van den Hout, M. | Search bioRxiv

bioRxiv2026

A role for tubulin in cellular quality control and proteostasis

Microtubules, stiff rods built up from tubulin dimers, form a cytoskeletal network whose structure, behaviour, and function have been extensively investigated, mainly from a mechanical perspective. Here, we describe a role for tubulin in the cellular stress response. We overexpressed tubulin dimers in a controlled fashion in 293F cells. Despite the engagement of autoregulation, a mechanism that degrades tubulin-encoding mRNAs when tubulin levels are high, a surplus of tubulin and microtubules is detected in overexpressing cells. This leads to altered microtubule behaviour, mitotic problems, deregulation of the cell cycle, and replication stress. Surprisingly, we also observe proteostasis defects in tubulin overexpressing cells, which we attribute to mitochondrial stress-related translation attenuation. Conversely, tubulin and microtubules are downregulated as part of the response to oxygen or glutamine deprivation. Together, our data link tubulin levels, and hence autoregulation, to cellular quality control and proteostasis. We propose that competitive interactions with key partners, including the mitochondrial protein import and general translation machinery, underlie the tubulin-mediated control of cellular homeostasis.

cell biology↗

bioRxiv2024

KIF2A maintains cytokinesis in mouse embryonic stem cells by stabilising intercellular bridge microtubules

Cytokinesis, the final stage of cell division, serves to physically separate daughter cells while ensuring correct segregation of cellular components. In cultured naive mouse embryonic stem cells cytokinesis lasts unusually long but the underlying mechanisms are not well understood. Here, using cellular and in vitro approaches, we describe a novel function for the kinesin-13 member KIF2A in this process. In genome-engineered mouse embryonic stem cells we find that KIF2A mainly localises to spindle poles during metaphase and regulates spindle length in a manner consistent with its known role as microtubule minus-end depolymerase. By contrast, during cytokinesis we observe tight binding of KIF2A on the lattices of intercellular bridge microtubules. At this stage KIF2A maintains microtubule length and number, and controls microtubule acetylation. Based on in vitro experiments we propose that the conversion of KIF2A from a depolymerase to a stabiliser is driven both by the inhibition of its ATPase activity, which increases affinity for the lattice, and by a preference of KIF2A for compacted lattices. We propose that during cytokinesis KIF2A maintains the compacted microtubule state, thereby dampening acetylation. As KIF2A depletion causes pluripotency problems and affects mRNA homeostasis our results furthermore indicate that KIF2A-mediated microtubule stabilisation prolongs cytokinesis to maintain pluripotency.

cell biology↗