Structural basis of filopodia formation induced by the IRSp53/MIM homology domain of human IRSp53.
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.
Millard
Thomas H
TH
School of Biosciences, The University of Birmingham, Edgbaston, Birmingham, UK.
Bompard
Guillaume
G
Heung
Man Yeung
MY
Dafforn
Timothy R
TR
Scott
David J
DJ
Machesky
Laura M
LM
Fütterer
Klaus
K
D000595:Amino Acid Sequence; D019281:Dimerization; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D011487:Protein Conformation; D011554:Pseudopodia / Q000737:chemistry / Q000502:physiology*; D017386:Sequence Homology, Amino Acid
C119539:BAIAP2 protein, human; D009419:Nerve Tissue Proteins