title: Physical interaction of calmodulin with the 5-hydroxytryptamine2C receptor C-terminus is essential for G protein-independent, arrestin-dependent receptor signaling.
abstract: The serotonin (5-hydroxytryptamine; 5-HT)(2C) receptor is a G protein-coupled receptor (GPCR) exclusively expressed in CNS that has been implicated in numerous brain disorders, including anxio-depressive states. Like many GPCRs, 5-HT(2C) receptors physically interact with a variety of intracellular proteins in addition to G proteins. Here, we show that calmodulin (CaM) binds to a prototypic Ca(2+)-dependent "1-10" CaM-binding motif located in the proximal region of the 5-HT(2C) receptor C-terminus upon receptor activation by 5-HT. Mutation of this motif inhibited both beta-arrestin recruitment by 5-HT(2C) receptor and receptor-operated extracellular signal-regulated kinase (ERK) 1,2 signaling in human embryonic kidney-293 cells, which was independent of G proteins and dependent on beta-arrestins. A similar inhibition was observed in cells expressing a dominant-negative CaM or depleted of CaM by RNA interference. Expression of the CaM mutant also prevented receptor-mediated ERK1,2 phosphorylation in cultured cortical neurons and choroid plexus epithelial cells that endogenously express 5-HT(2C) receptors. Collectively, these findings demonstrate that physical interaction of CaM with recombinant and native 5-HT(2C) receptors is critical for G protein-independent, arrestin-dependent receptor signaling. This signaling pathway might be involved in neurogenesis induced by chronic treatment with 5-HT(2C) receptor agonists and their antidepressant-like activity.
authors.affiliation: Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut de Génomique Fonctionnelle, Montpellier F-34094, France.
authors.forename: Marilyne
authors.initials: M
authors.lastname: Labasque
authors.forename: Eric
authors.initials: E
authors.lastname: Reiter
authors.forename: Carine
authors.initials: C
authors.lastname: Becamel
authors.forename: Joël
authors.initials: J
authors.lastname: Bockaert
authors.forename: Philippe
authors.initials: P
authors.lastname: Marin