title: Structural Basis of Arp2/3 Complex Inhibition by GMF, Coronin, and Arpin.
abstract: The evolutionarily conserved Arp2/3 complex plays a central role in nucleating the branched actin filament arrays that drive cell migration, endocytosis, and other processes. To better understand Arp2/3 complex regulation, we used single-particle electron microscopy to compare the structures of Arp2/3 complex bound to three different inhibitory ligands: glia maturation factor (GMF), Coronin, and Arpin. Although the three inhibitors have distinct binding sites on Arp2/3 complex, they each induced an "open" nucleation-inactive conformation. Coronin promoted a standard (previously described) open conformation of Arp2/3 complex, with the N-terminal β-propeller domain of Coronin positioned near the p35/ARPC2 subunit of Arp2/3 complex. GMF induced two distinct open conformations of Arp2/3 complex, which correlated with the two suggested binding sites for GMF. Furthermore, GMF synergized with Coronin in inhibiting actin nucleation by Arp2/3 complex. Arpin, which uses VCA-related acidic (A) motifs to interact with the Arp2/3 complex, induced the standard open conformation, and two new masses appeared at positions near Arp2 and Arp3. Furthermore, Arpin showed additive inhibitory effects on Arp2/3 complex with Coronin and GMF. Together, these data suggest that Arp2/3 complex conformation is highly polymorphic and that its activities can be controlled combinatorially by different inhibitory ligands.
authors.affiliation: Department of Biology, Moscow M.V. Lomonosov University, Moscow 119234, Russia.
authors.forename: Olga S
authors.initials: OS
authors.lastname: Sokolova
authors.affiliation: Department of Biology, Moscow M.V. Lomonosov University, Moscow 119234, Russia; Ecole Polytechnique, CNRS UMR7654, Palaiseau 91120, France.
authors.forename: Angelina
authors.initials: A
authors.lastname: Chemeris
authors.affiliation: Department of Biology, Brandeis University, Waltham, MA 02453, USA.
authors.forename: Siyang
authors.initials: S
authors.lastname: Guo
authors.affiliation: Department of Biology, Brandeis University, Waltham, MA 02453, USA.
authors.forename: Salvatore L
authors.initials: SL
authors.lastname: Alioto
authors.affiliation: Department of Biology, Brandeis University, Waltham, MA 02453, USA.
authors.forename: Meghal
authors.initials: M
authors.lastname: Gandhi
authors.affiliation: Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA.
authors.forename: Shae
authors.initials: S
authors.lastname: Padrick
authors.affiliation: V.A. Shoubnikov Institute of Crystallography RAS, Moscow 119333, Russia.
authors.forename: Evgeniya
authors.initials: E
authors.lastname: Pechnikova
authors.affiliation: Ecole Polytechnique, CNRS UMR7654, Palaiseau 91120, France.
authors.forename: Violaine
authors.initials: V
authors.lastname: David
authors.affiliation: Ecole Polytechnique, CNRS UMR7654, Palaiseau 91120, France.
authors.forename: Alexis
authors.initials: A
authors.lastname: Gautreau
authors.affiliation: Department of Biology, Brandeis University, Waltham, MA 02453, USA. Electronic address: goode@brandeis.edu.
authors.forename: Bruce L
authors.initials: BL
authors.lastname: Goode
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000494:pharmacology; D051376:Actin-Related Protein 2-3 Complex / Q000037:antagonists & inhibitors / Q000737:chemistry*; D001665:Binding Sites; D002352:Carrier Proteins / Q000494:pharmacology*; D002465:Cell Movement / Q000187:drug effects; D004705:Endocytosis / Q000187:drug effects; D020904:Glia Maturation Factor / Q000494:pharmacology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D011487:Protein Conformation; D054378:Acetogenins
chemical_list: D015107:4-Butyrolactone; D051376:Actin-Related Protein 2-3 Complex; D002352:Carrier Proteins; D020904:Glia Maturation Factor; C000604273:arpin protein, human; C438920:coronin acetogenin; D054378:Acetogenins
keywords: actin nucleation; conformation; single-particle EM; yeast