Abstract
Epithelial cell junctions are essential for cell polarity, adhesion and morphogenesis. We have analysed VAB-9, a cell junction protein in Caenorhabditis elegans. VAB-9 is a predicted four-pass integral membrane protein that has greatest similarity to BCMP1 (brain cell membrane protein 1, a member of the PMP22/EMP/Claudin family of cell junction proteins) and localizes to the adherens junction domain of C. elegans apical junctions. Here, we show that VAB-9 requires HMR-1/cadherin for localization to the cell membrane, and both HMP-1/alpha-catenin and HMP-2/beta-catenin for maintaining its distribution at the cell junction. In vab-9 mutants, morphological defects correlate with disorganization of F-actin at the adherens junction; however, localization of the cadherin-catenin complex and epithelial polarity is normal. These results suggest that VAB-9 regulates interactions between the cytoskeleton and the adherens junction downstream of or parallel to alpha-catenin and/or beta-catenin. Mutations in vab-9 enhance adhesion defects through functional loss of the cell junction genes apical junction molecule 1 (ajm-1) and discs large 1 (dlg-1), suggesting that VAB-9 is involved in cell adhesion. Thus, VAB-9 represents the first characterized tetraspan adherens junction protein in C. elegans and defines a new family of such proteins in higher eukaryotes.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Actin Cytoskeleton / metabolism
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Adherens Junctions / genetics
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Adherens Junctions / metabolism
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Animals
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Cadherins / metabolism
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Caenorhabditis elegans / genetics
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Caenorhabditis elegans / metabolism*
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Caenorhabditis elegans / ultrastructure
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Caenorhabditis elegans Proteins / genetics
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Caenorhabditis elegans Proteins / isolation & purification*
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Caenorhabditis elegans Proteins / metabolism
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Cell Adhesion / genetics*
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Cell Size / genetics
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Claudin-1
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Cytoskeletal Proteins / metabolism
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DNA, Complementary / analysis
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DNA, Complementary / genetics
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Epidermis / metabolism*
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Epidermis / ultrastructure
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Epithelial Cells / metabolism*
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Epithelial Cells / ultrastructure
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Intercellular Junctions / genetics
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Intercellular Junctions / metabolism*
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Intercellular Junctions / ultrastructure
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Membrane Proteins / genetics
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Membrane Proteins / isolation & purification*
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Membrane Proteins / metabolism
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Microscopy, Electron
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Molecular Sequence Data
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Mutation / genetics
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Sequence Homology, Amino Acid
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Sequence Homology, Nucleic Acid
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Trans-Activators / metabolism
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alpha Catenin
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beta Catenin
Substances
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AJM-1 protein, C elegans
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Cadherins
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Caenorhabditis elegans Proteins
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Claudin-1
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Cytoskeletal Proteins
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DNA, Complementary
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Membrane Proteins
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Trans-Activators
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VAB-9 protein, C elegans
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alpha Catenin
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beta Catenin
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hmr-1 protein, C elegans