Combining Magnetic Resonance strategies and computational modelling to decipher the dynamics of the disordered microtubule-associated protein Tau – MAGNETAU

Intrinsically Disordered Proteins (IDPs) play key roles in protein interaction networks and their dysfunctions are often related to severe diseases such as cancers or neurodegenerative diseases. Defined by their lack of stable secondary and tertiary structures in physiological conditions, these proteins that are functional remain difficult to characterize by classical bio-structural techniques due to their large conformational heterogeneity and dynamics. The objective of MAGNETAU is to develop an integrative methodology combining nitroxide-based spin labels for NMR and EPR studies associated to computational modeling to decipher, at the molecular level, the conformational dynamics of the long IDP Tau. Tau is a microtubule-associated protein that regulates the assembly, the dynamic behavior and the spatial organization of 20nm-diameter and µm-long cylinders called microtubules (MTs) constituted of tubulin dimers. Tau/MTs interaction is an archetype of a “fuzzy complex” underlining the dynamic nature of the association that remains difficult to study with classical structural biological methods. In Alzheimer’s disease, loss of Tau/MTs binding and increased post-translational modifications such as phosphorylations of Tau are observed. In this context, our aim is to characterize the structural dynamics of Tau/MTs complexes and its (dys)regulation induced by phosphorylation. The novelty of this project resides in the analysis of site-specific phosphorylation patterns, such as those of the AT8 and AT180 epitopes largely involved in neurodegenerative diseases and to establish a link between the structural parameters and the functional consequences.
To reach this goal, the consortium associates four partners with skills that are highly complementary to fulfill different tasks of this interdisciplinary project that comprises advanced magnetic spectroscopies, computational modeling as well as other biophysical techniques for the functional aspects. We will combine two complementary nitroxide-based MR spectroscopies: Site Directed Spin Labeling SDSL-EPR (Partner 1) and Paramagnetic Relaxation Enhancement/Interference PRE/PRI-NMR (Partner 2) to study the structural determinants of Tau without/with specific phosphorylation related to its capacity to bind to tubulin and/or MTs (functional aspects, Partner 3). Computational modeling will be used both to guide the strategy of spin labeling and to generate a conformational landscape of Tau/MTs interface at the atomic scale that will integrate the information from spectroscopies (Partner 4). The feasibility of this project is ensured by the expertise of each partner from the experimental, theoretical and thematic point of views associated with the availability of their infrastructures.
The combination of our expertise is unique and should give us a competitive advantage to bring new ideas in this field. Thanks to our association, we will represent the most advanced consortium working on the topic of Tau and the effect of site-specific phosphorylation on its interaction with MTs, combining structural, computational and functional studies. In conclusion, MAGNETAU will focus on one particular case-study where precise insight into the conformational ensemble is a clear missing link for understanding biological function. On the long term, the methodology of this project will contribute to a better description of conformational ensembles in large biological complexes, by maximizing the amount of spectral information to implement molecular dynamics, allowing to resolve how biopolymers such as IDPs are functional. We think that the association of our expertise could inspire other groups working in the field of IDPs and their interaction to biological partners.