title: Vinculin is part of the cadherin-catenin junctional complex: complex formation between alpha-catenin and vinculin.
abstract: In epithelial cells, alpha-, beta-, and gamma-catenin are involved in linking the peripheral microfilament belt to the transmembrane protein E-cadherin. alpha-Catenin exhibits sequence homologies over three regions to vinculin, another adherens junction protein. While vinculin is found in cell-matrix and cell-cell contacts, alpha-catenin is restricted to the latter. To elucidate, whether vinculin is part of the cell-cell junctional complex, we investigated complex formation and intracellular targeting of vinculin and alpha-catenin. We show that alpha-catenin colocalizes at cell-cell contacts with endogenous vinculin and also with the transfected vinculin head domain forming immunoprecipitable complexes. In vitro, the vinculin NH2-terminal head binds to alpha-catenin, as seen by immunoprecipitation, dot overlay, cosedimentation, and surface plasmon resonance measurements. The Kd of the complex was determined to 2-4 x 10(-7) M. As seen by overlays and affinity mass spectrometry, the COOH-terminal region of alpha-catenin is involved in this interaction. Complex formation of vinculin and alpha-catenin was challenged in transfected cells. In PtK2 cells, intact alpha-catenin and alpha-catenin1-670, harboring the beta-catenin- binding site, were directed to cell-cell contacts. In contrast, alpha-catenin697-906 fragments were recruited to cell-cell contacts, focal adhesions, and stress fibers. Our results imply that in vivo alpha-catenin, like vinculin, is tightly regulated in its ligand binding activity.
authors.affiliation: Cell Biology, Zoological Institute, Technical University, 38092 Braunschweig, Germany.
authors.forename: E E
authors.initials: EE
authors.lastname: Weiss
authors.forename: M
authors.initials: M
authors.lastname: Kroemker
authors.forename: A H
authors.initials: AH
authors.lastname: Rüdiger
authors.forename: B M
authors.initials: BM
authors.lastname: Jockusch
authors.forename: M
authors.initials: M
authors.lastname: Rüdiger
mesh_terms: D000818:Animals; D015820:Cadherins / Q000378:metabolism*; D002417:Cattle; D002450:Cell Communication; D002460:Cell Line; D003432:Cross-Linking Reagents; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D007365:Intercellular Junctions / Q000378:metabolism*; D051379:Mice; D014162:Transfection; D016596:Vinculin / Q000235:genetics / Q000378:metabolism*; D051178:alpha Catenin
chemical_list: D015820:Cadherins; D003432:Cross-Linking Reagents; C495272:Ctnna1 protein, mouse; D003598:Cytoskeletal Proteins; D051178:alpha Catenin; D016596:Vinculin