Regulation of Neuronal Survival by Ras-like GTPase

Ras 样 GTP 酶对神经元存活的调节

• 批准号: 7068618
• 负责人: Douglas Allen Andres
• 金额: $ 34.16万
• 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: 2003-07-01 至 2008-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7068618
• 关键词: DNA damage; Drosophilidae; apoptosis; biological signal transduction; developmental genetics; enzyme activity; genetic screening; guanine nucleotide binding protein; guanine nucleotide exchange factors; guanosinetriphosphatases; laboratory rat; mitogen activated protein kinase; neurons; neuroprotectants; neuroregulation; neurotrophic factors; newborn animals; oxidative stress; phosphatidylinositol 3 kinase; tissue /cell culture; transcription factor; transfection

DESCRIPTION (provided by applicant): Aberrant apoptosis contributes to various neurodegenerative disorders. Elaborating the signal transduction mechanisms that regulate neuronal survival is thus important for understanding both basic biology and for therapeutic intervention. Neurotrophins potently stimulate neuronal survival in part by activating the small GTP-binding protein Ras, which functions by translating and directing neurotrophin-initiated signals into multiple signaling pathways. Recent data indicate that the Ras-dependent signaling pathways, PI-3 kinase/Akt and MEK/ERK, and the Ras-independent MEK5/ERK5 signaling cascade, are the primary mediators of neurotrophin-dependent survival. We have discovered a novel, evolutionarily conserved group of Ras-related proteins. There are at least two highly related human genes (Rit and Rin), while Drosophila express only one family member (Ric). These proteins represent a gene family that functions to regulate signaling networks that have been conserved from flies to man. Overexpression of a constitutively active mutant of Rit in pheochromocytoma cells induces neurite outgrowth and survival by activating a MEK-dependent, but PI-3 kinase/Akt-independent, signaling pathway. In addition, activated Rit expression in primary neurons inhibits trophic factor-withdrawal induced apoptosis and promotes axonal outgrowth. Thus, Rit controls survival pathway(s) in a manner distinct from that of Ras, likely functioning to control MEK5/ERK5 signaling, or regulating a novel signaling pathway, which activates ERK kinases. We hypothesize that Rit functions to translate and direct neurotrophin-initiated signals to pro-survival signaling cascades in a manner distinct from Ras. Three specific aims are described to evaluate this hypothesis. Specific Aim 1 will determine if activation of Rit signaling pathways promotes the survival of primary cultured neurons and if Rit function is essential for neuronal cell survival. Specific Aim 2 will examine the extracellular stimuli that regulate Rit function, via neurotrophin-associated or neurotrophin-independent pathways. Specific Aim 3 will examine the mechanism of Rit-mediated ERK activation and determine if established ERK-dependent pro-survival signaling pathways are important for Rit-mediated neuronal survival. Preliminary studies have demonstrated that Drosophila is sensitive to altered Ric activity, resulting in developmental defects in the wing and eye. We will undertake a genetic screening approach to identify genes that interact with Ric, and vertebrate homologues will be analyzed for their ability to contribute to Rit function in neuronal cells. Through the combined use of biochemistry, molecular biology, and genetics, these studies will form the foundation for understanding the function of this unique regulator of neuronal survival.

描述（由申请人提供）：异常细胞凋亡导致各种神经退行性疾病。因此，阐明调节神经元存活的信号转导机制对于理解基础生物学和治疗干预都很重要。神经营养因子部分通过激活小GTP结合蛋白Ras来有效刺激神经元存活，小GTP结合蛋白Ras通过将神经营养因子引发的信号翻译和引导到多个信号传导途径中来发挥作用。最近的数据表明，Ras依赖性信号通路，PI-3激酶/Akt和MEK/ERK，以及Ras非依赖性MEK 5/ERK 5信号级联，是神经营养因子依赖性生存的主要介质。我们发现了一个新的，进化上保守的Ras相关蛋白质组。至少有两个高度相关的人类基因（Rit和Rin），而果蝇只表达一个家族成员（Ric）。这些蛋白质代表了一个基因家族，其功能是调节信号网络，已被保守的从苍蝇到man. Overexpression的一个组成型活性突变体的Rit在嗜铬细胞瘤细胞诱导神经突生长和生存激活MEK依赖，但PI-3激酶/Akt独立的信号通路。此外，在原代神经元中激活的Rit表达抑制营养因子戒断诱导的细胞凋亡并促进轴突生长。因此，Rit以与Ras不同的方式控制存活途径，可能起到控制MEK 5/ERK 5信号传导或调节激活ERK激酶的新信号传导途径的作用。我们假设Rit的功能是以不同于Ras的方式将神经营养因子启动的信号翻译并引导至促生存信号级联。三个具体的目标来评估这一假设。具体目标1将确定Rit信号通路的激活是否促进原代培养神经元的存活，以及Rit功能是否对神经元细胞存活至关重要。具体目标2将检查调节Rit功能的细胞外刺激，通过神经营养相关或神经营养独立的途径。具体目标3将检查Rit介导的ERK激活的机制，并确定是否建立ERK依赖性促生存信号通路是重要的Rit介导的神经元存活。初步研究表明，果蝇对Ric活性的改变很敏感，导致翅膀和眼睛的发育缺陷。我们将进行遗传筛选的方法，以确定与Ric相互作用的基因，并将分析脊椎动物同源物的能力，以促进Rit在神经元细胞中的功能。通过生物化学、分子生物学和遗传学的结合使用，这些研究将为理解这种独特的神经元存活调节因子的功能奠定基础。