Anti-SLIP1-reactive proteins exist on human spermatozoa and are involved in zona pellucida binding.
Sulpholipid immobilizing protein 1 (SLIP1) is an evolutionarily conserved 68 kDa plasma membrane protein, present selectively in germ cells. We have previously shown that mouse sperm SLIP1 is involved in sperm-zona pellucida (ZP) binding. In this report, we extended our study to the human system. Immunoblotting demonstrated that anti-SLIP1-reactive proteins (mol. wt 68 and 48 kDa) could be extracted from human spermatozoa by an ATP-containing solution, a result that is consistent with observations in other species. Direct immunofluorescence, using Cy3-conjugated anti-SLIP1 IgG, revealed SLIP1 staining over the acrosomal region, with higher intensity at the posterior area. Using the human sperm-ZP binding assay, we demonstrated that pretreatment of human spermatozoa from three donors with anti-SLIP1 IgG revealed lower numbers of zona-bound spermatozoa, as compared to the corresponding control spermatozoa treated with normal rabbit serum IgG. This decrease in zona pellucida binding was not from an antibody-induced decline in sperm motility or an increase in the premature acrosome reaction. The results strongly suggest that anti-SLIP-reactive proteins on human spermatozoa play an important role in ZP binding.
Rattanachaiyanont
M
M
Hormones/Growth/Development Research Group, Loeb Health Research Institute, Ottawa Hospital-Civic Campus, University of Ottawa, 1053 Carling Ave., Ottawa, Ontario K1Y 4E9, Canada.
Weerachatyanukul
W
W
Léveillé
M C
MC
Taylor
T
T
D'Amours
D
D
Rivers
D
D
Leader
A
A
Tanphaichitr
N
N
D000177:Acrosome / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D018797:Cell Cycle Proteins; D005260:Female; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D016601:RNA-Binding Proteins; D051381:Rats; D013084:Sperm-Ovum Interactions / Q000502:physiology; D013094:Spermatozoa / Q000378:metabolism / Q000502:physiology*; D015044:Zona Pellucida / Q000502:physiology*
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C489104:MIF4GD protein, human; D008565:Membrane Proteins; D016601:RNA-Binding Proteins; C489106:Slip1 protein, mouse; C051337:Slip1 protein, rat