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Coronin1A Regulates the Trafficking of Alpha Synuclein in Microglia
Karl E Biggs1,2, Emma N Fikse1, Faith L Anderson1
1Departments of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03766.
Abstract:
Microglia respond to cytotoxic protein aggregates associated with the progression of neurodegenerative disease. Pathological protein aggregates activate the microglial NLRP3 inflammasome resulting in proinflammatory signaling, secretion, and potentially pyroptotic cell death. We characterized mixed sex primary mouse microglia exposed to microbial stressors and alpha synuclein preformed fibrils (αsyn PFFs) to identify cellular mechanisms related to Parkinson's disease. Microglia package and release the endosome fate regulator Coronin1A (Coro1A) in EVs in an Nlrp3-dependent manner in widely used experimental activation conditions. We were surprised to find that Coro1A packaging and release was not Nlrp3-dependent in αsyn PFF exposure conditions. Coro1A-/- microglia exposed to αsyn PFFs trafficked more αsyn to the lysosomal compartment increasing lysosomal membrane permeabilization. This corresponds to a decrease in αsyn released in EVs suggesting that Coro1A functions to shunt pathological proteins to a secretory pathway to attenuate lysosomal stress. αsyn PFF-driven lysosomal stress resulting from Coro1a loss was associated with enhanced cytotoxicity. Intrinsic apoptosis signaling was unaffected, but we observed elevated cytosolic cathepsin B and the presence of a cathepsin-associated 55 kD PARP cleavage product. Postmortem analysis of the PD mesencephalon supported a role for Coro1A in microglia, revealing elevated levels of Coro1A protein in human PD brains compared with those of healthy donors. Findings are relevant to the distribution of pathological αsyn and indicate that Coro1a protects microglia from lysosomal overload, inflammasome activation, and pyroptotic demise.
Insights
Coronin1A (Coro1A) in microglia protects against alpha synuclein toxicity in Parkinson's disease by shunting protein aggregates away from lysosomes. Loss of Coro1A increases cell death and inflammasome activation.
Area of Science:
- Neuroscience
- Cell Biology
- Immunology
Background:
- Microglia, the brain's immune cells, respond to toxic protein aggregates in neurodegenerative diseases like Parkinson's.
- Activation of the NLRP3 inflammasome in microglia leads to inflammation and cell death.
- Alpha-synuclein (αsyn) preformed fibrils (PFFs) are key pathological protein aggregates in Parkinson's disease.
Purpose of the Study:
- To investigate the role of Coronin1A (Coro1A) in microglial response to αsyn PFFs.
- To identify cellular mechanisms by which microglia handle pathological protein aggregates.
- To explore Coro1A's involvement in Parkinson's disease pathogenesis.
Main Methods:
- Primary mouse microglia were exposed to microbial stressors and αsyn PFFs.
- Extracellular vesicles (EVs) released by microglia were analyzed for Coro1A content.
- αsyn trafficking, lysosomal integrity, and cell death pathways were assessed in Coro1A-deficient microglia.
- Postmortem human brain tissue from Parkinson's disease patients was analyzed.
Main Results:
- Microglia release Coro1A in EVs in an NLRP3-dependent manner under general activation, but surprisingly not with αsyn PFFs.
- Loss of Coro1A in microglia leads to increased αsyn trafficking to lysosomes, causing lysosomal membrane permeabilization.
- Coro1A deficiency results in enhanced αsyn PFF-induced cytotoxicity, elevated cytosolic cathepsin B, and a PARP cleavage product.
- Elevated Coro1A protein levels were observed in the mesencephalon of human Parkinson's disease brains.
Conclusions:
- Coro1A acts as a crucial regulator, shunting pathological αsyn away from lysosomes to a secretory pathway via EVs, thereby mitigating lysosomal stress.
- Loss of Coro1A function in microglia exacerbates αsyn-induced lysosomal damage and cytotoxicity, contributing to neurodegeneration.
- These findings highlight Coro1A's protective role in microglia against inflammasome activation and pyroptotic cell death, relevant to Parkinson's disease progression.
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