The chaperone-like protein 14-3-3η interacts with human α-synuclein aggregation intermediates rerouting the amyloidogenic pathway and reducing α-synuclein cellular toxicity

Abstract

Familial and idiopathic Parkinson's disease (PD) is associated with the abnormal neuronal accumulation of α-synuclein (aS) leading to β-sheet-rich aggregates called Lewy Bodies (LBs). Moreover, single point mutation in aS gene and gene multiplication lead to autosomal dominant forms of PD. A connection between PD and the 14-3-3 chaperone-like proteins was recently proposed, based on the fact that some of the 14-3-3 isoforms can interact with genetic PD-associated proteins such as parkin, LRRK2 and aS and were found as components of LBs in human PD. In particular, a direct interaction between 14-3-3η and aS was reported when probed by co-immunoprecipitation from cell models, from parkinsonian brains and by surface plasmon resonance in vitro. However, the mechanisms through which 14-3-3η and aS interact in PD brains remain unclear. Herein, we show that while 14-3-3η is unable to bind monomeric aS, it interacts with aS oligomers which occur during the early stages of aS aggregation. This interaction diverts the aggregation process even when 14-3-3η is present in sub-stoichiometric amounts relative to aS. When aS level is overwhelmingly higher than that of 14-3-3η, the fibrillation process becomes a sequestration mechanism for 14-3-3η, undermining all processes governed by this protein. Using a panel of complementary techniques, we single out the stage of aggregation at which the aS/14-3-3η interaction occurs, characterize the products of the resulting processes, and show how the processes elucidated in vitro are relevant in cell models. Our findings constitute a first step in elucidating the molecular mechanism of aS/14-3-3η interaction and in understanding the critical aggregation step at which 14-3-3η has the potential to rescue aS-induced cellular toxicity.

Dysregulation of 14‐3‐3 proteins in neurodegenerative diseases with Lewy body or Alzheimer pathology

“…As several of 14‐3‐3s’ interactors include key aggregation‐prone proteins implicated in neurodegeneration, such as α syn or A β , loss of soluble 14‐3‐3s and thus loss of chaperone function could promote aggregation and insolubilization of these proteins. Indeed, 14‐3‐3s reduce α syn fibrillization, but this chaperone function can be overcome when 14‐3‐3 levels are low relative to α syn 43. Consistent with this idea, we did observe that lower soluble pan 14‐3‐3 levels correlated with higher α syn‐related tangle, or plaque pathology, suggesting that aggregation‐related pathology is associated with 14‐3‐3 insolubilization.…”

“…Consistent with this, we observed a correlation between soluble 14‐3‐3 levels and MMSE scores. Another consequence of reduced soluble 14‐3‐3 levels is impairment of 14‐3‐3s’ chaperone function 2, 43, 44. As several of 14‐3‐3s’ interactors include key aggregation‐prone proteins implicated in neurodegeneration, such as α syn or A β , loss of soluble 14‐3‐3s and thus loss of chaperone function could promote aggregation and insolubilization of these proteins.…”

DOPAL derived alpha-synuclein oligomers impair synaptic vesicles physiological function

“…The kinetic analysis of the aggregation behaviour of aS control, as measured by the increase of ThT fluorescence intensity over time, showed a typical sigmoidal curve40. Conversely, when aS-DOPAL molecules were subjected to the same aggregation protocol, no increase in the ThT fluorescence signal was observed.…”

“…We incubated a sample of 15 N labelled aS (160.5 μM) produced as previously described40 in the presence of an equimolar amount of DOPAL (160.5 μM) in PBS (pH 7.4) at room temperature for 30 days. The reaction was monitored by recording 15N-1H HSQC spectra of the mixture at 25 °C.…”

The K-segments of wheat dehydrin WZY2 are essential for its protective functions under temperature stress

“…LEA proteins are not classical chaperones but are more likely unstructured proteins, such as α-synuclein (Kumar et al, 2014; Manda et al, 2014) and Eh PDI (Mares et al, 2014). Chaperones will translocate to specific locations to carry out their functions (Vaseva et al, 2012), and DHNs behave in the same way.…”