Proton-sensing receptor is involved in pH homeostasis. GPR68 may represents an osteoblastic pH sensor regulating cell-mediated responses to acidosis in bone. GPR68 mediates its action by association with G proteins that stimulates inositol phosphate (IP) production or Ca2+ mobilization. The receptor is almost silent at pH 7.8 but fully activated at pH 6.8. Function also as a metastasis suppressor gene in prostate cancer.