title: Proteasome inhibition protects HT22 neuronal cells from oxidative glutamate toxicity.
abstract: Oxidative stress caused by glutathione depletion after prolonged exposure to extracellular glutamate leads to a form of neuronal cell death that exhibits morphologically mixed features of both apoptosis and necrosis. However, specific downstream executioners involved in this form of cell death have yet to be identified. We report here that glutamate exposure does not activate caspase-3 in the HT22 neuronal cell line. Furthermore, no cytoprotection was achieved with either the pan-caspase inhibitor Z-VAD-fmk or the caspase-3-specific inhibitor DEVD-CHO. In contrast, inhibition of the proteasome by lactacystin protected both HT22 cells and rat primary neuronal cells against cell lysis. In parallel, oxidatively altered and ubiquitinated proteins accumulated in the mitochondrial fraction of cells after proteasome inhibition. These findings suggest that caspases can be decoupled from oxidative stress under some conditions, and implicate the ubiquitin/proteasome pathway in neuronal cell death caused by oxidative glutamate toxicity.
authors.affiliation: Neuroprotection Research Laboratory, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA. Klaus_vanleyen@hms.harvard.edu
authors.forename: Klaus
authors.initials: K
authors.lastname: van Leyen
authors.forename: Ambreena
authors.initials: A
authors.lastname: Siddiq
authors.forename: Rajiv R
authors.initials: RR
authors.lastname: Ratan
authors.forename: Eng H
authors.initials: EH
authors.lastname: Lo
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D018698:Glutamic Acid / Q000633:toxicity*; D051379:Mice; D009474:Neurons / Q000187:drug effects* / Q000201:enzymology; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D051381:Rats
chemical_list: D015853:Cysteine Proteinase Inhibitors; D061988:Proteasome Inhibitors; D018698:Glutamic Acid; D046988:Proteasome Endopeptidase Complex