A pertussis toxin-insensitive calcium influx mediated by neuropeptide Y2 receptors in a human neuroblastoma cell line.
Stimulation of neuropeptide Y (NPY) Y2 receptors induced an intracellular free Ca2+ ([Ca2+]i) increase in a human neuroblastoma cell line, CHP-234. When NPY in a Ca(2+)-free solution was applied, this increase was abolished. Depolarization with high KCl evoked no response, suggesting that the responses were not mediated by voltage-gated Ca2+ channels. There was no evidence that the NPY response consisted of a capacitative Ca2+ entry sensitive to internal Ca2+ store levels. The [Ca2+]i elevation was diminished by Ni2+, a blocker of Ca2+ entry. Mn2+ induced a quench of the fura-2 fluorescence, which ceased promptly upon the removal of NPY, indicating that Ca2+ entry was linked tightly to receptor activation. Although thapsigargin- and ryanodine-sensitive Ca2+ stores were present, NPY-induced responses were not impaired by pretreatment with either drug. Furthermore, NPY had no effect on the thapsigargin-sensitive store. Pertussis toxin did not affect the NPY-stimulated [Ca2+]i increase, although it abolished the NPY-dependent inhibition of cAMP production. It is concluded that the Y2 receptors couple directly to receptor-operated Ca2+ channels without the involvement of intracellular Ca2+ stores. The results also indicate that Y2 receptors can activate both pertussis toxin-sensitive and -insensitive mechanisms in the same cell.
Lynch
J W
JW
Université Louis Pasteur de Strasbourg, Laboratoire de Pharmacologie Cellulaire et Moleculaire, Centre National de la Recherche Scientifique URA600, Illkirch, France.
Lemos
V S
VS
Bucher
B
B
Stoclet
J C
JC
Takeda
K
K
D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism*; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D006801:Humans; D007700:Kinetics; D008856:Microscopy, Fluorescence; D009447:Neuroblastoma; D009478:Neuropeptide Y / Q000494:pharmacology*; D009532:Nickel / Q000378:metabolism; D037342:Pertussis Toxin; D011189:Potassium Chloride / Q000494:pharmacology; D017476:Receptors, Neuropeptide Y / Q000187:drug effects / Q000502:physiology*; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D013997:Time Factors; D014407:Tumor Cells, Cultured; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D015220:Calcium Channels; D005456:Fluorescent Dyes; D009478:Neuropeptide Y; D017476:Receptors, Neuropeptide Y; D013729:Terpenes; D010566:Virulence Factors, Bordetella; C049925:fura-2-am; D011189:Potassium Chloride; D019284:Thapsigargin; D009532:Nickel; D000242:Cyclic AMP; D037342:Pertussis Toxin; D000252:Calcium-Transporting ATPases; D002118:Calcium; D016257:Fura-2