Synapsins regulate α-synuclein functions

Atias, Merav; Tevet, Yaara; Sun, Jichao; Stavsky, Alexandra; Tal, Shani; Kahn, Joy; Roy, Subhojit; Gitler, Daniel

doi:10.1073/pnas.1903054116

Cited by 85 publications

(87 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In this context, our results suggest that droplet formation by a-synuclein may be involved in a physiological mechanism to cluster synaptic vesicles, possibly in conjunction with other proteins such as synapsins, which have also been shown to phase-separate into liquid-like assemblies [55]. Indeed, synapsins are implicated in synaptic function in conjunction with synuclein [57,58] and are components of Lewy bodies [59].…”

Section: Resultsmentioning

confidence: 68%

Observation of an α-synuclein liquid droplet state and its maturation into Lewy body-like assemblies

Hardenberg

Sinnige

Casford

et al. 2020

Preprint

View full text Add to dashboard Cite

Misfolded a-synuclein is a major component of Lewy bodies, which are a hallmark of Parkinson's disease. A large body of evidence shows that a-synuclein can self-assemble into amyloid fibrils, but the relationship between amyloid formation and Lewy body formation still remains unclear. Here we show, both in vitro and in a C. elegans model of Parkinson's disease, that a-synuclein undergoes liquid-liquid phase separation by forming a liquid droplet state, which converts into an amyloid-rich hydrogel. This maturation process towards the amyloid state is delayed in the presence of model synaptic vesicles in vitro. Taken together, these results suggest that the formation of Lewy bodies is linked to the arrested maturation of a-synuclein condensates in the presence of lipids and other cellular components.Parkinson's disease (PD) is the most common neurodegenerative movement disorder, affecting over 2% of the world's population over 65 years of age [1,2]. The molecular origins of this disease are not fully understood, although they have been closely associated with dysregulation of the behaviour of a-synuclein [1, 3, 4], a disordered protein whose function appears to involve the regulation of synaptic vesicle trafficking [5][6][7][8]. This gap in our knowledge of the disease aetiology is no doubt partly responsible for the lack of disease modifying therapies for PD [9][10][11][12].The pathological hallmark of PD is the presence of Lewy bodies within dopaminergic neurons in the brains of affected patients [13]. Although misfolded a-synuclein is a major constituent of Lewy bodies [14,15], ultrastructural and proteome studies have indicated that these aberrant deposits contain a plethora of cellular components, including lipid membranes and organelle fragments [16][17][18][19][20]. These findings have led to the suggestion that the processes associated with the formation of Lewy bodies could be major drivers of neurotoxicity in PD [16,18,21].Since it has also been shown that a-synuclein can aggregate into ordered amyloid fibrils in vitro [22][23][24][25][26] and in vivo [27][28][29][30][31][32], we asked how such a-synuclein aggregation can be reconciled with the formation of highly complex and heterogeneous assemblies such as Lewy bodies. We hypothesised that a-synuclein may be capable of irreversibly capturing cellular components through liquid-liquid phase separation, as this mechanism has been shown to drive the self-assembly of various disease-associated proteins on-pathway to the formation of solid aggregates [33][34][35][36]. Under healthy conditions, the condensation of proteins into a dense liquid droplet state through liquid-liquid phase separation is normally reversible, and exploited in a variety of ways to carry out cellular functions, including RNA metabolism, ribosome biogenesis, DNA damage response and signal transduction [33,34,37]. Upon dysregulation, however, liquid droplets can mature into gel-like deposits, which irreversibly sequester important cellular components and lead to pathological processes [38...

show abstract

Section: Resultsmentioning

confidence: 68%

Observation of an α-synuclein liquid droplet state and its maturation into Lewy body-like assemblies

Hardenberg

Sinnige

Casford

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…While it is clear that excess α-syn-112 is associated with a number of 40 neurodegenerative diseases, very little is known about its biochemical properties 41 or neuronal functions. 42 43 We therefore set out to perform a more detailed characterization of α-syn- 2017; Atias et al, 2019). When overexpressed at mammalian synapses to levels 3 comparable to those in familial PD, α-syn-140 impaired synaptic vesicle 4…”

mentioning

confidence: 99%

α-Synuclein-112 impairs synaptic vesicle recycling consistent with its enhanced membrane binding properties

Soll

Eisen

Vargas

et al. 2020

Preprint

View full text Add to dashboard Cite

Synucleinopathies are neurological disorders associated with α-synuclein overexpression and aggregation. While it is well established that overexpression of wild type α-synuclein (α-syn-140) leads to cellular toxicity and neurodegeneration, much less is known about other naturally occurring α-synuclein splice isoforms. In this study we provide the first detailed examination of the synaptic effects caused by one of these splice isoforms, α-synuclein-112 (α-syn-112). α-Syn-112 is produced by an in-frame excision of exon 5, resulting in deletion of amino acids 103-130 in the C-terminal region. α-Syn-112 is upregulated in the substantia nigra, frontal cortex, and cerebellum of parkinsonian brains and is correlated with susceptibility to sporadic Parkinson’s disease (PD), dementia with Lewy bodies (DLB) and multiple systems atrophy (MSA). We report here that α-syn-112 binds strongly to anionic phospholipids when presented in highly-curved liposomes, similar to α-syn-140. However, α-syn-112 bound significantly stronger to all phospholipids tested, including the phosphoinositides. α-Syn-112 also dimerized and trimerized on isolated synaptic membranes, while α-syn-140 remained largely monomeric. When introduced acutely to lamprey synapses, α-syn-112 robustly inhibited synaptic vesicle recycling. Interestingly, α-syn-112 produced effects on the plasma membrane and clathrin-mediated synaptic vesicle endocytosis that were phenotypically intermediate between those caused by monomeric and dimeric α-syn-140. These findings indicate that α-syn-112 exhibits enhanced phospholipid binding and oligomerization in vitro and consequently interferes with synaptic vesicle recycling in vivo in ways that are consistent with its biochemical properties. This study provides additional evidence suggesting that impaired vesicle endocytosis is a cellular target of excess α-synuclein and advances our understanding of potential mechanisms underlying disease pathogenesis in the synucleinopathies.

show abstract

“…NH4Cl, to expose the total pool of vesicles (Fmax; (Atias et al, 2019)). The background-corrected 158 fluorescence values recorded for each synapse were normalized either by the peak response during the 159 stimulation train, or by the size of the total pool of vesicles, as indicated.…”

Section: Introduction 59mentioning

confidence: 99%

“…BafA blocks the vesicle proton pump, thus 163 masking the endocytotic segment of SV cycle (Burrone et al, 2006) without affecting the kinetics of 164 endocytosis (Qiu et al, 2015). Quantification was performed with the NIS-Elements software (Nikon), 165 by placing equal circular regions of interests (ROI)s on 30-50 synapses in each field and extracting the 166 background-subtracted average fluorescence value of each ROI (Atias et al, 2019). A local 167 background was obtained adjacently to each ROI.…”

Section: Introduction 59mentioning

confidence: 99%

See 1 more Smart Citation

α-Synuclein facilitates endocytosis by elevating the steady-state levels of phosphatidylinositol 4,5-bisphosphate

Schechter

Atias

Elhadi³

et al. 2020

Preprint

View full text Add to dashboard Cite

Abstractα-Synuclein (α-Syn) is a protein implicated in the pathogenesis of Parkinson’s disease (PD). It is an intrinsically disordered protein that binds acidic phospholipids. Growing evidence supports a role for α-Syn in membrane trafficking, including, mechanisms of endocytosis and exocytosis, although the exact role of α-Syn in these mechanisms is currently unclear. Here we have investigated the role of α-Syn in membrane trafficking through its association with acidic phosphoinositides (PIPs), such as phosphatidylinositol 4,5-bisphosphate (PI4,5P2) and phosphatidylinositol 3,4-bisphosphate (PI3,4P2). Our results show that α-Syn colocalizes with PIP2 and the phosphorylated active form of the clathrin adaptor AP2 at clathrin-coated pits. Using endocytosis of transferrin, an indicator of clathrin mediated endocytosis (CME), we find that α-Syn involvement in endocytosis is specifically mediated through PI4,5P2 levels. We further show that the rate of synaptic vesicle (SV) endocytosis is differentially affected by α-Syn mutations. In accord with their effects on PI4,5P2 levels at the plasma membrane, the PD associated E46K and A53T mutations further enhance SV endocytosis. However, neither A30P mutation, nor Lysine to Glutamic acid substitutions at the KTKEGV repeat domain of α-Syn, that interfere with phospholipid binding, affect SV endocytosis. This study provides evidence for a critical involvement of PIPs in α-Syn-mediated membrane trafficking.Significance Statementα-Synuclein (α-Syn) protein is known for its causative role in Parkinson’s disease. α-Syn is normally involved in mechanisms of membrane trafficking, including endocytosis, exocytosis and synaptic vesicles cycling. However, a certain degree of controversy regarding the exact role of α-Syn in these mechanisms persists. Here we show that α-Syn acts to increase plasma membrane levels PI4,5P2 and PI3,4P2 to facilitate clathrin mediated and synaptic vesicles endocytosis. Based on the results, we suggest that α-Syn interactions with the acidic phosphoinositides facilitate a shift in their homeostasis to support endocytosis.

show abstract

Synapsins regulate α-synuclein functions

Cited by 85 publications

References 21 publications

Observation of an α-synuclein liquid droplet state and its maturation into Lewy body-like assemblies

Observation of an α-synuclein liquid droplet state and its maturation into Lewy body-like assemblies

α-Synuclein-112 impairs synaptic vesicle recycling consistent with its enhanced membrane binding properties

α-Synuclein facilitates endocytosis by elevating the steady-state levels of phosphatidylinositol 4,5-bisphosphate

Contact Info

Product

Resources

About