Synaptopodin Couples Epithelial Contractility to α-actinin-4-dependent Junction Maturation

J Cell Biol. 2015 Oct 26;211(2):407-34. doi: 10.1083/jcb.201412003.

Abstract

The epithelial junction experiences mechanical force exerted by endogenous actomyosin activities and from interactions with neighboring cells. We hypothesize that tension generated at cell-cell adhesive contacts contributes to the maturation and assembly of the junctional complex. To test our hypothesis, we used a hydraulic apparatus that can apply mechanical force to intercellular junction in a confluent monolayer of cells. We found that mechanical force induces α-actinin-4 and actin accumulation at the cell junction in a time- and tension-dependent manner during junction development. Intercellular tension also induces α-actinin-4-dependent recruitment of vinculin to the cell junction. In addition, we have identified a tension-sensitive upstream regulator of α-actinin-4 as synaptopodin. Synaptopodin forms a complex containing α-actinin-4 and β-catenin and interacts with myosin II, indicating that it can physically link adhesion molecules to the cellular contractile apparatus. Synaptopodin depletion prevents junctional accumulation of α-actinin-4, vinculin, and actin. Knockdown of synaptopodin and α-actinin-4 decreases the strength of cell-cell adhesion, reduces the monolayer permeability barrier, and compromises cellular contractility. Our findings underscore the complexity of junction development and implicate a control process via tension-induced sequential incorporation of junctional components.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Actin Cytoskeleton / metabolism
  • Actinin / genetics
  • Actinin / metabolism*
  • Actins / metabolism
  • Actomyosin / metabolism
  • Adherens Junctions / metabolism*
  • Amino Acid Sequence
  • Animals
  • Cell Adhesion / genetics
  • Cell Adhesion / physiology
  • Cell Adhesion Molecules / metabolism
  • Cell Line
  • Dogs
  • Epithelial Cells / physiology*
  • Humans
  • Madin Darby Canine Kidney Cells
  • Mechanotransduction, Cellular*
  • Molecular Sequence Data
  • Multiprotein Complexes / metabolism
  • Myosin Type II / metabolism
  • Protein Structure, Tertiary
  • Synaptophysin / genetics
  • Synaptophysin / metabolism*
  • Tensile Strength*
  • Vinculin / metabolism
  • beta Catenin / metabolism

Substances

  • Actins
  • Cell Adhesion Molecules
  • Multiprotein Complexes
  • Synaptophysin
  • beta Catenin
  • Actinin
  • Vinculin
  • Actomyosin
  • Myosin Type II