Role of Ion Channels in Kidney Diseases

描述（由申请人提供）：该项目的长期目标是确定肾脏中离子通道的调节，并将我们的发现与肾脏疾病相结合。本研究将确定atp结合盒转运蛋白A1 （ABCA1）如何调节肾上皮钠通道（ENaC）。本文提出的体内和体外实验将验证一个中心假设，即ABCA1缺失使皮质集管（CCD）主细胞中的Cho升高，这种升高的Cho稳定了顶端微绒毛中的磷脂酰肌醇-4,5-二磷酸（PIP2），这种位于微绒毛中的PIP2增加ENaC活性，从而增强钠潴留并导致高血压。该假设是基于先前的研究和两个关键的初步数据，表明ABCA1 KO小鼠血压和ENaC活性升高，抑制Cho合成导致PIP2扩散出微绒毛并降低ENaC活性。该建议具有临床意义，因为研究abca1控制的膜和细胞内Cho稳态可能为使用Cho生物合成抑制剂（如他汀类药物）治疗高血压提供理论依据。这个项目是创新的，因为它

DESCRIPTION (provided by applicant): The long term goals of this project are to determine the regulation of ion channels in the kidney and to integrate our findings to kidney diseases. This proposal will determine how the renal epithelial sodium channel (ENaC) is regulated by ATP-binding cassette transporter A1 (ABCA1). The proposed in vivo and in vitro experiments will test a central hypothesis that deletion of ABCA1 elevates Cho in cortical collecting duct (CCD) principal cells, this elevated Cho stabilizes phosphatidylinositol-4,5-bisphosphate (PIP2) in apical microvilli, and this microvilli- located PIP2 increases ENaC activity to enhance sodium retention and cause hypertension. The hypothesis is based on previous studies and two key preliminary data showing that both blood pressure and ENaC activity are elevated in ABCA1 KO mice and that inhibition of Cho synthesis causes PIP2 diffusion out of microvilli and reduces ENaC activity. The proposal is clinically significant, because investigation of ABCA1-controlled membrane and intracellular Cho homeostasis may provide a rationale for using Cho biosynthesis inhibitors such as statins to treat hypertension. The project is innovative because it will provide the first evidence for the role of ABCA1 in regulating ENaC activity and PIP2 lateral movement between two specialized apical membrane domains (microvilli and planar regions). A variety of experimental approaches including scanning ion conductance microscopy and the high resolution scanning patch-clamp techniques will be used to test three hypotheses (1) that deletion of ABCA1 increases ENaC activity and Na+ absorption thereby causing hypertension; (2) that Cho increases ENaC activity by stabilizing PIP2 in microvilli; and (3) that PIP2 in planar regions promotes formation of endocytic pits containing inactive ENaC.