A mouse sperm decapacitation factor receptor is phosphatidylethanolamine-binding protein 1.
Capacitation is a pivotal event for mammalian spermatozoa, involving the loss of surface proteins known as decapacitation factors (DF) and consequent acquisition of fertilizing ability. Earlier studies showed that a mouse sperm DF binds to a receptor, DF-R, whose attachment to the sperm plasma membrane appears to involve a glycosylphosphatidylinositol (GPI) anchor. In the present study, purification and subsequent sequencing of DF-R has identified this approximately 23 kDa protein as phosphatidylethanolamine-binding protein 1 (PEBP 1). To obtain functional evidence that supports sequence homology data, purified recombinant PEBP 1 and PEBP 2 were evaluated for biological activity. While PEBP 1 was able to remove DF activity in solution at concentrations above approximately 1 nmol/l, PEBP 2 was ineffective, even at 600 nmol/l; this confirmed that DF-R is PEBP 1. Anti-PEBP 1 antiserum recognized recombinant PEBP 1 and a approximately 23 kDa protein in both mouse and human sperm lysates. Immunolocalization studies revealed that DF-R/PEBP 1 is located on the acrosomal cap, the post-acrosomal region and the flagellum of both mouse and human spermatozoa, with epitope accessibility being capacitation state-dependent and reversible. Treatment of cells with a phospholipase able to cleave GPI anchors essentially abolished immunostaining, thus confirming the extracellular location of DF-R/PEBP 1. We suggest that DF-R/PEBP 1 plays its fundamental role in capacitation by causing alterations in the sperm plasma membrane in both head and flagellum, with functional consequences for membrane-associated proteins. Obtaining more detail about DF <--> DF-R interactions could lead to useful applications in both fertility treatments and new contraceptive approaches.
Gibbons
Rachel
R
Reproduction and Rhythms Group, School of Biomedical Sciences, King's College London, Guy's Campus, London SE1 1UL, UK.
Adeoya-Osiguwa
Susan A
SA
Fraser
Lynn R
LR
D000818:Animals; D000911:Antibodies, Monoclonal / Q000302:isolation & purification; D001483:Base Sequence; D015153:Blotting, Western / Q000379:methods; D002352:Carrier Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D002751:Chlortetracycline; D002853:Chromatography, Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D007150:Immunohistochemistry / Q000379:methods; D037102:Lectins; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D008970:Molecular Weight; D049488:Phosphatidylethanolamine Binding Protein / Q000032:analysis / Q000235:genetics / Q000302:isolation & purification*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D013075:Sperm Capacitation / Q000187:drug effects*; D013094:Spermatozoa / Q000737:chemistry*
D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D037102:Lectins; C471030:Pbp2 protein, mouse; D049488:Phosphatidylethanolamine Binding Protein; D011994:Recombinant Proteins; D002751:Chlortetracycline