POLARITY ESTABLISHMENT IN YEAST

CDC42p在细胞对多种信号的极化中起着关键作用(例如，T细胞对抗原提呈细胞的极化，成纤维细胞对伤口部位的极化，或酵母芽的形成)。人的CDC42可以在功能上替代酵母，这表明CDC42P的关键功能已经被高度保守，并且应用遗传、生化和细胞生物学方法的能力使酵母成为描述CDC42P在细胞极化中作用机制的非常强大的系统。在这个系统中，细胞周期信号由细胞周期蛋白依赖的蛋白CDC28P提供，触发CDC42P的极化，进而促进肌动蛋白细胞骨架的极化，组装一环的间隔素丝，并将分泌靶向指定的斑块。这项拟议的研究的目标是了解CDC28P如何促进CDC42P极化，以及CDC42P如何促进下游事件。癌细胞表现出细胞形状、细胞间黏附和细胞运动的变化(所有依赖于肌动蛋白的过程都由CDC42P调节)，这些变化可能对恶性转化的许多方面起着重要作用。哺乳动物细胞中CDC42P的解除调控促进了锚定非依赖性生长，并且对于RAS转化的细胞中发生的形态变化(以及锚定独立性)是必要的。因此，CDC42p的去调控影响癌细胞的增殖和转移潜能。了解CDC42P的正常调控和功能是解决它们的错误调控可能如何促进癌症的重要的第一步。

Cdc42p plays a key role in the polarization of cells towards a variety of signals (e.g., T cell polarization towards antigen-presenting cells, fibroblast polarization towards wound sites, or yeast bud formation). Human CDC42 can functionally substitute for its yeast counterpart, suggesting that key functions of Cdc42p have been highly conserved, and the ability to apply genetic, biochemical, and cell biological approaches makes yeast a very powerful system for delineating the mechanism of Cdc42p action in cell polarization. In this system, a cell-cycle signal provided by the cyclin-dependent kinase Cdc28p triggers the polarization of Cdc42p, which in turn promotes the polarization of the actin cytoskeleton, the assembly of a ring of septin filaments, and the targeting of secretion towards the designated patch. The goal of the proposed research is to understand how Cdc28p promotes Cdc42p polarization, and how Cdc42p promotes downstream events. Cancer cells display alterations of cell shape, cell-cell adhesion, and cell motility (all actin-dependent processes regulated by Cdc42p), which are likely to be important for numerous aspects of malignant transformation. Deregulation of Cdc42p in mammalian cells promotes anchorage-independent growth, and is necessary for the morphological changes (as well as anchorage independence) that occur in Ras-transformed cells. Thus, Cdc42p deregulation affects the proliferation as well as the metastatic potential of cancer cells. Understanding the normal regulation and function of Cdc42p is an important first step towards addressing how their misregulation might promote cancer.