Browsing by Author "Grauso, M"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Heavy metals modulate the activity of the purinergic P2X4 receptor
    (2005) Coddou, C; Lorca, RA; Acuña-Castillo, C; Grauso, M; Rassendren, F; Huidobro-Toro, JP
    To further characterize the nature of the regulatory metal-binding sites of the rat P2X(4) receptor, several transition heavy metals were tested to examine their ability to mimic the facilitator action of zinc or the inhibitory action of copper. cDNA coding for the rat P2X(4) receptor was injected into Xenopus laevis oocytes; the two-electrode voltage-clamp technique was used to measure and quantify the ATP-evoked currents in the absence or presence of the metals. Cadmium facilitated the ATP-gated currents in a reversible and voltage-independent manner; maximal potentiation occurred within less than 1 min.
  • No Thumbnail Available
    Item
    Histidine 140 plays a key role in the inhibitory modulation of the P2X4 nucleotide receptor by copper but not zinc
    (2003) Coddou, C; Morales, B; González, J; Grauso, M; Gordillo, F; Bull, P; Rassendren, F; Huidobro-Toro, JP
    To elucidate the role of extracellular histidines in the modulation of the rat P2X(4) receptor by trace metals, we generated single, double, and triple histidine mutants for residues 140, 241, and 286, replacing them with alanines. cDNAs for the wild-type and receptor mutants were expressed in Xenopus laevis oocytes and in human embryonic kidney 293 cells and examined by the two electrode and patch clamp techniques, respectively. Whereas copper inhibited concentration-dependently the ATP-gated currents in the wild-type and in the single or double H241A and H286A receptor mutants, all receptors containing H140A were insensitive to copper in both cell systems. The characteristic bell-shaped concentration-response curve of zinc observed in the wildtype receptor became sigmoid in both oocytes and human embryonic kidney cells expressing the H140A mutant; in these mutants, the zinc potentiation was 2.5-4-fold larger than in the wild-type. Results with the H140T and H140R mutants further support the importance of a histidine residue at this position. We conclude that His-140 is critical for the action of copper, indicating that this histidine residue, but not His-241 or His-286, forms part of the inhibitory allosteric metal-binding site of the P2X4 receptor, which is distinct from the putative zinc facilitator binding site.