Insulin stimulates phosphorylation of c-Jun, c-Fos, and Fos-related proteins in cultured adipocytes.
In differentiated 3T3-F442A adipocytes, insulin stimulated rapid and transient phosphorylation of c-Jun. Insulin also stimulated phosphorylation of c-Fos and several Fos-related proteins (pp72, pp45, and pp39) as indicated by precipitation with anti-c-Fos antibody following exposure to denaturating conditions. Phosphorylation of c-Fos was stimulated by 7-fold by 60 min, while phosphorylation of Fos-related proteins reached maxima of 3.5-5.5-fold at 15 to 60 min. The increase in phosphorylated c-Fos was due to an increase in both c-Fos protein and the stoichiometry of c-Fos phosphorylation, and was not observed in c-fos (-/-) cells. Additionally, insulin stimulated phosphorylation of a protein with molecular mass of approximately 82 kDa on tyrosine residues by 2.5-fold within 30 min; this protein appeared to be immunologically related to c-Fos. These increases in the phosphorylation of AP-1 transcription factors correlated with a > 5-fold stimulation of expression of a 12-O-tetradecanoylphorbol-13-acetate-responsive element-chloramphenicol acetyltransferase reporter gene transiently transfected into 3T3-F442A cells. These results indicate that insulin stimulates the phosphorylation of AP-1 transcription factors and several Fos-related proteins on serine and tyrosine residues. This is associated with changes in AP-1-mediated gene expression in vivo, suggesting that AP-1 phosphorylation by insulin plays a role in insulin-regulated gene expression.
Kim
S J
SJ
Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02215.
Kahn
C R
CR
D016475:3T3 Cells; D000255:Adenosine Triphosphate / Q000378:metabolism; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D015870:Gene Expression; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D051379:Mice; D010710:Phosphates / Q000378:metabolism; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine; D016760:Proto-Oncogene Proteins c-fos / Q000302:isolation & purification / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000302:isolation & purification / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D007328:Insulin; D010710:Phosphates; D010750:Phosphoproteins; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D019000:Phosphotyrosine; D014443:Tyrosine; D000255:Adenosine Triphosphate; D015500:Chloramphenicol O-Acetyltransferase; D013755:Tetradecanoylphorbol Acetate