Journal
DEVELOPMENTAL BIOLOGY
Volume 347, Issue 1, Pages 147-153Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.ydbio.2010.08.019
Keywords
Acrosome reaction; Steroidal saponin; Membrane microdomain; GM1 ganglioside; Caveolae-break assay; Sperm capacitation
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Funding
- Japan Society for the Promotion of Science
- Grants-in-Aid for Scientific Research [22310121] Funding Source: KAKEN
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Cofactor for acrosome reaction-inducing substance (Co-ARIS) is a steroidal saponin from the starfish Asterias amurensis. Saponins exist in many plants and few animals as self-defensive chemicals, but Co-ARIS has been identified as a cofactor for inducing the acrosome reaction (AR). In A. amurensis, the AR is induced by the cooperative action of egg coat components (ARIS. Co-ARIS, and asterosap): however, the mechanism of action of Co-ARIS is obscure. In this study we elucidated the membrane dynamics involved in the action of Co-ARIS. We found that cholesterol specifically inhibited the Co-ARIS activity for AR induction and detected the binding of labeled compounds with sperm using radioisotope-labeled Co-ARIS. Co-ARIS treatment did not reduce the content of sperm sterols, however, the condition was changed and localization of GM1 ganglioside on the periacrosomal region disappeared. We then developed a caveola-breaking assay, a novel method to detect the effect of chemicals on microdomains of culture cell, and confirmed the disturbance of somatic cell caveolae in the presence of Co-ARIS. Finally, by atomic force microscopy observations and surface plasmon resonance measurements using an artificial membrane, we revealed that Co-ARIS colocalized with GM1 clusters on the microdomains. Through this study, we revealed a capacitation-like event for AR in starfish sperm. (c) 2010 Elsevier Inc. All rights reserved.
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