A Role for the Migrating Sperm Surface Antigen PH-20 in Guinea Pig Sperm Binding to the Egg Zona Pellucida

• Published in: The Journal of cell biology 1985-12, Vol.101 (6), p.2239-2244
• Main Authors: Primakoff, Paul, Hyatt, Hilary, Myles, Diana G.
• Format: Article
• Language: English
• Subjects: Acrosome - immunology; Acrosome reaction; Animals; Antibodies; Antibodies, Monoclonal; Antigens; Antigens, Surface - physiology; Binding, Competitive; Biological and medical sciences; Cell Membrane - ultrastructure; Early stages. Segmentation. Gastrulation. Neurulation; Embryology: invertebrates and vertebrates. Teratology; Epitopes; Female; Fundamental and applied biological sciences. Psychology; Gametes; Guinea Pigs; Herpes zoster; Male; Membrane Fluidity; Membrane Proteins - immunology; Membrane Proteins - physiology; Molecular Weight; Ova; Ovum - physiology; Polysaccharides - metabolism; Sperm-Ovum Interactions; Spermatozoa; Spermatozoa - immunology; Spermatozoa - physiology; Zona pellucida; Zona Pellucida - physiology
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.101.6.2239

After the acrosome reaction, the PH-20 surface antigen of guinea pig sperm migrates from its original location on the posterior head surface to a new location on the inner acrosomal membrane. We have isolated three monoclonal antibodies (MAbs) of the IgG1 subclass, PH-20, PH-21, and PH-22, that bind to the PH-20 antigen. The PH-20 MAb strongly inhibited (∼90%) sperm binding to the guinea pig egg zona pellucida at saturating antibody concentrations (>20 μg/ml). Half-maximal inhibition of sperm binding to the zona was obtained with ∼2 μg/ml PH-20 MAb. The PH-21 MAb at saturating concentration (50 μg/ml) partially inhibited (∼45%) sperm-zona binding, and the PH-22 MAb (50 μg/ml) did not inhibit (0%) sperm-zona binding. Essentially the same amounts of the three MAbs were bound to sperm under the conditions where inhibition (PH-20, PH-21) or no inhibition (PH-22) of sperm-zona binding was observed, which indicates that the different levels of inhibition did not arise from different levels of MAb binding. Competition binding assays with125I-labeled MAbs showed that PH-21 binding to sperm was not affected by the binding of PH-20 or PH-22. However, that PH-20 and PH-22 blocked each other's binding to sperm suggests that their recognized determinants may be relatively close to one another. The results indicate that the migrating PH-20 antigen has a required function in sperm binding to the zona pellucida and that the PH-20 MAb affects its active site.