Modification of protein by disulfide S-monoxide and disulfide S-dioxide: distinctive effects on PKC.

Disulfide S-monoxide (DSMO) and disulfide S-dioxide (DSDO) have been proposed as proximal mediators for the oxidant-mediated modification of proteins. These disulfide S-oxides (DSOs) derived from glutathione (GSH) and captopril (CPSH) were synthesized by iron- or methyltrioxorhenium (VII)-catalyzed oxidation of the thiols with H2O2. Treatment of mouse hippocampal extracts with [35S]GS-DSOs revealed that a large number of proteins were susceptible to thionylation; however, only a limited number of the them were detectable by the commonly used antibody against GS-associated proteins. Using protein kinase C (PKC) as a model, we found that DSOs derived from different thiols modified this kinase with different efficacy and specificity; for example, the inhibitory potency of the kinase was glutathione disulfide S-dioxide (GS-DSDO) (IC50, approximately 30 microM) > captopril disulfide S-dioxide (CPS-DSDO) (IC50, approximately 450 microM) > glutathione disulfide S-monoxide (GS-DSMO) and captopril disulfide S-monoxide (CPS-DSMO). The stoichiometries of thionylation of PKC beta mediated by [35S]GS-DSMO and [35S]GS-DSDO were approximately 1 and 5 mol/mol, respectively, and at least four glutathionylation sites were identified in the GS-DSDO-treated kinase. Modification of PKC by GS-DSDO and CPS-DSDO rendered the kinase very susceptible to limited proteolysis; the former preferentially caused the degradation of the catalytic and the latter the regulatory domain of the kinase. Furthermore, CPS-DSDO-mediated modification of PKC increased the autonomous kinase activity; this was not the case for GS-DSDO-mediated modification. Since DSOs of different oxidative states as well as those derived from different thiols exert different effects on a target protein, these molecules could cause distinct cellular responses if derived from endogenous cellular reactions or even if they arise from exogenous sources.