The evolutionarily conserved soluble adenylyl cyclase (sAC, ADCY10) mediates cAMP signaling exclusively in intracellular compartments. Because sAC activity is sensitive to local concentrations of ATP, bicarbonate, and free Ca²⁺, sAC is potentially an important metabolic sensor. Nonetheless, little is known about how sAC regulates energy metabolism in intact cells. In this study, we demonstrated that both pharmacological and genetic suppression of sAC resulted in increased lactate secretion and decreased pyruvate secretion in multiple cell lines and primary cultures of mouse hepatocytes and cholangiocytes. The increased extracellular lactate-to-pyruvate ratio upon sAC suppression reflected an increased cytosolic free [NADH]/[NAD⁺] ratio, which was corroborated by using the NADH/NAD⁺ redox biosensor Peredox-mCherry. Mechanistic studies in permeabilized HepG2 cells showed that sAC inhibition specifically suppressed complex I of the mitochondrial respiratory chain. A survey of cAMP effectors revealed that only selective inhibition of exchange protein activated by cAMP 1 (Epac1), but not protein kinase A (PKA) or Epac2, suppressed complex I-dependent respiration and significantly increased the cytosolic NADH/NAD⁺ redox state. Analysis of the ATP production rate and the adenylate energy charge showed that inhibiting sAC reciprocally affects ATP production by glycolysis and oxidative phosphorylation while maintaining cellular energy homeostasis. In conclusion, our study shows that, via the regulation of complex I-dependent mitochondrial respiration, sAC-Epac1 signaling regulates the cytosolic NADH/NAD⁺ redox state, and coordinates oxidative phosphorylation and glycolysis to maintain cellular energy homeostasis. As such, sAC is effectively a bioenergetic switch between aerobic glycolysis and oxidative phosphorylation at the post-translational level.

进化保守的可溶性腺苷酸环化酶（sAC，ADCY10）仅在细胞内区室中介导cAMP信号传导。由于sAC活性对ATP，碳酸氢根和游离Ca ^2+的局部浓度敏感，因此sAC可能是重要的代谢传感器。但是，关于sAC如何调节完整细胞中能量代谢的了解很少。在这项研究中，我们证明了sAC的药理学和基因抑制均导致小鼠肝细胞和胆管细胞的多种细胞系和原代培养物中乳酸分泌增加，丙酮酸分泌减少。抑制sAC后，胞外乳酸与丙酮酸的比率增加，反映出胞浆游离[NADH] / [NAD ⁺比率，这可以通过使用NADH / NAD ⁺氧化还原生物传感器Peredox-mCherry得到证实。在透化的HepG2细胞中的机理研究表明，sAC抑制可特异性抑制线粒体呼吸链的复合物I。对cAMP效应子的调查显示，只有选择性抑制被cAMP 1（Epac1）激活的交换蛋白，而不能抑制蛋白激酶A（PKA）或Epac2，抑制复杂的I依赖呼吸作用，并显着增加胞浆NADH / NAD ⁺氧化还原状态。对ATP产生速率和腺苷酸能电荷的分析表明，抑制sAC通过糖酵解和氧化磷酸化相互影响ATP产生，同时保持细胞能量稳态。总之，我们的研究表明，sAC-Epac1信号通过调节复杂的I依赖性线粒体呼吸，调节细胞质中的NADH / NAD ⁺氧化还原状态，并协调氧化磷酸化和糖酵解，以维持细胞能量的稳态。因此，sAC在翻译后水平上有效地是有氧糖酵解和氧化磷酸化之间的生物能转换。