Oncotarget

Research Papers:

Aberrant DR5 transport through disruption of lysosomal function suggests a novel mechanism for receptor activation

Birce Akpinar, Barbora Safarikova, Jarmila Laukova, Shubhranshu Debnath, Alena Hyrslova Vaculova, Boris Zhivotovsky _ and Magnus Olsson

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Oncotarget. 2016; 7:58286-58301. https://doi.org/10.18632/oncotarget.11073

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Abstract

Birce Akpinar1, Barbora Safarikova2, Jarmila Laukova2, Shubhranshu Debnath1, Alena Hyrslova Vaculova2, Boris Zhivotovsky1, Magnus Olsson1

1Division of Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden

2Department of Cytokinetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic

Correspondence to:

Boris Zhivotovsky, email: [email protected]

Keywords: apoptosis, autophagy, chloroquine, DR5, lysosomes

Received: March 22, 2016    Accepted: July 13, 2016    Published: August 05, 2016

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.


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