Bernasconi Romain, Soodla Kärol, Sirp Alex, Zovo Kairit, Kuhtinskaja Maria, Lukk Tiit, Vendelin Marko, Birkedal Rikke
Laboratory of Systems Biology, Department of Cybernetics, Tallinn University of Technology, Tallinn, Estonia.
Laboratory of Molecular Neurobiology, Department of Chemistry and Biotechnology, Tallinn University of Technology, Tallinn, Estonia.
Am J Physiol Endocrinol Metab. 2025 Jan 1;328(1):E21-E33. doi: 10.1152/ajpendo.00261.2024. Epub 2024 Nov 28.
AMP-activated protein kinase (AMPK) is an energy-sensing serine/threonine kinase involved in metabolic regulation. It is phosphorylated by the upstream liver kinase B1 (LKB1) or calcium/calmodulin-dependent kinase kinase 2 (CaMKKβ). In cultured cells, AMPK activation correlates with LKB1 activity. The phosphorylation activates AMPK, shifting metabolism toward catabolism and promoting mitogenesis. In muscles, inactivity reduces AMPK activation, shifting the phenotype of oxidative muscles toward a more glycolytic profile. Here, we compared the basal level of AMPK activation in glycolytic and oxidative muscles and analyzed whether this relates to LKB1 or CaMKKβ. Using Western blotting, we assessed AMPK expression and phosphorylation in soleus, gastrocnemius (GAST), extensor digitorum longus (EDL), and heart from C57BL6J mice. We also assessed LKB1 and CaMKKβ expression, and CaMKKβ activity in tissue homogenates. AMPK activation was higher in oxidative (soleus and heart) than in glycolytic muscles (gastrocnemius and EDL). This correlated with AMPK α1-isoform expression, but not LKB1 and CaMKKβ. LKB1 expression was sex dependent and lower in male than female muscles. CaMKKβ expression was very low in skeletal muscles and did not phosphorylate AMPK in muscle lysates. The higher AMPK activation in oxidative muscles is in line with the fact that activated AMPK maintains an oxidative phenotype. However, this could not be explained by LKB1 and CaMKKβ. These results suggest that the regulation of AMPK activation is more complex in muscle than in cultured cells. As AMPK has been proposed as a therapeutic target for several diseases, future research should consider AMPK isoform expression and localization, and energetic compartmentalization. It is important to understand how AMP-activated kinase, AMPK, is regulated, as it is a potential therapeutic target for several diseases. AMPK is activated by liver kinase B1, LKB1, and calcium/calmodulin-dependent kinase kinase 2, CaMKKβ. In cultured cells, AMPK activation correlates with LKB1 expression. In contrast, we show that AMPK-activation was higher in oxidative than glycolytic muscle, without correlating with LKB1 or CaMKKβ expression. Thus, AMPK regulation is more complex in highly compartmentalized muscle cells.
AMP激活的蛋白激酶（AMPK）是一种参与代谢调节的能量感应丝氨酸/苏氨酸激酶。它由上游的肝脏激酶B1（LKB1）或钙/钙调蛋白依赖性激酶激酶2（CaMKKβ）磷酸化。在培养细胞中，AMPK的激活与LKB1的活性相关。磷酸化激活AMPK，使代谢向分解代谢转变并促进有丝分裂。在肌肉中，不活动会降低AMPK的激活，使氧化型肌肉的表型向更糖酵解的方向转变。在此，我们比较了糖酵解型肌肉和氧化型肌肉中AMPK激活的基础水平，并分析了这是否与LKB1或CaMKKβ有关。我们使用蛋白质免疫印迹法评估了C57BL6J小鼠的比目鱼肌、腓肠肌（GAST）、趾长伸肌（EDL）和心脏中AMPK的表达和磷酸化情况。我们还评估了组织匀浆中LKB1和CaMKKβ的表达以及CaMKKβ的活性。氧化型肌肉（比目鱼肌和心脏）中的AMPK激活高于糖酵解型肌肉（腓肠肌和EDL）。这与AMPK α1亚型的表达相关，但与LKB1和CaMKKβ无关。LKB1的表达存在性别差异，在雄性肌肉中低于雌性。CaMKKβ在骨骼肌中的表达非常低，并且在肌肉裂解物中不能使AMPK磷酸化。氧化型肌肉中较高的AMPK激活与激活的AMPK维持氧化表型这一事实相符。然而，这无法用LKB1和CaMKKβ来解释。这些结果表明，与培养细胞相比，肌肉中AMPK激活的调节更为复杂。由于AMPK已被提出作为多种疾病的治疗靶点，未来的研究应考虑AMPK亚型的表达和定位以及能量分隔。了解AMP激活的激酶AMPK如何被调节很重要，因为它是多种疾病的潜在治疗靶点。AMPK由肝脏激酶B1（LKB1）和钙/钙调蛋白依赖性激酶激酶2（CaMKKβ）激活。在培养细胞中，AMPK的激活与LKB1的表达相关。相比之下，我们发现氧化型肌肉中的AMPK激活高于糖酵解型肌肉，且与LKB1或CaMKKβ的表达无关。因此，在高度分隔的肌肉细胞中，AMPK的调节更为复杂。
