The African clawed frog (Xenopus laevis) naturally tolerates severe dehydration using biochemical adaptation, one of which is the elevation of antioxidant defenses during whole-body dehydration. The present study investigated the role and regulation of a pathway known to regulate oxidative stress response, the Akt-FoxO signaling pathway, in clawed frog skeletal muscle, responding to medium (15%) and high (30%) dehydration. Protein levels of total and phosphorylated Akt, FoxO1, and FoxO3 were assessed via immunoblotting, in addition to the levels of the E3 ubiquitin ligase known to be associated with muscle atrophy, MAFbx. Akt activity/phosphorylation in addition to its total protein levels were decreased in the skeletal muscle during dehydration, and this corresponded with decreases in the relative phosphorylation of FoxO1 and FoxO3 as well on several residues. Akt is an inhibitor of FoxO1 and FoxO3 activity via phosphorylation, suggesting that FoxO activities were increased during dehydration stress. Furthermore, MAFbx showed decreased protein expression during high dehydration as well, suggesting that the clawed frog may exhibit some natural resistance to skeletal muscle atrophy during severe dehydration conditions. In addition to identifying that the suppression of Akt could lead to an activation of FoxO transcription factors in X. laevis during dehydration, these investigations suggest that X. laevis dehydration may implicate FoxO1 and FoxO3 in controlling skeletal muscle atrophy in X. laevis exposed to dehydration. This study implicates the Akt signaling pathway, its regulation of FoxO transcription factors, and FoxO-controlled targets, in stress adaptation against dehydration.

非洲爪蛙（ Xenopus laevis ）通过生化适应自然地耐受严重脱水，其中之一是全身脱水期间抗氧化防御能力的提高。本研究调查了爪蛙骨骼肌中已知调节氧化应激反应的通路（Akt-FoxO 信号通路）的作用和调节，对中度（15%）和高度（30%）脱水做出反应。除了已知与肌肉萎缩 MAFbx 相关的 E3 泛素连接酶水平外，还通过免疫印迹评估总 Akt 和磷酸化 Akt、FoxO1 和 FoxO3 的蛋白质水平。脱水期间，骨骼肌中的 Akt 活性/磷酸化及其总蛋白水平均降低，这与 FoxO1 和 FoxO3 以及几个残基上的相对磷酸化的降低相对应。 Akt 是一种通过磷酸化抑制 FoxO1 和 FoxO3 活性的抑制剂，表明 FoxO 活性在脱水应激期间增加。此外，MAFbx 在高度脱水期间也显示出蛋白质表达下降，这表明爪蛙在严重脱水条件下可能表现出对骨骼肌萎缩的一些天然抵抗力。除了确定 Akt 的抑制可能导致非洲虎在脱水过程中激活 FoxO 转录因子外，这些研究还表明，非洲虎脱水可能表明 FoxO1 和 FoxO3 控制了暴露于脱水的非洲虎的骨骼肌萎缩。 。这项研究表明 Akt 信号通路、其对 FoxO 转录因子的调节以及 FoxO 控制的靶标在对抗脱水的应激适应中发挥着重要作用。