Switch Associated Protein 70 (SWAP70)

SWAP70 specifically binds phosphatidylinositol-3,4,5-triphosphate. On stimulation by growth factors, cytoplasmic SWAP70, which is dependent on phosphoinositide-3-hydroxykinase but independent of Ras, moved to cell membrane rearrangements known as ruffles. However, mutant SWAP70 lacking the ability to bind phosphatidylinositol-3,4,5-triphosphate blocked membrane ruffling induced by epidermal growth factor (EGF) or platelet-derived growth factor. SWAP70 shows low homology with Rac-guanine nucleotide exchange factors, and catalyzes phosphatidylinositol-3,4,5-triphosphate-dependent guanine nucleotide exchange to Rac. SWAP70-deficient fibroblasts showed impaired membrane ruffling after stimulation with EGF, and failed to activate Rac fully.