title: Aberrant DR5 transport through disruption of lysosomal function suggests a novel mechanism for receptor activation.
abstract: To examine reciprocal or unilateral implications between two cell destruction processes, autophagy and apoptosis, in 5-Fluorouracil (5-FU)-treated tumor cells, a combination of chemical inhibitors, RNAi and genetic approaches were used. In contrast to cancer cells harboring obstructed apoptosis, either at the DISC or the mitochondrial level, p53-deficiency generated signs of autophagy deregulation upon chemotherapy. On the other, hand disruption of lysosomal function by chloroquine, caused a profound decrease in apoptotic markers appearing in response to 5-FU. DR5, which is essential for 5-FU-induced apoptosis, accumulated in lysosomes and autophagosomes upon chloroquine treatment. Since neither 3-MA, RNAi of critical autophagy regulators or inhibition of cathepsins reversed apoptosis in a similar manner, it is likely that not autophagy per se but rather correct receptor transport is an important factor for 5-FU cytotoxicity. We found that apoptosis generated by TRAIL, the cognate ligand for DR5, remained unchanged upon chloroquine lysosomal interference, indicating that 5-FU activates the receptor by a discrete mechanism. In support, depletion of membrane cholesterol or hampering cholesterol transport drastically reduced 5-FU cytotoxicity. We conclude that targeting of lysosomes by chloroquine deregulates DR5 trafficking and abrogates 5-FU- but not TRAIL-stimulated cell elimination, hence suggesting a novel mechanism for receptor activation.
authors: Division of Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors: Birce
authors: B
authors: Akpinar
authors: Department of Cytokinetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic.
authors: Barbora
authors: B
authors: Safarikova
authors: Department of Cytokinetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic.
authors: Jarmila
authors: J
authors: Laukova
authors: Division of Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors: Shubhranshu
authors: S
authors: Debnath
authors: Department of Cytokinetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic.
authors: Alena Hyrslova
authors: AH
authors: Vaculova
authors: Division of Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors: Boris
authors: B
authors: Zhivotovsky
authors: Division of Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors: Magnus
authors: M
authors: Olsson
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis; D001343:Autophagy; D002462:Cell Membrane / Q000378:metabolism; D002738:Chloroquine / Q000737:chemistry; D002784:Cholesterol / Q000737:chemistry; D005472:Fluorouracil / Q000737:chemistry; D045325:HCT116 Cells; D006801:Humans; D008024:Ligands; D008247:Lysosomes / Q000378:metabolism*; D018942:Macrolides / Q000737:chemistry; D008928:Mitochondria / Q000378:metabolism; D010588:Phagosomes; D021381:Protein Transport; D034622:RNA Interference; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D000964:Antimetabolites, Antineoplastic; D008024:Ligands; D018942:Macrolides; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; C505639:TNFRSF10B protein, human; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C057620:bafilomycin A; D002738:Chloroquine; D002784:Cholesterol; D005472:Fluorouracil
keywords: DR5; apoptosis; autophagy; chloroquine; lysosomes