Cellular Prion Protein Mediates α‐Synuclein Uptake, Localization, and Toxicity In Vitro and In Vivo

Abstract

A BS TRACT: Background: The cellular prion protein (PrP C ) is a membrane-bound, multifunctional protein mainly expressed in neuronal tissues. Recent studies indicate that the native trafficking of PrP C can be misused to internalize misfolded amyloid beta and α-synuclein (aSyn) oligomers. Objectives: We define PrP C 's role in internalizing misfolded aSyn in α-synucleinopathies and identify further involved proteins. Methods: We performed comprehensive behavioral studies on four transgenic mouse models (ThySyn and ThySynPrP00, TgM83 and TgMPrP00) at different ages. We developed PrP C -(over)-expressing cell models (cell line and primary cortical neurons), used confocal laser microscopy to perform colocalization studies, applied mass spectrometry to identify interactomes, and determined disassociation constants using surface plasmon resonance (SPR) spectroscopy. Results: Behavioral deficits (memory, anxiety, locomotion, etc.), reduced lifespans, and higher oligomeric aSyn levels were observed in PrP C -expressing mice (ThySyn and TgM83), but not in homologous Prnp ablated mice (ThySynPrP00 and TgMPrP00). PrP C colocalized with and facilitated aSyn (oligomeric and monomeric) internalization in our cell-based models. Glimepiride treatment of PrP Coverexpressing cells reduced aSyn internalization in a dosedependent manner. SPR analysis showed that the binding affinity of PrP C to monomeric aSyn was lower than to oligomeric aSyn. Mass spectrometry-based proteomic studies identified clathrin in the immunoprecipitates of PrP C and aSyn. SPR was used to show that clathrin binds to recombinant PrP, but not aSyn. Experimental disruption of clathrincoated vesicles significantly decreased aSyn internalization. Conclusion: PrP C 's native trafficking can be misused to internalize misfolded aSyn through a clathrin-based mechanism, which may facilitate the spreading of pathological aSyn. Disruption of aSyn-PrP C binding is, therefore, an appealing therapeutic target in α-synucleinopathies.

Is Multiple System Atrophy a Prion-like Disorder?

“…Although the molecular mechanisms responsible for spreading pathologic αSyn are poorly understood, a growing body of evidence indicates that de novo misfolding and/or neuronal internalization of aggregated αSyn facilitates conformational templating of endogenous αSyn monomers in a prion-like manner [77]. Recent studies demonstrating that cellular prion protein (PrP C ) mediates αSyn uptake, localization, and toxicity in vitro and in vivo confirmed previous results which showed that PrP C internalizes soluble misfolded αSyn, indicating its important role in its internalization required for the intercellular spread of αSyn [78]. Cell intrinsic features also may play a critical role in the formation of pathologic αSyn, such as mechanisms that increase endogenous αSyn levels, selective expression profiles in distinct neuron types, altered function of proteins involved in αSyn synthesis and degradation, and oxidative stress.…”

Sigma-2 Receptors—From Basic Biology to Therapeutic Target: A Focus on Age-Related Degenerative Diseases

“…The S2R is a therapeutic target under investigation for α-synucleinopathies and CT1812 is currently in Phase 2 trials, being developed by Cognition Therapeutics, for dementia with Lewy bodies (NCT05225415). Support for targeting the S2R derives from α-synuclein binding to PrP c [ 42 ], and the finding that S2R modulators block α-synuclein oligomer toxicity in neurons [ 4 ]; this is a topic discussed in greater detail below.…”

“…S2R in close association with PGRMC1 regulates cell pathways known to be impaired in α-synucleinopathies, such as autophagy, vesicle trafficking, and lipid synthesis. Similar to amyloid-β oligomers, α-synuclein oligomers interact with PrP c [ 42 ]. α-Synuclein interacts with PrP c to induce cognitive impairment through metabotropic glutamate receptors, and blockage of these glutamate receptor-mediated signaling events restores cognitive deficits [ 42 ].…”

Oligomeropathies, inflammation and prion protein binding

“…Besides minimal methodological differences in recombinant α-syn purification and oligomer preparation, no obvious evidence justifies these contradictory results. A role of prion protein in α-synOs intercellular transport and pathological transmission has been recently hypothesized ( Urrea et al, 2018 ; Rösener et al, 2020 ) but the link with the direct binding of α-synOs to PrP c still needs further investigation ( Legname and Scialò, 2020 ; Thom et al, 2021 ).…”