Presenilin-1 is present in boar spermatozoa and regulates acrosome reaction in the absence of glucose.

The acrosome reaction (AR) is a calcium-dependent exocytotic event essential for fertilization and can be induced in boar spermatozoa by glucose deprivation. In this study, we demonstrate for the first time in the literature the presence of presenilin-1 (PSEN1) in boar spermatozoa and investigate its potential role in the regulation of the AR. Our findings demonstrate that PSEN1 is present in boar spermatozoa (∼27.8 kDa) and testis (∼26.3 kDa). Deglycosylation assays with PNGase F suggest that PSEN1 is N-glycosylated in boar spermatozoa, explaining the molecular weight differences between spermatozoa and testis samples. After AR induction using the calcium ionophore 4-Br-A23187, PSEN1 protein levels were significantly reduced compared to the control. Immunofluorescence analyses showed that PSEN1 is located in the post-acrosomal region in basal conditions and becomes detectable in the acrosomal region after AR induction, suggesting its localization in the inner membrane of the acrosome. Interestingly, inhibition of PSEN1 with MRK-560 significantly increased AR in glucose-free medium in a dose-dependent manner. Additionally, PSEN1 inhibition induced AR even in the absence of extracellular calcium, suggesting a possible role in calcium release from internal stores. In conclusion, our results demonstrate that PSEN1 is present in boar spermatozoa and may regulate calcium homeostasis essential for AR under glucose-deprived conditions. Further studies are needed to elucidate the underlying molecular mechanisms and the physiological relevance of PSEN1 in fertilization.