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Co-assembly of proteins and lipids : From lipodiscs to amyloid aggregates

Frankel Willén, Rebecca LU (2021)
Abstract
Assemblies of different molecules is a prevalent phenomenon in nature, and crucial in biological life. Most of the biological assemblies are co-assembled
composites, made up from several different components, either of the
same biomolecular type or a combination of different ones. Knowledge regarding amyloid fibril structure and the mechanism behind it has been elucidated through the development of protocols rendering reproducible kinetic data in buffer systems. The vast majority of these studies have been focused on the self-assembly of the peptides.
However, peptide aggregation in vivo typically occurs in a more complex environment, surrounded by either different proteins or lipids, or both.
In this thesis, different... (More)
Assemblies of different molecules is a prevalent phenomenon in nature, and crucial in biological life. Most of the biological assemblies are co-assembled
composites, made up from several different components, either of the
same biomolecular type or a combination of different ones. Knowledge regarding amyloid fibril structure and the mechanism behind it has been elucidated through the development of protocols rendering reproducible kinetic data in buffer systems. The vast majority of these studies have been focused on the self-assembly of the peptides.
However, peptide aggregation in vivo typically occurs in a more complex environment, surrounded by either different proteins or lipids, or both.
In this thesis, different systems of self- and co-assembly has been studied. We use both top-down and bottom-up approaches to explore the aggregation of the Aβ peptide involved in Alzheimer’s disease. In an in vivo-like environment (cerebrospinal fluid, CSF), we find that Aβ42 fibrillisation is retarded, but occurring through the same mechanism as inferred for Aβ in a buffer system, including the secondary nucleation mechanism. We further investigated the possible effectors of CSF and the minimum component requirement to replicate the effect from this environment through the creation of HDL-like particles. This was achieved through the development of methodology for the expression and purification of ApoA-I from a CSF-free host. Further, the effect of Aβ in the presence of both lipids and other proteins was investigated. We find that we can replicate the effect seen in CSF by the HDL-like particles, in that we see a retarding effect, more pronounced when ApoA-I is added in lipid-free form. We also find that ApoA-I will readily aggregate, and the morphology of the aggregates depend on both extrinsic and intrinsic factors. Finally, we investigated if the inhibiting effect of DNAJB6 on Aβ fibril formation could be reproduced by an isolated chaperone domain. We found that the C-terminal domain of DNAJB6 – suggested to be involved in peptide binding after dimerization – will inhibit the secondary nucleation of Aβ fibril formation as opposed to the intact protein which inhibits the primary nucleation. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Associate professor Esbjörner Winters, Elin, Chalmers tekniska högskola, Göteborg.
organization
publishing date
type
Thesis
publication status
published
subject
keywords
amyloid, Aβ42, apolipoprotein A-1, aggregation, high-density lipoprotein, DNAJB6, Alzheimer's disease, protein-lipid interactions
pages
200 pages
publisher
Lund University, Faculty of Science, Department of Chemistry
defense location
KC:A. Join via zoom: https://lu-se.zoom.us/j/67633038108
defense date
2021-11-12 09:15:00
ISBN
978-91-7422-843-4
978-91-7422-842-7
language
English
LU publication?
yes
id
ca2dde1f-c00c-41c0-acce-f27c1fc0eaf7
date added to LUP
2021-10-11 10:00:00
date last changed
2022-04-12 13:58:23
@phdthesis{ca2dde1f-c00c-41c0-acce-f27c1fc0eaf7,
  abstract     = {{Assemblies of different molecules is a prevalent phenomenon in nature, and crucial in biological life. Most of the biological assemblies are co-assembled<br/>composites, made up from several different components, either of the<br/>same biomolecular type or a combination of different ones. Knowledge regarding amyloid fibril structure and the mechanism behind it has been elucidated through the development of protocols rendering reproducible kinetic data in buffer systems. The vast majority of these studies have been focused on the self-assembly of the peptides.<br/>However, peptide aggregation in vivo typically occurs in a more complex environment, surrounded by either different proteins or lipids, or both.<br/>In this thesis, different systems of self- and co-assembly has been studied. We use both top-down and bottom-up approaches to explore the aggregation of the Aβ peptide involved in Alzheimer’s disease. In an in vivo-like environment (cerebrospinal fluid, CSF), we find that Aβ42 fibrillisation is retarded, but occurring through the same mechanism as inferred for Aβ in a buffer system, including the secondary nucleation mechanism. We further investigated the possible effectors of CSF and the minimum component requirement to replicate the effect from this environment through the creation of HDL-like particles. This was achieved through the development of methodology for the expression and purification of ApoA-I from a CSF-free host. Further, the effect of Aβ in the presence of both lipids and other proteins was investigated. We find that we can replicate the effect seen in CSF by the HDL-like particles, in that we see a retarding effect, more pronounced when ApoA-I is added in lipid-free form. We also find that ApoA-I will readily aggregate, and the morphology of the aggregates depend on both extrinsic and intrinsic factors. Finally, we investigated if the inhibiting effect of DNAJB6 on Aβ fibril formation could be reproduced by an isolated chaperone domain. We found that the C-terminal domain of DNAJB6 – suggested to be involved in peptide binding after dimerization – will inhibit the secondary nucleation of Aβ fibril formation as opposed to the intact protein which inhibits the primary nucleation.}},
  author       = {{Frankel Willén, Rebecca}},
  isbn         = {{978-91-7422-843-4}},
  keywords     = {{amyloid; Aβ42; apolipoprotein A-1; aggregation; high-density lipoprotein; DNAJB6; Alzheimer's disease; protein-lipid interactions}},
  language     = {{eng}},
  publisher    = {{Lund University, Faculty of Science, Department of Chemistry}},
  school       = {{Lund University}},
  title        = {{Co-assembly of proteins and lipids : From lipodiscs to amyloid aggregates}},
  url          = {{https://lup.lub.lu.se/search/files/103587901/Rebecca_Frankel_Will_n_WEBB.pdf}},
  year         = {{2021}},
}