Phosphorylated full-length Tau interacts with 14-3-3 proteins via two short phosphorylated sequences, each occupying a binding groove of 14-3-3 dimer

International audienceProtein-protein interactions (PPIs) remain poorly explored targets for the treatment of Alzheimer’s disease (AD). The interaction of 14-3-3 proteins with Tau was shown to have detrimental effects on neuronal cells and to be linked to Tau pathology. This PPI is therefore seen as a potential target for AD. When Tau is phosphorylated by PKA (Tau-PKA), two 14-3-3 binding epitopes are generated, surrounding the phosphorylated serines 214 and 324 of Tau. The crystal structures of 14-3-3 in complex with peptides surrounding these Tau phosphosites show that both these motifs are anchored in the amphipathic binding groove of 14-3-3. However, in the absence of structural data with the full-length Tau protein, the stoichiometry of the complex or the interface and affinity of the partners, are still unclear. In this work, we addressed these points, using a broad range of biophysical techniques. The interaction of the long disordered Tau-PKA protein with 14-3-3σ is restricted to two short sequences, containing phosphorylated serines, which bind in the amphipathic binding groove of 14-3-3. Phosphorylation of Tau is fundamental for the formation of this stable complex, and the affinity of the Tau-PKA/14-3-3 interaction is in the 1-10 micromolar range. Each monomer of the 14-3-3σ dimer binds one of the two different phosphorylated peptides of Tau-PKA, suggesting a 14-3-3/Tau-PKA stoichiometry of 2:1, confirmed by analytical ultracentrifugation. These results contribute to a better understanding of this PPI and provide useful insights for drug discovery projects aiming at the inhibition of this interaction