Int. J. Dev. Biol. 52: 523 - 526 (2008)

https://doi.org/10.1387/ijdb.072511mm

Vol 52, Issue 5-6

Special Issue: Fertilization

Regulation of the starfish sperm acrosome reaction by cGMP, pH, cAMP and Ca²⁺

Published: 1 July 2008

Midori Matsumoto^1,*, Osamu Kawase^1,2, M. Sadiqul Islam¹, Masahiro Naruse¹, Shin-Nosuke Watanabe¹, Riho Ishikawa¹ and Motonori Hoshi³

¹Department of Biosciences and Informatics, Keio University Kouhoku-ku, Yokohama, ²Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido and ³The Open University of Japan, Mihama-ku, Chiba City, Japan

Abstract

In the starfish, Asterias amurensis, three components in the jelly coat of eggs, namely acrosome reaction-inducing substance (ARIS), Co-ARIS and asterosap, act in concert on homologous spermatozoa to induce the acrosome reaction (AR). Molecular recognition between the sperm surface molecules and the egg jelly molecules must underlie signal transduction events triggering the AR. Asterosap is a sperm-activating molecule, which stimulates rapid synthesis of intracellular cGMP, pH and Ca²⁺. This transient elevation of Ca²⁺ level is caused by a K⁺-dependent Na⁺/Ca²⁺ exchanger, and the increase of intracellular pH is sufficient for ARIS to induce the AR. The concerted action of ARIS and asterosap could induce elevate intracellular cAMP levels in starfish sperm and the sustained increase in [Ca²⁺], which is essential for the AR. The signaling pathway induced by these factors seems to be synergistically regulated to trigger the AR in starfish sperm.

Keywords

invertebrate fertilization, cyclic nucleotides, signal transduction, ion channel, spermatozoa