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Rac1 contributes to maximal activation of STAT1 and STAT3 in IFN-gamma-stimulated rat astrocytes.

Authors
Park, EJ; Ji, KA; Jeon, SB; Choi, WH; Han, IO; You, HJ; Kim, JH; Jou, I; Joe, EH
Citation
Journal of immunology (Baltimore, Md. : 1950), 173(9):5697-5703, 2004
Journal Title
Journal of immunology (Baltimore, Md. : 1950)
ISSN
0022-17671550-6606
Abstract
Rac1 GTPase is implicated as a signaling mediator in various cellular events. In this study, we show that Rac1 contributes to IFN-gamma-induced inflammatory responses in rat astrocytes. We revealed that IFN-gamma rapidly stimulated activation of Rac1 in C6 astroglioma cells by investigating GST-PAK-PBD-binding ability. We also found that Rac1 deficiency led to attenuation of IFN-gamma-responsive transcriptional responses. Compared with levels in control cells, IFN-gamma-induced IFN-gamma-activated sequence promoter activity was markedly reduced in both C6 astroglioma cells and primary astrocytes expressing RacN17, a well-characterized Rac1-negative mutant. The expression of several IFN-gamma-responsive genes, such as MCP-1 and ICAM-1, was also reduced in cells expressing RacN17. Consistent with these observations, IFN-gamma-induced phosphorylation of STAT1 and STAT3 was lower in C6 cells expressing RacN17 (referred to as C6-RacN17) than in control cells. However, there was no difference in expression level of IFN-gammaRalpha subunit and IFN-gamma-induced phosphorylation of JAK1 between C6 control and C6-RacN17 cells. Interestingly, Rac1 appeared to associate with IFN-gammaRalpha and augment the interaction of IFN-gammaR with either STAT1 or STAT3 in response to IFN-gamma. Taken together, we suggest that Rac1 may serve as an auxiliary mediator of IFN-gamma-signaling, at least at the level of STAT activation, thus contributing to maximal activation of IFN-gamma-responsive inflammatory signaling in rat astrocytes.
MeSH terms
AnimalsAstrocytes/*immunology/*metabolismCell Line, TumorDNA-Binding Proteins/antagonists & inhibitors/biosynthesis/genetics/*metabolismGene Expression Regulation/immunologyInterferon-gamma/antagonists & inhibitors/*physiologyJanus Kinase 1PhosphorylationProtein Subunits/biosynthesis/metabolismProtein-Tyrosine Kinases/metabolismRatsRats, Sprague-DawleyReceptors, Interferon/biosynthesis/metabolismResponse Elements/geneticsSTAT1 Transcription FactorSTAT3 Transcription FactorSignal Transduction/*immunologyTrans-Activators/antagonists & inhibitors/biosynthesis/genetics/*metabolismTransfectionrac1 GTP-Binding Protein/biosynthesis/genetics/metabolism/*physiology
PMID
15494521
Appears in Collections:
Journal Papers > School of Medicine / Graduate School of Medicine > Pharmacology
Journal Papers > Research Organization > Chronic Inflammatory Disease Research Center
AJOU Authors
박, 은정주, 일로조, 은혜
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