Hsp40s play complementary roles in the prevention of tau amyloid formation

Irwin, Rose; Faust, Ofrah; Petrović, Ivana; Wolf, Sharon G.; Hofmann, Hagen; Rosenzweig, Rina

doi:10.7554/elife.69601

Cited by 36 publications

(34 citation statements)

References 72 publications

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“…We previously demonstrated that DNAJB8 H31Q is effective for profiling the misfoldome in response to cellular stress 20 , due to seemingly irreversible binding to its client proteins in the cell. DNAJB1 is one of the best studied Hsp40s due to its high concentration, promiscuous activity, selectivity for misfolded protein, and high similarity to yeast Sis1 15,36,46,47 , leading us to consider whether DNAJB1 could be similarly used to recover its cellular clients. We find that DNAJB1 WT preferentially associates with Hsp70 family members, pulling down a far less diverse proteome than DNAJB8 ( Figure S5 ), consistent with its primarily ATP (and presumably Hsp70)-dependent biological function.…”

Section: Discussionmentioning

confidence: 99%

Factors Affecting Protein Recovery During Hsp40 Affinity Profiling

Montoya

Quanrud

Mei

et al. 2022

Preprint

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Hsp40s play a central role in cellular protein homeostasis by promiscuously surveying the proteome for misfolded proteins. These misfolded client proteins are then delivered to Hsp70. Mutation of the Hsp40 J-domain blocks Hsp70 binding, inhibiting client protein release from Hsp40. We previously integrated misfolded protein recognition by Hsp40 into a platform to identify proteins that are destabilized by cellular stress. However, the dependences of Hsp40 interactions and client recovery on J-domain activity, Hsp40 identity, and crosslinking have not been addressed. Herein, we apply quantitative proteomics to systematically characterize the interactions networks of human Hsp40s DNAJB8 and DNAJB1 with intact or inactivated J-domains. We find that DNAJB8 irreversibly binds over a thousand protein interactors even in the absence of stress. Inactivation of the J-domain decreases interaction with Hsp70 family and associated proteins, but does not generally affect client binding. By contrast, J-domain inactivation and cellular crosslinking substantially increase the relative recovery of proteins from DNAJB1 co-immunoprecipitation. This advantage is completely offset by loss of DNAJB1 recovery under these conditions, making DNAJB1 a poor bait for client protein recovery as compared to DNAJB8. The J-domain inactivated DNAJB8H31Q has increased affinity to its client proteins under heat stress, while no such change in affinity is observed for the wild-type protein, despite their similar client binding profiles under basal conditions. Hence, we find that DNAJB8H31Q is an effective recognition element for the recovery of destabilized client proteins following cellular stress.

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Section: Discussionmentioning

confidence: 99%

Factors Affecting Protein Recovery During Hsp40 Affinity Profiling

Montoya

Quanrud

Mei

et al. 2022

Preprint

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“…, 2016 ). Related Hsp40s have also been found to bind in different ways to a given substrate ( Irwin et al. , 2021 ).…”

Section: Discussionmentioning

confidence: 99%

Hsp40s play distinct roles during the initial stages of apolipoprotein B biogenesis

Kumari

Fisher

Brodsky

2022

MBoC

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Apolipoprotein B (ApoB) is the primary component of atherogenic lipoproteins, which transport serum fats and cholesterol. Therefore, elevated levels of circulating ApoB are a primary risk factor for cardiovascular disease. During ApoB biosynthesis in the liver and small intestine under nutrient-rich conditions, ApoB cotranslationally translocates into the endoplasmic reticulum (ER) and is lipidated and ultimately secreted. Under lipid-poor conditions, ApoB is targeted for ER Associated Degradation (ERAD). Although prior work identified select chaperones that regulate ApoB biogenesis, the contributions of cytoplasmic Hsp40s are undefined. To this end, we screened ApoB-expressing yeast and determined that a class A ER-associated Hsp40, Ydj1, associates with and facilitates the ERAD of ApoB. Consistent with these results, a homologous Hsp40, DNAJA1, functioned similarly in rat hepatoma cells. DNAJA1 deficient cells also secreted hyperlipidated lipoproteins, in accordance with attenuated ERAD. In contrast to the role of DNAJA1 during ERAD, DNAJB1—a class B Hsp40—helped stabilize ApoB. Depletion of DNAJA1 and DNAJB1 also led to opposing effects on ApoB ubiquitination. These data represent the first example in which different Hsp40s exhibit disparate effects during regulated protein biogenesis in the ER, and highlight distinct roles that chaperones can play on a single ERAD substrate.

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“…the minimum oligomer size not in equilibrium with the monomer. 27 Although this nucleus is often assumed to be a dimer 28, 29 , estimates range from monomers 30 to tetramers. 31 The challenge with determining the critical nucleus size from experiments like those using ThT fluorescence is that any oligomer of the critical nucleus size or higher is assumed to be fibrillar and thus observable: this assumption couples the results of the kinetic modelling to resolution limit of the experiment and may explain some of the variability seen in critical nucleus size estimates.…”

Section: Discussionmentioning

confidence: 99%

Quantifying oligomer populations in real time during protein aggregation using single-molecule mass photometry

Paul

Lyons

Kirchner

et al. 2022

Preprint

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Protein aggregation is a hallmark of many neurodegenerative diseases. The early stages of the aggregation cascade are crucial because small oligomers are thought to be key neurotoxic species, but they are difficult to study because they feature heterogeneous mixtures of transient states. We show how the populations of different oligomers can be tracked as they evolve over time during aggregation by using single-molecule mass photometry to measure individually the masses of the oligomers present in solution. Applying the approach to tau protein, whose aggregates are linked to diseases including Alzheimer's and frontotemporal dementia, we found that tau existed in an equilibrium between monomers, dimers, and trimers before aggregation was triggered. Once aggregation commenced, the monomer population dropped continuously, paired first with a rise in the population of the smallest oligomers and then a steep drop as the protein was incorporated into larger oligomers and fibrils. Fitting these populations to kinetic models allowed different models of aggregation to be tested, identifying the most likely mechanism and quantifying the microscopic rates for each step in the mechanism. This work demonstrates a powerful new approach for characterizing previously inaccessible regimes in protein aggregation and building quantitative mechanistic models.

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Hsp40s play complementary roles in the prevention of tau amyloid formation

Cited by 36 publications

References 72 publications

Factors Affecting Protein Recovery During Hsp40 Affinity Profiling

Factors Affecting Protein Recovery During Hsp40 Affinity Profiling

Hsp40s play distinct roles during the initial stages of apolipoprotein B biogenesis

Quantifying oligomer populations in real time during protein aggregation using single-molecule mass photometry

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