NEUROTROPHIN SIGNALING THROUGH THE P75 RECEPTOR

描述(申请人提供)：神经细胞程序性死亡 系统是哺乳动物发育中一个自然发生的过程；然而， 异常细胞凋亡是许多神经病理的基础，例如阿尔茨海默氏症和 帕金森氏病和缺血性损伤。神经元之间微妙的平衡 生存和死亡在一定程度上是由神经营养因子调节的，神经营养因子促进 通过与Trks结合存活，Trks是一种酪氨酸激酶受体家族， 并通过75 kDa受体p75诱导细胞凋亡。虽然取得了重大进展 已经在阐明Trks促进生存的机制方面取得了进展， 关于p75是如何诱导细胞死亡的，我们知之甚少。神经生长因子 与p75的结合激活了一个分支信号，促进了两个细胞的存活 通过转录因子核因子-kB和细胞死亡通过 应激激活激酶，JNK。因此，一个细胞的最终命运是 神经系统的发育或受损只能通过阐明 这些信号是产生和调节的。为了实现这一目标，我们确定了一个 结合胞内结构域的新型锌指蛋白NRIF P75。我们的研究结果提示，NRIF在神经营养因子的介导中起作用。 体内的细胞凋亡。最近，我们发现NRIF与 细胞因子受体相关因子家族，TRAF6，也可以与 P75的LCD，这种相互作用将NRIF易位导向 亚核区。因此，我们假设NRIF和TRAF6都是 P75介导的细胞凋亡信号通路及其相互作用和 这一信号需要核转位。为了解决这一假设， 我们提出了三个综合的具体目标：i)确定p75的能力 在没有NRIF和TRAF6与受体结合的情况下诱导细胞凋亡。这 将包括对nrzf-I-和TRAF6-/-小鼠的分析。Ii)设立 TRAF6-NRIF相互作用的功能意义。通过将序列突变到 它们的结合和核转位所需的每一种蛋白质，我们将 评估这些信号蛋白的相互作用如何影响它们的能力 调节核因子-kB、JNK和细胞凋亡。三)确定NRIF通过哪些机制 调节细胞的活性。我们将调查NRIF是否推动 通过抑制转录而发生的细胞凋亡。这些研究将揭示 神经营养因子调节细胞活性的分子机制 神经系统。特别是，他们将阐明细胞凋亡的反应是如何 是通过p75受体产生的，具有潜在的临床意义 在制定各种治疗策略方面的应用 神经病理学。

DESCRIPTION (provided by applicant): Programmed cell death in the nervous system is a naturally occurring process in mammalian development; however, abnormal apoptosis is the basis for many neuropathologies, e.g. Alzheimer's and Parkinson's disease and ischemic injury. The delicate balance between neuronal survival and death is regulated, in part, by the neurotrophins, which promote survival through binding to the Trks, a family of tyrosine kinase receptors, and induce apoptosis through a 75kDa receptor, p75. While significant progress has been made in elucidating the mechanisms by which the Trks promote survival, much less is known about how p75 induces cell death. Nerve Growth Factor binding to p75 activates a bifurcating signal, promoting both cell survival through the transcription factor NF-kB, and cell death through the stress-activated kinase, JNK. Thus the ultimate fate of a cell in the developing or lesioned nervous system can only be understood by elucidating how these signals are generated and regulated. To meet this goal, we identified a novel zinc finger protein, NRIF, which binds to the intracellular domain (lCD) of p75. Our findings suggested that NRIF plays a role in neurotrophin mediated apoptosis in vivo. Recently, we found that NRIF binds to a member of the cytokine receptor associated factor family, TRAF6, which can also bind to the lCD of p75, and that this interaction directed NRIF translocation to a subnuclear domain. Therefore, we hypothesize that both NRIF and TRAF6 are part of the p75-mediated apoptotic signaling pathway and that their interaction and nuclear translocation are required for this signal. To address this hypothesis, we propose three integrated specific aims: I) Determine the ability of p75 to induce apoptosis in the absence of NRIF and TRAF6 binding to the receptor. This will include analysis of the nrzf-I- and traf6-/- mice. II) Establish the functional significance of TRAF6-NRIF interaction. By mutating the sequences on each protein required for their association and nuclear translocation, we will assess how the interaction of these signaling proteins affects their ability to regulate NF-kB, JNK, and apoptosis. III) Determine the mechanisms by which NRIF regulates cellular viability. We will investigate whether NRIF promotes apoptosis through repression of transcription. These studies will reveal the molecular mechanisms by which neurotrophins regulate cellular viability in the nervous system. In particular, they will elucidate how the apoptotic response is generated through the p75 receptor, which has potential clinical applications in developing therapeutic strategies for a variety of neuropathologies.