Calcium dynamics in the regulation of flagellar movement of swimming spermatozoa

海胆精子鞭毛运动受胞内Ca2+调控。为了研究鞭毛运动背后的Ca2+动力学机制，我们分析了鞭毛运动的机械感觉行为反应。在10 mM Ca2+存在的情况下，精子以圆形路径游动(C)。当对头部施加机械刺激时，精子表现出一系列鞭毛反应，包括停止跳动(Q)和恢复沿直线游动(S)，然后再次沿圆周游动；结果精子避开了障碍。Ca2+成像显示细胞内Ca2+在Q期和S期前期较高，其后逐渐降低。Ca2+内流是由Ca2+通道诱导的，Ca2+外排是由鞭毛蛋白相关的Ca2+外排系统、PMCA和NCKX诱导的。单独的实验表明，鞭毛运动的开始是由细胞内Ca2+通过Ca2+储存调节的。

Flagellar movement of the sea urchin sperm is regulated by intracellular Ca2+. To study the mechanism of Ca2+ dynamics underlying flagellar movement, we analyzed the mechanosensory behavioural responses. In the presence of 10 mM Ca2+, the sperm swim in circular paths (C). When a mechanical stimulus was applied to the head, the sperm showed a series of flagellar responses, consisting of a stoppage of beating (Q) and a recovery of swimming in a straight path (S), followed by swimming in a circular path again; as the result the sperm avoided the obstacle. Ca2+-imaging showed that the intracellular Ca2+ was high in the Q and the early stage of S, and gradually decreased after that. The Ca2+ influx was induced by Ca2+ channels and the Ca2+ efflux was induced by a flagellasialin-related Ca2+-efflux system, PMCA and the NCKX. Separate experiments revealed that the initiation of flagellar movement of the sperm was regulated by the intracellular Ca2+ through the Ca2+ stores.