Lipid Signaling in Chemotaxis

描述（由申请人提供）：趋化性是细胞向更高浓度的趋化剂迁移的过程，对各种生理事件如轴突引导、伤口愈合和组织形态发生都很重要。不适当的趋化性导致许多人类疾病，包括肿瘤转移、哮喘、关节炎和动脉粥样硬化。我们的长期研究目标是揭示趋化性的分子机制，了解趋化性相关人类疾病的发病机制。利用盘状盘基骨菌作为实验模型系统，我们证明了磷脂酰肌醇3,4,5三磷酸（PIP3）在趋化性的细胞内信号传导中起关键作用。PIP3在细胞边缘高度富集，并激活下游信号事件，如肌动蛋白细胞骨架的重塑。我们已经证明，PIP3的细胞内水平和定位是由脂质磷酸酶PTEN调节的。PTEN位于趋化细胞的后端，限制了PIP3在前端的产生。PIP3的局部积累刺激肌动蛋白聚合，使假足向化学引诱剂的源头延伸。迄今为止，PTEN的定位和活性是如何被调节的，以及PIP3信号是如何被翻译成肌动蛋白细胞骨架的重组的尚不清楚。在本研究计划中，我们将结合遗传学、生物化学、细胞生物学和蛋白质组学来实现以下具体目标：1)确定磷酸化如何调节PTEN的定位和活性；2)确定趋化所需的两种蛋白的功能——亨廷顿蛋白和GxcT，一种新的Rho GTPases的鸟嘌呤核苷酸交换因子；3)利用蛋白质组学方法以及含ph结构域蛋白的全基因组特征鉴定连接PIP3信号和肌动蛋白细胞骨架的新成分。我们的研究结果有望为趋化性的分子机制提供新的见解，并可能导致基于趋化性的癌症和炎症治疗的发展。

DESCRIPTION (provided by applicant): Chemotaxis, a process in which cells migrate toward higher concentrations of chemoattractants, is important for a variety of physiological events such as axon guidance, wound healing, and tissue morphogenesis. Inappropriate chemotaxis leads to many human diseases including tumor metastasis, asthma, arthritis and atherosclerosis. The long-term goal of our research is to reveal the molecular mechanism of chemotaxis and to understand the pathogenesis of chemotaxis- related human diseases. Using Dictyostelium discoideum as our experimental model system, we have demonstrated that phosphatidylinositol 3,4,5 triphosphate (PIP3) plays a critical role for intracellular signaling in chemotaxis. PIP3 is highly enriched at the leading edge of cells and activates downstream signaling events such as remodeling of the actin cytoskeleton. We have demonstrated that the intracellular level and localization of PIP3 are regulated by a lipid phosphatase, PTEN. PTEN is located at the rear end of chemotaxing cells and restricts the production of PIP3 at the leading edge. The local accumulation of PIP3 stimulates actin polymerization to extend pseudopods toward the source of chemoattractant. To date, it is unknown how the localization and activity of PTEN are regulated, and how PIP3 signaling is translated into reorganization of the actin cytoskeleton. In this research proposal, we will use a combination of genetics, biochemistry, cell biology and proteomics to achieve the following specific aims: 1) To determine how phosphorylation regulates the localization and activity of PTEN; 2) To define the functions of two proteins required for chemotaxis - Huntingtin and GxcT, a novel guanine nucleotide exchange factor for Rho GTPases; 3) To identify novel components that link PIP3 signaling and the actin cytoskeleton using proteomic approaches as well as genome-wide characterization of PH-domain containing proteins. The outcomes of our research are expected to provide novel insights into molecular mechanisms of chemotaxis and may lead to development of chemotaxis-based treatments for cancer and inflammation. PUBLIC HEALTH RELEVANCE: We study chemotaxis, a process in which cells sense extracellular chemical compounds and move toward the source of chemicals. Chemotaxis is highly relevant to development and maintenance of healthy human body as well as the pathogenesis of many diseases such as cancer, asthma, arthritis and atherosclerosis. The long-term goal of our study is to understand how chemotaxis works and how defects in chemotaxis cause human diseases using a variety of approaches including genetics, biochemistry, cell biology and proteomics.