Tropomodulin protects α-catenin-dependent junctional-actin networks under stress during epithelial morphogenesis

Curr Biol. 2012 Aug 21;22(16):1500-5. doi: 10.1016/j.cub.2012.06.025. Epub 2012 Jul 5.

Abstract

α-catenin is central to recruitment of actin networks to the cadherin-catenin complex, but how such networks are subsequently stabilized against stress applied during morphogenesis is poorly understood. To identify proteins that functionally interact with α-catenin in this process, we performed enhancer screening using a weak allele of the C. elegans α-catenin, hmp-1, thereby identifying UNC-94/tropomodulin. Tropomodulins (Tmods) cap the minus ends of F-actin in sarcomeres. They also regulate lamellipodia, can promote actin nucleation, and are required for normal cardiovascular development and neuronal growth-cone morphology. Tmods regulate the morphology of cultured epithelial cells, but their role in epithelia in vivo remains unexplored. We find that UNC-94 is enriched within a HMP-1-dependent junctional-actin network at epidermal adherens junctions subject to stress during morphogenesis. Loss of UNC-94 leads to discontinuity of this network, and high-speed filming of hmp-1(fe4);unc-94(RNAi) embryos reveals large junctional displacements that depend on the Rho pathway. In vitro, UNC-94 acts in combination with HMP-1, leading to longer actin bundles than with HMP-1 alone. Our data suggest that Tmods protect actin filaments recruited by α-catenin from minus-end subunit loss, enabling them to withstand the stresses of morphogenesis.

Publication types

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

MeSH terms

  • Actins / metabolism*
  • Animals
  • Caenorhabditis elegans
  • Epidermis / embryology
  • Morphogenesis*
  • Stress, Mechanical*
  • Tropomodulin / metabolism*
  • alpha Catenin / metabolism*

Substances

  • Actins
  • Tropomodulin
  • alpha Catenin