Interferon Gamma Effects on Oligodendrocytes

性状（由申请人提供）：干扰素-？(IFN-?)被认为在免疫介导的CNS疾病多发性硬化症（MS）及其小鼠模型实验性自身免疫性脑脊髓炎（EAE）中起关键作用。我们已经证明，IFN-？激活髓鞘形成和髓鞘再生少突胶质细胞中的严重内质网（ER）应激反应，导致少突胶质细胞凋亡和髓鞘异常。然而，存在可比水平的IFN-？在成年小鼠未受干扰的CNS中，仅诱导适度的ER应激，并且不减少成熟的少突胶质细胞存活或导致髓鞘不规则。事实上，我们已经表明，在成年少突胶质细胞中激活的应激反应提供了对随后的少突胶质细胞损伤的保护。ER应激反应激活胰腺ER激酶（PERK），其使真核翻译起始因子21磷酸化并特异性地维持应激ER中的客户蛋白稳态。我们的研究表明，发展和髓鞘再生少突胶质细胞从小鼠是单倍不足的PERK更敏感的IFN-？并且来自这些动物的成熟少突胶质细胞不受细胞因子的保护。我们还发现，调节蛋白生长停滞和DNA损伤34（GADD 34），一个应激诱导的磷酸酶复合物的调节亚基，去磷酸化eIF 2a，选择性上调髓鞘少突胶质细胞在小鼠异位表达IFN-？在CNS。在本研究中，我们计划进一步详细描述髓鞘化少突胶质细胞的ER应激反应。对于这些研究，我们将操纵PERK（目的1）以及GADD 34（目的2）在髓鞘细胞中的活性，以更好地了解这些细胞对ER应激反应的超敏性。此外，我们将探讨IFN-？增强少突胶质细胞的内质网应激反应。两种可能性，这不是相互排斥的，将探讨：在目标3，我们将确定如果IFN-？在ER中加工的抗原呈递（MHC）分子的刺激表达有助于应激反应，并且在目的4中，我们将确定是否由IFN-β诱导的一氧化氮（NO）的存在增加，导致内质网应激反应的激活。总之，这些研究应提供必要的机制的洞察力的策略，对少突胶质细胞的ER应激反应的操作发展。集中于ER应激反应的调节的治疗方法可能证明在减少脱髓鞘病变的数量和/或增强免疫介导的脱髓鞘疾病中的髓鞘修复方面是有益的。公共卫生相关性：多发性硬化是一种以中枢神经系统炎症和脱髓鞘为特征的自身免疫性疾病，与少突胶质细胞凋亡和轴突变性有关。本提案中描述的研究的基本前提是少突胶质细胞（CNS的髓鞘形成细胞）对炎症反应特别敏感。我们的研究表明，炎症反应导致少突胶质细胞分泌途径的破坏，这可能显示出对这种破坏的敏感性增强，因为它们在髓鞘生成中的主要作用。当前提案中描述的研究旨在进一步表征免疫介导的脱髓鞘疾病中的这一潜在重要临床靶点。

DESCRIPTION (provided by applicant): Interferon-? (IFN-?) is believed to play a critical role in the immune-mediated CNS disorder multiple sclerosis (MS) and its mouse model experimental autoimmune encephalomyelitis (EAE). We have demonstrated that IFN-? activates a severe endoplasmic reticulum (ER) stress response in myelinating and remyelinating oligodendrocytes that causes oligodendrocyte apoptosis and myelin abnormalities. Nevertheless, the presence of comparable levels of IFN-? in the unperturbed CNS of adult mice induces only modest ER stress, and does not diminish mature oligodendrocyte survival or result in myelin irregularity. In fact we have shown that the stress response activated in adult oligodendrocytes provides protection against subsequent oligodendroglial insults. The ER stress response activates the pancreatic ER kinase (PERK), which phosphorylates the eukaryotic translation initiation factor 21 and specifically maintains client protein homeostasis in the stressed ER. Our studies demonstrate that developing and remyelinating oligodendrocytes from mice that are haploinsufficient for PERK are more sensitive to the presence of IFN-? and that mature oligodendrocytes from these animals are not protected by the cytokine. We have also found that the regulatory protein growth arrest and DNA damage 34 (GADD34), a stress-inducible regulatory subunit of a phosphatase complex that dephosphorylates eIF2a, is selectively upregulated in myelinating oligodendrocytes in mice that ectopically express IFN-? in the CNS. In the studies outlined in this proposal we plan to characterize in further detail the ER stress response in myelinating oligodendrocytes. For these studies we will manipulate PERK (aim 1) as well as GADD34 (aim 2) activity in myelinating cells to gain a better understanding of the hypersensitive of these cells to the ER stress response. In addition, we will explore the molecular mechanism by which IFN-? elicits the ER stress response in oligodendrocytes. Two possibilities, which are not mutually exclusive, will be explored: in aim 3 we will determine if IFN-? -stimulated expression of antigen presenting (MHC) molecules, which are processed in the ER, contributes to the stress response, and in aim 4 we will determine whether the increased presence of nitric oxide (NO), which is induced by IFN-?, leads to an activation of the ER stress response. Together, these studies should provide the mechanistic insight necessary for the development of strategies toward the manipulation of the ER stress response in oligodendrocytes. Therapeutic approaches focused on the modulation of the ER stress response might prove beneficial in reducing the number of demyelinated lesions and/or enhancing myelin repair in immune-mediated demyelinating disorders. PUBLIC HEALTH RELEVANCE: Multiple sclerosis is an autoimmune disease characterized by CNS inflammation and demyelination, which are associated with oligodendrocyte apoptosis and axonal degeneration. The underlying premise of the studies described in this proposal is that oligodendrocytes, the myelinating cell of the CNS, are particularly sensitive to the inflammatory reaction. Our studies indicate that the inflammatory response results in a disruption of the secretory pathway in oligodendrocytes, which likely display enhanced sensitivity to such disruptions because of their primary role in the generation of the myelin sheath. The studies described in the current proposal are designed to further characterize this potentially important clinical target in immune-mediated demyelinating disorders.