Misregulation of receptor tyrosine kinase signaling in PKD

描述(申请人提供)：多囊肾病(PKD)是一种遗传性疾病，发病率高，无法治愈。PKD的特点是患者的肾脏内有大量的囊肿。在PKD中形成的囊变可使肾脏大大增大，同时取代正常的肾脏结构，导致肾功能下降，进展为终末期肾病，只能通过终生透析或肾移植来治疗。作为一种每800~1000人中就有1人患病的疾病，PKD是最常见的遗传病之一。在美国，有60万人患有PKD，全世界有1250万人[1]。因此，PKD是一个重大的公共卫生问题，占卫生保健费用的数亿美元(也许超过10亿美元)，特别是用于透析治疗的费用和防止移植排斥反应的药物费用，以及涉及生产力下降和PKD患者生活质量受损的费用。由于所有这些原因，寻找直接影响PKD分子病因的治疗方法是非常重要的，这将防止进展到终末期肾脏疾病和透析或移植。PKD的囊性形成机制尚不清楚，有常染色体显性遗传(ADPKD)和常染色体隐性遗传(ARPKD)两种类型。ADPKD更为常见，由分别编码Polycystin1或Polycystin2的PKD1或PKD2基因突变引起[2]。尽管许多实验室进行了大量的密集研究，但对包囊形成的机制仍不完全清楚。PKD研究的最新进展提示：(1)肾小管上皮细胞增殖和/或凋亡增加；(2)肾小管腔内液体分泌增加；(3)上皮细胞与基底膜的相互作用异常(细胞-基质黏附)或相互作用(细胞-细胞黏附)；(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整合素的作用除了细胞与基质的黏附外，还包括细胞与细胞间的黏附。我们还证明了受体酪氨酸激酶c-Met需要与31整合素相互作用才能最大限度地激活其配体HGF。在将这项工作扩展到PKD的过程中，我们发现31整合素没有正确地定位在质膜上，c-Met在PKD-/-细胞中过表达。这似乎是由于HGF刺激后未能泛化c-Met所致。C-Met未能被取代是由于E3泛素连接酶c-Cbl被31整合素封闭在高尔基体中。这项资助将研究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.