Regulation of Polarized Traffic by PI-Metabolizing Enzymes

描述(由申请人提供)：局部产生不同的磷脂酰肌醇(PI)类脂物种与许多膜转运事件的调节和细胞骨架动力学的控制有关。PI代谢酶对不可互换的PI池的分区合成对于细胞独立控制这些依赖于PI的多个功能的能力至关重要。我们对磷脂酰肌醇激酶和肌醇多磷酸磷酸酶在肾上皮细胞极化膜运输中的作用感兴趣，并发现顶端和基底外侧的生物合成途径对PI代谢酶PI-4激酶β和PI-5激酶α的过度表达具有不同的敏感性。此外，观察到Lowe综合征(一种严重的肾脏表现的疾病)是由高尔基体化的PI分解代谢酶的分子缺陷引起的，这表明肌醇多聚磷酸5-磷酸酶的活性在生物合成运输中发挥了作用。在这个提议中，我们将把表达单个PI代谢酶对转运的影响与跨高尔基复合体的PI脂组成的实际变化相关联，并检验假设以解释不同的PI物种调节膜运输的机制。这些实验将显著提高我们对局部PI合成如何在分子水平上调节正常和疾病状态下的极化生物合成交通的理解。

DESCRIPTION (provided by applicant): The local generation of distinct phosphatidylinositol (PI) lipid species has been implicated in the regulation of numerous membrane trafficking events and in the control of cytoskeletal dynamics. The compartmentalized synthesis of noninterchangeable pools of PIs by PI-metabolizing enzymes is critical to the cell's ability to control these multiple PI-dependent functions independently. We are interested in the role of phosphatidylinositol kinases and inositol polyphosphate phosphatases in polarized membrane traffic in renal epithelial cells, and have found that apical and basolateral biosynthetic pathways are differentially sensitive to overexpression of the PI metabolizing enzymes PI-4 kinase beta and PI-5 kinase alpha. Moreover, the observation that Lowe Syndrome (a disease with severe renal manifestations) is caused by molecular defects in a Golgi-tocalized PI-catabolizing enzyme suggests a role for inositol polyphosphate 5-phosphatase activity in biosynthetic transport. In this proposal, we will correlate the effects of expressing individual PI-metabolizing enzymes on transport with actual changes in PI lipid composition across the Golgi complex and test hypotheses to explain the mechanisms by which distinct PI species regulate membrane traffic. These experiments will significantly enhance our understanding of how localized PI synthesis operates at a molecular level to regulate polarized biosynthetic traffic in normal and disease states.