alpha-synuclein and 2-tert-butylhydroquinone

Many neurodegenerative diseases are associated with neuronal misfolded protein accumulation, indicating a need for proteostasis-promoting strategies. Here we show that de-repressing the transcription factor Nrf2, epigenetically shut-off in early neuronal development, can prevent protein aggregate accumulation. Using a paradigm of α-synuclein accumulation and clearance, we find that the classical electrophilic Nrf2 activator tBHQ promotes endogenous Nrf2-dependent α-synuclein clearance in astrocytes, but not cortical neurons, which mount no Nrf2-dependent transcriptional response. Moreover, due to neuronal Nrf2 shut-off and consequent weak antioxidant defences, electrophilic tBHQ actually induces oxidative neurotoxicity, via Nrf2-independent Jun induction. However, we find that epigenetic de-repression of neuronal Nrf2 enables them to respond to Nrf2 activators to drive α-synuclein clearance. Moreover, activation of neuronal Nrf2 expression using gRNA-targeted dCas9-based transcriptional activation complexes is sufficient to trigger Nrf2-dependent α-synuclein clearance. Thus, targeting reversal of the developmental shut-off of Nrf2 in forebrain neurons may alter neurodegenerative disease trajectory by boosting proteostasis.

Topics: alpha-Synuclein; Animals; Astrocytes; Cell Death; Cells, Cultured; Clustered Regularly Interspaced Short Palindromic Repeats; Coculture Techniques; CRISPR-Associated Protein 9; CRISPR-Cas Systems; Epigenetic Repression; Female; Gene Targeting; Hydroquinones; Lewy Body Disease; Male; Mice, Inbred C57BL; Mice, Knockout; Neurons; Neuroprotective Agents; NF-E2-Related Factor 2; Prosencephalon; Proteostasis

α-synuclein (SNCA) accumulation in the substantia nigra is one of the characteristic pathologies of Parkinson's disease (PD). A53T missense mutations in the SNCA gene has been proved to enhance the expression of SNCA and accelerate the onset of PD. Mitochondrial dysfunction in SNCA aggregation has been under debate for decades but the causal relationship remains uncertain. At a later stage of PD, the cellular dysfunctions are complicated and multiple factors are tangled. Our aim here is to investigate the mitochondrial functional changes and clarify the main causal mechanism at earlier-stage of PD.. We used the mutant A53T SNCA-expressed neuro 2a (N2a) cells without detectable cell death to investigate: 1) whether SNCA overexpression impairs the mitochondrial respiration and biogenesis. 2) The role of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) signal in SNCA-induced mitochondria dysfunction.. Accompanying with the increment of SNCA, reactive oxygen species (ROS) accumulation was increased. The maximal respiratory capacity was suppressed. Meanwhile, mitochondrial complex 1 activity and the activity of nicotinamide adenine dinucleotide (NADH) cytochrome C reductase (NCCR) were decreased. Moreover, the mitochondrial DNA (mtDNA) copy number was decreased. On the other hand, the nuclear peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α), Nrf2, and the cytosolic mitochondrial transcription factor A (TFAM) were increased at an early stage and declined thereafter. Above factors triggered by SNCA were reversed by tBHQ, a Nrf2 activator.. These results suggested that at an early stage, SNCA-overexpressed increase mtROS accumulation, mitochondrial dysfunction and mtDNA decrement. Nrf2, PGC-1α and TFAM were upregulated to compromise mitochondrial dysfunction. tBHQ effectively reversed the SNCA-induced mitochondrial dysfunction.

Topics: alpha-Synuclein; Animals; Cell Line, Tumor; Hydroquinones; Mice; Mitochondria; NF-E2-Related Factor 2; Oxygen Consumption; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; Reactive Oxygen Species; Tumor Suppressor Protein p53

Mutations in leucine-rich repeat kinase 2 (LRRK2) and α-synuclein lead to Parkinson's disease (PD). Disruption of protein homeostasis is an emerging theme in PD pathogenesis, making mechanisms to reduce the accumulation of misfolded proteins an attractive therapeutic strategy. We determined if activating nuclear factor erythroid 2-related factor (Nrf2), a potential therapeutic target for neurodegeneration, could reduce PD-associated neuron toxicity by modulating the protein homeostasis network. Using a longitudinal imaging platform, we visualized the metabolism and location of mutant LRRK2 and α-synuclein in living neurons at the single-cell level. Nrf2 reduced PD-associated protein toxicity by a cell-autonomous mechanism that was time-dependent. Furthermore, Nrf2 activated distinct mechanisms to handle different misfolded proteins. Nrf2 decreased steady-state levels of α-synuclein in part by increasing α-synuclein degradation. In contrast, Nrf2 sequestered misfolded diffuse LRRK2 into more insoluble and homogeneous inclusion bodies. By identifying the stress response strategies activated by Nrf2, we also highlight endogenous coping responses that might be therapeutically bolstered to treat PD.

Topics: alpha-Synuclein; Animals; Cerebral Cortex; Genes, Reporter; HEK293 Cells; Humans; Hydroquinones; Inclusion Bodies; Induced Pluripotent Stem Cells; Leucine-Rich Repeat Serine-Threonine Protein Kinase-2; Nerve Tissue Proteins; Neurons; NF-E2-Related Factor 2; Parkinson Disease; Primary Cell Culture; Protein Aggregation, Pathological; Proteostasis; Rats; Recombinant Fusion Proteins; Single-Cell Analysis; Time Factors