RGD Reference Report - Sensitization by extracellular Ca(2+) of rat P2X(5) receptor and its pharmacological properties compared with rat P2X(1). - Rat Genome Database

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Sensitization by extracellular Ca(2+) of rat P2X(5) receptor and its pharmacological properties compared with rat P2X(1).

Authors: Wildman, SS  Brown, SG  Rahman, M  Noel, CA  Churchill, L  Burnstock, G  Unwin, RJ  King, BF 
Citation: Wildman SS, etal., Mol Pharmacol 2002 Oct;62(4):957-66.
RGD ID: 727431
Pubmed: (View Article at PubMed) PMID:12237343

The recombinant rat P2X(5) (rP2X(5)) receptor, a poorly understood ATP-gated ion channel, was studied under voltage-clamp conditions and compared with the better understood homomeric rP2X(1) receptor with which it may coexist in vivo. Expressed in defolliculated Xenopus laevis oocytes, rP2X(5) responded to ATP with slowly desensitizing inward currents that, for successive responses, ran down in the presence of extracellular Ca(2+) (1.8 mM). Replacement of Ca(2+) with either Ba(2+) or Mg(2+) prevented rundown, although agonist responses were very small, whereas reintroduction of Ca(2+) for short periods of time (<300 s) before and during agonist application yielded consistently larger responses. Using this Ca(2+)-pulse conditioning, rP2X(5) responded to ATP and other nucleotides (ATP, 2-methylthio-ATP, adenosine-5'-O-(thiotriphosphate), 2'-&-3'-O-(4-benzoylbenzoyl)-ATP, alpha,beta-methylene-ATP, P(1)-P((4))-diadenosine-5'-phosphate, and more) with pEC(50) values within 1 log unit of respective determinations for rP2X(1). Only GTP was selective for rP2X(5), although 60-fold less potent than ATP. At rP2X(5), lowering extracellular pH reduced the potency and efficacy of ATP, whereas extracellular Zn(2+) ions (0.1-1000 microM) potentiated then inhibited ATP responses in a concentration-dependent manner. However, these modulators affected rP2X(1) receptors in subtly different ways-with increasing H(+) and Zn(2+) ion concentrations reducing agonist potency. For P2 receptor antagonists, the potency order at rP2X(5) was pyridoxal-5-phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) > 2',3'-O-(2,4,6-trinitrophenyl)ATP (TNP-ATP) > suramin > reactive blue 2 (RB-2) > diinosine pentaphosphate (Ip(5)I). In contrast, the potency order at rP2X(1) was TNP-ATP = Ip(5)I > PPADS > suramin = RB-2. Thus, the Ca(2+)-sensitized homomeric rP2X(5) receptor is similar in agonist profile to homomeric rP2X(1)-although it can be distinguished from the latter by GTP agonism, antagonist profile, and the modulatory effects of H(+) and Zn(2+) ions.


Gene-Chemical Interaction Annotations    
nucleoside pentaphosphate  (EXP,ISO)
purinergic receptor P2X antagonist  (EXP,ISO)
Reactive blue 2  (EXP,ISO)
suramin  (EXP,ISO)

Gene Ontology Annotations    

Cellular Component

Molecular Function

Objects Annotated

Genes (Rattus norvegicus)
P2rx1  (purinergic receptor P2X 1)
P2rx5  (purinergic receptor P2X 5)

Genes (Mus musculus)
P2rx1  (purinergic receptor P2X, ligand-gated ion channel, 1)
P2rx5  (purinergic receptor P2X, ligand-gated ion channel, 5)

Genes (Homo sapiens)
P2RX1  (purinergic receptor P2X 1)
P2RX5  (purinergic receptor P2X 5)

Additional Information