Lipid transporter that specifically mediates export of sphingosine-1-phosphate in red blood cells and platelets. Sphingosine-1-phosphate is a signaling sphingolipid and its export from red blood cells into in the plasma is required for red blood cell morphology. Sphingosine-1-phosphate export from platelets is required for platelet aggregation and thrombus formation. In addition to export, also able to mediate S1P import. sphing-4-enine 1-phosphate(in) = sphing-4-enine 1-phosphate(out) sphinganine 1-phosphate(in) = sphinganine 1-phosphate(out) sphinga-4E,14Z-dienine-1-phosphate(in) = sphinga-4E,14Z-dienine-1-phosphate(out) Localizes to the cell membrane and intracellular membranes. Belongs to the major facilitator superfamily.