Suppression effect of seminal vesicle autoantigen on platelet‐activating factor‐induced mouse sperm capacitation

Abstract

Mammalian sperm gain the ability to fertilize an egg successfully by the capacitation process. An unregulated capacitation process causes sperm to undergo a spontaneous acrosome reaction (AR) and resulting in loss of their fertilization activity. Thus, functional sperm activation is tightly regulated by a capacitation and suppression (decapacitation) mechanism. Factors, such as platelet-activating factor (PAF) present in both sperm and the female genital tract, are able to stimulate sperm capacitation. Seminal plasma is thought to have the ability to suppress sperm capacitation; however, the regulatory mechanisms of seminal plasma protein on sperm capacitation are not well understood. Recently, we demonstrated that seminal vesicle autoantigen (SVA), a major seminal vesicle secretory protein, is able to suppress mouse sperm capacitation. To further study the suppression spectra of SVA on sperm capacitation, we investigated the effect of SVA on PAF-induced mouse sperm capacitation-related signals. Here, we demonstrate that SVA decreases the [Ca(2+)](i) to suppress the PAF's effects on [Ca(2+)](i), the cAMP level, protein tyrosine phosphorylation, and capacitation. The inhibition of PAF-induced protein tyrosine phosphorylation and capacitation by SVA can be reversed by cAMP agonists. Characterization of the interactions of SVA with PAF by TLC overlay and tryptophan fluorescence spectrum analyses indicates that SVA is capable of binding PAF with an apparent dissociation constant K(d) > 50 microM. Together with these results, we demonstrate that SVA deceases [Ca(2+)](i) and cross-talks with PAF-induced intracellular signals to regulate mouse sperm capacitation.

Seminal Plasma Proteins as Potential Markers of Relative Fertility in Boars

“…Protein 27 was also identified as PSP-I, which supports our hypothesis that PSP-I may limit fertility because of an inhibitory effect of these spermadhesins on sperm performance in a low-sperm insemination dose scenario. Specific seminal plasma components have been described as decapacitation factors in humans (Zhu et al, 2006), mice (Huang et al, 2007), and other species (as reviewed in Tö pferPetersen et al, 1998) and are assumed to protect sperm from factors in the female tract that could trigger early capacitation, thus reducing the possibility of spermoocyte binding. These suggestions are consistent with the observations that preincubation of sperm from the Sperm-Peak fraction with seminal plasma from the Sperm-Free fraction reduced oocyte penetration rate in vitro (Zhu et al, 2000), whereas inclusion of seminal plasma in sperm samples sorted by flow cytometry increased the percentage of uncapacitated, acrosomeintact sperm and reduced oocyte penetration rate in vitro (Maxwell and Johnson, 1999).…”

The CAP Superfamily: Cysteine-Rich Secretory Proteins, Antigen 5, and Pathogenesis-Related 1 Proteins—Roles in Reproduction, Cancer, and Immune Defense

“…Decapacitation factors, of which there appear to be many, are often of epididymal or accessory organ origin (67,(215)(216)(217)(218)(219) and are removed from sperm after entry into the reproductive tract or by incubation in vitro in capacitating conditions.…”

Platelet‐activating Factor in Iberian Pig Spermatozoa: Receptor Expression and Role as Enhancer of the Calcium‐Induced Acrosome Reaction

“…1996), stallion (Odeh et al. 2003), mouse (Huo and Yang 2000; Huang et al. 2007) and cattle (Aravindakshan and Sharma 1995).…”

“…2002), bull (Aravindakshan and Sharma 1995), stallion (Odeh et al. 2003) and mouse (Huo and Yang 2000; Huang et al. 2007), and this capacitating effect is blocked in mouse by PAF receptor antagonists (Kuzan et al.…”