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细胞群在糖尿病中的重要性，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是被鉴定为诱导β细胞增殖和存活的潜在靶标的有前途的分子之一。初步研究表明，Akt通过激活细胞周期蛋白D/cdk 4复合物来改变β细胞增殖。本研究的目的是阐明Akt与细胞周期蛋白D/cdk 4复合物激活之间的分子遗传学机制。待检验的假设是Akt信号传导通过细胞周期蛋白D/cdk 4复合物组分的翻译控制诱导β细胞增殖。这将通过三种不同的策略来实现：目标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信号传导增加和减少的动物模型中进行。使用来自这些小鼠的胰岛的细胞周期蛋白D/cdk 4复合物组分的体外表征、细胞周期分析和蛋白质评估将通过胰岛素瘤细胞系的体外实验来补充。目的2建立雷帕霉素敏感通路（TORC 1）和不敏感通路（TORC 2）在Akt/mTOR信号通路激活诱导的β细胞增殖中的作用。所使用的方法包括TORC 1和2复合物组分在具有改变的TORC 1和2信号传导的胰岛和胰岛素瘤细胞中的表征、活性和增殖作用。目的3：探讨S6 K依赖性信号通路在Akt/mTOR/TORC 1依赖性信号通路诱导β细胞增殖中的作用。实验包括β细胞中S6 K信号传导增加和减少的转基因和体外模型。已知Akt的致癌潜力，本申请中提出的研究是重要的，因为它将描绘将增殖反应与致癌潜力分开的潜在下游事件和组分。预期这将对设计选择性诱导β细胞增殖而不改变致癌转化风险的药剂产生积极影响。这些试剂可用于转化实验，通过在体内扩增β细胞群来治疗糖尿病，增加可移植胰岛的库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.