A C-terminal lysine that controls human P2X4 receptor desensitization.
Receptor desensitization can determine the time course of transmitter action and profoundly alter sensitivity to drugs. Among P2X receptors, ion currents through homomeric P2X4 receptors exhibit intermediate desensitization when compared with P2X1 and P2X3 (much faster) and P2X2 and P2X7 (slower). We recorded membrane currents in HEK293 cells transfected to express the human P2X4 receptor. The decline in current during a 4-s application of ATP (100 microm) was about 30%; this was not different during whole-cell or perforated patch recording. Alanine-scanning mutagenesis of the intracellular C terminus identified two positions with much accelerated desensitization kinetics (Lys373: 92% and Tyr374: 74%). At position 373, substitution of Arg or Cys also strongly accelerated desensitization: however, in the case of K373C the wild-type phenotype was fully restored by adding ethylammonium methanethiosulfonate. At position 374, phenylalanine could replace tyrosine. These results indicate that wild-type desensitization properties requires an aromatic moiety at position 374 and an amino rather than a guanidino group at position 373. These residues lie between previously identified motifs involved in membrane trafficking (YXXXK and YXXGL) and implicates the C-terminal also in rearrangements leading to channel closing during the presence of agonist.
Faculty of Life Sciences, Michael Smith Building, University of Manchester, Manchester, M13 9PT, United Kingdom. Samuel.fountain@manchester.ac.uk
Samuel J
SJ
Fountain
R Alan
RA
North
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D002460:Cell Line; D006801:Humans; D066298:In Vitro Techniques; D008239:Lysine / Q000737:chemistry; D008564:Membrane Potentials / Q000187:drug effects; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D018048:Receptors, Purinergic P2 / Q000737:chemistry* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D058848:Receptors, Purinergic P2X4; D011994:Recombinant Proteins / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D014162:Transfection
C548226:P2RX4 protein, human; D018048:Receptors, Purinergic P2; D058848:Receptors, Purinergic P2X4; D011994:Recombinant Proteins; D000255:Adenosine Triphosphate; D008239:Lysine