Interferon Gamma Effects on Oligodendrocytes

描述（申请人提供）：干扰素-？（IFN-?）被认为在免疫介导的中枢神经系统疾病多发性硬化症（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。我们已经证明了IFN-？在髓鞘形成和再髓鞘形成的少突胶质细胞中激活严重的内质网应激反应，导致少突胶质细胞凋亡和髓鞘异常。然而，IFN-？在未受干扰的成年小鼠中枢神经系统中，仅诱导适度的内质网应激，并且不会减少成熟少突胶质细胞的存活或导致髓鞘不规则。事实上，我们已经证明，在成人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损伤的保护。内质网应激反应激活胰腺内质网激酶（PERK），该激酶磷酸化真核翻译起始因子21，并在应激内质网中特异性维持客户蛋白稳态。我们的研究表明，来自PERK单倍不足的小鼠的发育和再生少突胶质细胞对IFN-？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，调控蛋白生长阻滞和DNA损伤34 （GADD34）是一种脱除eIF2a的磷酸酶复合体的应激诱导调控亚基，在异位表达IFN-？中枢神经系统。在本提案中概述的研究中，我们计划进一步详细描述髓鞘少突胶质细胞的内质网应激反应。在这些研究中，我们将操纵髓鞘细胞中的PERK（目标1）和GADD34（目标2）活性，以更好地了解这些细胞对内质网应激反应的超敏感性。此外，我们将探讨IFN-？引起少突胶质细胞内质网应激反应。我们将探讨两种并非相互排斥的可能性：在目标3中，我们将确定IFN-？-刺激抗原呈递（MHC）分子的表达，在内质网中处理，有助于应激反应，在目标4中，我们将确定IFN-诱导的一氧化氮（NO）的增加是否会导致应激反应。导致内质网应激反应的激活。总之，这些研究应该为少突胶质细胞内质网应激反应调控策略的发展提供必要的机制见解。在免疫介导的脱髓鞘疾病中，专注于调节内质网应激反应的治疗方法可能有助于减少脱髓鞘病变的数量和/或增强髓鞘修复。公共卫生相关性：多发性硬化症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。本提案所述研究的基本前提是，中枢神经系统的髓鞘细胞少突胶质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通路的破坏，由于它们在髓鞘的生成中起主要作用，因此可能对这种破坏表现出增强的敏感性。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这一潜在重要的临床靶点。

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.