Differential role of extracellular histidines in copper, zinc, magnesium and proton modulation of the P2X7 purinergic receptor

• Published in: Journal of neurochemistry Vol. 101; no. 1; pp. 17 - 26
• Main Authors: Acuña‐Castillo, Claudio, Coddou, Claudio, Bull, Paulina, Brito, Jocelyn, Huidobro‐Toro, J. Pablo
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.04.2007; Blackwell
• Subjects: Adenosine Triphosphate - metabolism; allosteric metal modulation; Allosteric Regulation - drug effects; Allosteric Regulation - physiology; Amino acids; Animals; Binding Sites - drug effects; Binding Sites - physiology; Biochemistry; Biological and medical sciences; Cations, Divalent - metabolism; Cations, Divalent - pharmacology; Cell Membrane - drug effects; Cell Membrane - metabolism; Cell receptors; Cell structures and functions; Central nervous system; Central neurotransmission. Neuromudulation. Pathways and receptors; Copper; Copper - metabolism; Copper - pharmacology; copper/zinc modulation; divalent metals; Extracellular Fluid - metabolism; extracellular histidines; Female; Fundamental and applied biological sciences. Psychology; Histidine - metabolism; Hydrogen-Ion Concentration; Inhibitor drugs; Ion Channel Gating - drug effects; Ion Channel Gating - physiology; Magnesium; Magnesium - metabolism; Magnesium - pharmacology; magnesium modulation; Metals - metabolism; Metals - pharmacology; Molecular and cellular biology; Monoamines receptors (catecholamine, serotonine, histamine, acetylcholine); Mutation - genetics; Neurosciences; Oocytes; P2X7 receptor; pH and protons inhibition; Protons; Rats; Receptors, Purinergic P2 - drug effects; Receptors, Purinergic P2 - genetics; Receptors, Purinergic P2 - metabolism; Receptors, Purinergic P2X7; Rodents; Vertebrates: nervous system and sense organs; Xenopus laevis; Zinc; Zinc - metabolism; Zinc - pharmacology; Rat; Amphibia; divalent metals; Germinal cell; extracellular histidines; pH and protons inhibition; Modulation; Proton; Magnesium; Copper; P2X7 receptor; Biological receptor; Alanine; Xenopus laevis; Rodentia; allosteric metal modulation; Salientia; magnesium modulation; P2X7 purinergic receptor; Extracellular; Zinc; copper/zinc modulation; Vertebrata; Mammalia; P2X purinergic receptor; ATP
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2006.04343.x

The P2X7 receptor is a non‐selective cationic channel activated by extracellular ATP, belonging to the P2X receptor family. To assess the role of extracellular histidines on the allosteric modulation of the rat P2X7 receptor by divalent metals (copper, zinc and magnesium) and protons, these amino acid residues were singly substituted for corresponding alanines. Wild‐type and mutated receptors were injected to Xenopus laevis oocytes; metal‐related effects were evaluated by the two‐electrode voltage‐clamp technique. Copper inhibited the ATP‐gated currents with a median inhibitory concentration of 4.4 ± 1.0 µmol/L. The inhibition was non‐competitive and time‐dependent; copper was 60‐fold more potent than zinc. The mutant H267A, resulted in a copper resistant receptor; mutants H201A and H130A were less sensitive to copper inhibition (p < 0.05). The rest of the mutants examined, H62A, H85A, and H219A, conserved the copper‐induced inhibition. Only mutants H267A and H219A were less sensitive to the modulator action of zinc. Moreover, the magnesium‐induced inhibition was abolished exclusively on the H130A and H201A mutants, suggesting that this metal may act at a novel cationic modulator site. Media acidification inhibited the ATP‐gated current 87 ± 3%; out of the six mutants examined, only H130A was significantly less sensitive to the change in pH, suggesting that His‐130 could be involved as a pH sensor. In conclusion, while His‐267 is critically involved in the copper or zinc allosteric modulation, the magnesium inhibitory effects is related to His‐130 and His‐201, His‐130 is involved in proton sensing, highlighting the role of defined extracellular histidines in rat P2X7 receptor allosteric modulation.