The Disulfide Bond, but Not Zinc or Dimerization, Controls Initiation and Seeded Growth in Amyotrophic Lateral Sclerosis-linked Cu,Zn Superoxide Dismutase (SOD1) Fibrillation.
Aggregation of copper-zinc superoxide dismutase (SOD1) is a defining feature of familial ALS caused by inherited mutations in the sod1 gene, and misfolded and aggregated forms of wild-type SOD1 are found in both sporadic and familial ALS cases. Mature SOD1 owes its exceptional stability to a number of post-translational modifications as follows: formation of the intramolecular disulfide bond, binding of copper and zinc, and dimerization. Loss of stability due to the failure to acquire one or more of these modifications is proposed to lead to aggregation in vivo. Previously, we showed that the presence of apo-, disulfide-reduced SOD1, the most immature form of SOD1, results in initiation of fibrillation of more mature forms that have an intact Cys-57-Cys-146 disulfide bond and are partially metallated. In this study, we examine the ability of each of the above post-translational modifications to modulate fibril initiation and seeded growth. Cobalt or zinc binding, despite conferring great structural stability, neither inhibits the initiation propensity of disulfide-reduced SOD1 nor consistently protects disulfide-oxidized SOD1 from being recruited into growing fibrils across wild-type and a number of ALS mutants. In contrast, reduction of the disulfide bond, known to be necessary for fibril initiation, also allows for faster recruitment during seeded amyloid growth. These results identify separate factors that differently influence seeded growth and initiation and indicate a lack of correlation between the overall thermodynamic stability of partially mature SOD1 states and their ability to initiate fibrillation or be recruited by a growing fibril.
From the Department of Chemistry and Biochemistry UCLA, Los Angeles, California 90095, madhuri@gmail.com.
Madhuri
M
Chattopadhyay
From the Department of Chemistry and Biochemistry UCLA, Los Angeles, California 90095.
Ekeoma
E
Nwadibia
the Department of Chemistry, Cornell College, Mt. Vernon, Iowa 52314, and.
Cynthia D
CD
Strong
From the Department of Chemistry and Biochemistry UCLA, Los Angeles, California 90095.
Edith Butler
EB
Gralla
From the Department of Chemistry and Biochemistry UCLA, Los Angeles, California 90095.
Joan Selverstone
JS
Valentine
From the Department of Chemistry and Biochemistry UCLA, Los Angeles, California 90095, the The Pasarow Mass Spectrometry Laboratory, NPI-Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine at UCLA, Los Angeles, California 90095 jpw@chem.ucla.edu.
Julian P
http://orcid.org/0000-0003-2763-7733
JP
Whitelegge
D000682:Amyloid / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000690:Amyotrophic Lateral Sclerosis / Q000201:enzymology* / Q000235:genetics; D004220:Disulfides / Q000737:chemistry* / Q000378:metabolism; D004795:Enzyme Stability / Q000235:genetics; D006801:Humans; D009154:Mutation; D055503:Protein Multimerization; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000072105:Superoxide Dismutase-1; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
D000682:Amyloid; D004220:Disulfides; D011994:Recombinant Proteins; C000606290:SOD1 protein, human; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D015032:Zinc
amyloid; amyotrophic lateral sclerosis (ALS) (Lou Gehrig disease); neurodegenerative disease; protein aggregation; protein misfolding; superoxide dismutase (SOD)