PHASI/TOR PATHWAY AND MITOGENIC SIGNALING

PHASI/TOR 通路和有丝分裂信号传导

• 批准号: 2906341
• 负责人: MICHAEL L. MCDANIEL
• 金额: $ 20.02万
• 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 2003-09-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2906341
• 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） 本提案的重点是评估第一阶段/中期职权范围的作用 生长因子和营养素介导的β细胞生长中的信号通路。 mRNA翻译成蛋白质的增加是需要的， 细胞的有丝分裂反应。PHAS-I，最近鉴定的结合蛋白 起始因子eIF-4 E在这一过程中起关键作用。 PHAS-I的磷酸化导致PHAS-I的解离。 复杂，允许eIF-4与其他因素相互作用，并启动 翻译、细胞周期进展和增殖。最近的研究， 雷帕霉素是一种免疫抑制剂和抗增殖剂， 涉及哺乳动物雷帕霉素靶蛋白（mTOR）作为上游调控因子， PHAS-I磷酸化的调节剂。我们的研究结果表明，在 β-细胞，葡萄糖通过刺激PHAS-I的磷酸化来介导PHAS-I的磷酸化。 胰岛素分泌以自分泌的方式与其自身的 胰岛素受体此外，雷帕霉素抑制葡萄糖刺激的 胰岛的蛋白质合成和血清诱导的细胞增殖 β细胞系RINm 5 F，表明PHAS-I/mTOR通路在 β细胞生长本提案具体目标1的目的是 确定胰岛素和其他生长因子是否利用相同的PHAS-I/mTOR 上调蛋白质翻译的信号通路，细胞周期 进展和β细胞增殖。我们最近的研究， 胰岛和β-细胞系已经表明氨基酸是 是胰岛素和生长因子激活PHAS所必需的 I/mTOR通路。此外，单独的氨基酸剂量依赖性地刺激 PHAS-I的磷酸化被胰岛素进一步增强， 生长因子具体目标2的目的是定义细胞 氨基酸单独以及与胰岛素和其他药物协同作用的机制 生长因子可以利用PHAS-I/mTOR途径。研究将 进行鉴定哪些氨基酸能够介导这些 影响，以及在何种程度上生长因子的能力，以促进 β-细胞生长与增强的运输和/或代谢有关。 这些活跃的氨基酸。在旨在确定内源性 可能通过PHAS-I/mTOR促进β细胞生长的生长因子 途径，我们发现角质细胞生长因子（KGF），一种新的 FGF家族成员，和KGF受体（KGFR）表达 内源性的胰岛和β细胞系，RINm 5 F。的目标 具体目标3是进一步表征KGF和KGFR的调节 胰岛和β细胞系在mRNA水平的表达， 蛋白质和活性，并评估KGF是否介导其作用， 旁分泌方式对导管细胞和/或自分泌方式对β- 细胞通过PHAS-I/mTOR信号通路。对PHAS的理解- I/mTOR信号通路产生促有丝分裂介质将提供 重要的新见解，以提高能力的生长因子和 刺激β细胞生长的营养素