Regulation of the Subcellular Localization of the G-protein Subunit Regulator GPSM3 through Direct Association with 14-3-3 Protein
From the Department of Pharmacology and.Journal of Biological Chemistry (Impact Factor: 4.57). 07/2012; 287(37):31270-9. DOI: 10.1074/jbc.M112.394379
G-protein signaling modulator-3 (GPSM3), also known as G18 or AGS4, is a member of the Gα(i/o)-Loco (GoLoco) motif containing proteins. GPSM3 acts through its two GoLoco motifs to exert GDP dissociation inhibitor activity over Gα(i) subunits; recently revealed is the existence of an additional regulatory site within GPSM3 directed toward monomeric Gβ subunits during their biosynthesis. Here, using in silico and proteomic approaches, we have found that GPSM3 also interacts directly with numerous members of the 14-3-3 protein family. This interaction is dependent on GPSM3 phosphorylation, creating a mode II consensus 14-3-3 binding site. 14-3-3 binding to the N-terminal disordered region of GPSM3 confers stabilization from protein degradation. The complex of GPSM3 and 14-3-3 is exclusively cytoplasmic, and both moieties mutually control their exclusion from the nucleus. Phosphorylation of GPSM3 by a proline-directed serine/threonine kinase and the resultant association of 14-3-3 is the first description of post-translational regulation of GPSM3 subcellular localization, a process that likely regulates important spatio-temporal aspects of G-protein-coupled receptor signaling modulation by GPSM3.
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- "In the present study, we detected AGS4/Gpsm3 mRNA in the rat kidney similar to previously published studies (Cao et al. 2004), but we were unable to confirm the protein translation or localization in the kidney. A recent study has shown that AGS4/GPSM3 can interact with intracellular proteins, such as 14-3-3, to reduce protein degradation (Giguere et al. 2012), which may be absent in the kidney. This could alter the rate of degradation of AGS4/GPSM3 protein and could be one contributing factor leading to the inability to detect this protein in the kidney sections. "
ABSTRACT: Activators of G-protein Signaling (AGS) are a family of accessory proteins that were discovered as modulators of heterotrimeric G-protein subunits. The primary aim of the present study was to localize Group I and II AGS proteins and determine the renal expression profile using immunohistochemistry and quantitative RT-PCR, respectively, during normal and injured states of the kidney. Group I AGS1 was found to be predominantly localized to the proximal tubule, Group II AGS3 and AGS5 were exclusively localized to the distal tubular segments, and Group II AGS6 was ubiquitously expressed in every nephron segment of the rodent kidney. In rat kidneys following ischemia-reperfusion injury (IRI), Group I AGS1 mRNA was dramatically increased after 24 h by fivefold (P < 0.05), whereas Group II AGS3 and AGS4 mRNA was significantly decreased at the same time point (P < 0.05). No significant change in the transcript levels were detected at other time points for any of the AGS genes between control and IRI groups. In polycystic diseased kidneys, mRNA levels for AGS3, AGS4 and AGS6 was significantly increased (P < 0.05) by 75-80 % in PCK rat kidneys. The identification of Group I and II AGS mRNA and protein in the kidney may provide insight into the potential mechanism of action during normal and varying states of renal disease or injury.Journal of Molecular Histology 12/2014; 46(2). DOI:10.1007/s10735-014-9605-0 · 1.82 Impact Factor
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ABSTRACT: Group II activators of G-protein signaling play diverse functional roles through their interaction with Gαi, Gαt, and Gαo via a G-protein regulatory (GPR) motif that serves as a docking site for Gα-GDP. We recently reported the regulation of the AGS3-Gαi signaling module by a cell surface, seven-transmembrane receptor. Upon receptor activation, AGS3 reversibly dissociates from the cell cortex, suggesting that it may function as a signal transducer with downstream signaling implications, and this question is addressed in the current report. In HEK-293 and COS-7 cells expressing the α2A/D-AR and Gαi3, receptor activation resulted in the translocation of endogenous AGS3 and AGS3-GFP from the cell cortex to a juxtanuclear region, where it co-localized with markers of the Golgi apparatus (GA). The agonist-induced translocation of AGS3 was reversed by the α2-AR antagonist rauwolscine. The TPR domain of AGS3 was required for agonist-induced translocation of AGS3 from the cell cortex to the GA, and the translocation was blocked by pertussis toxin pretreatment or by the phospholipase Cβ inhibitor U73122. Agonist-induced translocation of AGS3 to the GA altered the functional organization and protein sorting at the trans-Golgi network. The regulated movement of AGS3 between the cell cortex and the GA offers unexpected mechanisms for modulating protein secretion and/or endosome recycling events at the trans-Golgi network.Journal of Biological Chemistry 06/2013; 288(33). DOI:10.1074/jbc.M112.444505 · 4.57 Impact Factor
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ABSTRACT: 3,4-Methylenedioxymethamphetamine (MDMA or 'ecstasy') is a psychostimulant drug, widely used recreationally among young people in Europe and North America. Although its neurotoxicity has been extensively described, little is known about its ability to strengthen neural circuits when administered in a manner that reproduces human abuse (i.e. repeated exposure to a low dose). C57BL/6J mice were repeatedly injected with MDMA (10 mg kg(-1), intraperitoneally) and studied after a 4-day or a 1-month withdrawal. We show, using in vivo microdialysis and locomotor activity monitoring, that repeated injections of MDMA induce a long-term sensitization of noradrenergic and serotonergic neurons, which correlates with behavioral sensitization. The development of this phenomenon, which lasts for at least 1 month after withdrawal, requires repeated stimulation of α1B-adrenergic and 5-hydroxytryptamine (5-HT)2A receptors. Moreover, behavioral and neuroendocrine assays indicate that hyper-reactivity of noradrenergic and serotonergic networks is associated with a persistent desensitization of somatodendritic α2A-adrenergic and 5-HT1A autoreceptor function. Finally, molecular analysis including radiolabeling, western blot and quantitative reverse transcription-polymerase chain reaction reveals that mice repeatedly treated with MDMA exhibit normal α2A-adrenergic and 5-HT1A receptor binding, but a long-lasting downregulation of Gαi proteins expression in both locus coeruleus and dorsal raphe nucleus. Altogether, our results show that repeated MDMA exposure causes strong neural and behavioral adaptations and that inhibitory feedback mediated by α2A-adrenergic and 5-HT1A autoreceptors has an important role in the physiopathology of addictive behaviors.Molecular Psychiatry advance online publication, 20 August 2013; doi:10.1038/mp.2013.97.Molecular Psychiatry 08/2013; 19(7). DOI:10.1038/mp.2013.97 · 14.50 Impact Factor
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