Biology subjects

Veiveris, D.

Publications and source records attributed to Veiveris, D..

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

Calcium-mediated amyloid co-aggregation of S100A1 and S100A8 proteins

The S100 family consists of calcium binding proteins that are largely known for their contribution to the neuroinflammatory processes. They are associated with various cardiac and neurological functions as well as related diseases. A few S100 proteins can form unspecific or amyloid aggregates in neuropathologies and thus play a part in dementia pathogenesis. Among all S100 proteins, S100B and S100A9 aggregation properties are the most investigated, however, there is a lack of studies regarding other S100 members. In particular, S100A1 and S100A8 are also associated with neuropathies, but their interactions or aggregation are poorly understood. Therefore, in this study, we explored whether S100A1 and S100A8 proteins can form heterodimers, interact or co-aggregate. Our results revealed that S100A1 and S100A8 interactions and amyloid aggregation are driven by calcium ions. We observed that while S100A1 remains mostly stable, S100A8 forms various types of spherical or unspecific aggregates. While they do not form stable heterodimers like calprotectin, their transient interactions facilitate the formation of worm-like amyloid fibrils and the process is regulated by different calcium ion concentrations. At calcium ions saturation, both proteins are stabilized leading to inhibition of aggregation. Overall, by employing a diverse range of techniques from amyloid and protein-specific fluorescence detection to electron-electron double resonance spectroscopy, we elucidated interactions between S100 proteins that might otherwise be overlooked, enhancing our understanding of their aggregation behaviour.

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↗

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↗