title: Arp2/3 complex inhibition radically alters lamellipodial actin architecture, suspended cell shape, and the cell spreading process.
abstract: Recent studies have investigated the dendritic actin cytoskeleton of the cell edge's lamellipodial (LP) region by experimentally decreasing the activity of the actin filament nucleator and branch former, the Arp2/3 complex. Here we extend these studies via pharmacological inhibition of the Arp2/3 complex in sea urchin coelomocytes, cells that possess an unusually broad LP region and display correspondingly exaggerated centripetal flow. Using light and electron microscopy, we demonstrate that Arp2/3 complex inhibition via the drug CK666 dramatically altered LP actin architecture, slowed centripetal flow, drove a lamellipodial-to-filopodial shape change in suspended cells, and induced a novel actin structural organization during cell spreading. A general feature of the CK666 phenotype in coelomocytes was transverse actin arcs, and arc generation was arrested by a formin inhibitor. We also demonstrate that CK666 treatment produces actin arcs in other cells with broad LP regions, namely fish keratocytes and Drosophila S2 cells. We hypothesize that the actin arcs made visible by Arp2/3 complex inhibition in coelomocytes may represent an exaggerated manifestation of the elongate mother filaments that could possibly serve as the scaffold for the production of the dendritic actin network.
authors.affiliation: Department of Biology, Dickinson College, Carlisle, PA 17013 Marine Biological Laboratory, Woods Hole, MA 02543 henson@dickinson.edu.
authors.forename: John H
authors.initials: JH
authors.lastname: Henson
authors.affiliation: Department of Biology, Dickinson College, Carlisle, PA 17013.
authors.forename: Mesrob
authors.initials: M
authors.lastname: Yeterian
authors.affiliation: Department of Biology, Dickinson College, Carlisle, PA 17013.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Weeks
authors.affiliation: Department of Biology, Dickinson College, Carlisle, PA 17013.
authors.forename: Angela E
authors.initials: AE
authors.lastname: Medrano
authors.affiliation: Department of Biology, Dickinson College, Carlisle, PA 17013.
authors.forename: Briana L
authors.initials: BL
authors.lastname: Brown
authors.affiliation: Department of Biology, Dickinson College, Carlisle, PA 17013.
authors.forename: Heather L
authors.initials: HL
authors.lastname: Geist
authors.affiliation: Department of Biology, Dickinson College, Carlisle, PA 17013.
authors.forename: Mollyann D
authors.initials: MD
authors.lastname: Pais
authors.affiliation: Marine Biological Laboratory, Woods Hole, MA 02543.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Oldenbourg
authors.affiliation: Marine Biological Laboratory, Woods Hole, MA 02543 Department of Biology, New Mexico State University, Las Cruces, NM 88003.
authors.forename: Charles B
authors.initials: CB
authors.lastname: Shuster
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000648:ultrastructure*; D051376:Actin-Related Protein 2-3 Complex / Q000037:antagonists & inhibitors*; D000818:Animals; D048430:Cell Shape / Q000187:drug effects; D004330:Drosophila / Q000187:drug effects; D006054:Goldfish; D007211:Indoles / Q000494:pharmacology; D008854:Microscopy, Electron; D011554:Pseudopodia / Q000187:drug effects / Q000648:ultrastructure*; D047269:Strongylocentrotus / Q000187:drug effects
chemical_list: D051376:Actin-Related Protein 2-3 Complex; C543733:CK-0944666; D007211:Indoles