ADAM15 participates in fertilization through a physical interaction with acrogranin

Area of Science:

• Reproductive Biology
• Molecular Biology
• Cell Biology

Background:

• Mammalian fertilization involves sperm-egg interaction mediated by surface proteins.
• ADAM proteins, including ADAM1, 2, and 3, are implicated in sperm-egg binding.

Purpose of the Study:

• To investigate the processing and localization of ADAM15 during guinea pig sperm maturation.
• To identify proteins associated with ADAM15 on spermatozoa.
• To explore the role of ADAM15 and its associated proteins in sperm-egg interactions.

Main Methods:

• Proteolytic processing analysis of ADAM15 in epididymal spermatozoa.
• Indirect immunofluorescence to determine ADAM15 localization.
• Immunoprecipitation to identify ADAM15-associated proteins.
• Cell-surface labeling and heterologous fertilization assays.

Main Results:

• ADAM15 is proteolytically processed during epididymal maturation, resulting in a 45 kDa mature form lacking pro-domain and metalloprotease domain.
• Mature ADAM15 is localized to the acrosome, equatorial region, and flagellum of spermatozoa, with redistribution after acrosome reaction.
• A 65 kDa protein, identified as acrogranin, co-immunoprecipitated with ADAM15.
• ADAM15 and acrogranin are present on the sperm cell surface, and anti-acrogranin antibodies inhibit sperm-egg adhesion.
• ADAM15 and acrogranin association was also observed in breast cancer cell lines.

Conclusions:

• ADAM15 undergoes significant processing during sperm maturation.
• ADAM15 and acrogranin are cell-surface associated proteins on guinea pig spermatozoa.
• ADAM15 and acrogranin likely play a role in mediating sperm-egg binding.