Clough Courtnee A, Cunningham Claire, Philbrook Sophia Y, Hueneman Kathleen M, Sampson Avery M, Choi Kwangmin, Greis Kenneth D, Starczynowski Daniel
Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
Department of Cancer Biology, University of Cincinnati, Cincinnati, OH, USA.
Leukemia. 2025 Jun 30. doi: 10.1038/s41375-025-02671-x.
VEXAS syndrome is a clonal hematopoietic disorder characterized by hyperinflammation, bone marrow failure, and high mortality. The molecular hallmark of VEXAS is somatic mutations at methionine 41 (M41) in the E1 ubiquitin enzyme, UBA1. These mutations induce a protein isoform switch, but the mechanisms underlying disease pathogenesis remain unclear. Here, we developed a human cell model of VEXAS syndrome by engineering the male monocytic THP1 cell line to express the common UBA1 mutation. We found that mutant UBA1 cells exhibit aberrant UBA1 isoform expression, increased vacuolization, and upregulation of the unfolded protein response, recapitulating key features of VEXAS. Moreover, proteomic analyses revealed dysregulated ubiquitination and proteotoxic stress in UBA1 cells, with alterations in inflammatory and stress-response pathways. Functional studies demonstrated that UBA1 cells were highly sensitive to genetic or pharmacological inhibition of E1 ubiquitin enzymes. Treatment with the E1 enzyme inhibitor TAK-243 preferentially suppressed colony formation of UBA1 cells as compared to WT cells. Moreover, UBA1 cells exhibited greater sensitivity to TAK-243 in competition assays and showed increased apoptosis. Interestingly, TAK-243 preferentially inhibited UBA6 activity over UBA1, suggesting that UBA6 may compensate for UBA1 dysfunction in UBA1 cells. Targeting UBA6 using shRNA or the UBA6-specific inhibitor phytic acid further revealed an acquired dependency on UBA6 in UBA1 cells. Phytic acid selectively impaired growth and colony formation in UBA1 cells while sparing WT cells, highlighting a potential therapeutic vulnerability. Together, these findings establish a novel human model of VEXAS syndrome, identify key roles for UBA1 and UBA6 in disease pathogenesis, and demonstrate that UBA6 inhibition represents a promising therapeutic strategy for selectively targeting UBA1 mutant clones.
VEXAS综合征是一种克隆性造血疾病，其特征为炎症反应过度、骨髓衰竭和高死亡率。VEXAS的分子标志是泛素E1酶UBA1中蛋氨酸41（M41）位点的体细胞突变。这些突变诱导了蛋白质异构体转换，但疾病发病机制背后的机制仍不清楚。在此，我们通过对男性单核细胞THP1细胞系进行工程改造以表达常见的UBA1突变，建立了VEXAS综合征的人类细胞模型。我们发现，突变型UBA1细胞表现出异常的UBA1异构体表达、空泡化增加以及未折叠蛋白反应的上调，概括了VEXAS的关键特征。此外，蛋白质组学分析揭示了UBA1细胞中泛素化失调和蛋白毒性应激，炎症和应激反应途径发生改变。功能研究表明，UBA1细胞对E1泛素酶的基因或药理学抑制高度敏感。与野生型细胞相比，用E1酶抑制剂TAK-243处理可优先抑制UBA1细胞的集落形成。此外，在竞争试验中，UBA1细胞对TAK-243表现出更高的敏感性，并显示出凋亡增加。有趣的是，与UBA1相比，TAK-243优先抑制UBA6活性，这表明UBA6可能补偿UBA1细胞中UBA1的功能障碍。使用短发夹RNA或UBA6特异性抑制剂植酸靶向UBA6进一步揭示了UBA1细胞对UBA6的获得性依赖性。植酸选择性损害UBA1细胞的生长和集落形成，而对野生型细胞无影响，突出了潜在的治疗脆弱性。总之，这些发现建立了一种新的VEXAS综合征人类模型，确定了UBA1和UBA6在疾病发病机制中的关键作用，并证明抑制UBA6代表了一种有前景的治疗策略，可选择性靶向UBA1突变克隆。
