Profilin-1 serves as a gatekeeper for actin assembly by Arp2/3-dependent and -independent pathways

Dev Cell. 2015 Jan 12;32(1):54-67. doi: 10.1016/j.devcel.2014.10.026. Epub 2014 Dec 24.


Cells contain multiple F-actin assembly pathways, including the Arp2/3 complex, formins, and Ena/VASP, which have largely been analyzed separately. They collectively generate the bulk of F-actin from a common pool of G-actin; however, the interplay and/or competition between these pathways remains poorly understood. Using fibroblast lines derived from an Arpc2 conditional knockout mouse, we established matched-pair cells with and without the Arp2/3 complex. Arpc2(-/-) cells lack lamellipodia and migrate more slowly than WT cells but have F-actin levels indistinguishable from controls. Actin assembly in Arpc2(-/-) cells was resistant to cytochalasin-D and was highly dependent on profilin-1 and Ena/VASP but not formins. Profilin-1 depletion in WT cells increased F-actin and Arp2/3 complex in lamellipodia. Conversely, addition of exogenous profilin-1 inhibited Arp2/3 complex actin nucleation in vitro and in vivo. Antagonism of the Arp2/3 complex by profilin-1 in cells appears to maintain actin homeostasis by balancing Arp2/3 complex-dependent and -independent actin assembly pathways.

Publication types

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

MeSH terms

  • Actin Cytoskeleton / metabolism*
  • Actin-Related Protein 2-3 Complex / metabolism*
  • Actins / metabolism*
  • Animals
  • Female
  • Fetal Proteins
  • Fibroblasts / cytology
  • Formins
  • Image Processing, Computer-Assisted
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Microfilament Proteins
  • Microscopy, Fluorescence
  • Nuclear Proteins
  • Profilins / metabolism*
  • Signal Transduction
  • Stress Fibers


  • Actin-Related Protein 2-3 Complex
  • Actins
  • Fetal Proteins
  • Formins
  • Microfilament Proteins
  • Nuclear Proteins
  • Profilins