Peptidylglycine α-amidating monooxygenase heterozygosity alters brain copper handling with region specificity

Copper (Cu), an essential trace element present throughout the mammalian nervous system, is crucial for normal synaptic function. Neuronal handling of Cu is poorly understood. We studied the localization and expression of Atp7a, the major intracellular Cu transporter in the brain, and its relation to peptidylglycine -amidating monooxygenase (PAM), an essential cuproenzyme and regulator of Cu homeostasis in neuroendocrine cells. Based on biochemical fractionation and immunostaining of dissociated neurons, Atp7a was enriched in post-synaptic vesicular fractions. Cu followed a similar pattern, with similar to 20% of total Cu in synaptosomes. A mouse model heterozygous for the Pam gene (PAM(+/-)) was selectively Cu deficient in the amygdala. As in cortex and hippocampus, Atp7a and PAM expression overlap in the amygdala, with highest expression in interneurons. Messenger RNA levels of Atox-1 and Atp7a, which deliver Cu to the secretory pathway, were reduced in the amygdala but not in the hippocampus in PAM(+/-) mice, GABA(B) receptor mRNA levels were similarly affected. Consistent with Cu deficiency, dopamine -monooxygenase function was impaired as evidenced by elevated dopamine metabolites in the amygdala, but not in the hippocampus, of PAM(+/-) mice. These alterations in Cu delivery to the secretory pathway in the PAM(+/-) amygdala may contribute to the physiological and behavioral deficits observed.