TY - JOUR T1 - Palmitoylation of the 5-Hydroxytryptamine<sub>4a</sub> Receptor Regulates Receptor Phosphorylation, Desensitization, and β-Arrestin-Mediated Endocytosis JF - Molecular Pharmacology JO - Mol Pharmacol SP - 1434 LP - 1443 DO - 10.1124/mol.104.008748 VL - 67 IS - 5 AU - Evgeni Ponimaskin AU - Aline Dumuis AU - Florence Gaven AU - Gaël Barthet AU - Martin Heine AU - Konstantin Glebov AU - Diethelm W. Richter AU - Martin Oppermann Y1 - 2005/05/01 UR - http://molpharm.aspetjournals.org/content/67/5/1434.abstract N2 - The mouse 5-hydroxytryptamine4a (5-HT4a) receptor is an unusual member of the G protein-coupled receptor superfamily because it possesses two separate carboxyl-terminal palmitoylation sites, which may allow the receptor to adopt different conformations in an agonist-dependent manner (J Biol Chem 277:2534–2546, 2002). By targeted mutation of the proximal (Cys-328/329) or distal (Cys-386) palmitoylation sites, or a combination of both, we generated 5-HT4a receptor variants with distinct functional characteristics. In this study, we showed that upon 5-HT stimulation, the 5-HT4a receptor undergoes rapid (t½ ∼ 2 min) and dose-dependent (EC50 ∼ 180 nM) phosphorylation on serine residues by a staurosporine-insensitive receptor kinase. Overexpression of GRK2 significantly reduced the receptor-promoted cAMP formation. The Cys328/329-Ser mutant, which is constitutively active in the absence of ligand, exhibited enhanced receptor phosphorylation under both basal and agonist-stimulated conditions and was more effectively desensitized and internalized via a β-arrestin-2 mediated pathway compared with the wild-type 5-HT4a. In contrast, G protein activation, phosphorylation, desensitization, and internalization of the other palmitoylation-deficient receptor mutants were affected differently. These findings suggest that palmitoylation plays an important role in modulating 5-HT4a receptor functions and that G protein activation, phosphorylation, desensitization, and internalization depend on the different receptor conformations. ER -