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Lee J, Ryu B, Kim T, Kim KK. Cryo-EM structure of a 16.5-kDa small heat-shock protein from Methanocaldococcus jannaschii. Int J Biol Macromol 2024; 258:128763. [PMID: 38103675 DOI: 10.1016/j.ijbiomac.2023.128763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 12/07/2023] [Accepted: 12/11/2023] [Indexed: 12/19/2023]
Abstract
The small heat-shock protein (sHSP) from the archaea Methanocaldococcus jannaschii, MjsHSP16.5, functions as a broad substrate ATP-independent holding chaperone protecting misfolded proteins from aggregation under stress conditions. This protein is the first sHSP characterized by X-ray crystallography, thereby contributing significantly to our understanding of sHSPs. However, despite numerous studies assessing its functions and structures, the precise arrangement of the N-terminal domains (NTDs) within this sHSP cage remains elusive. Here we present the cryo-electron microscopy (cryo-EM) structure of MjsHSP16.5 at 2.49-Å resolution. The subunits of MjsHSP16.5 in the cryo-EM structure exhibit lesser compaction compared to their counterparts in the crystal structure. This structural feature holds particular significance in relation to the biophysical properties of MjsHSP16.5, suggesting a close resemblance to this sHSP native state. Additionally, our cryo-EM structure unveils the density of residues 24-33 within the NTD of MjsHSP16.5, a feature that typically remains invisible in the majority of its crystal structures. Notably, these residues show a propensity to adopt a β-strand conformation and engage in antiparallel interactions with strand β1, both intra- and inter-subunit modes. These structural insights are corroborated by structural predictions, disulfide bond cross-linking studies of Cys-substitution mutants, and protein disaggregation assays. A comprehensive understanding of the structural features of MjsHSP16.5 expectedly holds the potential to inspire a wide range of interdisciplinary applications, owing to the renowned versatility of this sHSP as a nanoscale protein platform.
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Affiliation(s)
- Joohyun Lee
- Department of Precision Medicine, Graduate School of Basic Medical Science (GSBMS), Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon 16419, Republic of Korea
| | - Bumhan Ryu
- Research Solution Center, Institute for Basic Science (IBS), Daejeon 34126, Republic of Korea
| | - Truc Kim
- Department of Precision Medicine, Graduate School of Basic Medical Science (GSBMS), Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon 16419, Republic of Korea.
| | - Kyeong Kyu Kim
- Department of Precision Medicine, Graduate School of Basic Medical Science (GSBMS), Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon 16419, Republic of Korea.
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2
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Multiple nanocages of a cyanophage small heat shock protein with icosahedral and octahedral symmetries. Sci Rep 2021; 11:21023. [PMID: 34697325 PMCID: PMC8546028 DOI: 10.1038/s41598-021-00172-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Accepted: 09/28/2021] [Indexed: 11/08/2022] Open
Abstract
The structures of a cyanophage small heat shock protein (sHSP) were determined as octahedrons of 24-mers and 48-mers and as icosahedrons of 60-mers. An N-terminal deletion construct of an 18 kDa sHSP of Synechococcus sp. phage S-ShM2 crystallized as a 24-mer and its structure was determined at a resolution of 7 Å. The negative stain electron microscopy (EM) images showed that the full-length protein is a mixture of a major population of larger and a minor population of smaller cage-like particles. Their structures have been determined by electron cryomicroscopy 3D image reconstruction at a resolution of 8 Å. The larger particles are 60-mers with icosahedral symmetry and the smaller ones are 48-mers with octahedral symmetry. These structures are the first of the viral/phage origin and the 60-mer is the largest and the first icosahedral assembly to be reported for sHSPs.
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3
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Kurre D, Suguna K. Network of Entamoeba histolytica HSP18.5 dimers formed by two overlapping [IV]-X-[IV] motifs. Proteins 2021; 89:1039-1054. [PMID: 33792100 DOI: 10.1002/prot.26081] [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: 03/17/2020] [Revised: 02/19/2021] [Accepted: 03/22/2021] [Indexed: 11/11/2022]
Abstract
Small heat shock proteins (sHSPs) are ATP-independent molecular chaperones with low molecular weight that prevent the aggregation of proteins during stress conditions and maintain protein homeostasis in the cell. sHSPs exist in dynamic equilibrium as a mixture of oligomers of various sizes with a constant exchange of subunits between them. Many sHSPs form cage-like assemblies that may dissociate into smaller oligomers during stress conditions. We carried out the functional and structural characterization of a small heat shock protein, HSP18.5, from Entamoeba histolytica (EhHSP18.5). It showed a pH-dependent change in its oligomeric state, which varied from a tetramer to larger than 48-mer. EhHSP18.5 protected Nde I and lysozyme substrates from temperature and chemical stresses, respectively. The crystal structure of EhHSP18.5 was determined at a resolution of 3.28 Å in C2221 cell with four subunits in the asymmetric unit forming two non-metazoan sHSP-type dimers. Unlike the reported cage-like structures, EhHSP18.5 formed a network of linear chains of molecules in the crystal. Instead of a single [IV]-X-[IV] motif, EhHSP18.5 has two overlapping I/V-X-I/V sequences at the C-terminus giving rise to novel interactions between the dimers. Negative staining Electron Microscopy images of EhHSP18.5 showed the presence of multiple oligomers: closed structures of various sizes and long tube-like structures.
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Affiliation(s)
- Devanshu Kurre
- Molecular Biophysics unit, Indian Institute of Science, Bangalore, India
| | - Kaza Suguna
- Molecular Biophysics unit, Indian Institute of Science, Bangalore, India
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4
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Liu D, Chen Q, Zhang L, Hu H, Yin C. AgsA oligomer acts as a functional unit. Biochem Biophys Res Commun 2020; 530:22-28. [PMID: 32828289 DOI: 10.1016/j.bbrc.2020.07.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 07/08/2020] [Indexed: 11/18/2022]
Abstract
AgsA (aggregation-suppressing protein) is an ATP-independent molecular chaperone machine belonging to the family of small heat shock proteins (sHSP), and it can prevent the aggregation of non-natural proteins. However, the substrate-binding site of AgsA and the functional unit that captures and binds the substrate remain unknown. In this study, different N-terminal and C-terminal deletion mutants of AgsA were constructed and their effects on AgsA oligomer assembly and chaperone activity were investigated. We found that the IXI motif at the C-terminus and the α-helix at the N-terminus affected the oligomerization and molecular chaperone activity of AgsA. In this work, we obtained a 6.8 Å resolution structure of AgsA using Electron cryo-microscopy (cryo-EM), and found that the functional form of AgsA was an 18-mer with D3 symmetry. Through amino acid mutations, disulfide bonds were introduced into two oligomeric interfaces, namely dimeric interface and non-partner interface. Under oxidation and reduction conditions, the chaperone activity of the disulfide-bonded AgsA did not change significantly, indicating that AgsA would not dissociate to achieve chaperone activity. Therefore, we concluded that the oligomer, especially 18-mer, was the primary functional unit.
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Affiliation(s)
- Dongmei Liu
- Department of Biochemistry and Biophysics, The Health Science Center, Peking University, Beijing, 100191, China.
| | - Qiang Chen
- The Chinese University of Hong Kong, Shenzhen, Shenzhen, Guangdong, 518172, PR China.
| | - Lei Zhang
- Department of Biochemistry and Biophysics, The Health Science Center, Peking University, Beijing, 100191, China; Electron Microscopy Analysis Laboratory, Center of Medical and Health Analysis, Peking University, Beijing, 100191, China.
| | - Hongli Hu
- The Chinese University of Hong Kong, Shenzhen, Shenzhen, Guangdong, 518172, PR China.
| | - Changcheng Yin
- Department of Biochemistry and Biophysics, The Health Science Center, Peking University, Beijing, 100191, China; Electron Microscopy Analysis Laboratory, Center of Medical and Health Analysis, Peking University, Beijing, 100191, China.
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5
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Baughman HER, Pham THT, Adams CS, Nath A, Klevit RE. Release of a disordered domain enhances HspB1 chaperone activity toward tau. Proc Natl Acad Sci U S A 2020; 117:2923-2929. [PMID: 31974309 PMCID: PMC7022203 DOI: 10.1073/pnas.1915099117] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Small heat shock proteins (sHSPs) are a class of ATP-independent molecular chaperones that play vital roles in maintaining protein solubility and preventing aberrant protein aggregation. They form highly dynamic, polydisperse oligomeric ensembles and contain long intrinsically disordered regions. Experimental challenges posed by these properties have greatly impeded our understanding of sHSP structure and mechanism of action. Here we characterize interactions between the human sHSP HspB1 (Hsp27) and microtubule-associated protein tau, which is implicated in multiple dementias, including Alzheimer's disease. We show that tau binds both to a well-known binding groove within the structured alpha-crystallin domain (ACD) and to sites within the enigmatic, disordered N-terminal region (NTR) of HspB1. However, only interactions involving the NTR lead to productive chaperone activity, whereas ACD binding is uncorrelated with chaperone function. The tau-binding groove in the ACD also binds short hydrophobic regions within HspB1 itself, and HspB1 mutations that disrupt these intrinsic ACD-NTR interactions greatly enhance chaperone activity toward tau. This leads to a mechanism in which the release of the disordered NTR from a binding groove on the ACD enhances chaperone activity toward tau. The study advances understanding of the mechanisms by which sHSPs achieve their chaperone activity against amyloid-forming clients and how cells defend against pathological tau aggregation. Furthermore, the resulting mechanistic model points to ways in which sHSP chaperone activity may be increased, either by native factors within the cell or by therapeutic intervention.
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Affiliation(s)
- Hannah E R Baughman
- Department of Biochemistry, School of Medicine, University of Washington, Seattle, WA 98195
- Department of Medicinal Chemistry, School of Pharmacy, University of Washington, Seattle, WA 98195
| | - Thanh-Hau T Pham
- Department of Biochemistry, School of Medicine, University of Washington, Seattle, WA 98195
- Department of Medicinal Chemistry, School of Pharmacy, University of Washington, Seattle, WA 98195
| | - Chloe S Adams
- Department of Biochemistry, School of Medicine, University of Washington, Seattle, WA 98195
| | - Abhinav Nath
- Department of Medicinal Chemistry, School of Pharmacy, University of Washington, Seattle, WA 98195
| | - Rachel E Klevit
- Department of Biochemistry, School of Medicine, University of Washington, Seattle, WA 98195;
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Clouser AF, Baughman HER, Basanta B, Guttman M, Nath A, Klevit RE. Interplay of disordered and ordered regions of a human small heat shock protein yields an ensemble of 'quasi-ordered' states. eLife 2019; 8:e50259. [PMID: 31573509 PMCID: PMC6791718 DOI: 10.7554/elife.50259] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 09/30/2019] [Indexed: 12/14/2022] Open
Abstract
Small heat shock proteins (sHSPs) are nature's 'first responders' to cellular stress, interacting with affected proteins to prevent their aggregation. Little is known about sHSP structure beyond its structured α-crystallin domain (ACD), which is flanked by disordered regions. In the human sHSP HSPB1, the disordered N-terminal region (NTR) represents nearly 50% of the sequence. Here, we present a hybrid approach involving NMR, hydrogen-deuterium exchange mass spectrometry, and modeling to provide the first residue-level characterization of the NTR. The results support a model in which multiple grooves on the ACD interact with specific NTR regions, creating an ensemble of 'quasi-ordered' NTR states that can give rise to the known heterogeneity and plasticity of HSPB1. Phosphorylation-dependent interactions inform a mechanism by which HSPB1 is activated under stress conditions. Additionally, we examine the effects of disease-associated NTR mutations on HSPB1 structure and dynamics, leveraging our emerging structural insights.
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Affiliation(s)
- Amanda F Clouser
- Department of BiochemistryUniversity of WashingtonSeattleUnited States
| | - Hannah ER Baughman
- Department of BiochemistryUniversity of WashingtonSeattleUnited States
- Department of Medicinal ChemistryUniversity of WashingtonSeattleUnited States
| | - Benjamin Basanta
- Department of BiochemistryUniversity of WashingtonSeattleUnited States
| | - Miklos Guttman
- Department of Medicinal ChemistryUniversity of WashingtonSeattleUnited States
| | - Abhinav Nath
- Department of Medicinal ChemistryUniversity of WashingtonSeattleUnited States
| | - Rachel E Klevit
- Department of BiochemistryUniversity of WashingtonSeattleUnited States
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7
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Mogk A, Ruger-Herreros C, Bukau B. Cellular Functions and Mechanisms of Action of Small Heat Shock Proteins. Annu Rev Microbiol 2019; 73:89-110. [PMID: 31091419 DOI: 10.1146/annurev-micro-020518-115515] [Citation(s) in RCA: 99] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Small heat shock proteins (sHsps) constitute a diverse chaperone family that shares the α-crystallin domain, which is flanked by variable, disordered N- and C-terminal extensions. sHsps act as the first line of cellular defense against protein unfolding stress. They form dynamic, large oligomers that represent inactive storage forms. Stress conditions cause a rapid increase in cellular sHsp levels and trigger conformational rearrangements, resulting in exposure of substrate-binding sites and sHsp activation. sHsps bind to early-unfolding intermediates of misfolding proteins in an ATP-independent manner and sequester them in sHsp/substrate complexes. Sequestration protects substrates from further uncontrolled aggregation and facilitates their refolding by ATP-dependent Hsp70-Hsp100 disaggregases. Some sHsps with particularly strong sequestrase activity, such as yeast Hsp42, are critical factors for forming large, microscopically visible deposition sites of misfolded proteins in vivo. These sites are organizing centers for triaging substrates to distinct quality control pathways, preferentially Hsp70-dependent refolding and selective autophagy.
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Affiliation(s)
- Axel Mogk
- Center for Molecular Biology of the University of Heidelberg and German Cancer Research Center, DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany; ,
| | - Carmen Ruger-Herreros
- Center for Molecular Biology of the University of Heidelberg and German Cancer Research Center, DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany; ,
| | - Bernd Bukau
- Center for Molecular Biology of the University of Heidelberg and German Cancer Research Center, DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany; ,
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Bhandari S, Biswas S, Chaudhary A, Dutta S, Suguna K. Dodecameric structure of a small heat shock protein from Mycobacterium marinum M. Proteins 2019; 87:365-379. [PMID: 30632633 DOI: 10.1002/prot.25657] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 12/24/2018] [Accepted: 01/05/2019] [Indexed: 12/31/2022]
Abstract
Small heat shock proteins (sHSPs) are ATP-independent molecular chaperones present ubiquitously in all kingdoms of life. Their low molecular weight subunits associate to form higher order structures. Under conditions of stress, sHSPs prevent aggregation of substrate proteins by undergoing rapid changes in their conformation or stoichiometry. Polydispersity and dynamic nature of these proteins have made structural investigations through crystallography a daunting task. In pathogens like Mycobacteria, sHSPs are immuno-dominant antigens, enabling survival of the pathogen within the host and contributing to disease persistence. We characterized sHSPs from Mycobacterium marinum M and determined the crystal structure of one of these. The protein crystallized in three different conditions as dodecamers, with dimers arranged in a tetrahedral fashion to form a closed cage-like architecture. Interestingly, we found a pentapeptide bound to the dodecamers revealing one of the modes of sHSP-substrate interaction. Further, we have observed that ATP inhibits the chaperoning activity of the protein.
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Affiliation(s)
- Spraha Bhandari
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Sreeparna Biswas
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Anuradha Chaudhary
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Somnath Dutta
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Kaza Suguna
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
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Haslbeck M, Weinkauf S, Buchner J. Small heat shock proteins: Simplicity meets complexity. J Biol Chem 2018; 294:2121-2132. [PMID: 30385502 DOI: 10.1074/jbc.rev118.002809] [Citation(s) in RCA: 165] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Small heat shock proteins (sHsps) are a ubiquitous and ancient family of ATP-independent molecular chaperones. A key characteristic of sHsps is that they exist in ensembles of iso-energetic oligomeric species differing in size. This property arises from a unique mode of assembly involving several parts of the subunits in a flexible manner. Current evidence suggests that smaller oligomers are more active chaperones. Thus, a shift in the equilibrium of the sHsp ensemble allows regulating the chaperone activity. Different mechanisms have been identified that reversibly change the oligomer equilibrium. The promiscuous interaction with non-native proteins generates complexes that can form aggregate-like structures from which native proteins are restored by ATP-dependent chaperones such as Hsp70 family members. In recent years, this basic paradigm has been expanded, and new roles and new cofactors, as well as variations in structure and regulation of sHsps, have emerged.
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Affiliation(s)
- Martin Haslbeck
- From the Department of Chemie and Center for Integrated Protein Science, Technische Universität München, Lichtenbergstrasse 4, 85 748 Garching, Germany
| | - Sevil Weinkauf
- From the Department of Chemie and Center for Integrated Protein Science, Technische Universität München, Lichtenbergstrasse 4, 85 748 Garching, Germany
| | - Johannes Buchner
- From the Department of Chemie and Center for Integrated Protein Science, Technische Universität München, Lichtenbergstrasse 4, 85 748 Garching, Germany
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Song Z, Si N, Xiao W. A novel mutation in the CRYAA gene associated with congenital cataract and microphthalmia in a Chinese family. BMC MEDICAL GENETICS 2018; 19:190. [PMID: 30340470 PMCID: PMC6194747 DOI: 10.1186/s12881-018-0695-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 09/24/2018] [Indexed: 11/10/2022]
Abstract
Background Congenital cataract is the leading cause of blindness in children worldwide. Approximately half of all congenital cataracts have a genetic basis. Protein aggregation is the single most important factor in cataract formation. Methods A four-generation Chinese family diagnosed with autosomal dominant congenital cataracts and microphthalmia was recruited at the Shengjing Hospital of China Medical University. Genomic DNA was extracted from the peripheral blood of the participants. All coding exons and flanking regions of seven candidate genes (CRYAA, CRYBA4, CRYBB2, CRYGC, GJA8, MAF, and PITX3) were amplified and sequenced. Restriction fragment length polymorphism (RFLP) assays were performed to confirm the candidate causative variant, c.35G > T in the CRYAA gene. We constructed pcDNA3.1(+)-CRYAA expression plasmids containing either the wild-type or the R12L mutant alleles and respectively transfected them into HEK293T cells and into HeLa cells. Western blotting was performed to determine protein expression levels and protein solubility. Immunofluorescence was performed to determine protein sub-cellular localization. Results A heterozygous variant c.35G > T was identified in exon 1 of CRYAA, which resulted in a substitution of arginine to leucine at codon 12 (p.R12L). The nucleotide substitution c.35G > T was co-segregated with the disease phenotype in the family. The mutant R12L-CRYAA in HEK293T cells showed a significant increase in the expression level of the CRYAA protein compared with the wild-type cells. Moreover, a large amount of the mutant protein aggregated in the precipitate where the wild-type protein was not detected. Immunofluorescence studies showed that the overexpressed mutant CRYAA in HeLa cells formed large cytoplasmic aggregates and aggresomes. Conclusions In summary, we described a case of human congenital cataract and microphthalmia caused by a novel mutation in the CRYAA gene, which substituted an arginine at position 12 in the N-terminal region of αA-crystallin. The molecular mechanisms that underlie the pathogenesis of human congenital cataract may be characterized by the prominent effects of the p.R12L mutation on αA-crystallin aggregation and solubility. Our study also expands the spectrum of known CRYAA mutations.
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Affiliation(s)
- Zixun Song
- Department of Ophthalmology, Shengjing Hospital, China Medical University, Shenyang, 110004, Liaoning, China
| | - Nuo Si
- McKusick-Zhang Center for Genetic Medicine, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine Peking Union Medical College, Beijing, 100005, China
| | - Wei Xiao
- Department of Ophthalmology, Shengjing Hospital, China Medical University, Shenyang, 110004, Liaoning, China.
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11
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Roy M, Gupta S, Patranabis S, Ghosh A. The oligomeric plasticity of Hsp20 of Sulfolobus acidocaldarius protects environment-induced protein aggregation and membrane destabilization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2549-2565. [PMID: 30293966 DOI: 10.1016/j.bbamem.2018.09.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 08/29/2018] [Accepted: 09/05/2018] [Indexed: 12/21/2022]
Abstract
Small heat shock proteins (sHsps) are a ubiquitous family of molecular chaperones that rescue misfolded proteins from irreversible aggregation during cellular stress. Many such sHsps exist as large polydisperse species in solution, and a rapid dynamic subunit exchange between oligomeric and dissociated forms modulates their function under a variety of stress conditions. Here, we investigated the structural and functional properties of Hsp20 from thermoacidophilic crenarchaeon Sulfolobus acidocaldarius. To provide a framework for investigating the structure-function relationship of Hsp20 and understanding its dynamic nature, we employed several biophysical and biochemical techniques. Our data suggested the existence of a ~24-mer of Hsp20 at room temperature (25 °C) and a higher oligomeric form at higher temperature (50 °C-70 °C) and lower pH (3.0-5.0). To our surprise, we identified a dimeric form of protein as the functional conformation in the presence of aggregating substrate proteins. The hydrophobic microenvironment mainly regulates the oligomeric plasticity of Hsp20, and it plays a key role in the protection of stress-induced protein aggregation. In Sulfolobus sp., Hsp20, despite being a non-secreted protein, has been reported to be present in secretory vesicles and it is still unclear whether it stabilizes substrate proteins or membrane lipids within the secreted vesicles. To address such an issue, we tested the ability of Hsp20 to interact with membrane lipids along with its ability to modulate membrane fluidity. Our data revealed that Hsp20 interacts with membrane lipids via a hydrophobic interaction and it lowers the propensity of in vitro phase transition of bacterial and archaeal lipids.
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Affiliation(s)
- Mousam Roy
- Department of Biochemistry, Bose Institute, Centenary Campus, P 1/12, C. I. T. Road, Scheme - VIIM, Kolkata 700054, West Bengal, India
| | - Sayandeep Gupta
- Department of Biochemistry, Bose Institute, Centenary Campus, P 1/12, C. I. T. Road, Scheme - VIIM, Kolkata 700054, West Bengal, India
| | - Somi Patranabis
- Department of Biochemistry, Bose Institute, Centenary Campus, P 1/12, C. I. T. Road, Scheme - VIIM, Kolkata 700054, West Bengal, India
| | - Abhrajyoti Ghosh
- Department of Biochemistry, Bose Institute, Centenary Campus, P 1/12, C. I. T. Road, Scheme - VIIM, Kolkata 700054, West Bengal, India.
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12
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Jovcevski B, Andrew Aquilina J, Benesch JLP, Ecroyd H. The influence of the N-terminal region proximal to the core domain on the assembly and chaperone activity of αB-crystallin. Cell Stress Chaperones 2018; 23:827-836. [PMID: 29520626 PMCID: PMC6111084 DOI: 10.1007/s12192-018-0889-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 02/19/2018] [Accepted: 02/24/2018] [Indexed: 01/24/2023] Open
Abstract
αB-Crystallin (HSPB5) is a small heat-shock protein that is composed of dimers that then assemble into a polydisperse ensemble of oligomers. Oligomerisation is mediated by heterologous interactions between the C-terminal tail of one dimer and the core "α-crystallin" domain of another and stabilised by interactions made by the N-terminal region. Comparatively little is known about the latter contribution, but previous studies have suggested that residues in the region 54-60 form contacts that stabilise the assembly. We have generated mutations in this region (P58A, S59A, S59K, R56S/S59R and an inversion of residues 54-60) to examine their impact on oligomerisation and chaperone activity in vitro. By using native mass spectrometry, we found that all the αB-crystallin mutants were assembly competent, populating similar oligomeric distributions to wild-type, ranging from 16-mers to 30-mers. However, circular dichroism spectroscopy, intrinsic tryptophan and bis-ANS fluorescence studies demonstrated that the secondary structure differs to wild type, the 54-60 inversion mutation having the greatest impact. All the mutants exhibited a dramatic decrease in exposed hydrophobicity. We also found that the mutants in general were equally active as the wild-type protein in inhibiting the amorphous aggregation of insulin and seeded amyloid fibrillation of α-synuclein in vitro, except for the 54-60 inversion mutant, which was significantly less effective at inhibiting insulin aggregation. Our data indicate that alterations in the part of the N-terminal region proximal to the core domain do not drastically affect the oligomerisation of αB-crystallin, reinforcing the robustness of αB-crystallin in functioning as a molecular chaperone.
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Affiliation(s)
- Blagojce Jovcevski
- Illawarra Health and Medical Research Institute and School of Biological Sciences, University of Wollongong, Northfields Ave, Wollongong, NSW, 2522, Australia
| | - J Andrew Aquilina
- Illawarra Health and Medical Research Institute and School of Biological Sciences, University of Wollongong, Northfields Ave, Wollongong, NSW, 2522, Australia
| | - Justin L P Benesch
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK
| | - Heath Ecroyd
- Illawarra Health and Medical Research Institute and School of Biological Sciences, University of Wollongong, Northfields Ave, Wollongong, NSW, 2522, Australia.
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13
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Mishra S, Chandler SA, Williams D, Claxton DP, Koteiche HA, Stewart PL, Benesch JLP, Mchaourab HS. Engineering of a Polydisperse Small Heat-Shock Protein Reveals Conserved Motifs of Oligomer Plasticity. Structure 2018; 26:1116-1126.e4. [PMID: 29983375 DOI: 10.1016/j.str.2018.05.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 04/10/2018] [Accepted: 05/18/2018] [Indexed: 01/21/2023]
Abstract
Small heat-shock proteins (sHSPs) are molecular chaperones that bind partially and globally unfolded states of their client proteins. Previously, we discovered that the archaeal Hsp16.5, which forms ordered and symmetric 24-subunit oligomers, can be engineered to transition to an ordered and symmetric 48-subunit oligomer by insertion of a peptide from human HspB1 (Hsp27). Here, we uncovered the existence of an array of oligomeric states (30-38 subunits) that can be populated as a consequence of altering the sequence and length of the inserted peptide. Polydisperse Hsp16.5 oligomers displayed higher affinity to a model client protein consistent with a general mechanism for recognition and binding that involves increased access of the hydrophobic N-terminal region. Our findings, which integrate structural and functional analyses from evolutionarily distant sHSPs, support a model wherein the modular architecture of these proteins encodes motifs of oligomer polydispersity, dissociation, and expansion to achieve functional diversity and regulation.
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Affiliation(s)
- Sanjay Mishra
- Chemical & Physical Biology Program, Vanderbilt University, Nashville 37232, TN, USA; Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville 37232, TN, USA
| | - Shane A Chandler
- Department of Chemistry, University of Oxford, Oxford OX1 3TA, UK
| | - Dewight Williams
- John M. Cowley Center for High Resolution Electron Microscopy, Arizona State University, Tempe 85287, AZ, USA
| | - Derek P Claxton
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville 37232, TN, USA
| | - Hanane A Koteiche
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville 37232, TN, USA
| | - Phoebe L Stewart
- Department of Pharmacology Case Western Reserve University, Cleveland, OH 44106, USA
| | | | - Hassane S Mchaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville 37232, TN, USA.
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14
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Mishra S, Wu SY, Fuller AW, Wang Z, Rose KL, Schey KL, Mchaourab HS. Loss of αB-crystallin function in zebrafish reveals critical roles in the development of the lens and stress resistance of the heart. J Biol Chem 2017; 293:740-753. [PMID: 29162721 DOI: 10.1074/jbc.m117.808634] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 11/17/2017] [Indexed: 12/12/2022] Open
Abstract
Genetic mutations in the human small heat shock protein αB-crystallin have been implicated in autosomal cataracts and skeletal myopathies, including heart muscle diseases (cardiomyopathy). Although these mutations lead to modulation of their chaperone activity in vitro, the in vivo functions of αB-crystallin in the maintenance of both lens transparency and muscle integrity remain unclear. This lack of information has hindered a mechanistic understanding of these diseases. To better define the functional roles of αB-crystallin, we generated loss-of-function zebrafish mutant lines by utilizing the CRISPR/Cas9 system to specifically disrupt the two αB-crystallin genes, αBa and αBb We observed lens abnormalities in the mutant lines of both genes, and the penetrance of the lens phenotype was higher in αBa than αBb mutants. This finding is in contrast with the lack of a phenotype previously reported in αB-crystallin knock-out mice and suggests that the elevated chaperone activity of the two zebrafish orthologs is critical for lens development. Besides its key role in the lens, we uncovered another critical role for αB-crystallin in providing stress tolerance to the heart. The αB-crystallin mutants exhibited hypersusceptibility to develop pericardial edema when challenged by crowding stress or exposed to elevated cortisol stress, both of which activate glucocorticoid receptor signaling. Our work illuminates the involvement of αB-crystallin in stress tolerance of the heart presumably through the proteostasis network and reinforces the critical role of the chaperone activity of αB-crystallin in the maintenance of lens transparency.
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Affiliation(s)
- Sanjay Mishra
- From the Departments of Molecular Physiology and Biophysics and
| | - Shu-Yu Wu
- From the Departments of Molecular Physiology and Biophysics and
| | | | - Zhen Wang
- Biochemistry and.,Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
| | - Kristie L Rose
- Biochemistry and.,Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
| | - Kevin L Schey
- Biochemistry and.,Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
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15
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Moutaoufik MT, Morrow G, Finet S, Tanguay RM. Effect of N-terminal region of nuclear Drosophila melanogaster small heat shock protein DmHsp27 on function and quaternary structure. PLoS One 2017; 12:e0177821. [PMID: 28520783 PMCID: PMC5433770 DOI: 10.1371/journal.pone.0177821] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 05/03/2017] [Indexed: 01/12/2023] Open
Abstract
The importance of the N-terminal region (NTR) in the oligomerization and chaperone-like activity of the Drosophila melanogaster small nuclear heat shock protein DmHsp27 was investigated by mutagenesis using size exclusion chromatography and native gel electrophoresis. Mutation of two sites of phosphorylation in the N-terminal region, S58 and S75, did not affect the oligomerization equilibrium or the intracellular localization of DmHsp27 when transfected into mammalian cells. Deletion or mutation of specific residues within the NTR region delineated a motif (FGFG) important for the oligomeric structure and chaperone-like activity of this sHsp. While deletion of the full N-terminal region, resulted in total loss of chaperone-like activity, removal of the (FGFG) at position 29 to 32 or single mutation of F29A/Y, G30R and G32R enhanced oligomerization and chaperoning capacity under non-heat shock conditions in the insulin assay suggesting the importance of this site for chaperone activity. Unlike mammalian sHsps DmHsp27 heat activation leads to enhanced association of oligomers to form large structures of approximately 1100 kDa. A new mechanism of thermal activation for DmHsp27 is presented.
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Affiliation(s)
- Mohamed Taha Moutaoufik
- Laboratoire de génétique cellulaire et développementale, Département de biologie moléculaire, biochimie médicale et pathologie, Institut de biologie intégrative et des systèmes (IBIS) and PROTEO, Université Laval, Québec, Canada
| | - Geneviève Morrow
- Laboratoire de génétique cellulaire et développementale, Département de biologie moléculaire, biochimie médicale et pathologie, Institut de biologie intégrative et des systèmes (IBIS) and PROTEO, Université Laval, Québec, Canada
| | - Stéphanie Finet
- IMPMC UMR7590, CNRS, UPMC Paris 6, 4 place Jussieu, Paris, France
| | - Robert M. Tanguay
- Laboratoire de génétique cellulaire et développementale, Département de biologie moléculaire, biochimie médicale et pathologie, Institut de biologie intégrative et des systèmes (IBIS) and PROTEO, Université Laval, Québec, Canada
- * E-mail:
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16
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Fonseca EMB, Scorsato V, Dos Santos ML, Júnior AT, Tada SFS, Dos Santos CA, de Toledo MAS, de Souza AP, Polikarpov I, Aparicio R. Crystal structure of a small heat-shock protein from Xylella fastidiosa reveals a distinct high-order structure. Acta Crystallogr F Struct Biol Commun 2017; 73:222-227. [PMID: 28368281 PMCID: PMC5379172 DOI: 10.1107/s2053230x17004101] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 03/14/2017] [Indexed: 11/10/2022] Open
Abstract
Citrus variegated chlorosis is a disease that attacks economically important citrus plantations and is caused by the plant-pathogenic bacterium Xylella fastidiosa. In this work, the structure of a small heat-shock protein from X. fastidiosa (XfsHSP17.9) is reported. The high-order structures of small heat-shock proteins from other organisms are arranged in the forms of double-disc, hollow-sphere or spherical assemblies. Unexpectedly, the structure reported here reveals a high-order architecture forming a nearly square cavity.
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Affiliation(s)
- Emanuella Maria Barreto Fonseca
- Laboratory of Structural Biology and Crystallography, Institute of Chemistry, University of Campinas, CP6154, 13083-970 Campinas-SP, Brazil
| | - Valéria Scorsato
- Laboratory of Structural Biology and Crystallography, Institute of Chemistry, University of Campinas, CP6154, 13083-970 Campinas-SP, Brazil
| | - Marcelo Leite Dos Santos
- Laboratory of Structural Biology and Crystallography, Institute of Chemistry, University of Campinas, CP6154, 13083-970 Campinas-SP, Brazil
| | - Atilio Tomazini Júnior
- Molecular Biotechnology Group, Department of Physics and Interdisciplinary Science, Sao Carlos Institute of Physics (IFSC), University of Sao Paulo (USP), Avenida Trabalhador São-carlense 400, Parque Arnold Schimidt, 13566-590 São Carlos-SP, Brazil
| | - Susely Ferraz Siqueira Tada
- Laboratory of Molecular and Genetic Analysis, Center for Molecular Biology and Genetic Engineering, Institute of Biology, University of Campinas, CP6010, 13083-875 Campinas-SP, Brazil
| | - Clelton Aparecido Dos Santos
- Laboratory of Molecular and Genetic Analysis, Center for Molecular Biology and Genetic Engineering, Institute of Biology, University of Campinas, CP6010, 13083-875 Campinas-SP, Brazil
| | - Marcelo Augusto Szymanski de Toledo
- Laboratory of Molecular and Genetic Analysis, Center for Molecular Biology and Genetic Engineering, Institute of Biology, University of Campinas, CP6010, 13083-875 Campinas-SP, Brazil
| | - Anete Pereira de Souza
- Laboratory of Molecular and Genetic Analysis, Center for Molecular Biology and Genetic Engineering, Institute of Biology, University of Campinas, CP6010, 13083-875 Campinas-SP, Brazil
| | - Igor Polikarpov
- Molecular Biotechnology Group, Department of Physics and Interdisciplinary Science, Sao Carlos Institute of Physics (IFSC), University of Sao Paulo (USP), Avenida Trabalhador São-carlense 400, Parque Arnold Schimidt, 13566-590 São Carlos-SP, Brazil
| | - Ricardo Aparicio
- Laboratory of Structural Biology and Crystallography, Institute of Chemistry, University of Campinas, CP6154, 13083-970 Campinas-SP, Brazil
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17
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Zhou Q, Shi X, Zhang K, Shi C, Huang L, Chang Z. The Function of Ile-X-Ile Motif in the Oligomerization and Chaperone-Like Activity of Small Heat Shock Protein AgsA at Room Temperature. Protein J 2016; 35:401-406. [PMID: 27812886 DOI: 10.1007/s10930-016-9681-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Small heat shock proteins assemble as large oligomers in vitro and exhibit ATP-independent chaperone activities. Ile-X-Ile motif is essential in both the function and oligomer formation. AgsA of Salmonella enterica serovar Typhimurium has been demonstrated to adopt large oligomeric structure and possess strong chaperone activity. Size exclusion chromatography, non-denaturing pore gradient PAGE, and negatively stain electron microscopic analysis of the various C-terminal truncated mutants were performed to investigate the role of Ile-X-Ile motif in the oligomer assembly of AgsA. By measuring the ability to prevent insulin from aggregating induced by TCEP, the chaperone-like activity of AgsA and the C-terminal truncated mutants at room temperature were determined. We found that the truncated mutants with Ile-X-Ile motif partially or fully deleted lost the ability to form large oligomers. Contrast to wild type AgsA which displayed weak chaperone-like activity, those mutants shown significantly enhanced activities at room temperature. In summary, biochemical experiment, activity assay and electron microscopic analysis suggested that Ile-X-Ile motif is essential in oligomer assembly of AgsA and might take the role of an inhibitor for its chaperone-like activity at room temperature.
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Affiliation(s)
- Qiuhu Zhou
- Department of Biophysics, School of Basic Medical Sciences, Peking University Health Science Center, 38 Xue-Yuan Road, Beijing, 100191, People's Republic of China
| | - Xiaodong Shi
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, 221004, People's Republic of China
| | - Kaiming Zhang
- Department of Biophysics, School of Basic Medical Sciences, Peking University Health Science Center, 38 Xue-Yuan Road, Beijing, 100191, People's Republic of China
| | - Chao Shi
- Department of Biophysics, School of Basic Medical Sciences, Peking University Health Science Center, 38 Xue-Yuan Road, Beijing, 100191, People's Republic of China
| | - Lixin Huang
- Department of Biophysics, School of Basic Medical Sciences, Peking University Health Science Center, 38 Xue-Yuan Road, Beijing, 100191, People's Republic of China
| | - Zhenzhan Chang
- Department of Biophysics, School of Basic Medical Sciences, Peking University Health Science Center, 38 Xue-Yuan Road, Beijing, 100191, People's Republic of China.
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18
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Mani N, Bhandari S, Moreno R, Hu L, Prasad BVV, Suguna K. Multiple oligomeric structures of a bacterial small heat shock protein. Sci Rep 2016; 6:24019. [PMID: 27053150 PMCID: PMC4823740 DOI: 10.1038/srep24019] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 03/14/2016] [Indexed: 11/23/2022] Open
Abstract
Small heat shock proteins are ubiquitous molecular chaperones that form the first line of defence against the detrimental effects of cellular stress. Under conditions of stress they undergo drastic conformational rearrangements in order to bind to misfolded substrate proteins and prevent cellular protein aggregation. Owing to the dynamic nature of small heat shock protein oligomers, elucidating the structural basis of chaperone action and oligomerization still remains a challenge. In order to understand the organization of sHSP oligomers, we have determined crystal structures of a small heat shock protein from Salmonella typhimurium in a dimeric form and two higher oligomeric forms: an 18-mer and a 24-mer. Though the core dimer structure is conserved in all the forms, structural heterogeneity arises due to variation in the terminal regions.
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Affiliation(s)
- Nandini Mani
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Spraha Bhandari
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Rodolfo Moreno
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, United States
| | - Liya Hu
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, United States
| | - B V Venkataram Prasad
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, United States
| | - Kaza Suguna
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
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19
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Liu L, Chen JY, Yang B, Wang FH, Wang YH, Yun CH. Active-State Structures of a Small Heat-Shock Protein Revealed a Molecular Switch for Chaperone Function. Structure 2015; 23:2066-75. [PMID: 26439766 DOI: 10.1016/j.str.2015.08.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 08/27/2015] [Accepted: 08/29/2015] [Indexed: 01/09/2023]
Abstract
Small heat-shock proteins (sHsps) maintain cellular homeostasis by binding to denatured client proteins to prevent aggregation. Numerous studies indicate that the N-terminal domain (NTD) of sHsps is responsible for binding to client proteins, but the binding mechanism and chaperone activity regulation remain elusive. Here, we report the crystal structures of the wild-type and mutants of an sHsp from Sulfolobus solfataricus representing the inactive and active state of this protein, respectively. All three structures reveal well-defined NTD, but their conformations are remarkably different. The mutant NTDs show disrupted helices presenting a reformed hydrophobic surface compatible with recognizing client proteins. Our functional data show that mutating key hydrophobic residues in this region drastically altered the chaperone activity of this sHsp. These data suggest a new model in which a molecular switch located in NTD facilitates conformational changes for client protein binding.
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Affiliation(s)
- Liang Liu
- Institute of Systems Biomedicine, Department of Biophysics, Beijing Key Laboratory of Tumor Systems Biology and Center for Molecular and Translational Medicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, P.R. China; School of Bioscience and Bioengineering, South China University of Technology, Guangzhou 510006, P.R. China; Co-first author
| | - Ji-Yun Chen
- Institute of Systems Biomedicine, Department of Biophysics, Beijing Key Laboratory of Tumor Systems Biology and Center for Molecular and Translational Medicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, P.R. China; Co-first author
| | - Bo Yang
- School of Bioscience and Bioengineering, South China University of Technology, Guangzhou 510006, P.R. China
| | - Fang-Hua Wang
- College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510641, P.R. China
| | - Yong-Hua Wang
- College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510641, P.R. China.
| | - Cai-Hong Yun
- Institute of Systems Biomedicine, Department of Biophysics, Beijing Key Laboratory of Tumor Systems Biology and Center for Molecular and Translational Medicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, P.R. China.
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20
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Koteiche HA, Claxton DP, Mishra S, Stein RA, McDonald ET, Mchaourab HS. Species-Specific Structural and Functional Divergence of α-Crystallins: Zebrafish αBa- and Rodent αA(ins)-Crystallin Encode Activated Chaperones. Biochemistry 2015; 54:5949-58. [PMID: 26378715 DOI: 10.1021/acs.biochem.5b00678] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In addition to contributing to lens optical properties, the α-crystallins are small heat shock proteins that possess chaperone activity and are predicted to bind and sequester destabilized proteins to delay cataract formation. The current model of α-crystallin chaperone mechanism envisions a transition from the native oligomer to an activated form that has higher affinity to non-native states of the substrate. Previous studies have suggested that this oligomeric plasticity is encoded in the primary sequence and controls access to high affinity binding sites within the N-terminal domain. Here, we further examined the role of sequence variation in the context of species-specific α-crystallins from rat and zebrafish. Alternative splicing of the αA gene in rodents produces αA(ins), which is distinguished by a longer N-terminal domain. The zebrafish genome includes duplicate αB-crystallin genes, αBa and αBb, which display divergent primary sequence and tissue expression patterns. Equilibrium binding experiments were employed to quantitatively define chaperone interactions with a destabilized model substrate, T4 lysozyme. In combination with multiangle light scattering, we show that rat αA(ins) and zebrafish α-crystallins display distinct global structural properties and chaperone activities. Notably, we find that αA(ins) and αBa demonstrate substantially enhanced chaperone function relative to other α-crystallins, binding the same substrate more than 2 orders of magnitude higher affinity and mimicking the activity of fully activated mammalian small heat shock proteins. These results emphasize the role of sequence divergence as an evolutionary strategy to tune chaperone function to the requirements of the tissues and organisms in which they are expressed.
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Affiliation(s)
- Hanane A Koteiche
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine , Nashville, Tennessee 37232, United States
| | - Derek P Claxton
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine , Nashville, Tennessee 37232, United States
| | - Sanjay Mishra
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine , Nashville, Tennessee 37232, United States
| | - Richard A Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine , Nashville, Tennessee 37232, United States
| | - Ezelle T McDonald
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine , Nashville, Tennessee 37232, United States
| | - Hassane S Mchaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine , Nashville, Tennessee 37232, United States
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21
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Delbecq SP, Rosenbaum JC, Klevit RE. A Mechanism of Subunit Recruitment in Human Small Heat Shock Protein Oligomers. Biochemistry 2015; 54:4276-84. [PMID: 26098708 PMCID: PMC4512712 DOI: 10.1021/acs.biochem.5b00490] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Small heat shock proteins (sHSPs) make up a class of molecular chaperones broadly observed across organisms. Many sHSPs form large oligomers that undergo dynamic subunit exchange that is thought to play a role in chaperone function. Though remarkably heterogeneous, sHSP oligomers share three types of intermolecular interactions that involve all three defined regions of a sHSP: the N-terminal region (NTR), the conserved α-crystallin domain (ACD), and a C-terminal region (CTR). Here we define the structural interactions involved in incorporation of a subunit into a sHSP oligomer. We demonstrate that a minimal ACD dimer of the human sHSP, HSPB5, interacts with an HSPB5 oligomer through two types of interactions: (1) interactions with CTRs in the oligomer and (2) via exchange into and out of the dimer interface composed of two ACDs. Unexpectedly, although dimers are thought to be the fundamental building block for sHSP oligomers, our results clearly indicate that subunit exchange into and out of oligomers occurs via monomers. Using structure-based mutants, we show that incorporation of a subunit into an oligomer is predicated on recruitment of the subunit via its interaction with CTRs on an oligomer. Both the rate and extent of subunit incorporation depend on the accessibility of CTRs within an HSPB5 oligomer. We show that this mechanism also applies to formation of heterooligomeric sHSP species composed of HSPB5 and HSPB6 and is likely general among sHSPs. Finally, our observations highlight the importance of NTRs in the thermodynamic stability of sHSP oligomers.
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Affiliation(s)
- Scott P Delbecq
- Department of Biochemistry, University of Washington, Seattle, Washington 98195-7350, United States
| | - Joel C Rosenbaum
- Department of Biochemistry, University of Washington, Seattle, Washington 98195-7350, United States
| | - Rachel E Klevit
- Department of Biochemistry, University of Washington, Seattle, Washington 98195-7350, United States
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22
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Haslbeck M, Peschek J, Buchner J, Weinkauf S. Structure and function of α-crystallins: Traversing from in vitro to in vivo. Biochim Biophys Acta Gen Subj 2015; 1860:149-66. [PMID: 26116912 DOI: 10.1016/j.bbagen.2015.06.008] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 06/10/2015] [Accepted: 06/22/2015] [Indexed: 12/11/2022]
Abstract
BACKGROUND The two α-crystallins (αA- and αB-crystallin) are major components of our eye lenses. Their key function there is to preserve lens transparency which is a challenging task as the protein turnover in the lens is low necessitating the stability and longevity of the constituent proteins. α-Crystallins are members of the small heat shock protein family. αB-crystallin is also expressed in other cell types. SCOPE OF THE REVIEW The review summarizes the current concepts on the polydisperse structure of the α-crystallin oligomer and its chaperone function with a focus on the inherent complexity and highlighting gaps between in vitro and in vivo studies. MAJOR CONCLUSIONS Both α-crystallins protect proteins from irreversible aggregation in a promiscuous manner. In maintaining eye lens transparency, they reduce the formation of light scattering particles and balance the interactions between lens crystallins. Important for these functions is their structural dynamics and heterogeneity as well as the regulation of these processes which we are beginning to understand. However, currently, it still remains elusive to which extent the in vitro observed properties of α-crystallins reflect the highly crowded situation in the lens. GENERAL SIGNIFICANCE Since α-crystallins play an important role in preventing cataract in the eye lens and in the development of diverse diseases, understanding their mechanism and substrate spectra is of importance. To bridge the gap between the concepts established in vitro and the in vivo function of α-crystallins, the joining of forces between different scientific disciplines and the combination of diverse techniques in hybrid approaches are necessary. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.
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Affiliation(s)
- Martin Haslbeck
- Center for Integrated Protein Science at the Department Chemie, Technische Universität München, Lichtenbergstr. 4, D-85747 Garching, Germany
| | - Jirka Peschek
- Center for Integrated Protein Science at the Department Chemie, Technische Universität München, Lichtenbergstr. 4, D-85747 Garching, Germany
| | - Johannes Buchner
- Center for Integrated Protein Science at the Department Chemie, Technische Universität München, Lichtenbergstr. 4, D-85747 Garching, Germany.
| | - Sevil Weinkauf
- Center for Integrated Protein Science at the Department Chemie, Technische Universität München, Lichtenbergstr. 4, D-85747 Garching, Germany.
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23
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Mymrikov EV, Haslbeck M. Medical implications of understanding the functions of human small heat shock proteins. Expert Rev Proteomics 2015; 12:295-308. [PMID: 25915440 DOI: 10.1586/14789450.2015.1039993] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Small heat shock proteins (sHsps) are ubiquitous molecular chaperones that are implicated in a variety of diseases. Upon stress, they stabilize unfolding proteins and prevent them from aggregating. However, under physiological conditions without severe stress, some sHsps interact with other proteins. In a perspective view, their ability to bind specific client proteins might allow them to fine-tune the availability of the client for other, client-dependent cellular processes. Additionally, some sHsps seem to interact with specific co-chaperones. These co-chaperones are usually part of large protein machineries that are functionally modulated upon sHsps interaction. Finally, secreted human sHsps seem to interact with receptor proteins, potentially as signal molecules transmitting the stress status from one cell to another. This review focuses on the mechanistic description of these different binding modes for human sHsps and how this might help to understand and modulate the function of sHsps in the context of disease.
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Affiliation(s)
- Evgeny V Mymrikov
- Department Chemie, Technische Universität München, D-85747 Garching, Germany
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24
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Park SM, Kim KP, Joe MK, Lee MO, Koo HJ, Hong CB. Tobacco class I cytosolic small heat shock proteins are under transcriptional and translational regulations in expression and heterocomplex prevails under the high-temperature stress condition in vitro. PLANT, CELL & ENVIRONMENT 2015; 38:767-76. [PMID: 25158805 DOI: 10.1111/pce.12436] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 08/17/2014] [Indexed: 05/23/2023]
Abstract
Seven genomic clones of tobacco (Nicotiana tabacum W38) cytosolic class I small heat shock proteins (sHSPs), probably representing all members in the class, were isolated and found to have 66 to 92% homology between their nucleotide sequences. Even though all seven sHSP genes showed heat shock-responsive accumulation of their transcripts and proteins, each member showed discrepancies in abundance and timing of expression upon high-temperature stress. This was mainly the result of transcriptional regulation during mild stress conditions and transcriptional and translational regulation during strong stress conditions. Open reading frames (ORFs) of these genomic clones were expressed in Escherichia coli and the sHSPs were purified from E. coli. The purified tobacco sHSPs rendered citrate synthase and luciferase soluble under high temperatures. At room temperature, non-denaturing pore exclusion polyacrylamide gel electrophoresis on three sHSPs demonstrated that the sHSPs spontaneously formed homo-oligomeric complexes of 200 ∼ 240 kDa. However, under elevated temperatures, hetero-oligomeric complexes between the sHSPs gradually prevailed. Atomic force microscopy showed that the hetero-oligomer of NtHSP18.2/NtHSP18.3 formed a stable oligomeric particle similar to that of the NtHSP18.2 homo-oligomer. These hetero-oligomers positively influenced the revival of thermally inactivated luciferase. Amino acid residues mainly in the N-terminus are suggested for the exchange of the component sHSPs and the formation of dominant hetero-oligomers under high temperatures.
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Affiliation(s)
- Soo Min Park
- School of Biological Sciences and Institute of Molecular Biology and Genetics, Seoul National University, Seoul, 151-742, Korea
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25
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Berni C, Bellocci M, Sala GL, Rossini GP. Palytoxin induces dissociation of HSP 27 oligomers through a p38 protein kinase pathway. Chem Res Toxicol 2015; 28:752-64. [PMID: 25710824 DOI: 10.1021/tx500511q] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Palytoxin (PlTX) induces a stress response in MCF-7 cells that involves the phosphorylation of HSP 27 at serines 15, 78, and 82 by an as yet undetermined mechanism. We have studied the involvement of major groups of the mitogen-activated protein kinase (MAPK) family in this molecular response and focused our analyses on the ERK1/2, JNK, p38 protein kinase (p38K), and ERK5 pathways. The results show that PlTX induces the activation of JNK and p38 kinase but not ERK1/2 and 5 in MCF-7 cells. Through the use of protein kinase inhibitors, we established that blocking p38K, but not JNK, prevents the phosphorylation of HSP 27 induced by PlTX and that MAPKAPK2 participates in the response induced by the toxin under our experimental conditions. The cell death response induced by PlTX was inhibited by preventing JNK phosphorylation but not by blocking p38K/MAPKAPK2 and HSP 27 phosphorylation. Sucrose density gradient centrifugation revealed that MCF-7 cell extracts contain a heterodisperse population of HSP 27, including oligomers and smaller forms. Treating MCF-7 cells with PlTX caused the dissociation of HSP 27 oligomers, and using inhibitors of the JNK and p38K pathways showed that the dissociation of HSP 27 oligomers induced by PlTX involves a p38K-dependent process. We conclude that the changes induced by PlTX in the HSP 27 stress response protein system proceed through a molecular mechanism involving the activation of the p38 kinase pathway and its substrate, MAPKAK2, leading to dissociation of HSP 27 oligomers and the stabilization of a cellular pool of monomers phosphorylated at serines 15, 78 and 82, which could play a protective role against the death response induced by PlTX.
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Affiliation(s)
- Chiara Berni
- Dipartimento di Scienze della Vita, Università di Modena e Reggio Emilia, Via Campi 287, I-41125 Modena, Italy
| | - Mirella Bellocci
- Dipartimento di Scienze della Vita, Università di Modena e Reggio Emilia, Via Campi 287, I-41125 Modena, Italy
| | - Gian Luca Sala
- Dipartimento di Scienze della Vita, Università di Modena e Reggio Emilia, Via Campi 287, I-41125 Modena, Italy
| | - Gian Paolo Rossini
- Dipartimento di Scienze della Vita, Università di Modena e Reggio Emilia, Via Campi 287, I-41125 Modena, Italy
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Haslbeck M, Vierling E. A first line of stress defense: small heat shock proteins and their function in protein homeostasis. J Mol Biol 2015; 427:1537-48. [PMID: 25681016 DOI: 10.1016/j.jmb.2015.02.002] [Citation(s) in RCA: 380] [Impact Index Per Article: 42.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Revised: 02/03/2015] [Accepted: 02/04/2015] [Indexed: 10/24/2022]
Abstract
Small heat shock proteins (sHsps) are virtually ubiquitous molecular chaperones that can prevent the irreversible aggregation of denaturing proteins. sHsps complex with a variety of non-native proteins in an ATP-independent manner and, in the context of the stress response, form a first line of defense against protein aggregation in order to maintain protein homeostasis. In vertebrates, they act to maintain the clarity of the eye lens, and in humans, sHsp mutations are linked to myopathies and neuropathies. Although found in all domains of life, sHsps are quite diverse and have evolved independently in metazoans, plants and fungi. sHsp monomers range in size from approximately 12 to 42kDa and are defined by a conserved β-sandwich α-crystallin domain, flanked by variable N- and C-terminal sequences. Most sHsps form large oligomeric ensembles with a broad distribution of different, sphere- or barrel-like oligomers, with the size and structure of the oligomers dictated by features of the N- and C-termini. The activity of sHsps is regulated by mechanisms that change the equilibrium distribution in tertiary features and/or quaternary structure of the sHsp ensembles. Cooperation and/or co-assembly between different sHsps in the same cellular compartment add an underexplored level of complexity to sHsp structure and function.
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Affiliation(s)
- Martin Haslbeck
- Department Chemie, Technische Universität München, Lichtenbergstrasse 4, 85 748 Garching, Germany.
| | - Elizabeth Vierling
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Life Science Laboratories, N329 240 Thatcher Road, Amherst, MA 01003-9364, USA.
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27
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28
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Slingsby C, Wistow GJ. Functions of crystallins in and out of lens: roles in elongated and post-mitotic cells. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 115:52-67. [PMID: 24582830 PMCID: PMC4104235 DOI: 10.1016/j.pbiomolbio.2014.02.006] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Accepted: 02/18/2014] [Indexed: 12/25/2022]
Abstract
The vertebrate lens evolved to collect light and focus it onto the retina. In development, the lens grows through massive elongation of epithelial cells possibly recapitulating the evolutionary origins of the lens. The refractive index of the lens is largely dependent on high concentrations of soluble proteins called crystallins. All vertebrate lenses share a common set of crystallins from two superfamilies (although other lineage specific crystallins exist). The α-crystallins are small heat shock proteins while the β- and γ-crystallins belong to a superfamily that contains structural proteins of uncertain function. The crystallins are expressed at very high levels in lens but are also found at lower levels in other cells, particularly in retina and brain. All these proteins have plausible connections to maintenance of cytoplasmic order and chaperoning of the complex molecular machines involved in the architecture and function of cells, particularly elongated and post-mitotic cells. They may represent a suite of proteins that help maintain homeostasis in such cells that are at risk from stress or from the accumulated insults of aging.
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Affiliation(s)
- Christine Slingsby
- Department of Biological Sciences, Crystallography, Institute of Structural and Molecular Biology, Birkbeck College, Malet Street, London WC1E 7HX, UK.
| | - Graeme J Wistow
- Section on Molecular Structure and Functional Genomics, National Eye Institute, Bg 6, Rm 106, National Institutes of Health, Bethesda, MD 20892-0608, USA
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29
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De novo mutation in the dopamine transporter gene associates dopamine dysfunction with autism spectrum disorder. Mol Psychiatry 2013; 18:1315-23. [PMID: 23979605 PMCID: PMC4046646 DOI: 10.1038/mp.2013.102] [Citation(s) in RCA: 154] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 07/08/2013] [Accepted: 07/15/2013] [Indexed: 01/02/2023]
Abstract
De novo genetic variation is an important class of risk factors for autism spectrum disorder (ASD). Recently, whole-exome sequencing of ASD families has identified a novel de novo missense mutation in the human dopamine (DA) transporter (hDAT) gene, which results in a Thr to Met substitution at site 356 (hDAT T356M). The dopamine transporter (DAT) is a presynaptic membrane protein that regulates dopaminergic tone in the central nervous system by mediating the high-affinity reuptake of synaptically released DA, making it a crucial regulator of DA homeostasis. Here, we report the first functional, structural and behavioral characterization of an ASD-associated de novo mutation in the hDAT. We demonstrate that the hDAT T356M displays anomalous function, characterized as a persistent reverse transport of DA (substrate efflux). Importantly, in the bacterial homolog leucine transporter, substitution of A289 (the homologous site to T356) with a Met promotes an outward-facing conformation upon substrate binding. In the substrate-bound state, an outward-facing transporter conformation is required for substrate efflux. In Drosophila melanogaster, the expression of hDAT T356M in DA neurons-lacking Drosophila DAT leads to hyperlocomotion, a trait associated with DA dysfunction and ASD. Taken together, our findings demonstrate that alterations in DA homeostasis, mediated by aberrant DAT function, may confer risk for ASD and related neuropsychiatric conditions.
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30
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Abstract
A crystal structure of a yeast small heat shock protein reported by Hanazono and colleagues in this issue of Structure reveals the versatility of the α-crystallin domain dimer for building assemblies of different size and symmetry. The domains assemble into a vessel filled with hydrophobic sequence extensions enriched with phenylalanines.
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Affiliation(s)
- Christine Slingsby
- Department of Biological Sciences, Crystallography, Institute of Structural and Molecular Biology, Birkbeck College, Malet Street, London WC1E 7HX, UK.
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31
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Slingsby C, Wistow GJ, Clark AR. Evolution of crystallins for a role in the vertebrate eye lens. Protein Sci 2013; 22:367-80. [PMID: 23389822 PMCID: PMC3610043 DOI: 10.1002/pro.2229] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 01/16/2013] [Accepted: 01/17/2013] [Indexed: 12/18/2022]
Abstract
The camera eye lens of vertebrates is a classic example of the re-engineering of existing protein components to fashion a new device. The bulk of the lens is formed from proteins belonging to two superfamilies, the α-crystallins and the βγ-crystallins. Tracing their ancestry may throw light on the origin of the optics of the lens. The α-crystallins belong to the ubiquitous small heat shock proteins family that plays a protective role in cellular homeostasis. They form enormous polydisperse oligomers that challenge modern biophysical methods to uncover the molecular basis of their assembly structure and chaperone-like protein binding function. It is argued that a molecular phenotype of a dynamic assembly suits a chaperone function as well as a structural role in the eye lens where the constraint of preventing protein condensation is paramount. The main cellular partners of α-crystallins, the β- and γ-crystallins, have largely been lost from the animal kingdom but the superfamily is hugely expanded in the vertebrate eye lens. Their structures show how a simple Greek key motif can evolve rapidly to form a complex array of monomers and oligomers. Apart from remaining transparent, a major role of the partnership of α-crystallins with β- and γ-crystallins in the lens is to form a refractive index gradient. Here, we show some of the structural and genetic features of these two protein superfamilies that enable the rapid creation of different assembly states, to match the rapidly changing optical needs among the various vertebrates.
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Affiliation(s)
- Christine Slingsby
- Department of Biological Sciences, Crystallography, Institute of Structural and Molecular Biology, Birkbeck College, Malet Street, London WC1E 7HX, United Kingdom.
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32
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Quinlan RA, Zhang Y, Lansbury A, Williamson I, Pohl E, Sun F. Changes in the quaternary structure and function of MjHSP16.5 attributable to deletion of the IXI motif and introduction of the substitution, R107G, in the α-crystallin domain. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120327. [PMID: 23530263 PMCID: PMC3638399 DOI: 10.1098/rstb.2012.0327] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The archael small heat-shock protein (sHSP), MjHSP16.5, forms a 24-subunit oligomer with octahedral symmetry. Here, we demonstrate that the IXI motif present in the C-terminal domain is necessary for the oligomerization of MjHSP16.5. Removal increased the in vitro chaperone activity with citrate synthase as the client protein. Less predictable were the effects of the R107G substitution in MjHSP16.5 because of the differences in the oligomerization of metazoan and non-metazoan sHSPs. We present the crystal structure for MjHSP16.5 R107G and compare this with an improved (2.5 Å) crystal structure for wild-type (WT) MjHSP16.5. Although no significant structural differences were found in the crystal, using cryo-electron microscopy, we identified two 24mer species with octahedral symmetry for the WT MjHSP16.5 both at room temperature and at 60°C, all showing two major species with the same diameter of 12.4 nm. Similarly, at room temperature, there are also two kinds of 12.4 nm oligomers for R107G MjHSP16.5, but in the 60°C sample, a larger 24mer species with a diameter of 13.6 nm was observed with significant changes in the fourfold symmetry axis and dimer–dimer interface. This highly conserved arginine, therefore, contributes to the quaternary organization of non-metazoan sHSP oligomers. Potentially, the R107G substitution has functional consequences as R107G MjHSP16.5 was far superior to the WT protein in protecting βL-crystallin against heat-induced aggregation.
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Affiliation(s)
- Roy A Quinlan
- Biophysical Sciences Institute, University of Durham, , South Road, Durham DH1 LE, UK
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33
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Delbecq SP, Klevit RE. One size does not fit all: the oligomeric states of αB crystallin. FEBS Lett 2013; 587:1073-80. [PMID: 23340341 DOI: 10.1016/j.febslet.2013.01.021] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 01/09/2013] [Accepted: 01/10/2013] [Indexed: 11/25/2022]
Abstract
Small Heat Shock Proteins (sHSPs) are a diverse family of molecular chaperones that delay protein aggregation through interactions with non-native and aggregate-prone protein states. This function has been shown to be important to cellular viability and sHSP function/dysfunction is implicated in many diseases, including Alzheimer's and Alexander disease. Though their gene products are small, many sHSPs assemble into a distribution of large oligomeric states that undergo dynamic subunit exchange. These inherent properties present significant experimental challenges for characterizing sHSP oligomers. Of the human sHSPs, αB crystallin is a paradigm example of sHSP oligomeric properties. Advances in our understanding of sHSP structure, oligomeric distribution, and dynamics have prompted the proposal of several models for the oligomeric states of αB. The aim of this review is to highlight characteristics of αB crystallin (αB) that are key to understanding its structure and function. The current state of knowledge, existing models, and outstanding questions that remain to be addressed are presented.
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Affiliation(s)
- Scott P Delbecq
- Department of Biochemistry, Box 357350, University of Washington, Seattle, WA 98195-7350, USA
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34
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Shi J, Koteiche HA, McDonald ET, Fox TL, Stewart PL, McHaourab HS. Cryoelectron microscopy analysis of small heat shock protein 16.5 (Hsp16.5) complexes with T4 lysozyme reveals the structural basis of multimode binding. J Biol Chem 2012; 288:4819-30. [PMID: 23277356 DOI: 10.1074/jbc.m112.388132] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Small heat shock proteins (sHSPs) are ubiquitous chaperones that bind and sequester non-native proteins preventing their aggregation. Despite extensive studies of sHSPs chaperone activity, the location of the bound substrate within the sHSP oligomer has not been determined. In this paper, we used cryoelectron microscopy (cryoEM) to visualize destabilized mutants of T4 lysozyme (T4L) bound to engineered variants of the small heat shock protein Hsp16.5. In contrast to wild type Hsp16.5, binding of T4L to these variants does not induce oligomer heterogeneity enabling cryoEM analysis of the complexes. CryoEM image reconstruction reveals the sequestration of T4L in the interior of the Hsp16.5 oligomer primarily interacting with the buried N-terminal domain but also tethered by contacts with the α-crystallin domain shell. Analysis of Hsp16.5-WT/T4L complexes uncovers oligomer expansion as a requirement for high affinity binding. In contrast, a low affinity mode of binding is found to involve T4L binding on the outer surface of the oligomer bridging the formation of large complexes of Hsp16.5. These mechanistic principles were validated by cryoEM analysis of an expanded variant of Hsp16.5 in complex with T4L and Hsp16.5-R107G, which is equivalent to a mutant of human αB-crystallin linked to cardiomyopathy. In both cases, high affinity binding is found to involve conformational changes in the N-terminal region consistent with a central role of this region in substrate recognition.
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Affiliation(s)
- Jian Shi
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
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35
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Hanazono Y, Takeda K, Oka T, Abe T, Tomonari T, Akiyama N, Aikawa Y, Yohda M, Miki K. Nonequivalence observed for the 16-meric structure of a small heat shock protein, SpHsp16.0, from Schizosaccharomyces pombe. Structure 2012; 21:220-8. [PMID: 23273429 DOI: 10.1016/j.str.2012.11.015] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 11/12/2012] [Accepted: 11/21/2012] [Indexed: 10/27/2022]
Abstract
Small heat shock proteins (sHsps) play a role in preventing the fatal aggregation of denatured proteins in the presence of stresses. The sHsps exist as monodisperse oligomers in their resting state. Because the hydrophobic N-terminal regions of sHsps are possible interaction sites for denatured proteins, the manner of assembly of the oligomer is critical for the activation and inactivation mechanisms. Here, we report the oligomer architecture of SpHsp16.0 from Schizosaccharomyces pombe determined with X-ray crystallography and small angle X-ray scattering. Both results indicate that eight dimers of SpHsp16.0 form an elongated sphere with 422 symmetry. The monomers show nonequivalence in the interaction with neighboring monomers and conformations of the N- and C-terminal regions. Variants for the N-terminal phenylalanine residues indicate that the oligomer formation ability is highly correlated with chaperone activity. Structural and biophysical results are discussed in terms of their possible relevance to the activation mechanism of SpHsp16.0.
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Affiliation(s)
- Yuya Hanazono
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
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