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The M3 Muscarinic Acetylcholine Receptor Expressed in HEK-293 Cells Signals to Phospholipase D via G12 but Not Gq-type G Proteins

2001; Elsevier BV; Volume: 276; Issue: 4 Linguagem: Inglês

10.1074/jbc.m004957200

1083-351X

Ulrich Rümenapp, Melanie Asmus, Helge Schablowski, Markus Woznicki, Li Han, Karl H. Jakobs, Mercedeh Fahimi-Vahid, Christina Michalek, Thomas Wieland, Martina Schmidt,

Protein Kinase Regulation and GTPase Signaling

The M 3 muscarinic acetylcholine receptor (mAChR) expressed in HEK-293 cells couples to G q and G 12 proteins and stimulates phospholipase C (PLC) and phospholipase D (PLD) in a pertussis toxin-insensitive manner. To determine the type of G protein mediating M 3 mAChR-PLD coupling in comparison to M 3 mAChR-PLC coupling, we expressed various Gα proteins and regulators of the G protein signaling (RGS), which act as GTPase-activating proteins for G q - or G 12 -type G proteins. PLD stimulation by the M 3 mAChR was enhanced by the overexpression of Gα 12 and Gα 13 , whereas the overexpression of Gα q strongly increased PLC activity without affecting PLD activity. Expression of the RGS homology domain of Lsc, which acts specifically on Gα 12 and Gα 13 , blunted the M 3 mAChR-induced PLD stimulation without affecting PLC stimulation. On the other hand, overexpression of RGS4, which acts on Gα q - but not Gα 12 -type G proteins, suppressed the M 3 mAChR-induced PLC stimulation without altering PLD stimulation. We conclude that the M 3 mAChR in HEK-293 cells apparently signals to PLD via G 12 - but not G q -type G proteins and that G protein subtype-selective RGS proteins can be used as powerful tools to dissect the pertussis toxin-resistant G proteins and their role in receptor-effector coupling.