Amyotrophic lateral sclerosis (ALS) is a progressive, late-onset neurodegenerative disorder for which there is currently no effective treatment, and which affects nearly 30,000 people in the United States. A subset of ALS cases are caused by mutations in the ubiquitous antioxidant enzyme Cu, Zn superoxide dismutase (SOD1) through an ill-defined toxic gain of function. The accumulation of misfolded and/or aggregated SOD1 in dying motor neurons suggests that SOD1-related ALS is primarily a protein deposition disorder. However, little is known about the causes, mechanism, and consequences of SOD1 oligomerization in ALS. The long term objective of the proposed work is the elucidation of the mechanism(s) by which SOD1 forms non-native oligomers. As ALS symptoms typically do not appear until late in life, we hypothesize that factors in the cellular environment likely influence oligomer formation and subsequent motor neuron toxicity. In the aims proposed here, we will examine the effect of two physiological post-translational modifications, phosphorylation and glutathionylation, on the structural transitions of SOD1 from native to aggregated states. The first specific aim will focus on the first step in oligomer formation, dissociation of the native SOD1 homodimer. Crystal structures of modified SOD1 will be solved and assessed for any perturbations in the dimeric structure.
Aim 2 will test the effect of modification on the oligomerization dynamics of wild type and mutant SOD1. Biophysical techniques such as surface plasmon resonance and size exclusion chromatography will be used to monitor the rate of dimer dissociation and appearance of non-native oligomeric species. By studying modified and unmodified forms of wild-type SOD1 as well as a diverse set of ALS-associated mutants, we will determine whether modifications and mutations produce a cumulative increase in SOD1 aggregation propensity. The studies proposed here would enhance the currently meager understanding of the general SOD1 oligomerization pathway and provide novel insight on how this process is affected by physiological post-translation modifications. As aggregation is a central pathological feature of SOD1-related ALS, knowledge of this process and its cellular determinants would lead to more effective treatments and preventative measures.

Public Health Relevance

Amyotrophic lateral sclerosis (ALS) is an aggressive neurodegenerative disorder in which misfolded and aggregated forms of Cu, Zn- superoxide dismutase (SOD1) cause selective death of motor neurons. This project will examine how post-translational modifications and mutations of SOD1, individually and in tandem, affect the tendency of the protein to aggregate. Understanding of the factors that influence SOD1 aggregation can be used to develop novel therapeutic approaches to the prevention or mitigation of ALS symptoms.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Predoctoral Individual National Research Service Award (F31)
Project #
5F31NS073435-03
Application #
8416974
Study Section
Special Emphasis Panel (ZRG1-F03A-F (20))
Program Officer
Gubitz, Amelie
Project Start
2011-02-01
Project End
2014-01-31
Budget Start
2013-02-01
Budget End
2014-01-31
Support Year
3
Fiscal Year
2013
Total Cost
$30,526
Indirect Cost
Name
University of North Carolina Chapel Hill
Department
Biochemistry
Type
Schools of Medicine
DUNS #
608195277
City
Chapel Hill
State
NC
Country
United States
Zip Code
27599
Redler, Rachel L; Fee, Lanette; Fay, James M et al. (2014) Non-native soluble oligomers of Cu/Zn superoxide dismutase (SOD1) contain a conformational epitope linked to cytotoxicity in amyotrophic lateral sclerosis (ALS). Biochemistry 53:2423-32
Nedd, Sean; Redler, Rachel L; Proctor, Elizabeth A et al. (2014) Cu,Zn-superoxide dismutase without Zn is folded but catalytically inactive. J Mol Biol 426:4112-24
Redler, Rachel L; Shirvanyants, David; Dagliyan, Onur et al. (2014) Computational approaches to understanding protein aggregation in neurodegeneration. J Mol Cell Biol 6:104-15
Redler, Rachel L; Wilcox, Kyle C; Proctor, Elizabeth A et al. (2011) Glutathionylation at Cys-111 induces dissociation of wild type and FALS mutant SOD1 dimers. Biochemistry 50:7057-66