title: Proteasomes act in the pre-mitochondrial signal transduction route towards roscovitine-induced apoptosis.
abstract: The role of the ubiquitin-proteasome pathway during roscovitine induced apoptosis was evaluated in the non-small cell lung carcinoma cell line MR65. To this end specific inhibitors of proteasome activity, MG132 and lactacystin were used. Addition of MG132 or lactacystin, 1 h prior to the addition of the CDK-inhibitor roscovitine to the cell cultures inhibited apoptosis significantly, as measured by PS exposure, cytokeratin 18 cleavage and caspase-3 activation. Furthermore, we show that inhibition of proteasome activation prior to induction of apoptosis by roscovitine prevents loss of mitochondrial inner transmembrane potential (DeltaPsim). In addition we found that MG132 and lactacystin prevent release of cytochrome c from the mitochondrion. In contrast to the above findings we see no effect of proteasome inhibition in Fas-mediated apoptosis. Taken together our data suggest a specific role for proteasomes very early in roscovitine-induced apoptosis, upstream from the caspase cascade and mitochondrion.
authors.affiliation: Department of Molecular Cell Biology, University of Maastricht, PO Box 616, 6200 MD Maastricht, The Netherlands. m.henfling@molcelb.unimaas.nl
authors.forename: M E R
authors.initials: ME
authors.lastname: Henfling
authors.forename: F C S
authors.initials: FC
authors.lastname: Ramaekers
authors.forename: B
authors.initials: B
authors.lastname: Schutte
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D008175:Lung Neoplasms / Q000473:pathology*; D008564:Membrane Potentials; D008928:Mitochondria / Q000187:drug effects* / Q000502:physiology*; D046988:Proteasome Endopeptidase Complex / Q000502:physiology*; D011687:Purines / Q000494:pharmacology*; D000077546:Roscovitine; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D011687:Purines; D000077546:Roscovitine; C067713:lactacystin; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D000111:Acetylcysteine