RESUMO
Oxidative stress from excess H2O2 activates transcription factors that restore redox balance and repair oxidative damage. Although many transcription factors are activated by H2O2, it is unclear whether they are activated at the same H2O2 concentration, or time. Dose-dependent activation is likely as oxidative stress is not a singular state and exhibits dose-dependent outcomes including cell-cycle arrest and cell death. Here, we show that transcription factor activation is both dose-dependent and coordinated over time. Low levels of H2O2 activate p53, NRF2 and JUN. Yet under high H2O2, these transcription factors are repressed, and FOXO1, NF-κB, and NFAT1 are activated. Time-lapse imaging revealed that the order in which these two groups of transcription factors are activated depends on whether H2O2 is administered acutely by bolus addition, or continuously through the glucose oxidase enzyme. Finally, we provide evidence that 2-Cys peroxiredoxins control which group of transcription factors are activated.
Assuntos
Peróxido de Hidrogênio , Estresse Oxidativo , Fatores de Transcrição , Peróxido de Hidrogênio/metabolismo , Peróxido de Hidrogênio/farmacologia , Estresse Oxidativo/efeitos dos fármacos , Fatores de Transcrição/metabolismo , Fatores de Transcrição/genética , Humanos , Peroxirredoxinas/metabolismo , Peroxirredoxinas/genética , Proteína Supressora de Tumor p53/metabolismo , Proteína Supressora de Tumor p53/genética , Fator 2 Relacionado a NF-E2/metabolismo , Fator 2 Relacionado a NF-E2/genética , NF-kappa B/metabolismo , Proteína Forkhead Box O1/metabolismo , Proteína Forkhead Box O1/genética , Fatores de Transcrição NFATC/metabolismo , Glucose Oxidase/metabolismo , AnimaisRESUMO
Recently, several ATP-binding cassette (ABC) importers have been found to adopt the typical fold of type IV ABC exporters. Presumably, these importers would function under the transport scheme of "alternating access" like those exporters, cycling through inward-open, occluded, and outward-open conformations. Understanding how the exporter-like importers move substrates in the opposite direction requires structural studies on all the major conformations. To shed light on this, here we report the structure of yersiniabactin importer YbtPQ from uropathogenic Escherichia coli in the occluded conformation trapped by ADP-vanadate (ADP-Vi) at a 3.1 Å resolution determined by cryo-electron microscopy. The structure shows unusual local rearrangements in multiple helices and loops in its transmembrane domains (TMDs). In addition, the dimerization of the nucleotide-binding domains (NBDs) promoted by the vanadate trapping is highlighted by the "screwdriver" action at one of the two hinge points. These structural observations are rare and thus provide valuable information to understand the structural plasticity of the exporter-like ABC importers.
