The E3 ubiquitin ligase RNF186 and RNF186 risk variants regulate innate receptor-induced outcomes

Abstract

Significance This study identifies a previously undefined role for the inflammatory bowel disease–associated gene RNF186 in innate immunity. RNF186 is expressed in human macrophages and promotes outcomes downstream of receptors responding to microbial products. Upon stimulation of microbial response receptors, RNF186 contributes to assembly and ubiquitination of the signaling complex and subsequent cytokine secretion and antimicrobial pathway induction. Importantly, through different mechanisms, both rare (through impaired ubiquitination) and common (through reduced expression) disease-risk genetic variants in RNF186 lead to a loss in RNF186 function and impaired bacterial clearance in primary human macrophages. These studies highlight a key role for RNF186 in promoting essential innate immune functions contributing to intestinal immune homeostasis. Balancing microbial-induced cytokines and microbial clearance is critical at mucosal sites such as the intestine. How the inflammatory bowel disease (IBD)–associated gene RNF186 regulates this balance is unclear. We found that macrophages from IBD-risk rs6426833 carriers in the RNF186 region showed reduced cytokines to stimulation through multiple pattern recognition receptors (PRRs). Upon stimulation of PRRs, the E3-ubiquitin ligase RNF186 promoted ubiquitination of signaling complex molecules shared across PRRs and those unique to select PRRs. Furthermore, RNF186 was required for PRR-initiated signaling complex assembly and downstream signaling. RNF186, along with its intact E3-ubiquitin ligase activity, was required for optimal PRR-induced antimicrobial reactive oxygen species, reactive nitrogen species, and autophagy pathways and intracellular bacterial clearance in human macrophages and for bacterial clearance in intestinal myeloid cells. Cells transfected with the rare RNF186-A64T IBD-risk variant and macrophages from common rs6426833 RNF186 IBD-risk carriers demonstrated a reduction in these RNF186-dependent outcomes. These studies identify mechanisms through which RNF186 regulates innate immunity and show that RNF186 IBD-risk variants demonstrate a loss of function in PRR-initiated outcomes.