Browsing by Author "Yuan, Chun-Su"

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    Ginseng metabolite Protopanaxadiol induces Sestrin2 expression and AMPK activation through GCN2 and PERK
    (Springer Nature, 2019-04-05) Jin, Hong Ri; Du, Charles H.; Wang, Chong-Zhi; Yuan, Chun-Su; Du, Wei; Pathology and Laboratory Medicine, School of Medicine
    Ginseng is one of the most commonly used herbs that is believed to have a variety of biological activities, including reducing blood sugar and cholesterol levels, anti-cancer, and anti-diabetes activities. However, little is known about the molecular mechanisms involved. In this study, we showed that protopanaxadiol (PPD), a metabolite of the protopanaxadiol group ginsenosides that are the major pharmacological constituents of ginsengs, significantly altered the expression of genes involved in metabolism, elevated Sestrin2 (Sesn2) expression, activated AMPK, and induced autophagy. Using CRISPR/CAS9-mediated gene editing and shRNA-mediated gene silencing, we demonstrated that Sesn2 is required for PPD-induced AMPK activation and autophagy. Interestingly, we showed that PPD-induced Sesn2 expression is mediated redundantly by the GCN2/ATF4 amino acid-sensing pathway and the PERK/ATF4 endoplasmic reticulum (ER) stress pathway. Our results suggest that ginseng metabolite PPD modulates the metabolism of amino acids and lipids, leading to the activation of the stress-sensing kinases GCN2 and PERK to induce Sesn2 expression, which promotes AMPK activation, autophagy, and metabolic health.
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    Ginseng metabolite protopanaxadiol interferes with lipid metabolism and induces endoplasmic reticulum stress and p53 activation to promote cancer cell death
    (Wiley, 2019-03) Jin, Hong Ri; Du, Charles H.; Wang, Chong-Zhi; Yuan, Chun-Su; Du, Wei; Pathology and Laboratory Medicine, School of Medicine
    Protopanaxadiol (PPD), a ginseng metabolite generated by the gut bacteria, was shown to induce colorectal cancer cell death and enhance the anticancer effect of chemotherapeutic agent 5-FU. However, the mechanism by which PPD promotes cancer cell death is not clear. In this manuscript, we showed that PPD activated p53 and ER stress and induced expression of BH3-only proteins Puma and Noxa to promote cell death. Induction of Puma by PPD was p53-dependent while induction of Noxa was p53-independent. On the other hand, PPD also induced pro-survival mechanisms including autophagy and expression of Bcl2 family apoptosis regulator Mcl-1. Inhibition of autophagy or knockdown of Mcl-1 significantly enhanced PPD-induced cell death. Interestingly, PPD inhibited expression of genes involved in fatty acid and cholesterol biosynthesis and induced synergistic cancer cell death with fatty acid synthase inhibitor cerulenin. As PPD-induced ER stress was not significantly affected by inhibition of new protein synthesis, we suggest PPD may induce ER stress directly through causing lipid disequilibrium.