Microtubule shaft dynamics

Microtubules are dynamic polymers composed of tubulin subunits which are organized in a highly controlled dense network. Individual microtubules undergo dynamic instability: they stochastically switch between growing and shrinking at the microtubule tip. This seems to imply that the control of the network dynamics occurs at the filament tips, while the tube itself ("the shaft") appears like a passive element. Is the shaft really passive? Recent works, shows that tubulin subunits exchange along the shaft results in patches "freshly"-incorporated GTP-tubulin. Here I will show how these GTP- patches cause an effective prolongation of the microtubule lifetime, because they promote regrowth. A local regulation of microtubule lifetime e.g. by specific photo-manipulation of the microtubule shaft can indeed challenge the cell polarity. I will further show that kinesin motor proteins remove tubulin subunits from the shaft as they walk, thereby stabilizing those particular microtubules which are most used for trafficking.