A short motif in the N-terminal region of α-synuclein is critical for both aggregation and function

Using computational, spectroscopic and in vivo approaches, two short motifs in the N-terminal region of human alpha-synuclein are shown to be critical for toxic protein aggregation but also for membrane fusion. Aggregation of human alpha-synuclein (alpha Syn) is linked to Parkinson's disease (PD) pathology. The central region of the alpha Syn sequence contains the non-amyloid beta-component (NAC) crucial for aggregation. However, how NAC flanking regions modulate alpha Syn aggregation remains unclear. Using bioinformatics, mutation and NMR, we identify a 7-residue sequence, named P1 (residues 36-42), that controls alpha Syn aggregation. Deletion or substitution of this 'master controller' prevents aggregation at pH 7.5 in vitro. At lower pH, P1 synergises with a sequence containing the preNAC region (P2, residues 45-57) to prevent aggregation. Deleting P1 (Delta P1) or both P1 and P2 (Delta Delta) also prevents age-dependent alpha Syn aggregation and toxicity in C. elegans models and prevents alpha Syn-mediated vesicle fusion by altering the conformational properties of the protein when lipid bound. The results highlight the importance of a master-controller sequence motif that controls both alpha Syn aggregation and function-a region that could be targeted to prevent aggregation in disease.