EDG6 (S1P4) belongs to a family of G-protein coupled receptors whose ligands are lysophospholipids. The ligand for EDG6 (S1P4) is sphingosine-1-phosphate. There are 8 known members of the EDG receptor family and they are implicated in mediating growth related effects such as induction of cellular proliferation, alterations in differentiation and survival and suppression of apoptosis. They also evoke cellular effector functions that are dependent on cytoskeletal responses such as contraction, secretion, adhesion and chemotaxis. EDG receptors are developmentally regulated and differ in tissue distribution. They couple to multiple types of G proteins to signal through ras and MAP kinase, rho, phospholipase C and several protein tyrosine kinases. EDG6 (S1P4) is expressed in lymphoid and hematopoietic tissue and in the lungs.