28 - A guanylyl cyclase-thioredoxin transnitrosation complex

Abstract

Nitric Oxide (NO) is best known for its ability to stimulate soluble guanylyl cyclase (sGC) to produce cGMP and stimulate its downstream signaling pathways. However, NO can also covalently modify cysteines via S-nitrosation (addition of a NO moiety to the cysteine of a protein, SNO). Although this reversible post-translational modification is increasingly recognized as an important regulatory mechanism of protein function, and to play a role in cardiac protection, dynamic regulation of protein nitrosation specificity is poorly understood. Combining proteomics quantification and molecular biological methods, we observed that sGC, the key NO receptor, modulates the level of nitrosation of specific proteins in cardiomyocytes and smooth muscle cells. Preliminary data showed that sGC increases nitrosation by a protein-protein interaction-driven SNO transfer (transnitrosation). Moreover, this increased nitrosation is due, for a specific subset of proteins, to the association of sGC with thioredoxin 1 (Trx1), a cardiac protective thiol-redox protein with both transnitrosation and denitrosation activities. Initial mass spectrometry and biochemical analyses showed that sGC transnitrosates Trx1, which in turn nitrosates a specific subset of targets in cardiomyocytes. These observations lead to the provocative idea that sGC modulates S-nitrosation specificity via a transnitrosation cascade that includes Trx1.