The Human 2-Cys Peroxiredoxins Form Widespread, Cysteine-Dependent- And Isoform-Specific Protein-Protein Interactions.

Redox signaling is controlled by the reversible oxidation of cysteine thiols, a post-translational modification triggered by H2O2 acting as a second messenger. However, H2O2 reacts poorly with most cysteine thiols and it is not clear how it discriminates between cysteines to trigger appropriate signaling cascades in the presence of dedicated H2O2 scavengers like peroxiredoxins. It was suggested that peroxiredoxins act as peroxidases to facilitate H2O2-dependent oxidation of proteins via disulfide exchange reactions. It is unknown how the peroxiredoxin-based relay model achieves the selective substrate targeting required for adequate cellular signaling. Using a systematic mass-spectrometry-based approach to identify cysteine-dependent interactors of peroxiredoxins, we show that all five human 2-cys peroxiredoxins can form disulfide-dependent heterodimers with a large set of proteins. Each isoform displays a preference for a subset of disulfide-dependent binding partners, and we explore isoform-specific properties that might underlie this precedence. We provide evidence that peroxiredoxin-based redox relays can proceed via two distinct molecular mechanisms. Altogether, our results support the theory that peroxiredoxins could play a role in providing not only reactivity but also selectivity in the transduction of peroxide signals to generate complex cellular signaling responses.

氧化还原信号转导受半胱氨酸巯基的可逆氧化调控，该类翻译后修饰由作为第二信使的过氧化氢（H₂O₂）所触发。然而，过氧化氢与大多数半胱氨酸巯基的反应活性极低，且目前尚不清楚在过氧还蛋白（peroxiredoxins）这类专一性过氧化氢清除剂存在的情况下，它如何区分不同半胱氨酸残基以触发恰当的信号级联反应。有研究提出，过氧还蛋白可作为过氧化物酶，通过二硫键交换反应介导依赖于过氧化氢的蛋白质氧化过程。目前仍不清楚基于过氧还蛋白的信号中继模型，如何实现满足有效细胞信号转导所需的底物选择性靶向。本研究采用基于质谱（mass spectrometry）的系统性方法，鉴定过氧还蛋白的半胱氨酸依赖性互作蛋白，结果显示，人类体内全部5种2-半胱氨酸型过氧还蛋白（2-cys peroxiredoxins），均可与大量蛋白质形成依赖于二硫键的异二聚体。每种过氧还蛋白亚型均对特定子集的二硫键依赖性结合伴侣表现出偏好性，本研究还探索了可能构成该偏好性基础的亚型特异性特性。本研究提供证据表明，基于过氧还蛋白的氧化还原信号中继可通过两种截然不同的分子机制进行。综上，本研究结果支持如下理论：过氧还蛋白不仅可在过氧化物信号转导过程中赋予反应活性，还可赋予选择性，进而介导复杂的细胞信号转导应答。