Division of Biology , Glaxo Research Institute , Research Triangle Park , North Carolina 27709 .
Am J Physiol 263 : E205-9 ( 1992)
Abstract
We have studied the association between protein tyrosine phosphorylation and the mitogenic effect induced by platelet-derived growth factor ( PDGF ) in the osteoblast-like cell line MC3T3-E1 .
PDGF caused a dose-dependent increase in [ 3H]thymidine incorporation in MC3T3-E1 cells , reaching a plateau at 10 ng/ml .
Vanadate , a potent phosphatase inhibitor , induced a twofold increase in thymidine incorporation .
The combination of vanadate and PDGF resulted in a dose-dependent synergistic effect on thymidine incorporation .
Genistein , a tyrosine kinase inhibitor , inhibited in a dose-related manner ( 2-20 microM ) the mitogenic effect induced by either PDGF or the combination of vanadate and PDGF .
These observations suggest that tyrosine kinases are involved in mediating the mitogenic effect of PDGF in these cells .
PDGF treatment of MC3T3-E1 cells and subsequent immunoblotting with antiphosphotyrosine antibodies resulted in a marked phosphorylation of the PDGF receptor .
Vanadate had a lesser effect on PDGF receptor phosphorylation , but given together with PDGF it induced a significant increase in the intensity of receptor phosphorylation .
Preincubation with genistein abrogated these effects .
Taken together , these findings indicate a direct correlation between thymidine incorporation and tyrosine phosphorylation in MC3T3-E1 cells and suggest that tyrosine phosphorylation plays a role in PDGF-induced mitogenic activity in osteoblast-like cells .