The Proteolytic Cleavage of Polycystin-1: How and Why

描述（由申请人提供）：常染色体显性多囊肾病（ADPKD）是人类最常见的遗传性疾病之一，在美国影响千分之一的人。患者双肾出现多发囊肿。囊肿逐渐导致正常肾脏结构的破坏，并最终导致约50%的患者在60岁时出现终末期肾功能衰竭。目前还没有治愈这种疾病的方法。ADPKD主要由编码多胱氨酸-1 （PC1）蛋白的PKD1基因突变引起。因此，了解PC1的正常结构和功能对于开发有效的治疗方法至关重要。我们之前已经发现，在体内几乎所有细胞类型和组织中，PC1在g蛋白偶联受体蛋白水解位点（GPS）发生蛋白水解裂解。这种反应，即GPS解理，产生了许多以前未被识别的PC1产物。在部分ADPKD患者中发现了PC1的GPS切割缺陷。我们假设GPS裂解对于PC1在肾脏中的完整功能至关重要。我们最近使用一种新的小鼠模型证明，PC1的GPS切割对于肾脏远端肾元段的正常结构和功能是必不可少的，但对于近端肾元段和胚胎发育显然不是必需的。我们现在提出PC1的裂解产物对于肾脏远端肾元的结构完整性是至关重要的。这项资助旨在了解GPS切割调节PC1在肾脏中的重要功能的机制。我们建议在三个互补的特定目标的研究使用生化，生物物理，细胞生物学方法和动物模型的组合。Specific Aim 1将在体外MDCK模型系统中分析GPS裂解产生的PC1产物的结构和功能。这项研究可能会建立GPS功能的基本原理。特异性目标2然后着眼于PC1切割产物在原代细胞和最终在小鼠中的作用。具体目标3检查近段不需要GPS切割的原因。拟议的研究可能会对PC1在肾脏正常和疾病状态中的功能产生重要的见解。

DESCRIPTION (provided by applicant): Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common inherited disorders in humans, affecting one in a thousand people in the United States. Patients develop multiple cysts in both kidneys. The cysts progressively result in the destruction of the normal kidney structure and eventually lead to end-stage renal failure in approximately 50% of the patients by the age of 60. There are currently no cures for the disease. ADPKD is caused primarily by mutations of the PKD1 gene, which encodes polycystin-1 (PC1) protein. Therefore understanding of the normal structure and function of PC1 will be critical for the development of effective therapies. We have previously discovered that PC1 is proteolytically cleaved at the G-protein coupled receptor proteolytic site (GPS) in virtually all cell types and tissues in vivo. This reaction, the GPS cleavage, generates a number of previously unrecognized PC1 products. Defective GPS cleavage of PC1 has been found in a subset of ADPKD patients. We hypothesized that GPS cleavage is essential for the complete function of PC1 in the kidney. We have recently demonstrated using a novel mouse model that GPS cleavage of PC1 is essential for proper structure and function of the distal nephron segments in the kidney, but is apparently not required for that of the proximal segments and for embryonic development. We now propose that the cleavage products of PC1 are critically required for the structural integrity of distal segments of the nephron in the kidney. This grant aims at understanding the mechanism by which GPS cleavage regulates the important function of PC1 in the kidney. We propose the studies in three complementary Specific Aims using a combination of biochemical, biophysical, cell-biological methods and animal models. Specific Aim 1 will analyze structure and function of PC1 products generated by GPS cleavage in an in vitro MDCK model system. This study will likely establish basic principles of GPS functioning. Specific Aim 2 then looks at the role of the PC1 cleavage products in primary cells and finally in mice. Specific Aim 3 examines the reason why the proximal segments do not require GPS cleavage. The proposed studies will likely yield important insights into the function of PC1 in normal and disease states of the kidney. PUBLIC HEALTH RELEVANCE Polycystin-1 is the protein that when defective causes a complicated kidney disease known as autosomal dominant polycystic kidney disease, which at this point has no cure. This study aims to understand Polycystin-1, the reasons it becomes defective, and the ways to prevent it.