Le « code tubuline » : un mécanisme qui adapte les fonctions des microtubules à la demande – TUBTUNE

The microtubule cytoskeleton is an evolutionarily conserved macromolecular assembly with a large variety of functions in living cells. Adaptation to specific functions is likely controlled by the tubulin code, a molecular mechanism to diversify microtubules. Here we will develop a systems approach to determine the molecular mechanisms and biological role of the posttranslational modification polyglutamylation, which due to its complexity and dynamic nature generates many combinatory patterns on microtubules. Polyglutamylation plays an important role in controlling microtubule functions in neurons, however its precise roles have so far not been determined.
In our project, we aim at demonstrating how specific polyglutamylation patterns determine specific functions of microtubules in neurons by visualizing and reconstructing their local and temporal distribution and functions. To reach this goal, we will identify the physiological roles of tubulin polyglutamylation by investigating neurons from our established mouse models with altered polyglutamylation levels and patterns, use quantitative proteomics to determine microtubule-interacting proteins sensitive to the polyglutamylation status of the microtubules, and perform in vitro reconstitution experiments to decipher by which molecular mechanisms polyglutamylation controls its biological functions. We will further develop novel detection tools (nanobodies) which we will use in superresolution-microscopy based settings to visualize different polyglutamylation patterns in cells at a much higher resolution as previously possible. This approach will allow us to determine the diversity of polyglutamylation in neurons at single-microtubule resolution, thus allowing us to attribute precise functions of polyglutamylation patterns, determined in the in vitro assays of this project, to single microtubules in cells.
Our project will have a great impact on the understanding of the tubulin code, an emerging mechanism to control the functions of the microtubule cytoskeleton. Our consortium unites four internationally recognized teams with the unique and complementary scientific expertise necessary to tackle the goals set in the project. Considering the potential implication of tubulin polyglutamylation in neurodegeneration, our project could have a strong societal impact, as it will advance the understanding of molecular mechanisms, and might in a longer-term help the development of novel therapies.