P2X₄: An ATP-activated ionotropic receptor cloned from rat brain

Extracellular ATP exerts pronounced biological actions in virtually every organ or tissue that has been studied. In the central and peripheral nervous system, ATP acts as a fast excitatory transmitter in certain synaptic pathways [Evans, R. J., Derkach, V. and Surprenant, A. (1992) Nature (London) 357, 503-505; Edwards, F. A., Gigg, A. J. and Colquhoun, D. (1992) Nature (London) 359, 144-147]. Here, we report the cloning and characterization of complementary DNA from rat brain, encoding an additional member (P2X₄) of the emerging multigenic family of ligand-gated ATP channels, the P2X receptors. Expression in Xenopus oocytes gives an ATP-activated cation- selective channel that is highly permeable to Ca²⁺ and whose sensitivity is modulated by extracellular Zn²⁺. Surprisingly, the current elicited by ATP is almost insensitive to the common P2X antagonist suramin. In situ hybridization reveals the expression of P2X₄ mRNA in central nervous system neurons. Northern blot and reverse transcription-PCR (RT-PCR) analysis demonstrate a wide distribution of P2X₄ transcripts in various tissues, including blood vessels and leukocytes. This suggests that the P2X₄ receptor might mediate not only ATP-dependent synaptic transmission in the central nervous system but also a wide repertoire of biological responses in diverse tissues.