Characterization of voltage-dependent gating of P2X2 receptor/channel

The role of a voltage-dependent gate of recombinant P2X2 receptor/channel was investigated in Xenopus oocytes. When a voltage step to −110 mV was applied from a holding potential of −50 mV, a gradual increase was observed in current evoked by 30 μM ATP. Contribution of this voltage-dependent component to total ATP-evoked current was greater when the current was evoked by lower concentrations of ATP. The voltage-dependent gate closed upon depolarization, and half the gates were closed at −80 mV. On the other hand, a potential at which half the gates opened was about −30 mV or more positive, which was determined using a series of hyperpolarization steps. The results of the present study suggest that the voltage-dependent gate behavior of P2X2 receptor is not due to simple activation and deactivation of a single gate, but rather due to transition from a low to a high ATP affinity state.