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J. Cell Biol.,
Volume 141, Number 3, May 4, 1998 755-764
-Catenin and Vinculin
* Cell Biology, Zoological Institute, Technical University, 38092 Braunschweig, Germany; and In epithelial cells, Complex formation of vinculin and Division of Cell Biology and
Immunology, National Research Centre for Biotechnology, 38124 Braunschweig, Germany
-, 
-, and 
-catenin are
involved in linking the peripheral microfilament belt to
the transmembrane protein E-cadherin. -Catenin
exhibits sequence homologies over three regions to
vinculin, another adherens junction protein. While
vinculin is found in cell-matrix and cell-cell contacts, -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 -catenin. We show that
-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
-catenin, as seen by immunoprecipitation, dot overlay,
cosedimentation, and surface plasmon resonance measurements. The Kd of the complex was determined to
2-4 × 10
7 M. As seen by overlays and affinity mass
spectrometry, the COOH-terminal region of -catenin
is involved in this interaction.
-catenin was
challenged in transfected cells. In PtK2 cells, intact
-catenin and -catenin1-670, harboring the -catenin-
binding site, were directed to cell-cell contacts. In contrast, -catenin697-906 fragments were recruited to
cell-cell contacts, focal adhesions, and stress fibers. Our results imply that in vivo -catenin, like vinculin, is
tightly regulated in its ligand binding activity.
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