Products of S-nitrosylation of glyceraldehyde-3-phosphate dehydrogenase: Relation between S-nitrosylation and oxidation

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is one of the major targets of NO in cells, especially in neurodegenerative diseases. S-Nitrosylation of GAPDH is accompanied by its translocation into the nucleus with subsequent apoptosis. The product of GAPDH modification by NO is considered to be S-nitrosylated GAPDH (GAPDH-SNO). However, this has not been confirmed by direct methods.Products of GAPDH modification in the presence of the NO donor diethylamine NONOate were analyzed by MALDI- and ESI- mass spectrometry methods.The adduct between GAPDH and dimedone was detected by MALDI-MS analysis after incubation of S-nitrosylated GAPDH with dimedone, which points to the formation of cysteine-sulfenic acid (GAPDH-SOH) in the protein. Analysis of the protein hydrolysate revealed the incorporation of dimedone into the catalytic residue Cys150. An additional peak that corresponded to GAPDH-SNO was detected by ESI-MS analysis in GAPDH after the incubation with the NO donor. The content of GAPDH-SNO and GAPDH-SOH in the modified GAPDH was evaluated by different approaches and constituted 2.3 and 0.7 mol per mol GAPDH, respectively. A small fraction of GAPDH was irreversibly inactivated after NO treatment, suggesting that a minor part of the products includes cysteine-sulfinic or cysteine-sulfonic acids.The main products of GAPDH modification by NO are GAPDH-SNO and GAPDH-SOH that is presumably formed due to the hydrolysis of GAPDH-SNO.The obtained results are important for understanding the molecular mechanism of redox regulation of cell functions and the role of GAPDH in the development of neurodegenerative disorders.