Attention has focused recently on cross talk between signaling pathways in mammalian cells. Indeed, activation of G protein-coupled receptors (GPCR) can result in activation of growth factor receptor tyrosine kinases even when the ligand for the latter is not present. Hobson et al. now show that cell motility induced by stimulation of the platelet-derived growth factor receptor (PDGFR, a receptor tyrosine kinase) requires signaling through the receptor EDG-1 (a GPCR). In this case, stimulation of the PDGF receptor causes increased production of sphingosine-1-phosphate, which acts in an autocrine or paracrine manner as an activating ligand for EDG-1. In mouse embryo fibroblasts lacking sphingosine kinase or EDG-1, chemotaxis of the cells toward PDGF was inhibited.
J. P. Hobson, H. M. Rosenfeldt, L. S. Barak, A. Olivera, S. Poulton, M. G. Caron, S. Milstien, S. Spiegel, Role of the sphingosine-1-phosphate receptor EDG-1 in PDGF-induced cell motility. Science 291, 1800-1803 (2001). [Abstract] [Full Text]