Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT 06030-3305.
Mol Biol Cell. 2023 Jun 1;34(7):ar75. doi: 10.1091/mbc.E23-03-0104. Epub 2023 May 3.
Light chain 1 (LC1) is a highly conserved leucine-rich repeat protein associated with the microtubule-binding domain of the outer-dynein arm γ heavy chain. LC1 mutations in humans and trypanosomes lead to motility defects, while its loss in oomycetes results in aciliate zoospores. Here we describe a LC1 null mutant (). This strain has reduced swimming velocity and beat frequency, can undergo waveform conversion, but often exhibits loss of hydrodynamic coupling between the cilia. Following deciliation, cells rapidly rebuild cytoplasmic stocks of axonemal dyneins. Loss of LC1 disrupts the kinetics of this cytoplasmic preassembly so that most outer-arm dynein heavy chains remain monomeric even after several hours. This suggests that association of LC1 with its heavy chain-binding site is a key step or checkpoint in the outer-arm dynein assembly process. Similarly to strains lacking the entire outer arm and inner arm I1/f, we found that loss of LC1 and I1/f in double mutants resulted in cells unable to build cilia under normal conditions. Furthermore, cells do not exhibit the usual ciliary extension in response to lithium treatment. Together, these observations suggest that LC1 plays an important role in the maintenance of axonemal stability.
轻链 1（LC1）是一种高度保守的富含亮氨酸的重复蛋白，与外动力蛋白臂γ重链的微管结合域相关。人类和原生动物中的 LC1 突变导致运动缺陷，而在卵菌中 LC1 的缺失导致纤毛游动孢子。在这里，我们描述了一个 LC1 缺失突变体（）。该菌株的游动速度和拍频降低，可以进行波形转换，但经常表现出纤毛之间的水动力耦合丧失。去纤毛后，细胞迅速重建轴丝动力蛋白的细胞质储备。LC1 的缺失破坏了这种细胞质预组装的动力学，以至于即使在几个小时后，大多数外臂动力蛋白重链仍然是单体。这表明 LC1 与其重链结合位点的结合是外臂动力蛋白组装过程中的关键步骤或检查点。与缺乏整个外臂和内臂 I1/f 的菌株类似，我们发现 LC1 和 I1/f 在 双缺失突变体中缺失会导致细胞在正常条件下无法构建纤毛。此外，细胞在锂处理下不会表现出通常的纤毛延伸。总之，这些观察结果表明 LC1 在维持轴丝稳定性方面发挥着重要作用。
