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James Shorter - One of the best experts on this subject based on the ideXlab platform.
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The mammalian disaggregase machinery: Hsp110 synergizes with Hsp70 and Hsp40 to catalyze protein Disaggregation and reactivation in a cell-free system
2013Co-Authors: James ShorterAbstract:Bacteria, fungi, protozoa, chromista and plants all harbor homologues of Hsp104, a AAA+ ATPase that collaborates with Hsp70 and Hsp40 to promote protein Disaggregation and reactivation. Curiously, however, metazoa do not possess an Hsp104 homologue. Thus, whether animal cells renature large protein aggregates has long remained unclear. Here, it is established that mammalian cytosol prepared from different sources possesses a potent, ATP-dependent protein disaggregase and reactivation activity, which can be accelerated and stimulated by Hsp104. This activity did not require the AAA+ ATPase, p97. Rather, mammalian Hsp110 (Apg-2), Hsp70 (Hsc70 or Hsp70) and Hsp40 (Hdj1) were necessary and sufficient to slowly dissolve large disordered aggregates and recover natively folded protein. This slow disaggregase activity was conserved to yeast Hsp110 (Sse1), Hsp70 (Ssa1) and Hsp40 (Sis1 or Ydj1). Hsp110 must engage substrate, engage Hsp70, promote nucleotide exchange on Hsp70, and hydrolyze ATP to promote Disaggregation of disordered aggregates. Similarly, Hsp70 must engage substrate and Hsp110, and hydrolyze ATP for protein Disaggregation. Hsp40 must harbor a functional J domain to promote protein Disaggregation, but the J domain alone is insufficient. Optimal disaggregase activity is achieved when the Hsp40 can stimulate the ATPase activity of Hsp110 and Hsp70. Finally, Hsp110, Hsp70 and Hsp40 fail to rapidly remodel amyloid forms of the yeast prion protein, Sup35, or the Parkinson’s disease protein, alpha-synuclein. However, Hsp110, Hsp70 and Hsp40 enhanced the activity of Hsp104 against these amyloid substrates. Taken together
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the mammalian disaggregase machinery hsp110 synergizes with hsp70 and hsp40 to catalyze protein Disaggregation and reactivation in a cell free system
PLOS ONE, 2011Co-Authors: James ShorterAbstract:Bacteria, fungi, protozoa, chromista and plants all harbor homologues of Hsp104, a AAA+ ATPase that collaborates with Hsp70 and Hsp40 to promote protein Disaggregation and reactivation. Curiously, however, metazoa do not possess an Hsp104 homologue. Thus, whether animal cells renature large protein aggregates has long remained unclear. Here, it is established that mammalian cytosol prepared from different sources possesses a potent, ATP-dependent protein disaggregase and reactivation activity, which can be accelerated and stimulated by Hsp104. This activity did not require the AAA+ ATPase, p97. Rather, mammalian Hsp110 (Apg-2), Hsp70 (Hsc70 or Hsp70) and Hsp40 (Hdj1) were necessary and sufficient to slowly dissolve large disordered aggregates and recover natively folded protein. This slow disaggregase activity was conserved to yeast Hsp110 (Sse1), Hsp70 (Ssa1) and Hsp40 (Sis1 or Ydj1). Hsp110 must engage substrate, engage Hsp70, promote nucleotide exchange on Hsp70, and hydrolyze ATP to promote Disaggregation of disordered aggregates. Similarly, Hsp70 must engage substrate and Hsp110, and hydrolyze ATP for protein Disaggregation. Hsp40 must harbor a functional J domain to promote protein Disaggregation, but the J domain alone is insufficient. Optimal disaggregase activity is achieved when the Hsp40 can stimulate the ATPase activity of Hsp110 and Hsp70. Finally, Hsp110, Hsp70 and Hsp40 fail to rapidly remodel amyloid forms of the yeast prion protein, Sup35, or the Parkinson's disease protein, alpha-synuclein. However, Hsp110, Hsp70 and Hsp40 enhanced the activity of Hsp104 against these amyloid substrates. Taken together, these findings suggest that Hsp110 fulfils a subset of Hsp104 activities in mammals. Moreover, they suggest that Hsp104 can collaborate with the mammalian disaggregase machinery to rapidly remodel amyloid conformers.
Tim Brown - One of the best experts on this subject based on the ideXlab platform.
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financial statement Disaggregation decisions and auditors tolerance for misstatement
The Accounting Review, 2013Co-Authors: Robert Libby, Tim BrownAbstract:ABSTRACT : Current IFRS requires significant Disaggregation of income statement numbers while such Disaggregation is voluntary and much less common under U.S. GAAP. We examine whether voluntary Disaggregation of income statement numbers increases the reliability of income statement subtotals because auditors permit less misstatement in the disaggregated numbers. In our experiment, experienced auditors require correction of smaller errors in disaggregated numbers. Auditors also believe that greater Disaggregation will increase SEC scrutiny of uncorrected financial statement errors in the disaggregated numbers. However, the effects are substantially reduced if the disaggregated numbers are presented in the notes. Furthermore, there is significant disagreement among participants on whether disaggregated numbers are relevant materiality benchmarks, and on what current auditing guidance requires. These results suggest a potential deficiency in current audit guidance, which traditionally has been aimed at promo...
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financial statement Disaggregation decisions and auditors tolerance for misstatement
Social Science Research Network, 2012Co-Authors: Robert Libby, Tim BrownAbstract:Current IFRS requires significant Disaggregation of income statement numbers while such Disaggregation is voluntary and much less common under U.S. GAAP. We examine whether voluntary Disaggregation of income statement numbers increases the reliability of income statement subtotals because auditors permit less misstatement in the disaggregated numbers. In our experiment, experienced auditors require correction of smaller errors in disaggregated numbers. Auditors also believe that greater Disaggregation will increase SEC scrutiny of uncorrected financial statement errors in the disaggregated numbers. However, the effects are substantially reduced if the disaggregated numbers are presented in the notes. Furthermore, there is significant disagreement among participants on whether disaggregated numbers are relevant materiality benchmarks, and on what current auditing guidance requires. These results suggest a potential deficiency in current audit guidance, which traditionally has been aimed at promoting consensus in practice among auditors. They also suggest an unintended positive consequence of voluntary Disaggregation for the reliability of income statement subtotals. Possible effects of management behavior and required Disaggregation resulting from U.S. adoption of IFRS or the recommendations of the joint FASB/IASB financial statement presentation project are also discussed.
Axel Mogk - One of the best experts on this subject based on the ideXlab platform.
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chaperone mediated protein Disaggregation triggers proteolytic clearance of intra nuclear protein inclusions
Cell Reports, 2020Co-Authors: Fabian Den Brave, Lucas V Cairo, Chandhuru Jagadeesan, Carmen Rugerherreros, Axel Mogk, Bernd Bukau, Stefan JentschAbstract:The formation of insoluble inclusions in the cytosol and nucleus is associated with impaired protein homeostasis and is a hallmark of several neurodegenerative diseases. Due to the absence of the autophagic machinery, nuclear protein aggregates require a solubilization step preceding degradation by the 26S proteasome. Using yeast, we identify a nuclear protein quality control pathway required for the clearance of protein aggregates. The nuclear J-domain protein Apj1 supports protein Disaggregation together with Hsp70 but independent of the canonical disaggregase Hsp104. Disaggregation mediated by Apj1/Hsp70 promotes turnover rather than refolding. A loss of Apj1 activity uncouples Disaggregation from proteasomal turnover, resulting in accumulation of toxic soluble protein species. Endogenous substrates of the Apj1/Hsp70 pathway include both nuclear and cytoplasmic proteins, which aggregate inside the nucleus upon proteotoxic stress. These findings demonstrate the coordinated activity of the Apj1/Hsp70 Disaggregation system with the 26S proteasome in facilitating the clearance of toxic inclusions inside the nucleus.
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disassembly of tau fibrils by the human hsp70 Disaggregation machinery generates small seeding competent species
bioRxiv, 2019Co-Authors: Eliana Nachman, Anne S. Wentink, Harm H Kampinga, Karine Madiona, Luc Bousset, Taxiarchis Katsinelos, William A Mcewan, Thomas R Jahn, Ronald Melki, Axel MogkAbstract:Abstract The accumulation of amyloid Tau aggregates is implicated in Alzheimer’s disease and other Tauopathies. Molecular chaperones are known for their function in maintaining protein homeostasis by preventing the formation or promoting the Disaggregation of amorphous and amyloid protein aggregates. Here we show that an ATP-dependent human chaperone system disassembles Tau fibrils in vitro. This function is mediated by the core chaperone Hsc70, assisted by specific co-chaperones, in particular class B J-domain proteins and an Hsp110-type NEF. Recombinant fibrils assembled from all six Tau isoforms as well as Sarkosyl-resistant Tau aggregates extracted from cell culture were processed by the Hsp70 Disaggregation machinery, demonstrating the ability of this machinery to recognize a broad range of Tau aggregates. Chaperone treatment released monomeric, and small oligomeric Tau species, which induced the aggregation of self-propagating Tau species in a Tau cell culture model. We infer from these results that the activity of the Hsp70 Disaggregation machinery is a double-sided sword as it attempts to eliminate Tau amyloids but with the price of generating new seeds. The Hsp70 disaggregase therefore has a crucial function in the Tau propagation cycle, rendering it a potential drug target in Tauopathies.
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cellular handling of protein aggregates by Disaggregation machines
Molecular Cell, 2018Co-Authors: Axel Mogk, Bernd Bukau, Harm H KampingaAbstract:Both acute proteotoxic stresses that unfold proteins and expression of disease-causing mutant proteins that expose aggregation-prone regions can promote protein aggregation. Protein aggregates can interfere with cellular processes and deplete factors crucial for protein homeostasis. To cope with these challenges, cells are equipped with diverse folding and degradation activities to rescue or eliminate aggregated proteins. Here, we review the different chaperone Disaggregation machines and their mechanisms of action. In all these machines, the coating of protein aggregates by Hsp70 chaperones represents the conserved, initializing step. In bacteria, fungi, and plants, Hsp70 recruits and activates Hsp100 disaggregases to extract aggregated proteins. In the cytosol of metazoa, Hsp70 is empowered by a specific cast of J-protein and Hsp110 co-chaperones allowing for standalone Disaggregation activity. Both types of Disaggregation machines are supported by small Hsps that sequester misfolded proteins.
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hsp70 proteins bind hsp100 regulatory m domains to activate aaa disaggregase at aggregate surfaces
Nature Structural & Molecular Biology, 2012Co-Authors: Fabian Seyffer, Bernd Bukau, Eva Kummer, Yuki Oguchi, Juliane Winkler, Mohit Kumar, Regina Zahn, Victor Sourjik, Axel MogkAbstract:Bacteria, fungi and plants rescue aggregated proteins using a powerful bichaperone system composed of an Hsp70 chaperone and an Hsp100 AAA+ disaggregase. In Escherichia coli, the Hsp70 chaperone DnaK binds aggregates and targets the disaggregase ClpB to the substrate. ClpB hexamers use ATP to thread substrate polypeptides through the central pore, driving Disaggregation. How ClpB finds DnaK and regulates threading remains unclear. To dissect the Disaggregation mechanism, we separated these steps using primarily chimeric ClpB-ClpV constructs that directly recognize alternative substrates, thereby obviating DnaK involvement. We show that ClpB has low intrinsic Disaggregation activity that is normally repressed by the ClpB middle (M) domain. In the presence of aggregate, DnaK directly binds M-domain motif 2, increasing ClpB ATPase activity to unleash high ClpB threading power. Our results uncover a new function for Hsp70: the coupling of substrate targeting to AAA+ chaperone activation at aggregate surfaces.
Bernd Bukau - One of the best experts on this subject based on the ideXlab platform.
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Molecular dissection of amyloid Disaggregation by human HSP70
Nature, 2020Co-Authors: Anne S. Wentink, Nadinath B Nillegoda, Jennifer Feufel, Gabrielė Ubartaitė, Carolyn P. Schneider, Paolo De Los Rios, Janosch Hennig, Alessandro Barducci, Bernd BukauAbstract:The molecular steps that lead to the Disaggregation of amyloid fibrils are shown to involve the synergistic action of HSP70 and its co-chaperones DNAJB1 and HSP110. The deposition of highly ordered fibrillar-type aggregates into inclusion bodies is a hallmark of neurodegenerative diseases such as Parkinson’s disease. The high stability of such amyloid fibril aggregates makes them challenging substrates for the cellular protein quality-control machinery^ 1 , 2 . However, the human HSP70 chaperone and its co-chaperones DNAJB1 and HSP110 can dissolve preformed fibrils of the Parkinson’s disease-linked presynaptic protein α-synuclein in vitro^ 3 , 4 . The underlying mechanisms of this unique activity remain poorly understood. Here we use biochemical tools and nuclear magnetic resonance spectroscopy to determine the crucial steps of the Disaggregation process of amyloid fibrils. We find that DNAJB1 specifically recognizes the oligomeric form of α-synuclein via multivalent interactions, and selectively targets HSP70 to fibrils. HSP70 and DNAJB1 interact with the fibril through exposed, flexible amino and carboxy termini of α-synuclein rather than the amyloid core itself. The synergistic action of DNAJB1 and HSP110 strongly accelerates Disaggregation by facilitating the loading of several HSP70 molecules in a densely packed arrangement at the fibril surface, which is ideal for the generation of ‘entropic pulling’ forces. The cooperation of DNAJB1 and HSP110 in amyloid Disaggregation goes beyond the classical substrate targeting and recycling functions that are attributed to these HSP70 co-chaperones and constitutes an active and essential contribution to the remodelling of the amyloid substrate. These mechanistic insights into the essential prerequisites for amyloid Disaggregation may provide a basis for new therapeutic interventions in neurodegeneration.
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chaperone mediated protein Disaggregation triggers proteolytic clearance of intra nuclear protein inclusions
Cell Reports, 2020Co-Authors: Fabian Den Brave, Lucas V Cairo, Chandhuru Jagadeesan, Carmen Rugerherreros, Axel Mogk, Bernd Bukau, Stefan JentschAbstract:The formation of insoluble inclusions in the cytosol and nucleus is associated with impaired protein homeostasis and is a hallmark of several neurodegenerative diseases. Due to the absence of the autophagic machinery, nuclear protein aggregates require a solubilization step preceding degradation by the 26S proteasome. Using yeast, we identify a nuclear protein quality control pathway required for the clearance of protein aggregates. The nuclear J-domain protein Apj1 supports protein Disaggregation together with Hsp70 but independent of the canonical disaggregase Hsp104. Disaggregation mediated by Apj1/Hsp70 promotes turnover rather than refolding. A loss of Apj1 activity uncouples Disaggregation from proteasomal turnover, resulting in accumulation of toxic soluble protein species. Endogenous substrates of the Apj1/Hsp70 pathway include both nuclear and cytoplasmic proteins, which aggregate inside the nucleus upon proteotoxic stress. These findings demonstrate the coordinated activity of the Apj1/Hsp70 Disaggregation system with the 26S proteasome in facilitating the clearance of toxic inclusions inside the nucleus.
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cellular handling of protein aggregates by Disaggregation machines
Molecular Cell, 2018Co-Authors: Axel Mogk, Bernd Bukau, Harm H KampingaAbstract:Both acute proteotoxic stresses that unfold proteins and expression of disease-causing mutant proteins that expose aggregation-prone regions can promote protein aggregation. Protein aggregates can interfere with cellular processes and deplete factors crucial for protein homeostasis. To cope with these challenges, cells are equipped with diverse folding and degradation activities to rescue or eliminate aggregated proteins. Here, we review the different chaperone Disaggregation machines and their mechanisms of action. In all these machines, the coating of protein aggregates by Hsp70 chaperones represents the conserved, initializing step. In bacteria, fungi, and plants, Hsp70 recruits and activates Hsp100 disaggregases to extract aggregated proteins. In the cytosol of metazoa, Hsp70 is empowered by a specific cast of J-protein and Hsp110 co-chaperones allowing for standalone Disaggregation activity. Both types of Disaggregation machines are supported by small Hsps that sequester misfolded proteins.
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hsp70 proteins bind hsp100 regulatory m domains to activate aaa disaggregase at aggregate surfaces
Nature Structural & Molecular Biology, 2012Co-Authors: Fabian Seyffer, Bernd Bukau, Eva Kummer, Yuki Oguchi, Juliane Winkler, Mohit Kumar, Regina Zahn, Victor Sourjik, Axel MogkAbstract:Bacteria, fungi and plants rescue aggregated proteins using a powerful bichaperone system composed of an Hsp70 chaperone and an Hsp100 AAA+ disaggregase. In Escherichia coli, the Hsp70 chaperone DnaK binds aggregates and targets the disaggregase ClpB to the substrate. ClpB hexamers use ATP to thread substrate polypeptides through the central pore, driving Disaggregation. How ClpB finds DnaK and regulates threading remains unclear. To dissect the Disaggregation mechanism, we separated these steps using primarily chimeric ClpB-ClpV constructs that directly recognize alternative substrates, thereby obviating DnaK involvement. We show that ClpB has low intrinsic Disaggregation activity that is normally repressed by the ClpB middle (M) domain. In the presence of aggregate, DnaK directly binds M-domain motif 2, increasing ClpB ATPase activity to unleash high ClpB threading power. Our results uncover a new function for Hsp70: the coupling of substrate targeting to AAA+ chaperone activation at aggregate surfaces.
Angshul Majumdar - One of the best experts on this subject based on the ideXlab platform.
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deep sparse coding for non intrusive load monitoring
arXiv: Signal Processing, 2019Co-Authors: Shikha Singh, Angshul MajumdarAbstract:Energy Disaggregation is the task of segregating the aggregate energy of the entire building (as logged by the smartmeter) into the energy consumed by individual appliances. This is a single channel (the only channel being the smart-meter) blind source (different electrical appliances) separation problem. The traditional way to address this is via stochastic finite state machines (e.g. Factorial Hidden Markov Model). In recent times dictionary learning based approaches have shown promise in addressing the Disaggregation problem. The usual technique is to learn a dictionary for every device and use the learnt dictionaries as basis for blind source separation during Disaggregation. Prior studies in this area are shallow learning techniques, i.e. they learn a single layer of dictionary for every device. In this work, we propose a deep learning approach, instead of learning one level of dictionary, we learn multiple layers of dictionaries for each device. These multi-level dictionaries are used as a basis for source separation during Disaggregation. Results on two benchmark datasets and one actual implementation show that our method outperforms state-of-the-art techniques.
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deep sparse coding for non intrusive load monitoring
IEEE Transactions on Smart Grid, 2018Co-Authors: Shikha Singh, Angshul MajumdarAbstract:Energy Disaggregation is the task of segregating the aggregate energy of the entire building (as logged by the smartmeter) into the energy consumed by individual appliances. This is a single channel (the only channel being the smart-meter) blind source (different electrical appliances) separation problem. The traditional way to address this is via stochastic finite state machines (e.g., factorial hidden Markov model). In recent times, dictionary learning-based approaches have shown promise in addressing the Disaggregation problem. The usual technique is to learn a dictionary for every device and use the learned dictionaries as basis for blind source separation during Disaggregation. Prior studies in this area are shallow learning techniques, i.e., they learn a single layer of dictionary for every device. In this paper, we propose a deep learning approach—instead of learning one level of dictionary, we learn multiple layers of dictionaries for each device. These multi-level dictionaries are used as a basis for source separation during Disaggregation. Results on two benchmark datasets and one actual implementation show that our method outperforms state-of-the-art techniques.
