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，对于多种生理事件（如轴突引导、伤口愈合和组织形态发生）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，了解与趋化性相关的人类疾病的发病机制。利用盘基网柄藻作为实验模型系统，我们已经证明了磷脂酰肌醇3，4，5三磷酸（PIP 3）在趋化性的细胞内信号转导中起着关键作用。PIP 3在细胞的前沿高度富集，并激活下游信号传导事件，如肌动蛋白细胞骨架的重塑。我们已经证明，PIP 3的细胞内水平和定位由脂质磷酸酶，PTEN调节。PTEN位于趋化细胞的后端，并在前沿限制PIP 3的产生。PIP 3的局部积累刺激肌动蛋白聚合以将伪足向化学引诱物的来源延伸。迄今为止，尚不清楚PTEN的定位和活性是如何调节的，以及PIP 3信号传导如何转化为肌动蛋白细胞骨架的重组。本研究将综合运用遗传学、生物化学、细胞生物学和蛋白质组学的方法，以实现以下具体目标：1）确定磷酸化如何调节PTEN的定位和活性; 2）确定趋化性所需的两种蛋白- Huntingtin和GxcT的功能，GxcT是Rho GTPases的一种新的鸟嘌呤核苷酸交换因子; 3）使用蛋白质组学方法以及含PH结构域蛋白质的全基因组表征来鉴定连接PIP 3信号传导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。 公共卫生相关性：我们研究趋化性，这是细胞感知细胞外化学化合物并向化学物质来源移动的过程。趋化性与人体健康的发育和维持密切相关，也是癌症、哮喘、关节炎、动脉粥样硬化等多种疾病的发病机制。我们研究的长期目标是了解趋化性是如何工作的，以及趋化性的缺陷如何使用各种方法导致人类疾病，包括遗传学，生物化学，细胞生物学和蛋白质组学。

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.