GTP-BINDING PROTEINS AND SIGNAL TRANSDUCTION--STRUCTURE AND FUNCTION

GTP 结合蛋白和信号转导——结构和功能

• 批准号: 3755503
• 负责人: M RODBELL
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/3755503
• 关键词: G protein; adrenergic receptor; biological signal transduction; calcium; cyclic AMP; hormone regulation /control mechanism; muscarinic receptor; protein structure function; receptor coupling; second messengers; tissue /cell culture; transfection

Previous work indicated that GTP-binding proteins (G-proteins) are associated as multimeric proteins with the plasma membrane of cells. The theory was proposed that coupling of receptors to multimeric G- proteins can be likened to the association of myosin with multimeric actin; regulation of the latter is governed by the binding and hydrolysis of ATP to ADP whereas receptor-G protein coupling is governed by the concerted binding of hormone and GTP, and degradation of the latter to DGP. In other theories of hormonal activation of G proteins, the products of activation are the dissociated alpha and betagamma subunits of the heterotrimeric G proteins. Using digitonin for extracting multimeric G proteins, we have found that the products of activation of various species of G proteins extracted from brain membranes are monomoers (i.e., heterotrimers) rather than dissociated alpha and betagamma subunits as observed when the same membranes are extracted with Lubrol, which is generally used for extraction. These findings raise new issues regarding the nature of the activation of various effector systems by G proteins. In a second line of investigation, polyclonal antibodies raised against several types of G proteins were used for determining the cellular disposition of G proteins utilizing both normal optics and confocal microscopy for immunodetection of the alpha-subunits of the G proteins. One type, Galphai, was found in three different cell types to be located in the cytosolic compartment in the form of punctate structures, possibly vesicular in nature. In 3T3 fibroblasts, the punctate structures are associated with stress fibers indicating an association with the cytoskeletal matrix; microtubulin filaments were not prominently associated with Galphai. These studies raise fundamental questions regarding how G proteins function in cells not only as transducers linked to surface receptors but possibly also as regulators of movement and targeting of vesicles associated with the cytoskeletal matrix of cells.

以前的工作表明，GTP结合蛋白（G蛋白）是 作为多聚体蛋白与细胞质膜结合。 提出了受体与多聚体G- 蛋白质可以被比作肌球蛋白与多聚体的结合， 肌动蛋白;后者的调节受约束， ATP水解为ADP，而受体-G蛋白偶联受 通过激素和GTP的协同结合， 后为DGP。 在G蛋白的激素激活的其他理论中， 活化的产物是解离的α和β γ 异源三聚体G蛋白的亚基。 毛地黄皂苷用于 提取多聚体G蛋白，我们发现， 从脑中提取的各种G蛋白的活化 膜是单体（即，异源三聚体）而不是解离的 α和β γ亚基，如当相同的膜被 用通常用于萃取的Lubrol萃取。 这些 研究结果提出了新的问题，关于激活的性质， G蛋白的各种效应系统。 在第二行 调查，针对几种类型的G 蛋白质用于确定G 利用普通光学和共聚焦显微镜 G蛋白的α-亚单位的免疫检测。 一类， Galphai，在三种不同的细胞类型中被发现， 细胞质区室以点状结构的形式，可能 本质上是泡状的。 在3 T3成纤维细胞中， 与应力纤维相关，表明与 细胞骨架基质;微管蛋白丝不显着 与Galphai有关。 这些研究提出了一些基本问题 关于G蛋白在细胞中的功能不仅是作为转换器 与表面受体有关，但也可能是运动的调节器 和靶向与细胞骨架基质相关的囊泡， 细胞