Direct and indirect effects of tubulin post-translational modifications on microtubule stability: Insights and regulations.

Microtubules (MTs) mediate various cellular functions such as structural support, chromosome segregation, and intracellular transport. To achieve this, the pivotal properties of MTs have to be changeable and tightly controlled. This is enabled by a high variety of tubulin posttranslational modifications, which influence MT properties directly, via altering the MT lattice structurally, or indirectly by changing MT interaction partners. Here, the distinction between these direct and indirect effects of MT PTMs are exemplified by acetylation of the luminal α-tubulin K40 resulting in decreased rigidity of MTs, and by MT detyrosination which decreases interaction with depolymerizing proteins, thus causing more stable MTs. We discuss how these PTMs are reversed and regulated, e.g. on the level of enzyme transcription, localization, and activity via various signalling pathways including the conventional calcium-dependent proteases calpains and how advances in microscopy techniques and development of live-sensors facilitate the understanding of MT PTM interaction and effects.