1
|
Guseman AJ, González JJ, Yang D, Gronenborn AM. Cumulative asparagine to aspartate deamidation fails to perturb γD-crystallin structure and stability. Protein Sci 2024; 33:e5120. [PMID: 39022918 PMCID: PMC11255865 DOI: 10.1002/pro.5120] [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: 01/30/2024] [Revised: 06/05/2024] [Accepted: 07/07/2024] [Indexed: 07/20/2024]
Abstract
Deamidation frequently is invoked as an important driver of crystallin aggregation and cataract formation. Here, we characterized the structural and biophysical consequences of cumulative Asn to Asp changes in γD-crystallin. Using NMR spectroscopy, we demonstrate that N- or C-terminal domain-confined or fully Asn to Asp changed γD-crystallin exhibits essentially the same 1H-15N HSQC spectrum as the wild-type protein, implying that the overall structure is retained. Only a very small thermodynamic destabilization for the overall Asn to Asp γD-crystallin variants was noted by chaotropic unfolding, and assessment of the colloidal stability, by measuring diffusion interaction parameters, yielded no substantive differences in association propensities. Furthermore, using molecular dynamics simulations, no significant changes in dynamics for proteins with Asn to Asp or iso-Asp changes were detected. Our combined results demonstrate that substitution of all Asn by Asp residues, reflecting an extreme case of deamidation, did not affect the structure and biophysical properties of γD-crystallin. This suggests that these changes alone cannot be the major determinant in driving cataract formation.
Collapse
Affiliation(s)
- Alex J. Guseman
- Department of Structural BiologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| | - Jeremy J. González
- Department of Structural BiologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| | - Darian Yang
- Department of Structural BiologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| | - Angela M. Gronenborn
- Department of Structural BiologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| |
Collapse
|
2
|
Hill JA, Nyathi Y, Horrell S, von Stetten D, Axford D, Owen RL, Beddard GS, Pearson AR, Ginn HM, Yorke BA. An ultraviolet-driven rescue pathway for oxidative stress to eye lens protein human gamma-D crystallin. Commun Chem 2024; 7:81. [PMID: 38600176 PMCID: PMC11006947 DOI: 10.1038/s42004-024-01163-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 03/27/2024] [Indexed: 04/12/2024] Open
Abstract
Human gamma-D crystallin (HGD) is a major constituent of the eye lens. Aggregation of HGD contributes to cataract formation, the leading cause of blindness worldwide. It is unique in its longevity, maintaining its folded and soluble state for 50-60 years. One outstanding question is the structural basis of this longevity despite oxidative aging and environmental stressors including ultraviolet radiation (UV). Here we present crystallographic structures evidencing a UV-induced crystallin redox switch mechanism. The room-temperature serial synchrotron crystallographic (SSX) structure of freshly prepared crystallin mutant (R36S) shows no post-translational modifications. After aging for nine months in the absence of light, a thiol-adduct (dithiothreitol) modifying surface cysteines is observed by low-dose SSX. This is shown to be UV-labile in an acutely light-exposed structure. This suggests a mechanism by which a major source of crystallin damage, UV, may also act as a rescuing factor in a finely balanced redox system.
Collapse
Affiliation(s)
- Jake A Hill
- School of Chemistry and Biosciences, University of Bradford, Richmond Road, Bradford, BD7 1DP, United Kingdom
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
| | - Yvonne Nyathi
- Faculty of Biological Sciences, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
| | - Sam Horrell
- Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, OX11 0DE, United Kingdom
| | - David von Stetten
- European Molecular Biology Laboratory, Notkestraße 85, 22607, Hamburg, Germany
| | - Danny Axford
- Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, OX11 0DE, United Kingdom
| | - Robin L Owen
- Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, OX11 0DE, United Kingdom
| | - Godfrey S Beddard
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom
- School of Chemistry, University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ, United Kingdom
| | - Arwen R Pearson
- HARBOR, Institute for Nanostructure and Solid State Physics, Hamburg, 22761, Germany
| | - Helen M Ginn
- HARBOR, Institute for Nanostructure and Solid State Physics, Hamburg, 22761, Germany.
- Center for Free-Electron Laser Science, CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607, Hamburg, Germany.
| | - Briony A Yorke
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, United Kingdom.
| |
Collapse
|
3
|
Heath SL, Guseman AJ, Gronenborn AM, Horne WS. Probing effects of site-specific aspartic acid isomerization on structure and stability of GB1 through chemical protein synthesis. Protein Sci 2024; 33:e4883. [PMID: 38143426 PMCID: PMC10868458 DOI: 10.1002/pro.4883] [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: 11/15/2023] [Revised: 12/18/2023] [Accepted: 12/20/2023] [Indexed: 12/26/2023]
Abstract
Chemical modifications of long-lived proteins, such as isomerization and epimerization, have been evoked as prime triggers for protein-damage related diseases. Deamidation of Asn residues, which results in formation of a mixture of l- and d-Asp and isoAsp via an intermediate aspartyl succinimide, can result in the disruption of cellular proteostasis and toxic protein depositions. In contrast to extensive data on the biological prevalence and functional implications of aspartyl succinimide formation, much less is known about the impact of the resulting altered backbone composition on properties of individual proteins at a molecular level. Here, we report the total chemical synthesis, biophysical characterization, and NMR structural analysis of a series of variants of the B1 domain of protein G from Streptococcal bacteria (GB1) in which all possible Asp isomers as well as an aspartyl succinimide were individually incorporated at a defined position in a solvent-exposed loop. Subtle local structural effects were observed; however, these were accompanied by notable differences in thermodynamic folded stability. Surprisingly, the noncanonical backbone connectivity of d-isoAsp led to a variant that exhibited enhanced stability relative to the natural protein.
Collapse
Affiliation(s)
- Shelby L. Heath
- Department of ChemistryUniversity of PittsburghPittsburghPennsylvaniaUSA
| | - Alex J. Guseman
- Department of Structural BiologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| | - Angela M. Gronenborn
- Department of ChemistryUniversity of PittsburghPittsburghPennsylvaniaUSA
- Department of Structural BiologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| | - W. Seth Horne
- Department of ChemistryUniversity of PittsburghPittsburghPennsylvaniaUSA
| |
Collapse
|
4
|
Kato K, Nakayoshi T, Kitamura Y, Kurimoto E, Oda A, Ishikawa Y. Identification of the Most Impactful Asparagine Residues for γS-Crystallin Aggregation by Deamidation. Biochemistry 2023. [PMID: 37155656 DOI: 10.1021/acs.biochem.3c00097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Crystallin aggregation in the eye lens is involved in the pathogenesis of cataracts. The aggregation is considered to be promoted by non-enzymatic post-translational modifications, such as the deamidation and stereoinversion of amino acid residues. Although in a previous study, the deamidated asparagine residues were detected in γS-crystallin in vivo, it is unclear which deamidated residues have the most impact on the aggregation under physiological conditions. In this study, we investigated the deamidation impacts of all Asn residues in γS-crystallin for the structural and aggregation properties utilizing deamidation mimetic mutants (N14D, N37D, N53D, N76D, and N143D). The structural impacts were investigated using circular dichroism analysis and molecular dynamics simulations, and the aggregation properties were analyzed by gel filtration chromatography and spectrophotometric methods. No significant structural impacts of all mutations were detected. However, the N37D mutation decreased thermal stability and changed some intermolecular hydrogen-bond formations. Aggregation analysis indicated that the superiority of the aggregation rate in each mutant varied with temperature. Deamidation at any Asn residues promoted γS-crystallin aggregation, and the deamidation at Asn37, Asn53, and Asn76 were suggested to be the most impactful in the formation of insoluble aggregations.
Collapse
Affiliation(s)
- Koichi Kato
- Faculty of Pharmaceutical Sciences, Shonan University of Medical Sciences, 16-48 Kamishinano, Totsuka-ku, Yokohama, Kanagawa 244-0806, Japan
- College of Pharmacy, Kinjo Gakuin University, 2-1723 Omori, Moriyama-ku, Nagoya, Aichi 463-8521, Japan
- Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya, Aichi 468-8503, Japan
| | - Tomoki Nakayoshi
- Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya, Aichi 468-8503, Japan
- Graduate School of Information Sciences, Hiroshima City University, 3-4-1 Ozukahigasi, Asaminami-ku, Hiroshima, Hiroshima 731-3194, Japan
| | - Yuki Kitamura
- College of Pharmacy, Kinjo Gakuin University, 2-1723 Omori, Moriyama-ku, Nagoya, Aichi 463-8521, Japan
- School of Medicine, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke-shi, Tochigi 329-0498, Japan
| | - Eiji Kurimoto
- Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya, Aichi 468-8503, Japan
| | - Akifumi Oda
- Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya, Aichi 468-8503, Japan
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yoshinobu Ishikawa
- Faculty of Pharmaceutical Sciences, Shonan University of Medical Sciences, 16-48 Kamishinano, Totsuka-ku, Yokohama, Kanagawa 244-0806, Japan
| |
Collapse
|
5
|
Quinlan RA, Clark JI. Insights into the biochemical and biophysical mechanisms mediating the longevity of the transparent optics of the eye lens. J Biol Chem 2022; 298:102537. [PMID: 36174677 PMCID: PMC9638808 DOI: 10.1016/j.jbc.2022.102537] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 09/20/2022] [Accepted: 09/22/2022] [Indexed: 11/18/2022] Open
Abstract
In the human eye, a transparent cornea and lens combine to form the "refracton" to focus images on the retina. This requires the refracton to have a high refractive index "n," mediated largely by extracellular collagen fibrils in the corneal stroma and the highly concentrated crystallin proteins in the cytoplasm of the lens fiber cells. Transparency is a result of short-range order in the spatial arrangement of corneal collagen fibrils and lens crystallins, generated in part by post-translational modifications (PTMs). However, while corneal collagen is remodeled continuously and replaced, lens crystallins are very long-lived and are not replaced and so accumulate PTMs over a lifetime. Eventually, a tipping point is reached when protein aggregation results in increased light scatter, inevitably leading to the iconic protein condensation-based disease, age-related cataract (ARC). Cataracts account for 50% of vision impairment worldwide, affecting far more people than other well-known protein aggregation-based diseases. However, because accumulation of crystallin PTMs begins before birth and long before ARC presents, we postulate that the lens protein PTMs contribute to a "cataractogenic load" that not only increases with age but also has protective effects on optical function by stabilizing lens crystallins until a tipping point is reached. In this review, we highlight decades of experimental findings that support the potential for PTMs to be protective during normal development. We hypothesize that ARC is preventable by protecting the biochemical and biophysical properties of lens proteins needed to maintain transparency, refraction, and optical function.
Collapse
Affiliation(s)
- Roy A Quinlan
- Department of Biosciences, Durham University, South Road Science Site, Durham, United Kingdom; Department of Biological Structure, University of Washington, Seattle, Washington, USA.
| | - John I Clark
- Department of Biological Structure, University of Washington, Seattle, Washington, USA.
| |
Collapse
|
6
|
Islam S, Do M, Frank BS, Hom GL, Wheeler S, Fujioka H, Wang B, Minocha G, Sell DR, Fan X, Lampi KJ, Monnier VM. α-Crystallin chaperone mimetic drugs inhibit lens γ-crystallin aggregation: potential role for cataract prevention. J Biol Chem 2022; 298:102417. [PMID: 36037967 PMCID: PMC9525908 DOI: 10.1016/j.jbc.2022.102417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 08/15/2022] [Accepted: 08/16/2022] [Indexed: 11/29/2022] Open
Abstract
Γ-Crystallins play a major role in age-related lens transparency. Their destabilization by mutations and physical chemical insults are associated with cataract formation. Therefore, drugs that increase their stability should have anticataract properties. To this end, we screened 2560 Federal Drug Agency–approved drugs and natural compounds for their ability to suppress or worsen H2O2 and/or heat-mediated aggregation of bovine γ-crystallins. The top two drugs, closantel (C), an antihelminthic drug, and gambogic acid (G), a xanthonoid, attenuated thermal-induced protein unfolding and aggregation as shown by turbidimetry fluorescence spectroscopy dynamic light scattering and electron microscopy of human or mouse recombinant crystallins. Furthermore, binding studies using fluorescence inhibition and hydrophobic pocket–binding molecule bis-8-anilino-1-naphthalene sulfonic acid revealed static binding of C and G to hydrophobic sites with medium-to-low affinity. Molecular docking to HγD and other γ-crystallins revealed two binding sites, one in the “NC pocket” (residues 50–150) of HγD and one spanning the “NC tail” (residues 56–61 to 168–174 in the C-terminal domain). Multiple binding sites overlap with those of the protective mini αA-crystallin chaperone MAC peptide. Mechanistic studies using bis-8-anilino-1-naphthalene sulfonic acid as a proxy drug showed that it bound to MAC sites, improved Tm of both H2O2 oxidized and native human gamma D, and suppressed turbidity of oxidized HγD, most likely by trapping exposed hydrophobic sites. The extent to which these drugs act as α-crystallin mimetics and reduce cataract progression remains to be demonstrated. This study provides initial insights into binding properties of C and G to γ-crystallins.
Collapse
Affiliation(s)
- Sidra Islam
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Michael Do
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Brett S Frank
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Grant L Hom
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Samuel Wheeler
- Dept of Integrative Biosciences, Oregon Health & Sciences University, Portland, OR 97239
| | - Hisashi Fujioka
- Cryo-EM Core Facility, School of Medicine, Case Western Reserve University, Case Western Reserve University, Cleveland, OH 44016
| | - Benlian Wang
- Center for Proteomics and Bioinformatics, Dept of Nutrition, Case Western Reserve University, Cleveland, OH 44106
| | - Geeta Minocha
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - David R Sell
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106
| | - Xingjun Fan
- Dept of Cell Biology and Anatomy, Augusta University, Georgia, GA 30912
| | - Kirsten J Lampi
- Dept of Integrative Biosciences, Oregon Health & Sciences University, Portland, OR 97239
| | - Vincent M Monnier
- Dept of Pathology and Biochemistry, Case Western Reserve University, Cleveland, OH 44106; Dept of Biochemistry, Case Western Reserve University, Cleveland OH 44106.
| |
Collapse
|
7
|
Norton-Baker B, Mehrabi P, Kwok AO, Roskamp KW, Rocha MA, Sprague-Piercy MA, von Stetten D, Miller RJD, Martin RW. 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] [MESH Headings] [Grants] [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
Affiliation(s)
- Brenna Norton-Baker
- Department of Chemistry, University of California, Irvine, CA 92697-2025, USA; Department for Atomically Resolved Dynamics, Max-Planck-Institute for Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Pedram Mehrabi
- Department for Atomically Resolved Dynamics, Max-Planck-Institute for Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany; Institute for Nanostructure and Solid-State Physics, Universität Hamburg, HARBOR, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Ashley O Kwok
- Department of Chemistry, University of California, Irvine, CA 92697-2025, USA
| | - Kyle W Roskamp
- Department of Chemistry, University of California, Irvine, CA 92697-2025, USA
| | - Megan A Rocha
- Department of Chemistry, University of California, Irvine, CA 92697-2025, USA
| | - Marc A Sprague-Piercy
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, USA
| | - David von Stetten
- European Molecular Biology Laboratory, Hamburg Unit C/O Deutsches Elektronen-Synchrotron, Hamburg, Germany
| | - R J Dwayne Miller
- 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, CA 92697-2025, USA; Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, USA.
| |
Collapse
|
8
|
Naturally occurring deamidated triosephosphate isomerase is a promising target for cell-selective therapy in cancer. Sci Rep 2022; 12:4028. [PMID: 35256749 PMCID: PMC8901631 DOI: 10.1038/s41598-022-08051-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 02/28/2022] [Indexed: 11/08/2022] Open
Abstract
Human triosephosphate isomerase (HsTIM) is a central glycolytic enzyme and is overexpressed in cancer cells with accelerated glycolysis. Triple-negative breast cancer is highly dependent on glycolysis and is typically treated with a combination of surgery, radiation therapy, and chemotherapy. Deamidated HsTIM was recently proposed as a druggable target. Although thiol-reactive drugs affect cell growth in deamidated HsTIM-complemented cells, the role of this protein as a selective target has not been demonstrated. To delve into the usefulness of deamidated HsTIM as a selective target, we assessed its natural accumulation in breast cancer cells. We found that deamidated HsTIM accumulates in breast cancer cells but not in noncancerous cells. The cancer cells are selectively programmed to undergo cell death with thiol-reactive drugs that induced the production of methylglyoxal (MGO) and advanced glycation-end products (AGEs). In vivo, a thiol-reactive drug effectively inhibits the growth of xenograft tumors with an underlying mechanism involving deamidated HsTIM. Our findings demonstrate the usefulness of deamidated HsTIM as target to develop new therapeutic strategies for the treatment of cancers and other pathologies in which this post translationally modified protein accumulates.
Collapse
|
9
|
Gronenborn AM. Meet the IUPAB councilor - Angela M. Gronenborn. Biophys Rev 2021; 13:835-838. [PMID: 35059003 PMCID: PMC8724357 DOI: 10.1007/s12551-021-00886-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 11/01/2021] [Indexed: 01/23/2023] Open
Abstract
As an incoming IUPAB Councilor, I have been asked to write a short commentary describing myself and my career in science. Throughout my scientific life, my interests have evolved from initially trying to understand the physical and chemical properties of small molecules toward unraveling biological systems. To that end, I now apply biophysical, biochemical and chemistry tools. Along my journey, I developed and applied nuclear magnetic resonance (NMR) spectroscopy methods to figure out how proteins work at the atomic level and this voyage took me from Germany, where I earned degrees in Physics and Chemistry, to the UK and back to Germany, finally dropping anchor in the USA, where I have led research programs at both the National Institutes of Health and the University of Pittsburgh. I am now the UPMC Rosalind Franklin Professor and Chair of the Department of Structural Biology, University of Pittsburgh School of Medicine, a Professor of Bioengineering, Swanson School of Engineering, and a Professor of Chemistry, Dietrich School of Arts and Sciences, University of Pittsburgh.
Collapse
Affiliation(s)
- Angela M. Gronenborn
- Department of Structural Biology, School of Medicine, and Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Biomedical Science Tower 3, Room 1051, 3501 Fifth Avenue, Pittsburgh, PA 15260 USA
| |
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
|