The neurodegenerative polyglutamine diseases are caused various disease proteins. Although these mutant proteins are by an expansion of unstable polyglutamine repeats in expressed ubiquitously in neuronal and non-neur...The neurodegenerative polyglutamine diseases are caused various disease proteins. Although these mutant proteins are by an expansion of unstable polyglutamine repeats in expressed ubiquitously in neuronal and non-neuronal cells, they cause selective degeneration of specific neuronal populations. Recently, increasing evidence shows that polyglutamine disease proteins also affect non-neuronal cells. However, it remains unclear how the expression of polyglutamine proteins in non-neuronal cells contributes to the course of the polyglutamine diseases. Here, we discuss recent findings about the expression of mutant polyglutamine proteins in non-neuronal cells and their influence on neurological symptoms. Understanding the contribution of non-neuronal polyglutamine proteins to disease progres- sion will help elucidate disease mechanisms and also help in the development of new treatment options.展开更多
Proteins containing an expanded polyglutamine tract are neurotoxins. The expanded polyglutamine proteins influence a variety of cellular functions. In Drosophila the GMR-Gal4/UAS expression system has been widely used...Proteins containing an expanded polyglutamine tract are neurotoxins. The expanded polyglutamine proteins influence a variety of cellular functions. In Drosophila the GMR-Gal4/UAS expression system has been widely used in an eye-based model to study human neurodegenerative diseases. This system has facilitated the isolation and characterization of abundant Drosophilagenes that interact with the expanded polyglutamine proteins. We used the GMR-Gal4/UAS system to express three proteins containing an expanded polyglutamine tract, or an expanded polyglutamine tract alone. Doubling the dose of these proteins resulted in pupal lethality, indicating that these toxic proteins induced a sensitized condition that is prone to synthetic lethality. By using the GMR-Gal4/UAS system, we showed that a Drosophilagene interacts with three expanded polyglutamine proteins to induce a synthetic lethal phenotype. We further demonstrated that the synthetic lethality was mediated through the toxic expanded polyglutamine tract. Our study raises a possibility that conventional genetic screens may not recover synthetic lethal alleles, which are presumably stronger interacting alleles than the currently known modifiers of an expanded polyglutamine tract, due to synthetic lethality.展开更多
Mutant proteins containing an expanded polyglutamine tract induce cell death and cause neurodegenerative diseases. These toxic proteins interfere with a variety of physiological pathways, but the key interactions betw...Mutant proteins containing an expanded polyglutamine tract induce cell death and cause neurodegenerative diseases. These toxic proteins interfere with a variety of physiological pathways, but the key interactions between the toxins and cellular factors remain unclear. To model the diseases in Drosophila, the GMR-Gal4/UAS gene expression system has been used extensively, which operates in the eyes. By using the system, genome-wide studies have resulted in the isolation of functionally diverse groups of Drosophila genes that interact with the disease proteins. We previously reported that coexpressing the Drosophila Dikar gene and an expanded polyglutamine tract by GMR-Gal4/UAS induced a synthetic lethality. We carried out follow-up experiments to isolate additional synthetic lethal alleles. Our data provide evidence that synthetic lethality associated with expressing an expanded polyglutamine tract is more common than thought to be and could have escaped the conventional genetic screens. Our results also suggest that 1) the gene expression system is leaky, allowing expression outside of the primary target eye cell types;2) expressing an expanded polyglutamine tract is extremely toxic to cells;and 3) combining the leaky expression and the toxicity results in a lethal-prone condition. Thus, genetic modifications to the disease proteins’ acute toxicity could frequently lead to synthetic lethality. However, synthetic lethal alleles are excluded from most conventional screens, necessitating alternative approaches such as a two-step method used in this study to isolate the modifiers. Since synthetic lethality reflects essential genetic buffering networks, studying these alleles may hold the keys to identify the critical interactions in the disease development between the toxic proteins and the physiological pathways.展开更多
Polyglutamine （polyQ） diseases are a family of neurodegenerative disorders including Huntington’s disease, spinobulbar muscular atrophy,dentatorubral-pallidoluysian atrophy and several spinocerebellar ataxias.polyQ...Polyglutamine （polyQ） diseases are a family of neurodegenerative disorders including Huntington’s disease, spinobulbar muscular atrophy,dentatorubral-pallidoluysian atrophy and several spinocerebellar ataxias.polyQ diseases are caused by abnormal expansion of CAG repeats in certain genes.The expanded CAG repeats are then translated into a series of abnormally expanded polyQ tracts.Such polyQ tracts may induce misfolding of the disease-causing proteins.The present review mainly focuses on the common characteristics of the pathogenesis of these polyQ diseases,including conformational transition of proteins and its influence on the function of these proteins,the correlation between decreased ability of proteoly-sis and late-onset polyQ diseases,and the relationship between wide expression of disease-causing proteins and selective neuronal death.展开更多
Spinal and bulbar muscular atrophy is a neurodegenerative disease caused by extended CAG trinucleotide repeats in the androgen receptor gene,which encodes a ligand-dependent transcription facto r.The mutant androgen r...Spinal and bulbar muscular atrophy is a neurodegenerative disease caused by extended CAG trinucleotide repeats in the androgen receptor gene,which encodes a ligand-dependent transcription facto r.The mutant androgen receptor protein,characterized by polyglutamine expansion,is prone to misfolding and forms aggregates in both the nucleus and cytoplasm in the brain in spinal and bulbar muscular atrophy patients.These aggregates alter protein-protein interactions and compromise transcriptional activity.In this study,we reported that in both cultured N2a cells and mouse brain,mutant androgen receptor with polyglutamine expansion causes reduced expression of mesencephalic astrocyte-de rived neurotrophic factor.Overexpressio n of mesencephalic astrocyte-derived neurotrophic factor amelio rated the neurotoxicity of mutant androgen receptor through the inhibition of mutant androgen receptor aggregation.Conversely.knocking down endogenous mesencephalic astrocyte-derived neurotrophic factor in the mouse brain exacerbated neuronal damage and mutant androgen receptor aggregation.Our findings suggest that inhibition of mesencephalic astrocyte-derived neurotrophic factor expression by mutant androgen receptor is a potential mechanism underlying neurodegeneration in spinal and bulbar muscular atrophy.展开更多
Spinocerebellar ataxias are heritable neurodegenerative diseases caused by a cytosine-adenine-guanine expansion,which encodes a long glutamine tract(polyglutamine)in the respective wild-type protein causing misfolding...Spinocerebellar ataxias are heritable neurodegenerative diseases caused by a cytosine-adenine-guanine expansion,which encodes a long glutamine tract(polyglutamine)in the respective wild-type protein causing misfolding and protein aggregation.Clinical features of polyglutamine spinocerebellar ataxias include neuronal aggregation,mitochondrial dysfunction,decreased proteasomal activity,and autophagy impairment.Mutant polyglutamine protein aggregates accumulate within neurons and cause neural dysfunction and death in specific regions of the central nervous system.Spinocerebellar ataxias are mostly characterized by progressive ataxia,speech and swallowing problems,loss of coordination and gait deficits.Over the past decade,efforts have been made to ameliorate disease symptoms in patients,yet no cure is available.Previous studies have been proposing the use of stem cells as promising tools for central nervous system tissue regeneration.So far,pre-clinical trials have shown improvement in various models of neurodegenerative diseases following stem cell transplantation,including animal models of spinocerebellar ataxia types 1,2,and 3.However,contrasting results can be found in the literature,depending on the animal model,cell type,and route of administration used.Nonetheless,clinical trials using cellular implants into degenerated brain regions have already been applied,with the expectation that these cells would be able to differentiate into the specific neuronal subtypes and re-populate these regions,reconstructing the affected neural network.Meanwhile,the question of how feasible it is to continue such treatments remains unanswered,with long-lasting effects being still unknown.To establish the value of these advanced therapeutic tools,it is important to predict the actions of the transplanted cells as well as to understand which cell type can induce the best outcomes for each disease.Further studies are needed to determine the best route of administration,without neglecting the possible risks of repetitive transplantation that these approaches so far appear to demand.Despite the challenges ahead of us,cell-transplantation therapies are reported to have transient but beneficial outcomes in spinocerebellar ataxias,which encourages efforts towards their improvement in the future.展开更多
Trehalose,a unique nonreducing crystalline disaccharide,is a potential disease-modifying treatment for neurodegenerative diseases associated with protein misfolding and aggregation due to aging,intrinsic mutations,or ...Trehalose,a unique nonreducing crystalline disaccharide,is a potential disease-modifying treatment for neurodegenerative diseases associated with protein misfolding and aggregation due to aging,intrinsic mutations,or autophagy dysregulation.This systematic review summarizes the effects of trehalose on its underlying mechanisms in animal models of selected neurodegenerative disorders(tau pathology,synucleinopathy,polyglutamine tract,and motor neuron diseases).All animal studies on neurodegenerative diseases treated with trehalose published in Medline(accessed via EBSCOhost)and Scopus were considered.Of the 2259 studies screened,29 met the eligibility criteria.According to the SYstematic Review Center for Laboratory Animal Experiment(SYRCLE)risk of bias tool,we reported 22 out of 29 studies with a high risk of bias.The present findings support the purported role of trehalose in autophagic flux and protein refolding.This review identified several other lesser-known pathways,including modifying amyloid precursor protein processing,inhibition of reactive gliosis,the integrity of the blood-brain barrier,activation of growth factors,upregulation of the downstream antioxidant signaling pathway,and protection against mitochondrial defects.The absence of adverse events and improvements in the outcome parameters were observed in some studies,which supports the transition to human clinical trials.It is possible to conclude that trehalose exerts its neuroprotective effects through both direct and indirect pathways.However,heterogeneous methodologies and outcome measures across the studies rendered it impossible to derive a definitive conclusion.Translational studies on trehalose would need to clarify three important questions:1)bioavailability with oral administration,2)optimal time window to confer neuroprotective benefits,and 3)optimal dosage to confer neuroprotection.展开更多
Objective Machado-Joseph disease （MJD）, also known as spinocerebellar ataxia type 3 （SCA3）, is a dominant neurodegenerative disorder caused by an expansion of the polyglutamine （polyQ） tract in MJD-1 gene produc...Objective Machado-Joseph disease （MJD）, also known as spinocerebellar ataxia type 3 （SCA3）, is a dominant neurodegenerative disorder caused by an expansion of the polyglutamine （polyQ） tract in MJD-1 gene product, ataxin-3 （AT3）. This disease is characterized by the formation of intraneuronal inclusions, but the mechanism underlying their formation is still poorly understood. The present study is to explore the relationship between wild type （WT） AT3 and polyQ expanded AT3. Methods Mouse neuroblastoma （N2a） cells or HEK293 cells were co-transfected with WTAT3 and different truncated forms of expanded AT3. The expressions of WT AT3 and the truncated forms of expanded AT3 were detected by Western blotting, and observed by an inverted fluorescent microscope. The interactions between AT3 and different truncated forms of expanded AT3 were detected by immunoprecipitation and GST pull-down assays. Results Using fluorescent microscope, we observed that the truncated forms of expanded AT3 aggregate in transfected cells, and the full-length WT AT3 is recruited onto the aggregates. However, no aggregates were observed in cells transfected with the truncated forms of WT AT3. Immunoprecipitation and GST pull-down analyses indicate that WT AT3 interacts with the truncated AT3 in a polyQ length-dependent manner. Conclusion WT AT3 deposits in the aggregation that was formed by polyQ expanded AT3, which suggests that the formation of AT3 aggregation may affect the normal function of WT AT3 and increase polyQ protein toxicity in MJD.展开更多
<div style="text-align:justify;"> <span style="font-family:Verdana;">Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph Disease (MJD), is an autosomal dominant neurodege...<div style="text-align:justify;"> <span style="font-family:Verdana;">Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph Disease (MJD), is an autosomal dominant neurodegenerative disorder that predominantly involves the cerebellar, pyramidal, extrapyramidal, motor neuron and oculomotor systems. SCA3 presents strong phenotypic heterogeneity and its causative mutation of SCA3 consists of an expansion of a CAG tract in exon 10 of the <em>ATXN3</em> gene, situated at 14q32.1. The <em>ATXN3</em> gene is ubiquitously expressed in neuronal and non-neuronal tissues, and also participates in cellular protein quality control pathways. Mutated <em>ATXN3</em> alleles present about 45 to 87CAG repeats, which result in an expanded polyglutamine tract in ataxin-3. After mutation, the polyQ tract reaches the pathological threshold (about 50 glutamine residues);the protein is considered that it might gain a neurotoxic function through some unclear mechanisms. We reviewed the literature on the pathogenesis and therapeutic strategies of spinocerebellar ataxia type 3 patients. Conversion of the expanded protein is possible by enhancing protein refolding and degradation or preventing proteolytic cleavage and prevents the protein to reach the site of toxicity by altering its ability to translocate between the nucleus and cytoplasm. Proteasomal degradation and enhancing autophagic aggregate clearance are currently proposed remarkable therapy. In spite of extensive research, the molecular mechanisms of cellular toxicity resulting from mutant ataxin-3 remain no preventive treatment is currently available. These therapeutic strategies might be able to improve sign symptoms of SCA3 as well as slow the disease progression.</span> </div>展开更多
Huntington＇s disease （HD） is caused by abnormal CAG repeat expansion in the 5＇-end of the Huntingtin （HTT） gene. In addition to the canonical C-terminal full-length huntingtin （htt） nuclear export signal, a cy...Huntington＇s disease （HD） is caused by abnormal CAG repeat expansion in the 5＇-end of the Huntingtin （HTT） gene. In addition to the canonical C-terminal full-length huntingtin （htt） nuclear export signal, a cytoplasmic localization-related domain （CLRD） in the N-terminus of htt has recently been reported. Here, we analyzed this domain by introducing deletion and substitution mutations in a truncated N-terminal htt protein and subsequently monitored htt expression, aggregation and subcellular localization by immunocytochemistry and Western blot analysis. We demonstrated that Htt1-17 was the essential sequence for htt cytoplasmic localization. We also found that the subcellular distribution of htt was altered when Htt1_17 was mutated to contain amino acids of different charges, suggesting a structural requirement of Htt1-17 for the cytoplasmic localization of htt. Deletion of the first three amino acids did not affect its association with mitochondria. We observed that defective cytoplasmic localization resulted in a reduction of total htt aggregates and increased nuclear aggregates, indicating that the subcellular distribution of the protein might influence the aggregation process. These studies provide new insight into the molecular mechanism of htt aggregation in HD.展开更多
Transgenic animal models have revealed much about the pathogenesis of age-dependent neurodegenerative diseases and proved to be a useful tool for uncovering therapeutic targets. Huntington＇s disease is a well-charact...Transgenic animal models have revealed much about the pathogenesis of age-dependent neurodegenerative diseases and proved to be a useful tool for uncovering therapeutic targets. Huntington＇s disease is a well-characterized neurodegenerative disorder that is caused by expansion of a CAG repeat, which results in expansion of a polyglutamine tract in the N-terminal region of huntingtin （HTT）. Similar CAG/glutamine expansions are also found to cause eight other neurodegenerative diseases that affect distinct brain regions in an age- dependent manner. Identification of this CAG/glutamine expansion has led to the generation of a variety of transgenic animal models. Of these different animal models, transgenic mice have been investigated extensively, and they show similar neuropathology and phenotypes as seen in their respective diseases. The common pathological hallmark of age-dependent neurodegeneration is the formation of aggregates or inclusions consisting of misfolded proteins in the affected brain regions; however, overt or striking neurodegeneration and apoptosis have not been reported in most transgenic mouse models for age-dependent diseases, including HD. By comparing the neuropathology of transgenic HD mouse, pig, and monkey models, we found that mutant HTT is more toxic to larger animals than mice, and larger animals also show neuropathology that has not been uncovered by transgenic mouse models. This review will discuss the importance of transgenic large animal models for analyzing the treatments. pathogenesis of neurodegenerative diseases and developing effective展开更多
文摘The neurodegenerative polyglutamine diseases are caused various disease proteins. Although these mutant proteins are by an expansion of unstable polyglutamine repeats in expressed ubiquitously in neuronal and non-neuronal cells, they cause selective degeneration of specific neuronal populations. Recently, increasing evidence shows that polyglutamine disease proteins also affect non-neuronal cells. However, it remains unclear how the expression of polyglutamine proteins in non-neuronal cells contributes to the course of the polyglutamine diseases. Here, we discuss recent findings about the expression of mutant polyglutamine proteins in non-neuronal cells and their influence on neurological symptoms. Understanding the contribution of non-neuronal polyglutamine proteins to disease progres- sion will help elucidate disease mechanisms and also help in the development of new treatment options.
文摘Proteins containing an expanded polyglutamine tract are neurotoxins. The expanded polyglutamine proteins influence a variety of cellular functions. In Drosophila the GMR-Gal4/UAS expression system has been widely used in an eye-based model to study human neurodegenerative diseases. This system has facilitated the isolation and characterization of abundant Drosophilagenes that interact with the expanded polyglutamine proteins. We used the GMR-Gal4/UAS system to express three proteins containing an expanded polyglutamine tract, or an expanded polyglutamine tract alone. Doubling the dose of these proteins resulted in pupal lethality, indicating that these toxic proteins induced a sensitized condition that is prone to synthetic lethality. By using the GMR-Gal4/UAS system, we showed that a Drosophilagene interacts with three expanded polyglutamine proteins to induce a synthetic lethal phenotype. We further demonstrated that the synthetic lethality was mediated through the toxic expanded polyglutamine tract. Our study raises a possibility that conventional genetic screens may not recover synthetic lethal alleles, which are presumably stronger interacting alleles than the currently known modifiers of an expanded polyglutamine tract, due to synthetic lethality.
文摘Mutant proteins containing an expanded polyglutamine tract induce cell death and cause neurodegenerative diseases. These toxic proteins interfere with a variety of physiological pathways, but the key interactions between the toxins and cellular factors remain unclear. To model the diseases in Drosophila, the GMR-Gal4/UAS gene expression system has been used extensively, which operates in the eyes. By using the system, genome-wide studies have resulted in the isolation of functionally diverse groups of Drosophila genes that interact with the disease proteins. We previously reported that coexpressing the Drosophila Dikar gene and an expanded polyglutamine tract by GMR-Gal4/UAS induced a synthetic lethality. We carried out follow-up experiments to isolate additional synthetic lethal alleles. Our data provide evidence that synthetic lethality associated with expressing an expanded polyglutamine tract is more common than thought to be and could have escaped the conventional genetic screens. Our results also suggest that 1) the gene expression system is leaky, allowing expression outside of the primary target eye cell types;2) expressing an expanded polyglutamine tract is extremely toxic to cells;and 3) combining the leaky expression and the toxicity results in a lethal-prone condition. Thus, genetic modifications to the disease proteins’ acute toxicity could frequently lead to synthetic lethality. However, synthetic lethal alleles are excluded from most conventional screens, necessitating alternative approaches such as a two-step method used in this study to isolate the modifiers. Since synthetic lethality reflects essential genetic buffering networks, studying these alleles may hold the keys to identify the critical interactions in the disease development between the toxic proteins and the physiological pathways.
基金supported by the grants from the National Natural Science Foundation of China(No.30600197)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20050285017)
文摘Polyglutamine （polyQ） diseases are a family of neurodegenerative disorders including Huntington’s disease, spinobulbar muscular atrophy,dentatorubral-pallidoluysian atrophy and several spinocerebellar ataxias.polyQ diseases are caused by abnormal expansion of CAG repeats in certain genes.The expanded CAG repeats are then translated into a series of abnormally expanded polyQ tracts.Such polyQ tracts may induce misfolding of the disease-causing proteins.The present review mainly focuses on the common characteristics of the pathogenesis of these polyQ diseases,including conformational transition of proteins and its influence on the function of these proteins,the correlation between decreased ability of proteoly-sis and late-onset polyQ diseases,and the relationship between wide expression of disease-causing proteins and selective neuronal death.
基金supported by the National Key R&D Program of China,No.2021YFA0805200(to SY)the National Natural Science Foundation of China,No.31970954(to SY)two grants from the Department of Science and Technology of Guangdong Province,Nos.2021ZT09Y007,2020B121201006(both to XJL)。
文摘Spinal and bulbar muscular atrophy is a neurodegenerative disease caused by extended CAG trinucleotide repeats in the androgen receptor gene,which encodes a ligand-dependent transcription facto r.The mutant androgen receptor protein,characterized by polyglutamine expansion,is prone to misfolding and forms aggregates in both the nucleus and cytoplasm in the brain in spinal and bulbar muscular atrophy patients.These aggregates alter protein-protein interactions and compromise transcriptional activity.In this study,we reported that in both cultured N2a cells and mouse brain,mutant androgen receptor with polyglutamine expansion causes reduced expression of mesencephalic astrocyte-de rived neurotrophic factor.Overexpressio n of mesencephalic astrocyte-derived neurotrophic factor amelio rated the neurotoxicity of mutant androgen receptor through the inhibition of mutant androgen receptor aggregation.Conversely.knocking down endogenous mesencephalic astrocyte-derived neurotrophic factor in the mouse brain exacerbated neuronal damage and mutant androgen receptor aggregation.Our findings suggest that inhibition of mesencephalic astrocyte-derived neurotrophic factor expression by mutant androgen receptor is a potential mechanism underlying neurodegeneration in spinal and bulbar muscular atrophy.
基金funded by national fundsthrough the Foundation for Science and Technology (FCT)-project UIDB/50026/2020 and UIDP/50026/2020by the National Ataxia Foundation (NAF)
文摘Spinocerebellar ataxias are heritable neurodegenerative diseases caused by a cytosine-adenine-guanine expansion,which encodes a long glutamine tract(polyglutamine)in the respective wild-type protein causing misfolding and protein aggregation.Clinical features of polyglutamine spinocerebellar ataxias include neuronal aggregation,mitochondrial dysfunction,decreased proteasomal activity,and autophagy impairment.Mutant polyglutamine protein aggregates accumulate within neurons and cause neural dysfunction and death in specific regions of the central nervous system.Spinocerebellar ataxias are mostly characterized by progressive ataxia,speech and swallowing problems,loss of coordination and gait deficits.Over the past decade,efforts have been made to ameliorate disease symptoms in patients,yet no cure is available.Previous studies have been proposing the use of stem cells as promising tools for central nervous system tissue regeneration.So far,pre-clinical trials have shown improvement in various models of neurodegenerative diseases following stem cell transplantation,including animal models of spinocerebellar ataxia types 1,2,and 3.However,contrasting results can be found in the literature,depending on the animal model,cell type,and route of administration used.Nonetheless,clinical trials using cellular implants into degenerated brain regions have already been applied,with the expectation that these cells would be able to differentiate into the specific neuronal subtypes and re-populate these regions,reconstructing the affected neural network.Meanwhile,the question of how feasible it is to continue such treatments remains unanswered,with long-lasting effects being still unknown.To establish the value of these advanced therapeutic tools,it is important to predict the actions of the transplanted cells as well as to understand which cell type can induce the best outcomes for each disease.Further studies are needed to determine the best route of administration,without neglecting the possible risks of repetitive transplantation that these approaches so far appear to demand.Despite the challenges ahead of us,cell-transplantation therapies are reported to have transient but beneficial outcomes in spinocerebellar ataxias,which encourages efforts towards their improvement in the future.
基金supported by Dana Impak Perdana Grant(DIP-2019-007)received by NMI from Universiti Kebangsaan Malaysia.
文摘Trehalose,a unique nonreducing crystalline disaccharide,is a potential disease-modifying treatment for neurodegenerative diseases associated with protein misfolding and aggregation due to aging,intrinsic mutations,or autophagy dysregulation.This systematic review summarizes the effects of trehalose on its underlying mechanisms in animal models of selected neurodegenerative disorders(tau pathology,synucleinopathy,polyglutamine tract,and motor neuron diseases).All animal studies on neurodegenerative diseases treated with trehalose published in Medline(accessed via EBSCOhost)and Scopus were considered.Of the 2259 studies screened,29 met the eligibility criteria.According to the SYstematic Review Center for Laboratory Animal Experiment(SYRCLE)risk of bias tool,we reported 22 out of 29 studies with a high risk of bias.The present findings support the purported role of trehalose in autophagic flux and protein refolding.This review identified several other lesser-known pathways,including modifying amyloid precursor protein processing,inhibition of reactive gliosis,the integrity of the blood-brain barrier,activation of growth factors,upregulation of the downstream antioxidant signaling pathway,and protection against mitochondrial defects.The absence of adverse events and improvements in the outcome parameters were observed in some studies,which supports the transition to human clinical trials.It is possible to conclude that trehalose exerts its neuroprotective effects through both direct and indirect pathways.However,heterogeneous methodologies and outcome measures across the studies rendered it impossible to derive a definitive conclusion.Translational studies on trehalose would need to clarify three important questions:1)bioavailability with oral administration,2)optimal time window to confer neuroprotective benefits,and 3)optimal dosage to confer neuroprotection.
基金the National Natural Sciences Foundation of China (No.30770664)a grant from Anhui Educational Committee(No. ZD2008008-2)
文摘Objective Machado-Joseph disease （MJD）, also known as spinocerebellar ataxia type 3 （SCA3）, is a dominant neurodegenerative disorder caused by an expansion of the polyglutamine （polyQ） tract in MJD-1 gene product, ataxin-3 （AT3）. This disease is characterized by the formation of intraneuronal inclusions, but the mechanism underlying their formation is still poorly understood. The present study is to explore the relationship between wild type （WT） AT3 and polyQ expanded AT3. Methods Mouse neuroblastoma （N2a） cells or HEK293 cells were co-transfected with WTAT3 and different truncated forms of expanded AT3. The expressions of WT AT3 and the truncated forms of expanded AT3 were detected by Western blotting, and observed by an inverted fluorescent microscope. The interactions between AT3 and different truncated forms of expanded AT3 were detected by immunoprecipitation and GST pull-down assays. Results Using fluorescent microscope, we observed that the truncated forms of expanded AT3 aggregate in transfected cells, and the full-length WT AT3 is recruited onto the aggregates. However, no aggregates were observed in cells transfected with the truncated forms of WT AT3. Immunoprecipitation and GST pull-down analyses indicate that WT AT3 interacts with the truncated AT3 in a polyQ length-dependent manner. Conclusion WT AT3 deposits in the aggregation that was formed by polyQ expanded AT3, which suggests that the formation of AT3 aggregation may affect the normal function of WT AT3 and increase polyQ protein toxicity in MJD.
文摘<div style="text-align:justify;"> <span style="font-family:Verdana;">Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph Disease (MJD), is an autosomal dominant neurodegenerative disorder that predominantly involves the cerebellar, pyramidal, extrapyramidal, motor neuron and oculomotor systems. SCA3 presents strong phenotypic heterogeneity and its causative mutation of SCA3 consists of an expansion of a CAG tract in exon 10 of the <em>ATXN3</em> gene, situated at 14q32.1. The <em>ATXN3</em> gene is ubiquitously expressed in neuronal and non-neuronal tissues, and also participates in cellular protein quality control pathways. Mutated <em>ATXN3</em> alleles present about 45 to 87CAG repeats, which result in an expanded polyglutamine tract in ataxin-3. After mutation, the polyQ tract reaches the pathological threshold (about 50 glutamine residues);the protein is considered that it might gain a neurotoxic function through some unclear mechanisms. We reviewed the literature on the pathogenesis and therapeutic strategies of spinocerebellar ataxia type 3 patients. Conversion of the expanded protein is possible by enhancing protein refolding and degradation or preventing proteolytic cleavage and prevents the protein to reach the site of toxicity by altering its ability to translocate between the nucleus and cytoplasm. Proteasomal degradation and enhancing autophagic aggregate clearance are currently proposed remarkable therapy. In spite of extensive research, the molecular mechanisms of cellular toxicity resulting from mutant ataxin-3 remain no preventive treatment is currently available. These therapeutic strategies might be able to improve sign symptoms of SCA3 as well as slow the disease progression.</span> </div>
基金supported by the National Natural Science Foundation of China(Grant Nos.30770761 and 30971000)
文摘Huntington＇s disease （HD） is caused by abnormal CAG repeat expansion in the 5＇-end of the Huntingtin （HTT） gene. In addition to the canonical C-terminal full-length huntingtin （htt） nuclear export signal, a cytoplasmic localization-related domain （CLRD） in the N-terminus of htt has recently been reported. Here, we analyzed this domain by introducing deletion and substitution mutations in a truncated N-terminal htt protein and subsequently monitored htt expression, aggregation and subcellular localization by immunocytochemistry and Western blot analysis. We demonstrated that Htt1-17 was the essential sequence for htt cytoplasmic localization. We also found that the subcellular distribution of htt was altered when Htt1_17 was mutated to contain amino acids of different charges, suggesting a structural requirement of Htt1-17 for the cytoplasmic localization of htt. Deletion of the first three amino acids did not affect its association with mitochondria. We observed that defective cytoplasmic localization resulted in a reduction of total htt aggregates and increased nuclear aggregates, indicating that the subcellular distribution of the protein might influence the aggregation process. These studies provide new insight into the molecular mechanism of htt aggregation in HD.
基金supported by NIH grants NS036232, AG019206,NS041669 for X.J.L. and AG031153 for S.H.L.
文摘Transgenic animal models have revealed much about the pathogenesis of age-dependent neurodegenerative diseases and proved to be a useful tool for uncovering therapeutic targets. Huntington＇s disease is a well-characterized neurodegenerative disorder that is caused by expansion of a CAG repeat, which results in expansion of a polyglutamine tract in the N-terminal region of huntingtin （HTT）. Similar CAG/glutamine expansions are also found to cause eight other neurodegenerative diseases that affect distinct brain regions in an age- dependent manner. Identification of this CAG/glutamine expansion has led to the generation of a variety of transgenic animal models. Of these different animal models, transgenic mice have been investigated extensively, and they show similar neuropathology and phenotypes as seen in their respective diseases. The common pathological hallmark of age-dependent neurodegeneration is the formation of aggregates or inclusions consisting of misfolded proteins in the affected brain regions; however, overt or striking neurodegeneration and apoptosis have not been reported in most transgenic mouse models for age-dependent diseases, including HD. By comparing the neuropathology of transgenic HD mouse, pig, and monkey models, we found that mutant HTT is more toxic to larger animals than mice, and larger animals also show neuropathology that has not been uncovered by transgenic mouse models. This review will discuss the importance of transgenic large animal models for analyzing the treatments. pathogenesis of neurodegenerative diseases and developing effective
