Motor usage imprints microtubule stability in the shaft

Abstract

Tubulin dimers assemble into dynamic microtubules which are used by molecular motors as tracks for intracellular transport. Organization and dynamics of the microtubule network is commonly thought to be regulated at the polymer ends, where tubulin-dimers can be added or removed. Here we show that molecular motors running on microtubules cause exchange of dimers along the shaft. These sites of dimer exchange act as rescue sites where depolymerising microtubules stop shrinking and start re-growing. Consequently, the average length of microtubules increases depending on how frequently they are used as motor tracks. An increase of motor activity densifies the cellular microtubule network and enhances cell polarity. Running motors leave marks in the shaft serving as traces of microtubule usage to organize the polarity landscape of the cell.

A kinesin-1 variant reveals motor-induced microtubule damage in cells

“…We also observed microtubule destruction in cells upon expression of other KIF5C variants with truncation (D3, D7, D8, D9) or mutation [24] of the coverstrand. These results extend previous reports demonstrating that kinesins and dyneins can cause microtubule destruction in reconstituted systems [17,44] to show that motor-induced damage occurs in cells. These findings emphasize that while cells are able to repair motor-induced damage under normal conditions, and even upon overexpression of active kinesin-1 motors, the excessive ability of the D6 variant to damage microtubules overwhelms the cells' ability to repair and/or resolve lattice defects, resulting in broken and fragmented microtubules.…”

“…We also demonstrate that the activity of KIF5C(1-560)-D6 motors results in an increase in the size of the lattice repair sites compared to the KIF5C(1-560)-WT motor (Figure 6). Together with recent reports [17,44], our work suggests that while stepping along the microtubule lattice, kinesin-1 motor proteins induce defects in the microtubule lattice that can be repaired by the incorporation of soluble tubulin.…”

“…Lattice repair in response to KIF5C(1-560)-WT activity led to an increase in microtubule rescue events and overall microtubule growth (Figure 5), as also reported by [44]. However, the excessive damage caused by KIF5C(1-560)-D6 motors and insufficient repair of those defects resulted in a lack of rescue events (Figure 5).…”

“…To test these possibilities, we performed microtubule repair assays in which single kinesin motors walk along immobilized microtubules in the presence of soluble tubulin [17,44]; the incorporation of soluble tubulin into the microtubule lattice is measured as an indication of the amount of microtubule damage and repair. As motor-induced damage was observed to occur along GDP-tubulin microtubules, but not GMPCPP-or taxol-microtubules [17], we generated GDP-lattice microtubules by growing GTP-tubulin microtubules from GMPCPP-seeds and capping them with GMPCPP-tubulin (Figure 6A).…”

Cellular cartography: Towards an atlas of the neuronal microtubule cytoskeleton

“…Another idea that has recently garnered a lot of interest is that motor proteins might stabilize the microtubule tracks they use most by promoting the exchange of tubulin along the length of the lattice such that there are more GTP-tubulin islands (i.e., small patches of microtubule rich in GTP-tubulin) peppered throughout the microtubule (Théry and Blanchoin, 2021;Triclin et al, 2021;Andreu-Carbó et al, 2022); however, the extent to which wildtype and motile motors do this might be limited (Budaitis et al, 2021). The idea is that the GTP islands along the length of the microtubule might help to protect the microtubule from catastrophe by serving as rescue sites to prevent complete catastrophes (Vemu et al, 2018;Bollinger et al, 2020).…”