Mechanisms involved in HIV-1 Tat mediated neuronal damage

描述(申请人提供)：目前，全球有4000多万人感染了HIV-1，艾滋病是全球第四大死因。高效抗逆转录病毒疗法(HAART)的引入大大减少了艾滋病毒介导的免疫抑制和死亡率。然而，它可能无法阻止与HIV-1感染相关的神经元损伤，随着艾滋病患者寿命的延长，中枢神经系统的进行性损伤可能会成为一个新出现的问题。在已被证明促进神经元毒性的因素中，病毒调节蛋白TAT引起了特别的关注。Tat蛋白是由HIV-1感染的宿主细胞分泌的，已被证明进入包括神经元在内的旁观者未感染的细胞。最近，我们发现了TAT引起神经元损伤的新机制。它涉及TAT与微管蛋白的结合，泛素-蛋白酶体系统在微管附近的募集，以及细胞骨架的关键组成部分微管相关蛋白2(MAP2)的降解。对HIV-1脑病(HIVE)脑组织临床标本的免疫组织化学分析显示，TAT主要存在于小胶质细胞结节附近的神经元胞浆中，而MAP2在70%的受影响神经细胞中丢失。TAT可以解除对细胞骨架因素的调控，这一观察结果让我们假设，依赖于细胞骨架完整性的分子事件，如RNA贩运，也可能受到损害。我们的初步数据证实了TAT改变小RNA子集的表达的能力，称为microRNAs，这是已知的翻译抑制因子。在这些结果的基础上，我们将检验这样的假设，即在神经元中，TAT可以通过调节细胞骨架、蛋白酶体的活性和microRNAs翻译抑制物的表达来改变蛋白质的合成。我们希望这项研究的结果将重新定义我们对TAT介导的神经毒性的认识，并为更有效的治疗干预提供潜在的靶点。

DESCRIPTION (provided by applicant): Presently, more than 40 millions people are infected with HIV-1, and AIDS is the fourth leading cause of death worldwide. The introduction of highly active antiretroviral therapy (HAART) has greatly reduced HIV-mediated immunosuppression and mortality. However, it may not prevent neuronal damage associated with HIV-1 infection, and progressive damage to the Central Nervous System may be an emerging problem as AIDS patients live longer. Among the factors that have been shown to promote neuronal toxicity, the viral regulatory protein Tat has captured special attention. Tat protein is secreted by HIV-1 infected host cells and has been shown to enter bystander non-infected cells, including neurons. Recently, we have identified a new mechanism by which Tat can induce neuronal damage. It involves the binding of Tat to tubulin, recruitment of the ubiquitin-proteasome system to the proximity of microtubules, and degradation of microtubule-associated protein 2 (MAP2), a critical component of the cytoskeleton. Immunohistochemical analysis of clinical samples from HIV-1 encephalopathy (HIVE) brain tissues demonstrated a predominantly cytoplasmic presence of Tat in neurons near microglial nodules, and loss of MAP2 in 70% of the affected neuronal cells. The observation that Tat can deregulate cytoskeletal factors led us to hypothesize that molecular events that depend on cytoskeletal integrity such as RNA trafficking could be also impaired. Our preliminary data confirm the ability of Tat to alter the expression of a subset of small RNAs, called microRNAs, which are known translational repressers. On the basis of these results, we will test the hypothesis that in neurons Tat can alter protein synthesis by modulating the activity of the cytoskeleton, the proteasome and the expression of microRNAs translational repressers. We expect that results from this study will critically redefine our knowledge of Tat-mediated neurotoxicity, and can provide potential targets for more effective therapeutic intervention.