Differential coupling of muscarinic receptors to Ca2+ mobilization and cyclic AMP in SH-SY5Y and IMR 32 neuroblastoma cells.
Muscarinic receptor-linked Ca2+ mobilization and changes in cyclic AMP were studied in SH-SY5Y and IMR 32 human neuroblastoma cell lines. Muscarinic agonists acetylcholine, carbachol, methacholine and muscarine induced an increase in cytosolic free Ca2+ in a pertussis toxin (100 ng/ml)-insensitive manner in both cell lines. The ED50 values in IMR 32 cells (8-98 microM) were one order of magnitude higher than in SH-SY5Y cells (0.3-1.6 microM). Oxotremorine and pilocarpine failed to mobilize Ca2+ in IMR 32 cells. Pirenzepine antagonized carbachol-induced Ca2+ mobilization in SH-SY5Y cells with a Ki value in the range of 150-189 nM whereas the corresponding values in IMR 32 cells were 24-28 nM. Atropine inhibited a carbachol-stimulated increase in cytosolic Ca2+ with an equal potency in both cell lines (Ki 2-3 nM). Carbachol stimulated cyclic AMP (cAMP) accumulation in SH-SY5Y cells in a pertussis toxin-insensitive manner. In IMR 32 cells carbachol inhibited prostaglandin E1-stimulated cAMP accumulation. Treatment of IMR 32 cells with pertussis toxin abolished the inhibition of stimulated cAMP accumulation. These results suggest that in SH-SY5Y cells the M3 muscarinic receptor couples to both Ca2+ mobilization and stimulation of cAMP accumulation. In IMR 32 cells the M1 receptor seems to couple to Ca2+ mobilization whereas the inhibition of stimulated cAMP accumulation is coupled to a non-M1 subtype by an inhibitory G-protein.
Heikkilä
J
J
Department of Biochemistry and Pharmacy, Abo Akademi University, Turku, Finland.
Jansson
C
C
Akerman
K E
KE
D000109:Acetylcholine / Q000494:pharmacology; D000527:Alprostadil / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D006801:Humans; D016210:Methacholine Chloride / Q000494:pharmacology; D009116:Muscarine / Q000494:pharmacology; D009447:Neuroblastoma / Q000378:metabolism*; D037342:Pertussis Toxin; D010890:Pirenzepine / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D011976:Receptors, Muscarinic; D010566:Virulence Factors, Bordetella; D016210:Methacholine Chloride; D010890:Pirenzepine; D001285:Atropine; D009116:Muscarine; D002217:Carbachol; D000242:Cyclic AMP; D037342:Pertussis Toxin; D000527:Alprostadil; D000109:Acetylcholine; D002118:Calcium