Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455, USA.
J Biol Chem. 2010 Feb 12;285(7):4781-7. doi: 10.1074/jbc.M109.058511. Epub 2009 Dec 11.
The R7 subfamily of RGS proteins critically regulates neuronal G protein-signaling pathways that are essential for vision, nociception, motor coordination, and reward processing. A member of the R7 RGS family, RGS11, is a GTPase-accelerating protein specifically expressed in retinal ON-bipolar cells where it forms complexes with the atypical G protein beta subunit, Gbeta(5), and transmembrane protein R9AP. Association with R9AP has been shown to be critical for the proteolytic stability of the complex in the retina. In this study we report that R9AP can in addition stimulate the GTPase-accelerating protein activity of the RGS11 x Gbeta(5) complex at Galpha(o). Single turnover GTPase assays reveal that R9AP co-localizes RGS11 x Gbeta(5) and Galpha(o) on the membrane and allosterically potentiates the GTPase-accelerating function of RGS11 x Gbeta(5). Reconstitution of mGluR6-Galpha(o) signaling in Xenopus oocytes indicates that RGS11 x Gbeta(5)-mediated GTPase acceleration in this system requires co-expression of R9AP. The results provide new insight into the regulation of mGluR6-Galpha(o) signaling by the RGS11 x Gbeta(5) x R9AP complex and establish R9AP as a general GTPase-accelerating protein activity regulator of R7 RGS complexes.
R7 亚家族的 RGS 蛋白对神经元 G 蛋白信号通路的调节至关重要，这些信号通路对于视觉、疼痛感知、运动协调和奖励处理都是必不可少的。R7 RGS 家族的一个成员，RGS11，是一种 GTPase 加速蛋白，特异性表达在视网膜的 ON-双极细胞中，在那里它与非典型 G 蛋白β亚基 Gβ(5)和跨膜蛋白 R9AP 形成复合物。与 R9AP 的结合对于复合物在视网膜中的蛋白水解稳定性至关重要。在这项研究中，我们报告 R9AP 可以另外刺激 RGS11 x Gβ(5)复合物在 Galpha(o)上的 GTPase 加速蛋白活性。单次转换 GTPase 测定表明，R9AP 将 RGS11 x Gβ(5)和 Galpha(o)共定位在膜上，并变构增强 RGS11 x Gβ(5)的 GTPase 加速功能。在 Xenopus 卵母细胞中重建 mGluR6-Galpha(o)信号表明，在这个系统中，RGS11 x Gβ(5)介导的 GTPase 加速需要 R9AP 的共表达。研究结果为 RGS11 x Gβ(5) x R9AP 复合物对 mGluR6-Galpha(o)信号的调节提供了新的见解，并确立 R9AP 为 R7 RGS 复合物的通用 GTPase 加速蛋白活性调节剂。
