Deubiquitination of RIPK3 by OTUB2 potentiates neuronal necroptosis after ischemic stroke

As a common and severe cerebrovascular disease, ischemic stroke casts a significant shadow over global health. Unfortunately, the mechanisms regulating neuronal death in the affected areas remain largely unclear. Here, we found that deletion of the deubiquitinating enzyme Otubain-2 (OTUB2) significantly alleviated ischemia-induced cerebral infarction and neurological deficits, accompanied by a reduction in neuronal loss, glial activation, and neuroinflammation. OTUB2 was predominantly expressed in neurons and its deletion decreased receptor-interacting protein kinase 3 (RIPK3)-mediated neuronal necroptosis. Moreover, OTUB2 increased RIPK3 protein abundance by inhibiting the proteasomal degradation of RIPK3. Mechanistically, OTUB2 removed K48-linked polyubiquitin chains from RIPK3 through its active site C51. Importantly, pharmacological inhibition of OTUB2 alleviated ischemic brain injury in mice and reduced oxygen-glucose deprivation-induced neuronal death in human brain organoids. These results demonstrate that OTUB2 critically regulates ischemic stroke injury by potentiating neuronal necroptosis, suggesting that OTUB2 inhibition may become a potential therapeutic approach for treating ischemic stroke.

缺血性脑卒中（ischemic stroke）作为一种常见且严重的脑血管疾病，给全球公共健康带来了沉重负担。遗憾的是，缺血灶区域神经元死亡的调控机制目前仍未完全阐明。本研究发现，敲除去泛素化酶Otubain-2（OTUB2）可显著减轻缺血诱导的脑梗死与神经功能缺损，并同时减少神经元丢失、胶质细胞活化及神经炎症反应。OTUB2主要在神经元中表达，敲除OTUB2可抑制受体相互作用蛋白激酶3（RIPK3）介导的神经元坏死性凋亡。此外，OTUB2可通过抑制RIPK3的蛋白酶体降解，提升其蛋白丰度。从机制上来说，OTUB2可通过其活性位点C51，去除RIPK3上的K48连接型多泛素链。值得注意的是，对OTUB2进行药物抑制，可减轻小鼠的缺血性脑损伤，并降低氧糖剥夺诱导的人类脑类器官中神经元死亡水平。上述研究结果表明，OTUB2通过增强神经元坏死性凋亡，关键调控缺血性脑卒中的损伤进程，提示抑制OTUB2或可成为治疗缺血性脑卒中的潜在治疗策略。