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Mammalian fertilization: the strange case of sperm protein 56

Paul M Wassarman1

  • 1Department of Developmental and Regenerative Biology, Mount Sinai School of Medicine, One Gustave L Levy Place, New York, NY 10029-6574, USA. paul.wassarman@mssm.edu

Bioessays : News and Reviews in Molecular, Cellular and Developmental Biology
|February 11, 2009
PubMed

Insights

Sperm protein 56 (sp56) is released to the sperm surface during capacitation, enabling binding to the egg zona pellucida (ZP). This explains why uncapacitated sperm cannot bind to the ZP.

Area of Science:

  • Reproductive biology
  • Cellular and molecular biology
  • Biochemistry

Background:

  • Mammalian fertilization involves sperm binding to the egg's zona pellucida (ZP) after capacitation.
  • Sperm protein 56 (sp56) was previously identified as a zona pellucida glycoprotein mZP3 binding partner.
  • sp56 is located in the sperm's acrosomal matrix, posing a question about its binding availability.

Purpose of the Study:

  • To resolve the apparent paradox of sp56 binding to mZP3.
  • To investigate the role of sp56 release during sperm capacitation.

Main Methods:

  • Photoaffinity cross-linking of acrosome-intact sperm.
  • Analysis of acrosomal matrix (AM) protein localization during capacitation.

Main Results:

  • sp56 is a component of the sperm acrosomal matrix.
  • sp56 is released to the sperm surface during capacitation.
  • This release mechanism potentially explains sperm-zona pellucida binding.

Conclusions:

  • Capacitation-induced release of sp56 to the sperm surface facilitates binding to the zona pellucida.
  • This finding clarifies the mechanism of sperm-egg interaction during fertilization.

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