Regulación del factor de transcripción Nrf2 por el glucógeno sintasa quinasa 3

• Autores: Patricia P. Rada Llano
• Directores de la Tesis: Antonio Cuadrado (dir. tes.)
• Lectura: En la Universidad Autónoma de Madrid ( España ) en 2012
• Idioma: español
• Tribunal Calificador de la Tesis: Jesús Ávila de Grado (presid.), José Manuel González Sancho (secret.), Miguel Soares (voc.), Albena T. Dinkova-Kostova (voc.), Juan Domínguez (voc.)
• Materias:
  • Química
    • Bioquímica
  • Ciencias de la vida
    • Biología molecular
• Enlaces
  • Tesis en acceso abierto en: Biblos-e Archivo
• Resumen

  • Defense against oxidative stress is executed by an antioxidant system that is tightly controlled by the transcription factor Nrf2. Nrf2 is the master regulator of a genetic program termed the phase II response that controls redox homeostasis and participates in multiple aspects of physiology and pathology. Classical regulation of Nrf2 involves redoxsensitive degradation by the E3 ubiquitin ligase Keap1/Cul3. However, Nrf2 is controlled by other mechanisms that have not yet been elucidated. In this Thesis, we described a novel mechanism that involves glycogen synthase kinase 3 (GSK-3) in the stabilization of Nrf2 by a Keap1-independent pathway implicating the E3 ubiquitin ligase SCF/ß-TrCP.

    Taking nordihydroguaiaretic acid (NDGA) as a prototype chemopreventive agent, we show that this compound activates PI3K/Akt and the MAP kinases ERK1/2, p38, and JNK, promoting the stabilization of Nrf2. We also show that these pathways cause inhibitory phosphorylation of GSK-3ß at Ser9 and at Thr390. These results identify GSK-3ß as an integrator of several signaling pathways.

    We found that GSK-3 phosphorylates a group of Ser residues within the Neh6 domain of Nrf2 that overlap with an SCF/ß-TrCP destruction motif (DSGIS).

    Phosphorylation of this Ser cluster stimulated the degradation of Nrf2 by a SCF/ß-TrCP complex. 2D-Gel electrophoresis and site directed mutagenesis allowed us to identify two serines that are phosphorylated by GSK-3ß in the DSGIS sequence. In addition, Nuclear Magnetic Resonance studies defined key hydrophilic and hydrophobic interactions of this phospho-sequence involved in docking to ß-TrCP.

    Mice with a conditional depletion of neuronal GSK-3ß exhibited in hippocampus increased levels of Nrf2 and phase II gene products as well as increased levels of reduced glutathione and lower levels of malondialdehyde and carbonylated proteins. Moreover, GSK-3 inhibitors induced an increase of Nrf2 and its target genes and prevented excitotoxic neuronal death mediated by kainate in hippocampal slices.

    This Thesis establishes the structural parameters for the interaction of Nrf2 with the GSK-3/ß-TrCP axis and its functional relevance in the regulation of Nrf2 by the signaling pathways that impinge on GSK-3.