Role of receptor tyrosine kinases in G-protein-coupled receptor regulation of Ras: transactivation or parallel pathways?

Ras protein regulation by G-protein-coupled receptors has been thought to occur through transactivation of receptor tyrosine kinases. New evidence suggests that these two receptor types independently control different pathways leading to Ras activation in response to lysophosphatidic acid (LPA). Epidermal growth factor receptor function is needed for basal nucleotide exchange on Ras, whereas the LPA receptor controls an inducible exchange activity.