title: 5-Hydroxytryptamine 4(a) receptor expressed in Sf9 cells is palmitoylated in an agonist-dependent manner.
abstract: The mouse 5-hydroxytryptamine 4(a) receptor [5-HT(4(a))] was expressed with a baculovirus system in insect cells and analysed for acylation. [(3)H]Palmitic acid was effectively incorporated into 5-HT(4(a)) and label was sensitive to the treatment with reducing agents indicating a thioester-type bond. Analysis of protein-bound fatty acids revealed that 5-HT(4(a)) contains predominantly palmitic acid. Treatment of infected Sf9 (Spodoptera frugiperda) cells with BIMU8 [(endo-N-8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2,3-dehydro-2-oxo-3-(prop-2-yl)-1H-benzimid-azole-1-carboxamide], a 5-HT(4) receptor-selective agonist, generated a dose-dependent increase in [(3)H]palmitate incorporation into 5-HT(4(a)) with an EC(50) of approx. 10 nM. The change in receptor labelling after stimulation with agonist was receptor-specific and did not result from general metabolic effects. We also used both pulse labelling and pulse-chase labelling to address the dynamics of 5-HT(4(a)) palmitoylation. Incorporation studies revealed that the rate of palmitate incorporation was increased approx. 3-fold after stimulation with agonist. Results of pulse-chase experiments show that activation with BIMU8 promoted the release of radiolabel from 5-HT(4(a)), thereby reducing the levels of receptor-bound palmitate to approximately one-half. Taken together, our results demonstrate that palmitoylation of 5-HT(4(a)) is a reversible process and that stimulation of 5-HT(4(a)) with agonist increases the turnover rate for receptor-bound palmitate. This provides evidence for a regulated cycling of receptor-bound palmitate and suggests a functional role for palmitoylation/depalmitoylation in 5-hydroxytryptamine-mediated signalling.
authors.affiliation: Abteilung Neuro- und Sinnesphysiologie, Physiologisches Institut, Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany.
authors.forename: E G
authors.initials: EG
authors.lastname: Ponimaskin
authors.forename: M F
authors.initials: MF
authors.lastname: Schmidt
authors.forename: M
authors.initials: M
authors.lastname: Heine
authors.forename: U
authors.initials: U
authors.lastname: Bickmeyer
authors.forename: D W
authors.initials: DW
authors.lastname: Richter
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019084:Fluorescent Antibody Technique, Indirect; D008969:Molecular Sequence Data; D019308:Palmitic Acid / Q000378:metabolism*; D011985:Receptors, Serotonin / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D044422:Receptors, Serotonin, 5-HT4; D012701:Serotonin / Q000378:metabolism; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D018411:Spodoptera
chemical_list: D011985:Receptors, Serotonin; D017366:Serotonin Receptor Agonists; D044422:Receptors, Serotonin, 5-HT4; D019308:Palmitic Acid; D012701:Serotonin