Recombinant human zona pellucida protein C produced in Chinese hamster ovary cells binds to human spermatozoa and inhibits sperm–zona pellucida interaction

Glucose-regulated protein 78 (Grp78/BiP) is secreted by human oviduct epithelial cells and the recombinant protein modulates sperm–zona pellucida binding

“…The studies with the recombinant protein have demonstrated that an exogenous Grp78 associates to the human sperm acrosomal cap. The percentage of spermatozoa found to bind rec-Grp78 is in agreement with the small proportion of cells with the ability of undergoing capacitation at a given period of time (46), responding chemotactically to physiologic stimuli (47) and/or binding to recombinant ZP3 protein (48). A tight association of Grp78 to the sperm surface has also been described in bull sperm cells incubated with OEC membrane preparations (20); these results suggest the binding of the oviductal Grp78 to the sperm surface during its passage through the female reproductive tract and/or during its contact with OEC.…”