Localization of Low-Density Detergent-Resistant Membrane Proteins in Intact and Acrosome-Reacted Mouse Sperm

PATRICIA V. MIRANDA; ALICIA ALLAIRE; JULIAN SOSNIK; PABLO E. VISCONTI

BIOLOGY OF REPRODUCTION

Society for the Study of Reproduction

Lugar: Madison; Año: 2009 vol. 80 p. 897 - 904

0006-3363

Mammalian sperm become fertile after completing capacitation, a process associated with cholesterol loss and with changes in the biophysical properties of the sperm membranes that prepares the sperm to undergo the acrosome reaction. Different laboratories have hypothesized that cholesterol efflux can influence the extent and/or the movement of lipid raft microdomains. In a previous study, our laboratory investigated the identity of sperm proteins putatively associated with rafts. After extraction with Triton X-100 and ultracentrifugation in sucrose gradients, proteins distributing to the light buoyant density fractions were cored from polyacrylamide gels and microsequenced. In this report, a subset of these proteins (TEX101, Basigin, Hexokinase 1, Facilitated glucose transporter 3, IZUMO and SPAM1) and other molecules  known to be enriched in membrane rafts (Caveolin 2, Flotillin 1, Flotillin 2 and the ganglioside GM3) were selected to investigate their localization in the sperm and their behavior during capacitation and the acrosome reaction. These molecules localize to multiple sperm domains including the acrosomal cap (IZUMO, Caveolin 2 and Flotillin2), the equatorial segment (GM3), the cytoplasmic droplet (TEX101), the mid-piece (Basigin, Facilitated glucose transporter 3, Flotillin 2) and the principal piece (Facilitated glucose transporter 3). Interestingly, some of these markers modified their immunofluorescence pattern after sperm incubation under capacitating conditions and these changes correlated with the occurrence of the acrosome reaction. While GM3 and Caveolin 2 were not detected after the acrosome reaction, Flotillin 2 was found in the equatorial segment of acrosome-reacted sperm and IZUMO distributed along the sperm head reaching the post and para-acrosomal area. Taking into consideration the requirement of the acrosome reaction for sperm to become fusogenic, these results suggest that membrane raft dynamics might play a role in sperm-egg membrane interaction.