title: Each one of certain histidine residues in G-protein-coupled receptor GPR4 is critical for extracellular proton-induced stimulation of multiple G-protein-signaling pathways.
abstract: GPR4, previously proposed as the receptor for sphingosylphosphorylcholine, has recently been identified as the proton-sensing G-protein-coupled receptor coupling to multiple intracellular signaling pathways, including the G(s)-protein/cAMP, G(12/13)-protein/Rho, and G(q)-protein/phospholipase C pathways. In the present study, we examined whether extracellularly located histidine residues of GPR4 sense extracellular protons and, if so, whether a certain histidine residue is critical for coupling to the single or multiple signaling pathway(s). We found that the mutation of histidine residue at 79, 165, or 269 from the N-terminal of GPR4 to phenylalanine shifted the half-maximal effective concentration (EC(50)) of proton-induced signaling activities to the right, including cAMP accumulation, SRE promoter activity reflecting Rho activity, and NFAT promoter activity reflecting phospholipase C signaling activity, without an appreciable change in the maximal activities. These results suggest that the protonation of each one of histidine residues at 79, 165, and 269 in GPR4 may be critical for conformational change of the receptor for coupling to multiple intracellular signaling pathways through G-proteins.
authors.affiliation: Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan.
authors.forename: Jin-Peng
authors.initials: JP
authors.lastname: Liu
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakakura
authors.forename: Hideaki
authors.initials: H
authors.lastname: Tomura
authors.forename: Masayuki
authors.initials: M
authors.lastname: Tobo
authors.forename: Chihiro
authors.initials: C
authors.lastname: Mogi
authors.forename: Ju-Qiang
authors.initials: JQ
authors.lastname: Wang
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: He
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Takano
authors.forename: Alatangaole
authors.initials: A
authors.lastname: Damirin
authors.forename: Mayumi
authors.initials: M
authors.lastname: Komachi
authors.forename: Koichi
authors.initials: K
authors.lastname: Sato
authors.forename: Fumikazu
authors.initials: F
authors.lastname: Okajima
mesh_terms: D002460:Cell Line; D006639:Histidine / Q000235:genetics*; D006801:Humans; D017354:Point Mutation; D011522:Protons; D043562:Receptors, G-Protein-Coupled / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: C091670:GPR4 protein, human; D011522:Protons; D043562:Receptors, G-Protein-Coupled; D006639:Histidine