title: Tyrosine phosphorylation of phospholipase C-gamma 1 induced by cross-linking of the high-affinity or low-affinity Fc receptor for IgG in U937 cells.
abstract: The human monocytic cell line U937 possesses two classes of the IgG Fc receptor (Fc gamma R), a high-affinity 72-kDa Fc gamma R (Fc gamma RI) and a low-affinity 40-kDa Fc gamma R (Fc gamma RII). Cross-linking of either class of Fc gamma R in U937 cells elicits an increase in the concentration of free intracellular Ca2+. A rapid rise in the concentration of inositol 1,4,5-trisphosphate (Ins-1,4,5-P3) and of several other inositol phosphates derived from Ins-1,4,5-P3 was observed after cross-linking of Fc gamma Rs in U937 cells. This result suggests that Ins-1,4,5-P3, generated by the action of phospholipase C (PLC), acts as a second messenger by which Fc gamma Rs mobilize intracellular Ca2+ in U937 cells. The mechanism by which the cross-linking of Fc gamma Rs triggers activation of PLC was studied. Cross-linking of Fc gamma RI or Fc gamma RII resulted in a rapid and transient phosphorylation of PLC-gamma 1 on tyrosine residues. It has previously been shown that phosphorylation of PLC-gamma 1 on tyrosine residues activates its enzymatic activity in cells. Prior incubation of U937 cells with a protein tyrosine kinase inhibitor, herbimycin A, prevented the tyrosine phosphorylation of PLC-gamma 1 and the hydrolysis of phosphatidylinositol 4,5-bisphosphate induced by the cross-linking of Fc gamma Rs. Thus, Fc gamma RI and Fc gamma RII appear to be functionally coupled to a nonreceptor tyrosine kinase that phosphorylates PLC-gamma 1 after receptor cross-linking, thereby causing activation of PLC-gamma 1.
authors.affiliation: Department of Molecular Biology and Genetics, Johns Hopkins University, School of Medicine, Baltimore, MD 21205.
authors.forename: F
authors.initials: F
authors.lastname: Liao
authors.forename: H S
authors.initials: HS
authors.lastname: Shin
authors.forename: S G
authors.initials: SG
authors.lastname: Rhee
mesh_terms: D000943:Antigens, Differentiation / Q000378:metabolism*; D001152:Arsenicals / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003432:Cross-Linking Reagents / Q000494:pharmacology; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism*; D007700:Kinetics; D010710:Phosphates / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine; D011961:Receptors, Fc / Q000378:metabolism*; D017452:Receptors, IgG; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
chemical_list: D000943:Antigens, Differentiation; D001152:Arsenicals; D003432:Cross-Linking Reagents; D007074:Immunoglobulin G; D007295:Inositol Phosphates; D010710:Phosphates; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D011961:Receptors, Fc; D017452:Receptors, IgG; C029341:oxophenylarsine; D019000:Phosphotyrosine; D014443:Tyrosine; D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D002118:Calcium