Regulation of Akt signaling activation by polyubiquitination

描述(申请人提供)：AKT/PKB信号在许多生物学功能中发挥核心作用，如细胞增殖、凋亡、细胞代谢和蛋白质翻译。虽然众所周知Akt的激活受磷酸化的调节，但尚不清楚是否其他类型的翻译后修饰，如泛素化，也参与了Akt的激活。在这个方案中，我们已经确定TRAF6是一种潜在的Akt E3连接酶，它可以诱导Akt K63连接的多泛素化，并且对Akt的磷酸化和激活至关重要。我们的结果表明，Akt K63的多泛素化可能代表了一种新的机制，通过它调控致癌的Akt信号，该研究可能对癌症的治疗具有重要的临床意义。这项应用的目标是确定TRAF6和Akt K63连接的多泛素化在癌症进展和转移中的潜在作用，这是追求该目标的下一步。该应用的中心假设是TRAF6诱导的Akt K63连接的多泛素化协调Akt膜定位和随后的磷酸化。我们的中心假设是在我们强大的初步数据的基础上提出的。这项研究的理论基础是，一旦TRAF6和Akt多泛素化在癌症进展和转移中的重要作用得到确认和确立，就可以实现对人类癌症的更好治疗或靶点。我们计划检验我们的中心假说，并通过追求以下特定目标来实现这一应用的目标：目的1)确定Akt多泛素化调节Akt激活的分子机制。目的2)研究Akt泛素化和去泛素化的分子调控机制。目的3)探讨TRAF6在肿瘤发生和转移中的作用。这项提案工作具有创新性，因为它首次提供了TRAF6是Akt的E3连接酶，Akt K63连接的多泛素化协调Akt的磷酸化和激活。在受到尊重的结果下，这项提案中的工作组合有望共同揭示TRAF6和Akt K63相关的多泛素化在癌症发展和转移中的关键作用。这些结果将产生重要的积极影响，因为识别TRAF6和Akt K63连接的多泛素化在癌症进展和转移中的重要作用可能因此为癌症治疗提供潜在的治疗靶点。我们的结果也将从根本上促进我们目前对致癌Akt信号如何调控的理解，并可能具有重要的临床意义。 公共卫生相关性：虽然已经对PI3K/Akt信号在癌症中的作用进行了广泛的研究，但Akt膜的定位和磷酸化是如何调节的仍然很大程度上是未知的。我们的研究表明，Akt被进行了一种新的翻译后修饰，并且通过E3连接酶TRAF6与Akt K63连接的多泛素可能在Akt膜的定位、磷酸化和肿瘤发生中发挥重要作用。了解Akt激活的调控机制不仅有助于深入了解致癌Akt信号的调控机制，而且对人类癌症的治疗具有重要意义。

DESCRIPTION (provided by applicant): Akt/PKB signaling plays a central role in many biological functions, such as cell proliferation, apoptosis, cell metabolism, and protein translation. Although it is well known that Akt activation is regulated by phosphorylation, it is unclear whether other types of the posttranslational modifications, such as ubiquitination, are also involved in Akt activation. In this proposal, we have identified TRAF6 as a potential Akt E3 ligase that induces Akt K63-linked polyubiquitination and is critical for Akt phosphorylation and activation. Our results reveal that Akt K63 polyubiquitination may represent a novel mechanism by which oncogenic Akt signaling is regulated and that this study may have important clinical implications for the treatment of cancer. The objective of this application, which is the next step in pursuit of that goal, is to determine the potential role of TRAF6 and Akt K63-linked polyubiquitination in cancer progression and metastasis. The central hypothesis of the application is that Akt K63-linked polyubiquitination induced by TRAF6 orchestrates Akt membrane localization and subsequent phosphorylation. Our central hypothesis has been formulated on the basis of our strong preliminary data. The rationale of the proposed research is that, once the important role of TRAF6 and Akt polyubiquitination is confirmed and established in cancer progression and metastasis, the better treatment or target for human cancers can be achieved. We plan to test our central hypothesis and accomplish the objective of this application by pursuing the following specific aims: Aim 1) To determine the molecular mechanism by which Akt polyubiquitination regulates Akt activation. Aim 2) To determine the molecular mechanism by which Akt ubiquitination and deubiquitination are regulated. Aim 3) To determine in vivo role of TRAF6 in tumorigenesis and metastasis. This proposal work is innovative, because it provides for the first time that TRAF6 is an E3 ligase for Akt and Akt K63-linked polyubiquitination orchestrate Akt phosphorylation and activation. With respected outcomes, the combination of work in this proposal is collectively expected to uncover the critical role of TRAF6 and Akt K63-linked polyubiquitination in cancer development and metastasis. Such results will have an important positive impact, because identification of the important role of TRAF6 and Akt K63-linked polyubiquitination in cancer progression and metastasis may therefore provide potentially therapeutic targets for cancer treatment. Our results will also fundamentally advance our current understandings of how oncogenic Akt signaling is regulated and may have important clinical implications. PUBLIC HEALTH RELEVANCE: Although the extensive studies have been made for the role of PI3K/Akt signaling in cancers, how Akt membrane localization and phosphorylation is regulated remains largely unknown. Our study reveals that a novel posttranslational modification is operated on Akt and that Akt K63-linked polyubiquitnation by E3 ligase TRAF6 may play important roles in Akt membrane localization, phosphorylation, and tumorigenesis. Understanding the mechanism by which Akt activation is regulated may not only provide a great insight into how the oncogenic Akt signaling is regulated, but also offer the important therapeutic implications for human cancers.