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Role of sialic acid in bovine sperm–zona pellucida binding
Author(s) -
Velásquez José Guillermo,
Canovas Sebastián,
Barajas Patricia,
Marcos Julián,
JiménezMovilla María,
Gallego Ricardo Gutiérrez,
Ballesta José,
Avilés Manuel,
Coy Pilar
Publication year - 2007
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.20619
Subject(s) - sialic acid , zona pellucida , neuraminidase , glycoprotein , biology , fetuin , sperm , biochemistry , lectin , n acetylneuraminic acid , sialidase , oocyte , microbiology and biotechnology , enzyme , genetics , embryo
Sperm binding activity has been detected in zona pellucida (ZP) glycoproteins and it is generally accepted that this activity resides in the carbohydrate moieties. In the present study we aim to identify some of the specific carbohydrate molecules involved in the bovine sperm–ZP interaction. We performed sperm binding competition assays, in vitro fecundation (IVF) in combination with different lectins, antibodies and neuraminidase digestion, and chemical and cytochemical analysis of the bovine ZP. Both MAA lectin recognising α‐2,3‐linked sialic acid and neuraminidase from Salmonella typhimurium with catalytic activity for α‐2,3‐linked sialic acid, demonstrated a high inhibitory effect on the sperm–ZP binding and oocyte penetration. These results suggest that bovine sperm–ZP binding is mediated by α‐2,3‐linked sialic acid. Experiments with trisaccharides (sialyllactose, 3′‐sialyllactosamine and 6′‐sialyllactosamine) and glycoproteins (fetuin and asialofetuin) corroborated this and suggest that at least the sequence Neu5Ac(α2‐3)Gal(β1‐4)GlcNAc is involved in the sperm–ZP interaction. Moreover, these results indicate the presence of a sperm plasma membrane specific protein for the sialic acid. Chemical analysis revealed that bovine ZP glycoproteins contain mainly Neu5Ac (84.5%) and Neu5GC (15.5%). These two types of sialic acid residues are probably linked to Galβ1,4GlcNAc and GalNAc by α‐2,3‐ and α‐2,6‐linkages, respectively, as demonstrated by lectin cytochemical analysis. The use of a neuraminidase inhibitor resulted in an increased number of spermatozoa bound to the ZP and penetrating the oocyte. From this last result we hypothesize that a neuraminidase from cortical granules would probably participate in the block to polyspermy by removing sialic acid from the ZP. Mol. Reprod. Dev. 74: 617–628, 2007. © 2006 Wiley‐Liss, Inc.