Pasternak C, Spudich J A, Elson E L
Department of Cell Biology, Stanford University School of Medicine, California 94305.
Nature. 1989 Oct 12;341(6242):549-51. doi: 10.1038/341549a0.
We have investigated the role of cytoskeletal contraction in the capping of surface proteins crosslinked by concanavalin A on mutant Dictyostelium cells lacking conventional myosin. Measurements of cellular deformability to indicate the development of cortical tension show that cells of the wild-type parental strain, AX4, stiffen early during capping and relax back towards the softer resting state as the process is completed. Mutant cells lacking myosin (mhcA-) have a lower resting-state stiffness, and fail to stiffen and to cap crosslinked proteins on binding concanavalin A. Hence conventional myosin is essential both for capping and for the concomitant increase in cell stiffness. Furthermore, depletion of cellular ATP by azide causes a 'rigor' contraction in AX4 cells which makes them stiffen and become spherical. By contrast, the mhcA- cells fail to respond in these ways. These measurements of cortical tension in non-muscle cells can thus be directly correlated with the presence of conventional myosin, demonstrating that contractile tension generated by myosin can drive both a change of cell shape and the capping of crosslinked surface receptors.
我们研究了细胞骨架收缩在缺乏传统肌球蛋白的突变盘基网柄菌细胞上，伴刀豆球蛋白A交联的表面蛋白帽化过程中的作用。通过测量细胞变形性以指示皮质张力的发展，结果显示野生型亲本菌株AX4的细胞在帽化早期变硬，并在过程完成时松弛回到较软的静止状态。缺乏肌球蛋白的突变细胞（mhcA-）具有较低的静止状态硬度，并且在结合伴刀豆球蛋白A时不能变硬，也不能使交联蛋白形成帽状。因此，传统肌球蛋白对于帽化以及伴随的细胞硬度增加都是必不可少的。此外，叠氮化物消耗细胞内ATP会导致AX4细胞发生“强直”收缩，使其变硬并变成球形。相比之下，mhcA-细胞不会以这些方式做出反应。因此，这些对非肌肉细胞皮质张力的测量可以直接与传统肌球蛋白的存在相关联，表明肌球蛋白产生的收缩张力可以驱动细胞形状的改变以及交联表面受体的帽化。
