YEAST PHEROMONE SIGNAL TRANSDUCTION

描述(申请人提供)：细胞行为通常由细胞外环境中的信号控制。其影响可能是戏剧性的，例如决定扩散或差异化，因此应对措施必须受到高度监管和精心策划。虽然已经确定了许多信号通路及其分子成分，但一些研究得很好的系统提供了一个独特的机会来测试多个成分如何实现统一的细胞反应，该反应整合了来自不同亚细胞区域的信息以及关于细胞生理状态的信息。酿酒酵母中由胞外交配信息素激活的信号转导途径为探索构建在细胞反应中的复杂因素提供了一个理想的模型系统。在这个系统中，信号涉及到质膜定位的信号复合体的动态组装，这些复合体包括从酵母到人类的各种信号通路中普遍存在的蛋白质，如PAK家族激酶、异源三聚体G蛋白、MAP激酶级联和支架蛋白。在这里，我们利用丰富的信息和遗传试剂来测试几个有趣的模型，这些模型关于传播细胞内信号的机制及其与细胞生物结构的接口，特别强调亚细胞定位的作用。一个目标将是确定MAP激酶级联支架蛋白Ste5的膜募集如何通过激酶级联放大信号，以及这种信号主要发生在单个支架分子之间还是内部。另一个目标将是剖析交配MAPK级联抑制有丝分裂细胞周期的多种途径，并确定为什么在细胞分裂时这一信号通路失活是重要的。此外，还将研究PAK家族激酶Ste20中一个小的膜结合结构域的作用，以及类似结构域在其他极化蛋白中的普遍存在。总体而言，我们希望这些研究通过揭示信号系统中内置的允许细胞内动态和综合反应的机制，有助于对信号转导的深入理解。

DESCRIPTION (provided by applicant): Cellular behavior is commonly controlled by signals in the extracellular environment. The effects can be dramatic, such as the decision to proliferate or to differentiate, and so the responses must be highly regulated and carefully orchestrated. While many signaling pathways and their molecular components have been identified, some well-studied systems offer a unique opportunity to test how multiple components achieve a unified cellular response that integrates information from different subcellular regions as well as information about the physiological status of the cell. The signal transduction pathway that is activated by extracellular mating pheromones in the yeast Saccharomyces cerevisiae presents an ideal model system in which to probe the intricacies that are built into a cellular response. Signaling in this system involves the dynamic assembly of plasma membrane-localized signaling complexes, which include proteins found ubiquitously in a variety of signaling pathways from yeast to humans, such as a PAK-family kinase, a heterotrimeric G protein, a MAP kinase cascade, and a scaffold protein. Here we make use of a rich foundation of information and genetic reagents to test several intriguing models about the mechanisms that propagate intracellular signaling and their interface with cell biological structures, with particular emphasis on the role of subcellular localization. One goal will be to determine how membrane recruitment of the MAP kinase cascade scaffold protein Ste5 amplifies signaling through the kinase cascade, and whether this signaling occurs predominantly between or within individual scaffold molecules. Another goal will be to dissect the multiple routes by which the mating MAP kinase cascade can inhibit the mitotic cell cycle, and to determine why it is important for this signaling pathway to be inactivated as cells commit to division. Also under investigation will be the role of a small membrane-binding domain in the PAK-family kinase Ste20, and the prevalence of similar domains in other polarized proteins. Overall, we expect these studies to contribute to a sophisticated understanding of signal transduction by revealing mechanisms that are built into signaling systems to allow dynamic and integrative responses within a cell.