RT Journal Article SR Electronic T1 Oligomerization of Recombinant and Endogenously Expressed Human Histamine H4 Receptors JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 604 OP 615 DO 10.1124/mol.105.020818 VO 70 IS 2 A1 Richard M. van Rijn A1 Paul L. Chazot A1 Fiona C. Shenton A1 Kamonchanok Sansuk A1 Remko A. Bakker A1 Rob Leurs YR 2006 UL http://molpharm.aspetjournals.org/content/70/2/604.abstract AB In this study, we report the homo- and hetero-oligomerization of the human histamine H4R by both biochemical (Western blot and immobilized metal affinity chromatography) and biophysical [bioluminescence resonance energy transfer and time-resolved fluorescence resonance energy transfer (tr-FRET)] techniques. The H4R receptor is the most recently discovered member of the histamine family of G-protein-coupled receptors. Using specific polyclonal antibodies raised against the C-terminal tail of the H4R, we demonstrate the presence of H4R oligomers in human embryonic kidney 293 and COS-7 cells heterologously overexpressing H4Rs and putative native H4R oligomers in human phytohaemagglutinin blasts endogenously expressing H4Rs. Moreover, we show that H4R homo-oligomers are formed constitutively, are formed at low receptor densities (300 fmol/mg of protein), and are present at the cell surface, as detected by tr-FRET. The formation of these oligomers is independent of N-glycosylation and is not modulated by H4R ligands, covering the full spectrum of agonists, neutral antagonists, and inverse agonists. Although we show H4R homo-oligomer formation at physiological expression levels, the detection of H1R-H4R hetero-oligomers was achieved only at higher H1R expression levels and are most likely not physiologically relevant.