Biotin-switch technique/proximity ligation assay-based method for in situ analysis of S-nitrosylated proteins

Nitric oxide (NO) influences a multitude of physiological and pathological processes. A major part of NO signaling involves S-nitrosylation (SNO), a post-translational modification in which an NO moiety is added to a selective cysteine thiol of a protein to form an S-nitrosothiol. Per se, S-nitrosylation is implicated in the control of tissue homeostasis and dysregulated basal levels of S-nitrosylation can contribute to malignant diseases. Importantly, exploiting NO bioactivity through S-nitrosylation represents a therapeutic interest in many diseases. S-nitrosylated protein analysis has been the subject of various methods of detection, quantification and identification, and the Biotin-Switch Technique (BST) is the reference method. Here, a new methodology combining BST and Proximity Ligation Assay (PLA) is presented for the in situ analysis of selective protein S-nitrosylation. This newly developed method termed "SNO-Biotin-PLA" provides the advantage of filling a gap in current methods for studying protein S-nitrosylation in situ.