scholarly journals DNAJB chaperones inhibit aggregation of destabilised proteins via a C-terminal region distinct from that used to prevent amyloid formation

2020 ◽  
Author(s):  
Shannon McMahon ◽  
Steven Bergink ◽  
Harm H. Kampinga ◽  
Heath Ecroyd
Keyword(s):  
Protein Aggregation ◽  
Molecular Chaperones ◽  
Firefly Luciferase ◽  
Amyloid Formation ◽  
Protein Homeostasis ◽  
Formation Processes ◽  
Inclusion Formation ◽  
Different Types ◽  
Summary Statement ◽  
Client Proteins

AbstractDisturbances to protein homeostasis (proteostasis) can lead to protein aggregation and inclusion formation, processes associated with a variety of neurodegenerative disorders. DNAJBs are molecular chaperones previously identified as potent suppressors of disease-related protein aggregation. In this work, we over-expressed a destabilised isoform of firefly luciferase (R188Q/R261Q Fluc; FlucDM) in cells to assess the capacity of DNAJBs to inhibit inclusion formation. Co-expression of all DNAJBs tested significantly inhibited the intracellular aggregation of FlucDM. Moreover, we show that DNAJBs suppress aggregation by supporting the Hsp70-dependent degradation of FlucDM via the proteasome. The serine-rich stretch in DNAJB6 and DNAJB8, essential for preventing fibrillar aggregation, is not involved in the suppression of FlucDM inclusion formation. Conversely, deletion of the C-terminal TTK-LKS region in DNAJB8, a region not required to suppress polyQ aggregation, abolished its ability to inhibit inclusion formation by FlucDM. Thus, our data suggest that DNAJB6 and DNAJB8 possess two distinct domains involved in the inhibition of protein aggregation, one responsible for binding to β-hairpins that form during amyloid formation and another that mediates the degradation of destabilised client proteins via the proteasome.Summary statementSpecialised DNAJB molecular chaperones are potent suppressors of protein aggregation and interact with different types of client proteins via distinct C-terminal regions

scholarly journals DNAJB chaperones suppress destabilised protein aggregation via a region unique from that used to inhibit amyloidogenesis

2021 ◽  
pp. jcs.255596
Author(s):  
Shannon McMahon ◽  
Steven Bergink ◽  
Harm H. Kampinga ◽  
Heath Ecroyd
Keyword(s):  
Protein Aggregation ◽  
Molecular Chaperones ◽  
Neurodegenerative Disorders ◽  
Firefly Luciferase ◽  
Amyloid Formation ◽  
Protein Homeostasis ◽  
Formation Processes ◽  
Related Protein ◽  
Inclusion Formation ◽  
In Cells

Disturbances to protein homeostasis (proteostasis) can lead to protein aggregation and inclusion formation, processes associated with a variety of neurodegenerative disorders. DNAJBs are molecular chaperones which have been identified as potent suppressors of disease-related protein aggregation. In this work, a destabilised isoform of firefly luciferase (R188Q/R261Q Fluc; FlucDM) was overexpressed in cells to assess the capacity of DNAJBs to inhibit inclusion formation. Co-expression of all DNAJBs tested significantly inhibited the intracellular aggregation of FlucDM. Moreover, we show that DNAJBs suppress aggregation by supporting the Hsp70-dependent degradation of FlucDM via the proteasome. The serine-rich stretch in DNAJB6 and DNAJB8, essential for preventing fibrillar aggregation, is not involved in the suppression of FlucDM inclusion formation. Conversely, deletion of the C-terminal TTK-LKS motif in DNAJB6 and DNAJB8, a region not required to suppress polyQ aggregation, abolished its ability to inhibit inclusion formation by FlucDM. Thus, our data suggest that DNAJB6 and DNAJB8 possess two distinct regions for binding substrates, one that is responsible for binding β-hairpins that form during amyloid formation and another that interacts with exposed hydrophobic patches in aggregation-prone clients.

scholarly journals Hsp70 molecular chaperones: multifunctional allosteric holding and unfolding machines

2019 ◽  
Vol 476 (11) ◽  
pp. 1653-1677 ◽  
Author(s):  
Eugenia M. Clerico ◽  
Wenli Meng ◽  
Alexandra Pozhidaeva ◽  
Karishma Bhasne ◽  
Constantine Petridis ◽  
...  
Keyword(s):  
Molecular Chaperones ◽  
Protein Homeostasis ◽  
Nucleotide Exchange ◽  
Cellular Functions ◽  
The Past ◽  
Hsp70 Family ◽  
Nucleotide Exchange Factors ◽  
Client Proteins ◽  
Structural Insights ◽  
Insight Into

AbstractThe Hsp70 family of chaperones works with its co-chaperones, the nucleotide exchange factors and J-domain proteins, to facilitate a multitude of cellular functions. Central players in protein homeostasis, these jacks-of-many-trades are utilized in a variety of ways because of their ability to bind with selective promiscuity to regions of their client proteins that are exposed when the client is unfolded, either fully or partially, or visits a conformational state that exposes the binding region in a regulated manner. The key to Hsp70 functions is that their substrate binding is transient and allosterically cycles in a nucleotide-dependent fashion between high- and low-affinity states. In the past few years, structural insights into the molecular mechanism of this allosterically regulated binding have emerged and provided deep insight into the deceptively simple Hsp70 molecular machine that is so widely harnessed by nature for diverse cellular functions. In this review, these structural insights are discussed to give a picture of the current understanding of how Hsp70 chaperones work.

scholarly journals Suppression of aggregate and amyloid formation by a novel intrinsically disordered region in metazoan Hsp110 chaperones

2021 ◽  
Author(s):  
Unekwu M. Yakubu ◽  
Kevin A. Morano
Keyword(s):  
Protein Aggregation ◽  
Molecular Chaperones ◽  
Citrate Synthase ◽  
Neuronal Cell ◽  
Amyloid Formation ◽  
Nucleotide Exchange ◽  
Aggregation Assay ◽  
Intrinsically Disordered ◽  
Intrinsically Disordered Region

AbstractMolecular chaperones maintain protein homeostasis (proteostasis) by ensuring the proper folding of polypeptides. Loss of proteostasis has been linked to the onset of numerous neurodegenerative disorders including Alzheimer’s, Parkinson’s, and Huntington’s disease. Hsp110 is related to the canonical Hsp70 class of protein folding molecular chaperones and interacts with Hsp70 as a nucleotide exchange factor (NEF), promoting rapid cycling of ADP for ATP. In addition to its NEF activity, Hsp110 possesses an Hsp70-like substrate binding domain (SBD) whose biological roles remain undefined. Previous work in Drosophila melanogaster has shown that loss of the sole Hsp110 gene (Hsc70cb) accelerates the aggregation of polyglutamine (polyQ)-expanded human Huntingtin, while its overexpression protects against polyQ-mediated neuronal cell death. We hypothesize that in addition to its role as an Hsp70 NEF, Drosophila Hsp110 may function in the fly as a protective protein “holdase”, preventing the aggregation of unfolded polypeptides via the SBD-β subdomain. Using an in vitro protein aggregation assay we demonstrate for the first time that Drosophila Hsp110 effectively prevents aggregation of the model substrate citrate synthase. We also report the discovery of a redundant and heretofore unknown potent holdase capacity in a 138 amino-acid region of Hsp110 carboxyl-terminal to both SBD-β and SBD-α (henceforth called the C-terminal extension). This sequence is highly conserved in metazoan Hsp110 genes, completely absent from fungal representatives, including Saccharomyces cerevisiae SSE1, and is computationally predicted to contain an intrinsically disordered region (IDR). We demonstrate that this IDR sequence within the human Hsp110s, Apg-1 and Hsp105α, inhibits the formation of amyloid Aβ-42 and α-synuclein fibrils in vitro but cannot mediate fibril disassembly. Together these findings demonstrate the existence of a second independent, passive holdase property of metazoan Hsp110 chaperones capable of suppressing both general protein aggregation and amyloidogenesis and raise the possibility of exploitation of this IDR for therapeutic benefit in combating neurodegenerative disease.

scholarly journals Redefining Molecular Chaperones as Chaotropes

2021 ◽  
Vol 8 ◽  
Author(s):  
Jakub Macošek ◽  
Guillaume Mas ◽  
Sebastian Hiller
Keyword(s):  
Molecular Chaperones ◽  
Protein Denaturation ◽  
Protein Homeostasis ◽  
Bacterial Protein ◽  
Client Protein ◽  
Dynamic Interactions ◽  
Biophysical Mechanism ◽  
Functional Regulation ◽  
Client Proteins

Molecular chaperones are the key instruments of bacterial protein homeostasis. Chaperones not only facilitate folding of client proteins, but also transport them, prevent their aggregation, dissolve aggregates and resolve misfolded states. Despite this seemingly large variety, single chaperones can perform several of these functions even on multiple different clients, thus suggesting a single biophysical mechanism underlying. Numerous recently elucidated structures of bacterial chaperone–client complexes show that dynamic interactions between chaperones and their client proteins stabilize conformationally flexible non-native client states, which results in client protein denaturation. Based on these findings, we propose chaotropicity as a suitable biophysical concept to rationalize the generic activity of chaperones. We discuss the consequences of applying this concept in the context of ATP-dependent and -independent chaperones and their functional regulation.

scholarly journals Hsp40s display class-specific binding profiles, serving complementary roles in the prevention of tau amyloid formation

2021 ◽  
Author(s):  
Rose Irwin ◽  
Ofrah Faust ◽  
Ivana Petrovic ◽  
Sharion Grayer Wolf ◽  
Hagen Hofmann ◽  
...  
Keyword(s):  
Molecular Chaperones ◽  
Specific Binding ◽  
Small Heat Shock Protein ◽  
Fiber Formation ◽  
Amyloid Formation ◽  
Protein Homeostasis ◽  
Protein Tau ◽  
Amyloid Fiber Formation ◽  
Tau Aggregation ◽  
Insight Into

The microtubule-associated protein, tau, is the major subunit of neurofibrillary tangles, forming insoluble, amyloid-type aggregates associated with neurodegenerative conditions, such as Alzheimer's disease. Tau aggregation, however, can be prevented in the cell by a class of proteins known as molecular chaperones, which play important roles in maintaining protein homeostasis. While numerous chaperones are known to interact with tau, though, little is known about the detailed mechanisms by which these prevent tau aggregation. Here, we describe the effects of the ATP-independent Hsp40 chaperones, DNAJA2 and DNAJB1, on tau amyloid fiber formation and compare these to the well-studied small heat shock protein HSPB1. We find that each chaperone prevents tau aggregation differently, by interacting with distinct sets of tau species along the aggregation pathway and thereby affecting their incorporation into fibers. Whereas HSPB1 only binds tau monomers, DNAJB1 and DNAJA2 recognize aggregation-prone tau conformers and even mature fibers, thus efficiently preventing formation of tau amyloids. In addition, we find that both Hsp40s bind tau seeds and fibers via their C-terminal domain II (CTDII), with DNAJA2 being further capable of recognizing tau monomers by a second, different site in CTDI. These results provide important insight into the molecular mechanism by which the different members of the Hsp40 chaperone family counteract the formation, propagation, and toxicity of tau aggregates. Furthermore, our findings highlight the fact that chaperones from different families and different classes play distinct, but complementary roles in preventing pathological protein aggregation.

The physical chemistry of the amyloid phenomenon: thermodynamics and kinetics of filamentous protein aggregation

2014 ◽  
Vol 56 ◽  
pp. 11-39 ◽  
Author(s):  
Alexander K. Buell ◽  
Christopher M. Dobson ◽  
Tuomas P.J. Knowles
Keyword(s):  
Protein Aggregation ◽  
Molecular Chaperones ◽  
Amyloid Fibrils ◽  
Theoretical Modelling ◽  
Amyloid Formation ◽  
Recent Developments ◽  
The Individual ◽  
Kinetics Of ◽  
Soluble State ◽  
Insight Into

In this chapter, we present an overview of the kinetics and thermodynamics of protein aggregation into amyloid fibrils. The perspective we adopt is largely experimental, but we also discuss recent developments in data analysis and we show that only a combination of well-designed experiments with appropriate theoretical modelling is able to provide detailed mechanistic insight into the complex pathways of amyloid formation. In the first part of the chapter, we describe measurements of the thermodynamic stability of the amyloid state with respect to the soluble state of proteins, as well as the magnitude and origin of this stability. In the second part, we discuss in detail the kinetics of the individual molecular steps in the overall mechanism of the conversion of soluble protein into amyloid fibrils. Finally, we highlight the effects of external factors, such as salt type and concentration, chemical denaturants and molecular chaperones on the kinetics of aggregation.

Fluctuations

2018 ◽  
Author(s):  
Richard Wigmans
Keyword(s):  
Energy Dependence ◽  
Energy Resolution ◽  
Practical Importance ◽  
Shower Particle ◽  
Formation Processes ◽  
Instrumental Effects ◽  
Important Type ◽  
High Energies ◽  
Different Types ◽  
Electromagnetic Component

The energy resolution, i.e. the precision with which the energy of a showering particle can be measured, is one of the most important characteristics of a calorimeter. This resolution is determined by fluctuations in the absorption and signal formation processes. In this chapter, the different types of fluctuations that may play a role are examined, and their relative practical importance is addressed. Sources of fluctuations include fluctuations in the number of signal quanta, sampling fluctuations, fluctuations in shower leakage, as well as a variety of instrumental effects. Since the energy dependence of the different types of fluctuations is not the same, different types of fluctuations may dominate the energy resolution at low and and at high energies. An important type of fluctuations is part of the non-compensation phenomena. It concerns fluctuations in the strength of the electromagnetic component of hadronic showers. The effects of these fluctuations, which typically dominate the energy resolution for hadron and jet detection, are examined in detail. In sampling calorimeters, one particular shower particle may sometimes have catastrophic effects on the calorimeter performance. Several examples of such cases are discussed.

scholarly journals Valorization of Apple Peels through the Study of the Effects on the Amyloid Aggregation Process of κ-Casein

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2371
Author(s):  
Valeria Guarrasi ◽  
Giacoma Cinzia Rappa ◽  
Maria Assunta Costa ◽  
Fabio Librizzi ◽  
Marco Raimondo ◽  
...  
Keyword(s):  
Protein Aggregation ◽  
Environmental Sustainability ◽  
Bovine Milk ◽  
Amyloid Formation ◽  
Aggregation Process ◽  
Amyloid Aggregation ◽  
Social Challenges ◽  
Force Microscopy ◽  
Atomic Force ◽  
Apple Peels

Waste valorization represents one of the main social challenges when promoting a circular economy and environmental sustainability. Here, we evaluated the effect of the polyphenols extracted from apple peels, normally disposed of as waste, on the amyloid aggregation process of κ-casein from bovine milk, a well-used amyloidogenic model system. The effect of the apple peel extract on protein aggregation was examined using a thioflavin T fluorescence assay, Congo red binding assay, circular dichroism, light scattering, and atomic force microscopy. We found that the phenolic extract from the peel of apples of the cultivar “Fuji”, cultivated in Sicily (Caltavuturo, Italy), inhibited κ-casein fibril formation in a dose-dependent way. In particular, we found that the extract significantly reduced the protein aggregation rate and inhibited the secondary structure reorganization that accompanies κ-casein amyloid formation. Protein-aggregated species resulting from the incubation of κ-casein in the presence of polyphenols under amyloid aggregation conditions were reduced in number and different in morphology.

scholarly journals Hsp90 and its co-chaperone Sti1 control TDP-43 misfolding and toxicity

2020 ◽  
Author(s):  
Lilian Tsai-Wei Lin ◽  
Abdul Razzaq ◽  
Sonja E. Di Gregorio ◽  
Soojie Hong ◽  
Brendan Charles ◽  
...  
Keyword(s):  
Neurodegenerative Diseases ◽  
Molecular Chaperones ◽  
Protein Misfolding ◽  
Central Feature ◽  
Dependent Manner ◽  
Cellular Toxicity ◽  
Inclusion Formation ◽  
Dose Dependent ◽  
Lateral Sclerosis ◽  
Strong Capacity

AbstractProtein misfolding is a central feature of most neurodegenerative diseases. Molecular chaperones can modulate the toxicity associated with protein misfolding, but it remains elusive which molecular chaperones and co-chaperones interact with specific misfolded proteins. TDP-43 misfolding and inclusion formation is a hallmark of amyotrophic lateral sclerosis (ALS) and other neurodegenerative diseases. Using yeast and mammalian neuronal cells we find that Hsp90 and its co-chaperones have a strong capacity to alter TDP-43 misfolding, inclusion formation, aggregation, and cellular toxicity. Our data also demonstrate that impaired Hsp90 function sensitizes cells to TDP-43 toxicity. We further show that the co-chaperone Sti1 specifically interacts with and modulates TDP-43 toxicity in a dose-dependent manner. Our study thus uncovers a previously unrecognized tie between Hsp90, Sti1, TDP-43 misfolding, and its cellular toxicity.

Is it possible to determine formation processes of organic deposits through polysaccharides? Pilot study from the prehistoric site in Brandýs nad Labem, Czech Republic

The Holocene ◽  
2017 ◽  
Vol 27 (9) ◽  
pp. 1273-1280
Author(s):  
Klement Rejšek ◽  
Jan Turek ◽  
Valerie Vranová ◽  
Roman Hadacz ◽  
Lenka Lisá
Keyword(s):  
Czech Republic ◽  
Pilot Study ◽  
Organic Material ◽  
Archaeological Site ◽  
Soil Samples ◽  
Formation Processes ◽  
Cultural Layer ◽  
Different Types ◽  
Organic Deposits

This paper deals with a possible interpretation value of biochemical methods in comparison with the classic tools of geoarchaeology for the evaluation of formation processes. Organic rich layers from the archaeological site Brandýs nad Labem-Vrábí were tested with the aim to determine the origin of several different types of soil organic material by analyzing the content of different sugars. The studied soil body showed signs of cultural layer, redeposited soils, and in situ developed soil. The analysis of different sugars was highlighted: soil samples taken from these layers were analyzed to assess the ratios of mannose + galactose to arabinose + xylose, and of rhamnose + fucose to arabinose + xylose, content of Corg and different nitrates, as well as different rates of absorbance. The results show that the interpretation values of polysaccharides evaluation didn’t bring significant results itself, but in combination with classical tools of geoarchaeology may bring interpretable and new results.

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