Participation of RGS8 in the ternary complex of agonist, receptor and G-protein

被引:8
作者
Benians, A
Nobles, M
Tinker, A
机构
[1] UCL, British Heart Fdn Labs, London WC1E 6JJ, England
[2] UCL, Dept Med, London WC1E 6JJ, England
关键词
G-protein gated inwardly rectifying K+ (GIRK); kinetics; regulators of G-protein signalling; RGS8;
D O I
10.1042/BST0321045
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The RGS (regulators of G-protein signalling) protein family sharpen signalling kinetics through heterotrimeric G-proteins by enhancing the GTPase activity of the G-protein alpha subunit. Paradoxically, they also accelerate receptor-stimulated activation. We investigated this paradox using the cloned G-protein gated K+ channel as a reporter of the G-protein cycle, and FRET (fluorescence resonance energy transfer) between cyan and yellow fluorescent protein tagged proteins to detect physical interactions. Our results with the neuronal protein, RGS8, show that the enhancement of activation kinetics is a variable phenomenon determined by receptor type, G-protein isoform and RGS8 expression levels. in contrast, deactivation was consistently accelerated after removal of agonist. FRET microscopy revealed a stable physical interaction between RGS8-yellow fluorescent protein and G(o) alpha(A)-cyan fluorescent protein that occurred in the presence and absence of receptor activation and was not competed away by Gbetagamma overexpression. FRET was also seen between RGS8 and Ggamma, demonstrating that RGS8 binds to the heterotrimeric G-protein as well as G-protein alpha subunit-GTP and the transition complex. We propose a novel model for the action of RGS proteins on the G-protein cycle involving participation of the RGS in the ternary complex: for certain combinations of agonist, receptor and G-protein, RGS8 expression improves upon the 'kinetic efficacy' of G-protein activation.
引用
收藏
页码:1045 / 1047
页数:3
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