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J. Cell Biol.,
Volume 144, Number 1, January 11, 1999 59-69






* Craniofacial Developmental Biology and Regeneration Branch, National Institute of Dental and Craniofacial Research,
National Institutes of Health, Bethesda, Maryland 20892; Using the yeast two-hybrid system and an in
vitro binding assay, we have identified a novel protein
termed vinexin as a vinculin-binding protein. By Northern blotting, we identified two types of vinexin mRNA
that were 3 and 2 kb in length. Screening for full-length cDNA clones and sequencing indicated that the two
mRNA encode 82- and 37-kD polypeptides termed vinexin
Laboratory of Biochemistry, Division of Applied Life Science, Kyoto
University, Kyoto 606-01, Japan; § Laboratory of Molecular Carcinogenesis, National Institute of Environmental Health Science,
Research Triangle Park, North Carolina 27709; and
Biomolecular Engineering Research Institute, Osaka 565-0874, Japan
and
, respectively. Both forms of vinexin share
a common carboxyl-terminal sequence containing three
SH3 domains. The larger vinexin
contains an additional amino-terminal sequence. The interaction between vinexin and vinculin was mediated by two SH3
domains of vinexin and the proline-rich region of vinculin. When expressed, vinexin
and
localized to focal
adhesions in NIH 3T3 fibroblasts, and to cell-cell junctions in epithelial LLC-PK1 cells. Furthermore, expression of vinexin increased focal adhesion size. Vinexin
also promoted upregulation of actin stress fiber formation. In addition, cell lines stably expressing vinexin
showed enhanced cell spreading on fibronectin. These
data identify vinexin as a novel focal adhesion and cell-
cell adhesion protein that binds via SH3 domains to the
hinge region of vinculin, which can enhance actin cytoskeletal organization and cell spreading.
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