Khatun Amena, Rahman Md Saidur, Ryu Do-Yeal, Kwon Woo-Sung, Pang Myung-Geol
Department of Animal Science and Technology, Chung-Ang University, Anseong, Republic of Korea.
PLoS One. 2017 Aug 31;12(8):e0184294. doi: 10.1371/journal.pone.0184294. eCollection 2017.
Aminopeptidase N (APN) is a naturally occurring ectopeptidase present in mammalian semen. Previous studies have demonstrated that APN adversely affects male fertility through the alteration of sperm motility. This enzyme constitutes 0.5 to 1% of the seminal plasma proteins, which can be transferred from the prostasomes to sperms by a fusion process. In the present study, we investigated the molecular mechanism of action of APN and its role in regulating sperm functions and male fertility. In this in vitro study, epididymal mouse spermatozoa were incubated in a capacitating media (pH 7) containing 20 ng/mL of recombinant mouse APN for 90 min. Our results demonstrated that the supplementation of recombinant APN in sperm culture medium significantly increased APN activity, and subsequently altered motility, hyperactivated motility, rapid and medium swimming speeds, viability, and the acrosome reaction of mouse spermatozoa. These effects were potentially caused by increased toxicity in the spermatozoa. Further, altered APN activity in sperm culture medium affected early embryonic development. Interestingly, the effect of elevated APN activity in sperm culture medium was independent of protein tyrosine phosphorylation and protein kinase A activity. On the basis of these results, we concluded that APN plays a significant role in the regulation of several sperm functions and early embryonic development. In addition, increased APN activity could potentially lead to several adverse consequences related to male fertility.
氨肽酶N（APN）是一种天然存在的外肽酶，存在于哺乳动物精液中。先前的研究表明，APN通过改变精子活力对男性生育能力产生不利影响。这种酶占精浆蛋白的0.5%至1%，可通过融合过程从前列腺小体转移到精子上。在本研究中，我们研究了APN的分子作用机制及其在调节精子功能和男性生育能力中的作用。在这项体外研究中，将附睾小鼠精子在含有20 ng/mL重组小鼠APN的获能培养基（pH 7）中孵育90分钟。我们的结果表明，在精子培养基中添加重组APN可显著提高APN活性，随后改变小鼠精子的活力、超激活运动能力、快速和中等游泳速度、活力以及顶体反应。这些影响可能是由精子毒性增加引起的。此外，精子培养基中APN活性的改变影响早期胚胎发育。有趣的是，精子培养基中APN活性升高的影响与蛋白质酪氨酸磷酸化和蛋白激酶A活性无关。基于这些结果，我们得出结论，APN在调节多种精子功能和早期胚胎发育中起重要作用。此外，APN活性增加可能会导致与男性生育能力相关的若干不良后果。
