Inhibition of the mouse sperm surface alpha-D-mannosidase inhibits sperm-egg binding in vitro.
In previous reports from this laboratory, we identified the presence of a novel alpha-D-mannosidase on the surface of rat, mouse, hamster, and human spermatozoa [J Cell Biol 1989; 109:1257-1267 and Biol Reprod 1990; 42:843-858]. Since it has been suggested that mannosyl residues on the egg zona pellucida may be important for sperm-egg binding, studies were undertaken to examine the potential role of the sperm alpha-D-mannosidase during fertilization. Incubation of mouse spermatozoa in the presence of increasing concentrations of the inhibitory sugars, alpha-methyl mannoside, alpha-methyl glucoside, D-mannose, or D-mannitol, resulted in a dose-dependent decrease in the number of spermatozoa bound per egg without a deleterious effect on sperm motility or on the sperm acrosome, and a dose-dependent inhibition of the sperm mannosidase activity. Galactose, however had no effect on sperm-egg binding or on sperm mannosidase activity. Two nucleotide sugars (UDP-GlcNAc and UDP-gal) were also tested and shown to reduce sperm-egg binding but with only a minimal effect on sperm mannosidase activity. In additional studies, spermatozoa incubated in the presence of a mannose-containing oligosaccharide exhibited a dramatic reduction in sperm-egg binding that correlated with a similar inhibition of sperm mannosidase activity. The oligosaccharide substrate did not affect sperm motility or the sperm acrosome. These studies suggest that the sperm alpha-D-mannosidase may play an important role during fertilization.
Cornwall
G A
GA
Department of Obstetrics and Gynecology Vanderbilt University School of Medicine, Nashville, Tennessee 37232-2633.
Tulsiani
D R
DR
Orgebin-Crist
M C
MC
D000818:Animals; D002240:Carbohydrate Sequence; D002462:Cell Membrane / Q000201:enzymology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008361:Mannosidases / Q000037:antagonists & inhibitors* / Q000502:physiology; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry; D013084:Sperm-Ovum Interactions / Q000502:physiology*; D013094:Spermatozoa / Q000201:enzymology* / Q000502:physiology; D013379:Substrate Specificity; D043323:alpha-Mannosidase
D009844:Oligosaccharides; D008361:Mannosidases; D043323:alpha-Mannosidase