Copper chaperone for superoxide dismutase is essential to activate mammalian Cu/Zn superoxide dismutase

Abstract

Recent studies in Saccharomyces cerevisiae suggest that the delivery of copper to Cu͞Zn superoxide dismutase (SOD1) is mediated by a cytosolic protein termed the copper chaperone for superoxide dismutase (CCS). To determine the role of CCS in mammalian copper homeostasis, we generated mice with targeted disruption of CCS alleles (CCS ؊/؊ mice). Although CCS ؊/؊ mice are viable and possess normal levels of SOD1 protein, they reveal marked reductions in SOD1 activity when compared with control littermates. Metabolic labeling with 64 Cu demonstrated that the reduction of SOD1 activity in CCS ؊/؊ mice is the direct result of impaired Cu incorporation into SOD1 and that this effect was specific because no abnormalities were observed in Cu uptake, distribution, or incorporation into other cuproenzymes. Consistent with this loss of SOD1 activity, CCS ؊/؊ mice showed increased sensitivity to paraquat and reduced female fertility, phenotypes that are characteristic of SOD1-deficient mice. These results demonstrate the essential role of any mammalian copper chaperone and have important implications for the development of novel therapeutic strategies in familial amyotrophic lateral sclerosis.

Mechanisms for activating Cu- and Zn-containing superoxide dismutase in the absence of the CCS Cu chaperone

“…In each case, the absence of CCS did not preclude motor neuron disease effected by mutant SOD1, demonstrating that Cu inserted by means of CCS is not required for SOD1-linked FALS (17). These studies revealed also that a limited degree of SOD1 activity persists in mice lacking CCS (16,17); hence, mammalian SOD1 can obtain some Cu independent of CCS. This secondary pathway for activating SOD1 may not be unique to the mammalian cell host.…”

“…Immortalized fibroblasts from mice that were either homozygous wild type (CCS ϩ/ϩ ) or null (CCS Ϫ/Ϫ ) for CCS (16), and expressing where indicated, FALS SOD1 mutant G37R (line 42, ref. 17) were cultured in the presence of 50 M BSO to deplete intracellular glutathione.…”

“…Recently, a mouse strain bearing a homozygous deletion in CCS was created (16), and these CCS Ϫ/Ϫ mice were crossed to transgenic mouse models for SOD1-linked FALS. In each case, the absence of CCS did not preclude motor neuron disease effected by mutant SOD1, demonstrating that Cu inserted by means of CCS is not required for SOD1-linked FALS (17).…”

Copper Chaperone-Dependent and -Independent Activation of Three Copper-Zinc Superoxide Dismutase Homologs Localized in Different Cellular Compartments in Arabidopsis

“…In Arabidopsis, a single AtCCS gene product activated CSDs in the cytoplasm and chloroplast (Chu et al, 2005); however, the phenotype of the AtCCS-knockout mutant (Atccs) was found to be normal (Chu et al, 2005;Cohu et al, 2009). Similarly, a CCS-independent activation pathway for CSD was found in mice (Wong et al, 2000). These data suggest the existence of additional CSD-activating factors.…”

XIAP: Cell death regulation meets copper homeostasis

“…Mutations in SOD1 are associated with amyotrophic lateral sclerosis (ALS), a neurodegenerative disorder characterized by the loss of upper and lower motor neurons and muscle atrophy [44,45]. CCS-mediated delivery of copper to SOD1 is important for the stability of this protein as Ccs-deficient mice exhibit severe reductions in SOD1 levels and activity in various organs despite normal mRNA expression [46].…”