Gamete Biology

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

Abstract
In a previous paper we suggested that gp273, the ligand molecule for sperm egg interaction in the bivalve mollusc Unio elongatulus has functional carbohydrate epitopes in common with a human zona pellucida glycoprotein, probably ZP3. We demonstrated that 1) anti-gp273 purified IgG that 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 signalling receptors since exposure of spermatozoa to this glycoprotein results in significant stimulation of PKC activity. Since the PKC inihibitor, BIM, 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.

Key words: Acrosome reaction • Fertilization • Kinases • Signal transduction • Sperm

This article has been cited by other articles:

				S. Canovas, P. Coy, and E. Gomez First Steps in the Development of a Functional Assay for Human Sperm Using Pig Oocytes J Androl, March 1, 2007; 28(2): 273 - 281. [Abstract] [Full Text] [PDF]