Szamel M, Ebel U, Uciechowski P, Kaever V, Resch K
Institute of Molecular Pharmacology, Medical School Hannover, Germany.
Biochim Biophys Acta. 1997 Apr 24;1356(2):237-48. doi: 10.1016/s0167-4889(96)00174-7.
Activation and translocation of protein kinases C is a key event in the regulation of T lymphocyte activation, proliferation and function. Stimulation of human peripheral blood lymphocytes with the monoclonal antibody BMA 031 raised against the T cell antigen receptor led to a bimodal activation of protein kinases C. The immediate activation and translocation of the protein kinase C isoform PKC-alpha was followed by activation and translocation of the protein kinase C-beta isoenzyme after 90 min of stimulation. Pretreatment of the cells with cholera toxin for 90 min completely abolished activation of protein kinase C-alpha. In sharp contrast, activation and translocation of protein kinase C-beta was not influenced by the bacterial toxin, suggesting that activation and translocation of different protein kinase C isoenzymes are regulated by distinct mechanisms of transmembrane signalling coupled to the T cell antigen receptor/CD3 complex. The expression of high affinity IL-2 receptors was completely inhibited by cholera toxin, while IL-2 synthesis and secretion were not influenced in BMA 031-stimulated human lymphocytes. Extensive control experiments have shown that the effects of cholera toxin were not mediated by its B subunit, and were independent of elevation of intracellular cAMP concentration, suggesting that cholera toxin interfered with a signalling pathway leading to activation of protein kinase C-alpha, which could be responsible for the inhibition of IL-2 receptor expression. This hypothesis was substantiated by the finding that upon introduction of antibodies against protein kinase C-alpha, IL-2 receptor gene expression was completely suppressed. The results suggest, that protein kinase C-alpha might be the major protein kinase C isoenzyme of a signal transduction cascade regulating IL-2 receptor expression in stimulated human lymphocytes.
蛋白激酶C的激活和转位是调节T淋巴细胞激活、增殖和功能的关键事件。用针对T细胞抗原受体的单克隆抗体BMA 031刺激人外周血淋巴细胞，导致蛋白激酶C出现双峰激活。蛋白激酶C同工型PKC-α立即激活并转位，随后在刺激90分钟后蛋白激酶C-β同工酶激活并转位。用霍乱毒素预处理细胞90分钟可完全消除蛋白激酶C-α的激活。与之形成鲜明对比的是，蛋白激酶C-β的激活和转位不受该细菌毒素的影响，这表明不同蛋白激酶C同工酶的激活和转位受与T细胞抗原受体/CD3复合物偶联的跨膜信号传导不同机制的调节。霍乱毒素完全抑制高亲和力IL-2受体的表达，而在BMA 031刺激的人淋巴细胞中，IL-2的合成和分泌不受影响。大量对照实验表明，霍乱毒素的作用不是由其B亚基介导的，且与细胞内cAMP浓度升高无关，这表明霍乱毒素干扰了导致蛋白激酶C-α激活的信号通路，而这可能是抑制IL-2受体表达的原因。这一假设得到了以下发现的证实：引入抗蛋白激酶C-α抗体后，IL-2受体基因表达被完全抑制。结果表明，蛋白激酶C-α可能是调节受刺激人淋巴细胞中IL-2受体表达的信号转导级联反应中的主要蛋白激酶C同工酶。
