Soluble guanylyl cyclase (GC1) is an α/β heterodimer producing cGMP when stimulated by nitric oxide (NO). The NO-GC1-cGMP pathway is essential for cardiovascular homeostasis but is disrupted by oxidative stress, which causes GC1 desensitization to NO by heme oxidation and S-nitrosation (SNO) of specific cysteines. We discovered that under these conditions, GC1-α subunit increases cellular S-nitrosation via transfer of nitrosothiols to other proteins (transnitrosation) in cardiac and smooth muscle cells. One of the GC1 SNO-targets was the oxidized form of Thioredoxin1 (oTrx1), which is unidirectionally transnitrosated by GC1 with αC610 as a SNO-donor. Because oTrx1 itself drives transnitrosation, we sought and identified SNO-proteins targeted by both GC1 and Trx1. We found that transnitrosation of the small GTPase RhoA by SNO-GC1 requires oTrx1 as a nitrosothiol relay, suggesting a SNO-GC1→oTrx1→RhoA cascade. The RhoA signaling pathway, which is antagonized by the canonical NO-cGMP pathway, was alternatively inhibited by GC1-α-dependent S-nitrosation under oxidative conditions. We propose that SNO-GC1, via transnitrosation, mediates adaptive responses triggered by oxidation of the canonical NO-cGMP pathway.

可溶性鸟苷酸环化酶 (GC1) 是一种 α/β 异二聚体，在受到一氧化氮 (NO) 刺激时产生 cGMP。NO-GC1-cGMP 途径对于心血管稳态至关重要，但会受到氧​​化应激的破坏，氧化应激会通过血红素氧化和特定半胱氨酸的 S-亚硝化 (SNO) 导致 GC1 对 NO 脱敏。我们发现，在这些条件下，GC1-α 亚基通过将亚硝基硫醇转移到心脏和平滑肌细胞中的其他蛋白质（转亚硝化）来增加细胞 S-亚硝化。GC1 SNO 靶标之一是硫氧还蛋白 1 (oTrx1) 的氧化形式，它被 GC1 以 αC610 作为 SNO 供体单向转亚硝基化。由于 oTrx1 本身驱动转亚硝基作用，因此我们寻找并鉴定了 GC1 和 Trx1 共同靶向的 SNO 蛋白。我们发现 SNO-GC1 对小 GTP 酶 RhoA 的转亚硝化需要 oTrx1 作为亚硝基硫醇中继，表明 SNO-GC1→oTrx1→RhoA 级联。RhoA 信号通路被经典的 NO-cGMP 通路拮抗，在氧化条件下又被 GC1-α 依赖性 S-亚硝化作用抑制。我们提出 SNO-GC1 通过转亚硝化作用介导由经典 NO-cGMP 途径氧化引发的适应性反应。