title: Differential functional effects of two 5-HT4 receptor isoforms in adult cardiomyocytes.
abstract: Serotonin 5-HT4 receptors are present in human atrial myocytes and have been proposed to contribute to the generation of atrial fibrillation. However, 5-HT4 receptors have so far been only found in human and pig atria and are absent from the heart of small laboratory animals, such as rat, guinea pig, rabbit and frog, which limits the experimental settings for studying their functional properties. In this study, we developed an adenovirus expression system to examine the properties of two human 5-HT4 receptor splice variants, h5-HT4(b) and h5-HT4(d), expressed in adult cardiomyocytes devoid of native 5-HT4 receptors. When expressed in the HL-1 murine cell line of atrial origin, both receptors caused specific binding of the 5-HT4 selective antagonist GR113808 and activated adenylyl cyclase in the presence of serotonin (5-HT, 1 microM). When expressed in freshly isolated adult rat ventricular cardiomyocytes, a stimulation of the L-type Ca2+ current (ICa,L) by 5-HT (100 nM) was revealed. Both effects were blocked by GR113808. In HL-1 cells, the h5-HT4(d) receptor was found to be more efficiently coupled to adenylyl cyclase than the h5-HT4(b). Pertussis toxin treatment (250 ng/ml for 5 h) potentiated the stimulatory effect of 5-HT on ICa,L in rat myocytes expressing the h5-HT4(b) but not the h5-HT4(d) receptor, indicating a likely coupling of the (b) isoform to both Gs and Gi/o proteins. Adenoviral expression of h5-HT4 receptor isoforms in adult cardiac myocytes provides a valuable means for the exploration of the receptor signaling cascades in normal and pathological situations.
authors.affiliation: Inserm U-446, Laboratoire de Cardiologie Cellulaire et Moléculaire, Faculté de Pharmacie, Université Paris-Sud, 5, Rue J.-B. Clément, F-92296 Châtenay-Malabry cedex, France.
authors.forename: Liliana
authors.initials: L
authors.lastname: Castro
authors.forename: Jeanne
authors.initials: J
authors.lastname: Mialet-Perez
authors.forename: Aurélie
authors.initials: A
authors.lastname: Guillemeau
authors.forename: Francesca
authors.initials: F
authors.lastname: Stillitano
authors.forename: Oliver
authors.initials: O
authors.lastname: Zolk
authors.forename: Thomas
authors.initials: T
authors.lastname: Eschenhagen
authors.forename: Frank
authors.initials: F
authors.lastname: Lezoualc'h
authors.forename: Pascal
authors.initials: P
authors.lastname: Bochet
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Fischmeister
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D051379:Mice; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D037342:Pertussis Toxin / Q000494:pharmacology; D011485:Protein Binding; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000378:metabolism; D044422:Receptors, Serotonin, 5-HT4 / Q000378:metabolism*; D058832:Serotonin 5-HT4 Receptor Antagonists; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D020746:Calcium Channels, L-Type; D007211:Indoles; D020033:Protein Isoforms; D058832:Serotonin 5-HT4 Receptor Antagonists; D013449:Sulfonamides; D044422:Receptors, Serotonin, 5-HT4; D037342:Pertussis Toxin; D000262:Adenylyl Cyclases; D007545:Isoproterenol; C082871:GR 113808