Phospholipase C-gamma is a substrate for the PDGF and EGF receptor protein-tyrosine kinases in vivo and in vitro.
Phospholipase C-gamma (PLC-gamma) was rapidly phosphorylated on tyrosines and serines following PDGF and EGF treatment of quiescent 3T3 mouse fibroblasts and A431 human epidermoid cells, respectively, PDGF treatment increased PLC-gamma phosphorylation within 30 sec. This lasted for up to 1 hr, and occurred at high stoichiometry. Continuous receptor occupancy was required to maintain this phosphorylation. Three major sites of tyrosine phosphorylation were detected in PLC-gamma, two of which were phosphorylated in EGF-treated A431 cells. Under certain conditions PDGF receptor coimmunoprecipitated with PLC-gamma, suggesting that PDGF receptor can phosphorylate PLC-gamma directly. Indeed, purified PDGF or EGF receptor phosphorylated purified PLC-gamma on tyrosines identical to those phosphorylated in vivo. Tyrosine phosphorylation of PLC-gamma was not induced by bombesin, TPA, or insulin. Stimulation of PLC-gamma tyrosine phosphorylation and the reported ability of PDGF and EGF to induce phosphatidylinositol turnover in different cells were strongly correlated. We propose that tyrosine phosphorylation of PLC-gamma by PDGF and EGF receptors leads to its activation, and a consequent increase in phosphatidylinositol turnover.
Meisenhelder
J
J
Molecular Biology and Virology Laboratory, Salk Institute, San Diego, California 92138.
Suh
P G
PG
Rhee
S G
SG
Hunter
T
T
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D066246:ErbB Receptors / Q000378:metabolism*; D006801:Humans; D051379:Mice; D010449:Peptide Mapping; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D019000:Phosphotyrosine; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor; D013997:Time Factors; D010738:Type C Phospholipases / Q000276:immunology / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D010982:Platelet-Derived Growth Factor; D011956:Receptors, Cell Surface; D010768:Phosphoserine; D019000:Phosphotyrosine; D014443:Tyrosine; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D017479:Receptors, Platelet-Derived Growth Factor; D010738:Type C Phospholipases