title: 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.
abstract: 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.
authors.affiliation: 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.
authors.forename: Hui
authors.initials: H
authors.lastname: Miao
authors.forename: Klaus
authors.initials: K
authors.lastname: Strebhardt
authors.forename: Elena B
authors.initials: EB
authors.lastname: Pasquale
authors.forename: Tang-Long
authors.initials: TL
authors.lastname: Shen
authors.forename: Jun-Lin
authors.initials: JL
authors.lastname: Guan
authors.forename: Bingcheng
authors.initials: B
authors.lastname: Wang
mesh_terms: 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
chemical_list: D036387:Ephrin-B1; D005353:Fibronectins; D016023:Integrins; D017228:Hepatocyte Growth Factor; D036223:Receptor, EphB3; D020741:rho GTP-Binding Proteins