Gröner M, Malchow D
Fakultät für Biologie, Universität, Germany.
Cell Calcium. 1996 Feb;19(2):105-11. doi: 10.1016/s0143-4160(96)90079-2.
Chemotactic stimulation by cAMP elicits Ca2+ entry across the plasma membrane and uptake into intracellular Ca2+ stores. In order to better understand Ca2+ regulation in Dictyostelium we measured 45Ca2+ uptake in homogenates of aggregation competent cells. Besides the InsP3-sensitive store the acidosomes are responsible for Ca2+ transport. About 50% of the vesicular 45Ca2+ accumulation was inhibited by the calmodulin antagonist W-7 and 14% by the less efficacious analogue W-5. Half maximal inhibition by W-7 occurred at 37 microM concentration. Calmodulin antagonised the activity of W-7, and a monoclonal antibody against Dictyostelium calmodulin inhibited Ca2+ sequestration as did calmodulin antagonists of different classes. 100 microM BHQ-a SERCA-type Ca2+ transport ATPase blocker-inhibited most of the W-7 sensitive compartment and oxalate increased Ca2+ uptake into this compartment indicating that intracellular Ca2+ stores are the target of W-7. Ca2+/calmodulin thus seems to provide for a feedback regulation of Ca2+ sequestration.
环磷酸腺苷（cAMP）引发的趋化刺激会引起钙离子（Ca2+）跨质膜进入并摄取到细胞内的钙离子储存库中。为了更好地理解盘基网柄菌（Dictyostelium）中的钙离子调节机制，我们测量了具备聚集能力的细胞匀浆中45Ca2+的摄取情况。除了对肌醇三磷酸（InsP3）敏感的储存库外，酸泡也负责钙离子的运输。约50%的囊泡45Ca2+积累受到钙调蛋白拮抗剂W-7的抑制，而效果较差的类似物W-5则抑制了14%。W-7在37微摩尔浓度时出现半数最大抑制作用。钙调蛋白拮抗W-7的活性，一种针对盘基网柄菌钙调蛋白的单克隆抗体与不同类别的钙调蛋白拮抗剂一样抑制钙离子螯合。100微摩尔的丁基羟基喹啉（BHQ）——一种肌浆网Ca2+转运ATP酶阻滞剂——抑制了大部分对W-7敏感的区室，而草酸盐增加了该区域的Ca2+摄取，这表明细胞内的钙离子储存库是W-7的作用靶点。因此，Ca2+/钙调蛋白似乎为钙离子螯合提供了一种反馈调节机制。
