title: Identification of a histamine H4 receptor on human eosinophils--role in eosinophil chemotaxis.
abstract: Eosinophils are recruited to sites of inflammation via the action of a number of chemical mediators, including PAF, leukotrienes, eotaxins, ECF-A and histamine. Although many of the cell-surface receptors for these mediators have been identified, histamine-driven chemotaxis has not been conclusively attributed to any of the three known histamine receptor subtypes, suggesting the possibility of a 4th histamine-responsive receptor on eosinophils. We have identified and cloned a novel G protein-coupled receptor (GPCR), termed Pfi-013, from an IL-5 stimulated eosinophil cDNA library which is homologous to the human histamine H3 receptor, both at the sequence and gene structure level. Expression data indicates that Pfi-013 is predominantly expressed in peripheral blood leukocytes, with lower expression levels in spleen, testis and colon. Ligand-binding studies using Pfi-013 expressed in HEK-293Galpha15 cells, demonstrates specific binding to histamine with a Kd of 3.28 +/- 0.76 nM and possesses a unique rank order of potency against known histaminergic compounds in a competitive ligand-binding assay (histamine > clobenpropit > iodophenpropit > thioperamide > R-alpha-methylhistamine > cimetidine > pyrilamine). We have therefore termed this receptor human histamine H4. Chemotaxis studies on isolated human eosinophils have confirmed that histamine is chemotactic and that agonists of the known histamine receptors (H1, H2, and H3) do not induce such a response. Furthermore, studies employing histamine-receptor antagonists have shown an inhibition of chemotaxis only by the H3 antagonists clobenpropit and thioperamide. Since these compounds are also antagonists of hH4 we postulate that the receptor mediating histaminergic chemotaxis is this novel histamine H4 receptor.
authors.affiliation: Department of Genetic Technologies and Allergy Respiratory Biology, Pfizer Global Research Development, Ramsgate Road, Sandwich, Kent, UK. mark_oreilly@sandwich.pfizer.com
authors.forename: Mark
authors.initials: M
authors.lastname: O'Reilly
authors.forename: Robbin
authors.initials: R
authors.lastname: Alpert
authors.forename: Stephen
authors.initials: S
authors.lastname: Jenkinson
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Gladue
authors.forename: Shane
authors.initials: S
authors.lastname: Foo
authors.forename: Steven
authors.initials: S
authors.lastname: Trim
authors.forename: Beate
authors.initials: B
authors.lastname: Peter
authors.forename: Mike
authors.initials: M
authors.lastname: Trevethick
authors.forename: Mark
authors.initials: M
authors.lastname: Fidock
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D015152:Blotting, Northern; D002634:Chemotaxis, Leukocyte / Q000502:physiology*; D004804:Eosinophils / Q000737:chemistry / Q000502:physiology*; D015870:Gene Expression; D017442:Histamine Agonists / Q000494:pharmacology; D006633:Histamine Antagonists / Q000494:pharmacology; D006801:Humans; D015848:Interleukin-5 / Q000494:pharmacology; D007668:Kidney / Q000166:cytology; D008297:Male; D008969:Molecular Sequence Data; D011956:Receptors, Cell Surface / Q000302:isolation & purification* / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled; D011968:Receptors, Histamine; D000074040:Receptors, Histamine H4; D017386:Sequence Homology, Amino Acid
chemical_list: C418607:HRH4 protein, human; D017442:Histamine Agonists; D006633:Histamine Antagonists; D015848:Interleukin-5; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D011968:Receptors, Histamine; D000074040:Receptors, Histamine H4