title: Inhibition of the 26S proteasome induces expression of GLCLC, the catalytic subunit for gamma-glutamylcysteine synthetase.
abstract: The majority of short- and long-lived cellular proteins are degraded by the activities of the 26S proteasome, a large multi-catalytic protease. Its unique function places it as a central regulatory activity for many important physiological processes. Lactacystin is a very specific 26S proteasome inhibitor and represents an excellent tool for demonstrating that a pathway exhibits proteasome-dependent biochemical regulation. Exposure of HepG2 cells to lactacystin resulted in robust elevation of GLCLC mRNA levels, followed by an increase in GSH concentrations. GLCLC is the gene that encodes the catalytic subunit for gamma-glutamylcysteine synthetase, the rate-limiting enzyme for the synthesis of glutathione (GSH). Inhibition of non-proteasome, protease activities did not induce GLCLC. Gel mobility shift assays and expression of CAT activity from heterologous reporter vectors identified Nrf2 mediation of the GLCLC antioxidant response element, ARE4, as the mechanism by which lactacystin induced GLCLC. These studies have identified 26S proteasome activity as a central regulatory pathway for glutathione synthesis.
authors.affiliation: Department of Radiation Oncology and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
authors.forename: K R
authors.initials: KR
authors.lastname: Sekhar
authors.forename: S R
authors.initials: SR
authors.lastname: Soltaninassab
authors.forename: M J
authors.initials: MJ
authors.lastname: Borrelli
authors.forename: Z Q
authors.initials: ZQ
authors.lastname: Xu
authors.forename: M J
authors.initials: MJ
authors.lastname: Meredith
authors.forename: F E
authors.initials: FE
authors.lastname: Domann
authors.forename: M L
authors.initials: ML
authors.lastname: Freeman
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001384:Azetidines / Q000494:pharmacology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D005721:Glutamate-Cysteine Ligase / Q000096:biosynthesis / Q000235:genetics*; D005978:Glutathione / Q000378:metabolism; D008099:Liver / Q000166:cytology; D051267:NF-E2-Related Factor 2; D009363:Neoplasm Proteins / Q000378:metabolism; D010447:Peptide Hydrolases / Q000187:drug effects*; D046988:Proteasome Endopeptidase Complex; D020836:Protein Structure, Quaternary; D020218:Response Elements; D015534:Trans-Activators / Q000378:metabolism
chemical_list: D001384:Azetidines; D004268:DNA-Binding Proteins; D051267:NF-E2-Related Factor 2; D009363:Neoplasm Proteins; D015534:Trans-Activators; C067713:lactacystin; C082735:azetidine; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; D000111:Acetylcysteine