CK2 alpha prime and alpha-synuclein pathogenic functional interaction mediates synaptic dysregulation in huntington's disease

Microcystin-LR Exposure Damages Neurons by Inducing α-Syn Aggregation via MAPK4/GATA2/SNCA and PP2A/GRKs Pathways

Microcystin-LR (MC-LR) is a natural neurotoxin with strong toxicity, and studies have demonstrated that chronic MC-LR exposure generated Parkinson-like dyskinesia in mice. Parkinson's disease (PD) is a neurologic degenerative disease mostly occurring in elderly people, and the progressive loss of dopaminergic neurons and the formation of Lewy bodies are the hallmark pathological features. The main component of Lewy bodies is α-synuclein (α-syn) encoded by the SNCA gene, and the copy number mutation of SNCA gene can promote the overexpression of α-syn. A mouse model of MC-LR exposure for 15 months was established to confirm the deposition of Lewy bodies. SH-SY5Y cells exposed to MC-LR were constructed as an in vitro model of PD, and the transcription factor that regulated the SNCA gene (the encoding gene of α-syn) was identified through the database. MC-LR enhanced the transcription level of SNCA gene and upregulated α-syn protein expression by promoting MAPK4 into the nucleus and binding to GATA2 295-480 fragment. In addition, MC-LR inhibited PP2A activity and activated GRKs kinase to promote α-syn phosphorylation at Ser129. These results suggest that MC-LR is involved in α-syn aggregate formation and PD pathogenesis by enhancing SNCA transcriptional activity to promote α-syn elevation via the MAPK4/GATA2 pathway and inducing α-syn phosphorylation via the PP2A/GRKs pathway.

Subunit specific altered expression and activity of casein kinase 2 in the brain tissues resected from mesial temporal lobe epilepsy with hippocampal sclerosis patients & rodent temporal lobe epilepsy model

INTRODUCTION

Mesial temporal lobe epilepsy (MTLE), is associated with dysregulated excitatory-inhibitory balance in the brain. Numerous enzymes, protein kinases, that are modulated through phosphorylation, have been linked with key processes involved in the pathogenesis of epilepsy. Therefore, in this study, we determined the subunit specific expression and activity of multi-subunit casein Kinase 2 (CK2) which influences NMDARs through phosphorylation events, in MTS patients as well as pilocarpine model of TLE.

METHODS

mRNA expression of CK2 (α, α', β) & NR2B was measured by real time PCR andprotein expression of CK2 (α, α', β), NR2B, and NR2B Ser1480 were evaluated using western blotting and immunohistochemistry in experimental models of TLE and MTS patients. CK2 α and α' activity was measured by kinase assay.

RESULTS

Significant increase in CK2α', CK2β, and NR2B mRNA expression were noted in chronic TLE rat model. Similarly, MTS patients displayed upregulated CK2α' and CK2β expressions, but NR2B mRNA remained unchanged. CK2α', CK2β, and NR2B Ser1480 protein expressions were higher in chronic TLE and MTS patients in relation to controls (p < 0.05), as was kinase activity (p < 0.05). In acute TLE rats, only NR2B protein expression was upregulated (p < 0.05).

CONCLUSION

Our research demonstrated for the first time the upregulation of CK2α' subunit and its increased kinase activityin resected brain samples from MTS patients as well as pilocarpine model of TLE. Altered expression and higher activity of CK2 α' highlights subunit specific contribution, suggesting the modulation of NMDA receptors by Casein Kinase 2 may contribute to hyperexcitability in MTLE.

Peripherally administered TNF inhibitor is not protective against α-synuclein-induced dopaminergic neuronal death in rats

The underlying cause of neuronal loss in Parkinson's disease (PD) remains unknown, but evidence implicates neuroinflammation in PD pathobiology. The pro-inflammatory cytokine soluble tumor necrosis factor (TNF) seems to play an important role and thus has been proposed as a therapeutic target for modulation of the neuroinflammatory processes in PD. In this regard, dominant-negative TNF (DN-TNF) agents are promising antagonists that selectively inhibit soluble TNF signaling, while preserving the beneficial effects of transmembrane TNF. Previous studies have tested the protective potential of DN-TNF-based therapy in toxin-based PD models. Here we test for the first time the protective potential of a DN-TNF therapeutic against α-synuclein-driven neurodegeneration in the viral vector-based PD female rat model. To do so, we administered the DN-TNF agent XPro1595 subcutaneously for a period of 12 weeks. In contrast to previous studies using different PD models, neuroprotection was not achieved by systemic XPro1595 treatment. α-Synuclein-induced loss of nigrostriatal neurons, accumulation of pathological inclusions and microgliosis was detected in both XPro1595- and saline-treated animals. XPro1595 treatment increased the percentage of the hypertrophic/ameboid Iba1+ cells in SN and reduced the striatal MHCII+ expression in the α-synuclein-overexpressing animals. However, the treatment did not prevent the MHCII upregulation seen in the SN of the model, nor the increase of CD68+ phagocytic cells. Therefore, despite an apparently immunomodulatory effect, this did not suffice to protect against viral vector-derived α-synuclein-induced neurotoxicity. Further studies are warranted to better elucidate the therapeutic potential of soluble TNF inhibitors in PD.

Absence of hippocampal pathology persists in the Q175DN mouse model of Huntington's disease despite elevated HTT aggregation

BackgroundHuntington's disease (HD) is a neurodegenerative disorder causing motor, cognitive, and psychiatric impairments, with the striatum being the most affected brain region. However, the role of other regions, such as the hippocampus, in HD remains less understood.ObjectiveHere, we study the comparative impact of enhanced mHTT aggregation and neuropathology in the striatum and hippocampus of two HD mouse models.MethodsWe utilized the zQ175 as a control HD mouse model and the Q175DN mice lacking the PGK-Neomycin cassette generated in house. We performed a comparative characterization of the neuropathology between zQ175 and Q175DN mice in the striatum and the hippocampus by assessing HTT aggregation, neuronal and glial pathology, chaperone expression, and synaptic density.ResultsWe showed that Q175DN mice presented enhanced mHTT aggregation in both striatum and hippocampus compared to zQ175. Striatal neurons showed a greater susceptibility to enhanced accumulation of mHTT in Q175DN. On the contrary, no signs of hippocampal pathology were found in zQ175 and absence of hippocampal pathology persisted in Q175DN mice despite higher levels of mHTT. In addition, Q175DN hippocampus presented increased synaptic density, decreased Iba1+ microglia density and enhanced HSF1 levels in specific subregions of the hippocampus compared to zQ175.ConclusionsQ175DN mice are a valuable tool to understand the fundamental susceptibility differences to mHTT toxicity between striatal neurons and other neuronal subtypes. Furthermore, our findings also suggest that cognitive deficits observed in HD animals might arise from either striatum dysfunction or other regions involved in cognitive processes but not from hippocampal degeneration.

Enhanced Hippocampal Spare Capacity in Q175DN Mice Despite Elevated mHTT Aggregation

Background

Huntington's disease (HD) is a neurodegenerative disease resulting in devastating motor, cognitive, and psychiatric deficits. The striatum is a brain region that controls movement and some forms of cognition and is most significantly impacted in HD. However, despite well-documented deficits in learning and memory in HD, knowledge of the potential implication of other brain regions such as the hippocampus remains limited.

Objective

Here, we study the comparative impact of enhanced mHTT aggregation and neuropathology in the striatum and hippocampus of two HD mouse models.

Methods

We utilized the zQ175 as a control HD mouse model and the Q175DN mice lacking the PGK-Neomycin cassette generated in house. We performed a comparative characterization of the neuropathology between zQ175 and Q175DN mice in the striatum and the hippocampus by assessing HTT aggregation, neuronal and glial pathology, chaperone expression, and synaptic density.

Results

We showed that Q175DN mice presented enhanced mHTT aggregation in both striatum and hippocampus compared to zQ175. Striatal neurons showed a greater susceptibility to enhanced accumulation of mHTT than hippocampal neurons in Q175DN despite high levels of mHTT in both regions. Contrary to the pathology seen in the striatum, Q175DN hippocampus presented enhanced spare capacity showing increased synaptic density, decreased Iba1+ microglia density and enhanced HSF1 levels in specific subregions of the hippocampus compared to zQ175.

Conclusions

Q175DN mice are a valuable tool to understand the fundamental susceptibility differences to mHTT toxicity between striatal neurons and other neuronal subtypes. Furthermore, our findings also suggest that cognitive deficits observed in HD animals might arise from either striatum dysfunction or other regions involved in cognitive processes but not from hippocampal degeneration.

Therapeutic approaches targeting aging and cellular senescence in Huntington's disease

Huntington's disease (HD) is a devastating neurodegenerative disease that is manifested by a gradual loss of physical, cognitive, and mental abilities. As the disease advances, age has a major impact on the pathogenic signature of mutant huntingtin (mHTT) protein aggregation. This review aims to explore the intricate relationship between aging, mHTT toxicity, and cellular senescence in HD. Scientific data on the interplay between aging, mHTT, and cellular senescence in HD were collected from several academic databases, including PubMed, Google Scholar, Google, and ScienceDirect. The search terms employed were "AGING," "HUNTINGTON'S DISEASE," "MUTANT HUNTINGTIN," and "CELLULAR SENESCENCE." Additionally, to gather information on the molecular mechanisms and potential therapeutic targets, the search was extended to include relevant terms such as "DNA DAMAGE," "OXIDATIVE STRESS," and "AUTOPHAGY." According to research, aging leads to worsening HD pathophysiology through some processes. As a result of the mHTT accumulation, cellular senescence is promoted, which causes DNA damage, oxidative stress, decreased autophagy, and increased inflammatory responses. Pro-inflammatory cytokines and other substances are released by senescent cells, which may worsen the neuronal damage and the course of the disease. It has been shown that treatments directed at these pathways reduce some of the HD symptoms and enhance longevity in experimental animals, pointing to a new possibility of treating the condition. Through their amplification of the harmful effects of mHTT, aging and cellular senescence play crucial roles in the development of HD. Comprehending these interplays creates novel opportunities for therapeutic measures targeted at alleviating cellular aging and enhancing HD patients' quality of life.

Discovery of a CK2α'-Biased ATP-Competitive Inhibitor from a High-Throughput Screen of an Allosteric-Inhibitor-Like Compound Library

Protein kinase CK2 is a holoenzyme composed of two regulatory subunits (CK2β) and two catalytic subunits (CK2α and CK2α'). CK2 controls several cellular processes, including proliferation, inflammation, and cell death. However, CK2α and CK2α' possess different expression patterns and substrates and therefore impact each of these processes differently. Elevated CK2α participates in the development of cancer, while increased CK2α' has been associated with neurodegeneration, especially Huntington's disease (HD). HD is a fatal disease for which no effective therapies are available. Genetic deletion of CK2α' in HD mouse models has ameliorated neurodegeneration. Therefore, pharmacological inhibition of CK2α' presents a promising therapeutic strategy for treating HD. However, current CK2 inhibitors are unable to discriminate between CK2α and CK2α' due to their high structural homology, especially in the targeted ATP-binding site. Using computational analyses, we found a potential type IV ("D" pocket) allosteric site that contained different residues between CK2α and CK2α' and was distal from the ATP-binding pocket featured in both kinases. We decided to look for allosteric modulators that might interact in a biased fashion with the type IV pocket on both CK2α and CK2α'. We screened a commercial library containing ∼29,000 allosteric-kinase-inhibitor-like compounds using a CK2α' activity-dependent ADP-Glo Kinase assay. Obtained hits were counter-screened against CK2α using the ADP-Glo Kinase assay, revealing two CK2α'-biased compounds. These two compounds might serve as the basis for further medicinal chemistry optimization for the potential treatment of HD.

α-Synuclein pathology from the body to the brain: so many seeds so close to the central soil

ABSTRACT

α-Synuclein is a protein that mainly exists in the presynaptic terminals. Abnormal folding and accumulation of α-synuclein are found in several neurodegenerative diseases, including Parkinson's disease. Aggregated and highly phosphorylated α-synuclein constitutes the main component of Lewy bodies in the brain, the pathological hallmark of Parkinson's disease. For decades, much attention has been focused on the accumulation of α-synuclein in the brain parenchyma rather than considering Parkinson's disease as a systemic disease. Recent evidence demonstrates that, at least in some patients, the initial α-synuclein pathology originates in the peripheral organs and spreads to the brain. Injection of α-synuclein preformed fibrils into the gastrointestinal tract triggers the gut-to-brain propagation of α-synuclein pathology. However, whether α-synuclein pathology can occur spontaneously in peripheral organs independent of exogenous α-synuclein preformed fibrils or pathological α-synuclein leakage from the central nervous system remains under investigation. In this review, we aimed to summarize the role of peripheral α-synuclein pathology in the pathogenesis of Parkinson's disease. We also discuss the pathways by which α-synuclein pathology spreads from the body to the brain.

Identification of CK2α' selective inhibitors by the screening of an allosteric-kinase-inhibitor-like compound library

Protein Kinase CK2 is a holoenzyme composed of two regulatory subunits (CK2β) and two catalytic subunits (CK2α and CK2α'). CK2 controls several cellular processes including proliferation, inflammation, and cell death. However, CK2α and CK2α' possess different expression patterns and substrates and therefore impact each of these processes differently. Elevated CK2α participates in the development of cancer, while increased CK2α' has been associated with neurodegeneration, especially Huntington's disease (HD). HD is a fatal disease for which no effective therapies are available. Genetic deletion of CK2α' in HD mouse models has ameliorated neurodegeneration. Therefore, pharmacological inhibition of CK2α' presents a promising therapeutic strategy for treating HD. However, current CK2 inhibitors are unable to discriminate between CK2α and CK2α' due to their high structural homology, especially in the targeted ATP binding site. Using computational analyses, we found a potential Type IV ("D" pocket) allosteric site on CK2α' that contained different residues than CK2α and was distal from the ATP binding pocket featured in both kinases. With this potential allosteric site in mind, we screened a commercial library containing ~29,000 allosteric-kinase-inhibitor-like compounds using a CK2α' activity-dependent ADP-Glo™ Kinase assay. Obtained hits were counter-screened against CK2α revealing two CK2α' selective compounds. These two compounds might serve as the basis for further medicinal chemistry optimization for the potential treatment of HD.

Casein Kinase 2 Affects Epilepsy by Regulating Ion Channels: A Potential Mechanism

Epilepsy, characterized by recurrent seizures and abnormal brain discharges, is the third most common chronic disorder of the Central Nervous System (CNS). Although significant progress has been made in the research on antiepileptic drugs (AEDs), approximately one-third of patients with epilepsy are refractory to these drugs. Thus, research on the pathogenesis of epilepsy is ongoing to find more effective treatments. Many pathological mechanisms are involved in epilepsy, including neuronal apoptosis, mossy fiber sprouting, neuroinflammation, and dysfunction of neuronal ion channels, leading to abnormal neuronal excitatory networks in the brain. CK2 (Casein kinase 2), which plays a critical role in modulating neuronal excitability and synaptic transmission, has been shown to be associated with epilepsy. However, there is limited research on the mechanisms involved. Recent studies have suggested that CK2 is involved in regulating the function of neuronal ion channels by directly phosphorylating them or their binding partners. Therefore, in this review, we will summarize recent research advances regarding the potential role of CK2 regulating ion channels in epilepsy, aiming to provide more evidence for future studies.

Protein Kinase CK2α', More than a Backup of CK2α

The serine/threonine protein kinase CK2 is implicated in the regulation of fundamental processes in eukaryotic cells. CK2 consists of two catalytic α or α' isoforms and two regulatory CK2β subunits. These three proteins exist in a free form, bound to other cellular proteins, as tetrameric holoenzymes composed of CK2α2/β2, CK2αα'/β2, or CK2α'2/β2 as well as in higher molecular forms of the tetramers. The catalytic domains of CK2α and CK2α' share a 90% identity. As CK2α contains a unique C-terminal sequence. Both proteins function as protein kinases. These properties raised the question of whether both isoforms are just backups of each other or whether they are regulated differently and may then function in an isoform-specific manner. The present review provides observations that the regulation of both CK2α isoforms is partly different concerning the subcellular localization, post-translational modifications, and aggregation. Up to now, there are only a few isoform-specific cellular binding partners. The expression of both CK2α isoforms seems to vary in different cell lines, in tissues, in the cell cycle, and with differentiation. There are different reports about the expression and the functions of the CK2α isoforms in tumor cells and tissues. In many cases, a cell-type-specific expression and function is known, which raises the question about cell-specific regulators of both isoforms. Another future challenge is the identification or design of CK2α'-specific inhibitors.

Striatal spatial heterogeneity, clustering, and white matter association of GFAP+ astrocytes in a mouse model of Huntington's disease

Introduction

Huntington's disease (HD) is a neurodegenerative disease that primarily affects the striatum, a brain region that controls movement and some forms of cognition. Neuronal dysfunction and loss in HD is accompanied by increased astrocyte density and astrocyte pathology. Astrocytes are a heterogeneous population classified into multiple subtypes depending on the expression of different gene markers. Studying whether mutant Huntingtin (HTT) alters specific subtypes of astrocytes is necessary to understand their relative contribution to HD.

Methods

Here, we studied whether astrocytes expressing two different markers; glial fibrillary acidic protein (GFAP), associated with astrocyte activation, and S100 calcium-binding protein B (S100B), a marker of matured astrocytes and inflammation, were differentially altered in HD.

Results

First, we found three distinct populations in the striatum of WT and symptomatic zQ175 mice: GFAP+, S100B+, and dual GFAP+S100B+. The number of GFAP+ and S100B+ astrocytes throughout the striatum was increased in HD mice compared to WT, coinciding with an increase in HTT aggregation. Overlap between GFAP and S100B staining was expected, but dual GFAP+S100B+ astrocytes only accounted for less than 10% of all tested astrocytes and the number of GFAP+S100B+ astrocytes did not differ between WT and HD, suggesting that GFAP+ astrocytes and S100B+ astrocytes are distinct types of astrocytes. Interestingly, a spatial characterization of these astrocyte subtypes in HD mice showed that while S100B+ were homogeneously distributed throughout the striatum, GFAP+ preferentially accumulated in "patches" in the dorsomedial (dm) striatum, a region associated with goal-directed behaviors. In addition, GFAP+ astrocytes in the dm striatum of zQ175 mice showed increased clustering and association with white matter fascicles and were preferentially located in areas with low HTT aggregate load.

Discussion

In summary, we showed that GFAP+ and S100B+ astrocyte subtypes are distinctly affected in HD and exist in distinct spatial arrangements that may offer new insights to the function of these specific astrocytes subtypes and their potential implications in HD pathology.

Tumor suppressor p53 regulates heat shock factor 1 protein degradation in Huntington's disease

p53 and HSF1 are two major transcription factors involved in cell proliferation and apoptosis, whose dysregulation contributes to cancer and neurodegeneration. Contrary to most cancers, p53 is increased in Huntington's disease (HD) and other neurodegenerative diseases, while HSF1 is decreased. p53 and HSF1 reciprocal regulation has been shown in different contexts, but their connection in neurodegeneration remains understudied. Using cellular and animal models of HD, we show that mutant HTT stabilized p53 by abrogating the interaction between p53 and E3 ligase MDM2. Stabilized p53 promotes protein kinase CK2 alpha prime and E3 ligase FBXW7 transcription, both of which are responsible for HSF1 degradation. Consequently, p53 deletion in striatal neurons of zQ175 HD mice restores HSF1 abundance and decrease HTT aggregation and striatal pathology. Our work shows the mechanism connecting p53 stabilization with HSF1 degradation and pathophysiology in HD and sheds light on the broader molecular differences and commonalities between cancer and neurodegeneration.

Neurochemical correlates of synapse density in a Huntington's disease mouse model

Striatal medium spiny neurons are highly susceptible in Huntington's disease (HD), resulting in progressive synaptic perturbations that lead to neuronal dysfunction and death. Non-invasive imaging techniques, such as proton magnetic resonance spectroscopy (1 H-MRS), are used in HD mouse models and patients with HD to monitor neurochemical changes associated with neuronal health. However, the association between brain neurochemical alterations and synaptic dysregulation remains unknown, limiting our ability to monitor potential treatments that may affect synapse function. We conducted in vivo longitudinal 1 H-MRS in the striatum followed by ex vivo analyses of excitatory synapse density of two synaptic circuits disrupted in HD, thalamo-striatal (T-S), and cortico-striatal (C-S) pathways, to assess the relationship between neurochemical alterations and changes in synapse density. We used the zQ175(Tg/0) HD mouse model as well as zQ175 mice lacking one allele of CK2α'(zQ175(Tg/0) :CK2α'(+/-) ), a kinase previously shown to regulate synapse function in HD. Longitudinal analyses of excitatory synapse density showed early and sustained reduction in T-S synapses in zQ175 mice, preceding C-S synapse depletion, which was rescued in zQ175:CK2α'(+/-) . Changes in T-S and C-S synapses were accompanied by progressive alterations in numerous neurochemicals between WT and HD mice. Linear regression analyses showed C-S synapse number positively correlated with 1 H-MRS-measured levels of GABA, while T-S synapse number positively correlated with levels of phosphoethanolamine and negatively correlated with total creatine levels. These associations suggest that these neurochemical concentrations measured by 1 H-MRS may facilitate monitoring circuit-specific synaptic dysfunction in the zQ175 mouse model and in other HD pre-clinical studies.

The Emerging Landscape of Natural Small-molecule Therapeutics for Huntington's Disease

Huntington's disease (HD) is a rare and fatal neurodegenerative disorder with no diseasemodifying therapeutics. HD is characterized by extensive neuronal loss and is caused by the inherited expansion of the huntingtin (HTT) gene that encodes a toxic mutant HTT (mHTT) protein having expanded polyglutamine (polyQ) residues. Current HD therapeutics only offer symptomatic relief. In fact, Food and Drug Administration (FDA) approved two synthetic small-molecule VMAT2 inhibitors, tetrabenazine (1) and deutetrabenazine (2), for managing HD chorea and various other diseases in clinical trials. Therefore, the landscape of drug discovery programs for HD is evolving to discover disease- modifying HD therapeutics. Likewise, numerous natural products are being evaluated at different stages of clinical development and have shown the potential to ameliorate HD pathology. The inherent anti-inflammatory and antioxidant properties of natural products mitigate the mHTT-induced oxidative stress and neuroinflammation, improve mitochondrial functions, and augment the anti-apoptotic and pro-autophagic mechanisms for increased survival of neurons in HD. In this review, we have discussed HD pathogenesis and summarized the anti-HD clinical and pre-clinical natural products, focusing on their therapeutic effects and neuroprotective mechanism/s.

Protein Kinase CK2 and Its Potential Role as a Therapeutic Target in Huntington's Disease

Huntington's Disease (HD) is a devastating neurodegenerative disorder caused by a CAG trinucleotide repeat expansion in the HTT gene, for which no disease modifying therapies are currently available. Much of the recent research has focused on developing therapies to directly lower HTT expression, and while promising, these therapies have presented several challenges regarding administration and efficacy. Another promising therapeutic approach is the modulation of HTT post-translational modifications (PTMs) that are dysregulated in disease and have shown to play a key role in HTT toxicity. Among all PTMs, modulation of HTT phosphorylation has been proposed as an attractive therapeutic option due to the possibility of orally administering specific kinase effectors. One of the kinases described to participate in HTT phosphorylation is Protein Kinase CK2. CK2 has recently emerged as a target for the treatment of several neurological and psychiatric disorders, although its role in HD remains controversial. While pharmacological studies in vitro inhibiting CK2 resulted in reduced HTT phosphorylation and increased toxicity, genetic approaches in mouse models of HD have provided beneficial effects. In this review we discuss potential therapeutic approaches related to the manipulation of HTT-PTMs with special emphasis on the role of CK2 as a therapeutic target in HD.