM630. The WIN55,212-2-mediated increase in [Ca2+]i was pertussis toxin (PTX)-insensitive, therefore, independent of Gi/o coupling, but was attenuated by a dominant negative Gαq/11 subunit, implicating a Gq/11 signalling pathway. The increase in [Ca2+]i was dependent upon PLC activation and mobilization of intracellular Ca2+ stores. A PTX-sensitive increase in extracellular signal-regulated kinase (ERK1/2) phosphorylation was also observed in response to WIN55,212-2, indicative of a Gi/o signalling pathway. CB1-Gq/11 coupling to activate PLC-dependent increases in Ca2+ appeared to be specific to WIN55,212-2 and were not observed with other CB1 agonists, including CP55,940 and methanandamide. CP55940 produced PTX-sensitive increases in [Ca2+]i at concentrations ≥15 μM, and PTX-sensitive increases in ERK1/2 phosphorylation. Conclusions and implications: This study demonstrates that endogenous CB1 couples to both Gq/11 and Gi/o in hTM cells in an agonist-dependent manner. Cannabinoid activation of multiple CB1 signalling pathways in TM tissue could lead to differential changes in aqueous humour outflow and IOP. PMID:17922024

  12. Buprenorphine signalling is compromised at the N40D polymorphism of the human μ opioid receptor in vitro

    PubMed Central

    Knapman, Alisa; Santiago, Marina; Connor, Mark

    2014-01-01

    Background and Purpose There is significant variation in individual response to opioid drugs, which may result in inappropriate opioid therapy. Polymorphisms of the μ opioid receptor (MOP receptor) may contribute to individual variation in opioid response by affecting receptor function, and the effect may be ligand-specific. We sought to determine functional differences in MOP receptor signalling at several signalling pathways using a range of structurally distinct opioid ligands in cells expressing wild-type MOP receptors (MOPr-WT) and the commonly occurring MOP receptor variant, N40D. Experimental Approach MOPr-WT and MOPr-N40D were stably expressed in CHO cells and in AtT-20 cells. Assays of AC inhibition and ERK1/2 phosphorylation were performed on CHO cells, and assays of K activation were performed on AtT-20 cells. Signalling profiles for each ligand were compared between variants. Key Results Buprenorphine efficacy was reduced by over 50% at MOPr-N40D for AC inhibition and ERK1/2 phosphorylation. Buprenorphine potency was reduced threefold at MOPr-N40D for K channel activation. Pentazocine efficacy was reduced by 50% for G-protein-gated inwardly rectifying K channel activation at MOPr-N40D. No other differences were observed for any other ligands tested. Conclusions and Implications The N40D variant is present in 10–50% of the population. Buprenorphine is a commonly prescribed opioid analgesic, and many individuals do not respond to buprenorphine therapy. This study demonstrates that buprenorphine signalling to several effectors via the N40D variant of MOP receptors is impaired, and this may have important consequences in a clinical setting for individuals carrying the N40D allele. PMID:24846673

  13. Endogenous lysophosphatidic acid (LPA1 ) receptor agonists demonstrate ligand bias between calcium and ERK signalling pathways in human lung fibroblasts.

    PubMed

    Sattikar, Afrah; Dowling, Mark R; Rosethorne, Elizabeth M

    2017-02-01

    Human lung fibroblasts (HLF) express high levels of the LPA1 receptor, a GPCR that responds to the endogenous lipid mediator, lysophosphatidic acid (LPA). Several molecular species or analogues of LPA exist and have been detected in biological fluids such as serum and plasma. The most widely expressed of the LPA receptor family is the LPA1 receptor, which predominantly couples to Gq/11 , Gi/o and G12/13 proteins. This promiscuity of coupling raises the possibility that some of the LPA analogues may bias the LPA1 receptor towards one signalling pathway over another. Here, we have explored the signalling profiles of a range of LPA analogues in HLF that endogenously express the LPA1 receptor. HLF were treated with LPA analogues and receptor activation monitored via calcium mobilization and ERK phosphorylation. These analyses demonstrated that the 16:0, 17:0, 18:2 and C18:1 LPA analogues appear to exhibit ligand bias between ERK phosphorylation and calcium mobilization when compared with 18:1 LPA, one of the most abundant forms of LPA that has been found in human plasma. The importance of LPA as a key signalling molecule is shown by its widespread occurrence in biological fluids and its association with disease conditions such as fibrosis and cancer. These findings have important, as yet unexplored, implications for the (patho-) physiological signalling of the LPA1 receptor, as it may be influenced not only by the concentration of endogenous ligand but the isoform as well. © 2016 The British Pharmacological Society.

  14. Specificity and Structure of a High Affinity Activin Receptor-like Kinase 1 (ALK1) Signaling Complex

    PubMed Central

    Townson, Sharon A.; Martinez-Hackert, Erik; Greppi, Chloe; Lowden, Patricia; Sako, Dianne; Liu, June; Ucran, Jeffrey A.; Liharska, Katia; Underwood, Kathryn W.; Seehra, Jasbir; Kumar, Ravindra; Grinberg, Asya V.

    2012-01-01

    Activin receptor-like kinase 1 (ALK1), an endothelial cell-specific type I receptor of the TGF-β superfamily, is an important regulator of normal blood vessel development as well as pathological tumor angiogenesis. As such, ALK1 is an important therapeutic target. Thus, several ALK1-directed agents are currently in clinical trials as anti-angiogenic cancer therapeutics. Given the biological and clinical importance of the ALK1 signaling pathway, we sought to elucidate the biophysical and structural basis underlying ALK1 signaling. The TGF-β family ligands BMP9 and BMP10 as well as the three type II TGF-β family receptors ActRIIA, ActRIIB, and BMPRII have been implicated in ALK1 signaling. Here, we provide a kinetic and thermodynamic analysis of BMP9 and BMP10 interactions with ALK1 and type II receptors. Our data show that BMP9 displays a significant discrimination in type II receptor binding, whereas BMP10 does not. We also report the crystal structure of a fully assembled ternary complex of BMP9 with the extracellular domains of ALK1 and ActRIIB. The structure reveals that the high specificity of ALK1 for BMP9/10 is determined by a novel orientation of ALK1 with respect to BMP9, which leads to a unique set of receptor-ligand interactions. In addition, the structure explains how BMP9 discriminates between low and high affinity type II receptors. Taken together, our findings provide structural and mechanistic insights into ALK1 signaling that could serve as a basis for novel anti-angiogenic therapies. PMID:22718755

  15. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Pyrimidine-based compounds modulate CXCR2-mediated signaling and receptor turnover.

    PubMed

    Ha, Helen; Neamati, Nouri

    2014-07-07

    Chemokine receptor CXCR2 is expressed on various immune cells and is essential for neutrophil recruitment and angiogenesis at sites of acute and chronic inflammation caused by tissue injury or infection. Because of its role in inflammation, it has been implicated in a number of immune-mediated inflammatory diseases such as psoriasis, arthritis, COPD, cystic fibrosis, asthma, and various types of cancer. CXCR2 and its ligands are up-regulated in cancer cells as well as the tumor microenvironment, promoting tumor growth, angiogenesis, and invasiveness. Although pharmaceutical companies have pursued the development of CXCR2-specific small-molecule inhibitors as anti-inflammatory agents within the last decades, there are currently no clinically approved CXCR2 inhibitors. Using a high-throughput, cell-based assay specific for CXCR2, we screened an in-house library of structurally diverse compounds and identified a class of pyrimidine-based compounds that alter CXCR2-mediated second messenger signaling. Our lead compound, CX797, inhibited IL8-mediated cAMP signaling and receptor degradation while specifically up-regulating IL8-mediated β-arrestin-2 recruitment. CX797 also inhibited IL8-mediated cell migration. Mechanistic comparison of CX797 and a previously reported CXCR2 inhibitor, SB265610, show these two classes of compounds have a distinct mechanism of action on CXCR2.

  17. Lung injury pathways: Adenosine receptor 2B signaling limits development of ischemic bronchiolitis obliterans organizing pneumonia.

    PubMed

    Densmore, John C; Schaid, Terry R; Jeziorczak, Paul M; Medhora, Meetha; Audi, Said; Nayak, Shraddha; Auchampach, John; Dwinell, Melinda R; Geurts, Aron M; Jacobs, Elizabeth R

    2017-02-01

    Purpose/Aim of the Study: Adenosine signaling was studied in bronchiolitis obliterans organizing pneumonia (BOOP) resulting from unilateral lung ischemia. Ischemia was achieved by either left main pulmonary artery or complete hilar ligation. Sprague-Dawley (SD) rats, Dahl salt sensitive (SS) rats and SS mutant rat strains containing a mutation in the A2B adenosine receptor gene (Adora2b) were studied. Adenosine concentrations were measured in bronchoalveolar lavage (BAL) by HPLC. A2A (A2AAR) and A2B adenosine receptor (A2BAR) mRNA and protein were quantified. Twenty-four hours after unilateral PA ligation, BAL adenosine concentrations from ischemic lungs were increased relative to contralateral lungs in SD rats. A2BAR mRNA and protein concentrations were increased after PA ligation while miR27a, a negatively regulating microRNA, was decreased in ischemic lungs. A2AAR mRNA and protein concentrations remained unchanged following ischemia. A2BAR protein was increased in PA ligated lungs of SS rats after 7 days, and 4 h after complete hilar ligation in SD rats. SS-Adora2b mutants showed a greater extent of BOOP relative to SS rats, and greater inflammatory changes. Increased A2BAR and adenosine following unilateral lung ischemia as well as more BOOP in A2BAR mutant rats implicate a protective role for A2BAR signaling in countering ischemic lung injury.

  18. Constitutively Active Lck Kinase in T Cells Drives Antigen Receptor Signal Transduction

    PubMed Central

    Nika, Konstantina; Soldani, Cristiana; Salek, Mogjiborahman; Paster, Wolfgang; Gray, Adrian; Etzensperger, Ruth; Fugger, Lars; Polzella, Paolo; Cerundolo, Vincenzo; Dushek, Omer; Höfer, Thomas; Viola, Antonella; Acuto, Oreste

    2010-01-01

    Summary T cell antigen receptor (TCR) and coreceptor ligation is thought to initiate signal transduction by inducing activation of the kinase Lck. Here we showed that catalytically active Lck was present in unstimulated naive T cells and thymocytes and was readily detectable in these cells in lymphoid organs. In naive T cells up to ∼40% of total Lck was constitutively activated, part of which was also phosphorylated on the C-terminal inhibitory site. Formation of activated Lck was independent of TCR and coreceptors but required Lck catalytic activity and its maintenance relied on monitoring by the HSP90-CDC37 chaperone complex to avoid degradation. The amount of activated Lck did not change after TCR and coreceptor engagement; however it determined the extent of TCR-ζ phosphorylation. Our findings suggest a dynamic regulation of Lck activity that can be promptly utilized to initiate T cell activation and have implications for signaling by other immune receptors. PMID:20541955

  19. MAPK signaling pathways mediate AMPA receptor trafficking in an in vitro model of classical conditioning.

    PubMed

    Keifer, Joyce; Zheng, Zhao-Qing; Zhu, Dantong

    2007-03-01

    The mitogen-activated protein kinase (MAPK) signal transduction pathways have been implicated in underlying mechanisms of synaptic plasticity and learning. However, the differential roles of the MAPK family members extracellular signal-regulated kinase (ERK) and p38 in learning remain to be clarified. Here, an in vitro model of classical conditioning was examined to assess the roles of ERK and p38 MAPK in this form of learning. Previous studies showed that NMDA-mediated trafficking of synaptic glutamate receptor 4 (GluR4)-containing AMPA receptors (AMPARs) underlies conditioning in this preparation and that this is accomplished through GluR4 interactions with the immediate-early gene protein Arc and the actin cytoskeleton. Here, it is shown that attenuation of conditioned responses (CRs) by ERK and p38 MAPK antagonists is associated with significantly reduced synaptic localization of GluR4 subunits. Western blotting reveals that p38 MAPK significantly increases its activation levels during late stages of conditioning during CR expression. In contrast, ERK MAPK activation is enhanced in early conditioning during CR acquisition. The results suggest that MAPKs have a central role in the synaptic delivery of GluR4-containing AMPARs during in vitro classical conditioning.

  20. Peroxisome-proliferator-activated receptors regulate redox signaling in the cardiovascular system.

    PubMed

    Kim, Teayoun; Yang, Qinglin

    2013-06-26

    Peroxisome-proliferator-activated receptors (PPARs) comprise three subtypes (PPARα, δ and γ) to form a nuclear receptor superfamily. PPARs act as key transcriptional regulators of lipid metabolism, mitochondrial biogenesis, and anti-oxidant defense. While their roles in regulating lipid metabolism have been well established, the role of PPARs in regulating redox activity remains incompletely understood. Since redox activity is an integral part of oxidative metabolism, it is not surprising that changes in PPAR signaling in a specific cell or tissue will lead to alteration of redox state. The effects of PPAR signaling are directly related to PPAR expression, protein activities and PPAR interactions with their coregulators. The three subtypes of PPARs regulate cellular lipid and energy metabolism in most tissues in the body with overlapping and preferential effects on different metabolic steps depending on a specific tissue. Adding to the complexity, specific ligands of each PPAR subtype may also display different potencies and specificities of their role on regulating the redox pathways. Moreover, the intensity and extension of redox regulation by each PPAR subtype are varied depending on different tissues and cell types. Both beneficial and adverse effects of PPAR ligands against cardiovascular disorders have been extensively studied by many groups. The purpose of the review is to summarize the effects of each PPAR on regulating redox and the underlying mechanisms, as well as to discuss the implications in the cardiovascular system.

  1. Signal transduction and functional selectivity of F15599, a preferential post-synaptic 5-HT1A receptor agonist

    PubMed Central

    Newman-Tancredi, A; Martel, J-C; Assié, M-B; Buritova, J; Lauressergues, E; Cosi, C; Heusler, P; Slot, L Bruins; Colpaert, FC; Vacher, B; Cussac, D

    2009-01-01

    Background and purpose: Activation of post-synaptic 5-HT1A receptors may provide enhanced therapy against depression. We describe the signal transduction profile of F15599, a novel 5-HT1A receptor agonist. Experimental approach: F15599 was compared with a chemical congener, F13714, and with (+)8-OH-DPAT in models of signal transduction in vitro and ex vivo. Key results: F15599 was highly selective for 5-HT1A receptors in binding experiments and in [35S]-GTPγS autoradiography of rat brain, where F15599 increased labelling in regions expressing 5-HT1A receptors. In cell lines expressing h5-HT1A receptors, F15599 more potently stimulated extracellular signal-regulated kinase (ERK1/2) phosphorylation, compared with G-protein activation, internalization of h5-HT1A receptors or inhibition of cAMP accumulation. F13714, (+)8-OH-DPAT and 5-HT displayed a different rank order of potency for these responses. F15599 stimulated [35S]-GTPγS binding more potently in frontal cortex than raphe. F15599, unlike 5-HT, more potently and efficaciously stimulated Gαi than Gαo activation. In rat prefrontal cortex (a region expressing post-synaptic 5-HT1A receptors), F15599 potently activated ERK1/2 phosphorylation and strongly induced c-fos mRNA expression. In contrast, in raphe regions (expressing pre-synaptic 5-HT1A receptors) F15599 only weakly or did not induce c-fos mRNA expression. Finally, despite its more modest affinity in vitro, F15599 bound to 5-HT1A receptors in vivo almost as potently as F13714. Conclusions and implications: F15599 showed a distinctive activation profiles for 5-HT1A receptor-mediated signalling pathways, unlike those of reference agonists and consistent with functional selectivity at 5-HT1A receptors. In rat, F15599 potently activated signalling in prefrontal cortex, a feature likely to underlie its beneficial effects in models of depression and cognition. PMID:19154445

  2. NMDA and PACAP Receptor Signaling Interact to Mediate Retinal-Induced SCN Cellular Rhythmicity in the Absence of Light

    PubMed Central

    Webb, Ian C.; Coolen, Lique M.; Lehman, Michael N.

    2013-01-01

    The “core” region of the suprachiasmatic nucleus (SCN), a central clock responsible for coordinating circadian rhythms, shows a daily rhythm in phosphorylation of extracellular regulated kinase (pERK). This cellular rhythm persists under constant darkness and, despite the absence of light, is dependent upon inputs from the eye. The neural signals driving this rhythmicity remain unknown and here the roles of glutamate and PACAP are examined. First, rhythmic phosphorylation of the NR1 NMDA receptor subunit (pNR1, a marker for receptor activation) was shown to coincide with SCN core pERK, with a peak at circadian time (CT) 16. Enucleation and intraocular TTX administration attenuated the peak in the pERK and pNR1 rhythms, demonstrating that activation of the NMDA receptor and ERK in the SCN core at CT16 are dependent on retinal inputs. In contrast, ERK and NR1 phosphorylation in the SCN shell region were unaffected by these treatments. Intraventricular administration of the NMDA receptor antagonist MK-801 also attenuated the peak in SCN core pERK, indicating that ERK phosphorylation in this region requires NMDA receptor activation. As PACAP is implicated in photic entrainment and is known to modulate glutamate signaling, the effects of a PAC1 receptor antagonist (PACAP 6-38) on SCN core pERK and pNR1 also were examined. PACAP 6-38 administration attenuated SCN core pERK and pNR1, suggesting that PACAP induces pERK directly, and indirectly via a modulation of NMDA receptor signaling. Together, these data indicate that, in the absence of light, retinal-mediated NMDA and PAC1 receptor activation interact to induce cellular rhythms in the SCN core. These results highlight a novel function for glutamate and PACAP release in the hamster SCN apart from their well-known roles in the induction of photic circadian clock resetting. PMID:24098484

  3. 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.

  4. Anabolic Androgenic Steroids and Intracellular Calcium Signaling: A Mini Review on Mechanisms and Physiological Implications

    PubMed Central

    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.

    2015-01-01

    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. PMID:21443511

  5. Signal transmission within the P2X2 trimeric receptor

    PubMed Central

    Kubo, Yoshihiro

    2014-01-01

    P2X2 receptor channel, a homotrimer activated by the binding of extracellular adenosine triphosphate (ATP) to three intersubunit ATP-binding sites (each located ∼50 Å from the ion permeation pore), also shows voltage-dependent activation upon hyperpolarization. Here, we used tandem trimeric constructs (TTCs) harboring critical mutations at the ATP-binding, linker, and pore regions to investigate how the ATP activation signal is transmitted within the trimer and how signals generated by ATP and hyperpolarization converge. Analysis of voltage- and [ATP]-dependent gating in these TTCs showed that: (a) Voltage- and [ATP]-dependent gating of P2X2 requires binding of at least two ATP molecules. (b) D315A mutation in the β-14 strand of the linker region connecting the ATP-binding domains to the pore-forming helices induces two different gating modes; this requires the presence of the D315A mutation in at least two subunits. (c) The T339S mutation in the pore domains of all three subunits abolishes the voltage dependence of P2X2 gating in saturating [ATP], making P2X2 equally active at all membrane potentials. Increasing the number of T339S mutations in the TTC results in gradual changes in the voltage dependence of gating from that of the wild-type channel, suggesting equal and independent contributions of the subunits at the pore level. (d) Voltage- and [ATP]-dependent gating in TTCs differs depending on the location of one D315A relative to one K308A that blocks the ATP binding and downstream signal transmission. (e) Voltage- and [ATP]-dependent gating does not depend on where one T339S is located relative to K308A (or D315A). Our results suggest that each intersubunit ATP-binding signal is directly transmitted on the same subunit to the level of D315 via the domain that contributes K308 to the β-14 strand. The signal subsequently spreads equally to all three subunits at the level of the pore, resulting in symmetric and independent contributions of the three

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

    PubMed Central

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

    2015-01-01

    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) β/γ 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 RARγ activation. Furthermore, inhibition of basal RAR signaling in the skin promoted BCC carcinogenesis, suggesting that endogenous RAR signaling restrains BCC growth. PMID:18483315

  7. Dopamine receptor-interacting proteins: the Ca(2+) connection in dopamine signaling.

    PubMed

    Bergson, Clare; Levenson, Robert; Goldman-Rakic, Patricia S; Lidow, Michael S

    2003-09-01

    Abnormal activity of the dopamine system has been implicated in several psychiatric and neurological illnesses; however, lack of knowledge about the precise sites of dopamine dysfunction has compromised our ability to improve the efficacy and safety of dopamine-related drugs used in treatment modalities. Recent work suggests that dopamine transmission is regulated via the concerted efforts of a cohort of cytoskeletal, adaptor and signaling proteins called dopamine receptor-interacting proteins (DRIPs). The discovery that two DRIPs, calcyon and neuronal Ca(2+) sensor 1 (NCS-1), are upregulated in schizophrenia highlights the possibility that altered protein interactions and defects in Ca(2+) homeostasis might contribute to abnormalities in the brain dopamine system in neuropsychiatric diseases.

  8. 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

  9. The Pollen Receptor Kinase LePRK2 Mediates Growth-Promoting Signals and Positively Regulates Pollen Germination and Tube Growth

    USDA-ARS?s Scientific Manuscript database

    In flowering plants, the process of pollen germination and tube growth is required for successful fertilization. A pollen receptor kinase from tomato, LePRK2, has been implicated in signaling during pollen germination and tube growth as well as in mediating pollen (tube)-pistil communication. Here w...

  10. Neuropilin 1 binds platelet-derived growth factor (PDGF)-D and is a co-receptor in PDGF-D/PDGF receptor β signaling.

    PubMed

    Muhl, Lars; Folestad, Erika Bergsten; Gladh, Hanna; Wang, Yixin; Moessinger, Christine; Jakobsson, Lars; Eriksson, Ulf

    2017-03-02

    Platelet-derived growth factor (PDGF)-D is a PDGF receptor β (PDGFRβ) specific ligand implicated in a number of pathological conditions, such as cardiovascular disease and cancer, but its biological function remains incompletely understood.In this study, we demonstrate that PDGF-D binds directly to NRP1, with the requirement of the C-terminal Arg residue of PDGF-D. Stimulation with PDGF-D, but not PDGF-B, induced PDGFRβ/NRP1 complex formation in fibroblasts. Additionally, PDGF-D induced translocation of NRP1 to cell-cell junctions in endothelial cells, independent of PDGFRβ, altering the availability of NRP1 for VEGF-A/VEGF receptor 2 signaling. PDGF-D showed differential effects on pericyte behavior in ex vivo sprouting assays, compared to PDGF-B. Furthermore, PDGF-D induced PDGFRβ/NRP1 interaction in the trans-configuration between endothelial cells and pericytes.In summary, we show that NRP1 can act as a co-receptor for PDGF-D in PDGFRβ signaling, possibly implicated in intercellular communication in the vascular wall.

  11. 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

  12. 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

  13. Science Signaling Podcast for 20 December 2016: Trans-inhibition by Fc receptors.

    PubMed

    Daëron, Marc; VanHook, Annalisa M

    2016-12-20

    This Podcast features an interview with Marc Daëron, author of a Research Article that appears in the 20 December 2016 issue of Science Signaling, about a mechanism by which an Fc receptor can inhibit signaling by other receptors without aggregating with those other receptors. Engagement of Fc receptors on basophils and mast cells can either activate these cells, which promotes autoimmune and allergic inflammation, or prevent these cells from being activated. Whether these cells are activated depends upon which Fc receptors are present in clusters, because some Fc receptors can inhibit signaling by other Fc receptors that are present in the same signalosome, a phenomenon known as cis-inhibition. Malbec et al. identified a mechanism whereby inhibitory Fc receptors limit signaling by activating Fc receptors without being present in the same signalosome. This mechanism of trans-inhibition also allowed inhibitory Fc receptors to limit signaling by growth factor receptors in mast cells and oncogene-induced proliferation in mastocytoma cells.Listen to Podcast. Copyright © 2016, American Association for the Advancement of Science.

  14. 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...

  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. The hepatocyte growth factor (HGF)-MET receptor tyrosine kinase signaling pathway: Diverse roles in modulating immune cell functions.

    PubMed

    Ilangumaran, Subburaj; Villalobos-Hernandez, Alberto; Bobbala, Diwakar; Ramanathan, Sheela

    2016-06-01

    Hepatocyte growth factor (HGF) signaling via the MET receptor is essential for embryonic development and tissue repair. On the other hand, deregulated MET signaling promotes tumor progression in diverse types of cancers. Even though oncogenic MET signaling remains the major research focus, the HGF-MET axis has also been implicated in diverse aspects of immune cell development and functions. In the presence of other hematopoietic growth factors, HGF promotes the development of erythroid, myeloid and lymphoid lineage cells and thrombocytes. In monocytes and macrophages responding to inflammatory stimuli, induction of autocrine HGF-MET signaling can contribute to tissue repair via stimulating anti-inflammatory cytokine production. HGF-MET signaling can also modulate adaptive immune response by facilitating the migration of Langerhans cells and dendritic cells to draining lymph nodes. However, MET signaling has also been shown to induce tolerogenic dendritic cells in mouse models of graft-versus-host disease and experimental autoimmune encephalomyelitis. HGF-MET axis is also implicated in promoting thymopoiesis and the survival and migration of B lymphocytes. Recent studies have shown that MET signaling induces cardiotropism in activated T lymphocytes. Further understanding of the HGF-MET axis in the immune system would allow its therapeutic manipulation to improve immune cell reconstitution, restore immune homeostasis and to treat immuno-inflammatory diseases.

  17. Roles of toll-like receptors signaling in organ transplantation.

    PubMed

    Li, Ting; Chen, Guodong; Zhang, Zheng

    2011-12-01

    Organ transplantation is the gold standard of treatment for patients with end-stage organ failure. However, transplant recipients must take immunosuppressive drugs lifelong to fight against rejection, which is inevitably caused by the recipient's immune system in response to transplanted foreign tissues. Despite advances in the prevention of acute rejection, it is still a significant and potentially devastating complication of solid organ transplantation. Moreover, chronic allograft dysfunction as a result of acute and chronic alloimmune-mediated injury still develops in a majority of transplant recipients regardless of continuous immunosuppression. While host adaptive immune responses elicited by T lymphocytes are primarily responsible for allotransplant rejection, emerging evidence supports an important role of the innate immune system in the development of organ rejection. Innate immune recognition is initiated by a set of diverse receptors that belong to different protein families including the family of toll-like receptors (TLRs). TLR signaling is a highly specialized system that can identify a variety of microbial and endogenous mediators, and activate the innate immune system in response to danger. The discovery of TLRs over the past 10 years has started a new era in understanding the molecular events that initiate and regulate the inflammatory response following organ transplantation. They influence the adaptive immune reactions and contribute to ischemic reperfusion injury, acute and chronic allograft rejection, and tolerance induction. Their role as potential targets for therapeutic intervention has just begun to be appreciated. In this article, we summarize the structural and functional characteristics of TLRs and their ligands. We focus on the studies to define the roles of TLRs in ischemic reperfusion injury, allotransplant rejection, and immune regulation in both animal models and clinical transplantation.

  18. 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

  19. Hepatitis B virus inhibits insulin receptor signaling and impairs liver regeneration via intracellular retention of the insulin receptor.

    PubMed

    Barthel, Sebastian Robert; Medvedev, Regina; Heinrich, Thekla; Büchner, Sarah Manon; Kettern, Nadja; Hildt, Eberhard

    2016-11-01

    Hepatitis B virus (HBV) causes severe liver disease but the underlying mechanisms are incompletely understood. During chronic HBV infection, the liver is recurrently injured by immune cells in the quest for viral elimination. To compensate tissue injury, liver regeneration represents a vital process which requires proliferative insulin receptor signaling. This study aims to investigate the impact of HBV on liver regeneration and hepatic insulin receptor signaling. After carbon tetrachloride-induced liver injury, liver regeneration is delayed in HBV transgenic mice. These mice show diminished hepatocyte proliferation and increased expression of fibrosis markers. This is in accordance with a reduced activation of the insulin receptor although HBV induces expression of the insulin receptor via activation of NF-E2-related factor 2. This leads to increased intracellular amounts of insulin receptor in HBV expressing hepatocytes. However, intracellular retention of the receptor simultaneously reduces the amount of functional insulin receptors on the cell surface and thereby attenuates insulin binding in vitro and in vivo. Intracellular retention of the insulin receptor is caused by elevated amounts of α-taxilin, a free syntaxin binding protein, in HBV expressing hepatocytes preventing proper targeting of the insulin receptor to the cell surface. Consequently, functional analyses of insulin responsiveness revealed that HBV expressing hepatocytes are less sensitive to insulin stimulation leading to delayed liver regeneration. This study describes a novel pathomechanism that uncouples HBV expressing hepatocytes from proliferative signals and thereby impedes compensatory liver regeneration after liver injury.

  20. Oncostatin M and interleukin-31: Cytokines, receptors, signal transduction and physiology.

    PubMed

    Hermanns, Heike M

    2015-10-01

    Oncostatin M (OSM) and interleukin-31 (IL-31) are two cytokines belonging to the IL-6 family which share a common signaling receptor subunit, the OSM receptor beta (OSMRβ). Both of them are released by monocytes/macrophages, dendritic cells and T lymphocytes in inflammatory situations and upon binding to their respective receptor complexes they signal mainly via the JAK/STAT pathway. Besides sharing many biochemical properties, both display divergent physiological functions. This review summarizes aspects of cytokine transcription and biosynthesis, cytokine-receptor interactions, cross-species activities, signal transduction and physiology delineated from recent findings in genetic mouse models for both cytokines, OSM and IL-31.

  1. 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

  2. C-type lectin-like receptors of the dectin-1 cluster: ligands and signaling pathways.

    PubMed

    Plato, Anthony; Willment, Janet A; Brown, Gordon D

    2013-04-01

    Innate immunity is constructed around genetically encoded receptors that survey the intracellular and extracellular environments for signs of invading microorganisms. These receptors recognise the invader and through complex intracellular networks of molecular signaling, they destroy the threat whilst instructing effective adaptive immune responses. Many of these receptors, like the Toll-like receptors in particular, are well-known for their ability to mediate downstream responses upon recognition of exogenous or endogenous ligands; however, the emerging family known as the C-type lectin-like receptors contains many members that have a huge impact on immune and homeostatic regulation. Of particular interest here are the C-type lectin-like receptors that make up the Dectin-1 cluster and their intracellular signaling motifs that mediate their functions. In this review, we aim to draw together current knowledge of ligands, motifs and signaling pathways, present downstream of Dectin-1 cluster receptors, and discuss how these dictate their role within biological systems.

  3. A novel insulinotropic mechanism of whole grain-derived γ-oryzanol via the suppression of local dopamine D2 receptor signalling in mouse islet

    PubMed Central

    Kozuka, Chisayo; Sunagawa, Sumito; Ueda, Rei; Higa, Moritake; Ohshiro, Yuzuru; Tanaka, Hideaki; Shimizu-Okabe, Chigusa; Takayama, Chitoshi; Matsushita, Masayuki; Tsutsui, Masato; Ishiuchi, Shogo; Nakata, Masanori; Yada, Toshihiko; Miyazaki, Jun-ichi; Oyadomari, Seiichi; Shimabukuro, Michio; Masuzaki, Hiroaki

    2015-01-01

    Background and Purpose γ-Oryzanol, derived from unrefined rice, attenuated the preference for dietary fat in mice, by decreasing hypothalamic endoplasmic reticulum stress. However, no peripheral mechanisms, whereby γ-oryzanol could ameliorate glucose dyshomeostasis were explored. Dopamine D2 receptor signalling locally attenuates insulin secretion in pancreatic islets, presumably via decreased levels of intracellular cAMP. We therefore hypothesized that γ-oryzanol would improve high-fat diet (HFD)-induced dysfunction of islets through the suppression of local D2 receptor signalling. Experimental Approach Glucose metabolism and regulation of molecules involved in D2 receptor signalling in pancreatic islets were investigated in male C57BL/6J mice, fed HFD and treated with γ-oryzanol. In isolated murine islets and the beta cell line, MIN6, the effects of γ-oryzanol on glucose-stimulated insulin secretion (GSIS) was analysed using siRNA for D2 receptors and a variety of compounds which alter D2 receptor signalling. Key Results In islets, γ-oryzanol enhanced GSIS via the activation of the cAMP/PKA pathway. Expression of molecules involved in D2 receptor signalling was increased in islets from HFD-fed mice, which were reciprocally decreased by γ-oryzanol. Experiments with siRNA for D2 receptors and D2 receptor ligands in vitro suggest that γ-oryzanol suppressed D2 receptor signalling and augmented GSIS. Conclusions and Implications γ-Oryzanol exhibited unique anti-diabetic properties. The unexpected effects of γ-oryzanol on D2 receptor signalling in islets may provide a novel; natural food-based, approach to anti-diabetic therapy. PMID:26140534

  4. Novel implications of Lingo-1 and its signaling partners in schizophrenia.

    PubMed

    Fernandez-Enright, F; Andrews, J L; Newell, K A; Pantelis, C; Huang, X F

    2014-01-21

    Myelination and neurite outgrowth both occur during brain development, and their disturbance has been previously been implicated in the pathophysiology of schizophrenia. Leucine-rich repeat and immunoglobulin domain-containing protein (Lingo-1) is a potent negative regulator of axonal myelination and neurite extension. As co-factors of Lingo-1 signaling (Nogo receptor (NgR), With No Lysine (K) (WNK1) and Myelin transcription factor 1 (Myt1)) have been implicated in the genetics of schizophrenia, we explored for the first time the role of Lingo-1 signaling pathways in this disorder. Lingo-1 protein, together with its co-receptor and co-factor proteins NgR, tumor necrosis factor (TNF) receptor orphan Y (TROY), p75, WNK1 and Myt1, have never been explored in the pathogenesis of schizophrenia. We examined protein levels of Lingo-1, NgR, TROY, p75, WNK1, Myt1 and myelin basic protein (MBP) (as a marker of myelination) within the post-mortem dorsolateral prefrontal cortex (DLPFC) (37 schizophrenia patients versus 37 matched controls) and hippocampus (Cornu Ammonis, CA1 and CA3) (20 schizophrenia patients versus 20 matched controls from the same cohort). Both of these brain regions are highly disrupted in the schizophrenia pathophysiology. There were significant increases in Lingo-1 (P<0.001) and Myt1 (P=0.023) and a reduction in NgR (P<0.001) in the DLPFC in schizophrenia subjects compared with controls. There were also increases in both TROY (P=0.001) and WNK1 (P=0.011) in the CA1 of schizophrenia subjects and, in contrast to the DLPFC, there was an increase in NgR (P=0.006) in the CA3 of schizophrenia subjects compared with controls. No significant difference was reported for MBP levels (P>0.05) between the schizophrenia and control groups in the three tested regions. This is the first time that a study has shown altered Lingo-1 signaling in the schizophrenia brain. Our novel findings may present a direct application for the use of a Lingo-1 antagonist to complement

  5. Imipramine protects retinal ganglion cells from oxidative stress through the tyrosine kinase receptor B signaling pathway

    PubMed Central

    Han, Ming-lei; Liu, Guo-hua; Guo, Jin; Yu, Shu-juan; Huang, Jing

    2016-01-01

    Retinal ganglion cell (RGC) degeneration is irreversible in glaucoma and tyrosine kinase receptor B (TrkB)-associated signaling pathways have been implicated in the process. In this study, we attempted to examine whether imipramine, a tricyclic antidepressant, may protect hydrogen peroxide (H2O2)-induced RGC degeneration through the activation of the TrkB pathway in RGC-5 cell lines. RGC-5 cell lines were pre-treated with imipramine 30 minutes before exposure to H2O2. Western blot assay showed that in H2O2 -damaged RGC-5 cells, imipramine activated TrkB pathways through extracellular signal-regulated protein kinase/TrkB phosphorylation. TUNEL staining assay also demonstrated that imipramine ameliorated H2O2 -induced apoptosis in RGC-5 cells. Finally, TrkB-IgG intervention was able to reverse the protective effect of imipramine on H2O2 -induced RGC-5 apoptosis. Imipramine therefore protects RGCs from oxidative stress-induced apoptosis through the TrkB signaling pathway. PMID:27127489

  6. 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

  7. Disrupting Androgen Receptor Signaling Induces Snail-Mediated Epithelial-Mesenchymal Plasticity in Prostate Cancer.

    PubMed

    Miao, Lu; Yang, Lin; Li, Rui; Rodrigues, Daniel N; Crespo, Mateus; Hsieh, Jer-Tsong; Tilley, Wayne D; de Bono, Johann; Selth, Luke A; Raj, Ganesh V

    2017-06-01

    Epithelial-to-mesenchymal plasticity (EMP) has been linked to metastasis, stemness, and drug resistance. In prostate cancer, EMP has been associated with both suppression and activation of the androgen receptor (AR) signaling. Here we investigated the effect of the potent AR antagonist enzalutamide on EMP in multiple preclinical models of prostate cancer and patient tissues. Enzalutamide treatment significantly enhanced the expression of EMP drivers (ZEB1, ZEB2, Snail, Twist, and FOXC2) and mesenchymal markers (N-cadherin, fibronectin, and vimentin) in prostate cancer cells, enhanced prostate cancer cell migration, and induced prostate cancer transformation to a spindle, fibroblast-like morphology. Enzalutamide-induced EMP required concomitant suppression of AR signaling and activation of the EMP-promoting transcription factor Snail, as evidenced by both knockdown and overexpression studies. Supporting these findings, AR signaling and Snail expression were inversely correlated in C4-2 xenografts, patient-derived castration-resistant metastases, and clinical samples. For the first time, we elucidate a mechanism explaining the inverse relationship between AR and Snail. Specifically, we found that AR directly repressed SNAI1 gene expression by binding to specific AR-responsive elements within the SNAI1 promoter. Collectively, our findings demonstrate that de-repression of Snail and induction of EMP is an adaptive response to enzalutamide with implications for therapy resistance. Cancer Res; 77(11); 3101-12. ©2017 AACR. ©2017 American Association for Cancer Research.

  8. Beta2-adrenergic receptor signaling mediates corneal epithelial wound repair.

    PubMed

    Ghoghawala, Shahed Y; Mannis, Mark J; Pullar, Christine E; Rosenblatt, Mark I; Isseroff, R Rivkah

    2008-05-01

    Beta-adrenergic receptor (AR) antagonists are frequently prescribed ophthalmic drugs, yet previous investigations into how catecholamines affect corneal wound healing have yielded conflicting With the use of an integrated pharmacologic and genetic approach, the authors investigated how the beta-AR impacts corneal epithelial healing. Migratory rates of cultured adult murine corneal epithelial (AMCE) cells and in vivo corneal wound healing were examined in beta2-AR(+/+) and beta2-AR(-/-) mice. Signaling pathways were evaluated by immunoblotting. results. The beta-AR agonist isoproterenol decreased AMCE cell migratory speed to 70% of untreated controls, and this was correlated with a 0.60-fold decrease in levels of activated phospho-ERK (P-ERK). Treatment with the beta-AR antagonist (timolol) increased speed 33% and increased P-ERK 2.4-fold (P < 0.05). The same treatment protocols had no effect on AMCE cells derived from beta2-AR(-/-) mice; all treatment groups showed statistically equivalent migratory speeds and ERK phosphorylation. In beta2-AR(+/+) animals, the beta-AR agonist (isoproterenol) delayed the rate of in vivo corneal wound healing by 79%, whereas beta-AR antagonist (timolol) treatment increased the rate of healing by 16% (P < 0.05) compared with saline-treated controls. In contrast, in the beta2-AR(-/-) mice, all treatment groups demonstrated equivalent rates of wound healing. Additionally, murine corneal epithelial cell expressed the catecholamine-synthesizing enzyme tyrosine hydroxylase and detectable levels of epinephrine (184.5 pg/mg protein). The authors provide evidence of an endogenous autocrine catecholamine signaling pathway dependent on an intact beta2-AR for the modulation of corneal epithelial wound repair.

  9. 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

    2013-11-05

    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.

  10. Biochemical Signaling of PD-1 on T Cells and Its Functional Implications

    PubMed Central

    Boussiotis, Vassiliki A.; Chatterjee, Pranam; Li, Lequn

    2014-01-01

    Maintenance of peripheral tolerance is essential for homeostasis of the immune system. While central tolerance mechanisms result in deletion of the majority of self-reactive T cells, T lymphocytes specific for self-antigens also escape this process and circulate in the periphery. To control the development of autoimmunity, multiple mechanisms of peripheral tolerance have evolved, including T cell anergy, deletion and suppression by regulatory T cells (Treg). The pathway consisting of the PD-1 receptor (CD279) and its ligands PD-L1 (B7-H1, CD274) and PD-L2 (B7-DC; CD273) plays a vital role in the induction and maintenance of peripheral tolerance. This pathway also regulates the balance between stimulatory and inhibitory signals needed for effective immunity and maintenance of T cell homeostasis. In contrast to this important beneficial role in maintaining T cell homeostasis, PD-1 mediates potent inhibitory signals that prevent the expansion and function of T effector cells and have detrimental effects on anti-viral and anti-tumor immunity. In spite of the compelling studies on the significant functional role of PD-1 in mediating inhibition of activated T cells, little is known about how PD-1 blocks T cell activation. Here, we will provide a brief overview of the signaling events that are regulated by PD-1 triggering and we will discuss their implications on cell intrinsic and extrinsic mechanisms that determine the fate and function of T effector cells. PMID:25098287

  11. Biochemical signaling of PD-1 on T cells and its functional implications.

    PubMed

    Boussiotis, Vassiliki A; Chatterjee, Pranam; Li, Lequn

    2014-01-01

    Maintenance of peripheral tolerance is essential for homeostasis of the immune system. While central tolerance mechanisms result in deletion of the majority of self-reactive T cells, T lymphocytes specific for self-antigens also escape this process and circulate in the periphery. To control the development of autoimmunity, multiple mechanisms of peripheral tolerance have evolved, including T cell anergy, deletion, and suppression by regulatory T (Treg) cells. The pathway consisting of the programmed cell death 1 (PD-1) receptor (CD279) and its ligands PD-L1 (B7-H1, CD274) and PD-L2 (B7-DC; CD273) plays a vital role in the induction and maintenance of peripheral tolerance. This pathway also regulates the balance between stimulatory and inhibitory signals needed for effective immunity and maintenance of T cell homeostasis. In contrast to this important beneficial role in maintaining T cell homeostasis, PD-1 mediates potent inhibitory signals that prevent the expansion and function of T effector cells and have detrimental effects on antiviral and antitumor immunity. Despite the compelling studies on the significant functional role of PD-1 in mediating inhibition of activated T cells, little is known about how PD-1 blocks T cell activation. Here, we will provide a brief overview of the signaling events that are regulated by PD-1 triggering, and we will discuss their implications on cell intrinsic and extrinsic mechanisms that determine the fate and function of T effector cells.

  12. Orexin/hypocretin signaling at the orexin 1 receptor regulates cue-elicited cocaine-seeking.

    PubMed

    Smith, Rachel J; See, Ronald E; Aston-Jones, Gary

    2009-08-01

    The orexin/hypocretin system has recently been implicated in reward-processing and addiction. We examined the involvement of the orexin system in cue-induced reinstatement of extinguished cocaine-seeking by administering the orexin 1 receptor antagonist SB-334867 (SB) or the orexin 2 receptor antagonist 4-pyridylmethyl (S)-tert-leucyl 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (4PT) prior to reinstatement testing. Male Sprague Dawley rats self-administered cocaine in 2-h sessions for 10 days, followed by extinction training. Reinstatement of cocaine-seeking was elicited by presentation of tone + light cues previously paired with cocaine infusions. SB (10, 20 and 30 mg/kg) dose-dependently decreased cue-induced reinstatement of cocaine-seeking without significantly affecting responding during late extinction. 4PT (10 and 30 mg/kg) did not significantly alter cue-induced reinstatement. In separate experiments, the highest doses of SB and 4PT had no significant effect on established cocaine self-administration, and 4PT reduced spontaneous activity in a locomotor test to a greater extent than SB. Finally, SB (30 mg/kg) had no effect on the acquisition of cocaine-paired cues during a Pavlovian cocaine-stimulus conditioning session in the operant chamber. Pretreatment with SB prior to the Pavlovian acquisition session had no effect on subsequent cue-induced reinstatement of cocaine-seeking elicited by those cues. However, pretreatment with SB prior to a second reinstatement session in the same animals significantly attenuated the expression of cue-induced reinstatement. These results show that orexin transmission at the orexin 1 receptor, but not the orexin 2 receptor, is necessary for the reinstatement of cocaine-seeking elicited by drug-paired cues and that orexin signaling is not critical for cocaine reinforcement or cocaine-stimulus conditioning.

  13. 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. © 2014 S. Karger AG, Basel.

  14. 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.

  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. A coding IRAK2 protein variant compromises Toll-like receptor (TLR) signaling and is associated with colorectal cancer survival.

    PubMed

    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

    2014-08-15

    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. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  17. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Glucocorticoid receptor signalling activates YAP in breast cancer

    PubMed Central

    Sorrentino, Giovanni; Ruggeri, Naomi; Zannini, Alessandro; Ingallina, Eleonora; Bertolio, Rebecca; Marotta, Carolina; Neri, Carmelo; Cappuzzello, Elisa; Forcato, Mattia; Rosato, Antonio; Mano, Miguel; Bicciato, Silvio; Del Sal, Giannino

    2017-01-01

    The Hippo pathway is an oncosuppressor signalling cascade that plays a major role in the control of cell growth, tissue homoeostasis and organ size. Dysregulation of the Hippo pathway leads to aberrant activation of the transcription co-activator YAP (Yes-associated protein) that contributes to tumorigenesis in several tissues. Here we identify glucocorticoids (GCs) as hormonal activators of YAP. Stimulation of glucocorticoid receptor (GR) leads to increase of YAP protein levels, nuclear accumulation and transcriptional activity in vitro and in vivo. Mechanistically, we find that GCs increase expression and deposition of fibronectin leading to the focal adhesion-Src pathway stimulation, cytoskeleton-dependent YAP activation and expansion of chemoresistant cancer stem cells. GR activation correlates with YAP activity in human breast cancer and predicts bad prognosis in the basal-like subtype. Our results unveil a novel mechanism of YAP activation in cancer and open the possibility to target GR to prevent cancer stem cells self-renewal and chemoresistance. PMID:28102225

  19. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Ligand Directed Signaling Differences between Rodent and Human κ-Opioid Receptors*

    PubMed Central

    Schattauer, Selena S.; Miyatake, Mayumi; Shankar, Haripriya; Zietz, Chad; Levin, Jamie R.; Liu-Chen, Lee-Yuan; Gurevich, Vsevolod V.; Rieder, Mark J.; Chavkin, Charles

    2012-01-01

    KOR activation of Gβγ dependent signaling results in analgesia, whereas the dysphoric effects of KOR agonists are mediated by a different pathway involving G protein receptor kinase and non-visual arrestin. Based on this distinction, a partial KOR agonist that does not efficiently activate arrestin-dependent biased signaling may produce analgesia without dysphoria. No KOR-selective partial agonists are currently available, and preclinical assessment is complicated by sequence differences between rodent (r) and human (h) KOR. In this study, we compared the signaling initiated by the available partial agonists. Pentazocine was significantly more potent at activating p38 MAPK in hKOR than rKOR expressed in HEK293 cells but equally potent at arrestin-independent activation of ERK1/2 in hKOR and rKOR. Similarly, butorphanol increased phospho-p38-ir in hKOR-expressing cells but did not activate p38 in rKOR-HEK293. Like pentazocine, butorphanol was equally efficacious at activating ERK1/2 in rKOR and hKOR. In contrast, levorphanol, nalorphine, and U50,488 did not distinguish between hKOR and rKOR in p38 MAPK activation. Consistent with its low potency at p38 activation, pentazocine did not produce conditioned place aversion in mice. hKOR lacks the Ser-369 phosphorylation site in rKOR required for G protein receptor kinase/arrestin-dependent p38 activation, but mutation of the Ser-358 to asparagine in hKOR blocked p38 activation without affecting the acute arrestin-independent activation of ERK1/2. This study shows that hKOR activates p38 MAPK through a phosphorylation and arrestin-dependent mechanism; however, activation differs between hKOR and rKOR for some ligands. These functional selectivity differences have important implications for preclinical screening of partial KOR agonists. PMID:23086943

  1. Genes targeted by the Hedgehog-signaling pathway can be regulated by Estrogen related receptor β.

    PubMed

    Lu, Yuan; Li, Jilong; Cheng, Jianlin; Lubahn, Dennis B

    2015-11-23

    Nuclear receptor family member, Estrogen related receptor β, and the Hedgehog signal transduction pathway are both reported to relate to tumorigenesis and induced pluripotent stem cell reprogramming. We hypothesize that Estrogen related receptor β can modulate the Hedgehog signaling pathway and affect Hedgehog driven downstream gene expression. We established an estrogen related receptor β-expressing Hedgehog-responsive NIH3T3 cell line by Esrrb transfection, and performed mRNA profiling using RNA-Seq after Hedgehog ligand conditioned medium treatment. Esrrb expression altered 171 genes, while Hedgehog signaling activation alone altered 339 genes. Additionally, estrogen related receptor β expression in combination with Hedgehog signaling activation affects a group of 109 Hedgehog responsive mRNAs, including Hsd11b1, Ogn, Smoc2, Igf1, Pdcd4, Igfbp4, Stmn1, Hp, Hoxd8, Top2a, Tubb4b, Sfrp2, Saa3, Prl2c3 and Dpt. We conclude that Estrogen related receptor β is capable of interacting with Hh-signaling downstream targets. Our results suggest a new level of regulation of Hedgehog signaling by Estrogen related receptor β, and indicate modulation of Estrogen related receptor β can be a new strategy to regulate various functions driven by the Hedgehog signaling pathway.

  2. Palmitoylethanolamide Modulates GPR55 Receptor Signaling in the Ventral Hippocampus to Regulate Mesolimbic Dopamine Activity, Social Interaction, and Memory Processing.

    PubMed

    Kramar, Cecilia; Loureiro, Michael; Renard, Justine; Laviolette, Steven R

    2017-01-01

    Introduction: The GPR55 receptor has been identified as an atypical cannabinoid receptor and is implicated in various physiological processes. However, its functional role in the central nervous system is not currently understood. The presence of GPR55 receptor in neural regions such as the ventral hippocampus (vHipp), which is critical for cognition, recognition memory, and affective processing, led us to hypothesize that intra-vHipp GPR55 transmission may modulate mesolimbic activity states and related behavioral phenomena. The vHipp is involved in contextual memory and affective regulation through functional interactions with the mesolimbic dopamine system. Materials and Methods: Using a combination of in vivo electrophysiology and behavioral pharmacological assays in rats, we tested whether intra-vHipp activation of GPR55 receptor transmission with the fatty acid amide, palmitoylethanolamide (PEA), a lipid neuromodulator with agonist actions at the GPR55 receptor, may modulate mesolimbic dopaminergic activity states. We further examined the potential effects of intra-vHipp PEA in affective, cognitive and contextual memory tasks. Discussion: We report that intra-vHipp PEA produces a hyper-dopaminergic state in the mesolimbic system characterized by increased firing and bursting activity of ventral tegmental area dopaminergic neuron populations. Furthermore, while PEA-induced activation of GPR55 transmission had no effects on opiate-related reward-related memory formation, we observed strong disruptions in social interaction and recognition memory, spatial location memory, and context-independent associative fear memory formation. Finally, the effects of intra-vHipp PEA were blocked by a selective GPR55 receptor antagonist, CID160 and were dependent upon NMDA receptor transmission, directly in the vHipp. Conclusions: The present results add to a growing body of evidence demonstrating important functional roles for GPR55 signaling in cannabinoid-related neuronal

  3. Structural and functional insights into nuclear receptor signaling

    PubMed Central

    Jin, Lihua; Li, Yong

    2010-01-01

    Nuclear receptors are important transcriptional factors that share high sequence identity and conserved domains, including a DNA-binding domain (DBD) and a ligand-binding domain (LBD). The LBD plays a crucial role in ligand-mediated nuclear receptor activity. Hundreds of different crystal structures of nuclear receptors have revealed a general mechanism for the molecular basis of ligand binding and ligand-mediated regulation of nuclear receptors. Despite the conserved fold of nuclear receptor LBDs, the ligand-binding pocket is the least conserved region among different nuclear receptor LBDs. Structural comparison and analysis show that several features of the pocket, like the size and also the shape, have contributed to the ligand binding affinity and specificity. In addition, the plastic nature of the ligand-binding pockets in many nuclear receptors provides greater flexibility to further accommodate specific ligands with a variety of conformations. Nuclear receptor coactivators usually contain multiple LXXLL motifs that are used to interact with nuclear receptors. The nuclear receptors respond differently to distinct ligands and readily exchange their ligands in different environments. The conformational flexibility of the AF-2 helix allows the nuclear receptor to sense the presence of the bound ligands, either an agonist or an antagonist, and to recruit the coactivators or corepressors that ultimately determine the transcriptional activation or repression of nuclear receptors. PMID:20723571

  4. Melanoma mouse model implicates metabotropic glutamate signaling in melanocytic neoplasia.

    PubMed

    Pollock, Pamela M; Cohen-Solal, Karine; Sood, Raman; Namkoong, Jin; Martino, Jeffrey J; Koganti, Aruna; Zhu, Hua; Robbins, Christiane; Makalowska, Izabela; Shin, Seung-Shick; Marin, Yari; Roberts, Kathleen G; Yudt, Laura M; Chen, Amy; Cheng, Jun; Incao, Arturo; Pinkett, Heather W; Graham, Christopher L; Dunn, Karen; Crespo-Carbone, Steven M; Mackason, Kerine R; Ryan, Kevin B; Sinsimer, Daniel; Goydos, James; Reuhl, Kenneth R; Eckhaus, Michael; Meltzer, Paul S; Pavan, William J; Trent, Jeffrey M; Chen, Suzie

    2003-05-01

    To gain insight into melanoma pathogenesis, we characterized an insertional mouse mutant, TG3, that is predisposed to develop multiple melanomas. Physical mapping identified multiple tandem insertions of the transgene into intron 3 of Grm1 (encoding metabotropic glutamate receptor 1) with concomitant deletion of 70 kb of intronic sequence. To assess whether this insertional mutagenesis event results in alteration of transcriptional regulation, we analyzed Grm1 and two flanking genes for aberrant expression in melanomas from TG3 mice. We observed aberrant expression of only Grm1. Although we did not detect its expression in normal mouse melanocytes, Grm1 was ectopically expressed in the melanomas from TG3 mice. To confirm the involvement of Grm1 in melanocytic neoplasia, we created an additional transgenic line with Grm1 expression driven by the dopachrome tautomerase promoter. Similar to the original TG3, the Tg(Grm1)EPv line was susceptible to melanoma. In contrast to human melanoma, these transgenic mice had a generalized hyperproliferation of melanocytes with limited transformation to fully malignant metastasis. We detected expression of GRM1 in a number of human melanoma biopsies and cell lines but not in benign nevi and melanocytes. This study provides compelling evidence for the importance of metabotropic glutamate signaling in melanocytic neoplasia.

  5. The Wnt Frizzled Receptor MOM-5 Regulates the UNC-5 Netrin Receptor through Small GTPase-Dependent Signaling to Determine the Polarity of Migrating Cells.

    PubMed

    Levy-Strumpf, Naomi; Krizus, Meghan; Zheng, Hong; Brown, Louise; Culotti, Joseph G

    2015-08-01

    Wnt and Netrin signaling regulate diverse essential functions. Using a genetic approach combined with temporal gene expression analysis, we found a regulatory link between the Wnt receptor MOM-5/Frizzled and the UNC-6/Netrin receptor UNC-5. These two receptors play key roles in guiding cell and axon migrations, including the migration of the C. elegans Distal Tip Cells (DTCs). DTCs migrate post-embryonically in three sequential phases: in the first phase along the Antero-Posterior (A/P) axis, in the second, along the Dorso-Ventral (D/V) axis, and in the third, along the A/P axis. Loss of MOM-5/Frizzled function causes third phase A/P polarity reversals of the migrating DTCs. We show that an over-expression of UNC-5 causes similar DTC A/P polarity reversals and that unc-5 deficits markedly suppress the A/P polarity reversals caused by mutations in mom-5/frizzled. This implicates MOM-5/Frizzled as a negative regulator of unc-5. We provide further evidence that small GTPases mediate MOM-5's regulation of unc-5 such that one outcome of impaired function of small GTPases like CED-10/Rac and MIG-2/RhoG is an increase in unc-5 function. The work presented here demonstrates the existence of cross talk between components of the Netrin and Wnt signaling pathways and provides further insights into the way guidance signaling mechanisms are integrated to orchestrate directed cell migration.

  6. The Wnt Frizzled Receptor MOM-5 Regulates the UNC-5 Netrin Receptor through Small GTPase-Dependent Signaling to Determine the Polarity of Migrating Cells

    PubMed Central

    Levy-Strumpf, Naomi; Krizus, Meghan; Zheng, Hong; Brown, Louise; Culotti, Joseph G.

    2015-01-01

    Wnt and Netrin signaling regulate diverse essential functions. Using a genetic approach combined with temporal gene expression analysis, we found a regulatory link between the Wnt receptor MOM-5/Frizzled and the UNC-6/Netrin receptor UNC-5. These two receptors play key roles in guiding cell and axon migrations, including the migration of the C. elegans Distal Tip Cells (DTCs). DTCs migrate post-embryonically in three sequential phases: in the first phase along the Antero-Posterior (A/P) axis, in the second, along the Dorso-Ventral (D/V) axis, and in the third, along the A/P axis. Loss of MOM-5/Frizzled function causes third phase A/P polarity reversals of the migrating DTCs. We show that an over-expression of UNC-5 causes similar DTC A/P polarity reversals and that unc-5 deficits markedly suppress the A/P polarity reversals caused by mutations in mom-5/frizzled. This implicates MOM-5/Frizzled as a negative regulator of unc-5. We provide further evidence that small GTPases mediate MOM-5’s regulation of unc-5 such that one outcome of impaired function of small GTPases like CED-10/Rac and MIG-2/RhoG is an increase in unc-5 function. The work presented here demonstrates the existence of cross talk between components of the Netrin and Wnt signaling pathways and provides further insights into the way guidance signaling mechanisms are integrated to orchestrate directed cell migration. PMID:26292279

  7. Cardiomyocyte glucagon receptor signaling modulates outcomes in mice with experimental myocardial infarction

    PubMed Central

    Ali, Safina; Ussher, John R.; Baggio, Laurie L.; Kabir, M. Golam; Charron, Maureen J.; Ilkayeva, Olga; Newgard, Christopher B.; Drucker, Daniel J.

    2014-01-01

    Objective Glucagon is a hormone with metabolic actions that maintains normoglycemia during the fasting state. Strategies enabling either inhibition or activation of glucagon receptor (Gcgr) signaling are being explored for the treatment of diabetes or obesity. However, the cardiovascular consequences of manipulating glucagon action are poorly understood. Methods We assessed infarct size and the following outcomes following left anterior descending (LAD) coronary artery ligation; cardiac gene and protein expression, acylcarnitine profiles, and cardiomyocyte survival in normoglycemic non-obese wildtype mice, and in newly generated mice with selective inactivation of the cardiomyocyte Gcgr. Complementary experiments analyzed Gcgr signaling and cell survival in cardiomyocyte cultures and cell lines, in the presence or absence of exogenous glucagon. Results Exogenous glucagon administration directly impaired recovery of ventricular pressure in ischemic mouse hearts ex vivo, and increased mortality from myocardial infarction after LAD coronary artery ligation in mice in a p38 MAPK-dependent manner. In contrast, cardiomyocyte-specific reduction of glucagon action in adult GcgrCM−/− mice significantly improved survival, and reduced hypertrophy and infarct size following myocardial infarction. Metabolic profiling of hearts from GcgrCM−/− mice revealed a marked reduction in long chain acylcarnitines in both aerobic and ischemic hearts, and following high fat feeding, consistent with an essential role for Gcgr signaling in the control of cardiac fatty acid utilization. Conclusions Activation or reduction of cardiac Gcgr signaling in the ischemic heart produces substantial cardiac phenotypes, findings with implications for therapeutic strategies designed to augment or inhibit Gcgr signaling for the treatment of metabolic disorders. PMID:25685700

  8. Opposite function of dopamine D1 and N-methyl-D-aspartate receptors in striatal cannabinoid-mediated signaling.

    PubMed

    Daigle, Tanya L; Wetsel, William C; Caron, Marc G

    2011-11-01

    It is well established that the cannabinoid and dopamine systems interact at various levels to regulate basal ganglia function. Although it is well known that acute administration of cannabinoids to mice can modify dopamine-dependent behaviors, the intraneuronal signaling pathways employed by these agents in the striatum are not well understood. Here we used knockout mouse models to examine the regulation of striatal extracellular-signal-regulated kinases 1 and 2 (ERK1/2) signaling by behaviorally relevant doses of cannabinoids. This cellular pathway has been implicated as a central mediator of drug reward and synaptic plasticity. In C57BL/6J mice, acute administration of the cannabinoid agonists, (-)-11-hydroxydimethylheptyl-Δ8-tetrahydrocannabinol (HU-210) and delta-9-tetrahydrocannabinol (Δ(9) -THC), promoted a dose- and time-dependent decrease in the phosphorylation of ERK1/2 in dorsal striatum. Co-administration of the CB1 cannabinoid receptor antagonist N-(Piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide(AM251) with HU-210 prevented ERK1/2 inactivation, indicating a requirement for activation of this receptor. In dopamine D1 receptor knockout animals treated with HU-210, the magnitude of the HU-210-dependent decrease in striatal ERK1/2 signaling was greater than in wild-type controls. In contrast, HU-210 administration to N-methyl-D-aspartate receptor knockdown mice was ineffective at promoting striatal ERK1/2 inactivation. Genetic deletion of other potential ERK1/2 mediators, the dopamine D2 receptors or β-arrestin-1 or -2, did not affect the HU-210-induced modulation of ERK1/2 signaling in the striatum. These results support the hypothesis that dopamine D1 receptors and N-methyl-D-aspartate receptors act in an opposite manner to regulate striatal CB1 cannabinoid receptor signal transduction. Published 2011. This article is a US Government work and is in the public domain in the USA.

  9. 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.

  10. 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

  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

    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; McCormick, Peter J

    2014-03-05

    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.

  12. 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.

  13. Potential Clinical Implications of the Urotensin II Receptor Antagonists

    PubMed Central

    Tsoukas, Philip; Kane, Émilie; Giaid, Adel

    2011-01-01

    Urotensin II (UII) binds to its receptor, UT, playing an important role in the heart, kidneys, pancreas, adrenal gland, and central nervous system. In the vasculature, it acts as a potent endothelium-independent vasoconstrictor and endothelium-dependent vasodilator. In disease states, however, this constriction–dilation equilibrium is disrupted. There is an upregulation of the UII system in heart disease, metabolic syndrome, and kidney failure. The increase in UII release and UT expression suggest that UII system may be implicated in the pathology and pathogenesis of these diseases by causing an increase in acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT-1) activity leading to smooth muscle cell proliferation and foam cell infiltration, insulin resistance (DMII), as well as inflammation, high blood pressure, and plaque formation. Recently, UT antagonists such as SB-611812, palosuran, and most recently a piperazino-isoindolinone based antagonist have been developed in the hope of better understanding the UII system and treating its associated diseases. PMID:21811463

  14. Receptor kinase signalling in plants and animals: distinct molecular systems with mechanistic similarities.

    PubMed

    Cock, J Mark; Vanoosthuyse, Vincent; Gaude, Thierry

    2002-04-01

    Plant genomes encode large numbers of receptor kinases that are structurally related to the tyrosine and serine/threonine families of receptor kinase found in animals. Here, we describe recent advances in the characterisation of several of these plant receptor kinases at the molecular level, including the identification of receptor complexes, small polypeptide ligands and cytosolic proteins involved in signal transduction and receptor downregulation. Phylogenetic analysis indicates that plant receptor kinases have evolved independently of the receptor kinase families found in animals. This hypothesis is supported by functional studies that have revealed differences between receptor kinase signalling in plants and animals, particularly concerning their interactions with cytosolic proteins. Despite these dissimilarities, however, plant and animal receptor kinases share many common features, such as their single membrane-pass structure, their inclusion in membrane-associated complexes, the involvement of dimerisation and trans autophosphorylation in receptor activation, and the existence of inhibitors and phosphatases that downregulate receptor activity. These points of convergence may represent features that are essential for a functional receptor-kinase signalling system.

  15. Therapeutic Implications of Targeting AKT Signaling in Melanoma

    PubMed Central

    Madhunapantula, SubbaRao V.; Robertson, Gavin P.

    2011-01-01

    Identification of key enzymes regulating melanoma progression and drug resistance has the potential to lead to the development of novel, more effective targeted agents for inhibiting this deadly form of skin cancer. The Akt3, also known as protein kinase B gamma, pathway enzymes regulate diverse cellular processes including proliferation, survival, and invasion thereby promoting the development of melanoma. Accumulating preclinical evidence demonstrates that therapeutic agents targeting these kinases alone or in combination with other pathway members could be effective for the long-term treatment of advanced-stage disease. However, currently, no selective and effective therapeutic agent targeting these kinases has been identified for clinical use. This paper provides an overview of the key enzymes of the PI3K pathway with emphasis placed on Akt3 and the negative regulator of this kinase called PTEN (phosphatase and tensin homolog deleted on chromosome 10). Mechanisms regulating these enzymes, their substrates and therapeutic implications of targeting these proteins to treat melanoma are also discussed. Finally, key issues that remain to be answered and future directions for interested researchers pertaining to this signaling cascade are highlighted. PMID:21461351

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

    PubMed Central

    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

    2015-01-01

    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. PMID:25643582

  17. Atypical Signaling and Functional Desensitization Response of MAS Receptor to Peptide Ligands

    PubMed Central

    Tirupula, Kalyan C.; Desnoyer, Russell; Speth, Robert C.; Karnik, Sadashiva S.

    2014-01-01

    MAS is a G protein-coupled receptor (GPCR) implicated in multiple physiological processes. Several physiological peptide ligands such as angiotensin-(1–7), angiotensin fragments and neuropeptide FF (NPFF) are reported to act on MAS. Studies of conventional G protein signaling and receptor desensitization upon stimulation of MAS with the peptide ligands are limited so far. Therefore, we systematically analyzed G protein signals activated by the peptide ligands. MAS-selective non-peptide ligands that were previously shown to activate G proteins were used as controls for comparison on a common cell based assay platform. Activation of MAS by the non-peptide agonist (1) increased intracellular calcium and D-myo-inositol-1-phosphate (IP1) levels which are indicative of the activation of classical Gαq-phospholipase C signaling pathways, (2) decreased Gαi mediated cAMP levels and (3) stimulated Gα12-dependent expression of luciferase reporter. In all these assays, MAS exhibited strong constitutive activity that was inhibited by the non-peptide inverse agonist. Further, in the calcium response assay, MAS was resistant to stimulation by a second dose of the non-peptide agonist after the first activation has waned suggesting functional desensitization. In contrast, activation of MAS by the peptide ligand NPFF initiated a rapid rise in intracellular calcium with very weak IP1 accumulation which is unlike classical Gαq-phospholipase C signaling pathway. NPFF only weakly stimulated MAS-mediated activation of Gα12 and Gαi signaling pathways. Furthermore, unlike non-peptide agonist-activated MAS, NPFF-activated MAS could be readily re-stimulated the second time by the agonists. Functional assays with key ligand binding MAS mutants suggest that NPFF and non-peptide ligands bind to overlapping regions. Angiotensin-(1–7) and other angiotensin fragments weakly potentiated an NPFF-like calcium response at non-physiological concentrations (≥100 µM). Overall, our data

  18. Atypical signaling and functional desensitization response of MAS receptor to peptide ligands.

    PubMed

    Tirupula, Kalyan C; Desnoyer, Russell; Speth, Robert C; Karnik, Sadashiva S

    2014-01-01

    MAS is a G protein-coupled receptor (GPCR) implicated in multiple physiological processes. Several physiological peptide ligands such as angiotensin-(1-7), angiotensin fragments and neuropeptide FF (NPFF) are reported to act on MAS. Studies of conventional G protein signaling and receptor desensitization upon stimulation of MAS with the peptide ligands are limited so far. Therefore, we systematically analyzed G protein signals activated by the peptide ligands. MAS-selective non-peptide ligands that were previously shown to activate G proteins were used as controls for comparison on a common cell based assay platform. Activation of MAS by the non-peptide agonist (1) increased intracellular calcium and D-myo-inositol-1-phosphate (IP1) levels which are indicative of the activation of classical Gαq-phospholipase C signaling pathways, (2) decreased Gαi mediated cAMP levels and (3) stimulated Gα12-dependent expression of luciferase reporter. In all these assays, MAS exhibited strong constitutive activity that was inhibited by the non-peptide inverse agonist. Further, in the calcium response assay, MAS was resistant to stimulation by a second dose of the non-peptide agonist after the first activation has waned suggesting functional desensitization. In contrast, activation of MAS by the peptide ligand NPFF initiated a rapid rise in intracellular calcium with very weak IP1 accumulation which is unlike classical Gαq-phospholipase C signaling pathway. NPFF only weakly stimulated MAS-mediated activation of Gα12 and Gαi signaling pathways. Furthermore, unlike non-peptide agonist-activated MAS, NPFF-activated MAS could be readily re-stimulated the second time by the agonists. Functional assays with key ligand binding MAS mutants suggest that NPFF and non-peptide ligands bind to overlapping regions. Angiotensin-(1-7) and other angiotensin fragments weakly potentiated an NPFF-like calcium response at non-physiological concentrations (≥100 µM). Overall, our data suggest

  19. Brain CB2 Receptors: Implications for Neuropsychiatric Disorders

    PubMed Central

    Roche, Michelle; Finn, David P

    2010-01-01

    Although previously thought of as the peripheral cannabinoid receptor, it is now accepted that the CB2 receptor is expressed in the central nervous system on microglia, astrocytes and subpopulations of neurons. Expression of the CB2 receptor in the brain is significantly lower than that of the CB1 receptor. Conflicting findings have been reported on the neurological effects of pharmacological agents targeting the CB2 receptor under normal conditions. Under inflammatory conditions, CB2 receptor expression in the brain is enhanced and CB2 receptor agonists exhibit potent anti-inflammatory effects. These findings have prompted research into the CB2 receptor as a possible