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J Biol Chem. 2018 Mar 2;293(9):3073-3087. doi: 10.1074/jbc.RA117.000809. Epub 2018 Jan 9.

ER-stress mobilization of death-associated protein kinase-1-dependent xenophagy counteracts mitochondria stress-induced epithelial barrier dysfunction.

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From the Gastrointestinal Research Group, Departments of Physiology and Pharmacology and
the Department of Clinical and Experimental Medicine, Division of Surgery, Linköping University, Linköping 581 83, Sweden, and.
From the Gastrointestinal Research Group, Departments of Physiology and Pharmacology and.
the Departments of Laboratory Medicine and Pathobiology and.
the Departments of Pediatrics, Clinical Neurosciences, and Physiology and Pharmacology and.
the Department of Microbiology, Immunology and Infectious Diseases, Cumming School of Medicine, University of Calgary, Calgary, Alberta T2N4N1, Canada.
Medicine, Calvin, Joan, and Phoebe Snyder Institute for Chronic Diseases, and.
Immunology, University of Toronto, Toronto, Ontario M5S1A1, Canada.
From the Gastrointestinal Research Group, Departments of Physiology and Pharmacology and


The gut microbiome contributes to inflammatory bowel disease (IBD), in which bacteria can be present within the epithelium. Epithelial barrier function is decreased in IBD, and dysfunctional epithelial mitochondria and endoplasmic reticulum (ER) stress have been individually associated with IBD. We therefore hypothesized that the combination of ER and mitochondrial stresses significantly disrupt epithelial barrier function. Here, we treated human colonic biopsies, epithelial colonoids, and epithelial cells with an uncoupler of oxidative phosphorylation, dinitrophenol (DNP), with or without the ER stressor tunicamycin and assessed epithelial barrier function by monitoring internalization and translocation of commensal bacteria. We also examined barrier function and colitis in mice exposed to dextran sodium sulfate (DSS) or DNP and co-treated with DAPK6, an inhibitor of death-associated protein kinase 1 (DAPK1). Contrary to our hypothesis, induction of ER stress (i.e. the unfolded protein response) protected against decreased barrier function caused by the disruption of mitochondrial function. ER stress did not prevent DNP-driven uptake of bacteria; rather, specific mobilization of the ATF6 arm of ER stress and recruitment of DAPK1 resulted in enhanced autophagic killing (xenophagy) of bacteria. Of note, epithelia with a Crohn's disease-susceptibility mutation in the autophagy gene ATG16L1 exhibited less xenophagy. Systemic delivery of the DAPK1 inhibitor DAPK6 increased bacterial translocation in DSS- or DNP-treated mice. We conclude that promoting ER stress-ATF6-DAPK1 signaling in transporting enterocytes counters the transcellular passage of bacteria evoked by dysfunctional mitochondria, thereby reducing the potential for metabolic stress to reactivate or perpetuate inflammation.


DAPK1; IBD basic research; autophagy; bacteria; bacterial translocation; endoplasmic reticulum stress (ER stress); epithelial barrier;; epithelial cell; inflammatory bowel disease; intestinal barrier function; mitochondria; mitochondrial stress; oxidative metabolism

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