EDG-1 is a heterotrimeric guanine nucleotide binding protein-coupled receptor 
(GPCR) for sphingosine-1-phosphate (SPP). Cell migration toward platelet-derived 
growth factor (PDGF), which stimulates sphingosine kinase and increases 
intracellular SPP, was dependent on expression of EDG-1. Deletion of edg-1 or 
inhibition of sphingosine kinase suppressed chemotaxis toward PDGF and also 
activation of the small guanosine triphosphatase Rac, which is essential for 
protrusion of lamellipodia and forward movement. Moreover, PDGF activated EDG-1, 
as measured by translocation of beta-arrestin and phosphorylation of EDG-1. Our 
results reveal a role for receptor cross-communication in which activation of a 
GPCR by a receptor tyrosine kinase is critical for cell motility.