title: Profilin-1 serves as a gatekeeper for actin assembly by Arp2/3-dependent and -independent pathways.
abstract: 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.
authors.affiliation: University of North Carolina Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Howard Hughes Medical Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Rotty
authors.affiliation: University of North Carolina Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Howard Hughes Medical Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Congying
authors.initials: C
authors.lastname: Wu
authors.affiliation: University of North Carolina Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Haynes
authors.affiliation: Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA.
authors.forename: Cristian
authors.initials: C
authors.lastname: Suarez
authors.affiliation: Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Winkelman
authors.affiliation: Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: Heath E
authors.initials: HE
authors.lastname: Johnson
authors.affiliation: Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Haugh
authors.affiliation: Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA; Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Kovar
authors.affiliation: University of North Carolina Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Howard Hughes Medical Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. Electronic address: jbear@email.unc.edu.
authors.forename: James E
authors.initials: JE
authors.lastname: Bear
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D005260:Female; D005326:Fetal Proteins; D005347:Fibroblasts / Q000166:cytology; D000080865:Formins; D007091:Image Processing, Computer-Assisted; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008840:Microfilament Proteins; D008856:Microscopy, Fluorescence; D009687:Nuclear Proteins; D051304:Profilins / Q000378:metabolism*; D015398:Signal Transduction; D022502:Stress Fibers
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D005326:Fetal Proteins; D000080865:Formins; D008840:Microfilament Proteins; D009687:Nuclear Proteins; D051304:Profilins