Cu/Zn Superoxide Dismutase Forms Amyloid Fibrils under Near-Physiological Quiescent Conditions : The Roles of Disulfide Bonds and Effects of Denaturant
Khan, Ashhar LU ; Respondek, Michal LU ; Kjellström, Sven LU ; Deep, Shashank ; Linse, Sara LU and Akke, Mikael LU
(2017)
In ACS Chemical Neuroscience
8(9).
p.2019-2026
- Abstract
Cu/Zn superoxide dismutase (SOD1) forms intracellular aggregates that are pathological indicators of amyotrophic lateral sclerosis. A large body of research indicates that the entry point to aggregate formation is a monomeric, metal-ion free (apo), and disulfide-reduced species. Fibril formation by SOD1 in vitro has typically been reported only for harsh solvent conditions or mechanical agitation. Here we show that monomeric apo-SOD1 in the disulfide-reduced state forms fibrillar aggregates under near-physiological quiescent conditions. Monomeric apo-SOD1 with an intact intramolecular disulfide bond is highly resistant to aggregation under the same conditions. A cysteine-free variant of SOD1 exhibits fibrillization behavior and fibril... (More)
Cu/Zn superoxide dismutase (SOD1) forms intracellular aggregates that are pathological indicators of amyotrophic lateral sclerosis. A large body of research indicates that the entry point to aggregate formation is a monomeric, metal-ion free (apo), and disulfide-reduced species. Fibril formation by SOD1 in vitro has typically been reported only for harsh solvent conditions or mechanical agitation. Here we show that monomeric apo-SOD1 in the disulfide-reduced state forms fibrillar aggregates under near-physiological quiescent conditions. Monomeric apo-SOD1 with an intact intramolecular disulfide bond is highly resistant to aggregation under the same conditions. A cysteine-free variant of SOD1 exhibits fibrillization behavior and fibril morphology identical to those of disulfide-reduced SOD1, firmly establishing that intermolecular disulfide bonds or intramolecular disulfide shuffling are not required for aggregation and fibril formation. The decreased lag time for fibril formation resulting from reduction of the intramolecular disulfide bond thus primarily reflects the decreased stability of the folded state relative to partially unfolded states, rather than an active role of free sulfhydryl groups in mediating aggregation. Addition of urea to increase the amount of fully unfolded SOD1 increases the lag time for fibril formation, indicating that the population of this species does not dominate over other factors in determining the onset of aggregation. Our results contrast with previous results obtained for agitated samples, in which case amyloid formation was accelerated by denaturant. We reconcile these observations by suggesting that denaturants destabilize monomeric and aggregated species to different extents and thus affect nucleation and growth.
(Less)
- author
- Khan, Ashhar
LU
; Respondek, Michal
LU
; Kjellström, Sven
LU
; Deep, Shashank
; Linse, Sara
LU
and Akke, Mikael
LU
- organization
- publishing date
- 2017-09-20
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Amyotrophic lateral sclerosis, disulfide reduction, protein aggregation, protein unfolding, ThT fluorescence, transmission electron microscopy
- in
- ACS Chemical Neuroscience
- volume
- 8
- issue
- 9
- pages
- 8 pages
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- scopus:85029620956
- pmid:28585802
- wos:000411662000025
- ISSN
- 1948-7193
- DOI
- 10.1021/acschemneuro.7b00162
- language
- English
- LU publication?
- yes
- id
- ccd8bc46-98f9-4e38-8b8c-6471e645cd68
- date added to LUP
- 2017-09-29 09:05:30
- date last changed
- 2024-04-14 18:35:12
@article{ccd8bc46-98f9-4e38-8b8c-6471e645cd68,
abstract = {{<p>Cu/Zn superoxide dismutase (SOD1) forms intracellular aggregates that are pathological indicators of amyotrophic lateral sclerosis. A large body of research indicates that the entry point to aggregate formation is a monomeric, metal-ion free (apo), and disulfide-reduced species. Fibril formation by SOD1 in vitro has typically been reported only for harsh solvent conditions or mechanical agitation. Here we show that monomeric apo-SOD1 in the disulfide-reduced state forms fibrillar aggregates under near-physiological quiescent conditions. Monomeric apo-SOD1 with an intact intramolecular disulfide bond is highly resistant to aggregation under the same conditions. A cysteine-free variant of SOD1 exhibits fibrillization behavior and fibril morphology identical to those of disulfide-reduced SOD1, firmly establishing that intermolecular disulfide bonds or intramolecular disulfide shuffling are not required for aggregation and fibril formation. The decreased lag time for fibril formation resulting from reduction of the intramolecular disulfide bond thus primarily reflects the decreased stability of the folded state relative to partially unfolded states, rather than an active role of free sulfhydryl groups in mediating aggregation. Addition of urea to increase the amount of fully unfolded SOD1 increases the lag time for fibril formation, indicating that the population of this species does not dominate over other factors in determining the onset of aggregation. Our results contrast with previous results obtained for agitated samples, in which case amyloid formation was accelerated by denaturant. We reconcile these observations by suggesting that denaturants destabilize monomeric and aggregated species to different extents and thus affect nucleation and growth.</p>}},
author = {{Khan, Ashhar and Respondek, Michal and Kjellström, Sven and Deep, Shashank and Linse, Sara and Akke, Mikael}},
issn = {{1948-7193}},
keywords = {{Amyotrophic lateral sclerosis; disulfide reduction; protein aggregation; protein unfolding; ThT fluorescence; transmission electron microscopy}},
language = {{eng}},
month = {{09}},
number = {{9}},
pages = {{2019--2026}},
publisher = {{The American Chemical Society (ACS)}},
series = {{ACS Chemical Neuroscience}},
title = {{Cu/Zn Superoxide Dismutase Forms Amyloid Fibrils under Near-Physiological Quiescent Conditions : The Roles of Disulfide Bonds and Effects of Denaturant}},
url = {{http://dx.doi.org/10.1021/acschemneuro.7b00162}},
doi = {{10.1021/acschemneuro.7b00162}},
volume = {{8}},
year = {{2017}},
}