Use of <beta>-Actin Mutants to Study the Mechanism of cellular Motility

我们最近报道了对细胞松弛素B （cytochalasin B， CB）的细胞毒性作用具有抗性的突变KB细胞（Cyt 1细胞）的分离。该突变体携带改变的< β >-肌动蛋白，即。肌动蛋白(富山,年代,<β>。1984年,S.Toyama, cell.37:609 - 614)。在本研究中，我们研究了肌动蛋白在Cyt - 1细胞中的功能特性。我们的研究结果表明，Cyt - 1细胞对CB的抗性增加反映在肌动蛋白本身特性的改变上。三个发现直接证明了这一点。首先，细胞核诱导的Cyt肌动蛋白聚合不受2< micmicrbb0 M CB的抑制。其次，与亲本KB细胞提取物相比，Cyt 1细胞提取物在较高浓度的CB存在下可以形成del。第三，Cyt肌动蛋白结合的CB比KB肌动蛋白少。观察结果进一步支持了Cyt 1细胞中肌动蛋白的功能改变，尽管用CB处理KB细胞增加了未聚合肌动蛋白库，但同样的处理并未影响未聚合肌动蛋白库的Cyt 1细胞，并且Cyt 1细胞的微丝比KB细胞更能抵抗CB的破坏作用。我们从这些研究中得出结论，CB对细胞运动过程的主要作用位点是肌动蛋白。

We recently described the isolation of mutant KB cells (Cyt 1 cells)resistant to the cytotoxic effect of cytochalasin B (CB).this mutant carried an altered <beta>-actin,i.e.,<beta>'-actin (Toyama,S.,and S.Toyama,1984,Cell.37:609-614).In the present study,we have examined the functional properties of actin in Cyt 1 cells.Our results showed that increased resistance of Cyt 1 cells to CB was reflected in altered properties of actin itself.This was shown directly by three findings.Firsd,the nuclei-induced polymerrization of Cyt actin was not inhidited by 2<micrn>M CB.Second,extracts from Cyt 1 cells could form dels in the presence of higher concentration of CB,as compared with extracts from parental KB cells.Third,Cyt actin bound less CB than KB actin.The functional altrtation of actin in Cyt 1 cells was further supported by the observation that,although treatment of KB cells with CB increased the pool of unpolymerized actin,the same treatment did not affect the pool of unpolymerized actin Cyt 1 cells,and that microfilaments of Cyt 1 cells were more resistant to the disrupting action of CB than those of KB cells.We conclude from these studies that the primary site of action of CB on cellular motility processes is actin.