SARS-CoV-2 N-protein induces the formation of composite α-synuclein/N-protein fibrils that transform into a strain of α-synuclein fibrils

The presence of deposits of alpha-synuclein (αS) fibrils in the cells of the brain is a hallmark of several α-synucleinopathies, including Parkinson's disease. As most disease cases are not familial, it is likely that external factors play a role in the disease onset. One of the external factors that may influence the disease onset is viral infection. It has recently been shown in in vitro assays that in the presence of SARS-Cov-2 N-protein, αS fibril formation is faster and proceeds in an unusual two-step aggregation process. Here, we show that faster fibril formation is not due to the SARS-CoV-2 N-protein-catalysed formation of an aggregation-prone nucleus. Instead, aggregation starts with the formation of a population of mixed αS/N-protein fibrils with low affinity for αS. Mixed amyloid fibrils, composed of two different proteins, have not been observed before. After the depletion of N-protein, fibril formation comes to a halt, until a slow transformation into fibrils with characteristics of a pure αS fibril strain occurs. This transformation into a strain of αS fibrils subsequently results in a second phase of fibril growth until a new equilibrium is reached. We hypothesize that this fibril strain transformation may be of relevance in the cell-to-cell spread of the αS pathology and disease onset

Cooperation of Helix Insertion and Lateral Pressure to Remodel Membranes

Nature has developed different protein mediated mechanisms to remodel cellular membranes. One of the proteins that is implicated in these processes is α-synuclein (αS). Here we investigate if besides αS's membrane bound amphipathic helix the disordered, solvent exposed tail of the protein contributes to membrane reshaping. We produced αS variants with elongated or truncated disordered solvent exposed domains. We observe a transformation of opaque multi lamellar vesicle solutions into nonscattering solutions containing smaller structures upon addition of all αS variants. Experimental data combined with model calculations show that the cooperation of helix insertion and lateral pressure exerted by the disordered domain makes the full length protein decidedly more efficient in membrane remodeling than the truncated version. Using disordered domains may not only be cost-efficient, it may also add a new level of control over vesicle fusion/fission by expansion or compaction of the domain

Quantification of the Retention and Disassembly of Virus Particles by a PEI-Functionalized Microfiltration Membrane

[Image: see text] Monitoring the performance of polymer-functionalized surfaces that aim at removing and inactivating viruses is typically labor-intensive and time-consuming. This hampers the development and optimization of such surfaces. Here we present experiments of low complexity that can be used to characterize and quantify the antiviral properties of polymer-functionalized surfaces. We showcase our approach on polyethylenimine (PEI)-coated poly(ether sulfone) (PES) microfiltration membranes. We use a fluorescently labeled model virus to quantify both virus removal and inactivation. We directly quantify the log removal of intact viruses by this membrane using single particle counting. Additionally, we exploit the change in photophysical properties upon disassembly of the virus to show that viruses are inactivated by the PEI coating. Although only a small fraction of intact viruses can pass the membrane, a considerable fraction of inactivated, disassembled viruses are found in the filtrate. Fluorescence microscopy experiments show that most of the viruses left behind on the microfiltration membrane are in the inactivated, disassembled state. Combined, our fluorescence microscopy and spectroscopy experiments show that not only does the model virus adsorb to the PEI coating on the membrane but also the interaction with PEI results in the disassembly of the virus capsid