Divergent effects of the H50Q and G51D SNCA mutations on the aggregation of α‐synuclein

Abstract

The discoveries of mutations in SNCA were seminal findings that resulted in the knowledge that a-synuclein (aS) is the major component of Parkinson's disease-associated Lewy bodies. Since the pathologic roles of these protein inclusions and SNCA mutations are not completely established, we characterized the aggregation properties of the recently identified SNCA mutations, H50Q and G51D, to provide novel insights. The properties of recombinant H50Q, G51D, and wild-type aS to polymerize and aggregate into amyloid were studied using (trans,trans)-1-bromo-2,5-bis-(4-hydroxy)styrylbenzene fluorometry, sedimentation analyses, electron microscopy, and atomic force microscopy. These studies showed that the H50Q mutation increases the rate of aS aggregation, whereas the G51D mutation has the opposite effect. However, H50Q and G51D aS could still be similarly induced to form intracellular aggregates from the exposure to exogenous amyloidogenic seeds under conditions that promote their cellular entry. Both mutant aS proteins, but especially G51D, promoted cellular toxicity under cellular stress conditions. These findings reveal that the novel pathogenic SNCA mutations, H50Q and G51D, have divergent effects on aggregation properties relative to the wild-type protein, with G51D aS demonstrating reduced aggregation despite presenting with earlier disease onset, suggesting that these mutants promote different mechanisms of aS pathogenesis.

α-synuclein dimer structures found from computational simulations

“…This region also contains several residues (A30, E46, H50 G51 and A53) whose mutations (A30P, E46K, H50Q, G51D, A53T) alter the aggregation process [16][17][18][19][20][21][22][23] and are linked to familial forms of Parkinson's disease [24,25]. The central region, consisting of residues 61-95, is highly hydrophobic [26,27].…”

Dimerization propensities of Synucleins are not predictive for Synuclein aggregation

“…Increases in αS protein levels which are observed in genomic multiplications of the αS gene (SNCA) were suggested to result in abnormal aggregate formation and neuronal degeneration in vitro [13][14][15] and in vivo [16,17]. Human αS wild type and diseaseassociated αS mutants readily assemble into filaments in vitro [18] and disease-associated mutants of αS show accelerated aggregation and fibril formation in vitro [19,20].…”

New insights into cellular α-synuclein homeostasis in health and disease

“…Indeed, the fPD mutants A53T, E46K and H50Q have been reported to accelerate aggregation from monomer into fibrils, thus boosting later stages of the pathogenic process [32][33][34]. The mutations A30P and G51D are instead associated with slower fibril formation [32,35], suggesting that their pathogenic effect may induce soluble oligomers and perhaps be stronger in the earlier stages of the pathogenic cascade, thus overcoming the putatively beneficial influence of these two mutations on actual amyloid fibril formation. In short, each mutation may exert its effects via different steps to produce the observed decrease in tetramer:monomer ratio, promote the formation of toxic oligomers and accelerate the rate of progression in the respective carriers.…”