DEP-induced fra-1 expression correlates with a distinct activation of AP-1-dependent gene transcription in the lung.
Recent studies indicate a potential role for Fra-1, a heterodimeric partner of activator protein (AP)-1, in toxicant-induced epithelial injury, repair, and cellular transformation. Here we have investigated the effects of diesel exhaust particles (DEP) on fra-1 expression in C10 cells, a murine lung epithelial cell line. DEP markedly upregulated fra-1, but not fra-2, expression. The increase in fra-1 mRNA expression correlated well with its protein- and DNA-binding activity. DNA-binding assays also revealed a predominant presence of Jun-B and Jun-D in the AP-1 complex. Interestingly, DEP did not alter Jun-B and Jun-D protein levels. Transcriptional analysis revealed that fra-1 induction is regulated in part at the transcriptional level. The -379 to +32 bp 5'-flanking region mediated this induction. Furthermore, inhibitors of ERK1/2, JNK1, and p38 mitogen-activated protein kinases (MAPKs) significantly suppressed DEP-stimulated fra-1 transcription, suggesting their involvement in the induction process. Consistent with this finding, DEP stimulated phosphorylation of ERK1/2, JNK1, and p38 MAPKs with a distinct activation pattern. Overexpression of Fra-1 downregulated c-Jun and Nrf2 enhanced AP-1- and ARE-mediated reporter gene expression, respectively. In contrast, Fra-1 had the opposite effect on matrix metalloproteinase (MMP)-9 promoter activity. In particular, it bound to the functional AP-1 site of the MMP-9 promoter after DEP stimulation. Consistent with this result, DEP also markedly upregulated MMP-9 promoter activity. Collectively, these findings suggest that fra-1 induction by DEP may play a role in selectively regulating gene expression involved in alveolar epithelial cell injury and repair.
Zhang
Qin
Q
The Johns Hopkins University, Department of Environmental Health Sciences, Bloomberg School of Public Health, Baltimore, MD 21205, USA.
Kleeberger
Steven R
SR
Reddy
Sekhar P
SP
D000818:Animals; D002461:Cell Line, Transformed; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology; D051921:Fos-Related Antigen-2; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D051267:NF-E2-Related Factor 2; D010766:Phosphorylation / Q000187:drug effects; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D020545:Respiratory Mucosa / Q000166:cytology / Q000502:physiology*; D015534:Trans-Activators / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects* / Q000502:physiology; D001335:Vehicle Emissions / Q000633:toxicity*; D048051:p38 Mitogen-Activated Protein Kinases; D000099169:Fos-Related Antigen 1
D004268:DNA-Binding Proteins; D051921:Fos-Related Antigen-2; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases; D051267:NF-E2-Related Factor 2; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D015534:Trans-Activators; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D001335:Vehicle Emissions; D048051:p38 Mitogen-Activated Protein Kinases; D000099169:Fos-Related Antigen 1; C497873:Fosl2 protein, mouse; C495636:Nfe2l2 protein, mouse