Direct Identification of Amyloid Peptide Fragments in Human α-Synuclein Based on Consecutive Hydrophobic Amino Acids

Yongzhu Chen; Fei Peng; Tao Su; Hao Yang; Feng Qiu

doi:10.1021/acsomega.0c00979

Direct Identification of Amyloid Peptide Fragments in Human α-Synuclein Based on Consecutive Hydrophobic Amino Acids

ACS Omega. 2020 May 12;5(20):11677-11686. doi: 10.1021/acsomega.0c00979. eCollection 2020 May 26.

Authors

Yongzhu Chen^{1

2}, Fei Peng^{1

3}, Tao Su⁴, Hao Yang⁵, Feng Qiu^{1

3}

Affiliations

¹ Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Center and National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu 610041, China.
² Periodical Press of West China Hospital, Sichuan University, Chengdu 610041, China.
³ Department of Anesthesiology, West China Hospital, Sichuan University, Chengdu 610041, China.
⁴ West China-Washington Mitochondria and Metabolism Research Center, West China Hospital, Sichuan University, Chengdu 610041, China.
⁵ Key Lab of Transplant Engineering and Immunology, MOH, West China Hospital, Sichuan University, Chengdu 610041, China.

Abstract

Formation of amyloid fibrils by misfolding α-synuclein is a characteristic feature of Parkinson's disease, but the exact molecular mechanism of this process has long been an unresolved mystery. Identification of critical amyloid peptide fragments from α-synuclein may hold the key to decipher this mystery. Focusing on consecutive hydrophobic amino acids (CHAA) in the protein sequence, in this study we proposed a sequence-based strategy for direct identification of amyloid peptide fragments in α-synuclein. We picked out three CHAA fragments (two hexapeptides and one tetrapeptide) from α-synuclein and studied their amyloidogenic property. The thioflavin-T binding test, transmission electron microscopy, Congo red staining, and Fourier transform infrared spectroscopy revealed that although only hexapeptides could undergo amyloid aggregation on their own, extended peptide fragments based on any of the three peptides could form typical amyloid fibrils. Primary amyloidogenic fragments based on the three peptides showed synergetic aggregation behavior and could accelerate the aggregation of full-length α-synuclein. It was proved that hydrophobic interaction played a predominant role for the aggregation of these peptides and full-length α-synuclein. A central alanine-to-lysine substitution in each hydrophobic fragment completely eliminated the peptides' amyloidogenic property, and alanine-to-lysine substitutions at corresponding sites in full-length α-synuclein also decreased the protein's amyloidogenic potency. These findings suggested that CHAA fragments were potentially amyloidogenic and played an important role for the aggregation of α-synuclein. The identification of these fragments might provide helpful information for eventually clarifying the molecular mechanism of α-synuclein aggregation. On the other hand, our study suggested that the CHAA fragment might be a simple motif for direct sequence-based identification of amyloid peptides.