Altered ATP7A expression and other compensatory responses in a murine model of Menkes disease.

Abstract Mutations in the copper-transporter ATP7A lead to severe neurodegeneration in the mottled brindled hemizygous male (Mo Br/y ) mouse and human patients with Menkes disease. Our earlier studies demonstrated cell-type- and -stage-specific changes in ATP7A protein expression during postnatal neurodevelopment. Here we examined copper and cuproenzyme levels in Mo Br/y mice to search for compensatory responses. While all Mo Br/y neocortical subcellular fractions had decreased copper levels, the greatest decrease (8-fold) was observed in cytosol. Immunostaining for ATP7A revealed decreased levels in Mo Br/y hippocampal pyramidal and cerebellar Purkinje neurons. In contrast, an upregulation of ATP7A protein occurred in Mo Br/y endothelial cells, perhaps to compensate for a lack of copper in the neuropil. Mo Br/y astrocytes and microglia increased their physical association with the blood–brain barrier. No alterations in ATP7A levels were observed in ependymal cells, arguing for specificity in the alteration observed at the blood–brain barrier. The decreased expression of ATP7A protein in Mo Br/y Purkinje cells was associated with impaired synaptogenesis and dramatic cytoskeletal dysfunction. Immunoblotting failed to reveal any compensatory increase in levels of ATP7B. While total levels of several cuproenzymes (peptide-amidating monooxygenase, SOD1, and SOD3) were unaltered in the Mo Br/y brain, levels of amidated cholecystokinin (CCK8) and amidated pituitary adenylate cyclase-activating polypeptide (PACAP38) were reduced in a tissue-specific fashion. The compensatory changes observed in the neurovascular unit provide insight into the success of copper injections within a defined neurodevelopmental period.