期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 280, 期 14, 页码 13383-13394出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M410163200
关键词
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Regulators of G-protein signaling (RGS) proteins modulate signaling through heterotrimeric G-proteins. They act to enhance the intrinsic GTPase activity of the G alpha subunit but paradoxically have also been shown to enhance receptor-stimulated activation. To study this paradox, we used a G-protein gated K+ channel to report the dynamics of the G-protein cycle and fluorescence resonance energy transfer techniques with cyan and yellow fluorescent protein-tagged proteins to report physical interaction. Our data show that the acceleration of the activation kinetics is dissociated from deactivation kinetics and dependent on receptor and RGS type, G-protein isoform, and RGS expression levels. By using fluorescently tagged proteins, fluorescence resonance energy transfer microscopy showed a stable physical interaction between the G-protein alpha subunit and RGS (RGS8 and RGS7) that is independent of the functional state of the G-protein. RGS8 does not directly interact with G-protein-coupled receptors. Our data show participation of the RGS in the ternary complex between agonist-receptor and G-protein to form a quaternary complex. Thus we propose a novel model for the action of RGS proteins in the G-protein cycle in which the RGS protein appears to enhance the kinetic efficacy of the ternary complex, by direct association with the G-protein alpha subunit.
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