Davis, M. Y. | bioRxiv Science

bioRxiv2026

GBA1 deficiency differentially affects endolysosomal trafficking in neurons versus astrocytes

Mutations in the gene glucosidase, beta acid 1 (GBA1) are the strongest genetic risk factor for Parkinsons disease (PD) and are associated with faster disease progression. GBA1 is expressed in all cell types of the central nervous system, with some evidence supporting higher expression in glial cells than neurons. To elucidate possible specific functions in neurons versus glia, we differentiated human induced pluripotent stem cells (iPSCs) generated from an individual with PD heterozygous for the GBA1 pathogenic null variant IVS2+1 (GBA1IVS/+), homozygous GBA1 IVS2+1 isogenic to GBA1IVS/+ (GBA1IVS/IVS) and a healthy unaffected age-and sex-matched individual (GBA1+/+). GBA1 expression was reduced in GBA1IVS/+ and GBA1IVS/IVS neurons and astrocytes. Endolysosomal trafficking was significantly altered in GBA1-deficient neurons with enlarged early and recycling endosome and lysosome compartments in neurons but not in astrocytes. High molecular weight oligomerization of -synuclein and phosphorylated Ser129 -synuclein were present in GBA1IVS/+ and GBA1IVS/IVS neurons but not in GBA1+/+ neurons, or in GBA1-deficient or GBA1+/+ astrocytes. Transcriptomic analysis of GBA1-deficient neurons and astrocytes revealed cell-type specific profiles. GBA1 deficiency in neurons downregulated immune response and upregulated cholesterol synthesis pathways, while GBA1 deficiency in astrocytes downregulated genes associated with translation and upregulated genes involved in extracellular matrix biogenesis. Transcriptomic analysis also suggests that GBA1 deficiency induces neurotoxic reactivity in astrocytes. Together, these findings indicate that GBA1 deficiency has cell type-specific effects, with increased neuronal vulnerability to endolysosomal trafficking leading to -synucleinopathy while GBA1 deficiency in astrocytes leads to increased neurotoxic reactivity independent of endolysosomal trafficking and -synucleinopathy. HighlightsO_LIiPSC-derived neurons and astrocytes modeled GBA1 deficiency C_LIO_LIEndolysosomal trafficking defects occurred only in GBA1-deficient neurons C_LIO_LI-synuclein oligomers accumulated in GBA1-deficient neurons, not astrocytes C_LIO_LIAstrocyte GBA1 loss drove neurotoxic reactive gene signatures C_LIO_LIGBA1 deficiency causes cell-type specific pathology C_LI

neuroscience↗

bioRxiv2020

Glucocerebrosidase reduces the spread of protein aggregation in a Drosophila melanogaster model of neurodegeneration by regulating proteins trafficked by extracellular vesicles

Abnormal protein aggregation within neurons is a key pathologic feature of Parkinsons disease (PD). The spread of protein aggregates in the brain is associated with clinical disease progression, but how this occurs remains unclear. Mutations in the gene glucosidase, beta acid 1 (GBA), which encodes the lysosomal enzyme glucocerebrosidase (GCase), are the most penetrant common genetic risk factor for PD and dementia with Lewy bodies, and also associate with faster disease progression. To explore the mechanism by which mutations in GBA influence pathogenesis of these diseases, we previously created a Drosophila model of GBA deficiency (Gba1b) that manifests neurodegeneration, motor and cognitive deficits, and accelerated protein aggregation. Proteomic analysis of Gba1b mutants revealed dysregulation of proteins involved in extracellular vesicle (EV) biology, and we found altered protein composition of EVs from Gba1b mutants. To further investigate this novel mechanism, we hypothesized that GBA may influence the spread of pathogenic protein aggregates throughout the brain via EVs. We found that protein aggregation is reduced cell-autonomously and non-cell-autonomously by expressing wildtype GCase in specific tissues. In particular, accumulation of insoluble ubiquitinated proteins and Ref(2)P in the brains of Gba1b flies are reduced by ectopic expression of GCase in muscle tissue. Neuronal expression of GCase also cell-autonomously rescued protein aggregation in brain as well as non-cell-autonomously rescued protein aggregation in muscle. Muscle-specific GBA expression rescued the elevated levels of EV-intrinsic proteins and Ref(2)P found in EVs from Gba1b flies. Genetically perturbing EV biogenesis in specific tissues in the absence of GCase revealed differential cell-autonomous effects on protein aggregation but could not replicate the non-cell-autonomous rescue observed with tissue-specific GBA expression. Additionally, we identified ectopically expressed GCase within isolated EVs. Together, our findings suggest that GCase deficiency mediates accelerated spread of protein aggregates between cells and tissues via dysregulated EVs, and EV-mediated trafficking of GCase may partially account for the reduction in aggregate spread. Authors SummaryParkinsons disease (PD) is a common neurodegenerative disease characterized by abnormal clumps of proteins (aggregates) within the brain and other tissues which can lead to cellular dysfunction and death. Mutations in the gene GBA, which encodes glucocerebrosidase (GCase), are the strongest genetic risk factor for PD, and are associated with faster disease progression. GCase-deficient mutant flies display features suggestive of PD including increased protein aggregation in brain and muscle. We found that restoring GCase protein in the muscle of mutant flies reduced protein aggregation in muscle and the brain, suggesting a mechanism involving interaction between tissues. Previous work indicated that GBA influences extracellular vesicles (EVs) - small membrane-bound structures released by cells to communicate and/or transport cargo from cell to cell. Here, we found increased aggregated proteins within EVs of mutant flies, which was reduced by restoring GCase in muscle. In addition, we found GCase within the EVs, possibly explaining how GCase in one tissue such as muscle could reduce protein aggregation in a distant tissue like the brain. Our findings suggest that GCase influences proteins within EVs, affecting the spread of protein aggregation. This may be important to understanding PD progression and could uncover new targets to slow neurodegeneration.

cell biology↗