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肪组成的极化质膜结构域对于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到这些蛋白质从细胞顶端和基底侧面内化的速度的调节。在这个过程开始的地方，货物重新聚集到笼状蛋白涂层坑的机制还知之甚少。磷脂酰肌醇4，5-二磷酸(PIP2)在内吞作用中起着多种作用，非极化细胞表面PIP2水平的调节可以不同地影响不同蛋白质的内化。这一建议的中心假设是，肾上皮细胞顶端和基底外侧的PIP2代谢是独立调节的，以选择性地调节这些区域的笼蛋白依赖的内吞作用。与这一观点一致的是，PI5-激酶的三种亚型(产生细胞表面PIP2的酶)在极化的肾上皮细胞中有不同的定位。我们建议的具体目的是确定PIP2的心尖池和基底侧池是否在肾上皮细胞中独立调节；研究激动剂刺激G蛋白偶联受体时PIP2水平的变化如何影响极化膜域的内吞作用；以及确定顶端定位的PI5-激酶mPI5KI1如何调节心尖细胞内吞作用。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，以及在正常信号转导和肾脏疾病中这一过程是如何影响的具有重要意义。与公共健康相关：肾脏细胞表面被分成不同的区域，面向尿液和血流，具有独特的蛋白质和脂肪成分。这种表面成分的不对称分布对于肾脏细胞从形成的尿液中适当地重新吸收水、离子和代谢物是必不可少的。这些过程由受体和离子转运体控制，这些受体和离子转运体的转运和清除受到多种细胞因子的调节。我们的目标是了解肾脏细胞如何不同地调节这些蛋白质从表面的去除，以及这些机制是如何在对特定生理信号的反应中被选择性地调节的。我们的研究结果将为在正常条件下和在生理应激条件下如何调节肾脏蛋白质的转运提供新的信息。

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.