![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
Biophysics Section, the Blackett Laboratory, Imperial College London, United Kingdom
Received February 24, 2004; accepted May 19, 2004
 |
Abstract |
|---|
 Top Abstract Materials and MethodsResultsDiscussionReferences |
|---|
; Ono et al., 1997) and have been localized to several specific brain regions (Kozma et al., 1981; Sato et al., 1994; Ono et al., 1997). Copper and zinc are present in synaptic vesicles and, after depolarization, are released from nerve terminals (Assaf and Chung, 1984; Howell et al., 1984; Hartter and Barnea, 1988; Kardos et al., 1989) into the synaptic cleft, where they may achieve concentrations on the order of 100 µM or more. During the last few years, it has been shown that both metals can modulate (usually inhibit) several ligand-gated ion channels, including N-methyl-D-aspartate receptors (Vlachova et al., 1996; Paoletti et al., 1997), GABAA receptors (Sharonova et al., 1998; Hosie et al., 2003), glycine receptors (Bloomenthal et al., 1994; Wang et al., 2002), 5-HT3 receptors (Lovinger, 1991) and P2X receptors (Xiong et al., 1999), as well as affecting a variety of voltagegated ion channels (Horning and Trombley, 2001).
In the course of experiments designed to study the modulation of two-pore-domain K+ channels by general anesthetics (Gruss et al., 2004), we found that solutions delivered from glass syringe barrels with metal tips produced potent, but variable, degrees of inhibition. We subsequently identified that the problem was caused by micromolar concentrations of zinc being released from the metal tips (chromiumplated brass). During our investigation, we found that two-pore-domain K+ channels were also sensitive to micromolar concentrations of copper, the other major component of brass.
Two-pore-domain K+ channels play an important role in modulating neuronal excitability (Goldstein et al., 2001; Patel and Honoré, 2001) and are often described as "background" or "leak" channels. In humans, the superfamily has 15 known members, which have a complex and varied anatomical distribution and differ largely in the ways in which they can be modulated and regulated. They can be affected by internal and external pH, certain general anesthetics, membrane stretch, temperature, arachidonic acid, and membrane lipids, as well as by a variety of internal second messenger systems. There are reports that the TASK channels in this superfamily are inhibited by high concentrations of zinc (Leonoudakis et al., 1998; Buckler et al., 2000), but no work has been done on other members of the superfamily or, to our knowledge, with copper.
Herein, we show that TASK-3 (also known as KCNK9) and TREK-1 (also known as KCNK2) channels are sensitive to both copper and zinc, although responses differ both qualitatively and quantitatively. TREK-1 channels are potently activated by copper, whereas TASK-3 channels are potently inhibited. In addition, both channels are inhibited by zinc, but TASK-3 channels are approximately 50 times more sensitive than TREK-1 channels. We show that the amino acids His98, which acts as a proton sensor (Rajan et al., 2000), and Glu70, which is required for inhibition by ruthenium red (Czirjak and Enyedi, 2003), are not involved in copper inhibition. In contrast, these two amino acids have previously been shown (Clarke et al., 2003) to be critical for the zinc inhibition of TASK-3. Using site-directed mutagenesis, we identified an amino acid (Asp128) that is critical for the copper-activation of TREK-1. We conclude that the differential modulation of two-pore-domain K+ channels by copper and zinc may provide a novel explanation for some of the observed effects of these metal ions on neuronal excitability.
|
Materials and Methods |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
The HEK-293 cells were transiently transfected using the calcium phosphate method. One microgram of cDNA encoding a K+ channel subunit was added to each 35-mm well, and 1 µg of a plasmid encoding the cDNA of green fluorescent protein was included to identify cells expressing two-pore-domain K+ channels. After a 24-h incubation period at 3% CO2/97% air the cells were rinsed with saline, and fresh growth medium was added to the wells. The cells were incubated at 37°C with 5% CO2/95% air for 12 to 72 h before electrophysiological measurements were made. A number of experiments were performed with mock-transfected cells; these were treated identically, except that the cDNA coding for the K+ channel was replaced by water.
A cell-line of HEK-293 cells stably-transfected with human TREK-1 was maintained in 5% CO2/95% air in a humidified incubator at 37°C in growth media [89.9% Dulbecco's modified Eagle's medium, 8.9% heat-inactivated fetal bovine serum, and 1.8% Geneticin (20 mg/ml)]. When the cells were 80% confluent, they were split and plated onto glass coverslips coated with poly-D-lysine (1 mg/ml) and stored in an incubator at 5% CO2/95% air. The cells were used after 4 to 5 days for electrophysiological measurements.
HEK-293 cells stably expressing human TREK-1 two-pore-domain K+ channels, and human TASK-3 (Chapman et al., 2000) and TREK-1 (Meadows et al., 2000) two-pore-domain K+ channel clones in the pcDNA 3.1 vector were kindly provided by Dr. Helen Meadows at GlaxoSmithKline (Harlow, Essex, UK).
Mutations and Truncations. To generate mutations and truncations, point mutations were introduced into the K+ channel clones using the QuikChange kit (Stratagene, Amsterdam, The Netherlands). A pair of short (33–45 bases) complementary oligonucleotide primers, incorporating the intended mutation, was synthesized (MWG-Biotech, Ebersberg, Germany). To aid identification of successful mutants, a diagnostic restriction site was included in the primer sequence. Mutant DNA constructs were sequenced (MWG-Biotech, Centre for Medical Education, University of Dundee, or Advanced Biomedical Services, Imperial College) to confirm the introduction of the correct mutated bases.
Solution Preparation. Stock solutions of CuCl2 (100 µM) and ZnCl2 (1 or 2.5 mM) were prepared in standard extracellular solution or high-K+ solution for inside-out patch experiments and diluted to the test concentrations. Stock solutions of arachidonic acid (100 mM) in ethanol were diluted in external solution before the experiments. The stock solutions were kept under nitrogen, stored at -20°C and used within three days. For experiments with arachidonic acid, the control solution contained the same concentration of ethanol as the test solution. The halothane solution was prepared and used as described previously (Gruss et al., 2004).
Electrophysiology. The composition of the control extracellular solution was 140 mM NaCl, 2.5 mM KCl, 2 mM MgCl2, 1 mM CaCl2, 10 mM D-glucose, 10 mM HEPES, titrated to pH 7.4 with NaOH; total Na+ concentration was 145 mM. Glass microelectrodes were pulled from thick-walled borosilicate glass capillaries (GC150F-10; Harvard Apparatus, Edenbridge, Kent, UK) using a two-stage vertical puller (PP-830; Narishige, Tokyo, Japan). Fire-polished pipettes were back-filled with intracellular solution passed through a 0.2 µm filter (120 mM KCH3SO4, 4 mM NaCl, 1 mM MgCl2, 1 mM CaCl2, 10 mM EGTA, 10 mM HEPES, 3 mM MgATP, and 0.3 mM Na2GTP, titrated to pH 7.2 with KOH; total K+ concentration was 155 mM. The pipette resistance ranged from 2 to 7 M
. Series resistance was compensated by 75 to 90%. Voltage-clamp recordings were made using outside-out patches, inside-out patches, or the whole-cell recording technique. Cells and patches were usually held at -80 mV, and 750-ms voltage-ramps from -120 to 0 mV or +40 mV were recorded every 10 s. For continuous recordings, cells or patches were clamped at a fixed potential (-50 mV, unless otherwise stated). Only whole-cell recordings with a positive holding current at -80 mV (indicating a negligible ohmic leak conductance) and an access resistance <10 M were included in the analysis. Current-voltage curves from outside-out and inside-out patches were corrected for an ohmic leak using the equation Icorr = Iobs - IrevVm/Vrev where Icorr is the corrected current, Iobs is the observed current at a membrane potential Vm and Irev is the current measured at the K+ reversal potential. For inside-out patches, the pipettes were filled with external solution, and the bath was perfused with a high potassium solution containing 150 mM KCl and 10 mM HEPES. The pH was adjusted to pH 7.2 by adding KOH giving a final potassium concentration of 153 mM. Inside-out patches were held at -80 mV and 1-s voltage-ramp from -120 to + 120 mV were recorded every 5 or 10 s. For analysis, the data were filtered at 1 kHz, three consecutive traces were averaged, and an ohmic leak was subtracted as described above. The slope conductance between -80 and +40 mV was measured, and the percentage change was calculated. In all cases, the percentage activation or inhibition was calculated relative to the average of controls taken just before and just after the test application.
Recordings were usually digitized at 10 kHz (2 kHz for continuous recordings) and the output of the patch-clamp amplifier (Axopatch 200B; Axon Instruments, Union City, CA) was usually filtered at 5 kHz (corner frequency at -3 dB) using the four-pole Bessel filter of the patch-clamp amplifier. Continuous recordings were digitally filtered at 100 Hz (corner frequency at -3 dB) using an eight-pole Bessel filter (Axon Instruments), unless otherwise stated, before analysis using Clampfit software (Axon Instruments). All recordings were stored on a computer hard disk. All electrophysiological measurements were carried out at room temperature (21–23°C).
The concentration-response data for copper activating TREK-1 channels were fitted to a Hill equation of the form I = [Imax CnH x 100]/[CnH + (EC50)nH], where I is the observed K+ current, Imax is the maximum current, C is the concentration of metal ion, nH is the Hill coefficient, and EC50 is the concentration for a half-maximal effect.
The concentration-response data for copper or zinc inhibiting the two-pore-domain channels were fitted to an inhibitory Hill equation of the form 
, where I is the observed K+ current, C is the concentration of metal ion, nH is the Hill coefficient, and IC50 is the concentration for 50% inhibition.
Values throughout this paper are given as means ± SEMs. In graphs in which error bars are not shown, they are smaller than the size of the symbols. Statistical significance was assessed using the Student's t test.
|
Results |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
; Patel and Honoré, 2001). These TREK-1 currents were markedly activated by micromolar concentrations of copper (see Fig. 1). The current-voltage curves (Fig. 1A) showed that the percentage activation was concentration dependent and showed a clear voltage dependence; the activation was significantly greater at more negative potentials (Fig. 1A, inset). The activation was rapid and completely reversible (Fig. 1B). The concentration-response curve for the activation is shown in Fig. 1C with the data fitted to a Hill equation (see Materials and Methods). The EC50 for the effect was 3.0 ± 1.0 µM, the Vmax was 83 ± 11%, and the Hill coefficient was 1.7 ± 0.8. As shown by the error bars in Fig. 1C, the degree of activation was quite variable at concentrations of copper higher than 10 µM. Experiments with outside-out patches (Fig. 1D) showed a degree of activation that was comparable with that seen in whole-cell recordings, indicating that the intact cell is not required for the effect. Moreover, copper had no significant effect on inside-out patches (Fig. 1E), showing that copper must be acting on the external surface of the membrane.
|
In contrast to TREK-1 channels, TASK-3 channels were potently inhibited by copper ions (Fig. 2). The percentage inhibition was also reversible and concentration-dependent (Fig. 2, B and C), and there was a modest amount of voltage dependence (Fig. 2A, inset), with inhibition increasing slightly at more negative membrane potentials. The concentration dependence is shown in Fig. 2C with the data fitted to an inhibitory Hill equation (see Materials and Methods) with an IC50 of 2.7 ± 0.4 µM and a Hill coefficient of 1.8 ± 0.4. As with the activation of TREK-1 channels, the inhibition of TASK-3 channels by copper ions did not require the intact cell because channel currents in outside-out patches showed a sensitivity comparable with that seen with whole-cell recordings (Fig. 2D) but were unaffected by copper applied to the inside surface of the membrane (Fig. 2E).
|
The data in Fig. 3 show that TREK-1 and TASK-3 channels were both rapidly and reversibly inhibited by zinc ions but with very different sensitivities. TREK-1 channels (Fig. 3, A–C) were relatively insensitive to zinc, with an IC50 of 659 ± 94 µM and a Hill coefficient of 0.6 ± 0.1 (see Fig. 3C). TASK-3 channels were also inhibited by zinc (Fig. 3, D–F) but at much lower concentrations, with an IC50 of 12.7 ± 1.0 µM and a Hill coefficient of 1.7 ± 0.2 (see Fig. 3F). For both channels, the inhibition was essentially independent of voltage.
|
Because certain amino acids (Glu70 and His98) have been shown (Clarke et al., 2003) to be important in the zinc inhibition of TASK-3, we investigated their possible involvement in the copper inhibition of TASK-3. We found that mutating these amino acids (E70K and H98A, respectively) had no significant effect on the copper inhibition of TASK-3 (Fig. 4).
|
An amino acid in TREK-1, Glu306, that has been shown (Honoré et al., 2002) to be crucial in the modulation of the channel by arachidonic acid, membrane stretch, internal acidosis, and, most recently, gaseous anesthetics (Gruss et al., 2004) is also important in TREK-1 activation by copper. When this amino acid was mutated to an alanine, the copper (10 µM) activation was reduced by half (53.2 ± 6.3% activation, n = 9, for the wild-type compared with 22.5 ± 7.3%, activation, n = 5, for the E306A mutant).
Next, we investigated the possible location of copper binding sites on TREK-1 that might be responsible for the copper activation. We first mutated, in turn, each of the presumed extracellular histidine and cysteine residues (to alanine) because these amino acids are often involved in copper binding sites on proteins (Glusker, 1991). It is surprising that none of these mutations (H72A, H91A, C93A, H126A, and H232A) had any significant effect on copper activation (Fig. 5A), although the mean activations were all smaller than the control value, in no case did this reach statistical significance. We went on to mutate each of the presumed extracellular glutamic acid and aspartic acid residues, which would bear a negative charge at physiological pH. Only one of these mutations had a significant effect; the mutation of Asp128 to an alanine reduced the copper activation by about 60% (Fig. 5, B–D). Single mutations of four other residues (E69A, E234A, D240A, and D256A) and the double mutant (E69A/E73A) resulted in channel constructs that did not give measurable currents.
|
To provide confidence that the D128A mutation was disrupting copper binding per se, rather than perturbing the channel in a more general way, we determined the voltage-dependence, activation kinetics, arachidonic acid, and halothane activation and zinc sensitivity of the mutated channel and found them to be essentially indistinguishable from the wild-type channel (see Fig. 6).
|
|
Discussion |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
; Puig and Thiele, 2002) confirms the importance of zinc and copper homeostasis, and imbalances in the concentrations of these metals lead to serious pathological conditions, usually accompanied by disturbances of the nervous system. The physiological roles that these metals play in the nervous system, however, are poorly understood. They are present in the blood at a total concentration of around 15 µM; almost all of this is complexed with proteins. The total concentration in the brain, however, is believed to be on the order of 100 µM, with both metals being found in many different brain regions (Kozma et al., 1981; Sato et al., 1994; Ono et al., 1997).
In the case of zinc, approximately 10% of brain Zn2+ is concentrated in the presynaptic terminals of certain glutamatergic synapses (Frederickson, 1989) and is released after depolarization (Assaf and Chung, 1984; Howell et al., 1984). This results in transient, local concentrations that are thought to be as high as 100 to 300 µM. The corelease of zinc with the neurotransmitter glutamate has been shown to modulate its actions on its postsynaptic receptors (Smart et al., 1994). However, because of the high concentrations of zinc released at glutamatergic synapses, it seems probable that other receptors and ion channels on neighboring cells would also be affected because of "spillover". Indeed, the effects of zinc (almost invariably an inhibition) have been reported for numerous ion channels and receptors; binding affinities vary over several orders of magnitude (Lovinger, 1991; Bloomenthal et al., 1994; Paoletti et al., 1997; Magistretti et al., 2003).
A similar picture is emerging with copper, although this has been much less intensively studied. As with zinc, copper is also released at synapses after depolarization, and concentrations as high as those reported for zinc have been estimated to occur in the synaptic cleft after neurotransmitter release (Hartter and Barnea, 1988; Kardos et al., 1989). Copper has also been shown to interact with a large number of molecular targets, again with widely varying affinities (Lovinger, 1991; Vlachova et al., 1996; Sharonova et al., 1998; Wang et al., 2002).
The data we present here on the effects of copper and zinc ions on two-pore-domain K+ channels provide an additional explanation for some of the CNS effects of these metals. Two-pore-domain K+ channels are found throughout the brain and have a complex anatomical distribution that is highly specific for each member of the superfamily (Talley et al., 2001), and it is clear that they play a central role in modulating neuronal excitability. Depending on the member of the superfamily, they can be modulated by internal and external pH, membrane stretch, temperature, phosphorylation, arachidonic acid, various complex lipids and certain general anesthetics (Goldstein et al., 2001; Patel and Honoré, 2001). There is very little information on how these channels respond to trace metals.
The data in Fig. 1 show that TREK-1 channels are activated by copper at micromolar concentrations. Almost all previous reports on the interactions of copper with ion channels or receptors show an inhibitory effect, with IC50 values generally on the order of tens of micromolar (for example, see Lovinger, 1991; Wang et al., 2002), although there are reports of binding sites with much higher affinities (Vlachova et al., 1996; Sharonova et al., 1998). The magnitude of the maximum activation of TREK-1 (Fig. 1) is modest (
80%) compared with the activation that is possible with agents such as arachidonic acid (Patel et al., 1998); nonetheless, this degree of channel activation will occur at concentrations that are likely to be encountered physiologically, and this would result in a very significant reduction in neuronal excitability in neurons expressing these channels. In qualitative contrast to this activation of TREK-1 channels, TASK-3 channels were equally potently inhibited by Cu2+ (Fig. 2), achieving an almost complete block at around 10 µM. The copper modulation of TREK-1 and TASK-3 is potent in the sense that it occurs in the micromolar range and is likely to have some physiological significance given the relatively high concentrations that are thought to be released at some synapses (Hartter and Barnea, 1988; Kardos et al., 1989). Thus, neuronal excitability could be markedly increased or reduced depending upon the type of two-pore-domain channel that was expressed as well as its cellular distribution.
Because the effects of Cu2+ on outside-out patches were so rapid, and because Cu2+ had no effect on inside-out patches, it is safe to assume binding sites on the external surface of the membrane. For both TREK-1 and TASK-3, the effects of Cu2+ were voltage-dependent, with this being particularly marked in the case of TREK-1. The activation of TREK-1 and the inhibition of TASK-3 both increased at more negative potentials, which is consistent with an external Cu2+ binding site that lies within the membrane field. However, the presence of other divalent cations, such as Mg2+, have been shown to affect the current-voltage characteristics of TREK-1 (Maingret et al., 2002), so more work is required to understand the basis for this voltage-dependence.
The effects of zinc were qualitatively and quantitatively different. Zinc has been reported to inhibit TASK channels with an IC50 of around 200 µM (Leonoudakis et al., 1998; Buckler et al., 2000). We find (Fig. 3) that TASK-3 channels are more than an order of magnitude more sensitive [see also Clarke et al. (2003)]. Given that Zn2+ is thought to be released at synapses at concentrations considerably in excess of this IC50 value, it seems plausible that the Zn2+ sensitivity of TASK-3 channels is physiologically relevant. In contrast, TREK-1 channels were very much less sensitive, with an IC50 of 659 ± 94 µM. The high value of the IC50, together with the low value of the Hill coefficient, is consistent with a number of very weak binding sites, and it seems unlikely that this effect is of physiological relevance.
We investigated certain mutations (Glu70 and His98) that have been shown to affect TASK-3 modulation by zinc (Clarke et al., 2003) to determine whether they also affected copper modulation. However, although we confirmed that mutating these amino acids almost completely eliminated the zinc inhibition of TASK-3, we found these mutations had no significant effect on the inhibitory effects of copper. Thus, whereas these amino acids clearly play a role in zinc modulation (Clarke et al., 2003), as well as in modulation by ruthenium red (Czirjak and Enyedi, 2003) and pH (Rajan et al., 2000), they are not involved in the inhibition of TASK-3 by copper.
We also investigated an amino acid (Glu306) in TREK-1 that has recently been shown (Honoré et al., 2002) to be critical in the mechanosensitivity of the channel and that we have found (Gruss et al., 2004) to be important for the activation of TREK-1 by anesthetic gases. We investigated here whether Glu306 was similarly important for the Cu2+ activation of TREK-1 by mutating this amino acid to an alanine. This mutation did indeed reduce the extent to which Cu2+ could activate the channel, but the loss of the glutamic acid did not have the dramatic effect that it has on the mechanosensitivity of the channel (Honoré et al., 2002) or its activation by anesthetic gases (Gruss et al., 2004).
There are many examples in which Cu2+ binding sites on proteins have been shown to involve interactions with histidine and/or cysteine groups (Glusker, 1991). For this reason, we investigated the roles of each of the histidine and cysteine groups that are presumed to lie on the extracellular surface of the membrane. There are five such amino acids, but the mutation of each, in turn, to an alanine had no significant effect on the extent to which Cu2+ was able to activate the channel. We then investigated all of the presumed extracellular amino acids that would bear a negative charge at physiological pH and would thus be prime candidates to interact with Cu2+ ions. Although the roles of five amino acids could not be determined because their mutation to alanine resulted in nonfunctional (or nonexpressing) channels, we did find a single mutation D128A that caused a substantial reduction in activation by Cu2+. This amino acid is near the first pore-forming loop (on the N-terminal side), and it seems probable that it is involved in Cu2+ binding; indeed, such a site might be expected to experience the membrane field and this would account for the clear voltage dependence of the activation. Moreover, the data in Fig. 6 show that the D128A mutation has no significant effect on the kinetics and voltage-dependence of the channel or on its sensitivity to arachidonic acid, halothane, or zinc. It therefore seems likely that Asp128 plays a direct role in coordinating copper in a binding site. A more complete analysis is required to identify other amino acids that are presumably necessary to co-ordinate the metal ion.
There are a number of well-known human disorders that are known to involve abnormal levels of Cu2+ in the brain, such as Wilson's disease and Menke's syndrome (Strausak et al., 2001), and there is increasing evidence (Horning et al., 2000; Weiss et al., 2000; Squitti et al., 2002) that the disruption of Zn2+ and Cu2+ homeostasis might be an important mediator of acute brain injury, as well as the neuronal degeneration that occurs during Alzheimer's disease. These disease states all involve complex and often severe neurological malfunction, and it is possible that the abnormal modulation of two-pore-domain potassium channels plays a direct role in their pathology.
In conclusion, our observation that Cu2+ and Zn2+ can potently modulate two-pore-domain potassium channels provides a novel explanation for how these ions might affect neuronal excitability under both normal physiological conditions as well as during diseases in which Cu2+ or Zn2+ homeostasis has been disrupted.
|
Acknowledgements |
|---|
|
Footnotes |
|---|
ABBREVIATIONS: TASK, acid-sensitive K+ channel; TREK, weakly inwardly rectifying K+ channel-related K+ channel; HEK, human embryonic kidney.
Address correspondence to: Nicholas P. Franks, Biophysics Section, The Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom. E-mail: n.franks{at}imperial.ac.uk
|
References |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
Bloomenthal AB, Goldwater E, Pritchett DB, and Harrison NL (1994) Biphasic modulation of the strychnine-sensitive glycine receptor by Zn2+. Mol Pharmacol 46: 1156-1159.[Abstract]
Buckler KJ, Williams BA, and Honoré E (2000) An oxygen-, acid- and anaesthetic-sensitive TASK-like background potassium channel in rat arterial chemoreceptor cells. J Physiol 525: 135-142.
Chapman CG, Meadows HJ, Godden RJ, Campbell DA, Duckworth M, Kelsell RE, Murdock PR, Randall AD, Rennie GI, and Gloger IS (2000) Cloning, localisation and functional expression of a novel human, cerebellum specific, two pore domain potassium channel. Brain Res Mol Brain Res 82: 74-83.[Medline]
Clarke CE, Green PJ, Veale EL, Meadows HJ, and Mathie A (2003) The involvement of residues H98 and E70 in the block of the human two pore domain potassium channel, TASK-3, by zinc. J Physiol 547P: C46.
Czirjak G and Enyedi P (2003) Ruthenium red inhibits TASK-3 potassium channel by interconnecting glutamate 70 of the two subunits. Mol Pharmacol 63: 646-652.
Frederickson CJ (1989) Neurobiology of zinc and zinc-containing neurons. Int Rev Neurobiol 31: 145-238.[Medline]
Glusker JP (1991) Structural aspects of metal liganding to functional groups in proteins. Adv Protein Chem 42: 1-76.[Medline]
Goldstein SA, Bockenhauer D, O'Kelly I, and Zilberberg N (2001) Potassium leak channels and the KCNK family of two-P-domain subunits. Nat Rev Neurosci 2: 175-184.[Medline]
Gruss M, Bushell TJ, Bright DP, Lieb WR, Mathie A, and Franks NP (2004) Two-pore-domain K+ channels are a novel target for the anesthetic gases xenon, nitrous oxide, and cyclopropane. Mol Pharmacol 65: 443-452.
Harris ED (2002) Cellular transporters for zinc. Nutr Rev 60: 121-124.[CrossRef][Medline]
Hartter DE and Barnea A (1988) Evidence for release of copper in the brain: depolarization-induced release of newly taken-up 67copper. Synapse 2: 412-415.[CrossRef][Medline]
Honoré E, Maingret F, Lazdunski M, and Patel AJ (2002) An intracellular proton sensor commands lipid- and mechanogating of the K+ channel TREK-1. EMBO (Eur Mol Biol Organ) J 21: 2968-2976.[CrossRef][Medline]
Horning MS, Blakemore LJ, and Trombley PQ (2000) Endogenous mechanisms of neuroprotection: role of zinc, copper and carnosine. Brain Res 852: 56-61.[CrossRef][Medline]
Horning MS and Trombley PQ (2001) Zinc and copper influence excitability of rat olfactory bulb neurons by multiple mechanisms. J Neurophysiol 86: 1652-1660.
Hosie AM, Dunne EL, Harvey RJ, and Smart TG (2003) Zinc-mediated inhibition of GABAA receptors: discrete binding sites underlie subtype specificity. Nat Neurosci 6: 362-369.[CrossRef][Medline]
Howell GA, Welch MG, and Frederickson CJ (1984) Stimulation-induced uptake and release of zinc in hippocampal slices. Nature (Lond) 308: 736-738.[CrossRef][Medline]
Kardos J, Kovacs I, Hajos F, Kalman M, and Simonyi M (1989) Nerve endings from rat brain tissue release copper upon depolarization. A possible role in regulating neuronal excitability. Neurosci Lett 103: 139-144.[CrossRef][Medline]
Kozma M, Szerdahelyi P, and Kasa P (1981) Histochemical detection of zinc and copper in various neurons of the central nervous system. Acta Histochem 69: 12-17.[Medline]
Leonoudakis D, Gray AT, Winegar BD, Kindler CH, Harada M, Taylor DM, Chavez RA, Forsayeth JR, and Yost CS (1998) An open rectifier potassium channel with two pore domains in tandem cloned from rat cerebellum. J Neurosci 18: 868-877.
Lovinger DM (1991) Inhibition of 5-HT3 receptor-mediated ion current by divalent metal cations in NCB-20 neuroblastoma cells. J Neurophysiol 66: 1329-1337.
Magistretti J, Castelli L, Taglietti V, and Tanzi F (2003) Dual effect of Zn2+ on multiple types of voltage-dependent Ca2+ currents in rat palaeocortical neurons. Neuroscience 117: 249-264.[CrossRef][Medline]
Maingret F, Honoré E, Lazdunski M, and Patel AJ (2002) Molecular basis of the voltage-dependent gating of TREK-1, a mechano-sensitive K+ channel. Biochem Biophys Res Commun 292: 339-346.[CrossRef][Medline]
Meadows HJ, Benham CD, Cairns W, Gloger I, Jennings C, Medhurst AD, Murdock P, and Chapman CG (2000) Cloning, localisation and functional expression of the human orthologue of the TREK-1 potassium channel. Pflueg Arch Eur J Physiol 439: 714-722.[CrossRef][Medline]
Ono S, Koropatnick DJ, and Cherian MG (1997) Regional brain distribution of metallothionein, zinc and copper in toxic milk mutant and transgenic mice. Toxicology 124: 1-10.[CrossRef][Medline]
Paoletti P, Ascher P, and Neyton J (1997) High-affinity zinc inhibition of NMDA NR1-NR2A receptors. J Neurosci 17: 5711-5725.
Patel AJ and Honoré E (2001) Properties and modulation of mammalian 2P domain K+ channels. Trends Neurosci 24: 339-346.[CrossRef][Medline]
Patel AJ, Honoré E, Maingret F, Lesage F, Fink M, Duprat F, and Lazdunski M (1998) A mammalian two pore domain mechano-gated S-like K+ channel. EMBO (Eur Mol Biol Organ) J 17: 4283-4290.[CrossRef][Medline]
Puig S and Thiele DJ (2002) Molecular mechanisms of copper uptake and distribution. Curr Opin Chem Biol 6: 171-180.[CrossRef][Medline]
Rajan S, Wischmeyer E, Xin Liu G, Preisig-Muller R, Daut J, Karschin A, and Derst C (2000) TASK-3, a novel tandem pore domain acid-sensitive K+ channel. An extracellular histiding as pH sensor. J Biol Chem 275: 16650-7.
Sato M, Ohtomo K, Daimon T, Sugiyama T, and Iijima K (1994) Localization of copper to afferent terminals in rat locus ceruleus, in contrast to mitochondrial copper in cerebellum. J Histochem Cytochem 42: 1585-1591.[Abstract]
Sharonova IN, Vorobjev VS, and Haas HL (1998) High-affinity copper block of GABAA receptor-mediated currents in acutely isolated cerebellar Purkinje cells of the rat. Eur J Neurosci 10: 522-528.[CrossRef][Medline]
Smart TG, Xie X, and Krishek BJ (1994) Modulation of inhibitory and excitatory amino acid receptor ion channels by zinc. Prog Neurobiol 42: 393-341.[CrossRef][Medline]
Squitti R, Lupoi D, Pasqualetti P, Dal Forno G, Vernieri F, Chiovenda P, Rossi L, Cortesi M, Cassetta E, and Rossini PM (2002) Elevation of serum copper levels in Alzheimer's disease. Neurology 59: 1153-1161.
Strausak D, Mercer JF, Dieter HH, Stremmel W, and Multhaup G (2001) Copper in disorders with neurological symptoms: Alzheimer's, Menkes and Wilson diseases. Brain Res Bull 55: 175-185.[CrossRef][Medline]
Talley EM, Solorzano G, Lei Q, Kim D, and Bayliss DA (2001) Cns distribution of members of the two-pore-domain (KCNK) potassium channel family. J Neurosci 21: 7491-7505.
Vlachova V, Zemkova H, and Vyklicky L Jr (1996) Copper modulation of NMDA responses in mouse and rat cultured hippocampal neurons. Eur J Neurosci 8: 2257-2264.[CrossRef][Medline]
Wang DS, Zhu HL, Hong Z, and Li JS (2002) Cu2+ inhibition of glycine-activated currents in rat sacral dorsal commissural neurons. Neurosci Lett 328: 117-120.[CrossRef][Medline]
Weiss JH, Sensi SL, and Koh JY (2000) Zn2+: a novel ionic mediator of neural injury in brain disease. Trends Pharmacol Sci 21: 395-401.[CrossRef][Medline]
Xiong K, Peoples RW, Montgomery JP, Chiang Y, Stewart RR, Weight FF, and Li C (1999) Differential modulation by copper and zinc of P2X2 and P2X4 receptor function. J Neurophysiol 81: 2088-2094.
This article has been cited by other articles:
|
|
 |
|
  Z. Ma, K. Y. Wong, and F. T. Horrigan An Extracellular Cu2+ Binding Site in the Voltage Sensor of BK and Shaker Potassium Channels J. Gen. Physiol., May 1, 2008; 131(5): 483 - 502. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Liu, J. A. Enyeart, and J. J. Enyeart Potent Inhibition of Native TREK-1 K+ Channels by Selected Dihydropyridine Ca2+ Channel Antagonists J. Pharmacol. Exp. Ther., October 1, 2007; 323(1): 39 - 48. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Andres-Enguix, A. Caley, R. Yustos, M. A. Schumacher, P. D. Spanu, R. Dickinson, M. Maze, and N. P. Franks Determinants of the Anesthetic Sensitivity of Two-pore Domain Acid-sensitive Potassium Channels: MOLECULAR CLONING OF AN ANESTHETIC-ACTIVATED POTASSIUM CHANNEL FROM LYMNAEA STAGNALIS J. Biol. Chem., July 20, 2007; 282(29): 20977 - 20990. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Lutsenko, N. L. Barnes, M. Y. Bartee, and O. Y. Dmitriev Function and Regulation of Human Copper-Transporting ATPases Physiol Rev, July 1, 2007; 87(3): 1011 - 1046. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Traboulsie, J. Chemin, M. Chevalier, J.-F. Quignard, J. Nargeot, and P. Lory Subunit-specific modulation of T-type calcium channels by zinc J. Physiol., January 1, 2007; 578(1): 159 - 171. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
X. Liu, C. Alexander, J. Serrano, E. Borg, and D. C. Dawson Variable Reactivity of an Engineered Cysteine at Position 338 in Cystic Fibrosis Transmembrane Conductance Regulator Reflects Different Chemical States of the Thiol J. Biol. Chem., March 24, 2006; 281(12): 8275 - 8285. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Czirjak and P. Enyedi Zinc and Mercuric Ions Distinguish TRESK from the Other Two-Pore-Domain K+ Channels Mol. Pharmacol., March 1, 2006; 69(3): 1024 - 1032. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J.-S. Kim, J.-Y. Park, H.-W. Kang, E.-J. Lee, H. Bang, and J.-H. Lee Zinc Activates TREK-2 Potassium Channel Activity J. Pharmacol. Exp. Ther., August 1, 2005; 314(2): 618 - 625. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 |
 |
 |
|
 |
 |
 |
= 7.4 ± 0.6; n = 7) and the D128A mutant (