title: Regulator of G-protein signalling and GoLoco proteins suppress TRPC4 channel function via acting at Gαi/o.
abstract: Transient receptor potential canonical 4 (TRPC4) forms non-selective cation channels implicated in the regulation of diverse physiological functions. Previously, TRPC4 was shown to be activated by the Gi/o subgroup of heterotrimeric G-proteins involving Gαi/o, rather than Gβγ, subunits. Because the lifetime and availability of Gα-GTP are regulated by regulators of G-protein signalling (RGS) and Gαi/o-Loco (GoLoco) domain-containing proteins via their GTPase-activating protein (GAP) and guanine-nucleotide-dissociation inhibitor (GDI) functions respectively, we tested how RGS and GoLoco domain proteins affect TRPC4 currents activated via Gi/o-coupled receptors. Using whole-cell patch-clamp recordings, we show that both RGS and GoLoco proteins [RGS4, RGS6, RGS12, RGS14, LGN or activator of G-protein signalling 3 (AGS3)] suppress receptor-mediated TRPC4 activation without causing detectable basal current or altering surface expression of the channel protein. The inhibitory effects are dependent on the GAP and GoLoco domains and facilitated by enhancing membrane targeting of the GoLoco protein AGS3. In addition, RGS, but not GoLoco, proteins accelerate desensitization of receptor-activation evoked TRPC4 currents. The inhibitory effects of RGS and GoLoco domains are additive and are most prominent with RGS12 and RGS14, which contain both RGS and GoLoco domains. Our data support the notion that the Gα, but not Gβγ, arm of the Gi/o signalling is involved in TRPC4 activation and unveil new roles for RGS and GoLoco domain proteins in fine-tuning TRPC4 activities. The versatile and diverse functions of RGS and GoLoco proteins in regulating G-protein signalling may underlie the complexity of receptor-operated TRPC4 activation in various cell types under different conditions.
authors.affiliation: Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030, U.S.A.
authors.forename: Jae-Pyo
authors.initials: JP
authors.lastname: Jeon
authors.affiliation: Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030, U.S.A. Graduate Program in Cell and Regulatory Biology, The University of Texas Health Science Center at Houston, Houston, TX 77030, U.S.A.
authors.forename: Dhananjay P
authors.initials: DP
authors.lastname: Thakur
authors.affiliation: Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030, U.S.A.
authors.forename: Jin-Bin
authors.initials: JB
authors.lastname: Tian
authors.affiliation: Department of Physiology, Seoul National University, College of Medicine, Seoul 110-799, South Korea.
authors.forename: Insuk
authors.initials: I
authors.lastname: So
authors.affiliation: Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030, U.S.A. Graduate Program in Cell and Regulatory Biology, The University of Texas Health Science Center at Houston, Houston, TX 77030, U.S.A. michael.x.zhu@uth.tmc.edu.
authors.forename: Michael X
authors.initials: MX
authors.lastname: Zhu
mesh_terms: D015153:Blotting, Western; D004594:Electrophysiology; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding; D020710:RGS Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: C525615:GPSM1 protein, human; C102754:GPSM2 protein, human; D020730:Guanine Nucleotide Dissociation Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D020710:RGS Proteins; C106375:RGS12 protein, human; C491400:RGS14 protein, human; C400194:RGS6 protein, human; D050052:TRPC Cation Channels; C489571:TRPC4 ion channel; C098799:RGS4 protein; D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020962:Heterotrimeric GTP-Binding Proteins
keywords: G-proteins; GTPase-activating protein (GAP); TRP channels; guanine-nucleotide-dissociation inhibitor (GDI)