Neuropeptide Y2-type receptor-mediated activation of large-conductance Ca(2+)-sensitive K+ channels in a human neuroblastoma cell line.
We have proposed recently that a pertussistoxin-insensitive Ca2+ influx stimulated by Y2-type receptor activation in CHP-234 human neuroblastoma cells underlies increases in intracellular free Ca2+ concentration ([Ca2+]i) induced by neuropeptide Y (NPY), which were strictly dependent on extracellular Ca2+ and independent of internal Ca2+ stores. We describe here the actions of NPY in these same cells, using the activity of Ca(2+)-activated K+ channels as an indicator of [Ca2+]i. The elementary slope conductance of these channels was 110 +/- 3 pS (with an asymmetrical K+ gradient), their activity was greatly increased by application of ionomycin, and they were reversibly blocked by 1 mM tetraethylammonium (TEA) and 100 nM charybdotoxin. Application of 100 nM NPY, in the presence but not in the absence of extracellular Ca2+, increased the channel open probability. ATP applied in the absence of external Ca2+ caused rises both in channel open probability and [Ca2+]i. Inositol trisphosphate production was stimulated by ATP but not by NPY. In outside-out patches, NPY increased channel open probability, indicating that NPY-associated Ca2+ influx does not require all the intracellular machinery present in intact cells. Channel activation by NPY was unaffected by the replacement of guanosine 5'-triphosphate (GTP) by (guanosine 5'-O-(2-thiodiphosphate) (GDP[ beta S]), a non-hydrolysable GDP analogue, in the pipette internal solution, consistent with the lack of involvement of G-proteins in the coupling of Y2-type receptors to Ca2+ influx in CHP-234 cells.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D001932:Brain Neoplasms / Q000378:metabolism*; D002118:Calcium / Q000502:physiology*; D004594:Electrophysiology; D019204:GTP-Binding Proteins / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D007293:Inosine Triphosphate / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D009447:Neuroblastoma / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism*; D017476:Receptors, Neuropeptide Y / Q000378:metabolism*; D013873:Thionucleotides / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D007476:Ionophores; D015221:Potassium Channels; D017476:Receptors, Neuropeptide Y; D013873:Thionucleotides; D007293:Inosine Triphosphate; D006153:Guanosine Diphosphate; D015759:Ionomycin; C023427:guanosine 5'-O-(2-thiodiphosphate); D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D019204:GTP-Binding Proteins; D002118:Calcium