Kos F J, Bear H D
Department of Microbiology and Immunology, Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298-0037, USA.
Immunology. 1998 Aug;94(4):575-9. doi: 10.1046/j.1365-2567.1998.00558.x.
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.
人白血病自然杀伤样YT细胞表面表达的CD28分子的连接会触发细胞内信号，导致表达CD80或CD86分子的靶细胞发生细胞溶解。已知的细胞内事件包括酪氨酸磷酸化、磷脂酰肌醇3激酶的激活以及蛋白激酶C（PKC）。在本研究中，我们报告PKC-δ同工酶活性是YT细胞介导的CD28触发的细胞毒性所必需的，并且我们还证明PKC活性调节剂苔藓抑素1的主要靶点之一是PKC-δ。用苔藓抑素1处理YT细胞会导致PKC-δ降解，但不会导致其他PKC同工酶降解，并完全阻断YT细胞的细胞溶解活性。此外，通过电穿孔导入YT细胞的PKC-δ特异性抗体部分抑制了B淋巴母细胞系JY的YT细胞介导的细胞毒性。这种作用是特异性的，因为在电穿孔时向YT细胞中加入抗PKC-δ抗体阻断肽与抗PKC-δ抗体，可中和该抗体的作用。这些结果表明，YT细胞的细胞溶解活性依赖于PKC-δ，而PKC-δ会被苔藓抑素1选择性地下调。
