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 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 signaling (RGS) and GoLoco domain-containing proteins via their GTPase-activating protein (GAP) and guanosine 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 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 signaling 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 signaling may underlie the complexity of receptor-operated TRPC4 activation in various cell types under different conditions.
- transient receptor potential channels
- GTPase-activating protein
- ©2016 The Author(s)
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