Sphingosine 1-Phosphate–Induced Motility and Endocytosis of Dendritic Cells Is Regulated by SWAP-70 through RhoA

Abstract

The phospholipid mediator sphingosine 1-phosphate (S1P) enhances motility and endocytosis of mature dendritic cells (DCs). We show that in vitro migration of Swap-70−/− bone marrow-derived DCs (BMDCs) in response to S1P and S1P-induced upregulation of endocytosis are significantly reduced. S1P-stimulated movement of Swap-70−/− BMDCs, specifically retraction of their trailing edge, in a collagen three-dimensional environment is impaired. These in vitro observations correlate with delayed entry into lymphatic vessels and migration to lymph nodes of skin DCs in Swap-70−/− mice. Expression of S1P receptors (S1P1–3) by wild-type and Swap-70−/− BMDCs is similar, but Swap-70−/− BMDCs fail to activate RhoA and to localize Rac1 and RhoA into areas of actin polymerization after S1P stimulus. The Rho-activating G protein Gαi interacts with SWAP-70, which also supports the localization of Gα13 to membrane rafts in BMDCs. LPS-matured Swap-70−/− BMDCs contain significantly more active RhoA than wild-type DCs. Preinhibition of Rho activation restored migration to S1P, S1P-induced upregulation of endocytosis in mature Swap-70−/− BMDCs, and localization of Gα13 to membrane rafts. These data demonstrate SWAP-70 as a novel regulator of S1P signaling necessary for DC motility and endocytosis.