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1.
Int J Mol Sci ; 22(11)2021 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-34070858

RESUMO

Variants in STUB1 cause both autosomal recessive (SCAR16) and dominant (SCA48) spinocerebellar ataxia. Reports from 18 STUB1 variants causing SCA48 show that the clinical picture includes later-onset ataxia with a cerebellar cognitive affective syndrome and varying clinical overlap with SCAR16. However, little is known about the molecular properties of dominant STUB1 variants. Here, we describe three SCA48 families with novel, dominantly inherited STUB1 variants (p.Arg51_Ile53delinsProAla, p.Lys143_Trp147del, and p.Gly249Val). All the patients developed symptoms from 30 years of age or later, all had cerebellar atrophy, and 4 had cognitive/psychiatric phenotypes. Investigation of the structural and functional consequences of the recombinant C-terminus of HSC70-interacting protein (CHIP) variants was performed in vitro using ubiquitin ligase activity assay, circular dichroism assay and native polyacrylamide gel electrophoresis. These studies revealed that dominantly and recessively inherited STUB1 variants showed similar biochemical defects, including impaired ubiquitin ligase activity and altered oligomerization properties of the CHIP. Our findings expand the molecular understanding of SCA48 but also mean that assumptions concerning unaffected carriers of recessive STUB1 variants in SCAR16 families must be re-evaluated. More investigations are needed to verify the disease status of SCAR16 heterozygotes and elucidate the molecular relationship between SCA48 and SCAR16 diseases.


Assuntos
Demência Frontotemporal/genética , Genes Dominantes , Genes Recessivos , Ataxias Espinocerebelares/genética , Ubiquitina-Proteína Ligases , Adulto , Idade de Início , Idoso , Família , Feminino , Demência Frontotemporal/diagnóstico , Demência Frontotemporal/metabolismo , Demência Frontotemporal/patologia , Expressão Gênica , Heterozigoto , Humanos , Masculino , Pessoa de Meia-Idade , Mutação , Linhagem , Dobramento de Proteína , Ataxias Espinocerebelares/diagnóstico , Ataxias Espinocerebelares/metabolismo , Ataxias Espinocerebelares/patologia
2.
Oxid Med Cell Longev ; 2021: 9875639, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33688396

RESUMO

Background: Spinocerebellar ataxia type 2 (SCA2) is a neurodegenerative disease presenting with redox imbalance. However, the nature and implications of redox imbalance in SCA2 physiopathology have not been fully understood. Objective: The objective of this study is to assess the redox imbalance and its association with disease severity in SCA2 mutation carriers. Methods: A case-control study was conducted involving molecularly confirmed SCA2 patients, presymptomatic individuals, and healthy controls. Several antioxidant parameters were assessed, including serum thiol concentration and the superoxide dismutase, catalase, and glutathione S-transferase enzymatic activities. Also, several prooxidant parameters were evaluated, including thiobarbituric acid-reactive species and protein carbonyl concentrations. Damage, protective, and OXY scores were computed. Clinical correlates were established. Results: Significant differences were found between comparison groups for redox markers, including protein carbonyl concentration (F = 3.30; p = 0.041), glutathione S-transferase activity (F = 4.88; p = 0.009), and damage (F = 3.20; p = 0.045), protection (F = 12.75; p < 0.001), and OXY (F = 7.29; p = 0.001) scores. Protein carbonyl concentration was positively correlated with CAG repeat length (r = 0.27; p = 0.022), while both protein carbonyl concentration (r = -0.27; p = 0.018) and OXY score (r = -0.25; p = 0.013) were inversely correlated to the disease duration. Increasing levels of antioxidants and decreasing levels of prooxidant parameters were associated with clinical worsening. Conclusions: There is a disruption of redox balance in SCA2 mutation carriers which depends on the disease stage. Besides, redox changes associate with markers of disease severity, suggesting a link between disruption of redox balance and SCA2 physiopathology.


Assuntos
Ataxias Espinocerebelares/metabolismo , Ataxias Espinocerebelares/patologia , Adulto , Idoso , Biomarcadores/metabolismo , Estudos de Casos e Controles , Feminino , Heterozigoto , Humanos , Masculino , Pessoa de Meia-Idade , Mutação/genética , Oxirredução , Ataxias Espinocerebelares/genética , Expansão das Repetições de Trinucleotídeos/genética
3.
Mol Cell ; 81(7): 1515-1533.e5, 2021 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-33571423

RESUMO

Loss of the ataxia-telangiectasia mutated (ATM) kinase causes cerebellum-specific neurodegeneration in humans. We previously demonstrated that deficiency in ATM activation via oxidative stress generates insoluble protein aggregates in human cells, reminiscent of protein dysfunction in common neurodegenerative disorders. Here, we show that this process is driven by poly-ADP-ribose polymerases (PARPs) and that the insoluble protein species arise from intrinsically disordered proteins associating with PAR-associated genomic sites in ATM-deficient cells. The lesions implicated in this process are single-strand DNA breaks dependent on reactive oxygen species, transcription, and R-loops. Human cells expressing Mre11 A-T-like disorder mutants also show PARP-dependent aggregation identical to ATM deficiency. Lastly, analysis of A-T patient cerebellum samples shows widespread protein aggregation as well as loss of proteins known to be critical in human spinocerebellar ataxias that is not observed in neocortex tissues. These results provide a hypothesis accounting for loss of protein integrity and cerebellum function in A-T.


Assuntos
Proteínas Mutadas de Ataxia Telangiectasia/deficiência , Quebras de DNA de Cadeia Simples , Proteína Homóloga a MRE11/deficiência , Neocórtex/metabolismo , Poli ADP Ribosilação , Proteostase , Ataxias Espinocerebelares/metabolismo , Adulto , Linhagem Celular Tumoral , Feminino , Humanos , Masculino , Neocórtex/patologia , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/patologia
4.
JCI Insight ; 6(3)2021 02 08.
Artigo em Inglês | MEDLINE | ID: mdl-33554954

RESUMO

Spinocerebellar ataxia type 1 (SCA1) is an adult-onset neurodegenerative disorder characterized by motor incoordination, mild cognitive decline, respiratory dysfunction, and early lethality. It is caused by the expansion of the polyglutamine (polyQ) tract in Ataxin-1 (ATXN1), which stabilizes the protein, leading to its toxic accumulation in neurons. Previously, we showed that serine 776 (S776) phosphorylation is critical for ATXN1 stability and contributes to its toxicity in cerebellar Purkinje cells. Still, the therapeutic potential of disrupting S776 phosphorylation on noncerebellar SCA1 phenotypes remains unstudied. Here, we report that abolishing S776 phosphorylation specifically on the polyQ-expanded ATXN1 of SCA1-knockin mice reduces ATXN1 throughout the brain and not only rescues the cerebellar motor incoordination but also improves respiratory function and extends survival while not affecting the hippocampal learning and memory deficits. As therapeutic approaches are likely to decrease S776 phosphorylation on polyQ-expanded and WT ATXN1, we further disrupted S776 phosphorylation on both alleles and observed an attenuated rescue, demonstrating a potential protective role of WT allele. This study not only highlights the role of S776 phosphorylation to regulate ATXN1 levels throughout the brain but also suggests distinct brain region-specific disease mechanisms and demonstrates the importance of developing allele-specific therapies for maximal benefits in SCA1.


Assuntos
Ataxina-1/química , Ataxina-1/metabolismo , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/metabolismo , Alelos , Animais , Ataxina-1/genética , Comportamento Animal , Encéfalo/metabolismo , Modelos Animais de Doenças , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Mutantes , Modelos Neurológicos , Peptídeos/química , Peptídeos/genética , Peptídeos/metabolismo , Fosforilação , Estabilidade Proteica , Células de Purkinje/metabolismo , Serina/química , Ataxias Espinocerebelares/terapia , Expansão das Repetições de Trinucleotídeos
5.
J Neurosci ; 41(9): 2053-2068, 2021 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-33478986

RESUMO

Spinocerebellar ataxias (SCAs) are diseases characterized by cerebellar atrophy and loss of Purkinje neurons caused by mutations in diverse genes. In SCA14, the disease is caused by point mutations or small deletions in protein kinase C γ (PKCγ), a crucial signaling protein in Purkinje cells. It is still unclear whether increased or decreased PKCγ activity may be involved in the SCA14 pathogenesis. In this study, we present a new knock-in mouse model related to SCA14 with a point mutation in the pseudosubstrate domain, PKCγ-A24E, known to induce a constitutive PKCγ activation. In this protein conformation, the kinase domain of PKCγ is activated, but at the same time the protein is subject to dephosphorylation and protein degradation. As a result, we find a dramatic reduction of PKCγ protein expression in PKCγ-A24E mice of either sex. Despite this reduction, there is clear evidence for an increased PKC activity in Purkinje cells from PKCγ-A24E mice. Purkinje cells derived from PKCγ-A24E have short thickened dendrites typical for PKC activation. These mice also develop a marked ataxia and signs of Purkinje cell dysfunction making them an interesting new mouse model related to SCA. Recently, a similar mutation in a human patient was discovered and found to be associated with overt SCA14. RNA profiling of PKCγ-A24E mice showed a dysregulation of related signaling pathways, such as mGluR1 or mTOR. Our results show that the induction of PKCγ activation in Purkinje cells results in the SCA-like phenotype indicating PKC activation as one pathogenetic avenue leading to a SCA.SIGNIFICANCE STATEMENT Spinocerebellar ataxias (SCAs) are hereditary diseases affecting cerebellar Purkinje cells and are a one of neurodegenerative diseases. While mutation in several genes have been identified as causing SCAs, it is unclear how these mutations cause the disease phenotype. Mutations in PKCγ cause one subtype of SCAs, SCA14. In this study, we have generated a knock-in mouse with a mutation in the pseudosubstrate domain of PKCγ, which keeps PKCγ in the constitutive active open conformation. We show that this mutation leading to a constant activation of PKCγ results in a SCA-like phenotype in these mice. Our findings establish the constant activation of PKC signaling as one pathogenetic avenue leading to an SCA phenotype and a mechanism causing a neurodegenerative disease.


Assuntos
Proteína Quinase C/genética , Proteína Quinase C/metabolismo , Células de Purkinje/metabolismo , Ataxias Espinocerebelares/genética , Animais , Diferenciação Celular/fisiologia , Modelos Animais de Doenças , Feminino , Técnicas de Introdução de Genes , Humanos , Masculino , Camundongos , Atividade Motora/fisiologia , Mutação , Células de Purkinje/patologia , Ataxias Espinocerebelares/metabolismo , Ataxias Espinocerebelares/patologia
6.
Development ; 147(24)2020 12 16.
Artigo em Inglês | MEDLINE | ID: mdl-33234719

RESUMO

The mechanism underlying the geometrical patterning of axon and dendrite wiring remains elusive, despite its crucial importance in the formation of functional neural circuits. The cerebellar Purkinje cell (PC) arborizes a typical planar dendrite, which forms an orthogonal network with granule cell (GC) axons. By using electrospun nanofiber substrates, we reproduce the perpendicular contacts between PC dendrites and GC axons in culture. In the model system, PC dendrites show a preference to grow perpendicularly to aligned GC axons, which presumably contribute to the planar dendrite arborization in vivo We show that ßIII spectrin, a causal protein for spinocerebellar ataxia type 5, is required for the biased growth of dendrites. ßIII spectrin deficiency causes actin mislocalization and excessive microtubule invasion in dendritic protrusions, resulting in abnormally oriented branch formation. Furthermore, disease-associated mutations affect the ability of ßIII spectrin to control dendrite orientation. These data indicate that ßIII spectrin organizes the mouse dendritic cytoskeleton and thereby regulates the oriented growth of dendrites with respect to the afferent axons.


Assuntos
Comunicação Celular/genética , Citoesqueleto/genética , Células de Purkinje/metabolismo , Espectrina/genética , Animais , Axônios/metabolismo , Células Cultivadas , Cerebelo/crescimento & desenvolvimento , Cerebelo/metabolismo , Dendritos/genética , Dendritos/metabolismo , Humanos , Camundongos , Células de Purkinje/patologia , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/metabolismo
7.
Neurosci Lett ; 738: 135337, 2020 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-32877710

RESUMO

Spinocerebellar ataxia type 17 (SCA17) is an autosomal dominant neurodegenerative disease caused by CAG expansion in the gene encoding the TATA-binding protein (TBP). The neurological features of SCA17 are Purkinje cell loss and gliosis. We have generated SCA17 transgenic mice which recapitulate the patients' phenotypes and are suitable for the study of the SCA17 pathomechanism. Our previous study identified the activation of mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) occurred in the SCA17 cerebella, this study aims to study the role of ERK activation in SCA17. The levels of pERK, calbindin, and gliosis markers on the mouse cerebellum at 4-8 weeks old were analyzed to elucidate the correlation among behavioral performance, ERK activation and Purkinje cell degeneration. The motor incoordination was initiated in SCA17 mice at 6 weeks old. We found that the presence of TBP nuclear aggregation and microglia activation were observed at 4 weeks old. Gliosis of astrocytes and Bergmann glia, pERK, Bax/Bcl2 ratio, and caspase-3 were significantly increased in the 6-week-old SCA17 mouse cerebellum. In addition to the polyglutamine-protein aggregation in Purkinje cells caused apoptosis cell-autonomously, a significant body of evidence have shown that ERK pathways involves in neuronal apoptosis. Our study showed that the activation of ERK in the astrocytes and Bergmann glia was identified as preceding motor deficits, which suggest the elevated gliosis by ERK activation may contribute to neuronal apoptosis in SCA17 mice.


Assuntos
Cerebelo/metabolismo , Gliose/metabolismo , Sistema de Sinalização das MAP Quinases/fisiologia , Células de Purkinje/metabolismo , Ataxias Espinocerebelares/metabolismo , Animais , Calcineurina/metabolismo , Morte Celular/fisiologia , Cerebelo/patologia , Modelos Animais de Doenças , Gliose/genética , Gliose/patologia , Camundongos , Camundongos Transgênicos , Destreza Motora/fisiologia , Fenótipo , Fosforilação , Células de Purkinje/patologia , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/patologia , Proteína de Ligação a TATA-Box/genética
8.
Int J Mol Sci ; 21(14)2020 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-32709127

RESUMO

BACKGROUND: Genetic variants in voltage-gated sodium channels (Nav) encoded by SCNXA genes, responsible for INa, and Kv4.3 channels encoded by KCND3, responsible for the transient outward current (Ito), contribute to the manifestation of both Brugada syndrome (BrS) and spinocerebellar ataxia (SCA19/22). We examined the hypothesis that Kv4.3 and Nav variants regulate each other's function, thus modulating INa/Ito balance in cardiomyocytes and INa/I(A) balance in neurons. METHODS: Bicistronic and other constructs were used to express WT or variant Nav1.5 and Kv4.3 channels in HEK293 cells. INa and Ito were recorded. RESULTS: SCN5A variants associated with BrS reduced INa, but increased Ito. Moreover, BrS and SCA19/22 KCND3 variants associated with a gain of function of Ito, significantly reduced INa, whereas the SCA19/22 KCND3 variants associated with a loss of function (LOF) of Ito significantly increased INa. Auxiliary subunits Navß1, MiRP3 and KChIP2 also modulated INa/Ito balance. Co-immunoprecipitation and Duolink studies suggested that the two channels interact within the intracellular compartments and biotinylation showed that LOF SCN5A variants can increase Kv4.3 cell-surface expression. CONCLUSION: Nav and Kv4.3 channels modulate each other's function via trafficking and gating mechanisms, which have important implications for improved understanding of these allelic cardiac and neuronal syndromes.


Assuntos
Síndrome de Brugada/metabolismo , Canalopatias/metabolismo , Canais de Potássio Shal/metabolismo , Ataxias Espinocerebelares/metabolismo , Canais de Sódio Disparados por Voltagem/metabolismo , Síndrome de Brugada/genética , Canalopatias/genética , Variação Genética , Células HEK293 , Humanos , Canal de Sódio Disparado por Voltagem NAV1.1/genética , Canal de Sódio Disparado por Voltagem NAV1.1/metabolismo , Canal de Sódio Disparado por Voltagem NAV1.5/genética , Canal de Sódio Disparado por Voltagem NAV1.5/metabolismo , Mutação Puntual , Canais de Potássio Shal/genética , Ataxias Espinocerebelares/genética , Canais de Sódio Disparados por Voltagem/genética
9.
Nat Commun ; 11(1): 3343, 2020 07 03.
Artigo em Inglês | MEDLINE | ID: mdl-32620905

RESUMO

The expanded polyglutamine (polyQ) tract form of ataxin-1 drives disease progression in spinocerebellar ataxia type 1 (SCA1). Although known to form distinctive intranuclear bodies, the cellular pathways and processes that polyQ-ataxin-1 influences remain poorly understood. Here we identify the direct and proximal partners constituting the interactome of ataxin-1[85Q] in Neuro-2a cells, pathways analyses indicating a significant enrichment of essential nuclear transporters, pointing to disruptions in nuclear transport processes in the presence of elevated levels of ataxin-1. Our direct assessments of nuclear transporters and their cargoes confirm these observations, revealing disrupted trafficking often with relocalisation of transporters and/or cargoes to ataxin-1[85Q] nuclear bodies. Analogous changes in importin-ß1, nucleoporin 98 and nucleoporin 62 nuclear rim staining are observed in Purkinje cells of ATXN1[82Q] mice. The results highlight a disruption of multiple essential nuclear protein trafficking pathways by polyQ-ataxin-1, a key contribution to furthering understanding of pathogenic mechanisms initiated by polyQ tract proteins.


Assuntos
Ataxina-1/metabolismo , Núcleo Celular/metabolismo , Proteínas de Transporte Nucleocitoplasmático/metabolismo , Células de Purkinje/metabolismo , Transporte Ativo do Núcleo Celular/genética , Animais , Ataxina-1/genética , Linhagem Celular Tumoral , Modelos Animais de Doenças , Células HeLa , Humanos , Camundongos , Mutação , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Proteínas de Transporte Nucleocitoplasmático/genética , Peptídeos/genética , Ligação Proteica , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/metabolismo , Expansão das Repetições de Trinucleotídeos/genética
10.
Nat Commun ; 11(1): 3298, 2020 07 03.
Artigo em Inglês | MEDLINE | ID: mdl-32620747

RESUMO

Communication between organelles is essential for their cellular homeostasis. Neurodegeneration reflects the declining ability of neurons to maintain cellular homeostasis over a lifetime, where the endolysosomal pathway plays a prominent role by regulating protein and lipid sorting and degradation. Here we report that TMEM16K, an endoplasmic reticulum lipid scramblase causative for spinocerebellar ataxia (SCAR10), is an interorganelle regulator of the endolysosomal pathway. We identify endosomal transport as a major functional cluster of TMEM16K in proximity biotinylation proteomics analyses. TMEM16K forms contact sites with endosomes, reconstituting split-GFP with the small GTPase RAB7. Our study further implicates TMEM16K lipid scrambling activity in endosomal sorting at these sites. Loss of TMEM16K function led to impaired endosomal retrograde transport and neuromuscular function, one of the symptoms of SCAR10. Thus, TMEM16K-containing ER-endosome contact sites represent clinically relevant platforms for regulating endosomal sorting.


Assuntos
Anoctaminas/metabolismo , Retículo Endoplasmático/metabolismo , Endossomos/metabolismo , Lisossomos/metabolismo , Animais , Anoctaminas/genética , Transporte Biológico , Células COS , Linhagem Celular Tumoral , Células Cultivadas , Chlorocebus aethiops , Retículo Endoplasmático/ultraestrutura , Endossomos/ultraestrutura , Células HEK293 , Humanos , Metabolismo dos Lipídeos , Lisossomos/ultraestrutura , Camundongos Knockout , Microscopia Eletrônica , Mutação , Transporte Proteico , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/metabolismo
11.
Int J Mol Sci ; 21(11)2020 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-32466579

RESUMO

Heme and Fe-S clusters regulate a plethora of essential biological processes ranging from cellular respiration and cell metabolism to the maintenance of genome integrity. Mutations in genes involved in heme metabolism and Fe-S cluster biogenesis cause different forms of ataxia, like posterior column ataxia and retinitis pigmentosa (PCARP), Friedreich's ataxia (FRDA) and X-linked sideroblastic anemia with ataxia (XLSA/A). Despite great efforts in the elucidation of the molecular pathogenesis of these disorders several important questions still remain to be addressed. Starting with an overview of the biology of heme metabolism and Fe-S cluster biogenesis, the review discusses recent progress in the understanding of the molecular pathogenesis of PCARP, FRDA and XLSA/A, and highlights future line of research in the field. A better comprehension of the mechanisms leading to the degeneration of neural circuity responsible for balance and coordinated movement will be crucial for the therapeutic management of these patients.


Assuntos
Anemia Sideroblástica/metabolismo , Ataxia/metabolismo , Ataxia de Friedreich/metabolismo , Doenças Genéticas Ligadas ao Cromossomo X/metabolismo , Heme/metabolismo , Proteínas Ferro-Enxofre/metabolismo , Retinite Pigmentosa/metabolismo , Ataxias Espinocerebelares/metabolismo , Anemia Sideroblástica/genética , Animais , Ataxia/genética , Ataxia de Friedreich/genética , Doenças Genéticas Ligadas ao Cromossomo X/genética , Heme/genética , Humanos , Proteínas Ferro-Enxofre/genética , Retinite Pigmentosa/genética , Ataxias Espinocerebelares/genética
12.
Oxid Med Cell Longev ; 2020: 3129497, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32377295

RESUMO

Spinocerebellar ataxia type 17 (SCA17) is caused by a CAG/CAA expansion mutation encoding an expanded polyglutamine (polyQ) tract in TATA-box binding protein (TBP), a general transcription initiation factor. Suppression of cAMP-responsive element binding protein- (CREB-) dependent transcription, impaired nuclear factor erythroid 2-related factor 2 (NRF2) signaling, and interaction of AMP-activated protein kinase (AMPK) with increased oxidative stress have been implicated to be involved in pathogenic mechanisms of polyQ-mediated diseases. In this study, we demonstrated decreased pCREB and NRF2 and activated AMPK contributing to neurotoxicity in SCA17 SH-SY5Y cells. We also showed that licochalcone A and the related in-house derivative compound 3-benzoyl-5-hydroxy-2H-chromen-2-one (LM-031) exhibited antiaggregation, antioxidative, antiapoptosis, and neuroprotective effects in TBP/Q79-GFP-expressing cell models. LM-031 and licochalcone A exerted neuroprotective effects by upregulating pCREB and its downstream genes, BCL2 and GADD45B, and enhancing NRF2. Furthermore, LM-031, but not licochalcone A, reduced activated AMPKα. Knockdown of CREB and NRF2 and treatment of AICAR (5-aminoimidazole-4-carboxamide 1-ß-D-ribofuranoside), an AMPK activator, attenuated the aggregation-inhibiting and neurite outgrowth promoting effects of LM-031 on TBP/Q79 SH-SY5Y cells. The study results suggest the LM-031 as potential therapeutics for SCA17 and probable other polyQ diseases.


Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Cromonas/farmacologia , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Fator 2 Relacionado a NF-E2/metabolismo , Crescimento Neuronal/efeitos dos fármacos , Peptídeos/antagonistas & inibidores , Ataxias Espinocerebelares/tratamento farmacológico , Ataxias Espinocerebelares/metabolismo , Aminoimidazol Carboxamida/análogos & derivados , Aminoimidazol Carboxamida/farmacologia , Chalconas/farmacologia , Humanos , Peptídeos/metabolismo , Ribonucleotídeos/farmacologia , Ataxias Espinocerebelares/patologia , Proteína de Ligação a TATA-Box/metabolismo
13.
Sci Rep ; 10(1): 5418, 2020 03 25.
Artigo em Inglês | MEDLINE | ID: mdl-32214165

RESUMO

Spinocerebellar ataxia 1 (SCA1) is a devastating neurodegenerative disease associated with cerebellar degeneration and motor deficits. However, many patients also exhibit neuropsychiatric impairments such as depression and apathy; nevertheless, the existence of a causal link between the psychiatric symptoms and SCA1 neuropathology remains controversial. This study aimed to explore behavioral deficits in a knock-in mouse SCA1 (SCA1154Q/2Q) model and to identify the underlying neuropathology. We found that the SCA1 mice exhibit previously undescribed behavioral impairments such as increased anxiety- and depressive-like behavior and reduced prepulse inhibition and cognitive flexibility. Surprisingly, non-motor deficits characterize the early SCA1 stage in mice better than does ataxia. Moreover, the SCA1 mice exhibit significant hippocampal atrophy with decreased plasticity-related markers and markedly impaired neurogenesis. Interestingly, the hippocampal atrophy commences earlier than the cerebellar degeneration and directly reflects the individual severity of some of the behavioral deficits. Finally, mitochondrial respirometry suggests profound mitochondrial dysfunction in the hippocampus, but not in the cerebellum of the young SCA1 mice. These findings imply the essential role of hippocampal impairments, associated with profound mitochondrial dysfunction, in SCA1 behavioral deficits. Moreover, they underline the view of SCA1 as a complex neurodegenerative disease and suggest new avenues in the search for novel SCA1 therapies.


Assuntos
Cerebelo/patologia , Hipocampo/patologia , Transtornos Mentais/patologia , Mitocôndrias/patologia , Ataxias Espinocerebelares/patologia , Animais , Atrofia/metabolismo , Atrofia/patologia , Biomarcadores/metabolismo , Cerebelo/metabolismo , Modelos Animais de Doenças , Hipocampo/metabolismo , Masculino , Transtornos Mentais/metabolismo , Camundongos , Mitocôndrias/metabolismo , Ataxias Espinocerebelares/metabolismo
14.
Sci Rep ; 10(1): 1557, 2020 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-32005838

RESUMO

A mutant form of the ataxin-1 protein with an expanded polyglutamine (polyQ) tract is the underlying cause of the inherited neurodegenerative disease spinocerebellar ataxia 1 (SCA1). In probing the biophysical features of the nuclear bodies (NBs) formed by polyQ-ataxin-1, we defined ataxin-1 NBs as spherical liquid protein/RNA droplets capable of rapid fusion. We observed dynamic exchange of the ataxin-1 protein into these NBs; notably, cell exposure to a pro-oxidant stress could trigger a transition to slower ataxin-1 exchange, typical of a hydrogel state, which no longer showed the same dependence on RNA or sensitivity to 1,6-hexanediol. Furthermore, we could alter ataxin-1 exchange dynamics either through modulating intracellular ATP levels, RNA helicase inhibition, or siRNA-mediated depletion of select RNA helicases. Collectively, these findings reveal the tunable dynamics of the liquid RNA/protein droplets formed by polyQ-ataxin-1.


Assuntos
Ataxina-1/metabolismo , Gotículas Lipídicas/metabolismo , RNA/metabolismo , Ataxias Espinocerebelares/metabolismo , Animais , Ataxina-1/genética , Linhagem Celular Tumoral , Humanos , Fusão de Membrana , Camundongos , Modelos Moleculares , Mutação/genética , Peptídeos/química , Ligação Proteica , Ataxias Espinocerebelares/genética
15.
Cerebellum ; 19(2): 165-181, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31898278

RESUMO

Spinocerebellar ataxia type 2 (SCA2), a rare polyglutamine neurodegenerative disorder caused by a CAG repeat expansion in the ataxin-2 gene, exhibits common cellular phenotypes with other neurodegenerative disorders, including oxidative stress and mitochondrial dysfunction. Here, we show that SCA2 patient cells exhibit higher levels of caspase-8- and caspase-9-mediated apoptotic activation than control cells, cellular phenotypes that we find to be exacerbated by reactive oxygen species (ROS) and inhibition of autophagy. We also suggest that oligomerization of mutant ataxin-2 protein is likely to be the cause of the observed cellular phenotypes by causing inhibition of autophagy and by inducing ROS generation. Finally, we show that removal of ataxin-2 oligomers, either by increasing autophagic clearance or by oligomer dissolution, appears to alleviate the cellular phenotypes. Our results suggest that oligomerized ataxin-2 and oxidative stress affect autophagic clearance in SCA2 cells, contributing to the pathophysiology, and that activation of autophagy or clearance of oligomers may prove to be effective therapeutic strategies.


Assuntos
Apoptose/fisiologia , Ataxina-2/metabolismo , Autofagia/fisiologia , Ataxias Espinocerebelares/metabolismo , Células Cultivadas , Fibroblastos/metabolismo , Humanos , Estresse Oxidativo/fisiologia , Ataxias Espinocerebelares/fisiopatologia
16.
Hum Mol Genet ; 29(1): 117-131, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31696233

RESUMO

Spinocerebellar ataxia type 1 (SCA1) is a fatal neurodegenerative disease caused by abnormal expansion of glutamine (Q) encoding CAG repeats in the gene Ataxin-1 (ATXN1). Although motor and balance deficits are the core symptoms of SCA1, cognitive decline is also commonly observed in patients. While mutant ATXN1 is expressed throughout the brain, pathological findings reveal severe atrophy of cerebellar cortex in SCA1 patients. The cerebellum has recently been implicated in diverse cognitive functions, yet to what extent cerebellar neurodegeneration contributes to cognitive alterations in SCA1 remains poorly understood. Much of our understanding of the mechanisms underlying pathogenesis of motor symptoms in SCA1 comes from mouse models. Reasoning that mouse models could similarly offer important insights into the mechanisms of cognitive alterations in SCA1, we tested cognition in several mouse lines using Barnes maze and fear conditioning. We confirmed cognitive deficits in Atxn1154Q/2Q knock-in mice with brain-wide expression of mutant ATXN1 and in ATXN1 null mice. We found that shorter polyQ length and haploinsufficiency of ATXN1 do not cause significant cognitive deficits. Finally, ATXN1[82Q ] transgenic mice-with cerebellum limited expression of mutant ATXN1-demonstrated milder impairment in most aspects of cognition compared to Atxn1154Q/2Q mice, supporting the concept that cognitive deficits in SCA1 arise from a combination of cerebellar and extra-cerebellar dysfunctions.


Assuntos
Ataxina-1/metabolismo , Cerebelo/metabolismo , Disfunção Cognitiva/metabolismo , Animais , Ataxina-1/genética , Ataxina-3/genética , Ataxina-3/metabolismo , Cognição/fisiologia , Disfunção Cognitiva/genética , Modelos Animais de Doenças , Feminino , Masculino , Camundongos , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/metabolismo
17.
Cell Mol Life Sci ; 77(6): 977-996, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31552448

RESUMO

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.


Assuntos
Proteínas de Choque Térmico HSP70/metabolismo , Peptídeos/metabolismo , Agregação Patológica de Proteínas/metabolismo , Animais , Humanos , Doença de Huntington/tratamento farmacológico , Doença de Huntington/metabolismo , Terapia de Alvo Molecular , Atrofia Muscular Espinal/tratamento farmacológico , Atrofia Muscular Espinal/metabolismo , Agregação Patológica de Proteínas/tratamento farmacológico , Dobramento de Proteína/efeitos dos fármacos , Deficiências na Proteostase/tratamento farmacológico , Deficiências na Proteostase/metabolismo , Ataxias Espinocerebelares/tratamento farmacológico , Ataxias Espinocerebelares/metabolismo
18.
Neuron ; 105(4): 630-644.e9, 2020 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-31859031

RESUMO

Sirtuin 1 (Sirt1) is a NAD+-dependent deacetylase capable of countering age-related neurodegeneration, but the basis of Sirt1 neuroprotection remains elusive. Spinocerebellar ataxia type 7 (SCA7) is an inherited CAG-polyglutamine repeat disorder. Transcriptome analysis of SCA7 mice revealed downregulation of calcium flux genes accompanied by abnormal calcium-dependent cerebellar membrane excitability. Transcription-factor binding-site analysis of downregulated genes yielded Sirt1 target sites, and we observed reduced Sirt1 activity in the SCA7 mouse cerebellum with NAD+ depletion. SCA7 patients displayed increased poly(ADP-ribose) in cerebellar neurons, supporting poly(ADP-ribose) polymerase-1 upregulation. We crossed Sirt1-overexpressing mice with SCA7 mice and noted rescue of neurodegeneration and calcium flux defects. NAD+ repletion via nicotinamide riboside ameliorated disease phenotypes in SCA7 mice and patient stem cell-derived neurons. Sirt1 thus achieves neuroprotection by promoting calcium regulation, and NAD+ dysregulation underlies Sirt1 dysfunction in SCA7, indicating that cerebellar ataxias exhibit altered calcium homeostasis because of metabolic dysregulation, suggesting shared therapy targets.


Assuntos
Cálcio/fisiologia , Homeostase/fisiologia , Neuroproteção/fisiologia , Niacinamida/metabolismo , Sirtuína 1/metabolismo , Ataxias Espinocerebelares/metabolismo , Animais , Linhagem Celular , Cerebelo/metabolismo , Feminino , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Técnicas de Cultura de Órgãos , Transdução de Sinais/fisiologia , Sirtuína 1/genética , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/prevenção & controle
19.
Neurosci Biobehav Rev ; 108: 854-865, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31838195

RESUMO

Magnetic resonance spectroscopy (MRS) is applied to investigate the neurochemical profiles of degenerative hereditary ataxias. This meta-analysis provides a quantitative review and reappraisal of MRS findings in spinocerebellar ataxias (SCA) and Friedreich ataxia (FA) available to date. From each study, changes in N-acetyl aspartate (NAA), choline-containing compounds (Cho) and myo-Inositol (mI) ratios to total creatine (Cr) were calculated for groups of patients (1499 patients in total: SCA1 = 223, SCA2 = 298, SCA3 = 711, SCA6 = 165, and FA = 102) relative to their own control group, mostly in cerebellum and pons. SCA1, 2, 3, 6, and FA patients showed overall decreased NAA/Cr compared to controls. Decreased Cho/Cr was visible in SCA1, 2, and 3 and elevated mI/Cr in SCA2 patients in cerebellum. In SCA6 and FA Cho/Cr and mI/Cr did not differ with respect to controls but SCA6 patients indicated higher Cho/Cr compared to SCA1 patients in cerebellum. SCA2 subjects showed the lowest NAA/Cr and Cho/Cr in cerebellum and the highest mI/Cr compared to controls and other genotypes, and therefore the most promising results for a potential biomarker.


Assuntos
Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Ataxia de Friedreich/diagnóstico por imagem , Ataxia de Friedreich/metabolismo , Espectroscopia de Ressonância Magnética , Ataxias Espinocerebelares/diagnóstico por imagem , Ataxias Espinocerebelares/metabolismo , Humanos
20.
Int J Mol Sci ; 20(23)2019 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-31766565

RESUMO

Ataxin-2 (human gene symbol ATXN2) acts during stress responses, modulating mRNA translation and nutrient metabolism. Ataxin-2 knockout mice exhibit progressive obesity, dyslipidemia, and insulin resistance. Conversely, the progressive ATXN2 gain of function due to the fact of polyglutamine (polyQ) expansions leads to a dominantly inherited neurodegenerative process named spinocerebellar ataxia type 2 (SCA2) with early adipose tissue loss and late muscle atrophy. We tried to understand lipid dysregulation in a SCA2 patient brain and in an authentic mouse model. Thin layer chromatography of a patient cerebellum was compared to the lipid metabolome of Atxn2-CAG100-Knockin (KIN) mouse spinocerebellar tissue. The human pathology caused deficits of sulfatide, galactosylceramide, cholesterol, C22/24-sphingomyelin, and gangliosides GM1a/GD1b despite quite normal levels of C18-sphingomyelin. Cerebellum and spinal cord from the KIN mouse showed a consistent decrease of various ceramides with a significant elevation of sphingosine in the more severely affected spinal cord. Deficiency of C24/26-sphingomyelins contrasted with excess C18/20-sphingomyelin. Spinocerebellar expression profiling revealed consistent reductions of CERS protein isoforms, Sptlc2 and Smpd3, but upregulation of Cers2 mRNA, as prominent anomalies in the ceramide-sphingosine metabolism. Reduction of Asah2 mRNA correlated to deficient S1P levels. In addition, downregulations for the elongase Elovl1, Elovl4, Elovl5 mRNAs and ELOVL4 protein explain the deficit of very long-chain sphingomyelin. Reduced ASMase protein levels correlated to the accumulation of long-chain sphingomyelin. Overall, a deficit of myelin lipids was prominent in SCA2 nervous tissue at prefinal stage and not compensated by transcriptional adaptation of several metabolic enzymes. Myelination is controlled by mTORC1 signals; thus, our human and murine observations are in agreement with the known role of ATXN2 yeast, nematode, and mouse orthologs as mTORC1 inhibitors and autophagy promoters.


Assuntos
Ataxina-2/genética , Ceramidas/metabolismo , Esfingomielinas/metabolismo , Ataxias Espinocerebelares/genética , Expansão das Repetições de Trinucleotídeos/genética , Animais , Ataxina-2/metabolismo , Modelos Animais de Doenças , Proteínas do Olho/genética , Proteínas do Olho/metabolismo , Humanos , Metabolismo dos Lipídeos/genética , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Camundongos Knockout , Esfingomielina Fosfodiesterase/genética , Esfingomielina Fosfodiesterase/metabolismo , Esfingosina N-Aciltransferase/genética , Esfingosina N-Aciltransferase/metabolismo , Ataxias Espinocerebelares/metabolismo , Ataxias Espinocerebelares/patologia
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