title: Dissecting individual current components of co-expressed human P2X1 and P2X7 receptors.
abstract: Purinergic P2X(1) and P2X(7) receptors are co-expressed in several cell types such as lymphocytes or epithelial cells. Here we examined whether these two P2X subtypes interact with each other in a manner that results in a mutual alteration of their electrophysiologic behaviour. Furthermore, since specific pharmacological tools are needed to assign distinct effects to a particular receptor subtype in native cells, we assessed a series of compounds for their capacity to separate individual current components in cells that co-expressed both receptor subtypes. In Xenopus oocytes, co-expression neither changed the time courses of activation, desensitization and deactivation nor recovery from desensitization when compared to oocytes that express either hP2X(1) or hP2X(7) receptors alone. A selective activation of hP2X(7) receptors was achieved with benzoyl-benzoyl-ATP, which did not activate P2X(1) receptor currents. P2X(7) receptors could also be selectively activated by ATP when co-applied with 1 microM NF449, a suramin derivative, which is 100,000 fold more potent in blocking P2X(1) than P2X(7) receptors. alphabeta-methylene-ATP, a reportedly hP2X(1) receptor-specific agonist, as well as oxidized-ATP, brilliant blue or KN62, reported hP2X(7) receptor antagonists, were found to be ineffective in separating hP2X(1) receptor current from the P2X(7) current. The best way for a selective activation of the hP2X(1) receptor component in cells co-expressing the P2X(7) receptor is the application of low concentrations of ATP (< 1 microM) or the addition of Mg2+ when using higher concentrations of ATP.
authors.affiliation: Julius-Bernstein-Institute for Physiology, Martin-Luther-University Halle, Magdeburger Strasse 6, D-06097 Halle/Saale, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Seyffert
authors.forename: Günther
authors.initials: G
authors.lastname: Schmalzing
authors.forename: Fritz
authors.initials: F
authors.lastname: Markwardt
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001557:Benzenesulfonates / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058469:Receptors, Purinergic P2X; D058486:Receptors, Purinergic P2X7; D013498:Suramin / Q000031:analogs & derivatives / Q000494:pharmacology; D013997:Time Factors; D014982:Xenopus laevis
chemical_list: D001557:Benzenesulfonates; C546468:P2RX7 protein, human; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D058486:Receptors, Purinergic P2X7; D013498:Suramin; C063302:KN 62; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000255:Adenosine Triphosphate; C006796:brilliant blue; D008274:Magnesium