Lipid transporter that specifically mediates export of sphingosine-1-phosphate in red blood cells and platelets (PubMed:29045386, PubMed:29563527, PubMed:33334894, PubMed:33863882). 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 (PubMed:29045386). Sphingosine-1-phosphate export from platelets is required for platelet aggregation and thrombus formation (PubMed:33863882). Mediates the export of different sphingosine-1-phosphate (S1P) species, including S1P(d18:0) (sphinganine 1-phosphate), S1P (d18:1) (sphing-4-enine 1-phosphate) and S1P (d18:2) (sphinga-4E,14Z-dienine-1-phosphate) (PubMed:33863882). Release of sphingosine-1-phosphate is facilitated by a proton gradient (PubMed:33334894). In contrast, cations, such as sodium, are not required to drive sphingosine-1-phosphate transport (PubMed:29563527, PubMed:33334894). In addition to export, also able to mediate S1P import (PubMed:33785361). Does not transport lysophosphatidylcholine (LPC) (PubMed:29045386). 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. Widely expressed with highest expression in spleen, lung and testis (PubMed:18694395). Predominantly expressed in erythroid lineages giving rise to erythrocytes and platelets, but absent in lymphoid lineages (PubMed:29045386, PubMed:29563527). Mice were born with normal gross appearance and thrived (PubMed:29045386). An accumulation of sphingosine-1-phosphate in red blood cells is observed, while sphingosine-1-phosphate level in plasma is significantly reduced (PubMed:29045386). Mice display hemolysis associated with red blood cell stomatocytes, and the hemolytic phenotype is severely increased with signs of membrane fragility under stress erythropoiesis (PubMed:29045386). Mice significantly reduced thrombus formation (PubMed:33863882). Belongs to the major facilitator superfamily. Extended C-terminus.