Misregulation of receptor tyrosine kinase signaling in PKD

描述（由申请人提供）：多囊肾病（PKD）是一种遗传性疾病，患病率高，无法治愈。PKD的特征在于患病个体的肾脏内有许多囊肿。在PKD中形成的囊肿可以大大扩大肾脏，同时取代正常的肾脏结构，导致肾功能降低并进展为终末期肾病，只能通过终身透析或肾移植治疗。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 [1]。因此，PKD代表了一个主要的公共卫生问题，并且占数亿美元（并且可能超过十亿美元）的医疗保健成本，特别是用于透析治疗和防止移植排斥的药物的成本，以及PKD个体的生产力降低和生活质量受损所涉及的成本。由于所有这些原因，发现直接影响PKD分子原因的治疗方法非常重要，并且可以防止进展为终末期肾病和透析或移植。 PKD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更常见，由PKD 1或PKD 2基因突变引起，分别编码多囊蛋白1或多囊蛋白2 [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研究的最新进展表明，以下可能导致囊肿形成的潜在机制：（1）肾小管上皮细胞增殖和/或凋亡增加;（2）向管腔内分泌液体增加;（3）上皮细胞与其基底膜相互作用异常（细胞-基质粘附）或彼此粘附（细胞-细胞粘附）;（4）上皮细胞极性改变;和（5）纤毛功能异常。 在我们以前的工作中，我们证明了31整合素的作用是细胞-细胞粘附，除了细胞-基质粘附。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，以响应其配体HGF的最大活化。在将这项工作扩展到PKD时，我们发现31整合素不能正确定位于质膜，并且c-Met在Pkd 1-/-细胞中过表达。这似乎是由于用HGF刺激后未能泛素化c-Met。泛素化c-Met的失败是由于高尔基体中的整合素对E3泛素连接酶c-Cbl的螯合。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.