| 1999 |
Mutations in human SCO2 cause fatal infantile cardioencephalomyopathy with COX deficiency; immunohistochemical studies showed the enzymatic deficiency was due to loss of mtDNA-encoded COX subunits (COX I–III), most severely in cardiac and skeletal muscle, establishing SCO2 as a COX assembly factor. |
Patient mutation identification, immunohistochemistry of COX subunits in patient tissues |
Nature genetics |
High |
10545952
|
| 1996 |
Yeast SCO2 (Sco2p) is a mitochondrial membrane-localized protein that, when overexpressed, can partially suppress respiratory defects caused by absence of the copper recruitment factor Cox17p, but cannot suppress loss of Sco1p, indicating Sco1p and Sco2p have overlapping but non-identical functions in mitochondrial copper delivery to cytochrome oxidase. |
Multicopy suppressor screen in Saccharomyces cerevisiae, respiratory growth assays, genetic epistasis with cox17 and sco1 null mutants |
The Journal of biological chemistry |
High |
8702795
|
| 2004 |
Human SCO1 and SCO2 have non-overlapping, cooperative functions in mitochondrial copper delivery to COX. Overexpression of COX17 rescued COX deficiency in SCO2 but not SCO1 patient cells. Overexpression of either SCO protein in the reciprocal patient background produced a dominant-negative phenotype, suggesting physical interaction. Size exclusion chromatography indicated both proteins function as homodimers. A model was proposed in which COX17 delivers copper to SCO2, which transfers it to the CuA site, a reaction facilitated by SCO1. |
Immunoblot analysis, overexpression rescue experiments in patient cell lines, chimeric protein complementation, size exclusion chromatography |
Human molecular genetics |
High |
15229189
|
| 2005 |
Human Sco1 and Sco2 bind copper ions; both can bind Cu(I) (trigonal geometry) and Cu(II) (type II site). The two conserved cysteines and a histidyl residue critical for copper binding in yeast Sco1 are also critical for in vivo function of human Sco1 and Sco2. Asp238 in human Sco1 (conserved in yeast) is required for Cu(II) binding and normal function; its mutation abrogates the Cu(II) visible transitions and renders the protein nonfunctional. |
Expression of soluble domains in bacteria and yeast cytoplasm, X-ray absorption spectroscopy (EXAFS/XANES), site-directed mutagenesis, in vivo yeast complementation assays |
The Journal of biological chemistry |
High |
16091356
|
| 2007 |
Human SCO1 and SCO2 have additional roles in cellular copper homeostasis beyond COX assembly. Mutations in either SCO cause cellular copper deficiency that is tissue- and allele-specific and dissociable from COX assembly defects. This phenotype reflects increased copper efflux rather than reduced uptake, and can be suppressed by overexpression of SCO2 but not SCO1, suggesting a mitochondrial pathway for regulating cellular copper content that signals through SCO1 and SCO2. |
Patient cell line analysis, shRNA knockdown, copper efflux/uptake measurements, overexpression rescue experiments |
Cell metabolism |
High |
17189203
|
| 2007 |
NMR structure of the soluble domain of human Sco2 was determined in apo and Cu(I)-loaded forms. The structural and metal-binding features of Cu(I)Sco2 are similar to Sco1, but the dynamic properties and conformational disorder of the apo forms differ substantially between Sco1 and Sco2, accounting for their different physicochemical properties. Known pathogenic mutations were mapped onto this structure. |
NMR spectroscopy (structure determination and dynamics), copper(I) binding characterization |
Structure (London, England : 1993) |
High |
17850752
|
| 2009 |
SCO2 acts upstream of SCO1 in COX II (CO II) biogenesis and is indispensable for CO II synthesis. Pulse-labeling showed CO II synthesis is reduced in SCO2, but not SCO1, patient cells. SCO2 also acts as a thiol-disulphide oxidoreductase to oxidize the copper-coordinating cysteines in SCO1 during CO II maturation; perturbation of the ratio of oxidized to reduced cysteines in SCO1 occurs in both SCO backgrounds and is corrected by SCO2 modulation. |
Mitochondrial translation pulse-labeling, RNAi knockdown, thiol-trapping/redox state analysis of SCO1 cysteines, patient cell lines |
Human molecular genetics |
High |
19336478
|
| 2000 |
In a yeast model, the S240F mutation in Sco1p (corresponding to a human SCO2 pathogenic mutation) allows partial but incorrect assembly of cytochrome oxidase with altered cytochrome aa3 spectrum and a specific absence of subunit 2 from the assembled complex, indicating Sco1p (and by orthology SCO2) provides copper to the CuA site on subunit 2 at a late step in the assembly pathway. |
Yeast site-directed mutagenesis, respiratory growth assays, spectrophotometric cytochrome analysis, immunoblot of COX subunits |
The Journal of biological chemistry |
Medium |
10854440
|
| 2001 |
Recombinant human Sco2 protein binds copper with 1:1 stoichiometry and forms homomeric complexes in vitro independent of the CxxxC metal-binding motif. In patient myoblasts, COX activity was completely rescued by retroviral SCO2 gene transduction, and also by copper-histidine supplementation (300 µM) to culture medium, establishing that exogenous copper can bypass Sco2 function. |
Recombinant protein production and copper-binding assay, retroviral gene complementation in patient myoblasts, copper supplementation rescue assay |
Human molecular genetics |
Medium |
11751685
|
| 2002 |
COX deficiency in SCO2-mutant fibroblasts, myoblasts, and myotubes can be restored to near-normal levels by addition of CuCl2 to culture medium, confirming that the primary defect is in copper delivery to COX. |
Copper supplementation in cultured patient cells, spectrophotometric COX activity assay |
The Biochemical journal |
Medium |
11931660
|
| 2004 |
Mutant Sco2 proteins (E140K and S225F) differ from wild-type in physical conformation (circular dichroism, thermal denaturation) and copper-binding capacity: E140K binds markedly less copper and forms a non-reducible dimer (vs. monomer for wild-type), while S225F binds more copper than wild-type. These data show pathogenic mutations alter protein conformation and disrupt normal copper transport. |
Recombinant protein production, circular dichroism spectroscopy, thermal denaturation, copper-binding assays, gel electrophoresis |
Molecular genetics and metabolism |
Medium |
14972329
|
| 2005 |
In SCO2 patient tissues (heart, skeletal muscle, brain), COX assembly intermediates accumulate including a COX1·COX4·COX5A subcomplex and free COX4·COX5A subcomplex, with virtual absence of free COX2, indicating that absence of the CuA centre reduces COX2 stability and that association of COX4 and COX5A precedes their addition to COX1. Liver in SCO2 patients contained normal holoenzyme levels despite reduced SCO2 protein. |
Blue native PAGE of patient tissues, immunoblot of COX subunits and subcomplexes, analysis across multiple tissues |
The Biochemical journal |
Medium |
16083427
|
| 2010 |
SCO2 is required for COX assembly in vivo; homozygous Sco2 knockout mice are embryonic lethal. Compound heterozygous knock-in/knockout mice (KI/KO, expressing E129K corresponding to human E140K) are viable but show muscle weakness, respiratory chain deficiencies, COX assembly defects, and reduced mitochondrial copper content in multiple tissues, without reduction in total tissue copper. |
Mouse knockout and knock-in model generation, respiratory chain enzyme assays, COX assembly analysis, copper content measurement (ICP-MS) |
Human molecular genetics |
High |
19837698
|
| 2011 |
Using the mitochondria-targeted copper sensor Mito-CS1, total copper and exchangeable mitochondrial Cu(+) pools in SCO1 and SCO2 patient fibroblasts are largely unaltered relative to wild-type controls despite global cellular copper deficiency, demonstrating that cells prioritize mitochondrial copper homeostasis even when SCO metallochaperones are defective. |
Targetable fluorescent copper sensor (Mito-CS1) live-cell imaging, biochemical copper measurements in patient fibroblasts |
Journal of the American Chemical Society |
Medium |
21563821
|
| 2010 |
SCO1 localizes predominantly to blood vessels (endothelium) in mouse and human tissues, whereas SCO2 is barely detectable in this tissue; conversely, SCO1 expression is very high in liver while SCO2 is high in muscle. This differential tissue distribution provides a mechanistic basis for the distinct tissue-specific COX deficiencies and different clinical phenotypes associated with SCO1 vs. SCO2 mutations. |
Immunofluorescence and immunohistochemistry of mouse and human tissue sections, tissue fractionation |
The American journal of pathology |
Medium |
20864674
|
| 2014 |
COX20 acts as an early chaperone that stabilizes newly synthesized COX2 and presents it to the SCO1/SCO2 metallochaperone module. Immunoprecipitation showed COX20 interacts with newly synthesized COX2, and SCO1 and SCO2 act on COX20-bound COX2. Loss of COX20 generates COX1·COX4-containing subassemblies similar to those in SCO1/SCO2 patient fibroblasts, establishing the pathway order: COX20 → COX2 stabilization → SCO1/SCO2 maturation. |
siRNA knockdown, TALEN knockout cell lines, mitochondrial translation pulse-labeling, co-immunoprecipitation with COX20-FLAG, blue native PAGE |
Human molecular genetics |
High |
24403053
|
| 2015 |
COA6 interacts transiently with the copper-containing catalytic domain of newly synthesized COX2, and COA6 and SCO2 physically interact; pathogenic mutations in either protein disrupt the COA6-SCO2 complex. Genetic epistasis in yeast showed that simultaneous deletion of Coa6 and Sco2 completely abrogates Cox2 biogenesis, and overexpression of Sco proteins partially rescues the coa6Δ phenotype, placing COA6 in the SCO2-containing copper relay system for COX2 metallation. |
Co-immunoprecipitation, pulse-labeling, yeast genetic epistasis (double deletion), overexpression rescue, biochemical interaction studies |
Cell metabolism |
High |
25959673
|
| 2015 |
In yeast, simultaneous deletion of Coa6 and Sco2 completely abrogates Cox2 biogenesis, and copper supplementation fails to rescue Cox2 levels in these double mutants (unlike coa6Δ single mutants). Physical interactions between Coa6, Cox2, Cox12, and Sco proteins were demonstrated biochemically, placing COA6/SCO2 in the same copper delivery pathway to Cox2. |
Yeast genetic epistasis (comprehensive double deletions), biochemical co-precipitation, western blot, copper supplementation rescue assays |
Human molecular genetics |
High |
26669719
|
| 2013 |
SCO2 induces apoptosis by increasing ROS generation, which causes dissociation of the ASK-1/thioredoxin (Trx) inhibitory complex and phosphorylation of ASK-1 at Thr845, activating downstream JNK/p38 apoptotic cascades in tumor xenografts. This establishes an apoptotic function for SCO2 via the ROS-ASK-1 kinase pathway downstream of p53. |
Tumor xenograft model, ROS measurement, co-immunoprecipitation (ASK-1/Trx), kinase phosphorylation assays, exogenous SCO2 gene addition |
Molecular and cellular biology |
Medium |
23319048
|
| 2010 |
Recombinant full-length TAT-L-Sco2 fusion protein can be transduced into mitochondria of human cell lines and processed to the mature Sco2 protein; transduction into SCO2/COX-deficient patient fibroblasts led to partial recovery of COX activity, demonstrating that exogenous delivery of functional Sco2 protein to mitochondria is sufficient to restore enzymatic activity. |
Protein transduction domain (PTD/TAT) technology, subcellular fractionation, cell-free translation/import assay with 35S-labeling, COX activity assay in patient fibroblasts |
Biochimica et biophysica acta |
Medium |
20193760
|
| 2018 |
SCO2 patient fibroblasts with compound heterozygous mutations near the conserved CxxxC copper-binding motif show reduced SCO2 protein levels, decreased cellular copper levels, and COX deficiency, establishing that SCO2 mutations cause cellular copper deficiency as part of the pathogenic mechanism in axonal Charcot-Marie-Tooth disease. |
Patient fibroblast analysis, immunoblot, copper content measurement, COX activity assay |
Brain : a journal of neurology |
Medium |
29351582
|
| 2000 |
COX deficiency in SCO2 patient fibroblasts can be rescued by transfer of chromosome 22 (which carries SCO2) but not other chromosomes, confirming SCO2 is the causative gene. The COX deficiency (~50%) in patient fibroblasts did not result in a decrease in steady-state levels of COX subunit polypeptides, suggesting a functional rather than structural assembly defect. |
Chromosome transfer rescue experiment (microcell-mediated chromosome transfer), COX enzyme activity assay, immunoblot of COX subunits |
Human molecular genetics |
Medium |
10749987
|