The exocyst complex binds the small GTPase RalA to mediate filopodia formation

Nat Cell Biol. 2002 Jan;4(1):73-8. doi: 10.1038/ncb720.


The Ras-related small GTPase RalA is involved in controlling actin cytoskeletal remodelling and vesicle transport in mammalian cells. We identified the mammalian homologue of Sec5, a subunit of the exocyst complex determining yeast cell polarity, as a specific binding partner for GTP-ligated RalA. Inhibition of RalA binding to Sec5 prevents filopod production by tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1) and by activated forms of RalA and Cdc42, signalling intermediates downstream of these inflammatory cytokines. We propose that the RalA-exocyst complex interaction integrates the secretory and cytoskeletal pathways.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Binding Sites
  • COS Cells
  • Cytoskeleton / physiology
  • Cytoskeleton / ultrastructure
  • Exocytosis / drug effects
  • Exocytosis / physiology*
  • GTP Phosphohydrolases / chemistry
  • GTP Phosphohydrolases / physiology*
  • Humans
  • Interleukin-1 / pharmacology
  • K562 Cells
  • Membrane Proteins / chemistry
  • Membrane Proteins / physiology*
  • Protein Binding
  • Pseudopodia / drug effects
  • Pseudopodia / physiology*
  • Pseudopodia / ultrastructure
  • Rats
  • Signal Transduction
  • Tumor Necrosis Factor-alpha / pharmacology
  • Vesicular Transport Proteins
  • cdc42 GTP-Binding Protein / physiology
  • ral GTP-Binding Proteins*


  • Exoc2 protein, rat
  • Interleukin-1
  • Membrane Proteins
  • Tumor Necrosis Factor-alpha
  • Vesicular Transport Proteins
  • GTP Phosphohydrolases
  • RALA protein, human
  • Rala protein, rat
  • cdc42 GTP-Binding Protein
  • ral GTP-Binding Proteins