Carbohydrate binding activity in human spermatozoa: localization, specificity, and involvement in sperm-egg fusion.
Sperm carbohydrate binding activity is involved in gamete recognition. We identified a human sperm protein extracted under reducing conditions, and with a molecular mass of 65 kDa on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), and which binds D-mannose coupled to albumin (DMA) in presence of cations and a neutral pH. Epifluorescence microscopy showed that fluorescein-DMA binds to dead or permeabilized sperm heads. The DMA-binding activity of human sperm heads was highly specific for a polysaccharide structure containing charged sugar residues. After capacitation, or induction of the acrosome reaction using solubilized zonae pellucidae, fluorescein-DMA was bound respectively to 10.3% (+/- 3.5%) and to 37.6% (+/- 2.1%) of viable sperm heads. The sequential analysis of viable spermatozoa for fluorescein-DMA binding and for rhodamine-Pisum sativum agglutinin binding, showed that DMA-binding sites are present in viable acrosome-reacted spermatozoa. Three dimensional analysis of fluorescence and ultrastructural studies showed that DMA-binding sites are mostly restricted to the sub-acrosomal space of the equatorial segment. Incubation of spermatozoa and zona-free hamster eggs in the presence of DMA was associated with a dose-dependent significant reduction in the number of spermatozoa bound to the oolemma, compared with a control, and to a dose-dependent inhibition of oocyte penetration. This effect was highly specific for DMA, suggesting that DMA-binding sites in human spermatozoa are involved in sperm-egg fusion.
Gabriele
A
A
Department of Internal Medicine, University of L'Aquila, Italy.
D'Andrea
G
G
Cordeschi
G
G
Properzi
G
G
Giammatteo
M
M
De Stefano
C
C
Romano
R
R
Francavilla
F
F
Francavilla
S
S
D000328:Adult; D000818:Animals; D001667:Binding, Competitive; D050260:Carbohydrate Metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D006224:Cricetinae; D004527:Egg Proteins / Q000378:metabolism; D005260:Female; D019793:Fluorescein / Q000378:metabolism; D005456:Fluorescent Dyes; D005643:Fucose / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D037102:Lectins / Q000378:metabolism; D037181:Lectins, C-Type; D008297:Male; D008358:Mannose / Q000378:metabolism*; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D008562:Membrane Glycoproteins / Q000378:metabolism; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008970:Molecular Weight; D009865:Oocytes / Q000166:cytology / Q000187:drug effects; D037121:Plant Lectins; D011134:Polysaccharides / Q000378:metabolism; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D012709:Serum Albumin / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000378:metabolism; D013075:Sperm Capacitation; D013077:Sperm Head / Q000378:metabolism / Q000648:ultrastructure; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000378:metabolism*; D013379:Substrate Specificity; D013463:Sulfuric Acid Esters / Q000378:metabolism; D000072216:Zona Pellucida Glycoproteins
D002352:Carrier Proteins; D004527:Egg Proteins; D005456:Fluorescent Dyes; D037102:Lectins; D037181:Lectins, C-Type; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D008562:Membrane Glycoproteins; D037121:Plant Lectins; D011134:Polysaccharides; D011956:Receptors, Cell Surface; D012709:Serum Albumin; D013463:Sulfuric Acid Esters; D000072216:Zona Pellucida Glycoproteins; C053610:fucose-bovine serum albumin conjugate; C023840:mannose-bovine serum albumin conjugate; C036292:pea lectin; D012710:Serum Albumin, Bovine; D005643:Fucose; D008358:Mannose; D019793:Fluorescein