Lafer
Eileen M.
Lafer
Eileen M.
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ArticleHsc70 ameliorates the vesicle recycling defects caused by excess alpha-synuclein at synapses(Society for Neuroscience, 2020-01-15) Banks, Susan M. L. ; Medeiros, Audrey T. ; McQuillan, Molly ; Busch, David J. ; Ibarraran-Viniegra, Ana Sofia ; Sousa, Rui ; Lafer, Eileen M. ; Morgan, Jennifer R.α-Synuclein overexpression and aggregation are linked to Parkinson’s disease (PD), dementia with Lewy bodies (DLB), and several other neurodegenerative disorders. In addition to effects in the cell body, α-synuclein accumulation occurs at presynapses where the protein is normally localized. While it is generally agreed that excess α-synuclein impairs synaptic vesicle trafficking, the underlying mechanisms are unknown. We show here that acute introduction of excess human α-synuclein at a classic vertebrate synapse, the lamprey reticulospinal (RS) synapse, selectively impaired the uncoating of clathrin-coated vesicles (CCVs) during synaptic vesicle recycling, leading to an increase in endocytic intermediates and a severe depletion of synaptic vesicles. Furthermore, human α-synuclein and lamprey γ-synuclein both interact in vitro with Hsc70, the chaperone protein that uncoats CCVs at synapses. After introducing excess α-synuclein, Hsc70 availability was reduced at stimulated synapses, suggesting Hsc70 sequestration as a possible mechanism underlying the synaptic vesicle trafficking defects. In support of this hypothesis, increasing the levels of exogenous Hsc70 along with α-synuclein ameliorated the CCV uncoating and vesicle recycling defects. These experiments identify a reduction in Hsc70 availability at synapses, and consequently its function, as the mechanism by which α-synuclein induces synaptic vesicle recycling defects. To our knowledge, this is the first report of a viable chaperone-based strategy for reversing the synaptic vesicle trafficking defects associated with excess α-synuclein, which may be of value for improving synaptic function in PD and other synuclein-linked diseases.
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ArticleA role for an Hsp70 nucleotide exchange factor in the regulation of synaptic vesicle endocytosis(Society for Neuroscience, 2013-05-01) Morgan, Jennifer R. ; Jiang, Jianwen ; Oliphint, Paul A. ; Jin, Suping ; Gimenez, Luis E. ; Busch, David J. ; Foldes, Andrea E. ; Zhuo, Yue ; Sousa, Rui ; Lafer, Eileen M.Neurotransmission requires a continuously available pool of synaptic vesicles (SVs) that can fuse with the plasma membrane and release their neurotransmitter contents upon stimulation. After fusion, SV membranes and membrane proteins are retrieved from the presynaptic plasma membrane by clathrin-mediated endocytosis. After the internalization of a clathrin-coated vesicle, the vesicle must uncoat to replenish the pool of SVs. Clathrin-coated vesicle uncoating requires ATP and is mediated by the ubiquitous molecular chaperone Hsc70. In vitro, depolymerized clathrin forms a stable complex with Hsc70*ADP. This complex can be dissociated by nucleotide exchange factors (NEFs) that release ADP from Hsc70, allowing ATP to bind and induce disruption of the clathrin:Hsc70 association. Whether NEFs generally play similar roles in vesicle trafficking in vivo and whether they play such roles in SV endocytosis in particular is unknown. To address this question, we used information from recent structural and mechanistic studies of Hsp70:NEF and Hsp70:co-chaperone interactions to design a NEF inhibitor. Using acute perturbations at giant reticulospinal synapses of the sea lamprey (Petromyzon marinus), we found that this NEF inhibitor inhibited SV endocytosis. When this inhibitor was mutated so that it could no longer bind and inhibit Hsp110 (a NEF that we find to be highly abundant in brain cytosol), its ability to inhibit SV endocytosis was eliminated. These observations indicate that the action of a NEF, most likely Hsp110, is normally required during SV trafficking to release clathrin from Hsc70 and make it available for additional rounds of endocytosis.
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ArticleChaperone proteins as ameliorators of alpha-synuclein-induced synaptic pathologies: Insights into Parkinson's disease(Medknow Publications, 2020-11-27) Banks, Susan M. L. ; Medeiros, Audrey T. ; Sousa, Rui ; Lafer, Eileen M. ; Morgan, Jennifer R.α-Synuclein accumulation causes synaptic vesicle trafficking defects and may underlie neurodegenerative disorders: Neurodegenerative disorders, such as Parkinson’s disease (PD) and other synucleinopathies, impact the lives of millions of patients and their caregivers. Synucleinopathies include PD, dementia with Lewy Bodies (DLB), multiple system atrophy, and several Alzheimer’s Disease variants. They are clinically characterized by intracellular inclusions called Lewy Bodies, which are rich in atypical aggregates of the protein α-synuclein. While dopaminergic neurons in the substantia nigra are particularly susceptible to α-synuclein-induced aggregation and neurodegeneration, glutamatergic neurons in other brain regions (e.g. cortex) are also frequently affected in PD and other synucleinopathies (Schulz-Schaeffer 2010). Several point mutations in the α-synuclein gene (SNCA), as well as duplication/triplication of SNCA, are linked to familial Parkinson’s disease. In animal models, these genetic alterations lead to overexpression and aberrant accumulation of α-synuclein within neurons, and eventually to neurodegeneration. Interestingly, in both animal models and human patients, α-synuclein aggregation often occurs at neuronal synapses and within axons prior to the appearance of larger aggregates (i.e. Lewy bodies) and other signs of neurodegeneration (Schulz-Schaeffer 2010; Volpicelli-Daley et al., 2011). The level of synaptic aggregation of α-synuclein is highly correlated with greater cognitive deficits in PD and DLB patients (Schulz-Schaeffer 2010). Thus, it is essential to understand how excess α-synuclein impacts synapses, as this may represent an early stage in the neurodegenerative disease progression and thus a viable target for therapeutic intervention, particularly with respect to cognitive impairment.
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ArticleHsc70 rescues the synaptic vesicle trafficking defects caused by α-synuclein dimers(Caltech Library, 2023-03-01) Brady, Emily B ; McQuillan, Molly ; Medeiros, Audrey T ; Bubacco, Luigi ; Sousa, Rui ; Lafer, Eileen M ; Morgan, Jennifer RAberrant buildup of α-synuclein is associated with Parkinson's disease (PD) and other neurodegenerative disorders. At synapses, α-synuclein accumulation leads to severe synaptic vesicle trafficking defects. We previously demonstrated that different molecular species of α-synuclein produce distinct effects on synaptic vesicle recycling, and that the synaptic phenotypes caused by monomeric α-synuclein were ameliorated by Hsc70. Here, we tested whether Hsc70 could also correct synaptic deficits induced by α-synuclein dimers. Indeed, co-injection of Hsc70 with α-synuclein dimers completely reversed the synaptic deficits, resulting in synapses with normal appearance. This work lends additional support for pursuing chaperone-based strategies to treat PD and other synucleinopathies.