PP2A and GSK3 act as modifiers of FUS-ALS by modulating mitochondrial transport

• Published in: Acta neuropathologica Vol. 147; no. 1; p. 41
• Main Authors: Tziortzouda, Paraskevi, Steyaert, Jolien, Scheveneels, Wendy, Sicart, Adria, Stoklund Dittlau, Katarina, Barbosa Correia, Adriana Margarida, Burg, Thibaut, Pal, Arun, Hermann, Andreas, Van Damme, Philip, Moens, Thomas G., Van Den Bosch, Ludo
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-06-2024; Springer Nature B.V
• Subjects: Amyotrophic lateral sclerosis; Amyotrophic Lateral Sclerosis - pathology; Animals; Drosophila; Drosophila - genetics; Drosophila - metabolism; FUS gene; FUS protein; Genomes; Glycogen; Glycogen synthase kinase 3; Glycogen Synthase Kinase 3 - genetics; Glycogen Synthase Kinase 3 - metabolism; Humans; Hyperactivity; Insects; Kinases; Kinesin; Kinesins - genetics; Kinesins - metabolism; Lethality; Medicine; Medicine & Public Health; Mice; Motor neurons; Motor Neurons - metabolism; Mutants; Mutation - genetics; Neurodegenerative diseases; Neurodegenerative Diseases - pathology; Neurosciences; Original Paper; Pathogenesis; Pathology; Phenotypes; Phosphoprotein phosphatase; Phosphorylation; Protein phosphatase; Protein Phosphatase 2 - genetics; Protein Phosphatase 2 - metabolism; Proteins; RNA-binding protein; RNA-Binding Protein FUS - genetics; RNA-Binding Protein FUS - metabolism; Toxicity; Amyotrophic lateral sclerosis; PP2A; GSK3; Kinesin; Drosophila
• ISSN: 0001-6322; 1432-0533; 1432-0533
• DOI: 10.1007/s00401-024-02689-y

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease which currently lacks effective treatments. Mutations in the RNA-binding protein FUS are a common cause of familial ALS, accounting for around 4% of the cases. Understanding the mechanisms by which mutant FUS becomes toxic to neurons can provide insight into the pathogenesis of both familial and sporadic ALS. We have previously observed that overexpression of wild-type or ALS-mutant FUS in
Drosophila
motor neurons is toxic, which allowed us to screen for novel genetic modifiers of the disease. Using a genome-wide screening approach, we identified Protein Phosphatase 2A (PP2A) and Glycogen Synthase Kinase 3 (GSK3) as novel modifiers of FUS-ALS. Loss of function or pharmacological inhibition of either protein rescued FUS-associated lethality in
Drosophila
. Consistent with a conserved role in disease pathogenesis, pharmacological inhibition of both proteins rescued disease-relevant phenotypes, including mitochondrial trafficking defects and neuromuscular junction failure, in patient iPSC-derived spinal motor neurons (iPSC-sMNs). In FUS-ALS flies, mice, and human iPSC-sMNs, we observed reduced GSK3 inhibitory phosphorylation, suggesting that FUS dysfunction results in GSK3 hyperactivity. Furthermore, we found that PP2A acts upstream of GSK3, affecting its inhibitory phosphorylation. GSK3 has previously been linked to kinesin-1 hyperphosphorylation. We observed this in both flies and iPSC-sMNs, and we rescued this hyperphosphorylation by inhibiting GSK3 or PP2A. Moreover, increasing the level of kinesin-1 expression in our
Drosophila
model strongly rescued toxicity, confirming the relevance of kinesin-1 hyperphosphorylation. Our data provide in vivo evidence that PP2A and GSK3 are disease modifiers, and reveal an unexplored mechanistic link between PP2A, GSK3, and kinesin-1, that may be central to the pathogenesis of FUS-ALS and sporadic forms of the disease.