title: Induction of the lysosomal apoptosis pathway by inhibitors of the ubiquitin-proteasome system.
abstract: The lysosomal apoptosis pathway is a potentially interesting therapeutic target. Since apoptosis involving the lysosomal pathway has been described to involve cathepsins, we screened a drug library for agents that induce cathepsin-dependent apoptosis. Using pharmacological inhibitors and siRNA, we identified 2 structurally related agents (NSC687852 and NSC638646) that induced cathepsin D-dependent caspase-cleavage activity in human breast cancer cells. Both agents were found to induce the mitochondrial apoptosis pathway. NSC687852 and NSC638646 were found to inhibit the activity of ubiquitin isopeptidases and to induce the accumulation of high-molecular-mass ubiquitins in cells. We show that 3 other inhibitors of the proteasome degradation pathway induce lysosomal membrane permeabilization (LMP) and that cathepsin-D siRNA inhibits apoptosis induced by these agents. We conclude that a screen for cathepsin-dependent apoptosis-inducing agents resulted in the identification of ubiquitin isopeptidase inhibitors and that proteasome inhibitors with different mechanisms of action induce LMP and cathepsin D-dependent apoptosis.
authors.affiliation: Cancer Center Karolinska, Department of Oncology and Pathology, Karolinska Institute, Stockholm, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Berndtsson
authors.forename: Melanie
authors.initials: M
authors.lastname: Beaujouin
authors.forename: Linda
authors.initials: L
authors.lastname: Rickardson
authors.forename: Aleksandra Mandic
authors.initials: AM
authors.lastname: Havelka
authors.forename: Rolf
authors.initials: R
authors.lastname: Larsson
authors.forename: Jacob
authors.initials: J
authors.lastname: Westman
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Liaudet-Coopman
authors.forename: Stig
authors.initials: S
authors.lastname: Linder
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D002401:Cathepsin B / Q000378:metabolism; D002402:Cathepsin D / Q000378:metabolism; D045744:Cell Line, Tumor; D015853:Cysteine Proteinase Inhibitors / Q000627:therapeutic use*; D006801:Humans; D007425:Intracellular Membranes / Q000502:physiology; D020014:K562 Cells / Q000187:drug effects; D008247:Lysosomes / Q000473:pathology*; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000502:physiology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D025801:Ubiquitin / Q000037:antagonists & inhibitors*
chemical_list: D015853:Cysteine Proteinase Inhibitors; D061988:Proteasome Inhibitors; D025801:Ubiquitin; D002401:Cathepsin B; D002402:Cathepsin D; D046988:Proteasome Endopeptidase Complex