Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.25.1 (proteasome)
28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Frontotemporal dementia with inclusion body myopathy and Paget's disease of bone (IBMPFD) is a rare, autosomal dominant disorder caused by mutations in the gene valosin-containing protein (VCP). The CNS pathology is characterized by a novel pattern of ubiquitin pathology distinct from sporadic and familial frontotemporal lobar degeneration with ubiquitin-positive inclusions without VCP mutations. Yet, the ubiquitin-positive inclusions in IBMPFD also stain for TAR DNA binding protein, a feature that links this rare disease with the pathology associated with the majority of sporadic FTD as well as disease resulting from different genetic alterations. VCP, a member of the AAA-ATPase gene family, associates with a plethora of protein adaptors to perform a variety of cellular processes including Golgi assembly/disassembly and regulation of the ubiquitin-proteasome system. However, the mechanism whereby mutations in VCP lead to CNS, muscle, and bone disease is largely unknown. In this report, we review current literature on IBMPFD, focusing on the pathology of the disease and the biology of VCP with respect to IBMPFD.
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PMID:Valosin-containing protein and the pathogenesis of frontotemporal dementia associated with inclusion body myopathy. 1745 94

Neurodegenerative disorders share a process of aggregation of insoluble protein. Frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U) is characterized by the presence of ubiquitin and TDP-43 positive aggregates which are likely related to specific gene expression profiles. We carried out gene expression microarray analysis on post-mortem brain tissue from FTLD-U, FTLD-MND, and controls. Using total RNA from carefully dissected frontal cortical layer II, we obtained gene expression profiles showing that FTLD-U and controls differ in over 100 networks, including those involved in synapse formation, the ubiquitin-proteasome system, endosomal sorting, and apoptosis. We performed qRT-PCR validation for three genes, representative of three different networks. Dynein axonemal light intermediate chain 1 (DNALI1) (microtubule/cytoskeleton network associated) expression was 3-fold higher and myeloid differentiation primary response gene 88 (MYD88) (signal transduction network) was 3.3 times higher in FTLD-U than FTLD-MND and controls; annexin A2 (ANXA2) (endosomal sorting) expression was 11.3-fold higher in FTLD-U than FTLD-MND and 2.3-fold higher than controls. The identification of progranulin (PGRN) gene mutations and TDP-43 as the major protein component of the ubiquitinated inclusions, are two recent landmark discoveries in the field of FTLD-U. We found 1.5-fold increase in TDP-43 in both FTLD-MND and FTLD-U while progranulin showed no gene expression differences between controls and FTLD-MND. However, one of the FTLD-U cases tested by Affymetrix microarray showed "absence call" of this transcript, suggesting absent or decreased gene expression. Our findings point to specific gene-linked-pathways which may be influenced by neurodegenerative disease process and may be targeted for further exploration.
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PMID:Gene expression analysis of frontotemporal lobar degeneration of the motor neuron disease type with ubiquitinated inclusions. 1756 64

Inclusion body myopathy (IBM) associated with Paget disease of the bone (PDB) and frontotemporal dementia (FTD) (now called IBMPFD), is a progressive autosomal dominant disorder that was recently identified as being caused by mutations in the VCP (p97 or CDC48) gene which plays a key role in the ubiquitin-proteasome dependent degradation of cytosolic proteins and in the retro translocation of misfolded proteins from the endoplasmic reticulum into the cytoplasm. Approximately 90% of the affected persons in the study have myopathy or muscle weakness particularly of the shoulder and hip girdles, which can lead to loss of walking ability and even death by complications of respiratory and cardiac failure. About half of affected study participants have Paget disease of bone characterized by abnormal rates of bone growth that can result in bone pain, enlargement and fractures. Findings of premature FTD affecting behavior and personality are seen in a third of affected individuals. Within 20 IBMPFD families whose data was analyzed for this study, ten missense mutations have been identified, the majority of which are located in the N-terminal ubiquitin binding domain. Inclusions seen in the muscle, brain and heart in VCP disease contain ubiquitin, beta amyloid and TDP-43, also seen in other neurodegenerative disorders thus implicating common pathways in their pathogenesis.
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PMID:VCP disease associated with myopathy, Paget disease of bone and frontotemporal dementia: review of a unique disorder. 1884 50

TDP-43 (43-kDa TAR DNA-binding domain protein) is a major constituent of ubiquitin-positive cytoplasmic aggregates present in neurons of patients with fronto-temporal lobular dementia and amyotrophic lateral sclerosis (ALS). The pathologic significance of TDP-43 aggregation is not known; however, dominant mutations in TDP-43 cause a subset of ALS cases, suggesting that misfolding and/or altered trafficking of TDP-43 is relevant to the disease process. Here, we show that the presenilin-binding protein ubiquilin 1 (UBQLN) plays a role in TDP-43 aggregation. TDP-43 interacted with UBQLN both in yeast and in vitro, and the carboxyl-terminal ubiquitin-associated domain of UBQLN was both necessary and sufficient for binding to polyubiquitylated forms of TDP-43. Overexpression of UBQLN recruited TDP-43 to detergent-resistant cytoplasmic aggregates that colocalized with the autophagosomal marker, LC3. UBQLN-dependent aggregation required the UBQLN UBA domain, was mediated by non-overlapping regions of TDP-43, and was abrogated by a mutation in UBQLN previously linked to Alzheimer disease. Four ALS-associated alleles of TDP-43 also coaggregated with UBQLN, and the extent of aggregation correlated with in vitro UBQLN binding affinity. Our findings suggest that UBQLN is a polyubiquitin-TDP-43 cochaperone that mediates the autophagosomal delivery and/or proteasome targeting of TDP-43 aggregates.
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PMID:Potentiation of amyotrophic lateral sclerosis (ALS)-associated TDP-43 aggregation by the proteasome-targeting factor, ubiquilin 1. 1911 76

Frontotemporal lobar degeneration (FTLD) with inclusion body myopathy and Paget disease of bone is a rare, autosomal dominant disorder caused by mutations in the VCP (valosin-containing protein) gene. The disease is characterized neuropathologically by frontal and temporal lobar atrophy, neuron loss and gliosis, and ubiquitin-positive inclusions (FTLD-U), which are distinct from those seen in other sporadic and familial FTLD-U entities. The major component of the ubiquitinated inclusions of FTLD with VCP mutation is TDP-43 (TAR DNA-binding protein of 43 kDa). TDP-43 proteinopathy links sporadic amyotrophic lateral sclerosis, sporadic FTLD-U, and most familial forms of FTLD-U. Understanding the relationship between individual gene defects and pathologic TDP-43 will facilitate the characterization of the mechanisms leading to neurodegeneration. Using cell culture models, we have investigated the role of mutant VCP in intracellular trafficking, proteasomal function, and cell death and demonstrate that mutations in the VCP gene 1) alter localization of TDP-43 between the nucleus and cytosol, 2) decrease proteasome activity, 3) induce endoplasmic reticulum stress, 4) increase markers of apoptosis, and 5) impair cell viability. These results suggest that VCP mutation-induced neurodegeneration is mediated by several mechanisms.
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PMID:VCP mutations causing frontotemporal lobar degeneration disrupt localization of TDP-43 and induce cell death. 1923 41

TDP-43 (43-kDa TAR DNA-binding protein) is a major constituent of ubiquitin-positive cytosolic aggregates present in neurons of patients with amyotrophic lateral sclerosis (ALS) and ubiquitin-positive fronto-temporal lobar degeneration (FTLD-U). Inherited mutations in TDP-43 have been linked to familial forms of ALS, indicating a key role for TDP-43 in disease pathogenesis. Here, we describe a Drosophila melanogaster model of TDP-43 proteinopathy. Expression of wild-type human TDP-43 protein in Drosophila motor neurons led to motor dysfunction and dramatic reduction of life span. Interestingly, coexpression of ubiquilin 1, a previously identified TDP-43-interacting protein with suspected functions in autophagy and proteasome targeting, reduced steady-state TDP-43 expression but enhanced the severity of TDP-43 phenotypes. Finally, ectopically expressed TDP-43 was largely localized to motor neuron nuclei, suggesting that expression of wild-type TDP-43 alone is detrimental even in the absence of cytosolic aggregation. Our findings demonstrate that TDP-43 exerts cell-autonomous neurotoxicity in Drosophila and further imply that dose-dependent alterations of TDP-43 nuclear function may underlie motor neuron death in ALS.
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PMID:Ubiquilin modifies TDP-43 toxicity in a Drosophila model of amyotrophic lateral sclerosis (ALS). 2015 90

The presence of protein inclusions within the central nervous system is a characteristic of most neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Aggregates may induce cell death trough several mechanisms, such as sequestration of essential cellular components, clogging of the proteasome system, and/or disruption of axonal transport. The neuropathological signature of ALS is represented by the presence of ubiquitinated inclusions immunoreactive for the protein TDP-43 in the cytoplasm of motor neurons. Recent studies demonstrated that a significant percentage of familial ALS cases are caused by pathogenic mutations in the TAR DNA binding protein and fused in sarcoma/translocated in liposarcoma genes encoding, respectively, for TDP-43 and FUS proteins. Both TDP-43 and FUS are DNA/RNA-binding proteins involved in transcriptional regulation and splicing, shuttling, maturation and transport of mRNA molecules. Mutations in the two genes seem to induce a nucleo-cytoplasmic redistribution of FUS and TDP-43, possibly promoting aggregate formation and/or disrupting their physiological nuclear functions or their interactions with specific RNA targets. Those findings collectively suggest that alterations in cellular RNA metabolism may trigger motor neuron degeneration.
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PMID:Protein aggregation and defective RNA metabolism as mechanisms for motor neuron damage. 2040 82

Several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), are characterized by the presence of misfolded proteins, thought to trigger neurotoxicity. Some familial forms of ALS (fALS), clinically indistinguishable from sporadic ALS (sALS), are linked to superoxide dismutase 1 (SOD1) gene mutations. It has been shown that the mutant SOD1 misfolds, forms insoluble aggregates and impairs the proteasome. Using transgenic G93A-SOD1 mice, we found that spinal cord motor neurons, accumulating mutant SOD1 also over-express the small heat shock protein HspB8. Using motor neuronal fALS models, we demonstrated that HspB8 decreases aggregation and increases mutant SOD1 solubility and clearance, without affecting wild-type SOD1 turnover. Notably, HspB8 acts on mutant SOD1 even when the proteasome activity is specifically blocked. The pharmacological blockage of autophagy resulted in a dramatic increase of mutant SOD1 aggregates. Immunoprecipitation studies, performed during autophagic flux blockage, demonstrated that mutant SOD1 interacts with the HspB8/Bag3/Hsc70/CHIP multiheteromeric complex, known to selectively activate autophagic removal of misfolded proteins. Thus, HspB8 increases mutant SOD1 clearance via autophagy. Autophagy activation was also observed in lumbar spinal cord of transgenic G93A-SOD1 mice since several autophago-lysosomal structures were present in affected surviving motor neurons. Finally, we extended our observation to a different ALS model and demonstrated that HspB8 exerts similar effects on a truncated version of TDP-43, another protein involved both in fALS and in sALS. Overall, these results indicate that the pharmacological modulation of HspB8 expression in motor neurons may have important implications to unravel the molecular mechanisms involved both in fALS and in sALS.
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PMID:The small heat shock protein B8 (HspB8) promotes autophagic removal of misfolded proteins involved in amyotrophic lateral sclerosis (ALS). 2057 Sep 67

Protein aggregation is a major pathological hallmark of many neurodegenerative disorders including polyglutamine diseases. Aggregation of the mutated form of the disease protein ataxin-3 into neuronal nuclear inclusions is well described in the polyglutamine disorder spinocerebellar ataxia type 3 (SCA3 or Machado-Joseph disease), although these inclusions are not thought to be directly pathogenic. Neuropil aggregates have not yet been described in SCA3. We performed a systematic immunohistochemical study of serial thick sections through brains of seven clinically diagnosed and genetically confirmed SCA3 patients. Using antibodies against ataxin-3, p62, ubiquitin, the polyglutamine marker 1C2 as well as TDP-43, we analyzed neuronal localization, composition and distribution of aggregates within SCA3 brains. The analysis revealed widespread axonal aggregates in fiber tracts known to undergo neurodegeneration in SCA3. Similar to neuronal nuclear inclusions, the axonal aggregates were ubiquitinated and immunopositive for the proteasome and autophagy associated shuttle protein p62, indicating involvement of neuronal protein quality control mechanisms. Rare TDP-43 positive axonal inclusions were also observed. Based on the correlation between affected fiber tracts and degenerating neuronal nuclei, we hypothesize that these novel axonal inclusions may be detrimental to axonal transport mechanisms and thereby contribute to degeneration of nerve cells in SCA3.
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PMID:Axonal inclusions in spinocerebellar ataxia type 3. 2063 90

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive loss of upper and lower motor neurons. As with other age-dependent neurodegenerative disorders, ALS is linked to the presence of misfolded proteins that may perturb several intracellular mechanisms and trigger neurotoxicity. Misfolded proteins aggregate intracellularly generating insoluble inclusions that are a key neuropathological hallmark of ALS. Proteins involved in the intracellular degradative systems, signaling pathways and the human TAR DNA-binding protein TDP-43 are major components of these inclusions. While their role and cytotoxicity are still largely debated, aggregates represent a powerful marker to follow protein misfolding in the neurodegenerative processes. Using in vitro and in vivo models of mutant SOD1 associated familial ALS (fALS), we and other groups demonstrated that protein misfolding perturbs one of the major intracellular degradative pathways, the ubiquitin proteasome system, giving rise to a vicious cycle that leads to the further deposit of insoluble proteins and finally to the formation of inclusions. The aberrant response to mutated SOD1 thus leads to the activation of the cascade of events ultimately responsible for cell death. Hence, our idea is that, by assisting protein folding, we might reduce protein aggregation, restore a fully functional proteasome activity and/or other cascades of events triggered by the mutant proteins responsible for motor neuron death in ALS. This could be obtained by stimulating mutant protein turnover, using an alternative degradative pathway that could clear mutant SOD1, namely autophagy.
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PMID:A role of small heat shock protein B8 (HspB8) in the autophagic removal of misfolded proteins responsible for neurodegenerative diseases. 2069 40


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