Rivera D T, Langford G M, Weiss D G, Nelson D J
Marine Biological Laboratory, Woods Hole, MA 02543, USA.
Brain Res Bull. 1995;37(1):47-52. doi: 10.1016/0361-9230(94)00256-8.
The role of calmodulin (CaM) in organelle motility (fast axonal transport) in the axoplasm of the squid giant axon was evaluated directly using video-enhanced microscopy. Addition of 6 microM CaM to extruded squid axoplasm produced a 2.6-fold increase in the number of organelles moving per minute per unit area of axoplasm. When lower concentrations of CaM, including physiological concentration (2 micrograms/ml), were added to extruded axoplasm, the number of organelles moving was equally increased. CaM had no significant effect on the mean velocity of organelle translocations. The stimulatory effect of CaM was reduced significantly by the CaM inhibitors melittin (36 microM) and trifluoperazine (50 microM). Parvalbumin, a high-affinity calcium binding protein, did not stimulate motile activity. These results suggest that CaM is a positive regulator of fast axonal transport. At the molecular level, this regulation may involve microtubule-and/or actin-based motor proteins. Several possible molecular mechanisms are proposed.
利用视频增强显微镜直接评估了钙调蛋白（CaM）在枪乌贼巨大轴突轴浆中细胞器运动（快速轴突运输）中的作用。向挤出的枪乌贼轴浆中添加6微摩尔/升的CaM，使得每单位轴浆面积每分钟移动的细胞器数量增加了2.6倍。当向挤出的轴浆中添加较低浓度的CaM，包括生理浓度（2微克/毫升）时，移动的细胞器数量同样增加。CaM对细胞器转运的平均速度没有显著影响。CaM抑制剂蜂毒肽（36微摩尔/升）和三氟拉嗪（50微摩尔/升）可显著降低CaM的刺激作用。小清蛋白是一种高亲和力的钙结合蛋白，它不会刺激运动活性。这些结果表明，CaM是快速轴突运输的正向调节因子。在分子水平上，这种调节可能涉及基于微管和/或肌动蛋白的运动蛋白。文中提出了几种可能的分子机制。
