Thrombin stimulates phosphorylation of insulin-like growth factor-1 receptor, insulin receptor substrate-1, and phospholipase C-gamma 1 in rat aortic smooth muscle cells.
It has recently been reported that protein-tyrosine kinase activity is required for thrombin-induced growth in vascular smooth muscle cells (VSMC). In the present study, we have identified several phosphoproteins that are tyrosine-phosphorylated in response to thrombin in quiescent VSMC. These proteins are insulin-like growth factor-1 receptor beta-subunit (IGF-IR beta), insulin receptor substrate-1 (IRS-1), and phospholipase C-gamma 1 (PLC-gamma 1). Thrombin-stimulated phosphorylation of these proteins was rapid; it was maximal at 1 min and reduced thereafter. Thrombin also activated mitogen-activated protein kinases (MAPK) in quiescent VSMC in a biphasic manner with a rapid and larger peak at 10 min (6-fold) followed by a sustained smaller second peak at 2 h (2-fold). Inhibition of protein-tyrosine kinase activity by the use of two structurally different protein-tyrosine kinase inhibitors, genistein and herbimycin A, significantly blocked the thrombin-induced tyrosine phosphorylation of IGF-1R beta, IRS-1, and PLC-gamma 1 and decreased thrombin-stimulated DNA synthesis. In contrast, however, inhibition of protein-tyrosine kinase activity had no effect on thrombin activation of MAPK. Collectively, these findings suggest a role for tyrosine phosphorylation of IGF-IR beta, IRS-1, and PLC-gamma 1 in thrombin-induced mitogenic signaling events in VSMC. Furthermore, while protein tyrosine phosphorylation is essential for thrombin-induced DNA synthesis, it is not required for thrombin-stimulated MAPK activation. Since thrombin rapidly activated Src in VSMC, Src may be involved in the cross-talk between the G-protein-coupled receptor agonist and a tyrosine kinase receptor such as IGF-1R.
D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016227:Benzoquinones; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004261:DNA Replication / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019833:Genistein; D055504:Insulin Receptor Substrate Proteins; D007527:Isoenzymes / Q000378:metabolism; D007529:Isoflavones / Q000494:pharmacology; D047029:Lactams, Macrocyclic; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011809:Quinones / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D017828:Rifabutin / Q000031:analogs & derivatives; D013917:Thrombin / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000378:metabolism*
D016227:Benzoquinones; D004791:Enzyme Inhibitors; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D007527:Isoenzymes; D007529:Isoflavones; D047029:Lactams, Macrocyclic; D010750:Phosphoproteins; D011809:Quinones; D017828:Rifabutin; D019000:Phosphotyrosine; C020754:herbimycin; D004247:DNA; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D017526:Receptor, IGF Type 1; D010738:Type C Phospholipases; D013917:Thrombin