PT  - JOURNAL ARTICLE
AU  - Gonzalo E. Torres
AU  - William R. Haines
AU  - Terrance M. Egan
AU  - Mark M. Voigt
TI  - Co-Expression of P2X<sub>1</sub> and P2X<sub>5</sub> Receptor Subunits Reveals a Novel ATP-Gated Ion Channel
AID  - 10.1124/mol.54.6.989
DP  - 1998 Dec 01
TA  - Molecular Pharmacology
PG  - 989--993
VI  - 54
IP  - 6
4099  - http://molpharm.aspetjournals.org/content/54/6/989.short
4100  - http://molpharm.aspetjournals.org/content/54/6/989.full
SO  - Mol Pharmacol1998 Dec 01; 54
AB  - P2X receptors are a family of ion channels gated by extracellular ATP. Each member of the family can form functional homomeric channels, but only P2X2 and P2X3 have been shown to combine to form a unique heteromeric channel. Data from in situhybridization studies suggest that P2X1 and P2X5 may also co-assemble. In this study, we tested this hypothesis by expressing recombinant P2X1 and P2X5 receptor subunits either individually or together in human embryonic kidney 293 cells. In cells expressing the homomeric P2X1 receptor, 30 μm α,β-methylene ATP (α,β-me-ATP) evoked robust currents that completely desensitized in less than 1 sec, whereas α,β-me-ATP failed to evoke current in cells expressing the homomeric P2X5 receptor. By contrast, α,β-me-ATP evoked biphasic currents with a pronounced nondesensitizing plateau phase in cells that co-expressed both subunits. Further, the EC50 for α,β-me-ATP was greater in cells expressing both P2X1 and P2X5 than in cells expressing P2X1 alone (5 and 1.6 μm, respectively). Heteromeric assembly was confirmed using a co-immunoprecipitation assay of epitope-tagged P2X1 and P2X5 subunits. In summary, this study provides biochemical and functional evidence of a novel channel formed by P2X subunit heteropolymerization. This finding suggests that heteromeric subunit assembly constitutes an important mechanism for generating functional diversity of ATP-mediated responses.