SEARCH

SEARCH BY CITATION

Keywords:

  • ATP;
  • Ca2+-activated K+ current;
  • Cl conductance;
  • P2X7 receptor;
  • Schwann cell

Abstract

Extracellular ATP, by acting on P2 purinergic receptors, is a potent mediator of cell-to-cell communication both within and between the nervous and the immune systems. We show here by patch-clamp recording, fluorescent dye uptake and immunocytochemistry that, in cultured mouse Schwann cells, ATP activates a P2X7 receptor associated with three different ionic conductances. In control conditions, ATP activated an inward current (IATP) with a low potency (EC50, 7.2 mm). Replacing ATP either by the ATP analogue 2′,3′-O-(4-benzoyl-4-benzoyl)-ATP (BzATP) or by the tetraacidic form ATP4– potentiated the inward current (ATP4– EC50, 375 µm). ATP and BzATP currents were strongly reduced by periodate oxidized ATP (oATP), an antagonist of P2X7 receptors. IATP was a mixed current composed of a nonselective cationic conductance, a cationic conductance selective for K+ and an anionic conductance selective for Cl. The activation of the K+ conductance was dependent on an influx of Ca2+, and was blocked by charybdotoxin (ChTX) and tetraethylammonium (TEA), two potent antagonists of large conductance Ca2+-activated K+ channels (BK channels). The activation of the Cl conductance was insensitive to Ca2+ but required the presence of K+. Total removal of K+ blocked both the Ca 2+-activated K+ conductance and the Cl conductance, unveiling the P2X7 nonselective cationic conductance. The P2X7 receptor was localized by immunocytochemistry using a polyclonal antibody, anti-P2X7, whilst its expression and functionality were both detected by the uptake of Lucifer Yellow. This receptor could regulate the synthesis and the release of cytokines by Schwann cells during pathophysiological events.