α-Tubulin detyrosination impairs mitotic error correction by suppressing MCAK centromeric activity

Abstract

Incorrect kinetochore–microtubule attachments during mitosis can lead to chromosomal instability, a hallmark of human cancers. Mitotic error correction relies on the kinesin-13 MCAK, a microtubule depolymerase whose activity in vitro is suppressed by α-tubulin detyrosination—a posttranslational modification enriched on long-lived microtubules. However, whether and how MCAK activity required for mitotic error correction is regulated by α-tubulin detyrosination remains unknown. Here we found that detyrosinated α-tubulin accumulates on correct, more stable, kinetochore–microtubule attachments. Experimental manipulation of tubulin tyrosine ligase (TTL) or carboxypeptidase (Vasohibins-SVBP) activities to constitutively increase α-tubulin detyrosination near kinetochores compromised efficient error correction, without affecting overall kinetochore microtubule stability. Rescue experiments indicate that MCAK centromeric activity was required and sufficient to correct the mitotic errors caused by excessive α-tubulin detyrosination independently of its global impact on microtubule dynamics. Thus, microtubules are not just passive elements during mitotic error correction, and the extent of α-tubulin detyrosination allows centromeric MCAK to discriminate correct vs. incorrect kinetochore–microtubule attachments, thereby promoting mitotic fidelity.

The Tubulin Code in Mitosis and Cancer

“…In agreement, stimulation of kinetochore microtubule dynamics in otherwise chromosomally unstable cancer cells by increasing Kinesin-13 depolymerase activity reestablished chromosomal stability [55,74]. Building on the previous finding that MCAK´s microtubule depolymerizing activity is reduced four fold in the presence of detyrosinated microtubules in vitro [75,76], it was recently shown that the mitotic error correction activity of MCAK and Kif2b is regulated by α-tubulin detyrosination [37]. Accordingly, experimental depletion of TTL or overexpression of VASH1-SVBP, which caused a constitutive increase of α-tubulin detyrosination in the vicinity of the kinetochores, compromised error correction, leading to chromosome segregation errors.…”

“…Similar to dynein/dynactin, kinesin-5 appears to have increased affinity to tyrosinated dendritic microtubules in neurons [80], but direct evidence from in vitro reconstitution assays is still lacking. Nonetheless, recent work in which centrosome positioning in human mitotic cells was tracked in 3D indicated that centrosome separation at nuclear envelope breakdown is insensitive to the tyrosinated state of -tubulin [37]. This reinforces the idea that the observed increase in mitotic errors associated with excessive αtubulin detyrosination is due to the incapacity to correct, rather than an increased propensity to make errors.…”

“…Indeed, the overexpression of Kif2b or MCAK, in addition to reestablishing the stability of chromosomally unstable cancer cells [55,74], inhibits metastasis in vitro and in vivo, with a consequent increase in survival [74]. Given that excessive tubulin detyrosination might lead to chromosomal instability by suppressing the error correction activity of MCAK and Kif2b [37], together with the observed upregulation of tubulin detyrosination in invasive cancer and with poor prognosis (Table 1), it raises the exciting possibility that an increase in tubulin detyrosination might promote cancer progression through inhibition of the mitotic error correction machinery. However, an extensive analysis of tubulin detyrosination in chromosomal instability-prone cancers, together with the elucidation of its implications for cancer metastasis, is necessary for its establishment as potential diagnostic and prognostic biomarkers.…”

“…remain essentially non-modified (note that most gene-encoded α-tubulin isoforms carry a last Tyrosine residue at their C-terminal tails; see Figure 1). As some spindle microtubules become gradually stabilized due to the establishment of chromosome attachments at the kinetochore, as well as possible interactions between some interpolar microtubules, they become increasingly detyrosinated [19,[36][37][38][39][40] (Figure 2). Likewise, kinetochore microtubules are highly acetylated on K40 of α-tubulin [36,41], polyglutamylated [42], and accumulate Δ2-tubulin [43].…”

Molecular determinants for α-tubulin methylation by SETD2

“…Other tubulin PTMs have been shown to impact mitotic progression and may also underlie cancer phenotypes. Recent work has shown that a disruption of α-tubulin detyrosination leads to reduced chromosome congression and increased errors of kinetochore-microtubule attachment (60–63). Further investigations into tubulin PTMs and their modifying enzymes are required to understand the nuanced interaction between histone and tubulin modifications in cells and the implications for cancer progression.…”