Abstract
The tetrameric G protein-gated K+ channels (GIRKs) mediate inhibitory effects of neurotransmitters that activate Gi/o-coupled receptors. GIRKs are activated by binding of the Gβγ dimer, via contacts with Gβ. Gγ underlies membrane targeting of Gβγ, but has not been implicated in channel gating. We observed that, in Xenopus oocytes, expression of Gγ alone activated homotetrameric GIRK1* and heterotetrameric GIRK1/3 channels, without affecting the surface expression of GIRK or Gβ. Gγ and Gβ acted interdependently: the effect of Gγ required the presence of ambient Gβ and was enhanced by low doses of coexpressed Gβ, whereas excess of either Gβ or Gγ imparted suboptimal activation, possibly by sequestering the other subunit “away” from the channel. The unique distal C-terminus of GIRK1, G1-dCT, was important but insufficient for Gγ action. Notably, GIRK2 and GIRK1/2 were not activated by Gγ. Our results suggest that Gγ regulates GIRK1* and GIRK1/3 channel’s gating, aiding Gβ to trigger the channel’s opening. We hypothesize that Gγ helps to relax the inhibitory effect of a gating element (“lock”) encompassed, in part, by the G1-dCT; GIRK2 acts to occlude the effect of Gγ, either by setting in motion the same mechanism as Gγ, or by triggering an opposing gating effect.
Highlights
G1-Distal C-terminus of GIRK1 (dCT), was important but insufficient for Gγ action
We serendipitously discovered that heterologous expression of Gγ2, without Gβ, activated the GIRK1* channel
The PM level of Gβ was 70 ± 19% of control when 0.2 ng Gγ was coexpressed of (Fig. 1E, n = 5; p = 0.17). These results indicate that expression of Gγ at doses that cause maximal activation of GIRK1* is not associated with a significant recruitment of endogenous Gβ
Summary
G1-dCT, was important but insufficient for Gγ action. Notably, GIRK2 and GIRK1/2 were not activated by Gγ. In response to neurotransmitters, following the GPCR-catalyzed separation of Gβγ from Gαi/o, GIRKs are activated by direct binding of up to four Gβγ subunits[19,20,21,22,23,24,25,26,27,28]. GIRK1 contains a 121 amino acid-long distal C-terminus (G1-dCT) that endows GIRK1-containing channels with unique characteristics This labile (and absent form crystal structures) protein segment does not strongly bind Gβγ but it imparts high functional activity upon GIRK1-containing channels[30,31] and high-affinity binding (“anchoring”) of Gβγ to the full cytosolic domain of GIRK118,32–34. The Gγ is thought to be primarily responsible for membrane targeting and attachment of the www.nature.com/scientificreports/
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
