ABSTRACT
Dendritic cells (DCs) and lymphocytes are known to show a migratory response to the phospholipid mediator, sphingosine 1-phosphate (S1P). However, it is unclear whether the same S1P receptor subtype mediates the migration of lymphocytes and DCs toward S1P. In this study, we investigated the involvement of S1P receptor subtypes in S1P-induced migration of CD4 T cells and bone marrow-derived DCs in mice. A potent S1P receptor agonist, the (S)-enantiomer of FTY720-phosphate [(S)-FTY720-P], at 0.1 nM or higher and a selective S1P receptor type 1 (S1P(1)) agonist, SEW2871, at 0.1 muM or higher induced a dose-dependent down-regulation of S1P(1). The pretreatment with these compounds resulted in a significant inhibition of mouse CD4 T cell migration toward S1P. Thus, it is revealed that CD4 T cell migration toward S1P is highly dependent on S1P(1). Mature DCs, when compared with CD4 T cells or immature DCs, expressed a relatively higher level of S1P(3) mRNA. S1P at 10-1000 nM induced a marked migration and significantly enhanced the endocytosis of FITC-dextran in mature but not immature DCs. Pretreatment with (S)-FTY720-P at 0.1 microM or higher resulted in a significant inhibition of S1P-induced migration and endocytosis in mature DCs, whereas SEW2871 up to 100 microM did not show any clear effect. Moreover, we found that S1P-induced migration and endocytosis were at an extremely low level in mature DCs prepared from S1P(3)-knockout mice. These results indicate that S1P regulates migration and endocytosis of murine mature DCs via S1P(3) but not S1P(1).
Subject(s)
CD4-Positive T-Lymphocytes/immunology , Cell Movement/immunology , Dendritic Cells/immunology , Endocytosis/immunology , Lysophospholipids/immunology , Receptors, Lysosphingolipid/immunology , Sphingosine/analogs & derivatives , Animals , CD4-Positive T-Lymphocytes/cytology , CD4-Positive T-Lymphocytes/metabolism , Cell Movement/drug effects , Cell Movement/genetics , Cells, Cultured , Dendritic Cells/cytology , Dendritic Cells/metabolism , Dose-Response Relationship, Drug , Down-Regulation/drug effects , Down-Regulation/genetics , Down-Regulation/immunology , Endocytosis/drug effects , Endocytosis/genetics , Fingolimod Hydrochloride , Immunosuppressive Agents/pharmacology , Mice , Mice, Knockout , Oxadiazoles/pharmacology , Propylene Glycols/pharmacology , Receptors, Lysosphingolipid/agonists , Receptors, Lysosphingolipid/deficiency , Sphingosine/immunology , Sphingosine/pharmacology , Sphingosine-1-Phosphate Receptors , Thiophenes/pharmacologyABSTRACT
Circulation of mature lymphocytes between blood and secondary lymphoid tissues plays a central role in the immune system. Homing of lymphocytes from blood into secondary lymphoid tissues beyond high endothelial venules is highly dependent on the interaction between the chemokines CCL19, CCL21, CXCL12, and CXCL13, and their receptors CCR7, CXCR4 and CXCR5. However, the molecular mechanism(s) of lymphocyte egress from secondary lymphoid tissues to lymph remained unclear. We have found a new class of immunomodulator, FTY720 by chemical modification of vegetative wasp-derived natural product, ISP-I (myriocin). FTY720 has been shown to be highly effective in experimental allograft and autoimmune disease models. A striking feature of FTY720 is the induction of a marked decrease in peripheral blood lymphocytes at doses that show immunomodulating activity in these models. The reduction of circulating lymphocytes by FTY720 is caused by sequestration of lymphocytes into secondary lymphoid tissues and thymus. FTY720 is rapidly converted to (S)-enantiomer of FTY720-phosphate [(S)-FTY720-P] by sphingosine kinase 2 in vivo. (S)-FTY720-P acting as a potent agonist of S1P receptor type 1 (S1P1), induces long-term down-regulation of S1P1 on lymphocytes, and thereby inhibits the migration of lymphocytes toward S1P. Thus, it is presumed that FTY720-induced lymphocyte sequestration is due to the inhibition of S1P/S1P1-dependent lymphocyte egress from secondary lymphoid tissues and thymus by its active metabolite (S)-FTY720-P. Throughout the analysis of the mechanism of action of FTY720, it is clarified that S1P/S1P1 interaction plays an important role for lymphocyte egress from secondary lymphoid tissues and thymus.
Subject(s)
Cell Movement/immunology , Chemokines/immunology , Lymphocytes/immunology , Receptors, Chemokine/immunology , Receptors, Lysosphingolipid/immunology , Thymus Gland/immunology , Animals , Cell Movement/drug effects , Down-Regulation/drug effects , Down-Regulation/immunology , Fingolimod Hydrochloride , Humans , Immunosuppressive Agents/pharmacology , Lymph/immunology , Lymphocytes/chemistry , Molecular Structure , Propylene Glycols/chemistry , Propylene Glycols/pharmacology , Sphingosine/analogs & derivatives , Sphingosine/chemistry , Sphingosine/pharmacology , Stereoisomerism , Structure-Activity RelationshipABSTRACT
Sphingosine 1-phosphate (S1P), a pleiotropic lysophospholipid, regulates signal transduction pathway via G-protein-coupled receptors termed S1P1-5 in several types of the cells including lymphocytes. Higher levels of S1P4 mRNA as well as S1P1 mRNA are expressed in lymphoid tissues such as the spleen, thymus, lymph nodes, and Payer's patches. In contrast to S1P1 that plays an essential role in lymphocyte egress, little is known about the role of S1P4 in immune system. In this study, we found that S1P at 10 to 100 nM significantly induced the cell migration and the significant levels of S1P1 and S1P4 mRNA were expressed in mouse CD4 T cells, D10.G4.1 mouse Th2 cells, and EL-4.IL-2 mouse thymoma cells. In D10.G4.1 and EL-4.IL-2 cells, S1P-induced migration was almost completely inhibited by pretreatment with pertussis toxin, Clostoridium difficile toxin B, and (S)-enantiomer of FTY720-phosphate, a potent agonist at S1P1 and S1P4. The members of the Rho family small GTPase, Cdc42 and Rac were activated by S1P stimulation in these cells. The transfection with dominant negative or constitutively active forms of Cdc42 and Rac revealed that the activation of both Cdc42 and Rac is essential for S1P-induced migration of these cells. The immunoprecipitation assays using CHO cells co-expressing both S1P4 and S1P1 receptors indicated that S1P4 and S1P1 are associated on the cell surface. These results suggest that the association of S1P4 and S1P1 plays an important role in migratory response of mouse T cells toward S1P.
Subject(s)
Chemotaxis, Leukocyte/physiology , Lysophospholipids/physiology , Receptors, Lysosphingolipid/physiology , Sphingosine/analogs & derivatives , T-Lymphocytes/physiology , Animals , Cell Line , Mice , Mice, Inbred C57BL , RNA, Messenger/metabolism , Receptors, Lysosphingolipid/genetics , Sphingosine/physiologyABSTRACT
BACKGROUND: Sphingosine 1-phosphate (Sph-1-P) is a bioactive lipid mediator released from activated platelets, which regulates diverse signal transduction pathways via cell surface receptors. Recent studies have revealed that the seven-transmembrane-spanning receptors, Edg-1, Edg-3, Edg-5, Edg-6 and Edg-8 are specific Sph-1-P receptors. Northern blot analysis has demonstrated that Edg-6 is expressed in lymphocyte-containing tissues such as spleen and lung. Little is known about the molecular mechanisms of Edg-6 functions, probably because of the difficulties in expressing Edg-6 on the cell surface. RESULTS: Here, our studies revealed that N-terminal FLAG-tagged Edg-6 or Edg-6-GFP fusion protein was expressed in the endoplasmic reticulum, but was not expressed on the cell surface. On the other hand, C-terminally tagged Edg-6 or both N-terminally and C-terminally tagged Edg-6 was able to localize to the cell surface. Using these cells, we found that Sph-1-P induced cell migration through cell surface-expressed Edg-6 in a pertussis toxin-sensitive manner. This motility was mediated through the activation of a member of the Rho family of small GTPases, Cdc42. CONCLUSION: These results support a role for Sph-1-P signalling via Edg-6 in the pathways involved in cell motility.
