title: Regulation of CD3-induced phospholipase C-gamma 1 (PLC gamma 1) tyrosine phosphorylation by CD4 and CD45 receptors.
abstract: Stimulation of the signal transduction cascade in T cells through the T-cell receptor (CD3) coincides with activation of the phosphatidylinositol-phospholipase C (PI-PLC) pathway. activation of phospholipase C-gamma 1 (PLC gamma 1) occurs through tyrosine phosphorylation in T cells following surface ligation of CD3 receptors with CD3-specific monoclonal antibodies (mAb). Here we show that cross-linking of CD4 molecules with CD3 augments the tyrosine phosphorylation of PLC gamma 1, while co-ligation of CD3 with CD45 (a receptor tyrosine phosphatase) results in reduced PLC gamma 1 tyrosine phosphorylation. Mobilization of intracellular calcium correlated with the extent of PLC gamma 1 tyrosine phosphorylation, indicating that PLC gamma 1 enzymatic activity in T cells may be regulated by its phosphorylation state. The time-course of PLC gamma 1 tyrosine phosphorylation in cells stimulated by soluble anti-CD3 was transient and closely paralleled that of calcium mobilization, while the kinetics in cells stimulated by immobilized anti-CD3 were prolonged. The PI-PLC pathway in T cells was not stimulated by tyrosine phosphorylation of PLC gamma 2, a homologue of PLC gamma 1, demonstrating the strict regulation of PLC gamma isoform usage in CD3-stimulated T cells. A 35,000/36,000 MW tyrosine phosphorylated protein in T cells formed stable complexes with PLC gamma 1, and its tyrosine phosphorylation was co-regulated with that of PLC gamma 1 by CD4 and CD45 receptors. Enzymatic activation and tyrosine phosphorylation of PLC gamma 1 occurs during growth factor stimulation of fibroblasts, where PLC gamma 1 exists in multi-component complexes. The observation that PLC gamma 1 exists in complexes with unique tyrosine phosphorylated proteins in T cells suggests that haematopoietic lineage-specific proteins associated with PLC gamma 1 may play roles in cellular signalling.
authors.affiliation: Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, WA 98121.
authors.forename: S B
authors.initials: SB
authors.lastname: Kanner
authors.forename: J P
authors.initials: JP
authors.lastname: Deans
authors.forename: J A
authors.initials: JA
authors.lastname: Ledbetter
mesh_terms: D015703:Antigens, CD / Q000502:physiology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000502:physiology*; D015153:Blotting, Western; D017252:CD3 Complex; D015704:CD4 Antigens / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D006649:Histocompatibility Antigens / Q000502:physiology*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D017493:Leukocyte Common Antigens; D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D015398:Signal Transduction / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D015704:CD4 Antigens; D006649:Histocompatibility Antigens; D007527:Isoenzymes; D011948:Receptors, Antigen, T-Cell; D014443:Tyrosine; D017493:Leukocyte Common Antigens; D010738:Type C Phospholipases; D002118:Calcium