Mechanisms in HIV-Tat mediated neurotoxicity

描述（由申请人提供）：最近的研究表明，大多数HIV感染患者在抗逆转录病毒治疗后仍出现轻度或无症状的神经认知功能障碍。再加上观察到大脑中的病毒负荷可能比先前预期的要大得多，需要考虑长时间少量病毒产物可能直接导致神经元功能障碍的可能性。Tat是这些病毒蛋白中的一种，特别有吸引力，因为它在hiv感染细胞中的产生和释放不受目前可用的抗逆转录病毒药物的影响。在过去的15年里，我们实验室的大量数据清楚地表明，Tat直接与NMDA受体相互作用，导致神经元损伤。在过去五年的资助下，我们进一步表征了Tat介导的神经元损伤的机制，并发现Tat对NMDA受体的兴奋机制不同于任何其他已知的激动剂。为了进一步表征这些相互作用，我们将结合体外和体内模型来确定Tat-NMDA受体相互作用在介导突触树突损伤中的作用，并使用包括晶体学在内的分子研究来确定这些蛋白质-蛋白质相互作用的确切分子基础。我们预计这些研究不仅将对理解HIV相关神经认知障碍的病理生理学具有重要意义，而且还将推进我们对NMDA受体发挥作用的生理和病理状态的理解。该资助申请将研究三个具体目标：目标1：表征介导其神经毒性特性的Tat的翻译后修饰和基本残基。目的2：确定Tat-NMDA受体相互作用在突触树突损伤中的作用。目的3：确定Tat与NMDA受体相互作用的结构基础。

DESCRIPTION (provided by applicant): Recent studies suggest that the majority of HIV infected patients develop mild or asymptomatic neurocognitive dysfunction despite being aviremic on antiretroviral therapy. Coupled with the observation that the viral burden in the brain may be much larger than previously anticipated, the possibility that small amounts of viral products over extended periods of time may directly cause neuronal dysfunction needs to be considered. One of these viral proteins, Tat is particularly attractive since its production and release from HIV-infected cells is not impacted by currently available antiretroviral agents. Substantial amount of data from our laboratory over the last 15 years clearly shows that Tat interacts directly with the NMDA receptors to cause neuronal injury. Over the previous five years of funding we further characterized the mechanisms of Tat-mediated neuronal injury and discovered that the mechanism of excitation of the NMDA receptor by Tat is unlike any other known agonist. To further characterize these interactions we will use a combination of in vitro and in vivo models to determine the role of Tat-NMDA receptor interactions in mediating synaptodendritic injury and using molecular studies including crystallography we will determine the exact molecular basis of these protein-protein interactions. We anticipate that these studies will not only have important implications for understanding the pathophysiology of HIV associated neurocognitive disorders but will also advance our understanding of the physiological and pathological states in which the NMDA receptor plays a role. The grant application will examine three specific aims: Aim 1: To characterize the post-translational modifications and essential residues of Tat that mediates its neurotoxic properties. Aim 2: To determine the role of Tat-NMDA receptor interaction in mediating synaptodendritic injury Aim 3: To determine the structural basis of the interactions between Tat and the NMDA receptor. PUBLIC HEALTH RELEVANCE: Currently, there is no available treatment for neurocognitive impairment in patients with HIV infection who are aviremic on antiretroviral therapy. We will study the mechanisms by which HIV proteins such as Tat can cause injury to neurons. The mechanisms by which this molecule interacts with cell surface receptors on neurons will be characterized. This would eventually lead to a rational design of new molecules that may block receptor action.