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Protein S-nitrosylation is a reversible post-translational modification of protein cysteines that is increasingly being considered as a signal transduction mechanism. The ‘‘biotin switch’’ technique marked the beginning of the study of the S-nitrosoproteome, based on the specific replacement of the labile S-nitrosylation by a more stable biotinylation that allowed further detection and purification. However, its application for proteomic studies is limited by its relatively low sensitivity. Thus, typical proteomic experiments require high quantities of protein extracts, which precludes the use of this method in a number of biological settings. We have developed a ‘‘fluorescence switch’’ technique that, when coupled to 2-DE proteomic methodologies, allows the detection and identification of S-nitrosylated proteins by using limited amounts of starting material, thus significantly improving the sensitivity. We have applied this methodology to detect proteins that become S-nitrosylated in endothelial cells when exposed to S-nitroso-L-cysteine, a physiological S-nitrosothiol, identifying already known S-nitrosylation targets, as well as proteins that are novel targets. This ‘‘fluorescence switch’’ approach also allowed us to identify several proteins that are denitrosylated by thioredoxin in cytokine-activated RAW264.7 (murine macrophage) cells. We believe that this method represents an improvement in order to approach the identification of S-nitrosylated proteins in physiological conditions., Gobierno de España, Depto. de Bioquímica y Biología Molecular, TRUE, pub

Nitric oxide is implicated in a variety of signaling pathways in different systems, notably in endothelial cells. Some of its effects can be exerted through covalent modifications of proteins and, among these modifications, increasing attention is being paid to S-nitrosylation as a signaling mechanism. In this work, we show by a variety of methods (ozone chemiluminescence, biotin switch, and mass spectrometry) that the molecular chaperone Hsp90 is a target of S-nitrosylation and identify a susceptible cysteine residue in the region of the C-terminal domain that interacts with endothelial nitric oxide synthase (eNOS). We also show that the modification occurs in endothelial cells when they are treated with S-nitrosoL-cysteine and when they are exposed to eNOS activators. Hsp90 ATPase activity and its positive effect on eNOS activity are both inhibited by S-nitrosylation. Together, these data suggest that S-nitrosylation may functionally regulate the general activities of Hsp90 and provide a feedback mechanism for limiting eNOS activation., Plan Nacional de I+D+I, Ministerio de Ciencia y Tecnología, Comunidad Autónoma de Madrid, Ministerio de Sanidad y Consumo, Depto. de Bioquímica y Biología Molecular, TRUE, pub

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Nitric Oxide (NO) is involved in the development and progression of abdominal aortic aneurysms (AAA). We found that inhibition of inducible NO synthase (iNOS) protects mice in an elastase-induced AAA model, significantly inhibiting the production of matrix metalloproteinase-13 (MMP-13). The extracellular MMP inducer (EMMPRIN; CD147) was increased in human AAA biopsies and in wild-type murine AAA but not in AAA from iNOS null mice. In cells overexpressing ectopic EMMPRIN, MMP-13 secretion was stimulated, whereas silencing of EMMPRIN by RNA interference led to significant inhibition of MMP-13 expression. In addition, elastase infusion of MMP-13 null mouse aortas induced a significant increase of EMMPRIN but reduced aortic dilatation when compared with wild-type mice, suggesting that NO-mediated AAA may be mediated through EMMPRIN induction of MMP-13. These findings were further verified in elastase-infused iNOS null mice, in which daily administration of NO caused a significant aortic dilatation and the expression of EMMPRIN and MMP-13. By contrast, in iNOS wild-type mice, pharmacological inhibition of iNOS by administration of 1400 W induced a reduction of aortic diameter and inhibition of MMP-13 and EMMPRIN expression when compared with control mice. Our results suggest that NO may regulate the development of AAA in part by inducing the expression of EMMPRIN and modulating the activity of MMP-13 in murine and human aneurysms., Depto. de Bioquímica y Biología Molecular, Fac. de Ciencias Químicas, TRUE, pub