title: A novel role for WAVE1 in controlling actin network growth rate and architecture.
abstract: Branched actin filament networks in cells are assembled through the combined activities of Arp2/3 complex and different WASP/WAVE proteins. Here we used TIRF and electron microscopy to directly compare for the first time the assembly kinetics and architectures of actin filament networks produced by Arp2/3 complex and dimerized VCA regions of WAVE1, WAVE2, or N-WASP. WAVE1 produced strikingly different networks from WAVE2 or N-WASP, which comprised unexpectedly short filaments. Further analysis showed that the WAVE1-specific activity stemmed from an inhibitory effect on filament elongation both in the presence and absence of Arp2/3 complex, which was observed even at low stoichiometries of WAVE1 to actin monomers, precluding an effect from monomer sequestration. Using a series of VCA chimeras, we mapped the elongation inhibitory effects of WAVE1 to its WH2 ("V") domain. Further, mutating a single conserved lysine residue potently disrupted WAVE1's inhibitory effects. Taken together, our results show that WAVE1 has unique activities independent of Arp2/3 complex that can govern both the growth rates and architectures of actin filament networks. Such activities may underlie previously observed differences between the cellular functions of WAVE1 and WAVE2.
authors.affiliation: Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454;
authors.forename: Meredith O
authors.initials: MO
authors.lastname: Sweeney
authors.affiliation: Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454;
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Collins
authors.affiliation: Howard Hughes Medical Institute and Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390.
authors.forename: Shae B
authors.initials: SB
authors.lastname: Padrick
authors.affiliation: Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454; goode@brandeis.edu.
authors.forename: Bruce L
authors.initials: BL
authors.lastname: Goode
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure*; D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism; D000818:Animals; D002417:Cattle; D006801:Humans; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D058105:Polymerization; D017434:Protein Structure, Tertiary; D051300:Wiskott-Aldrich Syndrome Protein Family / Q000737:chemistry / Q000378:metabolism*
chemical_list: D051376:Actin-Related Protein 2-3 Complex; C114864:WASF1 protein, human; D051300:Wiskott-Aldrich Syndrome Protein Family