Evidence that extracellular signal-regulated kinases are the insulin-activated Raf-1 kinase kinases

Ruey Min Lee, Melanie H. Cobb, Perry J. Blackshear

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66 Scopus citations

Abstract

The Raf-1 proto-oncogene protein kinase can be phosphorylated and activated after stimulation of cells with insulin and a variety of other growth factors and mitogens. We recently presented evidence that insulin and certain other growth factors activated one or more Raf-1 kinase kinase activities (Lee, R. M., Rapp, U. R., and Blackshear, P. J. (1991) J. Biol. Chem. 266, 10351-10357). In the present study, four peaks of Raf-1 kinase kinase activity were identified after anion-exchange chromatography of cell lysates, and two of these were activated by insulin. Further chromatographic characterization of these two peaks of insulin-activated kinase activity indicated that they contained three apparently distinct kinase activities. Two of these activities comigrated with immunoreactive extracellular signal-regulated kinases (ERK) 1 and 2 (mitogen-activated protein kinase) through three different chromatographic separations. Both ERK1 and ERK2 phosphorylated Raf-1 with reasonably high affinity (K(m) for ERK1 = 90 nM; K(m) for ERK2 = 120 nM), and produced similar, complex phosphopeptide maps; both kinases also phosphorylated myelin basic protein. The third kinase activity also phosphorylated Raf-1 and myelin basic protein but did not comigrate exactly with either immunoreactive ERK1 or ERK2. We conclude that two and possibly three insulin-activated Raf-1 kinase kinases are members of the ERK family.

Original languageEnglish (US)
Pages (from-to)1088-1092
Number of pages5
JournalJournal of Biological Chemistry
Volume267
Issue number2
StatePublished - Jan 1 1992

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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