Insulin activates a novel adipocyte mitogen-activated protein kinase kinase kinase that shows rapid phasic kinetics and is distinct from c-Raf
| Autor: | C M, Haystead, P, Gregory, A, Shirazi, P, Fadden, C, Mosse, P, Dent, T A, Haystead |
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| Rok vydání: | 1994 |
| Předmět: |
Male
Mitogen-Activated Protein Kinase 1 Mitogen-Activated Protein Kinase Kinases Protein Serine-Threonine Kinases Protein-Tyrosine Kinases Chromatography Ion Exchange MAP Kinase Kinase Kinases Rats Enzyme Activation Proto-Oncogene Proteins c-raf Kinetics Proto-Oncogene Proteins Adipocytes Chromatography Gel Phosphoprotein Phosphatases Animals Insulin Tetradecanoylphorbol Acetate Protein Phosphatase 2 Rats Wistar |
| Zdroj: | The Journal of biological chemistry. 269(17) |
| ISSN: | 0021-9258 |
| Popis: | Treatment of adipocytes with insulin or phorbol 12-myristate 13-acetate (PMA) results in transient activation of mitogen-activated protein kinase kinase (MEK) (Tmax = 90 s) and mitogen-activated protein kinase (MAPK) (Tmax = 300 s). We have identified a novel insulin-stimulated MEK kinase (I-MEKK) in the 100,000 x g infranatant that shows rapid phasic kinetics that temporally precede that of MEK. Maximal activation of I-MEKK occurs within 20 +/- 5 s (S.D., n = 3) followed by complete inactivation by 30 +/- 10 s (S.D., n = 3). I-MEKK was characterized by anion-exchange and gel filtration chromatography and separated into two distinct activities of approximately 56 kDa that phosphorylated and activated MEK. I-MEKKs did not co-elute on anion exchange with c-Raf or 73-kDa MEK kinase (MEKK), suggesting they are distinct enzymes. Protein phosphatase 2A inactivated both I-MEKKs in vitro and in the intact cell okadaic acid blocked inactivation in the presence of insulin. These results suggest activation of I-MEKK involves phosphorylation on serine or threonine residues. I-MEKK was not activated by PMA, suggesting that in adipocytes the enzyme represents a divergence point between signal transduction pathways mediated by insulin and those activating protein kinase C. |
| Databáze: | OpenAIRE |
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