Competition between Zonae Pellucidae and a Proteinase Inhibitor for Sperm Binding

Abstract

Murine sperm bind a proteinase inhibitor of seminal vesicle origin at ejaculation. The inhibitor binds in the acrosomal region of the sperm head and is removed during in utero or in vitro incubation. Adding inhibitor to sperm reduces their ability to bind zonae, while adding the purified inhibitor binding site to cumulus-free, zona-intact oocytes reduces the ability of the oocytes to bind sperm. Immuno-aggregation of the inhibitor binding site results in exocytosis of the acrosome. These observations suggest that the inhibitor binding site may participate in zona binding and the acrosome reaction. If the inhibitor binding site binds both the zona and the seminal inhibitor, then these components should compete with each other for that site on the sperm. We show that purified seminal inhibitor, as well as other proteinase inhibitors, block zona-induced acrosome reactions. Likewise, zona glycopeptides block inhibitor/anti-inhibitor-induced acrosome reactions in a concentration-dependent fashion. The inhibitor/anti-inhibitor-induced acrosome reaction is sensitive to pertussis toxin and proteinase inhibitor and thus is similar to zona-induced reactions. These findings support the suggestion that the trypsin inhibitor binding site on the head of the sperm functions to insure sperm-zona binding and induction of the acrosome reaction.

Molecular characterization of epididymal proteins

“…Zaneveld et al (1971) found that the removal of extracellular or seminal plasma 'acrosin-inhibitors' from ejaculated spermatozoa is an essential part of the capacitation process. In mice, a trypsin-inhibitor binding site on the sperm surface that may be blocked by proteinase inhibitors seems to be associated with sperm-zona binding (Saling, 1989;Boettger-Tong et al, 1992). Various proteinase inhibitors with different substrate specificities have been identified in the secretions of the male genital tract and characterized on a molecular level.…”

Role of secretory protease inhibitor SPINK3 in mouse uterus during early pregnancy

“…SPINK3 has also been detected in the male accessory sexual glands and female uterus. The secretion of SPINK3 from the mouse seminal vesicles, coagulating gland, and prostate contributes to the seminal fluid and is involved in the sperm acrosome reaction and zona binding (Boettger-Tong et al 1992;Chen et al 1998). Two recently published papers have reported that progesterone (P 4 )-regulated Spink3 mRNA is expressed in pregnant mouse uterus, and its transcript level is higher at interimplantation sites on day 5 (Cheon et al 2002;Ma et al 2006).…”

Plasminogen activatior inhibitor type 1 in rat spermatozoa: localisation in the tail, in the acrosome and on the surface of the head

“…Both, spermatozoa and eggs are able specifically to bind plasminogen, and in vitro fertilisation was found to be inhibited by antibodies against the catalytic domain of plasmin (Huarte et al, 1993). In addition, sperm-egg interaction has frequently been described to be sensitive to serine proteinase inhibitors Boettger-Tong et al, 1992;Liu & Baker, 1993;Takano et al, 1993). Together these results suggest a role of the plasminogen activation system in sperm-egg interaction.…”