Regulation of Neuronal Survival by Ras-like GTPase

Ras 样 GTP 酶对神经元存活的调节

• 批准号: 6751578
• 负责人: Douglas Allen Andres
• 金额: $ 34.97万
• 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 2007-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6751578
• 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; 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）：异常凋亡会导致各种神经退行性疾病。因此，阐述调节神经元存活的信号转导机制对于理解基本生物学和治疗干预非常重要。神经营养蛋白通过激活小的GTP结合蛋白Ras来部分刺激神经元存活，该蛋白Ras通过将神经营养蛋白引起的信号转化为多个信号传导途径来发挥作用。最近的数据表明，RAS依赖性信号通路PI-3激酶/AKT和MEK/ERK以及与RAS无关MEK5/ERK5信号级联反应是神经营养蛋白依赖性生存的主要介体。我们发现了一种新型的，进化保守的与RAS相关的蛋白质。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庭成员（RIC）。这些蛋白质代表了一个基因家族，该基因家族可以调节从苍蝇到人的保守信号网络。通过激活MEK依赖性的，但PI-3激酶/非依赖性的信号传导途径，通过激活MEK依赖性的MEK依赖性，在嗜铬细胞瘤细胞中的组成性活性突变体的过表达可诱导神经突生长和存活。此外，原发性神经元中活化的RI​​T表达抑制了滴水诱导的细胞凋亡并促进轴突生长。因此，RIT以不同于RA的方式控制生存途径，可能在控制MEK5/ERK5信号传导或调节新型信号通路（激活ERK激酶）。我们假设RIT的功能以与RAS不同的方式转化和将神经营养蛋白引发的信号转化为促生物信号级联。描述了三个特定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了原代培养神经元的存活，以及RIT功能是否对于神经元细胞存活至关重要。具体目标2将检查通过神经营养蛋白相关或神经营养蛋白非依赖性途径来调节RIT功能的细胞外刺激。具体的目标3将检查RIT介导的ERK激活的机制，并确定已建立的ERK依赖性的促生存信号传导途径对于RIT介导的神经元存活至关重要。初步研究表明，果蝇对RIC活性的改变敏感，从而导致机翼和眼睛的发育缺陷。我们将采用一种遗传筛选方法来鉴定与RIC相互作用的基因，并将分析脊椎动物同源物，以表明它们有助于神经元细胞中RIT功能的能力。通过生物化学，分子生物学和遗传学的联合使用，这些研究将构成理解这种神经元生存的独特调节剂功能的基础。