Trans‐gnetin H isolated from the seeds of Paeonia species induces autophagy via inhibiting mTORC1 signalling through AMPK activation

Paeonia is a well‐known species of ornamental plants, traditional Chinese medicines, and emerging oilseed crops. Apart from nutritional unsaturated fatty acids, the seeds of peonies are rich in stilbenes characterized by their wide‐ranging health‐promoting properties. Although the typical stilbene resveratrol has been widely reported for its multiple bioactivities, it remains uncertain whether the trimer of resveratrol trans‐gnetin H has properties that regulate cancer cell viability, let alone the underlying mechanism. Autophagy regulated by trans‐gnetin H was detected by western blotting, immunofluorescence, and quantitative real‐time PCR. The effects of trans‐gnetin H on apoptosis and proliferation were examined by flow cytometry, colony formation and Cell Counting Kit‐8 assays. Trans‐gnetin H significantly inhibits cancer cell viability through autophagy by suppressing the phosphorylation of TFEB and promoting its nuclear transport. Mechanistically, trans‐gnetin H inhibits the activation and lysosome translocation of mTORC1 by inhibiting the activation of AMPK, indicating that AMPK is a checkpoint for mTORC1 inactivation induced by trans‐gnetin H. Moreover, the binding of TSC2 to Rheb was markedly increased in response to trans‐gnetin H stimulation. Similarly, trans‐gnetin H inhibited the interaction between Raptor and RagC in an AMPK‐dependent manner. More importantly, trans‐gnetin H‐mediated autophagy highly depends on the AMPK‐mTORC1 axis. We propose a regulatory mechanism by which trans‐gnetin H inhibits the activation of the mTORC1 pathway to control cell autophagy.