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Zhang Z, Huang G, Song Z, Gatch AJ, Ding F. Amyloid Aggregation and Liquid-Liquid Phase Separation from the Perspective of Phase Transitions. J Phys Chem B 2023; 127:6241-6250. [PMID: 37414583 PMCID: PMC10404378 DOI: 10.1021/acs.jpcb.3c01426] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/08/2023]
Abstract
Amyloid aggregation describes the aberrant self-assembly of peptides into ordered fibrils characterized by cross-β spine cores and is associated with many neurodegenerative diseases and Type 2 diabetes. Oligomers, populated during the early stage of aggregation, are found to be more cytotoxic than mature fibrils. Recently, many amyloidogenic peptides have been reported to undergo liquid-liquid phase separation (LLPS)─a biological process important for the compartmentalization of biomolecules in living cells─prior to fibril formation. Understanding the relationship between LLPS and amyloid aggregation, especially the formation of oligomers, is essential for uncovering disease mechanisms and mitigating amyloid toxicity. In this Perspective, available theories and models of amyloid aggregation and LLPS are first briefly reviewed. By drawing analogies to gas, liquid, and solid phases in thermodynamics, a phase diagram of protein monomer, droplet, and fibril states separated by coexistence lines can be inferred. Due to the high free energy barrier of fibrillization kinetically delaying the formation of fibril seeds out of the droplets, a "hidden" monomer-droplet coexistence line extends into the fibril phase. Amyloid aggregation can then be described as the equilibration process from the initial "out-of-equilibrium" state of a homogeneous solution of monomers to the final equilibrium state of stable amyloid fibrils coexisting with monomers and/or droplets via the formation of metastable or stable droplets as the intermediates. The relationship between droplets and oligomers is also discussed. We suggest that the droplet formation of LLPS should be considered in future studies of amyloid aggregation, which may help to better understand the aggregation process and develop therapeutic strategies to mitigate amyloid toxicity.
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Affiliation(s)
- Zhenzhen Zhang
- Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, United States
| | - Gangtong Huang
- Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, United States
| | - Zhiyuan Song
- Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, United States
| | - Adam J. Gatch
- Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, United States
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, United States
| | - Feng Ding
- Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, United States
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Buchanan JA, Varghese NR, Johnston CL, Sunde M. Functional Amyloids: Where Supramolecular Amyloid Assembly Controls Biological Activity or Generates New Functionality. J Mol Biol 2023; 435:167919. [PMID: 37330295 DOI: 10.1016/j.jmb.2022.167919] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 12/05/2022] [Accepted: 12/05/2022] [Indexed: 06/19/2023]
Abstract
Functional amyloids are a rapidly expanding class of fibrillar protein structures, with a core cross-β scaffold, where novel and advantageous biological function is generated by the assembly of the amyloid. The growing number of amyloid structures determined at high resolution reveal how this supramolecular template both accommodates a wide variety of amino acid sequences and also imposes selectivity on the assembly process. The amyloid fibril can no longer be considered a generic aggregate, even when associated with disease and loss of function. In functional amyloids the polymeric β-sheet rich structure provides multiple different examples of unique control mechanisms and structures that are finely tuned to deliver assembly or disassembly in response to physiological or environmental cues. Here we review the range of mechanisms at play in natural, functional amyloids, where tight control of amyloidogenicity is achieved by environmental triggers of conformational change, proteolytic generation of amyloidogenic fragments, or heteromeric seeding and amyloid fibril stability. In the amyloid fibril form, activity can be regulated by pH, ligand binding and higher order protofilament or fibril architectures that impact the arrangement of associated domains and amyloid stability. The growing understanding of the molecular basis for the control of structure and functionality delivered by natural amyloids in nearly all life forms should inform the development of therapies for amyloid-associated diseases and guide the design of innovative biomaterials.
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Affiliation(s)
- Jessica A Buchanan
- School of Medical Sciences and Sydney Nano, The University of Sydney, NSW 2006, Australia.
| | - Nikhil R Varghese
- School of Medical Sciences and Sydney Nano, The University of Sydney, NSW 2006, Australia.
| | - Caitlin L Johnston
- School of Medical Sciences and Sydney Nano, The University of Sydney, NSW 2006, Australia.
| | - Margaret Sunde
- School of Medical Sciences and Sydney Nano, The University of Sydney, NSW 2006, Australia.
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Liu Y, Liu J, He X. Different p Ka Shifts of Internal GLU8 in Human β-Endorphin Amyloid Revealing a Coupling of Internal Ionization and Stepwise Fibril Disassembly. J Phys Chem B 2023; 127:1089-1096. [PMID: 36696655 DOI: 10.1021/acs.jpcb.2c06706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
As a functional amyloid, human β-endorphin amyloid fibril features a β-solenoid conformation and store peptide hormones within acidic secretory granules, which would be released into the blood through fibril disassembly when the cellular milieu pH increases from acidic to neutral level on exocytosis. To gain detailed atomic mechanism of β-endorphin amyloid fibrils' pH-responsive disassembly, we conduct constant pH molecular dynamics simulations to investigate the structural and dynamical properties of β-endorphin amyloid fibrils in experiencing the environmental pH changes. Our results demonstrate a clear pKa shift of the internal ionizable residue of GLU8, and this shift becomes even more pronounced when it is buried more deeply in the amyloid fibrils. The unusual pKa of GLU8 reveals that its protonation state changes from the protonated state in the acidic secretory granule to the deprotonated state in the neutral pH conditions in the blood, where the deprotonation of GLU8 leads to unfavorable interactions within the hydrophobic core of the amyloid and subsequent fibril disassembly. The different pKa shifts of GLU8 relative to its positions in the amyloid fibril indicate that the β-endorphin amyloid fibril disassembly is a stepwise process, accounting for the experimental observation that the disassembly always initiates from the outermost layer. This study reveals the critical role of the protonation state of GLU8 in amyloid fibrils' pH-responsive disassembly, and provides clear insights for understanding the structural transitions of amyloids in hormone secretion. This study also provides theoretical basis for designing pH-sensitive biological tools for specific use with precise positioning of ionizable residues into the hydrophobic interior of proteins.
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Affiliation(s)
- Yiwei Liu
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, Shanghai Frontiers Science Center of Molecule Intelligent Syntheses, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China
| | - Jinfeng Liu
- Department of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Xiao He
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, Shanghai Frontiers Science Center of Molecule Intelligent Syntheses, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China.,New York University-East China Normal University Center for Computational Chemistry, New York University Shanghai, Shanghai, 200062, China
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Chen Y, Liu Q, Yang F, Yu H, Xie Y, Yao W. Lysozyme amyloid fibril: Regulation, application, hazard analysis, and future perspectives. Int J Biol Macromol 2022; 200:151-161. [PMID: 34995654 DOI: 10.1016/j.ijbiomac.2021.12.163] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 12/15/2021] [Accepted: 12/25/2021] [Indexed: 12/11/2022]
Abstract
Self-assembly of misfolded proteins into ordered fibrillar aggregates known as amyloid results in various human diseases. However, more and more proteins, whether in human body or in food, have been found to be able to form amyloid fibrils with in-depth researches. As a model protein for amyloid research, lysozyme has always been the focus of research in various fields. Firstly, the formation mechanisms of amyloid fibrils are discussed concisely. Researches on the regulation of lysozyme amyloid fibrils are helpful to find suitable therapeutic drugs and unfriendly substances. And this review article summarizes a number of exogenous substances including small molecules, nanoparticles, macromolecules, and polymers. Small molecules are mainly connected to lysozyme through hydrophobic interaction, electrostatic interaction, π-π interaction, van der Waals force and hydrogen bond. Nanoparticles inhibit the formation of amyloid fibers by stabilizing lysozyme and fixing β-sheet. Besides, the applications of lysozyme amyloid fibrils in food-related fields are considered furtherly due to outstanding physical and mechanical properties. Nevertheless, the potential health threats are still worthy of our attention. Finally, we also give suggestions and opinions on the future research direction of lysozyme amyloid fibrils.
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Affiliation(s)
- Yulun Chen
- State Key Laboratory of Food Science and Technology, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China; Engineering Research Center of Dairy Quality and Safety Control Technology, Ministry of Education, Inner Mongolia University, No.235 Daxue West Road, Hohhot 010021, Inner Mongolia Autonomous Region, China; School of Food Science and Technology, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China; Joint International Research Laboratory of Food Safety, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China
| | - Qingrun Liu
- State Key Laboratory of Food Science and Technology, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China; School of Food Science and Technology, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China; Joint International Research Laboratory of Food Safety, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China
| | - Fangwei Yang
- State Key Laboratory of Food Science and Technology, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China; Engineering Research Center of Dairy Quality and Safety Control Technology, Ministry of Education, Inner Mongolia University, No.235 Daxue West Road, Hohhot 010021, Inner Mongolia Autonomous Region, China; School of Food Science and Technology, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China; Joint International Research Laboratory of Food Safety, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China
| | - Hang Yu
- State Key Laboratory of Food Science and Technology, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China; School of Food Science and Technology, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China; Joint International Research Laboratory of Food Safety, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China
| | - Yunfei Xie
- State Key Laboratory of Food Science and Technology, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China; Engineering Research Center of Dairy Quality and Safety Control Technology, Ministry of Education, Inner Mongolia University, No.235 Daxue West Road, Hohhot 010021, Inner Mongolia Autonomous Region, China; School of Food Science and Technology, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China; Joint International Research Laboratory of Food Safety, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China
| | - Weirong Yao
- State Key Laboratory of Food Science and Technology, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China; School of Food Science and Technology, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China; Joint International Research Laboratory of Food Safety, Jiangnan University, No.1800 Lihu Avenue, Wuxi 214122, Jiangsu Province, China.
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