The sperm proteasome during sperm capacitation and fertilization

Area of Science:

• Reproductive Biology
• Molecular Biology
• Biochemistry

Background:

• The 26S proteasome is a key cellular machine for protein degradation.
• Sperm proteasomes have been implicated in fertilization, but their precise roles remain under investigation.
• Ubiquitinated proteins are present on egg coats, suggesting a role for proteasomes in sperm-egg interactions.

Purpose of the Study:

• To consolidate evidence on the function of sperm-borne 26S proteasomes in fertilization across diverse species.
• To elucidate the specific roles of proteasomal activity in sperm-egg coat interactions and fertilization outcomes.
• To identify potential applications of these findings in diagnostics and contraception.

Main Methods:

• Comparative analysis of studies involving mammalian and non-mammalian fertilization systems.
• Investigation of proteasome localization and activity in spermatozoa.
• Experimental inhibition of ubiquitination and proteasomal activity.
• Assessment of sperm-egg binding and penetration assays.
• Evaluation of the impact of ATP depletion on sperm proteasome function.

Main Results:

• Proteasomes are found in sperm acrosomes and on their surface, interacting with ubiquitinated egg coat proteins.
• Proteasomal proteolytic and deubiquitinating activities are present in motile sperm and persist post-acrosomal exocytosis.
• Inhibition of proteasomal activity or ATP depletion impairs fertilization, sperm capacitation, and zona pellucida penetration.
• Modulating deubiquitinating activity affects the balance of monospermic and polyspermic fertilization.

Conclusions:

• The 26S proteasome plays a multifaceted role in various stages of animal and human fertilization.
• Sperm proteasomes offer a novel model for understanding sperm-egg coat interactions.
• These findings highlight potential new biomarkers for sperm quality and novel contraceptive targets.