301
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Buratti E, De Conti L, Stuani C, Romano M, Baralle M, Baralle F. Nuclear factor TDP-43 can affect selected microRNA levels. FEBS J 2010; 277:2268-81. [PMID: 20423455 DOI: 10.1111/j.1742-4658.2010.07643.x] [Citation(s) in RCA: 173] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
TDP-43 has recently been described as the major component of the inclusions found in the brain of patients with a variety of neurodegenerative diseases, such as frontotemporal lobar degeneration and amyotrophic lateral sclerosis. TDP-43 is a ubiquitous protein whose specific functions are probably crucial to establishing its pathogenic role. Apart from its involvement in transcription, splicing and mRNA stability, TDP-43 has also been described as a Drosha-associated protein. However, our knowledge of the role of TDP-43 in the microRNA (miRNA) synthesis pathway is limited to the association mentioned above. Here we report for the first time which changes occur in the total miRNA population following TDP-43 knockdown in culture cells. In particular, we have observed that let-7b and miR-663 expression levels are down- and upregulated, respectively. Interestingly, both miRNAs are capable of binding directly to TDP-43 in different positions: within the miRNA sequence itself (let-7b) or in the hairpin precursor (miR-663). Using microarray data and real-time PCR we have also identified several candidate transcripts whose expression levels are selectively affected by these TDP-43-miRNA interactions.
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Affiliation(s)
- Emanuele Buratti
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy
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302
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Khurana V, Lindquist S. Modelling neurodegeneration in Saccharomyces cerevisiae: why cook with baker's yeast? Nat Rev Neurosci 2010; 11:436-49. [PMID: 20424620 DOI: 10.1038/nrn2809] [Citation(s) in RCA: 192] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In ageing populations, neurodegenerative diseases increase in prevalence, exacting an enormous toll on individuals and their communities. Multiple complementary experimental approaches are needed to elucidate the mechanisms underlying these complex diseases and to develop novel therapeutics. Here, we describe why the budding yeast Saccharomyces cerevisiae has a unique role in the neurodegeneration armamentarium. As the best-understood and most readily analysed eukaryotic organism, S. cerevisiae is delivering mechanistic insights into cell-autonomous mechanisms of neurodegeneration at an interactome-wide scale.
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Affiliation(s)
- Vikram Khurana
- Department of Neurology, Brigham and Women's and Massachusetts General Hospitals, Harvard Medical School, Boston, Massachusetts, USA
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303
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Esaki M, Ogura T. ATP-bound form of the D1 AAA domain inhibits an essential function of Cdc48p/p97. Biochem Cell Biol 2010; 88:109-17. [PMID: 20130684 DOI: 10.1139/o09-116] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Cdc48p/p97 is a highly conserved essential AAA protein that is required for many cellular processes, and is identified as a causative gene for an autosomal dominant human disorder, inclusion body myopathy associated with Paget's disease of the bone and frontotemporal dementia (IBMPFD). Cdc48p/p97 is composed of an N-terminal domain, followed by two AAA domains (D1 and D2) whose ATPase activities have been characterized extensively. In this study, effects of mutations on the essential functions of yeast Cdc48p/p97 in vivo were systematically analyzed. IBMPFD-related mutations do not affect the essential functions of Cdc48p/p97. Loss of ATPase activity of D2 leads to loss of function of the protein in vivo. In contrast, ATPase activity of D1 per se is not essential, but a mutation locking D1 in an ATP-bound form is exceptionally lethal. Site-directed and random mutagenesis analyses suggest that the ATP-bound form of D1 changes an inter-domain interaction, thereby perturbing an essential function of Cdc48p/p97.
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Affiliation(s)
- Masatoshi Esaki
- Department of Molecular Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan.
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304
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Lagier-Tourenne C, Polymenidou M, Cleveland DW. TDP-43 and FUS/TLS: emerging roles in RNA processing and neurodegeneration. Hum Mol Genet 2010; 19:R46-64. [PMID: 20400460 PMCID: PMC3167692 DOI: 10.1093/hmg/ddq137] [Citation(s) in RCA: 734] [Impact Index Per Article: 52.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Accepted: 04/06/2010] [Indexed: 12/11/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are neurodegenerative diseases with clinical and pathological overlap. Landmark discoveries of mutations in the transactive response DNA-binding protein (TDP-43) and fused in sarcoma/translocated in liposarcoma (FUS/TLS) as causative of ALS and FTLD, combined with the abnormal aggregation of these proteins, have initiated a shifting paradigm for the underlying pathogenesis of multiple neurodegenerative diseases. TDP-43 and FUS/TLS are both RNA/DNA-binding proteins with striking structural and functional similarities. Their association with ALS and other neurodegenerative diseases is redirecting research efforts toward understanding the role of RNA processing regulation in neurodegeneration.
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Affiliation(s)
| | | | - Don W. Cleveland
- Ludwig Institute for Cancer Research, Department of Cellular and Molecular Medicine, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-6070, USA
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305
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Xiong Y, Coombes CE, Kilaru A, Li X, Gitler AD, Bowers WJ, Dawson VL, Dawson TM, Moore DJ. GTPase activity plays a key role in the pathobiology of LRRK2. PLoS Genet 2010; 6:e1000902. [PMID: 20386743 PMCID: PMC2851569 DOI: 10.1371/journal.pgen.1000902] [Citation(s) in RCA: 161] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Accepted: 03/09/2010] [Indexed: 11/18/2022] Open
Abstract
Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are associated with late-onset, autosomal-dominant, familial Parkinson's disease (PD) and also contribute to sporadic disease. The LRRK2 gene encodes a large protein with multiple domains, including functional Roc GTPase and protein kinase domains. Mutations in LRRK2 most likely cause disease through a toxic gain-of-function mechanism. The expression of human LRRK2 variants in cultured primary neurons induces toxicity that is dependent on intact GTP binding or kinase activities. However, the mechanism(s) underlying LRRK2-induced neuronal toxicity is poorly understood, and the contribution of GTPase and/or kinase activity to LRRK2 pathobiology is not well defined. To explore the pathobiology of LRRK2, we have developed a model of LRRK2 cytotoxicity in the baker's yeast Saccharomyces cerevisiae. Protein domain analysis in this model reveals that expression of GTPase domain-containing fragments of human LRRK2 are toxic. LRRK2 toxicity in yeast can be modulated by altering GTPase activity and is closely associated with defects in endocytic vesicular trafficking and autophagy. These truncated LRRK2 variants induce similar toxicity in both yeast and primary neuronal models and cause similar vesicular defects in yeast as full-length LRRK2 causes in primary neurons. The toxicity induced by truncated LRRK2 variants in yeast acts through a mechanism distinct from toxicity induced by human alpha-synuclein. A genome-wide genetic screen identified modifiers of LRRK2-induced toxicity in yeast including components of vesicular trafficking pathways, which can also modulate the trafficking defects caused by expression of truncated LRRK2 variants. Our results provide insight into the basic pathobiology of LRRK2 and suggest that the GTPase domain may contribute to the toxicity of LRRK2. These findings may guide future therapeutic strategies aimed at attenuating LRRK2-mediated neurodegeneration.
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Affiliation(s)
- Yulan Xiong
- NeuroRegeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Departments of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Candice E. Coombes
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Austin Kilaru
- Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Xiaojie Li
- NeuroRegeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Departments of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Aaron D. Gitler
- Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - William J. Bowers
- Center for Neural Development and Disease, Department of Neurology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Valina L. Dawson
- NeuroRegeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Departments of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Ted M. Dawson
- NeuroRegeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Departments of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- * E-mail: (TMD); (DJM)
| | - Darren J. Moore
- NeuroRegeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Departments of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Brain Mind Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
- * E-mail: (TMD); (DJM)
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306
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Douglas PM, Cyr DM. Interplay between protein homeostasis networks in protein aggregation and proteotoxicity. Biopolymers 2010; 93:229-36. [PMID: 19768782 DOI: 10.1002/bip.21304] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The misfolding and aggregation of disease proteins is characteristic of numerous neurodegenerative diseases. Particular neuronal populations are more vulnerable to proteotoxicity while others are more apt to tolerate the misfolding and aggregation of disease proteins. Thus, the cellular environment must play a significant role in determining whether disease proteins are converted into toxic or benign forms. The endomembrane network of eukaryotes divides the cell into different subcellular compartments that possess distinct sets of molecular chaperones and protein interaction networks. Chaperones act as agonists and antagonists of disease protein aggregation to prevent the accumulation of toxic intermediates in the aggregation pathway. Interacting partners can also modulate the conformation and localization of disease proteins and thereby influence proteotoxicity. Thus, interplay between these protein homeostasis network components can modulate the self-association of disease proteins and determine whether they elicit a toxic or benign outcome.
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Affiliation(s)
- Peter M Douglas
- Department of Cell and Developmental Biology, School of Medicine, University of North Carolina, Chapel Hill, NC 27599-7090, USA
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307
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Chen-Plotkin AS, Lee VMY, Trojanowski JQ. TAR DNA-binding protein 43 in neurodegenerative disease. Nat Rev Neurol 2010; 6:211-20. [PMID: 20234357 DOI: 10.1038/nrneurol.2010.18] [Citation(s) in RCA: 338] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In 2006, TAR DNA-binding protein 43 (TDP-43), a highly conserved nuclear protein, was identified as the major disease protein in amyotrophic lateral sclerosis (ALS) and in the most common variant of frontotemporal lobar degeneration (FTLD), FTLD-U, which is characterized by cytoplasmic inclusions that stain positive for ubiquitin but negative for tau and alpha-synuclein. Since then, rapid advances have been made in our understanding of the physiological function of TDP-43 and the role of this protein in neurodegeneration. These advances link ALS and FTLD-U (now designated FTLD-TDP) to a shared mechanism of disease. In this Review, we summarize the current evidence regarding the normal function of TDP-43 and the TDP-43 pathology observed in FTLD-TDP, ALS, and other neurodegenerative diseases wherein TDP-43 pathology co-occurs with other disease-specific lesions (for example, with amyloid plaques and neurofibrillary tangles in Alzheimer disease). Moreover, we discuss the accumulating data that support our view that FTLD-TDP and ALS represent two ends of a spectrum of primary TDP-43 proteinopathies. Finally, we comment on the importance of recent advances in TDP-43-related research to neurological practice, including the new opportunities to develop better diagnostics and disease-modifying therapies for ALS, FTLD-TDP, and related disorders exhibiting TDP-43 pathology.
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Affiliation(s)
- Alice S Chen-Plotkin
- Department of Neurology, University of Pennsylvania School of Medicine, 3600 Spruce Street, Philadelphia, PA 19104-4283, USA
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308
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Gendron TF, Josephs KA, Petrucelli L. Review: transactive response DNA-binding protein 43 (TDP-43): mechanisms of neurodegeneration. Neuropathol Appl Neurobiol 2010; 36:97-112. [PMID: 20202122 DOI: 10.1111/j.1365-2990.2010.01060.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Since the identification of phosphorylated and truncated transactive response DNA-binding protein 43 (TDP-43) as a primary component of ubiquitinated inclusions in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitin-positive inclusions, and the discovery that mutations in the TDP-43 gene cause ALS, much effort has been directed towards establishing how TDP-43 contributes to the development of neurodegeneration. Although few in vivo models are presently available, findings thus far strongly support the involvement of abnormally modified TDP-43 in promoting TDP-43 aggregation and cellular mislocalization. Therefore, TDP-43-mediated neurotoxicity is likely to result from a combination of toxic gains of function conferred by TDP-43 inclusions as well as from the loss of normal TDP-43 function. Nonetheless, the exact neurotoxic TDP-43 species remain unclear, as do the mechanism(s) by which they cause neuronal death. Moreover, little is currently known about the roles of TDP-43, both in the nucleus and the cytoplasm, making it difficult to truly appreciate the detrimental consequences of aberrant TDP-43 function. This review will summarize what is currently understood regarding normal TDP-43 function and the involvement of TDP-43 in neurodegeneration, and will also highlight some of the many remaining questions in need of further investigation.
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Affiliation(s)
- T F Gendron
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA
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309
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TDP-43 transgenic mice develop spastic paralysis and neuronal inclusions characteristic of ALS and frontotemporal lobar degeneration. Proc Natl Acad Sci U S A 2010; 107:3858-63. [PMID: 20133711 DOI: 10.1073/pnas.0912417107] [Citation(s) in RCA: 428] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Neuronal cytoplasmic and intranuclear aggregates of RNA-binding protein TDP-43 are a hallmark feature of neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). ALS and FTLD show a considerable clinical and pathological overlap and occur as both familial and sporadic forms. Though missense mutations in TDP-43 cause rare forms of familial ALS, it is not yet known whether this is due to loss of TDP-43 function or gain of aberrant function. Moreover, the role of wild-type (WT) TDP-43, associated with the majority of familial and sporadic ALS/FTLD patients, is also currently unknown. Generating homozygous and hemizygous WT human TDP-43 transgenic mouse lines, we show here a dose-dependent degeneration of cortical and spinal motor neurons and development of spastic quadriplegia reminiscent of ALS. A dose-dependent degeneration of nonmotor cortical and subcortical neurons characteristic of FTLD was also observed. Neurons in the affected spinal cord and brain regions showed accumulation of TDP-43 nuclear and cytoplasmic aggregates that were both ubiquitinated and phosphorylated as observed in ALS/FTLD patients. Moreover, the characteristic approximately 25-kDa C-terminal fragments (CTFs) were also recovered from nuclear fractions and correlated with disease development and progression in WT TDP-43 mice. These findings suggest that approximately 25-kDa TDP-43 CTFs are noxious to neurons by a gain of aberrant nuclear function.
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310
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Cytoplasmic mislocalization of TDP-43 is toxic to neurons and enhanced by a mutation associated with familial amyotrophic lateral sclerosis. J Neurosci 2010; 30:639-49. [PMID: 20071528 DOI: 10.1523/jneurosci.4988-09.2010] [Citation(s) in RCA: 392] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Mutations in the gene encoding TDP-43-the major protein component of neuronal aggregates characteristic of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) with ubiquitin-positive inclusion bodies-have been linked to familial forms of both disorders. Aggregates of TDP-43 in cortical and spinal motorneurons in ALS, or in neurons of the frontal and temporal cortices in FTLD, are closely linked to neuron loss and atrophy in these areas. However, the mechanism by which TDP-43 mutations lead to neurodegeneration is unclear. To investigate the pathogenic role of TDP-43 mutations, we established a model of TDP-43 proteinopathies by expressing fluorescently tagged wild-type and mutant TDP-43 in primary rat cortical neurons. Expression of mutant TDP-43 was toxic to neurons, and mutant-specific toxicity was associated with increased cytoplasmic mislocalization of TDP-43. Inclusion bodies were not necessary for the toxicity and did not affect the risk of cell death. Cellular survival was unaffected by the total amount of exogenous TDP-43 in the nucleus, but the amount of cytoplasmic TDP-43 was a strong and independent predictor of neuronal death. These results suggest that mutant TDP-43 is mislocalized to the cytoplasm, where it exhibits a toxic gain-of-function and induces cell death.
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311
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TDP-43 Dimerizes in Human Cells in Culture. Cell Mol Neurobiol 2009; 30:641-52. [DOI: 10.1007/s10571-009-9489-9] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Accepted: 12/16/2009] [Indexed: 10/20/2022]
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312
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Braun RJ, Büttner S, Ring J, Kroemer G, Madeo F. Nervous yeast: modeling neurotoxic cell death. Trends Biochem Sci 2009; 35:135-44. [PMID: 19926288 DOI: 10.1016/j.tibs.2009.10.005] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 10/21/2009] [Accepted: 10/21/2009] [Indexed: 01/23/2023]
Abstract
Neurodegeneration is characterized by the disease-specific loss of neuronal activity, culminating in the irreversible destruction of neurons. Neuronal cell death can proceed via distinct subroutines such as apoptosis and necrosis, but the underlying molecular mechanisms remain poorly understood. Saccharomyces cerevisiae is an established model for programmed cell death, characterized by distinct cell death pathways conserved from yeast to mammals. Recently, yeast models for several major classes of neurodegeneration, namely alpha-synucleinopathies, polyglutamine disorders, beta-amyloid diseases, tauopathies, and TDP-43 proteinopathies, have been established. Heterologous expression of the human proteins implicated in these disorders has unraveled important insights in their detrimental function, pointing to ways in which yeast might advance the mechanistic dissection of cell death pathways relevant for human neurodegeneration.
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Affiliation(s)
- Ralf J Braun
- Institute of Molecular Biosciences, Department of Microbiology, Karl-Franzens-University of Graz, Graz, Austria
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313
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Gitcho MA, Bigio EH, Mishra M, Johnson N, Weintraub S, Mesulam M, Rademakers R, Chakraverty S, Cruchaga C, Morris JC, Goate AM, Cairns NJ. TARDBP 3'-UTR variant in autopsy-confirmed frontotemporal lobar degeneration with TDP-43 proteinopathy. Acta Neuropathol 2009; 118:633-45. [PMID: 19618195 PMCID: PMC2783457 DOI: 10.1007/s00401-009-0571-7] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2009] [Revised: 07/03/2009] [Accepted: 07/04/2009] [Indexed: 12/12/2022]
Abstract
Pathogenic mutations in the gene encoding TDP-43, TARDBP, have been reported in familial amyotrophic lateral sclerosis (FALS) and, more recently, in families with a heterogeneous clinical phenotype including both ALS and frontotemporal lobar degeneration (FTLD). In our previous study, sequencing analyses identified one variant in the 3'-untranslated region (3'-UTR) of the TARDBP gene in two affected members of one family with bvFTD and ALS and in one unrelated clinically assessed case of FALS. Since that study, brain tissue has become available and provides autopsy confirmation of FTLD-TDP in the proband and ALS in the brother of the bvFTD-ALS family and the neuropathology of those two cases is reported here. The 3'-UTR variant was not found in 982 control subjects (1,964 alleles). To determine the functional significance of this variant, we undertook quantitative gene expression analysis. Allele-specific amplification showed a significant increase of 22% (P < 0.05) in disease-specific allele expression with a twofold increase in total TARDBP mRNA. The segregation of this variant in a family with clinical bvFTD and ALS adds to the spectrum of clinical phenotypes previously associated with TARDBP variants. In summary, TARDBP variants may result in clinically and neuropathologically heterogeneous phenotypes linked by a common molecular pathology called TDP-43 proteinopathy.
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Affiliation(s)
- Michael A. Gitcho
- Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, MO, USA
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, USA
| | - Eileen H. Bigio
- Alzheimer Disease Center, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Manjari Mishra
- Alzheimer Disease Center, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Nancy Johnson
- Alzheimer Disease Center, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
- Department of Psychiatry, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Sandra Weintraub
- Alzheimer Disease Center, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
- Department of Cognitive Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Marsel Mesulam
- Alzheimer Disease Center, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
- Department of Cognitive Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Rosa Rademakers
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
| | - Sumi Chakraverty
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA
| | - Carlos Cruchaga
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA
| | - John C. Morris
- Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, MO, USA
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, USA
- Department of Pathology and Immunology, Washington University School of Medicine, Campus Box 8118, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Alison M. Goate
- Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, MO, USA
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, USA
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA
- Department of Genetics, Washington University School of Medicine, St. Louis, MO, USA
| | - Nigel J. Cairns
- Alzheimer's Disease Research Center, Washington University School of Medicine, St. Louis, MO, USA
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, USA
- Department of Pathology and Immunology, Washington University School of Medicine, Campus Box 8118, 660 South Euclid Avenue, St. Louis, MO 63110, USA
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314
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Colombrita C, Zennaro E, Fallini C, Weber M, Sommacal A, Buratti E, Silani V, Ratti A. TDP-43 is recruited to stress granules in conditions of oxidative insult. J Neurochem 2009; 111:1051-61. [PMID: 19765185 DOI: 10.1111/j.1471-4159.2009.06383.x] [Citation(s) in RCA: 386] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Transactive response DNA-binding protein 43 (TDP-43) forms abnormal ubiquitinated and phosphorylated inclusions in brain tissues from patients with amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration. TDP-43 is a DNA/RNA-binding protein involved in RNA processing, such as transcription, pre-mRNA splicing, mRNA stabilization and transport to dendrites. We found that in response to oxidative stress and to environmental insults of different types TDP-43 is capable to assemble into stress granules (SGs), ribonucleoprotein complexes where protein synthesis is temporarily arrested. We demonstrated that a specific aminoacidic interval (216-315) in the C-terminal region and the RNA-recognition motif 1 domain are both implicated in TDP-43 participation in SGs as their deletion prevented the recruitment of TDP-43 into SGs. Our data show that TDP-43 is a specific component of SGs and not of processing bodies, although we proved that TDP-43 is not necessary for SG formation, and its gene silencing does not impair cell survival during stress. The analysis of spinal cord tissue from ALS patients showed that SG markers are not entrapped in TDP-43 pathological inclusions. Although SGs were not evident in ALS brains, we speculate that an altered control of mRNA translation in stressful conditions may trigger motor neuron degeneration at early stages of the disease.
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Affiliation(s)
- Claudia Colombrita
- Department of Neurology and Laboratory of Neuroscience, Dino Ferrari Center, Università degli Studi di Milano - IRCCS Istituto Auxologico Italiano, Milan, Italy
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315
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Rohn TT. Cytoplasmic inclusions of TDP-43 in neurodegenerative diseases: a potential role for caspases. Histol Histopathol 2009; 24:1081-6. [PMID: 19554515 PMCID: PMC2791961 DOI: 10.14670/hh-24.1081] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
TAR DNA-binding protein-43 (TDP-43) proteinopathies are classified based upon the extent of modified TDP-43 inclusions and include a growing number of neurodegenerative diseases including amyotrophic lateral sclerosis (ALS), frontotemporal lobar degeneration with ubiquitin immunoreactive, tau negative inclusions (FTLD-U) and FTLD with motor neuron disease (FTLD-MND). In addition, TDP-43 inclusions have also been identified in a number of other neurodegenerative disorders including Alzheimer's disease, corticobasal degeneration, Lewy body related diseases and Pick's disease. Current understanding suggests that in these diseases, TDP-43 is relocated from the nucleus to the cytoplasm and sequestered into inclusions that contain modified TDP-43. Major modifications of TDP-43 have been identified as being hyperphosphorylation and proteolytic cleavage by caspases. In this review a summary of the major findings regarding the proteolytic modification of TDP-43 will be discussed as well as potential toxic-gain mechanisms these fragments may cause including cytoskeletal disruptions.
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Affiliation(s)
- Troy T Rohn
- Department of Biology, Science/Nursing Building, Room 228, Boise State University, Boise, Idaho 83725, USA.
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316
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Yamashita M, Nonaka T, Arai T, Kametani F, Buchman VL, Ninkina N, Bachurin SO, Akiyama H, Goedert M, Hasegawa M. Methylene blue and dimebon inhibit aggregation of TDP-43 in cellular models. FEBS Lett 2009; 583:2419-24. [PMID: 19560462 DOI: 10.1016/j.febslet.2009.06.042] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Revised: 06/10/2009] [Accepted: 06/22/2009] [Indexed: 12/12/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U) are major neurodegenerative diseases with TDP-43 pathology. Here we investigated the effects of methylene blue (MB) and dimebon, two compounds that have been reported to be beneficial in phase II clinical trials of Alzheimer's disease (AD), on the formation of TDP-43 aggregates in SH-SY5Y cells. Following treatment with 0.05 microM MB or 5 microM dimebon, the number of TDP-43 aggregates was reduced by 50% and 45%, respectively. The combined use of MB and dimebon resulted in a 80% reduction in the number. These findings were confirmed by immunoblot analysis. The results indicate that MB and dimebon may be useful for the treatment of ALS, FTLD-U and other TDP-43 proteinopathies.
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Affiliation(s)
- Makiko Yamashita
- Department of Molecular Neurobiology, Tokyo Institute of Psychiatry, Tokyo Metropolitan Organization for Medical Reearch, 2-1-8 Kamikitazawa, Setagaya-ku, Tokyo 156-8585, Japan
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317
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Verma A, Tandan R. TDP-43: a reliable immunohistochemistry marker for inclusion body myositis? Muscle Nerve 2009; 40:8-9. [PMID: 19533631 DOI: 10.1002/mus.21455] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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318
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Nonaka T, Kametani F, Arai T, Akiyama H, Hasegawa M. Truncation and pathogenic mutations facilitate the formation of intracellular aggregates of TDP-43. Hum Mol Genet 2009; 18:3353-64. [PMID: 19515851 DOI: 10.1093/hmg/ddp275] [Citation(s) in RCA: 232] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
TAR DNA binding protein of 43 kDa (TDP-43) is a major component of the ubiquitin-positive inclusions found in the brain of patients with frontotemporal lobar degeneration (FTLD-U) and amyotrophic lateral sclerosis (ALS). Here, we report that expression of TDP-43 C-terminal fragments as green fluorescent protein (GFP) fusions in SH-SY5Y cells results in the formation of abnormally phosphorylated and ubiquitinated inclusions that are similar to those found in FTLD-U and ALS. Co-expression of DsRed-tagged full-length TDP-43 with GFP-tagged C-terminal fragments of TDP-43 causes formation of cytoplasmic inclusions positive for both GFP and DsRed. Cells with GFP and DsRed positive inclusions lack normal nuclear staining for endogenous TDP-43. These results suggest that GFP-tagged C-terminal fragments of TDP-43 are bound not only to transfected DsRed-full-length TDP-43 but also to endogenous TDP-43. Endogenous TDP-43 may be recruited to cytoplasmic aggregates of TDP-43 C-terminal fragments, which results in the failure of its nuclear localization and function. Interestingly, expression of GFP-tagged TDP-43 C-terminal fragments harboring pathogenic mutations that cause ALS significantly enhances the formation of inclusions. We also identified cleavage sites of TDP-43 C-terminal fragments deposited in the FTLD-U brains using mass spectrometric analyses. We propose that generation and aggregation of phosphorylated C-terminal fragments of TDP-43 play a primary role in the formation of inclusions and resultant loss of normal TDP-43 localization, leading to neuronal degeneration in TDP-43 proteinopathy.
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Affiliation(s)
- Takashi Nonaka
- Department of Molecular Neurobiology, Tokyo Metropolitan Organization for Medical Research, Tokyo, Japan.
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319
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Johnson BS, Snead D, Lee JJ, McCaffery JM, Shorter J, Gitler AD. TDP-43 is intrinsically aggregation-prone, and amyotrophic lateral sclerosis-linked mutations accelerate aggregation and increase toxicity. J Biol Chem 2009; 284:20329-39. [PMID: 19465477 DOI: 10.1074/jbc.m109.010264] [Citation(s) in RCA: 590] [Impact Index Per Article: 39.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Non-amyloid, ubiquitinated cytoplasmic inclusions containing TDP-43 and its C-terminal fragments are pathological hallmarks of amyotrophic lateral sclerosis (ALS), a fatal motor neuron disorder, and frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U). Importantly, TDP-43 mutations are linked to sporadic and non-SOD1 familial ALS. However, TDP-43 is not the only protein in disease-associated inclusions, and whether TDP-43 misfolds or is merely sequestered by other aggregated components is unclear. Here, we report that, in the absence of other components, TDP-43 spontaneously forms aggregates bearing remarkable ultrastructural similarities to TDP-43 deposits in degenerating neurons of ALS and FTLD-U patients [corrected] . The C-terminal domain of TDP-43 is critical for spontaneous aggregation. Several ALS-linked TDP-43 mutations within this domain (Q331K, M337V, Q343R, N345K, R361S, and N390D) increase the number of TDP-43 aggregates and promote toxicity in vivo. Importantly, mutations that promote toxicity in vivo accelerate aggregation of pure TDP-43 in vitro. Thus, TDP-43 is intrinsically aggregation-prone, and its propensity for toxic misfolding trajectories is accentuated by specific ALS-linked mutations.
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Affiliation(s)
- Brian S Johnson
- Department of Cell and Developmental Biology, the University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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320
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Aberrant cleavage of TDP-43 enhances aggregation and cellular toxicity. Proc Natl Acad Sci U S A 2009; 106:7607-12. [PMID: 19383787 DOI: 10.1073/pnas.0900688106] [Citation(s) in RCA: 465] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Inclusions of TAR DNA-binding protein-43 (TDP-43), a nuclear protein that regulates transcription and RNA splicing, are the defining histopathological feature of frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-Us) and sporadic and familial forms of amyotrophic lateral sclerosis (ALS). In ALS and FTLD-U, aggregated, ubiquitinated, and N-terminally truncated TDP-43 can be isolated from brain tissue rich in neuronal and glial cytoplasmic inclusions. The loss of TDP-43 function resulting from inappropriate cleavage, translocation from the nucleus, or its sequestration into inclusions could play important roles in neurodegeneration. However, it is not known whether TDP-43 fragments directly mediate toxicity and, more specifically, whether their abnormal aggregation is a cause or consequence of pathogenesis. We report that the ectopic expression of a approximately 25-kDa TDP-43 fragment corresponding to the C-terminal truncation product of caspase-cleaved TDP-43 leads to the formation of toxic, insoluble, and ubiquitin- and phospho-positive cytoplasmic inclusions within cells. The 25-kDa C-terminal fragment is more prone to phosphorylation at S409/S410 than full-length TDP-43, but phosphorylation at these sites is not required for inclusion formation or toxicity. Although this fragment shows no biological activity, its exogenous expression neither inhibits the function nor causes the sequestration of full-length nuclear TDP-43, suggesting that the 25-kDa fragment can induce cell death through a toxic gain-of-function. Finally, by generating a conformation-dependent antibody that detects C-terminal fragments, we show that this toxic cleavage product is specific for pathologic inclusions in human TDP-43 proteinopathies.
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321
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The role of transactive response DNA-binding protein-43 in amyotrophic lateral sclerosis and frontotemporal dementia. Curr Opin Neurol 2009; 21:693-700. [PMID: 18989115 DOI: 10.1097/wco.0b013e3283168d1d] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
PURPOSE OF REVIEW We examine current evidence that the transactive response DNA-binding protein (TDP-43) plays a pathogenic role in both amyotrophic lateral sclerosis and frontotemporal dementia. RECENT FINDINGS TDP-43 was recently identified as the major pathological protein in sporadic amyotrophic lateral sclerosis and in the most common pathological subtype of frontotemporal dementia, frontotemporal lobar degeneration with ubiquitinated inclusions. In these conditions, abnormal C-terminal fragments of TDP-43 are ubiquitinated, hyperphosphorylated and accumulate as cellular inclusions in neurons and glia. Cells with inclusions show absence of the normal nuclear TDP-43 localization. Recently, missense mutations in the gene encoding TDP-43 have been identified in patients with sporadic and familial amyotrophic lateral sclerosis. SUMMARY The recent discovery of pathological TDP-43 in both amyotrophic lateral sclerosis and frontotemporal lobar degeneration with ubiquitinated inclusions confirms that these are closely related conditions within a new biochemical class of neurodegenerative disease, the TDP-43 proteinopathies.
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322
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Kim SH, Shi Y, Hanson KA, Williams LM, Sakasai R, Bowler MJ, Tibbetts RS. Potentiation of amyotrophic lateral sclerosis (ALS)-associated TDP-43 aggregation by the proteasome-targeting factor, ubiquilin 1. J Biol Chem 2009; 284:8083-92. [PMID: 19112176 PMCID: PMC2658102 DOI: 10.1074/jbc.m808064200] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2008] [Revised: 12/24/2008] [Indexed: 12/12/2022] Open
Abstract
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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Affiliation(s)
- Sang Hwa Kim
- Department of Pharmacology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, USA
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323
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Kametani F, Nonaka T, Suzuki T, Arai T, Dohmae N, Akiyama H, Hasegawa M. Identification of casein kinase-1 phosphorylation sites on TDP-43. Biochem Biophys Res Commun 2009; 382:405-9. [PMID: 19285963 DOI: 10.1016/j.bbrc.2009.03.038] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2009] [Accepted: 03/08/2009] [Indexed: 12/12/2022]
Abstract
TAR DNA-binding protein of 43 kDa (TDP-43) is deposited as hyperphosphorylated cytoplasmic and intranuclear inclusions in brains of patients with frontotemporal lobar degeneration with ubiquitinated inclusions and amyotrophic lateral sclerosis. In this study, we identified 29 phosphorylation sites on recombinant TDP-43 that are phosphorylated by casein kinase-1 (CK1). Interestingly, 18 of them were located in the C-terminal glycine-rich region of TDP-43. Our results indicate that CK1-mediated phosphorylation may play a role in the pathogenesis of these diseases.
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Affiliation(s)
- Fuyuki Kametani
- Department of Molecular Neurobiology, Tokyo Institute of Psychiatry, Tokyo Metropolitan Organization for Medical Research, Tokyo, Japan.
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324
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Igaz LM, Kwong LK, Chen-Plotkin A, Winton MJ, Unger TL, Xu Y, Neumann M, Trojanowski JQ, Lee VMY. Expression of TDP-43 C-terminal Fragments in Vitro Recapitulates Pathological Features of TDP-43 Proteinopathies. J Biol Chem 2009; 284:8516-24. [PMID: 19164285 DOI: 10.1074/jbc.m809462200] [Citation(s) in RCA: 282] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The disease protein in frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U) and amyotrophic lateral sclerosis (ALS) was identified recently as the TDP-43 (TAR DNA-binding protein 43), thereby providing a molecular link between these two disorders. In FTLD-U and ALS, TDP-43 is redistributed from its normal nuclear localization to form cytoplasmic insoluble aggregates. Moreover, pathological TDP-43 is abnormally ubiquitinated, hyperphosphorylated, and N-terminally cleaved to generate C-terminal fragments (CTFs). However, the specific cleavage site(s) and the biochemical properties as well as the functional consequences of pathological TDP-43 CTFs remained unknown. Here we have identified the specific cleavage site, Arg(208), of a pathological TDP-43 CTF purified from FTLD-U brains and show that the expression of this and other TDP-43 CTFs in cultured cells recapitulates key features of TDP-43 proteinopathy. These include the formation of cytoplasmic aggregates that are ubiquitinated and abnormally phosphorylated at sites found in FTLD-U and ALS brain and spinal cord samples. Furthermore, we observed splicing abnormalities in a cell culture system expressing TDP-43 CTFs, and this is significant because the regulation of exon splicing is a known function of TDP-43. Thus, our results show that TDP-43 CTF expression recapitulates key biochemical features of pathological TDP-43 and support the hypothesis that the generation of TDP-43 CTFs is an important step in the pathogenesis of FTLD-U and ALS.
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Affiliation(s)
- Lionel M Igaz
- Center for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, USA
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325
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Buratti E, Baralle FE. The molecular links between TDP-43 dysfunction and neurodegeneration. ADVANCES IN GENETICS 2009; 66:1-34. [PMID: 19737636 DOI: 10.1016/s0065-2660(09)66001-6] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
TDP-43 nuclear protein is involved in several major neurodegenerative diseases that include frontotemporal lobar degeneration with ubiquitin (FTLD-U) bodies and amyotrophic lateral sclerosis (ALS). As a consequence, the role played by this protein in both normal and diseased cellular metabolism has come under very close scrutiny. In the neuronal tissues of affected individuals TDP-43 undergoes aberrant localization to the cytoplasm to form insoluble aggregates. Furthermore, it is subject to degradation, ubiquitination, and phosphorylation. Understanding the pathways that lead to these changes will be crucial to define the functional role played by this protein in disease. Several recent biochemical and molecular studies have provided new information regarding the potential physiological consequences of these modifications. Moreover, the discovery of TDP-43 mutations associated with disease in a limited number of cases and the data from existing animal models have strengthened the proposed links between this protein and disease. In this review we will discuss the available data regarding the biochemical and functional changes that transform the wild-type endogenous TDP-43 in its pathological form. Furthermore, we will concentrate on examining the potential pathological mechanisms mediated by TDP-43 in different gain- versus loss-of-function scenarios. In the near future, this knowledge will hopefully increase our knowledge on disease progression and development. Moreover, it will allow the design of innovative therapeutic strategies for these pathologies based on the specific molecular defects causing the disease.
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Affiliation(s)
- Emanuele Buratti
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy
| | - Francisco E Baralle
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy
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326
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Current awareness on yeast. Yeast 2008. [DOI: 10.1002/yea.1559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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327
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Current world literature. Trauma and rehabilitation. Curr Opin Neurol 2008; 21:762-4. [PMID: 18989123 DOI: 10.1097/wco.0b013e32831cbb85] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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328
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Thorpe JR, Tang H, Atherton J, Cairns NJ. Fine structural analysis of the neuronal inclusions of frontotemporal lobar degeneration with TDP-43 proteinopathy. J Neural Transm (Vienna) 2008; 115:1661-71. [PMID: 18974920 DOI: 10.1007/s00702-008-0137-1] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2008] [Accepted: 10/05/2008] [Indexed: 12/12/2022]
Abstract
TAR DNA-binding protein of 43 kDa (TDP-43) is a major component of the pathological inclusions of frontotemporal lobar degeneration with TDP-43 proteinopathy, also called FTLD with ubiquitin-positive, tau-negative inclusions (FTLD-U), and motor neuron disease (MND). TDP-43 is predominantly expressed in the nucleus and regulates gene expression and splicing. In FTLD with TDP-43 proteinopathy, neuronal inclusions present variably as cytoplasmic inclusions (NCIs), dystrophic neurites (DNs), and intranuclear inclusions (NIIs), leading to a fourfold neuropathological classification correlating with genotype. There have been few fine structural studies of these inclusions. Thus, we undertook an immunoelectron microscopic study of FTLD with TDP-43 proteinopathy, including sporadic and familial cases with progranulin (GRN) mutation. TDP-43-immunoreactive inclusions comprised two components: granular and filamentous. Filament widths, expressed as mean (range) were: NCI, 9 nm (4-16 nm); DN, 10 nm (5-16 nm); NII, 18 nm (9-50 nm). Morphologically distinct inclusion components may reflect the process of TDP-43 aggregation and interaction with other proteins: determining these latter may contribute towards understanding the heterogeneous pathogenesis of FTLD with TDP-43 proteinopathy.
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Affiliation(s)
- Julian R Thorpe
- The Sussex Centre for Advanced Microscopy, University of Sussex, Falmer, Brighton, East Sussex, BN1 9QG, UK.
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329
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Ayala YM, Zago P, D'Ambrogio A, Xu YF, Petrucelli L, Buratti E, Baralle FE. Structural determinants of the cellular localization and shuttling of TDP-43. J Cell Sci 2008; 121:3778-85. [PMID: 18957508 DOI: 10.1242/jcs.038950] [Citation(s) in RCA: 437] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
TDP-43 (also known as TARDBP) regulates different processes of gene expression, including transcription and splicing, through RNA and DNA binding. Moreover, recent reports have shown that the protein interacts with the 3'UTRs of specific mRNAs. The aberrant cellular distribution and aggregation of TDP-43 were recently reported in neurodegenerative diseases, namely frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). A detailed description of the determinants for cellular localization has yet to emerge, including information on how the known functions of TDP-43 and cellular targeting affect each other. We provide the first experimental evidence that TDP-43 continuously shuttles between nucleus and cytoplasm in a transcription-dependent manner. Furthermore, we investigate the role of the functional TDP-43 domains in determining cellular targeting through a combination of immunofluorescence and biochemical fractionation methods. Our analyses indicate that the C-terminus is essential for solubility and cellular localization, because its deletion results in the formation of large nuclear and cytoplasmic aggregates. Disruption of the RNA-recognition domain required for RNA and DNA binding, however, alters nuclear distribution by decreasing TDP-43 presence in the nucleoplasm. Our findings suggest that TDP-43 solubility and localization are particularly sensitive to disruptions that extend beyond the newly found nuclear localization signal and depend on a combination of factors that are closely connected to the functional properties of this protein.
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Affiliation(s)
- Youhna M Ayala
- International Centre for Genetic Engineering and Biotechnology (ICGEB), 34012 Trieste, Italy
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330
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Wang IF, Wu LS, Shen CKJ. TDP-43: an emerging new player in neurodegenerative diseases. Trends Mol Med 2008; 14:479-85. [PMID: 18929508 DOI: 10.1016/j.molmed.2008.09.001] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Revised: 09/01/2008] [Accepted: 09/01/2008] [Indexed: 12/12/2022]
Abstract
Until a couple of years ago, TAR-DNA-binding protein-43 (TDP-43) was a relatively unknown nuclear protein implicated in transcriptional repression and splicing. Since 2006, when the protein was reported to be present in inclusions in the neurons and/or glial cells of a range of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), frontotemporal lobar degeneration with ubiquitin-positive, tau- and alpha-synuclein-negative inclusions (FTLD-U) and Alzheimer's disease (AD), many reports on the medical aspects of TDP-43 have been published. Here, we summarize the current literature on TDP-43, focusing on recent studies that provide clues to the function of TDP-43. Using this information and database analysis, we also suggest a molecular and cellular model for possible events in normal and diseased neurons in relation to the emerging importance of the function and dysfunction of this protein as a target for basic as well as translational research.
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Affiliation(s)
- I-Fan Wang
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
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331
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Bigio EH. TAR DNA-binding protein-43 in amyotrophic lateral sclerosis, frontotemporal lobar degeneration, and Alzheimer disease. Acta Neuropathol 2008; 116:135-40. [PMID: 18575875 DOI: 10.1007/s00401-008-0405-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Accepted: 06/12/2008] [Indexed: 12/12/2022]
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332
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Banks GT, Kuta A, Isaacs AM, Fisher EMC. TDP-43 is a culprit in human neurodegeneration, and not just an innocent bystander. Mamm Genome 2008; 19:299-305. [PMID: 18592312 PMCID: PMC2515551 DOI: 10.1007/s00335-008-9117-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Accepted: 05/22/2008] [Indexed: 12/12/2022]
Abstract
In 2006 the protein TDP-43 was identified as the major ubiquitinated component deposited in the inclusion bodies found in two human neurodegenerative diseases, amyotrophic lateral sclerosis and frontotemporal lobar degeneration. The pathogenesis of both disorders is unclear, although they are related by having some overlap of symptoms and now by the shared histopathology of TDP-43 deposition. Now, in 2008, several papers have been published in quick succession describing mutations in the TDP-43 gene, showing they can be a primary cause of amyotrophic lateral sclerosis. There are many precedents in neurodegenerative disease in which rare single-gene mutations have given great insight into understanding disease processes, which is why the TDP-43 mutations are potentially very important.
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Affiliation(s)
- Gareth T Banks
- Department of Neurodegenerative Disease, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
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