The A53T Mutation is Key in Defining the Differences in the Aggregation Kinetics of Human and Mouse α-Synuclein

Abstract

Despite a 95% sequence similarity, the aggregation of human and mouse α-synuclein is remarkably different, as the human form is slower than the mouse form in forming fibrils, but is associated with Parkinson’s disease both in humans and transgenic mice. Here, the amino acid code underlying these differences is investigated by comparing the lag times, growth rates and secondary structure propensities of a systematic series of eight human-mouse chimeras. Fluorescence analysis of the human-mouse variants shows that the A53T substitution dominates the growth kinetics, while the lag phase is affected by a combination of the A53T and S87N substitutions. The secondary structure propensities derived from an NMR chemical shift analysis of the monomeric forms of the human-mouse variants enables us to establish a link between the changes in the conformational properties in the region of position 53 upon mutation and the corresponding changes in growth rates. These results suggest that the presence of an alanine residue at position 53 may be an evolutionary adaptation to minimize Parkinson’s disease in humans and indicates that effective drug development efforts may be directed to target this N-terminal region of the sequence.

Structural Comparison of Mouse and Human α-Synuclein Amyloid Fibrils by Solid-State NMR

“…The highly similar morphology of the three samples indicates high reproducibility of our sample preparation, which is an essential requirement if different labeling schemes are to be used for ssNMR. However, both straight and helically twisted fibrils of mAS were observed by EM in the recent study by Kang et al 40 The observed differences of the mAS fibril morphology might be due to different fibrillization conditions and suggests the existence of two types of mAS fibrils (straight and twisted). In the case of hAS fibrils, the overall morphology was demonstrated to be strongly dependent on the fibrillization conditions, and both straight and twisted fibrils were observed and characterized.…”

“…9,40 mAS aggregates about twice faster, and the lag phase is reduced by almost 1 order of magnitude. 40 To characterize the structural differences between mAS and hAS fibrils at the atomic level, we recorded a set of high-resolution ssNMR spectra on mAS fibrils and compared it to existing data for hAS fibrils that were prepared under identical conditions. 46 As an example, Fig.…”

“…9 Meanwhile, one recent study on the detailed sequence-dependent fibrillization differences between mAS and hAS revealed that the Ala53Thr substitution dominates the aggregation growth rates, while the combination of the Ala53Thr and Ser87Asn mutations affects the lag phase of the aggregation. 40 Nevertheless, so far no structural details of mAS fibrils and their differences to hAS fibrils were available which motivated the present study.…”

Molecular and Biological Compatibility with Host Alpha-Synuclein Influences Fibril Pathogenicity

“…Substitution of the human sequence at either position 53 or 87 with the native mouse residue accelerates fibrillization rates substantially (Kang et al, 2011). Likewise, assembly rates for human-mouse chimeric α-Syn proteins fall between that of the two wildtype (wt) proteins and are proportional to their homology to wt mouse (Ms wt α-Syn).…”

Toxic Dopamine Metabolite DOPAL Forms an Unexpected Dicatechol Pyrrole Adduct with Lysines of α‐Synuclein

“…This latter effect is caused by modification of any of the Lys residues causing small chemical shift changes throughout the protein, analogous to what is observed upon mutating a residue. [20] …”