Role of the CCAAT-binding protein NFY in SCA17 pathogenesis

The role(s) of NF-Y in development and differentiation

NF-Y is a conserved sequence-specific trimeric Transcription Factor -TF- binding to the CCAAT element. We review here the role(s) in development, from pre-implantation embryo to terminally differentiated tissues, by rationalizing and commenting on genetic, genomic, epigenetic and biochemical studies. This effort brings to light the impact of NF-YA isoforms on stemness and differentiation, as well as binding to distal vs promoter proximal sites and connections with selected TFs.

Association of CaMK2A and MeCP2 signaling pathways with cognitive ability in adolescents

The glutamatergic signaling pathway is involved in molecular learning and human cognitive ability. Specific single variants (SNVs, formerly single-nucleotide polymorphisms) in the genes encoding N-methyl-d-aspartate receptor subunits have been associated with neuropsychiatric disorders by altering glutamate transmission. However, these variants associated with cognition and mental activity have rarely been explored in healthy adolescents. In this study, we screened for SNVs in the glutamatergic signaling pathway to identify genetic variants associated with cognitive ability. We found that SNVs in the subunits of ionotropic glutamate receptors, including GRIA1, GRIN1, GRIN2B, GRIN2C, GRIN3A, GRIN3B, and calcium/calmodulin-dependent protein kinase IIα (CaMK2A) are associated with cognitive function. Plasma CaMK2A level was correlated positively with the cognitive ability of Taiwanese senior high school students. We demonstrated that elevating CaMK2A increased its autophosphorylation at T286 and increased the expression of its downstream targets, including GluA1 and phosphor- GluA1 in vivo. Additionally, methyl-CpG binding protein 2 (MeCP2), a downstream target of CaMK2A, was found to activate the expression of CaMK2A, suggesting that MeCP2 and CaMK2A can form a positive feedback loop. In summary, two members of the glutamatergic signaling pathway, CaMK2A and MeCP2, are implicated in the cognitive ability of adolescents; thus, altering the expression of CaMK2A may affect cognitive ability in youth.

Therapeutic roles of natural remedies in combating hereditary ataxia: A systematic review

Background

Hereditary ataxia (HA) represents a group of genetically heterogeneous neurodegenerative diseases caused by dysfunction of the cerebellum or disruption of the connection between the cerebellum and other areas of the central nervous system. Phenotypic manifestation of HA includes unsteadiness of stance and gait, dysarthria, nystagmus, dysmetria and complaints of clumsiness. There are no specific treatments for HA. Management strategies provide supportive treatment to reduce symptoms.

Objectives

This systematic review aimed to identify, evaluate and summarise the published literature on the therapeutic roles of natural remedies in the treatment of HA to provide evidence for clinical practice.

Methods

A systematic literature search was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Web of Science, PubMed and Science Direct Scopus were thoroughly searched for relevant published articles from June 2007 to July 2020.

Results

Ten pre-clinical and two clinical studies were eligible for inclusion in this systematic review. We identified the therapeutic roles of medicinal plants Brassica napus, Gardenia jasminoides, Gastrodia elata, Ginkgo biloba, Glycyrrhiza inflata, Paeonia lactiflora, Pueraria lobata and Rehmannia glutinosa; herbal formulations Shaoyao Gancao Tang and Zhengan Xifeng Tang; and medicinal mushroom Hericium erinaceus in the treatment of HA. In this review, we evaluated the mode of actions contributing to their therapeutic effects, including activation of the ubiquitin–proteasome system, activation of antioxidant pathways, maintenance of intracellular calcium homeostasis and regulation of chaperones. We also briefly highlighted the integral cellular signalling pathways responsible for orchestrating the mode of actions.

Conclusion

We reviewed the therapeutic roles of natural remedies in improving or halting the progression of HA, which warrant further study for applications into clinical practice.

Gene Deregulation and Underlying Mechanisms in Spinocerebellar Ataxias With Polyglutamine Expansion

Polyglutamine spinocerebellar ataxias (polyQ SCAs) include SCA1, SCA2, SCA3, SCA6, SCA7, and SCA17 and constitute a group of adult onset neurodegenerative disorders caused by the expansion of a CAG repeat sequence located within the coding region of specific genes, which translates into polyglutamine tract in the corresponding proteins. PolyQ SCAs are characterized by degeneration of the cerebellum and its associated structures and lead to progressive ataxia and other diverse symptoms. In recent years, gene and epigenetic deregulations have been shown to play a critical role in the pathogenesis of polyQ SCAs. Here, we provide an overview of the functions of wild type and pathogenic polyQ SCA proteins in gene regulation, describe the extent and nature of gene expression changes and their pathological consequences in diseases, and discuss potential avenues to further investigate converging and distinct disease pathways and to develop therapeutic strategies.

Shaoyao Gancao Tang (SG-Tang), a formulated Chinese medicine, reduces aggregation and exerts neuroprotection in spinocerebellar ataxia type 17 (SCA17) cell and mouse models

Spinocerebellar ataxia (SCA) type 17 is an autosomal dominant ataxia caused by expanded polyglutamine (polyQ) tract in the TATA-box binding protein (TBP). Substantial studies have shown involvement of compromised mitochondria biogenesis regulator peroxisome proliferator-activated receptor gamma-coactivator 1 alpha (PGC-1α), nuclear factor erythroid 2-related factor 2 (NRF2), nuclear factor-Y subunit A (NFYA), and their downstream target genes in the pathogenesis of polyQ-expansion diseases. The extracts of Paeonia lactiflora (P. lactiflora) and Glycyrrhiza uralensis (G. uralensis) have long been used as a Chinese herbal medicine (CHM). Shaoyao Gancao Tang (SG-Tang) is a formulated CHM made of P. lactiflora and G. uralensis at a 1:1 ratio. In the present study, we demonstrated the aggregate-inhibitory and anti-oxidative effect of SG-Tang in 293 TBP/Q₇₉ cells. We then showed that SG-Tang reduced the aggregates and ameliorated the neurite outgrowth deficits in TBP/Q₇₉ SH-SY5Y cells. SG-Tang upregulated expression levels of NFYA, PGC-1α, NRF2, and their downstream target genes in TBP/Q₇₉ SH-SY5Y cells. Knock down of NFYA, PGC-1α, and NRF2 attenuated the neurite outgrowth promoting effect of SG-Tang on TBP/Q₇₉ SH-SY5Y cells. Furthermore, SG-Tang inhibited aggregation and rescued motor-deficits in SCA17 mouse model. The study results suggest the potential of SG-Tang in treating SCA17 and probable other polyQ diseases.

Targeting Hsp70 facilitated protein quality control for treatment of polyglutamine diseases

The polyglutamine (polyQ) diseases are a group of nine fatal, adult-onset neurodegenerative disorders characterized by the misfolding and aggregation of mutant proteins containing toxic expansions of CAG/polyQ tracts. The heat shock protein 90 and 70 (Hsp90/Hsp70) chaperone machinery is a key component of cellular protein quality control, playing a role in the regulation of folding, aggregation, and degradation of polyQ proteins. The ability of Hsp70 to facilitate disaggregation and degradation of misfolded proteins makes it an attractive therapeutic target in polyQ diseases. Genetic studies have demonstrated that manipulation of Hsp70 and related co-chaperones can enhance the disaggregation and/or degradation of misfolded proteins in models of polyQ disease. Therefore, the development of small molecules that enhance Hsp70 activity is of great interest. However, it is still unclear if currently available Hsp70 modulators can selectively enhance disaggregation or degradation of misfolded proteins without perturbing other Hsp70 functions essential for cellular homeostasis. This review discusses the multifaceted role of Hsp70 in protein quality control and the opportunities and challenges Hsp70 poses as a potential therapeutic target in polyQ disease.

Natural and pathogenic protein sequence variation affecting prion-like domains within and across human proteomes

BACKGROUND

Impaired proteostatic regulation of proteins with prion-like domains (PrLDs) is associated with a variety of human diseases including neurodegenerative disorders, myopathies, and certain forms of cancer. For many of these disorders, current models suggest a prion-like molecular mechanism of disease, whereby proteins aggregate and spread to neighboring cells in an infectious manner. The development of prion prediction algorithms has facilitated the large-scale identification of PrLDs among "reference" proteomes for various organisms. However, the degree to which intraspecies protein sequence diversity influences predicted prion propensity has not been systematically examined.

RESULTS

Here, we explore protein sequence variation introduced at genetic, post-transcriptional, and post-translational levels, and its influence on predicted aggregation propensity for human PrLDs. We find that sequence variation is relatively common among PrLDs and in some cases can result in relatively large differences in predicted prion propensity. Sequence variation introduced at the post-transcriptional level (via alternative splicing) also commonly affects predicted aggregation propensity, often by direct inclusion or exclusion of a PrLD. Finally, analysis of a database of sequence variants associated with human disease reveals a number of mutations within PrLDs that are predicted to increase prion propensity.

CONCLUSIONS

Our analyses expand the list of candidate human PrLDs, quantitatively estimate the effects of sequence variation on the aggregation propensity of PrLDs, and suggest the involvement of prion-like mechanisms in additional human diseases.

Multiple epigenetic biomarkers for evaluation of students' academic performance

Several reports have shown that methyl CpG-binding protein 2 (MeCP2), brain-derived neurotrophic factor (BDNF), phospho-cAMP response element-binding protein (p-CREB) and microRNAs may be important in regulating academic performance because of their roles in neuropsychiatry and cognitive diseases. The first goal of this study was to explore the associations among MeCP2, BDNF, CREB and academic performance. This study also examined the pathway responsible for the effects of MeCP2, BDNF, p-CREB and microRNAs on academic performance. Scores from the basic competency test, an annual national competitive entrance examination, were used to evaluate academic performance. Subjects' plasma RNA was extracted and analyzed. This study determined that participants in the higher academic performance group had a significant difference in MECP2 mRNA expression compared with the lower academic performance group. We then used neuronal human derived neuroblastoma cell line (SH-SY5Y) cells with inducible MeCP2 expression from a second copy of the gene as a gain-of-function model and found that MeCP2 overexpression positively affected p-CREB and BDNF expression initially. After negative feedback, the p-CREB and BDNF levels subsequently decreased. In the neuronal phenotype examination, we found a significant reduction in total outgrowth and branches in MeCP2-induced cells compared with noninduced cells. This work describes pathways that may be responsible for the effects of MeCP2, BDNF, p-CREB and microRNAs on academic performance. These results may shed light on the development of promising clinical treatment strategies in the area of neuropsychological adjustment.

The indole compound NC009-1 inhibits aggregation and promotes neurite outgrowth through enhancement of HSPB1 in SCA17 cells and ameliorates the behavioral deficits in SCA17 mice

Spinocerebellar ataxia type 17 (SCA17) is caused by the expansion of translated CAG repeat in the TATA box binding protein (TBP) gene encoding a long polyglutamine (polyQ) tract in the TBP protein, which leads to intracellular accumulation of aggregated TBP and cell death. The molecular chaperones act in preventing protein aggregation to ameliorate downstream harmful events. In this study, we used Tet-On cells with inducible SCA17 TBP/Q₇₉-GFP expression to test five in-house NC009 indole compounds for neuroprotection. We found that both aggregation and polyQ-induced reactive oxygen species can be significantly prohibited by the tested NC009 compounds in Tet-On TBP/Q₇₉ 293 cells. Among the five indole compounds, NC009-1 up-regulated expression of heat shock protein family B (small) member 1 (HSPB1) chaperone to reduce polyQ aggregation and promote neurite outgrowth in neuronal differentiated TBP/Q₇₉ SH-SY5Y cells. The increased HSPB1 thus ameliorated the increased BH3 interacting domain death agonist (BID), cytochrome c (CYCS) release, and caspase 3 (CASP3) activation which result in apoptosis. Knock down of HSPB1 attenuated the effects of NC009-1 on TBP/Q₇₉ SH-SY5Y cells, suggesting that HSPB1 might be one of the major pathways involved for NC009-1 effects. NC009-1 further reduced polyQ aggregation in Purkinje cells and ameliorated behavioral deficits in SCA17 TBP/Q₁₀₉ transgenic mice. Our results suggest that NC009-1 has a neuroprotective effect on SCA17 cell and mouse models to support its therapeutic potential in SCA17 treatment.

The dynamics of early-state transcriptional changes and aggregate formation in a Huntington's disease cell model

Background

Huntington’s disease (HD) is a fatal neurodegenerative disorder caused by a CAG expansion in the Huntingtin (HTT) gene. Proteolytic cleavage of mutant huntingtin (Htt) protein with an expanded polyglutamine (polyQ) stretch results in production of Htt fragments that aggregate and induce impaired ubiquitin proteasome, mitochondrial functioning and transcriptional dysregulation. To understand the time-resolved relationship between aggregate formation and transcriptional changes at early disease stages, we performed temporal transcriptome profiling and quantification of aggregate formation in living cells in an inducible HD cell model.

Results

Rat pheochromocytoma (PC12) cells containing a stably integrated, doxycycline-inducible, eGFP-tagged N-terminal human Htt fragment with an expanded polyQ domain were used to analyse gene expression changes at different stages of mutant Htt aggregation. At earliest time points after doxycycline induction no detectable aggregates and few changes in gene expression were observed. Aggregates started to appear at intermediate time points. Aggregate formation and subsequent enlargement of aggregates coincided with a rapid increase in the number of differentially expressed (DE) genes. The increase in number of large aggregates coincided with a decrease in the number of smaller aggregates whereas the transcription profile reverted towards the profile observed before mutant Htt induction. Cluster-based analysis of the 2,176 differentially expressed genes revealed fourteen distinct clusters responding differently over time. Functional enrichment analysis of the two major gene clusters revealed that genes in the up-regulated cluster were mainly involved in metabolic (antioxidant activity and cellular ketone metabolic processes) and genes in the down-regulated cluster in developmental processes, respectively. Promoter-based analysis of the identified gene clusters resulted in identification of a transcription factor network of which several previously have been linked to HD.

Conclusions

We demonstrate a time-resolved relationship between Htt aggregation and changes in the transcriptional profile. We identified two major gene clusters showing involvement of (i) mitochondrial dysfunction and (ii) developmental processes implying cellular homeostasis defects. We identified novel and known HD-linked transcription factors and show their interaction with known and predicted regulatory proteins. Our data provide a novel resource for hypothesis building on the role of transcriptional key regulators in early stages of HD and possibly other polyQ-dependent diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3745-z) contains supplementary material, which is available to authorized users.

Inferring condition-specific targets of human TF-TF complexes using ChIP-seq data

Background

Transcription factors (TFs) often interact with one another to form TF complexes that bind DNA and regulate gene expression. Many databases are created to describe known TF complexes identified by either mammalian two-hybrid experiments or data mining. Lately, a wealth of ChIP-seq data on human TFs under different experiment conditions are available, making it possible to investigate condition-specific (cell type and/or physiologic state) TF complexes and their target genes.

Results

Here, we developed a systematic pipeline to infer Condition-Specific Targets of human TF-TF complexes (called the CST pipeline) by integrating ChIP-seq data and TF motifs. In total, we predicted 2,392 TF complexes and 13,504 high-confidence or 127,994 low-confidence regulatory interactions amongst TF complexes and their target genes. We validated our predictions by (i) comparing predicted TF complexes to external TF complex databases, (ii) validating selected target genes of TF complexes using ChIP-qPCR and RT-PCR experiments, and (iii) analysing target genes of select TF complexes using gene ontology enrichment to demonstrate the accuracy of our work. Finally, the predicted results above were integrated and employed to construct a CST database.

Conclusions

We built up a methodology to construct the CST database, which contributes to the analysis of transcriptional regulation and the identification of novel TF-TF complex formation in a certain condition. This database also allows users to visualize condition-specific TF regulatory networks through a user-friendly web interface.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3450-3) contains supplementary material, which is available to authorized users.

NF-Y (CBF) regulation in specific cell types and mouse models

The CCAAT-binding factor CBF/NF-Y is needed for cell proliferation and early embryonic development. NF-Y can regulate the expression of different cell type-specific genes that are activated by various physiological signaling pathways. Dysregulation of NF-Y was observed in pathogenic conditions in humans such as scleroderma, neurodegenerative disease, and cancer. Conditional inactivation of the NF-YA gene in mice demonstrated that NF-Y activity is essential for normal tissue homeostasis, survival, and metabolic function. Altogether, NF-Y is an essential transcription factor that plays a critical role in mammalian development, from the early stages to adulthood, and in human pathogenesis. This article is part of a Special Issue entitled: Nuclear Factor Y in Development and Disease, edited by Prof. Roberto Mantovani.

Differential roles of NF-Y transcription factor in ER chaperone expression and neuronal maintenance in the CNS

The mammalian central nervous system (CNS) contains various types of neurons with different neuronal functions. In contrast to established roles of cell type-specific transcription factors on neuronal specification and maintenance, whether ubiquitous transcription factors have conserved or differential neuronal function remains uncertain. Here, we revealed that inactivation of a ubiquitous factor NF-Y in different sets of neurons resulted in cell type-specific neuropathologies and gene downregulation in mouse CNS. In striatal and cerebellar neurons, NF-Y inactivation led to ubiquitin/p62 pathologies with downregulation of an endoplasmic reticulum (ER) chaperone Grp94, as we previously observed by NF-Y deletion in cortical neurons. In contrast, NF-Y inactivation in motor neurons induced neuronal loss without obvious protein deposition. Detailed analysis clarified downregulation of another ER chaperone Grp78 in addition to Grp94 in motor neurons, and knockdown of both ER chaperones in motor neurons recapitulated the pathology observed after NF-Y inactivation. Finally, additional downregulation of Grp78 in striatal neurons suppressed ubiquitin accumulation induced by NF-Y inactivation, implying that selective ER chaperone downregulation mediates different neuropathologies. Our data suggest distinct roles of NF-Y in protein homeostasis and neuronal maintenance in the CNS by differential regulation of ER chaperone expression.

Molecular mechanisms underlying Spinocerebellar Ataxia 17 (SCA17) pathogenesis

Spinocerebellar ataxia 17 (SCA17) belongs to the family of 9 genetically inherited, late-onset neurodegenerative diseases, which are caused by polyglutamine (polyQ) expansion in different proteins. In SCA17, the polyQ expansion occurs in the TATA box binding protein (TBP), which functions as a general transcription factor. Patients with SCA17 suffer from a broad array of motor and non-motor defects, and their life expectancy is normally within 20 y after the initial appearance of symptoms. Currently there is no effective treatment, but remarkable efforts have been devoted to tackle this devastating disorder. In this review, we will summarize our current knowledge about the molecular mechanisms underlying the pathogenesis of SCA17, with a primary focus on transcriptional dysregulations. We believe that impaired transcriptional activities caused by mutant TBP with polyQ expansion is a major form of toxicity contributing to SCA17 pathogenesis, and rectifying the altered level of downstream transcripts represents a promising therapeutic approach for the treatment of SCA17.

Targeting the prodromal stage of spinocerebellar ataxia type 17 mice: G-CSF in the prevention of motor deficits via upregulating chaperone and autophagy levels

Spinocerebellar ataxia type 17 (SCA17), an autosomal dominant cerebellar ataxia, is a devastating, incurable disease caused by the polyglutamine (polyQ) expansion of transcription factor TATA binding protein (TBP). The polyQ expansion causes misfolding and aggregation of the mutant TBP, further leading to cytotoxicity and cell death. The well-recognized prodromal phase in many forms of neurodegeneration suggests a prolonged period of partial neuronal dysfunction prior to cell loss that may be amenable to therapeutic intervention. The objective of this study was to assess the effects and molecular mechanisms of granulocyte-colony stimulating factor (G-CSF) therapy during the pre-symptomatic stage in SCA17 mice. Treatment with G-CSF at the pre-symptomatic stage improved the motor coordination of SCA17 mice and reduced the cell loss, insoluble mutant TBP protein, and vacuole formation in the Purkinje neurons of these mice. The neuroprotective effects of G-CSF may be produced by increases in Hsp70, Beclin-1, LC3-II and the p-ERK survival pathway. Upregulation of chaperone and autophagy levels further enhances the clearance of mutant protein aggregation, slowing the progression of pathology in SCA17 mice. Therefore, we showed that the early intervention of G-CSF has a neuroprotective effect, delaying the progression of SCA17 in mutant mice via increases in the levels of chaperone expression and autophagy.

Role of high mobility group box 1 (HMGB1) in SCA17 pathogenesis

Spinocerebellar ataxia type 17 (SCA17) involves the expression of a polyglutamine (polyQ) expanded TATA-binding protein (TBP), a general transcription initiation factor. TBP interacts with other protein factors, including high mobility group box 1 (HMGB1), to regulate gene expression. Previously, our proteomic analysis of soluble proteins prepared from mutant TBP (TBP/Q₆₁) expressing cells revealed a reduced concentration of HMGB1. Here, we show that HMGB1 can be incorporated into mutant TBP aggregates, which leads to reduced soluble HMGB1 levels in TBP/Q_61∼79 expressing cells. HMGB1 overexpression reduced mutant TBP aggregation. HMGB1 cDNA and siRNA co-transfection, as well as an HSPA5 immunoblot and luciferase reporter assay demonstrated the important role of HMGB1 in the regulation of HSPA5 transcription. In starvation-stressed TBP/Q₃₆ and TBP/Q₇₉ cells, increased reactive oxygen species generation accelerated the cytoplasmic translocation of HMGB1, which accompanied autophagy activation. However, TBP/Q₇₉ cells displayed a decrease in autophagy activation as a result of the reduction in the cytoplasmic HMGB1 level. In neuronal SH-SY5Y cells with induced TBP/Q_61∼79 expression, HMGB1 expression was reduced and accompanied by a significant reduction in the total outgrowth and branches in the TBP/Q_61∼79 expressing cells compared with the non-induced cells. The decreased soluble HMGB1 and impaired starvation-induced autophagy in cells suggest that HMGB1 may be a critical modulator of polyQ disease pathology and may represent a target for drug development.

The promise and perils of HDAC inhibitors in neurodegeneration

Histone deacetylases (HDACs) represent emerging therapeutic targets in the context of neurodegeneration. Indeed, pharmacologic inhibition of HDACs activity in the nervous system has shown beneficial effects in several preclinical models of neurological disorders. However, the translation of such therapeutic approach to clinics has been only marginally successful, mainly due to our still limited knowledge about HDACs physiological role particularly in neurons. Here, we review the potential benefits along with the risks of targeting HDACs in light of what we currently know about HDAC activity in the brain.

Indole and synthetic derivative activate chaperone expression to reduce polyQ aggregation in SCA17 neuronal cell and slice culture models

In spinocerebellar ataxia type 17 (SCA17), the expansion of a translated CAG repeat in the TATA box binding protein (TBP) gene results in a long polyglutamine (polyQ) tract in the TBP protein, leading to intracellular accumulation of aggregated TBP and cell death. The molecular chaperones act in preventing protein aggregation to ameliorate downstream harmful events. In this study, we used Tet-On SH-SY5Y cells with inducible SCA17 TBP/Q₇₉-green fluorescent protein (GFP) expression to test indole and synthetic derivative NC001-8 for neuroprotection. We found that indole and NC001-8 up-regulated chaperone expression to reduce polyQ aggregation in neuronal differentiated TBP/Q₇₉ cells. The effects on promoting neurite outgrowth and on reduction of aggregation on Purkinje cells were also confirmed with cerebellar primary and slice cultures of SCA17 transgenic mice. Our results demonstrate how indole and derivative NC001-8 reduce polyQ aggregation to support their therapeutic potentials in SCA17 treatment.

Deactivation of TBP contributes to SCA17 pathogenesis

Spinocerebellar ataxia type 17 (SCA17) is an autosomal dominant cerebellar ataxia caused by the expansion of polyglutamine (polyQ) within the TATA box-binding protein (TBP). Previous studies have shown that polyQ-expanded TBP forms neurotoxic aggregates and alters downstream genes. However, how expanded polyQ tracts affect the function of TBP and the link between dysfunctional TBP and SCA17 is not clearly understood. In this study, we generated novel Drosophila models for SCA17 that recapitulate pathological features such as aggregate formation, mobility defects and premature death. In addition to forming neurotoxic aggregates, we determined that polyQ-expanded TBP reduces its own intrinsic DNA-binding and transcription abilities. Dysfunctional TBP also disrupts normal TBP function. Furthermore, heterozygous dTbp amorph mutant flies exhibited SCA17-like phenotypes and flies expressing polyQ-expanded TBP exhibited enhanced retinal degeneration, suggesting that loss of TBP function may contribute to SCA17 pathogenesis. We further determined that the downregulation of TBP activity enhances retinal degeneration in SCA3 and Huntington's disease fly models, indicating that the deactivation of TBP is likely to play a common role in polyQ-induced neurodegeneration.

FBXO7 Y52C polymorphism as a potential protective factor in Parkinson's disease

Mutations in the F-box only protein 7 gene (FBXO7), the substrate-specifying subunit of SCF E3 ubiquitin ligase complex, cause Parkinson's disease (PD)-15 (PARK15). To identify new variants, we sequenced FBXO7 cDNA in 80 Taiwanese early onset PD patients (age at onset ≤50) and only two known variants, Y52C (c.155A>G) and M115I (c.345G>A), were found. To assess the association of Y52C and M115I with the risk of PD, we conducted a case–control study in a cohort of PD and ethnically matched controls. There was a nominal difference in the Y52C G allele frequency between PD and controls (p = 0.045). After combining data from China [1], significant difference in the Y52C G allele frequency between PD and controls (p = 0.012) and significant association of G allele with decreased PD risk (p = 0.017) can be demonstrated. Upon expressing EGFP-tagged Cys52 FBXO7 in cells, a significantly reduced rate of FBXO7 protein decay was observed when compared with cells expressing Tyr52 FBXO7. In silico modeling of Cys52 exhibited a more stable feature than Tyr52. In cells expressing Cys52 FBXO7, the level of TNF receptor-associated factor 2 (TRAF2) was significantly reduced. Moreover, Cys52 FBXO7 showed stronger interaction with TRAF2 and promoted TRAF2 ubiquitination, which may be responsible for the reduced TRAF2 expression in Cys52 cells. After induced differentiation, SH-SY5Y cells expressing Cys52 FBXO7 displayed increased neuronal outgrowth. We therefore hypothesize that Cys52 variant of FBXO7 may contribute to reduced PD susceptibility in Chinese.

NF-Y inactivation causes atypical neurodegeneration characterized by ubiquitin and p62 accumulation and endoplasmic reticulum disorganization

Nuclear transcription factor-Y (NF-Y), a key regulator of cell-cycle progression, often loses its activity during differentiation into nonproliferative cells. In contrast, NF-Y is still active in mature, differentiated neurons, although its neuronal significance remains obscure. Here we show that conditional deletion of the subunit NF-YA in postmitotic mouse neurons induces progressive neurodegeneration with distinctive ubiquitin/p62 pathology; these proteins are not incorporated into filamentous inclusion but co-accumulated with insoluble membrane proteins broadly on endoplasmic reticulum (ER). The degeneration also accompanies drastic ER disorganization, that is, an aberrant increase in ribosome-free ER in the perinuclear region, without inducing ER stress response. We further perform chromatin immunoprecipitation and identify several NF-Y physiological targets including Grp94 potentially involved in ER disorganization. We propose that NF-Y is involved in a unique regulation mechanism of ER organization in mature neurons and its disruption causes previously undescribed novel neuropathology accompanying abnormal ubiquitin/p62 accumulation.

Paeoniflorin eliminates a mutant AR via NF-YA-dependent proteolysis in spinal and bulbar muscular atrophy

The accumulation of abnormal proteins is a common characteristic of neurodegenerative diseases. This accumulation reflects a severe disturbance of cellular homeostasis in pathogenic protein clearance. Here, we demonstrated that the activation of the two major proteolytic machineries, the molecular chaperone-ubiquitin proteasome system (UPS) and the autophagy system, were simultaneously enhanced by paeoniflorin (PF), a major component of Paeonia plants, and exerted therapeutic effects in models of spinal and bulbar muscular atrophy (SBMA). PF significantly increased the expression of nuclear factor-YA (NF-YA), which strongly upregulated the molecules involved in the proteolytic machinery [molecular chaperones, carboxyl terminus of Hsc70-interacting protein and transcription factor EB], which thus mitigated the behavioral and pathological impairments in an SBMA mouse model through the upregulation of pathogenic androgen receptor protein clearance in motor neurons and muscles. These findings demonstrated that PF is able to enhance both the UPS and autophagy systems by upregulating the expression of NF-YA, which promotes therapeutic effects in an SBMA model.

Downregulation of proteins involved in the endoplasmic reticulum stress response and Nrf2-ARE signaling in lymphoblastoid cells of spinocerebellar ataxia type 17

Spinocerebellar ataxia type 17 (SCA17) is caused by CAG repeat expansion in the TATA-box binding protein gene. Studies of several polyglutamine (polyQ) expansion diseases have suggested that the expanded polyQ proteins misfold and induce oxidative stress to contribute to cell death. Substantial deficits in peripheral tissues including lymphocytes have been shown and these peripheral abnormalities could also be found in neurons possessing polyQ disease proteins. In this study, we used a lymphoblastoid cell model to investigate the functional implication of SCA17 expanded alleles and assess the potential therapeutic strategies that may ameliorate the effects of expanded polyQ. Proteomics studies of patient/control pairs including two-dimensional (2-D) gel electrophoresis, mass spectrometry and immunoblotting were conducted. A total of 8 proteins with reduced expression changes greater than 1.3-fold were identified, including previously reported HSPA5 and HSPA8. Among 6 proteins further semi-quantified by immunoblotting and real-time PCR, the reduced expression of HYOU1, PDIA3, P4HB, NQO1 and HMOX1 was confirmed. Treatment with resveratrol and genipin up-regulated NQO1 and HMOX1 expression and reduced oxidative stress in patients' lymphoblastoid cells. The results illustrate downregulation of proteins involved in the endoplasmic reticulum stress response (HYOU1, HSPA5, PDIA3, and P4HB) and Nrf2-ARE signaling (NQO1 and HMOX1) in SCA17 lymphoblastoid cells. Compounds increasing anti-oxidative activity such as resveratrol and genipin may serve as a potential therapeutic strategy for SCA17.

Aqueous Extract of Paeonia lactiflora and Paeoniflorin as Aggregation Reducers Targeting Chaperones in Cell Models of Spinocerebellar Ataxia 3

Spinocerebellar ataxia (SCA) types 1, 2, 3, 6, 7, and 17 as well as Huntington's disease are a group of neurodegenerative disorders caused by expanded CAG repeats encoding a long polyglutamine (polyQ) tract in the respective proteins. Evidence has shown that the accumulation of intranuclear and cytoplasmic misfolded polyQ proteins leads to apoptosis and cell death. Thus suppression of aggregate formation is expected to inhibit a wide range of downstream pathogenic events in polyQ diseases. In this study, we established a high-throughput aggregation screening system using 293 ATXN3/Q75-GFP cells and applied this system to test the aqueous extract of Paeonia lactiflora (P. lactiflora) and its constituents. We found that the aggregation can be significantly prohibited by P. lactiflora and its active compound paeoniflorin. Meanwhile, P. lactiflora and paeoniflorin upregulated HSF1 and HSP70 chaperones in the same cell models. Both of them further reduced the aggregation in neuronal differentiated SH-SY5Y ATXN3/Q75-GFP cells. Our results demonstrate how P. lactiflora and paeoniflorin are likely to work on polyQ-aggregation reduction and provide insight into the possible working mechanism of P. lactiflora in SCA3. We anticipate our paper to be a starting point for screening more potential herbs for the treatment of SCA3 and other polyQ diseases.

Cyclic AMP-dependent protein phosphorylation in isolated neuronal growth cones from developing rat forebrain

We have shown recently that neuronal growth cones isolated from developing rat forebrain possess an appreciable activity of adenylate cyclase, which produces cyclic AMP and can be stimulated by various neurotransmitter receptor agonists and by forskolin. To investigate cyclic AMP-mediated biochemical mechanisms in isolated growth cones, we have centered the present study on cyclic AMP-dependent protein phosphorylation. One-dimensional gel electrophoretic analysis showed that cyclic AMP analogs increased incorporation of 32P into several phosphoproteins in molecular mass ranges of 50-58 and 76-82 kilodaltons, including those of 82, 76, and 51 kilodaltons. Two-dimensional electrophoresis, using isoelectric focusing in the first dimension, resolved phosphorylated alpha- and beta-tubulin species, actin, a very acidic protein (isoelectric point 4.0) with a molecular mass of 93 kilodaltons, and two proteins (x and x') closely neighboring beta-tubulin. Two other phosphoproteins seen in the gels had molecular masses of 56 and 51 kilodaltons (respective isoelectric points, 4.5 and 4.4) and, along with the 93-kilodalton phosphoprotein, were highly enriched in the isolated growth cones. Only the tubulin and actin species were major proteins in the isolated growth cones. Cyclic AMP analogs enhanced incorporation of 32P into phosphoproteins x and x', and, as assessed by immunoprecipitation, into beta-tubulin. Peptide digest experiments suggested that phosphoproteins x and x' are unrelated to beta-tubulin. Nonequilibrium two-dimensional electrophoresis resolved many phosphoproteins, of which a 79- and 75-kilodalton doublet, a 74-kilodalton species, and a 58-kilodalton doublet showed enhanced incorporation of 32P in the presence of cyclic AMP.