The M-3 muscarinic acetylcholine receptor expressed in HEK-293 cells signals to phospholipase D via G(12) but not G(q)-type G proteins - Regulators of G proteins as tools to dissect pertussis toxin-resistant G proteins in receptor-effector coupling
U. Rumenapp et al., The M-3 muscarinic acetylcholine receptor expressed in HEK-293 cells signals to phospholipase D via G(12) but not G(q)-type G proteins - Regulators of G proteins as tools to dissect pertussis toxin-resistant G proteins in receptor-effector coupling, J BIOL CHEM, 276(4), 2001, pp. 2474-2479
The M-3 muscarinic acetylcholine receptor (mAChR) expressed in HEK-293 cell
s couples to G(q) and G(12) proteins and stimulates phospholipase C (PLC) a
nd phospholipase D (PLD) in a pertussis toxin-insensitive manner. To determ
ine the type of G protein mediating M-3 mAChR-PLD coupling in comparison to
M-3 mAChR-PLC coupling, we expressed various G alpha proteins and regulato
rs of the G protein signaling (RGS), which act as GTPase-activating protein
s for G(q)- or G(12)-type G proteins. PLD stimulation by the M-3 mAChR was
enhanced by the overexpression of G alpha (12), and G alpha (13), whereas t
he overexpression of G alpha (q) strongly increased PLC activity without af
fecting PLD activity. Expression of the RGS homology domain of Lsc, which a
cts specifically on G alpha (12) and G alpha (13), blunted the M-3 mAChR-in
duced PLD stimulation without affecting PLC stimulation. On the other hand,
overexpression of RGS4, which acts on G alpha (q)- but not G alpha (12)-ty
pe G proteins, suppressed the M-3 mAChR-induced PLC stimulation without alt
ering PLD stimulation. We conclude that the M-3 mAChR in HEK-293 cells appa
rently signals to PLD via G alpha (q)- but not G alpha (12)-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.