LRG-47 (Irgm1), also known p47GTPase, is an interferon (IFN)-?-inducible family of intracellular 47 kDa GTPases. LRG-47 has been shown to contribute to host resistance to certain intracellular pathogens, such as mycobacterial tuberculosis and toxoplasmagondii etc. We performed microarray analysis to identify differences in gene expression between mice-induced by myelin basic protein (MBP) and naive mice. Prominent upregulation of LRG-47 was observed in experimental autoimmune encephalomyelitis (EAE)-induced animal, which was confirmed by quantitative real-time PCR and Western blot. Indeed, levels of LRG-47 were robustly elevated in multiple sclerosis (MS)-affected tissue from patients and in the central nervous system (CNS) of EAE mice, especially in cells of lymphoid and mononuclear phagocyte origin. These preliminary data indicate the potential significance of LRG-47 in the pathogenesis of EAE, and possibly, MS. We hypothesize that blockade of LRG-47 may have a protective effect in EAE-induced mice. Based on our preliminary studies, we propose that mechanisms underlying LRG-47-mediated survival of autoreactive T-cells, activation of transcription factors and signal transduction mechanisms linked to a cell survival pathway (PI3-K/Akt), and dysregulation of cytokines, such as IFN-? and IL-17, contribute to the pathogenesis of EAE relevant to MS. Lastly, we propose that LRG-47, expressed by oligodendrocytes may also have potential impact on the cellular events of EAE. The proposed studies are to determine the effect of blocking LRG-47 on induction of EAE and to delineate the mechanisms underlying LRG-47-mediated molecular and cellular events in EAE, focusing on encephalitogenic CD4+ T-cells, and oligodendrocytes. Utilizing a novel genetically manipulated transgenic mouse model (genetic global deficient-LRG-47 mice (LRG-47-/-) and Cre recombinase LRG-47 deficient mice targeted to oligodendrocytes under the control of mouse proteolipid protein (myelin, Plp-LRG-47-/-) 1 promoter, we will fully address our hypothesis and establish the benefits of LRG-47 blockade as a therapeutic strategy in a mouse model of EAE. Thus, we will address these concepts experimentally according to the following specific aims: 1) to establish whether blockade of LRG-47 in encephalitogenic CD4 T cells attenuates development of EAE;2) to determine whether LRG-47-mediated survival of autoreactive T cells and activation of signal transduction [phosphoinositide 3-kinase (PI3-K)/ protein kinase (Akt)] contribute to the induction of EAE;3) to determine whether LRG-47-induced cytokine production (IFN-3 and IL-17) contributes importantly to the development of EAE, and 4) to analyze the contribution of LRG-47 in oligodendrocytes to the development of EAE.
The goals of our proposal are to delineate new mechanisms through which LRG-47contributes to the pathogenesis of EAE, focusing on cell survival-related signal transduction, activation and termination of encephalitogenic T cell in response to MBP and regulation of cytokine production related to Th1 and Th17, oligodendrocyte function, and to establish the benefits of LRG-47 blockade as a therapeutic strategy in the EAE mouse model relevant to multiple sclerosis.
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