Localization of copper to afferent terminals in rat locus ceruleus, in contrast to mitochondrial copper in cerebellum

Markers of copper transport in the cingulum bundle in schizophrenia

Imaging and postmortem studies indicate that schizophrenia subjects exhibit abnormal connectivity in several white matter tracts, including the cingulum bundle. Copper chelators given to experimental animals damage myelin and myelin-producing oligodendrocytes, and the substantia nigra of schizophrenia subjects shows lower levels of copper, copper transporters, and copper-utilizing enzymes. This study aimed to elucidate the potential role of copper homeostasis in white matter pathology in schizophrenia. Protein levels of the copper transporters ATP7A and CTR1, and dysbindin-1, an upstream modulator of copper metabolism and schizophrenia susceptibility factor, were measured using Western blot analyses of the postmortem cingulum bundle of schizophrenia subjects (n=16) and matched controls (n=13). Additionally, the patient group was subdivided by treatment status: off- (n=8) or on-medication (n=8). Relationships between proteins from the current study were correlated among themselves and markers of axonal integrity previously measured in the same cohort. Schizophrenia subjects exhibited similar protein levels to controls, with no effect of antipsychotic treatment. The dysbindin-1A/1BC relationship was positive in controls and schizophrenia subjects; however, antipsychotic treatment appeared to reverse this relationship in a statistically different manner from that of controls and unmedicated subjects. The relationships between dysbindin-1A/neurofilament heavy and ATP7A/α-tubulin were positively correlated in the schizophrenia group that was significantly different from the lack of correlation in controls. Copper transporters and dysbindin-1 appear to be more significantly affected in the grey matter of schizophrenia subjects. However, the relationships among proteins in white matter may be more substantial and dependent on treatment status.

Abnormalities in the copper transporter CTR1 in postmortem hippocampus in schizophrenia: A subregion and laminar analysis

Dysbindin-1 modulates copper transport, which is crucial for cellular homeostasis. Several brain regions implicated in schizophrenia exhibit decreased levels of dysbindin-1, which may affect copper homeostasis therein. Our recent study showed decreased levels of dysbindin-1, the copper transporter-1 (CTR1) and copper in the substantia nigra in schizophrenia, providing the first evidence of disrupted copper transport in schizophrenia. In the present study, we hypothesized that there would be lower levels of dysbindin-1 and CTR1 in the hippocampus in schizophrenia versus a comparison group. Using semi-quantitative immunohistochemistry for dysbindin1 and CTR1, we measured the optical density in a layer specific fashion in the hippocampus and entorhinal cortex in ten subjects with schizophrenia and ten comparison subjects. Both regions were richly immunolabeled for CTR1 and dysbindin1 in both groups. In the superficial layers of the entorhinal cortex, CTR1 immunolabeled neuropil and cells showed lower optical density values in patients versus the comparison group. In the molecular layer of the dentate gyrus, patients had higher optical density values of CTR1 versus the comparison group. The density and distribution of dysbindin-1 immunolabeling was similar between groups. These laminar specific alterations of CTR1 in schizophrenia suggest abnormal copper transport in those locations.

Clozapine-induced transcriptional changes in the zebrafish brain

Clozapine is an atypical antipsychotic medication that is used to treat schizophrenia patients who are resistant to other antipsychotic drugs. The molecular mechanisms mediating the effects of clozapine are not well understood and its use is often associated with severe side-effects. In this study, we exposed groups of wild-type zebrafish to two doses of clozapine (‘low’ (20 µg/L) and ‘high’ (70 µg/L)) over a 72-h period, observing dose-dependent effects on behaviour. Using RNA sequencing (RNA-seq) we identified multiple genes differentially expressed in the zebrafish brain following exposure to clozapine. Network analysis identified co-expression modules characterised by striking changes in module connectivity in response to clozapine, and these were enriched for regulatory pathways relevant to the etiology of schizophrenia. Our study highlights the utility of zebrafish as a model for assessing the molecular consequences of antipsychotic medications and identifies genomic networks potentially involved in schizophrenia.

Copper and the brain noradrenergic system

Copper (Cu) plays an essential role in the development and function of the brain. In humans, genetic disorders of Cu metabolism may cause either severe Cu deficiency (Menkes disease) or excessive Cu accumulation (Wilson disease) in the brain tissue. In either case, the loss of Cu homeostasis results in catecholamine misbalance, abnormal myelination of neurons, loss of normal brain architecture, and a spectrum of neurologic and/or psychiatric manifestations. Several metabolic processes have been identified as particularly sensitive to Cu dis-homeostasis. This review focuses on the role of Cu in noradrenergic neurons and summarizes the current knowledge of mechanisms that maintain Cu homeostasis in these cells. The impact of Cu misbalance on catecholamine metabolism and functioning of noradrenergic system is discussed.

Impaired copper transport in schizophrenia results in a copper-deficient brain state: A new side to the dysbindin story

Objectives: Several schizophrenia brain regions exhibit decreased dysbindin. Dysbindin modulates copper transport crucial for myelination, monoamine metabolism and cellular homeostasis. Schizophrenia patients (SZP) exhibit increased plasma copper, while copper-decreasing agents produce schizophrenia-like behavioural and pathological abnormalities. Therefore, we sought to determine dysbindin and copper transporter protein expression and copper content in SZP.Methods: We studied the copper-rich substantia nigra (SN) using Western blot and inductively-coupled plasma mass spectrometry. We characterised specific protein domains of copper transporters ATP7A, CTR1, ATP7B and dysbindin isoforms 1 A and 1B/C in SZP (n = 15) and matched controls (n = 11), and SN copper content in SZP (n = 14) and matched controls (n = 11). As a preliminary investigation, we compared medicated (ON; n = 11) versus unmedicated SZP (OFF; n = 4).Results: SZP exhibited increased C terminus, but not N terminus, ATP7A. SZP expressed less transmembrane CTR1 and dysbindin 1B/C than controls. ON exhibited increased C terminus ATP7A protein versus controls. OFF exhibited less N terminus ATP7A protein than controls and ON, suggesting medication-induced rescue of the ATP7A N terminus. SZP exhibited less SN copper content than controls.Conclusions: These results provide the first evidence of disrupted copper transport in schizophrenia SN that appears to result in a copper-deficient state. Furthermore, copper homeostasis may be modulated by specific dysbindin isoforms and antipsychotic treatment.

Copper regulates rest-activity cycles through the locus coeruleus-norepinephrine system

The unusually high demand for metals in the brain along with insufficient understanding of how their dysregulation contributes to neurological diseases motivates the study of how inorganic chemistry influences neural circuitry. We now report that the transition metal copper is essential for regulating rest–activity cycles and arousal. Copper imaging and gene expression analysis in zebrafish identifies the locus coeruleus-norepinephrine (LC-NE) system, a vertebrate-specific neuromodulatory circuit critical for regulating sleep, arousal, attention, memory and emotion, as a copper-enriched unit with high levels of copper transporters CTR1 and ATP7A and the copper enzyme dopamine beta-hydroxylase (DBH) that produces NE. Copper deficiency induced by genetic disruption of ATP7A, which loads copper into DBH, lowers NE levels and hinders LC function as manifested by disruption in rest–activity modulation. Moreover, LC dysfunction caused by copper deficiency from ATP7A disruption can be rescued by restoring synaptic levels of NE, establishing a molecular CTR1-ATP7A-DBH-NE axis for copper-dependent LC function.

Copper: from neurotransmission to neuroproteostasis

Copper is critical for the Central Nervous System (CNS) development and function. In particular, different studies have shown the effect of copper at brain synapses, where it inhibits Long Term Potentation (LTP) and receptor pharmacology. Paradoxically, according to recent studies copper is required for a normal LTP response. Copper is released at the synaptic cleft, where it blocks glutamate receptors, which explain its blocking effects on excitatory neurotransmission. Our results indicate that copper also enhances neurotransmission through the accumulation of PSD95 protein, which increase the levels of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors located at the plasma membrane of the post-synaptic density. Thus, our findings represent a novel mechanism for the action of copper, which may have implications for the neurophysiology and neuropathology of the CNS. These data indicate that synaptic configuration is sensitive to transient changes in transition metal homeostasis. Our results suggest that copper increases GluA1 subunit levels of the AMPA receptor through the anchorage of AMPA receptors to the plasma membrane as a result of PSD-95 accumulation. Here, we will review the role of copper on neurotransmission of CNS neurons. In addition, we will discuss the potential mechanisms by which copper could modulate neuronal proteostasis (“neuroproteostasis”) in the CNS with focus in the Ubiquitin Proteasome System (UPS), which is particularly relevant to neurological disorders such as Alzheimer’s disease (AD) where copper and protein dyshomeostasis may contribute to neurodegeneration. An understanding of these mechanisms may ultimately lead to the development of novel therapeutic approaches to control metal and synaptic alterations observed in AD patients.

Micromolar copper modifies electrical properties and spontaneous discharges of nodose ganglion neurons in vitro

Copper plays a key role in aerobic cell physiology mainly related to mitochondrial metabolism. This element is also present at higher than basal levels in some central nuclei and indeed, current evidence support copper's role as a neuromodulator in the central nervous system. More recent data indicate that copper may also affect peripheral neuronal activity, but so far, there are not detailed descriptions of what peripheral neuronal characteristics are targeted by copper. Here, we studied the effect of physiological concentration of CuCl2 (μM range) on the activity of peripheral neurons using a preparation of nodose ganglion in vitro. By mean of conventional intracellular recordings passive and active electrical membrane properties were studied. Extracellular copper modified (in a redox-independent manner) the resting membrane potential and the input resistance of the nodose ganglion neurons, increasing the excitability in most of the tested neurons. These results suggest that Cu(2+) modulates the activity of nodose ganglion neurons and support nodose ganglion in vitro preparation as a simple model to study the subcellular mechanisms involved in the Cu(2+) effects on neuron electrical properties.

Potent and long-lasting inhibition of human P2X2 receptors by copper

P2X receptors are ion channels gated by ATP. In rodents these channels are modulated by zinc and copper. Zinc is co-released with neurotransmitter at some synapses and can modulate neuronal activity, but the role of copper in the brain is unclear. Rat P2X2 receptors show potentiation by 2-100 μM zinc or copper in the presence of a submaximal concentration of ATP but are inhibited by zinc or copper at concentrations above 100 μM. In contrast, human P2X2 (hP2X2) receptors show no potentiation and are strongly inhibited by zinc over the range of 2-100 μM. The effect of copper on hP2X2 is of interest because there are human brain disorders in which copper concentration is altered. We found that hP2X2 receptors are potently inhibited by copper (IC50 = 40 nM). ATP responsiveness recovered extremely slowly after copper washout, with full recovery requiring over 1 h. ATP binding facilitated copper binding but not unbinding from this inhibitory site. A mutant receptor in which the first six extracellular cysteines were deleted, C(1-6)S, showed normal copper inhibition, however reducing agents dramatically accelerated recovery from copper inhibition in wild type hP2X2 and the C(1-6)S mutant, indicating that the final two disulfide bonds are required to maintain the high affinity copper binding site. Three histidine residues required for normal zinc inhibition were also required for normal copper inhibition. Humans with untreated Wilson's disease have excess amounts of copper in the brain. The high copper sensitivity of hP2X2 receptors suggests that they are non-functional in these patients.

Effect of EGb761 supplementation on the content of copper in mouse brain in an animal model of Parkinson's disease

OBJECTIVE

EGb761 is a well-defined mixture of active compounds extracted from Ginkgo biloba leaves with neuroprotective effects in an animal model of Parkinson's disease induced by 1-methyl-4-phenylpyridinium (MPP(+)). Because copper has been implicated in Parkinson's disease, we investigated whether the protective effect of EGb761 in MPP(+) neurotoxicity is related to the regulation of copper in the brain.

METHODS

C-57BL/6 mice were pretreated with EGb761 (10 mg/kg) daily for 17 d followed by administration of MPP(+) (0.72 mg/kg); the mice were sacrificed 24 h later. The copper content of the striatum, midbrain, hippocampus, frontal cortex, and cerebellum was analyzed by graphite furnace atomic absorption spectrophotometry. Copper content is expressed as mug of copper per gram of wet tissue.

RESULTS

Copper content was reduced in the corpus striatum (45%; P < 0.05), and increased in the midbrain (65%; P < 0.05) and hippocampus (116%; P < 0.001) after MPP(+) administration. EGb761 pretreatment of the MPP(+) group prevented changes in the copper content of the striatum, midbrain, and hippocampus. No significant changes were found in the copper content of the cerebellum and frontal cortex in all treatment groups.

CONCLUSION

We showed that the protective effect of EGb761 against MPP(+) neurotoxicity may be due in part to the regulation of copper homeostasis in the brain.

An extracellular Cu2+ binding site in the voltage sensor of BK and Shaker potassium channels

Copper is an essential trace element that may serve as a signaling molecule in the nervous system. Here we show that extracellular Cu²⁺ is a potent inhibitor of BK and Shaker K⁺ channels. At low micromolar concentrations, Cu²⁺ rapidly and reversibly reduces macrosocopic K⁺ conductance (G_K) evoked from mSlo1 BK channels by membrane depolarization. G_K is reduced in a dose-dependent manner with an IC₅₀ and Hill coefficient of ∼2 μM and 1.0, respectively. Saturating 100 μM Cu²⁺ shifts the G_K-V relation by +74 mV and reduces G_Kmax by 27% without affecting single channel conductance. However, 100 μM Cu²⁺ fails to inhibit G_K when applied during membrane depolarization, suggesting that Cu²⁺ interacts poorly with the activated channel. Of other transition metal ions tested, only Zn²⁺ and Cd²⁺ had significant effects at 100 μM with IC₅₀s > 0.5 mM, suggesting the binding site is Cu²⁺ selective. Mutation of external Cys or His residues did not alter Cu²⁺ sensitivity. However, four putative Cu²⁺-coordinating residues were identified (D133, Q151, D153, and R207) in transmembrane segments S1, S2, and S4 of the mSlo1 voltage sensor, based on the ability of substitutions at these positions to alter Cu²⁺ and/or Cd²⁺ sensitivity. Consistent with the presence of acidic residues in the binding site, Cu²⁺ sensitivity was reduced at low extracellular pH. The three charged positions in S1, S2, and S4 are highly conserved among voltage-gated channels and could play a general role in metal sensitivity. We demonstrate that Shaker, like mSlo1, is much more sensitive to Cu²⁺ than Zn²⁺ and that sensitivity to these metals is altered by mutating the conserved positions in S1 or S4 or reducing pH. Our results suggest that the voltage sensor forms a state- and pH-dependent, metal-selective binding pocket that may be occupied by Cu²⁺ at physiologically relevant concentrations to inhibit activation of BK and other channels.

Copper and iron disorders of the brain

Copper and iron are transition elements essential for life. These metals are required to maintain the brain's biochemistry such that deficiency or excess of either copper or iron results in central nervous system disease. This review focuses on the inherited disorders in humans that directly affect copper or iron homeostasis in the brain. Elucidation of the molecular genetic basis of these rare disorders has provided insight into the mechanisms of copper and iron acquisition, trafficking, storage, and excretion in the brain. This knowledge permits a greater understanding of copper and iron roles in neurobiology and neurologic disease and may allow for the development of therapeutic approaches where aberrant metal homeostasis is implicated in disease pathogenesis.

Copper homeostasis in the CNS: a novel link between the NMDA receptor and copper homeostasis in the hippocampus

Copper is an essential nutrient that plays a fundamental role in the biochemistry of the central nervous system, as evidenced by patients with Menkes disease, a fatal neurodegenerative disorder of childhood resulting from the loss-of-function of a copper-transporting P-type adenosine triphosphatase (ATPase). Despite clinical and experimental data indicating a role for copper in brain function, the mechanisms and timing of the critical events affected by copper remain poorly understood. A novel role for the Menkes ATPase has been identified in the availability of an N-methyl-D-aspartate (NMDA) receptor-dependent, releasable pool of copper in hippocampal neurons, suggesting a unique mechanism linking copper homeostasis and neuronal activation within the central nervous system. This article explores the evidence that copper acts as a modulator of neuronal transmission, and that the release of endogenous copper from neurons may regulate NMDA receptor activity. The relationship between impaired copper homeostasis and neuropathophysiology suggests that impairment of copper efflux could alter neuronal function and thus contribute to rapid neuronal degeneration.

Zinc and copper: pharmacological probes and endogenous modulators of neuronal excitability

As well as being key structural components of many proteins, increasing evidence suggests that zinc and copper ions function as signaling molecules in the nervous system and are released from the synaptic terminals of certain neurons. In this review, we consider the actions of these two ions on proteins that regulate neuronal excitability. In addition to the established actions of zinc, and to a lesser degree copper, on excitatory and inhibitory ligand-gated ion channels, we show that both ions have a number of actions on selected members of the voltage-gated-like ion channel superfamily. For example, zinc is a much more effective blocker of one subtype of tetrodotoxin (TTX)-insensitive sodium (Na+) channel (NaV1.5) than other Na+ channels, whereas a certain T-type calcium (Ca2+) channel subunit (CaV3.2) is particularly sensitive to zinc. For potassium (K+) channels, zinc can have profound effects on the gating of certain KV channels whereas zinc and copper have distinct actions on closely related members of the 2 pore domain potassium channel (K2P) channel family. In addition to direct actions on these proteins, zinc is able to permeate a number of membrane proteins such as (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainate receptors, Ca2+ channels and some transient receptor potential (trp) channels. There are a number of important physiological and pathophysiological consequences of these many actions of zinc and copper on membrane proteins, in terms of regulation of neuronal excitability and neurotoxicity. Furthermore, the concentration of free zinc and copper either in the synaptic cleft or neuronal cytoplasm may contribute to the etiology of certain disease states such as Alzheimer's disease (AD) and epilepsy.

Apolipoprotein Abeta: black sheep in a good family

Amyloid-beta (Abeta) has for a long time been thought to play a central role in the pathogenesis of Alzheimer disease (AD). Analysis of available data indicates that Abeta possesses properties of a metal-binding apolipoprotein influencing lipid transport and metabolism. Protection of lipoproteins from oxidation by transition metals, synaptic activity and role in the acute phase response represent plausible physiological functions of Abeta. However, these important biochemical qualities which may critically influence the development of AD, have been largely ignored by mainstream AD researchers, making Abeta appear to be a "black sheep" in a "good apolipoprotein" family. New studies are needed to shed further light on the physiological role of Abeta in lipid metabolism in the brain.

Inhibition of transient K+ current by copper in Drosophila neurons

The transient K+ current (IK(A)) affects the rate of repetitive action potentials. The whole-cell patch-clamp technique was applied to cultured Drosophila neurons derived from embryonic neuroblasts. IK(A) was measured from neurons before and after application of 0.1 mM copper to the external saline. IK(A) was smaller in the copper-containing saline (12.0 +/- 1.6 pA) than in the control saline (37 +/- 6.5 pA). Activation and inactivation of IK(A) were unchanged by copper. These results suggest that copper can influence neuronal excitability and may affect neuronal function.

Cu2+, Co2+, and Mn2+ modify the gating kinetics of high-voltage-activated Ca2+ channels in rat palaeocortical neurons

The effects of three divalent metal cations (Mn2+, Co2+, and Cu2+) on high-voltage-activated (HVA) Ca2+ currents were studied in acutely dissociated pyramidal neurons of rat piriform cortex using the patch-clamp technique. Cu2+, Mn2+, and Co2+ blocked HVA currents conducted by Ba2+ ( IBa) with IC50 of approximately 920 nM, approximately 58 micro M, and approximately 65 micro M, respectively. Additionally, after application of non-saturating concentrations of the three cations, residual currents activated with substantially slower kinetics than control IBa. As a consequence, the current fraction abolished by the blocking cations typically displayed, in its early phase, an unusually fast-decaying transient. The latter phenomenon turned out to be a subtraction artifact, since none of the pharmacological components (L-, N-, P/Q-, and R-type) that constitute the total HVA currents under study showed a similarly fast early decay: hence, the slow activation kinetics of residual currents was not due to the preferential inhibition of a fast-activating/inactivating component, but rather to a true slowing effect of the blocker cations. The percent IBa-amplitude inhibition caused by Mn2+, Co2+, and Cu2+ was voltage-independent over the whole potential range explored (up to +30 mV), hence the slowing of IBa activation kinetics was not due to a mechanism of voltage- and time-dependent relief from block. Moreover, Mn2+, Co2+, and Cu2+ significantly reduced I(Ba) deactivation speed upon repolarization, which also is not compatible with a depolarization-dependent unblocking mechanism. The above results show that 1) Cu2+ is a particularly potent HVA Ca2+-channel blocker in rat palaeocortical neurons; and 2) Mn2+, Co2+, and Cu2+, besides exerting a blocking action on HVA Ca2+-channels, also modify Ca2+-current activation and deactivation kinetics, most probably by directly interfering with channel-state transitions.

Divalent metals differentially block cloned T-type calcium channels

We tested divalent metals including Cu2+, Pb2+, and Zn2+ to determine their pharmacological profiles for blockade of cloned T-type Ca2+ channels (alpha1G, alpha1 H, and alpha1I). Effects of the metals were also evaluated for native low and high voltage-activated Ca2+ channels in rat sympathetic pelvic neurons. Cu2+ and Zn2+ blocked three T-type channel isoforms in a concentration-dependent manner with a higher affinity for alpha1H currents (IC50 = 0.9 microM and 2.3 microM). In pelvic neurons, only Zn2+ showed strong selectivity for T-type Ca2+ currents over high voltage-activated Ca2+ currents. Conversely, Pb2+ block on Ca2+ channels did not show distinctive selectivity. Taken together, these results suggest that besides Ni2+, Cu2+ and Zn2+ can be used as selective blockers of alpha1 H at low concentrations.

Zinc and copper influence excitability of rat olfactory bulb neurons by multiple mechanisms

Zinc and copper are highly concentrated in several mammalian brain regions, including the olfactory bulb and hippocampus. Whole cell electrophysiological recordings were made from rat olfactory bulb neurons in primary culture to compare the effects of zinc and copper on synaptic transmission and voltage-gated ion channels. Application of either zinc or copper eliminated GABA-mediated spontaneous inhibitory postsynaptic potentials. However, in contrast to the similarity of their effects on inhibitory transmission, spontaneous glutamate-mediated excitatory synaptic activity was completely blocked by copper but only inhibited by zinc. Among voltage-gated ion channels, zinc or copper inhibited TTX-sensitive sodium channels and delayed rectifier-type potassium channels but did not prevent the firing of evoked single action potentials or dramatically alter their kinetics. Zinc and copper had distinct effects on transient A-type potassium currents. Whereas copper only inhibited the A-type current, zinc modulation of A-type currents resulted in either potentiation or inhibition of the current depending on the membrane potential. The effects of zinc and copper on potassium channels likely underlie their effects on repetitive firing in response to long-duration step depolarizations. Copper reduced repetitive firing independent of the initial membrane voltage. In contrast, whereas zinc reduced repetitive firing at membrane potentials associated with zinc-mediated enhancement of the A-type current (-50 mV), in a significant proportion of neurons, zinc increased repetitive firing at membrane potentials associated with zinc-mediated inhibition of the A-type current (-90 mV). Application of zinc or copper also inhibited voltage-gated Ca(2+) channels, suggesting a possible role for presynaptic modulation of neurotransmitter release. Despite similarities between the effects of zinc and copper on some ligand- and voltage-gated ion channels, these data suggest that their net effects likely contribute to differential modulation of neuronal excitability.

Expression profile of the copper homeostasis gene, rAtox1, in the rat brain

In humans the regulation of cellular copper homeostasis is essential for proper organ development and function. A novel cytosolic protein, named Atox 1, was recently identified in yeast that functions in shuttling intracellular mononuclear copper [Cu(I)] to copper-requiring proteins. Atox 1 and its human homolog, hAtox1, are members of an emerging family of proteins termed copper chaperones that are involved in the maintenance of copper homeostasis. Northern blot analysis demonstrates that Atox 1 is widely expressed at varying levels in a variety of rat tissues including brain. Using in situ hybridization histochemistry, we characterized the expression profile for the rat homolog of Atox1 (rAtox1) in the normal adult rat brain. There is widespread expression within the brain that appears to be primarily neuronal. The highest levels of Atox1 message consists of distinct neuronal subtypes that are also characterized by their high levels of metals like copper, iron, and zinc, which include the pyramidal neurons of the cerebral cortex and hippocampus in addition to the neurons of the locus coeruleus. The high levels of a metal chaperone like Atox1 in subsets of neurons that also sequester metals suggests that Atox1 may be important in maintaining the functionality of metal requiring enzymes. A detailed analysis of the restricted expression profile for a novel copper chaperone, rAtox1, is described in the adult rat CNS. Further analysis shows that Atoxl expression is associated with neuronal populations that sequester copper.