The Cellular Prion Protein Prevents Copper-Induced Inhibition of P2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>X</mml:mtext><mml:mtext>4</mml:mtext></mml:msub></mml:mrow></mml:math> Receptors

Lorca, Ramón A.; Varela-Nallar, Lorena; Inestrosa, Nibaldo C.; Huidobro-Toro, J. Pablo

doi:https://doi.org/10.4061/2011/706576

International Journal of Alzheimer’s Disease

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Abstract Introduction Materials and Methods Results Discussion Abbreviations Acknowledgments References Copyright Related Articles

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Copper Status in Alzheimer's Disease and other Neurodegenerative Disorders: Genetics, Mechanisms, Neurophysiology, and Therapies

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Volume 2011 | Article ID 706576 | https://doi.org/10.4061/2011/706576

The Cellular Prion Protein Prevents Copper-Induced Inhibition of P2X4 Receptors

Ramón A. Lorca,¹Lorena Varela-Nallar,²Nibaldo C. Inestrosa,²and J. Pablo Huidobro-Toro¹

Academic Editor: Rosanna Squitti

Received01 Jun 2011

Accepted16 Aug 2011

Published19 Oct 2011

Abstract

Although the physiological function of the cellular prion protein (PrP^C) remains unknown, several evidences support the notion of its role in copper homeostasis. PrP^C binds Cu²⁺ through a domain composed by four to five repeats of eight amino acids. Previously, we have shown that the perfusion of this domain prevents and reverses the inhibition by Cu²⁺ of the adenosine triphosphate (ATP)-evoked currents in the P2X₄ receptor subtype, highlighting a modulatory role for PrP^C in synaptic transmission through regulation of Cu²⁺ levels. Here, we study the effect of full-length PrP^C in Cu²⁺ inhibition of P2X₄ receptor when both are coexpressed. PrP^C expression does not significantly change the ATP concentration-response curve in oocytes expressing P2X₄ receptors. However, the presence of PrP^C reduces the inhibition by Cu²⁺ of the ATP-elicited currents in these oocytes, confirming our previous observations with the Cu²⁺ binding domain. Thus, our observations suggest a role for PrP^C in modulating synaptic activity through binding of extracellular Cu²⁺.

1. Introduction

Prion diseases are a group of fatal neurodegenerative disorders that are sporadic, inherited, or transmissible [1]. These include kuru and Creutzfeldt-Jakob disease in humans, scrapie in sheep and bovine spongiform encephalopathy in cattle. These pathologies are caused by the conformational transition of the native and predominantly α-helical cellular prion protein (PrP^C) into a significantly more β-sheet-containing pathogenic isoform (PrP^Sc) [2], which unlike PrP^C, is insoluble in mild detergents and partially resistant to digestion with proteinase K [3]. PrP^C is a cell surface glycosylphosphatidylinositol-anchored protein that is mainly expressed in neurons and glial cells and to a lesser extent in several peripheral tissues [4, 5]. The normal physiological function of PrP^C remains elusive, although it has been related to signaling, neuroprotection, neuritogenesis, synaptic transmission, oxidative stress, and copper metabolism [6–11].

PrP^C binds copper ions with low micromolar affinity via histidine and glycine-containing peptide repeats in its N-terminal region [12–17]. This Cu²⁺ binding domain is located between residues 60–91 and consists of four identical repeats of the peptide sequence Pro-His-Gly-Gly-Gly-Trp-Gly-Gln. Although the number of octapeptide repeats varies in different species, in mammals this region is one of the most highly conserved [18] and therefore, very likely defines a functional domain of PrP^C. In vitro, the octarepeat region has the capacity to reduce Cu(II) to Cu(I) [19, 20]. In addition, there is another Cu²⁺ binding site outside the octarepeat region [21–24] of higher affinity, in the order of nanomolar, that involves His96 and His111 [24]. PrP^C is localized presynaptically at central synapses [25–27] and is found in synaptic membranes and in synaptic vesicles [9, 28]. Furthermore, PrP^C-null mice show an impaired long-term potentiation, suggesting that PrP^C is involved in normal synaptic function [10], and moreover, it has been shown that PrP^C is involved in regulating the presynaptic Cu²⁺ concentration and synaptic transmission [9].

The P2X family of nucleotide receptors forms non-selective cationic channels activated by extracellular adenosine triphosphate (ATP) [29]. These receptors are widely expressed in the central nervous system (CNS) [30–32] and are involved in synaptic transmission and plasticity including long-term potentiation as recently shown by us [33]. Interestingly, trace metals modulate P2X receptors, particularly, the P2X₄ receptor subtype is differentially modulated by trace metals at physiological concentrations [34–37]. While Zn²⁺ facilitates the ATP-evoked currents, Cu²⁺ inhibits it in a concentration-dependent manner [37]. Previously, we demonstrated that the N-terminal octarepeat fragment of the PrP^C prevents and reverses the inhibitory action of Cu²⁺ on the P2X₄ receptor when added to the media [38]. Herein, in an attempt to determine whether the PrP^C-Cu²⁺ interaction is relevant to synaptic activity, we extended our investigations to test whether the full-length PrP^Cco-expressed with the P2X₄ receptor may modulate in situ the Cu²⁺-induced inhibition of the ATP current gated by the P2X₄ receptor.

2. Materials and Methods

2.1. Drugs and Chemicals

Copper chloride, ATP (as the tetrasodium salt), collagenase IA, and penicillin-streptomycin were purchased from Sigma Chemical Co (St Louis, Mo). All the salts used to prepare the Barth’s incubation media and the recording solutions were analytically graded and were purchased from Merck (Darmstadt, Germany).

2.2. Oocyte Preparation, Injection, and Electrophysiological Recordings

A segment of the Xenopus laevis ovary lobe was surgically removed from adult anesthetized frogs; stages V-VI oocytes were manually defolliculated and then incubated with collagenase IA (1 mg/mL) for 30 min. Oocytes were manually injected with 7.5–12.5 ng cDNA coding for the rat P2X₄ receptor with or without cDNA coding for the hamster prion protein (PrP-3F4), both cDNAs in plasmid pcDNA3, at 250 ng/μL. After 48–72 h of incubation at 15°C in Barth’s solution (in mM): 88 NaCl, 1 KCl, 2.4 NaHCO₃, 10 HEPES, 0.82 MgSO₄, 0.33 Ca(NO₃)₂, pH 7.5, supplemented with 10 IU/L penicillin/10 mg streptomycin, oocytes were clamped at −70 mV using the two-electrode voltage clamp technique with an OC-725C oocyte clamper (Warner Instrument Corp, Hamden, CT). ATP and CuCl₂, dissolved in Barth’s solution, were superfused at 2 ml/min. ATP-evoked currents were recorded with a 10 s ATP exposure applied regularly at 10–15 min intervals. These intervals were increased up to 25 min for maximal ATP concentrations in concentration-response curves protocols to decrease desensitization. Copper was applied for 30 s prior 10 μM ATP (coapplied with CuCl₂).

2.3. Confocal Microscopy

To study the distribution of PrP, oocytes were coinjected with the cDNA coding for the rat P2X₄ receptor with the cDNA coding for mouse PrP-GFP (MmPrP-EGFP[25-266]-cDNA3). Oocytes, where P2X₄ receptor expression was validated electrophysiologically, were directly analyzed on a Zeiss LSM 5 Pascal confocal microscope.

2.4. Western Blotting

After electrophysiological protocols, each oocyte injected with cDNa coding for P2X₄ and PrP-3F4 was homogenized for 30 min in ice, using 40 μL of lysis buffer per oocyte (100 mM NaCl, 20 mM Tris-HCl pH 7.4, 1% Triton X-100) supplemented with a protease inhibitors cocktail [39]. The extracts were centrifuged for 30 s at 14000 r.p.m. at 4°C and the supernatant was removed and resolved by 12% SDS-PAGE and transferred to nitrocellulose. Nonspecific binding sites were blocked with 5% (w/v) milk in Tris-Buffered Saline (TBS) 0.1% Tween (TBST) for 1 h. After blocking, blots were incubated with monoclonal anti-3F4 antibody [40], diluted 1 : 5000 in 3% (w/v) milk in TBST for 1 h at room temperature, followed by three 15 min washes in TBST at room temperature. The reactions were followed by incubation with anti-mouse antibody peroxidase labeled (Pierce, Rockford, IL) and developed by enhanced chemiluminescence.

2.5. Data Analysis

The average reduction of the ATP-gated current was normalized. The ATP and Cu²⁺ concentration-response curves were fitted to a sigmoid function using the GraphPad Prism software (San Diego, Cal). The median effective (EC₅₀) or median inhibitory concentrations (IC₅₀) for ATP or copper, respectively, were interpolated from these curves. Each protocol was performed in separate oocytes coming from at least two separate batches of oocytes. Mann-Whitney nonparametric Student’s t-test was used for statistical analysis. A was considered significant.

3. Results

3.1. The Expression of PrP-3F4 Did Not Change the ATP Concentration-Response Curve of P2X₄ Receptors

To evaluate whether the expression of PrP^C modulates the inhibition of the P2X₄ receptor by Cu²⁺, we first evaluated the expression of PrP^C in oocytes co-injected with the cDNA coding for the hamster prion protein (PrP-3F4) and the cDNA coding for the rat P2X₄ receptor. Figure 1(a) shows the detection by western blot of P2X₄ receptor and PrP-3F4 using an antibody that recognizes the 3F4 epitope [40]. β-Tubulin detection was used as a loading control. As observed, both proteins are strongly detected in an injected oocyte and not in the control noninjected oocyte. Then we analyzed the distribution of PrP^C in oocytes co-injected with the cDNA coding for the rat P2X₄ receptor and the cDNA coding for PrP-GFP. Oocytes in which the expression of P2X₄ receptor was verified electrophysiologically were analyzed in a confocal microscope to study the localization of PrP-GFP. As observed in Figure 1(b), PrP-GFP is located on the surface of injected oocytes.

(a)

(b)

Then, we evaluated the ATP concentration-response curves in oocytes expressing the P2X₄ receptor and coexpressing the P2X₄ receptor and PrP-3F4. The presence of PrP-3F4 caused a slight, but not significant, reduction in the potency of ATP, reflected as an increase in its EC₅₀ from 11.2 ± 1.1 μM for P2X₄ alone to 45.2 ± 9.4 μM for P2X₄/PrP-3F4 (, , Figure 2), this slight displacement of ATP concentration-response curve in the presence of PrP-3F4 could represent a minor regulation of PrP-3F4 on P2X₄ receptor activity.

3.2. The Co-Expression of P2X₄ Receptors and PrP-3F4 Partially Prevents the Copper-Induced Inhibition of the ATP-Evoked Currents

We assess the Cu²⁺-induced inhibition of 10 μM ATP currents in oocytes expressing P2X₄ receptors. The magnitude of the inhibition by 10 μM Cu²⁺, preapplied during 30 s, was 51.5 ± 5.3% of the 10 μM ATP-evoked currents (, Figures 3(a) and 3(b)). However, the 10 μM Cu²⁺-induced inhibition was reduced only to 71.9 ± 5% of the 10 μM ATP-evoked currents in oocytes co-expressing P2X₄ receptors and the PrP-3F4 (, compared to P2X₄ alone, Figures 3(a) and 3(b)), showing that PrP-3F4 prevented the Cu²⁺-induced inhibition of P2X₄ receptors compared to the Cu²⁺ inhibition elicited in oocytes expressing only this receptor. Furthermore, the presence of PrP-3F4 in the oocytes caused a rightward displacement of the Cu²⁺ concentration-response curve obtained in oocytes expressing only P2X₄ receptor, an IC₅₀ of 11.5 ± 1.9 μM was obtained for P2X₄ and 34.1 ± 7.6 μM for P2X₄/PrP-3F4 (, , Figure 3(c)), confirming that PrP-3F4 prevented the Cu²⁺-induced inhibition not only at low micromolar concentrations of Cu²⁺, but even at higher physiological concentrations of the metal.

(a)

(b)

(c)

Figure 3

PrP^C prevents Cu²⁺-induced inhibition of P2X₄ receptor. (a) Representative recordings obtained from oocytes expressing P2X₄ receptor (left traces, P2X₄) or coexpressing P2X₄ receptor and PrP-3F4 (right traces, P2X₄/PrP-3F4) showing 10 μM ATP-evoked currents (open bars) and its inhibition by 10 μM Cu²⁺ (closed bars). (b) Statistical analysis of Cu²⁺ inhibition showed in (a), performed in different oocytes (, * versus ATP, ^# versus P2X₄ alone). Bars are mean values ± SEM. (c), Cu²⁺ concentration-response curves of 10 μM ATP inhibition in oocytes expressing P2X₄ receptor (open circles) or co-expressing P2X₄ receptor and PrP-3F4 (closed circles). Symbols are mean values ± SEM, numbers in parenthesis are number of oocytes.

4. Discussion

Several functions have been attributed to PrP^C, including immunoregulation, signal transduction, copper binding, neurite outgrowth, induction of apoptosis or prevention of apoptosis against apoptotic stimuli, and others [41]. In addition, PrP^C has been related to synapse formation and maintenance and synaptic transmission [9, 10, 42], although the mechanisms by which it exerts its role is still unknown. One of the proposed targets for PrP^C in synapse is to modulate Cu²⁺ homeostasis, based on a highly conserved Cu²⁺-binding sequence located on its N-terminal domain, which includes four identical repeats of the peptide sequence Pro-His-Gly-Gly-Gly-Trp-Gly-Gln [12, 15, 16]. It is known that PrP^C binds Cu²⁺ with high affinity [14–17], and the octarepeat region of the human PrP^C (PrP_59-91) reduces Cu(II) to Cu(I) in vitro, which depends on the tryptophan residues present in the octapeptide repeats [19, 20]. Cu²⁺ modulates synaptic transmission at micromolar concentrations by a wide range of mechanisms, be one of the most relevanting modulations of neurotransmitter receptors within glutamatergic, gabaergic, and purinergic synapses, among others [43, 44]. In a previous study, we demonstrated that Cu²⁺ at micromolar concentrations inhibits the ATP-evoked currents of P2X₄ receptors [37]. Here we show that the full-length prion protein-expressed in Xenopus oocytes localizes in the cell surface and modulates the Cu²⁺ interaction with P2X₄ receptor; oocytes which coexpressed PrP-3F4 and P2X₄ receptors have a diminished Cu²⁺-induced inhibition of the ATP-evoked currents compared with oocytes which only expressed the P2X₄ receptor. This reduced inhibition by Cu²⁺ was observed on Cu²⁺ concentration-response curves, where the IC₅₀ of Cu²⁺ was significantly increased in the presence of PrP-3F4, indicating that PrP-3F4 can exert its modulatory role even at high micromolar concentrations of Cu²⁺, reached in the synaptic cleft after depolarization [45]. These results, together with our previous findings showing that coapplication of Cu²⁺ with the N-terminal PrP fragment (PrP_59-91) prevents the inhibitory effect of copper on P2X₄ receptors and even reverts the established Cu²⁺-induced inhibition of the P2X₄ receptors [38], strongly support the idea that PrP^C could modulate synaptic copper and therefore affect the function of P2X₄ receptors and synaptic transmission.

In addition to the potential synaptic role of PrP^C driven by its ability to bind Cu²⁺, a known modulator of neuronal excitability [43, 44], there is increasing evidence of direct interaction between PrP^C and neurotransmitter receptors. PrP^C directly interacts with the NR2D subunit of the NMDA receptor, inhibiting it and preventing NMDA-induced excitoxicity in the hippocampus [46]. On the other hand, PrP^C also exerts a neuroprotective role against kainate-induced neurotoxicity in the hippocampus, probably by regulating differentially the expression of GluR6 and GluR7 kainate receptor subunits [47]. Moreover, PrP^C can modulate the activity of serotoninergic receptors signaling pathways in 1C11^5-HTcells [48]. We observed a slight, although not significant, reduction on ATP affinity of P2X₄ receptor in the presence of PrP-3F4, this might suggest an interference with ATP binding or stabilization of closed states, although further experiments are required to evaluate this hypothesis. Altogether, these studies and the presented here highlight the modulatory role of PrP^C at synaptic transmission in CNS, involving direct regulation of neurotransmitter receptors and/or their signaling cascade, or indirectly, by controlling the synaptic levels of Cu²⁺.

The understanding of the physiological function of PrP^C on synaptic transmission may clarify the pathogenic processes underlying prion diseases. Based on our results, it is possible to suggest that the resulting cognitive deterioration of prion diseases could involve a loss of the modulatory role of PrP^C on brain function, as it is converted to the pathogenic isoform.

Abbreviations

PrP^C:	Cellular prion protein
ATP:	Adenosine triphosphate
CNS:	Central nervous system
EC₅₀:	Median effective concentration
IC₅₀:	Median inhibitory concentration.

Acknowledgments

The authors would like to thank Dr. Claudio Soto (Department of Neurology, The University of Texas Medical School, Tex, USA) for his kind gift of the PrP-GFP construct, and Dr. Richard Kascsak (New York State Institute for Basic Research, Staten Island, NY, USA) for mouse anti-3F4 antibody. This work was supported by Basal Center of Excellence in Aging and Regeneration (CONICYT-PFB12/2007). Ramón A. Lorca is currently with Department of Obstetrics and Gynecology, Center for Women's Reproductive Sciences Research, BJC Institute of Health, Washington University in St. Louis, St. Louis, MO, USA.

References

S. B. Prusiner, “Prions,” Proceedings of the National Academy of Sciences of the United States of America, vol. 95, no. 23, pp. 13363–13383, 1998.
View at: Publisher Site | Google Scholar
K. M. Pan, M. Baldwin, J. Nguyen et al., “Conversion of α-helices into β-sheets features in the formation of the scrapie prion proteins,” Proceedings of the National Academy of Sciences of the United States of America, vol. 90, no. 23, pp. 10962–10966, 1993.
View at: Publisher Site | Google Scholar
B. Caughey and G. J. Raymond, “The scrapie-associated form of PrP is made from a cell surface precursor that is both protease- and phospholipase-sensitive,” Journal of Biological Chemistry, vol. 266, no. 27, pp. 18217–18223, 1991.
View at: Google Scholar
H. A. Kretzschmar, S. B. Prusiner, L. E. Stowring, and S. J. DeArmond, “Scrapie prion proteins are synthesized in neurons,” American Journal of Pathology, vol. 122, no. 1, pp. 1–5, 1986.
View at: Google Scholar
M. Moser, R. J. Colello, U. Pott, and B. Oesch, “Developmental expression of the prion protein gene in glial cells,” Neuron, vol. 14, no. 3, pp. 509–517, 1995.
View at: Google Scholar
S. Mouillet-Richard, M. Ermonval, C. Chebassier et al., “Signal transduction through prion protein,” Science, vol. 289, no. 5486, pp. 1925–1928, 2000.
View at: Publisher Site | Google Scholar
X. Roucou, M. Gains, and A. C. LeBlanc, “Neuroprotective Functions of Prion Protein,” Journal of Neuroscience Research, vol. 75, no. 2, pp. 153–161, 2004.
View at: Publisher Site | Google Scholar
N. Vassallo and J. W. Herms, “Cellular prion protein function in copper homeostasis and redox signalling at the synapse,” Journal of Neurochemistry, vol. 86, no. 3, pp. 538–544, 2003.
View at: Publisher Site | Google Scholar
J. Herms, T. Tings, S. Gall et al., “Evidence of presynaptic location and function of the prion protein,” Journal of Neuroscience, vol. 19, no. 20, pp. 8866–8875, 1999.
View at: Google Scholar
J. Collinge, M. A. Whittington, K. C. L. Sidle et al., “Prion protein is necessary for normal synaptic function,” Nature, vol. 370, no. 6487, pp. 295–297, 1994.
View at: Publisher Site | Google Scholar
L. Varela-Nallar, A. González, and N. C. Inestrosa, “Role of copper in prion diseases: deleterious or beneficial?” Current Pharmaceutical Design, vol. 12, no. 20, pp. 2587–2595, 2006.
View at: Publisher Site | Google Scholar
M. P. Hornshaw, J. R. McDermott, J. M. Candy, and J. H. Lakey, “Copper binding to the N-terminal tandem repeat region of mammalian and avian prion protein: structural studies using synthetic peptides,” Biochemical and Biophysical Research Communications, vol. 214, no. 3, pp. 993–999, 1995.
View at: Publisher Site | Google Scholar
T. Miura, A. Hori-i, and H. Takeuchi, “Metal-dependent α-helix formation promoted by the glycine-rich octapeptide region of prion protein,” FEBS Letters, vol. 396, no. 2-3, pp. 248–252, 1996.
View at: Publisher Site | Google Scholar
D. R. Brown, K. Qin, J. W. Herms et al., “The cellular prion protein binds copperin vivo,” Nature, vol. 390, no. 6661, pp. 684–687, 1997.
View at: Publisher Site | Google Scholar
J. H. Viles, F. E. Cohen, S. B. Prusiner, D. B. Goodin, P. E. Wright, and H. J. Dyson, “Copper binding to the prion protein: structural implications of four identical cooperative binding sites,” Proceedings of the National Academy of Sciences of the United States of America, vol. 96, no. 5, pp. 2042–2047, 1999.
View at: Publisher Site | Google Scholar
J. Stöckel, J. Safar, A. C. Wallace, F. E. Cohen, and S. B. Prusiner, “Prion protein selectively binds copper(II) ions,” Biochemistry, vol. 37, no. 20, pp. 7185–7193, 1998.
View at: Publisher Site | Google Scholar
R. M. Whittal, H. L. Ball, F. E. Cohen, A. L. Burlingame, S. B. Prusiner, and M. A. Baldwin, “Copper binding to octarepeat peptides of the prion protein monitored by mass spectrometry,” Protein Science, vol. 9, no. 2, pp. 332–343, 2000.
View at: Google Scholar
J. D. F. Wadsworth, A. F. Hill, S. Joiner, G. S. Jackson, A. R. Clarke, and J. Collinge, “Strain-specific prion-protein conformation determined by metal ions,” Nature Cell Biology, vol. 1, no. 1, pp. 55–59, 1999.
View at: Google Scholar
C. Opazo, M. Inés Barría, F. H. Ruiz, and N. C. Inestrosa, “Copper reduction by copper binding proteins and its relation to neurodegenerative diseases,” BioMetals, vol. 16, no. 1, pp. 91–98, 2003.
View at: Publisher Site | Google Scholar
F. H. Ruiz, E. Silva, and N. C. Inestrosa, “The N-terminal tandem repeat region of human prion protein reduces copper: role of tryptophan residues,” Biochemical and Biophysical Research Communications, vol. 269, no. 2, pp. 491–495, 2000.
View at: Publisher Site | Google Scholar
C. S. Burns, E. Aronoff-Spencer, G. Legname et al., “Copper coordination in the full-length, recombinant prion protein,” Biochemistry, vol. 42, no. 22, pp. 6794–6803, 2003.
View at: Publisher Site | Google Scholar
G. S. Jackson, I. Murray, L. L. P. Hosszu et al., “Location and properties of metal-binding sites on the human prion protein,” Proceedings of the National Academy of Sciences of the United States of America, vol. 98, no. 15, pp. 8531–8535, 2001.
View at: Publisher Site | Google Scholar
K. Qin, Y. Yang, P. Mastrangelo, and D. Westaway, “Mapping Cu(II) binding sites in prion proteins by diethyl pyrocarbonate modification and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometric footprinting,” Journal of Biological Chemistry, vol. 277, no. 3, pp. 1981–1990, 2002.
View at: Publisher Site | Google Scholar
C. E. Jones, S. R. Abdelraheim, D. E. Brown, and J. H. Viles, “Preferential Cu²⁺ coordination by His96 and His 111 induces β-sheet formation in the unstructured amyloiodogenic region of the prion protein,” Journal of Biological Chemistry, vol. 279, no. 31, pp. 32018–32027, 2004.
View at: Publisher Site | Google Scholar
J. G. Fournier, F. Escaig-Haye, T. B. De Villemeur, and O. Robain, “Ultrastructural localization of cellular prion protein (PrPc) in synaptic boutons of normal hamster hippocampus,” Comptes Rendus de l'Academie des Sciences, vol. 318, no. 3, pp. 339–344, 1995.
View at: Google Scholar
N. Sales, K. Rodolfo, R. Hassig, B. Faucheux, L. Di Giamberardino, and K. L. Moya, “Cellular prion protein localization in rodent and primate brain,” European Journal of Neuroscience, vol. 10, no. 7, pp. 2464–2471, 1998.
View at: Publisher Site | Google Scholar
Y. Bailly, A. M. Haeberlé, F. Blanquet-Grossard et al., “Prion protein (PrPc) immunocytochemistry and expression of the green fluorescent protein reporter gene under control of the bovine PrP gene promoter in the mouse brain,” Journal of Comparative Neurology, vol. 473, no. 2, pp. 244–269, 2004.
View at: Publisher Site | Google Scholar
M. A. Chishti, R. Strome, G. A. Carlson, and D. Westaway, “Syrian hamster prion protein (PrP(c) is expressed in photoreceptor cells of the adult retina,” Neuroscience Letters, vol. 234, no. 1, pp. 11–14, 1997.
View at: Publisher Site | Google Scholar
V. Ralevic and G. Burnstock, “Receptors for purines and pyrimidines,” Pharmacological Reviews, vol. 50, no. 3, pp. 413–492, 1998.
View at: Google Scholar
R. Kanjhan, G. D. Housley, L. D. Burton et al., “Distribution of the P2X₂ receptor subunit of the ATP-gated ion channels in the rat central nervous system,” Journal of Comparative Neurology, vol. 407, no. 1, pp. 11–32, 1999.
View at: Google Scholar
W. Norenberg and P. Illes, “Neuronal P2X receptors: localisation and functional properties,” Naunyn-Schmiedeberg's Archives of Pharmacology, vol. 362, no. 4-5, pp. 324–339, 2000.
View at: Publisher Site | Google Scholar
M. E. Rubio and F. Soto, “Distinct localization of P2X receptors at excitatory postsynaptic specializations,” Journal of Neuroscience, vol. 21, no. 2, pp. 641–653, 2001.
View at: Google Scholar
R. A. Lorca, C. Rozas, S. Loyola et al., “Zinc enhances long-term potentiation through P2X receptor modulation in the hippocampal CA1 region,” European Journal of Neuroscience, vol. 33, no. 7, pp. 1175–1185, 2011.
View at: Publisher Site | Google Scholar
R. Cloues, S. Jones, and D. A. Brown, “Zn²⁺ potentiates ATP-activated currents in rat sympathetic neurons,” Pflugers Archiv, vol. 424, no. 2, pp. 152–158, 1993.
View at: Google Scholar
C. Li, R. W. Peoples, Z. Li, and F. F. Weight, “Zn²⁺ potentiates excitatory action of ATP on mammalian neurons,” Proceedings of the National Academy of Sciences of the United States of America, vol. 90, no. 17, pp. 8264–8267, 1993.
View at: Google Scholar
K. Xiong, R. W. Peoples, J. P. Montgomery et al., “Differential modulation by copper and zinc of P2X₂ and P2X₄ receptor function,” Journal of Neurophysiology, vol. 81, no. 5, pp. 2088–2094, 1999.
View at: Google Scholar
C. Acuña-Castillo, B. Morales, and J. P. Huidobro-Toro, “Zinc and copper modulate differentially the P2X₄ receptor,” Journal of Neurochemistry, vol. 74, no. 4, pp. 1529–1537, 2000.
View at: Publisher Site | Google Scholar
R. A. Lorca, M. Chacón, M. I. Barría, N. C. Inestrosa, and J. P. Huidobro-Toro, “The human prion octarepeat fragment prevents and reverses the inhibitory action of copper in the P2X₄ receptor without modifying the zinc action,” Journal of Neurochemistry, vol. 85, no. 3, pp. 709–716, 2003.
View at: Google Scholar
J. G. Connolly, R. J. Tate, N. F. McLennan et al., “Properties of the cellular prion protein expressed in Xenopus oocytes,” NeuroReport, vol. 13, no. 9, pp. 1229–1233, 2002.
View at: Google Scholar
R. J. Kascsak, R. Rubenstein, P. A. Merz et al., “Mouse polyclonal and monoclonal antibody to scrapie-associated fibril proteins,” Journal of Virology, vol. 61, no. 12, pp. 3688–3693, 1987.
View at: Google Scholar
A. Aguzzi, F. Baumann, and J. Bremer, “The prion's elusive reason for being,” Annual Review of Neuroscience, vol. 31, pp. 439–477, 2008.
View at: Publisher Site | Google Scholar
J. W. Herms, H. A. Kretzschmar, S. Titz, and B. U. Keller, “Patch-clamp analysis of synaptic transmission to cerebellar purkinje cells of prion protein knockout mice,” European Journal of Neuroscience, vol. 7, no. 12, pp. 2508–2512, 1995.
View at: Publisher Site | Google Scholar
J. P. Huidobro-Toro, R. A. Lorca, and C. Coddou, “Trace metals in the brain: allosteric modulators of ligand-gated receptor channels, the case of ATP-gated P2X receptors,” European Biophysics Journal, vol. 37, no. 3, pp. 301–314, 2008.
View at: Publisher Site | Google Scholar
A. Mathie, G. L. Sutton, C. E. Clarke, and E. L. Veale, “Zinc and copper: pharmacological probes and endogenous modulators of neuronal excitability,” Pharmacology and Therapeutics, vol. 111, no. 3, pp. 567–583, 2006.
View at: Publisher Site | Google Scholar
J. Kardos, I. Kovacs, F. Hajos, M. Kalman, and M. Simonyi, “Nerve endings from rat brain tissue release copper upon depolarization. A possible role in regulating neuronal excitability,” Neuroscience Letters, vol. 103, no. 2, pp. 139–144, 1989.
View at: Google Scholar
H. Khosravani, Y. Zhang, S. Tsutsui et al., “Prion protein attenuates excitotoxicity by inhibiting NMDA receptors,” Journal of Cell Biology, vol. 181, no. 3, pp. 551–555, 2008.
View at: Publisher Site | Google Scholar
A. Rangel, F. Burgaya, R. Gavín, E. Soriano, A. Aguzzi, and J. A. Del Río, “Enhanced susceptibility of Prnp-deficient mice to kainate-induced seizures, neuronal apoptosis, and death: role of AMPA/kainate receptors,” Journal of Neuroscience Research, vol. 85, no. 12, pp. 2741–2755, 2007.
View at: Publisher Site | Google Scholar
S. Mouillet-Richard, M. Pietri, B. Schneider et al., “Modulation of serotonergic receptor signaling and cross-talk by prion protein,” Journal of Biological Chemistry, vol. 280, no. 6, pp. 4592–4601, 2005.
View at: Publisher Site | Google Scholar

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Copyright © 2011 Ramón A. Lorca et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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