Prostaglandin I(2) production and cAMP accumulation in response to acidic extracellular pH through OGR1 in human aortic smooth muscle cells.
Ovarian cancer G-protein-coupled receptor 1 (OGR1) and GPR4 have recently been identified as proton-sensing or extracellular pH-responsive G-protein-coupled receptors stimulating inositol phosphate production and cAMP accumulation, respectively. In the present study, we found that OGR1 and GPR4 mRNAs were expressed in human aortic smooth muscle cells (AoSMCs). Acidic extracellular pH induced inositol phosphate production, a transient increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), and cAMP accumulation in these cells. When small interfering RNAs (siRNAs) targeted for OGR1 and GPR4 were transfected to the cells, the acid-induced inositol phosphate production and [Ca(2+)](i) increase were markedly inhibited by the OGR1 siRNA but not by the GPR4 siRNA. Unexpectedly, the acid-induced cAMP accumulation was also largely inhibited by OGR1 siRNA but only slightly by GPR4 siRNA. Acidic extracellular pH also stimulated prostaglandin I2 (PGI(2)) production, which was again inhibited by OGR1 siRNA. The specific inhibitors for extracellular signal-regulated kinase kinase and cyclooxygenase attenuated the acid-induced PGI(2) production and cAMP accumulation without changes in the inositol phosphate production. A specific inhibitor of phospholipase C also inhibited the acid-induced cAMP accumulation. In conclusion, OGR1 is a major receptor involved in the extracellular acid-induced stimulation of PGI(2) production and cAMP accumulation in AoSMCs. The cAMP accumulation may occur through OGR1-mediated stimulation of the phospholipase C/cyclooxygenase/PGI(2) pathway.
Tomura
Hideaki
H
Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371-8512, Japan. tomurah@showa.gunma-u.ac.jp
Wang
Ju-Qiang
JQ
Komachi
Mayumi
M
Damirin
Alatangaole
A
Mogi
Chihiro
C
Tobo
Masayuki
M
Kon
Junko
J
Misawa
Norihiko
N
Sato
Koichi
K
Okajima
Fumikazu
F
D001011:Aorta / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D011464:Epoprostenol / Q000096:biosynthesis* / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007295:Inositol Phosphates / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000166:cytology*; D034741:RNA, Small Interfering / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014162:Transfection; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
D004791:Enzyme Inhibitors; C504821:GPR1 protein, human; C486281:GPR68 protein, human; D007295:Inositol Phosphates; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled; D011464:Epoprostenol; D000242:Cyclic AMP; D010738:Type C Phospholipases; D002118:Calcium