Cdc42 induces filopodia by promoting the formation of an IRSp53:Mena complex

Curr Biol. 2001 Oct 30;11(21):1645-55. doi: 10.1016/s0960-9822(01)00506-1.


Background: The Rho GTPases Rho, Rac, and Cdc42 regulate the organization of the actin cytoskeleton by interacting with multiple, distinct downstream effector proteins. Cdc42 controls the formation of actin bundle-containing filopodia at the cellular periphery. The molecular mechanism for this remains as yet unclear.

Results: We report here that Cdc42 interacts with IRSp53/BAP2 alpha, an SH3 domain-containing scaffold protein, at a partial CRIB motif and that an N-terminal fragment of IRSp53 binds, via an intramolecular interaction, to the CRIB motif-containing central region. Overexpression of IRSp53 in fibroblasts leads to the formation of filopodia, and both this and Cdc42-induced filopodia are inhibited by expression of the N-terminal IRSp53 fragment. Using affinity chromatography, we have identified Mena, an Ena/VASP family member, as interacting with the SH3 domain of IRSp53. Mena and IRSp53 act synergistically to promote filopodia formation.

Conclusion: We conclude that the interaction of Cdc42 with the partial CRIB motif of IRSp53 relieves an intramolecular, autoinhibitory interaction with the N terminus, allowing the recruitment of Mena to the IRSp53 SH3 domain. This IRSp53:Mena complex initiates actin filament assembly into filopodia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Actins / metabolism
  • Amino Acid Motifs
  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • CHO Cells
  • Carrier Proteins / metabolism*
  • Cricetinae
  • Cytoskeletal Proteins*
  • HeLa Cells
  • Humans
  • Mice
  • Microfilament Proteins
  • Molecular Sequence Data
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism*
  • Peptide Fragments / metabolism
  • Protein Binding
  • Pseudopodia / metabolism*
  • Recombinant Proteins / metabolism
  • Two-Hybrid System Techniques
  • cdc42 GTP-Binding Protein / metabolism*


  • Actins
  • BAIAP2 protein, human
  • Carrier Proteins
  • Cytoskeletal Proteins
  • Enah protein, mouse
  • Microfilament Proteins
  • Nerve Tissue Proteins
  • Peptide Fragments
  • Recombinant Proteins
  • cdc42 GTP-Binding Protein