THE ROLE OF NEDD4-1 IN IGF-1R SIGNALING

描述(申请人提供)：NEDD4-1是一种E3泛素化连接酶，在人类癌症中经常过度表达。NEDD4-1在肿瘤发生中起重要作用。尽管已有研究表明NEDD4-1通过促进Akt的激活而发挥致癌蛋白的作用，但NEDD4-1激活Akt的分子机制仍不清楚。我们发现NEDD4-1通过调节IGF-1R信号激活Akt。值得注意的是，我们还发现NEDD4-1对Akt的激活受到复制蛋白A(RPA)的负调控，复制蛋白A是一种单链DNA(SsDNA)结合蛋白，通常被认为在DNA代谢中发挥关键作用。因此，我们建议进行一项研究来检验中心假设，即NEDD4-1通过激活IGF-1R信号而在细胞增殖中发挥作用，并且这一途径被RPA抑制。因此，IGF-1R通过IGF-1R抗体和/或RPA特异性地抑制过表达NEDD4-1的细胞的生长。为了检验我们的假设，本文提出了三个相互关联的具体目标。目的1研究NEDD4-1通过调节IGF-1R信号通路在细胞增殖中的作用。AIM 2将描述RPA如何调节NEDD4-1依赖的IGF-1R信号。目的3确定在过表达NEDD4-1的细胞中阻断IGF-1R信号转导的抗肿瘤活性。我们期望(1)确定NEDD4-1通过调节IGF-1R信号促进细胞增殖的分子机制；(2)确定RPA通过与NEDD4-1相互作用抑制IGF-1R信号的新功能；(3)发现通过RPA和/或IGF-1R抗体抑制过表达NEDD4-1的癌细胞的生长可以被IGF-1R特异性靶向。预期的结果将从根本上促进我们对NEDD4-1相关癌症发生的分子机制的理解。此外，发现RPA在抑制IGF-1R信号转导中的新功能将有助于开发针对NEDD4-1或IGF-1R的新药。此外，预期结果将通过识别NEDD4-1过表达的癌症患者来更好地预测肿瘤对IGR-1R抑制的反应，从而改进对癌症治疗计划的指导。

DESCRIPTION (provided by applicant): NEDD4-1 is an E3 ubiquitination ligase that is frequently over-expressed in human cancers. NEDD4-1 plays an important role in tumorigenesis. Although it has been suggested that NEDD4-1 functions as an oncogenic protein by facilitation of Akt activation, the molecular mechanisms by which NEDD4-1 activates Akt remain largely unknown. We found that NEDD4-1 activates Akt via regulation of IGF-1R signaling. Strikingly, we also found that activation of Akt by NEDD4-1 is negatively regulated by replication protein A (RPA), a single strand DNA (ssDNA) binding protein which is generally believed to play a critical role in DNA metabolism. Thus, we are proposing a study to test the central hypothesis that NEDD4-1 plays a role in cell proliferation via activation of IGF-1R signaling and this pathway is inhibited by RPA. Therefore, growth of cells overexpressing NEDD4-1 is specifically suppressed by IGF-1R inhibition through IGF-1R antibody and/or RPA. Three interrelated specific aims are proposed to test our hypothesis. Aim 1 will identify the role of NEDD4-1 in cell proliferation via regulation of IGF-1R signaling. Aim 2 will delineate how NEDD4-1 dependent IGF-1R signaling is regulated by RPA. Aim 3 will determine the antitumor activity of blocking IGF-1R signaling in cells over-expressing NEDD4-1. We anticipate to (1) define the molecular mechanisms by which NEDD4-1 promotes cell proliferation via regulation of IGF-1R signaling; (2) identify a novel function of RPA in suppression of IGF-1R signaling via interaction with NEDD4-1; (3) find that the growth of cancer cells over-expressing NEDD4-1 can be specifically targeted by IGF-1R inhibition through RPA and/or IGF-1R antibody. The expected results will fundamentally advance our understanding of the molecular mechanism underlying NEDD4-1 associated cancer development. In addition, identification of a novel function of RPA in suppression of IGF-1R signaling will facilitate the development of novel drugs targeting NEDD4-1 or IGF-1R. Moreover, the expected result will improve guidance for cancer treatment plans based on better predictions of tumor response to IGR-1R inhibition by identification of cancer patients with NEDD4-1 over-expression.