title: The distinct roles of Ras and Rac in PI 3-kinase-dependent protrusion during EGF-stimulated cell migration.
abstract: Cell migration involves the localized extension of actin-rich protrusions, a process that requires Class I phosphoinositide 3-kinases (PI 3-kinases). Both Rac and Ras have been shown to regulate actin polymerization and activate PI 3-kinase. However, the coordination of Rac, Ras and PI 3-kinase activation during epidermal growth factor (EGF)-stimulated protrusion has not been analyzed. We examined PI 3-kinase-dependent protrusion in MTLn3 rat adenocarcinoma cells. EGF-stimulated phosphatidyl-inositol (3,4,5)-trisphosphate [PtdIns(3,4,5)P(3)] levels showed a rapid and persistent response, as PI 3-kinase activity remained elevated up to 3 minutes. The activation kinetics of Ras, but not Rac, coincided with those of leading-edge PtdIns(3,4,5)P(3) production. Small interfering RNA (siRNA) knockdown of K-Ras but not Rac1 abolished PtdIns(3,4,5)P(3) production at the leading edge and inhibited EGF-stimulated protrusion. However, Rac1 knockdown did inhibit cell migration, because of the inhibition of focal adhesion formation in Rac1 siRNA-treated cells. Our data show that in EGF-stimulated MTLn3 carcinoma cells, Ras is required for both PtdIns(3,4,5)P(3) production and lamellipod extension, whereas Rac1 is required for formation of adhesive structures. These data suggest an unappreciated role for Ras during protrusion, and a crucial role for Rac in the stabilization of protrusions required for cell motility.
authors: Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
authors: Shu-Chin
authors: SC
authors: Yip
authors: Mirvat
authors: M
authors: El-Sibai
authors: Salvatore J
authors: SJ
authors: Coniglio
authors: Ghassan
authors: G
authors: Mouneimne
authors: Robert J
authors: RJ
authors: Eddy
authors: Beth E
authors: BE
authors: Drees
authors: Paul O
authors: PO
authors: Neilsen
authors: Sumanta
authors: S
authors: Goswami
authors: Marc
authors: M
authors: Symons
authors: John S
authors: JS
authors: Condeelis
authors: Jonathan M
authors: JM
authors: Backer
mesh_terms: D000230:Adenocarcinoma; D000818:Animals; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology*; D022081:Cell Surface Extensions / Q000378:metabolism*; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D018129:Phosphatidylinositol Phosphates; D011993:Recombinant Fusion Proteins; C060974:phosphatidylinositol 3,4,5-triphosphate; D004815:Epidermal Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D020744:rac GTP-Binding Proteins; D018631:ras Proteins
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