Disruption of Glutathione Homeostasis Causes Accumulation of <i>S</i>-Glutathionyl Proteins in Response to Exposure to Reactive Oxygen Species in Human Erythrocytes

Abstract

Oxidation of protein cysteine residues by disulfide bond formation with glutathione (GSH) is a reversible posttranslational modification following oxidative stress. Although S-glutathionylation seems to play a key role in cellular regulation and protect protein thiols from hyperoxidation, the molecular mechanism that mediates the glutathionyl protein is still unclear. We investigated the effect of disrupting GSH homeostasis on the S-glutathionylation of proteins via exposure to tert-butyl hydroperoxide (BHP) to study the formation of glutathionyl protein in human red blood cells (RBCs). Two independent treatments aimed at disrupting GSH homeostasis were devised to examine the influences of S-glutathionylation on RBC proteins. Glutathionyl proteins were detected transiently in intact RBCs during BHP exposure. Although glutathionyl proteins (220-240 kDa) disappeared immediately in the presence of glucose, they remained for a long time after BHP exposure in RBCs when the GSH-dependent system was disrupted. Furthermore, we identified that the high molecular weight glutathionyl protein is erythroid spectrin using immunodetection. Thus, it was indicated that the protein-bound GSH produced by peroxide exposure is immediately released by the GSH-dependent system in normal RBCs. However, disruption of GSH homeostasis causes accumulation of the glutathionyl protein. We propose that S-glutathionyl spectrin may be a useful biomarker for dysfunctions in GSH homeostasis and oxidative stress in human RBCs.