iPSC-derived neurons from GBA1-associated Parkinson’s disease patients show autophagic defects and impaired calcium homeostasis

Abstract

Mutations in the acid β-glucocerebrosidase (GBA1) gene, responsible for the lysosomal storage disorder Gaucher's disease (GD), are the strongest genetic risk factor for Parkinson's disease (PD) known to date. Here we generate induced pluripotent stem cells from subjects with GD and PD harbouring GBA1 mutations, and differentiate them into midbrain dopaminergic neurons followed by enrichment using fluorescence-activated cell sorting. Neurons show a reduction in glucocerebrosidase activity and protein levels, increase in glucosylceramide and α-synuclein levels as well as autophagic and lysosomal defects. Quantitative proteomic profiling reveals an increase of the neuronal calcium-binding protein 2 (NECAB2) in diseased neurons. Mutant neurons show a dysregulation of calcium homeostasis and increased vulnerability to stress responses involving elevation of cytosolic calcium. Importantly, correction of the mutations rescues such pathological phenotypes. These findings provide evidence for a link between GBA1 mutations and complex changes in the autophagic/lysosomal system and intracellular calcium homeostasis, which underlie vulnerability to neurodegeneration.

Glucosylceramide synthase inhibition alleviates aberrations in synucleinopathy models

“…For example, changes in the composition of sphingolipids have been reported to stabilize soluble oligomeric forms of isolated recombinant α-synuclein (13). Endogenously produced α-synuclein can also accumulate in induced pluripotent (iPS) cells from patients with PD who harbor homozygous or heterozygous GBA mutations, presumably because of the presence of increased levels of membrane glycosphingolipids (12,13,40). It appears reasonable, then, that persistent reduction in brain glycosphingolipids of the synucleinopathy animal slowed the accumulation of aggregated proteins (ubiquitin, α-synuclein, and tau), indicating the potential for the orally available brain-penetrant GCS inhibitor to modify disease progression in patients with PD carrying GBA mutations.…”

“…Small increases in GlcCer have been reported in dopaminergic neurons differentiated from inducible pluripotent stem cells harboring heterozygote GBA mutations and in primary cultured cortical neurons expressing ∼50% glucocerebrosidase activity. Interestingly, these cellular models display increased α-synuclein levels, presumably due to the changes in the sphingolipid composition (12,13). …”

Glucocerebrosidase Mutations in Parkinson Disease

“…These iPSCs can then be differentiated into especially disease-relevant cell types, such as dopaminergic neurons [28][29][30]. This allows for the characterisation of human dopaminergic neurons carrying GBA mutations.…”

“…This allows for the characterisation of human dopaminergic neurons carrying GBA mutations. In this way analysis and comparison of mutation carriers versus controls at a cellular and molecular level is possible, including live-cell imaging [28].…”

Relevance of the plasma membrane calcium-ATPase in the homeostasis of calcium in the fetal liver

“…48 Employing iPSCs derived from patients suffering from hypertrophic cardiomyopathy or Parkinson disease, alterations in calcium handling and an increase in the levels of intracellular Ca 2C have been found in close relationship to the genesis of these pathologies. 49,50 Therefore, the role of PMCAs in regulating calcium perturbations in excitable and nonexcitable tissues represents an active area of ongoing research.…”