DNA-binding protein-A promotes renal ischemia/reperfusion injury and participates in mitochondrial function

DNA-binding protein-A (DbpA; gene: Ybx3) belongs to the cold shock protein family with known functions in cell cycling, transcription, translation and tight junction communication. In chronic nephritis DbpA is upregulated, however its activities in acute injury models, such as renal ischemia/reperfusion injury (IRI), are unclear. Mice harboring Ybx3+/+, Ybx3+/- or Ybx3-/- genotype were characterized over a period of 24 months and following experimental renal IRI. Mitochondrial function, number and integrity were analyzed by mito stress tests, MitoTracker staining and electron microscopy. Immunohistochemistry, Western blotting and flow cytometry were performed to quantify tubular cell damage and immune cell infiltration. DbpA is dispensable for kidney development and tissue homeostasis under healthy conditions. Furthermore, endogenous DbpA protein localizes within mitochondria in primary tubular epithelial cells (TECs). Genetic deletion of Ybx3 elevates the mitochondrial membrane potential, the lipid uptake and metabolism, the oxygen consumption rates (OCR) and glycolytic activities of TECs. Ybx3-/- mice demonstrate protection from IRI with less immune cell infiltration, ER stress and tubular cell damage. A putative protective mechanism is identified via upregulated antioxidant activities and reduced ferroptosis, when Ybx3 is deleted. Here, experimental evidences reveal DbpA acts as a mitochondrial protein with profound adverse effects on cell metabolism and highlights a protective effect against IRI when Ybx3 is genetically deleted.DNA结合蛋白A（DNA-binding protein-A，DbpA；编码基因Ybx3）属于冷休克蛋白家族（cold shock protein family），已知其功能涉及细胞周期、转录、翻译及紧密连接通讯。在慢性肾炎中，DbpA表达上调，但其在急性损伤模型（如肾缺血/再灌注损伤（ischemia/reperfusion injury，IRI））中的作用尚不明确。研究人员对携带Ybx3+/+、Ybx3+/-及Ybx3-/-基因型的小鼠进行了为期24个月的表型表征，并在实验性肾IRI后开展了相关检测。通过线粒体应激试验、MitoTracker染色及电子显微镜，分析了线粒体的功能、数量与完整性。采用免疫组化、蛋白质印迹法（Western blotting）与流式细胞术，定量分析了肾小管细胞损伤与免疫细胞浸润情况。健康状态下，DbpA并非肾脏发育与组织稳态所必需的蛋白。此外，内源性DbpA蛋白定位于原代肾小管上皮细胞（tubular epithelial cells，TECs）的线粒体中。敲除Ybx3可提升原代肾小管上皮细胞的线粒体膜电位、脂质摄取与代谢水平、氧消耗速率（oxygen consumption rates，OCR）及糖酵解活性。Ybx3-/-小鼠可免受IRI损伤，表现为免疫细胞浸润减少、内质网应激（ER stress）减轻及肾小管细胞损伤程度降低。研究发现，敲除Ybx3后，机体抗氧化活性上调且铁死亡（ferroptosis）水平降低，由此揭示了一种潜在的保护机制。本研究通过实验证据表明，DbpA作为一种线粒体蛋白，对细胞代谢具有显著的负面影响，并揭示了遗传敲除Ybx3可对抗肾缺血/再灌注损伤的保护效应。