title: Mechanism regulating Ca2+-dependent mechanosensory behaviour in sea urchin spermatozoa.
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.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Kambara
authors.forename: Kogiku
authors.initials: K
authors.lastname: Shiba
authors.forename: Manabu
authors.initials: M
authors.lastname: Yoshida
authors.forename: Chihiro
authors.initials: C
authors.lastname: Sato
authors.forename: Ken
authors.initials: K
authors.lastname: Kitajima
authors.forename: Chikako
authors.initials: C
authors.lastname: Shingyoji
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000502:physiology*; D005407:Flagella / Q000737:chemistry / Q000502:physiology*; D006023:Glycoproteins / Q000737:chemistry / Q000502:physiology*; D008297:Male; D040542:Mechanotransduction, Cellular; D008565:Membrane Proteins / Q000737:chemistry / Q000502:physiology*; D012617:Sea Urchins / Q000502:physiology*; D012794:Sialic Acids / Q000737:chemistry; D013081:Sperm Motility; D013094:Spermatozoa / Q000502:physiology*; D013550:Swimming
chemical_list: D006023:Glycoproteins; D008565:Membrane Proteins; D012794:Sialic Acids; C021319:polysialic acid; D000251:Adenosine Triphosphatases; D002118:Calcium