Faculty Opinions recommendation of The interactions of molecular chaperones with client proteins: why are they so weak?

Age-dependent alterations in the proteostasis network are crucial in the progress of prevalent neurodegenerative diseases, such as Alzheimer’s, Parkinson’s, or amyotrophic lateral sclerosis, which are characterized by the presence of insoluble protein deposits in degenerating neurons. Because molecular chaperones deter misfolded protein aggregation, regulate functional phase separation, and even dissolve noxious aggregates, they are considered major sentinels impeding the molecular processes that lead to cell damage in the course of these diseases. Indeed, members of the chaperome, such as molecular chaperones and co-chaperones, are increasingly recognized as therapeutic targets for the development of treatments against degenerative proteinopathies. Chaperones must recognize diverse toxic clients of different orders (soluble proteins, biomolecular condensates, organized protein aggregates). It is therefore critical to understand the basis of the selective chaperone recognition to discern the mechanisms of action of chaperones in protein conformational diseases. This review aimed to define the selective interplay between chaperones and toxic client proteins and the basis for the protective role of these interactions. The presence and availability of chaperone recognition motifs in soluble proteins and in insoluble aggregates, both functional and pathogenic, are discussed. Finally, the formation of aberrant (pro-toxic) chaperone complexes will also be disclosed.

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Hsp70 molecular chaperones: multifunctional allosteric holding and unfolding machines

Biochemical Journal ◽

10.1042/bcj20170380 ◽

2019 ◽

Vol 476 (11) ◽

pp. 1653-1677 ◽

Cited By ~ 19

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.

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HSP90 Molecular Chaperones, Metabolic Rewiring, and Epigenetics: Impact on Tumor Progression and Perspective for Anticancer Therapy

Cells ◽

10.3390/cells8060532 ◽

2019 ◽

Vol 8 (6) ◽

pp. 532 ◽

Cited By ~ 19

Author(s):

Valentina Condelli ◽

Fabiana Crispo ◽

Michele Pietrafesa ◽

Giacomo Lettini ◽

Danilo Swann Matassa ◽

...

Keyword(s):

Cancer Progression ◽

Molecular Chaperones ◽

Heat Shock Protein 90 ◽

Anticancer Therapy ◽

Cellular Functions ◽

Master Regulators ◽

Cellular Processes ◽

Direct Binding ◽

Client Proteins ◽

The Relationship

Heat shock protein 90 (HSP90) molecular chaperones are a family of ubiquitous proteins participating in several cellular functions through the regulation of folding and/or assembly of large multiprotein complexes and client proteins. Thus, HSP90s chaperones are, directly or indirectly, master regulators of a variety of cellular processes, such as adaptation to stress, cell proliferation, motility, angiogenesis, and signal transduction. In recent years, it has been proposed that HSP90s play a crucial role in carcinogenesis as regulators of genotype-to-phenotype interplay. Indeed, HSP90 chaperones control metabolic rewiring, a hallmark of cancer cells, and influence the transcription of several of the key-genes responsible for tumorigenesis and cancer progression, through either direct binding to chromatin or through the quality control of transcription factors and epigenetic effectors. In this review, we will revise evidence suggesting how this interplay between epigenetics and metabolism may affect oncogenesis. We will examine the effect of metabolic rewiring on the accumulation of specific metabolites, and the changes in the availability of epigenetic co-factors and how this process can be controlled by HSP90 molecular chaperones. Understanding deeply the relationship between epigenetic and metabolism could disclose novel therapeutic scenarios that may lead to improvements in cancer treatment.

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Multifaceted roles of HEAT SHOCK PROTEIN 90 molecular chaperones in plant development

Journal of Experimental Botany ◽

10.1093/jxb/eraa177 ◽

2020 ◽

Vol 71 (14) ◽

pp. 3966-3985 ◽

Cited By ~ 5

Author(s):

Tereza Tichá ◽

Despina Samakovli ◽

Anna Kuchařová ◽

Tereza Vavrdová ◽

Jozef Šamaj

Keyword(s):

Heat Shock ◽

Plant Development ◽

Molecular Chaperones ◽

Current Knowledge ◽

Heat Shock Protein 90 ◽

Molecular Networks ◽

Genetic Perturbations ◽

Client Proteins ◽

Developmental Signalling ◽

Shock Proteins

Abstract HEAT SHOCK PROTEINS 90 (HSP90s) are molecular chaperones that mediate correct folding and stability of many client proteins. These chaperones act as master molecular hubs involved in multiple aspects of cellular and developmental signalling in diverse organisms. Moreover, environmental and genetic perturbations affect both HSP90s and their clients, leading to alterations of molecular networks determining respectively plant phenotypes and genotypes and contributing to a broad phenotypic plasticity. Although HSP90 interaction networks affecting the genetic basis of phenotypic variation and diversity have been thoroughly studied in animals, such studies are just starting to emerge in plants. Here, we summarize current knowledge and discuss HSP90 network functions in plant development and cellular homeostasis.

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Molecular chaperones and their denaturing effect on client proteins

Journal of Biomolecular NMR ◽

10.1007/s10858-020-00353-7 ◽

2020 ◽

Author(s):

Sebastian Hiller

Keyword(s):

Molecular Chaperone ◽

Molecular Chaperones ◽

Backbone Dynamics ◽

Future Research ◽

Chaperone Function ◽

Structure And Dynamics ◽

Client Proteins ◽

Biophysical Techniques ◽

Nmr Methods ◽

Insight Into

Abstract Advanced NMR methods combined with biophysical techniques have recently provided unprecedented insight into structure and dynamics of molecular chaperones and their interaction with client proteins. These studies showed that several molecular chaperones are able to dissolve aggregation-prone polypeptides in aqueous solution. Furthermore, chaperone-bound clients often feature fluid-like backbone dynamics and chaperones have a denaturing effect on clients. Interestingly, these effects that chaperones have on client proteins resemble the effects of known chaotropic substances. Following this analogy, chaotropicity could be a fruitful concept to describe, quantify and rationalize molecular chaperone function. In addition, the observations raise the possibility that at least some molecular chaperones might share functional similarities with chaotropes. We discuss these concepts and outline future research in this direction.

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GR chaperone cycle mechanism revealed by cryo-EM: inactivation of GR by GR:Hsp90:Hsp70:Hop client-loading complex

10.1101/2020.11.05.370247 ◽

2020 ◽

Author(s):

Ray Yu-Ruei Wang ◽

Chari M. Noddings ◽

Elaine Kirschke ◽

Alexander G. Myasnikov ◽

Jill L. Johnson ◽

...

Keyword(s):

Glucocorticoid Receptor ◽

Molecular Mechanism ◽

Molecular Chaperones ◽

Molecular Basis ◽

Atp Hydrolysis ◽

Binding Pocket ◽

The Other ◽

Client Proteins ◽

Partially Unfolded

AbstractMaintaining a healthy proteome is fundamental for organism survival1,2. Integral to this are Hsp90 and Hsp70 molecular chaperones that together facilitate the folding, remodeling and maturation of Hsp90’s many “client” proteins3–7. The glucocorticoid receptor (GR) is a model client strictly dependent upon Hsp90/Hsp70 for activity8–13. Chaperoning GR involves a cycle of inactivation by Hsp70, formation of an inactive GR:Hsp90:Hsp70:Hop “loading” complex, conversion to an active GR:Hsp90:p23 “maturation” complex, and subsequent GR release14. Unfortunately, a molecular understanding of this intricate chaperone cycle is lacking for any client. Here, we report the cryo-EM structure of the GR loading complex, in which Hsp70 loads GR onto Hsp90, revealing the molecular basis of direct Hsp90/Hsp70 coordination. The structure reveals two Hsp70s—one delivering GR and the other scaffolding Hop. Unexpectedly, the Hop cochaperone interacts with all components of the complex including GR, poising Hsp90 for subsequent ATP hydrolysis. GR is partially unfolded and recognized via an extended binding pocket composed of Hsp90, Hsp70 and Hop, revealing the mechanism of GR loading and inactivation. Together with the GR maturation complex (Noddings et al., 2020), we present the first complete molecular mechanism of chaperone-dependent client remodeling, establishing general principles of client recognition, inhibition, transfer and activation.

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Interplay between the Hsp90 Chaperone and the HslVU Protease To Regulate the Level of an Essential Protein in Shewanella oneidensis

mBio ◽

10.1128/mbio.00269-19 ◽

2019 ◽

Vol 10 (3) ◽

Cited By ~ 3

Author(s):

Flora Ambre Honoré ◽

Nathanael Jean Maillot ◽

Vincent Méjean ◽

Olivier Genest

Keyword(s):

Molecular Chaperones ◽

Shewanella Oneidensis ◽

Model Organism ◽

Cellular Level ◽

Growth Defect ◽

Hsp90 Inhibition ◽

Content Type ◽

Hsp90 Chaperone ◽

Bacterial Model ◽

Client Proteins

ABSTRACT Protein synthesis, folding, and degradation are an accurately regulated process occurring in every organism and called proteostasis. This process is essential to maintain a healthy proteome since proteostasis dysregulation is responsible for devastating cellular issues. Proteostasis is controlled by a complex network of molecular chaperones and proteases. Among them, eukaryotic Hsp90, assisted by many cochaperones and the Hsp70 chaperone system, plays a major role in activating hundreds of client proteins, and Hsp90 inhibition usually leads to proteasomal degradation of these clients. In bacteria, however, the precise function of Hsp90 remains quite unclear, and only a few clients are known. Recently, we have shown that Hsp90 is essential at elevated temperature in the aquatic model bacterium Shewanella oneidensis, and we have identified a client of Hsp90, TilS, involved in tRNA modification. Here we found that two members of the proteostasis network with antagonist activities, the Hsp90 chaperone and the HslVU protease, which is considered the proteasome ancestor, together regulate the level of TilS. In particular, we show that deletion of the genes coding for the HslVU protease suppresses the growth defect of an S. oneidensis strain with hsp90 deleted, by increasing the cellular level of the essential TilS protein. These results open up new avenues for understanding how proteostasis is controlled in bacteria, and new Hsp90 clients are much needed now to confirm the interplay between Hsp90 and proteases. IMPORTANCE Maintaining a healthy proteome is essential in every living cell from bacteria to humans. For example, proteostasis (protein homeostasis) imbalance in humans leads to devastating diseases, including neurodegenerative diseases and cancers. Therefore, proteins need to be assisted from their synthesis to their native folding and ultimately to their degradation. To ensure efficient protein turnover, cells possess an intricate network of molecular chaperones and proteases for protein folding and degradation. However, these networks need to be better defined and understood. Here, using the aquatic bacterium Shewanella oneidensis as a model organism, we demonstrate interplay between two proteins with antagonist activities, the Hsp90 chaperone and the HslVU protease, to finely regulate the level of an essential client of Hsp90. Therefore, this work provides a new bacterial model to better study protein regulation and turnover, and it sheds light on how proteostasis by Hsp90 and proteases could be controlled in bacteria.

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Molecular Chaperones Accelerate the Evolution of Their Protein Clients in Yeast

Genome Biology and Evolution ◽

10.1093/gbe/evz147 ◽

2019 ◽

Vol 11 (8) ◽

pp. 2360-2375 ◽

Cited By ~ 4

Author(s):

David Alvarez-Ponce ◽

José Aguilar-Rodríguez ◽

Mario A Fares

Keyword(s):

Protein Stability ◽

Time Scales ◽

Protein Evolution ◽

Protein Interactions ◽

Molecular Chaperones ◽

Interaction Network ◽

Evolutionary Divergence ◽

Evolutionary Time ◽

Genes Encoding ◽

Client Proteins

Abstract Protein stability is a major constraint on protein evolution. Molecular chaperones, also known as heat-shock proteins, can relax this constraint and promote protein evolution by diminishing the deleterious effect of mutations on protein stability and folding. This effect, however, has only been stablished for a few chaperones. Here, we use a comprehensive chaperone–protein interaction network to study the effect of all yeast chaperones on the evolution of their protein substrates, that is, their clients. In particular, we analyze how yeast chaperones affect the evolutionary rates of their clients at two very different evolutionary time scales. We first study the effect of chaperone-mediated folding on protein evolution over the evolutionary divergence of Saccharomyces cerevisiae and S. paradoxus. We then test whether yeast chaperones have left a similar signature on the patterns of standing genetic variation found in modern wild and domesticated strains of S. cerevisiae. We find that genes encoding chaperone clients have diverged faster than genes encoding non-client proteins when controlling for their number of protein–protein interactions. We also find that genes encoding client proteins have accumulated more intraspecific genetic diversity than those encoding non-client proteins. In a number of multivariate analyses, controlling by other well-known factors that affect protein evolution, we find that chaperone dependence explains the largest fraction of the observed variance in the rate of evolution at both evolutionary time scales. Chaperones affecting rates of protein evolution mostly belong to two major chaperone families: Hsp70s and Hsp90s. Our analyses show that protein chaperones, by virtue of their ability to buffer destabilizing mutations and their role in modulating protein genotype–phenotype maps, have a considerable accelerating effect on protein evolution.

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Redefining Molecular Chaperones as Chaotropes

Frontiers in Molecular Biosciences ◽

10.3389/fmolb.2021.683132 ◽

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.

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GR chaperone cycle mechanism revealed by cryo-EM: the GR-loading complex

10.21203/rs.3.rs-120723/v1 ◽

2020 ◽

Author(s):

David Agard ◽

Ray Wang ◽

Chari Noddings ◽

Elaine Kirschke ◽

Alexander Myasnikov ◽

...

Keyword(s):

Glucocorticoid Receptor ◽

Molecular Mechanism ◽

Molecular Chaperones ◽

Molecular Basis ◽

Atp Hydrolysis ◽

Binding Pocket ◽

The Other ◽

Client Proteins ◽

Partially Unfolded

Abstract Maintaining a healthy proteome is fundamental for organism survival1. Integral to this are Hsp90 and Hsp70 molecular chaperones that together facilitate the folding, remodeling and maturation of Hsp90’s many “client” proteins. The glucocorticoid receptor (GR) is a model client strictly dependent upon Hsp90/Hsp70 for activity. Chaperoning GR involves a cycle of inactivation by Hsp70, formation of an inactive GR:Hsp90:Hsp70:Hop “loading” complex, conversion to an active GR:Hsp90:p23 “maturation” complex, and subsequent GR release. Unfortunately, a molecular understanding of this intricate chaperone cycle is lacking for any client. Here, we report the cryo-EM structure of the GR loading complex, in which Hsp70 loads GR onto Hsp90, revealing the molecular basis of direct Hsp90/Hsp70 coordination. The structure reveals two Hsp70s––one delivering GR and the other scaffolding Hop. Unexpectedly, the Hop cochaperone interacts with all components of the complex including GR, poising Hsp90 for subsequent ATP hydrolysis. GR is partially unfolded and recognized via an extended binding pocket composed of Hsp90, Hsp70 and Hop, revealing the mechanism of GR loading and inactivation. Together with the GR maturation complex (Noddings et al., 2020), we present the first complete molecular mechanism of chaperone-dependent client remodeling, establishing general principles of client recognition, inhibition, transfer and activation.

Download Full-text