Mechanistic insights into the protective roles of polyphosphate against amyloid cytotoxicity.

Justine Lempart,Magdalena I Ivanova,Nicholas Yoo,Alexandra Sutter,Philipp Huettemann,Ursula Jakob,James A Lauer,Daniel Southworth,Eric Tse

doi:10.26508/lsa.201900486

Justine Lempart, Magdalena I Ivanova + Show 7 more

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https://doi.org/10.26508/lsa.201900486

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Abstract

The universally abundant polyphosphate (polyP) accelerates fibril formation of disease-related amyloids and protects against amyloid cytotoxicity. To gain insights into the mechanism(s) by which polyP exerts these effects, we focused on α-synuclein, a well-studied amyloid protein, which constitutes the major component of Lewy bodies found in Parkinson's disease. Here, we demonstrate that polyP is unable to accelerate the rate-limiting step of α-synuclein fibril formation but effectively nucleates fibril assembly once α-synuclein oligomers are formed. Binding of polyP to α-synuclein either during fibril formation or upon fibril maturation substantially alters fibril morphology and effectively reduces the ability of α-synuclein fibrils to interact with cell membranes. The effect of polyP appears to be α-synuclein fibril specific and successfully prevents the uptake of fibrils into neuronal cells. These results suggest that altering the polyP levels in the extracellular space might be a potential therapeutic strategy to prevent the spreading of the disease.

Highlights

Parkinson’s disease (PD), the second most common neurodegenerative disorder known (de Lau et al, 2004), is characterized by a loss of dopaminergic neurons in the substantia nigra (Rinne et al, 1989; Damier et al, 1999)
It is well established that deposition of α-synuclein fibrils associates with the disease and that cell death can be elicited by incubating neuronal cells with α-synuclein fibrils (Winner et al, 2011), many open questions remain concerning the mechanism of toxicity, the structural features of the toxic α-synuclein species, and the way(s) by which α-synuclein toxicity propagates in the brain
Amyloid fibril formation is most commonly monitored by measuring the fluorescence of thioflavin T (ThT), a small molecular dye that becomes highly emissive when intercalated into the β-sheets of amyloidogenic oligomers and fibrils (LeVine, 1999)

Summary

Introduction

Parkinson’s disease (PD), the second most common neurodegenerative disorder known (de Lau et al, 2004), is characterized by a loss of dopaminergic neurons in the substantia nigra (Rinne et al, 1989; Damier et al, 1999). It is well established that deposition of α-synuclein fibrils associates with the disease and that cell death can be elicited by incubating neuronal cells with α-synuclein fibrils (Winner et al, 2011), many open questions remain concerning the mechanism of toxicity, the structural features of the toxic α-synuclein species, and the way(s) by which α-synuclein toxicity propagates in the brain. In vitro studies demonstrated that upon prolonged incubation, α-synuclein monomers undergo conformational rearrangements, which lead to the formation of aggregation-sensitive oligomers (Conway et al, 2000b). These nuclei are capable of sequestering other α-synuclein monomers and will grow into protofibrils and eventually into insoluble, protease-resistant fibrils (Wood et al, 1999; Conway et al, 2000a). The precise roles that these additives play in in vivo fibril formation remain to be determined

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