Composition and significance of detergent resistant membranes in mouse spermatozoa

Abstract

Mammalian spermatozoa acquire the ability to fertilize an oocyte as they ascend the female reproductive tract. This process is characterized by a complex cascade of biophysical and biochemical changes collectively know as "capacitation." The attainment of a capacitated state is accompanied by a dramatic reorganization of the surface architecture to render spermatozoa competent to recognize the oocyte and initiate fertilization. Emerging evidence indicates that this process is facilitated by molecular chaperone-mediated assembly of a multimeric receptor complex on the sperm surface. However, the mechanisms responsible for gathering key recognition molecules within this putative complex have yet to be defined. In this study, we provide the first evidence that chaperones partition into detergent resistant membrane fractions (DRMs) within capacitated mouse spermatozoa and co-localize in membrane microdomains enriched with the lipid raft marker, G(M1) ganglioside. During capacitation, these microdomains coalesce within the apical region of the sperm head, a location compatible with a role in sperm-zona pellucida interaction. Significantly, DRMs isolated from spermatozoa possessed the ability to selectively bind to the zona pellucida of unfertilized, but not fertilized, mouse oocytes. A comprehensive proteomic analysis of the DRM fractions identified a total of 100 proteins, a number of which have previously been implicated in sperm-oocyte interaction. Collectively, these data provide compelling evidence that mouse spermatozoa possess membrane microdomains that provide a platform for the assembly of key recognition molecules on the sperm surface and thus present an important mechanistic insight into the fundamental cell biological process of sperm-oocyte interaction.

Capacitation in the presence of methyl-β-cyclodextrin results in enhanced zona pellucida-binding ability of stallion spermatozoa

“…Upon capacitation, and the resultant cholesterol efflux, membrane rafts undergo a dynamic reorganisation from a uniform pattern of distribution to one that is confined to the apical ridge of the sperm head, the region that mediates zona recognition and binding (van Gestel et al 2005a). Furthermore, among the key proteins identified within these microdomains are a subset of putative zona receptor molecules (Asano et al 2009, Nixon et al 2009. In the present study, incubation of sperm in the presence of mbcd in combination with PVAand SB-based BWW media resulted in a significant increase in the number of sperm displaying membrane raft aggregation within the peri-acrosomal region of the sperm head (Fig.…”

Sperm surface changes and physiological consequences induced by sperm handling and storage

“…Certain proteins, such as flotillin and caveolin (Anderson 1998, van Gestel et al 2005a, are well known to be permanently associated with lipid rafts, but since these structures aggregate in the exact area of the sperm head where initial zona recognition occurs (Cross 2004), they would be expected to also contain zona binding proteins. Indeed, lipid rafts isolated from in vitro-capacitated mouse (Nixon et al 2009), human and porcine (van Gestel et al 2005a spermatozoa were highly enriched in zona binding proteins. Therefore, it is likely that in vitro capacitation leads to delicate sperm surface alterations, which allow the formation of a multi-protein complex involved in zona recognition (for review, see Gadella (2010)).…”

More Than a Simple Lock and Key Mechanism: Unraveling the Intricacies of Sperm-Zona Pellucida Binding

“…Notably, the spatial distribution of membrane rafts within the sperm membrane is dramatically influenced by the capacitation status of the cells. Indeed, the uniform localization of rafts characteristically observed in non-capacitated spermatozoa is replaced by a pattern of confinement within the peri-acrosomal region of the sperm head following the induction of capacitation (Boerke, et al, 2008, Nixon, et al, 2009, Shadan, et al, 2004. This particularly interesting finding raises the possibility that membrane rafts are of significance in coordinating the functional competence of spermatozoa (Bou Khalil, et al, 2006).…”

“…However despite their stability, rafts remain highly dynamic entities and have been observed to display considerable lateral movement in various cell types as a response to physical stimuli or cellular activation events (Simons and Vaz, 2004). In sperm, membrane rafts have been identified by the presence of several somatic cell raft markers including GM1 gangliosides, flotillin and proteins that have raft affinity due to the presence of glycosylphophatidylinositol (GPI) anchors, including CD59 and SPAM1 (Nixon, et al, 2009, Sleight, et al, 2005, van Gestel, et al, 2005. Notably, the spatial distribution of membrane rafts within the sperm membrane is dramatically influenced by the capacitation status of the cells.…”