Homeostatic actin cytoskeleton networks are regulated by assembly factor competition for monomers

Curr Biol. 2014 Mar 3;24(5):579-85. doi: 10.1016/j.cub.2014.01.072. Epub 2014 Feb 20.


Controlling the quantity and size of organelles through competition for a limited supply of components is quickly emerging as an important cellular regulatory mechanism. Cells assemble diverse actin filament (F-actin) networks for fundamental processes including division, motility, and polarization. F-actin polymerization is tightly regulated by activation of assembly factors such as the Arp2/3 complex and formins at specific times and places. We directly tested an additional hypothesis that diverse F-actin networks are in homeostasis, whereby competition for actin monomers (G-actin) is critical for regulating F-actin network size. Here we show that inhibition of Arp2/3 complex in the fission yeast Schizosaccharomyces pombe not only depletes Arp2/3-complex-mediated endocytic actin patches, but also induces a dramatic excess of formin-assembled F-actin. Conversely, disruption of formin increases the density of Arp2/3-complex-mediated patches. Furthermore, modification of actin levels significantly perturbs the fission yeast actin cytoskeleton. Increasing actin favors Arp2/3-complex-mediated actin assembly, whereas decreasing actin favors formin-mediated contractile rings. Therefore, the specific actin concentration in a cell is critical, and competition for G-actin helps regulate the proper amount of F-actin assembly for diverse processes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actin-Related Protein 2-3 Complex / genetics
  • Actin-Related Protein 2-3 Complex / metabolism*
  • Actins / metabolism*
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / metabolism
  • Cytoskeleton / metabolism*
  • Formins
  • Microfilament Proteins / metabolism
  • Mutation
  • Schizosaccharomyces / cytology*
  • Schizosaccharomyces / metabolism
  • Schizosaccharomyces pombe Proteins / genetics
  • Schizosaccharomyces pombe Proteins / metabolism*


  • Actin-Related Protein 2-3 Complex
  • Actins
  • Cdc12 protein, S pombe
  • Cell Cycle Proteins
  • Cytoskeletal Proteins
  • FOR3 protein, S pombe
  • Formins
  • Microfilament Proteins
  • Schizosaccharomyces pombe Proteins