Coupling of m2 and m4 muscarinic acetylcholine receptor subtypes to Ca2+-dependent K+ channels in transformed NL308 neuroblastoma x fibroblast hybrid cells

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 251; no. 1332; pp. 215 - 224
• Main Authors: Noda, Mami, Katayama, Morio, Brown, David Anthony, Robbins, Jon, Marsh, Stephen J., Ishizaka, Nobuto, Fukuda, Kazuhiko, Hoshi, Naoto, Yokoyama, Shigeru, Higasida, Haruhiro
• Format: Journal Article
• Language: English
• Published: London The Royal Society 22-03-1993
• ISSN: 0962-8452; 1471-2954
• DOI: 10.1098/rspb.1993.0032

Muscarinic acetylcholine receptor (mAChR) subtype (m1-m4)-specific cDNAs were transfected into NL308 neuroblastoma-fibroblast hybrid cells and clones expressing each of the individual mAChR subtypes m1, m2, m3 and m4 obtained. Acetylcholine increased phosphoinositide (PI) turnover in in m1- and m3-transformed cells, but did not produce detectable changes in m2- and m4-transformed cells. In cells expressing m1 and m3 subtypes, ACh produced an initial outward K+ current, followed by a cationic current. In cells expressing m2 and m4 receptors, only the initial K+ current was detected. The outward currents were associated with a rise in intracellular Ca2+ as measured with Fura-2 or Indo-1, and were inhibited by chelating intracellular Ca2+ with external BAPTA-AM, or by external charybdotoxin or Ba2+: hence they were attributed to the activation of a Ca2+-dependent K+ current. However, the outward current produced in m2- and m4-transformed cells was blocked by pretreatment with 5 ng ml-1 Pertussis toxin (PTX), whereas that in m1- and m3-transformed cells was not. These results suggest that m2- and m4-receptors in transformed NL308 cells coupled to PTX-sensitive G-protein which is capable of mobilizing intracellular Ca2+ and activate Ik(Ca), whereas m1 and m3 receptors activate a similar process through a different, PTX-insensitive G-protein.