GBeta5/RGS proteins and GPCR signaling

描述（由申请方提供）：G蛋白信号传导调节（RGS）蛋白最初被鉴定为异源三聚体G蛋白的GTP酶激活蛋白（GAP）？亚单位。然而，许多RGS蛋白除了特征RGS盒之外还具有高度保守的结构域，其赋予多功能特性，该多功能特性是异源三聚体G蛋白信号级联的组分之间以及与其他信号通路之间的了解不多但生理学上重要的相互作用的基础。RGS蛋白的R7亚家族具有独特的G-？-样（GGL）结构域介导特异性和专性异源二聚体的形成与非典型G蛋白亚基，G？5，表明这些信号蛋白表现出类似于传统G？？二聚体。我们最近精炼的晶体结构的G？5/RGS 9支持这一想法，并提供了一个框架，用于测试与这种二聚体的各种结合界面相关的假设，这些结合界面可能有助于高阶多功能G蛋白/GPCR/RGS复合物的组织和整合。因此，我们建议：1）使用晶体学和突变分析，以确定完整的功能和G？特异性RGS结构域内全长G？？5/R7二聚体; 2）扩展我们的理解G？？5/R7二聚体及其锚定蛋白，R9 AP和R7 BP;和3）量化的G？？5/R7二聚体与GDP-G相互作用？亚基和GPCR使用纯化组分的重构系统。虽然很明显，R7蛋白是在各种生理环境下由G蛋白偶联受体介导的适当信号传导所必需的，但这些蛋白在协调这些信号传导事件中的作用相对知之甚少。这里提出的工作旨在将R7蛋白的详细结构和功能的背景下，相对于G蛋白偶联受体和异源三聚体G蛋白。预计这些研究将用于指导R7蛋白介导的协调信号传导失败的情况下的治疗方案。

DESCRIPTION (provided by applicant): The Regulator of G protein Signaling (RGS) proteins originally were identified as GTPase-activating proteins (GAPs) for heterotrimeric G protein ? subunits. However, many RGS proteins possess highly- conserved domains in addition to the signature RGS box, which empower a multifunctional character that underlies poorly understood but physiologically important interactions among components of heterotrimeric G protein signaling cascades as well as with other signaling pathways. The R7 subfamily of RGS proteins possess a distinctive G-?-like (GGL) domain that mediates specific and obligate heterodimer formation with the atypical G protein subunit, G?5, suggesting that these signaling proteins exhibit functions similar to conventional G?? dimers. Our recently refined crystal structure of G?5/RGS9 support this idea and provides a framework for testing hypotheses related to various binding interfaces of this dimer that likely subserve the organization and integration of higher-order, multifunctional G protein/GPCR/RGS complexes. Consequently, we propose to: 1) use crystallography and mutational analyses to define the complete functionality and G? specificity of RGS domains within full-length G??5/R7 dimers; 2) extend our understanding of the functional and structural relationships between G??5/R7 dimers and their anchoring proteins, R9AP and R7BP; and 3) quantify the functional capacities of G??5/R7 dimers to interact with GDP- G? subunits and GPCRs using reconstituted systems of purified components. While it is clear that R7 proteins are required for proper signaling mediated by G protein-coupled receptors under a variety of physiological settings, the roles of these proteins in coordinating these signaling events are relatively poorly understood. The work proposed here is designed to place R7 proteins within a detailed structural and functional context with respect to G protein-coupled receptors and heterotrimeric G proteins. It is anticipated that these studies will then be used to guide treatment regimens in cases where coordinated signaling mediated by R7 proteins has failed.