VEXAS syndrome is a severe adult-onset autoinflammatory disease caused by somatic mutations in UBA1 gene, disrupting cytoplasmic ubiquitin-activating enzyme E1 function in hematopoietic progenitors. The pathogenesis remains poorly understood, particularly how UBA1 mutations perturb myeloid function. Here, we combine a genetically engineered THP-1 monocytic model with ex vivo analyses of blood and tissue samples from VEXAS patients to investigate the consequences of the canonical UBA1 M41V mutation. We show that UBA1 -mutated monocytes exhibit TNF-α-induced cell death, characterized by RIPK1 phosphorylation, and MLKL-and caspase-8–mediated cell death. This is associated with defective transcriptional induction of NF-κB target genes and reduced cFLIP(L) expression in response to TNF-α. Monocytes also display blunted cytokine responses to multiple Toll-like receptor (TLR) agonists despite preserved TLR expression, linked to an impaired NF-κB response. UBA1 M41V -derived macrophages exhibit an inflammatory transcriptional profile and increased secretion of chemokines that promote monocyte recruitment. We demonstrate that these UBA1 M41V macrophages display impaired efferocytosis due to lysosomal dysfunction. Together, these findings reveal a pathogenic axis in VEXAS syndrome linking UBA1 loss of function and defective ubiquitination to RIPK1-mediated inflammatory cell death, impaired antimicrobial signaling, and defective resolution mechanisms. Our study provides novel mechanistic insights into the myeloid dysfunction that drives inflammation and cytopenia in VEXAS and highlights the necroptosis and efferocytosis pathways as potential therapeutic targets.
Key points
1/ UBA1 -mutated monocytes are susceptible to RIPK1 dependent cell death and display impaired NF-κB–mediated cytokine responses to TLR agonists.
2/ UBA1-mutated macrophages promote inflammation and chemokine-mediated monocyte recruitment, while exhibiting defective efferocytosis.