Stimulation of protein phosphatase activity by insulin and growth factors in 3T3 cells.
Incubation of Swiss mouse 3T3-D1 cells with physiological concentrations of insulin resulted in a rapid and transient activation of protein phosphatase activity as measured by using [32P]phosphorylase a as substrate. Activation reached a maximum level (140% of control value) within 5 min of addition and returned to control levels within 20 min. The effect of insulin was dose-dependent with half-maximal activation occurring at approximately 5 nM insulin. This activity could be completely inhibited by addition of the heat-stable protein inhibitor 2, which suggests the presence of an activated type-1 phosphatase. Similar effects on phosphatase activity were seen when epidermal growth factor and platelet-derived growth factor were tested. These results suggest that some of the intracellular effects caused by insulin and growth factors are mediated through the activation of a protein phosphatase.
Chan
C P
CP
Department of Pharmacology, University of Washington, Seattle 98195.
McNall
S J
SJ
Krebs
E G
EG
Fischer
E H
EH
D000818:Animals; D002413:Cations, Divalent; D002478:Cells, Cultured; D004492:Edetic Acid / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D051379:Mice; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010762:Phosphorylase a / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D014325:Tromethamine / Q000494:pharmacology; D014357:Trypsin / Q000494:pharmacology
D002413:Cations, Divalent; D007328:Insulin; D010982:Platelet-Derived Growth Factor; D014325:Tromethamine; D004815:Epidermal Growth Factor; D004492:Edetic Acid; D010762:Phosphorylase a; D010749:Phosphoprotein Phosphatases; D014357:Trypsin