Post-Translational Nitric Oxide-Dependent Modifications In Immune System

Nitric oxide non classical signalling is exerted through a series of covalent protein post-translational modifications, which include modification of cysteine residues by S-nitrosylation and S-glutathionylation. A key process in adaptive immunity is the immune synapse that tightly couples T cells with antigen presenting cells, triggering antigen recognition by T cells. In this highly regulated process, we have shown that eNOS is activated, inducing protein S-nitrosylation. While both N-Ras and K-Ras are present in T cells, only N-Ras, which colocalizes in the Golgi with eNOS, is S-nitrosylated and activated during the immune synapse, providing an example of short-range selectivity of NO signalling through S-nitrosylation. We have developed proteomic methods to detect S-nitrosylation and reversible cysteine oxidations. We have applied them to detecting S-nitrosylated proteins in macrophage activation, highlighting the role of denitrosylase mechanism, particularly the thioredoxin pathway, in protecting macrophages from self-modification. We have also applied these proteomic methods to studying protein modification in acute hypoxia. In endothelial cells, there is an increase in cysteine oxidation in several proteins that can mediate acute responses to hypoxia prior to the activation of the HIF pathway, and we are currently studying in more detail the role of protein S-nitrosylation. We have also recently shown that acute hypoxia produces a superoxide burst in cells, which can be converted in an oxidative signal through protein cysteine modification, and we are unraveling the molecular mechanisms producing this superoxide burst in mitochondria.