Spatial control of actin organization at adherens junctions by a synaptotagmin-like protein Btsz

Nature. 2006 Aug 3;442(7102):580-4. doi: 10.1038/nature04935. Epub 2006 Jul 9.

Abstract

Epithelial tissues maintain a robust architecture during development. This fundamental property relies on intercellular adhesion through the formation of adherens junctions containing E-cadherin molecules. Localization of E-cadherin is stabilized through a pathway involving the recruitment of actin filaments by E-cadherin. Here we identify an additional pathway that organizes actin filaments in the apical junctional region (AJR) where adherens junctions form in embryonic epithelia. This pathway is controlled by Bitesize (Btsz), a synaptotagmin-like protein that is recruited in the AJR independently of E-cadherin and is required for epithelial stability in Drosophila embryos. On loss of btsz, E-cadherin is recruited normally to the AJR, but is not stabilized properly and actin filaments fail to form a stable continuous network. In the absence of E-cadherin, actin filaments are stable for a longer time than they are in btsz mutants. We identify two polarized cues that localize Btsz: phosphatidylinositol (4,5)-bisphosphate, to which Btsz binds; and Par-3. We show that Btsz binds to the Ezrin-Radixin-Moesin protein Moesin, an F-actin-binding protein that is localized apically and is recruited in the AJR in a btsz-dependent manner. Expression of a dominant-negative form of Ezrin that does not bind F-actin phenocopies the loss of btsz. Thus, our data indicate that, through their interaction, Btsz and Moesin may mediate the proper organization of actin in a local domain, which in turn stabilizes E-cadherin. These results provide a mechanism for the spatial order of actin organization underlying junction stabilization in primary embryonic epithelia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / chemistry*
  • Actins / metabolism*
  • Adherens Junctions / chemistry
  • Adherens Junctions / metabolism*
  • Animals
  • Cadherins / chemistry
  • Cadherins / genetics
  • Cadherins / metabolism
  • Cell Line
  • Drosophila Proteins / chemistry
  • Drosophila Proteins / deficiency
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism*
  • Drosophila melanogaster / cytology*
  • Drosophila melanogaster / embryology
  • Drosophila melanogaster / genetics
  • Drosophila melanogaster / metabolism*
  • Epithelial Cells / cytology
  • Epithelial Cells / metabolism
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins / chemistry
  • Membrane Proteins / deficiency
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Microfilament Proteins / chemistry
  • Microfilament Proteins / metabolism
  • Phosphatidylinositol 4,5-Diphosphate / metabolism
  • Protein Binding
  • RNA Interference
  • Synaptotagmins*

Substances

  • Actins
  • Cadherins
  • Drosophila Proteins
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Microfilament Proteins
  • Phosphatidylinositol 4,5-Diphosphate
  • baz protein, Drosophila
  • btsz protein, Drosophila
  • Synaptotagmins
  • moesin