The S1P₂ Receptor Negatively Regulates Platelet-Derived Growth Factor-Induced Motility and Proliferation

Abstract

Sphingosine-1-phosphate (S1P), a bioactive sphingolipid metabolite, is the ligand for five specific G proteincoupled receptors, named S1P 1 to S1P 5 . In this study, we found that cross-communication between plateletderived growth factor receptor and S1P 2 serves as a negative damper of PDGF functions. Deletion of the S1P 2 receptor dramatically increased migration of mouse embryonic fibroblasts toward S1P, serum, and PDGF but not fibronectin. This enhanced migration was dependent on expression of S1P 1 and sphingosine kinase 1 (SphK1), the enzyme that produces S1P, as revealed by downregulation of their expression with antisense RNA and small interfering RNA, respectively. Although S1P 2 deletion had no significant effect on tyrosine phosphorylation of the PDGF receptors or activation of extracellular signal-regulated kinase 1/2 or Akt induced by PDGF, it reduced sustained PDGF-dependent p38 phosphorylation and markedly enhanced Rac activation. Surprisingly, S1P 2 -null cells not only exhibited enhanced proliferation but also markedly increased SphK1 expression and activity. Conversely, reintroduction of S1P 2 reduced DNA synthesis and expression of SphK1. Thus, S1P 2 serves as a negative regulator of PDGF-induced migration and proliferation as well as SphK1 expression. Our results suggest that a complex interplay between PDGFR and S1P receptors determines their functions.Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid metabolite formed by activation of SphK by many stimuli, including platelet-derived growth factor (PDGF) (43, 48). As a specific ligand for a family of five G protein-coupled receptors (GPCRs), S1P 1 to S1P 5 (2, 48), S1P regulates a wide variety of important cellular processes, including cytoskeletal rearrangements and cell movement (17,25,45,49,57), angiogenesis and vascular maturation (14,16,26,32,57), and immunity and lymphocyte trafficking (33,34). Interestingly, all of the S1P receptors (S1PRs) have been shown to play critical roles in cytoskeletal reorganization and cell migration (13,26,57). Activation of S1P 1 or S1P 3 increases directional or chemotactic migration (14, 27, 57), and both mediate activation of Rac via G i (26,38). In contrast, ligation of S1P 2 decreases chemotaxis and membrane ruffling (49), due to suppression of Rac activation, probably by stimulation of a GTPase-activating protein for Rac (38). Interestingly, the repellant receptor S1P 2 and the attractant receptor S1P 3 similarly stimulate RhoA activity, likely via G 12/13 (21). Recent studies suggest that the balance of counteracting signals from the G i -and the G 12/13 -Rho pathways directs either positive or negative regulation of Rac and cell migration (49). Similar to its functions in lower organisms, including yeasts and plants, which do not have S1PRs, S1P may also have intracellular actions important for calcium homeostasis (36), cell growth (40, 56), and stress responses (9,11,37,42). S1P, like various other GPCR agonists, can activate growth factor tyrosine kinase receptors in the absence of added...

Involvement of sphingosine 1-phosphate in palmitate-induced insulin resistance of hepatocytes via the S1P2 receptor subtype

“…Physiologically, insulin-mediated glycogen synthesis is diminished in response to S1P, suggesting that the sphingolipid mediator may contribute to hepatic insulin resistance keratinocytes via stimulation of the S1P 2 receptor subtype [14]. This is in accordance with a variety of studies indicating that S1P 2 inhibits proliferation in several cells such as mouse embryonic fibroblasts and germinal centre B cells [36,37]. The present study provides evidence that S1P 2 stimulation is able to attenuate insulin-dependent Akt phosphorylation.…”

Survival benefit of sphingosin‐1‐phosphate and receptors expressions in breast cancer patients

“…However, S1PR2 signaling negatively regulates tumor angiogenesis and tumor growth in vivo 43. S1PR2 is also involved in the reduction of platelet‐derived growth factor mediated‐cell motility and proliferation 44. A knockdown in the expression of S1PR2 by shRNA in satellite cells resulted in a twofold increase in cell migration 45.…”

Role of ABCC1 in export of sphingosine-1-phosphate from mast cells

“…Increased S1P formation, in turn, activates S1P receptors on the same and͞or neighboring cells in an autocrine or paracrine manner. It has been demonstrated that this type of ''inside-out'' signaling by S1P is critical for migratory responses of fibroblasts and smooth muscle cells toward PDGF (9,12) and human breast cancer cells toward EGF (8). Similarly, S1P secreted by mast cells is important for migration of mast cells toward antigen (Ag) and might be involved in the movement of mast cells to sites of inf lammation (13).…”