Uyeda T Q, Furuya M
Exp Cell Res. 1986 Aug;165(2):461-72. doi: 10.1016/0014-4827(86)90599-9.
Microfilament structures of the ridge and the backbone in Physarum flagellates disintegrated selectively within a few minutes upon cooling by ice-water. The elongated cells concurrently rounded up to spherical or irregular and amoeboid shape. When such rounded cells were warmed to 25 degrees C, the microfilament structures were reconstructed within 1 min and cells subsequently returned to an elongated shape. Disruption of microfilaments by cytochalasin A also caused the rounding up of cells, indicating that the rounding up resulted from disintegration of microfilament structures. This transformation induced by the cold treatment was retarded by preincubation of the cells with EGTA for 15 min, but addition of EGTA immediately before the onset of the cold treatment was less effective. The effect of EGTA was cancelled by simultaneous addition of excess Ca2+. Addition of procaine also inhibited the transformation induced by the cold treatment, while caffeine inhibited the recovery of the elongated shape when returned to 25 degrees C. Furthermore, addition of A23187 at 25 degrees C in the presence of Ca2+ mimicked the effect of the cold treatment. Thus, intracellular release of Ca2+ was suggested to be involved in the transformation induced by the cold treatment. Lability of the microfilament structures at a high concentration of Ca2+ was directly proved using Triton-permeabilized cells. Therefore we concluded that low temperature disrupts microfilament structures that are necessary for the maintenance of the elongated cell shape by inducing intracellular Ca2+ release. However, microfilament structures in Physarum amoeba cells were affected neither by the cold treatment nor by high Ca2+ concentration.
在冰水中冷却后，黏菌鞭毛虫的嵴和主干的微丝结构在几分钟内选择性地解体。细长的细胞同时变圆，呈球形或不规则的变形虫状。当这些变圆的细胞升温至25摄氏度时，微丝结构在1分钟内重建，随后细胞恢复细长形状。用细胞松弛素A破坏微丝也会导致细胞变圆，这表明细胞变圆是由微丝结构解体引起的。用EGTA对细胞进行15分钟的预孵育会延迟冷处理诱导的这种转变，但在冷处理开始前立即添加EGTA的效果较差。同时添加过量的Ca2+可消除EGTA的作用。添加普鲁卡因也会抑制冷处理诱导的转变，而咖啡因会抑制细胞回到25摄氏度时细长形状的恢复。此外，在25摄氏度下，在Ca2+存在的情况下添加A23187模拟了冷处理的效果。因此，提示细胞内Ca2+的释放参与了冷处理诱导的转变。使用Triton通透细胞直接证明了在高浓度Ca2+下微丝结构的不稳定性。因此我们得出结论，低温通过诱导细胞内Ca2+释放破坏维持细长细胞形状所必需的微丝结构。然而，黏菌变形虫细胞中的微丝结构既不受冷处理影响，也不受高Ca2+浓度影响。
