Njoroge Wambugu Enoc, Zhu Zhendong, Umehara Takashi, Yamanaka Takahiro, Zeng Wenxian, Okazaki Tetsuji, Shimada Masayuki
Laboratory of Reproductive Endocrinology, Graduate School of Integrated Sciences for Life, Hiroshima University, 1-4-4, Kagamiyama, Higashihiroshima, Hiroshima, 7398528, Japan.
College of Animal Science and Technology, Qingdao Agriculture University, 700 Chang-cheng Road., Qingdao, Shangdong, 266109, China.
Free Radic Biol Med. 2025 Feb 16;228:126-136. doi: 10.1016/j.freeradbiomed.2024.12.051. Epub 2024 Dec 29.
Sperm cells are highly susceptible to oxidative stress, which decreases their motility and fertility. However, glutathione (GSH) plays a critical role in protecting sperm cells from oxidative damage, a common byproduct of mitochondrial oxidative phosphorylation. On the other hand, GSH biosynthesis in sperm is limited by the availability of cysteine (Cys), which is inherently unstable and found at low concentrations in boar seminal plasma. In somatic cells, Cys can be produced through the transsulfuration pathway, catalyzed by cystathionine β-synthase (CBS) and cystathionine γ-lyase (CTH). In this study, we report that a group of enzymes involved in GSH synthesis is present in boar sperm. Notably, CBS and CTH protein levels increase during incubation, suggesting active regulation of their synthesis. This increase is inhibited by cycloheximide (CHX), indicating that ongoing protein synthesis is necessary for maintaining these levels. Our study also identified the presence of translation factors, such as eukaryotic initiation factor 4E (eIF4E), and their activation through phosphorylation of the ERK1/2-RSK-eIF4E pathway during incubation. Additionally, we found that CBS mRNA transcripts with short poly(A) tails are present in boar sperm, and polyadenylation of these short-tailed mRNAs occurs during incubation to enhance their translation. The use of cordycepin, a polyadenylation inhibitor, significantly reduced the translation of CBS, leading to decreased GSH synthesis and impaired sperm motility. However, the addition of cysteine counteracted the inhibitory effects of cordycepin, underscoring the essential role of cysteine in maintaining GSH levels. These findings provide new insights into the post-transcriptional regulation of GSH synthesis in sperm and suggest potential strategies for enhancing sperm preservation and fertility by targeting polyadenylation and translation mechanisms.
精子细胞对氧化应激高度敏感，氧化应激会降低其活力和生育能力。然而，谷胱甘肽（GSH）在保护精子细胞免受氧化损伤方面起着关键作用，氧化损伤是线粒体氧化磷酸化的常见副产物。另一方面，精子中谷胱甘肽的生物合成受到半胱氨酸（Cys）可用性的限制，半胱氨酸本身不稳定，在公猪精液中浓度较低。在体细胞中，半胱氨酸可以通过转硫途径产生，该途径由胱硫醚β-合酶（CBS）和胱硫醚γ-裂合酶（CTH）催化。在本研究中，我们报告了一组参与谷胱甘肽合成的酶存在于公猪精子中。值得注意的是，CBS和CTH蛋白水平在孵育过程中增加，表明它们的合成受到积极调控。这种增加被环己酰亚胺（CHX）抑制，表明持续的蛋白质合成对于维持这些水平是必要的。我们的研究还确定了翻译因子的存在，如真核起始因子4E（eIF4E），以及它们在孵育过程中通过ERK1/2-RSK-eIF4E途径的磷酸化而被激活。此外，我们发现公猪精子中存在具有短聚腺苷酸尾巴的CBS mRNA转录本，这些短尾mRNA在孵育过程中发生聚腺苷酸化以增强其翻译。使用聚腺苷酸化抑制剂虫草素显著降低了CBS的翻译，导致谷胱甘肽合成减少和精子活力受损。然而，添加半胱氨酸抵消了虫草素的抑制作用，强调了半胱氨酸在维持谷胱甘肽水平方面的重要作用。这些发现为精子中谷胱甘肽合成的转录后调控提供了新的见解，并提出了通过靶向聚腺苷酸化和翻译机制来提高精子保存和生育能力的潜在策略。
