Role of p53 family in neuropathogenesis in AIDS

描述(申请人提供)：尽管使用了高效抗逆转录病毒疗法(HAART)，神经细胞死亡仍然是HIV-1感染患者大脑中经常发现的一个问题。HAART已经成功地预防了许多艾滋病的早期终末期并发症，然而，随着生存时间的延长，艾滋病患者中与艾滋病毒相关的轻微认知障碍的患病率似乎正在上升。此外，艾滋病毒脑炎(HIVE)仍然在接受治疗的患者中流行，以及减轻形式的HIVE和中枢神经系统机会性疾病。艾滋病毒相关的认知障碍与中枢神经系统中激活的尽管不一定感染艾滋病毒-1的小胶质细胞和中枢神经系统巨噬细胞的存在增加有关。这表明，神经元损伤和丢失/死亡的间接机制发生在HIV/AIDS中，作为痴呆的基础，因为神经元本身不会有效地感染HIV-1。最近的证据表明，P53抑癌蛋白及其相关家族成员p73在调节神经元丢失/凋亡中起着重要作用。P53或P73的诱导导致树突回缩和神经元丢失的机制尚未完全阐明。在艾滋病患者神经元中观察到P53水平升高，这可能与HIV-1相关性痴呆(HAD)的发生有关。与神经元中的P53激活类似，小胶质细胞和星形胶质细胞中的P53激活也可能导致这些细胞的生理变化，最终导致神经毒性环境和神经元丢失。重要的是，为了让p53发挥功能和稳定，激活p73是必需的。基于这一发现，我们研究了p73与TAT的关系，并证明了HIV-1，特别是TAT，能够诱导p73的内源性水平。P73的诱导通过直接的物理作用阻止了TAT在赖氨酸28上的乙酰化，这也抑制了TAT的凋亡活性。TAT与p73的结合也减少了HIV-1 LTR的TAT激活，并阻止了P73导致星形胶质细胞的细胞死亡。这些数据为限制HIV-1在星形胶质细胞中的复制奠定了基础。我们还研究了TAT和p73在神经细胞中的相互作用。令人惊讶的是，在缺乏p73或p53的情况下，TAT不能促进神经元死亡，这表明TAT、p73、p53与神经细胞死亡之间存在很强的联系。因此，我们现在建议研究TAT诱导P73的机制(S)。这将包括对p73启动子的控制和p73蛋白周转的分析。我们还将研究TAT对p73的诱导是否会导致P53的激活和神经细胞的死亡。这项拟议研究的结果应该会提供有关艾滋病患者神经元丢失机制的新信息，并提出可能的新治疗方法。公共卫生相关性该提案侧重于HIV-1调节蛋白、TAT和细胞因子之间的关系。这些研究的结果将突出TAT对神经元造成损害的途径，并为开发安全有效的治疗方法以抑制艾滋病患者的神经退化开辟新的途径。

DESCRIPTION (provided by applicant): Despite the use of Highly active antiretroviral therapy (HAART), neuronal cell death remains a problem that is frequently found in the brains of HIV-1-infected patients. HAART has successfully prevented many of the former end-stage complications of AIDS, however, with increased survival times, the prevalence of minor HIV-associated cognitive impairment appears to be rising among AIDS patients. Further, HIV encephalitis (HIVE) is still prevalent in treated patients as well as attenuated forms of HIVE and CNS opportunistic disorders. HIV-associated cognitive impairment correlates with the increased presence in the CNS of activated, though not necessarily HIV-1- infected, microglia and CNS macrophages. This suggests that indirect mechanisms of neuronal injury and loss/death occur in HIV/AIDS as a basis for dementia since neurons are not themselves productively infected by HIV-1. Recent evidence indicates that the p53 tumor suppressor protein and its related family member, p73, play an essential role in regulating neuronal loss/apoptosis. The mechanisms involved in induction of p53 or p73 which lead to dendritic retraction and neuronal loss are not fully elucidated. Increased levels of p53 were observed in the neurons of AIDS patients, which may be connected to the occurrence of HIV-1-associated dementia (HAD) in those patients. Similar to p53 activation in neurons, p53 activation in microglia and astrocytes may also contribute to alterations in the physiology of these cells that eventually result in a neurotoxic environment and neuronal loss. Importantly, for p53 to be functional and stable, activated p73 is required. Based on this finding, we have studied the relationship between p73 and Tat, and have demonstrated the ability of HIV-1 in general and of Tat in particular, to induce the endogenous levels of p73. P73 induction prevents acetylation of Tat on lysine 28 through their direct physical interaction, which also inhibits Tat's apoptotic activity. The association of Tat with p73 also reduces Tat-activation of the HIV- 1 LTR, and prevents p73 from causing cell death in astrocytes. These data suggest a basis for the restricted replication of HIV-1 in astrocytes. We also investigated the interplay between Tat and p73 in neuronal cells. Surprisingly, Tat was unable to promote neuronal death in the absence of either p73 or p53, suggesting a strong link between Tat, p73, p53 and neuronal cell death. Hence, we now propose to study the mechanism(s) whereby Tat induces p73. This will include analysis of control of the p73 promoter and of p73 protein turnover. We will also examine whether induction of p73 by Tat leads to activation of p53 and induction of neuronal cell death. The outcome from the proposed studies should provide new information regarding mechanisms of neuronal loss in AIDS patients and suggest possible new therapeutic approaches. PUBLIC HEALTH RELEVANCE This proposal focuses on the relationship between the HIV-1 regulatory protein, Tat, and cellular factors. The results of these studies will highlight the pathways used by Tat to cause damage to neurons and lead to new avenues for the development of safe and effective therapeutic approaches to inhibit neurodegeneration seen in AIDS patients.