title: Functional interactions between P2X4 and P2X7 receptors from mouse salivary epithelia.
abstract: Mouse parotid acinar cells express P2X4 and P2X7 receptors (mP2X4R and mP2X7R) whose physiological function remains undetermined. Here we show that mP2X4R expressed in HEK-293 cells do not allow the passage of tetraethylammonium (TEA+) and promote little, if any, ethidium bromide (EtBr) uptake when stimulated with ATP or BzATP. In contrast, mP2X7R generates slowly decaying TEA+ current, sustained Na+ current and promotes robust EtBr uptake. However, ATP-activated TEA+ current from acinar cells was unlike that generated by mP2X7R or mP2X4R. Functional interactions between mP2X4R and mP2X7R were investigated in HEK cells co-transfected with different mP2X4 : mP2X7 cDNA ratios and using solutions containing either TEA+ or Na+ ions. Co-expressed channels generated a TEA+ current that displayed faster decay during ATP stimulation than mP2X7R alone. Moreover, cells transfected with a 2 : 1 cDNA ratio displayed decaying kinetics similar to those observed in acinar cells. Concentration-response curves in Na+-containing solutions were constructed for heterologously expressed mP2X4R, mP2X7R and mP2X4R:mP2X7R co-expressions as well as acinar cells. The EC50 values determined were 11, 220, 434 and 442 microM, respectively. Na+ currents generated by expressing mP2X4R or mP2X7R alone were potentiated by ivermectin (IVM). In contrast, IVM potentiation in acinar cells and HEK cells co-expressing P2X4 and P2X7 (1 : 1 or 2 : 1 cDNA ratios) was seen only when the ATP concentration was lowered from 5 to 0.03 mM. Taken together our observations indicate a functional interaction between murine P2X7 and P2X4 receptors. Such interaction might occur in acinar cells to shape the response to extracellular ATP in salivary epithelia.
authors.affiliation: School of Medicine, Universidad Autónoma de San Luis Potosí, San Luis Potosí, SLP, México.
authors.forename: Griselda
authors.initials: G
authors.lastname: Casas-Pruneda
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Reyes
authors.forename: Gabriela
authors.initials: G
authors.lastname: Pérez-Flores
authors.forename: Patricia
authors.initials: P
authors.lastname: Pérez-Cornejo
authors.forename: Jorge
authors.initials: J
authors.lastname: Arreola
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D003627:Data Interpretation, Statistical; D004594:Electrophysiology; D004848:Epithelium / Q000502:physiology; D004996:Ethidium / Q000378:metabolism; D005456:Fluorescent Dyes; D006801:Humans; D007559:Ivermectin / Q000494:pharmacology; D051379:Mice; D010306:Parotid Gland / Q000166:cytology / Q000502:physiology; D018408:Patch-Clamp Techniques; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058848:Receptors, Purinergic P2X4; D058486:Receptors, Purinergic P2X7; D012469:Salivary Glands / Q000502:physiology*; D062687:Sodium Channel Agonists; D015222:Sodium Channels / Q000502:physiology; D014162:Transfection
chemical_list: D005456:Fluorescent Dyes; C548226:P2RX4 protein, human; C546468:P2RX7 protein, human; C548227:P2rx4 protein, mouse; C546469:P2rx7 protein, mouse; D018048:Receptors, Purinergic P2; D058848:Receptors, Purinergic P2X4; D058486:Receptors, Purinergic P2X7; D062687:Sodium Channel Agonists; D015222:Sodium Channels; D007559:Ivermectin; D000255:Adenosine Triphosphate; D004996:Ethidium