title: Mitochondrial respiration inhibitors suppress protein translation and hypoxic signaling via the hyperphosphorylation and inactivation of translation initiation factor eIF2α and elongation factor eEF2.
abstract: Over 20,000 lipid extracts of plants and marine organisms were evaluated in a human breast tumor T47D cell-based reporter assay for hypoxia-inducible factor-1 (HIF-1) inhibitory activity. Bioassay-guided isolation and dereplication-based structure elucidation of an active extract from the Bael tree (Aegle marmelos) afforded two protolimonoids, skimmiarepin A (1) and skimmiarepin C (2). In T47D cells, 1 and 2 inhibited hypoxia-induced HIF-1 activation with IC50 values of 0.063 and 0.068 μM, respectively. Compounds 1 and 2 also suppressed hypoxic induction of the HIF-1 target genes GLUT-1 and VEGF. Mechanistic studies revealed that 1 and 2 inhibited HIF-1 activation by blocking the hypoxia-induced accumulation of HIF-1α protein. At the range of concentrations that inhibited HIF-1 activation, 1 and 2 suppressed cellular respiration by selectively inhibiting the mitochondrial electron transport chain at complex I (NADH dehydrogenase). Further investigation indicated that mitochondrial respiration inhibitors such as 1 and rotenone induced the rapid hyperphosphorylation and inhibition of translation initiation factor eIF2α and elongation factor eEF2. The inhibition of protein translation may account for the short-term exposure effects exerted by mitochondrial inhibitors on cellular signaling, while the suppression of cellular ATP production may contribute to the inhibitory effects following extended treatment periods.
authors.affiliation: Department of Pharmacognosy, Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, Mississippi 38677, United States.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Fakhri
authors.initials: F
authors.lastname: Mahdi
authors.forename: Lin
authors.initials: L
authors.lastname: Du
authors.forename: Sandipan
authors.initials: S
authors.lastname: Datta
authors.forename: Dale G
authors.initials: DG
authors.lastname: Nagle
authors.forename: Yu-Dong
authors.initials: YD
authors.lastname: Zhou
mesh_terms: D045471:Aegle / Q000737:chemistry*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015852:Eukaryotic Initiation Factor-2 / Q000037:antagonists & inhibitors*; D005260:Female; D006801:Humans; D051793:Hypoxia-Inducible Factor 1 / Q000037:antagonists & inhibitors*; D007214:Indonesia; D036701:Limonins; D008928:Mitochondria / Q000378:metabolism*; D015394:Molecular Structure; D009245:NADH Dehydrogenase / Q000037:antagonists & inhibitors; D012119:Respiration / Q000187:drug effects*; D014315:Triterpenes / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors / Q000235:genetics
chemical_list: D015852:Eukaryotic Initiation Factor-2; D051793:Hypoxia-Inducible Factor 1; D036701:Limonins; D014315:Triterpenes; D042461:Vascular Endothelial Growth Factor A; C567947:skimmiarepin A; C486120:skimmiarepin C; D009245:NADH Dehydrogenase