Mechanical stability of microtubule lattices under high crowdedness

Microtubules (MTs) are hollow cylindrical biopolymers of tubulin subunits that play key roles in cells. Understanding their functions in cilia or neurons is difficult because MTs associate in highly crowded bundled arrays. For example, it is unclear how this crowdedness or confinement and the mutual interaction between MTs chains relate to the anisotropy of MT lattices. Because of the large degree of confinement in MT bundles, the use of experimental techniques to answer such questions is not easy. In contrast, computational modeling methods do not exhibit the experimental limitations when studying MTs bundles. Still, most of the existing models treat MTs as an elastic polymer network, in which the anisotropy of the lattice is built in and which excludes the possibility of formation of cracks in the lattice during force application. Our coarse-grained molecular simulations of the response of MT lattices to applied forces allow us to study formation and propagation of cracks. We present a modified indentation protocol to determine the mechanical response of MT lattices under conditions which mimic high confinement. Our model shows that the strength of interactions between MT in bundles has substantial influence on the magnitude of the forces that induce cracks in MT lattices.