Abramow-Newerly Maria, Ming Hong, Chidiac Peter
Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada N6A 5C1.
Cell Signal. 2006 Dec;18(12):2209-22. doi: 10.1016/j.cellsig.2006.05.011. Epub 2006 May 23.
Regulator of G protein signalling (RGS) proteins are primarily known for their ability to act as GTPase activating proteins (GAPs) and thus attenuate G protein function within G protein-coupled receptor (GPCR) signalling pathways. However, RGS proteins have been found to interact with additional binding partners, and this has introduced more complexity to our understanding of their potential role in vivo. Here, we identify a novel interaction between RGS proteins (RGS4, RGS5, RGS16) and the multifunctional protein 14-3-3. Two isoforms, 14-3-3beta and 14-3-3epsilon, directly interact with all three purified RGS proteins and data from in vitro steady state GTP hydrolysis assays show that 14-3-3 inhibits the GTPase activity of RGS4 and RGS16, but has limited effects on RGS5 under comparable conditions. Moreover in a competitive pull-down experiment, 14-3-3epsilon competes with Galphao for RGS4, but not for RGS5. This mechanism is further reinforced in living cells, where 14-3-3epsilon sequesters RGS4 in the cytoplasm and impedes its recruitment to the plasma membrane by Galpha protein. Thus, 14-3-3 might act as a molecular chelator, preventing RGS proteins from interacting with Galpha, and ultimately prolonging the signal transduction pathway. In conclusion, our findings suggest that 14-3-3 proteins may indirectly promote GPCR signalling via their inhibitory effects on RGS GAP function.
G蛋白信号调节蛋白(RGS)主要因其作为GTP酶激活蛋白(GAP)的能力而闻名,从而在G蛋白偶联受体(GPCR)信号通路中减弱G蛋白功能。然而,已发现RGS蛋白可与其他结合伴侣相互作用,这使我们对其在体内潜在作用的理解更加复杂。在此,我们鉴定出RGS蛋白(RGS4、RGS5、RGS16)与多功能蛋白14-3-3之间的新型相互作用。两种亚型,即14-3-3β和14-3-3ε,直接与所有三种纯化的RGS蛋白相互作用,体外稳态GTP水解试验的数据表明,14-3-3抑制RGS4和RGS16的GTP酶活性,但在可比条件下对RGS5的影响有限。此外,在竞争性下拉实验中,14-3-3ε与Gαo竞争RGS4,但不竞争RGS5。在活细胞中,这种机制进一步得到加强,其中14-3-3ε将RGS4隔离在细胞质中,并阻止其被Gα蛋白募集到质膜。因此,14-3-3可能充当分子螯合剂,阻止RGS蛋白与Gα相互作用,并最终延长信号转导通路。总之,我们的研究结果表明,14-3-3蛋白可能通过其对RGS GAP功能的抑制作用间接促进GPCR信号传导。