YEAST HETEROTRIMERIC G PROTEIN AND CELL POLARITY

描述（由申请人提供）：几乎所有细胞的基本特性都是对周围环境的提示作出反应的能力。有关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，如朝着局部刺激生长或运动，这意味着检测刺激的信号转导分子与控制细胞形状、极性和运动的信号转导分子之间存在通信。本研究采用分子遗传学和细胞生物学的方法，以酵母的交配反应为模型系统，研究外部刺激对信号传导和细胞极性的控制。在这个系统中，细胞内信号通过从酵母到人类保守的蛋白质模块发生，如异源三聚体G蛋白、MAP激酶级联、pak家族激酶和rho家族gtpase。本项目的长期目标是提供酵母异三聚体G蛋白β - γ二聚体（gβ - γ）启动的信号转导和极化事件的分子描述。其中一个目标是了解gβ - γ诱导细胞极化的能力是如何受到其相关受体和α α亚基的空间调节的，重点是最近的观察表明，不同的α α - β界面在这种空间控制中具有不同的定性作用。gβ - γ与其他蛋白合作控制MAP激酶级联“支架”蛋白向细胞外周募集的机制也在研究之中。另一个目标将是研究支架蛋白对信号传递的影响，即支架如何帮助形成MAP激酶途径的剂量反应行为。通过探索SH3结构域蛋白Bem1在Ste20信号传导和定位中的作用，以及通过研究Ste20中赋予在交配途径中起作用的能力的决定因素，gβ - γ触发酵母PAK Ste20激活交配MAP激酶级联反应的方法将得到进一步的研究。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剂的信号转导和细胞骨架组织的理解，并与正常和病变细胞的增殖和细胞身份的细胞决定相关。

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.