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Biochimica Et Biophysica Acta Mar 2012Hsp90 is a ubiquitous and essential molecular chaperone that plays central roles in many signaling and other cellular pathways. The in vivo and in vitro activity of... (Review)
Review
Hsp90 is a ubiquitous and essential molecular chaperone that plays central roles in many signaling and other cellular pathways. The in vivo and in vitro activity of Hsp90 depends on its association with a wide variety of cochaperones and cofactors, which form large multi-protein complexes involved in folding client proteins. Based on our proteomic work mapping the molecular chaperone interaction networks in yeast, especially that of Hsp90, as well as, on experiments and results presented in the published literature, one major role of Hsp90 appears to be the promotion and maintenance of proper assembly of protein complexes. To highlight this role of Hsp90, the effect of the chaperone on the assembly of the following seven complexes is discussed in this review: snoRNP, RNA polymerase II, phosphatidylinositol-3 kinase-related protein kinase (PIKK), telomere complex, kinetochore, RNA induced silencing complexes (RISC), and 26S proteasome. For some complexes, it is observed that Hsp90 mediates complex assembly by stabilizing an unstable protein subunit and facilitating its incorporation into the complex; for other complexes, Hsp90 promotes change in the composition of that complex. In all cases, Hsp90 does not appear to be part of the final assembled complex. This article is part of a Special Issue entitled:Heat Shock Protein 90 (HSP90).
Topics: HSP90 Heat-Shock Proteins; Humans; Molecular Chaperones; Multiprotein Complexes; Protein Binding; Protein Folding; Proteomics; Signal Transduction
PubMed: 21945180
DOI: 10.1016/j.bbamcr.2011.09.001 -
Biochimica Et Biophysica Acta Feb 2013Chloroplasts are organelles of endosymbiotic origin that perform essential functions in plants. They contain about 3000 different proteins, the vast majority of which... (Review)
Review
Chloroplasts are organelles of endosymbiotic origin that perform essential functions in plants. They contain about 3000 different proteins, the vast majority of which are nucleus-encoded, synthesized in precursor form in the cytosol, and transported into the chloroplasts post-translationally. These preproteins are generally imported via envelope complexes termed TOC and TIC (Translocon at the Outer/Inner envelope membrane of Chloroplasts). They must navigate different cellular and organellar compartments (e.g., the cytosol, the outer and inner envelope membranes, the intermembrane space, and the stroma) before arriving at their final destination. It is generally considered that preproteins are imported in a largely unfolded state, and the whole process is energy-dependent. Several chaperones and cochaperones have been found to mediate different stages of chloroplast import, in similar fashion to chaperone involvement in mitochondrial import. Cytosolic factors such as Hsp90, Hsp70 and 14-3-3 may assist preproteins to reach the TOC complex at the chloroplast surface, preventing their aggregation or degradation. Chaperone involvement in the intermembrane space has also been proposed, but remains uncertain. Preprotein translocation is completed at the trans side of the inner membrane by ATP-driven motor complexes. A stromal Hsp100-type chaperone, Hsp93, cooperates with Tic110 and Tic40 in one such motor complex, while stromal Hsp70 is proposed to act in a second, parallel complex. Upon arrival in the stroma, chaperones (e.g., Hsp70, Cpn60, cpSRP43) also contribute to the folding, assembly or onward intraorganellar guidance of the proteins. In this review, we focus on chaperone involvement during preprotein translocation at the chloroplast envelope. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
Topics: Chloroplast Proteins; Chloroplasts; Cytosol; HSP70 Heat-Shock Proteins; HSP90 Heat-Shock Proteins; Membrane Transport Proteins; Molecular Chaperones; Plant Proteins; Protein Transport
PubMed: 22521451
DOI: 10.1016/j.bbamcr.2012.03.019 -
Cell Reports Apr 2020TRAP1 is the mitochondrial paralog of the heat shock protein 90 (HSP90) chaperone family. Its activity as an energy metabolism regulator has important implications in...
TRAP1 is the mitochondrial paralog of the heat shock protein 90 (HSP90) chaperone family. Its activity as an energy metabolism regulator has important implications in cancer, neurodegeneration, and ischemia. Selective inhibitors of TRAP1 could inform on its mechanisms of action and set the stage for targeted drug development, but their identification was hampered by the similarity among active sites in HSP90 homologs. We use a dynamics-based approach to identify a TRAP1 allosteric pocket distal to its active site that can host drug-like molecules, and we select small molecules with optimal stereochemical features to target the pocket. These leads inhibit TRAP1, but not HSP90, ATPase activity and revert TRAP1-dependent downregulation of succinate dehydrogenase activity in cancer cells and in zebrafish larvae. TRAP1 inhibitors are not toxic per se, but they abolish tumorigenic growth of neoplastic cells. Our results indicate that exploiting conformational dynamics can expand the chemical space of chaperone antagonists to TRAP1-specific inhibitors with wide therapeutic opportunities.
Topics: Allosteric Regulation; Animals; Antineoplastic Agents; Drug Design; Female; HSP90 Heat-Shock Proteins; Humans; Male; Mice; Molecular Chaperones; Molecular Dynamics Simulation; Nerve Sheath Neoplasms; Recombinant Proteins; Small Molecule Libraries; Zebrafish
PubMed: 32320652
DOI: 10.1016/j.celrep.2020.107531 -
The Journal of Biological Chemistry Jul 2009The molecular chaperone Hsp27 exists as a distribution of large oligomers that are disassembled by phosphorylation at Ser-15, -78, and -82. It is controversial whether...
The molecular chaperone Hsp27 exists as a distribution of large oligomers that are disassembled by phosphorylation at Ser-15, -78, and -82. It is controversial whether the unphosphorylated Hsp27 or the widely used triple Ser-to-Asp phospho-mimic mutant is the more active molecular chaperone in vitro. This question was investigated here by correlating chaperone activity, as measured by the aggregation of reduced insulin or alpha-lactalbumin, with Hsp27 self-association as monitored by analytical ultracentrifugation. Furthermore, because the phospho-mimic is generally assumed to reproduce the phosphorylated molecule, the size and chaperone activity of phosphorylated Hsp27 were compared with that of the phospho-mimic. Hsp27 was triply phosphorylated by MAPKAP-2 kinase, and phosphorylation was tracked by urea-PAGE. An increasing degree of suppression of insulin or alpha-lactalbumin aggregation correlated with a decreasing Hsp27 self-association, which was the least for phosphorylated Hsp27 followed by the mimic followed by the unphosphorylated protein. It was also found that Hsp27 added to pre-aggregated insulin did not reverse aggregation but did inhibit these aggregates from assembling into even larger aggregates. This chaperone activity appears to be independent of Hsp27 phosphorylation. In conclusion, the most active chaperone of insulin and alpha-lactalbumin was the Hsp27 (elongated) dimer, the smallest Hsp27 subunit observed under physiological conditions. Next, the Hsp27 phospho-mimic is only a partial mimic of phosphorylated Hsp27, both in self-association and in chaperone function. Finally, the efficient inhibition of insulin aggregation by Hsp27 dimer led to the proposal of two models for this chaperone activity.
Topics: Cross-Linking Reagents; Disulfides; Electrophoresis, Polyacrylamide Gel; Escherichia coli; HSP27 Heat-Shock Proteins; Heat-Shock Proteins; Insulin; Lactalbumin; MAP Kinase Signaling System; Molecular Chaperones; Phosphorylation; Protein Folding; Saccharomyces cerevisiae; Time Factors; Ultracentrifugation
PubMed: 19411251
DOI: 10.1074/jbc.M109.011353 -
PLoS Computational Biology Mar 2009Hsp90 is a molecular chaperone essential for protein folding and activation in normal homeostasis and stress response. ATP binding and hydrolysis facilitate Hsp90...
Hsp90 is a molecular chaperone essential for protein folding and activation in normal homeostasis and stress response. ATP binding and hydrolysis facilitate Hsp90 conformational changes required for client activation. Hsp90 plays an important role in disease states, particularly in cancer, where chaperoning of the mutated and overexpressed oncoproteins is important for function. Recent studies have illuminated mechanisms related to the chaperone function. However, an atomic resolution view of Hsp90 conformational dynamics, determined by the presence of different binding partners, is critical to define communication pathways between remote residues in different domains intimately affecting the chaperone cycle. Here, we present a computational analysis of signal propagation and long-range communication pathways in Hsp90. We carried out molecular dynamics simulations of the full-length Hsp90 dimer, combined with essential dynamics, correlation analysis, and a signal propagation model. All-atom MD simulations with timescales of 70 ns have been performed for complexes with the natural substrates ATP and ADP and for the unliganded dimer. We elucidate the mechanisms of signal propagation and determine "hot spots" involved in interdomain communication pathways from the nucleotide-binding site to the C-terminal domain interface. A comprehensive computational analysis of the Hsp90 communication pathways and dynamics at atomic resolution has revealed the role of the nucleotide in effecting conformational changes, elucidating the mechanisms of signal propagation. Functionally important residues and secondary structure elements emerge as effective mediators of communication between the nucleotide-binding site and the C-terminal interface. Furthermore, we show that specific interdomain signal propagation pathways may be activated as a function of the ligand. Our results support a "conformational selection model" of the Hsp90 mechanism, whereby the protein may exist in a dynamic equilibrium between different conformational states available on the energy landscape and binding of a specific partner can bias the equilibrium toward functionally relevant complexes.
Topics: Binding Sites; Computer Simulation; Dimerization; HSP90 Heat-Shock Proteins; Ligands; Models, Chemical; Models, Molecular; Molecular Chaperones; Protein Binding; Protein Conformation
PubMed: 19300478
DOI: 10.1371/journal.pcbi.1000323 -
Molecular Cell Jun 2021In this issue of Molecular Cell, Hammond et al. (2021) and Piette et al. (2021) identify the essential heat shock co-chaperone DNAJC9 as a new bona fide histone...
In this issue of Molecular Cell, Hammond et al. (2021) and Piette et al. (2021) identify the essential heat shock co-chaperone DNAJC9 as a new bona fide histone chaperone, linking ATP-dependent molecular chaperones to the histone supply and deposition pathways.
Topics: Histone Chaperones; Histones; Molecular Chaperones
PubMed: 34143966
DOI: 10.1016/j.molcel.2021.05.012 -
Cell Stress & Chaperones 2003Cdc37 is a relatively poorly conserved and yet essential molecular chaperone. It has long been thought to function primarily as an accessory factor for Hsp90, notably... (Review)
Review
Cdc37 is a relatively poorly conserved and yet essential molecular chaperone. It has long been thought to function primarily as an accessory factor for Hsp90, notably directing Hsp90 to kinases as substrates. More recent discoveries challenge this simplistic view. Cdc37 client proteins other than kinases have now been found, and Cdc37 displays a variety of Hsp90-independent activities both in vitro and in vivo. It can function as a molecular chaperone by itself, interact with other Hsp90 cochaperones in the absence of Hsp90, and even support yeast growth and protein folding without its Hsp90-binding domain. Thus, for many substrates, there may be many alternative chaperone pathways involving Cdc37, Hsp90, or both.
Topics: Amino Acid Sequence; Animals; Cell Cycle Proteins; Chaperonins; Drosophila Proteins; HSP90 Heat-Shock Proteins; Humans; Molecular Chaperones; Molecular Sequence Data; Protein Kinases; Protein Structure, Tertiary; Sequence Alignment
PubMed: 14627196
DOI: 10.1379/1466-1268(2003)008<0114:cgbhak>2.0.co;2 -
Physiological Reviews Apr 2018After synthesis, proteins are folded into their native conformations aided by molecular chaperones. Dysfunction in folding caused by genetic mutations in numerous genes... (Review)
Review
After synthesis, proteins are folded into their native conformations aided by molecular chaperones. Dysfunction in folding caused by genetic mutations in numerous genes causes protein conformational diseases. Membrane proteins are more prone to misfolding due to their more intricate folding than soluble proteins. Misfolded proteins are detected by the cellular quality control systems, especially in the endoplasmic reticulum, and proteins may be retained there for eventual degradation by the ubiquitin-proteasome system or through autophagy. Some misfolded proteins aggregate, leading to pathologies in numerous neurological diseases. In vitro, modulating mutant protein folding by altering molecular chaperone expression can ameliorate some misfolding. Some small molecules known as chemical chaperones also correct mutant protein misfolding in vitro and in vivo. However, due to their lack of specificity, their potential as therapeutics is limited. Another class of compounds, known as pharmacological chaperones (pharmacoperones), binds with high specificity to misfolded proteins, either as enzyme substrates or receptor ligands, leading to decreased folding energy barriers and correction of the misfolding. Because many of the misfolded proteins are misrouted but do not have defects in function per se, pharmacoperones have promising potential in advancing to the clinic as therapeutics, since correcting routing may ameliorate the underlying mechanism of disease. This review will comprehensively summarize this exciting area of research, surveying the literature from in vitro studies in cell lines to transgenic animal models and clinical trials in several protein misfolding diseases.
Topics: Animals; Endoplasmic Reticulum; Humans; Molecular Chaperones; Protein Conformation; Protein Folding; Protein Transport; Proteostasis Deficiencies
PubMed: 29442594
DOI: 10.1152/physrev.00029.2016 -
The Journal of Biological Chemistry Jul 2022The heat shock protein 90 (Hsp90) is a molecular chaperone central to client protein folding and maturation in eukaryotic cells. During its chaperone cycle, Hsp90...
The heat shock protein 90 (Hsp90) is a molecular chaperone central to client protein folding and maturation in eukaryotic cells. During its chaperone cycle, Hsp90 undergoes ATPase-coupled large-scale conformational changes between open and closed states, where the N-terminal and middle domains of the protein form a compact dimerized conformation. However, the molecular principles of the switching motion between the open and closed states remain poorly understood. Here we show by integrating atomistic and coarse-grained molecular simulations with small-angle X-ray scattering experiments and NMR spectroscopy data that Hsp90 exhibits rich conformational dynamics modulated by the charged linker, which connects the N-terminal with the middle domain of the protein. We show that the dissociation of these domains is crucial for the conformational flexibility of the open state, with the separation distance controlled by a β-sheet motif next to the linker region. Taken together, our results suggest that the conformational ensemble of Hsp90 comprises highly extended states, which could be functionally crucial for client processing.
Topics: HSP90 Heat-Shock Proteins; Models, Molecular; Molecular Chaperones; Molecular Dynamics Simulation; Protein Conformation; Protein Folding
PubMed: 35667441
DOI: 10.1016/j.jbc.2022.102101 -
Biochimica Et Biophysica Acta Mar 2012Molecular chaperones, as the name suggests, are involved in folding, maintenance, intracellular transport, and degradation of proteins as well as in facilitating cell... (Review)
Review
Molecular chaperones, as the name suggests, are involved in folding, maintenance, intracellular transport, and degradation of proteins as well as in facilitating cell signaling. Heat shock protein 90 (Hsp90) is an essential eukaryotic molecular chaperone that carries out these processes in normal and cancer cells. Hsp90 function in vivo is coupled to its ability to hydrolyze ATP and this can be regulated by co-chaperones and post-translational modifications. In this review, we explore the varied roles of known post-translational modifications of cytosolic and nuclear Hsp90 (phosphorylation, acetylation, S-nitrosylation, oxidation and ubiquitination) in fine-tuning chaperone function in eukaryotes. This article is part of a Special Issue entitled: Heat Shock Protein 90 (HSP90).
Topics: Adenosine Triphosphate; HSP90 Heat-Shock Proteins; Humans; Molecular Chaperones; Phosphorylation; Protein Processing, Post-Translational
PubMed: 21856339
DOI: 10.1016/j.bbamcr.2011.07.018