1
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Basith S, Manavalan B, Lee G. Unveiling local and global conformational changes and allosteric communications in SOD1 systems using molecular dynamics simulation and network analyses. Comput Biol Med 2024; 168:107688. [PMID: 37988788 DOI: 10.1016/j.compbiomed.2023.107688] [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: 08/29/2023] [Revised: 10/20/2023] [Accepted: 11/06/2023] [Indexed: 11/23/2023]
Abstract
BACKGROUND Amyotrophic lateral sclerosis (ALS) is a serious neurodegenerative disorder affecting nerve cells in the brain and spinal cord that is caused by mutations in the superoxide dismutase 1 (SOD1) enzyme. ALS-related mutations cause misfolding, dimerisation instability, and increased formation of aggregates. The underlying allosteric mechanisms, however, remain obscure as far as details of their fundamental atomistic structure are concerned. Hence, this gap in knowledge limits the development of novel SOD1 inhibitors and the understanding of how disease-associated mutations in distal sites affect enzyme activity. METHODS We combined microsecond-scale based unbiased molecular dynamics (MD) simulation with network analysis to elucidate the local and global conformational changes and allosteric communications in SOD1 Apo (unmetallated form), Holo, Apo_CallA (mutant and unmetallated form), and Holo_CallA (mutant form) systems. To identify hotspot residues involved in SOD1 signalling and allosteric communications, we performed network centrality, community network, and path analyses. RESULTS Structural analyses showed that unmetallated SOD1 systems and cysteine mutations displayed large structural variations in the catalytic sites, affecting structural stability. Inter- and intra H-bond analyses identified several important residues crucial for maintaining interfacial stability, structural stability, and enzyme catalysis. Dynamic motion analysis demonstrated more balanced atomic displacement and highly correlated motions in the Holo system. The rationale for structural disparity observed in the disulfide bond formation and R143 configuration in Apo and Holo systems were elucidated using distance and dihedral probability distribution analyses. CONCLUSION Our study highlights the efficiency of combining extensive MD simulations with network analyses to unravel the features of protein allostery.
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Affiliation(s)
- Shaherin Basith
- Department of Physiology, Ajou University School of Medicine, Suwon, 16499, Republic of Korea.
| | - Balachandran Manavalan
- Computational Biology and Bioinformatics Laboratory, Department of Integrative Biotechnology, College of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Gwang Lee
- Department of Physiology, Ajou University School of Medicine, Suwon, 16499, Republic of Korea; Department of Molecular Science and Technology, Ajou University, Suwon, 16499, Republic of Korea.
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2
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Hsueh SCC, Nijland M, Peng X, Hilton B, Plotkin SS. First Principles Calculation of Protein-Protein Dimer Affinities of ALS-Associated SOD1 Mutants. Front Mol Biosci 2022; 9:845013. [PMID: 35402516 PMCID: PMC8988244 DOI: 10.3389/fmolb.2022.845013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 02/08/2022] [Indexed: 01/03/2023] Open
Abstract
Cu,Zn superoxide dismutase (SOD1) is a 32 kDa homodimer that converts toxic oxygen radicals in neurons to less harmful species. The dimerization of SOD1 is essential to the stability of the protein. Monomerization increases the likelihood of SOD1 misfolding into conformations associated with aggregation, cellular toxicity, and neuronal death in familial amyotrophic lateral sclerosis (fALS). The ubiquity of disease-associated mutations throughout the primary sequence of SOD1 suggests an important role of physicochemical processes, including monomerization of SOD1, in the pathology of the disease. Herein, we use a first-principles statistical mechanics method to systematically calculate the free energy of dimer binding for SOD1 using molecular dynamics, which involves sequentially computing conformational, orientational, and separation distance contributions to the binding free energy. We consider the effects of two ALS-associated mutations in SOD1 protein on dimer stability, A4V and D101N, as well as the role of metal binding and disulfide bond formation. We find that the penalty for dimer formation arising from the conformational entropy of disordered loops in SOD1 is significantly larger than that for other protein-protein interactions previously considered. In the case of the disulfide-reduced protein, this leads to a bound complex whose formation is energetically disfavored. Somewhat surprisingly, the loop free energy penalty upon dimerization is still significant for the holoprotein, despite the increased structural order induced by the bound metal cations. This resulted in a surprisingly modest increase in dimer binding free energy of only about 1.5 kcal/mol upon metalation of the protein, suggesting that the most significant stabilizing effects of metalation are on folding stability rather than dimer binding stability. The mutant A4V has an unstable dimer due to weakened monomer-monomer interactions, which are manifested in the calculation by a separation free energy surface with a lower barrier. The mutant D101N has a stable dimer partially due to an unusually rigid β-barrel in the free monomer. D101N also exhibits anticooperativity in loop folding upon dimerization. These computational calculations are, to our knowledge, the most quantitatively accurate calculations of dimer binding stability in SOD1 to date.
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Affiliation(s)
- Shawn C. C. Hsueh
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada
| | - Mark Nijland
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada
- Laboratory of Organic Chemistry, Wageningen University and Research, Wageningen, Netherlands
- Laboratory of Physical Chemistry and Soft Matter, Wageningen University and Research, Wageningen, Netherlands
| | - Xubiao Peng
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada
- Center for Quantum Technology Research, School of Physics, Beijing Institute of Technology, Beijing, China
| | - Benjamin Hilton
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada
- Imperial College London, London, United Kingdom
| | - Steven S. Plotkin
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada
- Genome Science and Technology Program, University of British Columbia, Vancouver, BC, Canada
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3
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Trist BG, Hilton JB, Hare DJ, Crouch PJ, Double KL. Superoxide Dismutase 1 in Health and Disease: How a Frontline Antioxidant Becomes Neurotoxic. Angew Chem Int Ed Engl 2021; 60:9215-9246. [PMID: 32144830 PMCID: PMC8247289 DOI: 10.1002/anie.202000451] [Citation(s) in RCA: 81] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Indexed: 12/11/2022]
Abstract
Cu/Zn superoxide dismutase (SOD1) is a frontline antioxidant enzyme catalysing superoxide breakdown and is important for most forms of eukaryotic life. The evolution of aerobic respiration by mitochondria increased cellular production of superoxide, resulting in an increased reliance upon SOD1. Consistent with the importance of SOD1 for cellular health, many human diseases of the central nervous system involve perturbations in SOD1 biology. But far from providing a simple demonstration of how disease arises from SOD1 loss-of-function, attempts to elucidate pathways by which atypical SOD1 biology leads to neurodegeneration have revealed unexpectedly complex molecular characteristics delineating healthy, functional SOD1 protein from that which likely contributes to central nervous system disease. This review summarises current understanding of SOD1 biology from SOD1 genetics through to protein function and stability.
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Affiliation(s)
- Benjamin G. Trist
- Brain and Mind Centre and Discipline of PharmacologyThe University of Sydney, CamperdownSydneyNew South Wales2050Australia
| | - James B. Hilton
- Department of Pharmacology and TherapeuticsThe University of MelbourneParkvilleVictoria3052Australia
| | - Dominic J. Hare
- Brain and Mind Centre and Discipline of PharmacologyThe University of Sydney, CamperdownSydneyNew South Wales2050Australia
- School of BioSciencesThe University of MelbourneParkvilleVictoria3052Australia
- Atomic Medicine InitiativeThe University of Technology SydneyBroadwayNew South Wales2007Australia
| | - Peter J. Crouch
- Department of Pharmacology and TherapeuticsThe University of MelbourneParkvilleVictoria3052Australia
| | - Kay L. Double
- Brain and Mind Centre and Discipline of PharmacologyThe University of Sydney, CamperdownSydneyNew South Wales2050Australia
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4
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Trist BG, Hilton JB, Hare DJ, Crouch PJ, Double KL. Superoxide Dismutase 1 in Health and Disease: How a Frontline Antioxidant Becomes Neurotoxic. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202000451] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Benjamin G. Trist
- Brain and Mind Centre and Discipline of Pharmacology The University of Sydney, Camperdown Sydney New South Wales 2050 Australia
| | - James B. Hilton
- Department of Pharmacology and Therapeutics The University of Melbourne Parkville Victoria 3052 Australia
| | - Dominic J. Hare
- Brain and Mind Centre and Discipline of Pharmacology The University of Sydney, Camperdown Sydney New South Wales 2050 Australia
- School of BioSciences The University of Melbourne Parkville Victoria 3052 Australia
- Atomic Medicine Initiative The University of Technology Sydney Broadway New South Wales 2007 Australia
| | - Peter J. Crouch
- Department of Pharmacology and Therapeutics The University of Melbourne Parkville Victoria 3052 Australia
| | - Kay L. Double
- Brain and Mind Centre and Discipline of Pharmacology The University of Sydney, Camperdown Sydney New South Wales 2050 Australia
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5
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Trainor K, Palumbo JA, MacKenzie DWS, Meiering EM. Temperature dependence of NMR chemical shifts: Tracking and statistical analysis. Protein Sci 2019; 29:306-314. [PMID: 31730280 PMCID: PMC6933856 DOI: 10.1002/pro.3785] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 11/09/2019] [Accepted: 11/11/2019] [Indexed: 11/28/2022]
Abstract
Isotropic chemical shifts measured by solution nuclear magnetic resonance (NMR) spectroscopy offer extensive insights into protein structure and dynamics. Temperature dependences add a valuable dimension; notably, the temperature dependences of amide proton chemical shifts are valuable probes of hydrogen bonding, temperature‐dependent loss of structure, and exchange between distinct protein conformations. Accordingly, their uses include structural analysis of both folded and disordered proteins, and determination of the effects of mutations, binding, or solution conditions on protein energetics. Fundamentally, these temperature dependences result from changes in the local magnetic environments of nuclei, but correlations with global thermodynamic parameters measured via calorimetric methods have been observed. Although the temperature dependences of amide proton and nitrogen chemical shifts are often well approximated by a linear model, deviations from linearity are also observed and may be interpreted as evidence of fast exchange between distinct conformational states. Here, we describe computational methods, accessible via the Shift‐T web server, including an automated tracking algorithm that propagates initial (single temperature) 1H—15N cross peak assignments to spectra collected over a range of temperatures. Amide proton and nitrogen temperature coefficients (slopes determined by fitting chemical shift vs. temperature data to a linear model) are subsequently calculated. Also included are methods for the detection of systematic, statistically significant deviation from linearity (curvature) in the temperature dependences of amide proton chemical shifts. The use and utility of these methods are illustrated by example, and the Shift‐T web server is freely available at http://meieringlab.uwaterloo.ca/shiftt.
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Affiliation(s)
- Kyle Trainor
- Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada
| | - Jeffrey A Palumbo
- Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada
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6
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A quantitative model of human neurodegenerative diseases involving protein aggregation. Neurobiol Aging 2019; 80:46-55. [DOI: 10.1016/j.neurobiolaging.2019.04.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 04/02/2019] [Accepted: 04/02/2019] [Indexed: 12/12/2022]
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7
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Trist BG, Hare DJ, Double KL. A Proposed Mechanism for Neurodegeneration in Movement Disorders Characterized by Metal Dyshomeostasis and Oxidative Stress. Cell Chem Biol 2018; 25:807-816. [PMID: 29861271 DOI: 10.1016/j.chembiol.2018.05.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 04/09/2018] [Accepted: 05/01/2018] [Indexed: 02/07/2023]
Abstract
Shared molecular pathologies between distinct neurodegenerative disorders offer unique opportunities to identify common mechanisms of neuron death, and apply lessons learned from one disease to another. Neurotoxic superoxide dismutase 1 (SOD1) proteinopathy in SOD1-associated familial amyotrophic lateral sclerosis (fALS) is recapitulated in idiopathic Parkinson disease (PD), suggesting that these two phenotypically distinct disorders share an etiological pathway, and tractable therapeutic target(s). Despite 25 years of research, the molecular determinants underlying SOD1 misfolding and toxicity in fALS remain poorly understood. The absence of SOD1 mutations in PD highlights mounting evidence that SOD1 mutations are not the sole cause of SOD1 protein misfolding occasioning oligomerization and toxicity, reinforcing the importance of non-genetic factors, including protein metallation and post-translational modification in determining SOD1 stability and function. We propose that these non-genetic factors underlie the misfolding and dysfunction of SOD1 and other proteins in both PD and fALS, constituting a shared and tractable pathway to neurodegeneration.
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Affiliation(s)
- Benjamin Guy Trist
- Discipline of Biomedical Science and Brain and Mind Centre, Sydney Medical School, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW 2050, Australia
| | - Dominic James Hare
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC 3052, Australia; Department of Pathology, The University of Melbourne, Parkville, VIC 3052, Australia
| | - Kay Lorraine Double
- Discipline of Biomedical Science and Brain and Mind Centre, Sydney Medical School, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW 2050, Australia.
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8
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Effects of maturation on the conformational free-energy landscape of SOD1. Proc Natl Acad Sci U S A 2018; 115:E2546-E2555. [PMID: 29483249 DOI: 10.1073/pnas.1721022115] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a devastating fatal syndrome characterized by very rapid degeneration of motor neurons. A leading hypothesis is that ALS is caused by toxic protein misfolding and aggregation, as also occurs in many other neurodegenerative disorders, such as prion, Alzheimer's, Parkinson's, and Huntington's diseases. A prominent cause of familial ALS is mutations in the protein superoxide dismutase (SOD1), which promote the formation of misfolded SOD1 conformers that are prone to aberrant interactions both with each other and with other cellular components. We have shown previously that immature SOD1, lacking bound Cu and Zn metal ions and the intrasubunit disulfide bond (apoSOD12SH), has a rugged free-energy surface (FES) and exchanges with four other conformations (excited states) that have millisecond lifetimes and sparse populations on the order of a few percent. Here, we examine further states of SOD1 along its maturation pathway, as well as those off-pathway resulting from metal loss that have been observed in proteinaceous inclusions. Metallation and disulfide bond formation lead to structural transformations including local ordering of the electrostatic loop and native dimerization that are observed in rare conformers of apoSOD12SH; thus, SOD1 maturation may occur via a population-switch mechanism whereby posttranslational modifications select for preexisting structures on the FES. Metallation and oxidation of SOD1 stabilize the native, mature conformation and decrease the number of detected excited conformational states, suggesting that it is the immature forms of the protein that contribute to misfolded conformations in vivo rather than the highly stable enzymatically active dimer.
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9
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Luchinat E, Barbieri L, Banci L. A molecular chaperone activity of CCS restores the maturation of SOD1 fALS mutants. Sci Rep 2017; 7:17433. [PMID: 29234142 PMCID: PMC5727297 DOI: 10.1038/s41598-017-17815-y] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 11/30/2017] [Indexed: 02/07/2023] Open
Abstract
Superoxide dismutase 1 (SOD1) is an important metalloprotein for cellular oxidative stress defence, that is mutated in familiar variants of Amyotrophic Lateral Sclerosis (fALS). Some mutations destabilize the apo protein, leading to the formation of misfolded, toxic species. The Copper Chaperone for SOD1 (CCS) transiently interacts with SOD1 and promotes its correct maturation by transferring copper and catalyzing disulfide bond formation. By in vitro and in-cell NMR, we investigated the role of the SOD-like domain of CCS (CCS-D2). We showed that CCS-D2 forms a stable complex with zinc-bound SOD1 in human cells, that has a twofold stabilizing effect: it both prevents the accumulation of unstructured mutant SOD1 and promotes zinc binding. We further showed that CCS-D2 interacts with apo-SOD1 in vitro, suggesting that in cells CCS stabilizes mutant apo-SOD1 prior to zinc binding. Such molecular chaperone function of CCS-D2 is novel and its implications in SOD-linked fALS deserve further investigation.
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Affiliation(s)
- Enrico Luchinat
- Magnetic Resonance Centre (CERM), University of Florence, 50019, Sesto Fiorentino, Italy.,Department of Biomedical, Clinical and Experimental Sciences, University of Florence, 50134, Florence, Italy
| | - Letizia Barbieri
- Magnetic Resonance Centre (CERM), University of Florence, 50019, Sesto Fiorentino, Italy.,Interuniversity Consortium for Magnetic Resonance of Metallo Proteins (CIRMMP), 50019, Sesto Fiorentino, Italy
| | - Lucia Banci
- Magnetic Resonance Centre (CERM), University of Florence, 50019, Sesto Fiorentino, Italy. .,Department of Chemistry, University of Florence, 50019, Sesto Fiorentino, Florence, Italy.
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10
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Pickles S, Semmler S, Broom HR, Destroismaisons L, Legroux L, Arbour N, Meiering E, Cashman NR, Vande Velde C. ALS-linked misfolded SOD1 species have divergent impacts on mitochondria. Acta Neuropathol Commun 2016; 4:43. [PMID: 27121871 PMCID: PMC4847257 DOI: 10.1186/s40478-016-0313-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 04/13/2016] [Indexed: 12/13/2022] Open
Abstract
Approximately 20 % of familial Amyotrophic Lateral Sclerosis (ALS) is caused by mutations in superoxide dismutase (SOD1), which leads to misfolding of the SOD1 protein, resulting in a toxic gain of function. Several conformation-restricted antibodies have been generated that specifically recognize misfolded SOD1 protein, and have been used as therapeutics in pre-clinical models. Misfolded SOD1 selectively associates with spinal cord mitochondria in SOD1 rodent models. Using the SOD1(G93A) rat model, we find that SOD1 conformational specific antibodies AMF7-63 and DSE2-3H1 labeled a fibrillar network concentrated in the anterior horn; while A5C3, B8H10, C4F6 and D3H5 labeled motor neurons as well as puncta in the neuropil. There is a time-dependent accumulation of misfolded SOD1 at the surface of spinal cord mitochondria with AMF7-63-labeled mitochondria having increased volume in contrast to a mitochondrial subset labeled with B8H10. In spinal cord homogenates and isolated mitochondria, AMF7-63, DSE2-3H1 and B8H10 detect misfolded SOD1 aggregates. SOD1 that lacks its metal cofactors has an increased affinity for naïve mitochondria and misfolded SOD1 antibodies B8H10 and DSE2-3H1 readily detect demetalated mutant and wild-type SOD1. Together, these data suggest that multiple non-native species of misfolded SOD1 may exist, some of which are associated with mitochondrial damage. Conformational antibodies are invaluable tools to identify and characterize the variation in misfolded SOD1 species with regards to biochemical characteristics and toxicity. This information is highly relevant to the further development of these reagents as therapeutics.
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11
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Petrov D, Daura X, Zagrovic B. Effect of Oxidative Damage on the Stability and Dimerization of Superoxide Dismutase 1. Biophys J 2016; 110:1499-1509. [PMID: 27074676 PMCID: PMC4833831 DOI: 10.1016/j.bpj.2016.02.037] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 02/07/2016] [Accepted: 02/10/2016] [Indexed: 12/13/2022] Open
Abstract
During their life cycle, proteins are subject to different modifications involving reactive oxygen species. Such oxidative damage to proteins may lead to the formation of insoluble aggregates and cytotoxicity and is associated with age-related disorders including neurodegenerative diseases, cancer, and diabetes. Superoxide dismutase 1 (SOD1), a key antioxidant enzyme in human cells, is particularly susceptible to such modifications. Moreover, this homodimeric metalloenzyme has been directly linked to both familial and sporadic amyotrophic lateral sclerosis (ALS), a devastating, late-onset motor neuronal disease, with more than 150 ALS-related mutations in the SOD1 gene. Importantly, oxidatively damaged SOD1 aggregates have been observed in both familial and sporadic forms of the disease. However, the molecular mechanisms as well as potential implications of oxidative stress in SOD1-induced cytotoxicity remain elusive. In this study, we examine the effects of oxidative modification on SOD1 monomer and homodimer stability, the key molecular properties related to SOD1 aggregation. We use molecular dynamics simulations in combination with thermodynamic integration to study microscopic-level site-specific effects of oxidative "mutations" at the dimer interface, including lysine, arginine, proline and threonine carbonylation, and cysteine oxidation. Our results show that oxidative damage of even single residues at the interface may drastically destabilize the SOD1 homodimer, with several modifications exhibiting a comparable effect to that of the most drastic ALS-causing mutations known. Additionally, we show that the SOD1 monomer stability decreases upon oxidative stress, which may lead to partial local unfolding and consequently to increased aggregation propensity. Importantly, these results suggest that oxidative stress may play a key role in development of ALS, with the mutations in the SOD1 gene being an additional factor.
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Affiliation(s)
- Drazen Petrov
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
| | - Xavier Daura
- Institute of Biotechnology and Biomedicine, Universitat Autònoma de Barcelona, Bellaterra, Spain; Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain
| | - Bojan Zagrovic
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Vienna, Austria.
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12
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Broom HR, Vassall KA, Rumfeldt JAO, Doyle CM, Tong MS, Bonner JM, Meiering EM. Combined Isothermal Titration and Differential Scanning Calorimetry Define Three-State Thermodynamics of fALS-Associated Mutant Apo SOD1 Dimers and an Increased Population of Folded Monomer. Biochemistry 2016; 55:519-33. [PMID: 26710831 DOI: 10.1021/acs.biochem.5b01187] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Many proteins are naturally homooligomers, homodimers most frequently. The overall stability of oligomeric proteins may be described in terms of the stability of the constituent monomers and the stability of their association; together, these stabilities determine the populations of different monomer and associated species, which generally have different roles in the function or dysfunction of the protein. Here we show how a new combined calorimetry approach, using isothermal titration calorimetry to define monomer association energetics together with differential scanning calorimetry to measure total energetics of oligomer unfolding, can be used to analyze homodimeric unmetalated (apo) superoxide dismutase (SOD1) and determine the effects on the stability of structurally diverse mutations associated with amyotrophic lateral sclerosis (ALS). Despite being located throughout the protein, all mutations studied weaken the dimer interface, while concomitantly either decreasing or increasing the marginal stability of the monomer. Analysis of the populations of dimer, monomer, and unfolded monomer under physiological conditions of temperature, pH, and protein concentration shows that all mutations promote the formation of folded monomers. These findings may help rationalize the key roles proposed for monomer forms of SOD1 in neurotoxic aggregation in ALS, as well as roles for other forms of SOD1. Thus, the results obtained here provide a valuable approach for the quantitative analysis of homooligomeric protein stabilities, which can be used to elucidate the natural and aberrant roles of different forms of these proteins and to improve methods for predicting protein stabilities.
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Affiliation(s)
- Helen R Broom
- Department of Chemistry, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - Kenrick A Vassall
- Department of Chemistry, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - Jessica A O Rumfeldt
- Department of Chemistry, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - Colleen M Doyle
- Department of Chemistry, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - Ming Sze Tong
- Department of Chemistry, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - Julia M Bonner
- Department of Chemistry, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - Elizabeth M Meiering
- Department of Chemistry, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
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13
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Broom HR, Rumfeldt JAO, Vassall KA, Meiering EM. Destabilization of the dimer interface is a common consequence of diverse ALS-associated mutations in metal free SOD1. Protein Sci 2015; 24:2081-9. [PMID: 26362407 DOI: 10.1002/pro.2803] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 09/02/2015] [Accepted: 09/11/2015] [Indexed: 11/08/2022]
Abstract
Neurotoxic misfolding of Cu, Zn-superoxide dismutase (SOD1) is implicated in causing amyotrophic lateral sclerosis, a devastating and incurable neurodegenerative disease. Disease-linked mutations in SOD1 have been proposed to promote misfolding and aggregation by decreasing protein stability and increasing the proportion of less folded forms of the protein. Here we report direct measurement of the thermodynamic effects of chemically and structurally diverse mutations on the stability of the dimer interface for metal free (apo) SOD1 using isothermal titration calorimetry and size exclusion chromatography. Remarkably, all mutations studied, even ones distant from the dimer interface, decrease interface stability, and increase the population of monomeric SOD1. We interpret the thermodynamic data to mean that substantial structural perturbations accompany dimer dissociation, resulting in the formation of poorly packed and malleable dissociated monomers. These findings provide key information for understanding the mechanisms and energetics underlying normal maturation of SOD1, as well as toxic SOD1 misfolding pathways associated with disease. Furthermore, accurate prediction of protein-protein association remains very difficult, especially when large structural changes are involved in the process, and our findings provide a quantitative set of data for such cases, to improve modelling of protein association.
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Affiliation(s)
- Helen R Broom
- Department of Chemistry, Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
| | - Jessica A O Rumfeldt
- Department of Chemistry, Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
| | - Kenrick A Vassall
- Department of Chemistry, Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
| | - Elizabeth M Meiering
- Department of Chemistry, Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
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14
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Sekhar A, Rumfeldt JAO, Broom HR, Doyle CM, Bouvignies G, Meiering EM, Kay LE. Thermal fluctuations of immature SOD1 lead to separate folding and misfolding pathways. eLife 2015; 4:e07296. [PMID: 26099300 PMCID: PMC4475725 DOI: 10.7554/elife.07296] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 05/04/2015] [Indexed: 01/08/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease involving cytotoxic conformations of Cu, Zn superoxide dismutase (SOD1). A major challenge in understanding ALS disease pathology has been the identification and atomic-level characterization of these conformers. Here, we use a combination of NMR methods to detect four distinct sparsely populated and transiently formed thermally accessible conformers in equilibrium with the native state of immature SOD1 (apoSOD1(2SH)). Structural models of two of these establish that they possess features present in the mature dimeric protein. In contrast, the other two are non-native oligomers in which the native dimer interface and the electrostatic loop mediate the formation of aberrant intermolecular interactions. Our results show that apoSOD1(2SH) has a rugged free energy landscape that codes for distinct kinetic pathways leading to either maturation or non-native association and provide a starting point for a detailed atomic-level understanding of the mechanisms of SOD1 oligomerization.
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Affiliation(s)
- Ashok Sekhar
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | | | - Helen R Broom
- Department of Chemistry, University of Waterloo, Waterloo, Canada
| | - Colleen M Doyle
- Department of Chemistry, University of Waterloo, Waterloo, Canada
| | | | | | - Lewis E Kay
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
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Many roads lead to Rome? Multiple modes of Cu,Zn superoxide dismutase destabilization, misfolding and aggregation in amyotrophic lateral sclerosis. Essays Biochem 2014; 56:149-65. [DOI: 10.1042/bse0560149] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
ALS (amyotrophic lateral sclerosis) is a fatal neurodegenerative syndrome characterized by progressive paralysis and motor neuron death. Although the pathological mechanisms that cause ALS remain unclear, accumulating evidence supports that ALS is a protein misfolding disorder. Mutations in Cu,Zn-SOD1 (copper/zinc superoxide dismutase 1) are a common cause of familial ALS. They have complex effects on different forms of SOD1, but generally destabilize the protein and enhance various modes of misfolding and aggregation. In addition, there is some evidence that destabilized covalently modified wild-type SOD1 may be involved in disease. Among the multitude of misfolded/aggregated species observed for SOD1, multiple species may impair various cellular components at different disease stages. Newly developed antibodies that recognize different structural features of SOD1 represent a powerful tool for further unravelling the roles of different SOD1 structures in disease. Evidence for similar cellular targets of misfolded/aggregated proteins, loss of cellular proteostasis and cell–cell transmission of aggregates point to common pathological mechanisms between ALS and other misfolding diseases, such as Alzheimer's, Parkinson's and prion diseases, as well as serpinopathies. The recent progress in understanding the molecular basis for these devastating diseases provides numerous avenues for developing urgently needed therapeutics.
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16
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Rotunno MS, Bosco DA. An emerging role for misfolded wild-type SOD1 in sporadic ALS pathogenesis. Front Cell Neurosci 2013; 7:253. [PMID: 24379756 PMCID: PMC3863749 DOI: 10.3389/fncel.2013.00253] [Citation(s) in RCA: 167] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Accepted: 11/25/2013] [Indexed: 12/12/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder that targets motor neurons, leading to paralysis and death within a few years of disease onset. While several genes have been linked to the inheritable, or familial, form of ALS, much less is known about the cause(s) of sporadic ALS, which accounts for ~90% of ALS cases. Due to the clinical similarities between familial and sporadic ALS, it is plausible that both forms of the disease converge on a common pathway and, therefore, involve common factors. Recent evidence suggests the Cu,Zn-superoxide dismutase (SOD1) protein to be one such factor that is common to both sporadic and familial ALS. In 1993, mutations were uncovered in SOD1 that represent the first known genetic cause of familial ALS. While the exact mechanism of mutant-SOD1 toxicity is still not known today, most evidence points to a gain of toxic function that stems, at least in part, from the propensity of this protein to misfold. In the wild-type SOD1 protein, non-genetic perturbations such as metal depletion, disruption of the quaternary structure, and oxidation, can also induce SOD1 to misfold. In fact, these aforementioned post-translational modifications cause wild-type SOD1 to adopt a “toxic conformation” that is similar to familial ALS-linked SOD1 variants. These observations, together with the detection of misfolded wild-type SOD1 within human post-mortem sporadic ALS samples, have been used to support the controversial hypothesis that misfolded forms of wild-type SOD1 contribute to sporadic ALS pathogenesis. In this review, we present data from the literature that both support and contradict this hypothesis. We also discuss SOD1 as a potential therapeutic target for both familial and sporadic ALS.
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Affiliation(s)
- Melissa S Rotunno
- Department of Neurology, University of Massachusetts Medical Center Worcester, MA, USA
| | - Daryl A Bosco
- Department of Neurology, University of Massachusetts Medical Center Worcester, MA, USA
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17
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Mulligan VK, Chakrabartty A. Protein misfolding in the late-onset neurodegenerative diseases: Common themes and the unique case of amyotrophic lateral sclerosis. Proteins 2013; 81:1285-303. [DOI: 10.1002/prot.24285] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 02/27/2013] [Accepted: 02/28/2013] [Indexed: 12/12/2022]
Affiliation(s)
| | - Avijit Chakrabartty
- Department of Biochemistry; Toronto Ontario M5G 1L7 Canada
- Department of Medical Biophysics; University of Toronto; Toronto Ontario M5G 1L7 Canada
- Campbell Family Institute for Cancer Research, Ontario Cancer Institute/University Health Network; Toronto Ontario M5G 1L7 Canada
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18
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Das A, Plotkin SS. Mechanical Probes of SOD1 Predict Systematic Trends in Metal and Dimer Affinity of ALS-Associated Mutants. J Mol Biol 2013; 425:850-74. [DOI: 10.1016/j.jmb.2012.12.022] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 11/08/2012] [Accepted: 12/21/2012] [Indexed: 01/28/2023]
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19
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Doyle CM, Rumfeldt JA, Broom HR, Broom A, Stathopulos PB, Vassall KA, Almey JJ, Meiering EM. Energetics of oligomeric protein folding and association. Arch Biochem Biophys 2012; 531:44-64. [PMID: 23246784 DOI: 10.1016/j.abb.2012.12.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Revised: 11/29/2012] [Accepted: 12/05/2012] [Indexed: 12/11/2022]
Abstract
In nature, proteins most often exist as complexes, with many of these consisting of identical subunits. Understanding of the energetics governing the folding and misfolding of such homooligomeric proteins is central to understanding their function and misfunction, in disease or biotechnology. Much progress has been made in defining the mechanisms and thermodynamics of homooligomeric protein folding. In this review, we outline models as well as calorimetric and spectroscopic methods for characterizing oligomer folding, and describe extensive results obtained for diverse proteins, ranging from dimers to octamers and higher order aggregates. To our knowledge, this area has not been reviewed comprehensively in years, and the collective progress is impressive. The results provide evolutionary insights into the development of subunit interfaces, mechanisms of oligomer folding, and contributions of oligomerization to protein stability, function and regulation. Thermodynamic analyses have also proven valuable for understanding protein misfolding and aggregation mechanisms, suggesting new therapeutic avenues. Successful recent designs of novel, functional proteins demonstrate increased understanding of oligomer folding. Further rigorous analyses using multiple experimental and computational approaches are still required, however, to achieve consistent and accurate prediction of oligomer folding energetics. Modeling the energetics remains challenging but is a promising avenue for future advances.
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Affiliation(s)
- Colleen M Doyle
- Guelph-Waterloo Centre for Graduate Studies in Chemistry and Biochemistry, and Department of Chemistry, University of Waterloo, 200 University Ave. West, Waterloo, ON, Canada
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20
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Mulligan VK, Kerman A, Laister RC, Sharda PR, Arslan PE, Chakrabartty A. Early Steps in Oxidation-Induced SOD1 Misfolding: Implications for Non-Amyloid Protein Aggregation in Familial ALS. J Mol Biol 2012; 421:631-52. [DOI: 10.1016/j.jmb.2012.04.016] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2011] [Revised: 04/12/2012] [Accepted: 04/14/2012] [Indexed: 12/14/2022]
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21
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Proctor EA, Ding F, Dokholyan NV. Structural and thermodynamic effects of post-translational modifications in mutant and wild type Cu, Zn superoxide dismutase. J Mol Biol 2011; 408:555-67. [PMID: 21396374 PMCID: PMC3082150 DOI: 10.1016/j.jmb.2011.03.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2010] [Revised: 02/25/2011] [Accepted: 03/01/2011] [Indexed: 12/12/2022]
Abstract
Aggregation of Cu,Zn superoxide dismutase (SOD1) is implicated in amyotrophic lateral sclerosis. Glutathionylation and phosphorylation of SOD1 is omnipresent in the human body, even in healthy individuals, and has been shown to increase SOD1 dimer dissociation, which is the first step on the pathway toward SOD1 aggregation. We found that post-translational modification of SOD1, especially glutathionylation, promotes dimer dissociation. We discovered an intermediate state in the pathway to dissociation, a conformational change that involves a "loosening" of the β-barrels and a loss or shift of dimer interface interactions. In modified SOD1, this intermediate state is stabilized as compared to unmodified SOD1. The presence of post-translational modifications could explain the environmental factors involved in the speed of disease progression. Because post-translational modifications such as glutathionylation are often induced by oxidative stress, post-translational modification of SOD1 could be a factor in the occurrence of sporadic cases of amyotrophic lateral sclerosis, which represent 90% of all cases of the disease.
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Affiliation(s)
- Elizabeth A. Proctor
- Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC 27599
- Program in Molecular and Cellular Biophysics, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC 27599
| | - Feng Ding
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC 27599
- Center for Computational and Systems Biology, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC 27599
| | - Nikolay V. Dokholyan
- Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC 27599
- Program in Molecular and Cellular Biophysics, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC 27599
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC 27599
- Center for Computational and Systems Biology, University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC 27599
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22
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Kitamura F, Fujimaki N, Okita W, Hiramatsu H, Takeuchi H. Structural Instability and Cu-Dependent Pro-Oxidant Activity Acquired by the Apo Form of Mutant SOD1 Associated with Amyotrophic Lateral Sclerosis. Biochemistry 2011; 50:4242-50. [DOI: 10.1021/bi200338h] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Furi Kitamura
- Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama, Sendai 980-8578, Japan
| | - Nobuhiro Fujimaki
- Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama, Sendai 980-8578, Japan
| | - Wakana Okita
- Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama, Sendai 980-8578, Japan
| | - Hirotsugu Hiramatsu
- Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama, Sendai 980-8578, Japan
| | - Hideo Takeuchi
- Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama, Sendai 980-8578, Japan
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23
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Ip P, Mulligan VK, Chakrabartty A. ALS-causing SOD1 mutations promote production of copper-deficient misfolded species. J Mol Biol 2011; 409:839-52. [PMID: 21549128 DOI: 10.1016/j.jmb.2011.04.027] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Revised: 04/01/2011] [Accepted: 04/11/2011] [Indexed: 12/14/2022]
Abstract
Point mutations scattered throughout the sequence of Cu,Zn superoxide dismutase (SOD1) cause a subset of amyotrophic lateral sclerosis (ALS) cases. SOD1 is a homodimer in which each subunit binds one copper atom and one zinc atom. Inclusions containing misfolded SOD1 are seen in motor neurons of SOD1-associated ALS cases. The mechanism by which these diverse mutations cause misfolding and converge on the same disease is still not well understood. Previously, we developed several time-resolved techniques to monitor structural changes in SOD1 as it unfolds in guanidine hydrochloride. By measuring the rates of Cu and Zn release using an absorbance-based assay, dimer dissociation through chemical cross-linking, and β-barrel conformation changes by tryptophan fluorescence, we established that wild-type SOD1 unfolds by a branched pathway involving a Zn-deficient monomer as the dominant intermediate of the major pathway, and with various metal-loaded and Cu-deficient dimers populated along the minor pathway. We have now compared the unfolding pathway of wild-type SOD1 with those of A4V, G37R, G85R, G93A, and I113T ALS-associated mutant SOD1. The kinetics of unfolding of the mutants were generally much faster than those of wild type. However, all of the mutants utilize the minority pathway to a greater extent than the wild-type protein, leading to greater populations of Cu-deficient intermediates and decreases in Zn-deficient intermediates relative to the wild-type protein. The greater propensity of the mutants to populate Cu-deficient states potentially implicates these species as a pathogenic form of SOD1 in SOD1-associated ALS and provides a novel target for therapeutic intervention.
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Affiliation(s)
- Philbert Ip
- Campbell Family Institute for Cancer Research, Ontario Cancer Institute/University Health Network, Department of Biochemistry, University of Toronto, TMDT 4-305, 101 College Street, Toronto, Ontario, Canada M5G 1L7
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24
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Decreased stability and increased formation of soluble aggregates by immature superoxide dismutase do not account for disease severity in ALS. Proc Natl Acad Sci U S A 2011; 108:2210-5. [PMID: 21257910 DOI: 10.1073/pnas.0913021108] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Protein aggregation is a hallmark of many diseases, including amyotrophic lateral sclerosis (ALS), where aggregation of Cu/Zn superoxide dismutase (SOD1) is implicated in causing neurodegeneration. Recent studies have suggested that destabilization and aggregation of the most immature form of SOD1, the disulfide-reduced, unmetallated (apo) protein is particularly important in causing ALS. We report herein in depth analyses of the effects of chemically and structurally diverse ALS-associated mutations on the stability and aggregation of reduced apo SOD1. In contrast with previous studies, we find that various reduced apo SOD1 mutants undergo highly reversible thermal denaturation with little aggregation, enabling quantitative thermodynamic stability analyses. In the absence of ALS-associated mutations, reduced apo SOD1 is marginally stable but predominantly folded. Mutations generally result in slight decreases to substantial increases in the fraction of unfolded protein. Calorimetry, ultracentrifugation, and light scattering show that all mutations enhance aggregation propensity, with the effects varying widely, from subtle increases in most cases, to pronounced formation of 40-100 nm soluble aggregates by A4V, a mutation that is associated with particularly short disease duration. Interestingly, although there is a correlation between observed aggregation and stability, there is minimal to no correlation between observed aggregation, predicted aggregation propensity, and disease characteristics. These findings suggest that reduced apo SOD1 does not play a dominant role in modulating disease. Rather, additional and/or multiple forms of SOD1 and additional biophysical and biological factors are needed to account for the toxicity of mutant SOD1 in ALS.
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25
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Strategies for stabilizing superoxide dismutase (SOD1), the protein destabilized in the most common form of familial amyotrophic lateral sclerosis. Proc Natl Acad Sci U S A 2010; 107:21394-9. [PMID: 21098299 DOI: 10.1073/pnas.1015463107] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a disorder characterized by the death of both upper and lower motor neurons and by 3- to 5-yr median survival postdiagnosis. The only US Food and Drug Administration-approved drug for the treatment of ALS, Riluzole, has at best, moderate effect on patient survival and quality of life; therefore innovative approaches are needed to combat neurodegenerative disease. Some familial forms of ALS (fALS) have been linked to mutations in the Cu/Zn superoxide dismutase (SOD1). The dominant inheritance of mutant SOD1 and lack of symptoms in knockout mice suggest a "gain of toxic function" as opposed to a loss of function. A prevailing hypothesis for the mechanism of the toxicity of fALS-SOD1 variants, or the gain of toxic function, involves dimer destabilization and dissociation as an early step in SOD1 aggregation. Therefore, stabilizing the SOD1 dimer, thus preventing aggregation, is a potential therapeutic strategy. Here, we report a strategy in which we chemically cross-link the SOD1 dimer using two adjacent cysteine residues on each respective monomer (Cys111). Stabilization, measured as an increase in melting temperature, of ∼20 °C and ∼45 °C was observed for two mutants, G93A and G85R, respectively. This stabilization is the largest for SOD1, and to the best of our knowledge, for any disease-related protein. In addition, chemical cross-linking conferred activity upon G85R, an otherwise inactive mutant. These results demonstrate that targeting these cysteine residues is an important new strategy for development of ALS therapies.
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26
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Roman M, Cannizzo C, Pinault T, Isare B, Andrioletti B, van der Schoot P, Bouteiller L. Supramolecular balance: using cooperativity to amplify weak interactions. J Am Chem Soc 2010; 132:16818-24. [PMID: 21049995 DOI: 10.1021/ja105717u] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Gathering precise knowledge on weak supramolecular interactions is difficult yet is of utmost importance for numerous scientific fields, including catalysis, crystal engineering, ligand binding, and protein folding. We report on a combined theoretical and experimental approach showing that it is possible to vastly improve the sensitivity of current methods to probe weak supramolecular interactions in solution. The concept consists of using a supramolecular platform involving a highly cooperative configurational transition, the perturbation of which (by the modification of the molecular building blocks) can be monitored in a temperature scanning experiment. We tested this concept with a particular bisurea platform, and our first results show that it is possible to detect the presence of interaction differences as low as 60 J/mol, which may be due to steric repulsion between vinyl and alkyl groups or may be the result of solvation effects.
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Affiliation(s)
- Mihaela Roman
- Université Claude Bernard-Lyon 1, ICBMS-UMR 5246, 43 Boulevard du 11 Novembre 1918, F-69622 Villeurbanne cedex, France
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27
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Hwang YM, Stathopulos PB, Dimmick K, Yang H, Badiei HR, Tong MS, Rumfeldt JAO, Chen P, Karanassios V, Meiering EM. Nonamyloid aggregates arising from mature copper/zinc superoxide dismutases resemble those observed in amyotrophic lateral sclerosis. J Biol Chem 2010; 285:41701-11. [PMID: 20974846 DOI: 10.1074/jbc.m110.113696] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Protein aggregation is a hallmark of many diseases, including amyotrophic lateral sclerosis (ALS) where aggregation of copper/zinc superoxide dismutase (SOD1) is implicated in pathogenesis. We report here that fully metallated (holo) SOD1 under physiologically relevant solution conditions can undergo changes in metallation and/or dimerization over time and form aggregates that do not exhibit classical characteristics of amyloid. The relevance of the observed aggregation to disease is demonstrated by structural and tinctorial analyses, including the novel observation of binding of an anti-SOD1 antibody that specifically recognizes aggregates in ALS patients and mice models. ALS-associated SOD1 mutations can promote aggregation but are not essential. The SOD1 aggregation is characterized by a lag phase, which is diminished by self- or cross-seeding and by heterogeneous nucleation. We interpret these findings in terms of an expanded aggregation mechanism consistent with other in vitro and in vivo findings that point to multiple pathways for the formation of toxic aggregates by different forms of SOD1.
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Affiliation(s)
- Young-Mi Hwang
- Department of Chemistry and Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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28
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Byström R, Andersen PM, Gröbner G, Oliveberg M. SOD1 mutations targeting surface hydrogen bonds promote amyotrophic lateral sclerosis without reducing apo-state stability. J Biol Chem 2010; 285:19544-52. [PMID: 20189984 PMCID: PMC2885233 DOI: 10.1074/jbc.m109.086074] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Revised: 02/05/2010] [Indexed: 11/06/2022] Open
Abstract
In good accord with the protein aggregation hypothesis for neurodegenerative diseases, ALS-associated SOD1 mutations are found to reduce structural stability or net repulsive charge. Moreover there are weak indications that the ALS disease progression rate is correlated with the degree of mutational impact on the apoSOD1 structure. A bottleneck for obtaining more conclusive information about these structure-disease relationships, however, is the large intrinsic variability in patient survival times and insufficient disease statistics for the majority of ALS-provoking mutations. As an alternative test of the structure-disease relationship we focus here on the SOD1 mutations that appear to be outliers in the data set. The results identify several ALS-provoking mutations whose only effect on apoSOD1 is the elimination or introduction of a single charge, i.e. D76V/Y, D101N, and N139D/K. The thermodynamic stability and folding behavior of these mutants are indistinguishable from the wild-type control. Moreover, D101N is an outlier in the plot of stability loss versus patient survival time by having rapid disease progression. Common to the identified mutations is that they truncate conserved salt-links and/or H-bond networks in the functional loops IV or VII. The results show that the local impact of ALS-associated mutations on the SOD1 molecule can sometimes overrun their global effects on apo-state stability and net repulsive charge, and point at the analysis of property outliers as an efficient strategy for mapping out new ALS-provoking features.
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Affiliation(s)
- Roberth Byström
- Department of Chemistry, Umeå University, S-901 87 Umeå, Sweden
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29
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Svensson AKE, Bilsel O, Kayatekin C, Adefusika JA, Zitzewitz JA, Matthews CR. Metal-free ALS variants of dimeric human Cu,Zn-superoxide dismutase have enhanced populations of monomeric species. PLoS One 2010; 5:e10064. [PMID: 20404910 PMCID: PMC2852398 DOI: 10.1371/journal.pone.0010064] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Accepted: 02/22/2010] [Indexed: 12/05/2022] Open
Abstract
Amino acid replacements at dozens of positions in the dimeric protein human, Cu,Zn superoxide dismutase (SOD1) can cause amyotrophic lateral sclerosis (ALS). Although it has long been hypothesized that these mutations might enhance the populations of marginally-stable aggregation-prone species responsible for cellular toxicity, there has been little quantitative evidence to support this notion. Perturbations of the folding free energy landscapes of metal-free versions of five ALS-inducing variants, A4V, L38V, G93A, L106V and S134N SOD1, were determined with a global analysis of kinetic and thermodynamic folding data for dimeric and stable monomeric versions of these variants. Utilizing this global analysis approach, the perturbations on the global stability in response to mutation can be partitioned between the monomer folding and association steps, and the effects of mutation on the populations of the folded and unfolded monomeric states can be determined. The 2- to 10-fold increase in the population of the folded monomeric state for A4V, L38V and L106V and the 80- to 480-fold increase in the population of the unfolded monomeric states for all but S134N would dramatically increase their propensity for aggregation through high-order nucleation reactions. The wild-type-like populations of these states for the metal-binding region S134N variant suggest that even wild-type SOD1 may also be prone to aggregation in the absence of metals.
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Affiliation(s)
- Anna-Karin E. Svensson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Osman Bilsel
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Can Kayatekin
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Jessica A. Adefusika
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Jill A. Zitzewitz
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail: (JAZ); (CRM)
| | - C. Robert Matthews
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail: (JAZ); (CRM)
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30
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Disulfide-reduced ALS variants of Cu, Zn superoxide dismutase exhibit increased populations of unfolded species. J Mol Biol 2010; 398:320-31. [PMID: 20184893 DOI: 10.1016/j.jmb.2010.02.034] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Revised: 02/15/2010] [Accepted: 02/17/2010] [Indexed: 11/21/2022]
Abstract
Cu,Zn superoxide dismutase (SOD1) is a dimeric metal-binding enzyme responsible for the dismutation of toxic superoxide to hydrogen peroxide and oxygen in cells. Mutations at dozens of sites in SOD1 induce amyotrophic lateral sclerosis (ALS), a fatal gain-of-function neurodegenerative disease whose molecular basis is unknown. To obtain insights into effects of the mutations on the folded and unfolded populations of immature monomeric forms whose aggregation or self-association may be responsible for ALS, the thermodynamic and kinetic folding properties of a set of disulfide-reduced and disulfide-oxidized Zn-free and Zn-bound stable monomeric SOD1 variants were compared to properties of the wild-type (WT) protein. The most striking effect of the mutations on the monomer stability was observed for the disulfide-reduced metal-free variants. Whereas the WT and S134N monomers are >95% folded at neutral pH and 37 degrees C, A4V, L38V, G93A, and L106V ranged from 50% to approximately 90% unfolded. The reduction of the disulfide bond was also found to reduce the apparent Zn affinity of the WT monomer by 750-fold, into the nanomolar range, where it may be unable to compete for free Zn in the cell. With the exception of the S134N metal-binding variant, the Zn affinity of disulfide-oxidized SOD1 monomers showed little sensitivity to amino acid replacements. These results suggest a model for SOD1 aggregation where the constant synthesis of ALS variants of SOD1 on ribosomes provides a pool of species in which the increased population of the unfolded state may favor aggregation over productive folding to the native dimeric state.
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31
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Kinetic and thermodynamic properties of the folding and assembly of formate dehydrogenase. FEBS Lett 2009; 583:2887-92. [PMID: 19647736 DOI: 10.1016/j.febslet.2009.07.048] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 07/18/2009] [Accepted: 07/26/2009] [Indexed: 11/21/2022]
Abstract
The folding mechanism and stability of dimeric formate dehydrogenase from Candida methylica was analysed by exposure to denaturing agents and to heat. Equilibrium denaturation data yielded a dissociation constant of about 10(-13)M for assembly of the protein from unfolded chains and the kinetics of refolding and unfolding revealed that the overall process comprises two steps. In the first step a marginally stable folded monomeric state is formed at a rate (k(1)) of about 2x10(-3)s(-1) (by deduction k(-1) is about 10(-4)s(-1)) and assembles into the active dimeric state with a bimolecular rate constant (k(2)) of about 2x10(4)M(-1)s(-1). The rate of dissociation of the dimeric state in physiological conditions is extremely slow (k(-2) approximately 3x10(-7)s(-1)).
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32
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D'Orazio M, Cervoni L, Giartosio A, Rotilio G, Battistoni A. Thermal stability and redox properties of M. tuberculosis CuSOD. Arch Biochem Biophys 2009; 486:119-24. [PMID: 19383490 DOI: 10.1016/j.abb.2009.04.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2009] [Revised: 04/07/2009] [Accepted: 04/11/2009] [Indexed: 11/19/2022]
Abstract
The superoxide dismutase from Mycobacterium tuberculosis is the only Cu-containing superoxide dismutase that lacks zinc in the active site. To explore the structural properties of this unusual enzyme, we have investigated its stability by differential scanning calorimetry. We have found that the holo-enzyme is significantly more stable than the apo-protein or the partially metallated enzyme, but that its melting temperature is markedly lower than that of all the other characterized eukaryotic and prokaryotic Cu,Zn superoxide dismutases. We have also observed that, unlike the zinc-free eukaryotic or bacterial enzymes, the active site copper of the mycobacterial enzyme is not reduced by ascorbate, confirming that its redox properties are comparable to those typical of the enzymes containing zinc in the active site. Our findings highlight the role of zinc in conferring stability to Cu,Zn superoxide dismutases and indicate that the structural rearrangements observed in M. tuberculosis Cu,SOD compensate for the absence of zinc in achieving a fully active enzyme.
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Oztug Durer ZA, Cohlberg JA, Dinh P, Padua S, Ehrenclou K, Downes S, Tan JK, Nakano Y, Bowman CJ, Hoskins JL, Kwon C, Mason AZ, Rodriguez JA, Doucette PA, Shaw BF, Valentine JS. Loss of metal ions, disulfide reduction and mutations related to familial ALS promote formation of amyloid-like aggregates from superoxide dismutase. PLoS One 2009; 4:e5004. [PMID: 19325915 PMCID: PMC2659422 DOI: 10.1371/journal.pone.0005004] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Accepted: 03/03/2009] [Indexed: 12/18/2022] Open
Abstract
Mutations in the gene encoding Cu-Zn superoxide dismutase (SOD1) are one of the causes of familial amyotrophic lateral sclerosis (FALS). Fibrillar inclusions containing SOD1 and SOD1 inclusions that bind the amyloid-specific dye thioflavin S have been found in neurons of transgenic mice expressing mutant SOD1. Therefore, the formation of amyloid fibrils from human SOD1 was investigated. When agitated at acidic pH in the presence of low concentrations of guanidine or acetonitrile, metalated SOD1 formed fibrillar material which bound both thioflavin T and Congo red and had circular dichroism and infrared spectra characteristic of amyloid. While metalated SOD1 did not form amyloid-like aggregates at neutral pH, either removing metals from SOD1 with its intramolecular disulfide bond intact or reducing the intramolecular disulfide bond of metalated SOD1 was sufficient to promote formation of these aggregates. SOD1 formed amyloid-like aggregates both with and without intermolecular disulfide bonds, depending on the incubation conditions, and a mutant SOD1 lacking free sulfhydryl groups (AS-SOD1) formed amyloid-like aggregates at neutral pH under reducing conditions. ALS mutations enhanced the ability of disulfide-reduced SOD1 to form amyloid-like aggregates, and apo-AS-SOD1 formed amyloid-like aggregates at pH 7 only when an ALS mutation was also present. These results indicate that some mutations related to ALS promote formation of amyloid-like aggregates by facilitating the loss of metals and/or by making the intramolecular disulfide bond more susceptible to reduction, thus allowing the conversion of SOD1 to a form that aggregates to form resembling amyloid. Furthermore, the occurrence of amyloid-like aggregates per se does not depend on forming intermolecular disulfide bonds, and multiple forms of such aggregates can be produced from SOD1.
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Affiliation(s)
- Zeynep A. Oztug Durer
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Jeffrey A. Cohlberg
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
- * E-mail:
| | - Phong Dinh
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Shelby Padua
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Krista Ehrenclou
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Sean Downes
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - James K. Tan
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Yoko Nakano
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Christopher J. Bowman
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, California, United States of America
| | - Jessica L. Hoskins
- Department of Physics and Astronomy, California State University Long Beach, Long Beach, California, United States of America
| | - Chuhee Kwon
- Department of Physics and Astronomy, California State University Long Beach, Long Beach, California, United States of America
| | - Andrew Z. Mason
- Department of Biological Sciences, California State University Long Beach, Long Beach, California, United States of America
| | - Jorge A. Rodriguez
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America
| | - Peter A. Doucette
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America
| | - Bryan F. Shaw
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America
| | - Joan Selverstone Valentine
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America
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Rumfeldt JA, Lepock JR, Meiering EM. Unfolding and Folding Kinetics of Amyotrophic Lateral Sclerosis-Associated Mutant Cu,Zn Superoxide Dismutases. J Mol Biol 2009; 385:278-98. [DOI: 10.1016/j.jmb.2008.10.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Revised: 09/26/2008] [Accepted: 10/01/2008] [Indexed: 02/06/2023]
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Wang Q, Johnson JL, Agar NY, Agar JN. Protein aggregation and protein instability govern familial amyotrophic lateral sclerosis patient survival. PLoS Biol 2008; 6:e170. [PMID: 18666828 PMCID: PMC2486295 DOI: 10.1371/journal.pbio.0060170] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Accepted: 06/05/2008] [Indexed: 12/13/2022] Open
Abstract
The nature of the "toxic gain of function" that results from amyotrophic lateral sclerosis (ALS)-, Parkinson-, and Alzheimer-related mutations is a matter of debate. As a result no adequate model of any neurodegenerative disease etiology exists. We demonstrate that two synergistic properties, namely, increased protein aggregation propensity (increased likelihood that an unfolded protein will aggregate) and decreased protein stability (increased likelihood that a protein will unfold), are central to ALS etiology. Taken together these properties account for 69% of the variability in mutant Cu/Zn-superoxide-dismutase-linked familial ALS patient survival times. Aggregation is a concentration-dependent process, and spinal cord motor neurons have higher concentrations of Cu/Zn-superoxide dismutase than the surrounding cells. Protein aggregation therefore is expected to contribute to the selective vulnerability of motor neurons in familial ALS.
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Affiliation(s)
- Qi Wang
- Department of Chemistry, Brandeis University, Waltham, Massachusetts, United States of America
- Volen Center, Brandeis University, Waltham, Massachusetts, United States of America
| | - Joshua L Johnson
- Volen Center, Brandeis University, Waltham, Massachusetts, United States of America
- Department of Biochemistry, Brandeis University, Waltham, Massachusetts, United States of America
| | - Nathalie Y.R Agar
- Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jeffrey N Agar
- Department of Chemistry, Brandeis University, Waltham, Massachusetts, United States of America
- Volen Center, Brandeis University, Waltham, Massachusetts, United States of America
- * To whom correspondence should be addressed. E-mail:
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Mulligan VK, Kerman A, Ho S, Chakrabartty A. Denaturational Stress Induces Formation of Zinc-Deficient Monomers of Cu,Zn Superoxide Dismutase: Implications for Pathogenesis in Amyotrophic Lateral Sclerosis. J Mol Biol 2008; 383:424-36. [DOI: 10.1016/j.jmb.2008.08.024] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2008] [Revised: 08/11/2008] [Accepted: 08/13/2008] [Indexed: 11/25/2022]
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37
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Fernandes AT, Martins LO, Melo EP. The hyperthermophilic nature of the metallo-oxidase from Aquifex aeolicus. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1794:75-83. [PMID: 18930169 DOI: 10.1016/j.bbapap.2008.09.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Revised: 08/22/2008] [Accepted: 09/11/2008] [Indexed: 10/21/2022]
Abstract
The stability of the Aquifex aeolicus multicopper oxidase (McoA) was studied by spectroscopy, calorimetry and chromatography to understand its thermophilic nature. The enzyme is hyperthermostable as deconvolution of the differential scanning calorimetry trace shows that thermal unfolding is characterized by temperature values at the mid-point of 105, 110 and 114 degrees C. Chemical denaturation revealed however a very low stability at room temperature (2.8 kcal/mol) because copper bleaching/depletion occur before the unfolding of the tertiary structure and McoA is highly prone to aggregate. Indeed, unfolding kinetics measured with the stopped-flow technique quantified the stabilizing effect of copper on McoA (1.5 kcal/mol) and revealed quite an uncommon observation further confirmed by light scattering and gel filtration chromatography: McoA aggregates in the presence of guanidinium hydrochloride, i.e., under unfolding conditions. The aggregation process results from the accumulation of a quasi-native state of McoA that binds to ANS and is the main determinant of the stability curve of McoA. Kinetic partitioning between aggregation and unfolding leads to a very low heat capacity change and determines a flat dependence of stability on temperature.
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Affiliation(s)
- André T Fernandes
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, 2781-901 Oeiras, Portugal
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Kayatekin C, Zitzewitz JA, Matthews CR. Zinc binding modulates the entire folding free energy surface of human Cu,Zn superoxide dismutase. J Mol Biol 2008; 384:540-55. [PMID: 18840448 DOI: 10.1016/j.jmb.2008.09.045] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2008] [Revised: 09/17/2008] [Accepted: 09/18/2008] [Indexed: 10/21/2022]
Abstract
Over 100 amino acid replacements in human Cu,Zn superoxide dismutase (SOD) are known to cause amyotrophic lateral sclerosis, a gain-of-function neurodegenerative disease that destroys motor neurons. Supposing that aggregates of partially folded states are primarily responsible for toxicity, we determined the role of the structurally important zinc ion in defining the folding free energy surface of dimeric SOD by comparing the thermodynamic and kinetic folding properties of the zinc-free and zinc-bound forms of the protein. The presence of zinc was found to decrease the free energies of a peptide model of the unfolded monomer, a stable variant of the folded monomeric intermediate, and the folded dimeric species. The unfolded state binds zinc weakly with a micromolar dissociation constant, and the folded monomeric intermediate and the native dimeric form both bind zinc tightly, with subnanomolar dissociation constants. Coupled with the strong driving force for the subunit association reaction, the shift in the populations toward more well-folded states in the presence of zinc decreases the steady-state populations of higher-energy states in SOD under expected in vivo zinc concentrations (approximately nanomolar). The significant decrease in the population of partially folded states is expected to diminish their potential for aggregation and account for the known protective effect of zinc. The approximately 100-fold increase in the rate of folding of SOD in the presence of micromolar concentrations of zinc demonstrates a significant role for a preorganized zinc-binding loop in the transition-state ensemble for the rate-limiting monomer folding reaction in this beta-barrel protein.
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Affiliation(s)
- Can Kayatekin
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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39
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Abstract
Zinc bioinorganic chemistry has emphasized the role of the metal ion on the structure and function of the protein. There is, more recently, an increasing appreciation of the role of zinc proteins in a variety of human diseases. This critical review, aimed at both bioinorganic and medicinal chemists, shows how apparently widely-diverging diseases share the common mechanistic approaches of targeting the essential function of the metal ion to inhibit activity. Protein structure and function is briefly summarized in the context of its clinical relevance. The status of current and potential inhibitors is discussed along with the prospects for future developments (162 references).
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Affiliation(s)
- A I Anzellotti
- Department of Chemistry, Virginia Commonwealth University, PO Box 842006, Richmond, VA23284, USA
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40
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Rumfeldt JAO, Galvagnion C, Vassall KA, Meiering EM. Conformational stability and folding mechanisms of dimeric proteins. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 98:61-84. [PMID: 18602415 DOI: 10.1016/j.pbiomolbio.2008.05.004] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The folding of multisubunit proteins is of tremendous biological significance since the large majority of proteins exist as protein-protein complexes. Extensive experimental and computational studies have provided fundamental insights into the principles of folding of small monomeric proteins. Recently, important advances have been made in extending folding studies to multisubunit proteins, in particular homodimeric proteins. This review summarizes the equilibrium and kinetic theory and models underlying the quantitative analysis of dimeric protein folding using chemical denaturation, as well as the experimental results that have been obtained. Although various principles identified for monomer folding also apply to the folding of dimeric proteins, the effects of subunit association can manifest in complex ways, and are frequently overlooked. Changes in molecularity typically give rise to very different overall folding behaviour than is observed for monomeric proteins. The results obtained for dimers have provided key insights pertinent to understanding biological assembly and regulation of multisubunit proteins. These advances have set the stage for future advances in folding involving protein-protein interactions for natural multisubunit proteins and unnatural assemblies involved in disease.
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Affiliation(s)
- Jessica A O Rumfeldt
- Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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41
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Multistate folding of a hyperthermostable Fe-superoxide dismutase (TcSOD) in guanidinium hydrochloride: The importance of the quaternary structure. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:445-54. [DOI: 10.1016/j.bbapap.2007.12.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2007] [Revised: 11/15/2007] [Accepted: 12/03/2007] [Indexed: 11/22/2022]
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42
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Durão P, Chen Z, Fernandes AT, Hildebrandt P, Murgida DH, Todorovic S, Pereira MM, Melo EP, Martins LO. Copper incorporation into recombinant CotA laccase from Bacillus subtilis: characterization of fully copper loaded enzymes. J Biol Inorg Chem 2007; 13:183-93. [PMID: 17957391 DOI: 10.1007/s00775-007-0312-0] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Accepted: 10/04/2007] [Indexed: 11/26/2022]
Abstract
The copper content of recombinant CotA laccase from Bacillus subtilis produced by Escherichia coli cells is shown to be strongly dependent on the presence of copper and oxygen in the culture media. In copper-supplemented media, a switch from aerobic to microaerobic conditions leads to the synthesis of a recombinant holoenzyme, while the maintenance of aerobic conditions results in the synthesis of a copper-depleted population of proteins. Strikingly, cells grown under microaerobic conditions accumulate up to 80-fold more copper than aerobically grown cells. In vitro copper incorporation into apoenzymes was monitored by optical and electron paramagnetic resonance (EPR) spectroscopy. This analysis reveals that copper incorporation into CotA laccase is a sequential process, with the type 1 copper center being the first to be reconstituted, followed by the type 2 and the type 3 copper centers. The copper reconstitution of holoCotA derivatives depleted in vitro with EDTA results in the complete recovery of the native conformation as monitored by spectroscopic, kinetic and thermal stability analysis. However, the reconstitution of copper to apo forms produced in cultures under aerobic and copper-deficient conditions resulted in incomplete recovery of biochemical properties of the holoenzyme. EPR and resonance Raman data indicate that, presumably, folding in the presence of copper is indispensable for the correct structure of the trinuclear copper-containing site.
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Affiliation(s)
- Paulo Durão
- Universidade Nova de Lisboa, Av. Da República, 2781-901, Oeiras, Portugal
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43
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Wang J, Caruano-Yzermans A, Rodriguez A, Scheurmann JP, Slunt HH, Cao X, Gitlin J, Hart PJ, Borchelt DR. Disease-associated mutations at copper ligand histidine residues of superoxide dismutase 1 diminish the binding of copper and compromise dimer stability. J Biol Chem 2007; 282:345-52. [PMID: 17092942 PMCID: PMC2757151 DOI: 10.1074/jbc.m604503200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
A subset of superoxide dismutase 1 (Cu/Zn-SOD1) mutants that cause familial amyotrophic lateral sclerosis (FALS) have heightened reactivity with (-)ONOO and H(2)O(2) in vitro. This reactivity requires a copper ion bound in the active site and is a suggested mechanism of motor neuron injury. However, we have found that transgenic mice that express SOD1-H46R/H48Q, which combines natural FALS mutations at ligands for copper and which is inactive, develop motor neuron disease. Using a direct radioactive copper incorporation assay in transfected cells and the established tools of single crystal x-ray diffraction, we now demonstrate that this variant does not stably bind copper. We find that single mutations at copper ligands, including H46R, H48Q, and a quadruple mutant H46R/H48Q/H63G/H120G, also diminish the binding of radioactive copper. Further, using native polyacrylamide gel electrophoresis and a yeast two-hybrid assay, the binding of copper was found to be related to the formation of the stable dimeric enzyme. Collectively, our data demonstrate a relationship between copper and assembly of SOD1 into stable dimers and also define disease-causing SOD1 mutants that are unlikely to robustly produce toxic radicals via copper-mediated chemistry.
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Affiliation(s)
- Jiou Wang
- Department of Pathology, Johns Hopkins University, Baltimore, Maryland 21205
| | - Amy Caruano-Yzermans
- Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Angela Rodriguez
- Department of Biochemistry, South Texas Veterans Health Care System, The University of Texas San Antonio Health Sciences Center, San Antonio, Texas 78229
| | - Jonathan P. Scheurmann
- Department of Biochemistry, South Texas Veterans Health Care System, The University of Texas San Antonio Health Sciences Center, San Antonio, Texas 78229
| | - Hilda H. Slunt
- Department of Pathology, Johns Hopkins University, Baltimore, Maryland 21205
- Department of Neuroscience, Santa Fe Health Alzheimer’s Disease Research Center, McKnight Brain Institute, University of Florida, Gainesville, Florida 32611
| | - Xiaohang Cao
- Department of Biochemistry, South Texas Veterans Health Care System, The University of Texas San Antonio Health Sciences Center, San Antonio, Texas 78229
| | - Jonathan Gitlin
- Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110
| | - P. John Hart
- Department of Biochemistry, South Texas Veterans Health Care System, The University of Texas San Antonio Health Sciences Center, San Antonio, Texas 78229
- X-ray Crystallography Core Laboratory, South Texas Veterans Health Care System, The University of Texas San Antonio Health Sciences Center, San Antonio, Texas 78229
- Geriatric Research, Education, and Clinical Center, Department of Veteran’s Affairs, South Texas Veterans Health Care System, The University of Texas San Antonio Health Sciences Center, San Antonio, Texas 78229
| | - David R. Borchelt
- Department of Pathology, Johns Hopkins University, Baltimore, Maryland 21205
- Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland 21205
- Department of Neuroscience, Santa Fe Health Alzheimer’s Disease Research Center, McKnight Brain Institute, University of Florida, Gainesville, Florida 32611
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44
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Svensson AKE, Bilsel O, Kondrashkina E, Zitzewitz JA, Matthews CR. Mapping the folding free energy surface for metal-free human Cu,Zn superoxide dismutase. J Mol Biol 2006; 364:1084-102. [PMID: 17046019 DOI: 10.1016/j.jmb.2006.09.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Revised: 09/01/2006] [Accepted: 09/01/2006] [Indexed: 11/17/2022]
Abstract
Mutations at many different sites in the gene encoding human Cu,Zn superoxide dismutase (SOD) are known to be causative agents in amyotrophic lateral sclerosis (ALS). One explanation for the molecular basis of this pathology is the aggregation of marginally soluble, partially structured states whose populations are enhanced in the protein variants. As a benchmark for testing this hypothesis, the equilibrium and kinetic properties of the reversible folding reaction of a metal-free variant of SOD were investigated. Reversibility was achieved by replacing the two non-essential cysteine residues with non-oxidizable analogs, C6A/C111S, to produce apo-AS-SOD. The metal-free pseudo-wild-type protein is folded and dimeric in the absence of chemical denaturants, and its equilibrium folding behavior is well described by an apparent two-state mechanism involving the unfolded monomer and the native dimer. The apparent free energy of folding in the absence of denaturant and at standard state is -20.37(+/- 1.04) kcal (mol dimer)(-1). A global analysis of circular dichroism kinetic traces for both unfolding and refolding reactions, combined with results from small angle X-ray scattering and time-resolved fluorescence anisotropy measurements, supports a sequential mechanism involving the unfolded monomer, a folded monomeric intermediate, and the native dimer. The rate-limiting monomer folding reaction is followed by a near diffusion-limited self-association reaction to form the native dimer. The relative population of the folded monomeric intermediate is predicted not to exceed 0.5% at micromolar concentrations of protein under equilibrium and both strongly unfolding and refolding conditions for metal-free pseudo-wild-type SOD.
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Affiliation(s)
- Anna-Karin E Svensson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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