Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112-5650, USA.
Proc Natl Acad Sci U S A. 2010 Jul 20;107(29):12889-94. doi: 10.1073/pnas.1005938107. Epub 2010 Jun 29.
The ESCRT pathway helps mediate the final abscission step of cytokinesis in mammals and archaea. In mammals, two early acting proteins of the ESCRT pathway, ALIX and TSG101, are recruited to the midbody through direct interactions with the phosphoprotein CEP55. CEP55 resides at the centrosome through most of the cell cycle but then migrates to the midbody at the start of cytokinesis, suggesting that the ESCRT pathway may also have centrosomal links. Here, we have systematically analyzed the requirements for late-acting mammalian ESCRT-III and VPS4 proteins at different stages of mitosis and cell division. We found that depletion of VPS4A, VPS4B, or any of the 11 different human ESCRT-III (CHMP) proteins inhibited abscission. Remarkably, depletion of individual ESCRT-III and VPS4 proteins also altered centrosome and spindle pole numbers, producing multipolar spindles (most ESCRT-III/VPS4 proteins) or monopolar spindles (CHMP2A or CHMP5) and causing defects in chromosome segregation and nuclear morphology. VPS4 proteins concentrated at spindle poles during mitosis and then at midbodies during cytokinesis, implying that these proteins function directly at both sites. We conclude that ESCRT-III/VPS4 proteins function at centrosomes to help regulate their maintenance or proliferation and then at midbodies during abscission, thereby helping ensure the ordered progression through the different stages of cell division.
ESCRT 途径有助于调节哺乳动物和古菌细胞分裂的最终分离步骤。在哺乳动物中，ESCRT 途径的两个早期作用蛋白 ALIX 和 TSG101，通过与磷酸蛋白 CEP55 的直接相互作用，被招募到中体。CEP55 在细胞周期的大部分时间都位于中心体，但在细胞分裂开始时迁移到中体，这表明 ESCRT 途径也可能与中心体有关。在这里，我们系统地分析了晚期哺乳动物 ESCRT-III 和 VPS4 蛋白在有丝分裂和细胞分裂的不同阶段的要求。我们发现，VPS4A、VPS4B 或任何 11 种不同的人类 ESCRT-III（CHMP）蛋白的耗竭都抑制了分离。值得注意的是，单独耗尽 ESCRT-III 和 VPS4 蛋白也改变了中心体和纺锤极体的数量，产生多极纺锤体（大多数 ESCRT-III/VPS4 蛋白）或单极纺锤体（CHMP2A 或 CHMP5），并导致染色体分离和核形态的缺陷。VPS4 蛋白在有丝分裂期间集中在纺锤极体上，然后在细胞分裂期间集中在中体上，这意味着这些蛋白在这两个部位直接发挥作用。我们得出结论，ESCRT-III/VPS4 蛋白在中心体上发挥作用，以帮助调节它们的维持或增殖，然后在分离过程中在中体上发挥作用，从而有助于确保细胞分裂的不同阶段有序进行。
