Uromodulin-associated kidney disease (UAKD) is caused by mutations in the uromodulin (UMOD) gene that result in a misfolded form of UMOD protein, which is normally secreted by nephrons. In UAKD patients, mutant UMOD is poorly secreted and accumulates in the ER of distal kidney epithelium, but its role in disease progression is largely unknown. Here, we modeled UMOD accumulation in mice by expressing the murine equivalent of the human UMOD p.Cys148Trp point mutation (Umod^C147W/+ mice). Like affected humans, these Umod^C147W/+ mice developed spontaneous and progressive kidney disease with organ failure over 24 weeks. Analysis of diseased kidneys and purified UMOD-producing cells revealed early activation of the PKR-like ER kinase/activating transcription factor 4 (PERK/ATF4) ER stress pathway, innate immune mediators, and increased apoptotic signaling, including caspase-3 activation. Unexpectedly, we also detected autophagy deficiency. Human cells expressing UMOD p.Cys147Trp recapitulated the findings in Umod^C147W/+ mice, and autophagy activation with mTOR inhibitors stimulated the intracellular removal of aggregated mutant UMOD. Human cells producing mutant UMOD were susceptible to TNF-α– and TRAIL-mediated apoptosis due to increased expression of the ER stress mediator tribbles-3. Blocking TNF-α in vivo with the soluble recombinant fusion protein TNFR:Fc slowed disease progression in Umod^C147W/+ mice by reducing active caspase-3, thereby preventing tubule cell death and loss of epithelial function. These findings reveal a targetable mechanism for disease processes involved in UAKD.

中文翻译：

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Uromodulin p.Cys147Trp突变通过激活ER应激和细胞凋亡来驱动肾脏疾病

尿调节蛋白相关的肾脏疾病（UAKD）是由尿调节蛋白（UMOD）基因的突变引起的，该突变导致UMOD蛋白的错误折叠形式，通常由肾单位分泌。在UAKD患者中，突变型UMOD的分泌较差，并且在远端肾上皮的ER中积累，但是在疾病进展中的作用很大程度上未知。在这里，我们通过表达人类UMOD p.Cys148Trp点突变的鼠类等效物（Umod ^{C147W / +}小鼠）对小鼠中的UMOD积累进行建模。像受影响的人类一样，这些Umod ^{C147W / +}小鼠发展为自发性和进行性肾脏疾病，器官衰竭持续超过24周。对患病肾脏和纯化的产生UMOD的细胞的分析揭示了PKR样ER激酶/激活转录因子4（PERK / ATF4）ER应激途径的早期激活，先天性免疫介质和增加的凋亡信号传导，包括caspase-3激活。出乎意料的是，我们还检测到自噬缺陷。表达UMOD p.Cys147Trp的人类细胞概括了Umod ^{C147W / +中}的发现小鼠和自噬激活与mTOR抑制剂刺激聚集的突变UMOD的细胞内去除。由于ER应激介质tribbles-3的表达增加，产生突变型UMOD的人类细胞易受TNF-α和TRAIL介导的细胞凋亡的影响。用可溶性重组融合蛋白TNFR：Fc体内阻断TNF-α可通过降低活性caspase-3减慢Umod ^{C147W / +}小鼠的疾病进展，从而防止肾小管细胞死亡和上皮功能丧失。这些发现揭示了涉及UAKD的疾病过程的靶向机制。