Biology subjects

Sakalauskas, A.

Publications and source records attributed to Sakalauskas, A..

5 recordsLinked to original sources

bioRxiv2025

Formation of Condition-Dependent Alpha-Synuclein Fibril Strain in Artificial Cerebrospinal Fluid

-Synuclein (aSyn) is an intrinsically disordered protein involved in neurotransmission and synaptic plasticity. The pathological aggregation of this protein is a hallmark of synucleinopathies such as Parkinsons disease (PD) or Multiple System Atrophy (MSA). Misfolded aSyn, which primarily originates in cell cytosol, transmits between neurons, promoting a prion-like propagation. However, the extracellular environments such as interstitial and cerebrospinal fluids (ISF & CSF) play a major role in its clearance and pathological transformation. The molecular components of CSF, including proteins, glycosaminoglycans, and metal ions may influence the aggregate morphology, structure and cytotoxicity to cells. To better understand how extracellular composition affects aggregates and their formation, we employed artificial cerebrospinal fluid (aCSF) to mimic potential aggregation processes occurring in CSF. We observed distinct aCSF-specific aSyn fibrils that exhibited low stability outside aCSF, and the removal of key CSF components led to its structural alterations. Cryo-electron microscopy revealed that these fibrils possess an electron density pocket coordinated with polar basic AAs (K43, K45, H50) that is also observed in aggregates obtained from MSA patients. Our findings illustrate the importance of physiologically relevant conditions in studying aSyn aggregation and may explain why disease-related fibril structure replication in vitro has not yet been successful.

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↗

bioRxiv2023

Formation of amyloid fibrils by the regulatory 14-3-3ζ protein

The 14-3-3 is a highly conserved adaptor protein family with multi-layer functions, abundantly expressed in the brain. The 14-3-3 proteins modulate phosphorylation, regulate enzymatic activity and can act as chaperones. Most importantly, they play an important role in various neurodegenerative disorders due to their vast interaction partners. Particularly, the 14-3-3{xi} isoform is known to co-localize in aggregation tangles in both Alzheimers and Parkinsons diseases as a result of protein-protein interactions. These abnormal clumps consist of amyloid fibrils - insoluble aggregates, mainly formed by amyloid-{beta}, tau and -synuclein proteins. However, the molecular basis of if and how 14-3-3{xi} can aggregate into amyloid fibrils is unknown. In this study, we describe the formation of amyloid fibrils by 14-3-3{xi} utilizing a comprehensive approach that combines bioinformatic tools, amyloid-specific dye binding, secondary structure analysis and atomic force microscopy. The results presented herein characterize the amyloidogenic properties of 14-3-3{xi} and imply that the well-folded protein undergoes aggregation to {beta}-sheet-rich amyloid fibrils.

biochemistry↗