ROLE OF PHAS-I/TOR PATHWAY AND MITOGENIC SIGNALING

I/TOR 通路和有丝分裂信号传导的作用

• 批准号: 6523770
• 负责人: MICHAEL L. MCDANIEL
• 金额: $ 21.87万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-09-30 至 2004-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6523770
• 关键词: aminoacid metabolism; animal genetic material tag; autocrine; cell growth regulation; cyclins; enzyme activity; fibroblast growth factor; gene induction /repression; genetically modified animals; growth factor receptors; hormone regulation /control mechanism; insulin; laboratory mouse; laboratory rat; pancreatic islets; phosphatidylinositol 3 kinase; protein structure function; translation factor

DESCRIPTION (taken from the application) The focus of this proposal is to assess the role(s) of the PHAS-I/mTOR signaling pathway in growth factor and nutrient-mediated Beta-cell growth. An increase in translation of mRNA into protein is required for the mitogenic response of cells. PHAS-I, a recently identified binding protein of the initiation factor, eIF-4E, exerts a key role in this process. Phosphorylation of PHAS-I results in dissociation of the PHAS-I.eIF-4E complex, allowing eIF-4 to interact with other factors and initiate translation, cell cycle progression and proliferation. Recent studies with rapamycin, an immunosuppressant and anti-proliferative agent, have implicated the mammalian target of rapamycin (mTOR) as an upstream regulator of PHAS-I phosphorylation. Our findings indicate that in the Beta-cell, glucose mediates the phosphorylation of PHAS-I by stimulating insulin secretion which interacts in an autocrine manner with its own insulin receptor. Furthermore, rapamycin inhibits both glucose stimulated protein synthesis by islets and serum-induced cell proliferation by the Beta-cell line, RINm5F, suggesting a role for the PHAS-I/mTOR pathway in Beta-cell growth. The objective of specific aim 1 of this proposal is to determine if insulin and other growth factors utilize the same PHAS-I/mTOR signaling pathway to up-regulate protein translation, cell cycle progression and Beta-cell proliferation. Our recent studies with pancreatic islets and Beta-cell lines have indicated that amino acids are absolutely required for insulin and growth factors to activate the PHAS- I/mTOR pathway. Furthermore, amino acids alone dose-dependently stimulate the phosphorylation of PHAS-I which is further enhanced by insulin and growth factors. The objective of specific aim 2 is to define the cellular mechanism whereby amino acids alone and in synergy with insulin and other growth factors may utilize the PHAS-I/mTOR pathway. Studies will be performed to identify which amino acids are capable of mediating these effects, and to what extent the ability of growth factors to promoter Beta-cell growth are associated with enhanced transport and/or metabolism. of these active amino acids. In studies designed to identify endogenous growth factors that may promote Beta-cell growth via the PHAS-I/mTOR PATHWAY, we discovered that keratinocyte growth factor (KGF), a novel member of the FGF family, and KGF receptor (KGFR) are expressed endogenously by islets and the Beta-cell line, RINm5F. The objective of specific aim 3 is to further characterize the regulation of KGF and KGFR expression by pancreatic islets and Beta-cell lines at the level of mRNA, protein and activity, and also evaluate if KGF mediates its effects in a paracrine manner on ductal cells and/or in an autocrine manner on Beta- cells via the PHAS-I/mTOR signaling pathway. An understanding of the PHAS- I/mTOR signaling pathway to generate mitogenic mediators will provide important new insights to enhance the ability of growth factors and nutrients to stimulate Beta-cell growth.

描述(取自应用程序) 这项提案的重点是评估PHA-I/MTOR的作用(S 生长因子和营养物质介导的β细胞生长中的信号通路。 增加信使核糖核酸到蛋白质的翻译是必要的 细胞的有丝分裂反应。新近发现的一种结合蛋白--PHAS-I 在启动因子中，eIF-4E在这一过程中起着关键作用。 PHAs-I的磷酸化导致PHAs-I.eIF-4E的解离 复杂，允许EIF-4与其他因素相互作用并启动 翻译、细胞周期进程和增殖。最近的研究与 雷帕霉素，一种免疫抑制剂和抗增殖剂，有 牵涉到哺乳动物雷帕霉素(MTOR)的上游 PHAS-I磷酸化调节因子。我们的发现表明，在 β细胞，葡萄糖通过刺激介导PHAs-I的磷酸化 以自分泌的方式与自身相互作用的胰岛素分泌 胰岛素受体。此外，雷帕霉素抑制两种刺激的葡萄糖 胰岛蛋白质合成和血清诱导的细胞增殖 β细胞系，RINm5F，提示PHAS-I/mTOR途径在 贝塔细胞的生长。本提案具体目标1的目标是 确定胰岛素和其他生长因子是否利用相同的PHAs-I/mTOR 上调蛋白质翻译、细胞周期的信号通路 进展与β细胞增殖。我们最近对 胰岛和β细胞系已表明氨基酸是 胰岛素和生长因子激活PHA是绝对必要的- I/mTOR途径。此外，单独的氨基酸刺激呈剂量依赖关系。 PHAs-I的磷酸化，这一作用被胰岛素和 增长因素。具体目标2的目标是定义细胞 氨基酸单独以及与胰岛素和其他物质协同作用的机制 生长因子可能利用PHAs-I/mTOR途径。研究将会是 以确定哪些氨基酸能够调节这些 影响，以及生长因子在多大程度上促进 β细胞的生长与运输和/或新陈代谢的增强有关。 这些活性氨基酸中。在旨在识别内源性 可能通过PHAs-I/mTOR促进β细胞生长的生长因子 途径，我们发现角质形成细胞生长因子(KGF)，一种新的 表达成纤维细胞生长因子家族成员和KGF受体(KGFR) 由胰岛和Beta细胞系RINm5F内源性表达。的目标是 具体目标3是进一步描述KGF和KGFR的调节 胰岛和胰岛β细胞系在mRNA水平表达， 蛋白质和活性，并评估KGF是否在 在导管细胞上以旁分泌方式和/或在β细胞上以自分泌方式 细胞通过PHAS-I/mTOR信号通路。对PHA的理解- I/mTOR信号通路产生有丝分裂介质将提供 增强生长因子和能力的重要新见解 刺激贝塔细胞生长的营养物质。