Sphingosine 1-phosphate is released from the cytosol of rat platelets in a carrier-mediated manner

Abstract

Sphingosine 1-phosphate (S1P) is accumulated in platelets and released on stimulation by thrombin or Ca 21 . Thrombin-stimulated S1P release was inhibited by staurosporin, whereas Ca 21 -stimulated release was not. When the platelet plasma membrane was permeabilized with streptolysin O (SLO), S1P leaked out with cytosol markers, whereas granular markers remained in the platelets. The SLOinduced S1P leakage required BSA, probably for solubilization of S1P in the medium. These results indicate that S1P is localized in the inner leaflet of the plasma membrane and that its release is a carrier-mediated process. We also used alpha-toxin (ATX), which makes smaller pores in the plasma membrane than SLO and depletes cytosolic ATP without BSA-dependent S1P leakage. The addition of ATP drove S1P release from ATX platelets. The ATP-driven S1P release from ATX platelets was greatly enhanced by thrombin. An ATP binding cassette transporter inhibitor, glyburide, prevents ATP-and thrombin-induced S1P release from platelets. Ca 21 also stimulated S1P release from ATX platelets without ATP, whereas the Ca 21 -induced release was not inhibited by glyburide. Our results indicate that two independent S1P release systems might exist in the platelet plasma membrane, an ATP-dependent system stimulated by thrombin and an ATP-independent system stimulated by Ca

The immunomodulator FTY720 is phosphorylated and released from platelets

“…5A). Consistent with the previous report (Kobayashi et al, 2006), glyburide also inhibited the thrombin-dependent release of endogenously generated S1P (Fig. 5B).…”

“…The involvement of an ATP-binding cassette (ABC) transporter in stimulus-dependent S1P release from platelets has been suggested, since ATP is required, and the ABC transporter inhibitor glyburide/glibenclamide inhibited the release (Kobayashi et al, 2006).…”

“…Two transporters for S1P have been proposed to exist and function in S1P release from platelets, an ATP-dependent transporter stimulated by thrombin and an ATP-independent transporter (Kobayashi et al, 2006). To examine whether S1P and FTY720-P are released via one or more common transporter, we added FTY720, sphingosine, or both to platelets, with or without activation, and measured their released phosphorylated derivatives.…”

Estradiol Induces Export of Sphingosine 1-Phosphate from Breast Cancer Cells via ABCC1 and ABCG2

“…Studies from several laboratories, including ours, have suggested the involvement of ABC transporters in S1P export from mast cells (32), platelets (33), endothelial cells (34), astrocytes (35), thyroid follicular cell (45), fibroblasts (46), and erythrocytes (47). Similarly, using pharmacological and molecular approaches, we demonstrated that ABCC1 and ABCG2 are involved in E 2 -mediated transport of S1P and dihydro-S1P out of MCF-7 cells.…”

“…ABCC1 and ABCG2 Mediate E 2 -induced Export of S1P-Recent studies suggest that members of the ABC transporter family might be involved in release of S1P from several types of cells (32)(33)(34)(35). Three ABC transporters, ABCB1 (also known as multidrug resistant gene 1 (MDR1)) or p-glycoprotein, ABCC1 (also known as multidrug resistance protein 1 (MRP1)), and ABCG2 (also known as breast cancer resistance protein), appear to account for 80 -90% of multidrug-resistant human tumor cells (36).…”