title: Retention of a new-defined intron changes pharmacology and kinetics of the full-length P2X2 receptor found in myenteric neurons of the guinea pig.
abstract: P2X2 plays an important role in ATP signaling in guinea pig myenteric plexus. Here, we cloned and characterized three P2X2 isoforms expressed in myenteric neurons. RT/PCR was used to amplify the cDNA of P2X2 variants. These were expressed in Xenopus oocytes, and nucleotide-induced membrane currents were recorded with the two-electrode voltage clamp technique. Three P2X2 cDNAs were identified in myenteric single neurons, named P2X2-1, P2X2-2 and P2X2-4. Based on the analysis of the structural organization of these variants we predicted that P2X2-2 is the fully processed variant, which lead us to propose a new exon-intron arrangement of P2X2 receptor gene with 12 exons and 11 introns. In agreement with this new model, the intron 11 is retained in P2X2-1 and P2X2-4 variants by alternative splicing. Expression of P2X2-1, P2X2-2 and P2X2-4 were found in 92, 42 and 37%, respectively, out of 40 analyzed single neurons. P2X2-4 does not form functional channels, and homomeric channels formed by P2X2-1 and P2X2-2 have different pharmacological profile. Thus, the former receptor is more sensitive to ATP, BzATP, and PPADS, whereas, suramin inhibited both receptors in a biphasic- and monophasic-manner, respectively. α,β-meATP has very low efficacy on either channel. Furthermore, ionic currents mediated by P2X2-1 have slower desensitization than P2X2-2. These results indicate that P2X2-1 was the most common P2X2 transcript in myenteric neurons and displays significant phenotypical changes implicating that retention of the intron 11 plays a major role in ATP signaling in the intestinal myenteric plexus.
authors.affiliation: División de Biología Molecular, Instituto Potosino de Investigación Científica y Tecnológica-IPICYT, Camino a la Presa San José 2055, Col. Lomas 4a Sección, CP78216 San Luis Potosí, SLP, Mexico.
authors.forename: A
authors.initials: A
authors.lastname: Liñan-Rico
authors.forename: J
authors.initials: J
authors.lastname: Jaramillo-Polanco
authors.forename: R
authors.initials: R
authors.lastname: Espinosa-Luna
authors.forename: J F
authors.initials: JF
authors.lastname: Jiménez-Bremont
authors.forename: L
authors.initials: L
authors.lastname: Liñan-Rico
authors.forename: L M
authors.initials: LM
authors.lastname: Montaño
authors.forename: C
authors.initials: C
authors.lastname: Barajas-López
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D055724:Electrophysiological Phenomena; D005091:Exons / Q000235:genetics / Q000502:physiology; D005260:Female; D006168:Guinea Pigs; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism; D007438:Introns / Q000187:drug effects* / Q000235:genetics*; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D009197:Myenteric Plexus / Q000166:cytology / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects*; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms; D060888:Real-Time Polymerase Chain Reaction; D058476:Receptors, Purinergic P2X2 / Q000187:drug effects* / Q000235:genetics*; D014982:Xenopus laevis
chemical_list: D018076:DNA, Complementary; D020033:Protein Isoforms; D058476:Receptors, Purinergic P2X2