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能够对周围环境的信号做出反应。通过使用信号转导途径，有关细胞外刺激存在的信息被转化为细胞内行为。此外，许多细胞表现出定向反应，例如向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。这项工作使用酿酒酵母的交配反应作为模型系统，利用分子遗传学和细胞生物学方法来研究外部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。一个目标是了解 Gbeta-gamma 诱导细胞极化的能力如何受到其相关受体和 Galpha 亚基的空间调节，重点是最近的观察结果表明不同的 Galpha-Gbeta 界面在这种空间控制中具有不同的作用。此外，Gbeta-gamma 与其他蛋白质合作控制 MAP 激酶级联“支架”蛋白向细胞外周募集的机制也在研究中。另一个目标是检查支架蛋白对信号传输的影响，即支架如何帮助塑造 MAP 激酶途径的剂量反应行为。 Gbeta-gamma 触发酵母 PAK Ste20 激活交配 MAP 激酶级联的方法将通过探索 SH3 结构域蛋白 Bem1 在 Ste20 信号传导和定位中的作用以及研究 Ste20 内赋予在交配途径中作用的能力的决定因素来探究。这些研究将影响我们对信号转导和细胞骨架组织响应生长因子、激素、神经递质和化学引诱剂的理解，并与正常细胞和患病细胞的增殖和细胞身份的细胞决策相关。

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.