RESUMEN
Protein misfolding is implicated in neurodegenerative diseases such as ALS, where mutations of superoxide dismutase 1 (SOD1) account for about 20% of the inherited mutations. Human SOD1 (hSOD1) contains four cysteines, including Cys(57) and Cys(146), which have been linked to protein stability and folding via forming a disulfide bond, and Cys(6) and Cys(111) as free thiols. But the roles of the cellular oxidation-reduction (redox) environment in SOD1 folding and aggregation are not well understood. Here we explore the effects of cellular redox systems on the aggregation of hSOD1 proteins. We found that the known hSOD1 mutations G93A and A4V increased the capability of the thioredoxin and glutaredoxin systems to reduce hSOD1 compared with wild-type hSOD1. Treatment with inhibitors of these redox systems resulted in an increase of hSOD1 aggregates in the cytoplasm of cells transfected with mutants but not in cells transfected with wild-type hSOD1 or those containing a secondary C111G mutation. This aggregation may be coupled to changes in the redox state of the G93A and A4V mutants upon mild oxidative stress. These results strongly suggest that the thioredoxin and glutaredoxin systems are the key regulators for hSOD1 aggregation and may play critical roles in the pathogenesis of ALS.
Asunto(s)
Esclerosis Amiotrófica Lateral , Estrés Oxidativo , Agregación Patológica de Proteínas , Pliegue de Proteína , Superóxido Dismutasa-1 , Sustitución de Aminoácidos , Esclerosis Amiotrófica Lateral/enzimología , Esclerosis Amiotrófica Lateral/genética , Animales , Línea Celular Tumoral , Glutarredoxinas/genética , Glutarredoxinas/metabolismo , Humanos , Mutación Missense , Oxidación-Reducción , Agregación Patológica de Proteínas/enzimología , Agregación Patológica de Proteínas/genética , Ratas , Superóxido Dismutasa-1/genética , Superóxido Dismutasa-1/metabolismo , Tiorredoxinas/genética , Tiorredoxinas/metabolismoRESUMEN
Lou Gehrig's disease, a synonym of amyotrophic lateral sclerosis, is an adult-onset lethal neurodegenerative disorder. Irrespective of extensive efforts to elucidate the pathogenesis of the disease and searches for therapies, no favorable pharmacotherapeutic strategies have yet to be proposed. In a popular rodent model of ALS, G93A SOD1 strain of mouse, intracellular copper conditions were geared toward copper accumulation inside cells, resulting in an acceleration of oxidative stress and apoptotic process. Disruption of intracellular copper homeostasis was common to transgenic mice expressing human mutant SOD1s. In this review, the novel hypothesis that disruption of intracellular copper homeostasis could be involved in the development of the disease was introduced. Based upon the hypothesis, therapeutic outcomes of agents that are capable of correcting and/or modifying intracellular copper homeostasis are described. Administration of ammonium tetrathiomolybdate, a selective intracellular copper chelator, delayed onset, slowed progression, and prolonged survival of a rodent model of the disease (G93A SOD1 mice). Metallothionein is a low molecular weight, cysteine-rich, metal-binding cytoplasmic protein that has beneficial properties in detoxification of toxic heavy metals, homeostatic regulation of intracellular essential trace elements, including copper, antioxidant, and antiapoptotic roles. In animal experiments of the G93A SOD1 mice, an increase of metallothionein proteins by means of induction by exercise or dexamethasone, genetic overexpression, or intraperitoneal administration, all resulted in a preferable outcome. The therapeutic effects were not inferior to those of approved drugs for ALS in humans. These observations suggest that metallothionein could be worth investigating the therapeutic potential in clinical use.