Orlandi Cesare, Xie Keqiang, Masuho Ikuo, Fajardo-Serrano Ana, Lujan Rafael, Martemyanov Kirill A
From the Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida 33458 and.
the Instituto de Investigación en Descapacidades Neuronales (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad de Castilla-La Mancha, 02006 Albacete, Spain.
J Biol Chem. 2015 May 29;290(22):13622-39. doi: 10.1074/jbc.M115.645374. Epub 2015 Mar 19.
Regulators of G protein signaling control the duration and extent of signaling via G protein-coupled receptor (GPCR) pathways by accelerating the GTP hydrolysis on G protein α subunits thereby promoting termination of GPCR signaling. A member of this family, RGS7, plays a critical role in the nervous system where it regulates multiple neurotransmitter GPCRs that mediate vision, memory, and the action of addictive drugs. Previous studies have established that in vivo RGS7 forms mutually exclusive complexes with the membrane protein RGS7-binding protein or the orphan receptor GPR158. In this study, we examine the impact of GPR158 on RGS7 in the brain. We report that knock-out of GPR158 in mice results in marked post-transcriptional destabilization of RGS7 and substantial loss of its association with membranes in several brain regions. We further identified the RGS7-binding site in the C terminus of GPR158 and found that it shares significant homology with the RGS7-binding protein. The proximal portion of the GPR158 C terminus additionally contained a conserved sequence that was capable of enhancing RGS7 GTPase-activating protein activity in solution by an allosteric mechanism acting in conjunction with the regulators of the G protein signaling-binding domain. The distal portion of the GPR158 C terminus contained several phosphodiesterase E γ-like motifs and selectively recruited G proteins in their activated state. The results of this study establish GPR158 as an essential regulator of RGS7 in the native nervous system with a critical role in controlling its expression, membrane localization, and catalytic activity.
G蛋白信号调节因子通过加速G蛋白α亚基上的GTP水解，从而促进G蛋白偶联受体（GPCR）信号转导的终止，来控制GPCR信号转导的持续时间和程度。该家族成员RGS7在神经系统中起关键作用，它调节多种介导视觉、记忆和成瘾药物作用的神经递质GPCR。先前的研究已经证实，在体内RGS7与膜蛋白RGS7结合蛋白或孤儿受体GPR158形成互斥复合物。在本研究中，我们研究了GPR158对大脑中RGS7的影响。我们报告称，敲除小鼠中的GPR158会导致RGS7在转录后明显不稳定，并在几个脑区中使其与膜的结合大量丧失。我们进一步确定了GPR158 C末端的RGS7结合位点，发现它与RGS7结合蛋白具有显著的同源性。GPR158 C末端的近端部分还包含一个保守序列，该序列能够通过与G蛋白信号调节结合域的调节因子协同作用的变构机制，增强溶液中RGS7的GTP酶激活蛋白活性。GPR158 C末端的远端部分包含几个磷酸二酯酶Eγ样基序，并选择性地募集处于激活状态的G蛋白。本研究结果确立了GPR158作为天然神经系统中RGS7的重要调节因子，在控制其表达、膜定位和催化活性方面起关键作用。
