Lewis X-Containing Neoglycoproteins Mimic the Intrinsic Ability of Zona Pellucida Glycoprotein ZP3 to Induce the Acrosome Reaction in Capacitated Mouse Sperm

• Published in: Biology of reproduction 2004-09, Vol.71 (3), p.778-789
• Main Authors: HANNA, William F, KERR, Candace L, SHAPER, Joel H, WRIGHT, William W
• Format: Article
• Language: English
• Subjects: Acrosome Reaction - drug effects; Animals; Biological and medical sciences; Calcium - metabolism; Carbohydrate Sequence; Dose-Response Relationship, Drug; Egg Proteins - metabolism; Female; Fundamental and applied biological sciences. Psychology; Galactose - metabolism; Galactose - pharmacology; Glycoproteins - metabolism; Glycoproteins - pharmacology; Lactose - metabolism; Lactose - pharmacology; Male; Mammalian male genital system; Membrane Glycoproteins - metabolism; Mice; Mice, Inbred ICR; Molecular Sequence Data; Morphology. Physiology; N-Acetylneuraminic Acid - metabolism; N-Acetylneuraminic Acid - pharmacology; Receptors, Cell Surface - metabolism; Serum Albumin, Bovine - metabolism; Serum Albumin, Bovine - pharmacology; Signal Transduction - drug effects; Signal Transduction - physiology; Sperm Capacitation - physiology; Trisaccharides - metabolism; Trisaccharides - pharmacology; Vertebrates: reproduction; Zona Pellucida Glycoproteins
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod.103.023820

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 ; Galβ4[Fucα3]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 ∼70% of the ZP3 binding sites on capacitated, acrosome-intact mouse sperm, whereas Lewis A (Le a ; Galβ3[Fucα4]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 β4-lactosamine (Galβ4GlcNAc), Lewis B (Fucα2Galβ3[Fucα4]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.