Importance of copper chaperone Cox17p in early embryogenesis.

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It is well known that the deficiencies in cytochrome c oxidase (CCO) are relatively rare but most often lethal. CCO, one of the mitochodrial respiratory enzymes, requires Cu (I) to express its enzymatic activity. Cox17p, Scolp, and its homologue Sco2p are thought to be involved in mitochondrial transport of copper to CCO. By in vitro GST-pull down assay, both Sco1p and Sco2p interact with Cox17p. Furthermore, Cox17p, Scolp and Sco2p also interact with Cox2p, a subunit of the binuclear-copper centre Cu_A of CCO. Northern blot analysis demonstrated that Cox17p, Sco1p and Sco2p are widely expressed at varying levels in a variety of mouse tissues including brain. Using in situ hybridization histochemistry, we characterized the expression profiles for these molecules in different regions of the normal adult mouse brain. The highest levels of these messages were associated with distinct neuronal subtypes, including pyramidal cell layers of hippocampus and ventral cochlear nucleus of pons, that were also contained high levels of CCO activity. Although CCO activities and expression levels of Cox17p and Scolp were relatively high, the expression of Sco2p was quite low in some subsets of neurons such as cerebellum Purkinje cells. It was thought that the difference of expression profile between Sco1p and Sco2p is originated in that of genomic structures, especially the promoter regions.