Suppression ofAMPK/aak‐2by NRF2/SKN‐1 down‐regulates autophagy during prolonged oxidative stress

Abstract

NF-E2–related factor 2 (NRF2) transcription factor has a fundamental role in cell homeostasis maintenance as one of the master regulators of oxidative and electrophilic stress responses. Previous studies have shown that a regulatory connection exists between NRF2 and autophagy during reactive oxygen species–generated oxidative stress. The aim of the present study was to investigate how autophagy is turned off during prolonged oxidative stress, to avoid overeating and destruction of essential cellular components. AMPK is a key cellular energy sensor highly conserved in eukaryotic organisms, and it has an essential role in autophagy activation at various stress events. Here the role of human AMPK and its Caenorhabditis elegans counterpart AAK-2 was explored upon oxidative stress. We investigated the regulatory connection between NRF2 and AMPK during oxidative stress induced by tert-butyl hydroperoxide (TBHP) in HEK293T cells and C. elegans. Putative conserved NRF2/protein skinhead-1 binding sites were found in AMPK/aak-2 genes by in silico analysis and were later confirmed experimentally by using EMSA. After addition of TBHP, NRF2 and AMPK showed a quick activation; AMPK was later down-regulated, however, while NRF2 level remained high. Autophagosome formation and Unc-51–like autophagy activating kinase 1 phosphorylation were initially stimulated, but they returned to basal values after 4 h of TBHP treatment. The silencing of NRF2 resulted in a constant activation of AMPK leading to hyperactivation of autophagy during oxidative stress. We observed the same effects in C. elegans demonstrating the conservation of this self-defense mechanism to save cells from hyperactivated autophagy upon prolonged oxidative stress. We conclude that NRF2 negatively regulates autophagy through delayed down-regulation of the expression of AMPK upon prolonged oxidative stress. This regulatory connection between NRF2 and AMPK may have an important role in understanding how autophagy is regulated in chronic human morbidities characterized by oxidative stress, such as neurodegenerative diseases, certain cancer types, and in metabolic diseases.—Kosztelnik, M., Kurucz, A., Papp, D., Jones, E., Sigmond, T., Barna, J., Traka, M. H., Lorincz, T., Szarka, A., Banhegyi, G., Vellai, T., Korcsmaros, T., Kapuy, O. Suppression of AMPK/aak-2 by NRF2/SKN-1 down-regulates autophagy during prolonged oxidative stress.

Antioxidant activity of selenium-enriched Chrysomyia megacephala (Fabricius) larvae powder and its impact on intestinal microflora in D-galactose induced aging mice

“…Nrf2 is a transcription factor that controls the basal and inducible expression of an array of antioxidant including the HO-1, that a known target of Nrf2-regulated transcription and an antioxidative, cytoprotective protein in different types of cells, plays an important role in cytoprotection when oxidative stress occurs, and Nrf2 directly regulates its expression [ 34 ]. Recent studies have demonstrated that activation of the Nrf2 signaling pathway can protect the organism against oxidative damage [ 35 – 37 ]. Xu et al [ 38 ] reported that biogenic Se nanoparticles (SeNPs) synthesized by Lactobacillus casei ATCC 393 could protect the intestinal epithelial barrier function against oxidative damage by alleviating ROS-mediated mitochondrial dysfunction via the Nrf2 signaling pathway.…”

Complex interplay between autophagy and oxidative stress in the development of pulmonary disease

“…The regulation and co-ordination of Keap1–Nrf2 and the autophagy pathway are essential for cell growth, differentiation, redox signaling and survival, has been addressed in several studies [ 205 , 206 ]. A recent investigation showed that during prolonged exposure of oxidative stress, using tert-butyl hydroperoxide (TBHP), Nrf2 negatively regulates autophagy through the down-regulation of AMPK [ 207 ]. A recent report described a novel pathway for mitophagy where p62 translocates Keap1 to the mitochondria to ubiquitinate this organelle and trigger mitophagy [ 208 ].…”

HYAL‐1‐induced autophagy facilitates pancreatic fistula for patients who underwent pancreaticoduodenectomy

“…AMPK phosphorylates specific enzymes and growth control nodes to increase ATP generation and decrease ATP consumption. AMPK directly phosphorylates the mTOR upstream regulator TSC2 which eventually activates autophagy through attenuating the activation of mTOR and ameliorating ULK1 phosphorylation . Besides, AMPK phosphorylates residues on other core components of autophagy, including ATG9, Beclin1, VPS34, and RACK1 .…”

“…AMPK directly phosphorylates the mTOR upstream regulator TSC2 which eventually activates autophagy through attenuating the activation of mTOR and ameliorating ULK1 phosphorylation. [41][42][43] Besides, AMPK phosphorylates residues on other core components of autophagy, including ATG9, Beclin1, VPS34, and RACK1. [42][43][44][45][46][47] STAT3 has been implicated in several steps of autophagy, from the assembly of autophagosomes to their maturation.…”

“…[41][42][43] Besides, AMPK phosphorylates residues on other core components of autophagy, including ATG9, Beclin1, VPS34, and RACK1. [42][43][44][45][46][47] STAT3 has been implicated in several steps of autophagy, from the assembly of autophagosomes to their maturation. [48][49][50][51] STAT3 is the main transcriptional enhancer of several autophagy-related genes (ATGs) in the nucleus, and its activity contributes to a range of anti-autophagic or pro-autophagic effects.…”