BAG3 mediates interplay of HIV-1 and JCV in brain

描述（由申请方提供）：中枢神经系统（CNS）的HIV-1感染诱导应激状态，触发一系列细胞反应，能够影响HIV-1基因表达，改变宿主细胞的稳态，并刺激共存的机会性病原体。最近的结果，从评估脑组织获得的艾滋病患者的神经系统疾病揭示了增强的表达BAG 3的星形胶质细胞和血管周围的小胶质细胞。BAG 3是一种抗凋亡/促存活蛋白，其与关键应激反应伴侣蛋白HSP 70相关，并调节其对受损蛋白质的再折叠和将其货物递送至蛋白酶体的活性。这些事件影响涉及细胞存活和凋亡的若干途径，包括线粒体膜去极化、半胱天冬酶激活、DNA损伤、细胞周期进程等。在HIV-1感染小胶质细胞的过程中也可以观察到BAG 3的激活，小胶质细胞是一种支持病毒在大脑中复制的细胞类型。有趣的是，BAG 3的激活似乎增加了细胞存活，因为通过siRNA沉默BAG 3增加了HIV-1感染的小胶质细胞中的凋亡速率。BAG 3的诱导可能对HIV-1复制产生负面影响，因为BAG 3具有抑制小胶质细胞和星形胶质细胞中HIV-1基因转录的能力。事实上，一旦细胞中BAG 3的水平降低，这些事件就可以逆转。在神经胶质细胞中，这可以在人机会病毒JCV活化后实现，JCV的早期蛋白抑制BAG 3转录，并可能减轻BAG 3对HIV-1的负面影响，促进凋亡途径。这些观察结果与AIDS的神经发病机制有关，因为在AIDS患者中经常观察到JCV的复制，其导致进展性多灶性白质脑病（PML）的发展。所有这些观察使我们假设BAG 3通过帮助细胞在HIV-1的初始感染中存活，可以在将细胞转化为病毒的长期储存库方面发挥关键作用。有了这个概念，我们计划研究参与CNS细胞中BAG 3差异调节的分子事件，确定BAG 3抑制HIV-1表达和复制的途径，研究JCV通过抑制BAG 3对HIV-1表达的影响，并确定BAG 3介导的HIV-1感染细胞中细胞存活的机制。我们将采用分子、细胞和病毒学方法来解决这些问题，并通过对HIV-1 CNS疾病患者临床样本的免疫组化评价来研究我们研究结果的生物学相关性。

DESCRIPTION (provided by applicant): HIV-1 infection of the central nervous system (CNS) induces conditions of stress that trigger an array of cellular responses with the capacity to affect HIV-1 gene expression, alter the homeostatic state of the host cell, and stimulate co-existing opportunistic pathogens. Recent results from evaluating brain tissue obtained from AIDS patients with neurologic disorders have revealed enhanced expression of BAG3 in astrocytes and perivascular microglial cells. BAG3 is an anti-apoptotic/pro-survival protein that associates with a key stress response chaperone protein, HSP70, and modulates its activity on re-folding of damaged proteins and delivery of its cargo to proteasomes. These events influence several pathways involved in cell survival and apoptosis including mitochondrial membrane depolarization, caspase activation, DNA damage, cell cycle progression, and others. Activation of BAG3 can also be observed during the course of HIV-1 infection of microglia, a cell type that supports viral replication in the brain. Interestingly, activation of BAG3 appears to augment cell survival as silencing of BAG3 by siRNA increases the rate of apoptosis in HIV-1 infected microglial cells. Induction of BAG3 may have a negative impact on HIV-1 replication as BAG3 possesses the ability to suppress HIV-1 gene transcription in both microglia and astrocytes. Indeed these events may be reversed once the level of BAG3 is reduced in the cells. In glial cells this can be accomplished upon activation of the human opportunistic virus, JCV, whose early protein suppresses BAG3 transcription and may alleviate the negative effect of BAG3 on HIV-1 and promote apoptotic pathways. These observations are relevant to the neuropathogenesis of AIDS as replication of JCV, which results in the development of progressive multifocal leukoencephalopthy (PML), is frequently seen in AIDS patients. All of these observations have led us to hypothesize that BAG3, by assisting cells to survive the initial infection with HIV-1, can play a critical role in converting cells to become a long-term reservoir for the virus. With this notion, we plan to investigate the molecular events involved in the differential regulation of BAG3 in CNS cells, identify the pathway by which BAG3 suppresses HIV-1 expression and replication, investigate the impact of JCV via suppression of BAG3 upon HIV-1 expression, and determine the mechanism involved in BAG3 mediated cell survival in HIV-1 infected cells. We will employ molecular, cellular, and virological approaches to address these questions and examine the biological relevance of our findings by immunohistochemical evaluation of clinical samples from patients with HIV-1 CNS disease.