Functional and biochemical evidence for heteromeric ATP-gated channels composed of P2X(1) and P2X(5) subunits

The mammalian P2X receptor gene family encodes two-transmembrane domain non selective cation channels gated by extracellular ATP, Anatomical localizati on data obtained by in situ hybridization and immunocytochemistry have show n that neuronal P2X subunits are expressed in specific but overlapping dist ribution patterns, Therefore, the native ionotropic ATP receptors diversity most likely arises from interactions between different P2X subunits that g enerate hetero-multimers phenotypically distinct from homomeric channels, R at P2X(1) and P2X(5) mRNAs are localized within common subsets of periphera l and central sensory neurons as well as spinal motoneurons. The present st udy demonstrates a functional association between P2X(1) and P2X(5) subunit s giving rise to hybrid ATP-gated channels endowed with the pharmacology of P2X(1) and the kinetics of P2X(5). When expressed in Xenopus oocytes, hete ro-oligomeric: P2X(1+5) ATP receptors were characterized by slowly desensit izing currents highly sensitive to the agonist alpha,beta-methylene ATP (EC 50 = 1.1 mu M) and to the antagonist trinitrophenyl ATP (IC50 = 64 nM), obs erved with neither P2X(1) nor P2X(5) alone. Direct physical evidence for P2 X(1+5) co-assembly was provided by reciprocal subunit-specific co-purificat ions between epitope-tagged P2X(1) and P2X(5) subunits transfected in HEK-2 93A cells.