The lipid growth factor lysophosphatidic acid (LPA) is responsible for cell signaling in diverse pathways including survival, proliferation, motility, and differentiation. LPA acts upon target cells by activating its cognate receptors, which belong to the G protein-coupled endothelial differentiation gene (EDG) family. Four mammalian cell surface LPA receptors have been identified so far: EDG-2 (LPA1), EDG-4 (LPA2), EDG-7 (LPA3) and LPA4 (GPR23/P2Y9). EDG-2 is the most widely expressed receptor, with high-level mRNAs in the colons, small intestine, placenta, brain and heart. Heterologous expression studies have shown that EDG-2 couples to both Gi/o and Gq to mediate PLC activation, inhibition of cAMP accumulation and activation of the MAPK pathway. EDG-2 deficient mice show phenotypic changes observed in psychiatric disease as well as impaired suckling behavior attributable to defective olfaction.