Cdc42 and phosphoinositide 3-kinase drive Rac-mediated actin polymerization downstream of c-Met in distinct and common pathways.
Activation of c-Met, the hepatocyte growth factor (HGF)/scatter factor receptor induces reorganization of the actin cytoskeleton, which drives epithelial cell scattering and motility and is exploited by pathogenic Listeria monocytogenes to invade nonepithelial cells. However, the precise contributions of distinct Rho-GTPases, the phosphatidylinositol 3-kinases, and actin assembly regulators to c-Met-mediated actin reorganization are still elusive. Here we report that HGF-induced membrane ruffling and Listeria invasion mediated by the bacterial c-Met ligand internalin B (InlB) were significantly impaired but not abrogated upon genetic removal of either Cdc42 or pharmacological inhibition of phosphoinositide 3-kinase (PI3-kinase). While loss of Cdc42 or PI3-kinase function correlated with reduced HGF- and InlB-triggered Rac activation, complete abolishment of actin reorganization and Rac activation required the simultaneous inactivation of both Cdc42 and PI3-kinase signaling. Moreover, Cdc42 activation was fully independent of PI3-kinase activity, whereas the latter partly depended on Cdc42. Finally, Cdc42 function did not require its interaction with the actin nucleation-promoting factor N-WASP. Instead, actin polymerization was driven by Arp2/3 complex activation through the WAVE complex downstream of Rac. Together, our data establish an intricate signaling network comprising as key molecules Cdc42 and PI3-kinase, which converge on Rac-mediated actin reorganization essential for Listeria invasion and membrane ruffling downstream of c-Met.
Cytoskeleton Dynamics Group, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, D-38124, Braunschweig, Germany.
Tanja
T
Bosse
Julia
J
Ehinger
Aleksandra
A
Czuchra
Stefanie
S
Benesch
Anika
A
Steffen
Xunwei
X
Wu
Kathrin
K
Schloen
Hartmut H
HH
Niemann
Giorgio
G
Scita
Theresia E B
TE
Stradal
Cord
C
Brakebusch
Klemens
K
Rottner
D000199:Actins / Q000378:metabolism*; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D022081:Cell Surface Extensions / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D008089:Listeria monocytogenes / Q000378:metabolism / Q000472:pathogenicity; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019859:Proto-Oncogene Proteins c-met / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D051300:Wiskott-Aldrich Syndrome Protein Family / Q000378:metabolism; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal / Q000235:genetics / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D000199:Actins; D001426:Bacterial Proteins; D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019859:Proto-Oncogene Proteins c-met; D011993:Recombinant Fusion Proteins; D051300:Wiskott-Aldrich Syndrome Protein Family; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; C095768:inlB protein, Listeria monocytogenes