CKAP5 stabilizes CENP-E at kinetochores by regulating microtubule-chromosome attachments

Stabilization of microtubule plus end-directed kinesin CENP-E at the metaphase kinetochores is important for chromosome alignment, but its mechanism remains unclear. Here, we show that CKAP5, a conserved microtubule plus tip protein, regulates CENP-E at kinetochores in human cells. Depletion of CKAP5 impairs CENP-E localization at kinetochores at the metaphase plate and results in increased kinetochore-microtubule stability and attachment errors. Erroneous attachments are also supported by computational modeling. Analysis of CKAP5 knockout cancer cells of multiple tissue origins shows that CKAP5 is preferentially essential in aneuploid, chromosomally unstable cells, and the sensitivity to CKAP5 depletion is correlated to that of CENP-E depletion. CKAP5 depletion leads to reduction in CENP-E-BubR1 interaction and the interaction is rescued by TOG4-TOG5 domain of CKAP5. The same domain can rescue CKAP5 depletion-induced CENP-E removal from the kinetochores. Interestingly, CKAP5 depletion facilitates recruitment of PP1 to the kinetochores and furthermore, a PP1 target site-specific CENP-E phospho-mimicking mutant gets stabilized at kinetochores in the CKAP5-depleted cells. Together, the results support a model in which CKAP5 controls mitotic chromosome attachment errors by stabilizing CENP-E at kinetochores and by regulating stability of the kinetochore-attached microtubules. Microtubule +TIP protein CKAP5 stabilizes CENP-E kinesin at the kinetochores and is essential for chromosome congression. CKAP5 depletion results in hyper-stable kinetochore-attached microtubules and increases recruitment of PP1, thereby causing CENP-E removal from kinetochores.CKAP5 stabilizes CENP-E at aligned kinetochores. CKAP5 depletion induces hyper-stability of kinetochore-attached microtubule. CKAP5 depletion promotes merotelic attachment errors. CKAP5 maintains optimum levels of PP1 on attached kinetochores. CKAP5 mediated regulation on PP1 and microtubule stability ensure CENP-E stabilization at kinetochores. Microtubule +TIP protein CKAP5 stabilizes CENP-E kinesin at the kinetochores and is essential for chromosome congression. CKAP5 depletion results in hyper-stable kinetochore-attached microtubules and increases recruitment of PP1, thereby causing CENP-E removal from kinetochores.