Biology subjects

Mikalauskaite, K.

Publications and source records attributed to Mikalauskaite, K..

4 recordsLinked to original sources

bioRxiv2024

Heterotypic droplet formation by pro-inflammatory S100A9 and neurodegenerative disease-related alpha-synuclein

Liquid-liquid phase separation (LLPS) of proteins and nucleic acids is a rapidly emerging field of study, aimed at understanding the process of biomolecular condensate formation and its role in cellular functions. LLPS has been shown to be responsible for the generation of promyelocytic leukemia protein bodies, stress granules, and intrinsically disordered protein condensates. Recently, it has been discovered that different neurodegenerative disease-related proteins, such as alpha-synuclein (related to Parkinsons disease) and amyloid-beta (Alzheimers disease) are capable of forming heterotypic droplets. Other reports have also shown non-LLPS cross-interactions between various amyloidogenic proteins and the resulting influence on their amyloid fibril formation. This includes the new discovery of pro-inflammatory S100A9 affecting the aggregation of both amyloid-beta, as well as alpha-synuclein. Combined, these observations suggest that protein interactions during LLPS and heterotypic droplet formation may be a critical step in the onset of neurodegenerative diseases. In this study, we explore the formation of heterotypic droplets by S100A9 and alpha-synuclein using a range of different spectroscopic and microscopic techniques. We show that the protein mixture is capable of assembling into both homotypic, as well as heterotypic condensates and that this cross-interaction alters the aggregation mechanism of alpha-synuclein. In addition, it also stabilizes a specific fibril conformation, which has a higher propensity for self-replication. These results provide insight into the influence of S100A9 on the process of neurodegenerative disease-related protein LLPS and aggregation, bringing us one step closer to developing a potential cure or treatment modality.

biochemistry↗

bioRxiv2024

Diverse effects of fluorescent labels on alpha-synuclein condensate formation during liquid-liquid phase separation

Liquid-liquid phase separation is an emerging field of study, dedicated to understanding the mechanism and role of biomolecule assembly into membraneless organelles. One of the main methods employed in studying protein and nucleic acid droplet formation is fluorescence microscopy. Despite functioning as an excellent tool for monitoring biomolecule condensation, a few recent reports have presented possible drawbacks of using fluorescently labeled particles. It was observed that fluorescent tags could alter the process of protein liquid-liquid phase separation and even promote their aggregation. In this study, we examined the influence of three different protein labels on alpha-synuclein phase separation in vitro and determined that the changes in droplet formation were related to both the type, as well as concentration of the fluorescently tagged alpha-synuclein. Both protein-based labels (mCherry and eGFP) induced the formation of significantly larger droplets, while fluorescein-tagged alpha-synuclein generated an abundance of small condensates. The study also revealed that alpha-synuclein with protein-based labels could self-associate at much lower concentrations than its untagged counterpart, forming either large droplets or protein aggregates. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=63 SRC="FIGDIR/small/602219v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@bf034aorg.highwire.dtl.DTLVardef@70fe04org.highwire.dtl.DTLVardef@34d9a9org.highwire.dtl.DTLVardef@1be0419_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2024

Influence of S100A9 on Prion Protein Amyloid Aggregation

Protein aggregation in the form of amyloid fibrils has long been associated with the onset and development of various amyloidoses, including Alzheimers, Parkinsons or prion diseases. Recent studies of their fibril formation process have revealed that amyloidogenic protein cross-interactions may impact aggregation pathways and kinetic parameters, as well as the structure of the resulting aggregates. Despite a growing number of reports exploring this type of interaction, they only cover just a small number of possible amyloidogenic protein pairings. One such pair is between two neurodegeneration-associated proteins: the pro-inflammatory S100A9 and prion protein, which are known to co-localize in vivo. In this study, we examined their cross-interaction in vitro and discovered that the fibrillar form of S100A9 modulated the aggregation pathway of mouse prion protein 89-230 fragment, while non-aggregated S100A9 also significantly inhibited its primary nucleation process. These results complement previous observations of the pro-inflammatory proteins role in amyloid aggregation and highlight its potential role against neurodegenerative disorders.

biochemistry↗

bioRxiv2023

Liquid-liquid Phase Separation of Alpha-synuclein Increases the Structural Variability of Fibrils Formed during Amyloid Aggregation

Protein liquid-liquid phase separation (LLPS) is a rapidly emerging field of study on biomolecular condensate formation. In recent years, this phenomenon has been implicated in the process of amyloid fibril formation, serving as an intermediate step between the native protein transition into their aggregated state. The formation of fibrils via LLPS has been demonstrated for a number of proteins related to neurodegenerative disorders, as well as other amyloidoses. Despite the surge in amyloid-related LLPS studies, the influence of protein condensate formation on the end-point fibril characteristics is still far from fully understood. In this work, we compare alpha-synuclein aggregation under conditions, which promote or negate its LLPS and examine the differences between the formed aggregates. We show that alpha-synuclein phase separation generates a wide variety of assemblies with distinct secondary structures and morphologies. The LLPS-induced structures also possess higher levels of toxicity to cells, indicating that biomolecular condensate formation may be a critical step in the appearance of disease-related fibril variants.

biophysics↗