ROLE OF CELL CYCLE PROTEINS IN HIV ENCEPHALITIS

摘要 HIV相关性痴呆(HAD)患者的神经元损伤和丢失 与巨噬细胞浸润和中枢神经系统炎症关系最为密切。 这些因素中的大多数都会刺激细胞周期调节机制的变化 即使在没有细胞分裂的情况下，也可以确定细胞的结果。这让我们找到了 提出以下最重要的假设：HIV阳性HAD患者的神经元 表现出细胞周期蛋白活性的改变，这种活性决定了神经元的存活 对HIV感染的巨噬细胞释放的因子的反应。诱导细胞周期 机械通常导致E2F家族转录活性增加 导致DNA所需基因产物表达的转录因子 合成和进展到S阶段。E2F家族的活性受到直接抑制 视网膜母细胞瘤肿瘤抑制蛋白pRb及其家族的相互作用 成员，当PRB过度磷酸化时，这种相互作用被破坏。在支持中 在我们的假设中，我们观察到E2F1增加和过度磷酸化的pRb在 人类免疫缺陷病毒脑炎患者的中枢神经系统，在猿猴疾病模型中，在神经元中 在我们的体外HIV神经变性模型中。令人惊讶的是，E2F1被本地化到 细胞质，一个与其已知的转录作用不一致的位置。更改的E2F功能是 SIVE中E2F DNA结合活性的改变进一步支持了这一点。始终如一的 E2F1在神经元中的主要胞浆定位提示了这一新的作用 蛋白。有趣的是，据报道，E2F1与一种独特的RNA发夹结构结合 和至少一种信使核糖核酸的稳定，Axin 2；然而，鲜为人知。 关于E2F1函数的这一方面。因此，我们假设E2F1，作用于 不依赖于pRb，在调节HIV的神经变性中起着新的作用 通过核酸结合活性、亚细胞分布和钙蛋白的改变引起的感染 乳沟。为了验证这一假设，我们建议：1)确定潜在的细胞质 E2F1核酸结合域作为调控机制的作用 神经退行性变。2)测定钙蛋白裂解的E2F1对E2F1的调控能力 核酸结合和神经元存活等功能。3)确定以下对象的角色 E2F1在HIV神经毒性中的定位。鉴于其潜在的独特功能和 有丝分裂后神经元的调控，我们认为E2F1可能是防止 人类免疫缺陷病毒相关性痴呆的神经元丢失。

Abstract Neuronal damage and loss in patients with HIV-associated dementia (HAD) is most closely associated with macrophage infiltration and neuroinflammation of the CNS. Most of these factors stimulate changes in cell cycle regulatory machinery which determine cellular outcomes even in the absence of cell division. This has led us to propose the following overarching hypothesis: neurons in HIV-positive patients with HAD exhibit altered cell cycle protein activity and this activity determines neuronal survival in response to factors released by HIV infected macrophages. Induction of cell cycle machinery classically results in increased transcriptional activity of the E2F family of transcription factors leading to the expression of gene products necessary for DNA synthesis and progression to S-phase. Activity of the E2F family is repressed by direct interaction with the Retinoblastoma tumor suppressor protein, pRb, and its family members, an interaction that is disrupted when pRb is hyperphosphorylated. In support of our hypothesis, we have observed increased E2F1 and hyper-phosphorylated pRb in the CNS of patients with HIV encephalitis, in a simian model of disease, and in neurons in our in vitro HIV neurodegeneration model. Surprisingly, E2F1 is localized to the cytoplasm, a site inconsistent with its known transcriptional roles. Altered E2F function is further supported by altered E2F DNA binding activity in SIVE. The consistent and predominant cytoplasmic localization of E2F1 in neurons suggests a novel role for this protein. Interestingly, E2F1 has been reported to bind to a unique RNA hairpin structure and mediate stabilization of at least one mRNA species, Axin 2; however, little is known about this aspect of E2F1 function. We thus hypothesize that E2F1, acting independently of pRb, plays a novel role in modulating neurodegeneration in HIV infection via altered nucleic acid binding activity, subcellular distribution, and calpain cleavage. To test this hypothesis, we propose to: 1) determine the potential cytoplasmic role for the E2F1 nucleic acid binding domain as a mechanism modulating neurodegeneration. 2) determine the ability of calpain-cleaved E2F1 to modulate E2F1 functions such as nucleic acid binding and neuronal survival. 3) determine the role for E2F1 localization in HIV-induced neurotoxicity. Given its potentially unique function and regulation in post-mitotic neurons, we believe E2F1 may serve as a target to prevent neuronal loss in HIV associated dementia.