Nedd4类E3泛素连接酶在肿瘤发生发展中的作用机制的研究

泛素化调控的蛋白质降解的失调会导致包括癌症在内的许多重大疾病。目前已知Nedd4类E3泛素连接酶的异常与多种癌症的发生有着密切的关系，然而其分子机制还很不清楚。在前期工作中，我们鉴定出一个Nedd4-1新的结合蛋白，并通过蛋白水平影响、体内体外的结合以及泛素化的研究证明该蛋白是一个Nedd4-1新的底物蛋白分子。由于该蛋白分子是一个癌基因分子，提示我们Nedd4-1可能具有抑制肿瘤发生的作用。通过基因敲低Nedd4-1，我们的确在细胞水平上验证了Nedd4-1对癌细胞成团的抑制作用。在此基础上，我们将深入探讨Nedd4-1抑制肿瘤发生的用机理，并在小鼠模型和临床样本中进一步验证我们的结果，同时考察Nedd4类E3泛素连接酶其它家族成员对于肿瘤发生发展的影响及其分子机制，为阐明这些E3泛素连接酶调控肿瘤发生发展的作用机制并以其作为靶点进行癌症的早期诊断和治疗提供重要的理论基础和实验依据。

Defects in the ubiquitin-dependent protein degradation have been shown to be involved in pathogenesis of many human diseases including cancer. It is already known that the Nedd4-like E3 ubiquitin ligases are closely related to many different kinds of tumorigenesis, however, the molecular mechanism underlying still remains obscure. In our previous study we identified a novel binding protein of Nedd4-1, and verified that this protein is a new substrate of Nedd4-1 through protein degradation assay, in vivo and in vitro binding assay and ubiquitination assay. Since this new substrate of Nedd4-1 is an already known oncogene product, it suggested us that Nedd4-1 might function as a tumor suppressor in certain cancers. Indeed, knocking-down of endogenous Nedd4-1 by shRNA significantly increased the number and size of colonies formed in soft-agar experiments, confirmed the ability of Nedd4-1 in suppressing cell transformation. Therefore, we will further examine the relationship between the levels of Nedd4-1 and tumorigenesis using mouse model and clinical samples to validate the role of Nedd4-1 in tumor suppression. We will also explore the other family members of Nedd4-like E3 ubiquitin ligases in tumorigenesis and elucidate underlying mechanism. Our study will certainly provide important information for early diagnosis and therapeutic treatment of related cancers using these E3 ubiquitin ligases as target proteins.