title: Role of egg sulfolipidimmobilizing protein 1 on mouse sperm-egg plasma membrane binding.
abstract: We have shown that sperm sulfolipidimmobilizing protein 1 (SLIP1, molecular mass of 68 kDa), a sulfogalactosylglycerolipid (SGG)-binding protein, is significant in sperm-zona pellucida (ZP) interaction. The objective of this study was to localize SLIP1 on the egg and determine its role in gamete interaction. Immunofluorescence and immunoprotein A gold electron microscopy localized SLIP1 to the egg plasma membrane. In vitro gamete binding, using zona-free eggs preincubated with antiSLIP1 Fab before coincubation with sperm, showed a significant, dose-dependent decrease in sperm-egg plasma membrane binding. Similar results were obtained when affinity-purified antiSLIP1 IgG was used for egg pretreatment. The significance of egg SLIP1 in sperm-egg plasma membrane binding was further demonstrated by a decrease (36-52%) in in vitro fertilization when zona-intact eggs were pretreated with antiSLIP1 IgG. Since SLIP1 has been shown to bind SGG in vitro, we investigated the possibility that sperm SGG may participate in sperm-egg plasma membrane binding through egg SLIP1. Pretreatment of sperm with antiSGG Fab prior to coincubation with zona-free eggs resulted in a dose-dependent decrease in sperm-egg plasma membrane binding. Collectively, these findings strongly suggest a role for egg SLIP1 in sperm-egg plasma membrane interaction, which may be through its binding to sperm SGG.
authors.affiliation: Human IVF Program, Reproductive Biology Unit, Hormones/Growth/Development Research Group, Loeb Research Institute, Ottawa Civic Hospital, Department of Biochemistry, University of Ottawa, Ontario, Canada.
authors.forename: V
authors.initials: V
authors.lastname: Ahnonkitpanit
authors.forename: D
authors.initials: D
authors.lastname: White
authors.forename: S
authors.initials: S
authors.lastname: Suwajanakorn
authors.forename: F W
authors.initials: FW
authors.lastname: Kan
authors.forename: M
authors.initials: M
authors.lastname: Namking
authors.forename: G
authors.initials: G
authors.lastname: Wells
authors.forename: N
authors.initials: N
authors.lastname: Kamolvarin
authors.forename: N
authors.initials: N
authors.lastname: Tanphaichitr
mesh_terms: D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D002352:Carrier Proteins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology*; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D005260:Female; D019085:Fluorescent Antibody Technique, Direct; D015151:Immunoblotting; D008297:Male; D051379:Mice; D016253:Microscopy, Immunoelectron; D010063:Ovum / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure; D016601:RNA-Binding Proteins; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000502:physiology / Q000648:ultrastructure
chemical_list: D000906:Antibodies; D002352:Carrier Proteins; D016601:RNA-Binding Proteins; C489106:Slip1 protein, mouse