TDAG8 is a proton-sensing and psychosine-sensitive G-protein-coupled receptor.
T cell death-associated gene 8 (TDAG8) has been reported to be a receptor for psychosine. Ovarian cancer G-protein-coupled receptor 1 (OGR1) and GPR4, G-protein-coupled receptors (GPCRs) closely related to TDAG8, however, have recently been identified as proton-sensing or extracellular pH-responsive GPCRs that stimulate inositol phosphate and cAMP production, respectively. In the present study, we examined whether TDAG8 senses extracellular pH change. In the several cell types that were transfected with TDAG8 cDNA, cAMP was markedly accumulated in response to neutral to acidic extracellular pH, with a peak response at approximately pH 7.0-6.5. The pH effect was inhibited by copper ions and was reduced or lost in cells expressing mutated TDAG8 in which histidine residues were changed to phenylalanine. In the membrane fractions prepared from TDAG8-transfected cells, guanosine 5'-O-(3-thiotriphosphate) binding activity and adenylyl cyclase activity were remarkably stimulated in response to neutral and acidic pH. The concentration-dependent effect of extracellular protons on cAMP accumulation was shifted to the right in the presence of psychosine. The inhibitory psychosine effect was also observed for pH-dependent actions in OGR1- and GPR4-expressing cells but not for prostaglandin E(2)- and sphingosine 1-phosphate-induced actions in any pH in native and sphingosine 1-phosphate receptor-expressing cells. Glucosylsphingosine and sphingosylphosphorylcholine similarly inhibited the pH-dependent action, although to a lesser extent. Psychosine-sensitive and pH-dependent cAMP accumulation was also observed in mouse thymocytes. We concluded that TDAG8 is one of the proton-sensing GPCRs coupling to adenylyl cyclase and psychosine, and its related lysosphingolipids behave as if they were antagonists against protein-sensing receptors, including TDAG8, GPR4, and OGR1.
Laboratory of Signal Transduction and Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371-8512, Japan.
Ju-Qiang
JQ
Wang
Junko
J
Kon
Chihiro
C
Mogi
Masayuki
M
Tobo
Alatangaole
A
Damirin
Koichi
K
Sato
Mayumi
M
Komachi
Enkhzol
E
Malchinkhuu
Naoya
N
Murata
Takao
T
Kimura
Atsushi
A
Kuwabara
Kaori
K
Wakamatsu
Hideki
H
Koizumi
Toshimitsu
T
Uede
Gozoh
G
Tsujimoto
Hitoshi
H
Kurose
Takashi
T
Sato
Akihiro
A
Harada
Norihiko
N
Misawa
Hideaki
H
Tomura
Fumikazu
F
Okajima
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D051379:Mice; D008810:Mice, Inbred C57BL; D011609:Psychosine / Q000494:pharmacology*; D043562:Receptors, G-Protein-Coupled / Q000502:physiology*; D013601:T-Lymphocytes / Q000378:metabolism
C091670:GPR4 protein, human; C513334:GPR65 protein, human; C513337:GPR65 protein, mouse; C486281:GPR68 protein, human; D043562:Receptors, G-Protein-Coupled; D011609:Psychosine; D000242:Cyclic AMP