1
|
Cvekl A, Vijg J. Aging of the eye: Lessons from cataracts and age-related macular degeneration. Ageing Res Rev 2024; 99:102407. [PMID: 38977082 DOI: 10.1016/j.arr.2024.102407] [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: 03/11/2024] [Revised: 06/18/2024] [Accepted: 07/01/2024] [Indexed: 07/10/2024]
Abstract
Aging is the greatest risk factor for chronic human diseases, including many eye diseases. Geroscience aims to understand the effects of the aging process on these diseases, including the genetic, molecular, and cellular mechanisms that underlie the increased risk of disease over the lifetime. Understanding of the aging eye increases general knowledge of the cellular physiology impacted by aging processes at various biological extremes. Two major diseases, age-related cataract and age-related macular degeneration (AMD) are caused by dysfunction of the lens and retina, respectively. Lens transparency and light refraction are mediated by lens fiber cells lacking nuclei and other organelles, which provides a unique opportunity to study a single aging hallmark, i.e., loss of proteostasis, within an environment of limited metabolism. In AMD, local dysfunction of the photoreceptors/retinal pigmented epithelium/Bruch's membrane/choriocapillaris complex in the macula leads to the loss of photoreceptors and eventually loss of central vision, and is driven by nearly all the hallmarks of aging and shares features with Alzheimer's disease, Parkinson's disease, cardiovascular disease, and diabetes. The aging eye can function as a model for studying basic mechanisms of aging and, vice versa, well-defined hallmarks of aging can be used as tools to understand age-related eye disease.
Collapse
Affiliation(s)
- Ales Cvekl
- Departments of Genetics and Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Jan Vijg
- Departments of Genetics and Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| |
Collapse
|
2
|
Serebryany E, Martin RW, Takahashi GR. The Functional Significance of High Cysteine Content in Eye Lens γ-Crystallins. Biomolecules 2024; 14:594. [PMID: 38786000 PMCID: PMC11118217 DOI: 10.3390/biom14050594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 05/07/2024] [Accepted: 05/14/2024] [Indexed: 05/25/2024] Open
Abstract
Cataract disease is strongly associated with progressively accumulating oxidative damage to the extremely long-lived crystallin proteins of the lens. Cysteine oxidation affects crystallin folding, interactions, and light-scattering aggregation especially strongly due to the formation of disulfide bridges. Minimizing crystallin aggregation is crucial for lifelong lens transparency, so one might expect the ubiquitous lens crystallin superfamilies (α and βγ) to contain little cysteine. Yet, the Cys content of γ-crystallins is well above the average for human proteins. We review literature relevant to this longstanding puzzle and take advantage of expanding genomic databases and improved machine learning tools for protein structure prediction to investigate it further. We observe remarkably low Cys conservation in the βγ-crystallin superfamily; however, in γ-crystallin, the spatial positioning of Cys residues is clearly fine-tuned by evolution. We propose that the requirements of long-term lens transparency and high lens optical power impose competing evolutionary pressures on lens βγ-crystallins, leading to distinct adaptations: high Cys content in γ-crystallins but low in βB-crystallins. Aquatic species need more powerful lenses than terrestrial ones, which explains the high methionine content of many fish γ- (and even β-) crystallins. Finally, we discuss synergies between sulfur-containing and aromatic residues in crystallins and suggest future experimental directions.
Collapse
Affiliation(s)
- Eugene Serebryany
- Department of Physiology & Biophysics, Stony Brook University, SUNY, Stony Brook, NY 11794, USA
- Laufer Center for Physical & Quantitative Biology, Stony Brook University, SUNY, Stony Brook, NY 11794, USA
| | - Rachel W. Martin
- Department of Chemistry, UCI Irvine, Irvine, CA 92697-2025, USA
- Department of Molecular Biology & Biochemistry, UCI Irvine, Irvine, CA 92697-3900, USA
| | - Gemma R. Takahashi
- Department of Molecular Biology & Biochemistry, UCI Irvine, Irvine, CA 92697-3900, USA
| |
Collapse
|
3
|
Tovar-Ramírez ME, Schuth N, Rodríguez O, Kroll T, Saab-Rincon G, Costas M, Lampi K, Quintanar L. ATCUN-like Copper Site in βB2-Crystallin Plays a Protective Role in Cataract-Associated Aggregation. Inorg Chem 2023; 62:10592-10604. [PMID: 37379524 PMCID: PMC11156493 DOI: 10.1021/acs.inorgchem.3c00794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/30/2023]
Abstract
Cataract is the leading cause of blindness worldwide, and it is caused by crystallin damage and aggregation. Senile cataractous lenses have relatively high levels of metals, while some metal ions can directly induce the aggregation of human γ-crystallins. Here, we evaluated the impact of divalent metal ions in the aggregation of human βB2-crystallin, one of the most abundant crystallins in the lens. Turbidity assays showed that Pb2+, Hg2+, Cu2+, and Zn2+ ions induce the aggregation of βB2-crystallin. Metal-induced aggregation is partially reverted by a chelating agent, indicating the formation of metal-bridged species. Our study focused on the mechanism of copper-induced aggregation of βB2-crystallin, finding that it involves metal-bridging, disulfide-bridging, and loss of protein stability. Circular dichroism and electron paramagnetic resonance (EPR) revealed the presence of at least three Cu2+ binding sites in βB2-crystallin, one of them with spectroscopic features typical for Cu2+ bound to an amino-terminal copper and nickel (ATCUN) binding motif, which is found in Cu transport proteins. The ATCUN-like Cu binding site is located at the unstructured N-terminus of βB2-crystallin, and it could be modeled by a peptide with the first six residues in the protein sequence (NH2-ASDHQF-). Isothermal titration calorimetry indicates a nanomolar Cu2+ binding affinity for the ATCUN-like site. An N-truncated form of βB2-crystallin is more susceptible to Cu-induced aggregation and is less thermally stable, indicating a protective role for the ATCUN-like site. EPR and X-ray absorption spectroscopy studies reveal the presence of a copper redox active site in βB2-crystallin that is associated with metal-induced aggregation and formation of disulfide-bridged oligomers. Our study demonstrates metal-induced aggregation of βB2-crystallin and the presence of putative copper binding sites in the protein. Whether the copper-transport ATCUN-like site in βB2-crystallin plays a functional/protective role or constitutes a vestige from its evolution as a lens structural protein remains to be elucidated.
Collapse
Affiliation(s)
- Martin E. Tovar-Ramírez
- Department of Chemistry, Centro de Investigación y de Estudios Avanzados (Cinvestav), Mexico City, 07360, Mexico
| | - Nils Schuth
- Department of Chemistry, Centro de Investigación y de Estudios Avanzados (Cinvestav), Mexico City, 07360, Mexico
| | - Oscar Rodríguez
- Facultad de Química, Universidad Nacional Autónoma de México (UNAM), Mexico City, 04510, Mexico
| | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource (SSRL), SLAC National Accelerator Laboratory, Menlo Park, 94025, CA, USA
| | - Gloria Saab-Rincon
- Department of Biocatalysis and Cellular Engineering, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca, Morelos, 62210, Mexico
| | - Miguel Costas
- Facultad de Química, Universidad Nacional Autónoma de México (UNAM), Mexico City, 04510, Mexico
| | - Kirsten Lampi
- Integrative Biosciences, Oregon Health & Science University, Portland, Oregon, 97239, United States
| | - Liliana Quintanar
- Department of Chemistry, Centro de Investigación y de Estudios Avanzados (Cinvestav), Mexico City, 07360, Mexico
| |
Collapse
|
4
|
Rodríguez-Meza O, Palomino-Vizcaino G, Quintanar L, Costas M. Mercury ions impact the kinetic and thermal stabilities of human lens γ-crystallins via direct metal-protein interactions. J Inorg Biochem 2023; 242:112159. [PMID: 36827733 DOI: 10.1016/j.jinorgbio.2023.112159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 02/06/2023] [Accepted: 02/06/2023] [Indexed: 02/17/2023]
Abstract
Loss of metal homeostasis may be involved in several age-related diseases, such as cataracts. Cataracts are caused by the aggregation of lens proteins into light-scattering high molecular weight complexes that impair vision. Environmental exposure to heavy metals, such as mercury, is a risk factor for cataract development. Indeed, mercury ions induce the non-amyloid aggregation of human γC- and γS crystallins, while human γD-crystallin is not sensitive to this metal. Using Differential Scanning Calorimetry (DSC), we evaluate the impact of mercury ions on the kinetic stability of the three most abundant human γ-crystallins. The metal/crystallin interactions were characterized using Isothermal Titration Calorimetry (ITC). Human γD-crystallins exhibited kinetic stabilization due to the presence of mercury ions, despite its thermal stability being decreased. In contrast, human γC- and γS-crystallins are both, thermally and kinetically destabilized by this metal, consistent with their sensitivity to mercury-induced aggregation. The interaction of human γ-crystallins with mercury ions is highly exothermic and complex, since the protein interacts with the metal at more than three sites. The isolated domains of human γ-D and its variant with the H22Q mutation were also studied, revealing the importance of these regions in the mercury-induced stabilization by a direct metal-protein interaction.
Collapse
Affiliation(s)
- Oscar Rodríguez-Meza
- Laboratorio de Biofisicoquímica, Departamento de Fisicoquímica, Facultad de Química, Universidad Nacional Autónoma de México, CdMx 04510, Mexico
| | | | - Liliana Quintanar
- Departamento de Química, Centro de Investigación y Estudios Avanzados (Cinvestav), CdMx 07360, Mexico
| | - Miguel Costas
- Laboratorio de Biofisicoquímica, Departamento de Fisicoquímica, Facultad de Química, Universidad Nacional Autónoma de México, CdMx 04510, Mexico.
| |
Collapse
|
5
|
Palomino-Vizcaino G, Schuth N, Domínguez-Calva JA, Rodríguez-Meza O, Martínez-Jurado E, Serebryany E, King JA, Kroll T, Costas M, Quintanar L. Copper Reductase Activity and Free Radical Chemistry by Cataract-Associated Human Lens γ-Crystallins. J Am Chem Soc 2023; 145:6781-6797. [PMID: 36918380 DOI: 10.1021/jacs.2c13397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
Abstract
Cataracts are caused by high-molecular-weight aggregates of human eye lens proteins that scatter light, causing lens opacity. Metal ions have emerged as important potential players in the etiology of cataract disease, as human lens γ-crystallins are susceptible to metal-induced aggregation. Here, the interaction of Cu2+ ions with γD-, γC-, and γS-crystallins, the three most abundant γ-crystallins in the lens, has been evaluated. Cu2+ ions induced non-amyloid aggregation in all three proteins. Solution turbidimetry, sodium dodecyl sulfate poly(acrylamide) gel electrophoresis (SDS-PAGE), circular dichroism, and differential scanning calorimetry showed that the mechanism for Cu-induced aggregation involves: (i) loss of β-sheet structure in the N-terminal domain; (ii) decreased thermal and kinetic stability; (iii) formation of metal-bridged species; and (iv) formation of disulfide-bridged dimers. Isothermal titration calorimetry (ITC) revealed distinct Cu2+ binding affinities in the γ-crystallins. Electron paramagnetic resonance (EPR) revealed two distinct Cu2+ binding sites in each protein. Spin quantitation demonstrated the reduction of γ-crystallin-bound Cu2+ ions to Cu+ under aerobic conditions, while X-ray absorption spectroscopy (XAS) confirmed the presence of linear or trigonal Cu+ binding sites in γ-crystallins. Our EPR and XAS studies revealed that γ-crystallins' Cu2+ reductase activity yields a protein-based free radical that is likely a Tyr-based species in human γD-crystallin. This unique free radical chemistry carried out by distinct redox-active Cu sites in human lens γ-crystallins likely contributes to the mechanism of copper-induced aggregation. In the context of an aging human lens, γ-crystallins could act not only as structural proteins but also as key players for metal and redox homeostasis.
Collapse
Affiliation(s)
- Giovanni Palomino-Vizcaino
- Department of Chemistry, Centro de Investigación y de Estudios Avanzados (Cinvestav), Mexico City 07360, Mexico
| | - Nils Schuth
- Department of Chemistry, Centro de Investigación y de Estudios Avanzados (Cinvestav), Mexico City 07360, Mexico
| | - José A Domínguez-Calva
- Department of Chemistry, Centro de Investigación y de Estudios Avanzados (Cinvestav), Mexico City 07360, Mexico
| | - Oscar Rodríguez-Meza
- Laboratorio de Biofisicoquímica, Facultad de Química, Universidad Nacional Autónoma de México (UNAM), Mexico City 04510, Mexico
| | - Eduardo Martínez-Jurado
- Department of Chemistry, Centro de Investigación y de Estudios Avanzados (Cinvestav), Mexico City 07360, Mexico
| | - Eugene Serebryany
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, United States
| | - Jonathan A King
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, United States
| | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource (SSRL), SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Miguel Costas
- Laboratorio de Biofisicoquímica, Facultad de Química, Universidad Nacional Autónoma de México (UNAM), Mexico City 04510, Mexico
| | - Liliana Quintanar
- Department of Chemistry, Centro de Investigación y de Estudios Avanzados (Cinvestav), Mexico City 07360, Mexico
| |
Collapse
|
6
|
Manipulating polydispersity of lens β-crystallins using divalent cations demonstrates evidence of calcium regulation. Proc Natl Acad Sci U S A 2022; 119:e2212051119. [PMID: 36417439 PMCID: PMC9860307 DOI: 10.1073/pnas.2212051119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Crystallins comprise the protein-rich tissue of the eye lens. Of the three most common vertebrate subtypes, β-crystallins exhibit the widest degree of polydispersity due to their complex multimerization properties in situ. While polydispersity enables precise packing densities across the concentration gradient of the lens for vision, it is unclear why there is such a high degree of structural complexity within the β-crystallin subtype and what the role of this feature is in the lens. To investigate this, we first characterized β-crystallin polydispersity and then established a method to dynamically disrupt it in a process that is dependent on isoform composition and the presence of divalent cationic salts (CaCl2 or MgCl2). We used size-exclusion chromatography together with dynamic light scattering and mass spectrometry to show how high concentrations of divalent cations dissociate β-crystallin oligomers, reduce polydispersity, and shift the overall protein surface charge-properties that can be reversed when salts are removed. While the direct, physiological relevance of these divalent cations in the lens is still under investigation, our results support that specific isoforms of β-crystallin modulate polydispersity through multiple chemical equilibria and that this native state is disrupted by cation binding. This dynamic process may be essential to facilitating the molecular packing and optical function of the lens.
Collapse
|
7
|
Deamidation of the human eye lens protein γS-crystallin accelerates oxidative aging. Structure 2022; 30:763-776.e4. [PMID: 35338852 PMCID: PMC9081212 DOI: 10.1016/j.str.2022.03.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Revised: 12/14/2021] [Accepted: 03/01/2022] [Indexed: 11/23/2022]
Abstract
Cataract, a clouding of the eye lens from protein precipitation, affects millions of people every year. The lens proteins, the crystallins, show extensive post-translational modifications (PTMs) in cataractous lenses. The most common PTMs, deamidation and oxidation, promote crystallin aggregation; however, it is not clear precisely how these PTMs contribute to crystallin insolubilization. Here, we report six crystal structures of the lens protein γS-crystallin (γS): one of the wild-type and five of deamidated γS variants, from three to nine deamidation sites, after sample aging. The deamidation mutations do not change the overall fold of γS; however, increasing deamidation leads to accelerated disulfide-bond formation. Addition of deamidated sites progressively destabilized protein structure, and the deamidated variants display an increased propensity for aggregation. These results suggest that the deamidated variants are useful as models for accelerated aging; the structural changes observed provide support for redox activity of γS-crystallin in the lens.
Collapse
|
8
|
Affiliation(s)
- Roy Quinlan
- Biomedical Sciences, Department of Biosciences, The University of Durham, Upper Mountjoy Science Site, Durham, DH1 3LE, UK.
| | - Frank Giblin
- Biomedical Sciences Emeritus, Eye Research Institute, Oakland University, Rochester, MI, 48309, USA.
| |
Collapse
|
9
|
Jia ZK, Fu CX, Wang AL, Yao K, Chen XJ. Cataract-causing allele in CRYAA (Y118D) proceeds through endoplasmic reticulum stress in mouse model. Zool Res 2021; 42:300-309. [PMID: 33929105 PMCID: PMC8175955 DOI: 10.24272/j.issn.2095-8137.2020.354] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
As small heat shock proteins, α-crystallins function as molecular chaperones and inhibit the misfolding and aggregation of β/γ-crystallins. Genetic mutations of CRYAA are associated with protein aggregation and cataract occurrence. One possible process underlying cataract formation is that endoplasmic reticulum stress (ERS) induces the unfolded protein response (UPR), leading to apoptosis. However, the pathogenic mechanism related to this remains unexplored. Here, we successfully constructed a cataract-causing CRYAA (Y118D) mutant mouse model, in which the lenses of the CRYAA-Y118D mutant mice showed severe posterior rupture, abnormal morphological changes, and aberrant arrangement of crystallin fibers. Histological analysis was consistent with the clinical pathological characteristics. We also explored the pathogenic factors involved in cataract development through transcriptome analysis. In addition, based on key pathway analysis, up-regulated genes in CRYAA-Y118D mutant mice were implicated in the ERS-UPR pathway. This study showed that prolonged activation of the UPR pathway and severe stress response can cause proteotoxic and ERS-induced cell death in CRYAA-Y118D mutant mice.
Collapse
Affiliation(s)
- Zhe-Kun Jia
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China
| | - Chen-Xi Fu
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China
| | - Ai-Ling Wang
- Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310020, China
| | - Ke Yao
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China. E-mail:
| | - Xiang-Jun Chen
- Eye Center of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, China.,Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310020, China. E-mail:
| |
Collapse
|
10
|
Rocha MA, Sprague-Piercy MA, Kwok AO, Roskamp KW, Martin RW. Chemical Properties Determine Solubility and Stability in βγ-Crystallins of the Eye Lens. Chembiochem 2021; 22:1329-1346. [PMID: 33569867 PMCID: PMC8052307 DOI: 10.1002/cbic.202000739] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 12/17/2020] [Indexed: 11/10/2022]
Abstract
βγ-Crystallins are the primary structural and refractive proteins found in the vertebrate eye lens. Because crystallins are not replaced after early eye development, their solubility and stability must be maintained for a lifetime, which is even more remarkable given the high protein concentration in the lens. Aggregation of crystallins caused by mutations or post-translational modifications can reduce crystallin protein stability and alter intermolecular interactions. Common post-translational modifications that can cause age-related cataracts include deamidation, oxidation, and tryptophan derivatization. Metal ion binding can also trigger reduced crystallin solubility through a variety of mechanisms. Interprotein interactions are critical to maintaining lens transparency: crystallins can undergo domain swapping, disulfide bonding, and liquid-liquid phase separation, all of which can cause opacity depending on the context. Important experimental techniques for assessing crystallin conformation in the absence of a high-resolution structure include dye-binding assays, circular dichroism, fluorescence, light scattering, and transition metal FRET.
Collapse
Affiliation(s)
- Megan A. Rocha
- Department of Chemistry, University of California, Irvine, 1102 Natural Sciences 2, Irvine, CA 92697-2025 (USA)
| | - Marc A. Sprague-Piercy
- Department of Molecular Biology and Biochemistry, University of California Irvine, 3205 McGaugh Hall, Irvine, CA 92697-2525
| | - Ashley O. Kwok
- Department of Chemistry, University of California, Irvine, 1102 Natural Sciences 2, Irvine, CA 92697-2025 (USA)
| | - Kyle W. Roskamp
- Department of Chemistry, University of California, Irvine, 1102 Natural Sciences 2, Irvine, CA 92697-2025 (USA)
| | - Rachel W. Martin
- Department of Chemistry, University of California, Irvine, 1102 Natural Sciences 2, Irvine, CA 92697-2025 (USA)
- Department of Molecular Biology and Biochemistry, University of California Irvine, 3205 McGaugh Hall, Irvine, CA 92697-2525
| |
Collapse
|
11
|
Vetter CJ, Thorn DC, Wheeler SG, Mundorff CC, Halverson KA, Wales TE, Shinde UP, Engen JR, David LL, Carver JA, Lampi KJ. Cumulative deamidations of the major lens protein γS-crystallin increase its aggregation during unfolding and oxidation. Protein Sci 2020; 29:1945-1963. [PMID: 32697405 PMCID: PMC7454558 DOI: 10.1002/pro.3915] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Revised: 07/12/2020] [Accepted: 07/20/2020] [Indexed: 01/07/2023]
Abstract
Age-related lens cataract is the major cause of blindness worldwide. The mechanisms whereby crystallins, the predominant lens proteins, assemble into large aggregates that scatter light within the lens, and cause cataract, are poorly understood. Due to the lack of protein turnover in the lens, crystallins are long-lived. A major crystallin, γS, is heavily modified by deamidation, in particular at surface-exposed N14, N76, and N143 to introduce negative charges. In this present study, deamidated γS was mimicked by mutation with aspartate at these sites and the effect on biophysical properties of γS was assessed via dynamic light scattering, chemical and thermal denaturation, hydrogen-deuterium exchange, and susceptibility to disulfide cross-linking. Compared with wild type γS, a small population of each deamidated mutant aggregated rapidly into large, light-scattering species that contributed significantly to the total scattering. Under partially denaturing conditions in guanidine hydrochloride or elevated temperature, deamidation led to more rapid unfolding and aggregation and increased susceptibility to oxidation. The triple mutant was further destabilized, suggesting that the effects of deamidation were cumulative. Molecular dynamics simulations predicted that deamidation augments the conformational dynamics of γS. We suggest that these perturbations disrupt the native disulfide arrangement of γS and promote the formation of disulfide-linked aggregates. The lens-specific chaperone αA-crystallin was poor at preventing the aggregation of the triple mutant. It is concluded that surface deamidations cause minimal structural disruption individually, but cumulatively they progressively destabilize γS-crystallin leading to unfolding and aggregation, as occurs in aged and cataractous lenses.
Collapse
Affiliation(s)
- Calvin J. Vetter
- Integrative BiosciencesOregon Health & Science UniversityPortlandOregonUSA
| | - David C. Thorn
- Research School of Chemistry, College of ScienceThe Australian National UniversityActonAustralia
| | - Samuel G. Wheeler
- Integrative BiosciencesOregon Health & Science UniversityPortlandOregonUSA
| | - Charlie C. Mundorff
- Chemical Physiology & BiochemistryOregon Health & Science UniversityPortlandOregonUSA
- Department of Chemistry & Chemical BiologyNortheastern UniversityBostonMassachusettsUSA
| | - Kate A. Halverson
- Chemical Physiology & BiochemistryOregon Health & Science UniversityPortlandOregonUSA
| | - Thomas E. Wales
- Department of Chemistry & Chemical BiologyNortheastern UniversityBostonMassachusettsUSA
| | - Ujwal P. Shinde
- Chemical Physiology & BiochemistryOregon Health & Science UniversityPortlandOregonUSA
| | - John R. Engen
- Department of Chemistry & Chemical BiologyNortheastern UniversityBostonMassachusettsUSA
| | - Larry L. David
- Chemical Physiology & BiochemistryOregon Health & Science UniversityPortlandOregonUSA
| | - John A. Carver
- Research School of Chemistry, College of ScienceThe Australian National UniversityActonAustralia
| | - Kirsten J. Lampi
- Integrative BiosciencesOregon Health & Science UniversityPortlandOregonUSA
| |
Collapse
|
12
|
Roskamp KW, Azim S, Kassier G, Norton-Baker B, Sprague-Piercy MA, Miller RJD, Martin RW. Human γS-Crystallin-Copper Binding Helps Buffer against Aggregation Caused by Oxidative Damage. Biochemistry 2020; 59:2371-2385. [PMID: 32510933 DOI: 10.1021/acs.biochem.0c00293] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Divalent metal cations can play a role in protein aggregation diseases, including cataract. Here we compare the aggregation of human γS-crystallin, a key structural protein of the eye lens, via mutagenesis, ultraviolet light damage, and the addition of metal ions. All three aggregation pathways result in globular, amorphous-looking structures that do not elongate into fibers. We also investigate the molecular mechanism underlying copper(II)-induced aggregation. This work was motivated by the observation that zinc(II)-induced aggregation of γS-crystallin is driven by intermolecular bridging of solvent-accessible cysteine residues, while in contrast, copper(II)-induced aggregation of this protein is exacerbated by the removal of solvent-accessible cysteines via mutation. Here we find that copper(II)-induced aggregation results from a complex mechanism involving multiple interactions with the protein. The initial protein-metal interactions result in the reduction of Cu(II) to Cu(I) with concomitant oxidation of γS-crystallin. In addition to the intermolecular disulfides that represent a starting point for aggregation, intramolecular disulfides also occur in the cysteine loop, a region of the N-terminal domain that was previously found to mediate the early stages of cataract formation. This previously unobserved ability of γS-crystallin to transfer disulfides intramolecularly suggests that it may serve as an oxidation sink for the lens after glutathione levels have become depleted during aging. γS-Crystallin thus serves as the last line of defense against oxidation in the eye lens, a result that underscores the chemical functionality of this protein, which is generally considered to play a purely structural role.
Collapse
Affiliation(s)
- Kyle W Roskamp
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Sana Azim
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, Luruper Chaussee 149, Hamburg 22761, Germany
| | - Günther Kassier
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, Luruper Chaussee 149, Hamburg 22761, Germany
| | - Brenna Norton-Baker
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States.,Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, Luruper Chaussee 149, Hamburg 22761, Germany
| | - Marc A Sprague-Piercy
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, United States
| | - R J Dwyane Miller
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, Luruper Chaussee 149, Hamburg 22761, Germany.,Departments of Chemistry and Physics, University of Toronto, 80 St. George Street, Toronto, ON M5S 3H6, Canada
| | - Rachel W Martin
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States.,Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, United States
| |
Collapse
|
13
|
Fernández-Silva A, French-Pacheco L, Rivillas-Acevedo L, Amero C. Aggregation pathways of human γ D crystallin induced by metal ions revealed by time dependent methods. PeerJ 2020; 8:e9178. [PMID: 32566392 PMCID: PMC7295030 DOI: 10.7717/peerj.9178] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 04/22/2020] [Indexed: 12/17/2022] Open
Abstract
Cataract formation is a slow accumulative process due to protein aggregates promoted by different factors over time. Zinc and copper ions have been reported to induce the formation of aggregates opaque to light in the human gamma D crystallin (HγD) in a concentration and temperature dependent manner. In order to gain insight into the mechanism of metal-induced aggregation of HγD under conditions that mimic more closely the slow, accumulative process of the disease, we have studied the non-equilibrium process with the minimal metal dose that triggers HγD aggregation. Using a wide variety of biophysics techniques such as turbidimetry, dynamic light scattering, fluorescence, nuclear magnetic resonance and computational methods, we obtained information on the molecular mechanisms for the formation of aggregates. Zn(II) ions bind to different regions at the protein, probably with similar affinities. This binding induces a small conformational rearrangement within and between domains and aggregates via the formation of metal bridges without any detectable unfolded intermediates. In contrast, Cu(II)-induced aggregation includes a lag time, in which the N-terminal domain partially unfolds while the C-terminal domain and parts of the N-terminal domain remain in a native-like conformation. This partially unfolded intermediate is prone to form the high-molecular weight aggregates. Our results clearly show that different external factors can promote protein aggregation following different pathways.
Collapse
Affiliation(s)
- Arline Fernández-Silva
- Centro de Investigaciones Químicas, IICBA, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, Mexico
| | - Leidys French-Pacheco
- Centro de Investigaciones Químicas, IICBA, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, Mexico.,Centro de Investigación en Dinámica Celular, IICBA, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, Mexico
| | - Lina Rivillas-Acevedo
- Centro de Investigación en Dinámica Celular, IICBA, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, Mexico
| | - Carlos Amero
- Centro de Investigaciones Químicas, IICBA, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, Mexico
| |
Collapse
|
14
|
Puustinen MC, Sistonen L. Molecular Mechanisms of Heat Shock Factors in Cancer. Cells 2020; 9:cells9051202. [PMID: 32408596 PMCID: PMC7290425 DOI: 10.3390/cells9051202] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 05/08/2020] [Accepted: 05/09/2020] [Indexed: 12/12/2022] Open
Abstract
Malignant transformation is accompanied by alterations in the key cellular pathways that regulate development, metabolism, proliferation and motility as well as stress resilience. The members of the transcription factor family, called heat shock factors (HSFs), have been shown to play important roles in all of these biological processes, and in the past decade it has become evident that their activities are rewired during tumorigenesis. This review focuses on the expression patterns and functions of HSF1, HSF2, and HSF4 in specific cancer types, highlighting the mechanisms by which the regulatory functions of these transcription factors are modulated. Recently developed therapeutic approaches that target HSFs are also discussed.
Collapse
Affiliation(s)
- Mikael Christer Puustinen
- Cell Biology, Faculty of Science and Engineering, Åbo Akademi University, Tykistökatu 6, 20520 Turku, Finland;
- Turku Bioscience, University of Turku and Åbo Akademi University, Tykistökatu 6, 20520 Turku, Finland
| | - Lea Sistonen
- Cell Biology, Faculty of Science and Engineering, Åbo Akademi University, Tykistökatu 6, 20520 Turku, Finland;
- Turku Bioscience, University of Turku and Åbo Akademi University, Tykistökatu 6, 20520 Turku, Finland
- Correspondence: ; Tel.: +358-2215-3311
| |
Collapse
|
15
|
Roskamp KW, Paulson CN, Brubaker WD, Martin RW. Function and Aggregation in Structural Eye Lens Crystallins. Acc Chem Res 2020; 53:863-874. [PMID: 32271004 DOI: 10.1021/acs.accounts.0c00014] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Crystallins are transparent, refractive proteins that contribute to the focusing power of the vertebrate eye lens. These proteins are extremely soluble and resist aggregation for decades, even under crowded conditions. Crystallins have evolved to avoid strong interprotein interactions and have unusual hydration properties. Crystallin aggregation resulting from mutation, damage, or aging can lead to cataract, a disease state characterized by opacity of the lens.Different aggregation mechanisms can occur, following multiple pathways and leading to aggregates with varied morphologies. Studies of variant proteins found in individuals with childhood-onset cataract have provided insight into the molecular factors underlying crystallin stability and solubility. Modulation of exposed hydrophobic surface is critical, as is preventing specific intermolecular interactions that could provide nucleation sites for aggregation. Biophysical measurements and structural biology techniques are beginning to provide a detailed picture of how crystallins crowd into the lens, providing high refractivity while avoiding excessively tight binding that would lead to aggregation.Despite the central biological importance of refractivity, relatively few experimental measurements have been made for lens crystallins. Our work and that of others have shown that hydration is important to the high refractive index of crystallin proteins, as are interactions between pairs of aromatic residues and potentially other specific structural features.This Account describes our efforts to understand both the functional and disease states of vertebrate eye lens crystallins, particularly the γ-crystallins. We use a variety of biophysical techniques, notably NMR spectroscopy, to investigate crystallin stability and solubility. In the first section, we describe efforts to understand the relative stability and aggregation propensity of different γS-crystallin variants. The second section focuses on interactions of these proteins with the holdase chaperone αB-crystallin. The third, fourth, and fifth sections explore different modes of aggregation available to crystallin proteins, and the final section highlights the importance of refractive index and the sometimes conflicting demands of selection for refractivity and solubility.
Collapse
Affiliation(s)
- Kyle W. Roskamp
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Carolyn N. Paulson
- Institute for Therapeutics Discovery and Development, University of Minnesota, Minneapolis, Minnesota 55414, United States
| | - William D. Brubaker
- SRI International, 333 Ravenswood Avenue, Menlo Park, California 94025, United States
| | - Rachel W. Martin
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, United States
| |
Collapse
|