Class II MHC gene expression in microglia. Regulation by the cytokines IFN-gamma, TNF-alpha, and TGF-beta.
The molecular mechanism(s) by which three cytokines (IFN-gamma, TNF-alpha, TGF-beta) affect class II MHC gene expression in primary rat microglia was examined. IFN-gamma is a potent inducer of the class II gene, and this induction is unaffected by treatment with either TNF-alpha or TGF-beta. Transient transfection of primary rat microglia with an HLA-DRA promoter linked to the chloramphenicol acetyltransferase reporter gene (DRA-CAT) demonstrated that IFN-gamma acts at the transcriptional level to induce class II MHC gene expression, and that TNF-alpha and TGF-beta have no influence on IFN-gamma-induced promoter activity. Experiments using a series of DRA substitution mutants that individually affect the W, X1, X2, or Y elements, as well as a double mutation in both X1 and X2, indicate that all four of these elements are required for responsiveness of the DRA promoter to IFN-gamma. The effect of IFN-gamma and TNF-alpha on DNA binding proteins by microglia was examined. A constitutive complex with specificity for the X2 box was detected in extracts from unstimulated microglia. IFN-gamma treatment changed this complex to migrate with slower mobility, and TNF-alpha had no effect on either the constitutive or IFN-gamma-induced complexes. These studies provide information on the molecular regulation of the class II MHC gene in microglia, a cell type critically involved in immune regulation within the central nervous system.
Panek
R B
RB
Department of Cell Biology, University of Alabama at Birmingham 35294.
Benveniste
E N
EN
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000276:immunology; D006684:HLA-DR Antigens / Q000235:genetics; D059805:HLA-DR alpha-Chains; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis*; D007371:Interferon-gamma / Q000502:physiology*; D017628:Microglia / Q000276:immunology*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
D004268:DNA-Binding Proteins; D006684:HLA-DR Antigens; D059805:HLA-DR alpha-Chains; D000949:Histocompatibility Antigens Class II; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma