Recently, three G protein-coupled receptors (GPCR), T cell death-associated gene 8 (TDAG8 also known as GPR65), ovarian cancer G protein-coupled receptor 1 (OGR1 also known as GPR68) and G protein coupled receptor 4 (GPR4), have been shown to sense extracellular protons and stimulate a variety of signalling pathways [5–9]. The gene discussed is GPR4; the disease is ovarian carcinoma.