Sphingosine-1-phosphate transport and its role in immunology

Sphingosine-1-phosphate (S1P) is a sphingolipid metabolite with many important functions in cellular and systemic physiology, including the immune system. As it cannot traverse the membrane, it is exported from cells by transporters. Several members of the ATP-binding cassette (ABC) transporter family, ABCA1, ABCC1, ABCG2 and potentially ABCA7 have been identified as S1P transporters. In addition spinster 2 (SPNS2), a protein from the major facilitator superfamily (MFS), was identified as a S1P transporter. Here we review the current knowledge on S1P transport and discuss how this process creates S1P gradients in the body that are important in various functions of the immune system.