Metformin interacts with AMPK through binding to γ subunit

Metformin acts as an energy regulator by activating 5'-adenosine monophosphate-activated protein kinase (AMPK), which is a key player in the regulation of energy homeostasis, but it is uncertain whether AMPK is its direct target. This study aims to investigate the possible interaction between metformin and AMPK. First, we verified that metformin can promote AMPK activation and induce ACC inactivation in human HepG2 cells using western blot. Then we predicted that metformin may interact with the gamma subunit of AMPK by molecular docking analysis. The fluorescence spectrum and ForteBio assays indicated that metformin has a stronger binding ability to the gamma subunit of AMPK than to alpha subunit. In addition, interaction of metformin with gamma-AMPK resulted in a decrease in the alpha-helicity determined by CD spectra, but relatively little change was seen with alpha-AMPK. These results demonstrate that metformin may interact with AMPK through binding to the gamma subunit.