1,721,027 research outputs found
Molecular basis of ligand binding and receptor activation in the oxytocin and vasopressin receptor family
No full textAlthough it is now widely accepted that G-protein-coupled receptors exist in at least two allosteric states, inactive and active, and that the spontaneous equilibrium between the two is regulated by various events including the binding of specific agonists and antagonists, the molecular counterparts of these functionally different states are still poorly understood. In this paper, we review our current knowledge concerning the structure-function relationships of the oxytocin and vasopressin receptors, focusing in particular on the process of receptor activation. Using a combined approach of site-directed mutagenesis and molecular modelling, we investigated the molecular events leading to agonist-dependent and -independent receptor activation in the human oxytocin receptor. Our analysis allows us to propose that the active conformations of this receptor are characterised by similar rearrangements of its cytosolic regions that ultimately lead to the opening of a putative docking site for the G-protein. Furthermore, the dynamics of these motions are similar to that observed in the alpha1B-adrenergic receptor, thus suggesting that, although activated by different ligands, the process of receptor isomerization in these two receptors is regulated by the same cluster of highly conserved residues and that common molecular events are responsible for receptor activation in different G-protein-coupled receptors
Oxytocin stimulates migration and invasion in human endothelial cells
No full textBackground and purpose. It has recently been reported that oxytocin (OT) is produced by some tumoral cell types, and that OT receptors (OTRs) belonging to the G protein-coupled receptor (GPCR) family are expressed in a variety of cell types. Among these, human umbilical vein endothelial cells (HUVECs) respond to OT with an increased proliferation, suggesting a possible role for the hormone in the regulation of angiogenesis. Experimental approach. We employed chemotaxis and chemoinvasion assays to characterize the effect of OT on HUVEC motility, and immunoblot analysis to study its molecular mechanisms of action. Key results. We showed that OT stimulates migration and invasion in HUVECs via OTR activation. Searching for the molecular mechanism(s) responsible for OT’s pro-migratory effect, we identified the Gq coupling of OTRs and phospholipase C (PLC) as the main effectors of OT’s action in HUVECs. We also found that OT stimulates the phosphorylation of endothelial nitric oxide synthase (eNOS) via the phosphatidylinositol-3-kinase (PI-3-K)/AKT pathway, and that the activation of PI-3-K and formation of nitric oxide (NO) are required for the pro-migratory effect of OT. Conclusions and implications. The ability of OT to stimulate HUVEC motility and invasion suggests that the hormone can participate to physiopathological processes where activation of endothelial cells plays an important role, like for example angiogenesis. Interestingly, both the AKT and eNOS phosphorylation induced by OTR activation depend on PLC activity, thus suggesting the existence of a still undefined mechanism connecting PLC to the PI-3-K/AKT pathway upon OT stimulation
Multi-Physics Modeling and Finite Element Approximation of Charge Flow in Ionic Channels
No full textOxytocin receptor signaling in myoepithelial and cancer cells
No full textOxytocin (OT) plays a crucial role as a mediator of breast myoepithelial cell contraction, the process responsible for the ejection of milk during lactation, and is also involved in myoepithelial cell proliferation and postpartum mammary gland proliferation. Furthermore, although a number of breast cancer cells have oxytocin receptors (OTRs), it has been reported that OT stimulates, inhibits, or has no effect on cell proliferation. As these different effects seem to be mediated by different signaling pathways elicited by OTR stimulation, we here review the regulation of OTR signaling in different cell systems and discuss how understanding the molecular basis of receptor coupling specificity has become extremely important for understanding the role played by OTRs in regulating cell growth
Computational Models for The Numerical Simulation of Voltage Operated Channels in Nano--Bio--Electronics
No full textMolecular cloning of human neuronal nicotinic receptor alpha 3-subunit
No full textNeuronal nicotinic receptors (nAchRs) have been isolated or cloned in insect, bird and mammalian neurons, but no information exists on the primary structure of human neuronal nAchRs. By screening a cDNA library from the human neuroblastoma cell line IMR 32 with a cDNA probe corresponding to the full length of rat alpha 3-nicotinic subunit, we have identified an open reading frame encoding a protein of 502 amino acids. This protein shows all the features of members of the ligand-gated receptor superfamily and has two cysteine residues at positions 192, 193 which are typical of the nicotinic alpha-subunits. Because of its high homology to rat alpha 3 (93% amino acid identity), we conclude that we have cloned the human alpha 3-nicotinic subunit
Selective and potent agonists and antagonists for investigating the role of mouse oxytocin receptors
Full text linkThe neuropeptides oxytocin (OT) and vasopressin (AVP) have been shown to play a central role in social behaviors; as a consequence, they have been recognized as potential drugs to treat neurodevelopmental and psychiatric disorders characterized by impaired social interactions. However, despite the basic and preclinical relevance of mouse strains carrying genetic alterations in the OT/AVP systems to basic and preclinical translational neuroscience, the pharmacological profile of mouse OT/AVP receptor subtypes has not been fully characterized. To fill in this gap, we have characterized a number of OT and AVP agonists and antagonists at three murine OT/AVP receptors expressed in the nervous system as follows: the oxytocin (mOTR) and vasopressin V1a (mV1aR) and V1b (mV1bR) subtypes. These three receptors were transiently expressed in vitro for binding and intracellular signaling assays, and then a homology model of the mOTR structure was constructed to investigate how its molecular features compare with human and rat OTR orthologs. Our data indicate that the selectivity profile of the natural ligands, OT and AVP, is conserved in humans, rats, and mice. Furthermore, we found that the synthetic peptide [Thr4Gly7]OT (TGOT) is remarkably selective for the mOTR and, like the endogenous OT ligand, activates Gq and Gi and recruits b-arrestins. Finally, we report three antagonists that exhibit remarkably high affinities and selectivities at mOTRs. These highly selective pharmacological tools will contribute to the investigation of the specific physiologic and pathologic roles of mOTR for the development of selective OT-based therapeutics
Computational Modeling and Simulation of Complex Systems in Bio-Electronics
No full textIn this article, we discuss the mathematical and
computational framework required to develop a generalpurpose
simulation tool for bio-electronic applications.
Electrochemical and fluid-mechanical transport of substances,
chemical reactions and electrical transduction of
biological signals are described through the coupled use of
systems of partial and ordinary differential equations (PDEs
and ODEs). Functional iteration techniques for system decoupling
and mixed-hybridized finite element discretization
methods are proposed and validated in the simulation of realistic
problems in Electrophysiology and Biochemistr
Effects of cholesterol manipulation on the signaling of the human oxytocin receptor
No full textWe have recently shown that oxytocin inhibits cell growth when the vast majority of oxytocin receptors (OTRs) are excluded from detergent-resistant membranes (DRMs; the biochemical counterpart of lipid rafts), but has a strong mitogenic effect when the receptors are targeted to these plasma membrane domains upon fusion with caveolin-2, a resident raft protein. The aim of this study was to investigate whether the manipulation of total cell cholesterol can influence OTR localization and signaling. Our data indicate that cholesterol depletion in HEK-293 cells does not affect the signaling events mediated by the OTRs located outside DRMs. When treated with 2 mM methyl-beta-cyclodextrin (MbetaCD), the receptors remained outside and continued to inhibit cell growth. On the contrary, the MbetaCD treatment of cells expressing receptors fused to caveolin-2 led to their redistribution outside DRMs, and converted the receptor-mediated proliferative effect into cell growth inhibition. These data indicate that 1) once released from DRMs, the receptors fused to caveolin-2 signal exactly as wild-type OTRs and 2) their DRM location is responsible for the specific OTR signaling leading to cell proliferation. Finally, we evaluated whether cholesterol loading could force the OTRs into lipid rafts and change their signaling, but, after cell treatment with an MbetaCD/cholesterol complex, receptor stimulation continued to lead to cell growth inhibition, thus indicating that increasing cell cholesterol levels is not sufficient per se to affect OTR signaling
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