Nrf2 signaling and cell survival.
Nrf2:INrf2 acts as a sensor for oxidative/electrophilic stress. INrf2 serves as an adaptor to link Nrf2 to the ubiquitin ligase Cul3-Rbx1 complex that ubiquitinate and degrade Nrf2. Under basal conditions, cytosolic INrf2/Cul3-Rbx1 is constantly degrading Nrf2. When a cell encounters stress Nrf2 dissociates from the INrf2 and translocates into the nucleus. Oxidative/electrophilic stress induced modification of INrf2Cysteine151 and/or protein kinase C (PKC)-mediated phosphorylation of Nrf2Serine40 controls Nrf2 release from INrf2 followed by stabilization and nuclear translocation of Nrf2. Nrf2 binds to the antioxidant response element (ARE) and activates a myriad of genes that protect cells against oxidative/electrophilic stress and neoplasia. A delayed response of oxidative/electrophilic stress activates GSK-3beta that phosphorylates Fyn at unknown threonine residue(s). Phosphorylated Fyn translocates to the nucleus and phosphorylates Nrf2Tyrosine568 that leads to nuclear export and degradation of Nrf2. Prothymosin-alpha mediated nuclear translocation of INrf2 also degrades nuclear Nrf2. The degradation of Nrf2 both in cytosol and nuclear compartments rapidly brings down its levels to normal resulting in suppression of Nrf2 downstream gene expression. An auto-regulatory loop between Nrf2 and INrf2 controls their cellular abundance. Nrf2 regulates INrf2 by controlling its transcription, and INrf2 controls Nrf2 by degrading it. In conclusion, switching on and off of Nrf2 combined with promoting an auto-regulatory loop between them regulates activation/deactivation of defensive genes leading to protection of cells against adverse effects of oxidative and electrophilic stress and promote cell survival.
Niture
Suryakant K
SK
Department of Pharmacology, University of Maryland School of Medicine, 655 West Baltimore Street, Baltimore, MD 21201, USA.
Kaspar
James W
JW
Shen
Jun
J
Jaiswal
Anil K
AK
D021581:Active Transport, Cell Nucleus; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D001665:Binding Sites; D002470:Cell Survival; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004351:Drug Resistance; D006706:Homeostasis; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D000072019:Kelch-Like ECH-Associated Protein 1; D008969:Molecular Sequence Data; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D009369:Neoplasms / Q000378:metabolism / Q000517:prevention & control; D018384:Oxidative Stress; D010766:Phosphorylation; D020218:Response Elements; D015398:Signal Transduction
D048868:Adaptor Proteins, Signal Transducing; D000975:Antioxidants; D003598:Cytoskeletal Proteins; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; C117301:Keap1 protein, mouse; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2