Publications by authors named "Anand Goswami"

31 Publications

A serum microRNA sequence reveals fragile X protein pathology in amyotrophic lateral sclerosis.

Brain 2021 Apr 19. Epub 2021 Apr 19.

Department of Neurology, Ulm University, Ulm, Germany.

Knowledge about converging disease mechanisms in the heterogeneous syndrome amyotrophic lateral sclerosis (ALS) is rare, but may lead to therapies effective in most ALS cases. Previously, we identified serum microRNAs downregulated in familial ALS, the majority of sporadic ALS patients, but also in presymptomatic mutation carriers. A 5-nucleotide sequence motif (GDCGG; D = G, A or U) was strongly enriched in these ALS-related microRNAs. We hypothesized that deregulation of protein(s) binding predominantly to this consensus motif was responsible for the ALS-linked microRNA fingerprint. Using microRNA pull-down assays combined with mass spectrometry followed by extensive biochemical validation, all members of the fragile X protein family, FMR1, FXR1 and FXR2, were identified to directly and predominantly interact with GDCGG microRNAs through their structurally disordered RGG/RG domains. Preferential association of this protein family with ALS-related microRNAs was confirmed by in vitro binding studies on a transcriptome-wide scale. Immunohistochemistry of lumbar spinal cord revealed aberrant expression level and aggregation of FXR1 and FXR2 in C9orf72- and FUS-linked familial ALS, but also patients with sporadic ALS. Further analysis of ALS autopsies and induced pluripotent stem cell-derived motor neurons with FUS mutations showed co-aggregation of FXR1 with FUS. Hence, our translational approach was able to take advantage of blood microRNAs to reveal CNS pathology, and suggests an involvement of the fragile X-related proteins in familial and sporadic ALS already at a presymptomatic stage. The findings may uncover disease mechanisms relevant to many patients with ALS. They furthermore underscore the systemic, extra-CNS aspect of ALS.
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http://dx.doi.org/10.1093/brain/awab018DOI Listing
April 2021

Hsp90-mediated regulation of DYRK3 couples stress granule disassembly and growth via mTORC1 signaling.

EMBO Rep 2021 May 19;22(5):e51740. Epub 2021 Mar 19.

Department of Biomedical, Metabolic and Neural Sciences, Centre for Neuroscience and Nanotechnology, University of Modena and Reggio Emilia, Modena, Italy.

Stress granules (SGs) are dynamic condensates associated with protein misfolding diseases. They sequester stalled mRNAs and signaling factors, such as the mTORC1 subunit raptor, suggesting that SGs coordinate cell growth during and after stress. However, the molecular mechanisms linking SG dynamics and signaling remain undefined. We report that the chaperone Hsp90 is required for SG dissolution. Hsp90 binds and stabilizes the dual-specificity tyrosine-phosphorylation-regulated kinase 3 (DYRK3) in the cytosol. Upon Hsp90 inhibition, DYRK3 dissociates from Hsp90 and becomes inactive. Inactive DYRK3 is subjected to two different fates: it either partitions into SGs, where it is protected from irreversible aggregation, or it is degraded. In the presence of Hsp90, DYRK3 is active and promotes SG disassembly, restoring mTORC1 signaling and translation. Thus, Hsp90 links stress adaptation and cell growth by regulating the activity of a key kinase involved in condensate disassembly and translation restoration.
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http://dx.doi.org/10.15252/embr.202051740DOI Listing
May 2021

Aggregates of RNA Binding Proteins and ER Chaperones Linked to Exosomes in Granulovacuolar Degeneration of the Alzheimer's Disease Brain.

J Alzheimers Dis 2020 ;75(1):139-156

Institute of Neuropathology, RWTH Aachen University Medical School, Aachen, Germany.

Granulovacuolar degeneration (GVD) occurs in Alzheimer's disease (AD) brain due to compromised autophagy. Endoplasmic reticulum (ER) function and RNA binding protein (RBP) homeostasis regulate autophagy. We observed that the ER chaperones Glucose - regulated protein, 78 KDa (GRP78/BiP), Sigma receptor 1 (SigR1), and Vesicle-associated membrane protein associated protein B (VAPB) were elevated in many AD patients' subicular neurons. However, those neurons which were affected by GVD showed lower chaperone levels, and there was only minor co-localization of chaperones with GVD bodies (GVBs), suggesting that neurons lacking sufficient chaperone-mediated proteostasis enter the GVD pathway. Consistent with this notion, granular, incipient pTau aggregates in human AD and pR5 tau transgenic mouse neurons were regularly co-localized with increased chaperone immunoreactivity, whereas neurons with mature neurofibrillary tangles lacked both the chaperone buildup and significant GVD. On the other hand, APP/PS1 (APPswe/PSEN1dE9) transgenic mouse hippocampal neurons that are devoid of pTau accumulation displayed only few GVBs-like vesicles, which were still accompanied by prominent chaperone buildup. Identifying a potential trigger for GVD, we found cytoplasmic accumulations of RBPs including Matrin 3 and FUS as well as stress granules in GVBs of AD patient and pR5 mouse neurons. Interestingly, we observed that GVBs containing aggregated pTau and pTDP-43 were consistently co-localized with the exosomal marker Flotillin 1 in both AD and pR5 mice. In contrast, intraneuronal 82E1-immunoreactive amyloid-β in human AD and APP/PS1 mice only rarely co-localized with Flotillin 1-positive exosomal vesicles. We conclude that altered chaperone-mediated ER protein homeostasis and impaired autophagy manifesting in GVD are linked to both pTau and RBP accumulation and that some GVBs might be targeted to exocytosis.
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http://dx.doi.org/10.3233/JAD-190722DOI Listing
January 2020

Phenotypes and malignancy risk of different FUS mutations in genetic amyotrophic lateral sclerosis.

Ann Clin Transl Neurol 2019 12 4;6(12):2384-2394. Epub 2019 Nov 4.

Department of Neurology, Technische Universität Dresden, Dresden, Germany.

Objective: Mutations in Fused in Sarcoma (FUS or TLS) are the fourth most prevalent in Western European familial amyotrophic lateral sclerosis (ALS) populations and have been associated with causing both early and very late disease onset. FUS aggregation, DNA repair deficiency, and genomic instability are contributors to the pathophysiology of FUS-ALS, but their clinical significance per se and their influence on the clinical variability have yet to be sufficiently investigated. The aim of this study was to analyze genotype-phenotype correlations and malignancy rates in a newly compiled FUS-ALS cohort.

Methods: We cross-sectionally reviewed FUS-ALS patient histories in a multicenter cohort with 36 novel cases and did a meta-analysis of published FUS-ALS cases reporting the largest genotype-phenotype correlation of FUS-ALS.

Results: The age of onset (median 39 years, range 11-80) was positively correlated with the disease duration. C-terminal domain mutations were found in 90%. Among all, P525L and truncating/ frameshift mutations most frequently caused juvenile onset, rapid disease progression, and atypical ALS often associated with negative family history while the R521 mutation site was associated with late disease onset and pure spinal phenotype. Malignancies were found in one of 40 patients.

Interpretation: We report the largest genotype-phenotype correlation of FUS-ALS, which enables a careful prediction of the clinical course in newly diagnosed patients. In this cohort, FUS-ALS patients did not have an increased risk for malignant diseases.
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http://dx.doi.org/10.1002/acn3.50930DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6917314PMC
December 2019

FUS pathology in ALS is linked to alterations in multiple ALS-associated proteins and rescued by drugs stimulating autophagy.

Acta Neuropathol 2019 07 1;138(1):67-84. Epub 2019 Apr 1.

Technische Universität Dresden, Center for Regenerative Therapies Dresden, Fetscherstr. 105, 01307, Dresden, Germany.

Amyotrophic lateral sclerosis (ALS) is a lethal disease characterized by motor neuron degeneration and associated with aggregation of nuclear RNA-binding proteins (RBPs), including FUS. How FUS aggregation and neurodegeneration are prevented in healthy motor neurons remain critically unanswered questions. Here, we use a combination of ALS patient autopsy tissue and induced pluripotent stem cell-derived neurons to study the effects of FUS mutations on RBP homeostasis. We show that FUS' tendency to aggregate is normally buffered by interacting RBPs, but this buffering is lost when FUS mislocalizes to the cytoplasm due to ALS mutations. The presence of aggregation-prone FUS in the cytoplasm causes imbalances in RBP homeostasis that exacerbate neurodegeneration. However, enhancing autophagy using small molecules reduces cytoplasmic FUS, restores RBP homeostasis and rescues motor function in vivo. We conclude that disruption of RBP homeostasis plays a critical role in FUS-ALS and can be treated by stimulating autophagy.
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http://dx.doi.org/10.1007/s00401-019-01998-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6570784PMC
July 2019

Cuprizone-induced graded oligodendrocyte vulnerability is regulated by the transcription factor DNA damage-inducible transcript 3.

Glia 2019 02 3;67(2):263-276. Epub 2018 Dec 3.

Faculty of Medicine, LMU Munich, Chair of Neuroanatomy, Institute of Anatomy, Munich, Germany.

Oligodendrocytes are integral to efficient neuronal signaling. Loss of myelinating oligodendrocytes is a central feature of many neurological diseases, including multiple sclerosis (MS). The results of neuropathological studies suggest that oligodendrocytes react with differing sensitivity to toxic insults, with some cells dying early during lesion development and some cells being resistant for weeks. This proposed graded vulnerability has never been demonstrated but provides an attractive window for therapeutic interventions. Furthermore, the biochemical pathways associated with graded oligodendrocyte vulnerability have not been well explored. We used immunohistochemistry and serial block-face scanning electron microscopy (3D-SEM) to show that cuprizone-induced metabolic stress results in an "out of phase" degeneration of oligodendrocytes. Although expression induction of stress response transcription factors in oligodendrocytes occurs within days, subsequent oligodendrocyte apoptosis continues for weeks. In line with the idea of an out of phase degeneration of oligodendrocytes, detailed ultrastructural reconstructions of the axon-myelin unit demonstrate demyelination of single internodes. In parallel, genome wide array analyses revealed an active unfolded protein response early after initiation of the cuprizone intoxication. In addition to the cytoprotective pathways, the pro-apoptotic transcription factor DNA damage-inducible transcript 3 (DDIT3) was induced early in oligodendrocytes. In advanced lesions, DDIT3 was as well expressed by activated astrocytes. Toxin-induced oligodendrocyte apoptosis, demyelination, microgliosis, astrocytosis, and acute axonal damage were less intense in the Ddit3-null mutants. This study identifies DDIT3 as an important regulator of graded oligodendrocyte vulnerability in a MS animal model. Interference with this stress cascade might offer a promising therapeutic approach for demyelinating disorders.
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http://dx.doi.org/10.1002/glia.23538DOI Listing
February 2019

Golgin A4 in CSF and granulovacuolar degenerations of patients with Alzheimer disease.

Neurology 2018 11 10;91(19):e1799-e1808. Epub 2018 Oct 10.

From the Institute for Molecular Cardiovascular Research (F.K., J.J., H.N., V.J.), Department of Anesthesiology (F.K.), and Institute of Neuropathology (A.G., J.W., G.B., A.Y.), Medical Faculty, RWTH Aachen University, Germany; School for Cardiovascular Diseases (J.J.), Maastricht University; Department of (Neuro) Pathology (J.A., E.A.), Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands; mfd Diagnostics GmbH (S.F., C.H.), Wendelsheim; Charité-Universitätsmedizin Berlin (C.S., O.P.), corporate member of Freie Universität Berlin; Humboldt-Universität zu Berlin (C.S., O.P.); Berlin Institute of Health (C.S., O.P.), German Center for Neurodegenerative; Experimental and Clinical Research Center (C.S., O.P.), Memory Clinic, Berlin, Germany; and Department of Nephrology (M.T.), Odense University Hospital, Denmark.

Objective: To isolate and identify a new, as yet unknown molecule in CSF that could serve as marker for Alzheimer disease.

Methods: We immunized mice with human CSF and fused hybridomas for monoclonal antibodies and screened these antibodies for their capacity to discriminate CSF of patients with Alzheimer disease from CSF of controls. We then chromatographically isolated the antigen to the best discriminating antibody and identified the antigen using mass spectrometric methods. Thereafter, we quantified the CSF concentration of the antigen in a new cohort of patients with Alzheimer disease and controls and performed immunohistochemistry of postmortem brain tissue derived from patients with Alzheimer disease and controls.

Results: We generated >200 hybridomas and selected 1 antibody that discriminated CSF from patients with Alzheimer disease from that of controls. We identified golgin A4 as the antigen detected by this antibody. Golgin A4 concentration was significantly higher in CSF from patients with Alzheimer disease than in CSF of controls (145 [interquartile range 125-155] vs 115 [ 99-128] pg/mL, < 0.001) and demonstrated a substantial discriminative power (area under the receiver operating characteristic curve 0.80, 95% confidence interval 0.67-0.94). Immunohistochemistry of postmortem brain sections from patients with Alzheimer disease revealed a significant accumulation of golgin A4 in granulovacuolar degeneration bodies (GVBs).

Conclusions: These results support the notion that golgin A4 could serve as a diagnostic marker in Alzheimer disease. For validation of this notion, prospective multicenter diagnostic studies will evaluate golgin A4 as diagnostic marker for Alzheimer disease. Furthermore, it has to be determined whether the association of golgin A4 with GVBs is an epiphenomenon or whether golgin A4 plays a more direct role in Alzheimer disease, allowing it to serve as a target in therapeutic treatment strategies.

Classification Of Evidence: This study provides Class III evidence that elevated CSF golgin A4 levels identify patients with Alzheimer disease.
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http://dx.doi.org/10.1212/WNL.0000000000006457DOI Listing
November 2018

Monitoring α-synuclein multimerization in vivo.

FASEB J 2019 02 25;33(2):2116-2131. Epub 2018 Sep 25.

Department of Neurology, University Medical Center, Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen University, Aachen, Germany.

The pathophysiology of Parkinson's disease is characterized by the abnormal accumulation of α-synuclein (α-Syn), eventually resulting in the formation of Lewy bodies and neurites in surviving neurons in the brain. Although α-Syn aggregation has been extensively studied in vitro, there is limited in vivo knowledge on α-Syn aggregation. Here, we used the powerful genetics of Drosophila melanogaster and developed an in vivo assay to monitor α-Syn accumulation by using a bimolecular fluorescence complementation assay. We found that both genetic and pharmacologic manipulations affected α-Syn accumulation. Interestingly, we also found that alterations in the cellular protein degradation mechanisms strongly influenced α-Syn accumulation. Administration of compounds identified as risk factors for Parkinson's disease, such as rotenone or heavy metal ions, had only mild or even no impact on α-Syn accumulation in vivo. Finally, we show that increasing phosphorylation of α-Syn at serine 129 enhances the accumulation and toxicity of α-Syn. Altogether, our study establishes a novel model to study α-Syn accumulation and illustrates the complexity of manipulating proteostasis in vivo.-Prasad, V., Wasser, Y., Hans, F., Goswami, A., Katona, I., Outeiro, T. F., Kahle, P. J., Schulz, J. B., Voigt, A. Monitoring α-synuclein multimerization in vivo.
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http://dx.doi.org/10.1096/fj.201800148RRRDOI Listing
February 2019

Impaired DNA damage response signaling by FUS-NLS mutations leads to neurodegeneration and FUS aggregate formation.

Nat Commun 2018 01 23;9(1):335. Epub 2018 Jan 23.

Department of Neurology, Technische Universität Dresden, 01307, Dresden, Germany.

Amyotrophic lateral sclerosis (ALS) is the most frequent motor neuron disease. Cytoplasmic fused in sarcoma (FUS) aggregates are pathological hallmarks of FUS-ALS. Proper shuttling between the nucleus and cytoplasm is essential for physiological cell function. However, the initial event in the pathophysiology of FUS-ALS remains enigmatic. Using human induced pluripotent stem cell (hiPSCs)-derived motor neurons (MNs), we show that impairment of poly(ADP-ribose) polymerase (PARP)-dependent DNA damage response (DDR) signaling due to mutations in the FUS nuclear localization sequence (NLS) induces additional cytoplasmic FUS mislocalization which in turn results in neurodegeneration and FUS aggregate formation. Our work suggests that a key pathophysiologic event in ALS is upstream of aggregate formation. Targeting DDR signaling could lead to novel therapeutic routes for ameliorating ALS.
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http://dx.doi.org/10.1038/s41467-017-02299-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5780468PMC
January 2018

The ALS-linked E102Q mutation in Sigma receptor-1 leads to ER stress-mediated defects in protein homeostasis and dysregulation of RNA-binding proteins.

Cell Death Differ 2017 10 16;24(10):1655-1671. Epub 2017 Jun 16.

Institute of Neuropathology, RWTH Aachen University Medical School, Aachen, Germany.

Amyotrophic lateral sclerosis (ALS) is characterized by the selective degeneration of motor neurons (MNs) and their target muscles. Misfolded proteins which often form intracellular aggregates are a pathological hallmark of ALS. Disruption of the functional interplay between protein degradation (ubiquitin proteasome system and autophagy) and RNA-binding protein homeostasis has recently been suggested as an integrated model that merges several ALS-associated proteins into a common pathophysiological pathway. The E102Q mutation in one such candidate gene, the endoplasmic reticulum (ER) chaperone Sigma receptor-1 (SigR1), has been reported to cause juvenile ALS. Although loss of SigR1 protein contributes to neurodegeneration in several ways, the molecular mechanisms underlying E102Q-SigR1-mediated neurodegeneration are still unclear. In the present study, we showed that the E102Q-SigR1 protein rapidly aggregates and accumulates in the ER and associated compartments in transfected cells, leading to structural alterations of the ER, nuclear envelope and mitochondria and to subsequent defects in proteasomal degradation and calcium homeostasis. ER defects and proteotoxic stress generated by E102Q-SigR1 aggregates further induce autophagy impairment, accumulation of stress granules and cytoplasmic aggregation of the ALS-linked RNA-binding proteins (RBPs) matrin-3, FUS, and TDP-43. Similar ultrastructural abnormalities as well as altered protein degradation and misregulated RBP homeostasis were observed in primary lymphoblastoid cells (PLCs) derived from E102Q-SigR1 fALS patients. Consistent with these findings, lumbar α-MNs of both sALS as well as fALS patients showed cytoplasmic matrin-3 aggregates which were not co-localized with pTDP-43 aggregates. Taken together, our results support the notion that E102Q-SigR1-mediated ALS pathogenesis comprises a synergistic mechanism of both toxic gain and loss of function involving a vicious circle of altered ER function, impaired protein homeostasis and defective RBPs.
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http://dx.doi.org/10.1038/cdd.2017.88DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5596426PMC
October 2017

Autosomal dominant spinal muscular atrophy with lower extremity predominance: A recognizable phenotype of BICD2 mutations.

Muscle Nerve 2016 09 9;54(3):496-500. Epub 2016 Jul 9.

Institute of Human Genetics, Uniklinik RWTH Aachen, Aachen, Germany.

Introduction: Heterozygous BICD2 gene mutations cause a form of autosomal dominant spinal muscular atrophy with lower extremity predominance (SMALED).

Methods: We analyzed the BICD2 gene in a selected group of 25 index patients with neurogenic muscle atrophy.

Results: We identified 2 new BICD2 missense mutations, c.2515G>A, p.Gly839Arg, in a family with autosomal dominant inheritance, and c.2202G>T, p.Lys734Asn, as a de novo mutation in an isolated patient with similar phenotype. The patients had congenital foot contractures, muscle atrophy of the legs, and slowly progressive weakness of the shoulder girdle. There was no apparent sensory or brain dysfunction. One patient died of unrelated reasons at age 52 years. Autopsy revealed no upper motor neuron and only moderate lower motor neuron loss, but there was distal corticospinal tract degeneration and marked neurogenic muscular atrophy.

Conclusion: These findings give further insight into the clinical and pathoanatomical consequences of BICD2 mutations. Muscle Nerve 54: 496-500, 2016.
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http://dx.doi.org/10.1002/mus.25114DOI Listing
September 2016

Aberrant association of misfolded SOD1 with Na(+)/K(+)ATPase-α3 impairs its activity and contributes to motor neuron vulnerability in ALS.

Acta Neuropathol 2016 Mar 30;131(3):427-51. Epub 2015 Nov 30.

Institute of Cell Biology, University of Bern, Bern, Switzerland.

Amyotrophic lateral sclerosis (ALS) is an adult onset progressive motor neuron disease with no cure. Transgenic mice overexpressing familial ALS associated human mutant SOD1 are a commonly used model for examining disease mechanisms. Presently, it is well accepted that alterations in motor neuron excitability and spinal circuits are pathological hallmarks of ALS, but the underlying molecular mechanisms remain unresolved. Here, we sought to understand whether the expression of mutant SOD1 protein could contribute to altering processes governing motor neuron excitability. We used the conformation specific antibody B8H10 which recognizes a misfolded state of SOD1 (misfSOD1) to longitudinally identify its interactome during early disease stage in SOD1G93A mice. This strategy identified a direct isozyme-specific association of misfSOD1 with Na(+)/K(+)ATPase-α3 leading to the premature impairment of its ATPase activity. Pharmacological inhibition of Na(+)/K(+)ATPase-α3 altered glutamate receptor 2 expression, modified cholinergic inputs and accelerated disease pathology. After mapping the site of direct association of misfSOD1 with Na(+)/K(+)ATPase-α3 onto a 10 amino acid stretch that is unique to Na(+)/K(+)ATPase-α3 but not found in the closely related Na(+)/K(+)ATPase-α1 isozyme, we generated a misfSOD1 binding deficient, but fully functional Na(+)/K(+)ATPase-α3 pump. Adeno associated virus (AAV)-mediated expression of this chimeric Na(+)/K(+)ATPase-α3 restored Na(+)/K(+)ATPase-α3 activity in the spinal cord, delayed pathological alterations and prolonged survival of SOD1G93A mice. Additionally, altered Na(+)/K(+)ATPase-α3 expression was observed in the spinal cord of individuals with sporadic and familial ALS. A fraction of sporadic ALS cases also presented B8H10 positive misfSOD1 immunoreactivity, suggesting that similar mechanism might contribute to the pathology.
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http://dx.doi.org/10.1007/s00401-015-1510-4DOI Listing
March 2016

NLRP3 inflammasome is expressed by astrocytes in the SOD1 mouse model of ALS and in human sporadic ALS patients.

Glia 2015 Dec 21;63(12):2260-73. Epub 2015 Jul 21.

Institute of Neuroanatomy, RWTH Aachen University, Wendlingweg 2, Aachen, Germany.

Amyotrophic lateral sclerosis (ALS) is characterized by the degeneration of motoneurons in the cerebral cortex, brainstem and spinal cord. Neuroinflammation plays an important role in the pathogenesis of ALS and involves the activation of microglia and astrocytes. Intracellular inflammasome complexes are part of the innate immunity as they sense and execute host inflammatory responses. The best characterized component is the NLRP3 inflammasome comprised of the NLR protein NLRP3, the adaptor ASC and pro-caspase 1. The NLRP3 inflammasome is critical for the activation of caspase 1 and the processing and release of IL1β and IL18. In this study, we investigated the expression, activation and co-localization of the NLRP3 inflammasome in the spinal cord of male SOD1(G93A) mice carrying a mutant human superoxide dismutase 1 (SOD1) variant and regarded as an animal model for ALS as well as in post-mortem tissue of ALS patients. NLRP3 and its molecular components as well as IL1β were already detectable in SOD1 mice at a pre-symptomatic stage after 9 weeks and further increased in 14 week old animals. Spinal cord astrocytes were identified as the major cell type expressing NLRP3 components. In human ALS tissue, we also found increased NLRP3, ASC, IL18 and active caspase 1 levels compared to control patients. Our findings suggest that astroglial NLRP3 inflammasome complexes are critically involved in neuroinflammation in ALS.
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http://dx.doi.org/10.1002/glia.22891DOI Listing
December 2015

Marinesco-Sjögren syndrome protein SIL1 regulates motor neuron subtype-selective ER stress in ALS.

Nat Neurosci 2015 Feb 5;18(2):227-38. Epub 2015 Jan 5.

Institute of Cell Biology, University of Bern, Bern, Switzerland.

Mechanisms underlying motor neuron subtype-selective endoplasmic reticulum (ER) stress and associated axonal pathology in amyotrophic lateral sclerosis (ALS) remain unclear. Here we show that the molecular environment of the ER between motor neuron subtypes is distinct, with characteristic signatures. We identify cochaperone SIL1, mutated in Marinesco-Sjögren syndrome (MSS), as being robustly expressed in disease-resistant slow motor neurons but not in ER stress-prone fast-fatigable motor neurons. In a mouse model of MSS, we demonstrate impaired ER homeostasis in motor neurons in response to loss of SIL1 function. Loss of a single functional Sil1 allele in an ALS mouse model (SOD1-G93A) enhanced ER stress and exacerbated ALS pathology. In SOD1-G93A mice, SIL1 levels were progressively and selectively reduced in vulnerable fast-fatigable motor neurons. Mechanistically, reduction in SIL1 levels was associated with lowered excitability of fast-fatigable motor neurons, further influencing expression of specific ER chaperones. Adeno-associated virus-mediated delivery of SIL1 to familial ALS motor neurons restored ER homeostasis, delayed muscle denervation and prolonged survival.
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http://dx.doi.org/10.1038/nn.3903DOI Listing
February 2015

Accumulation of STIM1 is associated with the degenerative muscle fibre phenotype in ALS and other neurogenic atrophies.

Neuropathol Appl Neurobiol 2015 Apr;41(3):304-18

Institute of Neuropathology, RWTH Aachen University and JARA Brain Translational Medicine, Aachen, Germany.

Aim: Upon denervation, skeletal muscle fibres initiate complex changes in gene expression. Many of these genes are involved in muscle fibre remodelling and atrophy. Amyotrophic lateral sclerosis (ALS) leads to progressive neurodegeneration and neurogenic muscular atrophy (NMA). Disturbed calcium homeostasis and misfolded protein aggregation both in motor neurones and muscle fibres are key elements of ALS pathogenesis that are mutually interdependent. Therefore, we hypothesized that the calcium sensor STIM1 might be abnormally modified and involved in muscle fibre degeneration in ALS and other types of NMA.

Methods: We examined ALS and NMA patient biopsy and autopsy tissue and tissue from G93A SOD1 mice by immunohistochemistry and immunoblotting.

Results: In normal human and mouse muscle STIM1 was found to be differentially expressed in muscle fibres of different types and to concentrate at neuromuscular junctions, compatible with its known role in calcium sensing. Denervated muscle fibres of sALS and NMA cases and SOD1 mice showed diffusely increased STIM1 immunoreactivity along with ubiquitinated material. In addition, distinct focal accumulations of STIM1 were observed in target structures within denervated fibres of sALS and other NMA as well as SOD1 mouse muscles. Large STIM1-immunoreactive structures were found in ALS-8 patient muscle harbouring the P56S mutation in the ER protein VAPB.

Conclusion: These findings suggest that STIM1 is involved in several ways in the reaction of muscle fibres to denervation, probably reflecting alterations in calcium homeostasis in denervated muscle fibres.
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http://dx.doi.org/10.1111/nan.12164DOI Listing
April 2015

Cetuximab induces eme1-mediated DNA repair: a novel mechanism for cetuximab resistance.

Neoplasia 2014 Mar 13;16(3):207-20, 220.e1-4. Epub 2014 Apr 13.

Institute of Neuropathology, Medical Faculty, RWTH Aachen University and JARA-BRAIN (Jülich Aachen Research Alliance Brain) Translational Medicine, Aachen, Germany.

Overexpression of the epidermal growth factor receptor (EGFR) is observed in a large number of neoplasms. The monoclonal antibody cetuximab/Erbitux is frequently applied to treat EGFR-expressing tumors. However, the application of cetuximab alone or in combination with radio- and/or chemotherapy often yields only little benefit for patients. In the present study, we describe a mechanism that explains resistance of both tumor cell lines and cultured primary human glioma cells to cetuximab. Treatment of these cells with cetuximab promoted DNA synthesis in the absence of increased proliferation, suggesting that DNA repair pathways were activated. Indeed, we observed that cetuximab promoted the activation of the DNA damage response pathway and prevented the degradation of essential meiotic endonuclease 1 homolog 1 (Eme1), a heterodimeric endonuclease involved in DNA repair. The increased levels of Eme1 were necessary for enhanced DNA repair, and the knockdown of Eme1 was sufficient to prevent efficient DNA repair in response to ultraviolet-C light or megavoltage irradiation. These treatments reduced the survival of tumor cells, an effect that was reversed by cetuximab application. Again, this protection was dependent on Eme1. Taken together, these results suggest that cetuximab initiates pathways that result in the stabilization of Eme1, thereby resulting in enhanced DNA repair. Accordingly, cetuximab enhances DNA repair, reducing the effectiveness of DNA-damaging therapies. This aspect should be considered when using cetuximab as an antitumor agent and suggests that Eme1 is a negative predictive marker.
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http://dx.doi.org/10.1016/j.neo.2014.03.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4094794PMC
March 2014

Myopathy in Marinesco-Sjögren syndrome links endoplasmic reticulum chaperone dysfunction to nuclear envelope pathology.

Acta Neuropathol 2014 May 21;127(5):761-77. Epub 2013 Dec 21.

Institute of Neuropathology, RWTH Aachen University Hospital, Pauwelsstr. 30, 52074, Aachen, Germany,

Marinesco-Sjögren syndrome (MSS) features cerebellar ataxia, mental retardation, cataracts, and progressive vacuolar myopathy with peculiar myonuclear alterations. Most MSS patients carry homozygous or compound heterozygous SIL1 mutations. SIL1 is a nucleotide exchange factor for the endoplasmic reticulum resident chaperone BiP which controls a plethora of essential processes in the endoplasmic reticulum. In this study we made use of the spontaneous Sil1 mouse mutant woozy to explore pathomechanisms leading to Sil1 deficiency-related skeletal muscle pathology. We found severe, progressive myopathy characterized by alterations of the sarcoplasmic reticulum, accumulation of autophagic vacuoles, mitochondrial changes, and prominent myonuclear pathology including nuclear envelope and nuclear lamina alterations. These abnormalities were remarkably similar to the myopathy in human patients with MSS. In particular, the presence of perinuclear membranous structures which have been reported as an ultrastructural hallmark of MSS-related myopathy could be confirmed in woozy muscles. We found that these structures are derived from the nuclear envelope and nuclear lamina and associate with proliferations of the sarcoplasmic reticulum. In line with impaired function of BiP secondary to loss of its nucleotide exchange factor Sil1, we observed activation of the unfolded protein response and the endoplasmic-reticulum-associated protein degradation-pathway. Despite initiation of the autophagy-lysosomal system, autophagic clearance was found ineffective which is in agreement with the formation of autophagic vacuoles. This report identifies woozy muscle as a faithful phenocopy of the MSS myopathy. Moreover, we provide a link between two well-established disease mechanisms in skeletal muscle, dysfunction of chaperones and nuclear envelope pathology.
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http://dx.doi.org/10.1007/s00401-013-1224-4DOI Listing
May 2014

ROCK-phosphorylated vimentin modifies mutant huntingtin aggregation via sequestration of IRBIT.

Mol Neurodegener 2012 Aug 28;7:43. Epub 2012 Aug 28.

Laboratory for Structural Neuropathology, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.

Background: Huntington's Disease (HD) is a fatal hereditary neurodegenerative disease caused by the accumulation of mutant huntingtin protein (Htt) containing an expanded polyglutamine (polyQ) tract. Activation of the channel responsible for the inositol-induced Ca²⁺ release from ensoplasmic reticulum (ER), was found to contribute substantially to neurodegeneration in HD. Importantly, chemical and genetic inhibition of inositol 1,4,5-trisphosphate (IP3) receptor type 1 (IP3R1) has been shown to reduce mutant Htt aggregation.

Results: In this study, we propose a novel regulatory mechanism of IP3R1 activity by type III intermediate filament vimentin which sequesters the negative regulator of IP3R1, IRBIT, into perinuclear inclusions, and reduces its interaction with IP3R1 resulting in promotion of mutant Htt aggregation. Proteasome inhibitor MG132, which causes polyQ proteins accumulation and aggregation, enhanced the sequestration of IRBIT. Furthermore we found that IRBIT sequestration can be prevented by a rho kinase inhibitor, Y-27632.

Conclusions: Our results suggest that vimentin represents a novel and additional target for the therapy of polyQ diseases.
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http://dx.doi.org/10.1186/1750-1326-7-43DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3502191PMC
August 2012

Cetuximab induces mitochondrial translocalization of EGFRvIII, but not EGFR: involvement of mitochondria in tumor drug resistance?

Tumour Biol 2012 Feb 11;33(1):85-94. Epub 2011 Oct 11.

Medical Faculty, Institute of Neuropathology, RWTH Aachen University, Pauwelsstr 30, 52074 Aachen, Germany.

Dysregulation of growth factor receptors such as the epidermal growth factor receptor (EGFR) and of its truncated form EGFRvIII is frequently found in human tumors. EGFRvIII is a promising target for selective molecular tumor therapy because it is exclusively expressed by tumor cells. Cetuximab/Erbitux is a monoclonal antibody which targets EGFR and EGFRvIII. The effects of cetuximab on EGFRvIII but still the exact function and mechanism of cetuximab in relation to EGFR and EGFRvIII are incompletely understood. Therefore, we investigated the influence of cetuximab on EGFRvIII signaling and cellular survival. We found that cetuximab leads to increased internalization of EGFRvIII in NR6M cells but is unable to inhibit neither the activation of EGFRvIII nor its downstream signaling pathways. Incubation with cetuximab also did not alter the survival and proliferation of EGFRvIII-expressing cells. However, it caused increased mitochondrial activity and an increase in co-localization of EGFRvIII with mitochondria. These results demonstrate that interaction of EGFRvIII with mitochondria could play a role in survival of cetuximab-treated NR6M cells. Thus, a role of mitochondria in resistance to cetuximab has to be considered.
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http://dx.doi.org/10.1007/s13277-011-0248-4DOI Listing
February 2012

Harnessing chaperone-mediated autophagy for the selective degradation of mutant huntingtin protein.

Nat Biotechnol 2010 Mar 28;28(3):256-63. Epub 2010 Feb 28.

Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Wako-shi, Saitama, Japan.

Huntington's Disease (HD) is a dominantly inherited pathology caused by the accumulation of mutant huntingtin protein (HTT) containing an expanded polyglutamine (polyQ) tract. As the polyglutamine binding peptide 1 (QBP1) is known to bind an expanded polyQ tract but not the polyQ motif found in normal HTT, we selectively targeted mutant HTT for degradation by expressing a fusion molecule comprising two copies of QBP1 and copies of two different heat shock cognate protein 70 (HSC70)-binding motifs in cellular and mouse models of HD. Chaperone-mediated autophagy contributed to the specific degradation of mutant HTT in cultured cells expressing the construct. Intrastriatal delivery of a virus expressing the fusion molecule ameliorated the disease phenotype in the R6/2 mouse model of HD. Similar adaptor molecules comprising HSC70-binding motifs fused to an appropriate structure-specific binding agent(s) may have therapeutic potential for treating diseases caused by misfolded proteins other than those with expanded polyQ tracts.
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http://dx.doi.org/10.1038/nbt.1608DOI Listing
March 2010

Inhibition of Rho kinases enhances the degradation of mutant huntingtin.

J Biol Chem 2009 May 11;284(19):13153-64. Epub 2009 Mar 11.

Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan.

Huntington disease (HD) is a fatal hereditary neurodegenerative disease caused by an expansion of the polyglutamine (polyQ) stretch in huntingtin (htt). Whereas the pathological significance of the expanded polyQ has been clearly established and a tremendous effort to develop therapeutic tools for HD has been exerted, there is yet no effective cure. Whereas many molecules able to reduce the polyQ accumulation and aggregation have been identified, including several Rho kinase (ROCK) inhibitors, it remains very important to determine the mechanism of action of the potential drugs. ROCK inhibitors, including Y-27632 were reported to decrease aggregation of htt and androgen receptor (AR) through ROCK1 and protein kinase C-related protein kinase-2 (PRK-2). A downstream effector of ROCK1, actin-binding factor profilin, was shown to inhibit the mutant htt aggregation but not AR by direct interaction. We found that the anti-aggregation effect of ROCK inhibitors was not limited to the mutant htt and AR and that Y-27632 was also able to reduce the aggregation of ataxin-3 and atrophin-1 with expanded polyQ. These results suggested that in addition to the mechanism reported for htt and AR, there might also be other common mediators involved in the reduced aggregation of different polyQ proteins. In this study, we show that Y-27632 not only reduced the mutant htt aggregation by enhancing its degradation, but surprisingly was able to activate the main cellular degradation pathways, proteasome, and macroautophagy. We also show that this unique effect was mediated by ROCK1 and ROCK2.
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http://dx.doi.org/10.1074/jbc.M809229200DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2676047PMC
May 2009

The ubiquitin ligase E6-AP is induced and recruited to aggresomes in response to proteasome inhibition and may be involved in the ubiquitination of Hsp70-bound misfolded proteins.

J Biol Chem 2009 Apr 20;284(16):10537-45. Epub 2009 Feb 20.

Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon-122 050, India.

Cells are equipped with an efficient quality control system to selectively eliminate abnormally folded and damaged proteins. Initially the cell tries to refold the unfolded proteins with the help of molecular chaperones, and failure to refold leads to their degradation by the ubiquitin proteasome system. But how this proteolytic machinery recognizes the abnormally folded proteins is poorly understood. Here, we report that E6-AP, a HECT domain family ubiquitin ligase implicated in Angelman syndrome, interacts with the substrate binding domain of Hsp70/Hsc70 chaperones and promotes the degradation of chaperone bound substrates. The expression of E6-AP was dramatically induced under a variety of stresses, and overexpression of E6-AP was found to protect against endoplasmic reticulum stress-induced cell death. The inhibition of proteasome function not only increases the expression of E6-AP but also causes its redistribution around microtubule-organizing center, a subcellular structure for the degradation of the cytoplasmic misfolded proteins. E6-AP is also recruited to aggresomes containing the cystic fibrosis transmembrane conductance regulator or expanded polyglutamine proteins. Finally, we demonstrate that E6-AP ubiquitinates misfolded luciferase that is bound by Hsp70. Our results suggest that E6-AP functions as a cellular quality control ubiquitin ligase and, therefore, can be implicated not only in the pathogenesis of Angelman syndrome but also in the biology of neurodegenerative disorders involving protein aggregation.
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http://dx.doi.org/10.1074/jbc.M806804200DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2667740PMC
April 2009

Induction of chemokines, MCP-1, and KC in the mutant huntingtin expressing neuronal cells because of proteasomal dysfunction.

J Neurochem 2009 Feb;108(3):787-95

Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon, India.

Huntington's disease is a hereditary neurodegenerative disorder caused by an aberrant polyglutamine expansion in the amino terminus of the huntingtin protein. The resultant mutant huntingtin form aggregates in neurons and causes neuronal dysfunction and degeneration in many ways including transcriptional dysregulation. Here, we report that the expression of mutant huntingtin in the mouse neuroblastoma cell results in massive transcriptional induction of several chemokines including monocyte chemoattractant protein-1 (MCP-1) and murine chemokine (KC). The mutant huntingtin expressing cells also exhibit proteasomal dysfunction and down-regulation of NF-kappaB activity in a time-dependent manner and both these phenomena regulate the expression of MCP-1 and KC. The expression of MCP-1 and KC are increased in the mutant huntingtin expressing cells in response to mild proteasome inhibition. However, the expression of MCP-1 and KC and proteasome activity are not altered and inflammation is rarely observed in the brain of 12-week-old Huntington's disease transgenic mice in comparison with their age-matched controls. Our result suggests that the mutant huntingtin-induced proteasomal dysfunction can up-regulate the expression of MCP-1 and KC in the neuronal cells and therefore might trigger the inflammation process.
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http://dx.doi.org/10.1111/j.1471-4159.2008.05823.xDOI Listing
February 2009

Blocking acid-sensing ion channel 1 alleviates Huntington's disease pathology via an ubiquitin-proteasome system-dependent mechanism.

Hum Mol Genet 2008 Oct 24;17(20):3223-35. Epub 2008 Jul 24.

Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.

Huntington's disease (HD) is a fatal neurodegenerative disorder. Despite a tremendous effort to develop therapeutic tools in several HD models, there is no effective cure at present. Acidosis has been observed previously in cellular and in in vivo models as well as in the brains of HD patients. Here we challenged HD models with amiloride (Ami) derivative benzamil (Ben), a chemical agent used to rescue acid-sensing ion channel (ASIC)-dependent acidotoxicity, to examine whether chronic acidosis is an important part of the HD pathomechanism and whether these drugs could be used as novel therapeutic agents. Ben markedly reduced the huntingtin-polyglutamine (htt-polyQ) aggregation in an inducible cellular system, and the therapeutic value of Ben was successfully recapitulated in the R6/2 animal model of HD. To reveal the mechanism of action, Ben was found to be able to alleviate the inhibition of the ubiquitin-proteasome system (UPS) activity, resulting in enhanced degradation of soluble htt-polyQ specifically in its pathological range. More importantly, we were able to demonstrate that blocking the expression of a specific isoform of ASIC (asic1a), one of the many molecular targets of Ben, led to an enhancement of UPS activity and this blockade also decreased htt-polyQ aggregation in the striatum of R6/2 mice. In conclusion, we believe that chemical compounds that target ASIC1a or pharmacological alleviation of UPS inhibition would be an effective and promising approach to combat HD and other polyQ-related disorders.
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http://dx.doi.org/10.1093/hmg/ddn218DOI Listing
October 2008

Expression of expanded polyglutamine proteins suppresses the activation of transcription factor NFkappaB.

J Biol Chem 2006 Dec 6;281(48):37017-24. Epub 2006 Oct 6.

Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122050, India.

A major pathological hallmark of the polyglutamine diseases is the formation of neuronal intranuclear inclusions of the disease proteins that are ubiquitinated and often associated with various transcription factors, chaperones, and proteasome components. However, how the expanded polyglutamine proteins or their aggregates elicit complex pathogenic responses in the neuronal cells is not fully understood. Here, we have demonstrated that the expression of expanded polyglutamine proteins down-regulated the NFkappaB-dependent transcriptional activity. The expression of expanded polyglutamine proteins increased the stability and the levels of IkappaB-alpha and its phosphorylated derivatives. We have also found that various NFkappaB subunits and IkappaB-alpha aberrantly interacted with the expanded polyglutamine proteins and associated with their aggregates. Finally, we have shown that several NFkappaB-dependent genes are down-regulated in the expanded polyglutamine protein-expressing cells and down-regulation of NFkappaB activity enhances expanded polyglutamine protein-induced cell death. Because the NFkappaB pathway plays a very important role in cell survival, altered regulation of this pathway in expanded polyglutamine protein-expressing cells might be linked with the disease pathogenesis.
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http://dx.doi.org/10.1074/jbc.M608095200DOI Listing
December 2006

Aspirin induces apoptosis through the inhibition of proteasome function.

J Biol Chem 2006 Sep 31;281(39):29228-35. Epub 2006 Jul 31.

Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122050, India.

Aspirin and other nonsteroidal anti-inflammatory drugs inhibit cell proliferation and induce apoptosis in various cancer cell lines, which is considered to be an important mechanism for their anti-tumor activity and prevention of carcinogenesis. However, the molecular mechanisms through which these compounds induce apoptosis are not well understood. Here we have found that aspirin treatment of the mouse Neuro 2a cells impaired the proteasome function and caused severe mitochondrial abnormalities. Treatment with aspirin lead to a dose- and time-dependent decrease in proteasome activity and an increase in the accumulation of ubiquitylated proteins in the cells, which correlated with its effect on cell death. Aspirin exposure also resulted in an increase in the half-life of pd1EGFP, a model substrate of proteasome, as well as various intracellular substrates like Bax, IkappaB-alpha, p53, and p27(kip1). Aspirin-induced proteasomal malfunction might be responsible, at least in part, for the down-regulation of NF-kappaB activity and neurite outgrowth. Finally, we have shown that aspirin treatment caused changes in the mitochondrial membrane potential, release of cytochrome c from mitochondria, and activation of caspase-9 and -3, which could be because of the proteasomal dysfunction.
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http://dx.doi.org/10.1074/jbc.M602629200DOI Listing
September 2006

Curcumin enhances the polyglutamine-expanded truncated N-terminal huntingtin-induced cell death by promoting proteasomal malfunction.

Biochem Biophys Res Commun 2006 Apr 28;342(4):1323-8. Epub 2006 Feb 28.

Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122 050, India.

Formation of neuronal intranuclear inclusions of the disease proteins that are ubiquitinated and often associated with various proteasome components is the major hallmark of the polyglutamine diseases. Curcumin is a polyphenolic compound having anti-inflammatory, anti-tumor, and anti-oxidative properties. Recently, curcumin has been reported to suppress the amyloid-beta accumulation, oxidative damage, and inflammation in the transgenic mice model of Alzheimer's disease. Here, we found that the treatment of curcumin increases the polyglutamine-expanded truncated N-terminal huntingtin (mutant huntingtin) aggregation and mutant huntingtin-dependent cell death. Curcumin also causes rapid proteasomal malfunction in the mutant huntingtin expressing cells in comparison with normal glutamine repeat expressing cells. Finally, we show that N-acetyl cysteine (NAC), a potent antioxidant, reverted the curcumin-induced mutant huntingtin aggregation and proteasomal malfunction in the mutant huntingtin expressing cells. NAC also protects curcumin-induced cell death. Our result suggests that curcumin promotes mutant huntingtin-induced cell death by mimicking proteasomal dysfunction.
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http://dx.doi.org/10.1016/j.bbrc.2006.02.104DOI Listing
April 2006

Oxidative stress promotes mutant huntingtin aggregation and mutant huntingtin-dependent cell death by mimicking proteasomal malfunction.

Biochem Biophys Res Commun 2006 Mar 3;342(1):184-90. Epub 2006 Feb 3.

Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122 050, India.

Huntington's disease (HD) is a familial neurodegenerative disorder caused by an abnormal expansion of CAG repeats in the coding region of huntingtin gene. A major hallmark of HD is the proteolytic production of N-terminal fragments of huntingtin containing polyglutamine repeats that form ubiquitinated aggregates in the nucleus and cytoplasm of the affected neurons. However, the mechanism by which the mutant huntingtin causes neurodegeneration is not well understood. Here, we found that oxidative stimuli enhance the polyglutamine-expanded truncated N-terminal huntingtin (mutant huntingtin) aggregation and mutant huntingtin-induced cell death. Oxidative stimuli also lead to rapid proteasomal dysfunction in the mutant huntingtin expressing cells as compared to normal glutamine repeat expressing cells. Overexpression of Cu/Zn superoxide dismutase (SOD1), Hsp40 or Hsp70 reverses the oxidative stress-induced proteasomal malfunction, mutant huntingtin aggregation, and death of the mutant huntingtin expressing cells. Finally, we show the higher levels of expression of SOD1 and DJ-1 in the mutant huntingtin expressing cells. Our result suggests that oxidative stress-induced proteasomal malfunction might be linked with mutant huntingtin-induced cell death.
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http://dx.doi.org/10.1016/j.bbrc.2006.01.136DOI Listing
March 2006

Curcumin induces stress response, neurite outgrowth and prevent NF-kappaB activation by inhibiting the proteasome function.

Neurotox Res 2006 Jan;9(1):29-37

Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon - 122 050, India.

Curcumin, a natural polyphenolic compound, has long been known as an anti-tumour and anti-inflammatory compound; although, the common mechanism through which it exhibits such properties are remains unclear. Recently, we reported that the curcumin-induced apoptosis is mediated through the impairment of ubiquitin proteasome system (UPS). Here, we show that curcumin disrupts UPS function by directly inhibiting the enzyme activity of the proteasome's 20S core catalytic component. Like other proteasome inhibitors, curcumin exposure induces neurite outgrowth and the stress response, as evident from the induction of various cytosolic and endoplasmic reticulum chaperones as well as induction of transcription factor CHOP/GADD153. The direct inhibition of proteasome activity also causes an increase in half-life of IkappaB-alpha that ultimately leads to the down-regulation of NF-kappaB activation. These results suggest that curcumin-induced proteasomal malfunction might be linked with both anti-proliferative and anti-inflammatory activities.
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http://dx.doi.org/10.1007/BF03033305DOI Listing
January 2006

Co-chaperone CHIP associates with expanded polyglutamine protein and promotes their degradation by proteasomes.

J Biol Chem 2005 Mar 21;280(12):11635-40. Epub 2005 Jan 21.

Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122-050, India.

A major hallmark of the polyglutamine diseases is the formation of neuronal intranuclear inclusions of the disease proteins that are ubiquitinated and often associated with various chaperones and proteasome components. But, how the polyglutamine proteins are ubiquitinated and degraded by the proteasomes are not known. Here, we demonstrate that CHIP (C terminus of Hsp70-interacting protein) co-immunoprecipitates with the polyglutamine-expanded huntingtin or ataxin-3 and associates with their aggregates. Transient overexpression of CHIP increases the ubiquitination and the rate of degradation of polyglutamine-expanded huntingtin or ataxin-3. Finally, we show that overexpression of CHIP suppresses the aggregation and cell death mediated by expanded polyglutamine proteins and the suppressive effect is more prominent when CHIP is overexpressed along with Hsc70.
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http://dx.doi.org/10.1074/jbc.M412042200DOI Listing
March 2005