Rosenfeldt H M, Hobson J P, Maceyka M, Olivera A, Nava V E, Milstien S, Spiegel S
Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, D.C. 20007, USA.
FASEB J. 2001 Dec;15(14):2649-59. doi: 10.1096/fj.01-0523com.
Sphingosine-1-phosphate (SPP), formed by sphingosine kinase, is the ligand for EDG-1, a GPCR important for cell migration and vascular maturation. Here we show that cytoskeletal rearrangements, lamellipodia extensions, and cell motility induced by platelet-derived growth factor (PDGF) are abrogated in EDG-1 null fibroblasts. However, EDG-1 appears to be dispensable for mitogenicity and survival effects, even those induced by its ligand SPP and by PDGF. Furthermore, PDGF induced focal adhesion formation and activation of FAK, Src, and stress-activated protein kinase 2, p38, were dysregulated in the absence of EDG-1. In contrast, tyrosine phosphorylation of the PDGFR and activation of extracellular signal regulated kinase (ERK1/2), important for growth and survival, were unaltered. Our results suggest that EDG-1 functions as an integrator linking the PDGFR to lamellipodia extension and cell migration. PDGF, which stimulates sphingosine kinase, leading to increased SPP levels in many cell types, also induces translocation of sphingosine kinase to membrane ruffles. Hence, recruitment of sphingosine kinase to the cell's leading edge and localized formation of SPP may spatially and temporally stimulate EDG-1, resulting in activation and integration of downstream signals important for directional movement toward chemoattractants, such as PDGF. These results may also shed light on the vital role of EDG-1 in vascular maturation.
由鞘氨醇激酶形成的1-磷酸鞘氨醇（SPP）是EDG-1的配体，EDG-1是一种对细胞迁移和血管成熟很重要的G蛋白偶联受体（GPCR）。我们在此表明，血小板衍生生长因子（PDGF）诱导的细胞骨架重排、片状伪足延伸和细胞运动性在EDG-1基因敲除的成纤维细胞中被消除。然而，EDG-1对于促有丝分裂作用和存活效应似乎是可有可无的，即使是由其配体SPP和PDGF诱导的这些效应。此外，在没有EDG-1的情况下，PDGF诱导的粘着斑形成以及粘着斑激酶（FAK）、Src和应激激活蛋白激酶2（p38）的激活失调。相比之下，对生长和存活很重要的血小板衍生生长因子受体（PDGFR）的酪氨酸磷酸化以及细胞外信号调节激酶（ERK1/2）的激活未改变。我们的结果表明，EDG-1作为一个整合因子，将PDGFR与片状伪足延伸和细胞迁移联系起来。PDGF刺激鞘氨醇激酶，导致许多细胞类型中SPP水平升高，它还诱导鞘氨醇激酶转位到膜皱褶。因此，鞘氨醇激酶被招募到细胞前沿以及SPP的局部形成可能在空间和时间上刺激EDG-1，从而导致对向趋化因子（如PDGF）定向移动很重要的下游信号的激活和整合。这些结果也可能揭示EDG-1在血管成熟中的重要作用。
