title: Domain swapping in the human histamine H1 receptor.
abstract: G-protein-coupled receptors (GPCRs) represent the largest family of receptors involved in transmembrane signaling. Although these receptors were generally believed to be monomeric entities, accumulating evidence supports the presence of GPCRs in multimeric forms. Here, using immunoprecipitation as well as time-resolved fluorescence resonance energy transfer to assess protein-protein interactions in living cells, we unambiguously demonstrate the occurrence of dimerization of the human histamine H(1) receptor. We also show the presence of domain-swapped H(1) receptor dimers in which there is the reciprocal exchange of transmembrane domain TM domains 6 and 7 between the receptors present in the dimer. Mutation of aspartate(107) in transmembrane (TM) 3 or phenylalanine(432) in TM6 to alanine results in two radioligand-binding-deficient mutant H(1) receptors. Coexpression of H(1)D(107) A and H(1)F(432)A, however, results in a reconstituted radioligand binding site that exhibits a pharmacological profile that corresponds to the wild-type H(1) receptor. Interestingly, the H(1) receptor radioligands [(3)H]mepyramine and [(3)H]-(-)-trans-1-phenyl-3-N,N-dimethylamino-1,2,3,4-tetrahydronaphthalene show differential saturation binding values (B(max)) for wild-type H(1) receptors but not for the radioligand binding site that is formed upon coexpression of H(1) D(107)A and H(1) F(432)A receptors, suggesting the presence of different H(1) receptor populations.
authors.affiliation: Leiden/Amsterdam Center for Drug Research, Faculty of Sciences, Department of Medicinal Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands.
authors.forename: Remko A
authors.initials: RA
authors.lastname: Bakker
authors.forename: Guido
authors.initials: G
authors.lastname: Dees
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Carrillo
authors.forename: Raymond G
authors.initials: RG
authors.lastname: Booth
authors.forename: Juan F
authors.initials: JF
authors.lastname: López-Gimenez
authors.forename: Graeme
authors.initials: G
authors.lastname: Milligan
authors.forename: Philip G
authors.initials: PG
authors.lastname: Strange
authors.forename: Rob
authors.initials: R
authors.lastname: Leurs
mesh_terms: D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002522:Chlorocebus aethiops; D004734:Energy Metabolism; D005453:Fluorescence; D006634:Histamine H1 Antagonists / Q000494:pharmacology*; D006801:Humans; D047468:Immunoprecipitation; D017434:Protein Structure, Tertiary; D011738:Pyrilamine / Q000494:pharmacology*; D043562:Receptors, G-Protein-Coupled / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011969:Receptors, Histamine H1 / Q000032:analysis / Q000378:metabolism*; D013997:Time Factors; D014316:Tritium
chemical_list: D006634:Histamine H1 Antagonists; D043562:Receptors, G-Protein-Coupled; D011969:Receptors, Histamine H1; D014316:Tritium; D011738:Pyrilamine