Ponicidin Promotes Hepatocellular Carcinoma Mitochondrial Apoptosis by Stabilizing Keap1-PGAM5 Complex

Ponicidin is a diterpenoid with demonstrated antitumor activity in clinical trials. However, the specific function and mechanism of action against hepatocellular carcinoma (HCC) remain unknown. In this study, it is found that ponicidin significantly inhibited the proliferation and migration of HCC cells. It is shown that ponicidin targets Keap1 and promotes the formation of the Keap1-PGAM5 complex, leading to the ubiquitination of PGAM5, using biotin-labeled ponicidin for target fishing and the HuProt^TM Human Proteome Microarray V4.0. Ponicidin is found to activate the cysteine-dependent mitochondrial pathway via PGAM5, resulting in mitochondrial damage and ROS production, thereby promoting mitochondrial apoptosis in HepG2 cells. The first in vitro cocrystal structure of the PGAM5 IE 12-mer peptide and the Keap1 Kelch domain is obtained. Using molecular dynamics simulations to confirm the binding of ponicidin to the Keap1-PGAM5 complex. Based on the depth-based dynamic simulation, it is found that ponicidin can induce the tightening of the Keap1-PGAM5 interaction pocket, thereby stabilizing the formation of the protein complex. Finally, it is observed that ponicidin effectively inhibited tumor growth and promoted tumor cell apoptosis in a BALB/c nude mouse xenograft tumor model. The results provide insight into the anti-HCC properties of ponicidin based on a mechanism involving the Keap1-PGAM5 complex.