Bull Sperm Binding to Oviductal Epithelium Is Mediated by a Ca2+-Dependent Lectin on Sperm That Recognizes Lewis-a Trisaccharide1

Abstract

Sperm binding to oviductal epithelium produces a reservoir in vivo that may serve to maintain sperm fertility and provide sperm for fertilization when ovulation occurs. Previously, it was determined that bull sperm binding could be blocked by fucoidan and its component fucose; furthermore, treatment of epithelium with fucosidase prevented binding. The present study was conducted to further characterize binding. Because fucose would probably be present on the epithelium as part of oligosaccharide moieties of glycoproteins and/or glycolipids, competitive binding inhibition activity was tested for fucose in five linkages commonly found in oligosaccharides. Binding inhibition was assayed by determining the concentration of motile, frozen/thawed sperm bound to fresh epithelial explants in the presence of test inhibitors. Initially, 5 monosaccharides were tested at 30 mM (fucose, mannose, sialic acid, glucose, N-acetyl glucosamine, and galactose), and only fucose significantly reduced sperm binding compared to vehicle control (p = 0.03). Of the oligosaccharides tested (lacto-N-fucopentaose I, 3-fucosyllactose, Lewis-X, Lewis-a, and GlcNAcbeta1-4[Fucalpha1-6]GlcNAc-O-Me), only Lewis-a significantly reduced binding, and it did so in a dose-dependent fashion (p = 0.009 at 12.5 mM). Ca2+ dependency of binding was examined. Sperm were incubated with explants in Tyrode's albumin lactate pyruvate (TALP) containing 2 mM CaCl2 or lacking CaCl2 and containing 2 mM EGTA. Sperm-binding density was reduced significantly in EGTA (p < 0.03) but could be restored by readdition of CaCl2. Also, live sperm were labeled with the oligosaccharide ligand Lewis-a conjugated to fluorescein isothiocyanate-tagged polyacrylamide. Sperm exhibited labeling on the head only in the presence of Ca2+. Labeling could be blocked by fucose or Lewis-a-polyacrylamide. It was concluded that bull sperm bind to an oligosaccharide ligand on the oviductal epithelium that resembles Lewis-a and that binding is Ca2+-dependent.

Carbohydrate mediation of boar sperm binding to oviductal epithelial cells in vitro

“…However, evidence from other studies indicates the involvement of glycoproteins on the oviductal epithelial cell surface in conjunction with sperm plasma membrane carbohydrate recognition domains. Adherence of Lewis-a trisaccharide to acrosome intact bull spermatozoa (Suarez et al, 1998) and fetuin to hamster spermatozoa (DeMott et al, 1995) interfered with spermoviductal epithelial cell binding. In support of this finding, enzymatic removal of fucose residues from bovine oviductal epithelia resulted in a marked reduction in sperm binding (Lefebvre et al, 1997).…”

“…The effective inhibition of sperm-oviductal epithelial cell binding by larger carbohydrate molecules has been demonstrated in other species. In cattle (Lefebvre et al, 1997;Suarez et al, 1998), hamsters (DeMott et al, 1995 and horses (Dobrinski et al, 1996a), glycoproteins inhibit binding more effectively than their monosaccharide subunits. Ahuja (1985) suggested that these differences may be due to a decreased binding affinity of monosaccharides in comparison to oligosaccharides.…”

“…Expression of P-selectin has been detected on acrosomal membranes of boar spermatozoa (Geng et al, 1997) and P-selectin glycoprotein ligand-1 (PSGL-1), which is primarily located on a subset of myeloid and lymphoid cells, has also been detected on epithelial cells of the Fallopian tube in humans (Laszik et al, 1996). Indeed, binding of bull spermatozoa to oviductal epithelial cell monolayers is inhibited by Lewis-a trisaccharide (Suarez et al, 1998), a carbohydrate with high homology to sialyl-Lewis X that is part of the CD15 antigen recognized by selectin molecules (Fusi et al, 1996), providing further evidence for a possible function of selectins in sperm-oviductal epithelial cell interactions.…”

“…Studies in horses (Dobrinski et al, 1996a), hamsters (DeMott et al, 1995) and cattle (Lefebvre et al, 1997;Suarez et al, 1998) have demonstrated the presence of carbohydrate-mediated interactions between spermatozoa and oviductal epithelial cells in vitro. Interactions between spermatozoa and Sertoli cells (Raychoudhury and Millette, 1997), and spermatozoa and zona pellucida (Oehninger et al, 1991) involve carbohydrate recognition.…”

Identity and transfer of male reproductive gland proteins of the dengue vector mosquito, Aedes aegypti: Potential tools for control of female feeding and reproduction

“…In Xenopus, a CRISP-like protein in the egg jelly acts as a sperm attractant (Olson et al, 2001). AAEL001121 and AAEL10596 are predicted lectins, a family of proteins which have been found to influence gamete interactions during fertilization (Romero et al, 1997) and regulate sperm binding to the female oviduct (Suarez et al, 1998) in mammals and mediate the release of sperm from female sperm storage organs in D. melanogaster (Ravi Ram and Wolfner, In press). …”