Decreased Levels of Foldase and Chaperone Proteins Are Associated with an Early-Onset Amyotrophic Lateral Sclerosis

Abstract

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by a progressive upper and lower motor neuron degeneration. One of the peculiar clinical characteristics of ALS is the wide distribution in age of onset, which is probably caused by different combinations of intrinsic and exogenous factors. We investigated whether these modifying factors are converging into common pathogenic pathways leading either to an early or a late disease onset. This would imply the identification of phenotypic biomarkers, that can distinguish the two populations of ALS patients, and of relevant pathways to consider in a therapeutic intervention. Toward this aim a differential proteomic analysis was performed in peripheral blood mononuclear cells (PBMC) from a group of 16 ALS patients with an age of onset ≤55 years and a group of 16 ALS patients with an age of onset ≥75 years, and matched healthy controls. We identified 43 differentially expressed proteins in the two groups of patients. Gene ontology analysis revealed that there was a significant enrichment in annotations associated with protein folding and response to stress. We next validated a selected number of proteins belonging to this functional group in 85 patients and 83 age- and sex-matched healthy controls using immunoassays. The results of the validation study confirmed that there was a decreased level of peptidyl-prolyl cis-trans isomerase A (also known as cyclophilin A), heat shock protein HSP 90-alpha, 78 kDa glucose-regulated protein (also known as BiP) and protein deglycase DJ-1 in PBMC of ALS patients with an early onset. Similar results were obtained in PBMC and spinal cord from two SOD1G93A mouse models with an early and late disease onset. This study suggests that a different ability to upregulate proteins involved in proteostasis, such as foldase and chaperone proteins, may be at the basis of a different susceptibility to ALS, putting forward the development of therapeutic approaches aiming at boosting the protein quality control system.

Defective cyclophilin A induces TDP-43 proteinopathy: implications for amyotrophic lateral sclerosis and frontotemporal dementia

“…Similarly, in the cortex of PPIA-/-mice, the 25-kDa TDP-43 fragment was significantly enriched in the detergent-insoluble fraction, while the full-length was not. Biochemical analysis of the detergent-insoluble fraction of the cortex of PPIA-/-mice indicated general increases in insoluble, ubiquitinated proteins and TIA1 stress granule marker, confirming PPIA's involvement in regulating protein homeostasis, as already suggested by other work in this laboratory (Filareti et al, 2017;Luotti et al, 2020). We recently reported that ALS patients have low PPIA levels and a concomitant shift toward increased protein partitioning in the insoluble fraction, with high levels of insoluble TDP-43 and hnRNPA2/B1 (Luotti et al, 2020).…”

“…We firstly reported that PPIA is altered in amyotrophic lateral sclerosis (ALS) animal models and patients (Basso et al, 2009;Massignan et al, 2007;Nardo et al, 2011). Next, we demonstrated that low levels of PPIA in peripheral blood mononuclear cells (PBMCs) of ALS patients are associated with an early onset of the disease (Filareti et al, 2017) and a short disease duration (Luotti et al, 2020). In agreement with this, PPIA deficiency exacerbated aggregation and accelerated disease progression in a SOD1 G93A mouse model of ALS (Lauranzano et al, 2015).…”

“…Both protective and detrimental biological activities have been attributed to PPIA in different cell types and diseases (Hoffmann and Schiene-Fischer, 2014;Nigro et al, 2013), but its role in the brain is still not clear. In previous work we found that PPIA is a TDP-43 interactor that governs key TDP-43 functions and is altered in animal models and patients with ALS (Filareti et al, 2017;Lauranzano et al, 2015;Luotti et al, 2020;Nardo et al, 2011). Here, we further explore PPIA's functions in the brain by deep characterization in PPIA-/-mice.…”

“…For western blot (WB), samples (15 µg) were separated in 12% SDS-polyacrylamide gels and transferred to polyvinylidene difluoride membranes (Millipore), as described previously (Lauranzano et al, 2015). For dot blot, proteins (3 µg) were loaded directly onto nitrocellulose Trans-blot transfer membranes (0.45 µm; Bio-Rad),depositing each sample on the membrane by vacuum filtration, as described previously (Basso et al, 2009;Filareti et al, 2017;Massignan et al, 2007;Nardo et al, 2011;Pasetto et al, 2017). WB and dot blot membranes were blocked with 3% (w/v) BSA (Sigma-Aldrich) and 0.1% (v/v) Tween 20 in Tris-buffered saline, pH 7.5, and incubated with primary antibodies according to the manufacturer's protocol and then with peroxidaseconjugated secondary antibodies (GE Healthcare).…”

Rapidly progressive amyotrophic lateral sclerosis is associated with microglial reactivity and small heat shock protein expression in reactive astrocytes

“…In vivo , experimental induction of an HSPB5/8 homologue partially rescues TDP‐43 aggregation and increases life span in drosophila . In support of a protective role of HSPB in animal models of ALS, slow‐progressing SOD1 G93A mice have fivefold higher expression of HSPB5 when compared to fast‐progressing SOD1 G93A mice .…”