Essential role of the nonreducing terminal α-mannosyl residues of the N-linked carbohydrate chain of bovine zona pellucida glycoproteins in sperm-egg binding

• Published in: Molecular reproduction and development Vol. 59; no. 2; pp. 221 - 226
• Main Authors: Amari, S., Yonezawa, N., Mitsui, S., Katsumata, T., Hamano, S., Kuwayama, M., Hashimoto, Y., Suzuki, A., Takeda, Y., Nakano, M.
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 01.06.2001; Wiley-Liss
• Subjects: Animals; Biological and medical sciences; Carbohydrate Conformation; Carbohydrate Sequence; Cattle; Egg Proteins - chemistry; Egg Proteins - metabolism; Female; Fundamental and applied biological sciences. Psychology; glycoprotein; Humans; in vitro fertilization; Ligands; Male; Mammalian reproduction. General aspects; Mannose - chemistry; Mannose - metabolism; Membrane Glycoproteins - chemistry; Membrane Glycoproteins - metabolism; Molecular Sequence Data; Ovum - metabolism; Receptors, Cell Surface; sperm ligand; sperm-egg binding; Sperm-Ovum Interactions - physiology; Spermatozoa - metabolism; Vertebrates: reproduction; zona pellucida; Zona Pellucida - chemistry; Zona Pellucida - metabolism; Zona Pellucida Glycoproteins; Spermatozoa; Ligand; Glycoprotein; Ox; Mannose; Germinal cell; Fecundation; Zona pellucida; Vertebrata; Mammalia; Female; Artiodactyla; Oocyte; Ungulata
• ISSN: 1040-452X; 1098-2795
• DOI: 10.1002/mrd.1026

It has been proposed that mammalian sperm bind species‐specifically to carbohydrate chains of zona pellucida glycoproteins at fertilization. Although the sperm ligand carbohydrate chains have been characterized in mice and pigs, the existence of the ligands of other mammals remains unclear. In order to explore the bovine sperm ligand, two in vitro competition assay methods were applied. As a result, a high‐mannose‐type carbohydrate chain, Manα1‐6(Manα1‐3)Manα1‐6(Manα1‐3)Manβ1‐4GlcNAcβ1‐4GlcNAc, which is the major neutral chain in bovine egg zona glycoproteins, was shown to possess bovine sperm ligand activity. When nonreducing terminal α‐mannosyl residues were eliminated from the zona glycoproteins by α‐mannosidase digestion, the ligand activity was reduced, indicating that the α‐mannosyl residues play an essential role in bovine sperm‐egg binding. The number of sperm binding to eggs was reduced to about one‐half after fertilization. The ligand‐active high‐mannose‐type chain may be buried after fertilization, since its amount remains unchanged. Pretreatment of bovine sperm with the sperm ligand‐carbohydrate chain significantly inhibited penetration of the sperm into oocyte and the male pronucleus formation. Thus, a correlation between the sperm ligand activity and in vitro fertilization rate was observed. Mol. Reprod. Dev. 59:221–226, 2001. © 2001 Wiley‐Liss, Inc.