Formation of a stabilized cysteine sulfinic acid is critical for the mitochondrial function of the parkinsonism protein DJ-1

The formation of cysteine-sulfinic acid has recently become appreciated as a modification that links protein function to cellular oxidative status. Human DJ-1, a protein associated with inherited parkinsonism, readily forms cysteine-sulfinic acid at a conserved cysteine residue (Cys¹⁰⁶ in human DJ-1). Mutation of Cys¹⁰⁶ causes the protein to lose its normal protective function in cell culture and model organisms. However, it is unknown whether the loss of DJ-1 protective function in these mutants is due to the absence of Cys¹⁰⁶ oxidation or the absence of the cysteine residue itself. To address this question, we designed a series of substitutions at a proximal glutamic acid residue (Glu¹⁸) in human DJ-1 that alter the oxidative propensity of Cys¹⁰⁶ through changes in hydrogen bonding. We show that two mutations, E18N and E18Q, allow Cys¹⁰⁶ to be oxidized to Cys¹⁰⁶-sulfinic acid under mild conditions. In contrast, the E18D mutation stabilizes a cysteine-sulfenic acid that is readily reduced to the thiol in solution and in vivo. We show that E18N and E18Q can both partially substitute for wild-type DJ-1 using mitochondrial fission and cell viability assays. In contrast, the oxidatively impaired E18D mutant behaves as an inactive C106A mutant and fails to protect cells. We therefore conclude that formation of Cys¹⁰⁶-sulfinic acid is a key modification that regulates the protective function of DJ-1.