Some examples are TWIK-related acid-sensitive K + channel (TASK) [20], acid-sensing ion channels (ASICs) [24], insulin receptor–related receptor (IRRR) [34], soluble adenylyl cyclase (sAC) [98], ovarian cancer G protein-coupled receptor 1 (OGR1/Gpr68), G protein-coupled receptor 4 (GPR4), and T cell death-associated gene 8 (TDAG8/Gpr65) [57]. Here, GPR4 is linked to ovarian carcinoma.