title: Inhibitor of Nrf2 (INrf2 or Keap1) protein degrades Bcl-xL via phosphoglycerate mutase 5 and controls cellular apoptosis.
abstract: INrf2 (Keap1) is an adaptor protein that facilitates INrf2-Cul3-Rbx1-mediated ubiquitination/degradation of Nrf2, a master regulator of cytoprotective gene expression. Here, we present evidence that members of the phosphoglycerate mutase family 5 (PGAM5) proteins are involved in the INrf2-mediated ubiquitination/degradation of anti-apoptotic factor Bcl-xL. Mass spectrometry and co-immunoprecipitation assays revealed that INrf2, through its DGR domain, interacts with PGAM5, which in turn interacts with anti-apoptotic Bcl-xL protein. INrf2-Cul3-Rbx1 complex facilitates ubiquitination and degradation of both PGAM5 and Bcl-xL. Overexpression of PGAM5 protein increased INrf2-mediated degradation of Bcl-xL, whereas knocking down PGAM5 by siRNA decreased INrf2 degradation of Bcl-xL, resulting in increased stability of Bcl-xL. Mutation of PGMA5-E79A/S80A abolished INrf2/PGAM5/Bcl-xL interaction. Therefore, PGAM5 protein acts as a bridge between INrf2 and Bcl-xL interaction. Further studies showed that overexpression of INrf2 enhanced degradation of PGAM5-Bcl-xL complex, led to etoposide-mediated accumulation of Bax, increased release of cytochrome c from mitochondria, activated caspase-3/7, and enhanced DNA fragmentation and apoptosis. In addition, antioxidant (tert-butylhydroquinone) treatment destabilized the Nrf2-INrf2-PGAM5-Bcl-xL complex, which resulted in release of Nrf2 in cytosol and mitochondria, release of Bcl-xL in mitochondria, increase in Bcl-xL heterodimerization with Bax in mitochondria, and reduced cellular apoptosis. These data provide the first evidence that INrf2 controls Bcl-xL via PGAM5 and controls cellular apoptosis.
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
authors.forename: Suryakant K
authors.initials: SK
authors.lastname: Niture
authors.forename: Anil K
authors.initials: AK
authors.lastname: Jaiswal
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D019943:Amino Acid Substitution; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D053179:Caspase 7 / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D053938:DNA Fragmentation; D000072019:Kelch-Like ECH-Associated Protein 1; D051379:Mice; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D010736:Phosphoglycerate Mutase / Q000235:genetics / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D054875:Ubiquitination / Q000502:physiology; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C494812:Bcl2l1 protein, mouse; D002352:Carrier Proteins; C503646:Cul3 protein, mouse; D044842:Cullin Proteins; D003598:Cytoskeletal Proteins; C117301:Keap1 protein, mouse; D000072019:Kelch-Like ECH-Associated Protein 1; D046912:Multiprotein Complexes; C540494:RBX1 protein, mouse; D051020:bcl-X Protein; D045304:Cytochromes c; C570696:PGAM5 protein, mouse; D010749:Phosphoprotein Phosphatases; D010744:Phosphoric Monoester Hydrolases; C505409:Casp3 protein, mouse; C505524:Casp7 protein, mouse; D053148:Caspase 3; D053179:Caspase 7; D010736:Phosphoglycerate Mutase
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