Platelet-derived growth factor stimulates phosphorylation of growth factor receptor-binding protein-2 in vascular smooth muscle cells.
Growth factor receptor-binding protein-2 (GRB2) couples growth factor receptor activation to the p21ras nucleotide exchange factor son-of-sevenless (SOS). Son-of-sevenless can serve as a substrate for mitogen-activated protein kinases and may be subject to feed back regulation in mitogen-stimulated cells. Herein, we demonstrate phosphorylation on GRB2 in rat A10 vascular smooth muscle cells exposed to platelet-derived growth factor (PDGF). Lysates from smooth cells stimulated with PDGF revealed a shift in the electrophoretic mobility of GRB2. Further investigation confirmed that phosphorylation on GRB2 accompanied this mobility shift. Phosphorylation on GRB2 was time-dependent and correlated with PDGF receptor activation. The time-course for phosphorylation of GRB2 and subsequent decay corresponded with other events characteristic of platelet-derived growth factor signaling. GRB2 was not phosphorylated in cells treated with phorbol 12-myristate 13-acetate, and down-regulation of protein kinase C failed to attenuate phosphorylation on GRB2 in response to growth factor. Analysis of GRB2 immune complexes revealed a kinase activity capable of phosphorylating GRB2 in vitro and demonstrated that the kinase activated in response to PDGF may physically associate with GRB2 signaling complexes.
Benjamin
C W
CW
Upjohn Laboratories, Kalamazoo, Michigan 49001.
Linseman
D A
DA
Jones
D A
DA
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002478:Cells, Cultured; D066246:ErbB Receptors / Q000378:metabolism*; D051380:GRB2 Adaptor Protein; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D010769:Phosphothreonine / Q000378:metabolism; D019000:Phosphotyrosine; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495950:Grb2 protein, rat; D010982:Platelet-Derived Growth Factor; D011506:Proteins; D010769:Phosphothreonine; D010768:Phosphoserine; D019000:Phosphotyrosine; D014443:Tyrosine; D066246:ErbB Receptors; D011493:Protein Kinase C