Involvement of Trypsin-Like Activity in Binding of Mouse Spermatozoa to Zonae Pellucidae

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 78; no. 10; pp. 6231 - 6235
• Main Author: Saling, Patricia M.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 01.10.1981; National Acad Sciences
• Subjects: Animals; Cell membranes; Chemical suspensions; Female; Fertilization; Fertilization in Vitro; Gametes; Herpes zoster; Male; Mice; Ova; Ovum - physiology; Protease inhibitors; Protease Inhibitors - pharmacology; Sperm-Ovum Interactions - drug effects; Spermatozoa; Spermatozoa - drug effects; Spermatozoa - physiology; Trypsin - metabolism; Trypsin inhibitors; trysin; Zona pellucida; Zona Pellucida - drug effects; Zona Pellucida - physiology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.78.10.6231

Work from a number of laboratories has shown that fertilization is blocked in the presence of protease inhibitors, although the specific site of inhibition has not been identified. The present experiments were designed to discriminate between sperm binding to zonae pellucidae as opposed to sperm penetration through zonae, so as to assess the effect of protease inhibitors on these two distinct events. Exposure of capacitated mouse spermatozoa to a variety of protease inhibitors directed against trypsin blocked sperm binding to zonae in a concentration-dependent manner. A chymotrypsin-directed inhibitor was not capable of blocking sperm binding to zonae. The trypsin inhibitors did not affect sperm penetration through zonae nor gamete membrane fusion if the sperm had established a firm association with the zona surface before addition of the inhibitors. Previous incubation of zona-intact eggs with the inhibitors did not lead to a reduction in sperm binding, indicating that the activity affected by the inhibitors is borne by spermatozoa. Interaction between spermatozoa and the zona surface appeared to be the specific locus of inhibition; sperm binding to zona-free eggs (i.e., binding to the egg plasma membrane) was unaltered by the trypsin inhibitors. These results suggest a reevaluation of the function of proteases in fertilization focusing on their role in initial sperm contact with the zona pellucida.