Abstract
During their life cycle, proteins are subject to different modifications involving reactive oxygen species. Such oxidative damage to proteins may lead to the formation of insoluble aggregates and cytotoxicity and is associated with age-related disorders including neurodegenerative diseases, cancer, and diabetes. Superoxide dismutase 1 (SOD1), a key antioxidant enzyme in human cells, is particularly susceptible to such modifications. Moreover, this homodimeric metalloenzyme has been directly linked to both familial and sporadic amyotrophic lateral sclerosis (ALS), a devastating, late-onset motor neuronal disease, with more than 150 ALS-related mutations in the SOD1 gene. Importantly, oxidatively damaged SOD1 aggregates have been observed in both familial and sporadic forms of the disease. However, the molecular mechanisms as well as potential implications of oxidative stress in SOD1-induced cytotoxicity remain elusive. In this study, we examine the effects of oxidative modification on SOD1 monomer and homodimer stability, the key molecular properties related to SOD1 aggregation. We use molecular dynamics simulations in combination with thermodynamic integration to study microscopic-level site-specific effects of oxidative “mutations” at the dimer interface, including lysine, arginine, proline and threonine carbonylation, and cysteine oxidation. Our results show that oxidative damage of even single residues at the interface may drastically destabilize the SOD1 homodimer, with several modifications exhibiting a comparable effect to that of the most drastic ALS-causing mutations known. Additionally, we show that the SOD1 monomer stability decreases upon oxidative stress, which may lead to partial local unfolding and consequently to increased aggregation propensity. Importantly, these results suggest that oxidative stress may play a key role in development of ALS, with the mutations in the SOD1 gene being an additional factor.
Highlights
Reactive oxygen species (ROS) participate in a large number of different chemical reactions with proteins, leading to modified amino-acid side chains and backbone or even cross-linked and fragmented proteins [1]
An important and widely studied system for exploring this relationship has been Cu/Zn superoxide dismutase 1 (SOD1) [8,9]. This enzyme has been found to associate with 20% of the cases of familial amyotrophic lateral sclerosis, an agerelated neurodegenerative disease, with more than 150 different mutations in the SOD1 gene having been linked with this condition [8,10,11]
We have used thermodynamic integration to calculate the free-energy changes associated with the alchemical switching of nine native residues at the SOD1 homodimer interface (THR2, LYS3, CYS6, LYS9, THR54, PRO62, CYS111, ARG115, and THR116) to their oxidatively modified forms
Summary
Reactive oxygen species (ROS) participate in a large number of different chemical reactions with proteins, leading to modified amino-acid side chains and backbone or even cross-linked and fragmented proteins [1] Such oxidative modifications have been associated with aging and age-related disorders such as neurodegenerative diseases, cancer, or diabetes [2,3]. An important and widely studied system for exploring this relationship has been Cu/Zn superoxide dismutase 1 (SOD1) [8,9] This enzyme has been found to associate with 20% of the cases of familial amyotrophic lateral sclerosis (fALS), an agerelated neurodegenerative disease, with more than 150 different mutations in the SOD1 gene having been linked with this condition [8,10,11]. It is not clear to what extent oxidative damage in vivo is an actual cause of SOD1 aggregation or, alternatively, is a downstream consequence of aggregation
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
