P2X1 receptor activation in HL60 cells

Recent cloning of the human P2X1 receptor revealed high levels of its messenger RNA in differentiated promyelocytes (HL60 cells). We found expression of P2X1 receptor protein in HL60 cells by radioligand binding, by immunohistochemistry, using a receptor specific antibody, and by electrophysiology. The currents elicited by adenosine triphosphate (ATP) had the expected properties of P2X1 receptors (rapid desensitization, mimicked by alpha,beta-methylene-ATP). However, these currents were only observed in cells that were pretreated with apyrase, which destroys extracellular ATP, or with suramin, a P2X receptor antagonist. This implies that HL60 cells release ATP, which chronically desensitizes the receptor. ATP release was detected by direct measurement, using the luciferin-luciferase assay. It is concluded that functional P2X1 receptors are present in the membrane of differentiated HL60 cells.