Department of Biochemistry, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Charitéplatz 1, D-10117 Berlin, Germany.
Department of Transgenic Technologies, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Lindenberger Weg 80, D-13125 Berlin, Germany.
Int J Mol Sci. 2022 Aug 31;23(17):9907. doi: 10.3390/ijms23179907.
Glutathione peroxidase 4 (Gpx4) and arachidonic acid 15 lipoxygenase (Alox15) are counterplayers in oxidative lipid metabolism and both enzymes have been implicated in spermatogenesis. However, the roles of the two proteins in acrosomal exocytosis have not been explored in detail. Here we characterized Gpx4 distribution in mouse sperm and detected the enzyme not only in the midpiece of the resting sperm but also at the anterior region of the head, where the acrosome is localized. During sperm capacitation, Gpx4 translocated to the post-acrosomal compartment. Sperm from Gpx4 mice heterozygously expressing a catalytically silent enzyme displayed an increased expression of phosphotyrosyl proteins, impaired acrosomal exocytosis after in vitro capacitation and were not suitable for in vitro fertilization. Alox15-deficient sperm showed normal acrosome reactions but when crossed into a Gpx4-deficient background spontaneous acrosomal exocytosis was observed during capacitation and these cells were even less suitable for in vitro fertilization. Taken together, our data indicate that heterozygous expression of a catalytically silent Gpx4 variant impairs acrosomal exocytosis and in vitro fertilization. Alox15 deficiency hardly impacted the acrosome reaction but when crossed into the Gpx4-deficient background spontaneous acrosomal exocytosis was induced. The detailed molecular mechanisms for the observed effects may be related to the compromised redox homeostasis.
谷胱甘肽过氧化物酶 4（Gpx4）和花生四烯酸 15 脂加氧酶（Alox15）是氧化脂质代谢的对手，这两种酶都与精子发生有关。然而，这两种蛋白质在顶体反应中的作用尚未详细探讨。在这里，我们描述了 Gpx4 在小鼠精子中的分布，并检测到该酶不仅存在于静息精子的中段，也存在于头部的前区，即顶体所在的位置。在精子获能过程中，Gpx4 易位到顶体后区。来自杂合表达无催化活性酶的 Gpx4 小鼠的精子显示出磷酸酪氨酸蛋白表达增加，体外获能后的顶体反应受损，不适合体外受精。Alox15 缺陷型精子显示出正常的顶体反应，但当与 Gpx4 缺陷型背景交叉时，在获能过程中观察到自发的顶体反应，这些细胞甚至更不适合体外受精。总之，我们的数据表明，杂合表达无催化活性的 Gpx4 变体可损害顶体反应和体外受精。Alox15 缺乏几乎不影响顶体反应，但当与 Gpx4 缺陷型背景交叉时，会诱导自发的顶体反应。观察到的效应的详细分子机制可能与氧化还原稳态受损有关。
