title: Cytochalasin D does not produce net depolymerization of actin filaments in HEp-2 cells.
abstract: The altered morphology, disappearance or 'disruption' of actin filaments (microfilaments) in cells treated with cytochalasin has sometimes been attributed to depolymerization of filamentous actin (F-actin) to its globular subunit (G-actin), but attempts to confirm that mechanism have been inconclusive. Treatment of purified actin filaments with cytochalasin B (CB) decreased their viscosity, consistent with depolymerization, which was not, however, revealed by electron microscopy, although the filaments appeared abnormal. CB also increased the ATP-ase activity of F-actin, suggesting that it had been destabilized, while actin filaments in the acrosomal process were not depolymerized. CB or cytochalasin D (CD) can dissolve actin gels (reviewed in ref. 7, see also refs 8 and 9) without depolymerizing their filaments. The 'disrupted' actin structures in CD-treated cells bound heavy meromysin, indicating that at least some of the cellular actin was filamentous. Using a rapid assay for G- and F-actin in cell extracts, based on the inhibition of DNase I, we have found that neither short-nor long-term exposure of HEp-2 cells to CD produce net depolymerization of actin filaments.
mesh_terms: D000199:Actins / Q000378:metabolism*; D002460:Cell Line; D003572:Cytochalasins / Q000494:pharmacology*; D003599:Cytoskeleton / Q000187:drug effects*; D003851:Deoxyribonucleases / Q000037:antagonists & inhibitors; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D006801:Humans; D012995:Solubility; D013997:Time Factors
chemical_list: D000199:Actins; D003572:Cytochalasins; D003851:Deoxyribonucleases; D004121:Dimethyl Sulfoxide