Expression and Function of SOCS Proteins in Glial Cells

描述(由申请人提供)：我们的目标是了解中枢神经系统内免疫和炎症反应的基础。巨噬细胞/小胶质细胞和星形胶质细胞的免疫激活导致细胞因子的产生，影响神经胶质细胞和神经元的功能。细胞因子在中枢神经系统中具有深远的作用，包括启动和调节免疫/炎症反应。巨噬细胞/小胶质细胞和星形胶质细胞不仅产生 细胞因子，但也通过细胞表面受体对它们作出反应。巨噬细胞/小胶质细胞和星形胶质细胞的激活通常旨在促进濒危的中枢神经系统成分和功能的有益恢复。然而，对这些细胞的过度和持续刺激会导致急性和慢性神经病理。因此，巨噬细胞/小胶质细胞和星形胶质细胞细胞因子的产生和反应的失调可能会促进直接的神经毒性，并干扰神经细胞的功能。细胞因子的生物学效应是由细胞内信号转导途径介导的，最常见的是Janus Kinase(JAK)和信号转导和转录激活因子(STAT)途径(JAK-STAT)。涉及中枢神经系统病理的细胞因子包括干扰素-γ、干扰素-β和白介素6家族成员，所有这些成员都通过JAK-STAT通路传递信号。对JAK和STAT激活的幅度和持续时间进行精确的调控是至关重要的，因为JAK-STAT通路的失调具有病理意义。细胞因子信号转导抑制因子(SOCS)蛋白的功能是抑制JAK-STAT通路。SOCS蛋白可被细胞因子诱导，并通过直接与细胞因子受体链或相关JAK结合来抑制酪氨酸激酶活性，从而在负反馈循环中发挥作用。 关于SOCS蛋白在体内的表达和功能的信息有限 中枢神经系统。我们的初步结果表明，SOCS-1和SOCS-3都能减弱巨噬细胞/小胶质细胞和星形胶质细胞中免疫/炎症反应关键基因的表达。我们假设SOCS-1/SOCS-3的表达将通过抑制细胞因子诱导的炎症和免疫反应而减弱这些细胞的激活，从而对免疫介导的中枢神经系统疾病起到有利的作用。我们将检测星形胶质细胞、小胶质细胞和巨噬细胞在中枢神经系统相关刺激下表达SOCS-1/SOCS-3蛋白的能力，并阐明SOCS-1/SOCS-3基因转录的转录程序(目标1和3)。还将使用以诱导方式表达针对SOCS-1/SOCS-3的siRNA的巨噬细胞和星形胶质细胞系来检测SOCS-1/SOCS-3调节神经胶质细胞和巨噬细胞的免疫和炎症反应的能力(目标2和4)。我们提出的研究将首次对SOCS-1/SOCS-3在中枢神经系统细胞中的产生和功能进行生物学评估，从而为未来评估SOCS-1/SOCS-3作为中枢神经系统炎症和神经毒性反应的衰减剂提供基础。

DESCRIPTION (provided by applicant): Our goal is to understand the basis of immune and inflammatory responses within the CNS. Immunological activation of macrophages/microglia and astrocytes leads to the production of cytokines that impact on glial and neuronal function. Cytokines have far-reaching effects in the CNS, including the initiation and regulation of immune/inflammatory responses. Macrophages/microglia and astrocytes not only produce cytokines, but also respond to them via cell surface receptors. Macrophage/microglial and astrocytic activation in general is aimed at promoting a beneficial restoration of endangered CNS elements and functions. However, excessive and sustained stimulation of these cells contributes to acute and chronic neuropathologies. Therefore, dysregulation of macrophage/microglial and astrocytic cytokine production and responsiveness may promote direct neurotoxicity, as well as disturb neural cell functions. The biological effects of cytokines are mediated by intracellular signal transduction pathways; the most common being the Janus Kinase (JAK) and Signal Transducer and Activator of Transcription (STAT) pathway (JAK-STAT). Cytokines implicated in CNS pathology include IFN-y, IFN-p and IL-6 family members, all of which signal through the JAK-STAT pathway. A precise regulation of both the magnitude and duration of JAK and STAT activation is essential, as dysregulation of the JAK-STAT pathway has pathological implications. Suppressors of Cytokine Signaling (SOCS) proteins function to inhibit the JAK-STAT pathway. SOCS proteins are inducible by cytokines, and inhibit signaling by directly binding to cytokine receptor chains or associated JAKs to inhibit tyrosine kinase activity, thereby functioning in a negative feedback loop. There is limited information regarding the expression and function of SOCS proteins within the CNS. Our preliminary results indicate that both SOCS-1 and SOCS-3 function to attenuate expression of genes critical for immune/inflammatory responses in macrophages/microglia and astrocytes. We hypothesize that expression of SOCS-1/SOCS-3 will attenuate cytokine-induced inflammatory and immune responses by inhibiting activation of these cells, thereby exerting beneficial effects for immune-mediated CNS diseases. We will examine the ability of astrocytes, microglia and macrophages to express SOCS-1/SOCS-3 proteins in response to CNS-relevant stimuli, and elucidate the transcriptional programs underlying SOCS-1/SOCS-3 gene transcription (Aims 1 and 3). The ability of SOCS-1/SOCS-3 to modulate immunological and inflammatory responses in glial cells and macrophages will also be examined (Aims 2 and 4), using macrophage and astroglial cell lines that express siRNA against SOCS-1/SOCS-3 in an inducible manner. Our proposed studies will provide the first biological assessment of SOCS-1/SOCS-3 production and function in cells of the CNS, thereby providing the basis for future assessment of SOCS-1/SOCS-3 as attenuators of inflammatory and neurotoxic responses in the CNS.