Modulation of Kit/stem cell factor receptor-induced signaling by protein kinase C.
The Kit/stem cell factor receptor (Kit/SCF-R) is a transmembrane tyrosine kinase receptor of importance for the normal development of hemopoietic cells, melanoblasts, and germ cells. We recently reported that protein kinase C (PKC) is involved in a negative feedback loop regulating the Kit/SCF-R by direct phosphorylation on serine residues in the receptor. Inhibition of PKC led to increased SCF-induced tyrosine kinase activity and mitogenicity, but PKC was necessary for SCF-induced motility. In this report we have further examined the modulatory role of PKC on SCF-induced signaling. The ligand-activated Kit/SCF-R associated weakly with GRB2 and induced only little tyrosine phosphorylation of phospholipase C-gamma in porcine aortic endothelial cells transfected with Kit/SCF-R. In contrast, the SCF-stimulated Kit/SCF-R associated efficiently with, and induced tyrosine phosphorylation of, the p85 alpha regulatory subunit of phosphatidyl inositide-3'-kinase (PI-3'-kinase). Both receptor association and tyrosine phosphorylation of p85 alpha were increased after inhibition of PKC, while its serine phosphorylation was decreased. Concomitantly, the specific activity of receptor-associated PI-3'-kinase activity was increased. Inhibition of PI-3'-kinase with wortmannin inhibited SCF-induced mitogenicity. SCF-induced phosphorylation of Raf-1 and activation of ERK2 still occurred after PKC inhibition but was not increased. In conclusion, SCF-induced PI-3'-kinase activation paralleled the increased SCF-induced mitogenicity after inhibition of PKC.
Blume-Jensen
P
P
Ludwig Institute for Cancer Research, Biomedical Center, Uppsala, Sweden.
Rönnstrand
L
L
Gout
I
I
Waterfield
M D
MD
Heldin
C H
CH
D048868:Adaptor Proteins, Signal Transducing; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000033:anatomy & histology; D004730:Endothelium, Vascular / Q000166:cytology; D051380:GRB2 Adaptor Protein; D016298:Hematopoietic Cell Growth Factors / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1; D019869:Phosphatidylinositol 3-Kinases; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D019009:Proto-Oncogene Proteins c-kit; D019908:Proto-Oncogene Proteins c-raf; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D016184:Receptors, Colony-Stimulating Factor / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D019089:Stem Cell Factor; D013552:Swine; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D000077191:Wortmannin
D048868:Adaptor Proteins, Signal Transducing; D000730:Androstadienes; D051380:GRB2 Adaptor Protein; D016298:Hematopoietic Cell Growth Factors; D007527:Isoenzymes; D019950:Mitogen-Activated Protein Kinase 1; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D011506:Proteins; D011518:Proto-Oncogene Proteins; D019009:Proto-Oncogene Proteins c-kit; D019908:Proto-Oncogene Proteins c-raf; D020794:Receptor Protein-Tyrosine Kinases; D016184:Receptors, Colony-Stimulating Factor; D011994:Recombinant Proteins; D019089:Stem Cell Factor; D010738:Type C Phospholipases; D014443:Tyrosine; D000077191:Wortmannin