Annexin A2 is involved in pig (Sus scrofa)sperm-oviduct interaction.

The oviduct is a dynamic organ which modulates gamete physiology. Sperm-oviduct interaction provides the formation of a sperm storage reservoir and allows the selection of sperm with certain qualities in eutherian mammals. In sows, the oviductal sperm binding glycoprotein (SBG) has been proposed to be involved in sperm selection.

Annexins are candidate oviductal receptors for bovine sperm surface proteins and thus may serve to hold bovine sperm in the oviductal reservoir.

The sperm of eutherian mammals are held in a storage reservoir in the caudal segment of the oviduct by binding to the mucosal epithelium. The reservoir serves to maintain the fertility of sperm during storage and to reduce the incidence of polyspermic fertilization. Bovine sperm bind to the epithelium via seminal vesicle secretory proteins in the bovine seminal plasma protein (BSP) family, namely, PDC109 (BSPA1/A2), BSPA3, and BSP30K, which coat the sperm head.

Bovine seminal plasma proteins PDC-109, BSP-A3, and BSP-30-kDa share functional roles in storing sperm in the oviduct.

On ejaculation, sperm become coated with proteins secreted by the male accessory sex glands. In the bull, these proteins consist predominantly of the bovine seminal plasma family of proteins (BSPs): PDC-109 (BSP-A1/-A2), BSP-A3, and BSP-30-kDa. PDC-109 plays a role in forming an oviductal sperm reservoir by enabling sperm to bind to oviductal epithelium.

Calcium/calmodulin and calmodulin kinase II stimulate hyperactivation in demembranated bovine sperm.

Hyperactivated motility is observed among sperm in the mammalian oviduct near the time of ovulation. It is characterized by high-amplitude, asymmetrical flagellar beating and assists sperm in penetrating the cumulus oophorus and zona pellucida. Elevated intracellular Ca2+ is required for the initiation of hyperactivated motility, suggesting that calmodulin (CALM) and Ca2+/CALM-stimulated pathways are involved.

PDC-109 (BSP-A1/A2) promotes bull sperm binding to oviductal epithelium in vitro and may be involved in forming the oviductal sperm reservoir.

Sperm reservoirs have been found in the oviducts of several species of mammals. In cattle, the reservoir is formed by the binding of sperm to fucose-containing glycoconjugates on the surface of oviductal epithelial cells. A fucose-binding molecule was purified from sperm extracts and identified as PDC-109 (BSP-A1/A2), a protein that is secreted by the seminal vesicles and associates with the plasma membrane of sperm upon ejaculation.