Involvement of Survivin in the Development of PML

描述(申请人提供)：JC病毒是多维病毒科的成员，是进行性多灶性白质脑病(PML)的公认病原体，PML是一种致命的中枢神经系统(CNS)脱髓鞘疾病，常见于有潜在免疫抑制症状的患者。艾滋病大流行后，曾被认为与白血病和淋巴瘤相关的罕见疾病PML的病例急剧增加，现在，PML被认为是艾滋病的定义疾病。在初次感染后，病毒仍处于潜伏状态，很可能是在肾脏，在免疫抑制下进入大脑并在少突胶质细胞中有效复制，中枢神经系统的髓鞘产生细胞流产感染星形胶质细胞。少突胶质细胞的溶解破坏和星形胶质细胞对JCV感染的损伤反应，导致PML典型的组织病理学标志，广泛的髓鞘丢失，其中可见大量具有不典型和多形性核的奇怪的星形胶质细胞，以及核内含有嗜酸性小体的增大的少突胶质细胞。处理受损或感染细胞的自然反应是程序性细胞死亡。决定细胞死亡和细胞存活的内在机制取决于促凋亡蛋白和凋亡抑制因子之间的微妙平衡。我们在PML患者脑标本中的初步免疫组织化学数据显示，Survivin在奇怪的星形胶质细胞和JCV感染的少突胶质细胞的核内包涵体中表达增加，Survivin是凋亡抑制因子家族的成员。这种蛋白在发育过程中在胚胎增殖组织中大量表达，但在终末分化细胞中缺失。人们认为，抑制细胞凋亡的机制涉及到程序性细胞死亡执行者蛋白caspase的失活。我们的结果还表明，JCV感染原代少突胶质细胞培养后，免疫印迹和免疫细胞化学显示Survivin的表达增强。此外，感染细胞的细胞周期分析显示，凋亡细胞数量减少，抑制Survivin的siRNA导致细胞凋亡率显着增加。这些结果表明，JCV感染刺激Survivin的表达，从而阻止细胞凋亡，刺激细胞存活，以参与其感染周期。

DESCRIPTION (provided by applicant): JC Virus, a member of the Polyomaviridiae family, is the well-established etiological agent of Progressive Multifocal Leukoencephalopathy (PML), a fatal demyelinating disease of the Central Nervous System (CNS), frequently seen in patients with underlying immunosuppressive conditions. After the AIDS pandemic, cases of PML, once considered a rare disease associated with leukemias and lymphomas, has dramatically ncreased and now, PML is considered and AIDS defining condition. After primary infection the virus remains in latent state most likely in the kidney, and under immunosuppression enters the brain and efficiently replicates in oligodendrocytes, the myelin producing cells of the CNS ad abortively infects astrocytes. The lytic destruction of oligodendrocytes and the activation of astrocytes in response to injury caused y JCV infection, result in the characteristic histopathological landmarks of PML, extensive areas of myelin loss, in which numerous bizarre astrocytes with atypical and pleomorphic nuclei, and enlarged oligodendrocytes harboring intra-nuclear eosinophilic inclusion bodies can be found. The natural response to dispose of damaged or infected cells is programmed cell death. The intrincate mechanisms that will decide between cell death and cell survival depend on the delicate balance between pro-apoptotic proteins and inhibitor of apoptosis. Our preliminary immunohistochemical data in brain samples from patients with PML revealed increased expression of Survivin, a member of the inhibitors of apoptosis family, in bizarre astrocytes and in the intra-nuclear inclusion bodies of JCV infected oligodendrocytes. This protein is abundantly expressed during development in embryonic proliferating tissues, but is absent in terminally differenciated cells. It is believed that the mechanism of apoptosis inhibition involves the inactivation of caspases, the programmed cell death executioner proteins. Our results also show that JCV infected primary oligodendroglial cell cultures show enhanced expression of Survivin by Western blot and immunocytochemistry. In addition cell cycle analysis of infected cells demonstrated a reduction in the number of apoptotic cells and siRNA inhibition of Survivin resulted in a dramatic increase in apoptosis. These results suggest that JCV infection stimulates the expression of Survivin, which prevents apoptosis, and stimulates cell survival in order to compete its infectious cycle.