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    An interdomain sector mediating allostery in Hsp70 molecular chaperones. Smock Robert G,Rivoire Olivier,Russ William P,Swain Joanna F,Leibler Stanislas,Ranganathan Rama,Gierasch Lila M Molecular systems biology Allosteric coupling between protein domains is fundamental to many cellular processes. For example, Hsp70 molecular chaperones use ATP binding by their actin-like N-terminal ATPase domain to control substrate interactions in their C-terminal substrate-binding domain, a reaction that is critical for protein folding in cells. Here, we generalize the statistical coupling analysis to simultaneously evaluate co-evolution between protein residues and functional divergence between sequences in protein sub-families. Applying this method in the Hsp70/110 protein family, we identify a sparse but structurally contiguous group of co-evolving residues called a 'sector', which is an attribute of the allosteric Hsp70 sub-family that links the functional sites of the two domains across a specific interdomain interface. Mutagenesis of Escherichia coli DnaK supports the conclusion that this interdomain sector underlies the allosteric coupling in this protein family. The identification of the Hsp70 sector provides a basis for further experiments to understand the mechanism of allostery and introduces the idea that cooperativity between interacting proteins or protein domains can be mediated by shared sectors. 10.1038/msb.2010.65
    Nucleotides regulate the mechanical hierarchy between subdomains of the nucleotide binding domain of the Hsp70 chaperone DnaK. Bauer Daniela,Merz Dale R,Pelz Benjamin,Theisen Kelly E,Yacyshyn Gail,Mokranjac Dejana,Dima Ruxandra I,Rief Matthias,Žoldák Gabriel Proceedings of the National Academy of Sciences of the United States of America The regulation of protein function through ligand-induced conformational changes is crucial for many signal transduction processes. The binding of a ligand alters the delicate energy balance within the protein structure, eventually leading to such conformational changes. In this study, we elucidate the energetic and mechanical changes within the subdomains of the nucleotide binding domain (NBD) of the heat shock protein of 70 kDa (Hsp70) chaperone DnaK upon nucleotide binding. In an integrated approach using single molecule optical tweezer experiments, loop insertions, and steered coarse-grained molecular simulations, we find that the C-terminal helix of the NBD is the major determinant of mechanical stability, acting as a glue between the two lobes. After helix unraveling, the relative stability of the two separated lobes is regulated by ATP/ADP binding. We find that the nucleotide stays strongly bound to lobe II, thus reversing the mechanical hierarchy between the two lobes. Our results offer general insights into the nucleotide-induced signal transduction within members of the actin/sugar kinase superfamily. 10.1073/pnas.1504625112
    Mapping the conformation of a client protein through the Hsp70 functional cycle. Sekhar Ashok,Rosenzweig Rina,Bouvignies Guillaume,Kay Lewis E Proceedings of the National Academy of Sciences of the United States of America The 70 kDa heat shock protein (Hsp70) chaperone system is ubiquitous, highly conserved, and involved in a myriad of diverse cellular processes. Its function relies on nucleotide-dependent interactions with client proteins, yet the structural features of folding-competent substrates in their Hsp70-bound state remain poorly understood. Here we use NMR spectroscopy to study the human telomere repeat binding factor 1 (hTRF1) in complex with Escherichia coli Hsp70 (DnaK). In the complex, hTRF1 is globally unfolded with up to 40% helical secondary structure in regions distal to the binding site. Very similar conformational ensembles are observed for hTRF1 bound to ATP-, ADP- and nucleotide-free DnaK. The patterns in substrate helicity mirror those found in the unfolded state in the absence of denaturants except near the site of chaperone binding, demonstrating that DnaK-bound hTRF1 retains its intrinsic structural preferences. To our knowledge, our study presents the first atomic resolution structural characterization of a client protein bound to each of the three nucleotide states of DnaK and establishes that the large structural changes in DnaK and the associated energy that accompanies ATP binding and hydrolysis do not affect the overall conformation of the bound substrate protein. 10.1073/pnas.1508504112
    Substrate-binding domain conformational dynamics mediate Hsp70 allostery. Zhuravleva Anastasia,Gierasch Lila M Proceedings of the National Academy of Sciences of the United States of America Binding of ATP to the N-terminal nucleotide-binding domain (NBD) of heat shock protein 70 (Hsp70) molecular chaperones reduces the affinity of their C-terminal substrate-binding domain (SBD) for unfolded protein substrates. ATP binding to the NBD leads to docking between NBD and βSBD and releasing of the α-helical lid that covers the substrate-binding cleft in the SBD. However, these structural changes alone do not fully account for the allosteric mechanism of modulation of substrate affinity and binding kinetics. Through a multipronged study of the Escherichia coli Hsp70 DnaK, we found that changes in conformational dynamics within the βSBD play a central role in interdomain allosteric communication in the Hsp70 DnaK. ATP-mediated NBD conformational changes favor formation of NBD contacts with lynchpin sites on the βSBD and force disengagement of SBD strand β8 from strand β7, which leads to repacking of a βSBD hydrophobic cluster and disruption of the hydrophobic arch over the substrate-binding cleft. In turn, these structural rearrangements drastically enhance conformational dynamics throughout the entire βSBD and particularly around the substrate-binding site. This negative, entropically driven allostery between two functional sites of the βSBD-the NBD binding interface and the substrate-binding site-confers upon the SBD the plasticity needed to bind to a wide range of chaperone clients without compromising precise control of thermodynamics and kinetics of chaperone-client interactions. 10.1073/pnas.1506692112
    Allosteric signal transmission in the nucleotide-binding domain of 70-kDa heat shock protein (Hsp70) molecular chaperones. Zhuravleva Anastasia,Gierasch Lila M Proceedings of the National Academy of Sciences of the United States of America The 70-kDa heat shock protein (Hsp70) chaperones perform a wide array of cellular functions that all derive from the ability of their N-terminal nucleotide-binding domains (NBDs) to allosterically regulate the substrate affinity of their C-terminal substrate-binding domains in a nucleotide-dependent mechanism. To explore the structural origins of Hsp70 allostery, we performed NMR analysis on the NBD of DnaK, the Escherichia coli Hsp70, in six different states (ligand-bound or apo) and in two constructs, one that retains the conserved and functionally crucial portion of the interdomain linker (residues ) and another that lacks the linker. Chemical-shift perturbation patterns identify residues at subdomain interfaces that constitute allosteric networks and enable the NBD to act as a nucleotide-modulated switch. Nucleotide binding results in changes in subdomain orientations and long-range perturbations along subdomain interfaces. In particular, our findings provide structural details for a key mechanism of Hsp70 allostery, by which information is conveyed from the nucleotide-binding site to the interdomain linker. In the presence of ATP, the linker binds to the edge of the IIA β-sheet, which structurally connects the linker and the nucleotide-binding site. Thus, a pathway of allosteric communication leads from the NBD nucleotide-binding site to the substrate-binding domain via the interdomain linker. 10.1073/pnas.1014448108
    Hsp70 biases the folding pathways of client proteins. Sekhar Ashok,Rosenzweig Rina,Bouvignies Guillaume,Kay Lewis E Proceedings of the National Academy of Sciences of the United States of America The 70-kDa heat shock protein (Hsp70) family of chaperones bind cognate substrates to perform a variety of different processes that are integral to cellular homeostasis. Although detailed structural information is available on the chaperone, the structural features of folding competent substrates in the bound form have not been well characterized. Here we use paramagnetic relaxation enhancement (PRE) NMR spectroscopy to probe the existence of long-range interactions in one such folding competent substrate, human telomere repeat binding factor (hTRF1), which is bound to DnaK in a globally unfolded conformation. We show that DnaK binding modifies the energy landscape of the substrate by removing long-range interactions that are otherwise present in the unbound, unfolded conformation of hTRF1. Because the unfolded state of hTRF1 is only marginally populated and transiently formed, it is inaccessible to standard NMR approaches. We therefore developed a (1)H-based CEST experiment that allows measurement of PREs in sparse states, reporting on transiently sampled conformations. Our results suggest that DnaK binding can significantly bias the folding pathway of client substrates such that secondary structure forms first, followed by the development of longer-range contacts between more distal parts of the protein. 10.1073/pnas.1601846113
    Hsp70 forms antiparallel dimers stabilized by post-translational modifications to position clients for transfer to Hsp90. Morgner Nina,Schmidt Carla,Beilsten-Edmands Victoria,Ebong Ima-Obong,Patel Nisha A,Clerico Eugenia M,Kirschke Elaine,Daturpalli Soumya,Jackson Sophie E,Agard David,Robinson Carol V Cell reports Protein folding in cells is regulated by networks of chaperones, including the heat shock protein 70 (Hsp70) system, which consists of the Hsp40 cochaperone and a nucleotide exchange factor. Hsp40 mediates complex formation between Hsp70 and client proteins prior to interaction with Hsp90. We used mass spectrometry (MS) to monitor assemblies formed between eukaryotic Hsp90/Hsp70/Hsp40, Hop, p23, and a client protein, a fragment of the glucocorticoid receptor (GR). We found that Hsp40 promotes interactions between the client and Hsp70, and facilitates dimerization of monomeric Hsp70. This dimerization is antiparallel, stabilized by post-translational modifications (PTMs), and maintained in the stable heterohexameric client-loading complex Hsp902Hsp702HopGR identified here. Addition of p23 to this client-loading complex induces transfer of GR onto Hsp90 and leads to expulsion of Hop and Hsp70. Based on these results, we propose that Hsp70 antiparallel dimerization, stabilized by PTMs, positions the client for transfer from Hsp70 to Hsp90. 10.1016/j.celrep.2015.03.063
    A dancer caught midstep: the structure of ATP-bound Hsp70. Sousa Rui Molecular cell Hsp70 ATP binding induces substrate release, but the transiency of this state has inhibited its characterization. In this issue, Kityk et al. determine the Hsp70(∗)ATP structure utilizing engineered disulfide bonds, providing insights into the workings of this essential molecular machine. 10.1016/j.molcel.2012.12.008
    Systematic functional prioritization of protein posttranslational modifications. Beltrao Pedro,Albanèse Véronique,Kenner Lillian R,Swaney Danielle L,Burlingame Alma,Villén Judit,Lim Wendell A,Fraser James S,Frydman Judith,Krogan Nevan J Cell Protein function is often regulated by posttranslational modifications (PTMs), and recent advances in mass spectrometry have resulted in an exponential increase in PTM identification. However, the functional significance of the vast majority of these modifications remains unknown. To address this problem, we compiled nearly 200,000 phosphorylation, acetylation, and ubiquitination sites from 11 eukaryotic species, including 2,500 newly identified ubiquitylation sites for Saccharomyces cerevisiae. We developed methods to prioritize the functional relevance of these PTMs by predicting those that likely participate in cross-regulatory events, regulate domain activity, or mediate protein-protein interactions. PTM conservation within domain families identifies regulatory "hot spots" that overlap with functionally important regions, a concept that we experimentally validated on the HSP70 domain family. Finally, our analysis of the evolution of PTM regulation highlights potential routes for neutral drift in regulatory interactions and suggests that only a fraction of modification sites are likely to have a significant biological role. 10.1016/j.cell.2012.05.036
    Chaperone machines for protein folding, unfolding and disaggregation. Saibil Helen Nature reviews. Molecular cell biology Molecular chaperones are diverse families of multidomain proteins that have evolved to assist nascent proteins to reach their native fold, protect subunits from heat shock during the assembly of complexes, prevent protein aggregation or mediate targeted unfolding and disassembly. Their increased expression in response to stress is a key factor in the health of the cell and longevity of an organism. Unlike enzymes with their precise and finely tuned active sites, chaperones are heavy-duty molecular machines that operate on a wide range of substrates. The structural basis of their mechanism of action is being unravelled (in particular for the heat shock proteins HSP60, HSP70, HSP90 and HSP100) and typically involves massive displacements of 20-30 kDa domains over distances of 20-50 Å and rotations of up to 100°. 10.1038/nrm3658
    Structural basis for client recognition and activity of Hsp40 chaperones. Jiang Yajun,Rossi Paolo,Kalodimos Charalampos G Science (New York, N.Y.) Hsp70 and Hsp40 chaperones work synergistically in a wide range of biological processes including protein synthesis, membrane translocation, and folding. We used nuclear magnetic resonance spectroscopy to determine the solution structure and dynamic features of an Hsp40 in complex with an unfolded client protein. Atomic structures of the various binding sites in the client complexed to the binding domains of the Hsp40 reveal the recognition pattern. Hsp40 engages the client in a highly dynamic fashion using a multivalent binding mechanism that alters the folding properties of the client. Different Hsp40 family members have different numbers of client-binding sites with distinct sequence selectivity, providing additional mechanisms for activity regulation and function modification. Hsp70 binding to Hsp40 displaces the unfolded client. The activity of Hsp40 is altered in its complex with Hsp70, further regulating client binding and release. 10.1126/science.aax1280
    Conformation transitions of the polypeptide-binding pocket support an active substrate release from Hsp70s. Yang Jiao,Zong Yinong,Su Jiayue,Li Hongtao,Zhu Huanyu,Columbus Linda,Zhou Lei,Liu Qinglian Nature communications Cellular protein homeostasis depends on heat shock proteins 70 kDa (Hsp70s), a class of ubiquitous and highly conserved molecular chaperone. Key to the chaperone activity is an ATP-induced allosteric regulation of polypeptide substrate binding and release. To illuminate the molecular mechanism of this allosteric coupling, here we present a novel crystal structure of an intact human BiP, an essential Hsp70 in ER, in an ATP-bound state. Strikingly, the polypeptide-binding pocket is completely closed, seemingly excluding any substrate binding. Our FRET, biochemical and EPR analysis suggests that this fully closed conformation is the major conformation for the ATP-bound state in solution, providing evidence for an active release of bound polypeptide substrates following ATP binding. The Hsp40 co-chaperone converts this fully closed conformation to an open conformation to initiate productive substrate binding. Taken together, this study provided a mechanistic understanding of the dynamic nature of the polypeptide-binding pocket in the Hsp70 chaperone cycle. 10.1038/s41467-017-01310-z
    Experimental Milestones in the Discovery of Molecular Chaperones as Polypeptide Unfolding Enzymes. Finka Andrija,Mattoo Rayees U H,Goloubinoff Pierre Annual review of biochemistry Molecular chaperones control the cellular folding, assembly, unfolding, disassembly, translocation, activation, inactivation, disaggregation, and degradation of proteins. In 1989, groundbreaking experiments demonstrated that a purified chaperone can bind and prevent the aggregation of artificially unfolded polypeptides and use ATP to dissociate and convert them into native proteins. A decade later, other chaperones were shown to use ATP hydrolysis to unfold and solubilize stable protein aggregates, leading to their native refolding. Presently, the main conserved chaperone families Hsp70, Hsp104, Hsp90, Hsp60, and small heat-shock proteins (sHsps) apparently act as unfolding nanomachines capable of converting functional alternatively folded or toxic misfolded polypeptides into harmless protease-degradable or biologically active native proteins. Being unfoldases, the chaperones can proofread three-dimensional protein structures and thus control protein quality in the cell. Understanding the mechanisms of the cellular unfoldases is central to the design of new therapies against aging, degenerative protein conformational diseases, and specific cancers. 10.1146/annurev-biochem-060815-014124
    Mechanics of Hsp70 chaperones enables differential interaction with client proteins. Schlecht Rainer,Erbse Annette H,Bukau Bernd,Mayer Matthias P Nature structural & molecular biology Hsp70 chaperones interact with a wide spectrum of substrates ranging from unfolded to natively folded and aggregated proteins. Structural evidence suggests that bound substrates are entirely enclosed in a β-sheet cavity covered by a helical lid, which requires structural rearrangements including lid opening to allow substrate access. We analyzed the mechanics of the lid movement of bacterial DnaK by disulfide fixation of lid elements to the β-sheet and by electron paramagnetic resonance spectroscopy using spin labels in the lid and β-sheet. Our results indicate that the lid-forming helix B adopts at least three conformational states and, notably, does not close over bound proteins, implying that DnaK does not only bind to extended peptide stretches of protein substrates but can also accommodate regions with substantial tertiary structure. This flexible binding mechanism provides a basis for the broad spectrum of substrate conformers of Hsp70s. 10.1038/nsmb.2006
    Hsp70 chaperone dynamics and molecular mechanism. Mayer Matthias P Trends in biochemical sciences The chaperone functions of heat shock protein (Hsp)70 involve an allosteric control mechanism between the nucleotide-binding domain (NBD) and polypeptide substrate-binding domain (SBD): ATP binding and hydrolysis regulates the affinity for polypeptides, and polypeptide binding accelerates ATP hydrolysis. These data suggest that Hsp70s exist in at least two conformational states. Although structural information on the conformation with high affinity for polypeptides has been available for several years, the conformation with an open polypeptide binding cleft was elucidated only recently. In addition, other biophysical studies have revealed a more dynamic picture of Hsp70s, shedding light on the molecular mechanism by which Hsp70s assist protein folding. In this review recent insights into the structure and mechanism of Hsp70s are discussed. 10.1016/j.tibs.2013.08.001
    Structure and dynamics of the ATP-bound open conformation of Hsp70 chaperones. Kityk Roman,Kopp Jürgen,Sinning Irmgard,Mayer Matthias P Molecular cell Central to the chaperone function of Hsp70s is the transition between open and closed conformations of their polypeptide substrate binding domain (SBD), which is regulated through an allosteric mechanism via ATP binding and hydrolysis in their nucleotide binding domain (NBD). Although the structure of the closed conformation of Hsp70s is well studied, the open conformation has remained elusive. Here, we report on the 2.4 Å crystal structure of the ATP-bound open conformation of the Escherichia coli Hsp70 homolog DnaK. In the open DnaK structure, the β sheet and α-helical lid subdomains of the SBD are detached from one another and docked to different faces of the NBD. The contacts between the β sheet subdomain and the NBD reveal the mechanism of allosteric regulation. In addition, we demonstrate that docking of the β sheet and α-helical lid subdomains to the NBD is a sequential process influenced by peptide and protein substrates. 10.1016/j.molcel.2012.09.023
    An interdomain energetic tug-of-war creates the allosterically active state in Hsp70 molecular chaperones. Zhuravleva Anastasia,Clerico Eugenia M,Gierasch Lila M Cell The allosteric mechanism of Hsp70 molecular chaperones enables ATP binding to the N-terminal nucleotide-binding domain (NBD) to alter substrate affinity to the C-terminal substrate-binding domain (SBD) and substrate binding to enhance ATP hydrolysis. Cycling between ATP-bound and ADP/substrate-bound states requires Hsp70s to visit a state with high ATPase activity and fast on/off kinetics of substrate binding. We have trapped this "allosterically active" state for the E. coli Hsp70, DnaK, and identified how interactions among the NBD, the β subdomain of the SBD, the SBD α-helical lid, and the conserved hydrophobic interdomain linker enable allosteric signal transmission between ligand-binding sites. Allostery in Hsp70s results from an energetic tug-of-war between domain conformations and formation of two orthogonal interfaces: between the NBD and SBD, and between the helical lid and the β subdomain of the SBD. The resulting energetic tension underlies Hsp70 functional properties and enables them to be modulated by ligands and cochaperones and "tuned" through evolution. 10.1016/j.cell.2012.11.002
    Allosteric opening of the polypeptide-binding site when an Hsp70 binds ATP. Qi Ruifeng,Sarbeng Evans Boateng,Liu Qun,Le Katherine Quynh,Xu Xinping,Xu Hongya,Yang Jiao,Wong Jennifer Li,Vorvis Christina,Hendrickson Wayne A,Zhou Lei,Liu Qinglian Nature structural & molecular biology The 70-kilodalton (kDa) heat-shock proteins (Hsp70s) are ubiquitous molecular chaperones essential for cellular protein folding and proteostasis. Each Hsp70 has two functional domains: a nucleotide-binding domain (NBD), which binds and hydrolyzes ATP, and a substrate-binding domain (SBD), which binds extended polypeptides. NBD and SBD interact little when in the presence of ADP; however, ATP binding allosterically couples the polypeptide- and ATP-binding sites. ATP binding promotes polypeptide release; polypeptide rebinding stimulates ATP hydrolysis. This allosteric coupling is poorly understood. Here we present the crystal structure of an intact ATP-bound Hsp70 from Escherichia coli at 1.96-Å resolution. The ATP-bound NBD adopts a unique conformation, forming extensive interfaces with an SBD that has changed radically, having its α-helical lid displaced and the polypeptide-binding channel of its β-subdomain restructured. These conformational changes, together with our biochemical assays, provide a structural explanation for allosteric coupling in Hsp70 activity. 10.1038/nsmb.2583
    Crucial HSP70 co-chaperone complex unlocks metazoan protein disaggregation. Nillegoda Nadinath B,Kirstein Janine,Szlachcic Anna,Berynskyy Mykhaylo,Stank Antonia,Stengel Florian,Arnsburg Kristin,Gao Xuechao,Scior Annika,Aebersold Ruedi,Guilbride D Lys,Wade Rebecca C,Morimoto Richard I,Mayer Matthias P,Bukau Bernd Nature Protein aggregates are the hallmark of stressed and ageing cells, and characterize several pathophysiological states. Healthy metazoan cells effectively eliminate intracellular protein aggregates, indicating that efficient disaggregation and/or degradation mechanisms exist. However, metazoans lack the key heat-shock protein disaggregase HSP100 of non-metazoan HSP70-dependent protein disaggregation systems, and the human HSP70 system alone, even with the crucial HSP110 nucleotide exchange factor, has poor disaggregation activity in vitro. This unresolved conundrum is central to protein quality control biology. Here we show that synergic cooperation between complexed J-protein co-chaperones of classes A and B unleashes highly efficient protein disaggregation activity in human and nematode HSP70 systems. Metazoan mixed-class J-protein complexes are transient, involve complementary charged regions conserved in the J-domains and carboxy-terminal domains of each J-protein class, and are flexible with respect to subunit composition. Complex formation allows J-proteins to initiate transient higher order chaperone structures involving HSP70 and interacting nucleotide exchange factors. A network of cooperative class A and B J-protein interactions therefore provides the metazoan HSP70 machinery with powerful, flexible, and finely regulatable disaggregase activity and a further level of regulation crucial for cellular protein quality control. 10.1038/nature14884
    Structural characterization of the substrate transfer mechanism in Hsp70/Hsp90 folding machinery mediated by Hop. Alvira Sara,Cuéllar Jorge,Röhl Alina,Yamamoto Soh,Itoh Hideaki,Alfonso Carlos,Rivas Germán,Buchner Johannes,Valpuesta José M Nature communications In eukarya, chaperones Hsp70 and Hsp90 act coordinately in the folding and maturation of a range of key proteins with the help of several co-chaperones, especially Hop. Although biochemical data define the Hop-mediated Hsp70-Hsp90 substrate transfer mechanism, the intrinsic flexibility of these proteins and the dynamic nature of their complexes have limited the structural studies of this mechanism. Here we generate several complexes in the Hsp70/Hsp90 folding pathway (Hsp90:Hop, Hsp90:Hop:Hsp70 and Hsp90:Hop:Hsp70 with a fragment of the client protein glucocorticoid receptor (GR-LBD)), and determine their 3D structure using electron microscopy techniques. Our results show that one Hop molecule binds to one side of the Hsp90 dimer in both extended and compact conformations, through Hop domain rearrangement that take place when Hsp70 or Hsp70:GR-LBD bind to Hsp90:Hop. The compact conformation of the Hsp90:Hop:Hsp70:GR-LBD complex shows that GR-LBD binds to the side of the Hsp90 dimer opposite the Hop attachment site. 10.1038/ncomms6484
    Interaction of the cotranslational Hsp70 Ssb with ribosomal proteins and rRNA depends on its lid domain. Gumiero Andrea,Conz Charlotte,Gesé Genís Valentín,Zhang Ying,Weyer Felix Alexander,Lapouge Karine,Kappes Julia,von Plehwe Ulrike,Schermann Géza,Fitzke Edith,Wölfle Tina,Fischer Tamás,Rospert Sabine,Sinning Irmgard Nature communications Cotranslational chaperones assist in de novo folding of nascent polypeptides in all organisms. In yeast, the heterodimeric ribosome-associated complex (RAC) forms a unique chaperone triad with the Hsp70 homologue Ssb. We report the X-ray structure of full length Ssb in the ATP-bound open conformation at 2.6 Å resolution and identify a positively charged region in the α-helical lid domain (SBDα), which is present in all members of the Ssb-subfamily of Hsp70s. Mutational analysis demonstrates that this region is strictly required for ribosome binding. Crosslinking shows that Ssb binds close to the tunnel exit via contacts with both, ribosomal proteins and rRNA, and that specific contacts can be correlated with switching between the open (ATP-bound) and closed (ADP-bound) conformation. Taken together, our data reveal how Ssb dynamics on the ribosome allows for the efficient interaction with nascent chains upon RAC-mediated activation of ATP hydrolysis. 10.1038/ncomms13563
    Profiling Ssb-Nascent Chain Interactions Reveals Principles of Hsp70-Assisted Folding. Döring Kristina,Ahmed Nabeel,Riemer Trine,Suresh Harsha Garadi,Vainshtein Yevhen,Habich Markus,Riemer Jan,Mayer Matthias P,O'Brien Edward P,Kramer Günter,Bukau Bernd Cell The yeast Hsp70 chaperone Ssb interacts with ribosomes and nascent polypeptides to assist protein folding. To reveal its working principle, we determined the nascent chain-binding pattern of Ssb at near-residue resolution by in vivo selective ribosome profiling. Ssb associates broadly with cytosolic, nuclear, and hitherto unknown substrate classes of mitochondrial and endoplasmic reticulum (ER) nascent proteins, supporting its general chaperone function. Ssb engages most substrates by multiple binding-release cycles to a degenerate sequence enriched in positively charged and aromatic amino acids. Timely association with this motif upon emergence at the ribosomal tunnel exit requires ribosome-associated complex (RAC) but not nascent polypeptide-associated complex (NAC). Ribosome footprint densities along orfs reveal faster translation at times of Ssb binding, mainly imposed by biases in mRNA secondary structure, codon usage, and Ssb action. Ssb thus employs substrate-tailored dynamic nascent chain associations to coordinate co-translational protein folding, facilitate accelerated translation, and support membrane targeting of organellar proteins. 10.1016/j.cell.2017.06.038
    HSP70 Multi-Functionality in Cancer. Albakova Zarema,Armeev Grigoriy A,Kanevskiy Leonid M,Kovalenko Elena I,Sapozhnikov Alexander M Cells The 70-kDa heat shock proteins (HSP70s) are abundantly present in cancer, providing malignant cells selective advantage by suppressing multiple apoptotic pathways, regulating necrosis, bypassing cellular senescence program, interfering with tumor immunity, promoting angiogenesis and supporting metastasis. This direct involvement of HSP70 in most of the cancer hallmarks explains the phenomenon of cancer "addiction" to HSP70, tightly linking tumor survival and growth to the HSP70 expression. HSP70 operates in different states through its catalytic cycle, suggesting that it can multi-function in malignant cells in any of these states. Clinically, tumor cells intensively release HSP70 in extracellular microenvironment, resulting in diverse outcomes for patient survival. Given its clinical significance, small molecule inhibitors were developed to target different sites of the HSP70 machinery. Furthermore, several HSP70-based immunotherapy approaches were assessed in clinical trials. This review will explore different roles of HSP70 on cancer progression and emphasize the importance of understanding the flexibility of HSP70 nature for future development of anti-cancer therapies. 10.3390/cells9030587
    HSP70 is a negative regulator of NLRP3 inflammasome activation. Martine Pierre,Chevriaux Angélique,Derangère Valentin,Apetoh Lionel,Garrido Carmen,Ghiringhelli François,Rébé Cédric Cell death & disease The NOD-leucine rich repeat and pyrin containing protein 3 (NLRP3) inflammasome is a multi-protein complex, aimed at producing IL-1β in response to danger signals which must be tightly regulated. Here we investigated the importance of the stress sensor, Heat Shock Protein 70 (HSP70) on NLRP3 inflammasome activation. HSP70 deficiency leads to the worsening of NLRP3-dependent peritonitis in mice. HSP70 deficiency also enhances caspase-1 activation and IL-1β production in murine Bone Marrow-Derived Macrophages (BMDMs) under NLRP3 activator treatment in vitro. This observation is associated with an increased number and size of Apoptosis associated Speck-like protein containing a CARD domain (ASC)/NLRP3 specks. Conversely, the overexpression of HSP70 in BMDMs decreases caspase-1 activation and IL-1β production under NLRP3 activator treatment. HSP70 interacts with NLRP3 and this interaction is lost upon NLRP3 inflammasome activation. Heat shock inhibits NLRP3 inflammasome activation in vitro and inhibits peritonitis in mice. Therefore this study provides evidence on the inhibitory role of HSP70 on NLRP3 inflammasome and open the possibility of treating inflammatory diseases via HSP70 induction and/or by hyperthermia. 10.1038/s41419-019-1491-7
    Heat Shock Proteins Promote Cancer: It's a Protection Racket. Calderwood Stuart K,Gong Jianlin Trends in biochemical sciences Heat shock proteins (HSP) are expressed at high levels in cancer and form a fostering environment that is essential for tumor development. Here, we review the recent data in this area, concentrating mainly on Hsp27, Hsp70, and Hsp90. The overriding role of HSPs in cancer is to stabilize the active functions of overexpressed and mutated cancer genes. Thus, elevated HSPs are required for many of the traits that underlie the morbidity of cancer, including increased growth, survival, and formation of secondary cancers. In addition, HSPs participate in the evolution of cancer treatment resistance. HSPs are also released from cancer cells and influence malignant properties by receptor-mediated signaling. Current data strongly support efforts to target HSPs in cancer treatment. 10.1016/j.tibs.2016.01.003
    Lysosomal storage diseases: HSP70 reverses lysosomal pathology. Crunkhorn Sarah Nature reviews. Drug discovery 10.1038/nrd.2016.220
    Cellular Handling of Protein Aggregates by Disaggregation Machines. Mogk Axel,Bukau Bernd,Kampinga Harm H Molecular cell Both acute proteotoxic stresses that unfold proteins and expression of disease-causing mutant proteins that expose aggregation-prone regions can promote protein aggregation. Protein aggregates can interfere with cellular processes and deplete factors crucial for protein homeostasis. To cope with these challenges, cells are equipped with diverse folding and degradation activities to rescue or eliminate aggregated proteins. Here, we review the different chaperone disaggregation machines and their mechanisms of action. In all these machines, the coating of protein aggregates by Hsp70 chaperones represents the conserved, initializing step. In bacteria, fungi, and plants, Hsp70 recruits and activates Hsp100 disaggregases to extract aggregated proteins. In the cytosol of metazoa, Hsp70 is empowered by a specific cast of J-protein and Hsp110 co-chaperones allowing for standalone disaggregation activity. Both types of disaggregation machines are supported by small Hsps that sequester misfolded proteins. 10.1016/j.molcel.2018.01.004
    Heat shock proteins in the retina: Focus on HSP70 and alpha crystallins in ganglion cell survival. Piri Natik,Kwong Jacky M K,Gu Lei,Caprioli Joseph Progress in retinal and eye research Heat shock proteins (HSPs) belong to a superfamily of stress proteins that are critical constituents of a complex defense mechanism that enhances cell survival under adverse environmental conditions. Cell protective roles of HSPs are related to their chaperone functions, antiapoptotic and antinecrotic effects. HSPs' anti-apoptotic and cytoprotective characteristics, their ability to protect cells from a variety of stressful stimuli, and the possibility of their pharmacological induction in cells under pathological stress make these proteins an attractive therapeutic target for various neurodegenerative diseases; these include Alzheimer's, Parkinson's, Huntington's, prion disease, and others. This review discusses the possible roles of HSPs, particularly HSP70 and small HSPs (alpha A and alpha B crystallins) in enhancing the survival of retinal ganglion cells (RGCs) in optic neuropathies such as glaucoma, which is characterized by progressive loss of vision caused by degeneration of RGCs and their axons in the optic nerve. Studies in animal models of RGC degeneration induced by ocular hypertension, optic nerve crush and axotomy show that upregulation of HSP70 expression by hyperthermia, zinc, geranyl-geranyl acetone, 17-AAG (a HSP90 inhibitor), or through transfection of retinal cells with AAV2-HSP70 effectively supports the survival of injured RGCs. RGCs survival was also stimulated by overexpression of alpha A and alpha B crystallins. These findings provide support for translating the HSP70- and alpha crystallin-based cell survival strategy into therapy to protect and rescue injured RGCs from degeneration associated with glaucomatous and other optic neuropathies. 10.1016/j.preteyeres.2016.03.001
    ARD1-mediated Hsp70 acetylation balances stress-induced protein refolding and degradation. Seo Ji Hae,Park Ji-Hyeon,Lee Eun Ji,Vo Tam Thuy Lu,Choi Hoon,Kim Jun Yong,Jang Jae Kyung,Wee Hee-Jun,Lee Hye Shin,Jang Se Hwan,Park Zee Yong,Jeong Jaeho,Lee Kong-Joo,Seok Seung-Hyeon,Park Jin Young,Lee Bong Jin,Lee Mi-Ni,Oh Goo Taeg,Kim Kyu-Won Nature communications Heat shock protein (Hsp)70 is a molecular chaperone that maintains protein homoeostasis during cellular stress through two opposing mechanisms: protein refolding and degradation. However, the mechanisms by which Hsp70 balances these opposing functions under stress conditions remain unknown. Here, we demonstrate that Hsp70 preferentially facilitates protein refolding after stress, gradually switching to protein degradation via a mechanism dependent on ARD1-mediated Hsp70 acetylation. During the early stress response, Hsp70 is immediately acetylated by ARD1 at K77, and the acetylated Hsp70 binds to the co-chaperone Hop to allow protein refolding. Thereafter, Hsp70 is deacetylated and binds to the ubiquitin ligase protein CHIP to complete protein degradation during later stages. This switch is required for the maintenance of protein homoeostasis and ultimately rescues cells from stress-induced cell death in vitro and in vivo. Therefore, ARD1-mediated Hsp70 acetylation is a regulatory mechanism that temporally balances protein refolding/degradation in response to stress. 10.1038/ncomms12882
    Members of the Hsp70 Family Recognize Distinct Types of Sequences to Execute ER Quality Control. Behnke Julia,Mann Melissa J,Scruggs Fei-Lin,Feige Matthias J,Hendershot Linda M Molecular cell Protein maturation in the endoplasmic reticulum is controlled by multiple chaperones, but how they recognize and determine the fate of their clients remains unclear. We developed an in vivo peptide library covering substrates of the ER Hsp70 system: BiP, Grp170, and three of BiP's DnaJ-family co-factors (ERdj3, ERdj4, and ERdj5). In vivo binding studies revealed that sites for pro-folding chaperones BiP and ERdj3 were frequent and dispersed throughout the clients, whereas Grp170, ERdj4, and ERdj5 specifically recognized a distinct type of rarer sequence with a high predicted aggregation potential. Mutational analyses provided insights into sequence recognition characteristics for these pro-degradation chaperones, which could be readily introduced or disrupted, allowing the consequences for client fates to be determined. Our data reveal unanticipated diversity in recognition sequences for chaperones; establish a sequence-encoded interplay between protein folding, aggregation, and degradation; and highlight the ability of clients to co-evolve with chaperones, ensuring quality control. 10.1016/j.molcel.2016.07.012
    Alternative modes of client binding enable functional plasticity of Hsp70. Mashaghi Alireza,Bezrukavnikov Sergey,Minde David P,Wentink Anne S,Kityk Roman,Zachmann-Brand Beate,Mayer Matthias P,Kramer Günter,Bukau Bernd,Tans Sander J Nature The Hsp70 system is a central hub of chaperone activity in all domains of life. Hsp70 performs a plethora of tasks, including folding assistance, protection against aggregation, protein trafficking, and enzyme activity regulation, and interacts with non-folded chains, as well as near-native, misfolded, and aggregated proteins. Hsp70 is thought to achieve its many physiological roles by binding peptide segments that extend from these different protein conformers within a groove that can be covered by an ATP-driven helical lid. However, it has been difficult to test directly how Hsp70 interacts with protein substrates in different stages of folding and how it affects their structure. Moreover, recent indications of diverse lid conformations in Hsp70-substrate complexes raise the possibility of additional interaction mechanisms. Addressing these issues is technically challenging, given the conformational dynamics of both chaperone and client, the transient nature of their interaction, and the involvement of co-chaperones and the ATP hydrolysis cycle. Here, using optical tweezers, we show that the bacterial Hsp70 homologue (DnaK) binds and stabilizes not only extended peptide segments, but also partially folded and near-native protein structures. The Hsp70 lid and groove act synergistically when stabilizing folded structures: stabilization is abolished when the lid is truncated and less efficient when the groove is mutated. The diversity of binding modes has important consequences: Hsp70 can both stabilize and destabilize folded structures, in a nucleotide-regulated manner; like Hsp90 and GroEL, Hsp70 can affect the late stages of protein folding; and Hsp70 can suppress aggregation by protecting partially folded structures as well as unfolded protein chains. Overall, these findings in the DnaK system indicate an extension of the Hsp70 canonical model that potentially affects a wide range of physiological roles of the Hsp70 system. 10.1038/nature20137
    Protein polarization driven by nucleoid exclusion of DnaK(HSP70)-substrate complexes. Collet Clémence,Thomassin Jenny-Lee,Francetic Olivera,Genevaux Pierre,Tran Van Nhieu Guy Nature communications Many bacterial proteins require specific subcellular localization for function. How Escherichia coli proteins localize at one pole, however, is still not understood. Here, we show that the DnaK (HSP70) chaperone controls unipolar localization of the Shigella IpaC type III secretion substrate. While preventing the formation of lethal IpaC aggregates, DnaK promoted the incorporation of IpaC into large and dynamic complexes (LDCs) restricted at the bacterial pole through nucleoid occlusion. Unlike stable polymers and aggregates, LDCs show dynamic behavior indicating that nucleoid occlusion also applies to complexes formed through transient interactions. Fluorescence recovery after photobleaching analysis shows DnaK-IpaC exchanges between opposite poles and DnaKJE-mediated incorporation of immature substrates in LDCs. These findings reveal a key role for LDCs as reservoirs of functional DnaK-substrates that can be rapidly mobilized for secretion triggered upon bacterial contact with host cells. 10.1038/s41467-018-04414-2
    Structural insights into a unique Hsp70-Hsp40 interaction in the eukaryotic ribosome-associated complex. Weyer Felix Alexander,Gumiero Andrea,Gesé Genís Valentín,Lapouge Karine,Sinning Irmgard Nature structural & molecular biology Cotranslational chaperones assist de novo folding of nascent polypeptides, prevent them from aggregating and modulate translation. The ribosome-associated complex (RAC) is unique in that the Hsp40 protein Zuo1 and the atypical Hsp70 chaperone Ssz1 form a stable heterodimer, which acts as a cochaperone for the Hsp70 chaperone Ssb. Here we present the structure of the Chaetomium thermophilum RAC core comprising Ssz1 and the Zuo1 N terminus. We show how the conserved allostery of Hsp70 proteins is abolished and this Hsp70-Hsp40 pair is molded into a functional unit. Zuo1 stabilizes Ssz1 in trans through interactions that in canonical Hsp70s occur in cis. Ssz1 is catalytically inert and cannot adopt the closed conformation, but the substrate binding domain β is completed by Zuo1. Our study offers insights into the coupling of a special Hsp70-Hsp40 pair, which evolved to link protein folding and translation. 10.1038/nsmb.3349
    A Legionella pneumophila Kinase Phosphorylates the Hsp70 Chaperone Family to Inhibit Eukaryotic Protein Synthesis. Moss Steven M,Taylor Isabelle R,Ruggero Davide,Gestwicki Jason E,Shokat Kevan M,Mukherjee Shaeri Cell host & microbe Legionella pneumophila (L.p.), the microbe responsible for Legionnaires' disease, secretes ∼300 bacterial proteins into the host cell cytosol. A subset of these proteins affects a wide range of post-translational modifications (PTMs) to disrupt host cellular pathways. L.p. has 5 conserved eukaryotic-like Ser/Thr effector kinases, LegK1-4 and LegK7, which are translocated during infection. Using a chemical genetic screen, we identified the Hsp70 chaperone family as a direct host target of LegK4. Phosphorylation of Hsp70s at T495 in the substrate-binding domain disrupted Hsp70's ATPase activity and greatly inhibited its protein folding capacity. Phosphorylation of cytosolic Hsp70 by LegK4 resulted in global translation inhibition and an increase in the amount of Hsp70 on highly translating polysomes. LegK4's ability to inhibit host translation via a single PTM uncovers a role for Hsp70 in protein synthesis and directly links it to the cellular translational machinery. 10.1016/j.chom.2019.01.006
    Hsp70 interactions with membrane lipids regulate cellular functions in health and disease. Balogi Zsolt,Multhoff Gabriele,Jensen Thomas Kirkegaard,Lloyd-Evans Emyr,Yamashima Tetsumori,Jäättelä Marja,Harwood John L,Vígh László Progress in lipid research Beyond guarding the cellular proteome the major stress inducible heat shock protein Hsp70 has been shown to interact with lipids. Non-cytosolic Hsp70 stabilizes membranes during stress challenges and, in pathophysiological states, facilitates endocytosis, counteracts apoptotic mechanisms, sustains survival pathways or represents a signal that can be recognized by the immune system. Disease-coupled lipid-associated functions of Hsp70 may be targeted via distinct subcellular localizations of Hsp70 itself or its specific interacting lipids. With a special focus on interacting lipids, here we discuss localization-dependent roles of the membrane-bound Hsp70 in the context of its therapeutic potential, particularly in cancer and neurodegenerative diseases. 10.1016/j.plipres.2019.01.004
    Cellular sequestrases maintain basal Hsp70 capacity ensuring balanced proteostasis. Ho Chi-Ting,Grousl Tomas,Shatz Oren,Jawed Areeb,Ruger-Herreros Carmen,Semmelink Marije,Zahn Regina,Richter Karsten,Bukau Bernd,Mogk Axel Nature communications Maintenance of cellular proteostasis is achieved by a multi-layered quality control network, which counteracts the accumulation of misfolded proteins by refolding and degradation pathways. The organized sequestration of misfolded proteins, actively promoted by cellular sequestrases, represents a third strategy of quality control. Here we determine the role of sequestration within the proteostasis network in Saccharomyces cerevisiae and the mechanism by which it occurs. The Hsp42 and Btn2 sequestrases are functionally intertwined with the refolding activity of the Hsp70 system. Sequestration of misfolded proteins by Hsp42 and Btn2 prevents proteostasis collapse and viability loss in cells with limited Hsp70 capacity, likely by shielding Hsp70 from misfolded protein overload. Btn2 has chaperone and sequestrase activity and shares features with small heat shock proteins. During stress recovery Btn2 recruits the Hsp70-Hsp104 disaggregase by directly interacting with the Hsp70 co-chaperone Sis1, thereby shunting sequestered proteins to the refolding pathway. 10.1038/s41467-019-12868-1
    The Hsp70 chaperone network. Rosenzweig Rina,Nillegoda Nadinath B,Mayer Matthias P,Bukau Bernd Nature reviews. Molecular cell biology The 70-kDa heat shock proteins (Hsp70s) are ubiquitous molecular chaperones that act in a large variety of cellular protein folding and remodelling processes. They function virtually at all stages of the life of proteins from synthesis to degradation and are thus crucial for maintaining protein homeostasis, with direct implications for human health. A large set of co-chaperones comprising J-domain proteins and nucleotide exchange factors regulate the ATPase cycle of Hsp70s, which is allosterically coupled to substrate binding and release. Moreover, Hsp70s cooperate with other cellular chaperone systems including Hsp90, Hsp60 chaperonins, small heat shock proteins and Hsp100 AAA+ disaggregases, together constituting a dynamic and functionally versatile network for protein folding, unfolding, regulation, targeting, aggregation and disaggregation, as well as degradation. In this Review we describe recent advances that have increased our understanding of the molecular mechanisms and working principles of the Hsp70 network. This knowledge showcases how the Hsp70 chaperone system controls diverse cellular functions, and offers new opportunities for the development of chemical compounds that modulate disease-related Hsp70 activities. 10.1038/s41580-019-0133-3
    Nucleotide exchange factors Fes1 and HspBP1 mimic substrate to release misfolded proteins from Hsp70. Gowda Naveen K C,Kaimal Jayasankar M,Kityk Roman,Daniel Chammiran,Liebau Jobst,Öhman Marie,Mayer Matthias P,Andréasson Claes Nature structural & molecular biology Protein quality control depends on the tight regulation of interactions between molecular chaperones and polypeptide substrates. Substrate release from the chaperone Hsp70 is triggered by nucleotide-exchange factors (NEFs) that control folding and degradation fates via poorly understood mechanisms. We found that the armadillo-type NEFs budding yeast Fes1 and its human homolog HspBP1 employ flexible N-terminal release domains (RDs) with substrate-mimicking properties to ensure the efficient release of persistent substrates from Hsp70. The RD contacts the substrate-binding domain of the chaperone, competes with peptide substrate for binding and is essential for proper function in yeast and mammalian cells. Thus, the armadillo domain engages Hsp70 to trigger nucleotide exchange, whereas the RD safeguards the release of substrates. Our findings provide fundamental mechanistic insight into the functional specialization of Hsp70 NEFs and have implications for the understanding of proteostasis-related disorders, including Marinesco-Sjögren syndrome. 10.1038/s41594-017-0008-2
    Tumor induces muscle wasting in mice through releasing extracellular Hsp70 and Hsp90. Zhang Guohua,Liu Zhelong,Ding Hui,Zhou Yong,Doan Hoang Anh,Sin Ka Wai Thomas,Zhu Zhiren J,Flores Rene,Wen Yefei,Gong Xing,Liu Qingyun,Li Yi-Ping Nature communications Cachexia, characterized by muscle wasting, is a major contributor to cancer-related mortality. However, the key cachexins that mediate cancer-induced muscle wasting remain elusive. Here, we show that tumor-released extracellular Hsp70 and Hsp90 are responsible for tumor's capacity to induce muscle wasting. We detected high-level constitutive release of Hsp70 and Hsp90 associated with extracellular vesicles (EVs) from diverse cachexia-inducing tumor cells, resulting in elevated serum levels in mice. Neutralizing extracellular Hsp70/90 or silencing Hsp70/90 expression in tumor cells abrogates tumor-induced muscle catabolism and wasting in cultured myotubes and in mice. Conversely, administration of recombinant Hsp70 and Hsp90 recapitulates the catabolic effects of tumor. In addition, tumor-released Hsp70/90-expressing EVs are necessary and sufficient for tumor-induced muscle wasting. Further, Hsp70 and Hsp90 induce muscle catabolism by activating TLR4, and are responsible for elevation of circulating cytokines. These findings identify tumor-released circulating Hsp70 and Hsp90 as key cachexins causing muscle wasting in mice.Cachexia affects many cancer patients causing weight loss and increasing mortality. Here, the authors identify extracellular Hsp70 and Hsp90, either in soluble form or secreted as part of exosomes from tumor cells, to be responsible for tumor induction of cachexia. 10.1038/s41467-017-00726-x
    Cracking the Chaperone Code: Cellular Roles for Hsp70 Phosphorylation. Nitika ,Truman Andrew W Trends in biochemical sciences Heat shock protein 70 (Hsp70) is a molecular chaperone required for protein folding, cell viability, and cancer cell proliferation. Recent studies suggest that Hsp70 phosphorylation regulates important cellular processes, such as cell cycle progression, apoptosis, protein degradation, and resistance to anticancer therapeutics. 10.1016/j.tibs.2017.10.002
    Proteostasis by STUB1/HSP70 complex controls sensitivity to androgen receptor targeted therapy in advanced prostate cancer. Liu Chengfei,Lou Wei,Yang Joy C,Liu Liangren,Armstrong Cameron M,Lombard Alan P,Zhao Ruining,Noel Onika D V,Tepper Clifford G,Chen Hong-Wu,Dall'Era Marc,Evans Christopher P,Gao Allen C Nature communications Protein homeostasis (proteostasis) is a potential mechanism that contributes to cancer cell survival and drug resistance. Constitutively active androgen receptor (AR) variants confer anti-androgen resistance in advanced prostate cancer. However, the role of proteostasis involved in next generation anti-androgen resistance and the mechanisms of AR variant regulation are poorly defined. Here we show that the ubiquitin-proteasome-system (UPS) is suppressed in enzalutamide/abiraterone resistant prostate cancer. AR/AR-V7 proteostasis requires the interaction of E3 ubiquitin ligase STUB1 and HSP70 complex. STUB1 disassociates AR/AR-V7 from HSP70, leading to AR/AR-V7 ubiquitination and degradation. Inhibition of HSP70 significantly inhibits prostate tumor growth and improves enzalutamide/abiraterone treatments through AR/AR-V7 suppression. Clinically, HSP70 expression is upregulated and correlated with AR/AR-V7 levels in high Gleason score prostate tumors. Our results reveal a novel mechanism of anti-androgen resistance via UPS alteration which could be targeted through inhibition of HSP70 to reduce AR-V7 expression and overcome resistance to AR-targeted therapies. 10.1038/s41467-018-07178-x
    Nascent Polypeptide Domain Topology and Elongation Rate Direct the Cotranslational Hierarchy of Hsp70 and TRiC/CCT. Stein Kevin C,Kriel Allison,Frydman Judith Molecular cell Cotranslational protein folding requires assistance from elaborate ribosome-associated chaperone networks. It remains unclear how the changing information in a growing nascent polypeptide dictates the recruitment of functionally distinct chaperones. Here, we used ribosome profiling to define the principles governing the cotranslational action of the chaperones TRiC/CCT and Hsp70/Ssb. We show that these chaperones are sequentially recruited to specific sites within domain-encoding regions of select nascent polypeptides. Hsp70 associates first, binding select sites throughout domains, whereas TRiC associates later, upon the emergence of nearly complete domains that expose an unprotected hydrophobic surface. This suggests that transient topological properties of nascent folding intermediates drive sequential chaperone association. Moreover, cotranslational recruitment of both TRiC and Hsp70 correlated with translation elongation slowdowns. We propose that the temporal modulation of the nascent chain structural landscape is coordinated with local elongation rates to regulate the hierarchical action of Hsp70 and TRiC for cotranslational folding. 10.1016/j.molcel.2019.06.036
    Targeting the interaction of AIMP2-DX2 with HSP70 suppresses cancer development. Lim Semi,Cho Hye Young,Kim Dae Gyu,Roh Younah,Son Se-Young,Mushtaq Ameeq Ul,Kim Minkyoung,Bhattarai Deepak,Sivaraman Aneesh,Lee Youngjin,Lee Jihye,Yang Won Suk,Kim Hoi Kyoung,Kim Myung Hee,Lee Kyeong,Jeon Young Ho,Kim Sunghoon Nature chemical biology A tumorigenic factor, AIMP2 lacking exon 2 (AIMP2-DX2), is often upregulated in many cancers. However, how its cellular level is determined is not understood. Here, we report heat-shock protein HSP70 as a critical determinant for the level of AIMP2-DX2. Interaction of the two factors was identified by interactome analysis and structurally determined by X-ray crystallography and NMR analyses. HSP70 recognizes the amino (N)-terminal flexible region, as well as the glutathione S-transferase domain of AIMP2-DX2, via its substrate-binding domain, thus blocking the Siah1-dependent ubiquitination of AIMP2-DX2. AIMP2-DX2-induced cell transformation and cancer progression in vivo was further augmented by HSP70. A positive correlation between HSP70 and AIMP2-DX2 levels was shown in various lung cancer cell lines and patient tissues. Chemical intervention in the AIMP2-DX2-HSP70 interaction suppressed cancer cell growth in vitro and in vivo. Thus, this work demonstrates the importance of the interaction between AIMP2-DX2 and HSP70 on tumor progression and its therapeutic potential against cancer. 10.1038/s41589-019-0415-2
    Hsp70- and Hsp90-Mediated Regulation of the Conformation of p53 DNA Binding Domain and p53 Cancer Variants. Boysen Marta,Kityk Roman,Mayer Matthias P Molecular cell The activity of the tumor suppressor p53 has to be timed and balanced closely to prevent untimely induction of cell death. The stability of p53 depends on the ubiquitin ligase Mdm2 but also on Hsp70 and Hsp90 chaperones that interact with its DNA binding domain (DBD). Using hydrogen exchange mass spectrometry and biochemical methods, we analyzed conformational states of wild-type p53-DBD at physiological temperatures and conformational perturbations in three frequent p53 cancer mutants. We demonstrate that the Hsp70/Hdj1 system shifts the conformational equilibrium of p53 toward a flexible, more mutant-like, DNA binding inactive state by binding to the DNA binding loop. The analyzed cancer mutants are likewise destabilized by interaction with the Hsp70/Hdj1 system. In contrast, Hsp90 protects the DBD of p53 wild-type and mutant proteins from unfolding. We propose that the Hsp70 and Hsp90 chaperone systems assume complementary functions to optimally balance conformational plasticity with conformational stability. 10.1016/j.molcel.2019.03.032
    The Hsp70-Hsp90 Chaperone Cascade in Protein Folding. Morán Luengo Tania,Mayer Matthias P,Rüdiger Stefan G D Trends in cell biology Conserved families of molecular chaperones assist protein folding in the cell. Here we review the conceptual advances on three major folding routes: (i) spontaneous, chaperone-independent folding; (ii) folding assisted by repetitive Hsp70 cycles; and (iii) folding by the Hsp70-Hsp90 cascades. These chaperones prepare their protein clients for folding on their own, without altering their folding path. A particularly interesting role is reserved for Hsp90. The function of Hsp90 in folding is its ancient function downstream of Hsp70, free of cochaperone regulation and present in all kingdoms of life. Eukaryotic signalling networks, however, embrace Hsp90 by a plethora of cochaperones, transforming the profolding machinery to a folding-on-demand factor. We discuss implications for biology and molecular medicine. 10.1016/j.tcb.2018.10.004
    Molecular Mechanism of J-Domain-Triggered ATP Hydrolysis by Hsp70 Chaperones. Kityk Roman,Kopp Jürgen,Mayer Matthias P Molecular cell Efficient targeting of Hsp70 chaperones to substrate proteins depends on J-domain cochaperones, which in synergism with substrates trigger ATP hydrolysis in Hsp70s and concomitant substrate trapping. We present the crystal structure of the J-domain of Escherichia coli DnaJ in complex with the E. coli Hsp70 DnaK. The J-domain interacts not only with DnaK's nucleotide-binding domain (NBD) but also with its substrate-binding domain (SBD) and packs against the highly conserved interdomain linker. Mutational replacement of contacts between J-domain and SBD strongly reduces the ability of substrates to stimulate ATP hydrolysis in the presence of DnaJ and compromises viability at heat shock temperatures. Our data demonstrate that the J-domain and the substrate do not deliver completely independent signals for ATP hydrolysis, but the J-domain, in addition to its direct influence on Hsp70s catalytic center, makes Hsp70 more responsive for the hydrolysis-inducing signal of the substrate, resulting in efficient substrate trapping. 10.1016/j.molcel.2017.12.003