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Dysregulation of mitochondria-lysosome contacts by GBA1 dysfunction in dopaminergic neuronal models of Parkinson's disease.

ABSTRACT: Mitochondria-lysosome contacts are recently identified sites for mediating crosstalk between both organelles, but their role in normal and diseased human neurons remains unknown. In this study, we demonstrate that mitochondria-lysosome contacts can dynamically form in the soma, axons, and dendrites of human neurons, allowing for their bidirectional crosstalk. Parkinson's disease patient derived neurons harboring mutant GBA1 exhibited prolonged mitochondria-lysosome contacts due to defective modulation of the untethering protein TBC1D15, which mediates Rab7 GTP hydrolysis for contact untethering. This dysregulation was due to decreased GBA1 (β-glucocerebrosidase (GCase)) lysosomal enzyme activity in patient derived neurons, and could be rescued by increasing enzyme activity with a GCase modulator. These defects resulted in disrupted mitochondrial distribution and function, and could be further rescued by TBC1D15 in Parkinson's patient derived GBA1-linked neurons. Together, our work demonstrates a potential role of mitochondria-lysosome contacts as an upstream regulator of mitochondrial function and dynamics in midbrain dopaminergic neurons in GBA1-linked Parkinson's disease.

SUBMITTER: Kim S

PROVIDER: S-EPMC7985376 | biostudies-literature | 2021 Mar

REPOSITORIES: biostudies-literature

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Dysregulation of mitochondria-lysosome contacts by GBA1 dysfunction in dopaminergic neuronal models of Parkinson's disease.

Kim Soojin S Wong Yvette C YC Gao Fanding F Krainc Dimitri D

Nature communications 20210322 1

Mitochondria-lysosome contacts are recently identified sites for mediating crosstalk between both organelles, but their role in normal and diseased human neurons remains unknown. In this study, we demonstrate that mitochondria-lysosome contacts can dynamically form in the soma, axons, and dendrites of human neurons, allowing for their bidirectional crosstalk. Parkinson's disease patient derived neurons harboring mutant GBA1 exhibited prolonged mitochondria-lysosome contacts due to defective modu ...[more]

PMID: 33753743

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Project description:Mitochondrial network is constantly in a dynamic and regulated balance of fusion and fission processes, which is known as mitochondrial dynamics. Mitochondria make physical contacts with almost every other membrane in the cell thus impacting cellular functions. Mutations in mitochondrial dynamics genes are known to cause neurogenetic diseases. To better understand the consequences on the cellular phenotype and pathophysiology of neurogenetic diseases associated with defective mitochondrial dynamics, we have compared the fibroblasts phenotypes of (i) patients carrying pathogenic variants in genes involved in mitochondrial dynamics such as DRP1 (also known as DNM1L), GDAP1, OPA1, and MFN2, and (ii) patients carrying mutated genes that their dysfunction affects mitochondria or induces a mitochondrial phenotype, but that are not directly involved in mitochondrial dynamic network, such as FXN (encoding frataxin, located in the mitochondrial matrix), MED13 (hyperfission phenotype), and CHKB (enlarged mitochondria phenotype). We identified mitochondrial network alterations in all patients' fibroblasts except for CHKB Q198*/Q198*. Functionally, all fibroblasts showed mitochondrial oxidative stress, without membrane potential abnormalities. The lysosomal area and distribution were abnormal in GDAP1 W67L/W67L, DRP1 K75E/+, OPA1 F570L/+, and FXN R165C/GAA fibroblasts. These lysosomal alterations correlated with mitochondria-lysosome membrane contact sites (MCSs) defects in GDAP1 W67L/W67L exclusively. The study of mitochondrial contacts in all samples further revealed a significant decrease in MFN2 R104W/+ fibroblasts. GDAP1 and MFN2 are outer mitochondrial membrane (OMM) proteins and both are related to Charcot-Marie Tooth neuropathy. Here we identified their constitutive interaction as well as MFN2 interaction with LAMP-1. Therefore MFN2 is a new mitochondria-lysosome MCSs protein. Interestingly, GDAP1 W67L/W67L and MFN2 R104W/+ fibroblasts carry pathogenic changes that occur in their catalytic domains thus suggesting a functional role of GDAP1 and MFN2 in mitochondria-lysosome MCSs. Finally, we observed starvation-induced autophagy alterations in DRP1 K75E/+, GDAP1 W67L/W67L, OPA1 F570L/+, MFN2 R104W/+, and CHKB Q198*/Q198* fibroblasts. These genes are related to mitochondrial membrane structure or lipid composition, which would associate the OMM with starvation-induced autophagy. In conclusion, the study of mitochondrial dynamics and mitochondria-lysosome axis in a group of patients with different neurogenetic diseases has deciphered common and unique cellular phenotypes of degrading and non-degrading pathways that shed light on pathophysiological events, new biomarkers and pharmacological targets for these disorders.

Project description:BackgroundA key factor in the propagation of α-synuclein pathology is the compromised protein quality control system. Variations in membrane association and astrocytic uptake between different α-synuclein forms suggest differences in exocytosis or membrane cleavage, potentially impacting the secretome's influence on dopaminergic neurons. We aimed to understand differences in protein degradation mechanisms of astrocytes for both wild-type (WT) and mutant forms of α-synuclein, specifically during periods of reduced degradation efficiency. We also investigated α-synuclein release into the secretome and its effects on healthy dopaminergic neurons.MethodsCellular models used were rat primary astrocytes alongside hiPSC-derived astrocytes, whose impact on rat primary dopaminergic neurons and the human SH-SY5Y cell line was investigated. We examined the release and accumulation of α-synuclein resulting from impaired degradatory pathways, including matrix metalloprotease-MMP9, the ubiquitin proteasomal pathway-UPS, and the autophagy-lysosomal pathway-ALP, using immunocytochemical analysis and flow cytometry. Additionally, we explored the effect of astrocytic secretome on dopaminergic-neuronal survival, neurite collapse and function.ResultsAt early stages, astrocytes were able to deal efficiently with monomeric α-synuclein (via UPS), and larger aggregates (through MMP9 and autophagy), clearing extracellular α-synuclein and maintaining neuronal health. However, extended exposure to extracellular monomeric and aggregated α-synuclein compromised their proteasomal activity, inhibiting MMP9 and destabilizing autophagy, transforming astrocytes from protectors to promoters of neurodegeneration. This study is the first to elucidate the astrocytes' preferred degradation pathways for both monomeric and aggregated forms of α-synuclein, along with the subsequent effects of these payloads on the cellular degradation machinery. The astrocytic transformation is characterized by α-synuclein expulsion, increased release of inflammatory cytokines, and diminished secretion of growth factors leading to dopaminergic neuronal apoptosis and dysfunction, particularly neurite collapse, intracellular Ca2+ response and vesicular dopamine release. The presence of phosphorylated and nitrated α-synuclein species in astrocytes also suggests their potential involvement in modifying both forms of the protein.ConclusionThe initial protective action of astrocytes in clearing and degrading extracellular α-synuclein is severely compromised at latter stages, leading to astrocytic dysfunction and impairing neuron-glia cross-talk. This study underscores the criticality of integrating astrocytes into treatment paradigms in synucleinopathies.

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Dysregulation of mitochondria-lysosome contacts by GBA1 dysfunction in dopaminergic neuronal models of Parkinson's disease.

Publications

Dysregulation of mitochondria-lysosome contacts by GBA1 dysfunction in dopaminergic neuronal models of Parkinson's disease.

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