Kvanta A, Gerwins P, Jondal M, Fredholm B B
Department of Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Cell Signal. 1990;2(5):461-70. doi: 10.1016/0898-6568(90)90042-9.
It has recently been shown that elevation of cAMP by adenosine receptor stimulation may be potentiated by stimulation of the T-cell receptor/CD3 complex on human T-cells with the monoclonal antibody OKT3, and that this is mimicked by activation of protein kinase C [Kvanta, A. et al. (1989) Naunyn-Schmeideberg's Arch. Pharmac. 340, 715-717]. In this study the diterpene forskolin, which binds to and activates the adenylate cyclase, has been used to examine further how the CD3 complex may influence the adenylate cyclase pathway. Stimulation with OKT3 alone was found to cause a small dose-dependent increase in basal cAMP accumulation. When combining OKT3 with a concentration of forskolin (10 microM), which by itself had little effect on the cyclase activity, the cAMP accumulation was markedly potentiated. This potentiation was paralleled by an increase in [3H]forskolin binding to saponine permeabilized Jurkat cells from 24 to 41 fmol/10(6) cells. The OKT3 effect on cAMP was blocked by chelating extracellular Ca2+ with EGTA or intracellular Ca2+ with BAPTA and also by W-7, an inhibitor of calmodulin, but was unaffected by H-7, an inhibitor of protein kinase C. Even though OKT3 caused an increase in inositolphosphate turnover, and activated protein kinase C, neither phorbol 12,13 dibutyrate (PDBu) nor the Ca2(+)-ionophore A23187 could mimic the OKT3 effect, whereas a combination of PDBu and A23187 at high concentrations could potentiate forskolin stimulated cyclase activity. Together, these results indicated that stimulation of the CD3 complex could influence the adenylate cyclase by two different mechanisms, one involving activation of protein kinase C and another which does not.
最近研究表明，用单克隆抗体OKT3刺激人T细胞上的T细胞受体/CD3复合物可增强腺苷受体刺激引起的cAMP升高，并且蛋白激酶C的激活可模拟这种作用[Kvanta, A.等人（1989年），《瑙尼恩-施米德贝格药理学文献》340卷，715 - 717页]。在本研究中，与腺苷酸环化酶结合并激活它的二萜类化合物福斯高林已被用于进一步研究CD3复合物如何影响腺苷酸环化酶途径。单独用OKT3刺激发现会导致基础cAMP积累呈小剂量依赖性增加。当将OKT3与一定浓度（10微摩尔）的福斯高林联合使用时（福斯高林自身对环化酶活性影响很小），cAMP积累明显增强。这种增强伴随着[3H]福斯高林与皂角苷通透的Jurkat细胞的结合从24飞摩尔/10(6)个细胞增加到41飞摩尔/10(6)个细胞。OKT3对cAMP的作用被用EGTA螯合细胞外Ca2+或用BAPTA螯合细胞内Ca2+以及钙调蛋白抑制剂W - 7所阻断，但不受蛋白激酶C抑制剂H - 7的影响。尽管OKT3导致肌醇磷酸周转增加并激活了蛋白激酶C，但佛波醇12,13 - 二丁酸酯（PDBu）和Ca2(+)离子载体A23187都不能模拟OKT3的作用，而高浓度的PDBu和A23187组合可增强福斯高林刺激的环化酶活性。总之，这些结果表明，CD3复合物的刺激可通过两种不同机制影响腺苷酸环化酶，一种涉及蛋白激酶C的激活，另一种则不涉及。
