Tachikawa E, Nogimori K, Takahashi S, Mizuma K, Itoh K, Kashimoto T, Nagaoka Y, Iida A, Fujita T
Department of Pharmacology, School of Medicine, Iwate Medical University, Morioka, Japan.
Biochim Biophys Acta. 1996 Jun 13;1282(1):140-8. doi: 10.1016/0005-2736(96)00052-1.
Trichosporin (TS) -B-VIa, a fungal alpha-aminoisobutyric acid (Aib) -containing peptide consisting of 19 amino acid residues and a phenylalaninol, produced both 45Ca2+ influx into bovine adrenal chromaffin cells and catecholamine secretion from the cells. The secretion induced by TS-B-VIa at lower concentrations (2-5 microM) was completely dependent on the external Ca2+, while that induced by TS-B-VIa at higher concentrations (10-30 microM) was partly independent of the Ca2+. The concentration-response curves (2-5 microM) for the TS-B-VIa-induced Ca2+ influx and secretion correlated well. The TS-B-VIa (at 5 microM) -induced secretion was not antagonized by diltiazem, a blocker of L-type voltage-sensitive Ca2+ channels. The treatment of fura-2-loaded C6 glioma cells with TS-B-VIa (2-5 microM) led to an increase in the intracellular free Ca2+ concentration ([Ca2+]i) in a concentration-dependent manner but the stimulatory effects of TS-B-VIa on [Ca2+]i were only slightly observed in Ca(2+)-free medium, indicating that TS-B-VIa causes Ca2+ influx from the external medium into the C6 cells. The TS-B-VIa-induced increase in [Ca2+]i in the C6 cells was not antagonized by diltiazem and by SK&F 96365, a novel blocker of receptor-mediated Ca2+ entry. High K+ increased neither [Ca2+]1 in the C6 cells nor Mn2+ influx into the cells, while TS-B-VIa increased Mn2+ influx. Also in other non-excitable cells, bovine platelets, similar results were obtained. These results strongly suggest that the mechanism of Ca2+ influx by TS-B-VIa at the lower concentrations is distinct from the event of Ca2+ influx through receptor-operated or L-type voltage-sensitive Ca2+ channels in both excitable cells (the chrornaffin cells) and non-excitable cells (the C6 cells and the platelets) and that TS-B-VIa per se may form Ca(2+)-permeable ion channels in biological membranes. On the other hand, the peptide at the higher concentrations seems to damage cell membranes.
曲古抑菌素（TS）-B-VIa是一种含有真菌α-氨基异丁酸（Aib）的肽，由19个氨基酸残基和一个苯丙氨醇组成，它能使45Ca2+流入牛肾上腺嗜铬细胞并促使细胞分泌儿茶酚胺。TS-B-VIa在较低浓度（2 - 5微摩尔）时诱导的分泌完全依赖于细胞外Ca2+，而在较高浓度（10 - 30微摩尔）时诱导的分泌部分不依赖于Ca2+。TS-B-VIa诱导Ca2+流入和分泌的浓度 - 反应曲线（2 - 5微摩尔）具有良好的相关性。TS-B-VIa（5微摩尔）诱导的分泌不受L型电压敏感性Ca2+通道阻滞剂地尔硫卓的拮抗。用TS-B-VIa（2 - 5微摩尔）处理负载fura-2的C6胶质瘤细胞会导致细胞内游离Ca2+浓度（[Ca2+]i）以浓度依赖性方式增加，但在无Ca2+培养基中仅略微观察到TS-B-VIa对[Ca2+]i的刺激作用，这表明TS-B-VIa导致Ca2+从细胞外介质流入C6细胞。TS-B-VIa诱导的C6细胞中[Ca2+]i增加不受地尔硫卓和受体介导的Ca2+内流新型阻滞剂SK&F 96365的拮抗。高钾既不增加C6细胞中的[Ca2+]1也不增加Mn2+流入细胞，而TS-B-VIa增加Mn2+流入。在其他非兴奋性细胞牛血小板中也获得了类似结果。这些结果强烈表明，TS-B-VIa在较低浓度时Ca2+内流的机制与可兴奋细胞（嗜铬细胞）和非兴奋性细胞（C6细胞和血小板）中通过受体操纵或L型电压敏感性Ca2+通道的Ca2+内流事件不同，并且TS-B-VIa本身可能在生物膜中形成Ca(2+)-可渗透离子通道。另一方面，较高浓度的该肽似乎会损伤细胞膜。
