FHOD1 is a combined actin filament capping and bundling factor that selectively associates with actin arcs and stress fibers

J Cell Sci. 2013 Apr 15;126(Pt 8):1891-901. doi: 10.1242/jcs.126706. Epub 2013 Feb 26.


Formins are actin polymerization factors that are known to nucleate and elongate actin filaments at the barbed end. In the present study we show that human FHOD1 lacks actin nucleation and elongation capacity, but acts as an actin bundling factor with capping activity toward the filament barbed end. Constitutively active FHOD1 associates with actin filaments in filopodia and lamellipodia at the leading edge, where it moves with the actin retrograde flow. At the base of lamellipodia, FHOD1 is enriched in nascent, bundled actin arcs as well as in more mature stress fibers. This function requires actin-binding domains located N-terminally to the canonical FH1-FH2 element. The bundling phenotype is maintained in the presence of tropomyosin, confirmed by electron microscopy showing assembly of 5 to 10 actin filaments into parallel, closely spaced filament bundles. Taken together, our data suggest a model in which FHOD1 stabilizes actin filaments by protecting barbed ends from depolymerization with its dimeric FH2 domain, whereas the region N-terminal to the FH1 domain mediates F-actin bundling by simultaneously binding to the sides of adjacent F-actin filaments.

Keywords: Actin arcs; Actin bundling; FHOD1; Retrograde flow; Stress fibers.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actin Cytoskeleton / metabolism*
  • Actin Cytoskeleton / ultrastructure
  • Actins / metabolism
  • Animals
  • COS Cells
  • Chlorocebus aethiops
  • Fetal Proteins / metabolism*
  • Formins
  • Humans
  • Microfilament Proteins / metabolism
  • Nuclear Proteins / metabolism*
  • Protein Binding
  • Stress Fibers / metabolism*
  • Stress Fibers / ultrastructure


  • Actins
  • FHOD1 protein, human
  • Fetal Proteins
  • Formins
  • Microfilament Proteins
  • Nuclear Proteins