-
Trends in Biochemical Sciences Nov 2017Proteins are constantly challenged by environmental stress conditions that threaten their structure and function. Especially problematic are oxidative, acid, and severe... (Review)
Review
Proteins are constantly challenged by environmental stress conditions that threaten their structure and function. Especially problematic are oxidative, acid, and severe heat stress which induce very rapid and widespread protein unfolding and generate conditions that make canonical chaperones and/or transcriptional responses inadequate to protect the proteome. We review here recent advances in identifying and characterizing stress-activated chaperones which are inactive under non-stress conditions but become potent chaperones under specific protein-unfolding stress conditions. We discuss the post-translational mechanisms by which these chaperones sense stress, and consider the role that intrinsic disorder plays in their regulation and function. We examine their physiological roles under both non-stress and stress conditions, their integration into the cellular proteostasis network, and their potential as novel therapeutic targets.
Topics: Animals; Humans; Molecular Chaperones; Oxidative Stress; Protein Processing, Post-Translational; Protein Unfolding; Proteome
PubMed: 28893460
DOI: 10.1016/j.tibs.2017.08.006 -
The Biochemical Journal Feb 2020Deficits in protein homeostasis (proteostasis) are typified by the partial unfolding or misfolding of native proteins leading to amorphous or fibrillar aggregation,...
Deficits in protein homeostasis (proteostasis) are typified by the partial unfolding or misfolding of native proteins leading to amorphous or fibrillar aggregation, events that have been closely associated with diseases including Alzheimer's and Parkinson's diseases. Molecular chaperones are intimately involved in maintaining proteostasis, and their mechanisms of action are in part dependent on the morphology of aggregation-prone proteins. This study utilised native ion mobility-mass spectrometry to provide molecular insights into the conformational properties and dynamics of a model protein, α-lactalbumin (α-LA), which aggregates in an amorphous or amyloid fibrillar manner controlled by appropriate selection of experimental conditions. The molecular chaperone β-casein (β-CN) is effective at inhibiting amorphous and fibrillar aggregation of α-LA at sub-stoichiometric ratios, with greater efficiency against fibril formation. Analytical size-exclusion chromatography demonstrates the interaction between β-CN and amorphously aggregating α-LA is stable, forming a soluble high molecular weight complex, whilst with fibril-forming α-LA the interaction is transient. Moreover, ion mobility-mass spectrometry (IM-MS) coupled with collision-induced unfolding (CIU) revealed that α-LA monomers undergo distinct conformational transitions during the initial stages of amorphous (order to disorder) and fibrillar (disorder to order) aggregation. The structural heterogeneity of monomeric α-LA during fibrillation is reduced in the presence of β-CN along with an enhancement in stability, which provides a potential means for preventing fibril formation. Together, this study demonstrates how IM-MS and CIU can investigate the unfolding of proteins as well as examine transient and dynamic protein-chaperone interactions, and thereby provides detailed insight into the mechanism of chaperone action and proteostasis mechanisms.
Topics: Amyloid; Caseins; Lactalbumin; Mass Spectrometry; Molecular Chaperones; Protein Aggregates; Protein Folding; Proteostasis
PubMed: 31939601
DOI: 10.1042/BCJ20190638 -
Methods in Molecular Biology (Clifton,... 2023The molecular chaperone heat shock protein 90 (Hsp90) is essential in eukaryotes. Hsp90 chaperones proteins that are important determinants of multistep carcinogenesis....
The molecular chaperone heat shock protein 90 (Hsp90) is essential in eukaryotes. Hsp90 chaperones proteins that are important determinants of multistep carcinogenesis. There are multiple Hsp90 isoforms including the cytosolic Hsp90α and Hsp90β as well as GRP94 located in the endoplasmic reticulum and TRAP1 in the mitochondria. The chaperone function of Hsp90 is linked to its ability to bind and hydrolyze ATP. Co-chaperones and posttranslational modifications (such as phosphorylation, SUMOylation, and ubiquitination) are important for Hsp90 stability and regulation of its ATPase activity. Both mammalian and yeast cells can be used to express and purify Hsp90 and TRAP1 and also detect post-translational modifications by immunoblotting.
Topics: Animals; HSP90 Heat-Shock Proteins; Protein Processing, Post-Translational; Molecular Chaperones; Phosphorylation; Protein Isoforms; Ubiquitination; Saccharomyces cerevisiae; Mammals
PubMed: 37540432
DOI: 10.1007/978-1-0716-3342-7_11 -
Accounts of Chemical Research Apr 2018Molecular chaperones play a central role in protein homeostasis (a.k.a. proteostasis) by balancing protein folding, quality control, and turnover. To perform these... (Review)
Review
Molecular chaperones play a central role in protein homeostasis (a.k.a. proteostasis) by balancing protein folding, quality control, and turnover. To perform these diverse tasks, chaperones need the malleability to bind nearly any "client" protein and the fidelity to detect when it is misfolded. Remarkably, these activities are carried out by only ∼180 dedicated chaperones in humans. How do a relatively small number of chaperones maintain cellular and organismal proteostasis for an entire proteome? Furthermore, once a chaperone binds a client, how does it "decide" what to do with it? One clue comes from observations that individual chaperones engage in protein-protein interactions (PPIs)-both with each other and with their clients. These physical links coordinate multiple chaperones into organized, functional complexes and facilitate the "handoff" of clients between them. PPIs also link chaperones and their clients to other cellular pathways, such as those that mediate trafficking (e.g., cytoskeleton) and degradation (e.g., proteasome). The PPIs of the chaperone network have a wide range of affinity values (nanomolar to micromolar) and involve many distinct types of domain modules, such as J domains, zinc fingers, and tetratricopeptide repeats. Many of these motifs have the same binding surfaces on shared partners, such that members of one chaperone class often compete for the same interactions. Somehow, this collection of PPIs draws together chaperone families and creates multiprotein subnetworks that are able to make the "decisions" of protein quality control. The key to understanding chaperone-mediated proteostasis might be to understand how PPIs are regulated. This Account will discuss the efforts of our group and others to map, measure, and chemically perturb the PPIs within the molecular chaperone network. Structural biology methods, including X-ray crystallography, NMR spectroscopy, and electron microscopy, have all played important roles in visualizing the chaperone PPIs. Guided by these efforts and -omics approaches to measure PPIs, new advances in high-throughput chemical screening that are specially designed to account for the challenges of this system have emerged. Indeed, chemical biology has played a particularly important role in this effort, as molecules that either promote or inhibit specific PPIs have proven to be invaluable research probes in cells and animals. In addition, these molecules have provided leads for the potential treatment of protein misfolding diseases. One of the major products of this research field has been the identification of putative PPI drug targets within the chaperone network, which might be used to change chaperone "decisions" and rebalance proteostasis.
Topics: Animals; Humans; Models, Molecular; Molecular Chaperones; Protein Binding; Protein Interaction Mapping
PubMed: 29613769
DOI: 10.1021/acs.accounts.8b00036 -
The Journal of Biological Chemistry 2021This review contains a personal account of the role played by the PDB in the development of the field of molecular chaperones and protein homeostasis, from the viewpoint... (Review)
Review
This review contains a personal account of the role played by the PDB in the development of the field of molecular chaperones and protein homeostasis, from the viewpoint of someone who experienced the concurrent advances in the structural biology, electron microscopy, and chaperone fields. The emphasis is on some key structures, including those of Hsp70, GroEL, Hsp90, and small heat shock proteins, that were determined as the molecular chaperone concept and systems for protein quality control were emerging. These structures were pivotal in demonstrating how seemingly nonspecific chaperones could assist the specific folding pathways of a variety of substrates. Moreover, they have provided mechanistic insights into the ATPase machinery of complexes such as GroEL/GroES that promote unfolding and folding and the disaggregases that extract polypeptides from large aggregates and disassemble amyloid fibers. The PDB has provided a framework for the current success in curating, evaluating, and distributing structural biology data, through both the PDB and the EMDB.
Topics: Animals; Chaperonin 10; Chaperonin 60; Databases, Protein; HSP70 Heat-Shock Proteins; HSP90 Heat-Shock Proteins; Humans; Proteolysis
PubMed: 33957121
DOI: 10.1016/j.jbc.2021.100744 -
International Journal of Molecular... Feb 2022Despite recent developments in protein structure prediction, the process of the structure formation, folding, remains poorly understood. Notably, folding of multidomain... (Review)
Review
Despite recent developments in protein structure prediction, the process of the structure formation, folding, remains poorly understood. Notably, folding of multidomain proteins, which involves multiple steps of segmental folding, is one of the biggest questions in protein science. Multidomain protein folding often requires the assistance of molecular chaperones. Molecular chaperones promote or delay the folding of the client protein, but the detailed mechanisms are still unclear. This review summarizes the findings of biophysical and structural studies on the mechanism of multidomain protein folding mediated by molecular chaperones and explains how molecular chaperones recognize the client proteins and alter their folding properties. Furthermore, we introduce several recent studies that describe the concept of kinetics-activity relationships to explain the mechanism of functional diversity of molecular chaperones.
Topics: Humans; Kinetics; Molecular Chaperones; Protein Folding
PubMed: 35269628
DOI: 10.3390/ijms23052485 -
International Journal of Hyperthermia :... 2000Virtually all organisms respond to up-shifts in temperature (heat shock) by synthesizing a set of proteins called heat shock proteins (HSPs). The HSPs are induced not... (Comparative Study)
Comparative Study Review
Virtually all organisms respond to up-shifts in temperature (heat shock) by synthesizing a set of proteins called heat shock proteins (HSPs). The HSPs are induced not only by heat shock but also by various other environmental stresses. Induction of HSPs is regulated by the trans-acting heat shock factors (HSFs) and cis-acting heat shock element (HSE) present at the promoter region of each heat shock gene. Usually, HSPs are also expressed constitutively at normal growth temperatures and have basic and indispensable functions in the life cycle of proteins as molecular chaperones, as well as playing a role in protecting cells from the deleterious stresses. Molecular chaperones are able to inhibit the aggregation of partially denatured proteins and refold them using the energy of ATP. Recently, there are expectations for the use of molecular chaperones for the protection against and therapeutic treatment of inherited diseases caused by protein misfolding. In this review, the focus will be on the mammalian Hsp40, a homologue of bacterial DnaJ heat shock protein, and the beneficial functions of molecular chaperones.
Topics: Animals; Bacterial Proteins; Body Temperature Regulation; Genetic Diseases, Inborn; HSP40 Heat-Shock Proteins; HSP70 Heat-Shock Proteins; Heat-Shock Proteins; Humans; Mammals; Molecular Chaperones; Protein Folding; Species Specificity
PubMed: 10830586
DOI: 10.1080/026567300285259 -
Biochimica Et Biophysica Acta Mar 2012Heat shock protein 90 (HSP90) is a highly conserved and essential molecular chaperone involved in maturation and activation of signaling proteins in eukaryotes. HSP90... (Review)
Review
Heat shock protein 90 (HSP90) is a highly conserved and essential molecular chaperone involved in maturation and activation of signaling proteins in eukaryotes. HSP90 operates as a dimer in a conformational cycle driven by ATP binding and hydrolysis. HSP90 often functions together with co-chaperones that regulate the conformational cycle and/or load a substrate "client" protein onto HSP90. In plants, immune sensing NLR (nucleotide-binding domain and leucine-rich repeat containing) proteins are among the few known client proteins of HSP90. In the process of chaperoning NLR proteins, co-chaperones, RAR1 and SGT1 function together with HSP90. Recent structural and functional analyses indicate that RAR1 dynamically controls conformational changes of the HSP90 dimer, allowing SGT1 to bridge the interaction between NLR proteins and HSP90. Here, we discuss the regulation of NLR proteins by HSP90 upon interaction with RAR1 and SGT1, emphasizing the recent progress in our understanding of the structure and function of the complex. This article is part of a Special Issue entitled: Heat Shock Protein 90 (HSP90).
Topics: HSP90 Heat-Shock Proteins; Models, Molecular; Molecular Chaperones; Plant Proteins; Plants; Structure-Activity Relationship
PubMed: 22001401
DOI: 10.1016/j.bbamcr.2011.09.016 -
Protein Science : a Publication of the... Aug 2022Molecular chaperones are essential to maintain proteostasis. While the functions of intracellular molecular chaperones that oversee protein synthesis, folding and...
Molecular chaperones are essential to maintain proteostasis. While the functions of intracellular molecular chaperones that oversee protein synthesis, folding and aggregation, are established, those specialized to work in the extracellular environment are less understood. Extracellular proteins reside in a considerably more oxidizing milieu than cytoplasmic proteins and are stabilized by abundant disulfide bonds. Hence, extracellular proteins are potentially destabilized and sensitive to aggregation under reducing conditions. We combine biochemical and mass spectrometry experiments and elucidate that the molecular chaperone functions of the extracellular protein domain Bri2 BRICHOS only appear under reducing conditions, through the assembly of monomers into large polydisperse oligomers by an intra- to intermolecular disulfide bond relay mechanism. Chaperone-active assemblies of the Bri2 BRICHOS domain are efficiently generated by physiological thiol-containing compounds and proteins, and appear in parallel with reduction-induced aggregation of extracellular proteins. Our results give insights into how potent chaperone activity can be generated from inactive precursors under conditions that are destabilizing to most extracellular proteins and thereby support protein stability/folding in the extracellular space. SIGNIFICANCE: Chaperones are essential to cells as they counteract toxic consequences of protein misfolding particularly under stress conditions. Our work describes a novel activation mechanism of an extracellular molecular chaperone domain, called Bri2 BRICHOS. This mechanism is based on reducing conditions that initiate small subunits to assemble into large oligomers via a disulfide relay mechanism. Activated Bri2 BRICHOS inhibits reduction-induced aggregation of extracellular proteins and could be a means to boost proteostasis in the extracellular environment upon reductive stress.
Topics: Adenosine Triphosphate; Disulfides; Molecular Chaperones; Protein Domains; Protein Folding
PubMed: 35900025
DOI: 10.1002/pro.4378 -
Biomolecules Apr 2022Hsp90 (Heat Shock Protein 90) is an ATP (Adenosine triphosphate) molecular chaperone responsible for the activation and maturation of client proteins. The mechanism by... (Review)
Review
Hsp90 (Heat Shock Protein 90) is an ATP (Adenosine triphosphate) molecular chaperone responsible for the activation and maturation of client proteins. The mechanism by which Hsp90 achieves such activation, involving structurally diverse client proteins, has remained enigmatic. However, recent advances using structural techniques, together with advances in biochemical studies, have not only defined the chaperone cycle but have shed light on its mechanism of action. Hsp90 hydrolysis of ATP by each protomer may not be simultaneous and may be dependent on the specific client protein and co-chaperone complex involved. Surprisingly, Hsp90 appears to remodel client proteins, acting as a means by which the structure of the client protein is modified to allow its subsequent refolding to an active state, in the case of kinases, or by making the client protein competent for hormone binding, as in the case of the GR (glucocorticoid receptor). This review looks at selected examples of client proteins, such as CDK4 (cyclin-dependent kinase 4) and GR, which are activated according to the so-called 'remodelling hypothesis' for their activation. A detailed description of these activation mechanisms is paramount to understanding how Hsp90-associated diseases develop.
Topics: Adenosine Triphosphate; HSP90 Heat-Shock Proteins; Humans; Molecular Chaperones; Receptors, Glucocorticoid
PubMed: 35625528
DOI: 10.3390/biom12050600