RESUMO
Irreversible oxidation of Cys residues to sulfinic/sulfonic forms typically impairs protein function. We found that persulfidation (CysSSH) protects Cys from irreversible oxidative loss of function by the formation of CysSSO1-3H derivatives that can subsequently be reduced back to native thiols. Reductive reactivation of oxidized persulfides by the thioredoxin system was demonstrated in albumin, Prx2, and PTP1B. In cells, this mechanism protects and regulates key proteins of signaling pathways, including Prx2, PTEN, PTP1B, HSP90, and KEAP1. Using quantitative mass spectrometry, we show that (i) CysSSH and CysSSO3H species are abundant in mouse liver and enzymatically regulated by the glutathione and thioredoxin systems and (ii) deletion of the thioredoxin-related protein TRP14 in mice altered CysSSH levels on a subset of proteins, predicting a role for TRP14 in persulfide signaling. Furthermore, selenium supplementation, polysulfide treatment, or knockdown of TRP14 mediated cellular responses to EGF, suggesting a role for TrxR1/TRP14-regulated oxidative persulfidation in growth factor responsiveness.
Assuntos
Cisteína/genética , Oxirredução/efeitos dos fármacos , Tiorredoxina Redutase 1/genética , Tiorredoxinas/genética , Animais , Cisteína/química , Fator de Crescimento Epidérmico/genética , Proteínas de Choque Térmico HSP90/genética , Proteínas de Homeodomínio/química , Proteínas de Homeodomínio/genética , Humanos , Proteína 1 Associada a ECH Semelhante a Kelch/genética , Camundongos , PTEN Fosfo-Hidrolase/genética , Proteína Tirosina Fosfatase não Receptora Tipo 1/genética , Selênio/farmacologia , Transdução de Sinais/efeitos dos fármacos , Sulfetos/metabolismo , Sulfetos/farmacologia , Tiorredoxina Redutase 1/química , Tiorredoxinas/químicaRESUMO
The mechanism of cytotoxicity of the NO donor 3-morpholino-sydnonimine toward a human ovarian cancer cell line (OVCAR) was examined. It was found that the NO-mediated loss of cell viability was dependent on both NO and hydrogen peroxide (H2O2). Somewhat surprisingly, superoxide (O2) and its reaction product with NO, peroxynitrite (-OONO), did not appear to be di- rectly involved in the observed NO-mediated cytotoxicity against this cancer cell line. The toxicity of NO/H2O2 may be due to the production of a potent oxidant formed via a trace metal-, H202-, and NO-dependent process. Because the combination of NO and H2O2 was found to be particularly cytotoxic, the effect of NO on cellular defense mechanisms involving H2O2 degradation was investigated. It was found that NO was able to inhibit catalase activity but had no effect on the activity of the glutathione peroxidase (GSHPx)-glutathione reductase system. It might therefore be expected that cells that utilize primarily the GSHPx-glutathione reductase system for degrading H2O2 would be somewhat resistant to the cytotoxic effects of NO. Consistent with this idea, it was found that ebselen, a compound with GSHPx-like activity, was able to protect cells against NO toxicity. Also, lowering endogenous GSHPx activity via selenium depletion resulted in an increased susceptibility of the target cells to NO-mediated toxicity. Thus, a possible NO/H2O2/metal-mediated mechanism for cellular toxicity is presented as well as a possible explanation for cell resistance/susceptibility to this NO-initiated process.