The human P2X4 receptor gene is alternatively spliced

ATP acts as a fast excitatory neurotransmitter by binding to a large family of membrane proteins, P2X receptors, that have been shown to be ligand-gated, non-selective cation channels. We report the cloning of a full-length and alternatively spliced form of the human P2X(4) gene. Clones were identified from a human stomach cDNA library using a rat P2X(4) probe. Nucleotide sequence analysis of positive clones identified the full-length human P2X(4) cDNA, which codes for a 388-residue protein that is highly homologous (82 %) to the rat gene, and an alternatively spliced cDNA. In the alternatively spliced cDNA, the 5'-untranslated region and the first 90 amino acids in the coding region of full-length human P2X(4) are replaced by a 35 amino acid coding sequence that is highly homologous with a region of chaparonin proteins in the hsp-90 family. The open reading frames of the full-length and splice variant clones were confirmed by in vitro translation. Northern analysis indicated expression of the full-length P2X(4) message in numerous human tissues including smooth muscle, heart, and skeletal muscles. Alternatively spliced RNAs were identified in smooth muscle and brain by RT-PCR and confirmed by RNAse protection assays using a 710 bp anti-sense RNA probe that spanned the alternatively spliced and native P2X(4) regions. Injection of full-length, but not alternatively spliced, cRNA into Xenopus oocytes resulted in the expression of ATP gated non-selective cation currents. (C) 1998 Elsevier Science B.V.