Regulation of the alpha 2(I) collagen gene transcription in fat-storing cells derived from a cirrhotic liver.
Fat-storing cells (FSC) are the main producers of type I collagen in both normal and fibrotic livers. In order to elucidate the molecular mechanisms controlling collagen expression in FSC, we examined the transcription of the alpha 2(I) collagen gene (COL1A2) in two distinct FSC clones, CFSC-2G and CFSC-5H, derived from a single CCl4-induced cirrhotic liver. The phenotype of CFSC-2G resembles freshly isolated FSC, whereas that of CFSC-5H mimics activated myofibroblasts. Cell transfection experiments showed that the upstream sequence between nucleotides -378 and -183 is essential for COL1A2 transcription in both FSC clones. This is the same promoter region that is transcriptionally active and contains the binding site of a multimeric protein complex that mediates TGF-beta stimulation of COL1A2 expression in dermal fibroblasts. We therefore examined the relative levels of endogenous and transfected COL1A2 transcription and their response to TGF-beta treatment in the two FSC clones. The results showed that CFSC-5H expresses a significantly higher level of the COL1A2 mRNA than CFSC-2G. They also showed that TGF-beta treatment increases both endogenous and transfected COL1A2 transcription in CFSC-2G but not in CFSC-5H. Interestingly, nuclear proteins from both FSC clones bind to the TGF-beta-responsive element more strongly than those from dermal fibroblasts. Altogether, the data suggest that collagen production in CFSC-5H cells has been already activated by the autocrine stimulation of TGF-beta. In contrast, CFSC-2G cells are only partially activated but can be easily recruited to produce collagen when stimulated by exogenous TGF-beta.(ABSTRACT TRUNCATED AT 250 WORDS)
Inagaki
Y
Y
First Department of Internal Medicine, Kanazawa University School of Medicine, Japan.
Truter
S
S
Greenwel
P
P
Rojkind
M
M
Unoura
M
M
Kobayashi
K
K
Ramirez
F
F
D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D015152:Blotting, Northern; D002251:Carbon Tetrachloride; D003094:Collagen / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D008106:Liver Cirrhosis, Experimental / Q000139:chemically induced / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D009687:Nuclear Proteins; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D003094:Collagen; D002251:Carbon Tetrachloride