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Competition between zonae pellucidae and a proteinase inhibitor for sperm binding
H Boettger-Tong1, D Aarons, B Biegler
1Department of Biology, University of Alabama, Birmingham 35294-1170.
Biology of Reproduction
|November 1, 1992
Summary
A seminal vesicle proteinase inhibitor binds to sperm and affects their ability to bind eggs. This binding site on sperm is crucial for both sperm-zona binding and initiating the acrosome reaction.
Area of Science:
- Reproductive Biology
- Biochemistry
- Sperm-Oocyte Interactions
Background:
- Sperm encounter seminal vesicle proteinase inhibitors upon ejaculation.
- These inhibitors bind to the sperm's acrosomal region and are later removed.
- This binding influences sperm function.
Purpose of the Study:
- To investigate the role of the seminal inhibitor binding site on sperm.
- To determine if this site participates in sperm-zona binding and the acrosome reaction.
- To explore the competitive interaction between seminal inhibitor and zona pellucida components for this binding site.
Main Methods:
- Studied the binding of seminal vesicle proteinase inhibitor to murine sperm.
- Assessed the effect of inhibitor and its binding site on sperm-zona binding.
- Investigated the impact of immuno-aggregation of the inhibitor binding site on the acrosome reaction.
- Examined the competitive inhibition of acrosome reactions by seminal inhibitor and zona glycopeptides.
- Analyzed the sensitivity of inhibitor/anti-inhibitor-induced acrosome reactions to pertussis toxin and proteinase inhibitors.
Main Results:
- Seminal inhibitor binding to sperm reduces their zona binding ability.
- The inhibitor binding site on oocytes reduces sperm binding.
- Immuno-aggregation of the inhibitor binding site triggers acrosome exocytosis.
- Purified seminal inhibitor and other proteinase inhibitors block zona-induced acrosome reactions.
- Zona glycopeptides inhibit inhibitor/anti-inhibitor-induced acrosome reactions in a dose-dependent manner.
- Inhibitor/anti-inhibitor-induced acrosome reactions share sensitivity to pertussis toxin and proteinase inhibitors with zona-induced reactions.
Conclusions:
- The trypsin inhibitor binding site on sperm is essential for sperm-zona binding.
- This binding site plays a critical role in inducing the sperm acrosome reaction.
- Seminal inhibitors and zona components likely compete for this sperm binding site, regulating fertilization.