Altered cell spreading in cytochalasin B: a possible role for intermediate filaments.

Abstract

Trypsinized chicken embryo dermal fibroblasts plated in the presence of cytochalasin B (CB) quickly attached to the substrate and within 24 h obtained an arborized morphology. This morphology is the result of the pushing out of pseudopodial processes along the substrate from the round central cell body. There were no microfilament bundles in the processes of these cells plated in the presence of CB; however, the processes were packed with highly oriented, parallelaligned intermediate filaments. Rous sarcoma virus which is temperature sensitive for pp60src, formed arborized cells with properties similar to those of uninfected fibroblasts when plated in the presence of CB at the nonpermissive temperature (41°C). At the permissive temperature for transformation (36°C), the cells attached to the substrate but remained round. These round cells were not only deficient in microfilament bundles but also lacked the highly organized intermediate filaments found in the processes of the arborized cells at 41°C. Although both microfilament bundles and the fibronectin matrix were decreased after transformation with Rous sarcoma virus, neither was involved in the formation of processes in normal cells plated in CB. Therefore, the inability of the transformed cells to form or maintain processes in CB must be the result of another structural alteration in the transformed cells, such as that of the intermediate filaments.When trypsinized fibroblasts are plated in culture, they attach to and spread on the substrate within several hours. This spreading process involves cell movement and is accompanied by the establishment of an actin-containing microfilament network within the cytoplasm just under the plasma membrane. These microfilaments are implicated as an essential element in cell spreading (13) and are required for many cell movements, including cytokinesis and translational movement. The extracellular matrix proteins are another major element in cell spreading, particularly fibronectin, which is laid down as a network on the substrate under the spreading cell (see reference 33 for a review). There are conflicting data on the association of the fibronectin component of the extracellular matrix with the microfilaments and the microfilamentassociated proteins. One line of evidence indicates that the fibronectin matrix is present all along the plasma membrane leading up to but not including the area of adhesion plaques (5), whereas another group of investigators have evidence of a transmembrane linkage of fibronectin and vinculin fibers at the adhesion plaques (27). These fibronectin-vinculin complexes are aligned with the microfilament bundles found along the substrate within the cell.The role of fibronectin in cell spreading is demonstrated by the ability of exogenously added fibronectin to increase the spreading of poorly spread, transformed cells (34). Also, the addition of fibronectin to chondroblast floater cells induces both attachment and spreading of the cells (32). Cooperative effects of actin and fibronectin in the det...

Tumor promoters induce a specific morphological signature in the nuclear matrix-intermediate filament scaffold of Madin-Darby canine kidney (MDCK) cell colonies.

“…However, the resultant morphology was clearly different from that produced by tumor promoters. The colonies remained in tight clusters; although there was a partial breakdown of intercellular association (25), the major characteristics of changes induced by tumor promoters (i.e., rapid cell spreading and the formation of long, cytokeratin-rich filament bundles) were not observed in response to cytochalasin D. When TPA was added to MDCK colonies previously exposed to cytochalasin D (Fig. 5d), both cell spreading and process formation were observed.…”

“…4. Five structurally unrelated compounds, all known to be complete or secondstage tumor promoters (19,(22)(23)(24), are shown to induce iden- (25). When TPA at 5 ng/ml was added for 2 hr to cells previously treated with colchicine (b), the cytokeratin pattern observed was characteristic of cells treated with TPA alone (Fig.…”

Overexpression of the Myristoylated Alanine-rich C-kinase Substrate Inhibits Cell Adhesion to Extracellular Matrix Components

“…Various studies have demonstrated cytochalasin effects on cellular adhesion and/or cell spreading (52)(53)(54)(55)(56)(57)(58). In addition, several groups have demonstrated an intact focal adhesion signaling pathway in 293 cells and its sensitivity to cytochalasin D (59 -61).…”

Ganglioside composition of growth cone-deficient nerve cell cultures.

“…These neurites tended to have round tips and loop shapes like those continuously exposed to the drug (13). Cytochalasin B may inhibit the addition of actin subunits to the lengthening end of the actin filament (8,12,14). The control and our experimental cell cultures that had been extracted by the tetrahydrofuran method, respectively, contained 6.58 nmoles and 4.68 nmoles of total ganglioside-sialic acid per mg cell protein (Table 1).…”