G Protein Beta-Gamma and Beta-RGS Dimers--Structure and

G蛋白，或鸟嘌呤核苷酸结合调节蛋白，是一种异源三聚体，通过将细胞外刺激的受体与细胞内的效应器(酶、离子通道)偶联来发挥跨膜信号转导的作用。G蛋白是一个不同的家族，由特定的受体和效应器相互作用决定，而受体和效应器的相互作用又由三个组成亚基的结构决定。α亚基与鸟嘌呤核苷酸结合，并在效应器调节中起着公认的作用。β亚基和伽马亚基作为一个β-伽马复合体紧密联系在一起，组成一个单一的功能实体，就像阿尔法亚基一样，是G蛋白与受体相互作用必不可少的。贝塔-伽马复合体的效应调节作用现在被许多细胞系统所接受。本研究强调了β-γ复合体在G蛋白介导的信号转导中的作用。梅尔·西蒙和他的同事从大脑中克隆了一个结构不同的神经表达的Gβ亚基-β-5，后来在视网膜中发现了一种可选择性剪接的“长”形式(Gβ-5-L)。最近发现G beta-5表现出功能特化，因为它能够激活PLC，但不能激活MAPK或JNK级联。我们实验室目前的工作是以果蝇和培养的PC12细胞为模型系统，研究昆虫Gβ-5同源物和哺乳动物Gβ-5的共同功能。

G-proteins, or guanine-nucleotide binding regulatory proteins, are heterotrimers which function as transmembrane signal transducers by coupling receptors for extracellular stimuli to intracellular effectors (enzymes, ion channels). G-proteins constitute a diverse family distinguished by specific receptor and effector interactions which in turn are determined by the structure of the three constituent subunits. The alpha subunit binds guanine nucleotides and has a well-established role in effector modulation. The beta and gamma subunits are tightly associated as a beta-gamma complex, comprising a single functional entity which, like the alpha subunit, is absolutely required for G protein interaction with receptor. An effector-regulatory role for the beta-gamma complex is now accepted in many cellular systems. The present research emphasizes the role of the beta-gamma complex in G-protein-mediated signal transduction. A structurally divergent neurally expressed G beta subunit, beta-5, was cloned from brain by Mel Simon and coworkers, and later found in an alternatively spliced "long" form in retina (G beta5-L). G beta-5 was recently found to exhibit functional specialization, as it was able to activate PLC but not the MAPK or JNK cascades. Current work in our laboratory examines shared functions of the insect G beta-5 homolog and mammalian G beta-5, using Drosophila melanogaster and cultured PC12 cells as model systems.