Characterization and expression of ATP P2X4 receptor from embryonic chick skeletal muscle

✍ Scribed by Xuenong Bo; Min Liu; Ralf Schoepfer; Geoffrey Burnstock

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 301 KB
• Volume: 53
• Category: Article
• ISSN: 0272-4391
• DOI: 10.1002/ddr.1165

✦ Synopsis

Previous pharmacological experiments have indicated the existence of ATP P2X receptors in chick embryonic skeletal muscles. In this study we cloned a P2X 4 -like cDNA encoding a protein of 385 amino acids, which shares 75% and 76% identity with rat and human P2X 4 receptors, respectively. Functional studies of this cP2X 4 receptor expressed in Xenopus oocytes showed that ATP induced a fast inward current, which was partially desensitized upon prolonged application of ATP. The ATP-induced currents were concentration-dependent, with an EC 50 of 9.5 µM. Adenosine 5′-O-(thio)triphosphate and 2-methylthioATP very weak agonists. α,β-methyleneATP was almost inactive. In contrast to their potentiating effects on recombinant rat P2X 4 receptors, both suramin and pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid partially blocked ATP-induced currents. TrinitrophenylATP was able to block ATP-induced response completely, with an IC 50 of 4.7 µM. Northern blot and RT-PCR analysis showed that cP2X 4 mRNAs were mainly expressed in skeletal muscle, brain, and gizzard of day 10 chick embryos. Lower levels of expression were also detected in liver, heart, and retina. Whole-mount in situ hybridization showed that cP2X 4 mRNAs were expressed in the brain, spinal cord, notochord, gizzard, and skeletal muscle. The physiological functions of cP2X 4 receptors in embryonic skeletal muscle remain unclear at present. Drug Dev. Res. 53:22-28, 2001.