The role of copper in catecholamine metabolism in the brain
SCHMIDT-DISSERTATION-2018.pdf (8.083Mb) (embargoed until: 2022-05-01)
Schmidt, Katharina Henny
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Norepinephrine modulates alertness, arousal, addiction, and other complex behavioral processes. Norepinephrine is generated from another neuromodulator, dopamine, by a copper-dependent enzyme dopamine-β-hydroxylase, DBH. In several neuropsychiatric disorders, an abnormal dopamine/norepinephrine ratio coincides with copper (Cu) misbalance; however, the link between Cu homeostasis and DBH behavior remains largely unclear. To investigate this link, we apply a combination of biochemical, biophysical, and cell biological methods including SDS-PAGE, enzymatic assays, X-ray fluorescence spectroscopy of metals in brain slices, immunohistochemistry, and siRNA-mediated knockdown of Cu-ATPases. We show that Cu is enriched in the mouse locus coeruleus and is required for constitutive secretion of active DBH. Oxidation of the cellular environment and an impairment of the ability of Atox1 to deliver Cu to the secretory pathway, presumably to two Cu transporters ATP7A and ATP7B, specifically affected secretion of DBH, whereas constitutive secretion of transferrin was not impaired. Both ATP7A and ATP7B maintain Cu levels in DBH-expressing neurons by transporting Cu to distinct cellular compartments; these activities oppositely affect DBH secretion. Cu depletion alters morphogenesis of secretory granules and inhibits DBH secretion. Atp7b-/- mice (a model of Wilson disease) have less Cu and fewer DBH-positive vesicles/granules in their locus coeruleus despite Cu elevation elsewhere. Cu-dependent DBH secretion is a new mechanism through which Cu contributes to dopamine/norepinephrine balance. Loss of this Cu-dependent regulation may facilitate neuronal pathogenesis, especially in Wilson disease and Parkinson’s disease.