High-affinity receptor for 12-(S)-hydroxy-5,8,10,14-eicosatetraenoic acid (12-S-HETE), with much lower affinities for other HETE isomers (By similarity) (PubMed:29227475). 12-S-HETE is a eicosanoid, a 12-lipoxygenase (ALOX12) metabolite of arachidonic acid, involved in many physiologic and pathologic processes, such as cell growth, adhesion, inflammation and cancer promotion. 12-S-HETE-binding leads to activation of ERK1/2 (MAPK3/MAPK1), MEK, and NF-kappa-B pathways and leads to cell growth. Plays a crucial role for proliferation, survival and macropinocytosis of KRAS-dependent cancer cells by mediating the translocation of KRAS from the endoplasmic reticulum to the plasma membrane (PM) and its association with the PM (By similarity). Contributes to enhanced immune responses by inducing dendrite protrusion of small intestinal CX3CR1(+) phagocytes for the uptake of luminal antigens (PubMed:30675063). Acts also as a key receptor for 12-(S)-HETE-mediated liver ischemia reperfusion injury (PubMed:29227475). Proton-sensing G protein-coupled receptor. Interacts with KRAS; in a farnesylation-dependent manner. Deficient mice exhibit a reduced response to enteric bacteria, showing defective dendrite protrusions of CX3CR1(+) cells in the small intestine (PubMed:30675063). Under ischemia/reperfusion injury, liver dysfunction, cell death and inflammatory induction are consistently and significantly inhibited at 6 hours after reperfusion in GPR31-deficient mice (PubMed:29227475). Belongs to the G-protein coupled receptor 1 family.