A role for the migrating sperm surface antigen PH-20 in guinea pig sperm binding to the egg zona pellucida.
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 (Myles, D.G., and P. Primakoff, 1984, J. Cell Biol., 99:1634-1641). 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 (approximately 90%) sperm binding to the guinea pig egg zona pellucida at saturating antibody concentrations (greater than 20 micrograms/ml). Half-maximal inhibition of sperm binding to the zona was obtained with approximately 2 micrograms/ml PH-20 MAb. The PH-21 MAb at saturating concentration (50 micrograms/ml) partially inhibited (approximately 45%) sperm-zona binding, and the PH-22 MAb (50 micrograms/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 with 125I-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 is active site.
D000177:Acrosome / Q000276:immunology; D000818:Animals; D000911:Antibodies, Monoclonal; D000954:Antigens, Surface / Q000502:physiology*; D001667:Binding, Competitive; D002462:Cell Membrane / Q000648:ultrastructure; D005260:Female; D006168:Guinea Pigs; D008297:Male; D008560:Membrane Fluidity; D008565:Membrane Proteins / Q000276:immunology* / Q000502:physiology; D008970:Molecular Weight; D010063:Ovum / Q000502:physiology*; D011134:Polysaccharides / Q000378:metabolism; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000276:immunology / Q000502:physiology*; D015044:Zona Pellucida / Q000502:physiology*
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D008565:Membrane Proteins; D011134:Polysaccharides; C007789:fucoidan