![Sample our Bioscience journals, sign in here to start your access, Latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5925/TOC-Subject-Sample-2021-Bioscience.jpg"})
ABSTRACT
The intestinal mucosa of Crohn disease (CD) patients is abnormally colonized by adherent-invasive E. coli (AIEC). Upon AIEC infection, autophagy is induced in host cells to restrain bacterial intracellular replication. The underlying mechanism, however, remains unknown. Here, we investigated the role of the EIF2AK4-EIF2A/eIF2α-ATF4 pathway in the autophagic response to AIEC infection. We showed that infection of human intestinal epithelial T84 cells with the AIEC reference strain LF82 activated the EIF2AK4-EIF2A-ATF4 pathway, as evidenced by increased phospho-EIF2AK4, phospho-EIF2A and ATF4 levels. EIF2AK4 depletion inhibited autophagy activation in response to LF82 infection, leading to increased LF82 intracellular replication and elevated pro-inflammatory cytokine production. Mechanistically, EIF2AK4 depletion suppressed the LF82-induced ATF4 binding to promoters of several autophagy genes including MAP1LC3B, BECN1, SQSTM1, ATG3 and ATG7, and this subsequently inhibited transcription of these genes. LF82 infection of wild-type (WT), but not eif2ak4−/−, mice activated the EIF2AK4-EIF2A-ATF4 pathway, inducing autophagy gene transcription and autophagy response in enterocytes. Consequently, eif2ak4−/− mice exhibited increased intestinal colonization by LF82 bacteria and aggravated inflammation compared to WT mice. Activation of the EIF2AK4-EIF2A-ATF4 pathway was observed in ileal biopsies from patients with noninflamed CD, and this was suppressed in inflamed CD, suggesting that a defect in the activation of this pathway could be one of the mechanisms contributing to active disease. In conclusion, we show that activation of the EIF2AK4-EIF2A-ATF4 pathway upon AIEC infection serves as a host defense mechanism to induce functional autophagy to control AIEC intracellular replication.
ABBREVIATIONS
| AIEC | = | adherent-invasive Escherichia coli |
| ASNS | = | asparagine synthetase (glutamine-hydrolyzing) |
| ATF3 | = | activating transcription factor 3 |
| ATF4 | = | activating transcription factor 4 |
| ATG16L1 | = | autophagy-related 16 like 1 |
| ATG3 | = | autophagy-related 3 |
| ATG5 | = | autophagy-related 5 |
| ATG7 | = | autophagy-related 7 |
| BECN1 | = | Beclin 1, autophagy-related |
| CD | = | Crohn disease |
| CFU | = | colony-forming units |
| ChIP | = | chromatin immunoprecipitation |
| CXCL1 | = | chemokine (C-X-C motif) ligand 1 (melanoma growth stimulating activity, alpha) |
| DDIT3 | = | DNA damage inducible transcript 3 |
| DSS | = | dextran sodium sulfate |
| EIF2 | = | eukaryotic translation initiation factor 2 |
| EIF2AK4 | = | eukaryotic translation initiation factor 2 alpha kinase 4 |
| ELISA | = | enzyme-linked immunosorbent assay |
| IBD | = | inflammatory bowel diseases |
| IEC | = | intestinal epithelial cell |
| IL | = | interleukin |
| IL1B | = | interleukin 1 beta |
| IRGM | = | immunity-related GTPase family, M |
| KRB | = | Krebs-Ringer buffer |
| LRRK2 | = | leucine-rich repeat kinase 2 |
| MAP1LC3B | = | microtubule-associated protein 1 light chain 3 beta |
| MOI | = | multiplicity of infection |
| mRNA | = | messenger RNA |
| PTPN2 | = | protein tyrosine phosphatase, non-receptor type 2 |
| qRT-PCR | = | quantitative reverse-transcription polymerase chain reaction |
| SQSTM1 | = | sequestosome 1 |
| TNF | = | tumor necrosis factor |
| TRIB3 | = | tribbles pseudokinase 3 |
| ULK1 | = | unc-51 like autophagy activating kinase 1 |
| WT | = | wild type |
| XBP1 | = | X-box binding protein 1 |
Disclosure of potential conflicts of interest
No potential conflicts of interest were disclosed.
Acknowledgments
We dedicate this article to the memory of Prof. Arlette Darfeuille-Michaud, who sadly passed away on June 28, 2014. The authors thank the Imagerie Confocale Clermont-Ferrand (ICCF) platform (IFR79 Santé Université d'Auvergne, Clermont-Ferrand, France) for confocal microscopy and the Centre Imagerie Cellulaire Santé (Facultés de Médecine et Pharmacie) for tissue embedding and sectioning. We thank Drs. Emilie Vazeille, Marie-Agnès Bringer and Pierre Lapaquette for valuable discussion.
Funding
This work was supported by the Ministère de la Recherche et de la Technologie, Inserm (UMR1071), INRA (USC 2018), grant from the Association F. Aupetit (AFA), grant from Agence nationale de la recherche (ANR) “Jeune Chercheuse Jeune Chercheur” Nutribiote SVSE 1 Edition 2013 (to N.B.), the European Union FP7 People Marie Curie International Incoming Fellowship (to H.N.) and grant from Région Auvergne (“Nouveau chercheur” grant to H.N.).