LewisX-Containing Glycans on the Porcine Oviductal Epithelium Contribute to Formation of the Sperm Reservoir1

Abstract

In many mammals, after semen deposition, a subpopulation of the sperm is transported to the lower oviduct, or isthmus, to form a functional sperm reservoir that provides sperm to fertilize oocytes. The precise molecular interactions that allow formation of this reservoir are unclear. It is proposed that binding of sperm receptors (lectins) to their oviductal cell ligands is accomplished by glycans. Previous results indicated that Lewis trisaccharides are present in glycosphingolipids and O- and N-linked glycans of the porcine isthmus and that Le(X)-containing molecules bind porcine sperm. Immunohistochemistry indicated that the Lewis structures identified by mass spectrometry were, in fact, Lewis X (Le(X)) trisaccharides. These motifs were localized to the luminal border of the isthmus. Assays using fluoresceinated glycans showed that 3-O-sulfated Le(X) (suLe(X)) bound to receptors localized on the head of nearly 60% of uncapacitated boar sperm but that the positional isomer 3-O-sulfo-Le(A) (suLe(A)) bound to <5% of sperm. Sperm also bound preferentially to suLe(X) made insoluble by coupling to beads. Capacitation reduced the ability of suLe(X) to bind sperm to <10%, perhaps helping to explain why sperm are released at capacitation. Pretreatment of oviduct cell aggregates with the Le(X) antibody blocked 57% of sperm binding to isthmic aggregates. Blocking putative receptors on sperm with soluble Le(X) and suLe(X) glycans specifically reduced sperm binding to oviduct cells up to 61%. These results demonstrate that the oviduct isthmus contains Le(X)-related moieties and that sperm binding to these oviduct glycans is necessary and sufficient for forming the sperm reservoir.

Mammalian sperm interactions with the female reproductive tract

“…Furthermore, Lewis a tagged by conjugation to fluorescein-labeled polyacrylamide bound to the heads of live bull sperm (Suarez et al 1998). Similarly, boar sperm bind to Lewis x trisaccharide, which contains fucose in an alpha 1-3 linkage to N-acetylglucosamine and has been localized to the surfaces of epithelium in the porcine oviductal isthmus (Machado et al 2014). Altogether, these characterizations of oviductal receptors for sperm indicate that carbohydrates are part of the sperm binding site, although the particular carbohydrates vary among species.…”

Lactadherin is a candidate oviduct Lewis X trisaccharide receptor on porcine spermatozoa

“…A recent study using an array with 377 glycans, a much larger number than has been examined previously, has demonstrated that porcine spermatozoa recognize with high affinity, carbohydrate structures containing Lewis X (Le X ) or biantennary 6-sialylated N -acetyllactosamine (bi-SiaLN) motifs and that recognition of these motifs mediates porcine sperm binding to the oviduct cell aggregates (Kadirvel et al ., 2012; Machado et al ., 2014). Lewis X is a trisaccharide formed by the monosaccharides N -acetyl glucosamine, galactose and fucose.…”

Glycan profile of oviductal isthmus epithelium in normal and superovulated ewes

“…a2-3-linked sialic acids expressed on the luminal surface of NCs could have a role in the specific functions of the ovine isthmus epithelium. Indeed, sialoglycoconjugates on the epithelial surface are necessary for the head of sperm to bind to the apical side in rat [51] and pig [52,53]. The apical side of the epithelial cells is involved in the sperm-oviduct interaction by species-specific sugars: galactose in horses [54], fucose in cattles [55,56], and galactose, mannose, Neu5Aca2-6Gal, Lewis  antigen in pigs [53].…”