ASB3 expression aggravates inflammatory bowel disease by targeting TRAF6 protein stability and affecting the intestinal microbiota

Abstract

BACKGROUND & AIMS: E3 ubiquitin ligase (E3) plays a vital role in regulating inflammatory responses by mediating ubiquitination. Previous studies have shown that ankyrin repeat and SOCS box-containing protein 3 (ASB3) is involved in immunomodulatory functions associated with cancer. However, the impact of ASB3 on the dynamic interplay of microbiota and inflammatory responses in inflammatory bowel disease (IBD) is unclear. Our aim was to investigate the role of ASB3 in gut epithelium inflammation. METHODS: ASB3 was quantified in the lesions of IBD patients using Western blotting, qPCR and immunohistochemistry. We treated wild-type (WT) and ASB3-/- FVB-N mice and their derived colonic organoids with dextran sulfate sodium (DSS) or TNF-α as models of colitis and assessed inflammation onset, transcriptome, microbiome and ubiquitination modifications. RESULTS: ASB3-/- mice are resistant to DSS-induced colitis. IκBα phosphorylation levels and production of pro-inflammatory factors IL-1β, IL-6, and TNF-α were reduced in colonic tissues of ASB3-/- mice compared to WT mice. This colitis-resistant phenotype was suppressed after coprophagic microbial transfer and reversed after combined antibiotic clearance of the microbiota. In addition, ASB3 specifically interacts with TRAF6 and degrades it via the proteasomal pathway. Further analysis revealed that ASB3 enhances K48-linked polyubiquitination of TRAF6 through the interaction of its SOCS box (SOCX) domain with the TRAF6 C-terminal domain. CONCLUSIONS: ASB3 is associated with dysregulation of the colitis microbiota and promotes proinflammatory factors production by disrupting the TRAF6 stability. Strategies to limit the protein level of ASB3 in intestinal epithelial cells may help in the treatment of colitis.