title: Induction and attenuation of neuronal apoptosis by proteasome inhibitors in murine cortical cell cultures.
abstract: Evidence has accumulated showing that pharmacological inhibition of proteasome activity can both induce and prevent neuronal apoptosis. We tested the hypothesis that these paradoxical effects of proteasome inhibitors depend on the degree of reduced proteasome activity and investigated underlying mechanisms. Murine cortical cell cultures exposed to 0.1 microM MG132 underwent widespread neuronal apoptosis and showed partial inhibition of proteasome activity down to 30-50%. Interestingly, administration of 1-10 microM MG132 almost completely blocked proteasome activity but resulted in reduced neuronal apoptosis. Similar results were produced in cortical cultures exposed to other proteasome inhibitors, proteasome inhibitor I and lactacystin. Administration of 0.1 microM MG132 led to activation of a mitochondria-dependent apoptotic signaling cascade involving cytochrome c, caspase-9, caspase-3 and degradation of tau protein; such activation was markedly reduced with 10 microM MG132. High doses of MG132 prevented the degradation of inhibitor of apoptosis proteins (IAPs) cIAP and X chromosome-linked IAP, suggesting that complete blockade of proteasome activity interferes with progression of apoptosis. In support of this, addition of high doses of proteasome inhibitors attenuated apoptosis of cortical neurons deprived of serum. Taken together, the present results indicate that inhibition of proteasome activity can induce or prevent neuronal cell apoptosis through regulation of mitochondria-mediated apoptotic pathways and IAPs.
authors.affiliation: Department of Neuroscience and Pharmacology, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Jaehong
authors.initials: J
authors.lastname: Suh
authors.forename: Young Ae
authors.initials: YA
authors.lastname: Lee
authors.forename: Byoung Joo
authors.initials: BJ
authors.lastname: Gwag
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology*; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D051034:Inhibitor of Apoptosis Proteins; D007976:Leupeptins; D061988:Proteasome Inhibitors; D025801:Ubiquitin; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde