Structural basis of filopodia formation induced by the IRSp53/MIM homology domain of human IRSp53

Thomas Millard, Guillaume Bompard, Man Heung, Timothy Dafforn, DJ Scott, Laura Machesky, Klaus Futterer

Research output: Contribution to journalArticle

182 Citations (Scopus)


The scaffolding protein insulin receptor tyrosine kinase substrate p53 (IRSp53), a ubiquitous regulator of the actin cytoskeleton, mediates filopodia formation under the control of Rho-family GTPases. IRSp53 comprises a central SH3 domain, which binds to proline-rich regions of a wide range of actin regulators, and a conserved N-terminal IRSp53/MIM homology domain (IMD) that harbours F-actin-bundling activity. Here, we present the crystal structure of this novel actin-bundling domain revealing a coiled-coil domain that self-associates into a 180 A-long zeppelin-shaped dimer. Sedimentation velocity experiments confirm the presence of a single molecular species of twice the molecular weight of the monomer in solution. Mutagenesis of conserved basic residues at the extreme ends of the dimer abrogated actin bundling in vitro and filopodia formation in vivo, demonstrating that IMD-mediated actin bundling is required for IRSp53-induced filopodia formation. This study promotes an expanded view of IRSp53 as an actin regulator that integrates scaffolding and effector functions.
Original languageEnglish
Pages (from-to)240-50
Number of pages11
JournalThe EMBO journal
Issue number2
Publication statusPublished - 6 Jan 2005


  • X-ray crystallography
  • filopodia
  • IRSp53
  • cell motility
  • actin bundling


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