Poly (ADP-ribose) induces α-synuclein aggregation in neuronal-like cells and interacts with phosphorylated α-synuclein in post mortem PD samples

Abstract

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Poly (ADP-ribose) (PAR) is a negatively charged polymer that is biosynthesized by Poly (ADP-ribose) Polymerase-1 (PARP-1) and regulates various cellular processes. Alpha-synuclein (αSyn) is an intrinsically disordered protein (IDP) that has been directly implicated with driving the onset and progression of Parkinson’s disease (PD). The mechanisms by which αSyn elicits its neurotoxic effects remain unclear. Recent findings indicate that one of the key processes driving PD pathology are oligomeric species of αSyn. Furthermore, it is well established that the main components of Lewy bodies (LBs) and Lewy neurites (LNs) in PD patients are aggregated hyperphosphorylated (S129) forms of αSyn (pαSyn).</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We used biochemical and immunofluorescence-based assays to explore if PARP-1 enzymatic product (PAR) drives the conversion of monomeric αSyn into aggregated assemblies. We performed quantitative measurements using in situ proximity ligation assays (PLA) on a transgenic murine model of α-synucleinopathy (M83-SNCA*A53T) and post-mortem PD/PDD patient samples to characterize PAR-pαSyn interactions. Additionally, we used bioinformatic approaches and site-directed mutagenesis to identify PAR-binding regions on fibrillar αSyn.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Our studies show that elevated intracellular levels of PAR promote the transition of αSyn into higher molecular weight forms. We report that PAR-pαSyn interactions are predominant in pathological states. Moreover, we confirm that the interactions between PAR and αSyn involve electrostatic forces between negatively charged PAR and lysine residues on the N-terminal region of αSyn.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>PAR plays a critical role in the early stages of monomeric αSyn aggregation, thereby attributing to PD pathogenesis. Based on our results, we report that PAR seeds monomeric αSyn aggregation and directly interacts with phosphorylated αSyn in conditions that are pathologically relevant to PD.</jats:p></jats:sec>

Modulation of the Interactions Between α-Synuclein and Lipid Membranes by Post-translational Modifications

“…α-Synuclein does not readily aggregate spontaneously (55,56) and this process is affected by the environmental conditions (57)(58)(59). The binding to lipid membranes offers a possible interface for primary nucleation events to initiate the toxic cascade of αsynuclein aggregation (47,55).…”

Evaluation of ABT-888 in the amelioration of α-synuclein fibril-induced neurodegeneration

“… 35 The molecule ABT-888, known to block the formation of PAR polymer via PARP-1/2 inhibition, has been described to potently ablate the formation of seeded inclusions in neurons and block dopaminergic neurodegeneration caused by intracranial injections of mouse preformed α-synuclein fibrils. 19 , 20 One mechanism potentially underlying these observations is that endogenous PAR polymer may critically accelerate the formation of toxic α-synuclein fibrils. 19 , 20 To generate the α-synuclein sonicated fibrils (mPFF) particles for investigation in primary neurons and in vivo injections, we monitored α-synuclein fibrillization using a real-time quaking-induced conversion assay and observed typical branched fibrillar topology of mouse α-synuclein protein assemblies generated in the presence or absence of 10 nM PAR polymer ( Fig.…”

“…Recent studies provide evidence that PAR polymer and α-synuclein colocalize more in the brains of Parkinson’s disease patients than in neurologically normal controls. 19 Further, evidence in vitro and in primary neuronal cultures suggests that PAR polymer formation can both seed and accelerate α-synuclein aggregation. 19 , 20 PARP inhibition lessens the accumulation of A53T α-synuclein in transgenic models, 21 and thus might prevent α-synuclein fibril-induced inclusion formation both in primary neurons and in vivo and prevent dopaminergic neurodegeneration.…”

“… 19 Further, evidence in vitro and in primary neuronal cultures suggests that PAR polymer formation can both seed and accelerate α-synuclein aggregation. 19 , 20 PARP inhibition lessens the accumulation of A53T α-synuclein in transgenic models, 21 and thus might prevent α-synuclein fibril-induced inclusion formation both in primary neurons and in vivo and prevent dopaminergic neurodegeneration. 20 The PARP-1 isoform knockout has been reported to phenocopy PARP inhibition, so it is thought that PARP-1 is the primary target for the inhibition of PAR polymerization.…”

Distinct cryo-EM Structure of α-synuclein Filaments derived by Tau

“…However, the detailed molecular conformation and the degree of the helical twist are different from those of the polymorphs (Table S3). In addition, recent studies revealed that poly(ADP-ribose) may interact with α-synuclein in vivo 62 and induce the formation of a more toxic α-synuclein strain with distinct molecular conformations. 25 These results suggest that the interaction between co-factors and αsynuclein may direct the protein to a specific misfolding and aggregation pathway toward the distinct α-synuclein filament, highlighting the importance of cellular environments in protein misfolding and aggregation.…”