Proton-sensing G protein-coupled receptor activated by extracellular pH, which is required to monitor pH changes and generate adaptive reactions (PubMed:12955148, PubMed:29677517, PubMed:32865988, PubMed:33478938, PubMed:39753132, PubMed:40215959, PubMed:40215960). The receptor is almost silent at pH 7.8 but fully activated at pH 6.8 (PubMed:12955148, PubMed:39753132). Ligand binding causes a conformation change that triggers signaling via guanine nucleotide- binding proteins (G proteins) and modulates the activity of downstream effectors, such as phospholipase C (PubMed:29677517, PubMed:39753132). GPR68 is mainly coupled to G(q) G proteins and mediates production of diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3) (PubMed:29677517, PubMed:39753132). Acts as a key mechanosensor of fluid shear stress and membrane stretch (PubMed:29677517, PubMed:30471999). Expressed in endothelial cells of small-diameter resistance arteries, where it mediates flow-induced dilation in response to shear stress (PubMed:29677517). May represents an osteoblastic pH sensor regulating cell-mediated responses to acidosis in bone (By similarity). Acts as a regulator of calcium-sensing receptor CASR in a seesaw manner: GPR68-mediated signaling inhibits CASR signaling in response to protons, while CASR inhibits GPR68 in presence of extracellular calcium (By similarity). {ECO:0000250|UniProtKB:Q8BFQ3, ECO:0000269|PubMed:12955148, ECO:0000269|PubMed:29677517, ECO:0000269|PubMed:30471999, ECO:0000269|PubMed:32865988, ECO:0000269|PubMed:33478938, ECO:0000269|PubMed:39753132, ECO:0000269|PubMed:40215959, ECO:0000269|PubMed:40215960}. This is the function of GPR68 (G protein-coupled receptor 68, Ensembl gene identifier ENSG00000119714).