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MEDNIK (mental retardation, enteropathy, deafness, neuropathy, ichthyosis, and keratodermia) syndrome has been recently described as a new disorder of copper metabolism. This multisystem disease combines clinical and biochemical signs of both Menkes and Wilson's diseases, in which liver copper overload is treatable using zinc acetate therapy. MEDNIK syndrome is caused by mutation of the AP1S1 gene, which codes for the σ1A subunit of adaptor protein complex 1, and directs intracellular trafficking of copper pumps ATP7A and ATP7B. Adaptor protein complexes regulate clathrin-coated vesicle assembly, protein cargo sorting, and vesicular trafficking between organelles in eukaryotic cells. A growing number of diseases have been associated with mutations in genes coding for adaptor protein complexes subunits and we propose for them the term adaptinopathies, as a new organic category of disorders of intracellular trafficking, which offers the opportunity to dissect the mechanisms involved in the crosstalk between the Golgi apparatus and the other organelles. [ABSTRACT FROM AUTHOR]

In more than 40 years since copper deficiency was delineated in pediatric subjects with Menkes disease, remarkable advances in our understanding of the clinical, biochemical, and molecular aspects of the human copper transporter ATP7A have emerged. Mutations in the gene encoding this multitasking molecule are now implicated in at least two other distinctive phenotypes: occipital horn syndrome and ATP7A-related isolated distal motor neuropathy. Several other novel inherited disorders of copper metabolism have been identified in the past several years, aided by advances in human gene mapping and automated DNA sequencing. In this paper, I review the history and evolution of our understanding of disorders caused by impaired ATP7A function, and outline future challenges. [ABSTRACT FROM AUTHOR]