Barbar Elie, Rola-Pleszczynski Marek, Payet Marcel D, Dupuis Gilles
Graduate Program in Immunology, Faculty of Medicine, University of Sherbrooke, Sherbrooke, QC, Canada J1H 5N4.
Biochim Biophys Acta. 2003 Jul 23;1622(2):89-98. doi: 10.1016/s0304-4165(03)00120-x.
4-aminopyridine (4AP) is a general blocker of voltage-dependent K+ channels. This pyridine derivative has also been shown to inhibit T cell proliferation, to modulate immune responses and to alleviate some of the symptoms associated with neurological disorders such as multiple sclerosis, myasthenia gravis and Alzheimer's disease. 4AP triggers a Ca2+ response in lymphocytes, astrocytes, neurons and muscle cells but little is known about the regulation of the 4AP response in these cells. We report that 4AP induced a non-capacitative transplasma membrane influx of Ca2+ in Jurkat T lymphocytes. The influx of Ca2+ was not affected by activation or inhibition of protein kinase A (PKA). In contrast, activation of protein kinase C (PKC) by phorbol myristyl acetate (PMA), mezerein or 1-oleoyl-2-acetyl-sn-glycerol (OAG) inhibited the influx of Ca2+ triggered by 4AP. The inhibitory effect of PKC could be prevented by prior exposure of the cells to the PKC inhibitor GF 109203X. Under these conditions, mezerein and OAG no longer inhibited the 4AP-dependent Ca2+ response. Inhibition of serine and threonine protein phosphatases PP1 and PP2A by treating the cells with calyculin A (CalA) reduced the Ca2+ response to 4AP. Okadaic acid (OA) had no effect, suggesting an involvement of PP1. A combination of CalA and OAG (or PMA) abolished the influx of Ca2+ induced by 4AP, adding further evidence to the importance of protein phosphorylation in the modulation of the 4AP response. Our data suggest that the transplasma membrane influx of Ca2+ triggered by 4AP in Jurkat T cells can be modulated by the opposite actions of PKC and protein serine and threonine phosphatase(s).
4-氨基吡啶（4AP）是一种电压依赖性钾通道的通用阻滞剂。这种吡啶衍生物还被证明可抑制T细胞增殖、调节免疫反应并缓解与神经系统疾病（如多发性硬化症、重症肌无力和阿尔茨海默病）相关的一些症状。4AP可在淋巴细胞、星形胶质细胞、神经元和肌肉细胞中引发钙离子反应，但对于这些细胞中4AP反应的调节知之甚少。我们报告称，4AP在Jurkat T淋巴细胞中诱导了一种非容量性的跨质膜钙离子内流。钙离子内流不受蛋白激酶A（PKA）激活或抑制的影响。相反，佛波醇肉豆蔻酸酯（PMA）、芫花酯素或1-油酰基-2-乙酰基-sn-甘油（OAG）激活蛋白激酶C（PKC）可抑制4AP引发的钙离子内流。PKC的抑制作用可通过预先将细胞暴露于PKC抑制剂GF 109203X来预防。在这些条件下，芫花酯素和OAG不再抑制4AP依赖性钙离子反应。用花萼海绵诱癌素A（CalA）处理细胞抑制丝氨酸和苏氨酸蛋白磷酸酶PP1和PP2A可降低对4AP的钙离子反应。冈田酸（OA）没有影响，提示PP1参与其中。CalA与OAG（或PMA）联合使用可消除4AP诱导的钙离子内流，进一步证明了蛋白质磷酸化在调节4AP反应中的重要性。我们的数据表明，Jurkat T细胞中4AP引发的跨质膜钙离子内流可被PKC与蛋白丝氨酸和苏氨酸磷酸酶的相反作用所调节。
