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

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

Author information

1
Department of Molecular Genetics and Cell Biology, The University of Chicago, 920 East 58(th) Street, Chicago, IL 60637, USA.
2
Department of Cell and Developmental Biology, State University of New York (SUNY) Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA.
3
Department of Cell and Developmental Biology, State University of New York (SUNY) Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA. Electronic address: sirotkiv@upstate.edu.
4
Department of Molecular Genetics and Cell Biology, The University of Chicago, 920 East 58(th) Street, Chicago, IL 60637, USA; Department of Biochemistry and Molecular Biology, The University of Chicago, 920 East 58(th) Street, Chicago, IL 60637, USA. Electronic address: drkovar@uchicago.edu.

Abstract

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.

Comment in

PMID:
24560576
PMCID:
PMC3979332
DOI:
10.1016/j.cub.2014.01.072
[Indexed for MEDLINE]
Free PMC Article

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