Spatio-temporal correlations between catastrophe events in a microtubule bundle: a computational study

Abstract

We explore correlations between dynamics of different microtubules in a bundle, via numerical simulations, using a one-dimensional stochastic model of a microtubule. The GTP-bound tubulins undergo diffusion-limited binding to the tip. Random hydrolysis events take place along the filament, and converts GTP-tubulin to GDP-tubulin. The filament starts depolymerising when the monomer at the tip becomes GDP-bound; in this case, detachment of GDP-tubulin ensues and continues until either GTP-bound tubulin is exposed or complete depolymerisation is achieved. In the latter case, the filament is defined to have undergone a \"catastrophe\". Our results show that, in general, the dynamics of growth and catastrophe in different filaments are coupled to each other; closer the filaments are, the stronger the coupling. In particular, all filaments grow slower, on average, when brought closer together. The reduction in growth velocity also leads to more frequent catastrophes. More dramatically, catastrophe events in the different filaments forming a bundle are found to be correlated; a catastrophe event in one filament is more likely to be followed by a similar event in the same filament. This propensity of bunching disappears when the filaments move farther apart.