title: Asp73-dependent and -independent regulation of the affinity of ligands for human histamine H1receptors by Na.
abstract: The affinity of ligands for G-protein-coupled receptors (GPCRs) is allosterically regulated by Na+via a highly conserved aspartate residue (Asp2.50) in the second transmembrane domain of GPCRs. In the present study, we examined the Na+-mediated regulation of the affinity of ligands for Gq/11-protein-coupled human histamine H1receptors in Chinese hamster ovary cells. The affinities of 3 agonists and 20 antihistamines were evaluated by their displacement curves against the binding of [3H]-mepyramine to membrane preparations in the presence or absence of 100mM NaCl. The affinities of most drugs including histamine, an agonist, and d-chlorpheniramine, a first-generation antihistamine, were reduced by NaCl, with the extent of NaCl-mediated changes varying widely between drugs. In contrast, the affinities of some second-generation antihistamines such as fexofenadine were increased by NaCl. These changes were retained in intact cells. The mutation of Asp2.50(Asp73) to asparagine abrogated NaCl-induced reductions in affinities for histamine and d-chlorpheniramine, but not NaCl-induced increases in the affinity for fexofenadine. Quantitative structure-activity relationship (QSAR) analyses showed that these Na+-mediated changes were explained and predicted by a combination of the molecular energies and implicit solvation energies of the compounds. These results suggest that Na+diversely regulates the affinity of ligands for H1receptors from the extracellular sites of receptors via Asp73-dependent and -independent mechanisms in a manner that depends on the physicochemical properties of ligands. These results may contribute to a deeper understanding of the fundamental mechanisms by which the affinity of ligands for their receptors is allosterically regulated by Na+.
authors.affiliation: Department of Pharmacodynamics, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan. Electronic address: hishi@my-pharm.ac.jp.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Hishinuma
authors.affiliation: Department of Pharmacodynamics, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan.
authors.forename: Kiyoe
authors.initials: K
authors.lastname: Kosaka
authors.affiliation: Department of Pharmacodynamics, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan.
authors.forename: Chizuru
authors.initials: C
authors.lastname: Akatsu
authors.affiliation: Department of Clinical Pharmaceutics, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Uesawa
authors.affiliation: Department of Molecular Studies for Incurable Diseases, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto, Tokushima 770-8503, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Fukui
authors.affiliation: Department of Pharmacodynamics, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Shoji
mesh_terms: D000818:Animals; D001224:Aspartic Acid / Q000235:genetics*; D016466:CHO Cells; D002414:Cations, Monovalent; D002744:Chlorpheniramine / Q000494:pharmacology; D003412:Cricetulus; D006632:Histamine / Q000494:pharmacology; D017442:Histamine Agonists / Q000494:pharmacology; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006801:Humans; D008024:Ligands; D009154:Mutation; D021281:Quantitative Structure-Activity Relationship; D011869:Radioligand Assay; D011969:Receptors, Histamine H1 / Q000235:genetics / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology*; D016593:Terfenadine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D002414:Cations, Monovalent; D017442:Histamine Agonists; D006634:Histamine H1 Antagonists; D008024:Ligands; D011969:Receptors, Histamine H1; D001224:Aspartic Acid; D002744:Chlorpheniramine; D012965:Sodium Chloride; D016593:Terfenadine; D006632:Histamine; C093230:fexofenadine
keywords: Affinity; Allosteric; Aspartic acid; Histamine H(1) receptor; Sodium ion