Redox status changes exert critical impacts on necrotic/apoptotic and normal cellular processes. We report here a widely expressed Ca2+-permeable cation channel, LTRPC2, activated by micromolar levels of H2O2 and agents that produce reactive oxygen/nitrogen species. This sensitivity of LTRPC2 to redox state modifiers was attributable to an agonistic binding of nicotinamide adenine dinucleotide (beta-NAD+) to the MutT motif. Arachidonic acid and Ca2+ were important positive regulators for LTRPC2. Heterologous LTRPC2 expression conferred susceptibility to death on HEK cells. Antisense oligonucleotide experiments revealed physiological involvement of "native" LTRPC2 in H2O2- and TNFalpha-induced Ca2+ influx and cell death. Thus, LTRPC2 represents an important intrinsic mechanism that mediates Ca2+ and Na+ overload in response to disturbance of redox state in cell death.

Cysteine hydropersulfide (CysSSH) occurs in abundant quantities in various organisms, yet little is known about its biosynthesis and physiological functions. Extensive persulfide formation is apparent in cysteine-containing proteins in Escherichia coli and mammalian cells and is believed to result from post-translational processes involving hydrogen sulfide-related chemistry. Here we demonstrate effective CysSSH synthesis from the substrate l-cysteine, a reaction catalyzed by prokaryotic and mammalian cysteinyl-tRNA synthetases (CARSs). Targeted disruption of the genes encoding mitochondrial CARSs in mice and human cells shows that CARSs have a crucial role in endogenous CysSSH production and suggests that these enzymes serve as the principal cysteine persulfide synthases in vivo. CARSs also catalyze co-translational cysteine polysulfidation and are involved in the regulation of mitochondrial biogenesis and bioenergetics. Investigating CARS-dependent persulfide production may thus clarify aberrant redox signaling in physiological and pathophysiological conditions, and suggest therapeutic targets based on oxidative stress and mitochondrial dysfunction.