Mitogen-activated Protein Kinase Kinase Inhibition Does Not Block the Stimulation of Glucose Utilization by Insulin (∗)

• Published in: The Journal of biological chemistry Vol. 270; no. 35; pp. 20801 - 20807
• Main Authors: Lazar, Dan F., Wiese, Russell J., Brady, Matthew J., Mastick, Cynthia Corley, Waters, Steven B., Yamauchi, Keishi, Pessin, Jeffrey E., Cuatrecasas, Pedro, Saltiel, Alan R.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.1995; American Society for Biochemistry and Molecular Biology
• Subjects: 3T3 Cells; Animals; Biological Transport - drug effects; Calcium-Calmodulin-Dependent Protein Kinases - antagonists & inhibitors; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Enzyme Activation; Enzyme Inhibitors - pharmacology; Flavonoids - pharmacology; Genes, fos; Glucose - metabolism; Glycogen - biosynthesis; Insulin - pharmacology; Kinetics; L Cells; Mice; Mitogen-Activated Protein Kinase Kinases; Phosphatidylinositol 3-Kinases; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor) - metabolism; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-fos - biosynthesis; Receptor, Insulin - metabolism; Transcriptional Activation - drug effects
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.270.35.20801

Insulin stimulates the activity of mitogen-activated protein kinase (MAPK) via its upstream activator, MAPK kinase (MEK), a dual specificity kinase that phosphorylates MAPK on threonine and tyrosine. The potential role of MAPK activation in insulin action was investigated with the specific MEK inhibitor PD98059. Insulin stimulation of MAPK activity in 3T3-L1 adipocytes (2.7-fold) and L6 myotubes (1.4-fold) was completely abolished by pretreatment of cells with the MEK inhibitor, as was the phosphorylation of MAPK and pp90Rsk, and the transcriptional activation of c-fos. Insulin receptor autophosphorylation on tyrosine residues and activation of phosphatidylinositol 3′-kinase were unaffected. Pretreatment of cells with PD98059 had no effect on basal and insulin-stimulated glucose uptake, lipogenesis, and glycogen synthesis. Glycogen synthase activity in extracts from 3T3-L1 adipocytes and L6 myotubes was increased 3-fold and 1.7-fold, respectively, by insulin. Pretreatment with 10 μM PD98059 was without effect. Similarly, the 2-fold activation of protein phosphatase 1 by insulin was insensitive to PD98059. These results indicate that stimulation of the MAPK pathway by insulin is not required for many of the metabolic activities of the hormone in cultured fat and muscle cells.