title: Lewis X-containing neoglycoproteins mimic the intrinsic ability of zona pellucida glycoprotein ZP3 to induce the acrosome reaction in capacitated mouse sperm.
abstract: The binding of zona pellucida (ZP) glycoprotein ZP3 to mouse sperm surface receptors is mediated by protein-carbohydrate interactions. Subsequently, ZP3 induces sperm to undergo the acrosome reaction, an obligatory step in fertilization. We have previously identified Lewis X (Le(x); Gal beta 4[Fuc alpha 3]GlcNAc) as a potent inhibitor of in vitro sperm-ZP binding (Johnston et al. J Biol Chem 1998; 273:1888-1895). This glycan is recognized by approximately 70% of the ZP3 binding sites on capacitated, acrosome-intact mouse sperm, whereas Lewis A (Le(a); Gal beta 3[Fuc alpha 4]GlcNAc) is recognized by most of the remaining sites (Kerr et al. Biol Reprod 2004; 71:770-777). Herein, we test the hypothesis that Le(x)- and Le(a)-containing glycans, when clustered on a neoglycoprotein, bind ZP3 receptors on sperm and induce sperm to undergo the acrosome reaction via the same signaling pathways as ZP3. Results show that a Le(x)-containing neoglycoprotein induced the acrosome reaction in a dose-dependent and capacitation-dependent manner. A Le(a)-containing neoglycoprotein also induced sperm to undergo the acrosome reaction but was less potent than Le(x)-containing neoglycoproteins. In contrast, neoglycoproteins containing beta4-lactosamine (Gal beta 4GlcNAc), Lewis B (Fuc alpha 2Gal beta 3[Fuc alpha 4]GlcNAc), and sialyl-Le(x) glycans were inactive, as were four other neoglycoproteins with different nonfucosylated glycans. Consistent with these results, unconjugated Le(x)- and Le(a)-capped glycans were dose-dependent inhibitors, which at saturation, reduced the ZP-induced acrosome reaction by about 60% and 30%, respectively. Experiments utilizing pharmacological inhibitors suggest that induction of the acrosome reaction by solubilized ZP and Le(x)- and Le(a)-containing neoglycoproteins require the same calcium-dependent pathway. However, only the ZP-induced acrosome reaction requires a functional G(i) protein. Thus, Le(x)-containing neoglycoproteins bind to a major class of ZP3 receptors on capacitated sperm. A Le(a)-containing neoglycoprotein binds a second ZP3 receptor but is a less-potent inducer of the acrosome reaction.
authors.affiliation: Division of Reproductive Biology, Department of Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 21205, USA.
authors.forename: William F
authors.initials: WF
authors.lastname: Hanna
authors.forename: Candace L
authors.initials: CL
authors.lastname: Kerr
authors.forename: Joel H
authors.initials: JH
authors.lastname: Shaper
authors.forename: William W
authors.initials: WW
authors.lastname: Wright
mesh_terms: D020101:Acrosome Reaction / Q000187:drug effects*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002240:Carbohydrate Sequence; D004305:Dose-Response Relationship, Drug; D004527:Egg Proteins / Q000378:metabolism*; D005260:Female; D005690:Galactose / Q000378:metabolism / Q000494:pharmacology; D006023:Glycoproteins / Q000378:metabolism* / Q000494:pharmacology; D007785:Lactose / Q000378:metabolism / Q000494:pharmacology; D016256:Lewis X Antigen / Q000031:analogs & derivatives; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008813:Mice, Inbred ICR; D008969:Molecular Sequence Data; D019158:N-Acetylneuraminic Acid / Q000378:metabolism / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013075:Sperm Capacitation / Q000502:physiology*; D014312:Trisaccharides / Q000378:metabolism* / Q000494:pharmacology; D000072216:Zona Pellucida Glycoproteins
chemical_list: D004527:Egg Proteins; D006023:Glycoproteins; D016256:Lewis X Antigen; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D014312:Trisaccharides; D000072216:Zona Pellucida Glycoproteins; C000606521:Zp3 protein, mouse; C110530:galactosyl-(1,4)-fucopyranosyl-(1,3)-N-acetylglucosamine; D012710:Serum Albumin, Bovine; D019158:N-Acetylneuraminic Acid; D007785:Lactose; D002118:Calcium; D005690:Galactose