title: P2X receptor intermediate activation states have altered nucleotide selectivity.
abstract: Purinergic P2X receptors are widely distributed in the nervous system and are known to play roles in primary afferent transmission and central respiratory regulation. They are trimeric membrane proteins, with the extracellular domain that provides three intersubunit ATP binding sites. We expressed the rat P2X7 receptor in human embryonic kidney cells and measured membrane currents before and after photo-affinity labeling with the agonist 2'(3')-O-(4-benzoylbenzoyl)-ATP (BzATP). After tethering BzATP with ultraviolet light, a persistent current remained after washing out the agonist. Additional current could now be elicited by other nucleotides (CTP and ADP) that are not normally effective as P2X receptor agonists. Similar results were obtained at P2X2 receptors even without previous agonist tethering: exposure to low concentrations of ATP caused the receptor to become sensitive to activation by CTP and ADP. The results show that ATP binding to the first of the three binding sites causes a conformational change to an intermediate closed state that shows increased effectiveness of pyrimidine and diphosphate nucleotide analogs.
authors.affiliation: Faculties of Medical and Human Sciences, and Life Sciences, University of Manchester, Manchester, M13 9PT, United Kingdom.
authors.forename: Liam E
authors.initials: LE
authors.lastname: Browne
authors.forename: R Alan
authors.initials: RA
authors.lastname: North
mesh_terms: D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D049452:Green Fluorescent Proteins / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D009711:Nucleotides / Q000378:metabolism* / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D058920:Purinergic P2X Receptor Antagonists / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D058476:Receptors, Purinergic P2X2 / Q000235:genetics / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7 / Q000235:genetics / Q000378:metabolism*; D013777:Tetrazoles / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D014466:Ultraviolet Rays; D014544:Uridine Triphosphate; D015032:Zinc / Q000494:pharmacology
chemical_list: C523668:3-(5-(2,3-dichlorophenyl)-1H-tetrazol-1-yl)methylpyridine; D009711:Nucleotides; D010975:Platelet Aggregation Inhibitors; D058920:Purinergic P2X Receptor Antagonists; D011725:Pyridines; D058476:Receptors, Purinergic P2X2; D058486:Receptors, Purinergic P2X7; D013777:Tetrazoles; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D015032:Zinc; D014544:Uridine Triphosphate
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