Shimizu T
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
Dev Biol. 1996 Nov 25;180(1):54-62. doi: 10.1006/dbio.1996.0284.
Tubifex eggs contain two configurations of actin cytoskeleton (AC): a cortical thin shell of densely packed actin filaments and an endoplasmic loose network of actin filaments. Here we show that microinjection of botulinum C3 exoenzyme (ADP-ribosyltransferase) into Tubifex eggs disrupts the cortical AC, but not the endoplasmic AC. C3 exclusively ADP-ribosylates a 24-kDa protein in the Tubifex egg, suggesting the involvement of this protein in the regulation of the cortical AC. Among the actin-dependent processes that occur during maturation divisions and the first cell cycle, only outward migration of ooplasm (viz., early stage of the first step of ooplasmic segregation) occurs in C3-injected eggs, although migrating ooplasm is organized into patches rather than a continuous layer as observed in intact eggs. This ooplasmic movement is inhibited by cytochalasin D treatments. These results suggest that the endoplasmic AC is able to move ooplasm centrifugally in the absence of the cortical AC. In contrast, poleward movement of subcortical ooplasm along the egg surface (viz., the second step of ooplasmic segregation) is completely abolished in C3-injected eggs, even though the endoplasmic AC is present in the subcortical ooplasm.
颤蚓卵含有两种肌动蛋白细胞骨架（AC）构型：由紧密堆积的肌动蛋白丝组成的皮质薄壳和内质疏松的肌动蛋白丝网络。在此我们表明，向颤蚓卵显微注射肉毒杆菌C3外毒素（ADP核糖基转移酶）会破坏皮质AC，但不会破坏内质AC。C3专门将颤蚓卵中的一种24 kDa蛋白进行ADP核糖基化，表明该蛋白参与皮质AC的调节。在成熟分裂和第一个细胞周期中发生的肌动蛋白依赖性过程中，在注射C3的卵中，只有卵质向外迁移（即卵质分离第一步的早期阶段）会发生，尽管迁移的卵质被组织成斑块，而不是像在完整卵中观察到的那样形成连续层。这种卵质运动受到细胞松弛素D处理的抑制。这些结果表明，在内质AC存在而皮质AC缺失的情况下，内质AC能够使卵质离心移动。相反，在注射C3的卵中，皮质下卵质沿卵表面向极移动（即卵质分离的第二步）完全被消除，尽管内质AC存在于皮质下卵质中。
