Yeh J, Haarer B K
Department of Zoology and Institute for Cellular and Molecular Biology, The University of Texas, Austin 78712-1064, USA.
FEBS Lett. 1996 Dec 2;398(2-3):303-7. doi: 10.1016/s0014-5793(96)01259-8.
We have used a fluorometric assay to determine the relative amounts of polymerized actin (F-actin) in wild-type and profilin mutant yeast cells. Our results indicate that profilin plays a role in maintaining normal F-actin levels in response to shifts to high temperature. Cells lacking profilin display a greater drop in F-actin levels upon such temperature shifts, and are slower to recover to initial F-actin levels than are wild-type cells. Interestingly, shifts to cold temperatures result in rapid increases of F-actin levels in wild-type and profilin null cells. We have further determined that shifting to high-osmolarity growth conditions causes a relatively slow decrease in F-actin levels in wild-type cells, and a small but rapid increase in the F-actin levels in profilin null cells. Profilin null cells contain normal concentrations of F-actin while growing exponentially at room temperature, indicating that profilin is not essential for maintaining F-actin concentrations during steady-state growth. Our data suggest that actin is inherently unstable in vivo at high temperatures, and that profilin helps to maintain actin in its filamentous state at these temperatures, perhaps by stimulating actin polymerization in a proper temporal and spatial fashion.
我们使用了一种荧光测定法来确定野生型和原肌球蛋白突变酵母细胞中聚合肌动蛋白（F-肌动蛋白）的相对含量。我们的结果表明，原肌球蛋白在响应温度升高时维持正常F-肌动蛋白水平方面发挥作用。缺乏原肌球蛋白的细胞在这种温度变化时F-肌动蛋白水平下降幅度更大，并且比野生型细胞恢复到初始F-肌动蛋白水平的速度更慢。有趣的是，温度降低会导致野生型和原肌球蛋白缺失细胞中的F-肌动蛋白水平迅速增加。我们进一步确定，转变为高渗生长条件会导致野生型细胞中F-肌动蛋白水平相对缓慢下降，而原肌球蛋白缺失细胞中的F-肌动蛋白水平会有小幅但迅速的增加。原肌球蛋白缺失细胞在室温下指数生长时含有正常浓度的F-肌动蛋白，这表明原肌球蛋白在稳态生长期间对于维持F-肌动蛋白浓度并非必不可少。我们的数据表明，肌动蛋白在体内高温下本质上是不稳定的，并且原肌球蛋白可能通过以适当的时间和空间方式刺激肌动蛋白聚合，从而有助于在这些温度下将肌动蛋白维持在丝状状态。
