title: Broadening the spectrum of actin-based protrusive activity mediated by Arp2/3 complex-facilitated polymerization: motility of cytoplasmic ridges and tubular projections.
abstract: Arp2/3 complex-facilitated actin polymerization plays an essential role in a variety of cellular functions including motility, adherence, endocytosis, and trafficking. In the present study, we employ the sea urchin coelomocyte experimental model system to test the hypotheses that Arp2/3 complex-nucleated actin assembly mediates the motility of two unusual cellular protrusions; the cytoplasmic ridges present during coelomocyte spreading, and inducible, tubular-shaped, and neurite-like projections. Our investigations couple pharmacological manipulation employing inhibitors of actin polymerization and the Arp2/3 complex with a wide array of imaging methods including digitally enhanced phase contrast, DIC, and polarization light microscopy of live cells; conventional, confocal and super-resolution light microscopy of fluorescently labeled cells; and scanning and transmission electron microscopy. Taken together, the results of this study indicate that Arp2/3 complex-facilitated actin polymerization underlies the motility of coelomocyte cytoplasmic ridges and tubular projections, that these processes are related to each other, and that they have been preliminarily identified in other cell types. The results also highlight the broad spectrum of actin-based protrusive activities dependent on the Arp2/3 complex and provide additional insights into the pervasive nature of this ubiquitous actin nucleator. Furthermore, we provide the first evidence of a possible mechanistic difference between the impacts of the small molecule drugs BDM and CK666 on the Arp2/3 complex.
authors.affiliation: Department of Biology, Dickinson College, Carlisle, Pennsylvania; Mount Desert Island Biological Laboratory, Salisbury Cove, Maine; Marine Biological Laboratory, Woods Hole, Massachusetts.
authors.forename: John H
authors.initials: JH
authors.lastname: Henson
authors.forename: Anastasia D
authors.initials: AD
authors.lastname: Gianakas
authors.forename: Lauren H
authors.initials: LH
authors.lastname: Henson
authors.forename: Christina L
authors.initials: CL
authors.lastname: Lakin
authors.forename: Meagen K
authors.initials: MK
authors.lastname: Voss
authors.forename: Joerg
authors.initials: J
authors.lastname: Bewersdorf
authors.forename: Rudolf
authors.initials: R
authors.lastname: Oldenbourg
authors.forename: Robert L
authors.initials: RL
authors.lastname: Morris
mesh_terms: D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D012617:Sea Urchins
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000199:Actins
keywords: Arp2/3 complex; actin; cell motility; coelomocyte
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