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Background: Periodic fever syndromes are caused by deregulation of interleukin-1␤ release. Results: Defective autophagy leads to accumulation of damaged mitochondria in monocytes. Conclusion: Mitochondrial components in the cytosol cause priming of monocytes for interleukin-1␤ release. Significance: The molecular mechanism behind deregulated cytokine secretion provides new clues for intervention.Most hereditary periodic fever syndromes are mediated by deregulated IL-1␤ secretion. The generation of mature IL-1␤ requires two signals: one that induces synthesis of inflammasome components and substrates and a second that activates inflammasomes. The mechanisms that mediate autoinflammation in mevalonate kinase deficiency, a periodic fever disease characterized by a block in isoprenoid biosynthesis, are poorly understood. In studying the effects of isoprenoid shortage on IL-1 ␤ generation, we identified a new inflammasome activation signal that originates from defects in autophagy. We find that hypersecretion of IL-1␤ and IL-18 requires reactive oxygen species and is associated with an oxidized redox status of monocytes but not lymphocytes. IL-1␤ hypersecretion by monocytes involves decreased mitochondrial stability, release of mitochondrial content into the cytosol and attenuated autophagosomal degradation. Defective autophagy, as established by ATG7 knockdown, results in prolonged cytosolic retention of damaged mitochondria and increased IL-1␤ secretion. Finally, activation of autophagy in healthy but not mevalonate kinase deficiency patient cells reduces IL-1␤ secretion. Together, these results indicate that defective autophagy can prime monocytes for mitochondria-mediated NLRP3 inflammasome activation, thereby contributing to hypersecretion of IL-1␤ in mevalonate kinase deficiency.Periodic fever syndromes are characterized by inflammation that occurs in the absence of apparent infection or high titer autoantibodies (1, 2). In most periodic fever syndromes, the generalized inflammation is driven by IL-1␤ generated through proteolytic cleavage by the NLRP3 inflammasome. An additional feature associated with inflammation is the production of reactive oxygen species (ROS) 3 (3, 4). During infection, ROS produced by NADPH-oxidase subunits at the plasma membrane are beneficial because ROS in phagosomes contribute to the killing of intracellular pathogens (5). In several inflammatory diseases, including periodic fever syndromes, ROS levels are increased in the cytosol and contribute to pathology (6). ROS play roles as intracellular second messengers and have immediate effects on the intracellular redox status. In TNF receptor 1-associated periodic syndrome (TRAPS), for example, mitochondria-derived ROS facilitate inflammatory cytokine production (7). Mitochondria are believed to be the main source of ROS in several autoinflammatory disorders (8).ROS are normally generated within mitochondria as byproducts of oxidative phosphorylation, but when liberated in the cytosol ROS can facilitate activation of the NLRP3 inflammas...

Background: Shortage of isoprenoids causes aberrant activity of prenylated small GTPases. Results: Inactivation of RhoA due to lack of prenylation leads to Rac1 activation and subsequent priming for IL-1␤ secretion. Conclusion: RhoA inactivation contributes to the pathology of isoprenoid deficiency. Significance: Insight into the multiple networks involving RhoA will benefit new intervention strategies in prenylation-related pathologies.