INHIBITION OF G PROTEIN BETA-SUBUNIT SIGNALING IN YEAST

酵母中 G 蛋白 β 亚基信号传导的抑制

基本信息

批准号：
6628918
负责人：
Jeanne P. Hirsch
金额：
$ 21.27万
依托单位：
ICAHN SCHOOL OF MEDICINE AT MOUNT SINAI
依托单位国家：
美国
项目类别：
财政年份：
2001
资助国家：
美国
起止时间：
2001-02-01 至 2005-01-31
项目状态：
已结题

项目摘要

Signal transduction pathways that act through heterotrimeric G proteins mediate the response to a wide variety of extracellular signals in many different organisms. In yeast, the pheromone response pathway is activated by the binding of extracellular pheromones to G protein- coupled receptors that are specific to cells of either the MATa or MATalpha mating type. Activation of the G protein alpha-subunit results in release of the beta-gamma-subunits, which transmit the signal to downstream kinases. Studies described in this proposal will investigate a novel function of Ste3p, the a-factor receptor. This novel function, called receptor inhibition, causes a block in signal transmission by inhibiting the activity of the beta-subunit in a manner that is independent of the alpha-subunit. Receptor inhibition only occurs when cells contain both a- specific and alpha-specific proteins, and probably functions immediately after the fusion of two mating cells to ensure that the signaling pathway is rapidly turned off. This process requires the product of a newly identified a-specific gene called ASG7. Thus, when the same cell expresses both Asg7p, an a-specific protein, and Ste3p, an alpha-specific protein, a process is initiated that acts directly on the beta-subunit and inhibits its activity. This project will investigate how beta-subunit signaling is inhibited when the a-factor receptor and the novel regulator Asg7p are present in the same cell. One specific aim is to determine how the activity of the beta- subunit is blocked by this process. The effect of changes in Asg7p abundance, localization, and binding to the beta-subunit will be tested for their effects on beta-subunit activity. A screen for other genes required for receptor inhibition will also be carried out. A second specific aim is to determine how Asg7p is activated by the presence of the Ste3p receptor. The potential roles of membrane localization, posttranslational modification, and Ste3p binding in the activation of As97p will be determined. A final specific aim is to investigate the structure/function relationships of Ste3p with respect to its receptor inhibition function. By isolating specific mutations in STE3 and by constructing chimeric receptors, the region of Ste3p involved in receptor inhibition will be identified. Significant progress in elucidating signal transduction mechanisms has been made in organisms in which sophisticated genetic manipulations can easily be performed. Elucidation of the process of receptor inhibition in yeast is likely to provide information about the regulation of G protein beta-subunits in other systems in which the beta-subunit plays an active role in signal transmission.

通过异源三聚体 G 蛋白发挥作用的信号转导途径介导许多不同生物体对多种细胞外信号的反应。在酵母中，信息素反应途径通过胞外信息素与 G 蛋白偶联受体的结合而激活，该受体对 MATa 或 MATalpha 交配型细胞具有特异性。 G 蛋白 α 亚基的激活导致 β-γ 亚基的释放，从而将信号传递至下游激酶。该提案中描述的研究将调查 a 因子受体 Ste3p 的新功能。这种新功能称为受体抑制，通过以独立于 α 亚基的方式抑制 β 亚基的活性，导致信号传输受阻。受体抑制仅在细胞同时含有α特异性和α特异性蛋白质时发生，并且可能在两个交配细胞融合后立即发挥作用，以确保信号传导途径快速关闭。这个过程需要新鉴定的 a 特定基因（称为 ASG7）的产物。因此，当同一细胞同时表达 Asg7p（一种 α 特异性蛋白）和 Ste3p（一种 α 特异性蛋白）时，就会启动直接作用于 β 亚基并抑制其活性的过程。该项目将研究当 a 因子受体和新型调节剂 Asg7p 存在于同一细胞中时，β 亚基信号传导如何受到抑制。一个具体目标是确定这一过程如何阻断β亚基的活性。将测试 Asg7p 丰度、定位和与 β 亚基结合的变化对 β 亚基活性的影响。还将筛选受体抑制所需的其他基因。第二个具体目标是确定 Asg7p 如何被 Ste3p 受体的存在激活。将确定膜定位、翻译后修饰和 Ste3p 结合在 As97p 激活中的潜在作用。最终的具体目标是研究 Ste3p 与其受体抑制功能的结构/功能关系。通过分离STE3中的特定突变并构建嵌合受体，将鉴定参与受体抑制的Ste3p区域。在可以轻松进行复杂遗传操作的生物体中，在阐明信号转导机制方面已经取得了重大进展。阐明酵母中受体抑制的过程可能会提供有关其他系统中 G 蛋白 β 亚基调节的信息，在这些系统中 β 亚基在信号传递中发挥积极作用。