Neuropeptide Y2-type receptor-mediated activation of large-conductance Ca(2+)-sensitive K+ channels in a human neuroblastoma cell line

Pflugers Arch. 1995 Aug;430(4):534-40. doi: 10.1007/BF00373890.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / pharmacology
  • Brain Neoplasms / metabolism*
  • Calcium / physiology*
  • Electrophysiology
  • GTP-Binding Proteins / metabolism
  • Guanosine Diphosphate / analogs & derivatives
  • Guanosine Diphosphate / pharmacology
  • Humans
  • Inosine Triphosphate / pharmacology
  • Inositol 1,4,5-Trisphosphate / pharmacology
  • Ionomycin / pharmacology
  • Ionophores / pharmacology
  • Neuroblastoma / metabolism*
  • Patch-Clamp Techniques
  • Potassium Channels / metabolism*
  • Receptors, Neuropeptide Y / metabolism*
  • Thionucleotides / pharmacology
  • Tumor Cells, Cultured

Substances

  • Ionophores
  • Potassium Channels
  • Receptors, Neuropeptide Y
  • Thionucleotides
  • Inosine Triphosphate
  • Guanosine Diphosphate
  • Ionomycin
  • guanosine 5'-O-(2-thiodiphosphate)
  • Inositol 1,4,5-Trisphosphate
  • Adenosine Triphosphate
  • GTP-Binding Proteins
  • Calcium