Phosphorylation of elF-4E and initiation of protein synthesis in P19 embryonal carcinoma cells

✍ Scribed by Miranda Kleijn; Harry O. Voorma; Adri A. M. Thomas

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 1023 KB
• Volume: 59
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.240590405

✦ Synopsis

Mitogenic stimulation of protein synthesis is accompanied by an increase in elF-4E phosphorylation. The effect o n protein synthesis by induction of differentiation is less well known. We treated PI 9 embryonal carcinoma cells with the differentiating agent retinoic acid and found that protein synthesis increased during the first hour of addition. However, the phosphorylation state, as well as the turnover of phosphate on elF-4E, remained unchanged. Apparently, the change in protein synthesis after RA addition is regulated by another mechanism than elF-4E phosphorylation.

By using P I 9 cells overexpressing the EGF receptor, we show that the signal transduction pathway that leads to phosphorylation of elF-4E is present in P I 9 cells; the ECF-induced change in phosphorylation of elF-4E in these cells is likely to be regulated by a change in elF-4E phosphatase activity.

These results suggest that the onset of retinoic acid-induced differentiation is triggered by a signal transduction pathway which involves changes in protein synthesis, but not elF-4E phosphorylation.