title: CD45 cross-linking regulates phospholipase C activation and tyrosine phosphorylation of specific substrates in CD3/Ti-stimulated T cells.
abstract: In lymphocytes, CD45 regulates the increase in cytoplasmic calcium concentration that occurs after receptor cross-linking. Here we show that T cell receptor complex (CD3/Ti)-mediated inositol phosphate production was inhibited by CD45 ligation in Jurkat cells. CD3/Ti signaling in normal T cells was also inhibited by CD45 ligation, but coupling of CD4 with CD3/Ti gave augmented calcium signals that were entirely resistant to the inhibitory effect of CD45. In contrast, CD3-induced T cell proliferation was suppressed by immobilized CD45 mAb even in the presence of CD4 mAb. The effect of CD45 and CD4 ligation on tyrosine phosphorylation during T cell activation was directly examined by immunoblotting with anti-phosphotyrosine. Using immobilized mAb, CD45 ligation suppressed the tyrosine phosphorylation of specific substrates induced by CD3/Ti stimulation, including almost complete suppression of 150-, 36-, and 35-kDa proteins and partial suppression of 76- and 80-kDa proteins. Other tyrosine-phosphorylated proteins induced by CD3/Ti stimulation, including 135- and 21-kDa proteins, were not suppressed by simultaneous ligation of CD3/Ti and CD45. Simultaneous ligation of CD3 and CD4 enhanced tyrosine phosphorylation of all substrates, but did not overcome the CD45-mediated suppression of tyrosine phosphorylation of the 35- and 36-kDa proteins. The CD45-mediated suppression of phospholipase C activation is therefore modulated by association with CD4 without altering the specific inhibition of tyrosine phosphorylation and T cell proliferation after co-ligation of CD45 and CD3/Ti.
authors.affiliation: Bristol-Myers Squibb Corporation, Seattle, WA 98121.
authors.forename: J A
authors.initials: JA
authors.lastname: Ledbetter
authors.forename: G L
authors.initials: GL
authors.lastname: Schieven
authors.forename: F M
authors.initials: FM
authors.lastname: Uckun
authors.forename: J B
authors.initials: JB
authors.lastname: Imboden
mesh_terms: D015703:Antigens, CD / Q000502:physiology*; D000943:Antigens, Differentiation / Q000502:physiology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000502:physiology*; D017252:CD3 Complex; D015704:CD4 Antigens / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002455:Cell Division; D002460:Cell Line; D003432:Cross-Linking Reagents; D004789:Enzyme Activation; D006649:Histocompatibility Antigens / Q000502:physiology*; D006801:Humans; D007295:Inositol Phosphates / Q000096:biosynthesis; D017493:Leukocyte Common Antigens; D008213:Lymphocyte Activation; D008970:Molecular Weight; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D015704:CD4 Antigens; D003432:Cross-Linking Reagents; D006649:Histocompatibility Antigens; D007295:Inositol Phosphates; D011948:Receptors, Antigen, T-Cell; D014443:Tyrosine; D017493:Leukocyte Common Antigens; D010727:Phosphoric Diester Hydrolases; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D002118:Calcium