Anti-SLIP1-reactive proteins exist on human spermatozoa and are involved in zona pellucida binding

Abstract

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.

Investigation of the mechanisms by which the molecular chaperone HSPA2 regulates the expression of sperm surface receptors involved in human sperm-oocyte recognition

“…Consistent with proposed roles in cumulus dispersion and sperm-ZP interaction (Sabeur et al, 1997;Rattanachaiyanont et al, 2001;Tantibhedhyangkul et al, 2002), the proteins were co-localized within the peri-acrosomal region of the sperm head. Interestingly, the regulated alteration in the surface expression of both of these proteins does not occur until the latter stages of capacitation.…”

Sperm arylsulfatase A binds to mZP2 and mZP3 glycoproteins in a nonenzymatic manner

“…ASA in the remaining media was further purified using Q-sepharose resin and the total protein obtained and NCS desulfation activity was measured (after QS). Sperm arylsulfatase A and zona pellucida involved in sperm-ZP interaction and purified ASA binds to both intact and solubilized ZP (Rattanachaiyanont et al 2001, Carmona et al 2002a, Tantibhedhyangkul et al 2002, Wu et al 2007. In this report, we provided evidence that ASA was also present in the mouse AC and on the inner acrosomal membrane (Fig.…”

“…We have previously shown that sperm surface arylsulfatase A (ASA, EC 3.1.6.8) is involved in ZP binding in mice, pigs, and humans, and purified ASA can bind to intact or solubilized ZP directly (Rattanachaiyanont et al 2001, Carmona et al 2002a, Tantibhedhyangkul et al 2002. Nonetheless, the identity of the ZP glycoproteins to which ASA binds was not known, and this was one specific aim of the current research study.…”

Cellular mechanisms regulating sperm–zona pellucida interaction

“…This argument, however, appears to be at odds with the relatively high degree of cross-species conversation recorded among the known sperm-ZP receptors. 112,[126][127][128][129][130] Nonetheless, recent data regarding the role of the sperm protein, zonadhesin, promises to improve our understanding of the mechanisms behind the speciesspecific nature of sperm-ZP binding. 131 In this context, it has been shown that targeted deletion of zonadhesin leads to the production of mouse spermatozoa that bind promiscuously to the ZP of several divergent species.…”