Regulation of the Nrf2-Keap1 antioxidant response by the ubiquitin proteasome system: an insight into cullin-ring ubiquitin ligases.
Nrf2 is a transcription factor that has emerged as the cell's main defense mechanism against many harmful environmental toxicants and carcinogens. Nrf2 is negatively regulated by Keap1, a substrate adaptor protein for the Cullin3 (Cul3)-containing E3-ligase complex, which targets Nrf2 for ubiquitination and degradation by the ubiquitin proteasome system (UPS). Recent evidence suggests that constitutive activation of Nrf2, due to mutations in Keap1 or Nrf2, is prominent in many cancer types and contributes to chemoresistance. Regulation of Nrf2 by the Cul3-Keap1-E3 ligase provides strong evidence that tight regulation of Cullin-ring ligases (CRLs) is imperative to maintain cellular homeostasis. There are seven known Cullin proteins that form various CRL complexes. They are regulated by neddylation/deneddylation, ubiquitination/deubiquitination, CAND1-assisted complex assembly/disassembly, and subunit dimerization. In this review, we will discuss the regulation of each CRL using the Cul3-Keap1-E3 ligase complex as the primary focus. The substrates of CRLs are involved in many signaling pathways. Therefore, deregulation of CRLs affects several cellular processes, including cell cycle arrest, DNA repair, cell proliferation, senescence, and death, which may lead to many human diseases, including cancer. This makes CRLs a promising target for novel cancer drug therapies.
Villeneuve
Nicole F
NF
Department of Pharmacology and Toxicology, University of Arizona, Tucson, 85721, USA.
Lau
Alexandria
A
Zhang
Donna D
DD
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D000975:Antioxidants; D044842:Cullin Proteins; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; D015534:Trans-Activators; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex