Plant and Cell Physiology Advance Access published online on February 27, 2007
Plant and Cell Physiology, doi:10.1093/pcp/pcm030
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Wide-ranging Effects of Eight Cytochalasins and Latrunculin A and B on Intracellular Motility and Actin Filament Reorganization in Characean Internodal Cells
1 Department of Cell Biology, University of Salzburg
2 Department of Botany, University of British Columbia, Vancouver, Canada
* Corresponding author: E-mail, ilse.foissner{at}sbg.ac.at Fax, +43 662 8044 619.
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Abstract |
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Numerous forms of cytochalasins have been identified and although they share common biological activity, they may differ considerably in potency. We investigated the effects of cytochalasins A, B, C, D, E, H, J and dihydrocytochalasin B in an ideal experimental system for cell motility, the giant internodal cells of the characean alga Nitella pseudoflabellata. Cytochalasin D (60 µM) and H (30 µM) were found to be most suited for fast and reversible inhibition of actin-based motility, while cytochalasins A and E arrested streaming at lower concentrations but irreversibly. We observed no clear correlation between the ability of cytochalasins to inhibit motility and the actual disruption of the subcortical actin bundle tracks on which myosin-dependent motility occurs. Indeed, the actin bundles remained intact at the time of streaming cessation and disassembled only after one to several days' treatment. Even when applied at concentrations lower than that required to inhibit cytoplasmic streaming, all of the cytochalasins induced reorganization of the more labile cortical actin filaments into actin patches, swirling clusters or short rods. Latrunculins A and B arrested streaming only after disrupting the subcortical actin bundles, a process requiring relatively high concentrations (200 µM) and very long treatment periods of more than one day. Latrunculins, however, worked synergistically with cytochalasins. A 1 h treatment with 15 nM latrunculin A and 4 µM cytochalasin D induced reversible fragmentation of subcortical actin bundles and arrested cytoplasmic streaming. Our findings provide insights into the mechanisms by which cytochalasins and latrunculins interfere with characean actin to inhibit motility.
Keywords: Cytoplasmic streaming - Cytoskeleton - Cortical actin filaments - Nitella - Subcortical actin bundles
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