title: EphA2 engages Git1 to suppress Arf6 activity modulating epithelial cell-cell contacts.
abstract: ADP-ribosylation factor (Arf) 6 activity is crucially involved in the regulation of E-cadherin-based cell-cell adhesions. Erythropoietin-producing hepatocellular carcinoma (Eph)-family receptors recognize ligands, namely, ephrins, anchored to the membrane of apposing cells, and they mediate cell-cell contact-dependent events. Here, we found that Arf6 activity is down-regulated in Madin-Darby canine kidney cells, which is dependent on cell density and calcium ion concentration, and we provide evidence of a novel signaling pathway by which ligand-activated EphA2 suppresses Arf6 activity. This EphA2-mediated suppression of Arf6 activity was linked to the induction of cell compaction and polarization, but it was independent of the down-regulation of extracellular signal-regulated kinase 1/2 kinase activity. We show that G protein-coupled receptor kinase-interacting protein (Git) 1 and noncatalytic region of tyrosine kinase (Nck) 1 are involved in this pathway, in which ligand-activated EphA2, via its phosphorylated Tyr594, binds to the Src homology 2 domain of Nck1, and then via its Src homology 3 domain binds to the synaptic localizing domain of Git1 to suppress Arf6 activity. We propose a positive feedback loop in which E-cadherin-based cell-cell contacts enhance EphA-ephrinA signaling, which in turn down-regulates Arf6 activity to enhance E-cadherin-based cell-cell contacts as well as the apical-basal polarization of epithelial cells.
authors.affiliation: Department of Molecular Biology, Osaka Bioscience Institute, Suita, Osaka 565-0874, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Miura
authors.forename: Jin-Min
authors.initials: JM
authors.lastname: Nam
authors.forename: Chie
authors.initials: C
authors.lastname: Kojima
authors.forename: Naoki
authors.initials: N
authors.lastname: Mochizuki
authors.forename: Hisataka
authors.initials: H
authors.lastname: Sabe
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002449:Cell Aggregation / Q000187:drug effects; D002450:Cell Communication / Q000187:drug effects; D002452:Cell Count; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D016764:Cell Polarity / Q000187:drug effects; D004285:Dogs; D036382:Ephrin-A1 / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D005799:Genes, Dominant; D006801:Humans; D008024:Ligands; D051379:Mice; D015513:Oncogene Proteins / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D036104:Receptor, EphA2 / Q000378:metabolism*; D013347:Subcellular Fractions / Q000187:drug effects
chemical_list: D000089982:ADP-Ribosylation Factor 6; D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D036382:Ephrin-A1; D020690:GTPase-Activating Proteins; C120766:Git1 protein, mouse; D008024:Ligands; C078332:Nck protein; D015513:Oncogene Proteins; D036104:Receptor, EphA2; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715727:Arf6 protein, mouse; D002118:Calcium