Regulation of Ras Signaling by Rlf In Hypertrophy

Rlf 在肥大中对 Ras 信号传导的调节

• 批准号: 6707668
• 负责人: Steven Post
• 金额: $ 31.01万
• 依托单位: UNIVERSITY OF KENTUCKY
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-12-01 至 2008-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6707668
• 关键词: biological signal transduction; congestive heart failure; echocardiography; gene expression; genetically modified animals; guanine nucleotide binding protein; guanine nucleotide exchange factors; hypertrophic myocardiopathy; laboratory mouse; laboratory rat; myocardium disorder; pathologic process; phosphotransferases; ventricular hypertrophy; western blottings

DESCRIPTION (provided by applicant): Important recent advances derived from experimental models of cardiac hypertrophy suggest that distinct signaling pathways regulate compensated hypertrophy and decompensated heart failure. Ras is a small GTP binding protein that signals through multiple effectors, including the Raf-MEK-ERK pathway, PI3 kinase (PI3K), guanine exchange factors for Ral (RalGEFs) and cJun N-terminal kinase (JNK). In transgenic mice, V12Ras-mediated hypertrophy is associated with JNK activation and depressed cardiac function. However, certain Ras-dependent signaling cascades, including ERK and PI3K, activate compensatory hypertrophic responses that preserve contractile activity. To identify novel Ras effectors we screened a human heart cDNA library using Ras as bait and isolated Ral guanine nucleotide exchange factor-like factor (RIf). To examine the functional consequence of the Ras-RIf interaction, we expressed V12Ras in concert with RIf in neonatal ventricular rat myocytes (NRVM). Expression of RIf suppressed V12Ras-induced JNK activity and ANF expression but not other Ras effectors. RIf also inhibited sorbitol-induced JNK activation indicating that RIf expression negatively regulates JNK activation in response to multiple stimuli. These results demonstrate that RIf suppresses an effector pathway suggested to mediate depressed function of myocardial cells. We will test the hypothesis that RIf negatively regulates JNK activation and that function inhibits the development of hypertrophic cardiomyopathy in vivo. The signaling pathways that couple Ras to JNK activation are not known but may involve MEKK1 (MAPWERK kinase kinase 1), a Ras binding protein that preferentially activates JNK. In aim #1, we will define the role of MEKK1-JKK-JNK in RIf-mediated inhibition of V12Ras- and stress- signaling. In aims #2 and #3, the pathophysiological implications of RIf function will be investigated in transgenic mice that overexpress RIf. We will test the potential protective role of RIf on the pathogenesis of cardiac hypertrophy in response to pressure overload, isoproterenol infusion and V12Ras overexpression and investigate the signaling cascades involved. Elucidation of the mechanisms by which RIf regulates hypertrophic signaling pathways may lead the development of novel therapeutic approaches to prevent cardiac dysfunction.

描述（由申请人提供）：源自心脏肥大实验模型的重要最新进展表明，不同的信号传导途径调节代偿性肥大和失代偿性心力衰竭。 Ras 是一种小型 GTP 结合蛋白，通过多个效应器发出信号，包括 Raf-MEK-ERK 通路、PI3 激酶 (PI3K)、Ral 鸟嘌呤交换因子 (RalGEF) 和 cJun N 末端激酶 (JNK)。在转基因小鼠中，V12Ras 介导的肥大与 JNK 激活和心脏功能下降有关。然而，某些 Ras 依赖性信号级联，包括 ERK 和 PI3K，会激活代偿性肥大反应，从而保持收缩活性。为了鉴定新型 Ras 效应子，我们使用 Ras 作为诱饵筛选了人心脏 cDNA 文库，并分离了 Ral 鸟嘌呤核苷酸交换因子样因子 (RIf)。为了检查 Ras-RIf 相互作用的功能后果，我们在新生心室大鼠肌细胞 (NRVM) 中表达 V12Ras 与 RIf。 RIf 的表达抑制 V12Ras 诱导的 JNK 活性和 ANF 表达，但不抑制其他 Ras 效应子。 RIf 还抑制山梨醇诱导的 JNK 激活，表明 RIf 表达负向调节 JNK 激活以响应多种刺激。这些结果表明，RIf 抑制了介导心肌细胞功能低下的效应通路。我们将检验 RIf 负向调节 JNK 激活以及该功能抑制体内肥厚型心肌病发展的假设。将 Ras 与 JNK 激活偶联的信号通路尚不清楚，但可能涉及 MEKK1（MAPWERK 激酶激酶 1），这是一种优先激活 JNK 的 Ras 结合蛋白。在目标#1中，我们将定义 MEKK1-JKK-JNK 在 RIf 介导的 V12Ras 和应激信号传导抑制中的作用。在目标 #2 和 #3 中，将在过度表达 RIf 的转基因小鼠中研究 RIf 功能的病理生理学影响。我们将测试 RIf 对压力超负荷、异丙肾上腺素输注和 V12Ras 过度表达引起的心脏肥大发病机制的潜在保护作用，并研究所涉及的信号级联。阐明 RIf 调节肥大信号通路的机制可能会导致预防心脏功能障碍的新治疗方法的开发。