Specific conserved C-terminal amino acids of Caenorhabditis elegans HMP-1/α-catenin modulate F-actin binding independently of vinculin

J Biol Chem. 2013 Feb 22;288(8):5694-706. doi: 10.1074/jbc.M112.438093. Epub 2012 Dec 27.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actin Cytoskeleton / metabolism
  • Actins / metabolism*
  • Alleles
  • Animals
  • Cadherins / metabolism
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans Proteins / metabolism
  • Fluorescence Recovery After Photobleaching
  • Homozygote
  • Models, Biological
  • Mutation
  • Protein Binding
  • Protein Structure, Tertiary
  • Sequence Analysis, DNA
  • Vinculin / chemistry
  • Vinculin / metabolism*
  • alpha Catenin / metabolism

Substances

  • Actins
  • Cadherins
  • Caenorhabditis elegans Proteins
  • alpha Catenin
  • Vinculin