1
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Tripathi A, Del Galdo S, Chandramouli B, Kumar N. Distinct dynamical features of plasmodial and human HSP70-HSP110 highlight the divergence in their chaperone-assisted protein folding. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2023; 1871:140942. [PMID: 37516289 DOI: 10.1016/j.bbapap.2023.140942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2023] [Revised: 07/24/2023] [Accepted: 07/26/2023] [Indexed: 07/31/2023]
Abstract
HSP70 and its evolutionarily diverged co-chaperone HSP110, forms an important node in protein folding cascade. How these proteins maintain the aggregation-prone proteome of malaria parasite in functional state remains underexplored, in contrast to its human orthologs. In this study, we have probed into conformational dynamics of plasmodial HSP70 and HSP110 through multiple μs MD-simulations (ATP-state) and compared with their respective human counterparts. Simulations covered sampling of 3.4 and 2.8 μs for HSP70 and HSP110, respectively, for parasite and human orthologs. We provide a comprehensive description of the dynamic behaviors that characterize the systems and also introduce a parameter for quantifying protein rigidity. For HSP70, the interspecies comparison reveals enhanced flexibility in IA and IB subdomain within the conserved NBD, lesser solvent accessibility of the interdomain linker and distinct dynamics of the SBDβ of Pf HSP70 in comparison to Hs HSP70. In the case of HSP110, notable contrast in the dynamics of NBD, SBDβ and SBDα was observed between parasite and human ortholog. Although HSP70 and HSP110 are members of the same superfamily, we identified specific differences in the subdomain contacts in NBD, linker properties and interdomain movements in their human and parasite orthologs. Our study suggests that differences in conformational dynamics may translate into species-specific differences in the chaperoning activities of HSP70-HSP110 in the parasite and human, respectively. Dynamical features of Pf HSP70-HSP110 may contribute to the maintenance of proteostasis in the parasite during its intracellular survival in the host.
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Affiliation(s)
- Aradhya Tripathi
- Department of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute (CSIR-CDRI), Sector 10, Jankipuram Extension, Lucknow 226031, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Sara Del Galdo
- Science Department, University of Roma Tre, Via della Vasca Navale 84, Rome, Italy
| | | | - Niti Kumar
- Department of Molecular Microbiology and Immunology, CSIR-Central Drug Research Institute (CSIR-CDRI), Sector 10, Jankipuram Extension, Lucknow 226031, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.
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2
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Bracher A, Verghese J. Nucleotide Exchange Factors for Hsp70 Molecular Chaperones: GrpE, Hsp110/Grp170, HspBP1/Sil1, and BAG Domain Proteins. Subcell Biochem 2023; 101:1-39. [PMID: 36520302 DOI: 10.1007/978-3-031-14740-1_1] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Molecular chaperones of the Hsp70 family are key components of the cellular protein-folding machinery. Substrate folding is accomplished by iterative cycles of ATP binding, hydrolysis, and release. The ATPase activity of Hsp70 is regulated by two main classes of cochaperones: J-domain proteins stimulate ATPase hydrolysis by Hsp70, while nucleotide exchange factors (NEFs) facilitate the conversion from the ADP-bound to the ATP-bound state, thus closing the chaperone folding cycle. NEF function can additionally be antagonized by ADP dissociation inhibitors. Beginning with the discovery of the prototypical bacterial NEF, GrpE, a large diversity of nucleotide exchange factors for Hsp70 have been identified, connecting it to a multitude of cellular processes in the eukaryotic cell. Here we review recent advances toward structure and function of nucleotide exchange factors from the Hsp110/Grp170, HspBP1/Sil1, and BAG domain protein families and discuss how these cochaperones connect protein folding with cellular quality control and degradation pathways.
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Affiliation(s)
- Andreas Bracher
- Department of Cellular Biochemistry, Max-Planck-Institute of Biochemistry, Martinsried, Germany.
| | - Jacob Verghese
- Department of Cellular Biochemistry, Max-Planck-Institute of Biochemistry, Martinsried, Germany
- Trophic Communications GmbH, Munich, Germany
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3
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Sokolov PA, Rolich VI, Vezo OS, Belousov MV, Bondarev SA, Zhouravleva GA, Kasyanenko NA. Amyloid fibril length distribution from dynamic light scattering data. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2022; 51:325-333. [PMID: 35546203 DOI: 10.1007/s00249-022-01600-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 03/19/2022] [Accepted: 04/24/2022] [Indexed: 06/15/2023]
Abstract
The study of the aggregation of amyloid proteins is challenging. A new approach to processing dynamic light scattering data was developed and tested using aggregates of the well-known model Sup35NM amyloid. After filtering and calculating the moving averages of autocorrelation functions to reduce impacts of noise, each averaged autocorrelation function is converted to the fibril length distribution via numerical modeling. The processing results were verified using atomic force and scanning electron microscopy data. Analysis of fibril length distribution changes over time gives valuable information about the aggregation process.
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Affiliation(s)
- Petr A Sokolov
- Department of Physics, St. Petersburg University, 7-9-11 Universitetskaya Emb, St. Petersburg, 199034, Russia.
| | - Valeriy I Rolich
- Department of Physics, St. Petersburg University, 7-9-11 Universitetskaya Emb, St. Petersburg, 199034, Russia
| | - Olga S Vezo
- Department of Physics, St. Petersburg University, 7-9-11 Universitetskaya Emb, St. Petersburg, 199034, Russia
| | - Mikhail V Belousov
- Department of Genetics and Biotechnology, St. Petersburg University, 7-9-11 Universitetskaya Emb, St. Petersburg, 199034, Russia
- Laboratory for Proteomics of Supra-Organismal Systems, All-Russia Research Institute for Agricultural Microbiology, 3 Podbelsky chausse, St. Petersburg, 196608, Russia
| | - Stanislav A Bondarev
- Department of Genetics and Biotechnology, St. Petersburg University, 7-9-11 Universitetskaya Emb, St. Petersburg, 199034, Russia
| | - Galina A Zhouravleva
- Department of Genetics and Biotechnology, St. Petersburg University, 7-9-11 Universitetskaya Emb, St. Petersburg, 199034, Russia
| | - Nina A Kasyanenko
- Department of Physics, St. Petersburg University, 7-9-11 Universitetskaya Emb, St. Petersburg, 199034, Russia
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4
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Kojima R, Takai S, Osada H, Yamamoto L, Furukawa M, Gullans SR. Novel function of the C-Terminal region of the Hsp110 family member Osp94 in unfolded protein refolding. J Cell Sci 2022; 135:274905. [PMID: 35237814 DOI: 10.1242/jcs.258542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 01/18/2022] [Indexed: 11/20/2022] Open
Abstract
Osp94, a member of the Hsp110/Sse1 family of heat shock proteins, has a longer C-terminus than Hsc70/Hsp70, composed of the loop region with partial SBDβ (L), and SBDα and the C-terminal extension (H), but the functions of these domains are poorly understood. Osp94 suppressed heat-induced aggregation of luciferase (Luc). Osp94-bound heat-inactivated Luc was reactivated in the presence of rabbit reticulocyte lysate (RRL) and/or a combination of Hsc70 and Hsp40. Targeted deletion mutagenesis revealed that the SBDβ and H domains of Osp94 are critical for protein disaggregation and RRL-mediated refolding. Reactivation of Hsp90-bound heat-inactivated Luc was abolished in the absence of RRL but compensated by PA28α, a proteasome activator. Interestingly, the LH domain also reactivated heat-inactivated Luc, independent of PA28α. Biotin-tag cross-linking experiments indicated that the LH domain and PA28α interact with Luc bound by Hsp90 during refolding. A chimera protein in which the H domain was exchanged for PA28α also mediated disaggregation and reactivation of heat-inactivated Luc. These results indicate that Osp94 acts as a holdase and that the C-terminal region plays a PA28α-like role in the refolding of unfolded proteins.
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Affiliation(s)
- Ryoji Kojima
- Laboratory of Analytical Pharmacology, Faculty of Pharmacy, Meijo University, Nagoya, Aichi, 468-8503, Japan
| | - Shinichi Takai
- Laboratory of Analytical Pharmacology, Faculty of Pharmacy, Meijo University, Nagoya, Aichi, 468-8503, Japan
| | - Hinako Osada
- Laboratory of Analytical Pharmacology, Faculty of Pharmacy, Meijo University, Nagoya, Aichi, 468-8503, Japan
| | - Lina Yamamoto
- Laboratory of Analytical Pharmacology, Faculty of Pharmacy, Meijo University, Nagoya, Aichi, 468-8503, Japan
| | - Misa Furukawa
- Laboratory of Analytical Pharmacology, Faculty of Pharmacy, Meijo University, Nagoya, Aichi, 468-8503, Japan
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5
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Yakubu UM, Morano KA. Suppression of aggregate and amyloid formation by a novel intrinsically disordered region in metazoan Hsp110 chaperones. J Biol Chem 2021; 296:100567. [PMID: 33753171 PMCID: PMC8063735 DOI: 10.1016/j.jbc.2021.100567] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/15/2021] [Accepted: 03/18/2021] [Indexed: 12/26/2022] Open
Abstract
Molecular chaperones maintain proteostasis by ensuring the proper folding of polypeptides. Loss of proteostasis has been linked to numerous neurodegenerative disorders including Alzheimer's, Parkinson's, and Huntington's disease. Hsp110 is related to the canonical Hsp70 class of protein-folding molecular chaperones and interacts with Hsp70 as a nucleotide exchange factor (NEF). In addition to its NEF activity, Hsp110 possesses an Hsp70-like substrate-binding domain (SBD) whose biological roles remain undefined. Previous work in Drosophila melanogaster has implicated the sole Hsp110 gene (Hsc70cb) in proteinopathic neurodegeneration. We hypothesize that in addition to its role as an Hsp70 NEF, Drosophila Hsp110 may function as a protective protein "holdase," preventing the aggregation of unfolded polypeptides via the SBD-β subdomain. We demonstrate for the first time that Drosophila Hsp110 effectively prevents aggregation of the model substrate citrate synthase. We also report the discovery of a redundant and heretofore unknown potent holdase capacity in a 138-amino-acid region of Hsp110 carboxyl terminal to both SBD-β and SBD-α (henceforth called the C-terminal extension). This sequence is highly conserved in metazoan Hsp110 genes, completely absent from fungal representatives, and is computationally predicted to contain an intrinsically disordered region (IDR). We demonstrate that this IDR sequence within the human Hsp110s, Apg-1 and Hsp105α, inhibits the formation of amyloid Aβ-42 and α-synuclein fibrils in vitro but cannot mediate fibril disassembly. Together these findings establish capacity for metazoan Hsp110 chaperones to suppress both general protein aggregation and amyloidogenesis, raising the possibility of exploitation of this IDR for therapeutic benefit.
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Affiliation(s)
- Unekwu M Yakubu
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, Houston, Texas, USA; MD Anderson UTHealth Graduate School at UTHealth, Houston, Texas, USA
| | - Kevin A Morano
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, Houston, Texas, USA.
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6
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Zininga T, Shonhai A. Small Molecule Inhibitors Targeting the Heat Shock Protein System of Human Obligate Protozoan Parasites. Int J Mol Sci 2019; 20:E5930. [PMID: 31775392 PMCID: PMC6929125 DOI: 10.3390/ijms20235930] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/29/2019] [Accepted: 11/13/2019] [Indexed: 12/13/2022] Open
Abstract
Obligate protozoan parasites of the kinetoplastids and apicomplexa infect human cells to complete their life cycles. Some of the members of these groups of parasites develop in at least two systems, the human host and the insect vector. Survival under the varied physiological conditions associated with the human host and in the arthropod vectors requires the parasites to modulate their metabolic complement in order to meet the prevailing conditions. One of the key features of these parasites essential for their survival and host infectivity is timely expression of various proteins. Even more importantly is the need to keep their proteome functional by maintaining its functional capabilities in the wake of physiological changes and host immune responses. For this reason, molecular chaperones (also called heat shock proteins)-whose role is to facilitate proteostasis-play an important role in the survival of these parasites. Heat shock protein 90 (Hsp90) and Hsp70 are prominent molecular chaperones that are generally induced in response to physiological stress. Both Hsp90 and Hsp70 members are functionally regulated by nucleotides. In addition, Hsp70 and Hsp90 cooperate to facilitate folding of some key proteins implicated in cellular development. In addition, Hsp90 and Hsp70 individually interact with other accessory proteins (co-chaperones) that regulate their functions. The dependency of these proteins on nucleotide for their chaperone function presents an Achille's heel, as inhibitors that mimic ATP are amongst potential therapeutic agents targeting their function in obligate intracellular human parasites. Most of the promising small molecule inhibitors of parasitic heat shock proteins are either antibiotics or anticancer agents, whose repurposing against parasitic infections holds prospects. Both cancer cells and obligate human parasites depend upon a robust protein quality control system to ensure their survival, and hence, both employ a competent heat shock machinery to this end. Furthermore, some inhibitors that target chaperone and co-chaperone networks also offer promising prospects as antiparasitic agents. The current review highlights the progress made so far in design and application of small molecule inhibitors against obligate intracellular human parasites of the kinetoplastida and apicomplexan kingdoms.
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Affiliation(s)
| | - Addmore Shonhai
- Department of Biochemistry, School of Mathematical and Natural Sciences, University of Venda, Thohoyandou 0950, South Africa;
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7
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Kumar V, Peter JJ, Sagar A, Ray A, Jha MP, Rebeaud ME, Tiwari S, Goloubinoff P, Ashish F, Mapa K. Interdomain communication suppressing high intrinsic ATPase activity of Sse1 is essential for its co-disaggregase activity with Ssa1. FEBS J 2019; 287:671-694. [PMID: 31423733 DOI: 10.1111/febs.15045] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 07/08/2019] [Accepted: 08/16/2019] [Indexed: 01/19/2023]
Abstract
In eukaryotes, Hsp110s are unambiguous cognates of the Hsp70 chaperones, in primary sequence, domain organization, and structure. Hsp110s function as nucleotide exchange factors (NEFs) for the Hsp70s although their apparent loss of Hsp70-like chaperone activity, nature of interdomain communication, and breadth of domain functions are still puzzling. Here, by combining single-molecule FRET, small angle X-ray scattering measurements (SAXS), and MD simulation, we show that yeast Hsp110, Sse1 lacks canonical Hsp70-like interdomain allostery. However, the protein exhibits unique noncanonical conformational changes within its domains. Sse1 maintains an open-lid substrate-binding domain (SBD) in close contact with its nucleotide-binding domain (NBD), irrespective of its ATP hydrolysis status. To further appreciate such ATP-hydrolysis-independent exhaustive interaction between two domains of Hsp110s, NBD-SBD chimera was constructed between Hsp110 (Sse1) and Hsp70 (Ssa1). In Sse1/Ssa1 chimera, we observed undocking of two domains leading to complete loss of NEF activity of Sse1. Interestingly, chimeric proteins exhibited significantly enhanced ATPase rate of Sse1-NBD compared to wild-type protein, implying that intrinsic ATPase activity of the protein remains mostly repressed. Apart from repressing the high ATPase activity of its NBD, interactions between two domains confer thermal stability to Sse1 and play critical role in the (co)chaperoning function of Sse1 in Ssa1-mediated disaggregation activity. Altogether, Sse1 exhibits a unique interdomain interaction, which is essential for its NEF activity, suppression of high intrinsic ATPase activity, co-chaperoning activity in disaggregase machinery, and stability of the protein.
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Affiliation(s)
- Vignesh Kumar
- Proteomics and Structural Biology Unit, CSIR-Institute of Genomics and Integrative Biology, New Delhi, India.,Academy of Scientific and Innovative Research (AcSir), CSIR-HRDC, Ghaziabad, India
| | - Joshua Jebakumar Peter
- Proteomics and Structural Biology Unit, CSIR-Institute of Genomics and Integrative Biology, New Delhi, India
| | - Amin Sagar
- CSIR-Institute of Microbial Technology, Chandigarh, Uttar Pradesh, India
| | - Arjun Ray
- Proteomics and Structural Biology Unit, CSIR-Institute of Genomics and Integrative Biology, New Delhi, India.,Academy of Scientific and Innovative Research (AcSir), CSIR-HRDC, Ghaziabad, India
| | - Mainak Pratim Jha
- Department of Life Sciences, School of Natural Sciences, Shiv Nadar University, Greater Noida, India
| | - Mathieu E Rebeaud
- Department of Plant Molecular Biology, University of Lausanne, Switzerland
| | - Satyam Tiwari
- Department of Plant Molecular Biology, University of Lausanne, Switzerland
| | - Pierre Goloubinoff
- Department of Plant Molecular Biology, University of Lausanne, Switzerland
| | - Fnu Ashish
- CSIR-Institute of Microbial Technology, Chandigarh, Uttar Pradesh, India
| | - Koyeli Mapa
- Academy of Scientific and Innovative Research (AcSir), CSIR-HRDC, Ghaziabad, India.,Department of Life Sciences, School of Natural Sciences, Shiv Nadar University, Greater Noida, India
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8
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Chakafana G, Zininga T, Shonhai A. Comparative structure-function features of Hsp70s of Plasmodium falciparum and human origins. Biophys Rev 2019; 11:591-602. [PMID: 31280465 PMCID: PMC6682331 DOI: 10.1007/s12551-019-00563-w] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 06/20/2019] [Indexed: 01/18/2023] Open
Abstract
The heat shock protein 70 (Hsp70) family of molecular chaperones are crucial for the survival and pathogenicity of the main agent of malaria, Plasmodium falciparum. Hsp70 is central to cellular proteostasis and some of its isoforms are essential for survival of the malaria parasite. In addition, they are also implicated in the development of antimalarial drug resistance. For these reasons, they are thought to be potential drug targets, especially in antimalarial combination therapies. However, their high sequence conservation across species presents a hurdle with respect to their selective targeting. The human genome encodes 17 Hsp70 isoforms while P. falciparum encodes for only 6. The structural architecture of Hsp70s is typically characterized by a highly conserved N-terminal nucleotide-binding domain (NBD) and a less conserved C-terminal substrate-binding domain (SBD). The two domains are connected by a highly conserved linker. In spite of their fairly high sequence conservation, Hsp70s from various species possess unique signature motifs that appear to uniquely influence their function. In addition, their cooperation with co-chaperones further regulates their functional specificity. In the current review, bioinformatics tools were used to identify conserved and unique signature motifs in Hsp70s of P. falciparum versus their human counterparts. We discuss the common and distinctive structure-function features of these proteins. This information is important towards elucidating the prospects of selective targeting of parasite heat shock proteins as part of antimalarial design efforts.
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Affiliation(s)
- Graham Chakafana
- Department of Biochemistry, University of Venda, Private Bags X5050, Thohoyandou, 0950, South Africa
| | - Tawanda Zininga
- Department of Biochemistry, University of Venda, Private Bags X5050, Thohoyandou, 0950, South Africa
| | - Addmore Shonhai
- Department of Biochemistry, University of Venda, Private Bags X5050, Thohoyandou, 0950, South Africa.
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9
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Yakubu UM, Morano KA. Roles of the nucleotide exchange factor and chaperone Hsp110 in cellular proteostasis and diseases of protein misfolding. Biol Chem 2019; 399:1215-1221. [PMID: 29908125 DOI: 10.1515/hsz-2018-0209] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 05/30/2018] [Indexed: 01/15/2023]
Abstract
Cellular protein homeostasis (proteostasis) is maintained by a broad network of proteins involved in synthesis, folding, triage, repair and degradation. Chief among these are molecular chaperones and their cofactors that act as powerful protein remodelers. The growing realization that many human pathologies are fundamentally diseases of protein misfolding (proteopathies) has generated interest in understanding how the proteostasis network impacts onset and progression of these diseases. In this minireview, we highlight recent progress in understanding the enigmatic Hsp110 class of heat shock protein that acts as both a potent nucleotide exchange factor to regulate activity of the foldase Hsp70, and as a passive chaperone capable of recognizing and binding cellular substrates on its own, and its integration into the proteostasis network.
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Affiliation(s)
- Unekwu M Yakubu
- Department of Microbiology and Molecular Genetics, University of Texas McGovern Medical School at Houston, Houston, TX 77030, USA.,MD Anderson UT Health Graduate School of Biomedical Sciences, Houston, TX 77030, USA
| | - Kevin A Morano
- Department of Microbiology and Molecular Genetics, University of Texas McGovern Medical School at Houston, Houston, TX 77030, USA
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10
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Regulation of Human Hsc70 ATPase and Chaperone Activities by Apg2: Role of the Acidic Subdomain. J Mol Biol 2018; 431:444-461. [PMID: 30521813 DOI: 10.1016/j.jmb.2018.11.026] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 10/30/2018] [Accepted: 11/26/2018] [Indexed: 12/28/2022]
Abstract
Protein aggregate reactivation in metazoans is accomplished by the combined activity of Hsp70, Hsp40 and Hsp110 chaperones. Hsp110s support the refolding of aggregated polypeptides acting as specialized nucleotide exchange factors of Hsp70. We have studied how Apg2, one of the three human Hsp110s, regulates the activity of Hsc70 (HspA8), the constitutive Hsp70 in our cells. Apg2 shows a biphasic behavior: at low concentration, it stimulates the ATPase cycle of Hsc70, binding of the chaperone to protein aggregates and the refolding activity of the system, while it inhibits these three processes at high concentration. When the acidic subdomain of Apg2, a characteristic sequence present in the substrate binding domain of all Hsp110s, is deleted, the detrimental effects occur at lower concentration and are more pronounced, which concurs with an increase in the affinity of the Apg2 mutant for Hsc70. Our data support a mechanism in which Apg2 arrests the chaperone cycle through an interaction with Hsc70(ATP) that might lead to premature ATP dissociation before hydrolysis. In this line, the acidic subdomain might serve as a conformational switch to support dissociation of the Hsc70:Apg2 complex.
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11
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Mayer MP, Gierasch LM. Recent advances in the structural and mechanistic aspects of Hsp70 molecular chaperones. J Biol Chem 2018; 294:2085-2097. [PMID: 30455352 DOI: 10.1074/jbc.rev118.002810] [Citation(s) in RCA: 169] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Hsp70 chaperones are central hubs of the protein quality control network and collaborate with co-chaperones having a J-domain (an ∼70-residue-long helical hairpin with a flexible loop and a conserved His-Pro-Asp motif required for ATP hydrolysis by Hsp70s) and also with nucleotide exchange factors to facilitate many protein-folding processes that (re)establish protein homeostasis. The Hsp70s are highly dynamic nanomachines that modulate the conformation of their substrate polypeptides by transiently binding to short, mostly hydrophobic stretches. This interaction is regulated by an intricate allosteric mechanism. The J-domain co-chaperones target Hsp70 to their polypeptide substrates, and the nucleotide exchange factors regulate the lifetime of the Hsp70-substrate complexes. Significant advances in recent years are beginning to unravel the molecular mechanism of this chaperone machine and how they treat their substrate proteins.
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Affiliation(s)
- Matthias P Mayer
- From the Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH-Alliance, 69120 Heidelberg, Germany and
| | - Lila M Gierasch
- the Departments of Biochemistry and Molecular Biology and.,Chemistry, University of Massachusetts, Amherst, Massachusetts 01003
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12
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Garcia VM, Nillegoda NB, Bukau B, Morano KA. Substrate binding by the yeast Hsp110 nucleotide exchange factor and molecular chaperone Sse1 is not obligate for its biological activities. Mol Biol Cell 2017; 28:2066-2075. [PMID: 28539411 PMCID: PMC5509420 DOI: 10.1091/mbc.e17-01-0070] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 05/15/2017] [Accepted: 05/17/2017] [Indexed: 02/05/2023] Open
Abstract
The highly conserved heat shock protein 70 (Hsp70) is a ubiquitous molecular chaperone essential for maintaining cellular protein homeostasis. The related protein Hsp110 (Sse1/Sse2 in Saccharomyces cerevisiae) functions as a nucleotide exchange factor (NEF) to regulate the protein folding activity of Hsp70. Hsp110/Sse1 also can prevent protein aggregation in vitro via its substrate-binding domain (SBD), but the cellular roles of this "holdase" activity are poorly defined. We generated and characterized an Sse1 mutant that separates, for the first time, its nucleotide exchange and substrate-binding functions. Sse1sbd retains nucleotide-binding and nucleotide exchange activities while exhibiting severe deficiencies in chaperone holdase activity for unfolded polypeptides. In contrast, we observed no effect of the SBD mutation in reconstituted disaggregation or refolding reactions in vitro. In vivo, Sse1sbd successfully heterodimerized with the yeast cytosolic Hsp70s Ssa and Ssb and promoted normal growth, with the exception of sensitivity to prolonged heat but not other proteotoxic stress. Moreover, Sse1sbd was fully competent to support Hsp90-dependent signaling through heterologously expressed glucocorticoid receptor and degradation of a permanently misfolded protein, two previously defined roles for Sse1. We conclude that despite conservation among eukaryotic homologues, chaperone holdase activity is not an obligate function in the Hsp110 family.
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Affiliation(s)
- Veronica M Garcia
- Department of Microbiology and Molecular Genetics, University of Texas McGovern Medical School at Houston, Houston, TX 77030.,MD Anderson UT Health Graduate School of Biomedical Sciences, Houston, TX 77030
| | - Nadinath B Nillegoda
- Center for Molecular Biology of Heidelberg University and German Cancer Research Center, D-69120 Heidelberg, Germany
| | - Bernd Bukau
- Center for Molecular Biology of Heidelberg University and German Cancer Research Center, D-69120 Heidelberg, Germany
| | - Kevin A Morano
- Department of Microbiology and Molecular Genetics, University of Texas McGovern Medical School at Houston, Houston, TX 77030
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13
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Zininga T, Achilonu I, Hoppe H, Prinsloo E, Dirr HW, Shonhai A. Plasmodium falciparum Hsp70-z, an Hsp110 homologue, exhibits independent chaperone activity and interacts with Hsp70-1 in a nucleotide-dependent fashion. Cell Stress Chaperones 2016; 21:499-513. [PMID: 26894764 PMCID: PMC4837182 DOI: 10.1007/s12192-016-0678-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 02/03/2016] [Accepted: 02/05/2016] [Indexed: 11/11/2022] Open
Abstract
The role of molecular chaperones, among them heat shock proteins (Hsps), in the development of malaria parasites has been well documented. Hsp70s are molecular chaperones that facilitate protein folding. Hsp70 proteins are composed of an N-terminal nucleotide binding domain (NBD), which confers them with ATPase activity and a C-terminal substrate binding domain (SBD). In the ADP-bound state, Hsp70 possesses high affinity for substrate and releases the folded substrate when it is bound to ATP. The two domains are connected by a conserved linker segment. Hsp110 proteins possess an extended lid segment, a feature that distinguishes them from canonical Hsp70s. Plasmodium falciparum Hsp70-z (PfHsp70-z) is a member of the Hsp110 family of Hsp70-like proteins. PfHsp70-z is essential for survival of malaria parasites and is thought to play an important role as a molecular chaperone and nucleotide exchange factor of its cytosolic canonical Hsp70 counterpart, PfHsp70-1. Unlike PfHsp70-1 whose functions are fairly well established, the structure-function features of PfHsp70-z remain to be fully elucidated. In the current study, we established that PfHsp70-z possesses independent chaperone activity. In fact, PfHsp70-z appears to be marginally more effective in suppressing protein aggregation than its cytosol-localized partner, PfHsp70-1. Furthermore, based on coimmunoaffinity chromatography and surface plasmon resonance analyses, PfHsp70-z associated with PfHsp70-1 in a nucleotide-dependent fashion. Our findings suggest that besides serving as a molecular chaperone, PfHsp70-z could facilitate the nucleotide exchange function of PfHsp70-1. These dual functions explain why it is essential for parasite survival.
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Affiliation(s)
- Tawanda Zininga
- Department of Biochemistry, University of Venda, Private Bag X5050, Thohoyandou, 0950, South Africa
| | - Ikechukwu Achilonu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Heinrich Hoppe
- Department of Biochemistry and Microbiology, Rhodes University, P.O. Box 94, Grahamstown, 6140, South Africa
| | - Earl Prinsloo
- Biotechnology Innovation Centre, Rhodes University, P.O. Box 94, Grahamstown, 6140, South Africa
| | - Heini W Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Addmore Shonhai
- Department of Biochemistry, University of Venda, Private Bag X5050, Thohoyandou, 0950, South Africa.
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14
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Dancing through Life: Molecular Dynamics Simulations and Network-Centric Modeling of Allosteric Mechanisms in Hsp70 and Hsp110 Chaperone Proteins. PLoS One 2015; 10:e0143752. [PMID: 26619280 PMCID: PMC4664246 DOI: 10.1371/journal.pone.0143752] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 11/09/2015] [Indexed: 01/04/2023] Open
Abstract
Hsp70 and Hsp110 chaperones play an important role in regulating cellular processes that involve protein folding and stabilization, which are essential for the integrity of signaling networks. Although many aspects of allosteric regulatory mechanisms in Hsp70 and Hsp110 chaperones have been extensively studied and significantly advanced in recent experimental studies, the atomistic picture of signal propagation and energetics of dynamics-based communication still remain unresolved. In this work, we have combined molecular dynamics simulations and protein stability analysis of the chaperone structures with the network modeling of residue interaction networks to characterize molecular determinants of allosteric mechanisms. We have shown that allosteric mechanisms of Hsp70 and Hsp110 chaperones may be primarily determined by nucleotide-induced redistribution of local conformational ensembles in the inter-domain regions and the substrate binding domain. Conformational dynamics and energetics of the peptide substrate binding with the Hsp70 structures has been analyzed using free energy calculations, revealing allosteric hotspots that control negative cooperativity between regulatory sites. The results have indicated that cooperative interactions may promote a population-shift mechanism in Hsp70, in which functional residues are organized in a broad and robust allosteric network that can link the nucleotide-binding site and the substrate-binding regions. A smaller allosteric network in Hsp110 structures may elicit an entropy-driven allostery that occurs in the absence of global structural changes. We have found that global mediating residues with high network centrality may be organized in stable local communities that are indispensable for structural stability and efficient allosteric communications. The network-centric analysis of allosteric interactions has also established that centrality of functional residues could correlate with their sensitivity to mutations across diverse chaperone functions. This study reconciles a wide spectrum of structural and functional experiments by demonstrating how integration of molecular simulations and network-centric modeling may explain thermodynamic and mechanistic aspects of allosteric regulation in chaperones.
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15
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Nillegoda NB, Bukau B. Metazoan Hsp70-based protein disaggregases: emergence and mechanisms. Front Mol Biosci 2015; 2:57. [PMID: 26501065 PMCID: PMC4598581 DOI: 10.3389/fmolb.2015.00057] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 09/22/2015] [Indexed: 11/13/2022] Open
Abstract
Proteotoxic stresses and aging cause breakdown of cellular protein homeostasis, allowing misfolded proteins to form aggregates, which dedicated molecular machines have evolved to solubilize. In bacteria, fungi, protozoa and plants protein disaggregation involves an Hsp70•J-protein chaperone system, which loads and activates a powerful AAA+ ATPase (Hsp100) disaggregase onto protein aggregate substrates. Metazoans lack cytosolic and nuclear Hsp100 disaggregases but still eliminate protein aggregates. This longstanding puzzle of protein quality control is now resolved. Robust protein disaggregation activity recently shown for the metazoan Hsp70-based disaggregases relies instead on a crucial cooperation between two J-protein classes and interaction with the Hsp110 co-chaperone. An expanding multiplicity of Hsp70 and J-protein family members in metazoan cells facilitates different configurations of this Hsp70-based disaggregase allowing unprecedented versatility and specificity in protein disaggregation. Here we review the architecture, operation, and adaptability of the emerging metazoan disaggregation system and discuss how this evolved.
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Affiliation(s)
- Nadinath B Nillegoda
- Center for Molecular Biology (ZMBH) of the University of Heidelberg and German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance Heidelberg, Germany
| | - Bernd Bukau
- Center for Molecular Biology (ZMBH) of the University of Heidelberg and German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance Heidelberg, Germany
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16
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Nillegoda NB, Bukau B. Metazoan Hsp70-based protein disaggregases: emergence and mechanisms. Front Mol Biosci 2015; 2:57. [PMID: 26501065 DOI: 10.3389/fmolb.2015.00057/bibtex] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 09/22/2015] [Indexed: 05/25/2023] Open
Abstract
Proteotoxic stresses and aging cause breakdown of cellular protein homeostasis, allowing misfolded proteins to form aggregates, which dedicated molecular machines have evolved to solubilize. In bacteria, fungi, protozoa and plants protein disaggregation involves an Hsp70•J-protein chaperone system, which loads and activates a powerful AAA+ ATPase (Hsp100) disaggregase onto protein aggregate substrates. Metazoans lack cytosolic and nuclear Hsp100 disaggregases but still eliminate protein aggregates. This longstanding puzzle of protein quality control is now resolved. Robust protein disaggregation activity recently shown for the metazoan Hsp70-based disaggregases relies instead on a crucial cooperation between two J-protein classes and interaction with the Hsp110 co-chaperone. An expanding multiplicity of Hsp70 and J-protein family members in metazoan cells facilitates different configurations of this Hsp70-based disaggregase allowing unprecedented versatility and specificity in protein disaggregation. Here we review the architecture, operation, and adaptability of the emerging metazoan disaggregation system and discuss how this evolved.
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Affiliation(s)
- Nadinath B Nillegoda
- Center for Molecular Biology (ZMBH) of the University of Heidelberg and German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance Heidelberg, Germany
| | - Bernd Bukau
- Center for Molecular Biology (ZMBH) of the University of Heidelberg and German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance Heidelberg, Germany
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17
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Bhartiya D, Chandramouli B, Kumar N. Co-evolutionary analysis implies auxiliary functions of HSP110 in Plasmodium falciparum. Proteins 2015; 83:1513-25. [DOI: 10.1002/prot.24842] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2015] [Revised: 05/21/2015] [Accepted: 05/27/2015] [Indexed: 12/19/2022]
Affiliation(s)
- Deeksha Bhartiya
- Institute of Cytology and Preventive Oncology (ICMR); Noida 201301 Uttar Pradesh India
| | | | - Niti Kumar
- CSIR-Central Drug Research Institute; Lucknow 226031 Uttar Pradesh India
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18
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Bracher A, Verghese J. GrpE, Hsp110/Grp170, HspBP1/Sil1 and BAG domain proteins: nucleotide exchange factors for Hsp70 molecular chaperones. Subcell Biochem 2015; 78:1-33. [PMID: 25487014 DOI: 10.1007/978-3-319-11731-7_1] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Molecular chaperones of the Hsp70 family are key components of the cellular protein folding machinery. Substrate folding is accomplished by iterative cycles of ATP binding, hydrolysis and release. The ATPase activity of Hsp70 is regulated by two main classes of cochaperones: J-domain proteins stimulate ATPase hydrolysis by Hsp70, while nucleotide exchange factors (NEF) facilitate its conversion from the ADP-bound to the ATP-bound state, thus closing the chaperone folding cycle. Beginning with the discovery of the prototypical bacterial NEF GrpE, a large diversity of Hsp70 nucleotide exchange factors has been identified, connecting Hsp70 to a multitude of cellular processes in the eukaryotic cell. Here we review recent advances towards structure and function of nucleotide exchange factors from the Hsp110/Grp170, HspBP1/Sil1 and BAG domain protein families and discuss how these cochaperones connect protein folding with quality control and degradation pathways.
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Affiliation(s)
- Andreas Bracher
- Dept. of Cellular Biochemistry, Max-Planck-Institute of Biochemistry, 82152, Martinsried, Germany,
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19
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Bracher A, Verghese J. The nucleotide exchange factors of Hsp70 molecular chaperones. Front Mol Biosci 2015; 2:10. [PMID: 26913285 PMCID: PMC4753570 DOI: 10.3389/fmolb.2015.00010] [Citation(s) in RCA: 138] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 03/18/2015] [Indexed: 11/13/2022] Open
Abstract
Molecular chaperones of the Hsp70 family form an important hub in the cellular protein folding networks in bacteria and eukaryotes, connecting translation with the downstream machineries of protein folding and degradation. The Hsp70 folding cycle is driven by two types of cochaperones: J-domain proteins stimulate ATP hydrolysis by Hsp70, while nucleotide exchange factors (NEFs) promote replacement of Hsp70-bound ADP with ATP. Bacteria and organelles of bacterial origin have only one known NEF type for Hsp70, GrpE. In contrast, a large diversity of Hsp70 NEFs has been discovered in the eukaryotic cell. These NEFs belong to the Hsp110/Grp170, HspBP1/Sil1, and BAG domain protein families. In this short review we compare the structures and molecular mechanisms of nucleotide exchange factors for Hsp70 and discuss how these cochaperones contribute to protein folding and quality control in the cell.
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Affiliation(s)
- Andreas Bracher
- Department of Cellular Biochemistry, Max-Planck-Institute of Biochemistry Martinsried, Germany
| | - Jacob Verghese
- Department of Cellular Biochemistry, Max-Planck-Institute of Biochemistry Martinsried, Germany
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20
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Roth DM, Hutt DM, Tong J, Bouchecareilh M, Wang N, Seeley T, Dekkers JF, Beekman JM, Garza D, Drew L, Masliah E, Morimoto RI, Balch WE. Modulation of the maladaptive stress response to manage diseases of protein folding. PLoS Biol 2014; 12:e1001998. [PMID: 25406061 PMCID: PMC4236052 DOI: 10.1371/journal.pbio.1001998] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 10/07/2014] [Indexed: 12/31/2022] Open
Abstract
Diseases of protein folding arise because of the inability of an altered peptide sequence to properly engage protein homeostasis components that direct protein folding and function. To identify global principles of misfolding disease pathology we examined the impact of the local folding environment in alpha-1-antitrypsin deficiency (AATD), Niemann-Pick type C1 disease (NPC1), Alzheimer's disease (AD), and cystic fibrosis (CF). Using distinct models, including patient-derived cell lines and primary epithelium, mouse brain tissue, and Caenorhabditis elegans, we found that chronic expression of misfolded proteins not only triggers the sustained activation of the heat shock response (HSR) pathway, but that this sustained activation is maladaptive. In diseased cells, maladaptation alters protein structure-function relationships, impacts protein folding in the cytosol, and further exacerbates the disease state. We show that down-regulation of this maladaptive stress response (MSR), through silencing of HSF1, the master regulator of the HSR, restores cellular protein folding and improves the disease phenotype. We propose that restoration of a more physiological proteostatic environment will strongly impact the management and progression of loss-of-function and gain-of-toxic-function phenotypes common in human disease.
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Affiliation(s)
- Daniela Martino Roth
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Darren M. Hutt
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Jiansong Tong
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Marion Bouchecareilh
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Ning Wang
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, Illinois, United States of America
| | - Theo Seeley
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Johanna F. Dekkers
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Centre, Utrecht, The Netherlands
- Laboratory of Translational Immunology, Wilhelmina Children's Hospital, University Medical Centre, Utrecht, The Netherlands
| | - Jeffrey M. Beekman
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Centre, Utrecht, The Netherlands
- Laboratory of Translational Immunology, Wilhelmina Children's Hospital, University Medical Centre, Utrecht, The Netherlands
| | - Dan Garza
- Proteostasis Therapeutics Inc., Cambridge, Massachusetts, United States of America
| | - Lawrence Drew
- Proteostasis Therapeutics Inc., Cambridge, Massachusetts, United States of America
| | - Eliezer Masliah
- Department of Neurosciences, University of California, San Diego, La Jolla, California, United States of America
| | - Richard I. Morimoto
- Department of Molecular Biosciences, Rice Institute for Biomedical Research, Northwestern University, Evanston, Illinois, United States of America
| | - William E. Balch
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
- The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, United States of America
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, United States of America
- The Institute for Childhood and Neglected Diseases, The Scripps Research Institute, La Jolla, California, United States of America
- * E-mail:
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21
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Abrams JL, Verghese J, Gibney PA, Morano KA. Hierarchical functional specificity of cytosolic heat shock protein 70 (Hsp70) nucleotide exchange factors in yeast. J Biol Chem 2014; 289:13155-67. [PMID: 24671421 DOI: 10.1074/jbc.m113.530014] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Heat shock protein 70 (Hsp70) molecular chaperones play critical roles in protein homeostasis. In the budding yeast Saccharomyces cerevisiae, cytosolic Hsp70 interacts with up to three types of nucleotide exchange factors (NEFs) homologous to human counterparts: Sse1/Sse2 (Heat shock protein 110 (Hsp110)), Fes1 (HspBP1), and Snl1 (Bag-1). All three NEFs stimulate ADP release; however, it is unclear why multiple distinct families have been maintained throughout eukaryotic evolution. In this study we investigate NEF roles in Hsp70 cell biology using an isogenic combinatorial collection of NEF deletion mutants. Utilizing well characterized model substrates, we find that Sse1 participates in most Hsp70-mediated processes and is of particular importance in protein biogenesis and degradation, whereas Fes1 contributes to a minimal extent. Surprisingly, disaggregation and resolubilization of thermally denatured firefly luciferase occurred independently of NEF activity. Simultaneous deletion of SSE1 and FES1 resulted in constitutive activation of heat shock protein expression mediated by the transcription factor Hsf1, suggesting that these two factors are important for modulating stress response. Fes1 was found to interact in vivo preferentially with the Ssa family of cytosolic Hsp70 and not the co-translational Ssb homolog, consistent with the lack of cold sensitivity and protein biogenesis phenotypes for fes1Δ cells. No significant consequence could be attributed to deletion of the minor Hsp110 SSE2 or the Bag homolog SNL1. Together, these lines of investigation provide a comparative analysis of NEF function in yeast that implies Hsp110 is the principal NEF for cytosolic Hsp70, making it an ideal candidate for therapeutic intervention in human protein folding disorders.
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Affiliation(s)
- Jennifer L Abrams
- From the Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, Texas 77030
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22
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Torrente MP, Shorter J. The metazoan protein disaggregase and amyloid depolymerase system: Hsp110, Hsp70, Hsp40, and small heat shock proteins. Prion 2014; 7:457-63. [PMID: 24401655 PMCID: PMC4201613 DOI: 10.4161/pri.27531] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
A baffling aspect of metazoan proteostasis is the lack of an Hsp104 ortholog that rapidly disaggregates and reactivates misfolded polypeptides trapped in stress induced disordered aggregates, preamyloid oligomers, or amyloid fibrils. By contrast, in bacteria, protozoa, chromista, fungi, and plants, Hsp104 orthologs are highly conserved and confer huge selective advantages in stress tolerance. Moreover, in fungi, the amyloid remodeling activity of Hsp104 has enabled deployment of prions for various beneficial modalities. Thus, a longstanding conundrum has remained unanswered: how do metazoan cells renature aggregated proteins or resolve amyloid fibrils without Hsp104? Here, we highlight recent advances that unveil the metazoan protein-disaggregase machinery, comprising Hsp110, Hsp70, and Hsp40, which synergize to dissolve disordered aggregates, but are unable to rapidly solubilize stable amyloid fibrils. However, Hsp110, Hsp70, and Hsp40 exploit the slow monomer exchange dynamics of amyloid, and can slowly depolymerize amyloid fibrils from their ends in a manner that is stimulated by small heat shock proteins. Upregulation of this system could have key therapeutic applications in various protein-misfolding disorders. Intriguingly, yeast Hsp104 can interface with metazoan Hsp110, Hsp70, and Hsp40 to rapidly eliminate disease associated amyloid. Thus, metazoan proteostasis is receptive to augmentation with exogenous disaggregases, which opens a number of therapeutic opportunities.
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Affiliation(s)
- Mariana P Torrente
- Department of Biochemistry and Biophysics; 805b Stellar-Chance Laboratories; Perelman School of Medicine; University of Pennsylvania; Philadelphia, PA USA
| | - James Shorter
- Department of Biochemistry and Biophysics; 805b Stellar-Chance Laboratories; Perelman School of Medicine; University of Pennsylvania; Philadelphia, PA USA
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23
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Behnke J, Hendershot LM. The large Hsp70 Grp170 binds to unfolded protein substrates in vivo with a regulation distinct from conventional Hsp70s. J Biol Chem 2013; 289:2899-907. [PMID: 24327659 DOI: 10.1074/jbc.m113.507491] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The Hsp70 superfamily is a ubiquitous chaperone class that includes conventional and large Hsp70s. BiP is the only conventional Hsp70 in the endoplasmic reticulum (ER) whose functions include: assisting protein folding, targeting misfolded proteins for degradation, and regulating the transducers of the unfolded protein response. The ER also possesses a single large Hsp70, the glucose-regulated protein of 170 kDa (Grp170). Like BiP it is an essential protein, but its cellular functions are not well understood. Here we show that Grp170 can bind directly to a variety of incompletely folded protein substrates in the ER, and as expected for a bona fide chaperone, it does not interact with folded secretory proteins. Our data demonstrate that Grp170 and BiP associate with similar molecular forms of two substrate proteins, but while BiP is released from unfolded substrates in the presence of ATP, Grp170 remains bound. In comparison to conventional Hsp70s, the large Hsp70s possess two unique structural features: an extended C-terminal α-helical domain and an unstructured loop in the putative substrate binding domain with an unknown function. We find that in the absence of the α-helical domain the interaction of Grp170 with substrates is reduced. In striking contrast, deletion of the unstructured loop results in increased binding to substrates, suggesting the presence of unique intramolecular mechanisms of control for the chaperone functions of large Hsp70s.
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Affiliation(s)
- Julia Behnke
- From the Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105
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24
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Mutational analysis of Sse1 (Hsp110) suggests an integral role for this chaperone in yeast prion propagation in vivo. G3-GENES GENOMES GENETICS 2013; 3:1409-18. [PMID: 23797105 PMCID: PMC3737180 DOI: 10.1534/g3.113.007112] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The yeast Hsp110 chaperone Sse1 is a conserved protein that is a noncanonical member of the Hsp70 protein superfamily. Sse1 influences the cellular response to heat stress and has also been implicated in playing a role in the propagation of prions in yeast. Sse1 can seemingly exert its effects in vivo through direct or indirect actions by influencing the nucleotide exchange activity of canonical cytosolic Hsp70s. Using a genetic screen based on the inability to propagate the yeast [PSI(+)] prion, we have identified 13 new Sse1 mutants that are predicted to alter chaperone function through a variety of different mechanisms. Not only are these new Sse1 mutants altered in the ability to propagate and cure yeast prions but also to varying degrees in the ability to grow at elevated temperatures. The expression levels of chaperone proteins known to influence yeast prion propagation are unaltered in the Sse1 mutants, suggesting that the observed phenotypic effects are caused by direct functional alterations in these mutants. Mapping the location of the mutants onto the Sse1 crystal structure suggests that more than one functional alteration in Sse1 may result in changes in prion propagation and ability to function at elevated temperatures. All Sse1 mutants isolated provide essential functions in the cell under normal growth conditions, further demonstrating that essential chaperone functions in vivo can to some degree at least be detached from those related to propagation of prions. Our results suggest that Sse1 can influence prion propagation through a variety of different mechanisms.
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25
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Plasmodium falciparum heat shock protein 110 stabilizes the asparagine repeat-rich parasite proteome during malarial fevers. Nat Commun 2013; 3:1310. [PMID: 23250440 PMCID: PMC3639100 DOI: 10.1038/ncomms2306] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Accepted: 11/15/2012] [Indexed: 11/08/2022] Open
Abstract
One-fourth of Plasmodium falciparum proteins have asparagine repeats that increase the propensity for aggregation, especially at elevated temperatures that occur routinely in malaria-infected patients. Here we report that a Plasmodium Asn repeat-containing protein (PFI1155w) formed aggregates in mammalian cells at febrile temperatures, as did a yeast Asn/Gln-rich protein (Sup35). Co-expression of the cytoplasmic P. falciparum heat shock protein 110 (PfHsp110c) prevented aggregation. Human or yeast orthologs were much less effective. All-Asn and all-Gln versions of Sup35 were protected from aggregation by PfHsp110c, suggesting that this chaperone is not limited to handling runs of asparagine. PfHsp110c gene-knockout parasites were not viable and conditional knockdown parasites died slowly in the absence of protein-stabilizing ligand. When exposed to brief heat shock, these knockdowns were unable to prevent aggregation of PFI1155w or Sup35 and died rapidly. We conclude that PfHsp110c protects the parasite from harmful effects of its asparagine repeat-rich proteome during febrile episodes.
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26
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Mattoo RUH, Sharma SK, Priya S, Finka A, Goloubinoff P. Hsp110 is a bona fide chaperone using ATP to unfold stable misfolded polypeptides and reciprocally collaborate with Hsp70 to solubilize protein aggregates. J Biol Chem 2013; 288:21399-21411. [PMID: 23737532 DOI: 10.1074/jbc.m113.479253] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Structurally and sequence-wise, the Hsp110s belong to a subfamily of the Hsp70 chaperones. Like the classical Hsp70s, members of the Hsp110 subfamily can bind misfolding polypeptides and hydrolyze ATP. However, they apparently act as a mere subordinate nucleotide exchange factors, regulating the ability of Hsp70 to hydrolyze ATP and convert stable protein aggregates into native proteins. Using stably misfolded and aggregated polypeptides as substrates in optimized in vitro chaperone assays, we show that the human cytosolic Hsp110s (HSPH1 and HSPH2) are bona fide chaperones on their own that collaborate with Hsp40 (DNAJA1 and DNAJB1) to hydrolyze ATP and unfold and thus convert stable misfolded polypeptides into natively refolded proteins. Moreover, equimolar Hsp70 (HSPA1A) and Hsp110 (HSPH1) formed a powerful molecular machinery that optimally reactivated stable luciferase aggregates in an ATP- and DNAJA1-dependent manner, in a disaggregation mechanism whereby the two paralogous chaperones alternatively activate the release of bound unfolded polypeptide substrates from one another, leading to native protein refolding.
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Affiliation(s)
- Rayees U H Mattoo
- From the Department of Plant Molecular Biology, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland and
| | - Sandeep K Sharma
- From the Department of Plant Molecular Biology, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland and; the Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland
| | - Smriti Priya
- From the Department of Plant Molecular Biology, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland and
| | - Andrija Finka
- From the Department of Plant Molecular Biology, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland and
| | - Pierre Goloubinoff
- From the Department of Plant Molecular Biology, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland and.
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27
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Morgan JR, Jiang J, Oliphint PA, Jin S, Gimenez LE, Busch DJ, Foldes AE, Zhuo Y, Sousa R, Lafer EM. A role for an Hsp70 nucleotide exchange factor in the regulation of synaptic vesicle endocytosis. J Neurosci 2013; 33:8009-21. [PMID: 23637191 PMCID: PMC3707978 DOI: 10.1523/jneurosci.4505-12.2013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 03/20/2013] [Accepted: 03/29/2013] [Indexed: 12/28/2022] Open
Abstract
Neurotransmission requires a continuously available pool of synaptic vesicles (SVs) that can fuse with the plasma membrane and release their neurotransmitter contents upon stimulation. After fusion, SV membranes and membrane proteins are retrieved from the presynaptic plasma membrane by clathrin-mediated endocytosis. After the internalization of a clathrin-coated vesicle, the vesicle must uncoat to replenish the pool of SVs. Clathrin-coated vesicle uncoating requires ATP and is mediated by the ubiquitous molecular chaperone Hsc70. In vitro, depolymerized clathrin forms a stable complex with Hsc70*ADP. This complex can be dissociated by nucleotide exchange factors (NEFs) that release ADP from Hsc70, allowing ATP to bind and induce disruption of the clathrin:Hsc70 association. Whether NEFs generally play similar roles in vesicle trafficking in vivo and whether they play such roles in SV endocytosis in particular is unknown. To address this question, we used information from recent structural and mechanistic studies of Hsp70:NEF and Hsp70:co-chaperone interactions to design a NEF inhibitor. Using acute perturbations at giant reticulospinal synapses of the sea lamprey (Petromyzon marinus), we found that this NEF inhibitor inhibited SV endocytosis. When this inhibitor was mutated so that it could no longer bind and inhibit Hsp110 (a NEF that we find to be highly abundant in brain cytosol), its ability to inhibit SV endocytosis was eliminated. These observations indicate that the action of a NEF, most likely Hsp110, is normally required during SV trafficking to release clathrin from Hsc70 and make it available for additional rounds of endocytosis.
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Affiliation(s)
- Jennifer R. Morgan
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, Massachusetts 02543
- Section of Molecular Cell and Developmental Biology, Institute for Cell and Molecular Biology, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712, and
| | - Jianwen Jiang
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78212
| | - Paul A. Oliphint
- Section of Molecular Cell and Developmental Biology, Institute for Cell and Molecular Biology, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712, and
| | - Suping Jin
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78212
| | - Luis E. Gimenez
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78212
| | - David J. Busch
- Section of Molecular Cell and Developmental Biology, Institute for Cell and Molecular Biology, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712, and
| | - Andrea E. Foldes
- Section of Molecular Cell and Developmental Biology, Institute for Cell and Molecular Biology, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78712, and
| | - Yue Zhuo
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78212
| | - Rui Sousa
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78212
| | - Eileen M. Lafer
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78212
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28
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Liu ZJ, Lv YJ, Zhang M, Yue ZH, Tang S, Islam A, Rehana B, Bao ED, Hartung J. Hsp110 expression changes in rat primary myocardial cells exposed to heat stress in vitro. GENETICS AND MOLECULAR RESEARCH 2012; 11:4728-38. [PMID: 23315814 DOI: 10.4238/2012.november.29.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We investigated and described the kinetics of heat shock protein (Hsp) 110 expression and distribution in rat primary myocardial cells exposed to heat stress in vitro. After incubation at 37°C for 72 h, myocardial cells were heat stressed at 42°C for 0, 10, 20, 40, 60, 120, 240, 360, and 480 min. Significant increases in aspartate transaminase, lactate dehydrogenase, and creatine kinase enzymatic activities in the myocardial cell culture media were observed during heat stress, suggesting that the integrity of the myocardial cells was altered. Immunocytochemical analysis revealed that the expressed Hsp110 was constitutively localized in the cytoplasm and in the nuclei in small amounts characterized by a granular pattern. Nuclear Hsp110 levels increased significantly after 240 min of heat stress compared with levels in the control. The overall levels of Hsp110 expression increased significantly after 20 min. After 240 min, Hsp110 levels were approximately 1.2-fold higher than those in the control. Increasing levels of hsp110 messenger RNA detected using real-time quantitative polymerase chain reaction were observed after 20 min of heat stress, and the levels peaked with a 10-fold increase after 240 min of heat stress. These results indicate that the expression of Hsp110 in primary myocardial cells in vitro is sensitive to hyperthermic stress and that Hsp110 is involved in the potential acquisition of thermotolerance after heat stress. Therefore, Hsp110 might play a fundamental role in opposing and alleviating heat-induced damage caused by hyperthermic stress in primary myocardial cells.
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Affiliation(s)
- Z J Liu
- Animal Pathology Laboratory, Department of Basic Veterinary, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China
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29
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Rampelt H, Kirstein-Miles J, Nillegoda NB, Chi K, Scholz SR, Morimoto RI, Bukau B. Metazoan Hsp70 machines use Hsp110 to power protein disaggregation. EMBO J 2012; 31:4221-35. [PMID: 22990239 DOI: 10.1038/emboj.2012.264] [Citation(s) in RCA: 226] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Accepted: 08/28/2012] [Indexed: 12/29/2022] Open
Abstract
Accumulation of aggregation-prone misfolded proteins disrupts normal cellular function and promotes ageing and disease. Bacteria, fungi and plants counteract this by solubilizing and refolding aggregated proteins via a powerful cytosolic ATP-dependent bichaperone system, comprising the AAA+ disaggregase Hsp100 and the Hsp70-Hsp40 system. Metazoa, however, lack Hsp100 disaggregases. We show that instead the Hsp110 member of the Hsp70 superfamily remodels the human Hsp70-Hsp40 system to efficiently disaggregate and refold aggregates of heat and chemically denatured proteins in vitro and in cell extracts. This Hsp110 effect relies on nucleotide exchange, not on ATPase activity, implying ATP-driven chaperoning is not required. Knock-down of nematode Caenorhabditis elegans Hsp110, but not an unrelated nucleotide exchange factor, compromises dissolution of heat-induced protein aggregates and severely shortens lifespan after heat shock. We conclude that in metazoa, Hsp70-Hsp40 powered by Hsp110 nucleotide exchange represents the crucial disaggregation machinery that reestablishes protein homeostasis to counteract protein unfolding stress.
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Affiliation(s)
- Heike Rampelt
- Center for Molecular Biology of the University of Heidelberg and German Cancer Research Center, DKFZ-ZMBH Alliance, Heidelberg, Germany
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30
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Xu X, Sarbeng EB, Vorvis C, Kumar DP, Zhou L, Liu Q. Unique peptide substrate binding properties of 110-kDa heat-shock protein (Hsp110) determine its distinct chaperone activity. J Biol Chem 2011; 287:5661-72. [PMID: 22157767 DOI: 10.1074/jbc.m111.275057] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The molecular chaperone 70-kDa heat-shock proteins (Hsp70s) play essential roles in maintaining protein homeostasis. Hsp110, an Hsp70 homolog, is highly efficient in preventing protein aggregation but lacks the hallmark folding activity seen in Hsp70s. To understand the mechanistic differences between these two chaperones, we first characterized the distinct peptide substrate binding properties of Hsp110s. In contrast to Hsp70s, Hsp110s prefer aromatic residues in their substrates, and the substrate binding and release exhibit remarkably fast kinetics. Sequence and structure comparison revealed significant differences in the two peptide-binding loops: the length and properties are switched. When we swapped these two loops in an Hsp70, the peptide binding properties of this mutant Hsp70 were converted to Hsp110-like, and more impressively, it functionally behaved like an Hsp110. Thus, the peptide substrate binding properties implemented in the peptide-binding loops may determine the chaperone activity differences between Hsp70s and Hsp110s.
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Affiliation(s)
- Xinping Xu
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298, USA
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31
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Tian Z, Liu G, Zhang L, Yin H, Wang H, Xie J, Zhang P, Luo J. Identification of the heat shock protein 70 (HLHsp70) in Haemaphysalis longicornis. Vet Parasitol 2011; 181:282-90. [PMID: 21621329 DOI: 10.1016/j.vetpar.2011.04.026] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Revised: 04/09/2011] [Accepted: 04/12/2011] [Indexed: 10/18/2022]
Abstract
A Haemaphysalis longicornis heat shock protein 70 (HLHsp70) was identified from a cDNA library synthesized from tick eggs. The HLHsp70 cDNA is 2311 bp in length and encodes 661 amino acid residues with the predicted molecular weight of 72.5 kDa and an isoelectronic point (pI) of 5.2. It also contains the highly conserved functional motifs of the Hsp70 family and a specific endoplasmic reticulum (ER) retention signal "KDEL" that is common among ER-localized proteins. The HLHsp70 exhibits 90% amino acid identity to the putative Hsp70 of Ixodes scapularis, and 85% to Gallus gallus 78 kDa glucose-regulated protein precursor. Real time RT-PCR analysis showed that the expression levels of the Hsp70 in ovaries and salivary glands were significantly higher than in other tested tissues in partially fed females. Although the expression level of the HLHsp70 was constantly low in unfed ticks, it was significantly induced by blood-feeding. Further, the expression was positively correlated to the temperature (4-37°C, tested). Western blot analysis showed that the rabbit antiserum against the recombinant HLHsp70 protein (rHLHSP70) recognized bands of approximately 100, 72, and 28 kDa from egg lysates, as well as a 72kDa fragment in protein extracts from partially fed larvae. Immunization of rabbits with the rHLHSP70 did not result in a statistically significant reduction of female tick engorgement and oviposition. These results suggest that although HLHSP70 plays a role in the physiological activities of ticks, as a constitutive protein it was not suitable for selection as a candidate vaccine antigen against ticks.
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Affiliation(s)
- Zhancheng Tian
- State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, 1 Xujianping, Yanchangbu, Lanzhou, Gansu Province 730046, People's Republic of China
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32
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Hines JK, Li X, Du Z, Higurashi T, Li L, Craig EA. [SWI], the prion formed by the chromatin remodeling factor Swi1, is highly sensitive to alterations in Hsp70 chaperone system activity. PLoS Genet 2011; 7:e1001309. [PMID: 21379326 PMCID: PMC3040656 DOI: 10.1371/journal.pgen.1001309] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Accepted: 01/12/2011] [Indexed: 11/24/2022] Open
Abstract
The yeast prion [SWI+], formed of heritable amyloid aggregates of the Swi1 protein, results in a partial loss of function of the SWI/SNF chromatin-remodeling complex, required for the regulation of a diverse set of genes. Our genetic analysis revealed that [SWI+] propagation is highly dependent upon the action of members of the Hsp70 molecular chaperone system, specifically the Hsp70 Ssa, two of its J-protein co-chaperones, Sis1 and Ydj1, and the nucleotide exchange factors of the Hsp110 family (Sse1/2). Notably, while all yeast prions tested thus far require Sis1, [SWI+] is the only one known to require the activity of Ydj1, the most abundant J-protein in yeast. The C-terminal region of Ydj1, which contains the client protein interaction domain, is required for [SWI+] propagation. However, Ydj1 is not unique in this regard, as another, closely related J-protein, Apj1, can substitute for it when expressed at a level approaching that of Ydj1. While dependent upon Ydj1 and Sis1 for propagation, [SWI+] is also highly sensitive to overexpression of both J-proteins. However, this increased prion-loss requires only the highly conserved 70 amino acid J-domain, which serves to stimulate the ATPase activity of Hsp70 and thus to stabilize its interaction with client protein. Overexpression of the J-domain from Sis1, Ydj1, or Apj1 is sufficient to destabilize [SWI+]. In addition, [SWI+] is lost upon overexpression of Sse nucleotide exchange factors, which act to destabilize Hsp70's interaction with client proteins. Given the plethora of genes affected by the activity of the SWI/SNF chromatin-remodeling complex, it is possible that this sensitivity of [SWI+] to the activity of Hsp70 chaperone machinery may serve a regulatory role, keeping this prion in an easily-lost, meta-stable state. Such sensitivity may provide a means to reach an optimal balance of phenotypic diversity within a cell population to better adapt to stressful environments. Yeast prions are heritable genetic elements, formed spontaneously by aggregation of a single protein. Prions can thus generate diverse phenotypes in a dominant, non-Mendelian fashion, without a corresponding change in chromosomal gene structure. Since the phenotypes caused by the presence of a prion are thought to affect the ability of cells to survive under different environmental conditions, those that have global effects on cell physiology are of particular interest. Here we report the results of a study of one such prion, [SWI+], formed by a component of the SWI/SNF chromatin-remodeling complex, which is required for the regulation of a diverse set of genes. We found that, compared to previously well-studied prions, [SWI+] is highly sensitive to changes in the activities of molecular chaperones, particularly components of the Hsp70 machinery. Both under- and over-expression of components of this system initiated rapid loss of the prion from the cell population. Since expression of molecular chaperones, often known as heat shock proteins, are known to vary under diverse environmental conditions, such “chaperone sensitivity” may allow alteration of traits that under particular environmental conditions convey a selective advantage and may be a common characteristic of prions formed from proteins involved in global gene regulation.
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Affiliation(s)
- Justin K. Hines
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Xiaomo Li
- Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Zhiqiang Du
- Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Takashi Higurashi
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Liming Li
- Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
- * E-mail: (EAC); (LL)
| | - Elizabeth A. Craig
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
- * E-mail: (EAC); (LL)
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