Human copper chaperone for superoxide dismutase 1 mediates its own oxidation-dependent import into mitochondria

Abstract

Oxidative stress is counteracted by various cellular systems, including copper-zinc superoxide dismutase 1 (SOD1) and its activating chaperone, that is, the copper chaperone for SOD1 (CCS1). Both enzymes are structurally related, and both localize to the cytosol and the mitochondrial intermembrane space where they specifically counteract mitochondria-derived superoxide. The mechanism by which human CCS1 is transported into mitochondria is largely unclear. Here we show that CCS1 import depends on the presence of mature CCS1 in the mitochondria. During import, a disulphide bond is formed in CCS1 in a CCS1-dependent reaction. We demonstrate that oxidation and import depend on the presence of cysteine residues at positions 227 and 141/144 in CCS1. Notably, CCS1 import parallels SOD1 import that also depends on CCS1. Our observations suggest that CCS1 serves as a specialized import receptor in mitochondria that facilitates the import and folding of SOD1 and CCS1, thereby extending the substrate spectrum of oxidation-dependent protein import in the mitochondrial intermembrane space.

The interactome of the copper transporter ATP7A belongs to a network of neurodevelopmental and neurodegeneration factors

“…We predicted that transcripts of ATP7A and/or metallochaperones should be altered in COG deficient cells as a consequence of copper dyshomeostasis (Figure 7A). We focused on the metallochaperones ATOX1, which delivers copper to ATP7A (Strausak et al, 2003; Voskoboinik et al, 1999; Walker et al, 2002; Lutsenko et al, 1997); CCS, which carries copper to the mitochondrially localized SOD1 and that itself is imported into mitochondria (Suzuki et al, 2013; Wang et al, 2013); COX17, which is required for copper delivery to the mitochondrial cytochrome c oxidase (Cobine et al, 2006); and two isoforms of metallothioneins, both cysteine-rich proteins that bind metals in the cytoplasm (Palmiter, 1998). …”

Thiol‐based copper handling by the copper chaperone Atox1

“…Evidence indicates that these thiols undergo redox modulation in cells. Suzuki et al demonstrated that, in HEK293 cells, Cys residues in the domain II of CCS (SOD1‐like domain) are hardly oxidized in the cytosol, while they form disulfide bonds quickly (within about 2 h) on entering the mitochondrial IMS . As stated above, SOD1 can be oxidized for protein stability and, therefore, the corresponding site of the CCS domain II may be similarly modulated.…”

The cysteine proteome

“…Measurements of steady-state oxidation of proteins show that during processing, protein disulfide isomerase (PDI) is partially oxidized [33, 34]. Recent studies show similar redox processing of proteins occurs with mitochondrial protein import [35, 36]. Dynamic redox processes are also involved in nuclear protein import and export [37–39].…”

“…The following examples further illustrate the use of kinetically controlled systems in nuclear protein trafficking and in maintenance of the integrity of the genome. Recent reviews are also available on the redox processing in the secretory pathway [33, 34, 120] and in mitochondrial import [35, 36]. Relatively less information is available on vectorial redox processing during endocytosis and proteolysis in lysosomes, but evidence is available suggesting that analogous systems are present [121, 122].…”