THE 2RD INTRACELLULAR DOMAIN OF THE M3-MUSCARINIC-RECEPTOR DETERMINESCOUPLING TO CALCIUM INFLUX IN TRANSFECTED CHINESE-HAMSTER OVARY CELLS

The m2 and m3 muscarinic acetylcholine receptors were expressed in CHO cells and were shown to couple to the release of calcium from intrace llular stores, The m3 receptor, but not the m2 receptor, also coupled to calcium influx, Chimeric m2/m3 receptors were used to determine the structural domain of the m3 receptor linked to the regulation of calc ium influx. It was found that the third intracellular loop of m3 recep tor plays a fundamental role in regulating Ca2+ influx predicted to oc cur through Ca2+ channels located in the plasma membrane in CHO cells.