A mouse seminal vesicle‐secreted lysozyme c‐like protein modulates sperm capacitation

Abstract

Lysozyme (LYZ) c‐like proteins are primarily present in the testis and epididymis of male reproductive tissues. Here, we report a novel member of the c‐type LYZ family, the seminal vesicle‐secreted LYZ c‐like protein (SVLLP). Three forms of SVLLP were purified from mouse seminal vesicle secretions and characterized as glycoproteins with the same protein core but different N‐linked glycans. SVLLP is structurally similar to c‐type LYZ proteins. Only one of the 20 invariant residues was altered in the consensus sequence of c‐type LYZs; however, the changed residue (N53S) is one of two essential catalytic residues. LYZ activity assays demonstrated that the three glycoforms of SVLLP lacked enzyme activity. SVLLP is primarily expressed in seminal vesicles. Immunohistochemistry revealed that it occurs in the luminal fluid and mucosal epithelium of the seminal vesicles. Testosterone is not the primary regulator for its expression in the seminal vesicle. SVLLP binds to sperm and suppresses bovine serum albumin‐induced sperm capacitation, inhibits the acrosome reaction, and blocks sperm–oocyte interactions in vitro, suggesting that SVLLP is a sperm capacitation inhibitor.

Secretory mouse quiescin sulfhydryl oxidase 1 aggregates defected human and mouse spermatozoa in vitro and in vivo

“…The possible reason is that most QSOX1c-agglutinated sperm cells were defected and cannot undergo capacitation or acrosome reactions. Several seminal proteins in SVS, e.g., SERPINE2 ( Li et al., 2018 ; Lu et al., 2011 ), SPINKL ( Lin et al., 2008 ; Tseng et al., 2013 ), SVLLP ( Ou et al., 2021 ), and SVS2 ( Araki et al., 2015 ; Kawano and Yoshida, 2007 ), can prevent premature capacitation and subsequent acrosome reaction and preserve sperm ability to fertilize an egg before reaching the fertilization site. Thus, although more experimental evidence is needed, we speculate that QSOX1c may not exhibit similar preservation functions as the above-mentioned SVS proteins.…”

“…Epididymal spermatozoa were pre-incubated with or without QSOX1c (0.3, 0.6, or 0.9 mg/mL) in BWW medium for 15 min and then capacitated with or without BSA (3 mg/ml) and NaHCO 3 (25 mM), at 37°C in humidified air with 5% (v/v) CO 2 for 90 min. Sperm proteins were then extracted, resolved on an 8% SDS-PAGE gel, electrotransferred onto a nitrocellulose membrane, and Western blotting using an anti-phosphotyrosine monoclonal antibody (1:5000 dilution, clone 4G10, Millipore, Temecula, CA) following the previously published method ( Ou et al., 2021 ).…”

“…For the induction of acrosome reaction, the capacitated sperm were treated with or without 10 μM A23187 in 0.1% (v/v) dimethyl sulfoxide at 37°C for 30 min. Sperm were then washed and smeared onto a slide following the method mentioned above ( Ou et al., 2021 ). The acrosomal status was revealed by staining with 5 μg/mL of PNA-FITC (Sigma-Aldrich) for 10 min in the dark.…”

Antimicrobial peptides and proteins as alternative antibiotics for porcine semen preservation

“…Similarly, the presence of a seminal vesicle-secreted lysozyme c-like protein (SVLLP) has been reported in mice. This protein binds to spermatozoa and suppresses bovine serum albumin-induced sperm capacitation and inhibits acrosome reaction [ 58 ]. The enhanced sperm quality associated with an increased amount of lysozyme could be related not only to its antimicrobial properties but also to its ameliorative effect against oxidative stress.…”

Antimicrobial peptides and proteins as alternative antibiotics for porcine semen preservation

“…Similarly, the presence of a seminal vesicle-secreted lysozyme c-like protein (SVLLP) has been reported in mice. This protein binds to spermatozoa and suppresses bovine sperm albumin-induced sperm capacitation and inhibits acrosome reaction [51]. The enhanced sperm quality associated with an increased amount of lysozyme could be related not only to its antimicrobial properties but also to its ameliorative effect against oxidative stress.…”