Different Sensitivities to pH of ATP-Induced Currents at Four Cloned P2X Receptors

Abstract

Stoop, Ron, Annmarie Surprenant, and R. Alan North. Different sensitivities to pH of ATP-induced currents at four cloned P2X receptors. J. Neurophysiol. 78: 1837–1840, 1997. The effect of changing extracellular pH was studied on the currents induced by ATP or αβ-methylene-ATP in HEK293 cells transfected with different P2X receptor subunits. In cells expressing P2X 1, P2X 3, or P2X 4 receptors, the effect of ATP was decreased by acidification. In cells expressing P2X 2 receptors, acidification increased the ATP-induced current; this effect was also seen in cells expressing heteromeric P2X 2 and P2X 3 receptors. At P2X 2 receptors, acidification caused a leftward shift in the ATP concentration-response curve, without change in maximum; the pK a for this effect was 7.3. At P2X 4 receptors, acidification caused a rightward shift in the ATP concentration-response curve, without change in the maximum; the pK a for this effect was 6.8. The pH dependence of the action of ATP should be taken into account in studies of synaptic transmission, and it may provide a further tool to assign molecular identity to P2X receptors expressed by brain neurons.