title: Phosphorylated AKT inhibits the apoptosis induced by DRAM-mediated mitophagy in hepatocellular carcinoma by preventing the translocation of DRAM to mitochondria.
abstract: Increasing autophagy is beneficial for curing hepatocellular carcinoma (HCC). Damage-regulated autophagy modulator (DRAM) was recently reported to induce apoptosis by mediating autophagy. However, the effects of DRAM-mediated autophagy on apoptosis in HCC cells remain unclear. In this study, normal hepatocytes (7702) and HCC cell lines (HepG2, Hep3B and Huh7) were starved for 48 h. Starvation induced apoptosis and autophagy in all cell lines. We determined that starvation also induced DRAM expression and DRAM-mediated autophagy in both normal hepatocytes and HCC cells. However, DRAM-mediated autophagy was involved in apoptosis in normal hepatocytes but not in HCC cells, suggesting that DRAM-mediated autophagy fails to induce apoptosis in hepatoma in response to starvation. Immunoblot and immunofluorescence assays demonstrated that DRAM translocated to mitochondria and induced mitophagy, which led to apoptosis in 7702 cells. In HCC cells, starvation also activated the phosphatidylinositol 3-kinase (PI3K)/AKT pathway, which blocks the translocation of DRAM to mitochondria through the binding of p-AKT to DRAM in the cytoplasm. Inactivation of the PI3K/AKT pathway rescued DRAM translocation to mitochondria; subsequently, mitochondrial DRAM induced apoptosis in HCC cells by mediating mitophagy. Our findings open new avenues for the investigation of the mechanisms of DRAM-mediated autophagy and suggest that promoting DRAM-mediated autophagy together with PI3K/AKT inhibition might be more effective for autophagy-based therapy in hepatoma.
authors.affiliation: 1] Beijing Institute of Hepatology, Beijing, China [2] Beijing You'an Hospital, Capital Medical University, Beijing, China.
authors.forename: K
authors.initials: K
authors.lastname: Liu
authors.affiliation: 1] Beijing Institute of Hepatology, Beijing, China [2] Beijing You'an Hospital, Capital Medical University, Beijing, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Shi
authors.affiliation: 1] Beijing Institute of Hepatology, Beijing, China [2] Beijing You'an Hospital, Capital Medical University, Beijing, China.
authors.forename: X H
authors.initials: XH
authors.lastname: Guo
authors.affiliation: 1] Beijing Institute of Hepatology, Beijing, China [2] Beijing You'an Hospital, Capital Medical University, Beijing, China.
authors.forename: Y B
authors.initials: YB
authors.lastname: Ouyang
authors.affiliation: 1] Beijing Institute of Hepatology, Beijing, China [2] Beijing You'an Hospital, Capital Medical University, Beijing, China.
authors.forename: S S
authors.initials: SS
authors.lastname: Wang
authors.affiliation: 1] Beijing Institute of Hepatology, Beijing, China [2] Beijing You'an Hospital, Capital Medical University, Beijing, China.
authors.forename: D J
authors.initials: DJ
authors.lastname: Liu
authors.affiliation: 1] Beijing Institute of Hepatology, Beijing, China [2] Beijing You'an Hospital, Capital Medical University, Beijing, China.
authors.forename: A N
authors.initials: AN
authors.lastname: Wang
authors.affiliation: Beijing You'an Hospital, Capital Medical University, Beijing, China.
authors.forename: N
authors.initials: N
authors.lastname: Li
authors.affiliation: Beijing Institute of Hepatology, Beijing, China.
authors.forename: D X
authors.initials: DX
authors.lastname: Chen
mesh_terms: D017209:Apoptosis; D001343:Autophagy / Q000187:drug effects; D006528:Carcinoma, Hepatocellular / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D063306:Mitophagy / Q000187:drug effects; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D015398:Signal Transduction; D013312:Stress, Physiological; D013997:Time Factors; D014162:Transfection; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C512709:DRAM1 protein, human; D008565:Membrane Proteins; D009687:Nuclear Proteins; D047428:Protein Kinase Inhibitors; C495901:TP53 protein, human; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D051057:Proto-Oncogene Proteins c-akt