Loss of intestinal endosome associated protein sorting nexin 27 disrupts epithelial barrier and promotes inflammation

Backgrounds and aims SNX27, member of the sorting nexin (SNX) family, carries a unique PDZ domain and mediates recycling of endocytosed transmembrane proteins. SNX27 is critical for neurodevelopmental processes, however its role in intestine remains unexplored. We aim to determine the previously unknown roles of SNX27 in regulating intestinal homeostasis, epithelial barrier integrity, and inflammatory responses.

We used available datasets to analyze SNX27 expression in human IBD. We generated a novel mouse model of SNX27 conditional deletion from intestinal epithelial cells (SNX27ΔIEC) and challenged these mice with Dextran Sulfate Sodium (DSS).

SNX27 expression was significantly lower in human IBD, including UC and CD. SNX27ΔIEC mice had significantly lower bodyweight and exhibited increased proliferation and poor differentiation of secretory Paneth and Goblet cells. We found reduced mucin layer and downregulation of crucial epithelial barrier proteins Δ-catenin, E-cadherin, ZO-1, and Claudin10 in SNX27ΔIEC mice. SNX27ΔIEC mice showed high intestinal permeability and spontaneously developed intestinal inflammation. Moreover, SNX27ΔIEC mice were more susceptible towards DSS-induced colitis, compared to the SNX27Loxp mice.

Overall, deletion of intestinal epithelial SNX27 weakens barrier functions and promotes inflammation. Our results indicate a novel role of SNX27 in regulating intestinal physiology and protecting against intestinal disorders. Thus, understanding the mechanisms of SNX27 downregulation in IBD will provide insights into new prevention and targets against chronic inflammation. SNX27 recycles internalized transmembrane proteins in the endocytic pathway. Human IBD showed reduced levels of SNX27. SNX27 plays novel functions by maintaining intestinal homeostasis and inhibiting inflammation. SNX27 protects the host against losing intestinal integrity during inflammation. Competing Interest Statement The authors have declared no competing interest. Abbreviation list - AJ - Adherens junction - ANOVA - Analysis of variance - Bcl-xL - B cell lymphoma-extra large - BSA - Bovine serum albumin - CD - Crohn’s disease - DAB - Diaminobenzidine - DAPI - Diamidino-2-phenylindole - DNA - Deoxyribonucleic acid - DSS - Dextran sulfate sodium - ECL - Enhanced chemiluminescence - FERM - 4.1/ezrin/radixin/moesin - FISH - Fluorescence in situ hybridization - FITC - Fluorescein isothiocyanate - GEO - Gene expression omnibus - GC - Goblet cell - GFP - Green fluorescent protein - HBSS - Hanks balanced salt solution - H&E - Hematoxylin & Eosin - IBD - Inflammatory bowel disease - IEC - Intestinal epithelial cells - IHC - Immunohistochemistry - IF - Immunofluorescence - IL-6 - Interleukin 6 - LPS - Lipopolysaccharides - mRNA - Messenger ribonucleic acid - Muc2 - Mucin-2 - MW - Molecular weight - PBS - Phosphate buffered saline - PC - Paneth cell - PCNA - Proliferating cell nuclear antigen - PX - Phox homology - PDZ - Post-synaptic density 95/discs large/zonula occludens-1 - qPCR - Quantitative polymerase chain reaction - RNA - Ribonucleic acid - siRNA - Small interfering ribonucleic acid - SNX - Sorting nexin - SSC - Saline Sodium Citrate - TBST - Tris-buffered saline with 0.1% Tween 20 - TJ - Tight junctions - TNF-α - Tumor necrosis factor α - TUNEL - Terminal deoxynucleotidyl transferase dUTP nick end labeling - UIC - University of Illinois Chicago - UC - Ulcerative colitis - ZO-1 - Zonula ocludens-1