Protein disulfide isomerase ERp57 protects early muscle denervation in experimental ALS

Pablo Rozas,Jessica Mella,Lars Plate,Cristina Pinto,Danilo B Medinas,Juan Pablo Henríquez,Francisca Martínez Traub,Patricia Ojeda,Jorge Ojeda,Rodrigo Díaz,Viviana Pérez,Claudio Hetz,Madison T Wright,Daniela Becerra

doi:10.1186/s40478-020-01116-z

Abstract

Amyotrophic lateral sclerosis (ALS) is a progressive fatal neurodegenerative disease that affects motoneurons. Mutations in superoxide dismutase 1 (SOD1) have been described as a causative genetic factor for ALS. Mice overexpressing ALS-linked mutant SOD1 develop ALS symptoms accompanied by histopathological alterations and protein aggregation. The protein disulfide isomerase family member ERp57 is one of the main up-regulated proteins in tissue of ALS patients and mutant SOD1 mice, whereas point mutations in ERp57 were described as possible risk factors to develop the disease. ERp57 catalyzes disulfide bond formation and isomerization in the endoplasmic reticulum (ER), constituting a central component of protein quality control mechanisms. However, the actual contribution of ERp57 to ALS pathogenesis remained to be defined. Here, we studied the consequences of overexpressing ERp57 in experimental ALS using mutant SOD1 mice. Double transgenic SOD1G93A/ERp57WT animals presented delayed deterioration of electrophysiological activity and maintained muscle innervation compared to single transgenic SOD1G93A littermates at early-symptomatic stage, along with improved motor performance without affecting survival. The overexpression of ERp57 reduced mutant SOD1 aggregation, but only at disease end-stage, dissociating its role as an anti-aggregation factor from the protection of neuromuscular junctions. Instead, proteomic analysis revealed that the neuroprotective effects of ERp57 overexpression correlated with increased levels of synaptic and actin cytoskeleton proteins in the spinal cord. Taken together, our results suggest that ERp57 operates as a disease modifier at early stages by maintaining motoneuron connectivity.

Highlights

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal late-onset neurodegenerative disease characterized by loss of motoneurons leading to muscle weakness, paralysis and death [1]
ERp57 overexpression improves motor function of mutant SOD1G93A mice at early‐symptomatic stage To define the functional impact of increasing ERp57 levels on ALS onset and progression, we crossed SOD1G93A mice with a transgenic line overexpressing ERp57WT under the Prion promoter previously generated in our laboratory [24, 25] to obtain SOD1G93A/ERp57WT double transgenic mice and control littermates (Fig. 1a)
At 17 and 18 weeks of age, over half of the double transgenic mice were able to hold themselves on the wire while their SOD1G93A counterparts fell on the floor before 10 s (Fig. 1g)

Summary

Introduction

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal late-onset neurodegenerative disease characterized by loss of motoneurons leading to muscle weakness, paralysis and death [1]. Misfolding and aggregation of wild-type SOD1 have been reported in sALS cases [7, 8]. Independent studies identified two protein disulfide isomerase family members (PDIs), PDI and ERp57 ( known as PDIA3 or GRP58), among the main proteins induced in spinal cord of ALS rodents at different disease stages, suggesting that dysregulation of redox folding in the endoplasmic reticulum (ER) contributes to disease pathogenesis [9,10,11]. PDI and ERp57 were found up-regulated in post-mortem spinal cord tissue of sALS patients [10, 12]. Increased levels of PDI were detected in cerebrospinal fluid of sALS patients [10], while a proteomic screening in blood cells revealed ERp57 as the most reliable biomarker of sALS progression [13]

Methods

Results

Discussion

Conclusion