Misregulation of receptor tyrosine kinase signaling in PKD

描述（由申请人提供）：多囊肾病（PKD）是一种高患病率且无法治愈的遗传性疾病。PKD的特点是患者肾脏内有许多囊肿。PKD形成的囊肿在取代正常肾脏结构的同时，可使肾脏大大扩大，导致肾功能下降，发展为终末期肾病，只能通过终身透析或肾脏移植来治疗。PKD是最常见的遗传性疾病之一，发病率为1 / 800~1000。在美国，有60万人，全世界有1250万人患有PKD。因此，PKD是一个重大的公共卫生问题，在医疗保健费用中占数亿美元（可能超过10亿美元），特别是透析治疗和防止移植排斥的药物费用，以及PKD患者生产力下降和生活质量受损所涉及的费用。由于这些原因，发现直接影响PKD分子原因的治疗方法，防止进展为终末期肾脏疾病和透析或移植是非常重要的。PKD中囊肿形成的机制尚不清楚：PKD有常染色体显性（ADPKD）和常染色体隐性（ARPKD）两种形式。ADPKD更为常见，由编码多囊蛋白1或多囊蛋白2的PKD1或PKD2基因突变引起，分别为[2]。尽管在许多实验室进行了大量深入的研究，但囊肿形成的机制仍然不完全清楚。PKD研究的最新进展提示以下可能导致囊肿形成的机制：(1)肾上皮小管内细胞增殖和/或凋亡增加；(2)管状腔内液体分泌增强；(3)上皮细胞与其基底膜（细胞-基质粘连）或彼此（细胞-细胞粘连）相互作用异常；(4)上皮细胞极性改变；(5)纤毛功能异常。在我们之前的工作中，我们证明了31整合素在细胞-细胞粘附以及细胞-基质粘附中的作用。我们还证明了受体酪氨酸激酶c-Met需要与31整合素相互作用才能最大限度地激活其配体HGF。在将这项工作扩展到PKD中，我们发现31整合素不能正确定位到质膜上，c-Met在Pkd1-/-细胞中过表达。这似乎是由于HGF刺激后c-Met泛素化失败所致。c-Met的缺乏是由于E3泛素连接酶c-Cbl被31整合素在高尔基体中隔离。该基金将研究c-Cbl、c-Met和蛋白糖基化在PKD发病机制中的作用。

DESCRIPTION (provided by applicant): Polycystic kidney disease (PKD) is a hereditary disease with a high prevalence and without a cure. PKD is characterized by numerous cysts within the kidneys of afflicted individuals. The cysts formed in PKD can greatly enlarge the kidneys while replacing the normal kidney structures, resulting in reduced kidney function and progression to end-stage renal disease, that can only be treated by lifelong dialysis or kidney transplants. As a disease that affects 1 in 800~1000 individuals, PKD is among the most common genetic disorders. In the United States, there are 600,000 individuals, and worldwide 12.5 million, with PKD [1]. Thus, PKD represents a major public health issue, and accounts for hundreds of millions (and perhaps over a billion) of dollars in health care costs, particularly for dialysis treatments and the cost of drugs that prevent transplant rejections, as well as the cost involved of decreased productivity and impaired quality of life of individuals with PKD. For all these reasons, it is of great importance to discover treatments that directly affect the molecular causes of PKD, and that will prevent the progression to end-stage renal disease and dialysis or transplantation. The mechanism of cyst formation in PKD is unknown: There are both autosomal dominant (ADPKD) and autosomal recessive (ARPKD) forms of PKD. ADPKD is more common and is caused by mutations in either the PKD1 or PKD2 genes, that encode Polycystin1 or Polycystin2, respectively [2]. Despite an enormous amount of intensive study in many laboratories, the mechanism of cyst formation remains incompletely understood. Recent progress in PKD research suggests the following potential mechanisms that could lead to cyst formation: (1) increased cell proliferation and/or apoptosis within epithelial tubules of the kidney; (2) enhanced fluid secretion into tubular lumina; (3) abnormality in the interaction of epithelial cells with their underlying basement membrane (cell-matrix adhesion) or with each other (cell-cell adhesion); (4) alterations in epithelial cell polarity; and (5) abnormal ciliary function. In our previous work we demonstrated a role of 31 integrin is cell-cell adhesion, in addition to cell-matrix adhesion. We have also demonstrated that the receptor tyrosine kinase c-Met requires interaction with 31 integrin for maximal activation in response to its ligand, HGF. In extending this work to PKD, we have found that 31 integrin is not properly localized to the plasma membrane, and c-Met is over-expressed in Pkd1-/- cells. This appears to be due to a failure to ubiqutinate c-Met after stimulation with HGF. Failure to ubquitinate c-Met is due to sequestration of the E3 ubiquitin ligase c-Cbl by 31 integrin in the Golgi apparatus. This grant will investigate the roles of c-Cbl, c-Met and protein glycosylation in the pathogenesis of PKD.