Biology subjects

Volpicelli-Daley, L.

Publications and source records attributed to Volpicelli-Daley, L..

3 recordsLinked to original sources

bioRxiv2024

Cortico-amygdala synaptic structural abnormalities produced by templated aggregation of α-synuclein

Parkinsons disease (PD) and Dementia with Lewy bodies (DLB) are characterized by neuronal -synuclein (-syn) inclusions termed Lewy Pathology, which are abundant in the amygdala. The basolateral amygdala (BLA), in particular, receives projections from the thalamus and cortex. These projections play a role in cognition and emotional processing, behaviors which are impaired in -synucleinopathies. To understand if and how pathologic -syn impacts the BLA requires animal models of -syn aggregation. Injection of -synuclein pre-formed fibrils (PFFs) into the striatum induces robust -synuclein aggregation in excitatory neurons in the BLA that corresponds with reduced contextual fear conditioning. At early time points after aggregate formation, cortico-amygdala excitatory transmission is abolished. The goal of this project was to determine if -syn inclusions in the BLA induce synaptic degeneration and/or morphological changes. In this study, we used C57BL/6J mice injected bilaterally with PFFs in the dorsal striatum to induce -syn aggregate formation in the BLA. A method was developed using immunofluorescence and three-dimensional reconstruction to analyze excitatory cortico-amygdala and thalamo-amygdala presynaptic terminals closely juxtaposed to postsynaptic densities. The abundance and morphology of synapses were analyzed at 6- or 12-weeks post-injection of PFFs. -Syn aggregate formation in the BLA did not cause a significant loss of synapses, but cortico-amygdala and thalamo-amygdala presynaptic terminals and postsynaptic densities with aggregates of -synuclein show increased volumes, similar to previous findings in human DLB cortex, and in non-human primate models of PD. Transmission electron microscopy showed that PFF-injected mice showed reduced intervesicular distances similar to a recent study showing phospho-serine-129 -synuclein increases synaptic vesicle clustering. Thus, pathologic -synuclein causes major alterations to synaptic architecture in the BLA, potentially contributing to behavioral impairment and amygdala dysfunction observed in synucleinopathies.

neuroscience↗

bioRxiv2023

Parkinsons Disease Pathology is Directly Correlated to SIRT3 in Human Subjects and Animal Models: Implications for AAV.SIRT3-myc as a Disease-Modifying Therapy.

Degeneration of the dopaminergic nigro-striatal pathway and presence of Lewy bodies are pathological hallmarks of Parkinsons disease (PD). Postmortem studies in human tissue have also demonstrated that a decline in mitochondrial number and function is also central to PD pathology. Sirtuin 3 (SIRT3) is a mitochondrial protein deacetylase which has been linked with longevity and cytoprotective effects. SIRT3 serves as a metabolic sensor and regulates mitochondrial homeostasis and oxidative stress, which likely stabilises telomere integrity, delaying senescence. Previously, we have shown that over-expression of SIRT3 rescues motor function and prevents degeneration of dopaminergic neurons in a virally over-expressing mutant (A53T)--synuclein model of PD. In the present study, we show that in the substantia nigra pars compacta (SNc) of human subjects, SIRT3 levels are negatively correlated with age (p<0.05, R=0.6539). In the hippocampus, there was no correlation between SIRT3 levels and age. In human subjects with PD, SIRT3 was reduced by 56.8{+/-}15.5% and 34.0{+/-}5.6% in the SNc and hippocampus respectively regardless of age. Given that age is the primary risk factor for PD, this finding suggests that reduced SIRT3 may be a causative factor contributing to PD pathology. Next in human subjects with PD, we measured whether there was a correlation between the amount of aggregated -synuclein and SIRT3 levels by measuring immunofluorescence of phosphorylated -synuclein (p-syn), which is a marker for Lewy bodies. Interestingly, in the hippocampus, but not SNc, there was a positive correlation between SIRT3 and p-syn levels, despite p-syn being reduced compared to control. Next using an -synuclein seeding rat model of PD, we assessed the disease-modifying effects of viral-mediated SIRT3 infusion. Six months following infusion of -synuclein pre-formed fibrils (PFF) into the SNc, there was 38.8{+/-}4.5% loss of TH-positive neurons, impaired striatal dopamine metabolism and pathological -synuclein throughout the brain. Phosphorylated--synuclein immunoreactivity was present in the SNc, olfactory tubercle, striatum, amygdala, hippocampus and motor cortex. In PD subjects, synuclein positive aggregates have also been reported in these brain regions. In PFF rats, infusion of rAAV1.SIRT3-myc in the SNc reduced abundance of -synuclein inclusions in the SNc by 30.1{+/-}18.5% which was not seen when deacetylation deficient SIRT3H248Y was transduced. This demonstrates the importance of SIRT3deacetylation in reducing -synuclein aggregation. However, while SIRT3 transduction reduced aggregation in the SNc, it had no significant effect on phosphorylated--synuclein levels in other brain regions. These studies confirm that SIRT3 is directly correlated with senescence and aging in humans. We also provide evidence that reduced SIRT3 contributes to the pathology of clinical PD. Finally, by showing that over-expression of SIRT3 prevents -synuclein aggregation through de-acetylation-dependent mechanisms, we further validate AAV1.SIRT3-myc as a potential disease-modifying therapy for PD.

neuroscience↗

bioRxiv2020

Rab27 GTPases regulate alpha-synuclein uptake, cell-to-cell 1 transmission, and toxicity

Parkinsons disease and Dementia with Lewy Bodies are two common neurodegenerative disorders marked by proteinaceous aggregates composed primarily of the protein -synuclein. -Synuclein is hypothesized to have prion-like properties, by which misfolded -synuclein induces the pathological aggregation of endogenous -synuclein and neuronal loss. Rab27a and Rab27b are two highly homologous Rab GTPases that regulate -synuclein secretion, clearance, and toxicity in vitro. In this study, we tested the impact of Rab27a/b on the transmission of pathogenic -synuclein. Double knockout of both Rab27 isoforms eliminated -synuclein aggregation and neuronal toxicity in primary cultured neurons exposed to fibrillary -synuclein. In vivo, Rab27 double knockout mice lacked fibril-induced -synuclein inclusions, dopaminergic neuron loss, and behavioral deficits seen in wildtype mice with fibril-induced inclusions. Studies using AlexaFluor488-labeled -synuclein fibrils revealed that Rab27a/b knockout prevented -synuclein internalization without affecting bulk endocytosis. Rab27a/b knockout also blocked the cell-to-cell spread of -synuclein pathology in multifluidic, multichambered devices. This study provides critical insight into the role of Rab GTPases in Parkinsons disease and identifies Rab27s as key players in the progression of synucleinopathies.

neuroscience↗