Abstract
Sperm-oocyte interactions are among the most remarkable processes in cell biology. These cellular recognition events are initiated by an exquisitely specific adhesion of free-swimming spermatozoa to the zona pellucida, an acellular matrix that surrounds the ovulated oocyte. Decades of research focusing on this interaction have led to the establishment of a widely held paradigm that the zona pellucida receptor is a single molecular entity that is constitutively expressed on the sperm cell surface. In contrast, we have employed the techniques of blue native-polyacrylamide gel electrophoresis, far Western blotting, and proximity ligation to secure the first direct evidence in support of a novel hypothesis that zona binding is mediated by multimeric sperm receptor complex(es). Furthermore, we show that one such multimeric association, comprising the chaperonin-containing TCP1 complex (CCT/TRiC) and a zona-binding protein, zona pellucida-binding protein 2, is present on the surface of capacitated spermatozoa and could account for the zona binding activity of these cells. Collectively, these data provide an important biochemical insight into the molecular basis of sperm-zona pellucida interaction and a plausible explanation for how spermatozoa gain their ability to fertilize.
Highlights
Mammalian fertilization is initiated by sperm-zona pellucida (ZP) interactions
This system consistently resolved in excess of 10, high molecular mass (100 to 1100 kDa) entities, which we cautiously define as multiprotein complexes (MPCs), from populations of both caput and caudal epididymal spermatozoa (Fig. 1, A and B)
To explore the possibility that the putative protein complexes reside on the surface of spermatozoa, a position compatible with a role in sperm-zona pellucida interaction, populations of capacitated sperm were surface labeled with a membrane-impermeable derivative of biotin
Summary
Mammalian fertilization is initiated by sperm-zona pellucida (ZP) interactions. Results: The chaperonin-containing TCP1 complex (CCT/TRiC) was identified on the surface of mouse spermatozoa and shown to have an indirect role in ZP adhesion. We show that one such multimeric association, comprising the chaperonin-containing TCP1 complex (CCT/TRiC) and a zona-binding protein, zona pellucida-binding protein 2, is present on the surface of capacitated spermatozoa and could account for the zona binding activity of these cells These data provide an important biochemical insight into the molecular basis of sperm-zona pellucida interaction and a plausible explanation for how spermatozoa gain their ability to fertilize. Originally developed for the analysis of the large multienzyme complexes comprising the mitochondrial electron transport chain [31, 32], BN-PAGE has since been successfully adapted for the isolation and functional characterization of protein complexes embedded within the plasma membrane of a variety of cell types [31, 33, 34] Utilizing this technique, we have been able to substantiate the presence of chaperone-laden protein complexes on the surface of capacitating mouse spermatozoa and demonstrate that a subset of these complexes display high affinity binding to the zona pellucida
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
