Mechanism Regulating Ca2+-dependent Mechanosensory Behaviour in Sea Urchin Spermatozoa

Abstract

ABSTRACT. Flagellar movement of the sea urchin sperm is regulated by intracellular Ca 2+ . Flagellasialin, a polysialic acid-containing glycoprotein, as well as other membrane proteins seems responsible for the Ca 2+ control. To elucidate the mechanism of Ca 2+ dynamics underlying flagellar movement, we analysed the sperm's mechanosensory behavioural responses by using microtechniques. In sea water containing 10 mM Ca 2+ , the sperm swim in circular paths. When a mechanical stimulus was applied to the sperm head with a glass microstylus, the sperm showed a series of flagellar responses, consisting of a stoppage of beating (quiescence) and a recovery of swimming in a straight path, followed by swimming in a circular path again; as the result the sperm avoided the obstacle. Ca 2+ -imaging with Fluo-4 showed that the intracellular Ca 2+ was high in the quiescence and gradually decreased after that. The effects of blockers and antibodies against candidate components revealed that the Ca 2+ influx was induced by Ca 2+ channels and the Ca 2+ efflux was induced by a flagellasialin-related Ca 2+ -efflux system, plasma membrane Ca 2+ -ATPases and the K + -dependent Na + /Ca 2+ exchanger. The results show that the Ca 2+ -dependent mechanosensory behaviour of the sea urchin sperm is regulated by organized functioning of the membrane environment including the plasma membrane proteins and flagellasialin.

Sperm as microswimmers – navigation and sensing at the physical limit

“…However, it was noted that high Ca 2+ levels persist during straight swimming, i.e. when the path curvature is low [9,13,73,93,94], challenging the view that κ is directly set by [Ca 2+ ] i . To resolve this conundrum, we determined the signal transfer function between [Ca 2+ ] i (input) and κ (output) [7] (Fig.…”

The rate of change in Ca2+concentration controls sperm chemotaxis

“…Third, in reactivated flagella, the concentration, dynamics, and location of molecular components important for flagellar bending Salathe, 2007) might have been severely altered. Finally, in intact sperm, high [Ca 2+ ] i levels persist during low path curvature, i.e., straight swimming (Böhmer et al, 2005;Wood et al, 2005;Shiba et al, 2008;Guerrero et al, 2010a;Kambara et al, 2011) Fig. 3, A-C).…”

New Functions of Polysialic Acid and Its Relationship to Schizophrenia

“…We have also analyzed the Ca 2+ dependent motility of sea urchin tail and demonstrated that flagellasialin is involved in Ca 2+ efflux after mechanical stimulus (40). The motility of sperm tail can be classified as two types: one is propulsion and the other is directional regulation.…”

“…Thus, the movement of sea urchin sperm can be classified as follows: movement with a circular trace (CB)→mechanical stimulation→stopping (Q)→reverse change of sperm head→movement with a straight trace (S)→ movement with a circular trace (CA). Among these sequential movements, we identified that α2,9-linked polysialic acid on flagellasialin and suPMCA is involved in the course of Q→ S and that suNCKX is involved in the course of S→ CA (40). …”