Regulation of cell shape by Cdc42 is mediated by the synergic actin-bundling activity of the Eps8-IRSp53 complex

Nat Cell Biol. 2006 Dec;8(12):1337-47. doi: 10.1038/ncb1502. Epub 2006 Nov 19.

Abstract

Actin-crosslinking proteins organize actin into highly dynamic and architecturally diverse subcellular scaffolds that orchestrate a variety of mechanical processes, including lamellipodial and filopodial protrusions in motile cells. How signalling pathways control and coordinate the activity of these crosslinkers is poorly defined. IRSp53, a multi-domain protein that can associate with the Rho-GTPases Rac and Cdc42, participates in these processes mainly through its amino-terminal IMD (IRSp53 and MIM domain). The isolated IMD has actin-bundling activity in vitro and is sufficient to induce filopodia in vivo. However, the manner of regulation of this activity in the full-length protein remains largely unknown. Eps8 is involved in actin dynamics through its actin barbed-ends capping activity and its ability to modulate Rac activity. Moreover, Eps8 binds to IRSp53. Here, we describe a novel actin crosslinking activity of Eps8. Additionally, Eps8 activates and synergizes with IRSp53 in mediating actin bundling in vitro, enhancing IRSp53-dependent membrane extensions in vivo. Cdc42 binds to and controls the cellular distribution of the IRSp53-Eps8 complex, supporting the existence of a Cdc42-IRSp53-Eps8 signalling pathway. Consistently, Cdc42-induced filopodia are inhibited following individual removal of either IRSp53 or Eps8. Collectively, these results support a model whereby the synergic bundling activity of the IRSp53-Eps8 complex, regulated by Cdc42, contributes to the generation of actin bundles, thus promoting filopodial protrusions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actin Cytoskeleton / metabolism*
  • Actins / metabolism*
  • Adaptor Proteins, Signal Transducing
  • Animals
  • COS Cells
  • Cell Shape*
  • Chlorocebus aethiops
  • HeLa Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Nerve Tissue Proteins / metabolism*
  • Protein Binding
  • Protein Transport
  • Pseudopodia / metabolism
  • Wiskott-Aldrich Syndrome Protein Family / metabolism
  • cdc42 GTP-Binding Protein / metabolism*

Substances

  • Actins
  • Adaptor Proteins, Signal Transducing
  • BAIAP2 protein, human
  • EPS8 protein, human
  • Intracellular Signaling Peptides and Proteins
  • Nerve Tissue Proteins
  • Wiskott-Aldrich Syndrome Protein Family
  • cdc42 GTP-Binding Protein