Department of Molecular Microbiology and Immunology, Brown University, Providence, RI 02912, USA; Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA.
Department of Molecular Microbiology and Immunology, Brown University, Providence, RI 02912, USA.
Curr Biol. 2023 Mar 13;33(5):899-911.e5. doi: 10.1016/j.cub.2023.01.035. Epub 2023 Feb 13.
Many single-celled eukaryotes have complex cell morphologies defined by microtubules arranged into higher-order structures. The auger-like shape of the parasitic protist Trypanosoma brucei (T. brucei) is mediated by a parallel array of microtubules that underlies the plasma membrane. The subpellicular array must be partitioned and segregated using a microtubule-based mechanism during cell division. We previously identified an orphan kinesin, KLIF, that localizes to the ingressing cleavage furrow and is essential for the completion of cytokinesis. We have characterized the biophysical properties of a truncated KLIF construct in vitro to gain mechanistic insight into the function of this novel kinesin. We find that KLIF is a non-processive dimeric kinesin that dynamically crosslinks microtubules. Microtubules crosslinked by KLIF in an antiparallel orientation are translocated relative to one another, while microtubules crosslinked parallel to one another remain static, resulting in the formation of organized parallel bundles. In addition, we find that KLIF stabilizes the alignment of microtubule plus ends. These features provide a mechanistic understanding for how KLIF functions to form a new pole of aligned microtubule plus ends that defines the shape of the new cell posterior, which is an essential requirement for the completion of cytokinesis in T. brucei.
许多单细胞真核生物具有由微管排列成高级结构定义的复杂细胞形态。寄生原生动物锥虫（Trypanosoma brucei，T. brucei）的类似钻头的形状是由位于质膜下的平行微管阵列介导的。在细胞分裂过程中，亚质膜微管阵列必须通过基于微管的机制进行分隔和分离。我们之前鉴定了一个孤儿驱动蛋白 KLIF，它定位于入核分裂沟，并对胞质分裂的完成至关重要。我们已经对截断 KLIF 构建体的生物物理特性进行了表征，以深入了解这种新型驱动蛋白的功能。我们发现 KLIF 是一种非进行性二聚体驱动蛋白，可动态交联微管。KLIF 交联的反向平行微管相对于彼此移位，而平行交联的微管保持静止，从而形成组织有序的平行束。此外，我们发现 KLIF 稳定微管正极的对齐。这些特征为 KLIF 如何形成新的对齐微管正极的新极点提供了机制理解，该极点定义了新细胞后极的形状，这是锥虫胞质分裂完成的必要条件。
