The Interplay between Alpha-Synuclein Clearance and Spreading

Fonseca, Tomás Lopes da; Villar‐Piqué, Anna; Outeiro, Tiago F.

doi:10.3390/biom5020435

Cited by 84 publications

(70 citation statements)

References 277 publications

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“…VH14 would be expected to bind primarily to the monomeric form of α-Syn, since the NAC region may be rapidly bound in homo or heterologous multimers, with the epitope buried internally and inaccessible to the nanobody [7]. Clearance of higher order structures of α-Syn have been shown to require autophagy [46]. A recent publication showed that relative concentrations of the different forms of α-Syn, including extracellular forms of the monomer, may play important roles in PD [47].…”

Section: Discussionmentioning

confidence: 99%

Bifunctional Anti-Non-Amyloid Component α-Synuclein Nanobodies Are Protective In Situ

et al. 2016

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Misfolding, abnormal accumulation, and secretion of α-Synuclein (α-Syn) are closely associated with synucleinopathies, including Parkinson’s disease (PD). VH14 is a human single domain intrabody selected against the non-amyloid component (NAC) hydrophobic interaction region of α-Syn, which is critical for initial aggregation. Using neuronal cell lines, we show that as a bifunctional nanobody fused to a proteasome targeting signal, VH14PEST can counteract heterologous proteostatic effects of mutant α-Syn on mutant huntingtin Exon1 and protect against α-Syn toxicity using propidium iodide or Annexin V readouts. We compared this anti-NAC candidate to NbSyn87, which binds to the C-terminus of α-Syn. NbSyn87PEST degrades α-Syn as well or better than VH14PEST. However, while both candidates reduced toxicity, VH14PEST appears more effective in both proteostatic stress and toxicity assays. These results show that the approach of reducing intracellular monomeric targets with novel antibody engineering technology should allow in vivo modulation of proteostatic pathologies.

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Section: Discussionmentioning

confidence: 99%

Bifunctional Anti-Non-Amyloid Component α-Synuclein Nanobodies Are Protective In Situ

et al. 2016

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“…Intravesicular pH drops along the endocytic pathway to ϳ6 and in late endosomes and lysosomes to as low as 4.5 (25,27). In addition to its role in vesicular fusion and trafficking, ␣S is subject to lysosomal degradation (28), and it may enter the slightly alkaline mitochondrial environment (29). Furthermore, pH dysregulation accompanying oxidative stress can result in cytosolic acidification (30), and oxidative stress is a significant contributor to PD pathology (31).…”

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confidence: 99%

A pH-dependent switch promotes β-synuclein fibril formation via glutamate residues

Moriarty

Olson

Atieh

et al. 2017

Journal of Biological Chemistry

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Edited by Wolfgang Peti ␣-Synuclein (␣S) is the primary protein associated with Parkinson's disease, and it undergoes aggregation from its intrinsically disordered monomeric form to a cross-␤ fibrillar form. The closely related homolog ␤-synuclein (␤S) is essentially fibril-resistant under cytoplasmic physiological conditions. Toxic gain-of-function by ␤S has been linked to dysfunction, but the aggregation behavior of ␤S under altered pH is not wellunderstood. In this work, we compare fibril formation of ␣S and ␤S at pH 7.3 and mildly acidic pH 5.8, and we demonstrate that pH serves as an on/off switch for ␤S fibrillation. Using ␣S/␤S domain-swapped chimera constructs and single residue substitutions in ␤S, we localized the switch to acidic residues in the N-terminal and non-amyloid component domains of ␤S. Computational models of ␤S fibril structures indicate that key glutamate residues (Glu-31 and Glu-61) in these domains may be sites of pH-sensitive interactions, and variants E31A and E61A show dramatically altered pH sensitivity for fibril formation supporting the importance of these charged side chains in fibril formation of ␤S. Our results demonstrate that relatively small changes in pH, which occur frequently in the cytoplasm and in secretory pathways, may induce the formation of ␤S fibrils and suggest a complex role for ␤S in synuclein cellular homeostasis and Parkinson's disease. ␣-Synuclein (␣S),5 the primary protein component of intracytoplasmic inclusions known as Lewy bodies (LB) in Parkinson's disease (PD), is a 140-residue, predominantly monomeric, intrinsically disordered protein (IDP) (1-6). It is abundant in the cytosol but present in many organelles (7,8). The monomers of ␣S can aggregate to soluble oligomers as well as insoluble oligomers and fibrils, which are considered to be associated with the pathogenesis of PD (9). A closely related family member, ␤-synuclein (␤S) that co-localizes with ␣S, has ϳ60% sequence identity with ␣S but has not been detected in LBs of PD patients (10, 11). Instead, it has been proposed that ␤S may delay ␣S fibril formation and ameliorate ␣S toxicity in vivo by inhibiting ␣S aggregation (12-14). Furthermore, despite the high sequence similarity, ␤S itself does not form fibrils in vitro at cytoplasmic pH without facilitating agents (15). However, recent reports highlight a role for a possible toxic gain-of-function of ␤S in two different model systems (16,17), and ␤S is a component of vesicle-like lesions in the hippocampus, whose formation accompanies dementia in PD (18). In addition, two ␤S mutations, V70M and P123H, were found in sporadic and familial dementia with LBs and have been suggested to be involved in lysosomal pathology (19 -21). There is an emerging role for ␤S in the pathophysiology of PD, but the molecular determinants of this role remain poorly studied.Understanding the complex relationship of synucleins with neurodegeneration requires consideration of their structures and functions in diverse subcellular environments, beyond the cytoplasm. Altho...

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“…Here, we show evidence ( Figure 6) that OPTN localization with alpha-synuclein positive intracellular puncta are increasingly evident in rotenone treated animals. Given that alpha-synuclein can be degraded by the ubiquitinproteasome pathway, chaperone mediated autophagy, and macroautophagy, targeted studies will be required to understand OPTN and alpha-synuclein interactions (Lopes da Fonseca et al, 2015). Mechanistic in vitro studies will need to be conducted in the future to confirm and understand the role of OPTN in mediating aberrant autophagy and PD-relevant neurotoxicity.…”

Section: Discussionmentioning

confidence: 99%

From the Cover: Alterations in Optineurin Expression and Localization in Pre-clinical Parkinson’s Disease Models

Wise

Cannon

2016

Toxicol. Sci.

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Parkinson's disease (PD) is a progressive neurodegenerative disease that affects $5 million people around the world. PD etiopathogenesis is poorly understood and curative or disease modifying treatments are not available. Mechanistic studies have identified numerous pathogenic pathways that overlap with many other neurodegenerative diseases. Mutations in the protein optineurin (OPTN) have recently been identified as causative factors for glaucoma and amyotrophic lateral sclerosis. OPTN has multiple recognized roles in neurons, notably in mediating autophagic flux, which has been found to be disrupted in most neurodegenerative diseases. OPTN þ aggregates have preliminarily been identified in cytoplasmic inclusions in numerous neurodegenerative diseases, however, whether OPTN has a role in PD pathogenesis has yet to be tested. Thus, we chose to test the hypothesis that OPTN expression and localization would be modulated in pre-clinical PD models. To test our hypothesis, we characterized midbrain OPTN expression in normal rats and in a rat rotenone PD model. For the first time, we show that OPTN is enriched in dopamine neurons in the midbrain, and its expression is modulated by rotenone treatment in vivo. Here, animals were sampled at time-points both prior to overt neurodegeneration and after severe behavioral deficits, where a lesion to the nigrostriatal dopamine system is present. The effect and magnitude of OPTN expression changes are dependent on duration of treatment. Furthermore, OPTN colocalizes with LC3 (autophagic vesicle marker) and alpha-synuclein positive puncta in rotenone-treated animals, potentially indicating an important role in autophagy and PD pathogenesis.

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The Interplay between Alpha-Synuclein Clearance and Spreading

Cited by 84 publications

References 277 publications

Bifunctional Anti-Non-Amyloid Component α-Synuclein Nanobodies Are Protective In Situ

Bifunctional Anti-Non-Amyloid Component α-Synuclein Nanobodies Are Protective In Situ

A pH-dependent switch promotes β-synuclein fibril formation via glutamate residues

From the Cover: Alterations in Optineurin Expression and Localization in Pre-clinical Parkinson’s Disease Models

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