Involvement of protein kinase C-delta in CD28-triggered cytotoxicity mediated by a human leukaemic cell line YT.
Ligation of CD28 molecules expressed on the surface of human leukaemic natural killer-like YT cells triggers intracellular signals leading to cytolysis of target cells expressing CD80 or CD86 molecules. Known intracellular events include tyrosine phosphorylation, activation of phosphatidylinositol 3-kinase, and protein kinase C (PKC). In this study, we report that PKC-delta isoenzyme activity is required for CD28-triggered cytotoxicity mediated by YT cells and we also demonstrate that one of the primary targets of bryostatin 1, a modulator of PKC activity, is PKC-delta. Treatment of YT cells with bryostatin 1 caused degradation of PKC-delta, but not other PKC isoenzymes, and completely blocked the cytolytic activity of YT cells. In addition, PKC-delta-specific antibody introduced into YT cells by electroporation inhibited partially the YT cell-mediated cytotoxicity of B-lymphoblastoid cell line JY. This effect was specific, since addition of anti-PKC-delta antibody-blocking peptide in combination with anti-PKC-delta antibody to YT cells for electroporation, neutralized the effect of this antibody. These results demonstrate that YT cell cytolytic activity is dependent on PKC-delta, which is selectively down-regulated by bryostatin 1.
Department of Microbiology and Immunology, Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298-0037, USA.
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D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D015153:Blotting, Western; D054713:Bryostatins; D018106:CD28 Antigens / Q000276:immunology*; D002478:Cells, Cultured; D003601:Cytotoxicity Tests, Immunologic; D004789:Enzyme Activation; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D007694:Killer Cells, Natural / Q000187:drug effects / Q000276:immunology*; D007783:Lactones / Q000494:pharmacology*; D018942:Macrolides; D011493:Protein Kinase C / Q000378:metabolism*; D051745:Protein Kinase C-delta; D014407:Tumor Cells, Cultured
D000276:Adjuvants, Immunologic; D054713:Bryostatins; D018106:CD28 Antigens; D007527:Isoenzymes; D007783:Lactones; D018942:Macrolides; C046785:bryostatin 1; C497258:PRKCD protein, human; D011493:Protein Kinase C; D051745:Protein Kinase C-delta