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Domain Swapping in the Human Histamine H 1 Receptor

2004; American Society for Pharmacology and Experimental Therapeutics; Volume: 311; Issue: 1 Linguagem: Inglês

10.1124/jpet.104.067041

1521-0103

Remko A. Bakker, Guido Dees, Juan J. Carrillo, Raymond G. Booth, Juan F. López‐Giménez, Graeme Milligan, Philip G. Strange, Rob Leurs,

Chemical Synthesis and Analysis

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.