葡萄糖是支持精子能量产生和功能的关键底物。先前的研究表明,葡萄糖转运蛋白(GLUT)的几种同种型促进了精子葡萄糖的吸收。这里,我们报告说,精子也表达钠依赖性钠葡萄糖协同转运蛋白(SGLT)。我们的观察首次暗示了睾丸特异性Na的遗传缺失,K-ATPaseα4,损害精子质膜Na+梯度,减少葡萄糖摄取和ATP产生。免疫印迹分析显示精子中存在SGLT,具有同工型1(SGLT-1)的特异性表达,但不是同工型2(SGLT-2)。免疫细胞化学鉴定了精子鞭毛中部和主要部分中的SGLT-1。用同种型选择性抑制剂根皮苷抑制SGLT-1显著降低葡萄糖摄取,糖酵解活性,野生型小鼠的无能力和有能力的精子中的ATP产生。根皮苷也降低了精子的总活力,以及精子运动的其他参数。相比之下,抑制SGLT-1对精子过度激活没有显著影响,蛋白酪氨酸磷酸化,或者顶体反应。重要的是,根皮苷治疗损害了精子的受精能力。总之,这些结果表明,小鼠精子表达了一个功能性SGLT转运系统,该系统对于支持精子能量产生很重要,运动性,和生育能力。
Glucose is a key substrate for supporting sperm energy production and function. Previous studies have demonstrated that sperm glucose uptake is facilitated by several isoforms of the glucose transporters (GLUT). Here, we report that sperm also expresses the Na+-dependent sodium glucose cotransporter (
SGLT). This was first suggested by our observation that genetic deletion of the testis-specific Na,K-ATPase α4, which impairs the sperm plasma membrane Na+ gradient, reduces glucose uptake and ATP production. Immunoblot analysis revealed the presence of an
SGLT in sperm, with specific expression of isoform 1 (
SGLT-1), but not of isoform 2 (
SGLT-2). Immunocytochemistry identified
SGLT-1 in the mid- and principal piece of the sperm flagellum. Inhibition of SGLT-1 with the isotype-selective inhibitor phlorizin significantly reduced glucose uptake, glycolytic activity, and ATP production in noncapacitated and capacitated sperm from wild-type mice. Phlorizin also decreased total sperm motility, as well as other parameters of sperm movement. In contrast, inhibition of
SGLT-1 had no significant effect on sperm hyperactivation, protein tyrosine phosphorylation, or acrosomal reaction. Importantly, phlorizin treatment impaired the fertilizing capacity of sperm. Altogether, these results demonstrate that mouse sperm express a functional SGLT transport system that is important for supporting sperm energy production, motility, and fertility.