Multiple components in an epidermal growth factor-stimulated protein kinase cascade. In vitro activation of a myelin basic protein/microtubule-associated protein 2 kinase.
Epidermal growth factor stimulates the activity of several cytosolic serine/threonine protein kinases in quiescent Swiss 3T3 cells. Two of these, which use myelin basic protein (MBP) as substrate, act as kinase kinases in that they are able to activate a separate peptide kinase activity in vitro by a mechanism involving protein phosphorylation. In this study, we have identified two activities from extracts of epidermal growth factor-treated cells that stimulate an ATP-dependent activation of both of the MBP kinases, derived in their inactive precursor forms from extracts of untreated cells. The resulting MBP kinase activities are stable to further purification and can be inactivated with either tyrosine or serine/threonine protein phosphatases and then reactivated to their original levels of activity. Thus, we propose that the in vitro activation involves protein phosphorylation, stimulated by the action of novel MBP kinase activating factors that represent intermediate components in a growth factor-stimulated kinase cascade.
Ahn
N G
NG
Department of Biochemistry, University of Washington, Seattle 98195.
Seger
R
R
Bratlien
R L
RL
Diltz
C D
CD
Tonks
N K
NK
Krebs
E G
EG
D000595:Amino Acid Sequence; D000818:Animals; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000502:physiology*; D038362:Glycogen Synthase Kinase 3; D066298:In Vitro Techniques; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D004676:Myelin Basic Protein / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction
D008869:Microtubule-Associated Proteins; D004676:Myelin Basic Protein; D010455:Peptides; D010750:Phosphoproteins; D004815:Epidermal Growth Factor; D011494:Protein Kinases; D038362:Glycogen Synthase Kinase 3; D010749:Phosphoprotein Phosphatases