Regulation of Polarized Traffic by PI-Metabolizing Enz

描述（由申请人提供）：维持具有不同蛋白质和脂质组成的极化质膜结构域对有效的肾细胞功能至关重要。受体和离子转运体在这些细胞中的分布在一定程度上受这些蛋白质从细胞顶端和底外侧表面内化的速度的调节。该机制的货物招募到网格蛋白涂层坑，这一过程是启动的了解甚少。磷脂酰肌醇4,5-二磷酸（PIP2）在内吞位点的局部合成在内吞作用中发挥多种作用，非极化细胞中表面PIP2水平的调节可以不同地影响不同蛋白质的内化。该建议的中心假设是，肾上皮细胞的顶端和基底外侧PIP2代谢是独立调节的，以选择性地调节这些结构域的网格蛋白依赖性内吞作用。与这一观点一致的是，pi5激酶（产生细胞表面PIP2的酶）的三种同工异构体在极化的肾上皮细胞中存在差异定位。我们建议的具体目的是确定肾上皮细胞中PIP2的顶端和基底侧池是否独立调节；研究激动剂刺激G蛋白偶联受体后PIP2水平的变化如何影响极化膜结构域的内吞作用；以及确定顶端定位的pi5激酶mPI5KI1如何调节顶端内吞作用。我们的研究结果对我们理解极化细胞如何划分PI合成和分解代谢，以及这一过程在正常信号传导和肾脏疾病中如何受到影响具有重要意义。公共卫生相关性：肾细胞表面分离成不同的区域，具有独特的蛋白质和脂质组成，面向尿液和血液。这种表面成分的不对称分布对肾细胞正确地从形成的尿液中重新吸收水、离子和代谢物至关重要。这些过程是由受体和离子转运体控制的，这些受体和离子转运体到达和离开细胞表面是由许多细胞因子调节的。我们的目标是了解肾细胞如何以不同的方式调节这些蛋白质从表面的去除，以及这些机制如何在对特定生理信号的反应中被选择性地调节。我们的研究结果将为在正常条件下和生理应激条件下如何调节肾脏蛋白质的贩运提供新的信息。

DESCRIPTION (provided by applicant): The maintenance of polarized plasma membrane domains with distinct protein and lipid compositions is critical for efficient renal cell function. The distribution of receptors and ion transporters in these cells is regulated in part by the rate at which these proteins are internalized from the apical and basolateral cell surfaces. The mechanisms that underlie cargo recruitment to clathrin coated pits where this process is initiated are poorly understood. Localized synthesis of phosphatidylinositol 4,5-bisphosphate (PIP2) at endocytic sites plays multiple roles in endocytosis, and modulation of surface PIP2 levels in nonpolarized cells can differentially affect the internalization of distinct proteins. The central hypothesis of this proposal is that apical and basolateral PIP2 metabolism in renal epithelial cells is independently regulated to selectively modulate clathrin-dependent endocytosis from these domains. Consistent with this idea, that the three isoforms of PI5-kinase (the enzymes that generate cell surface PIP2) are differentially localized in polarized renal epithelial cells. The specific aims of our proposal are to determine whether apical and basolateral pools of PIP2 are independently modulated in renal epithelial cells; to examine how changes in PIP2 levels upon agonist stimulation of G protein coupled receptors affect endocytosis from polarized membrane domains; and to determine how the apically localized PI5-kinase mPI5KI1 regulates apical endocytosis. The results of our studies have important implications for our understanding of how polarized cells compartmentalize PI synthesis and catabolism and for how this process is affected during normal signaling and in renal disease. PUBLIC HEALTH RELEVANCE: The surface of kidney cells is segregated into distinct domains with unique protein and lipid compositions that face the urine and the bloodstream. This asymmetric distribution of surface components is essential for kidney cells to properly reabsorb water, ions, and metabolites from the forming urine. These processes are controlled by receptors and ion transporters whose delivery to and removal from the cell surface is regulated by numerous cellular factors. Our goal is to understand how kidney cells differentially regulate the removal of these proteins from the surface, and how these mechanisms are selectively adjusted during the response to specific physiological signals. The results of our research will provide new information about how the trafficking of kidney proteins is regulated under normal conditions and under conditions of physiological stress.