Sun B, Li J, Okahara K, Kambayashi J
Department of Thrombosis and Vascular Biology, Maryland Research Laboratories, Otsuka America Pharmaceutical, Inc., Rockville, Maryland 20850, USA.
J Biol Chem. 1998 May 8;273(19):11544-7. doi: 10.1074/jbc.273.19.11544.
ADP is an important physiological platelet agonist. The molecular identity of the ADP receptor(s) in human platelets, however, is still unclear. Although P2T purinoceptor was believed to be the ligand-gated cation channel for ADP in human platelets, recent patch clamp studies now suggest it is P2X1 type. In the present study, we have cloned a cDNA encoding a P2X1 purinoceptor from human platelets using degenerate reverse transcription and polymerase chain reaction. Northern blotting with a P2X1-specific probe revealed a band of 1.8 kilobases in human platelets as well as in several megakaryoblastic cell lines. 1321N1 human astrocytoma cells expressing the cloned P2X1 cDNA exhibited both ATP- and ADP-stimulated Ca2+ influx that could be blocked by the purinoceptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid and suramin. Additionally, a polyclonal antibody raised against glutathione-S-transferase-P2X1 fusion peptide reacted with a 70-kDa band on Western blot of human platelets. It is therefore concluded that functional P2X1 purinoceptors are present in human platelets.
