Dominant-negative effect of the c-fos family gene products on inducible NO synthase expression in macrophages.
Int Immunol
; 15(11): 1275-82, 2003 Nov.
Article
em En
| MEDLINE
| ID: mdl-14565925
Activation of murine peritoneal macrophages or the macrophage cell line RAW264 with IFN-gamma and bacterial lipopolysaccharide promotes a transient up-regulation of c-fos family gene expression following inducible NO synthase (iNOS) production. Since introduction of a double mutation into the two AP-1-binding sites in the iNOS promoter region reduced the promoter activity to 25% of the authentic one in activated RAW264 cells, the induced c-Fos/AP-1 may promote iNOS expression in activated macrophages. Surprisingly, overexpression of c-fos in activated macrophages completely suppressed the production of iNOS, but not that of IL-6 and IL-1beta. The regulatory effect was also observed by overexpression of c-fos, c-jun or fosB on the promoter activity as deduced from transfection experiments. However, the mutation of AP-1-binding sites in the promoter region did not abrogate the regulatory effect of c-fos and the effect of c-fos was diminished by co-transfection with c-jun, but not with fosB, suggesting no relation between the regulatory effect and a c-Fos/AP-1 complex. Expression of NF-IL6 (C/EBPbeta), whose gene product can make a non-functional heterodimer with c-Fos family proteins, was transiently induced in activated macrophages. Overexpression of NF-IL6 in activated RAW264 cells augmented iNOS promoter activity and reduced the regulatory effect of c-fos overexpression. Thus, overproduction of c-Fos family proteins acts as a dominant-negative-type regulator on iNOS expression in activated macrophages.
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Base de dados:
MEDLINE
Assunto principal:
Proteínas Proto-Oncogênicas c-fos
/
Óxido Nítrico Sintase
/
Macrófagos
Limite:
Animals
Idioma:
En
Ano de publicação:
2003
Tipo de documento:
Article