title: INrf2 (Keap1) targets Bcl-2 degradation and controls cellular apoptosis.
abstract: Cytosolic inhibitor of Nrf2 (INrf2) is an adaptor protein that mediates ubiquitination/degradation of NF-E2-related factor 2 (Nrf2), a master regulator of cytoprotective gene expression. In this paper, we demonstrate that INrf2 degrades endogenous antiapoptotic B-cell CLL/lymphoma 2 (Bcl-2) protein and controls cellular apoptosis. The DGR domain of INrf2 interacts with the BH2 domain of Bcl-2 and facilitates INrf2:Cul3-Rbx1-mediated ubiquitination of Bcl-2 by the conjugation of ubiquitin molecules to lysine17 of Bcl-2. Further studies showed that INrf2 enhanced etoposide-mediated accumulation of Bax, increased release of cytochrome c from mitochondria, activated caspase-3/7, and enhanced DNA fragmentation and apoptosis. Antioxidants antagonized Bcl-2:INrf2 interaction, led to the release and stabilization of Bcl-2, increased Bcl-2:Bax heterodimers and reduced apoptosis. Moreover, dysfunctional/mutant INrf2 in human lung cancer cells failed to degrade Bcl-2, resulting in decreased etoposide and UV/γ radiation-mediated DNA fragmentation. These data provide the first evidence of INrf2 control of Bcl-2 and apoptotic cell death, with implications in antioxidant protection, survival of cancer cells containing dysfunctional INrf2, and drug resistance.
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
authors.forename: S K
authors.initials: SK
authors.lastname: Niture
authors.forename: A K
authors.initials: AK
authors.lastname: Jaiswal
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002352:Carrier Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D044842:Cullin Proteins / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D053938:DNA Fragmentation / Q000187:drug effects / Q000528:radiation effects; D005047:Etoposide / Q000494:pharmacology; D005720:Gamma Rays; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D000072019:Kelch-Like ECH-Associated Protein 1; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology; D008239:Lysine / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D010768:Phosphoserine / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects / Q000528:radiation effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000528:radiation effects; D055550:Protein Stability / Q000187:drug effects / Q000528:radiation effects; D017434:Protein Structure, Tertiary; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects / Q000528:radiation effects; D014466:Ultraviolet Rays; D015854:Up-Regulation / Q000187:drug effects / Q000528:radiation effects; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000975:Antioxidants; D002352:Carrier Proteins; D044842:Cullin Proteins; D003598:Cytoskeletal Proteins; D006873:Hydroquinones; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; C117301:Keap1 protein, mouse; D000072019:Kelch-Like ECH-Associated Protein 1; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D010768:Phosphoserine; D005047:Etoposide; C018855:2-tert-butylhydroquinone; D008239:Lysine