The first transmembrane domain of the P2X receptor subunit participates in the agonist-induced gating of the channel.
Based on pharmacological properties, the P2X receptor family can be subdivided into those homo-oligomers that are sensitive to the ATP analog alphabeta-methylene ATP(alphabetameATP) (P2X(1) and P2X(3)) and those that are not (P2X(2), P2X(4), P2X(5), P2X(6), and P2X(7)). We exploited this dichotomy through the construction of chimeric receptors and site-directed mutagenesis in order to identify domains responsible for these differences in the abilities of extracellular agonists to gate P2X receptors. Replacement of the extracellular domain of the alphabetameATP-sensitive rat P2X(1) subunit with that of the alphabetameATP-insensitive rat P2X(2) subunit resulted in a receptor that was still alphabetameATP-sensitive, suggesting a non-extracellular domain was responsible for the differential gating of P2X receptors by various agonists. Replacement of the first transmembrane domain of the rat P2X(2) subunit with one from an alphabetameATP-sensitive subunit (either rat P2X(1) or P2X(3) subunit) converted the resulting chimera to alphabetameATP sensitivity. This conversion did not occur when the first transmembrane domain came from a non-alphabetameATP-sensitive subunit. Site-directed mutagenesis indicated that the C-terminal portion of the first transmembrane domain was important in determining the agonist selectivity of channel gating for these chimeras. These results suggest that the first transmembrane domain plays an important role in the agonist operation of the P2X receptor.
Haines
W R
WR
Department of Pharmacological and Physiological Sciences, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA.
Migita
K
K
Cox
J A
JA
Egan
T M
TM
Voigt
M M
MM
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D021122:Protein Subunits; D058910:Purinergic P2 Receptor Agonists; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000737:chemistry* / Q000502:physiology*; D058469:Receptors, Purinergic P2X; D058477:Receptors, Purinergic P2X3; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
C546410:P2rx3 protein, rat; D021122:Protein Subunits; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D058477:Receptors, Purinergic P2X3; D011993:Recombinant Fusion Proteins; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate