Overexpression of CCS in G93A-SOD1 mice leads to accelerated neurological deficits with severe mitochondrial pathology

Abstract

Cu, Zn superoxide dismutase (SOD1) has been detected within spinal cord mitochondria of mutant SOD1 transgenic mice, a model of familial ALS. The copper chaperone for SOD1 (CCS) provides SOD1 with copper, facilitates the conversion of immature apo-SOD1 to a mature holoform, and influences in yeast the cytosolic/ mitochondrial partitioning of SOD1. To determine how CCS affects G93A-SOD1-induced disease, we generated transgenic mice overexpressing CCS and crossed them to G93A-SOD1 or wild-type SOD1 transgenic mice. Both CCS transgenic mice and CCS/wild-type-SOD1 dual transgenic mice are neurologically normal. In contrast, CCS/G93A-SOD1 dual transgenic mice develop accelerated neurological deficits, with a mean survival of 36 days, compared with 242 days for G93A-SOD1 mice. Immuno-EM and subcellular fractionation studies on the spinal cord show that G93A-SOD1 is enriched within mitochondria in the presence of CCS overexpression. Our results indicate that CCS overexpression in G93A-SOD1 mice produces severe mitochondrial pathology and accelerates disease course.amyotrophic lateral sclerosis ͉ motor neuron ͉ neurodegeneration ͉ transgenic ͉ aggregation

Insights into the mechanisms of copper dyshomeostasis in amyotrophic lateral sclerosis

“…Interestingly, the disease phenotype in this double transgenic mouse was not related to toxicity due to aggregated SOD1 but instead to severe mitochondrial pathology in the SC (Ref. 62). Beyond this study, some evidence of ALS-related changes in certain copper-dependent enzymes with prominent roles in mitochondrial function support the view that mitochondrial copper is involved in the pathophysiology of ALS.…”

Oxidative Stress and Neurotoxicity

“…In fact, other studies suggest a lack of aberrant copper chemistry exerted by mutant SOD1 forms, including the finding that toxicity is not reduced in mutant SOD1 mice either lacking the chaperone for insertion of copper into SOD1 (CCS) (264) or where SOD1 binding of copper is negated by mutation of the key histidine ligands to alanine (265). A mutant SOD1 mouse model overexpressing CCS exhibited accelerated neurological deficits, but this appeared to reflect a mitochondriopathy not involving oxidative stress (266). Although the mitochondriopathy already evident in motor neurons of G93A-SOD1 mice does display features of a necrotic neuronal death associated with oxidative stress damage (267), this appears distinct from the apoptotic-like mechanism that appears to contribute to motor neuron degeneration in human sALS and fALS.…”

Import, Maturation, and Function of SOD1 and Its Copper Chaperone CCS in the Mitochondrial Intermembrane Space

“…In the G93A=CCS double-transgenic mice, the mutant SOD1 toxicity was attributed to COX deficiency, caused by functional and structural damage (57,58). How mutant G93A SOD1 causes COX deficiency is not clear, but it could be speculated that SOD1 and COX, both cupro-enzymes, compete for the same pool of copper in mitochondria.…”

“…KAWAMATA AND MANFREDI tion of mutant G93A SOD1 in mitochondria, which caused extensive mitochondrial swelling and dramatic worsening of the disease phenotype (58). Similarly, CCS overexpression worsened the disease in another wild-type-like mutant SOD1 (G37R) mouse model, but not in mice expressing G85R or L126Z SOD1 mutants, which are enzymatically defective (56).…”