Sperm plasma membrane

About: Sperm plasma membrane is a research topic. Over the lifetime, 1016 publications have been published within this topic receiving 49964 citations.

Human zona pellucida recognition associated with removal of sialic acid from human sperm surface

Abstract: The ability of human spermatozoa recovered from highly motile sperm fractions to bind wheat germ agglutinin (WGA) after discontinuous Percoll gradient centrifugation was studied. WGA could bind to almost all motile spermatozoa, whereas fewer than 25% of spermatozoa could bind peanut (PNA) and concanavalin A (Con A) agglutinin, two lectins that specifically bind acrosomal membranes. After removal of the plasma membrane with 0.04% Triton X100, WGA, PNA and Con A bound more than 80% of spermatozoa, but binding sites for WGA on the anterior acrosomal region were markedly reduced. The expression of sialic acid on human sperm plasma membrane was demonstrated, since WGA, which specifically recognizes both sialic acid (NeuNAc) and N-acetylglucosamine (GlcNAc), bound almost all intact motile spermatozoa, whereas succinylated WGA, which recognizes only GlcNAc, bound less than 10% of intact motile spermatozoa. Moreover, binding of WGA was compared with that of three other lectins (Sambucus nigra, SNA; Maackia amurensis, MAL and Limulus polyphemus, LPA) with specificity for different NeuNAc linkages. Only SNA, which requires the presence of the disaccharide structure NeuNAc alpha(2,6) Gal/GalNAc, showed a positive correlation with sperm motility as observed with WGA. Moreover, there was a strong inhibition of WGA binding on spermatozoa preincubated with bovine submaxillary mucin containing (2,6)-linked NeuNAc. These results demonstrate the presence of NeuNAc alpha(2,6) Gal/GalNAc glycoconjugate sequences on the plasma membrane of the motile human spermatozoon.(ABSTRACT TRUNCATED AT 250 WORDS)

Sperm-associated oocyte-activating factor is released from the spermatozoon within 30 minutes after injection as a result of the sperm-oocyte interaction.

Abstract: We have previously shown that sperm plasma membrane damage makes the sperm plasma membrane permeable and the sperm nucleus accessible for low molecular weight molecules such as eosin and dithiothreitol. In the present study, we investigated whether this damage is associated with a passive release of the sperm-associated oocyte activating factor (SAOAF) from the spermatozoon and, if so, its time sequence. In a first study, human oocytes remaining unfertilized after conventional in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) and freshly ovulated mouse oocytes were injected with a whole spermatozoon or a sperm head respectively. They were randomly allocated to one of three groups: oocytes in group 1 were injected with a spermatozoon immobilized or sperm head detached immediately prior to the injection; oocytes in group 2 were injected with a spermatozoon immobilized or sperm head detached 2-4 h before injection; oocytes in group 3 were injected with a spermatozoon or sperm head that had been subjected to heat treatment. The activation rate of oocytes injected with a spermatozoon or sperm head was the same for groups 1 and 2, and significantly higher than in group 3 (P < 0.001). In a second series of experiments, human oocytes remaining unfertilized after IVF or ICSI were injected with a sperm head that was subsequently removed from the ooplasm 20-30 min after injection. The activation rates were compared to that of oocytes injected with heat-treated spermatozoa which subsequently were removed from the ooplasm. We found that the removal of the spermatozoon 30 min after injection did not prevent oocyte activation. Our data indicate that the initial damage to the sperm plasma membrane induced at immobilization, although essential for the onset of sperm nuclear swelling after ICSI, does not by itself lead to the release of SAOAF from the spermatozoon. We postulate, however, that SAOAF is released during the sperm nuclear swelling phase, which is induced by the so-called sperm nucleus decondensing factor (SNDF) of the oocyte.

High Cholesterol Content and Decreased Membrane Fluidity in Human Spermatozoa Are Associated With Protein Tyrosine Phosphorylation and Functional Deficiencies

Abstract: Poor-quality sperm show reduced capacity to undergo capacitation-induced protein tyrosine phosphorylation and hyperactivation. Given that these deficiencies can be overcome by membrane-permeant stimulators of the cAMP-dependent kinase system, we hypothesize that the main defect underlying these deficiencies resides on the sperm plasma membrane. Spermatozoa from semen samples obtained from 15 consenting healthy donors were separated in 2 subpopulations, L45 (first interface) and L90 (pellet), using a 45:65:90 ISolate gradient centrifugation method. These sperm fractions were studied before and after a 6-hour capacitating incubation for sperm motion parameters (computer-assisted analysis), including hyperactivation, protein tyrosine phosphorylation (immunofluorescence), membrane fluidity (Laurdan fluorescence), and sterol and phospholipid content (high-performance thin-layer chromatography). In summary, data indicate that L45 (poor-motility) spermatozoa present an excess of cholesterol and desmosterol, which impairs the normal increase in membrane fluidity during capacitation and its consequent activation of protein tyrosine phosphorylation and hypermotility. Therefore, a defect in membrane composition and dynamics is underlying human sperm biochemical and functional deficiencies related to inadequate capacitation.

Osmotic characteristics of mouse spermatozoa in the presence of extenders and sugars.

Abstract: Successful cryopreservation requires cells to tolerate volume excursions experienced during permeating cryoprotectant equilibration and during cooling and warming. However, prior studies have demonstrated that mouse spermatozoa are extremely sensitive to osmotically induced volume changes. A series of three experiments were conducted 1) to test the efficacy of two commonly used extender media components, egg yolk (EY) and skim milk (SM), in broadening the osmotic tolerance limits (OTL) of ICR and B6C3F1 murine spermatozoa; 2) to determine if the extender components affected sperm plasma membrane permeability coefficients for water and cryoprotective agent (CPA) characteristics; and 3) to test the effects of permeating and nonpermeating CPA on mouse sperm morphology. In experiment 1, sperm samples were added to 150, 225, 300, 450, or 600 mOsm NaCl, EY, SM, sucrose, or choline chloride at 22°C and then returned to isosmotic conditions. In experiment 2, epididymal sperm were preequilibrated in 1 M g...

ADAM7 is associated with epididymosomes and integrated into sperm plasma membrane

Abstract: During epididymal transit, mammalian sperm acquire selected proteins secreted by the epididymis. We previously showed that a disintegrin and metalloprotease (ADAM) 7 is expressed specifically in the epididymis and transferred to the sperm surface during epididymal transit. Here, we show that mouse ADAM7 secreted to the epididymal lumen is associated with membranous vesicles known as epididymosomes. Furthermore, we found that ADAM7 can be transferred directly from epididymal vesicles to sperm and that it is an integral plasma membrane protein in sperm. Thus, our study provides new information regarding the unique mode of secretion and interaction of ADAM7 during the epididymis-to-sperm transfer process.