Inhibition of integrin-mediated cell adhesion but not directional cell migration requires catalytic activity of EphB3 receptor tyrosine kinase. Role of Rho family small GTPases.
Genetic studies have shown that Eph receptor tyrosine kinases have both kinase-dependent and kinase-independent functions through incompletely understood mechanisms. We report here that ephrin-B1 stimulation of endogenous EphB kinases in LS174T colorectal epithelial cells inhibited integrin-mediated adhesion and HGF/SF-induced directional cell migration. Using 293 cells stably transfected with wild type (WT)- or kinase-deficient (KD-EphB3), we found that inhibition of integrin-mediated cell adhesion and induction of cell rounding was kinase-dependent. Unexpectedly, in two independent assays, both KD- and WT-EphB3 significantly inhibited directional cell migration. Upon ephrin-B1 stimulation, the activities of Rac1 and Cdc42 were reduced in both WT- and KD-EphB3-expressing cells that were induced to migrate. Pharmacological evidence demonstrates that a relative increase in RhoA signaling as a result of decreased Rac1/Cdc42 activities contributes to the inhibitory effects. Furthermore, EphB3-mediated inhibitory effect on cell adhesion but not migration was abolished by the integrin activating antibodies, suggesting that the inhibition of cell migration is not because of down-regulation of integrin function. These results uncover a differential requirement for EphB3 catalytic activity in the regulation of cell adhesion and migration, and suggest that while catalytic activity of EphB3 is required for inhibition of integrin-mediated cell adhesion, a distinct signaling pathway to Rho GTPases shared by WT- and KD-EphB3 receptor mediates inhibition of directional cell migration.
Miao
Hui
H
Rammelkamp Center for Research, MetroHealth Campus, and Department of Pharmacology and Ireland Cancer Center, Case Western Reserve University School of Medicine, Cleveland, Ohio 44109, USA.
Strebhardt
Klaus
K
Pasquale
Elena B
EB
Shen
Tang-Long
TL
Guan
Jun-Lin
JL
Wang
Bingcheng
B
D002384:Catalysis; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D002465:Cell Movement; D022081:Cell Surface Extensions / Q000378:metabolism; D003106:Colon / Q000166:cytology; D004789:Enzyme Activation / Q000187:drug effects; D036387:Ephrin-B1 / Q000378:metabolism / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D017228:Hepatocyte Growth Factor / Q000494:pharmacology; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D036223:Receptor, EphB3 / Q000235:genetics / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000378:metabolism
D036387:Ephrin-B1; D005353:Fibronectins; D016023:Integrins; D017228:Hepatocyte Growth Factor; D036223:Receptor, EphB3; D020741:rho GTP-Binding Proteins