Gp273, the Ligand Molecule for Sperm-Egg Interaction in the Bivalve Mollusk, Unio elongatulus, Binds to and Induces Acrosome Reaction in Human Spermatozoa through a Protein Kinase C-Dependent Pathway

S. Delle Monache, F. Flori, C. Della Giovampaola, A. Capone, G. B. La Sala, F. Rosati, R. Colonna, C. Tatone, Riccardo Focarelli

Research output: Contribution to journalArticle


In a previous article, we suggested that gp273, the ligand molecule for sperm-egg interaction in the bivalve mollusk Unio elongatulus has functional carbohydrate epitopes in common with a human zona pellucida glycoprotein, probably ZP3. We demonstrated that: 1) anti-gp273-purified immunoglobulin G (IgG), which recognizes a carbohydrate gp273 epitope including a Lewis a-like structure, interacts with a zona pellucida protein; 2) human sperm specifically bind to gp273; and 3) binding is reversed by anti-gp273 IgG. In the present study, we confirm this suggestion by demonstrating that heat-solubilized zonae pellucidae reverse gp273-human sperm binding, that gp273-binding sites are restricted to the acrosomal region, and that gp273 induces the acrosome reaction in human sperm. We also demonstrated that gp273-binding sites on human sperm function as signaling receptors because exposure of spermatozoa to this glycoprotein results in significant stimulation of protein kinase C (PKC) activity. Because the PKC inhibitor, bisindolylmaleimide I, reverses both PKC activation and the acrosome reaction, this kinase is a key component of the signal transduction pathway activated by gp273 and leading to the exocytotic event.

Original languageEnglish
Pages (from-to)1779-1784
Number of pages6
JournalBiology of Reproduction
Issue number6
Publication statusPublished - Dec 2003



  • Acrosome reaction
  • Fertilization
  • Kinases
  • Signal transduction
  • Sperm

ASJC Scopus subject areas

  • Cell Biology
  • Developmental Biology
  • Embryology

Cite this