A central hallmark of tumorigenesis is metabolic alterations that increase mitochondrial reactive oxygen species (mROS). In response, cancer cells upregulate their antioxidant capacity and redox-responsive signaling pathways. A promising chemotherapeutic approach is to increase ROS to levels incompatible with tumor cell survival. Mitochondrial peroxiredoxin 3 (PRX3) plays a significant role in detoxifying hydrogen peroxide (H₂O₂). PRX3 is a molecular target of thiostrepton (TS), a natural product and FDA-approved antibiotic. TS inactivates PRX3 by covalently adducting its two catalytic cysteine residues and crosslinking the homodimer. Using cellular models of malignant mesothelioma, we show here that PRX3 expression and mROS levels in cells correlate with sensitivity to TS and that TS reacts selectively with PRX3 relative to other PRX isoforms. Using recombinant PRXs 1–5, we demonstrate that TS preferentially reacts with a reduced thiolate in the PRX3 dimer at mitochondrial pH. We also show that partially oxidized PRX3 fully dissociates to dimers, while partially oxidized PRX1 and PRX2 remain largely decameric. The ability of TS to react with engineered dimers of PRX1 and PRX2 at mitochondrial pH, but inefficiently with wild-type decameric protein at cytoplasmic pH, supports a novel mechanism of action and explains the specificity of TS for PRX3. Thus, the unique structure and propensity of PRX3 to form dimers contribute to its increased sensitivity to TS-mediated inactivation, making PRX3 a promising target for prooxidant cancer therapy.

中文翻译：

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人类线粒体过氧化物酶3的独特细胞和生化特征为它与硫排蛋白的特异性反应建立了分子基础

肿瘤发生的主要特征是增加线粒体活性氧（mROS）的代谢改变。作为响应，癌细胞上调其抗氧化能力和氧化还原反应性信号通路。一种有前途的化学疗法是将ROS增加到与肿瘤细胞存活不相容的水平。线粒体过氧化物酶3（PRX3）在使过氧化氢（H ₂ O ₂）。PRX3是天然产品和FDA批准的抗生素thiostrepton（TS）的分子靶标。TS通过共价加成其两个催化性半胱氨酸残基并使同型二聚体交联来灭活PRX3。使用恶性间皮瘤的细胞模型，我们在这里显示PRX3表达和细胞中的mROS水平与对TS的敏感性相关，并且相对于其他PRX同工型，TS与PRX3选择性反应。使用重组PRXs 1-5，我们证明TS在线粒体pH值下优先与PRX3二聚体中还原的硫醇盐反应。我们还显示，部分氧化的PRX3完全解离为二聚体，而部分氧化的PRX1和PRX2仍为十聚体。TS在线粒体pH下与PRX1和PRX2的工程二聚体反应的能力，但在细胞质pH下与野生型十聚蛋白的反应效率低下，支持一种新颖的作用机制，并解释了TS对于PRX3的特异性。因此，PRX3独特的结构和形成二聚体的倾向有助于增加其对TS介导的失活的敏感性，使PRX3成为抗氧化剂癌症治疗的有希望的靶标。