First published March 13, 2018 - More info
Recent studies reveal that airway epithelial cells are critical pulmonary circadian pacemaker cells, mediating rhythmic inflammatory responses. Using mouse models, we now identify the rhythmic circadian repressor REV-ERB as essential to the mechanism coupling the pulmonary clock to innate immunity, involving both myeloid, and bronchial epithelial cells in temporal gating and determining amplitude of response to inhaled endotoxin. Dual mutation of REV-ERBα and its paralog REV-ERBβ in bronchial epithelia further augmented inflammatory responses and chemokine activation, but also initiated a basal inflammatory state, revealing a critical homeostatic role for REV-ERB proteins in the suppression of the endogenous pro-inflammatory mechanism in un-challenged cells. However, REV-ERBα plays the dominant role as deletion of REV-ERBβ alone had no impact on inflammatory responses. In turn, inflammatory challenges cause striking changes in stability and degradation of REV-ERBα protein, driven by SUMOylation and ubiquitination. We developed a novel selective oxazole-based inverse agonist of REV-ERB, which protects REV-ERBα protein from degradation and used this to reveal how pro-inflammatory cytokines trigger rapid degradation of REV-ERα in the elaboration of an inflammatory response. Thus, dynamic changes in stability of REV-ERα protein couple the core clock to innate immunity.