Ludwig Institute for Cancer Research, La Jolla, CA.
Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA.
J Cell Biol. 2020 Dec 7;219(12). doi: 10.1083/jcb.202006010.
Centrosomes, composed of centrioles that recruit a pericentriolar material (PCM) matrix assembled from PCNT and CDK5RAP2, catalyze mitotic spindle assembly. Here, we inhibit centriole formation and/or remove PCNT-CDK5RAP2 in RPE1 cells to address their relative contributions to spindle formation. While CDK5RAP2 and PCNT are normally dispensable for spindle formation, they become essential when centrioles are absent. Acentriolar spindle assembly is accompanied by the formation of foci containing PCNT and CDK5RAP2 via a microtubule and Polo-like kinase 1-dependent process. Foci formation and spindle assembly require PCNT-CDK5RAP2-dependent matrix assembly and the ability of CDK5RAP2 to recruit γ-tubulin complexes. Thus, the PCM matrix can self-organize independently of centrioles to generate microtubules for spindle assembly; conversely, an alternative centriole-anchored mechanism supports spindle assembly when the PCM matrix is absent. Extension to three cancer cell lines revealed similar results in HeLa cells, whereas DLD1 and U2OS cells could assemble spindles in the absence of centrioles and PCNT-CDK5RAP2, suggesting cell type variation in spindle assembly mechanisms.
中心体由招募由 PCNT 和 CDK5RAP2 组装而成的中心体周围物质 (PCM) 基质的中心粒组成，它能催化有丝分裂纺锤体的组装。在这里，我们抑制 RPE1 细胞中的中心粒形成和/或去除 PCNT-CDK5RAP2，以解决它们对纺锤体形成的相对贡献。虽然 CDK5RAP2 和 PCNT 通常对纺锤体的形成不是必需的，但当中心粒不存在时，它们就变得必不可少了。无中心粒纺锤体的组装伴随着通过微管和 Polo 样激酶 1 依赖的过程形成含有 PCNT 和 CDK5RAP2 的焦点。焦点的形成和纺锤体的组装需要 PCNT-CDK5RAP2 依赖的基质组装以及 CDK5RAP2 招募 γ-微管蛋白复合物的能力。因此，PCM 基质可以独立于中心粒自我组织以生成用于纺锤体组装的微管；相反，当 PCM 基质不存在时，替代的中心粒锚定机制支持纺锤体的组装。在三种癌细胞系中的扩展揭示了在 HeLa 细胞中类似的结果，而 DLD1 和 U2OS 细胞在没有中心粒和 PCNT-CDK5RAP2 的情况下也可以组装纺锤体，这表明在纺锤体组装机制中存在细胞类型的变化。
