Proton-sensing receptor involved in pH homeostasis. May represents an osteoblastic pH sensor regulating cell-mediated responses to acidosis in bone. Mediates its action by association with G proteins that stimulates inositol phosphate (IP) production or Ca(2+) mobilization. The receptor is almost silent at pH 7.8 but fully activated at pH 6.8. Also functions as a metastasis suppressor gene in prostate cancer (By similarity). Found at low level in a wide range of tissues, but significantly expressed in lung, kidney, bone and nervous system. The disease is caused by variants affecting the gene represented in this entry. Belongs to the G-protein coupled receptor 1 family. Was originally (PubMed:10806476) thought to be a receptor for sphingosylphosphorylcholine (SPC). However, this work has been retracted (PubMed:16508674).