S100A9 Alters the Pathway of Alpha-Synuclein Amyloid Aggregation

• Main Authors: Zigmantas Toleikis, Mantas Ziaunys, Lina Baranauskiene, Vytautas Petrauskas, Kristaps Jaudzems, Vytautas Smirnovas
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: International Journal of Molecular Sciences
• Subjects: S100A9; synuclein; amyloid proteins; fibrils; FTIR; AFM
• Online Access: https://www.mdpi.com/1422-0067/22/15/7972
• ISSN: 1661-6596; 1422-0067

The formation of amyloid fibril plaques in the brain creates inflammation and neuron death. This process is observed in neurodegenerative disorders, such as Alzheimer’s and Parkinson’s diseases. Alpha-synuclein is the main protein found in neuronal inclusions of patients who have suffered from Parkinson’s disease. S100A9 is a calcium-binding, pro-inflammation protein, which is also found in such amyloid plaques. To understand the influence of S100A9 on the aggregation of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula>-synuclein, we analyzed their co-aggregation kinetics and the resulting amyloid fibril structure by Fourier-transform infrared spectroscopy and atomic force microscopy. We found that the presence of S100A9 alters the aggregation kinetics of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula>-synuclein and stabilizes the formation of a particular amyloid fibril structure. We also show that the solution’s ionic strength influences the interplay between S100A9 and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula>-synuclein, stabilizing a different structure of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula>-synuclein fibrils.