RORt-Raftlin1 complex regulates the pathogenicity of Th17 cells and intestinal inflammation

Abstract Th17 cells that produce IL-17 are pathogenic in many human diseases, including inflammatory bowel disease (IBD), but are, paradoxically, essential for maintaining the integrity of the intestinal barrier in a non-inflammatory state. However, the intracellular mechanisms that regulate distinct transcriptional profiles and functional diversity of Th17 cells remain unclear. We have found that Raftlin1, a lipid raft protein, is specifically upregulated in and forms a complex with RORγt via its conserved LLNSL motif in pathogenic Th17 cells. Disruption of the RORγt-Raftlin1 complex in Raftlin1 ΔLLNSLknock-in mice resulted in attenuated pathogenic Th17 cells elicited by Citrobacter rodentium; however, there was no effect on nonpathogenic Th17 cells induced by commensal segmented filamentous bacteria (SFB). Mechanistically, we found that Raftlin1 recruits distinct phospholipids to RORγt and promotes the pathogenicity of Th17 cells. Thus, we have identified a fundamental mechanism that drives the pathogenic function of Th17 cells, which could provide a platform for new therapeutic strategies to dampen Th17-mediated inflammatory diseases. This work was supported by funds from the National Institutes of Health (R01-DK115668, R01-AI155786) and Cancer Prevention Research Institute of Texas (RP190527) and a stimulus grant from the Harold C. Simmons Comprehensive Cancer Center, UT Southwestern Medical Center.