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.
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.
Delle Monache
S
S
Department of Biomedical Sciences and Technology, University of L'Aquila, 67100 L'Aquila, Italy.
Flori
F
F
Della Giovampaola
C
C
Capone
A
A
La Sala
G B
GB
Rosati
F
F
Colonna
R
R
Tatone
C
C
Focarelli
R
R
D020101:Acrosome Reaction / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001665:Binding Sites; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006023:Glycoproteins / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008024:Ligands; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D008974:Mollusca; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction; D012995:Solubility; D013084:Sperm-Ovum Interactions / Q000502:physiology*; D013094:Spermatozoa / Q000378:metabolism / Q000502:physiology; D015044:Zona Pellucida / Q000737:chemistry
D004791:Enzyme Inhibitors; D006023:Glycoproteins; D007211:Indoles; D008024:Ligands; D008301:Maleimides; D011493:Protein Kinase C; C070515:bisindolylmaleimide I