Inhibition of the Mitogen-activated Protein Kinase Pathway Triggers B16 Melanoma Cell Differentiation

• Published in: The Journal of biological chemistry Vol. 273; no. 16; pp. 9966 - 9970
• Main Authors: Englaro, W, Bertolotto, C, Buscà, R, Brunet, A, Pagès, G, Ortonne, J P, Ballotti, R
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 17.04.1998
• Subjects: Animals; Calcium-Calmodulin-Dependent Protein Kinases - antagonists & inhibitors; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Cell Differentiation - drug effects; Cellular Biology; Colforsin - pharmacology; Cyclic AMP - metabolism; Enzyme Inhibitors - pharmacology; Flavonoids - pharmacology; Life Sciences; Luciferases - metabolism; Melanoma, Experimental - pathology; Mice; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinase Kinases; Mitogen-Activated Protein Kinases; Monophenol Monooxygenase - metabolism; Protein Kinase Inhibitors; Protein Kinases - metabolism; Recombinant Fusion Proteins - metabolism; Tetradecanoylphorbol Acetate - pharmacology; Transfection; Tumor Cells, Cultured
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.273.16.9966

In B16 melanoma cells, mitogen-activated protein (MAP) kinases are activated during cAMP-induced melanogenesis (Englaro, W., Rezzonico, R., Durand-Clément, M., Lallemand, D., Ortonne, J. P., and Ballotti, R. (1995) J. Biol. Chem. 270, 24315–24320). To establish the role of the MAP kinases in melanogenesis, we studied the effects of a specific MAP kinase kinase (MEK) inhibitor PD 98059 on different melanogenic parameters. We showed that PD 98059 inhibits the activation of MAP kinase extracellular signal-regulated kinase 1 by cAMP, but does not impair the effects of cAMP either on the morphological differentiation, characterized by an increase in dendrite outgrowth, or on the up-regulation of tyrosinase that is the key enzyme in melanogenesis. On the contrary, PD 98059 promotes by itself cell dendricity and increases the tyrosinase amount and activity. Moreover, down-regulation of the MAP kinase pathway by PD 98059, or with dominant negative mutants of p21 ras and MEK, triggers a stimulation of the tyrosinase promoter activity and enhances the effect of cAMP on this parameter. Conversely, activation of the MAP kinase pathway, using constitutive active mutants of p21 ras and MEK, leads to an inhibition of basal and cAMP-induced tyrosinase gene transcription. These results demonstrate that the MAP kinase pathway activation is not required for cAMP-induced melanogenesis. Furthermore, the inhibition of this pathway induces B16 melanoma cell differentiation, while a sustained activation impairs the melanogenic effect of cAMP-elevating agents.