Enhancement of branching efficiency by the actin filament-binding activity of N-WASP/WAVE2

J Cell Sci. 2001 Dec;114(Pt 24):4533-42.

Abstract

The actin-related protein (Arp) 2/3 complex is an essential regulator of de novo actin filament formation. Arp2/3 nucleates the polymerization of actin and creates branched actin filaments when activated by Arp2/3-complex activating domain (VCA) of Wiskott-Aldrich syndrome proteins (WASP family proteins). We found that the branching of actin filaments on pre-existing ADP filaments mediated by the Arp2/3 complex is twice as efficient when Arp2/3 was activated by wild-type neural WASP (N-WASP) or WASP-family verprolin-homologous protein (WAVE) 2 than when activated by the VCA domain alone. By contrast, there was no difference between wild-type N-WASP or WAVE2 and VCA in the branching efficiency on de novo filaments, which are thought to consist mainly of ADP-phosphate filaments. This increased branching efficiency on ADP filaments is due to the basic region located in the center of N-WASP and WAVE2, which was found to associate with ADP actin filaments. Actin filaments and phosphatidylinositol bisphosphate (PIP2) associate with N-WASP at different sites. This association of N-WASP and WAVE2 with actin filaments enhanced recruitment of Arp2/3 to the pre-existing filaments, presumably leading to efficient nucleation and branch formation on pre-existing filaments. These data together suggest that the actin filament binding activity of N-WASP and WAVE2 in the basic region increases the number of barbed ends created on pre-existing filaments. Efficient branching on ADP filaments may be important for initiation of actin-based motility.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actin Cytoskeleton / metabolism
  • Actin-Related Protein 2
  • Actin-Related Protein 3
  • Actins / metabolism
  • Actins / physiology
  • Animals
  • Cytoskeletal Proteins*
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism
  • Microfilament Proteins / physiology*
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Nerve Tissue Proteins / physiology*
  • Phosphatidylinositol 4,5-Diphosphate / physiology
  • Protein Binding / genetics
  • Protein Structure, Tertiary / genetics
  • Rabbits
  • Wiskott-Aldrich Syndrome / metabolism
  • Wiskott-Aldrich Syndrome Protein, Neuronal

Substances

  • Actin-Related Protein 2
  • Actin-Related Protein 3
  • Actins
  • Cytoskeletal Proteins
  • Microfilament Proteins
  • Nerve Tissue Proteins
  • Phosphatidylinositol 4,5-Diphosphate
  • Wiskott-Aldrich Syndrome Protein, Neuronal