Mutant glucocerebrosidase impairs alpha-synuclein degradation by blockade of chaperone-mediated autophagy
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ABSTRACT:
PROVIDER: PRJNA781959 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR16986503.fastq.gz | Fastqsanger.gz | |||
| SRR16986504.fastq.gz | Fastqsanger.gz | |||
| SRR16986505.fastq.gz | Fastqsanger.gz | |||
| SRR16986506.fastq.gz | Fastqsanger.gz | |||
| SRR16986507.fastq.gz | Fastqsanger.gz |
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Project description:The most common genetic risk factors for Parkinson’s disease (PD) are a set of heterozygous mutant (MT) alleles of the GBA1 gene that encodes -glucocerebrosidase (GCase), an enzyme that is normally trafficked from the endoplasmic reticulum and Golgi apparatus to the lysosomal lumen. We examined isolated lysosomes from anterior cingulate cortex, a region of high alpha-synuclein accumulation in GBA-PD, and found that while lysosomal GCase is entirely luminal in healthy controls, half of the lysosomal GBA-PD GCase was present on the lysosomal surface. This lysosomal mislocalization is dependent on a pentapeptide motif in GCase used for targeting of cytosolic proteins to lysosomes for degradation by chaperone-mediated autophagy (CMA), a type of autophagy inhibited by PD-related pathogenic proteins including -synuclein and LRRK2. Single cell transcriptional analysis and comparative proteomics of brains from GBA-PD patients demonstrated reduced CMA activity and overall proteome changes similar to those observed in mouse models with CMA blockage. We found that the delivery of unfolded mutant GCase to lysosomes decreased CMA due to recognition of unfolded mutant GCase to the chaperone hsc70, and the resulting complex binds the CMA receptor LAMP2A at the lysosomal surface. Unfolded mutant GCase is a poor substrate for translocation into the lysosomal lumen, and by interfering with LAMP2A multimerization, blocks the translocation and causes cytosolic accumulation of other CMA substrates including -synuclein and tau. In primary substantia nigra dopamine neurons, MT GCase led to neuronal death, while loss of the GCase CMA motif or deletion of -synuclein rescued the neurons. These results indicate how MT GCase alleles may converge with other PD proteins to block CMA function and produce -synuclein accumulation.
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Project description:Altered degradation of alpha-synuclein (alpha-syn) has been implicated in the pathogenesis of Parkinson disease (PD). We have shown that alpha-syn can be degraded via chaperone-mediated autophagy (CMA), a selective lysosomal mechanism for degradation of cytosolic proteins. Pathogenic mutants of alpha-syn block lysosomal translocation, impairing their own degradation along with that of other CMA substrates. While pathogenic alpha-syn mutations are rare, alpha-syn undergoes posttranslational modifications, which may underlie its accumulation in cytosolic aggregates in most forms of PD. Using mouse ventral medial neuron cultures, SH-SY5Y cells in culture, and isolated mouse lysosomes, we have found that most of these posttranslational modifications of alpha-syn impair degradation of this protein by CMA but do not affect degradation of other substrates. Dopamine-modified alpha-syn, however, is not only poorly degraded by CMA but also blocks degradation of other substrates by this pathway. As blockage of CMA increases cellular vulnerability to stressors, we propose that dopamine-induced autophagic inhibition could explain the selective degeneration of PD dopaminergic neurons.
| S-EPMC2157565 | biostudies-literature