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Morris DL, Nyenhuis DA, Dean DN, Strub MP, Tjandra N. Observation of pH-Dependent Residual Structure in the Pmel17 Repeat Domain and the Implication for Its Amyloid Formation. Biochemistry 2023; 62:3222-3233. [PMID: 37917797 DOI: 10.1021/acs.biochem.3c00445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2023]
Abstract
The varying conformational states of amyloid-forming protein monomers can determine their fibrillation outcome. In this study, we utilize solution NMR and the paramagnetic relaxation enhancement (PRE) effect to observe monomer properties of the repeat domain (RPT) from a human functional amyloid, premelanosomal protein, Pmel17. After excision from the full-length protein, RPT can self-assemble into amyloid fibrils, functioning as a scaffold for melanin deposition. Here, we report possible conformational states of the short RPT (sRPT) isoform, which has been demonstrated to be a fibrillation nucleator. NMR experiments were performed to determine conformational differences in sRPT by comparing aggregation-prone vs nonaggregating solution conditions. We observed significant chemical shift perturbations localized to residues near the C-terminus, demonstrating that the local chemical environment of the amyloid core region is highly sensitive to changes in pH. Next, we introduced cysteine point mutations for the covalent attachment of PRE ligands to sRPT to facilitate the observation of intramolecular interactions. We also utilized solvent PRE molecules with opposing charges to measure changes in the electrostatic potential of sRPT in different pH environments. These observed PRE effects offer insight into initial molecular events that might promote intermolecular interactions, which can trigger fibrillation. Taken together, our results show that sRPT monomers adopt a conformation inconsistent with a fully random coil at neutral pH and undergo conformational changes at lower pH values. These observations highlight regulatory mechanisms via organelle-associated pH conditions that can affect the fibrillation activity of proteins like RPT.
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Affiliation(s)
- Daniel L Morris
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20814, United States
| | - David A Nyenhuis
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20814, United States
| | - Dexter N Dean
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20814, United States
| | - Marie-Paule Strub
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20814, United States
| | - Nico Tjandra
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20814, United States
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2
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Hodges ED, Chrystal PW, Footz T, Doucette LP, Noel NCL, Li Z, Walter MA, Allison WT. Disrupting the Repeat Domain of Premelanosome Protein (PMEL) Produces Dysamyloidosis and Dystrophic Ocular Pigment Reflective of Pigmentary Glaucoma. Int J Mol Sci 2023; 24:14423. [PMID: 37833870 PMCID: PMC10572516 DOI: 10.3390/ijms241914423] [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: 08/07/2023] [Revised: 09/11/2023] [Accepted: 09/14/2023] [Indexed: 10/15/2023] Open
Abstract
Pigmentary glaucoma has recently been associated with missense mutations in PMEL that are dominantly inherited and enriched in the protein's fascinating repeat domain. PMEL pathobiology is intriguing because PMEL forms functional amyloid in healthy eyes, and this PMEL amyloid acts to scaffold melanin deposition. This is an informative contradistinction to prominent neurodegenerative diseases where amyloid formation is neurotoxic and mutations cause a toxic gain of function called "amyloidosis". Preclinical animal models have failed to model this PMEL "dysamyloidosis" pathomechanism and instead cause recessively inherited ocular pigment defects via PMEL loss of function; they have not addressed the consequences of disrupting PMEL's repetitive region. Here, we use CRISPR to engineer a small in-frame mutation in the zebrafish homolog of PMEL that is predicted to subtly disrupt the protein's repetitive region. Homozygous mutant larvae displayed pigmentation phenotypes and altered eye morphogenesis similar to presumptive null larvae. Heterozygous mutants had disrupted eye morphogenesis and disrupted pigment deposition in their retinal melanosomes. The deficits in the pigment deposition of these young adult fish were not accompanied by any detectable glaucomatous changes in intraocular pressure or retinal morphology. Overall, the data provide important in vivo validation that subtle PMEL mutations can cause a dominantly inherited pigment pathology that aligns with the inheritance of pigmentary glaucoma patient pedigrees. These in vivo observations help to resolve controversy regarding the necessity of PMEL's repeat domain in pigmentation. The data foster an ongoing interest in an antithetical dysamyloidosis mechanism that, akin to the amyloidosis of devastating dementias, manifests as a slow progressive neurodegenerative disease.
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Affiliation(s)
- Elizabeth D. Hodges
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada; (E.D.H.); (P.W.C.)
- Faculty of Science, University of Alberta, Edmonton, AB T6G 2E9, Canada
| | - Paul W. Chrystal
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada; (E.D.H.); (P.W.C.)
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Tim Footz
- Department of Medical Genetics, University of Alberta, Edmonton, AB T6G 2R3, Canada (M.A.W.)
| | - Lance P. Doucette
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada; (E.D.H.); (P.W.C.)
| | - Nicole C. L. Noel
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada; (E.D.H.); (P.W.C.)
- Department of Medical Genetics, University of Alberta, Edmonton, AB T6G 2R3, Canada (M.A.W.)
- Institute of Ophthalmology, University College London, London EC1V 9EL, UK
| | - Zixuan Li
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada; (E.D.H.); (P.W.C.)
| | - Michael A. Walter
- Department of Medical Genetics, University of Alberta, Edmonton, AB T6G 2R3, Canada (M.A.W.)
| | - W. Ted Allison
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada; (E.D.H.); (P.W.C.)
- Department of Medical Genetics, University of Alberta, Edmonton, AB T6G 2R3, Canada (M.A.W.)
- Centre for Prions & Protein Folding Disease, University of Alberta, Edmonton, AB T6G 2M8, Canada
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Application of Amyloid-Based Hybrid Membranes in Drug Delivery. Polymers (Basel) 2023; 15:polym15061444. [PMID: 36987222 PMCID: PMC10052896 DOI: 10.3390/polym15061444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 03/07/2023] [Accepted: 03/13/2023] [Indexed: 03/15/2023] Open
Abstract
The properties of amyloid fibrils, e.g., unique structural characteristics and superior biocompatibility, make them a promising vehicle for drug delivery. Here, carboxymethyl cellulose (CMC) and whey protein isolate amyloid fibril (WPI-AF) were used to synthesize amyloid-based hybrid membranes as vehicles for the delivery of cationic and hydrophobic drugs (e.g., methylene blue (MB) and riboflavin (RF)). The CMC/WPI-AF membranes were synthesized via chemical crosslinking coupled with phase inversion. The zeta potential and scanning electron microscopy results revealed a negative charge and a pleated surface microstructure with a high content of WPI-AF. FTIR analysis showed that the CMC and WPI-AF were cross-linked via glutaraldehyde and the interacting forces between membrane and MB or RF was found to be electrostatic interaction and hydrogen bonding, respectively. Next, the in vitro drug release from membranes was monitored using UV-vis spectrophotometry. Additionally, two empirical models were used to analyze the drug release data and relevant rate constant and parameters were determined accordingly. Moreover, our results indicated that in vitro drug release rates depended on the drug–matrix interactions and transport mechanism, which could be controlled by altering the WPI-AF content in membrane. This research provides an excellent example of utilizing two-dimensional amyloid-based materials for drug delivery.
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Dean DN, Lee JC. Monitoring Kinetics of pH-Dependent Aggregation and Disaggregation of the Pmel17 Repeat Domain. Methods Mol Biol 2023; 2551:79-93. [PMID: 36310198 DOI: 10.1007/978-1-0716-2597-2_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The premelanosomal protein (Pmel17) is a human functional amyloid that promotes pigmentation by serving as a scaffold for melanin polymerization. This occurs within the melanosome, where Pmel17 is first proteolyzed into smaller domain(s) that are responsible for fibril formation. Our work has shown that the Pmel17 repeat domain (RPT, residues 315-444) forms amyloid fibrils in vitro under acidic conditions similar to those found in melanosomes. Mechanistically, this is driven by the protonation of acidic residues, resulting in charge neutralization and subsequent aggregation. Interestingly, the deprotonation of acidic residues leads to rapid disaggregation, highlighting a reversible mechanism of fibril formation and dissolution thus far only observed for functional amyloid proteins. In this chapter, we describe how to monitor pH-dependent RPT aggregation and disaggregation using extrinsic thioflavin-T and intrinsic tryptophan fluorescence, respectively. These methods can also be adapted more broadly to investigate the reversibility of other amyloid systems, both functional and pathogenic.
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Affiliation(s)
- Dexter N Dean
- The Laboratory of Protein Conformation and Dynamics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Jennifer C Lee
- The Laboratory of Protein Conformation and Dynamics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
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Quiñones-Ruiz T, Rosario-Alomar MF, Shanmugasundaram M, Ali MM, Lednev IK. Spontaneous Refolding of Amyloid Fibrils from One Polymorph to Another Caused by Changes in Environmental Hydrophobicity. Biochemistry 2022; 61:1456-1464. [PMID: 35786852 DOI: 10.1021/acs.biochem.2c00143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Here, we report a new phenomenon in which lysozyme fibrils formed in a solution of acetic acid spontaneously refold to a different polymorph through a disassembled intermediate upon the removal of acetic acid. The structural changes were revealed and characterized by deep-UV resonance Raman spectroscopy, nonresonance Raman spectroscopy, intrinsic tryptophan fluorescence spectroscopy, and atomic force microscopy. A PPII-like structure with highly solvent-exposed tryptophan residues predominates the intermediate aggregates before refolding to polymorph II fibrils. Furthermore, the disulfide (SS) bonds undergo significant rearrangements upon the removal of acetic acid from the lysozyme fibril environment. The main SS bond conformation changes from gauche-gauche-trans in polymorph I to gauche-gauche-gauche in polymorph II. Changing the hydrophobicity of the fibril environment was concluded to be the decisive factor causing the spontaneous refolding of lysozyme fibrils from one polymorph to another upon the removal of acetic acid. Potential biological implications of the discovered phenomenon are discussed.
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Affiliation(s)
- Tatiana Quiñones-Ruiz
- Department of Chemistry, University at Albany, SUNY, Albany, New York 12222, United States
| | | | | | - Muhammad M Ali
- Department of Chemistry, University at Albany, SUNY, Albany, New York 12222, United States
| | - Igor K Lednev
- Department of Chemistry, University at Albany, SUNY, Albany, New York 12222, United States
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Dean DN, Lee JC. Purification and characterization of an amyloidogenic repeat domain from the functional amyloid Pmel17. Protein Expr Purif 2021; 187:105944. [PMID: 34293440 DOI: 10.1016/j.pep.2021.105944] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 07/16/2021] [Accepted: 07/17/2021] [Indexed: 01/15/2023]
Abstract
The pre-melanosomal protein (Pmel17) is a human functional amyloid that supports melanin biosynthesis within melanocytes. This occurs in the melanosome, a membrane-bound organelle with an acidic intraluminal pH. The repeat region of Pmel17 (RPT, residues 315-444) has been previously shown to form amyloid aggregates under acidic melanosomal conditions, but not under neutral cytosolic conditions, when expressed and purified using a C-terminal hexa-histidine tag (RPT-His). Given the importance of protonation states in RPT-His aggregation, we questioned whether the histidine tag influenced the pH-dependent behavior. In this report, we generated a tagless RPT by inserting a tobacco etch virus (TEV) protease recognition sequence (ENLYGQ(G/S)) immediately upstream of a native glycine residue at position 312 in Pmel17. After purification of the fusion construct using a histidine tag, cleavage with TEV protease generated a fully native RPT (nRPT) spanning resides 312-444. We characterized the aggregation of nRPT, which formed amyloid fibrils under acidic conditions (pH ≤ 6) but not at neutral pH. Characterizing the morphologies of nRPT aggregates using transmission electron microscopy revealed a pH-dependent maturation from short, curved structures at pH 4 to paired, rod-like fibrils at pH 6. This was accompanied by a secondary structural transition from mixed random coil/β-sheet at pH 4 to canonical β-sheet at pH 6. We also show that pre-formed nRPT fibrils undergo disaggregation upon dilution into pH 7 buffer. More broadly, this strategy can be utilized to generate native amyloidogenic domains from larger proteins by utilizing intrinsic N-terminal glycine or serine residues.
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Affiliation(s)
- Dexter N Dean
- Laboratory of Protein Conformation and Dynamics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, United States
| | - Jennifer C Lee
- Laboratory of Protein Conformation and Dynamics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, United States.
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Daskalov A, El Mammeri N, Lends A, Shenoy J, Lamon G, Fichou Y, Saad A, Martinez D, Morvan E, Berbon M, Grélard A, Kauffmann B, Ferber M, Bardiaux B, Habenstein B, Saupe SJ, Loquet A. Structures of Pathological and Functional Amyloids and Prions, a Solid-State NMR Perspective. Front Mol Neurosci 2021; 14:670513. [PMID: 34276304 PMCID: PMC8280340 DOI: 10.3389/fnmol.2021.670513] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Accepted: 05/26/2021] [Indexed: 12/20/2022] Open
Abstract
Infectious proteins or prions are a remarkable class of pathogens, where pathogenicity and infectious state correspond to conformational transition of a protein fold. The conformational change translates into the formation by the protein of insoluble amyloid aggregates, associated in humans with various neurodegenerative disorders and systemic protein-deposition diseases. The prion principle, however, is not limited to pathogenicity. While pathological amyloids (and prions) emerge from protein misfolding, a class of functional amyloids has been defined, consisting of amyloid-forming domains under natural selection and with diverse biological roles. Although of great importance, prion amyloid structures remain challenging for conventional structural biology techniques. Solid-state nuclear magnetic resonance (SSNMR) has been preferentially used to investigate these insoluble, morphologically heterogeneous aggregates with poor crystallinity. SSNMR methods have yielded a wealth of knowledge regarding the fundamentals of prion biology and have helped to solve the structures of several prion and prion-like fibrils. Here, we will review pathological and functional amyloid structures and will discuss some of the obtained structural models. We will finish the review with a perspective on integrative approaches combining solid-state NMR, electron paramagnetic resonance and cryo-electron microscopy, which can complement and extend our toolkit to structurally explore various facets of prion biology.
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Affiliation(s)
- Asen Daskalov
- CNRS, CBMN UMR 5348, IECB, University of Bordeaux, Pessac, France
| | - Nadia El Mammeri
- CNRS, CBMN UMR 5348, IECB, University of Bordeaux, Pessac, France
| | - Alons Lends
- CNRS, CBMN UMR 5348, IECB, University of Bordeaux, Pessac, France
| | | | - Gaelle Lamon
- CNRS, CBMN UMR 5348, IECB, University of Bordeaux, Pessac, France
| | - Yann Fichou
- CNRS, CBMN UMR 5348, IECB, University of Bordeaux, Pessac, France
| | - Ahmad Saad
- CNRS, CBMN UMR 5348, IECB, University of Bordeaux, Pessac, France
| | - Denis Martinez
- CNRS, CBMN UMR 5348, IECB, University of Bordeaux, Pessac, France
| | - Estelle Morvan
- CNRS, INSERM, IECB, UMS 3033, University of Bordeaux, Pessac, France
| | - Melanie Berbon
- CNRS, CBMN UMR 5348, IECB, University of Bordeaux, Pessac, France
| | - Axelle Grélard
- CNRS, CBMN UMR 5348, IECB, University of Bordeaux, Pessac, France
| | - Brice Kauffmann
- CNRS, INSERM, IECB, UMS 3033, University of Bordeaux, Pessac, France
| | | | | | | | - Sven J. Saupe
- CNRS, IBGC UMR 5095, University of Bordeaux, Bordeaux, France
| | - Antoine Loquet
- CNRS, CBMN UMR 5348, IECB, University of Bordeaux, Pessac, France
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8
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Functional Domains and Evolutionary History of the PMEL and GPNMB Family Proteins. Molecules 2021; 26:molecules26123529. [PMID: 34207849 PMCID: PMC8273697 DOI: 10.3390/molecules26123529] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 05/31/2021] [Accepted: 06/02/2021] [Indexed: 11/17/2022] Open
Abstract
The ancient paralogs premelanosome protein (PMEL) and glycoprotein nonmetastatic melanoma protein B (GPNMB) have independently emerged as intriguing disease loci in recent years. Both proteins possess common functional domains and variants that cause a shared spectrum of overlapping phenotypes and disease associations: melanin-based pigmentation, cancer, neurodegenerative disease and glaucoma. Surprisingly, these proteins have yet to be shown to physically or genetically interact within the same cellular pathway. This juxtaposition inspired us to compare and contrast this family across a breadth of species to better understand the divergent evolutionary trajectories of two related, but distinct, genes. In this study, we investigated the evolutionary history of PMEL and GPNMB in clade-representative species and identified TMEM130 as the most ancient paralog of the family. By curating the functional domains in each paralog, we identified many commonalities dating back to the emergence of the gene family in basal metazoans. PMEL and GPNMB have gained functional domains since their divergence from TMEM130, including the core amyloid fragment (CAF) that is critical for the amyloid potential of PMEL. Additionally, the PMEL gene has acquired the enigmatic repeat domain (RPT), composed of a variable number of imperfect tandem repeats; this domain acts in an accessory role to control amyloid formation. Our analyses revealed the vast variability in sequence, length and repeat number in homologous RPT domains between craniates, even within the same taxonomic class. We hope that these analyses inspire further investigation into a gene family that is remarkable from the evolutionary, pathological and cell biology perspectives.
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Hervás R, Oroz J. Mechanistic Insights into the Role of Molecular Chaperones in Protein Misfolding Diseases: From Molecular Recognition to Amyloid Disassembly. Int J Mol Sci 2020; 21:ijms21239186. [PMID: 33276458 PMCID: PMC7730194 DOI: 10.3390/ijms21239186] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 11/29/2020] [Accepted: 11/29/2020] [Indexed: 12/14/2022] Open
Abstract
Age-dependent alterations in the proteostasis network are crucial in the progress of prevalent neurodegenerative diseases, such as Alzheimer’s, Parkinson’s, or amyotrophic lateral sclerosis, which are characterized by the presence of insoluble protein deposits in degenerating neurons. Because molecular chaperones deter misfolded protein aggregation, regulate functional phase separation, and even dissolve noxious aggregates, they are considered major sentinels impeding the molecular processes that lead to cell damage in the course of these diseases. Indeed, members of the chaperome, such as molecular chaperones and co-chaperones, are increasingly recognized as therapeutic targets for the development of treatments against degenerative proteinopathies. Chaperones must recognize diverse toxic clients of different orders (soluble proteins, biomolecular condensates, organized protein aggregates). It is therefore critical to understand the basis of the selective chaperone recognition to discern the mechanisms of action of chaperones in protein conformational diseases. This review aimed to define the selective interplay between chaperones and toxic client proteins and the basis for the protective role of these interactions. The presence and availability of chaperone recognition motifs in soluble proteins and in insoluble aggregates, both functional and pathogenic, are discussed. Finally, the formation of aberrant (pro-toxic) chaperone complexes will also be disclosed.
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Affiliation(s)
- Rubén Hervás
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA;
| | - Javier Oroz
- Rocasolano Institute for Physical Chemistry, Spanish National Research Council (IQFR-CSIC), Serrano 119, E-28006 Madrid, Spain
- Correspondence: ; Tel.: +34-915619400
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Tian X, Cui Z, Liu S, Zhou J, Cui R. Melanosome transport and regulation in development and disease. Pharmacol Ther 2020; 219:107707. [PMID: 33075361 DOI: 10.1016/j.pharmthera.2020.107707] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 10/10/2020] [Accepted: 10/13/2020] [Indexed: 02/06/2023]
Abstract
Melanosomes are specialized membrane-bound organelles that synthesize and organize melanin, ultimately providing color to the skin, hair, and eyes. Disorders in melanogenesis and melanosome transport are linked to pigmentary diseases, such as Hermansky-Pudlak syndrome, Chediak-Higashi syndrome, and Griscelli syndrome. Clinical cases of these pigmentary diseases shed light on the molecular mechanisms that control melanosome-related pathways. However, only an improved understanding of melanogenesis and melanosome transport will further the development of diagnostic and therapeutic approaches. Herein, we review the current literature surrounding melanosomes with particular emphasis on melanosome membrane transport and cytoskeleton-mediated melanosome transport. We also provide perspectives on melanosome regulatory mechanisms which include hormonal action, inflammation, autophagy, and organelle interactions.
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Affiliation(s)
- Xiaoyu Tian
- Institute of Biomedical Sciences, Shandong Provincial Key Laboratory of Animal Resistance Biology, Collaborative Innovation Center of Cell Biology in Universities of Shandong, College of Life Sciences, Shandong Normal University, Jinan 250014, China
| | - Ziyong Cui
- Harvard College, Cambridge, MA 02138, United States of America
| | - Song Liu
- Institute of Biomedical Sciences, Shandong Provincial Key Laboratory of Animal Resistance Biology, Collaborative Innovation Center of Cell Biology in Universities of Shandong, College of Life Sciences, Shandong Normal University, Jinan 250014, China
| | - Jun Zhou
- Institute of Biomedical Sciences, Shandong Provincial Key Laboratory of Animal Resistance Biology, Collaborative Innovation Center of Cell Biology in Universities of Shandong, College of Life Sciences, Shandong Normal University, Jinan 250014, China; State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin 300071, China.
| | - Rutao Cui
- Skin Disease Research Institute, The 2nd Hospital, Zhejiang University, Hangzhou 310058, China.
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Dean DN, Lee JC. Modulating functional amyloid formation via alternative splicing of the premelanosomal protein PMEL17. J Biol Chem 2020; 295:7544-7553. [PMID: 32277052 PMCID: PMC7247297 DOI: 10.1074/jbc.ra120.013012] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 04/07/2020] [Indexed: 12/30/2022] Open
Abstract
The premelanosomal protein (PMEL17) forms functional amyloid fibrils involved in melanin biosynthesis. Multiple PMEL17 isoforms are produced, two of which arise from excision of a cryptic intron within the amyloid-forming repeat (RPT) domain, leading to long (lRPT) and short (sRPT) isoforms with 10 and 7 imperfect repeats, respectively. Both lRPT and sRPT isoforms undergo similar pH-dependent mechanisms of amyloid formation and fibril dissolution. Here, using human PMEL17, we tested the hypothesis that the minor, but more aggregation-prone, sRPT facilitates amyloid formation of lRPT. We observed that cross-seeding by sRPT fibrils accelerates the rate of lRPT aggregation, resulting in propagation of an sRPT-like twisted fibril morphology, unlike the rodlike structure that lRPT normally adopts. This templating was specific, as the reversed reaction inhibited sRPT fibril formation. Despite displaying ultrastructural differences, self- and cross-seeded lRPT fibrils had a similar β-sheet structured core, revealed by Raman spectroscopy, limited-proteolysis, and fibril disaggregation experiments, suggesting the fibril twist is modulated by N-terminal residues outside the amyloid core. Interestingly, bioinformatics analysis of PMEL17 homologs from other mammals uncovered that long and short RPT isoforms are conserved among members of this phylogenetic group. Collectively, our results indicate that the short isoform of RPT serves as a "nucleator" of PMEL17 functional amyloid formation, mirroring how bacterial functional amyloids assemble during biofilm formation. Whereas bacteria regulate amyloid assembly by using individual genes within the same operon, we propose that the modulation of functional amyloid formation in higher organisms can be accomplished through alternative splicing.
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Affiliation(s)
- Dexter N Dean
- Laboratory of Protein Conformation and Dynamics, Biochemistry and Biophysics Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20892
| | - Jennifer C Lee
- Laboratory of Protein Conformation and Dynamics, Biochemistry and Biophysics Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20892.
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12
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Shin JH, Le NTK, Jang H, Lee T, Kang K. Supramolecular Regulation of Polydopamine Formation by Amyloid Fibers. Chemistry 2020; 26:5500-5507. [PMID: 32092201 DOI: 10.1002/chem.202000437] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 02/19/2020] [Indexed: 11/10/2022]
Abstract
Polydopamine (PD) and melanin species are chemically complex systems, the formation and properties of which are incompletely understood. Inspired by the role of functional amyloids in melanin biosynthesis, this paper examines the influences of the supramolecular structure of amyloids on oxidative polymerization of dopamine. Kinetic analyses on the formation of PD species in the presence of hen egg white lysozyme (HEWL) fibers or soluble HEWL revealed that both forms gave rise to the total quantity of PD species, but the rate of their formation could be accelerated only by the amyloid form. PD species formed with HEWL fibers showed a morphology of bundled fibers, whereas those with soluble HEWL had a mesh-like structure. Amyloid fibers of recombinant Pmel17 had properties similar to those of HEWL fibers in modulating PD formation. The results presented here suggest how nature designs functionality with an amyloid structure and can help understand and engineer chemistries of other functional amyloids.
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Affiliation(s)
- J H Shin
- Department of Applied Chemistry, Kyung Hee University, 1732 Deogyoung-daero, Yongin, Gyeonggi, 17104, Republic of Korea
| | - Nghia T K Le
- Department of Applied Chemistry, Kyung Hee University, 1732 Deogyoung-daero, Yongin, Gyeonggi, 17104, Republic of Korea
| | - Hongje Jang
- Department of Chemistry, Kwangwoon University, 20 Gwangwoon-ro, Nowon-gu, Seoul, 01897, Republic of Korea
| | - Taehoon Lee
- Department of Applied Chemistry, Kyung Hee University, 1732 Deogyoung-daero, Yongin, Gyeonggi, 17104, Republic of Korea
| | - Kyungtae Kang
- Department of Applied Chemistry, Kyung Hee University, 1732 Deogyoung-daero, Yongin, Gyeonggi, 17104, Republic of Korea
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13
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Lahola-Chomiak AA, Footz T, Nguyen-Phuoc K, Neil GJ, Fan B, Allen KF, Greenfield DS, Parrish RK, Linkroum K, Pasquale LR, Leonhardt RM, Ritch R, Javadiyan S, Craig JE, Allison WT, Lehmann OJ, Walter MA, Wiggs JL. Non-Synonymous variants in premelanosome protein (PMEL) cause ocular pigment dispersion and pigmentary glaucoma. Hum Mol Genet 2019; 28:1298-1311. [PMID: 30561643 DOI: 10.1093/hmg/ddy429] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 12/04/2018] [Accepted: 12/12/2018] [Indexed: 01/25/2023] Open
Abstract
Pigmentary glaucoma (PG) is a common glaucoma subtype that results from release of pigment from the iris, called pigment dispersion syndrome (PDS), and its deposition throughout the anterior chamber of the eye. Although PG has a substantial heritable component, no causative genes have yet been identified. We used whole exome sequencing of two independent pedigrees to identify two premelanosome protein (PMEL) variants associated with heritable PDS/PG. PMEL encodes a key component of the melanosome, the organelle essential for melanin synthesis, storage and transport. Targeted screening of PMEL in three independent cohorts (n = 394) identified seven additional PDS/PG-associated non-synonymous variants. Five of the nine variants exhibited defective processing of the PMEL protein. In addition, analysis of PDS/PG-associated PMEL variants expressed in HeLa cells revealed structural changes to pseudomelanosomes indicating altered amyloid fibril formation in five of the nine variants. Introduction of 11-base pair deletions to the homologous pmela in zebrafish by the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 method caused profound pigmentation defects and enlarged anterior segments in the eye, further supporting PMEL's role in ocular pigmentation and function. Taken together, these data support a model in which missense PMEL variants represent dominant negative mutations that impair the ability of PMEL to form functional amyloid fibrils. While PMEL mutations have previously been shown to cause pigmentation and ocular defects in animals, this research is the first report of mutations in PMEL causing human disease.
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Affiliation(s)
| | - Tim Footz
- Department of Medical Genetics, University of Alberta, Edmonton AB, Canada
| | - Kim Nguyen-Phuoc
- Department of Medical Genetics, University of Alberta, Edmonton AB, Canada
| | - Gavin J Neil
- Department of Biological Sciences, University of Alberta, Edmonton AB, Canada
| | - Baojian Fan
- Ocular Genomics Institute and Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
| | - Keri F Allen
- Ocular Genomics Institute and Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
| | - David S Greenfield
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Palm Beach Gardens, FL, USA
| | - Richard K Parrish
- Anne Bates Leach Eye Hospital, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Kevin Linkroum
- Ocular Genomics Institute and Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
| | - Louis R Pasquale
- Ocular Genomics Institute and Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
| | - Ralf M Leonhardt
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA
| | - Robert Ritch
- Einhorn Clinical Research Center, New York Eye and Ear Infirmary of Mount Sinai, New York, NY, USA
| | - Shari Javadiyan
- Department of Ophthalmology, Flinders Medical Centre, Adelaide, South Australia, Australia
| | - Jamie E Craig
- Department of Ophthalmology, Flinders Medical Centre, Adelaide, South Australia, Australia
| | - W T Allison
- Department of Medical Genetics, University of Alberta, Edmonton AB, Canada.,Department of Biological Sciences, University of Alberta, Edmonton AB, Canada
| | - Ordan J Lehmann
- Department of Medical Genetics, University of Alberta, Edmonton AB, Canada.,Department of Ophthalmology, University of Alberta, Edmonton AB, Canada
| | - Michael A Walter
- Department of Medical Genetics, University of Alberta, Edmonton AB, Canada
| | - Janey L Wiggs
- Ocular Genomics Institute and Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
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14
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Dean DN, Lee JC. pH-Dependent fibril maturation of a Pmel17 repeat domain isoform revealed by tryptophan fluorescence. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2019; 1867:961-969. [PMID: 30716507 DOI: 10.1016/j.bbapap.2019.01.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2018] [Revised: 01/24/2019] [Accepted: 01/28/2019] [Indexed: 11/19/2022]
Abstract
The pre-melanosomal protein (Pmel17) aggregates within melanosomes to form functional amyloid fibrils that facilitate melanin polymerization. The repeat domain (RPT) of Pmel17 fibrillates under strict acidic melanosomal pH. Alternative splicing results in a shortened repeat domain (sRPT), which also forms amyloid fibrils. Here, we explored the effects of pH and protein concentration on sRPT aggregation by monitoring the intrinsic fluorescence of the sole tryptophan at position 381 (381W). 381W emission properties revealed changes of local environment polarity for sRPT fibrils formed at different pH. At pH 4, fibrils formed rapidly with no lag phase. A high 381W intensity was observed with a slight blue shift (10 nm). These fibrils underwent further structural rearrangements at intermediate pH (5-6), mirroring that of melanosome maturation, which initiates at pH 4 and increases to near neutral pH. In contrast, typical sigmoidal kinetics were observed at pH 6 with slower rates and 381W exhibited quenched emission. Interestingly, biphasic kinetics were observed at pH 5 in a protein concentration-dependent manner. A large 381W blue shift (23 nm) was measured, indicating a more hydrophobic environment for fibrils made at pH 5. Consistent with 381W fluorescence, Raman spectroscopy revealed molecular level perturbations in sRPT fibrils that were not evident from circular dichroism, transmission electron microscopy, or limited proteolysis analysis. Finally, sRPT fibrils did not form at pH ≥7 and preformed fibrils rapidly disaggregated under these solution conditions. Collectively, this work yields mechanistic insights into pH-dependent sRPT aggregation in the context of melanosome maturation.
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Affiliation(s)
- Dexter N Dean
- Laboratory of Protein Conformation and Dynamics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States
| | - Jennifer C Lee
- Laboratory of Protein Conformation and Dynamics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States.
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15
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Abstract
Structural differences in pathological and functional amyloid fibrils have been investigated by Raman microspectroscopy. Second-derivative analyses of amide-I and amide-III bands distinguish parallel in-register β-sheets from a β-solenoid. Further, spatially resolved Raman spectra reveal molecular heterogeneity in amyloid structures.
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Affiliation(s)
- Jessica D Flynn
- Laboratory of Protein Conformation and Dynamics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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16
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Why Study Functional Amyloids? Lessons from the Repeat Domain of Pmel17. J Mol Biol 2018; 430:3696-3706. [PMID: 29886018 DOI: 10.1016/j.jmb.2018.06.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 05/18/2018] [Accepted: 06/04/2018] [Indexed: 11/24/2022]
Abstract
One of the current challenges facing biomedical researchers is the need to develop new approaches in preventing amyloid formation that is associated with disease. While amyloid is generally considered detrimental to the cell, examples of amyloids that maintain a benign nature and serve a specific function exist. Here, we review our work on the repeat domain (RPT) of the functional amyloid Pmel17. Specifically, the RPT domain contributes in generating amyloid fibrils in melanosomes upon which melanin biosynthesis occurs. Amyloid formation of RPT was shown to be pH sensitive, aggregating only under acidic conditions associated with melanosomal pH. Furthermore, preformed fibrils rapidly dissolved at neutral pH to generate benign monomeric species. From a biological perspective, this unique reversible aggregation/disaggregation is a safeguard against an event of releasing RPT fibrils in the cytosol, resulting in rapid fibril unfolding and circumventing cytotoxicity. Understanding how melanosomes preserve a safe environment will address vital questions that remain unanswered with pathological amyloids.
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17
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Som Chaudhury S, Das Mukhopadhyay C. Functional amyloids: interrelationship with other amyloids and therapeutic assessment to treat neurodegenerative diseases. Int J Neurosci 2017; 128:449-463. [PMID: 29076790 DOI: 10.1080/00207454.2017.1398153] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Sutapa Som Chaudhury
- Centre for Healthcare Science and Technology, Indian Institute of Engineering Science and Technology, Shibpur, West Bengal, India
| | - Chitrangada Das Mukhopadhyay
- Centre for Healthcare Science and Technology, Indian Institute of Engineering Science and Technology, Shibpur, West Bengal, India
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18
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McGlinchey RP, Lee JC. Reversing the amyloid trend: Mechanism of fibril assembly and dissolution of the repeat domain from a human functional amyloid. Isr J Chem 2017; 57:613-621. [PMID: 28993712 PMCID: PMC5630176 DOI: 10.1002/ijch.201600080] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Amyloids are traditionally observed in the context of disease. However, there is growing momentum that these structures can serve a beneficial role where the amyloid carries out a specific function. These so called 'functional amyloids' have all the structural hallmarks of disease-associated amyloids, raising the question as to what differentiates a well-behaved benign amyloid from a lethally destructive one. Here, we review our work on the repeat domain (RPT) from Pmel17, an important functional amyloid involved in melanin biosynthesis. Particularly, we focused our attention on the unique reversible aggregation-disaggregation process of RPT that is controlled strictly by solution pH. This pH dependence of RPT amyloid formation functions as a switch to control fibril assembly and maintains the benign nature that is associated with functional amyloids.
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Affiliation(s)
- Ryan P. McGlinchey
- Laboratory of Protein Conformation and Dynamics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - Jennifer C. Lee
- Laboratory of Protein Conformation and Dynamics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, U.S.A
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19
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Louros NN, Iconomidou VA. Identification of an amyloid fibril forming segment of human Pmel17 repeat domain (RPT domain). Biopolymers 2017; 106:133-9. [PMID: 26394553 DOI: 10.1002/bip.22746] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 08/24/2015] [Accepted: 09/18/2015] [Indexed: 12/20/2022]
Abstract
Pmel17 is the major component of functional amyloid fibrils that have an important role during pigment deposition. Pmel17 polymerization is promoted within the mildly acidic conditions of melanosomes, organelles located in pigment-specific cells. A repeat domain (RPT domain) of Pmel17, rich in glutamic acid residues has been extensively associated with the formation of the fibrous matrix. Here, we examine the RPT domain of human Pmel17 in order to provide information on this mechanism. Specifically, we have identified an aggregation-prone peptide segment ((405) VSIVVLSGT(413) ), close to the C-terminal part of the RPT domain. Experimental results utilizing electron microscopy, X-ray fiber diffraction, Congo red staining and ATR FT-IR spectroscopy indicate that this peptide segment self-assembles forming fibrils with evident amyloidogenic properties. Conclusively, our results demonstrate that the (405) VSIVVLSGT(413) peptide segment possibly has an essential role in RPT domain fibrillogenesis.
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Affiliation(s)
- Nikolaos N Louros
- Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Athens, 157 01, Greece
| | - Vassiliki A Iconomidou
- Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Athens, 157 01, Greece
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20
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Dogra P, Bhattacharya M, Mukhopadhyay S. pH-Responsive Mechanistic Switch Regulates the Formation of Dendritic and Fibrillar Nanostructures of a Functional Amyloid. J Phys Chem B 2017; 121:412-419. [DOI: 10.1021/acs.jpcb.6b11281] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Priyanka Dogra
- Centre
for Protein Science Design and Engineering, ‡Department of Biological Sciences, and §Department of
Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, SAS Nagar 140306, Punjab, India
| | - Mily Bhattacharya
- Centre
for Protein Science Design and Engineering, ‡Department of Biological Sciences, and §Department of
Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, SAS Nagar 140306, Punjab, India
| | - Samrat Mukhopadhyay
- Centre
for Protein Science Design and Engineering, ‡Department of Biological Sciences, and §Department of
Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, SAS Nagar 140306, Punjab, India
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21
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Bissig C, Rochin L, van Niel G. PMEL Amyloid Fibril Formation: The Bright Steps of Pigmentation. Int J Mol Sci 2016; 17:ijms17091438. [PMID: 27589732 PMCID: PMC5037717 DOI: 10.3390/ijms17091438] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 08/12/2016] [Accepted: 08/22/2016] [Indexed: 02/06/2023] Open
Abstract
In pigment cells, melanin synthesis takes place in specialized organelles, called melanosomes. The biogenesis and maturation of melanosomes is initiated by an unpigmented step that takes place prior to the initiation of melanin synthesis and leads to the formation of luminal fibrils deriving from the pigment cell-specific pre-melanosomal protein (PMEL). In the lumen of melanosomes, PMEL fibrils optimize sequestration and condensation of the pigment melanin. Interestingly, PMEL fibrils have been described to adopt a typical amyloid-like structure. In contrast to pathological amyloids often associated with neurodegenerative diseases, PMEL fibrils represent an emergent category of physiological amyloids due to their beneficial cellular functions. The formation of PMEL fibrils within melanosomes is tightly regulated by diverse mechanisms, such as PMEL traffic, cleavage and sorting. These mechanisms revealed increasing analogies between the formation of physiological PMEL fibrils and pathological amyloid fibrils. In this review we summarize the known mechanisms of PMEL fibrillation and discuss how the recent understanding of physiological PMEL amyloid formation may help to shed light on processes involved in pathological amyloid formation.
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Affiliation(s)
- Christin Bissig
- Institut Curie, Paris Sciences et Lettres Research University, UMR144, Centre de Recherche, 26 rue d'ULM, Paris F-75231, France.
- Centre National de la Recherche Scientifique, UMR144, Paris F-75248, France.
| | - Leila Rochin
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3BX, UK.
| | - Guillaume van Niel
- Institut Curie, Paris Sciences et Lettres Research University, UMR144, Centre de Recherche, 26 rue d'ULM, Paris F-75231, France.
- Centre National de la Recherche Scientifique, UMR144, Paris F-75248, France.
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22
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Louros NN, Baltoumas FA, Hamodrakas SJ, Iconomidou VA. A β-solenoid model of the Pmel17 repeat domain: insights to the formation of functional amyloid fibrils. J Comput Aided Mol Des 2016; 30:153-64. [PMID: 26754844 DOI: 10.1007/s10822-015-9892-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 12/21/2015] [Indexed: 10/22/2022]
Abstract
Pmel17 is a multidomain protein involved in biosynthesis of melanin. This process is facilitated by the formation of Pmel17 amyloid fibrils that serve as a scaffold, important for pigment deposition in melanosomes. A specific luminal domain of human Pmel17, containing 10 tandem imperfect repeats, designated as repeat domain (RPT), forms amyloid fibrils in a pH-controlled mechanism in vitro and has been proposed to be essential for the formation of the fibrillar matrix. Currently, no three-dimensional structure has been resolved for the RPT domain of Pmel17. Here, we examine the structure of the RPT domain by performing sequence threading. The resulting model was subjected to energy minimization and validated through extensive molecular dynamics simulations. Structural analysis indicated that the RPT model exhibits several distinct properties of β-solenoid structures, which have been proposed to be polymerizing components of amyloid fibrils. The derived model is stabilized by an extensive network of hydrogen bonds generated by stacking of highly conserved polar residues of the RPT domain. Furthermore, the key role of invariant glutamate residues is proposed, supporting a pH-dependent mechanism for RPT domain assembly. Conclusively, our work attempts to provide structural insights into the RPT domain structure and to elucidate its contribution to Pmel17 amyloid fibril formation.
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Affiliation(s)
- Nikolaos N Louros
- Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, 157 01, Athens, Greece
| | - Fotis A Baltoumas
- Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, 157 01, Athens, Greece
| | - Stavros J Hamodrakas
- Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, 157 01, Athens, Greece
| | - Vassiliki A Iconomidou
- Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, 157 01, Athens, Greece.
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23
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Trusova VM. Protein Fibrillar Nanopolymers: Molecular-Level Insights into Their Structural, Physical and Mechanical Properties. ACTA ACUST UNITED AC 2015. [DOI: 10.1142/s1793048015300029] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Amyloid fibrils represent a generic class of mechanically strong and stable biomaterials with extremely advantageous properties. Although amyloids were initially associated only with severe neurological disorders, the role of these structures nowadays is shifting from health debilitating to highly beneficial both in biomedical and technological aspects. Intensive involvement of fibrillar assemblies into the wide range of pathogenic and functional processes strongly necessitate the molecular level characterization of the structural, physical and elastic features of protein nanofibrils. In the present contribution, we made an attempt to highlight the up-to-date progress in the understanding of amyloid properties from the polymer physics standpoint. The fundamental insights into protein fibril behavior are essential not only for development of therapeutic strategies to combat the protein misfolding disorders but also for rational and precise design of novel biodegradable protein-based nanopolymers.
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Affiliation(s)
- Valeriya M. Trusova
- Department of Nuclear and Medical Physics, V. N. Karazin Kharkiv National University, 4 Svobody Sq. Kharkiv 61072, Ukraine
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24
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Srisuk P, Correlo VM, Leonor IB, Palladino P, Reis RL. Effect of Melanomal Proteins on Sepia Melanin Assembly. J MACROMOL SCI B 2015. [DOI: 10.1080/00222348.2015.1103430] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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25
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Bordelon JR, Sanchez MI, Grichnik JM. Melanomagenesis: multifaceted attacks on the genome. Exp Dermatol 2015; 24:175-6. [PMID: 25421308 DOI: 10.1111/exd.12600] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/20/2014] [Indexed: 11/28/2022]
Affiliation(s)
- Jenna R Bordelon
- Department of Dermatology and Cutaneous Surgery, University of Miami Miller School of Medicine, Miami, FL, USA
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26
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Liu-Smith F, Poe C, Farmer PJ, Meyskens FL. Amyloids, melanins and oxidative stress in melanomagenesis. Exp Dermatol 2014; 24:171-4. [PMID: 25271672 DOI: 10.1111/exd.12559] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/24/2014] [Indexed: 12/26/2022]
Abstract
Melanoma has traditionally been viewed as an ultraviolet (UV) radiation-induced malignancy. While UV is a common inducing factor, other endogenous stresses such as metal ion accumulation or the melanin pigment itself may provide alternative pathways to melanoma progression. Eumelanosomes within melanoma often exhibit disrupted membranes and fragmented pigment which may be due to alterations in their amyloid-based striated matrix. The melanosomal amyloid can itself be toxic, especially in combination with reactive oxygen species (ROS) and reactive nitrogen species (RNS) generated by endogenous NADPH oxidase (NOX) and nitric oxide synthase (NOS) enzymes, a toxic mix that may initiate melanomagenesis. Further understanding of the loss of the melanosomal organization, the behaviour of the exposed melanin and the induction of ROS/RNS in melanomas may provide critical insights into this deadly disease.
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Affiliation(s)
- Feng Liu-Smith
- Department of Epidemiology, University of California School of Medicine, Irvine, CA, USA; Department of Medicine, University of California School of Medicine, Irvine, CA, USA; Chao Family Comprehensive Cancer Center, University of California School of Medicine, Irvine, CA, USA
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27
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Lysophospholipid-containing membranes modulate the fibril formation of the repeat domain of a human functional amyloid, pmel17. J Mol Biol 2014; 426:4074-4086. [PMID: 25451784 DOI: 10.1016/j.jmb.2014.10.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2014] [Revised: 09/23/2014] [Accepted: 10/08/2014] [Indexed: 11/23/2022]
Abstract
Pmel17 is an important protein for pigmentation in human skin and eyes. Proteolytic fragments from Pmel17 form fibrils upon which melanin is deposited in melanosomes. The repeat domain (RPT) derived from Pmel17 only forms fibrils under acidic melanosomal conditions. Here, we examined the effects of lipids on RPT aggregation to explore whether intramelanosomal vesicles can facilitate fibrillogenesis. Using transmission electron microscopy, circular dichroism, and fluorescence spectroscopy, we monitored fibril formation at the ultrastructural, secondary conformational, and local levels, respectively. Phospholipid vesicles and lysophospholipid (lysolipid) micelles were employed as membrane mimics. The surfactant-like lysolipids are particularly pertinent due to their high content in melanosomal membranes. Interestingly, RPT aggregation kinetics were influenced only by lysolipid-containing phospholipid vesicles. While both vesicles containing either anionic lysophosphatidylglycerol (LPG) or zwitterionic lysophosphatidylcholine (LPC) stimulate aggregation, LPG exerted a greater effect on reducing the apparent nucleation time. A detailed comparison showed distinct behaviors of LPG versus LPC monomers and micelles plausibly originating from their headgroup hydrogen bonding capabilities. Acceleration and retardation of aggregation were observed for LPG monomers and micelles, respectively. Because a specific interaction between LPG and RPT was identified by intrinsic W423 fluorescence and induced α-helical structure, it is inferred that binding of LPG near the C-terminal amyloid core initiates intermolecular association, whereas stabilization of α-helical conformation inhibits β-sheet formation. Contrastingly, LPC promotes RPT aggregation at both submicellar and micellar concentrations via non-specific binding with undetectable secondary structural change. Our findings suggest that protein-lysolipid interactions within melanosomes may regulate amyloid formation in vivo.
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28
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Wolkow N, Li Y, Maminishkis A, Song Y, Alekseev O, Iacovelli J, Song D, Lee JC, Dunaief JL. Iron upregulates melanogenesis in cultured retinal pigment epithelial cells. Exp Eye Res 2014; 128:92-101. [PMID: 25277027 DOI: 10.1016/j.exer.2014.09.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 09/12/2014] [Accepted: 09/26/2014] [Indexed: 12/20/2022]
Abstract
The purpose of our studies was to examine the relationship between iron and melanogenesis in retinal pigment epithelial cells, as prior observations had suggested that iron may promote melanogenesis. This relationship has potential clinical importance, as both iron overload and hyperpigmentation are associated with age-related macular degeneration (AMD). Human fetal retinal pigment epithelial cells and ARPE-19 cells were treated with iron in the form of ferric ammonium citrate, after which quantitative RT-PCR and electron microscopy were performed. Melanogenesis genes tyrosinase, tyrosinase-related protein 1, Hermansky-Pudlak Syndrome 3, premelanosome protein and dopachrome tautomerase were upregulated, as was the melanogenesis-controlling transcription factor, microphthalmia-associated transcription factor (MITF). Iron-treated cells had increased pigmentation and melanosome number. Multiple transcription factors upstream of MITF were upregulated by iron.
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Affiliation(s)
- Natalie Wolkow
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, 305 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104, USA
| | - Yafeng Li
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, 305 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104, USA
| | - Arvydas Maminishkis
- Section of Epithelial and Retinal Physiology and Disease, National Eye Institute, National Institutes of Health, Bldg. 10, Rm. 10B04, MSC 1861, 10 Center Drive, Bethesda, MD 20892, USA
| | - Ying Song
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, 305 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104, USA
| | - Oleg Alekseev
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, 305 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104, USA
| | - Jared Iacovelli
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, 305 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104, USA
| | - Delu Song
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, 305 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104, USA
| | - Jennifer C Lee
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, 305 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104, USA
| | - Joshua L Dunaief
- F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine at the University of Pennsylvania, 305 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104, USA.
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29
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Colvin MT, Andreas LB, Chou JJ, Griffin RG. Proton association constants of His 37 in the Influenza-A M218-60 dimer-of-dimers. Biochemistry 2014; 53:5987-94. [PMID: 25184631 PMCID: PMC4179598 DOI: 10.1021/bi5005393] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
![]()
The membrane protein M2 from influenza-A
forms a single-pass transmembrane
helix that assembles in lipid membrane as homotetramers whose primary
function is to act as a proton transporter for viral acidification.
A single residue, histidine 37 (His 37), is known to be responsible
for selectivity and plays an integral role in the protein’s
function. We report pH-dependent 15N MAS NMR spectra of
His 37 within the influenza-A proton conduction domain of M2, M218–60, which has been previously shown to be a fully
functional construct and was recently determined to adopt a dimer-of-dimers
structure in lipids. By extracting the ratio of [His]/[HisH+] as a function of pH, we obtained two doubly degenerate proton disassociation
constants, 7.63 ± 0.15 and 4.52 ± 0.15, despite a possible
maximum of four. We also report the 1HNε chemical shifts at pH 6.5 recorded at 60 kHz MAS in a CP-based 1H–15N spectrum. We were unable to detect
resonances indicative of direct proton sharing among His 37 side chains
when the tetramer is in the +2 state. In the neutral state, His 37
is exclusively in the τ tautomer, indicating that the δ
nitrogen is protonated solely as a function of pH. We also found that
the plot of [HisH+]/[His] as a function of pH is qualitatively
similar to previously reported proton conduction rates, indicating
that proton conduction rate is proportional to the level of histidine
protonation within the channel. Two-dimensional 13C–13C and 13C–15N correlations suggest
that at low pH multiple conformations are populated as the spectra
broaden and eventually disappear as the acidity is increased. A second
highly resolved state at low pH was not observed.
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Affiliation(s)
- Michael T Colvin
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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30
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McGlinchey RP, Jiang Z, Lee JC. Molecular origin of pH-dependent fibril formation of a functional amyloid. Chembiochem 2014; 15:1569-72. [PMID: 24954152 PMCID: PMC4142984 DOI: 10.1002/cbic.201402074] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Indexed: 11/08/2022]
Abstract
Fibrils derived from Pmel17 are functional amyloids upon which melanin is deposited. Fibrils of the repeat domain (RPT) of Pmel17 form under strict melanosomal pH (4.5-5.5) and completely dissolve at pH≥6. To determine which Glu residue is responsible for this reversibility, aggregation of single, double, and quadruple Ala and Gln mutants were examined by intrinsic Trp fluorescence, circular dichroism spectroscopy, and transmission electron microscopy. Charge neutralization of E404, E422, E425, or E430, which are located in the putative amyloid-forming region, modulated aggregation kinetics. Remarkably, the removal of a single negative charge at E422, one of 16 carboxylic acids, shifted the pH dependence by a full pH unit. Mutation at E404, E425, or E430 had little to no effect. We suggest that protonation at E422 is essential for initiating amyloid formation and that the other Glu residues play an allosteric role in fibril stability.
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Affiliation(s)
- Ryan P. McGlinchey
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892 (USA)
| | - Zhiping Jiang
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892 (USA)
| | - Jennifer C. Lee
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892 (USA)
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31
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Hauser CAE, Maurer-Stroh S, Martins IC. Amyloid-based nanosensors and nanodevices. Chem Soc Rev 2014; 43:5326-45. [DOI: 10.1039/c4cs00082j] [Citation(s) in RCA: 132] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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32
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Goldbourt A. Biomolecular magic-angle spinning solid-state NMR: recent methods and applications. Curr Opin Biotechnol 2013; 24:705-15. [DOI: 10.1016/j.copbio.2013.02.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2012] [Revised: 02/06/2013] [Accepted: 02/08/2013] [Indexed: 12/28/2022]
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33
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Jeon J, Lodge MS, Dawson BD, Ishigami M, Shewmaker F, Chen B. Superb resolution and contrast of transmission electron microscopy images of unstained biological samples on graphene-coated grids. Biochim Biophys Acta Gen Subj 2013; 1830:3807-15. [DOI: 10.1016/j.bbagen.2013.03.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 02/27/2013] [Accepted: 03/01/2013] [Indexed: 11/26/2022]
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34
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Chai L, Romero D, Kayatekin C, Akabayov B, Vlamakis H, Losick R, Kolter R. Isolation, characterization, and aggregation of a structured bacterial matrix precursor. J Biol Chem 2013; 288:17559-68. [PMID: 23632024 DOI: 10.1074/jbc.m113.453605] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Biofilms are surface-associated groups of microbial cells that are embedded in an extracellular matrix (ECM). The ECM is a network of biopolymers, mainly polysaccharides, proteins, and nucleic acids. ECM proteins serve a variety of structural roles and often form amyloid-like fibers. Despite the extensive study of the formation of amyloid fibers from their constituent subunits in humans, much less is known about the assembly of bacterial functional amyloid-like precursors into fibers. Using dynamic light scattering, atomic force microscopy, circular dichroism, and infrared spectroscopy, we show that our unique purification method of a Bacillus subtilis major matrix protein component results in stable oligomers that retain their native α-helical structure. The stability of these oligomers enabled us to control the external conditions that triggered their aggregation. In particular, we show that stretched fibers are formed on a hydrophobic surface, whereas plaque-like aggregates are formed in solution under acidic pH conditions. TasA is also shown to change conformation upon aggregation and gain some β-sheet structure. Our studies of the aggregation of a bacterial matrix protein from its subunits shed new light on assembly processes of the ECM within bacterial biofilms.
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Affiliation(s)
- Liraz Chai
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts 02115, USA
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35
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Theos AC, Watt B, Harper DC, Janczura KJ, Theos SC, Herman KE, Marks MS. The PKD domain distinguishes the trafficking and amyloidogenic properties of the pigment cell protein PMEL and its homologue GPNMB. Pigment Cell Melanoma Res 2013; 26:470-86. [PMID: 23452376 DOI: 10.1111/pcmr.12084] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Accepted: 02/26/2013] [Indexed: 11/29/2022]
Abstract
Proteolytic fragments of the pigment cell-specific glycoprotein, PMEL, form the amyloid fibrillar matrix underlying melanins in melanosomes. The fibrils form within multivesicular endosomes to which PMEL is selectively sorted and that serve as melanosome precursors. GPNMB is a tissue-restricted glycoprotein with substantial sequence homology to PMEL, but no known function, and was proposed to localize to non-fibrillar domains of distinct melanosome subcompartments in melanocytes. Here we confirm that GPNMB localizes to compartments distinct from the PMEL-containing multivesicular premelanosomes or late endosomes in melanocytes and HeLa cells, respectively, and is largely absent from fibrils. Using domain swapping, the unique PMEL localization is ascribed to its polycystic kidney disease (PKD) domain, whereas the homologous PKD domain of GPNMB lacks apparent sorting function. The difference likely reflects extensive modification of the GPNMB PKD domain by N-glycosylation, nullifying its sorting function. These results reveal the molecular basis for the distinct trafficking and morphogenetic properties of PMEL and GPNMB and support a deterministic function of the PMEL PKD domain in both protein sorting and amyloidogenesis.
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Affiliation(s)
- Alexander C Theos
- Department of Pathology & Laboratory Medicine and Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
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36
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Watt B, van Niel G, Raposo G, Marks MS. PMEL: a pigment cell-specific model for functional amyloid formation. Pigment Cell Melanoma Res 2013; 26:300-15. [PMID: 23350640 DOI: 10.1111/pcmr.12067] [Citation(s) in RCA: 123] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2012] [Accepted: 01/15/2013] [Indexed: 12/15/2022]
Abstract
PMEL is a pigment cell-specific protein responsible for the formation of fibrillar sheets within the pigment organelle, the melanosome. The fibrillar sheets serve as a template upon which melanins polymerize as they are synthesized. The PMEL fibrils are required for optimal pigment cell function, as animals that either lack PMEL expression or express mutant PMEL variants show varying degrees of hypopigmentation and pigment cell inviability. The PMEL fibrils have biophysical properties of amyloid, a protein fold that is frequently associated with neurodegenerative and other diseases. However, PMEL is one of a growing number of non-pathogenic amyloid proteins that contribute to the function of the cell and/or organism that produces them. Understanding how PMEL generates amyloid in a non-pathogenic manner might provide insights into how to avoid toxicity due to pathological amyloid formation. In this review, we summarize and reconcile data concerning the fate of PMEL from its site of synthesis in the endoplasmic reticulum to newly formed melanosomes and the role of distinct PMEL subdomains in trafficking and amyloid fibril formation. We then discuss how its progression through the secretory pathway into the endosomal system might allow for the regulated and non-toxic conversion of PMEL into an ordered amyloid polymer.
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Affiliation(s)
- Brenda Watt
- Department of Pathology and Laboratory Medicine, Department of Physiology, and Cell and Molecular Biology Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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37
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McGlinchey RP, Gruschus JM, Nagy A, Lee JC. Probing fibril dissolution of the repeat domain of a functional amyloid, Pmel17, on the microscopic and residue level. Biochemistry 2011; 50:10567-9. [PMID: 22092386 PMCID: PMC3232329 DOI: 10.1021/bi201578h] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pmel17 is a human amyloid involved in melanin synthesis. A fragment of Pmel17, the repeat domain (RPT) rich in glutamic acids, forms amyloid only at mildly acidic pH. Unlike pathological amyloids, these fibrils dissolve at neutral pH, supporting a reversible aggregation-disaggregation process. Here, we study RPT dissolution using atomic force microscopy and solution-state nuclear magnetic resonance spectroscopy. Our results reveal asymmetric fibril disassembly proceeding in the absence of intermediates. We suggest that fibril unfolding involves multiple deprotonation events resulting in electrostatic charge repulsion and filament dissolution.
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Affiliation(s)
- Ryan P. McGlinchey
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - James M. Gruschus
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Attila Nagy
- Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Jennifer C. Lee
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
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38
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Hu KN, McGlinchey RP, Wickner RB, Tycko R. Segmental polymorphism in a functional amyloid. Biophys J 2011; 101:2242-50. [PMID: 22067164 DOI: 10.1016/j.bpj.2011.09.051] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Revised: 09/22/2011] [Accepted: 09/29/2011] [Indexed: 11/25/2022] Open
Abstract
Although amyloid fibrils are generally considered to be causative or contributing agents in amyloid diseases, several amyloid fibrils are also believed to have biological functions. Among these are fibrils formed by Pmel17 within melanosomes, which act as a template for melanin deposition. We use solid-state NMR to show that the molecular structures of fibrils formed by the 130-residue pseudo-repeat domain Pmel17:RPT are polymorphic even within the biologically relevant pH range. Thus, biological function in amyloid fibrils does not necessarily imply a unique molecular structure. Solid-state NMR spectra of three Pmel17:RPT polymorphs show that in all cases, only a subset (~30%) of the full amino acid sequence contributes to the immobilized fibril core. Although the repetitive nature of the sequence and incomplete spectral resolution prevent the determination of unique chemical shift assignments from two- and three-dimensional solid-state NMR spectra, we use a Monte Carlo assignment algorithm to identify protein segments that are present in or absent from the fibril core. The results show that the identity of the core-forming segments varies from one polymorph to another, a phenomenon known as segmental polymorphism.
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Affiliation(s)
- Kan-Nian Hu
- Laboratory of Chemical Physics, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
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39
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McGlinchey RP, Yap TL, Lee JC. The yin and yang of amyloid: insights from α-synuclein and repeat domain of Pmel17. Phys Chem Chem Phys 2011; 13:20066-75. [PMID: 21993592 DOI: 10.1039/c1cp21376h] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Amyloid has been traditionally viewed in the context of disease. However, the emerging concept of 'functional amyloid' has taken a new direction into how we view amyloid. Recent studies have identified amyloid fibrils ranging from bacteria to humans that have a beneficial role, instead of being associated with a misfolded state that has been implicated in diseases such as Alzheimer's, Parkinson's and prion diseases. Here, we review our work on two human amyloidogenic polypeptides, one associated with Parkinson's disease, α-synuclein (α-syn), and the other important for melanin synthesis, the repeat domain (RPT) from Pmel17. Particularly, we focused our attention on spectroscopic studies of protein conformation and dynamics and their impact on α-syn amyloid formation and for RPT, we discussed the strict pH dependence of amyloid formation and its role in melanin biosynthesis.
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Affiliation(s)
- Ryan P McGlinchey
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
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40
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Shewmaker F, McGlinchey RP, Wickner RB. Structural insights into functional and pathological amyloid. J Biol Chem 2011; 286:16533-40. [PMID: 21454545 PMCID: PMC3089495 DOI: 10.1074/jbc.r111.227108] [Citation(s) in RCA: 133] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Amyloid is traditionally viewed as a consequence of protein misfolding and aggregation and is most notorious for its association with debilitating and chronic human diseases. However, a growing list of examples of "functional amyloid" challenges this bad reputation and indicates that many organisms can employ the biophysical properties of amyloid for their benefit. Because of developments in the structural studies of amyloid, a clearer picture is emerging about what defines amyloid structure and the properties that unite functional and pathological amyloids. Here, we review various amyloids and place them within the framework of the latest structural models.
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Affiliation(s)
- Frank Shewmaker
- Department of Pharmacology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA.
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