DnaJ/Hsc70 chaperone complexes control the extracellular release of neurodegenerative‐associated proteins

Fontaine, Sarah N.; Zheng, Dechun; Sabbagh, Jonathan J.; Martin, Mackenzie D.; Chaput, Dale; Darling, April L.; Trotter, Justin H.; Stothert, Andrew R.; Nordhues, Bryce A.; Lussier, April L.; Baker, Jeremy D.; Shelton, Lindsey B.; Kahn, Mahnoor; Blair, Laura J.; Stevens, Stanley M.; Dickey, Chad A.

doi:10.15252/embj.201593489

Cited by 161 publications

(171 citation statements)

References 101 publications

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“…Although there is evidence that supports the neuronal release of tau [1, 9, 10, 56], our data also demonstrate that soluble intracellular phospho-tau could be toxic for microglia after phagocytosis. The phagocytic capacity of microglial cells is highly induced by apoptotic signals in the affected neurons [34, 52].…”

Section: Discussioncontrasting

confidence: 54%

Soluble phospho-tau from Alzheimer’s disease hippocampus drives microglial degeneration

et al. 2016

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The role of microglial cells in the development and progression of Alzheimer’s disease (AD) has not been elucidated. Here, we demonstrated the existence of a weak microglial response in human AD hippocampus which is in contrast to the massive microglial activation observed in APP-based models. Most importantly, microglial cells displayed a prominent degenerative profile (dentate gyrus > CA3 > CA1 > parahippocampal gyrus), including fragmented and dystrophic processes with spheroids, a reduced numerical density, and a significant decrease in the area of surveillance (“microglial domain”). Consequently, there was a substantial decline in the area covered by microglia which may compromise immune protection and, therefore, neuronal survival. In vitro experiments demonstrated that soluble fractions (extracellular/cytosolic) from AD hippocampi were toxic for microglial cells. This toxicity was abolished by AT8 and/or AT100 immunodepletion, validating that soluble phospho-tau was the toxic agent. These results were reproduced using soluble fractions from phospho-tau-positive Thy-tau22 hippocampi. Cultured microglial cells were not viable following phagocytosis of SH-SY5Y cells expressing soluble intracellular phospho-tau. Because the phagocytic capacity of microglial cells is highly induced by apoptotic signals in the affected neurons, we postulate that accumulation of intraneuronal soluble phospho-tau might trigger microglial degeneration in the AD hippocampus. This microglial vulnerability in AD pathology provides new insights into the immunological mechanisms underlying the disease progression and highlights the need to improve or develop new animal models, as the current models do not mimic the microglial pathology observed in the hippocampus of AD patients.Electronic supplementary materialThe online version of this article (doi:10.1007/s00401-016-1630-5) contains supplementary material, which is available to authorized users.

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Section: Discussioncontrasting

confidence: 54%

Soluble phospho-tau from Alzheimer’s disease hippocampus drives microglial degeneration

et al. 2016

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“…Although the transcellular spread of tau pathology has become a well-known, experimentally-confirmed phenomenon, the mechanisms through which this process occur have however remained elusive. It was recently reported that the internalisation of tau K18 fibrils occurs via binding with heparan sulphate proteoglycans [46] whilst the extracellular release of 4R0N tau occurs by exocytosis mediated by interaction with the DnaJC/Hsc70 molecular chaperone complex [47]. It however remains unknown as to whether all tau isoforms and fragments and their frontotemporal dementia variants are internalised and secreted through these same processes.…”

Section: Discussionmentioning

confidence: 99%

Expression and purification of tau protein and its frontotemporal dementia variants using a cleavable histidine tag

Karikari

Turner

Stass

et al. 2017

Protein Expression and Purification

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Recombinant tau protein is widely used to study the biochemical, cellular and pathological aspects of tauopathies, including Alzheimer's disease and frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTPD-17). Pure tau in high yield is a requirement for in vitro evaluation of the protein's physiological and toxic functions. However, the preparation of recombinant tau is complicated by the protein's propensity to aggregate and form truncation products, necessitating the use of multiple, time-consuming purification methods. In this study, we investigated parameters that influence the expression of wild type and FTPD-17 pathogenic tau, in an attempt to identify ways to maximise expression yield. Here, we report on the influence of the choice of host strain, induction temperature, duration of induction, and media supplementation with glucose on tau expression in Escherichia coli. We also describe a straightforward process to purify the expressed tau proteins using immobilised metal affinity chromatography, with favourable yields over previous reports. An advantage of the described method is that it enables high yield production of functional oligomeric and monomeric tau, both of which can be used to study the biochemical, physiological and toxic properties of the protein.

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“…Its overexpression leads to an increase in the concentration of tau in cell culture models, while an Hsc70 inhibitor causes a decrease in tau concentration in cell cultures and rescues long-term potentiation deficits in tauopathy model mouse brain slices (22,36). Hsc70 may also play roles in enhancing tau's association with microtubules (23) and in modulating the extracellular release of tau (37). While it is unclear how Hsc70 affects tau fibril formation, it has been shown to block the formation of fibrils by another amyloid-prone protein, α-synuclein, and even disaggregate pre-formed α-synuclein fibrils when combined with co-chaperones from the Hsp40 and Hsp110 families (33,38).…”

mentioning

confidence: 99%

HspB1 and Hsc70 chaperones engage distinct tau species and have different inhibitory effects on amyloid formation

Baughman

Clouser

Klevit

et al. 2018

Journal of Biological Chemistry

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The microtubule-associated protein tau forms insoluble, amyloid-type aggregates in various dementias, most notably Alzheimer's disease. Cellular chaperone proteins play important roles in maintaining protein solubility and preventing aggregation in the crowded cellular environment. While tau is known to interact with numerous chaperones, it remains unclear how these chaperones function mechanistically to prevent tau aggregation and how chaperones from different classes compare in terms of mechanism. Here, we focused on the small heat shock protein HspB1 and the constitutive chaperone Hsc70 (also known as HspA8), and report how each chaperone interacts with tau to prevent its fibril formation. Using fluorescence and NMR spectroscopy, we show that the two chaperones inhibit tau fibril formation by distinct mechanisms. HspB1 delayed tau fibril formation by weakly interacting with early species in the aggregation process, while Hsc70 was highly efficient at preventing tau fibril elongation possibly by capping the ends of tau fibrils. Both chaperones recognized aggregation-prone motifs within the microtubule-binding repeat region of tau. However, HspB1 binding remained transient in both aggregation-promoting and nonaggregating conditions, whereas Hsc70 binding was significantly tighter under aggregationpromoting conditions. These differences highlight the fact that chaperones from different families play distinct but complementary roles in the prevention of pathological protein aggregation.

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DnaJ/Hsc70 chaperone complexes control the extracellular release of neurodegenerative‐associated proteins

Cited by 161 publications

References 101 publications

Soluble phospho-tau from Alzheimer’s disease hippocampus drives microglial degeneration

Soluble phospho-tau from Alzheimer’s disease hippocampus drives microglial degeneration

Expression and purification of tau protein and its frontotemporal dementia variants using a cleavable histidine tag

HspB1 and Hsc70 chaperones engage distinct tau species and have different inhibitory effects on amyloid formation

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