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1 December 2003 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
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Abstract

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 Lewisa-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.

S. Delle Monache, F. Flori, C. Della Giovampaola, A. Capone, G. B. La Sala, F. Rosati, R. Colonna, C. Tatone, and R. Focarelli "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," Biology of Reproduction 69(6), 1779-1784, (1 December 2003). https://doi.org/10.1095/biolreprod.103.019976
Received: 4 June 2003; Accepted: 1 July 2003; Published: 1 December 2003
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