Hepatocyte growth factor activates the AP-1 complex: a comparison between normal and transformed rat hepatocytes.
OBJECTIVE
Stimulation of activator protein-1 (AP-1), a Fos/Jun complex, is a key event in the cell response to growth factors. We have investigated whether hepatocyte growth factor (HGF) induces differential AP-1 responses in normal and transformed rat hepatocytes, the 7777 cells.


METHODS
Primocultures of isolated hepatocytes or 7777 cells were stimulated with HGF. Gene expression was evaluated by ribonuclease protection assay and Western blot analysis. AP-1 DNA binding activity was measured by electrophoretic mobility shift assay. Identification of the proteins bound to the probes was made by supershift assays with specific antibodies. Cells were electroporated with plasmids containing an AP-1-dependent chloramphenicol acetyl transferase (CAT) gene, and CAT activity was measured 24 h after treatment with medium alone or HGF.


RESULTS
In both cell types, HGF triggered the same program of jun family mRNA activation, but distinct Fos/Jun proteins accumulated in the nucleus. HGF increased DNA-binding activity to the phorbol 12-O-tetradecanoate-13-acetate responsive element (TRE) in both cell types, but distinct TRE-binding proteins were recruited in the AP-1 dimers. HGF also increased consistently binding to a cAMP responsive element (CRE) in hepatocytes only. Finally, HGF triggered TRE- and CRE-dependent gene activations in hepatocytes but TRE-dependent gene activation alone in 7777 cells.


CONCLUSIONS
HGF-induced AP-1 activation leads to the formation of distinct dimers with different functional capacities in normal and transformed hepatocytes. These data suggest the importance of qualitative abnormalities of the AP-1 complex for the establishment or maintainance of a transformed phenotype.
Rahmani
M
M
Laboratoire de Biologie Cellulaire, INSERM U 327, Faculté de Médecine X, Bichat, Université Paris, France.
Nadori
F
F
Durand-Schneider
A M
AM
Lardeux
B
B
Bernuau
D
D
D000818:Animals; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000187:drug effects; D002478:Cells, Cultured; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D019281:Dimerization; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter; D016762:Genes, fos; D016758:Genes, jun; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D008114:Liver Neoplasms, Experimental; D008156:Luciferases / Q000235:genetics; D008297:Male; D009687:Nuclear Proteins / Q000378:metabolism; D010641:Phenotype; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured
D009687:Nuclear Proteins; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D017228:Hepatocyte Growth Factor; D008156:Luciferases; D015500:Chloramphenicol O-Acetyltransferase; D013755:Tetradecanoylphorbol Acetate