Soluble guanylyl cyclase (GC1) is recognized as the nitric oxide (NO) receptor that generates cGMP in smooth muscle to regulate vascular tone. Here, we uncover an endothelial role for GC1 through its ability to catalyze transnitrosation reactions. We previously demonstrated that GC1 transfers S-nitrosothiols (SNO) via oxidized thioredoxin 1 (oTrx1), with cysteine 610 (C610) serving as the SNO donor. To probe this pathway in vivo, we generated knock-in mice in which C610 was replaced with serine (αC610S), thereby abolishing GC1 transnitrosation while preserving NO-stimulated cGMP synthesis. When challenged with angiotensin II (Ang II), αC610S mice developed exacerbated cardiovascular pathology, including higher mean arterial pressure, cardiac hypertrophy, fibrosis, increased oxidation, and electrical dysfunction, compared with Ang II-treated wild-type littermates. These phenotypes correlated with globally reduced S-nitrosation and selective loss of SNO-Trx1 and SNO-RhoA. Importantly, GC1 enzymatic activity remained intact, demonstrating that the mutation disrupts a non-canonical function of GC1. Vascular assays revealed that αC610S mice exhibited impairment of endothelium-dependent relaxation to acetylcholine (ACh), while NO-dependent smooth muscle responses remained preserved. In primary endothelial cells, the C610S mutation blunted ACh-induced S-nitrosation of Trx1, reduced Ca 2+ influx and impaired membrane hyperpolarization mediated by small- and intermediate-conductance calcium-activated K + channels (SK/IK). Notably, direct activation of SK/IK channels rescued the hyperpolarization defect, indicating that the primary deficit lies upstream in endothelial Ca 2+ signaling. These alterations occurred despite preserved NO bioavailability and intact smooth muscle cGMP responses. Together, these findings establish for the first time that GC1 regulates vascular tone not only through its canonical smooth muscle cGMP pathway but also via a transnitrosation cascade that sustains endothelial Ca 2+ dynamics and SK/IK channel-dependent hyperpolarization. This endothelial function identifies GC1 transnitrosation as a critical determinant of resistance vessel relaxation and blood pressure regulation.
Burboa et al. (Sun,) studied this question.