Human LPA4 (also known as P2Y9 and GPR23) receptors are G protein-coupled receptors. The cDNA encodes a 370-amino-acid polypeptide. The LPA4 receptors are predominately expressed in ovary, and also present in kidney, skeletal muscle and other brain and peripheral tissues. In rat neuroblastoma cells overexpressing the receptors, LPA promotes neurite retraction and cell rounding indicating LPA4 may mediate morphological changes in neuronal cells. Studies in LPA4 knockout mice revealed a role of LPA4 in the negative control of cell migration.