期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2020
卷号：117
期号：35
页码：21723-21730
DOI：10.1073/pnas.2003787117
出版社：The National Academy of Sciences of the United States of America
摘要：G proteins are activated when they associate with G protein-coupled receptors (GPCRs), often in response to agonist-mediated receptor activation. It is generally thought that agonist-induced receptor-G protein association necessarily promotes G protein activation and, conversely, that activated GPCRs do not interact with G proteins that they do not activate. Here we show that GPCRs can form agonist-dependent complexes with G proteins that they do not activate. Using cell-based bioluminescence resonance energy transfer (BRET) and luminescence assays we find that vasopressin V 2 receptors (V 2 R) associate with both G s and G 12 heterotrimers when stimulated with the agonist arginine vasopressin (AVP). However, unlike V 2 R-G s complexes, V 2 R-G 12 complexes are not destabilized by guanine nucleotides and do not promote G 12 activation. Activating V 2 R does not lead to signaling responses downstream of G 12 activation, but instead inhibits basal G 12 -mediated signaling, presumably by sequestering G 12 heterotrimers. Overexpressing G 12 inhibits G protein receptor kinase (GRK) and arrestin recruitment to V 2 R and receptor internalization. Formyl peptide (FPR1 and FPR2) and Smoothened (Smo) receptors also form complexes with G 12 that are insensitive to nucleotides, suggesting that unproductive GPCR-G 12 complexes are not unique to V 2 R. These results indicate that agonist-dependent receptor-G protein association does not always lead to G protein activation and may in fact inhibit G protein activation.
关键词：GPCR ; ternary complex ; G protein-coupled receptor ; arrestin
