Loss of Intestinal SNX27 Promotes Barrier Dysfunction and Inflammatory Responses

Abstract

SNX27 belongs to the sorting nexin (SNX) family of proteins that play a crucial role in the endocytic pathway. SNX27 carries a unique PDZ domain, mediates recycling of endocytosed transmembrane proteins, and is critical for neurodevelopmental processes. However, its role in the intestine has not been explored yet. Here we aim to determine the previously unknown roles of SNX27 in regulating intestinal tissue homeostasis, epithelial barrier integrity, and related disorders. We have generated a novel mouse model of SNX27 deletion form intestinal epithelial cells (SNX27ΔIEC). We challenged the mice with DSS-induced colitis and AOM/DSS-induced colorectal cancer (CRC). We performed in vitro SNX27 loss of function studies via siRNA knockdown (KD) in SKCO15 cells. We further analyzed SNX27 expression in IBD and CRC patients via online human datasets. SNX27ΔIEC mice had shorter colon, small intestines, and heavier spleens. We found increased intestinal permeability upon SNX27 deletion. SNX27ΔIEC mice had significantly upregulated cleaved Caspase-3 (pro-apoptotic) and downregulated Bcl-xL (anti-apoptotic) protein levels. TUNEL staining also showed greater apoptotic cells in SNX27ΔIEC mice. Tight-junction proteins Claudin10 and ZO-1, as well as adherens-junction proteins ꞵ-catenin and E-cadherin, were downregulated in SNX27ΔIEC mice. The histological inflammation score and mRNA levels of pro-inflammatory cytokines IL-6 and TNF-α were higher in SNX27ΔIEC mice. Protein expression level of phospho-p65 was increased in SNX27ΔIEC mice, indicating NFkB pathway activation. Upon challenging with intestinal disorders, SNX27ΔIEC mice were more sensitive towards DSS and AOM/DSS treatments as they lost more bodyweight, had higher intestinal permeability levels, and heavier spleens. SNX27 KD in vitro reduced protein levels of PCNA and delayed wound closure in a wound healing assay. SNX27-KD cells had higher nuclear translocation of phospho-p65. Additionally, we observed cytoplasmic localization rearrangement and downregulation of ꞵ-catenin and E-cadherin, key mediators of epithelial-mesenchymal transition. Lastly, human datasets GSE11223, 6731, 8671, 21510 revealed significant downregulation of SNX27 expression in IBD and CRC patients, suggesting towards clinical relevance of SNX27 in intestinal disorders. Overall, intestinal deletion of SNX27 promotes apoptosis, inflammation, and disrupts epithelial barrier that increases susceptibility towards colonic inflammation and tumorigenesis. Our results indicate a novel role of SNX27 in regulating intestinal tissue homeostasis. Understanding the mechanisms of lower SNX27 in IBD and CRC will provide insights into new prevention and targets against these chronic diseases. We would like to acknowledge the VA Merit Award 1 I01BX004824-01, DOD CDMRP BC191198, the NIDDK/National Institutes of Health grants R01 DK105118 and R01DK114126 to Jun Sun. The study sponsors performed no role in the study design, data collection, analysis, and interpretation of data. The contents do not represent the views of the United States Department of Veterans Affairs or the United States Government. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.