Endothelin rapidly stimulates tyrosine phosphorylation in osteoblast-like cells.
The mitogenic activity of endothelin (ET) was studied in osteoblast-like cells, MC3T3-E1. [3H] Thymidine incorporation induced by ET was markedly lower than that of platelet-derived growth factor (PDGF). ET synergistically stimulated [3H] thymidine incorporation induced by PDGF with an apparent ED50 value of 2.5 nM. Treatment of MC3T3-E1 cells with ET and subsequent immunoblotting of the cell extracts with antiphosphotyrosine antibodies followed by labeling with [125I] protein A resulted in the identification of several phosphotyrosine-containing proteins. The intensity of these labeled phosphoproteins significantly increased when the cells were treated with a combination of ET and PDGF. Genistein, an inhibitor of tyrosine kinases, blocked [3H] thymidine incorporation as well as protein tyrosine phosphorylation stimulated by either ET, PDGF or the combination of ET and PDGF. These findings suggest that tyrosine phosphorylation could play a role in the comitogenic activity of ET in osteoblast-like cells.
Schvartz
I
I
Division of Biology, Glaxo Research Institute, Research Triangle Park, NC 27709.
Ittoop
O
O
Davidai
G
G
Hazum
E
E
D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D016232:Endothelins / Q000494:pharmacology*; D019833:Genistein; D007529:Isoflavones / Q000494:pharmacology; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011956:Receptors, Cell Surface / Q000187:drug effects; D017466:Receptors, Endothelin; D014443:Tyrosine / Q000378:metabolism*
D016232:Endothelins; D007529:Isoflavones; D010750:Phosphoproteins; D010982:Platelet-Derived Growth Factor; D011956:Receptors, Cell Surface; D017466:Receptors, Endothelin; D014443:Tyrosine; D019833:Genistein; D011505:Protein-Tyrosine Kinases