Functional and biochemical characterization of central ATP-gated P2x channels

Fast purinergic neurotransmission has recently been shown to be mediated through ionotropic P2X receptors activated by extracellular adenosine 5'-triphosphate (ATP). P2X protein mapping within central nervous system (CNS), P2X channel subunit composition pertaining to relevant native receptor phenotypes, and species-specific differences between mammalian P2X orthologs remain to be investigated.The first manuscript (Le et al., 1998a) reported the regional, cellular, and subcellular localization of P2X4 gene product within adult rat brain and spinal cord structures. P2X4 receptors were shown to be widely expressed on the postsynaptic side throughout the CNS.The second manuscript (Le et al., 1998b) documented a novel P2X receptor phenotype resulting from the heteropolymerization between major central P2X4 and P2X6 subunits. P2X 4+6 heteromultimeric channel phenotypes were characterized by distinct time-dependent protein expression levels and novel pharmacological profiles compared to P2X4 homo-oligomers.The third manuscript (Le et al., 1999) was undertaken based upon similar reasoning as well as experimental strategies as the P2X 4+6 study (Le et al., 1998b). The existence of heteromultimeric P2X1+5 receptors were screened with functional as well as biochemical assays demonstrating that this oligomeric complex gave rise to hybrid properties between homopolymeric P2X1 and P2X 5 subunits. Reciprocal co-purifications between interacting P2X 1 and P2X5 subunits were also demonstrated in this study.The fourth manuscript (Le et al., 1997) reported the molecular cloning of the human ortholog (hP2X5R) of rP2X 5 subunit, which is being the most rare transcript among all reported rat P2X cDNAs to date. hP2X5R subunit was found to be a 422 amino acid-long protein and having 62% homology to rP2X5 receptors.In an effort to contribute to a better assessment of the physiological roles of fast purinergic synaptic signaling (Le et al., 1998a) mediated likely by native receptors generated by heteromultimerization (Le et al., 1998b; Le et al., 1999) while keeping in mind that species-dependent differences between mammalian P2X orthologs (Le et al., 1997) should be taken into account whenever rodent systems would be used for drug screening studies. (Abstract shortened by UMI.