E3 Ubiquitin ligase RNF183 Is a Novel Regulator in Inflammatory Bowel Disease

Specific members of the RING finger [RNF] protein family serve as E3 ubiquitin ligases and play important roles in the regulation of inflammation. However, their roles in the pathogenesis of inflammatory bowel disease [IBD] have not been explored. Genomic microarray of inflamed colon samples from Crohn's disease [CD] patients was performed to identify potential up-regulated genes. Expression of the identified highly up-regulated RNF183 gene was subsequently examined by quantitative reverse transcription polymerase chain reaction [qRT-PCR], western blotting and immunohistochemistry of the intestinal tissues of IBD patients and the colons of trinitrobenzene sulphonic acid [TNBS]-induced colitic mice. RNF183-mediated interaction with the NF-kappa B pathway and ubiquitination of I kappa B alpha were examined by siRNA, plasmid transfection, and immunoprecipitation. The miRNA predicted to target RNF183 was explored and its role in the RNF183/ NF-kappa B pathway was investigated. RNF183 was up-regulated in intestinal epithelial cells in IBD patients and in colitic mice. RNF183 promoted intestinal inflammation via the activation of the NF-kappa B pathway by increasing the ubiquitination and degradation of I kappa B alpha. Computational analysis identified putative binding of miR-7 to RNF183. Transfection of intestinal cells with a miR-7 mimic or inhibitor confirmed its negative regulatory effect on RNF183 expression and ubiquitination of I kappa B alpha. miR-7 was down-regulated in inflamed colon tissues of IBD patients and colitic mice. RNF183, which is negatively regulated by miR-7, is a novel regulator promoting intestinal inflammation by increasing the ubiquitination and degradation of I kappa B alpha, thereby inducing NF-kappa B activation. The interaction between RNF183-mediated ubiquitination and miRNA may be an important novel epigenetic mechanism in the pathogenesis of IBD.