Christian Haass

Publications (194)1313.39 Total impact

• Article: Dual Cleavage of Neuregulin 1 Type III by BACE1 and ADAM17 Liberates Its EGF-Like Domain and Allows Paracrine Signaling.

  Daniel Fleck, Frauke van Bebber, Alessio Colombo, Chiara Galante, Benjamin M Schwenk, Linnea Rabe, Heike Hampel, Bozidar Novak, Elisabeth Kremmer, Sabina Tahirovic, Dieter Edbauer, Stefan F Lichtenthaler, Bettina Schmid, Michael Willem, Christian Haass
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  ABSTRACT: Proteolytic shedding of cell surface proteins generates paracrine signals involved in numerous signaling pathways. Neuregulin 1 (NRG1) type III is involved in myelination of the peripheral nervous system, for which it requires proteolytic activation by proteases of the ADAM family and BACE1. These proteases are major therapeutic targets for the prevention of Alzheimer's disease because they are also involved in the proteolytic generation of the neurotoxic amyloid β-peptide. Identification and functional investigation of their physiological substrates is therefore of greatest importance in preventing unwanted side effects. Here we investigated proteolytic processing of NRG1 type III and demonstrate that the ectodomain can be cleaved by three different sheddases, namely ADAM10, ADAM17, and BACE1. Surprisingly, we not only found cleavage by ADAM10, ADAM17, and BACE1 C-terminal to the epidermal growth factor (EGF)-like domain, which is believed to play a pivotal role in signaling, but also additional cleavage sites for ADAM17 and BACE1 N-terminal to that domain. Proteolytic processing at N- and C-terminal sites of the EGF-like domain results in the secretion of this domain from NRG1 type III. The soluble EGF-like domain is functionally active and stimulates ErbB3 signaling in tissue culture assays. Moreover, the soluble EGF-like domain is capable of rescuing hypomyelination in a zebrafish mutant lacking BACE1. Our data suggest that NRG1 type III-dependent myelination is not only controlled by membrane-retained NRG1 type III, but also in a paracrine manner via proteolytic liberation of the EGF-like domain.
  Journal of Neuroscience 05/2013; 33(18):7856-69. · 7.11 Impact Factor
• Article: Stress Granules in Neurodegeneration - Lessons learnt from TDP-43 and FUS.

  Eva Bentmann, Christian Haass, Dorothee Dormann
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  ABSTRACT: Stress granules (SGs) are cytoplasmic foci that rapidly form when cells are exposed to stress. They transiently store mRNAs encoding house-keeping proteins and allow the selective translation of stress-response proteins, for example heat shock proteins. Besides mRNA, SGs contain RNA-binding proteins, such as TIA-1 and PABP-1, which can serve as characteristic SG marker proteins. Recently, some of these SG marker proteins were found to label pathological TDP-43- or FUS-positive cytoplasmic inclusions in patients with amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). In addition, protein aggregates in other neurodegenerative diseases, e.g. Tau inclusions in Alzheimer's disease, show a co-localization with TIA-1 as well. Moreover, several RNA-binding proteins that are commonly found in SGs have been genetically linked to neurodegeneration. This suggests that SGs might play an important role in the pathogenesis of these proteinopathies, either by acting as a seed for pathological inclusions, by mediating translational repression, by trapping essential RNA-binding proteins or a combination of these mechanisms. This review gives an overview of the general biology of SGs and highlights the recently identified connection of SGs with TDP-43, FUS and other proteins involved in neurodegenerative diseases. We propose that pathological inclusions containing RNA-binding proteins, such as TDP-43 and FUS, might arise from SGs and discuss how SGs might contribute to neurodegeneration via toxic gain or loss-of-function mechanisms. This article is protected by copyright. All rights reserved.
  FEBS Journal 04/2013; · 3.79 Impact Factor
• Article: Fused in Sarcoma (FUS): An Oncogene Goes Awry in Neurodegeneration.

  Dorothee Dormann, Christian Haass
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  ABSTRACT: Fused in sarcoma (FUS) is a nuclear DNA/RNA binding protein that regulates different steps of gene expression, including transcription, splicing and mRNA transport. FUS has been implicated in neurodegeneration, since mutations in FUS cause familial amyotrophic lateral sclerosis (ALS-FUS) and lead to the cytosolic deposition of FUS in the brain and spinal cord of ALS-FUS patients. Moreover, FUS and two related proteins of the same protein family (FET family) are co-deposited in cytoplasmic inclusions in a subset of patients with frontotemporal lobar degeneration (FTLD-FUS). Cytosolic deposition of these otherwise nuclear proteins most likely causes the loss of a yet unknown essential nuclear function and/or the gain of a toxic function in the cytosol. Here we summarize what is known about the physiological functions of the FET proteins in the nucleus and cytoplasm and review the distinctive pathomechanisms that lead to the deposition of only FUS in ALS-FUS, but all three FET proteins in FTLD-FUS. We suggest that ALS-FUS is caused by a selective dysfunction of FUS, while FTLD-FUS may be caused by a dysfunction of the entire FET family.
  Molecular and Cellular Neuroscience 04/2013; · 3.66 Impact Factor
• Article: TRAP1 rescues PINK1 loss-of-function phenotypes.

  Li Zhang, Peter Karsten, Sabine Hamm, Joe H Pogson, A Kathrin Lutz, Nicole Exner, Christian Haass, Alexander Whitworth, Konstanze Winklhofer, Jörg B Schulz, Aaron Voigt
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  ABSTRACT: PTEN-induced Kinase 1 (PINK1) is a serine/threonine kinase that is localized to mitochondria. It protects cells from oxidative stress by suppressing mitochondrial Cytochrome c release, thereby preventing cell death. Mutations in Pink1 cause early-onset Parkinson's disease (PD). Consistently, mitochondrial function is impaired in Pink1-linked PD patients and model systems. Previously, in vitro analysis implied that the protective effects of PINK1 depend on phosphorylation of the downstream factor TNF receptor-associated protein 1 (TRAP1). Furthermore, TRAP1 has been shown to mitigate α-Synuclein-induced toxicity, linking α-Synuclein directly to mitochondrial dysfunction. These data suggest that TRAP1 seems to mediate protective effects on mitochondrial function in pathways that are affected in PD. Here we investigated the potential of TRAP1 to rescue dysfunction induced by either PINK1 or Parkin deficiency in vivo and in vitro. We show that overexpression of human TRAP1 is able to mitigate Pink1 but not parkin loss-of-function phenotypes in Drosophila. In addition, detrimental effects observed after RNAi-mediated silencing of Complex I subunits was rescued by TRAP1 in Drosophila. Moreover, TRAP1 was able to rescue mitochondrial fragmentation and dysfunction upon siRNA-induced silencing of Pink1 but not parkin in human neuronal SH-SY5Y cells. Thus, our data suggest a functional role of TRAP1 in maintaining mitochondrial integrity downstream of PINK1 and Complex I deficits but parallel to or upstream of Parkin.
  Human Molecular Genetics 03/2013; · 7.64 Impact Factor
• Article: Label-free quantitative analysis of the membrane proteome of Bace1 protease knock-out zebrafish brains.

  Sebastian Hogl, Frauke van Bebber, Bastian Dislich, Peer-Hendrik Kuhn, Christian Haass, Bettina Schmid, Stefan F Lichtenthaler
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  ABSTRACT: The aspartyl protease BACE1 cleaves neuregulin 1 and is involved in myelination and is a candidate drug target for Alzheimer's disease, where it acts as the β-secretase cleaving the amyloid precursor protein (APP). However, little is known about other substrates in vivo. Here, we provide a proteomic workflow for BACE1 substrate identification from whole brains, combining filter-aided sample preparation, strong-anion exchange fractionation and label-free quantification. We used bace1-deficient zebrafish and quantified differences in protein levels between wild-type and bace1 -/- zebrafish brains. Over 4,500 proteins were identified with at least two unique peptides and quantified in both wild-type and bace1 -/- zebrafish brains. The majority of zebrafish membrane proteins did not show altered protein levels, indicating that Bace1 has a restricted substrate specificity. 24 membrane proteins accumulated in the bace1 -/- brains and thus represent candidate Bace1 substrates. They include several known BACE1 substrates, such as the zebrafish homologs of APP and the cell adhesion protein L1, which validate the proteomic workflow. Additionally, several candidate substrates with a function in neurite outgrowth and axon guidance, such as plexin A3 and glypican-1 were identified, pointing to a function of Bace1 in neurodevelopment. Taken together, our study provides the first proteomic analysis of knock-out zebrafish tissue and demonstrates that combining gene knock-out models in zebrafish with quantitative proteomics is a powerful approach to address biomedical questions.
  Proteomics 03/2013; · 4.43 Impact Factor
• Article: Loss of ALS-associated TDP-43 in zebrafish causes muscle degeneration, vascular dysfunction, and reduced motor neuron axon outgrowth.

  Bettina Schmid, Alexander Hruscha, Sebastian Hogl, Julia Banzhaf-Strathmann, Katrin Strecker, Julie van der Zee, Mathias Teucke, Stefan Eimer, Jan Hegermann, Maike Kittelmann, Elisabeth Kremmer, Marc Cruts, Barbara Solchenberger, Laura Hasenkamp, Frauke van Bebber, Christine Van Broeckhoven, Dieter Edbauer, Stefan F Lichtenthaler, Christian Haass
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  ABSTRACT: Mutations in the Tar DNA binding protein of 43 kDa (TDP-43; TARDBP) are associated with amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with TDP-43+ inclusions (FTLD-TDP). To determine the physiological function of TDP-43, we knocked out zebrafish Tardbp and its paralogue Tardbp (TAR DNA binding protein-like), which lacks the glycine-rich domain where ALS- and FTLD-TDP-associated mutations cluster. tardbp mutants show no phenotype, a result of compensation by a unique splice variant of tardbpl that additionally contains a C-terminal elongation highly homologous to the glycine-rich domain of tardbp. Double-homozygous mutants of tardbp and tardbpl show muscle degeneration, strongly reduced blood circulation, mispatterning of vessels, impaired spinal motor neuron axon outgrowth, and early death. In double mutants the muscle-specific actin binding protein Filamin Ca is up-regulated. Strikingly, Filamin C is similarly increased in the frontal cortex of FTLD-TDP patients, suggesting aberrant expression in smooth muscle cells and TDP-43 loss-of-function as one underlying disease mechanism.
  Proceedings of the National Academy of Sciences 03/2013; · 9.68 Impact Factor
• Article: Loss of Bace2 in zebrafish affects melanocyte migration and is distinct from Bace1 knock out phenotypes.

  Frauke van Bebber, Alexander Hruscha, Michael Willem, Bettina Schmid, Christian Haass
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  ABSTRACT: Alzheimer's disease (AD) is the most frequent dementia. Pathologically, AD is characterized by the accumulation of senile plaques composed of amyloid β-peptide (Aβ). Two proteases, β- and γ-secretase proteolytically generate Aβ from its precursor, the ß-amyloid precursor protein (APP). Inhibition of β- secretase, also referred to as beta-site APP cleaving enzyme (BACE1) or γ-secretase is therefore of prime interest for the development of amyloid lowering drugs. To assess the in vivo function of zebrafish Bace1 (zBace1) we generated zBace1 knock out fish by zinc finger nuclease mediated genome editing. bace1 mutants (bace1 -/-) are hypomyelinated in the PNS while the CNS is not affected. Moreover the number of mechanosensory neuromasts is elevated in bace1 -/-. Mutations in zebrafish Bace2 (zBace2) revealed a distinct melanocyte migration phenotype, which is not observed in bace1 -/-. Double homozygous bace1 -/-; bace2 -/- fish do not enhance the single mutant phenotypes indicating non-redundant distinct physiological functions. Single homozygous bace1 mutants as well as double homozygous bace1 and bace2 mutants are viable and fertile suggesting that Bace1 is a promising drug target without major side effects. The identification of a specific bace2 -/- associated phenotype further allows improving selective Bace1 inhibitors and to distinguish between Bace 1 and Bace 2 inhibition in vivo. © 2013 International Society for Neurochemistry, J. Neurochem. (2013) 10.1111/jnc.12198.
  Journal of Neurochemistry 02/2013; · 4.06 Impact Factor
• Source

  Available from: Christine Van Broeckhoven

  Article: The C9orf72 GGGGCC Repeat Is Translated into Aggregating Dipeptide-Repeat Proteins in FTLD/ALS.

  Kohji Mori, Shih-Ming Weng, Thomas Arzberger, Stephanie May, Kristin Rentzsch, Elisabeth Kremmer, Bettina Schmid, Hans A Kretzschmar, Marc Cruts, Christine Van Broeckhoven, Christian Haass, Dieter Edbauer
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  ABSTRACT: Expansion of a GGGGCC hexanucleotide repeat upstream of the C9orf72 coding region is the most common cause of familial frontotemporal lobar degeneration and amyotrophic lateral sclerosis (FTLD/ALS), but the pathomechanisms involved are unknown. Like in other FTLD/ALS variants, characteristic intracellular inclusions of misfolded proteins define C9orf72 pathology, but the core proteins of the majority of inclusions are still unknown. Here we found that most of these characteristic inclusions contain poly-(Gly-Ala) and to a lesser extent poly-(Gly-Pro) and poly-(Gly-Arg) dipeptide-repeat proteins presumably generated by non-ATG-initiated translation from the expanded GGGGCC repeat in three reading frames. These findings directly link the FTLD/ALS-associated genetic mutation to the predominant pathology in patients with C9orf72 hexanucleotide expansion.
  Science 02/2013; · 31.20 Impact Factor
• Source

  Available from: Ignasi Forne

  Article: hnRNP A3 binds to GGGGCC repeats and is a constituent of p62-positive/TDP43-negative inclusions in the hippocampus of patients with C9orf72 mutations.

  Kohji Mori, Sven Lammich, Ian R A Mackenzie, Ignasi Forné, Sonja Zilow, Hans Kretzschmar, Dieter Edbauer, Jonathan Janssens, Gernot Kleinberger, Marc Cruts, Jochen Herms, Manuela Neumann, Christine Van Broeckhoven, Thomas Arzberger, Christian Haass
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  ABSTRACT: Genetic analysis revealed the hexanucleotide repeat expansion GGGGCC within the regulatory region of the gene C9orf72 as the most common cause of familial amyotrophic lateral sclerosis and the second most common cause of frontotemporal lobar degeneration. Since repeat expansions might cause RNA toxicity via sequestration of RNA-binding proteins, we searched for proteins capable of binding to GGGGCC repeats. In vitro-transcribed biotinylated RNA containing hexanucleotide GGGGCC or, as control, AAAACC repeats were incubated with nuclear protein extracts. Using stringent filtering protocols 20 RNA-binding proteins with a variety of different functions in RNA metabolism, translation and transport were identified. A subset of these proteins was further investigated by immunohistochemistry in human autopsy brains. This revealed that hnRNP A3 formed neuronal cytoplasmic and intranuclear inclusions in the hippocampus of patients with C9orf72 repeat extensions. Confocal microcopy showed that these inclusions belong to the group of the so far enigmatic p62-positive/TDP-43 negative inclusions characteristically seen in autopsy cases of diseased C9orf72 repeat expansion carriers. Thus, we have identified one protein component of these pathognomonic inclusions.
  Acta Neuropathologica 02/2013; · 9.32 Impact Factor
• Article: hnRNP A3 binds to GGGGCC repeats and is a constituent of p62 positive/TDP43 negative inclusions in the hippocampus of patients with C9orf72 mutations

  Khoji Mori, Sven Lammich, Ian R.A. Mackenzie, Ignasi Forne, Sonja Zilow, Hans Kretzschmar, Dieter Edbauer, Jonathan Janssens, Gernot Kleinberger, Marc Cruts, Jochen Herms, Manuela Neumann, Christine Van Broeckhoven, Thomas Arzberger, Christian Haass
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  ABSTRACT: Genetic analysis revealed the hexanucleotide repeat expansion GGGGCC within the regulatory region of the gene C9orf72 as the most common cause of familial amyotrophic lateral sclerosis and the second most common cause of frontotemporal lobar degeneration. Since repeat expansions might cause RNA toxicity via sequestration of RNA binding proteins we searched for proteins capable to bind to GGGGCC repeats. In vitro transcribed biotinylated RNA containing hexanucleotide GGGGCC or, as control, AAAACC repeats were incubated with nuclear protein extracts. Using stringent filtering protocols 20 RNA binding proteins with a variety of different functions in RNA metabolism, translation and transport were identified. A subset of these proteins was further investigated by immunohistochemistry in human autopsy brains. This revealed that hnRNP A3 formed neuronal cytoplasmic and intranuclear inclusions in the hippocampus of patients with C9orf72 repeat extensions. Confocal microcopy showed that these inclusions belong to the group of the so far enigmatic p62 positive/TDP-43 negative inclusions characteristically seen in autopsy cases of diseased C9orf72 repeat expansion carriers. Thus we have identified one protein component of these pathognomonic inclusions.
  Acta Neuropathologica 01/2013; · 9.32 Impact Factor
• Article: Loss of PAFAH1B2 Reduces Amyloid-β Generation by Promoting the Degradation of Amyloid Precursor Protein C-Terminal Fragments.

  Richard M Page, Anna Münch, Thomas Horn, Peer-Hendrik Kuhn, Alessio Colombo, Orly Reiner, Michael Boutros, Harald Steiner, Stefan F Lichtenthaler, Christian Haass
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  ABSTRACT: Amyloid-β peptide (Aβ) is believed to play a central role in the pathogenesis of Alzheimer's disease. In view of the side effects associated with inhibiting the secretases that produce Aβ, new molecular targets are required to provide alternative therapeutic options. We used RNA interference (RNAi) to systematically screen the Drosophila genome to identify genes that modulate Aβ production upon knockdown. RNAi of 41 genes in Drosophila cells significantly lowered Aβ without affecting general secretion or viability. After the γ-secretase complex components, the most potent effect was observed for platelet activating factor acetylhydrolase α (Paf-AHα), and, in mammalian cells, the effect was replicated for its ortholog PAFAH1B2. Knockdown of PAFAH1B2 strongly reduced Aβ secretion from human cells, and this effect was confirmed in primary cells derived from PAFAH1B2 knock-out mice. Reduced Aβ production was not attributable to altered β-amyloid precursor protein (APP) ectodomain shedding but was a result of an enhanced degradation of APP C-terminal fragments (CTFs) in the absence of PAFAH1B2 but not its close homolog PAFAH1B3. Enhanced degradation of APP CTFs was selective because no such effects were obtained for Notch or E-/N-cadherin. Thus, we have identified an important protein that can selectively modify Aβ generation via a novel mechanism, namely enhanced degradation of its immediate precursor. In view of the absence of a neurological phenotype in PAFAH1B2 knock-out mice, targeted downregulation of PAFAH1B2 may be a promising new strategy for lowering Aβ.
  Journal of Neuroscience 12/2012; 32(50):18204-18214. · 7.11 Impact Factor
• Article: Important functional role of residue x of the presenilin GxGD protease active site motif for APP substrate cleavage specificity and substrate selectivity of γ-secretase.

  Benedikt Kretner, Akio Fukumori, Peer-Hendrik Kuhn, Blanca Isabel Pérez-Revuelta, Stefan F Lichtenthaler, Christian Haass, Harald Steiner
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  ABSTRACT: γ-Secretase plays a central role in the generation of the Alzheimer disease (AD)-causing amyloid β-peptide (Aβ) from the β-amyloid precursor protein (APP) and is thus a major AD drug target. Since several other γ-secretase substrates including Notch1 and CD44 have crucial signaling functions, an understanding of the mechanism of substrate recognition and cleavage is key for the development of APP selective γ-secretase-targeting drugs. The γ-secretase active site domain in its catalytic subunit presenilin (PS) 1 has been implicated in substrate recognition/docking and cleavage. Highly critical in this process is its GxGD active site motif, whose invariant glycine residues cannot be replaced without causing severe functional losses in substrate selection and/or cleavage efficiency. Here we have investigated the contribution of the less well characterized residue x of the motif (L383 in PS1) to this function. Extensive mutational analysis showed that processing of APP was overall well tolerated over a wide range of hydrophobic and hydrophilic mutations. Interestingly however, most L383 mutants gave rise to reduced levels of Aβ(37-39) species, and several increased the pathogenic Aβ(42/43) species. Several of the Aβ(42/43) -increasing mutants severely impaired the cleavages of Notch1 and CD44 substrates, which were not affected by any other L383 mutation. Our data thus establish an important, but compared to the glycine residues of the motif, overall less critical functional role for L383. We suggest that L383 and the flanking glycine residues form a spatial arrangement in PS1 that is critical for docking and/or cleavage of different γ-secretase substrates. © 2012 International Society for Neurochemistry, J. Neurochem. (2012) 10.1111/jnc.12124.
  Journal of Neurochemistry 12/2012; · 4.06 Impact Factor
• Source

  Available from: Wiebke Möbius

  Dataset: KassmannFEBSLett2011

  Viktorija Velanac, Tilmann Unterbarnscheidt, Wilko Hinrichs, Maike N Gummert, Tobias M Fischer, Moritz J Rossner, Amelia Trimarco, Veronica Brivio, Carla Taveggia, Michael Willem, Christian Haass, Wiebke Möbius, Klaus-Armin Nave, Markus H Schwab
• Article: In Vivo Imaging of Disease-Related Mitochondrial Dynamics in a Vertebrate Model System.

  Gabriela Plucinska, Dominik Paquet, Alexander Hruscha, Leanne Godinho, Christian Haass, Bettina Schmid, Thomas Misgeld
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  ABSTRACT: Mitochondria provide ATP, maintain calcium homeostasis, and regulate apoptosis. Neurons, due to their size and complex geometry, are particularly dependent on the proper functioning and distribution of mitochondria. Thus disruptions of these organelles and their transport play a central role in a broad range of neurodegenerative diseases. While in vitro studies have greatly expanded our knowledge of mitochondrial dynamics, our understanding in vivo remains limited. To address this shortcoming, we developed tools to study mitochondrial dynamics in vivo in optically accessible zebrafish. We demonstrate here that our newly generated tools, including transgenic "MitoFish," can be used to study the in vivo "life cycle" of mitochondria and allows identifying pharmacological and genetic modulators of mitochondrial dynamics. Furthermore we observed profound mitochondrial transport deficits in real time in a zebrafish tauopathy model. By rescuing this phenotype using MARK2 (microtubule-affinity regulating kinase 2), we provide direct in vivo evidence that this kinase regulates axonal transport in a Tau-dependent manner. Thus, our approach allows detailed studies of the dynamics of mitochondria in their natural environment under normal and disease conditions.
  Journal of Neuroscience 11/2012; 32(46):16203-16212. · 7.11 Impact Factor
• Article: Foamy virus envelope protein is a substrate for signal peptide peptidase like-3 (SPPL3).

  Matthias Voss, Akio Fukumori, Peer-Hendrik Kuhn, Ulrike Künzel, Bärbel Klier, Gudula Grammer, Martina Haug-Kröper, Elisabeth Kremmer, Stefan Lichtenthaler, Harald Steiner, Bernd Schröder, Christian Haass, Regina Fluhrer
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  ABSTRACT: Signal peptide peptidase (SPP), its homologues the SPP-like proteases SPPL2a/b/c, and SPPL3 as well as presenilin, the catalytic subunit of the γ-secretase complex, are intramembrane-cleaving aspartyl proteases of the GxGD type. In this study we identified the 18 kDa leader peptide (LP18) of the foamy virus envelope protein (FVenv) as a new substrate for intramembrane proteolysis by human SPPL3 and SPPL2a/b. In contrast to SPPL2a/b and γ-secretase, which require substrates with an ectodomain shorter than 60 amino acids for efficient intramembrane proteolysis, SPPL3 cleaves mutant FVenv, lacking the pro-protein convertase cleavage site necessary for the preceding shedding. Moreover, the cleavage product of FVenv generated by SPPL3 serves as a new substrate for consecutive intramembrane cleavage by SPPL2a/b. Thus human SPPL3 is the first GxGD type aspartyl protease shown to be capable of acting like a sheddase, similar to members of the rhomboid family, which belong to the class of intramembrane cleaving serine proteases.
  Journal of Biological Chemistry 11/2012; · 4.77 Impact Factor
• Article: Arginine methylation next to the PY-NLS modulates Transportin binding and nuclear import of FUS.

  Dorothee Dormann, Tobias Madl, Chiara F Valori, Eva Bentmann, Sabina Tahirovic, Claudia Abou-Ajram, Elisabeth Kremmer, Olaf Ansorge, Ian R A Mackenzie, Manuela Neumann, Christian Haass
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  ABSTRACT: Fused in sarcoma (FUS) is a nuclear protein that carries a proline-tyrosine nuclear localization signal (PY-NLS) and is imported into the nucleus via Transportin (TRN). Defects in nuclear import of FUS have been implicated in neurodegeneration, since mutations in the PY-NLS of FUS cause amyotrophic lateral sclerosis (ALS). Moreover, FUS is deposited in the cytosol in a subset of frontotemporal lobar degeneration (FTLD) patients. Here, we show that arginine methylation modulates nuclear import of FUS via a novel TRN-binding epitope. Chemical or genetic inhibition of arginine methylation restores TRN-mediated nuclear import of ALS-associated FUS mutants. The unmethylated arginine-glycine-glycine domain preceding the PY-NLS interacts with TRN and arginine methylation in this domain reduces TRN binding. Inclusions in ALS-FUS patients contain methylated FUS, while inclusions in FTLD-FUS patients are not methylated. Together with recent findings that FUS co-aggregates with two related proteins of the FET family and TRN in FTLD-FUS but not in ALS-FUS, our study provides evidence that these two diseases may be initiated by distinct pathomechanisms and implicates alterations in arginine methylation in pathogenesis.
  The EMBO Journal 09/2012; · 9.20 Impact Factor
• Article: Mitochondrial dysfunction in Parkinson's disease: molecular mechanisms and pathophysiological consequences.

  Nicole Exner, Anne Kathrin Lutz, Christian Haass, Konstanze F Winklhofer
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  ABSTRACT: Neurons are critically dependent on mitochondrial integrity based on specific morphological, biochemical, and physiological features. They are characterized by high rates of metabolic activity and need to respond promptly to activity-dependent fluctuations in bioenergetic demand. The dimensions and polarity of neurons require efficient transport of mitochondria to hot spots of energy consumption, such as presynaptic and postsynaptic sites. Moreover, the postmitotic state of neurons in combination with their exposure to intrinsic and extrinsic neuronal stress factors call for a high fidelity of mitochondrial quality control systems. Consequently, it is not surprising that mitochondrial alterations can promote neuronal dysfunction and degeneration. In particular, mitochondrial dysfunction has long been implicated in the etiopathogenesis of Parkinson's disease (PD), based on the observation that mitochondrial toxins can cause parkinsonism in humans and animal models. Substantial progress towards understanding the role of mitochondria in the disease process has been made by the identification and characterization of genes causing familial variants of PD. Studies on the function and dysfunction of these genes revealed that various aspects of mitochondrial biology appear to be affected in PD, comprising mitochondrial biogenesis, bioenergetics, dynamics, transport, and quality control.
  The EMBO Journal 06/2012; 31(14):3038-62. · 9.20 Impact Factor
• Article: Secretome protein enrichment identifies physiological BACE1 protease substrates in neurons.

  Peer-Hendrik Kuhn, Katarzyna Koroniak, Sebastian Hogl, Alessio Colombo, Ulrike Zeitschel, Michael Willem, Christiane Volbracht, Ute Schepers, Axel Imhof, Albrecht Hoffmeister, Christian Haass, Steffen Roßner, Stefan Bräse, Stefan F Lichtenthaler
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  ABSTRACT: Cell surface proteolysis is essential for communication between cells and results in the shedding of membrane-protein ectodomains. However, physiological substrates of the contributing proteases are largely unknown. We developed the secretome protein enrichment with click sugars (SPECS) method, which allows proteome-wide identification of shedding substrates and secreted proteins from primary cells, even in the presence of serum proteins. SPECS combines metabolic glycan labelling and click chemistry-mediated biotinylation and distinguishes between cellular and serum proteins. SPECS identified 34, mostly novel substrates of the Alzheimer protease BACE1 in primary neurons, making BACE1 a major sheddase in the nervous system. Selected BACE1 substrates-seizure-protein 6, L1, CHL1 and contactin-2-were validated in brains of BACE1 inhibitor-treated and BACE1 knock-out mice. For some substrates, BACE1 was the major sheddase, whereas for other substrates additional proteases contributed to total substrate shedding. The new substrates point to a central function of BACE1 in neurite outgrowth and synapse formation. SPECS is also suitable for quantitative secretome analyses of primary cells and may be used for the discovery of biomarkers secreted from tumour or stem cells.
  The EMBO Journal 06/2012; 31(14):3157-68. · 9.20 Impact Factor
• Article: Loss of fused in sarcoma (FUS) promotes pathological Tau splicing.

  Denise Orozco, Sabina Tahirovic, Kristin Rentzsch, Benjamin M Schwenk, Christian Haass, Dieter Edbauer
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  ABSTRACT: A subset of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) patients present pathological redistribution and aggregation of the nuclear protein fused in sarcoma (FUS) in the cytoplasm. Although FUS associates with the spliceosomal complex, no endogenous neuronal splicing targets have been identified. Here we identify Tau mRNA as a physiological splicing target of FUS. In mouse brain, FUS directly binds to Tau pre-mRNA, and knockdown of FUS in hippocampal neurons leads to preferential inclusion of Tau exons 3 and 10. FUS knockdown causes significant growth cone enlargement and disorganization reminiscent of Tau loss of function. These findings suggest that disturbed cytoskeletal function and enhanced expression of the neurodegeneration-associated Tau exon 10 might contribute to FTLD/ALS with FUS inclusions.
  EMBO Reports 06/2012; 13(8):759-64. · 7.36 Impact Factor
• Article: Requirements for stress granule recruitment of fused in sarcoma (FUS) and TAR DNA-binding protein of 43 kDa (TDP-43).

  Eva Bentmann, Manuela Neumann, Sabina Tahirovic, Ramona Rodde, Dorothee Dormann, Christian Haass
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  ABSTRACT: Cytoplasmic inclusions containing TAR DNA-binding protein of 43 kDa (TDP-43) or Fused in sarcoma (FUS) are a hallmark of amyotrophic lateral sclerosis (ALS) and several subtypes of frontotemporal lobar degeneration (FTLD). FUS-positive inclusions in FTLD and ALS patients are consistently co-labeled with stress granule (SG) marker proteins. Whether TDP-43 inclusions contain SG markers is currently still debated. We determined the requirements for SG recruitment of FUS and TDP-43 and found that cytoplasmic mislocalization is a common prerequisite for SG recruitment of FUS and TDP-43. For FUS, the arginine-glycine-glycine zinc finger domain, which is the protein's main RNA binding domain, is most important for SG recruitment, whereas the glycine-rich domain and RNA recognition motif (RRM) domain have a minor contribution and the glutamine-rich domain is dispensable. For TDP-43, both the RRM1 and the C-terminal glycine-rich domain are required for SG localization. ALS-associated point mutations located in the glycine-rich domain of TDP-43 do not affect SG recruitment. Interestingly, a 25-kDa C-terminal fragment of TDP-43, which is enriched in FTLD/ALS cortical inclusions but not spinal cord inclusions, fails to be recruited into SG. Consistently, inclusions in the cortex of FTLD patients, which are enriched for C-terminal fragments, are not co-labeled with the SG marker poly(A)-binding protein 1 (PABP-1), whereas inclusions in spinal cord, which contain full-length TDP-43, are frequently positive for this marker protein.
  Journal of Biological Chemistry 05/2012; 287(27):23079-94. · 4.77 Impact Factor