title: Isoform-Specific Biased Agonism of Histamine H3 Receptor Agonists.
abstract: The human histamine H3receptor (hH3R) is subject to extensive gene splicing that gives rise to a large number of functional and nonfunctional isoforms. Despite the general acceptance that G protein-coupled receptors can adopt different ligand-induced conformations that give rise to biased signaling, this has not been studied for the H3R; further, it is unknown whether splice variants of the same receptor engender the same or differential biased signaling. Herein, we profiled the pharmacology of histamine receptor agonists at the two most abundant hH3R splice variants (hH3R445and hH3R365) across seven signaling endpoints. Both isoforms engender biased signaling, notably for 4-[3-(benzyloxy)propyl]-1H-imidazole (proxyfan) [e.g., strong bias toward phosphorylation of glycogen synthase kinase 3β (GSK3β) via the full-length receptor] and its congener 3-(1H-imidazol-4-yl)propyl-(4-iodophenyl)-methyl ether (iodoproxyfan), which are strongly consistent with the former's designation as a "protean" agonist. The 80 amino acid IL3 deleted isoform hH3R365is more permissive in its signaling than hH3R445: 2-(1H-imidazol-5-yl)ethyl imidothiocarbamate (imetit), proxyfan, and iodoproxyfan were all markedly biased away from calcium signaling, and principal component analysis of the full data set revealed divergent profiles for all five agonists. However, most interesting was the identification of differential biased signaling between the two isoforms. Strikingly, hH3R365was completely unable to stimulate GSK3β phosphorylation, an endpoint robustly activated by the full-length receptor. To the best of our knowledge, this is the first quantitative example of differential biased signaling via isoforms of the same G protein-coupled receptor that are simultaneously expressed in vivo and gives rise to the possibility of selective pharmacological targeting of individual receptor splice variants.
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (D.M.R., A.E.C., N.A.D., S.B., R.B., R.J.S., W.N.C., P.M.S., A.C., C.J.L.); and Institut de Recherches Internationales Servier, Suresnes, France (C.M.C., E.M.).
authors.forename: Darren M
authors.initials: DM
authors.lastname: Riddy
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (D.M.R., A.E.C., N.A.D., S.B., R.B., R.J.S., W.N.C., P.M.S., A.C., C.J.L.); and Institut de Recherches Internationales Servier, Suresnes, France (C.M.C., E.M.).
authors.forename: Anna E
authors.initials: AE
authors.lastname: Cook
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (D.M.R., A.E.C., N.A.D., S.B., R.B., R.J.S., W.N.C., P.M.S., A.C., C.J.L.); and Institut de Recherches Internationales Servier, Suresnes, France (C.M.C., E.M.).
authors.forename: Natalie A
authors.initials: NA
authors.lastname: Diepenhorst
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (D.M.R., A.E.C., N.A.D., S.B., R.B., R.J.S., W.N.C., P.M.S., A.C., C.J.L.); and Institut de Recherches Internationales Servier, Suresnes, France (C.M.C., E.M.).
authors.forename: Sanja
authors.initials: S
authors.lastname: Bosnyak
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (D.M.R., A.E.C., N.A.D., S.B., R.B., R.J.S., W.N.C., P.M.S., A.C., C.J.L.); and Institut de Recherches Internationales Servier, Suresnes, France (C.M.C., E.M.).
authors.forename: Ryan
authors.initials: R
authors.lastname: Brady
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (D.M.R., A.E.C., N.A.D., S.B., R.B., R.J.S., W.N.C., P.M.S., A.C., C.J.L.); and Institut de Recherches Internationales Servier, Suresnes, France (C.M.C., E.M.).
authors.forename: Clotilde
authors.initials: C
authors.lastname: Mannoury la Cour
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (D.M.R., A.E.C., N.A.D., S.B., R.B., R.J.S., W.N.C., P.M.S., A.C., C.J.L.); and Institut de Recherches Internationales Servier, Suresnes, France (C.M.C., E.M.).
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Mocaer
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (D.M.R., A.E.C., N.A.D., S.B., R.B., R.J.S., W.N.C., P.M.S., A.C., C.J.L.); and Institut de Recherches Internationales Servier, Suresnes, France (C.M.C., E.M.).
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Summers
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (D.M.R., A.E.C., N.A.D., S.B., R.B., R.J.S., W.N.C., P.M.S., A.C., C.J.L.); and Institut de Recherches Internationales Servier, Suresnes, France (C.M.C., E.M.).
authors.forename: William N
authors.initials: WN
authors.lastname: Charman
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (D.M.R., A.E.C., N.A.D., S.B., R.B., R.J.S., W.N.C., P.M.S., A.C., C.J.L.); and Institut de Recherches Internationales Servier, Suresnes, France (C.M.C., E.M.).
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Sexton
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (D.M.R., A.E.C., N.A.D., S.B., R.B., R.J.S., W.N.C., P.M.S., A.C., C.J.L.); and Institut de Recherches Internationales Servier, Suresnes, France (C.M.C., E.M.).
authors.forename: Arthur
authors.initials: A
authors.lastname: Christopoulos
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (D.M.R., A.E.C., N.A.D., S.B., R.B., R.J.S., W.N.C., P.M.S., A.C., C.J.L.); and Institut de Recherches Internationales Servier, Suresnes, France (C.M.C., E.M.) chris.langmead@monash.edu.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Langmead
mesh_terms: D000818:Animals; D001681:Biological Assay; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000378:metabolism; D017442:Histamine Agonists / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D025341:Principal Component Analysis; D020033:Protein Isoforms / Q000378:metabolism; D018100:Receptors, Histamine H3 / Q000378:metabolism*; D017384:Sequence Deletion
chemical_list: D017442:Histamine Agonists; D020033:Protein Isoforms; D018100:Receptors, Histamine H3; D000242:Cyclic AMP