The verprolin-like central (vc) region of Wiskott-Aldrich syndrome protein induces Arp2/3 complex-dependent actin nucleation

J Biol Chem. 2001 Sep 21;276(38):35761-7. doi: 10.1074/jbc.M106520200. Epub 2001 Jul 17.


Wiskott-Aldrich Syndrome protein (WASp) and related proteins stimulate actin filament nucleation by Arp2/3 complex. The isolated C-terminal VCA domain of WASp (containing Verprolin-like, Central and Acidic regions) is constitutively active but autoinhibited in the full-length protein. This study compared the ability of parts of VCA fused to the C terminus of glutathione S-transferase (GST) to bind actin and Arp2/3 complex in vitro and to activate actin polymerization in vitro and in cells. Fluorescence anisotropy measurements showed that GST-CA and GST-A bound Arp2/3 complex with K(d) values of 0.11 microm and 1.0 microm, respectively, whereas GST-VC displayed almost undetectable binding (K(d) > 1 mm). However, GST-VC activated actin nucleation through Arp2/3 complex in vitro, though requiring 70-fold higher concentration than GST-VCA while neither GST-CA nor GST-A activated Arp2/3 complex in vitro, though both GST-CA and GST-A inhibited Arp2/3 complex activation by WASp VCA. None of these constructs bound WASp from macrophage lysates. Both GST-VC and GST-CA induced actin accumulations when microinjected into primary human macrophages or human endothelial vein cells. However, only microinjection of GST-VC led to a significant increase of cellular polymerized actin. Additionally, endogenous Arp2/3 complex, but not WASp, colocalized with these GST-VC-induced actin accumulations. These data suggest that WASp constructs lacking the A region, previously thought to be indispensable for actin nucleation, are able to bind and activate Arp2/3 complex in vitro and in vivo.

Publication types

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

MeSH terms

  • Actin-Related Protein 2
  • Actin-Related Protein 3
  • Actins / metabolism*
  • Cells, Cultured
  • Cytoskeletal Proteins*
  • Fungal Proteins / chemistry
  • Fungal Proteins / physiology*
  • Glutathione Transferase / metabolism
  • Humans
  • Microfilament Proteins / chemistry
  • Microfilament Proteins / physiology*
  • Microinjections
  • Proteins / chemistry
  • Proteins / metabolism
  • Proteins / physiology*
  • Saccharomyces cerevisiae Proteins*
  • Wiskott-Aldrich Syndrome / metabolism*
  • Wiskott-Aldrich Syndrome Protein


  • ACTR2 protein, human
  • ACTR3 protein, human
  • Actin-Related Protein 2
  • Actin-Related Protein 3
  • Actins
  • Cytoskeletal Proteins
  • Fungal Proteins
  • Microfilament Proteins
  • Proteins
  • Saccharomyces cerevisiae Proteins
  • VRP1 protein, S cerevisiae
  • WAS protein, human
  • Wiskott-Aldrich Syndrome Protein
  • Glutathione Transferase