title: Specific conserved C-terminal amino acids of Caenorhabditis elegans HMP-1/α-catenin modulate F-actin binding independently of vinculin.
abstract: Stable intercellular adhesions formed through the cadherin-catenin complex are important determinants of proper tissue architecture and help maintain tissue integrity during morphogenetic movements in developing embryos. A key regulator of this stability is α-catenin, which connects the cadherin-catenin complex to the actin cytoskeleton. Although the C-terminal F-actin-binding domain of α-catenin has been shown to be crucial for its function, a more detailed in vivo analysis of discrete regions and residues required for actin binding has not been performed. Using Caenorhabditis elegans as a model system, we have characterized mutations in hmp-1/α-catenin that identify HMP-1 residues 687-742 and 826-927, as well as amino acid 802, as critical to the localization of junctional proximal actin during epidermal morphogenesis. We also find that the S823F transition in a hypomorphic allele, hmp-1(fe4), decreases actin binding in vitro. Using hmp-1(fe4) animals in a mutagenesis screen, we were then able to identify 11 intragenic suppressors of hmp-1(fe4) that revert actin binding to wild-type levels. Using homology modeling, we show that these amino acids are positioned at key conserved sites within predicted α-helices in the C terminus. Through the use of transgenic animals, we also demonstrate that HMP-1 residues 315-494, which correspond to a putative mechanotransduction domain that binds vinculin in vertebrate αE-catenin, are not required during epidermal morphogenesis but may aid efficient recruitment of HMP-1 to the junction. Our studies are the first to identify key conserved amino acids in the C terminus of α-catenin that modulate F-actin binding in living embryos of a simple metazoan.
authors.affiliation: Department of Zoology, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Maiden
authors.forename: Neale
authors.initials: N
authors.lastname: Harrison
authors.forename: Jack
authors.initials: J
authors.lastname: Keegan
authors.forename: Brian
authors.initials: B
authors.lastname: Cain
authors.forename: Allison M
authors.initials: AM
authors.lastname: Lynch
authors.forename: Jonathan
authors.initials: J
authors.lastname: Pettitt
authors.forename: Jeff
authors.initials: J
authors.lastname: Hardin
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D000483:Alleles; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism; D036681:Fluorescence Recovery After Photobleaching; D006720:Homozygote; D008954:Models, Biological; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017422:Sequence Analysis, DNA; D016596:Vinculin / Q000737:chemistry / Q000378:metabolism*; D051178:alpha Catenin / Q000378:metabolism
chemical_list: D000199:Actins; D015820:Cadherins; D029742:Caenorhabditis elegans Proteins; D051178:alpha Catenin; D016596:Vinculin