Factors Affecting Aggregate Formation in Cell Models of Huntington’s Disease and Amyotrophic Lateral Sclerosis

Abstract

Most neurodegenerative pathologies stem from the formation of aggregates of mutant proteins, causing dysfunction and ultimately neuronal death. This study was aimed at elucidating the role of the protein factors that promote aggregate formation or prevent the process, respectively, glyceraldehyde-3-dehydrogenase (GAPDH) and tissue transglutaminase (tTG) and Hsp70 molecular chaperone. The siRNA technology was used to show that the inhibition of GAPDH expression leads to a 45–50% reduction in the aggregation of mutant huntingtin, with a repeat of 103 glutamine residues in a model of Huntington’s disease (HD). Similarly, the blockage of GAPDH synthesis was found for the first time to reduce the degree of aggregation of mutant superoxide dismutase 1 (G93A) in a model of amyotrophic lateral sclerosis (ALS). The treatment of cells that imitate HD and ALS with a pharmacological GAPDH inhibitor, hydroxynonenal, was also shown to reduce the amount of the aggregating material in both disease models. Tissue transglutaminase is another factor that promotes the aggregation of mutant proteins; the inhibition of its activity with cystamine was found to prevent aggregate formation of mutant huntingtin and SOD1. In order to explore the protective function of Hsp70 in the control of the aggregation of mutant huntingtin, a cell model with inducible expression of the chaperone was used. The amount and size of polyglutamine aggregates were reduced by increasing the intracellular content of Hsp70. Thus, pharmacological regulation of the function of three proteins, GAPDH, tTG, and Hsp70, can affect the pathogenesis of two significant neurodegenerative diseases.

N-acetyl ornithine deacetylase is a moonlighting protein and is involved in the adaptation of Entamoeba histolytica to nitrosative stress

“…and it has been proposed that GAPDH may act as a NO scavenger62. On the other hand the formation of toxic GAPDH species in oxidatively- and nitrosatively-stressed cells is involved in the pathogenesis of Alzheimer’s disease38 and Huntington’s disease36. Our findings support a detrimental role of GAPDH in trophozoites exposed to NS.…”

“…that are naturally resistant to NS35 which suggest that GAPDH has a protective role against NS in this parasite. In contrast GAPDH can trigger cell death in oxidatively- and nitrosatively-stressed mammalian cells363738. GAPDH expression is upregulated in trophozoites exposed to NS5 however we have no knowledge about the beneficial or detrimental effect that GAPDH has on E. histolytica exposed to NS.…”

GAPDH binders as potential drugs for the therapy of polyglutamine diseases: Design of a new screening assay

“…1). With the addition of tTG, the aggregation increased even more, proving our recent observation that the enzyme is necessary for the strengthening polyQ-GAPDH or mutant SOD1-GAPDH complexes [25]. The results of the filter trap assay were confirmed by the data of atomic force microscopy, according to which the size of Q58 structures was approximately 10 nm; these data well correspond to results obtained by other groups [26,27].…”

Pharmacological protein targets in polyglutamine diseases: Mutant polypeptides and their interactors

“…Importantly, pharmacological GAPDH‐binding substances were also shown to reduce polyQ‐associated aggregation in SK–N–SH neuroblastoma cells [77]. It is noteworthy that GAPDH was also implicated in aggregation of mutant SOD1 (G93A) in a cell model of familial amyotrophic lateral sclerosis: both specific anti‐GAPDH siRNA and GAPDH binder hydroxynonnenal inhibitor decreased aggregates of mutant SOD1 in filter trap assay [78].…”