Independent mechanisms of irritation and myeloid bias in VEXAS syndrome

Somatically acquired mutations within the E1 ubiquitin-activating enzyme UBA1 inside hematopoietic stem and progenitor cells (HSPCs) had been just lately recognized as the reason for the adult-onset autoinflammatory syndrome VEXAS (vacuoles, E1 enzyme, X linked, autoinflammatory, somatic)¹. UBA1 mutations in VEXAS result in clonal enlargement throughout the HSPC and myeloid, however not lymphoid, compartments. Despite its severity and prevalence, the mechanisms whereby UBA1 mutations trigger multiorgan autoinflammation and hematologic illness are unknown. Here, we make use of somatic gene enhancing approaches to mannequin VEXAS-associated UBA1 mutations in main macrophages and HSPCs. Uba1-mutant macrophages uncovered to inflammatory stimuli underwent aberrant apoptotic and necroptotic cell demise mediated by Caspase-8 and RIPK3-MLKL, respectively. Accordingly, in mice challenged with TNF or LPS, the UBA1 inhibitor TAK-243 exacerbated irritation in a RIPK3-Caspase-8-dependent method. In distinction, Uba1 mutation in HSPCs induced an unfolded protein response and myeloid bias independently of RIPK3-Caspase-8. Mechanistically, aberrant cell demise of Uba1-mutant macrophages coincided with a kinetic defect in Lys63/Met1 (i.e., linear) polyubiquitylation of inflammatory signaling complexes. Collectively, our outcomes hyperlink VEXAS pathogenesis with that of rarer monogenic autoinflammatory syndromes; spotlight particular ubiquitin-associated defects stemming from an apical mutation within the ubiquitylation cascade; and assist therapeutic focusing on of the inflammatory cell demise axis in VEXAS.