Stimulation of translation in 3T3-L1 cells in response to insulin and phorbol ester is directly correlated with increased phosphate labelling of initiation factor (eIF-) 4F and ribosomal protein S6.
One of the earliest responses to growth-promoting compounds in quiescent or serum-starved cells is stimulation of phosphorylation of ribosomal protein S6. Exposure of 3T3-L1 cells to insulin or phorbol ester (phorbol 12-myristate 13-acetate, PMA) also promotes phosphorylation of specific initiation factors. In this study, stimulation of phosphate labelling of S6, eIF-4F and eIF-4B in response to insulin and PMA has been examined in 3T3-L1 cells and compared with changes in protein synthesis. The rate of phosphate incorporation into eIF-4F and S6 is rapid and parallels the transient stimulation of protein synthesis observed with insulin. Whilst a similar correlation exists with PMA, the response is not as great as with insulin, but is more sustained. A role for the co-ordinate phosphorylation of initiation factors and ribosomal protein S6 in the stimulation of protein synthesis is discussed.
Morley
S J
SJ
Department of Biochemistry, University of California, Riverside 92521-0129.
Traugh
J A
JA
D016475:3T3 Cells; D000818:Animals; D001345:Autoradiography; D004591:Electrophoresis, Polyacrylamide Gel; D039562:Eukaryotic Initiation Factor-4F; D039642:Eukaryotic Initiation Factors; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D010448:Peptide Initiation Factors / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000187:drug effects*; D038601:Ribosomal Protein S6; D012269:Ribosomal Proteins / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D039562:Eukaryotic Initiation Factor-4F; D039642:Eukaryotic Initiation Factors; D007328:Insulin; D010448:Peptide Initiation Factors; D010710:Phosphates; D038601:Ribosomal Protein S6; D012269:Ribosomal Proteins; C031799:eIF-4B; D013755:Tetradecanoylphorbol Acetate