Disassociation of MAPK activation and c-Fos expression in F9 embryonic carcinoma cells following retinoic acid-induced endoderm differentiation.

Abstract

Retinoic acid induces cell differentiation and suppresses cell growth in a wide spectrum of cell lines, and down-regulation of activator protein-1 activity by retinoic acid contributes to these effects. In embryonic stem cell-like F9 teratocarcinoma cells, which are widely used to study retinoic acid actions on gene regulation and early embryonic differentiation, retinoic acid treatment for 4 days resulted in suppression of cell growth and differentiation into primitive and then visceral endoderm-like cells, accompanied by a suppression of serum-induced c-Fos expression. The MAPK (ERK) pathway was involved in mitogenic signaling in F9 cells stimulated with serum. Surprisingly, although c-Fos expression was reduced, the MAPK activity was not decreased by retinoic acid treatment. We found that retinoic acid treatment inhibited the phosphorylation of Elk-1, a target of activated MAPK required for c-Fos transcription. In F9 cells, the MAPK/MEK inhibitor PD98059 suppressed Elk-1 phosphorylation and c-Fos expression, indicating that MAPK activity is required for Elk-1 phosphorylation/activation. Phosphoprotein phosphatase 2B (calcineurin), the major phosphatase for activated Elk-1, is not the target in the disassociation of MAPK activation and c-Fos expression since its inhibition by cyclosporin A or activation by ionomycin had no significant effects on serum-stimulated c-Fos expression and Elk-1 phosphorylation. Thus, we conclude that retinoic acid treatment to induce F9 cell differentiation uncouples Ras/MAPK activation from c-Fos expression by reduction of Elk-1 phosphorylation through a mechanism not involving the activation of phosphoprotein phosphatase 2B.

• Authors: E R Smith, J L Smedberg, M E Rula, T C Hamilton, X X Xu
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 276 Issue 34 Pg. 32094-100 (Aug 24 2001) ISSN: 0021-9258 [Print] United States
• PMID: 11402055 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• DNA-Binding Proteins
• Elk1 protein, mouse
• Enzyme Inhibitors
• Flavonoids
• Proto-Oncogene Proteins
• Proto-Oncogene Proteins c-fos
• Transcription Factors
• ets-Domain Protein Elk-1
• Tretinoin
• Mitogen-Activated Protein Kinases
• Calcineurin
• 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one

Topics

• Animals
• Calcineurin (metabolism)
• Carcinoma, Embryonal (enzymology, metabolism, pathology)
• Cell Differentiation (drug effects)
• DNA-Binding Proteins
• Enzyme Activation
• Enzyme Inhibitors (pharmacology)
• Flavonoids (pharmacology)
• Mice
• Mitogen-Activated Protein Kinases (antagonists & inhibitors, metabolism)
• Phosphorylation
• Proto-Oncogene Proteins (metabolism)
• Proto-Oncogene Proteins c-fos (metabolism)
• Transcription Factors
• Tretinoin (pharmacology)
• Tumor Cells, Cultured
• ets-Domain Protein Elk-1