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ATP-dependent activation of atrial muscarinic K+channels in the absence of agonist and G-nucleotides

✍ Scribed by Hein Heidbüchel; Geert Callewaert; Johan Vereecke; Edward Carmeliet

Publisher
Springer
Year
1990
Tongue
English
Weight
302 KB
Volume
416
Category
Article
ISSN
0031-6768

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✦ Synopsis

While opening of cardiac muscarinic K+ channels is mediated by a guanine nucleotide-binding protein, GK, and normally requires both ACh and cytosolic GTP, we demonstrate that in the absence of agonist and G-nucleotides guinea-pig atrial muscarinic K+ channels are activated by cytosolic ATP (K50 = 224 microM). This activation involves a phosphorylating reaction and is most probably related to a transphosphorylation by a nucleoside diphosphate kinase (NDPK) from ATP to GK-bound GDP. This ATP-induced response is completely inhibited by nanomolar concentrations of GDP or GTP, suggesting a G-nucleotide specific binding site on NDPK.

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