AKT/mTOR Signaling and Regulation of Cell Cycle in beta Cells

描述(由申请人提供)：胰腺β细胞衰竭是糖尿病发展的关键决定因素。尽管β细胞团在糖尿病中很重要，但缺乏以β细胞如何进入细胞周期和增殖为中心的知识基础。AKT是被认为是诱导β细胞增殖和存活的潜在靶点的分子之一。初步研究表明，Akt通过激活细胞周期蛋白D/CDK4复合体来改变β细胞的增殖。这项建议的目的是描述将Akt与细胞周期蛋白D/CDK4复合体激活联系起来的分子遗传学机制。需要检验的假设是Akt信号通过翻译控制Cyclin D/CDK4复合体成分来诱导β细胞增殖。这将通过三种不同的策略来实现：Aim 1将确定Akt/TSC/mTOR介导的翻译控制在β细胞增殖中的作用。这些实验将在β细胞中mTOR信号增加和减少的动物模型中进行。使用这些小鼠的胰岛进行细胞周期蛋白D/CDK4复合体成分的体外鉴定、细胞周期分析和蛋白质评估，将得到胰岛素瘤细胞系的体外实验的补充。目的研究雷帕霉素敏感通路(TORC1)和不敏感通路(TORC2)在Akt/mTOR信号通路激活诱导的胰岛β细胞增殖中的作用。所使用的方法包括TORC1和2信号改变的胰岛和胰岛素瘤细胞中TORC 1和2复合体成分的表征、活性和增殖作用。目的3明确S6K依赖通路在Akt/mTOR/TORC1依赖信号诱导的β细胞增殖中的重要性。实验包括转基因和体外模型，在β细胞中S6K信号增加和减少。了解Akt的致癌潜力，这项应用中提出的研究具有重要意义，因为它将描绘潜在的下游事件和将增殖反应与致癌潜力分开的成分。预计这将对药物制剂的设计产生积极影响，这些药物将在不改变致癌转化风险的情况下选择性地诱导β细胞增殖。这些药物可以用于转化实验，通过在体内扩大β细胞团来治疗糖尿病，增加可移植的胰岛池，并提高胰岛移植的成功率。这些研究的另一个主要影响是更好地了解雷帕霉素对β细胞质量和功能的影响。

DESCRIPTION (provided by applicant): Pancreatic beta-cell failure is a critical determinant for the development of diabetes. In spite of the importance of beta-cell mass in diabetes, there is a lack in the knowledge base that centers on how beta-cells enter the cell cycle and proliferate. Akt is one of the promising molecules identified as a potential target to induce proliferation and survival of beta-cells. Preliminary studies show that Akt alters beta-cell proliferation by activation of the cyclin D/cdk4 complex. The objective of this proposal is to delineate the molecular genetic mechanisms that link Akt to activation of the cyclin D/cdk4 complex. The hypothesis to be tested is that Akt signaling induces beta-cell proliferation by translational control of cyclin D/cdk4 complex components. This will be accomplished via three distinct strategies: Aim 1 will determine the effects of Akt/TSC/mTOR-mediated translational control in beta-cell proliferation. These experiments will performed in animal models with increased and decreased mTOR signaling in beta-cells. In vitro characterization, cell cycle analysis and assessment of protein of cyclin D/cdk4 complex components using islets from these mice will be complemented by in vitro experiments in insulinoma cell lines. Aim 2 will establish the role of rapamycin sensitive (TORC1) and insensitive pathways (TORC2) in beta-cell proliferation induced by activation of Akt/mTOR signaling. The approach used includes characterization, activity and proliferative role of TORC 1 and 2 complexes components in islets and insulinoma cells with altered TORC1 and 2 signaling. Aim 3 will identify the importance of S6K-dependent pathway in beta-cell proliferation induced by Akt/mTOR/TORC1 -dependent signaling. Experiments include transgenic and in vitro models with increased and decreased S6K signaling in beta-cells. Knowing the oncogenic potential of Akt, the research proposed in this application is significant because it will delineate potential downstream events and components that separate proliferative responses from oncogenic potential. This is expected to have a positive impact for the design of pharmaceutical agents that will induce selectively beta-cell proliferation without altering the risk of oncogenic transformation. These agents could be used in translational experiments to treat diabetes by expanding beta-cell mass in vivo, increase the pool of transplantable islets and enhance the success of islet transplantation. Another major impact of these studies is obtaining a better understanding of the effects of rapamycin in beta-cells mass and function.