Hirano K, Chartier L, Taylor R G, Allen R E, Fusetani N, Karaki H, Hartshorne D J
Department of Animal Sciences, University of Arizona, Tucson 85721.
J Muscle Res Cell Motil. 1992 Jun;13(3):341-53. doi: 10.1007/BF01766462.
Addition of the protein phosphatase inhibitor, calyculin-A, to 3T3 fibroblasts causes a marked change in cell morphology. Initially the cells become rounded, develop surface blebs and then detach from the substratum. In the detached cells an unusual ball-like structure is observed. This study focuses on the cytoskeleton during these calyculin-A-induced morphological changes. Stress fibres disappear as the cells begin to round and aggregates of actin are formed towards the apical surface of the cell. These aggregates condense, in the detached cells, to form the ball structure of approximately 3 microns diameter. Between the ball and the nucleus are cables of intermediate filaments that appear to be attached to the surface of the ball and to the nuclear lamina. Using a procedure designed for the isolation of nuclei the nucleus-ball complex can be obtained. Analysis of the nucleus-ball preparation by immunofluorescence and electron microscopy demonstrate that the ball contains actin and that intermediate filaments are located between the ball and the nucleus. In this preparation, the intermediate filaments also appear to attach to the surfaces of the ball and the nucleus. Electrophoretic analysis of the nucleus-ball preparation indicates that, in addition to actin, a major component of the ball is myosin. It is suggested that the formation of the ball is caused by an actin-myosin-based contractile process, initiated by the phosphorylation of myosin. The aggregation of the actomyosin draws together the intermediate filaments into the area between the ball and nucleus. This hypothesis requires that vimentin binds both to the nucleus and to some component of the ball.
向3T3成纤维细胞中添加蛋白磷酸酶抑制剂花萼海绵诱癌素A会导致细胞形态发生显著变化。最初，细胞变圆，出现表面气泡，然后从基质上脱离。在脱离的细胞中观察到一种不寻常的球状结构。本研究聚焦于花萼海绵诱癌素A诱导这些形态变化过程中的细胞骨架。随着细胞开始变圆，应力纤维消失，肌动蛋白聚集体在细胞顶端表面形成。在脱离的细胞中，这些聚集体浓缩形成直径约3微米的球状结构。在球状体和细胞核之间是中间丝束，它们似乎附着在球状体表面和核纤层上。使用一种设计用于分离细胞核的方法可以获得细胞核 - 球状体复合物。通过免疫荧光和电子显微镜对细胞核 - 球状体制剂的分析表明，球状体含有肌动蛋白，中间丝位于球状体和细胞核之间。在这种制剂中，中间丝似乎也附着在球状体和细胞核的表面。对细胞核 - 球状体制剂的电泳分析表明，除了肌动蛋白外，球状体的主要成分是肌球蛋白。有人提出，球状体的形成是由基于肌动蛋白 - 肌球蛋白的收缩过程引起的，该过程由肌球蛋白的磷酸化引发。肌动球蛋白的聚集将中间丝拉到球状体和细胞核之间的区域。这一假设要求波形蛋白既与细胞核结合，又与球状体的某些成分结合。
