Serine Protease Inhibitor SERPINE2 Reversibly Modulates Murine Sperm Capacitation

Abstract

SERPINE2 (serpin peptidase inhibitor, clade E, member 2), predominantly expressed in the seminal vesicle, can inhibit murine sperm capacitation, suggesting its role as a sperm decapacitation factor (DF). A characteristic of DF is its ability to reverse the capacitation process. Here, we investigated whether SERPINE2 can reversibly modulate sperm capacitation. Immunocytochemical staining revealed that SERPINE2 was bound onto both capacitated and uncapacitated sperm. It reversed the increase in BSA-induced sperm protein tyrosine phosphorylation levels. The effective dose and incubation time were found to be >0.1 mg/mL and >60 min, respectively. Calcium ion levels in the capacitated sperm were reduced to a level similar to that in uncapacitated sperm after 90 min of incubation with SERPINE2. In addition, the acrosome reaction of capacitated sperm was inhibited after 90 min of incubation with SERPINE2. Oviductal sperm was readily induced to undergo the acrosome reaction using the A23187 ionophore; however, the acrosome reaction was significantly reduced after incubation with SERPINE2 for 60 and 120 min. These findings suggested that SERPINE2 prevented as well as reversed sperm capacitation in vitro. It also prevented the acrosome reaction in in vivo-capacitated sperm isolated from the oviduct. Thus, SERPINE2 could reversibly modulate murine sperm capacitation.

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

“…The fluid proteins bind to the surface of sperm to modulate sperm capacitation. Previous studies have unveiled seminal plasma DFs such as SVS2 4 and SERPINE2 5 that can reverse capacitation to prevent sperm from premature capacitation. SPINKL can prevent sperm capacitation but cannot reverse capacitation 7 .…”

“…The ejaculated sperm must reside in the female reproductive tract for a period of time and undergo capacitation to gain the ability to fertilize an egg 1,2 . Capacitation can be reversed by decapacitation factors (DFs), which are present in the seminal plasma 3 and can bind to sperm to prevent prematurely capacitated sperm from losing its fertilization ability 4,5 . When spermatozoa enter the oviduct, DFs are removed from the sperm plasma membrane before or during the capacitation process 4,5 …”

“…Previous studies revealed SVS proteins involved in modulating sperm physiology. Seminal vesicle secretory protein 2 (SVS2) 4 and serpin family E member 2 (SERPINE2) 5 were demonstrated to be potential DFs. The serine protease inhibitor, Kazal type‐like (SPINKL), can inhibit sperm capacitation, 6,7 but it cannot reverse capacitation, and hence is not a DF 7 .…”

Proteomic characterization and comparison of ram (Ovis aries) and buck (Capra hircus) spermatozoa proteome using a data independent acquisition mass spectometry (DIA-MS) approach

“…It is reported that SERPINE2 could inhibit sperm capacitation by blocking the cholesterol outflow of sperm plasma membranes and inhibiting the increase in the level of tyrosine phosphorylation in rat sperm protein [38]. Li et al further confirmed that SERPINE2 could reversibly regulate mouse sperm from the state of capacitated to incapacitated [39]. Results indicated that capacitation inducers (such as BSA [36], cAMP analogs [40], and methyl-β-cyclodextrin [41]) or SERPINE2 inhibitor need to be added in buck sperm cryoprotectants for AI improvement.…”

Downregulation of testosterone production through luteinizing hormone receptor regulation in male rats exposed to 17α-ethynylestradiol

“…Sperm count and motility assay. The process of the sperm motility assay was modified from previous studies 61,62 . The rat cauda epididymis was punctured by scissors and 2 μl semen was mixed with 2 ml Medium 199 culture medium (containing 1% BSA and 1 g/L glucose).…”