Heparin induces α-synuclein to form new fibril polymorphs with attenuated neuropathology

Abstract

Abstractα-Synuclein (α-syn), as a primary pathogenic protein in Parkinson’s disease (PD) and other synucleinopathies, exhibits a high potential to form polymorphic fibrils. Chemical ligands have been found to involve in the assembly of α-syn fibrils in patients’ brains. However, how ligands influence the fibril polymorphism remains vague. Here, we report the near-atomic structures of α-syn fibrils in complex with heparin, a representative glycosaminoglycan (GAG), determined by cryo-electron microscopy (cryo-EM). The structures demonstrate that the presence of heparin completely alters the fibril assembly via rearranging the charge interactions of α-syn both at the intramolecular and the inter-protofilamental levels, which leads to the generation of four fibril polymorphs. Remarkably, in one of the fibril polymorphs, α-syn folds into a distinctive conformation that has not been observed previously. Moreover, the heparin-α-syn complex fibrils exhibit diminished neuropathology in primary neurons. Our work provides the structural mechanism for how heparin determines the assembly of α-syn fibrils, and emphasizes the important role of biological polymers in the conformational selection and neuropathology regulation of amyloid fibrils.

Inhibition of Amyloid Nucleation by Steric Hindrance

“…47 Heparin has been found to induce α-synuclein to form new fibril polymorphs with diminished neuropathology. 48 In a previous study, by using all-atom molecular dynamics (MD) simulations, we found that O-GlcNAcylation suppressed the oligomerization of α-synuclein via a steric effect, in which the additional O-linked glycosyl group decreased hydrogen bonds between α-synuclein monomers. 49 Knowledge of that mechanism illuminates recent experiments showing that proper O-GlcNAcylation can prevent the aggregation and fibrosis of α-synuclein, 41,43,50,51 as well as sheds light on the steric effect on protein aggregation.…”

“…For example, fibrils purified from patients with multiple system atrophy are believed to be modified via covalent PTMs as well as noncovalent binding with unidentified molecular ligands . Heparin has been found to induce α-synuclein to form new fibril polymorphs with diminished neuropathology …”

Rational design of functional amyloid fibrillar assemblies

“…Heparin, a heparan sulfate analog, has been shown to promote the fibrillation of α-syn. 235 In a recent structural study, it was found that heparin binds directly to several positively charged lysine residues (Lys32, Lys34, Lys43, Lys45, Lys58, Lys60, and Lys97) 236 and aligns on the positive surface along the fibril axis, resulting in intensive electrostatic interaction with the stacking lysine residues (Fig. 7a(i), top).…”

Structure of alpha-synuclein fibrils derived from human Lewy body dementia tissue

“…Different Asyn fibril polymorphs are produced by incubating human recombinant monomeric Asyn protein under different conditions to induce fibril formation, including differences in pH, buffers and salts, as demonstrated by SSNMR [14][15][16][17][18][19][20][21] and cryo-EM studies [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] . The structure of Asyn fibrils isolated from postmortem multiple system atrophy (MSA) brain tissue, where fibrils accumulate in oligodendroglial cells, has been determined by cryo-EM 37 .…”