Glu496Ala polymorphism of human P2X7 receptor does not affect its electrophysiological phenotype.
A glutamate to alanine exchange at amino acid position 496 of the human P2X(7) receptor was recently shown to be associated with a loss of function in human B lymphocytes in terms of ATP-induced ethidium(+) uptake, Ba(2+) influx, and induction of apoptosis (Gu BJ, Zhang WY, Worthington RA, Sluyter R, Dao-Ung P, Petrou S, Barden JA, and Wiley JS. J Biol Chem 276: 11135-11142, 2001). Here we analyzed the effect of the Glu(496) to Ala exchange on the channel properties of the human P2X(7) receptor expressed in Xenopus oocytes with the two-microelectrode voltage-clamp technique. The amplitudes of ATP-induced whole cell currents characteristic of functional expression, kinetic properties including ATP concentration dependence, and permeation behavior were not altered by this amino acid exchange. Also in HEK293 cells, the Ala(496) mutant mediated typical P2X(7) receptor-dependent currents like the parent Glu(496) hP2X(7) receptor. Because the function of the P2X(7) receptor as an ATP-gated channel for small cations including Ba(2+) remained unaffected by this mutation, we conclude that Glu(496) plays a critical role in pore formation but does not determine the ion channel properties of the human P2X(7) receptor.
Boldt
Wolfgang
W
Julius-Bernstein-Institut für Physiologie, Martin-Luther-Universität Halle-Wittenberg, D-06097 Halle/Saale, Germany.
Klapperstück
Manuela
M
Büttner
Cora
C
Sadtler
Sven
S
Schmalzing
Günther
G
Markwardt
Fritz
F
D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000409:Alanine / Q000235:genetics*; D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D002412:Cations / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005057:Eukaryotic Cells / Q000378:metabolism*; D005260:Female; D005973:Glutamine / Q000235:genetics*; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000235:genetics; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D009154:Mutation / Q000187:drug effects / Q000235:genetics*; D009865:Oocytes; D010641:Phenotype; D011110:Polymorphism, Genetic / Q000187:drug effects / Q000235:genetics*; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7; D014982:Xenopus laevis
D002412:Cations; D007473:Ion Channels; C546468:P2RX7 protein, human; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D005973:Glutamine; D000255:Adenosine Triphosphate; D000409:Alanine