The paradigm of protein acetylation in Parkinson's disease

HAT and HDAC: Enzyme with Contradictory Action in Neurodegenerative Diseases

In view of the increasing risk of neurodegenerative diseases, epigenetics plays a fundamental role in the field of neuroscience. Several modifications have been studied including DNA methylation, histone acetylation, histone phosphorylation, etc. Histone acetylation and deacetylation regulate gene expression, and the regular activity of histone acetyltransferases (HATs) and histone deacetylases (HDACs) provides regulatory stages for gene expression and cell cycle. Imbalanced homeostasis in these enzymes causes a detrimental effect on neurophysiological function. Intriguingly, epigenetic remodelling via histone acetylation in certain brain areas has been found to play a key role in the neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease. It has been demonstrated that a number of HATs have a role in crucial brain processes such regulating neuronal plasticity and memory formation. The most recent therapeutic methods involve the use of small molecules known as histone deacetylase (HDAC) inhibitors that antagonize HDAC activity thereby increase acetylation levels in order to prevent the loss of HAT function in neurodegenerative disorders. The target specificity of the HDAC inhibitors now in use raises concerns about their applicability, despite the fact that this strategy has demonstrated promising therapeutic outcomes. The aim of this review is to summarize the cross-linking between histone modification and its regulation in the pathogenesis of neurological disorders. Furthermore, these findings also support the notion of new pharmacotherapies that target particular areas of the brain using histone deacetylase inhibitors.

Protein modification in neurodegenerative diseases

Posttranslational modifications play a crucial role in governing cellular functions and protein behavior. Researchers have implicated dysregulated posttranslational modifications in protein misfolding, which results in cytotoxicity, particularly in neurodegenerative diseases such as Alzheimer disease, Parkinson disease, and Huntington disease. These aberrant posttranslational modifications cause proteins to gather in certain parts of the brain that are linked to the development of the diseases. This leads to neuronal dysfunction and the start of neurodegenerative disease symptoms. Cognitive decline and neurological impairments commonly manifest in neurodegenerative disease patients, underscoring the urgency of comprehending the posttranslational modifications' impact on protein function for targeted therapeutic interventions. This review elucidates the critical link between neurodegenerative diseases and specific posttranslational modifications, focusing on Tau, APP, α-synuclein, Huntingtin protein, Parkin, DJ-1, and Drp1. By delineating the prominent aberrant posttranslational modifications within Alzheimer disease, Parkinson disease, and Huntington disease, the review underscores the significance of understanding the interplay among these modifications. Emphasizing 10 key abnormal posttranslational modifications, this study aims to provide a comprehensive framework for investigating neurodegenerative diseases holistically. The insights presented herein shed light on potential therapeutic avenues aimed at modulating posttranslational modifications to mitigate protein aggregation and retard neurodegenerative disease progression.

The misfolding mystery: α-synuclein and the pathogenesis of Parkinson's disease

Neurodegenerative diseases such as Parkinson's disease (PD) are characterized by the death of neurons in specific areas of the brain. One of the proteins that is involved in the pathogenesis of PD is α-synuclein (α-syn). α-Syn is a normal protein that is found in all neurons, but in PD, it misfolds and aggregates into toxic fibrils. These fibrils can then coalesce into pathological inclusions, such as Lewy bodies and Lewy neurites. The pathogenic pathway of PD is thought to involve a number of steps, including misfolding and aggregation of α-syn, mitochondrial dysfunction, protein clearance impairment, neuroinflammation and oxidative stress. A deeper insight into the structure of α-syn and its fibrils could aid in understanding the disease's etiology. The prion-like nature of α-syn is also an important area of research. Prions are misfolded proteins that can spread from cell to cell, causing other proteins to misfold as well. It is possible that α-syn may behave in a similar way, spreading from cell to cell and causing a cascade of misfolding and aggregation. Various post-translational alterations have also been observed to play a role in the pathogenesis of PD. These alterations can involve a variety of nuclear and extranuclear activities, and they can lead to the misfolding and aggregation of α-syn. A better understanding of the pathogenic pathway of PD could lead to the development of new therapies for the treatment of this disease.

Sirtuin dysregulation in Parkinson's disease: Implications of acetylation and deacetylation processes

Parkinson's disease (PD) is a progressive neurodegenerative condition that primarily affects motor function and is caused by a gradual decline of dopaminergic neurons in the brain's substantia pars compacta (Snpc) region. Multiple molecular pathways are involved in the pathogenesis, which results in impaired cellular functions and neuronal degeneration. However, the role of sirtuins, a type of NAD+-dependent deacetylase, in the pathogenesis of Parkinson's disease has recently been investigated. Sirtuins are essential for preserving cellular homeostasis because they control a number of biological processes, such as metabolism, apoptosis, and DNA repair. This review shed lights on the dysregulation of sirtuin activity in PD, highlighting the role that acetylation and deacetylation processes play in the development of the disease. Key regulators of protein acetylation, sirtuins have been found to be involved in the aberrant acetylation of vital substrates linked to PD pathology when their balance is out of balance. The hallmark characteristics of PD such as neuroinflammation, oxidative stress, and mitochondrial dysfunction have all been linked to the dysregulation of sirtuin expression and activity. Furthermore, we have also explored how the modulators of sirtuins can be a promising therapeutic intervention in the treatment of PD.

Vitamin D Receptor Polymorphisms in a Spanish Cohort of Parkinson's Disease Patients

Background: Vitamin D receptor (VDR) is a nuclear hormone receptor widely expressed in the substantia nigra. Its association with an increased risk of Parkinson's disease (PD) is based on vitamin D deficiency and/or different polymorphisms in its gene receptor. This fact has been demonstrated by several case-control studies. Materials and Methods: Consequently, we investigated the association between VDR ApaI, BsmI, FokI, and TaqI gene polymorphisms and PD in a Spanish cohort that included 54 cases and 17 healthy controls. The detection of single nucleotide polymorphisms (SNPs) was performed using a polymerase chain reaction-restriction fragment length polymorphism. Results: Our data indicate that the SNPs were not associated with the age of onset of PD, nor with the occurrence of motor symptoms. However, only BsmI polymorphism was significantly associated with PD in this Spanish cohort. In fact, BsmI genotype was five times higher among PD patients than among controls, and the A allele was considered as a genetic risk for PD. Additionally, the combination of FokI and BsmI polymorphisms was significantly associated with PD and could represent a risk factor. Conclusion: We conclude that ApaI, TaqI, and FokI polymorphisms were not associated with PD, but BsmI could be a risk factor for PD in this randomized population.

Proteomics analysis of the p.G849D variant in neurexin 2 alpha may reveal insight into Parkinson's disease pathobiology

Parkinson's disease (PD), the fastest-growing neurological disorder globally, has a complex etiology. A previous study by our group identified the p.G849D variant in neurexin 2 (NRXN2), encoding the synaptic protein, NRXN2α, as a possible causal variant of PD. Therefore, we aimed to perform functional studies using proteomics in an attempt to understand the biological pathways affected by the variant. We hypothesized that this may reveal insight into the pathobiology of PD. Wild-type and mutant NRXN2α plasmids were transfected into SH-SY5Y cells. Thereafter, total protein was extracted and prepared for mass spectrometry using a Thermo Scientific Fusion mass spectrometer equipped with a Nanospray Flex ionization source. The data were then interrogated against the UniProt H. sapiens database and afterward, pathway and enrichment analyses were performed using in silico tools. Overexpression of the wild-type protein led to the enrichment of proteins involved in neurodegenerative diseases, while overexpression of the mutant protein led to the decline of proteins involved in ribosomal functioning. Thus, we concluded that the wild-type NRXN2α may be involved in pathways related to the development of neurodegenerative disorders, and that biological processes related to the ribosome, transcription, and tRNA, specifically at the synapse, could be an important mechanism in PD. Future studies targeting translation at the synapse in PD could therefore provide further information on the pathobiology of the disease.

Biological effects of olive oil phenolic compounds on mitochondria

Phenolic compounds derived from olive oil have beneficial health properties against cancer, neurodegenerative, and metabolic diseases. Therefore, there are discrepancies in their impact on mitochondrial function that result in changes in oxidative capacity, mitochondrial respiration, and energetic demands. This review focuses on the versatile role of oleuropein, a potent antioxidant that regulates the AMPK/SIRT1/mTOR pathway to modulate autophagy/mitophagy and maintain metabolic homeostasis.

CIITA expression is regulated by histone deacetylase enzymes and has a role in α-synuclein pre-formed fibril-induced antigen presentation in murine microglial cell line

AIM

Parkinson's disease(PD) is a chronic neurodegenerative disorder related with several genetic and epigenetic factors. In the context of epigenetic factors, histone acetylation is one of the most associated mechanisms with Parkinson's disease progression. This study investigates the effects of the increased histone acetylation on antigen presentation in microglial cells which were induced by pre-formed fibrils of α-synuclein(pFF α-synuclein).

METHODS

Parkinson's disease model was created with pFF α-synuclein administration to the BV-2 microglial cells. BV-2 cells were co-treated with CUDC-907 and TMP-195 to increase histone acetylation in the presence of α-synuclein. Antigen representation was evaluated by determining expression levels of major histocompatibility complex-II(MHC-II) and class-II major histocompatibility complex(CIITA).

RESULTS

Our results showed that pFF α-synuclein significantly increased MHC-II expression, and that effect was most severe at 6 hours of administration of α-synuclein. Increasing histone acetylation via CUDC-907 and TMP-195 enhanced MHC-II levels expression, which was more severe in CUDC-907. Additionally, CIITA expression levels were significantly increased with pFF α-synuclein administration and intensified with the co-treatment of CUDC-907 and TMP-195. Furthermore, pFF α-synuclein caused a time-dependent increase in the IFN-gamma(IFN-ɣ) and interleukin-16(IL-16) levels, and that increase was potentiated with CUDC-907 and TMP-195.

CONCLUSION

Changes in MHC-II and CIITA expression indicate that histone acetylation increases the antigen presentation properties of microglial cells after pFF α-synuclein or histone deacetylase inhibitor(HDACi) administration. Our results show that microglial antigen presentation might have an essential role in the pathology of Parkinson's disease, and α-synuclein likely to play a primary role in this mechanism.

Hydrogen sulfide enhances adult neurogenesis in a mouse model of Parkinson's disease

Hydrogen sulfide (H₂S) is regarded to be a protectant against diseases of the central nervous system and cardiovascular system. However, the mechanism by which H₂S elicits neuroprotective effects in the progression of Parkinson's disease (PD) remains unclear. To investigate the role of H₂S in delaying the pathological process of PD, we used the most common sodium hydrosulfide (NaHS) as an H₂S donor and established a mouse model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/probenecid (MPTP/p) in the present study. Our results show that H₂S reduced neuronal loss during the progression of PD. Notably, we found that H₂S exhibited protective effects on dopaminergic neurons. Excitingly, H₂S also increased the proliferation of neural stem cells in the subventricular zone. Next, we evaluated whether the neuroprotective effects of H₂S on dopaminergic neurons in PD are dependent on adult nerve regeneration by treating primary adult neural stem cells cultured ex vivo with 1-methyl-4-phenylpyridine. Our results show that H₂S could prevent nerve injury induced by 1-methyl-4-phenylpyridine, promote the growth of neurospheres, and promote neurogenesis by regulating Akt/glycogen synthase kinase-3β/β-catenin pathways in adult neural stem cells. These findings confirm that H₂S can increase neurogenesis in an adult mouse model of PD by regulating the Akt/glycogen synthase kinase-3β/β-catenin signaling pathway. This study was approved by the Animal Care and Use Committee of Nanjing Medical University, China (IACUC Approval No. 1601153-3).

Disruption of Tip60 HAT mediated neural histone acetylation homeostasis is an early common event in neurodegenerative diseases

Epigenetic dysregulation is a common mechanism shared by molecularly and clinically heterogenous neurodegenerative diseases (NDs). Histone acetylation homeostasis, maintained by the antagonistic activity of histone acetyltransferases (HATs) and histone deacetylases (HDACs), is necessary for appropriate gene expression and neuronal function. Disruption of neural acetylation homeostasis has been implicated in multiple types of NDs including Alzheimer's disease (AD), yet mechanisms underlying alterations remain unclear. We show that like AD, disruption of Tip60 HAT/HDAC2 balance with concomitant epigenetic repression of common Tip60 target neuroplasticity genes occurs early in multiple types of Drosophila ND models such as Parkinson's Disease (PD), Huntington's Disease (HD) and Amyotrophic Lateral Sclerosis (ALS). Repressed neuroplasticity genes show reduced enrichment of Tip60 and epigentic acetylation signatures at all gene loci examined with certain genes showing inappropriate HDAC2 repressor enrichment. Functional neuronal consequences for these disease conditions are reminiscent of human pathology and include locomotion, synapse morphology, and short-term memory deficits. Increasing Tip60 HAT levels specifically in the mushroom body learning and memory center in the Drosophila brain protects against locomotion and short-term memory function deficits in multiple NDs. Together, our results support a model by which Tip60 protects against neurological impairments in different NDs via similar modes of action.

Imbalance of Lysine Acetylation Contributes to the Pathogenesis of Parkinson's Disease

Parkinson’s disease (PD) is one of the most common neurodegenerative disorders. The neuropathological features of PD are selective and progressive loss of dopaminergic neurons in the substantia nigra pars compacta, deficiencies in striatal dopamine levels, and the presence of intracellular Lewy bodies. Interactions among aging and genetic and environmental factors are considered to underlie the common etiology of PD, which involves multiple changes in cellular processes. Recent studies suggest that changes in lysine acetylation and deacetylation of many proteins, including histones and nonhistone proteins, might be tightly associated with PD pathogenesis. Here, we summarize the changes in lysine acetylation of both histones and nonhistone proteins, as well as the related lysine acetyltransferases (KATs) and lysine deacetylases (KDACs), in PD patients and various PD models. We discuss the potential roles and underlying mechanisms of these changes in PD and highlight that restoring the balance of lysine acetylation/deacetylation of histones and nonhistone proteins is critical for PD treatment. Finally, we discuss the advantages and disadvantages of different KAT/KDAC inhibitors or activators in the treatment of PD models and emphasize that SIRT1 and SIRT3 activators and SIRT2 inhibitors are the most promising effective therapeutics for PD.