Mechanisms of MEK/ERK growth arrest signaling

MEK/ERK 生长抑制信号传导机制

• 批准号: 8090466
• 负责人: Jong-In Park
• 金额: $ 27.53万
• 依托单位: MEDICAL COLLEGE OF WISCONSIN
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2015-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8090466
• 关键词: Active Sites; Address; Affect; Affinity Chromatography; Basal Cell; Binding; Biochemical; Biological; Carcinoid Tumor; Cell Cycle; Cell Cycle Arrest; Cell Line; Cell Proliferation; Cells; Defense Mechanisms; Dependency; Development; Disabled Persons; Event; Fibroblasts; GRP75; Glioma; Goals; Growth; Knowledge; MAP Kinase Gene; MAP2K1 gene; MAPK3 gene; MEKs; Malignant Neoplasms; Mediating; Modeling; Molecular; Molecular Chaperones; Mutate; Mutation; Normal Cell; Oncogenic; Pathway interactions; Pheochromocytoma; Phosphotransferases; Prostate carcinoma; Proteins; Ras/Raf; Reagent; Regulation; Reporting; Research; Role; Signal Transduction; Specimen; Testing; Tissues; Tumor Tissue; Work; base; cancer cell; cancer type; carcinogenesis; cell type; experience; gastrointestinal; loss of function; lung small cell carcinoma; medullary thyroid carcinoma; mortalin; mutant; neoplastic cell; novel; novel therapeutics; overexpression; public health relevance; response; senescence; tumor; tumor progression

DESCRIPTION (provided by applicant): The goal of this project is to determine the mechanistic differences in MEK/ERK signaling that mediates growth arrest versus cell proliferation in response to aberrant Ras and/or Raf signals. Aberrant activation of the Ras/Raf/MEK/ERK pathway is a central feature in many cancers. However, paradoxically, sustained activation of the pathway induces cell cycle arrest and senescence in normal cells and certain cancer types. It has been proposed that growth arrest acts as a defense mechanism against Ras/Raf-mediated carcinogenesis and that overcoming this "growth arrest barrier" is a necessary step in tumor progression. Our understanding of this key event in carcinogenesis, controlled at the level of MEK/ERK, is currently quite limited. We have begun to address the underlying mechanisms of MEK/ERK signaling using normal and Ras/Raf-responsive tumor cells as models. The first intriguing finding is that ERK can mediate growth arrest by utilizing not only its "canonical" kinase activity but also, as yet unidentified, non-catalytic functions. We recently reported that oncogenic Raf signal-induced growth arrest is abrogated by ERK1/2 depletion but introduction of catalytically disabled mutant ERK into ERK1/2- depleted cells can selectively restore the growth arrest phenomenon. Based upon a hypothesis that MEK/ERK would interact with specific proteins to mediate growth arrest signaling, we conducted tandem affinity purification and identified mortalin as a potential negative regulator of MEK/ERK-growth arrest signaling. Our preliminary studies show that mortalin binds to inactive, but not active, MEK and that mortalin depletion increases basal as well as Raf-induced MEK/ERK activity. In addition, mortalin depletion promotes growth inhibitory signaling whereas mortalin overexpression exerts the opposite effects. These preliminary studies suggest that MEK/ERK utilizes a unique signaling mechanism to mediate growth arrest, for which mortalin has a negative-regulatory role possibly via its physical interaction with the pathway and ERK modulates a mechanism that requires its non-catalytic function. To test these hypotheses, we propose to (i) determine the role of mortalin in the regulation of Raf/MEK/ERK-mediated growth arrest signaling by gain or loss of function studies in normal and K-Rasor B-Raf mutated tumor cells and by comparing mortalin expression levels with altered MEK/ERK activity in tumor tissue specimens; (ii) determine whether mortalin regulates the Raf/MEK/ERK pathway by differentially sequestering MEK1 or MEK2; and (iii) determine molecular mechanisms underlying the non-catalytic ERK functions. This study will enhance our knowledge of the specific mechanisms of MEK/ERK signaling that interrupts Ras/Raf-driven carcinogenesis. PUBLIC HEALTH RELEVANCE: Activation of the MEK/ERK pathway induces terminal growth arrest in certain types of cancer lines derived from small cell lung carcinoma, medullary thyroid carcinoma, prostate carcinoma, pheochromocytoma, glioma, and gastrointestinal carcinoid. Exploration of the possibility that these cancer types can be effectively suppressed by modulating the pathway via mortalin into the direction of growth arrest may allow development of new therapeutic strategies to control them.

描述（由申请人提供）：该项目的目标是确定 MEK/ERK 信号传导的机制差异，该信号传导响应异常 Ras 和/或 Raf 信号而介导生长停滞与细胞增殖。 Ras/Raf/MEK/ERK 通路的异常激活是许多癌症的核心特征。然而，矛盾的是，该途径的持续激活会导致正常细胞和某些癌症类型的细胞周期停滞和衰老。有人提出，生长停滞是针对 Ras/Raf 介导的致癌作用的防御机制，克服这种“生长停滞屏障”是肿瘤进展的必要步骤。目前，我们对这一在 MEK/ERK 水平上控制的关键致癌事件的了解还相当有限。我们已经开始使用正常和 Ras/Raf 反应性肿瘤细胞作为模型来解决 MEK/ERK 信号传导的潜在机制。第一个有趣的发现是，ERK 不仅可以利用其“典型”激酶活性，而且还可以利用尚未识别的非催化功能来介导生长停滞。我们最近报道，致癌的 Raf 信号诱导的生长停滞被 ERK1/2 耗尽所消除，但将催化失效的突变体 ERK 引入 ERK1/2 耗尽的细胞中可以选择性地恢复生长停滞现象。基于 MEK/ERK 会与特定蛋白质相互作用以介导生长停滞信号传导的假设，我们进行了串联亲和纯化，并确定 mortalin 是 MEK/ERK 生长停滞信号传导的潜在负调节因子。我们的初步研究表明，mortalin 与无活性但不活跃的 MEK 结合，并且 mortalin 消耗会增加基础以及 Raf 诱导的 MEK/ERK 活性。此外，mortalin 耗竭会促进生长抑制信号传导，而 mortalin 过度表达则会产生相反的效果。这些初步研究表明，MEK/ERK 利用独特的信号机制来介导生长停滞，mortalin 可能通过其与该途径的物理相互作用发挥负调节作用，而 ERK 则调节需要其非催化功能的机制。为了检验这些假设，我们建议 (i) 通过正常和 K-Rasor B-Raf 突变肿瘤细胞的功能获得或丧失研究来确定 Mortalin 在调节 Raf/MEK/ERK 介导的生长停滞信号传导中的作用，以及通过比较肿瘤组织标本中 Mortalin 的表达水平与改变的 MEK/ERK 活性； (ii)确定mortalin是否通过差异性隔离MEK1或MEK2来调节Raf/MEK/ERK通路； (iii) 确定非催化 ERK 功能的分子机制。这项研究将增强我们对 MEK/ERK 信号传导中断 Ras/Raf 驱动的致癌作用的具体机制的了解。 公共健康相关性：MEK/ERK 通路的激活会诱导小细胞肺癌、甲状腺髓样癌、前列腺癌、嗜铬细胞瘤、神经胶质瘤和胃肠道类癌等某些类型的癌细胞系的终末生长停滞。通过将 Mortalin 调节至生长停滞方向来有效抑制这些癌症类型的可能性，探索可能有助于开发新的治疗策略来控制它们。