YEAST HETEROTRIMERIC G PROTEIN AND CELL POLARITY

描述（由申请人提供）：几乎所有细胞的一个基本特性是对来自周围环境的线索做出反应的能力。细胞外刺激存在的信息通过信号转导途径转化为细胞内行为。此外，许多细胞表现出定向反应，例如朝向局部刺激的生长或运动，这意味着检测刺激的信号转导分子与控制细胞形状、极性和运动性的信号转导分子之间的通信。本研究以酿酒酵母（Saccharomyces cerevisiae）的交配反应为模型系统，采用分子遗传学和细胞生物学方法，研究外界刺激对信号传导和细胞极性的控制。在该系统中，细胞内信号传导通过从酵母到人类保守的蛋白质模块发生，例如异源三聚体G蛋白、MAP激酶级联、PAK家族激酶和Rho家族GTP酶。该项目的长期目标是提供由酵母异源三聚体G蛋白β-γ二聚体（Gbeta-gamma）引发的信号转导和极化事件的分子描述。一个目标将是了解Gbeta-gamma诱导细胞极化的能力是如何通过其相关的受体和Galpha亚基进行空间调节的，重点是最近的观察结果表明，不同的Galpha-Gbeta-interface在这种空间控制中具有不同的作用。还将调查的机制，通过该机制，G β-γ与其他蛋白质合作，以控制招聘的MAP激酶级联“支架”蛋白的细胞周边。另一个目标是研究支架蛋白对信号传递的影响，即支架如何帮助塑造MAP激酶途径的剂量反应行为。将通过探索SH 3结构域蛋白Bem 1在Ste 20信号传导和定位中的作用，并通过研究Ste 20内赋予在交配途径中起作用的能力的决定因素，来探讨G β-γ触发酵母PAK Ste 20激活交配MAP激酶级联的方法。这些研究将影响我们对生长因子、激素、神经递质和化学引诱物的信号转导和细胞骨架组织的理解，并与正常和病变细胞中有关增殖和细胞身份的细胞决定有关。

DESCRIPTION (provided by applicant): A fundamental property of virtually all cells is the ability to respond to cues from the surrounding environment. Information about the presence of extracellular stimuli is converted into intracellular behaviors by the use of signal transduction pathways. In addition, many cells show directional responses such as growth or movement toward a localized stimulus, which implies communication between the signal transduction molecules that detect the stimulus and those that govern cell shape, polarity, and motility. This work uses the mating reaction of the yeast Saccharomyces cerevisiae as a model system to study the control of signaling and cell polarity by external stimuli, using a molecular genetic and cell biological approach. In this system, intracellular signaling occurs via modules of proteins that are conserved from yeast to humans, such as heterotrimeric G proteins, MAP kinase cascades, PAK-family kinases, and Rho-family GTPases. The long-term objective of this project is to provide a molecular description of signal transduction and polarization events initiated by the yeast heterotrimeric G protein beta-gamma dimer (Gbeta-gamma). One goal will be to understand how the ability of Gbeta-gamma to induce cell polarization is spatially regulated by its associated receptor and Galpha subunit, with emphasis on recent observations that suggest qualitatively different roles for different Galpha-Gbeta interfaces in this spatial control. Also under investigation will be mechanisms by which Gbeta-gamma cooperates with additional proteins to control the recruitment of a MAP kinase cascade "scaffold" protein to the cell periphery. Another goal will be to examine the effects of scaffold proteins on signal transmission, in terms of how scaffolds help shape the dose-response behavior of a MAP kinase pathway. The means by which Gbeta-gamma triggers the yeast PAK Ste20 to activate the mating MAP kinase cascade will be pursued by exploring the role of the SH3 domain protein Bem1 in Ste20 signaling and localization and by investigating determinants within Ste20 that confer the ability to act in the mating pathway. These studies will impact our understanding of signal transduction and cytoskeletal organization in response to growth factors, hormones, neurotransmitters, and chemoattractants, with relevance to cellular decisions about proliferation and cellular identity in both normal and diseased cells.