The cell junction protein VAB-9 regulates adhesion and epidermal morphology in C. elegans.
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.
Simske
Jeffrey S
JS
Department of Zoology, University of Wisconsin, Madison, 1117 West Johnson Street, Madison, WI 53706 USA. jsimske@metrohealth.org
Köppen
Mathias
M
Sims
Paul
P
Hodgkin
Jonathan
J
Yonkof
Alicia
A
Hardin
Jeff
J
D008841:Actin Cytoskeleton / Q000378:metabolism; D022005:Adherens Junctions / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D002448:Cell Adhesion / Q000235:genetics*; D048429:Cell Size / Q000235:genetics; D062445:Claudin-1; D003598:Cytoskeletal Proteins / Q000378:metabolism; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D004817:Epidermis / Q000378:metabolism* / Q000648:ultrastructure; D004847:Epithelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D007365:Intercellular Junctions / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D015534:Trans-Activators / Q000378:metabolism; D051178:alpha Catenin; D051176:beta Catenin
C441580:AJM-1 protein, C elegans; D015820:Cadherins; D029742:Caenorhabditis elegans Proteins; D062445:Claudin-1; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; D008565:Membrane Proteins; D015534:Trans-Activators; C476324:VAB-9 protein, C elegans; D051178:alpha Catenin; D051176:beta Catenin; C450060:hmr-1 protein, C elegans