Inert and seed-competent tau monomers suggest structural origins of aggregation

Mirbaha, Hilda; Chen, Dailu; Morozova, Olga A.; Ruff, Kiersten M.; Sharma, Apurwa M; Liu, Xiaohua; Pappu, Rohit V.; Colby, David W.; Mirzaei, Hamid; Joachimiak, Łukasz A.; Diamond, Marc I.

doi:10.1101/163394

Cited by 21 publications

(41 citation statements)

References 37 publications

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“…6D). This implies that low molecular weight species or even monomeric Tau might be seeding-competent, which is in line with a recent study showing that fibril-derived Tau monomers exhibit seeding activity (Mirbaha et al, 2018). Hence, monomeric or small oligomeric Tau liberated from fibrils by chaperone action might still maintain a seeding-competent conformation that is different than naïve monomeric Tau.…”

Section: Discussionsupporting

confidence: 84%

Disassembly of Tau fibrils by the human Hsp70 disaggregation machinery generates small seeding-competent species

Nachman

Wentink

Madiona

et al. 2019

Preprint

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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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Section: Discussionsupporting

confidence: 84%

Disassembly of Tau fibrils by the human Hsp70 disaggregation machinery generates small seeding-competent species

Nachman

Wentink

Madiona

et al. 2019

Preprint

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“…Indeed, it is unlikely that a single, unique toxic conformation exists. It is far more likely that an ensemble of toxic oligomers (differing in size, conformation and even molecular constituency) populates the amylogenic cascade [29][30][31][32][33][34][35] . This heterogeneity in potential tau oligomer targets highlights the need for an ultrasensitive screening platform capable of monitoring structural changes within the ensemble of tau assemblies.…”

Section: Discussionmentioning

confidence: 99%

“…However, these studies were done in vitro with purified proteins, and the compounds were protective only in the low micromolar range [22][23][24][25][26][27][28] . Tau oligomers exist as an ensemble of distinct assemblies which include both toxic and non-toxic, onand off-pathway species along the fibrillogenesis cascade [29][30][31][32][33][34][35] . The formation of these toxic tau oligomers has been associated with mutations and overexpression of numerous chaperone proteins [36][37] , highlighting the importance of other components of the tau-protein interactome in the pathogenesis of tauopathies.…”

Section: Introductionmentioning

confidence: 99%

“…The formation of these toxic tau oligomers has been associated with mutations and overexpression of numerous chaperone proteins [36][37] , highlighting the importance of other components of the tau-protein interactome in the pathogenesis of tauopathies. Capturing this complexity in an in vitro setting is extremely difficult, if even possible, and established protocols for aggregating purified tau protein into oligomers, PHFs, and NFTs have, not surprisingly, been shown to produce different tau assemblies depending on aggregation conditions 17,31,34,[38][39][40][41] . Critically, no specific toxic tau species has been isolated or identified to date 21,[42][43] .…”

Section: Introductionmentioning

confidence: 99%

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A novel small molecule screening platform for disrupting toxic tau oligomers in cells

Lim

Ding

et al. 2019

Preprint

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Tauopathies, including Alzheimer's disease, are a group of neurodegenerative disorders characterized by pathological aggregation of the microtubule binding protein tau. Recent studies suggest that toxic tau oligomers, which are soluble and distinct from insoluble beta-sheet fibrils, are central players in neuronal cell death. To exploit this new therapeutic window, we engineered two first-in-class FRET based biosensors that monitor tau conformations in cells. Because this new technology platform operates in cells, it enables high-throughput screening of small molecules that target tau oligomers while avoiding the uncertainties of idiosyncratic in vitro preparations of tau assemblies from purified protein. We found a small molecule, MK-886, that disrupts tau oligomers and reduces tau-induced cell cytotoxicity with nanomolar potency. Using SPR and an advanced single-molecule FRET technique, we show that MK-886 directly binds to tau and specifically perturbs the folding of tau monomer in the proline-rich and microtubule-binding regions. Furthermore, we show that MK-886 accelerates the tau aggregation lag phase using a thioflavin-T assay, implying that the compound stabilizes a non-toxic, on-pathway oligomer. The technology described here should generalize to the study and targeting of conformational ensembles within the aggregation pathways of most intrinsically disordered proteins.

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“…Together, our findings highlight the potential of targeting tau phosphorylation for the treatment of AD and tauopathies and underscore the critical importance of revisiting showed that monomeric tau exists in multiple conformations that possess distinct seeding activity 59 . These finding also imply that stabilizing the native seeding incompetent tau monomers could also provide an alternative mechanism for blocking aSyn aggregation, seeding and pathology formation.…”

Section: Discussionmentioning

confidence: 63%

Site-specific hyperphosphorylation of tau inhibits its fibrillization in vitro, blocks its seeding capacity in cells, and disrupts its microtubule binding; Implications for the native state stabilization of tau

Lashuel

Haj‐Yahya

Pushparathinam

et al. 2019

Preprint

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The consistent observation of aggregated phosopho-tau in the pathology of Alzheimer's disease and other tauopathies has contributed to the emergence of a model where hyperphosphorylation of tau causes its disassociation from microtubules and subsequent pathological polymerization. However, the large number of possible phosphorylation sites in tau and lack of robust methods that enable the preparation of homogeneously phosphorylated tau species have made it difficult to validate this model. Herein, we applied a total chemical synthetic approach to site-specifically phosphorylate single (pS356) or multiple (pS356/pS262 and pS356/pS262/pS258) residues within the microtubule binding repeat domain (MTBD) of tau and show that hyperphosphorylation within the microtubule MTBD inhibits K18 tau 1) aggregation in vitro; 2) its seeding activity in cells, and 3) its ability to promote microtubule polymerization. The inhibition increased with the number of phosphorylated sites, with phosphorylation at S262 having the strongest effect. On the basis of these findings, we propose that targeting the kinases that regulate phosphorylation at these sites could provide a viable strategy to stabilize the native state of tau and inhibit its aggregation. Taken together, our results argue against the pathogenic hyperphosphorylation hypothesis and underscore the critical importance of revisiting the role of site-specific hyperphosphorylation of tau in regulating its function in health and disease.Hilal A. Lashuel is the founder and CSO of ND BioSciences. Corresponding authorCorrespondence to Hilal A. Lashuel.

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Inert and seed-competent tau monomers suggest structural origins of aggregation

Cited by 21 publications

References 37 publications

Disassembly of Tau fibrils by the human Hsp70 disaggregation machinery generates small seeding-competent species

Disassembly of Tau fibrils by the human Hsp70 disaggregation machinery generates small seeding-competent species

A novel small molecule screening platform for disrupting toxic tau oligomers in cells

Site-specific hyperphosphorylation of tau inhibits its fibrillization in vitro, blocks its seeding capacity in cells, and disrupts its microtubule binding; Implications for the native state stabilization of tau

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