P2X2 and P2X5 subunits define a new heteromeric receptor with P2X7-like properties

Abstract

Ligand-gated ion channels are prototypic oligomeric membrane proteins whose stoichiometry determines their functional properties and subcellular localization. Deciphering the quaternary structureofsuch protein complexesis an arduous task and usually requires the combination of multiple approaches. ATP-gated P2X receptors are formed by the association of three subunits, but the quaternary arrangement of the seven P2X subunits at the plasma membrane remains poorly characterized. By combining bioluminescence resonance energy transfer, bifunctional fluorescence complementation and protein biochemistry, we developed an experimental approach that allows precise determinationofrat P2X receptor quaternary assembly. Wefound that P2X5 subunits associate with P2X1, P2X2, and P2X4 subunits. We demonstrate that P2X5 and P2X2 subunits interact to form as yet uncharacterized heteromeric receptors with alternate stoichiometries, both present at the plasma membrane. P2X2/5 receptors display functional properties suchaspore dilatation, membrane blebbing, and phosphatidylserine exposure that were previously thought to be characteristic hallmarksof the P2X7 receptor. Inmouse,P2X2 andP2X5subunitscolocalizeandphysicallyinteractinspecific neuronalpopulations suggestingthatother P2Xreceptors might contribute to cellular responses typically attributed to P2X7 receptor. © 2012 the authors.