The release of cholesterol appears to be necessary for the signaling events that accompany capacitation [3] [4] [5] , including the preparation of the sperm to undergo an agonist-induced acrosome reaction. However, our understanding of how sterol efflux couples to the regulation of signal transduction pathways intrinsic to capacitation remains rudimentary. Years after the description of the plasma membrane fluid mosaic model [6] , specialized platforms clustering signaling molecules were identified [7] . These structures are highly enriched in cholesterol and glycosphingolipids; this lipid composition provides their characteristic biochemical properties (insolubility in nonionic detergents such as Triton X-100 at 48C and light buoyant density after centrifugation in a sucrose gradient). Although several limitations should be taken into account [8] , sucrose light buoyant detergent-resistant membranes (DRMs) have been widely used as a first approach to identify membrane rafts [9] [10] [11] [12] [13] [14] [15] . Current concepts attribute important signaling properties to the existence of membrane rafts acting to bring protein assemblies together [16] [17] [18] . In the case of mammalian sperm, it has been hypothesized that cholesterol release during capacitation modifies the function/location of proteins in sperm raft microdomains [19] [20] [21] [22] [23] [24] . In an effort to elucidate the mechanisms by which the release of cholesterol couples to signaling events in the sperm, we previously conducted a proteomic analysis of the sperm light buoyant fractions and identified a number of proteins, including hexokinase 1 (HK1), testis serine proteases 1 and 2, TEX101, hyaluronidase (SPAM1), facilitated glucose transporter 3 (SLC2A3), lactate dehydrogenase A, carbonic anhydrase IV, IZUMO, pantophysin, basigin (BSG), and CRISP1 [20] .