Functional relevance of aromatic residues in the first transmembrane domain of P2X receptors.
The functional relevance of aromatic residues in the upper part of the transmembrane domain-1 of purinergic P2X receptors (P2XRs) was examined. Replacement of the conserved Tyr residue with Ala had a receptor-specific effect: the P2X1R was non-functional, the P2X2R, P2X4R, and P2X3R exhibited enhanced sensitivity to ATP and alphabeta-meATP accompanied by prolonged decay of current after washout of agonists, and the P2X7R sensitivity for agonists was not affected, though decay of current was delayed. The replacement of the P2X4R-Tyr42 with other amino acids revealed the relevance of an aromatic residue at this position. Mutation of the neighboring Phe and ipsilateral Tyr/Trp residues, but not the contralateral Phe residue, also affected the P2X2R, P2X3R, and P2X4R function. Double mutation of ipsilateral Tyr42 and Trp46 P2X4R residues restored receptor function, whereas the corresponding P2X2R double mutant was not functional. In contrast, mutation of the contralateral Phe48 residue in the P2X4R-Y42A mutant had no effect. These results indicate that aromatic residues in the upper part of TM1 play important roles in the three-dimensional structure of the P2XRs and that they are required not only for ion conductivity but also for specificity of agonist binding and/or channel gating.
Jindrichova
Marie
M
Department of Cellular and Molecular Neuroendocrinology, Institute of Physiology of the Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Vavra
Vojtech
V
Obsil
Tomas
T
Stojilkovic
Stanko S
SS
Zemkova
Hana
H
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000595:Amino Acid Sequence; D024322:Amino Acids, Aromatic / Q000235:genetics / Q000378:metabolism*; D001703:Biophysics; D002461:Cell Line, Transformed; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D016296:Mutagenesis / Q000235:genetics; D018408:Patch-Clamp Techniques / Q000379:methods; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D011487:Protein Conformation; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D018048:Receptors, Purinergic P2 / Q000145:classification / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014162:Transfection / Q000379:methods
D024322:Amino Acids, Aromatic; D018048:Receptors, Purinergic P2; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate