Sphingosine-1-phosphate, a novel lipid, involved in cellular proliferation.

Abstract

Abstract. Sphingosine, a metabolite of membrane sphingolipids, regulates proliferation of quiescent Swiss 3T3 fibroblasts (Zhang, H ., N. E. Buckley, K. Gibson, and S. Spiegel . 1990. J. Biol. Chem. 265:76-81) . The present study provides new insights into the formation and function of a unique phospholipid, a metabolite of sphingosine, which was unequivocally identified as sphingosine-l-phosphate . The rapid increase in 32P-labeled sphingosine-l-phosphate levels induced by sphingosine was concentration dependent and correlated with its effect on DNA synthesis . Similar to the mitogenic effects of sphingosine, low concentrations ofsphingosine-1-phosphate stimulated DNA synthesis and induced pronounced morphological alterations . Both sphingosine and sphingosine-l-phosphate stimulated DNA synthesis in cells made protein kinase C deficient by prolonged treatment with phorbol ester and sphingosine still T HE biochemical mechanisms whereby eukaryotic cells regulate their proliferation are not well understood . One approach to this problem is to identify the second messengers responsible for the initiation of the progression of Góarrested cells into S phase. In Swiss 3T3 cells, which are sensitive to a wide range of mitogenic agents, some growth factors appear to function through conventional second messengers such as cAMP, whereas others use the signal pathways associated with increased degradation ofpolyphosphoinositides leading to the generation of lipid second messengers. Diacylglycerol (DAG)' is an endogenous activator of protein kinase C (Nishizuka, 1986) and inositol trisphosphate (IP3) causes a release ofCal+ from intracellular stores (Berridge, 1984;Berridge et al., 1984) . Although the roles of these intracellular second messengers which appear to be important for the mitogenic response have been well characterized, it is evident that not all of the second messenger sys-

Activation of caspase-3-like proteases in apoptosis induced by sphingosine and other long-chain bases in Hep3B hepatoma cells

“…Similarly, different outcomes may be found when the same sphingolipid is added into the culture medium of different cell lines. For instance, sphingosine 1-phosphate stimulates cell proliferation of fibroblasts, whereas it induces growth arrest in breast cancer cells [39,40]. In addition, this sphingolipid can trigger apoptosis in HL60 and Hep3B cells [11,12].…”

Mice Deficient in Sphingosine Kinase 1 Are Rendered Lymphopenic by FTY720

“…For phosphorylation of sphingosine by cultured mouse embryonic fibroblasts, the cells, prepared as described previously (37), were washed with phosphate-free Dulbecco's modified Eagle's medium and subsequently incubated with this medium containing 32 P i (40 Ci/ml) for 24 h as described previously (36). The cells were then incubated with 10 M sphingosine or vehicle (controls) for 1 h, and S1P was extracted from the cells (38,39).…”

“…Tissue homogenates (5-20 g of protein in sphingosine kinase buffer: 50 mM Tris (pH 7.5), 10% glycerol, 1 mM ␤-mercaptoethanol, 1 mM EDTA, 1 mM sodium orthovanadate, 40 mM ␤-glycerophosphate, 15 mM NaF, 10 g/ml leupeptin and aprotinin, 1 mM phenylmethylsulfonyl fluoride, and 0.5 mM 4-deoxypyridoxine) were incubated with 50 M sphingosine (prepared either in mixed micelles with Triton X-100 or in bovine serum albumin complexes without Triton X-100), 10 Ci of [␥-32 P]ATP (1 mM), and 10 mMMgCl 2 . Labeled lipids were extracted and resolved by TLC as described previously (35,36). Labeled S1P was quantified with a PhosphorImager.…”

Sphingosine 1-Phosphate Stimulates Insulin Secretion in HIT-T 15 Cells and Mouse Islets.

“…Intracellular content of sphingosine 1-phosphate (S 1 P), a phosphorylated product of sphingosine by sphingosine kinase, was accumulated in response to plateletderived growth factor in Swiss 3T3 fibroblasts [4]. Furthermore, it was demonstrated that S 1 P is involved in the regulation of cellular processes including cell proliferation [5][6][7][8][9]. Recently, several lines of evidence have accumulated suggesting that sphingolipid metabolites may function as a new class of intracellular second messenger.…”