The Toca-1-N-WASP complex links filopodial formation to endocytosis

J Biol Chem. 2009 Apr 24;284(17):11622-36. doi: 10.1074/jbc.M805940200. Epub 2009 Feb 11.

Abstract

The transducer of Cdc42-dependent actin assembly (Toca-1)-N-WASP complex was isolated as an essential cofactor for Cdc42-driven actin polymerization in vitro. Toca-1 consists of an N-terminal F-BAR domain, followed by a Cdc42 binding site (HR1 domain) and an SH3 domain, (the N-WASP interacting site). N-WASP is an activator of actin nucleation through the Arp2/3 complex. The aim of the present study was to investigate the cellular function of the Toca-1-N-WASP complex. We report that Toca-1 induces filopodia and neurites as does N-WASP in N1E115 neuroblastoma cells. Toca-1 requires the F-BAR domain, Cdc42 binding site, and SH3 domain to induce filopodia. Toca-1 and N-WASP both require each other to induce filopodia. The expression of Toca-1 and N-WASP affects the distribution, size, and number of Rab5 positive membranes. Toca-1 interacts directly with N-WASP in filopodia and Rab5 membrane as seen by Forster resonance energy transfer. Thus the Toca-1-N-WASP complex localizes to and induces the formation of filopodia and endocytic vesicles. Last, three inhibitors of endocytosis, Dynamin-K44A, Eps15Delta95/295, and clathrin heavy chain RNA interference, block Toca-1-induced filopodial formation. Taken together, these data suggest that the Toca-1-N-WASP complex can link filopodial formation to endocytosis.

MeSH terms

  • Binding Sites
  • Carrier Proteins / metabolism
  • Carrier Proteins / physiology*
  • Cell Line, Tumor
  • Endocytosis*
  • Fluorescence Resonance Energy Transfer
  • Humans
  • Microscopy, Fluorescence / methods
  • Mutagenesis, Site-Directed
  • Neurites / metabolism
  • Pseudopodia / metabolism*
  • RNA Interference
  • Wiskott-Aldrich Syndrome Protein, Neuronal / metabolism*
  • cdc42 GTP-Binding Protein / chemistry
  • rab5 GTP-Binding Proteins / metabolism
  • src Homology Domains

Substances

  • Carrier Proteins
  • FNBP1L protein, human
  • WASL protein, human
  • Wiskott-Aldrich Syndrome Protein, Neuronal
  • cdc42 GTP-Binding Protein
  • rab5 GTP-Binding Proteins