PT - JOURNAL ARTICLE AU - Jiansong Luo AU - John M. Busillo AU - Jeffrey L. Benovic TI - M<sub>3</sub> Muscarinic Acetylcholine Receptor-Mediated Signaling Is Regulated by Distinct Mechanisms AID - 10.1124/mol.107.044750 DP - 2008 Aug 01 TA - Molecular Pharmacology PG - 338--347 VI - 74 IP - 2 4099 - http://molpharm.aspetjournals.org/content/74/2/338.short 4100 - http://molpharm.aspetjournals.org/content/74/2/338.full SO - Mol Pharmacol2008 Aug 01; 74 AB - We have used RNA interference previously to demonstrate that G protein-coupled receptor kinase 2 (GRK2) regulates endogenously expressed H1 histamine receptor in human embryonic kidney 293 cells. In this report, we investigate the regulation of endogenously expressed M3 muscarinic acetylcholine receptor (M3 mAChR). We show that knockdown of GRK2, GRK3, or GRK6, but not GRK5, significantly increased carbachol-mediated calcium mobilization. Stable expression of wild-type GRK2 or a kinase-dead mutant (GRK2-K220R) reduced calcium mobilization after receptor activation, whereas GRK2 mutants defective in Gαq binding (GRK2-D110A, GRK2-R106A, and GRK2-R106A/K220R) had no effect on calcium signaling, suggesting that GRK2 primarily regulates Gq after M3 mAChR activation. The knockdown of arrestin-2 or arrestin-3 also significantly increased carbachol-mediated calcium mobilization. Knockdown of GRK2 and the arrestins also significantly enhanced carbachol-mediated activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2), whereas prolonged ERK1/2 activation was only observed with GRK2 or arrestin-3 knockdown. We also investigated the role of casein kinase-1α (CK1α) and found that knockdown of CK1α increased calcium mobilization but not ERK activation. In summary, our data suggest that multiple proteins dynamically regulate M3 mAChR-mediated calcium signaling, whereas GRK2 and arrestin-3 play the primary role in regulating ERK activation. The American Society for Pharmacology and Experimental Therapeutics