Institute of Hydrobiology, Chinese Academy of Sciences, No. 7 Donghu South Road, Wuchang District, Wuhan 430072, Hubei, China; University of Chinese Academy of Sciences, No. 80 Zhongguancun East Road, Haidian District, Beijing 100049, China.
Institute of Hydrobiology, Chinese Academy of Sciences, No. 7 Donghu South Road, Wuchang District, Wuhan 430072, Hubei, China; Harbin Normal University, No. 1 Shida Road, Limin Economic Development Zone, Harbin 150025, Heilongjiang, China.
Curr Biol. 2024 Nov 4;34(21):4869-4883.e6. doi: 10.1016/j.cub.2024.09.003. Epub 2024 Sep 30.
Eukaryotic cells depend on dynamic changes in shape to fulfill a wide range of cellular functions, maintain essential biological processes, and regulate cellular behavior. The single-celled, predatory ciliate Lacrymaria exhibits extraordinary dynamic shape-shifting using a flexible "neck" that can stretch 7-8 times the length of its body to capture prey. The molecular mechanism behind this morphological change remains a mystery. We have observed that when in an active state, Lacrymaria repeatedly extends and contracts its neck to enable 360-degree space search and prey capture. This remarkable morphological change involves a unique actin-myosin system rather than the Ca-dependent system found in other contractile ciliates. Two cytoskeletons are identified in the cortex of the Lacrymaria cell, namely the myoneme cytoskeleton and the microtubule cytoskeleton. The myoneme cytoskeleton is composed of centrin-myosin proteins, exhibiting distinct patterns between the neck and body, with their boundary seemingly associated with the position of the macronucleus. A novel giant protein forming a ladder-like structure was discovered as a component of the microtubule cytoskeleton. Thick centrin-myosin fibers are situated very close to the right side of the ladders in the neck but are far away from such structures in the body. This arrangement enables the decoupling of the neck and body. Plasmodium-like unconventional actin has been discovered in Lacrymaria, and this may form highly dynamic short filaments that could attach to the giant protein and myosin, facilitating coordination between the two cytoskeletons in the neck. In summary, this fascinating organism employs unconventional cytoskeletal components to accomplish its extraordinary dynamic shape-shifting.
真核细胞依赖于形态的动态变化来完成广泛的细胞功能，维持基本的生物过程，并调节细胞行为。单细胞捕食性纤毛虫 Lacrymaria 利用灵活的“颈部”进行非凡的动态形状变化，其颈部可以伸展到身体长度的 7-8 倍，以捕捉猎物。这种形态变化背后的分子机制仍然是一个谜。我们观察到，当处于活跃状态时，Lacrymaria 会反复伸展和收缩颈部，以实现 360 度的空间搜索和猎物捕捉。这种显著的形态变化涉及到一个独特的肌动球蛋白系统，而不是在其他收缩纤毛虫中发现的 Ca 依赖性系统。在 Lacrymaria 细胞的皮层中，有两种细胞骨架被识别出来，即肌动蛋白-myosin 细胞骨架和微管细胞骨架。肌动蛋白-myosin 细胞骨架由中心体-myosin 蛋白组成，在颈部和身体之间表现出不同的模式，它们的边界似乎与大核的位置有关。一种新型的形成梯状结构的巨大蛋白被发现是微管细胞骨架的一个组成部分。在颈部，厚的中心体-myosin 纤维非常靠近梯子的右侧，但在身体中远离这种结构。这种排列使颈部和身体能够分离。在 Lacrymaria 中发现了类似于疟原虫的非常规肌动蛋白，它可能形成高度动态的短丝，能够附着在巨大的蛋白质和肌球蛋白上，促进颈部两个细胞骨架之间的协调。总之，这个迷人的生物利用非常规的细胞骨架成分来完成其非凡的动态形状变化。
