Role of proBNDF and p75NTR in HIV-mediated Axonal/Dendritic Degeneration

摘要 中枢神经系统的人类免疫缺陷病毒-1（HIV）感染损害突触， 促进神经元损伤，最终导致HIV相关的神经认知障碍（HAND）。艾滋病毒如何 神经突触损伤仍在调查中。病毒蛋白，包括包膜蛋白gp 120， 作为解释HIV介导的神经毒性的主要候选人，尽管其机制仍不清楚。 神经元存活和损伤之间的平衡主要由神经营养因子控制， 特别是脑源性神经营养因子（BDNF）及其前体proBDNF。proBDNF，当结合到 神经营养因子受体p75（p75 NTR）激活促凋亡信号。我们已经证明， 受试者以及暴露于gp 120的神经元表现出proBDNF的显著增加，这与 furin的表达减少，furin是处理proBDNF的关键酶。去除一个等位基因 p75 NTR（proBDNF的受体），挽救了在gp 120转基因小鼠中观察到的突触丢失。 因此，我们假设HIV通过增加gp 120的能力来损害突触， proBDNF并因此激活p75 NTR。这是一个重要的研究方向，因为突触 变性功能障碍与许多神经变性疾病有关， 手gp 120如何导致损害/损伤突触的分子和细胞机制仍然存在 在研究中本申请提出了一套全面的实验来测试主要假设。 特别是（AIM 1），我们将检验gp 120通过直接结合该蛋白降低弗林蛋白酶水平的假设。 内切蛋白酶我们将利用（AIM 2）p75 NTR-/-神经元和p75 NTR拮抗剂来研究其机制 和GP 120神经毒性的信号传导。我们将在gp 120中进行记忆功能（AIM 3）的行为研究 转基因（gp 120 tg）小鼠与p75 NTR缺失小鼠杂交以研究是否去除一个等位基因 对于p75 NTR，可挽救在gp 120 tg小鼠中观察到的记忆损伤。最后，（目标4）我们将使用人类 包括脑脊液（CSF）在内的样本，以确定脑源性神经营养因子原（proBDNF）的水平是否改变， HAND受试者的不同亚组。还将测量CSF中的gp 120水平。这些实验 可能建立了proBDNF，gp 120和神经认知障碍之间的相关性。我们期望 为p75 NTR在HIV介导的突触简化中的作用提供了新的重要数据。

Abstract Human immunodeficiency virus-1 (HIV) infection of the central nervous system damages synapses and promotes neuronal injury that culminates in HIV-associated neurocognitive disorders (HAND). How HIV damages synapses is still under investigation. Viral proteins, including the envelope protein gp120, have emerged as leading candidates to explain HIV-mediated neurotoxicity, though the mechanisms remain unclear. The balance between neuronal survival and damage is predominantly governed by neurotrophic factors, and in particular, brain-derived neurotrophic factor (BDNF) and its precursor proBDNF. proBDNF, when bound to the neurotrophin receptor p75 (p75NTR) activates a pro-apoptotic signal. We have shown that brains of HAND subjects, as well as neurons exposed to gp120, exhibit a significant increase of proBDNF, which correlates with a decreased expression of furin, a key enzyme in the processing of proBDNF. The removal of one allele of p75NTR, the receptor for proBDNF, rescues the loss of synapses seen in gp120 transgenic mice. Therefore, we hypothesize that HIV damages synapses through the ability of gp120 to increase proBDNF and therefore activating p75NTR. This is an important line of research because synaptic degeneration dysfunction has been linked to numerous neurodegenerative diseases but only preliminarily to HAND. The molecular and cellular mechanisms of how gp120 causes impairs/damages synapses remain under investigation. This application proposes a comprehensive set of experiments to test the main hypothesis. In particular (AIM 1), we will test the hypothesis that gp120 reduces furin levels by directly binding to this endoprotease. We will utilize (AIM 2) p75NTR-/- neurons and p75NTR antagonists to examine the mechanisms and signaling of gp120 neurotoxicity. We will perform behavioral studies for memory function (AIM 3) in gp120 transgenic (gp120tg) mice intercrossed with p75NTR null mice to investigate whether the removal of one allele for p75NTR rescues the memory impairment observed in gp120tg mice. Finally, (AIM 4) we will use human samples including the cerebrospinal fluid (CSF) to determine whether the levels of proBDNF are altered in different subgroups of HAND subjects. Levels of gp120 will also be measured in the CSF. These experiments might establish a correlation between levels of proBDNF, gp120 and neurocognitive impairment. We expect to provide new significant data on the role of p75NTR in HIV-mediated synaptic simplification.