Biology subjects

Sneideriene, G.

Publications and source records attributed to Sneideriene, G..

4 recordsLinked to original sources

bioRxiv2024

The Alzheimer's Aβ peptide forms biomolecular condensates that trigger amyloid aggregation

The onset and development of Alzheimers disease (AD) is linked to the accumulation of pathological aggregates formed from the normally monomeric amyloid-{beta} peptide within the central nervous system. These A{beta} aggregates are increasingly successfully targeted with clinical therapies, but the fundamental molecular steps that trigger the initial nucleation event leading to the conversion of monomeric A{beta} peptide into pathological aggregates remain unknown. Here we show that the A{beta} peptide can form biomolecular condensates on lipid bilayers both in molecular assays and in living cells. Our results reveal that these A{beta} condensates can significantly accelerate the primary nucleation step in the amyloid conversion cascade that leads to the formation of amyloid aggregates and plaque. We show that A{beta} condensates contain phospholipids, are intrinsically heterogenous, and are prone to undergo a liquid-to-solid transition leading to the formation amyloid fibrils. These findings uncover the liquid-liquid phase separation behaviour of the A{beta} peptide, and reveal a new molecular step very early in the amyloid-{beta} aggregation cascade that can form the basis for novel therapeutic intervention strategies. Significance statementThe hallmark of Alzheimers disease is the abnormal buildup of the normally soluble amyloid {beta} protein aggregates in the central nervous system. While the molecular mechanisms at the late stages of the amyloid {beta} aggregation cascade are well understood, the initial steps remained elusive until now. Our current study demonstrates that amyloid {beta} undergoes liquid-liquid phase separation on lipid surfaces, which triggers primary nucleation and initiates the amyloid {beta} aggregation cascade. This newly identified step in the molecular mechanism of Alzheimers disease represents a promising target for the development of alternative innovative therapeutic strategies.

biophysics↗

bioRxiv2023

Single-molecule digital sizing of proteins in solution

Proteins constitute the molecular machinery of life and exert their biological function by interacting with other proteins, as well as by assembling into biomolecular complexes and higher order structures. Characterizing the sizes, interactions, and assembly states of proteins is thus key for understanding the normal functional behavior of proteins and for elucidating aberrant processes and interactions that can lead to dysfunction and disease. However, the physical characterization of proteins has remained a challenging problem due to the inherent compositional heterogeneity of protein mixtures as well as the polydisperse nature of protein complexes. Here, we address this challenge by demonstrating measurements of molecular diffusivity of single proteins and protein assemblies in microchannels using single-molecule fluorescence detection. The approach, termed single-molecule microfluidic diffusional sizing (smMDS), allows individual molecules to be counted directly, that is, in a digital manner, to enable calibration-free single-molecule diffusional-sizing-based monitoring of protein hydrodynamic radii even within heterogenous multicomponent mixtures. Applying smMDS to a variety of protein systems, we show that the high sensitivity provided by smMDS enables ultrasensitive sizing of proteins down to the femtomolar concentration range. We further demonstrate the applicability of the approach towards affinity profiling of protein interactions at the single-molecule level and illustrate the potential of smMDS in resolving different assembly states of high- and low-molecular weight protein oligomers. Furthermore, we highlight the digital nature of the detection process by sizing multiple protein species within complex aggregation mixtures. Finally, we apply the approach to characterize nanoscale clusters of a phase separating protein system. Taken together, smMDS constitutes a versatile approach for digital, in-solution characterization of the sizes, interactions, and assembly states of proteins. We anticipate that smMDS will facilitate the discovery of new biomolecular mechanisms of proteins and will find broad applicability in the analysis of protein complexes in the biological, biophysical, and biomedical sciences, and beyond.

biophysics↗

bioRxiv2023

Alpha-synuclein oligomers displace monomeric alpha-synuclein from lipid membranes

Parkinsons disease (PD) is an increasingly prevalent and currently incurable neurodegenerative disorder linked to the accumulation of -synuclein (S) protein aggregates in the nervous system. While S binding to membranes in its monomeric state is correlated to its physiological role, S oligomerisation and subsequent aberrant interactions with lipid bilayers have emerged as key steps in PD-associated neurotoxicity. However, little is known of the mechanisms that govern the interactions of oligomeric S (OS) with lipid membranes and the factors that modulate such interactions. This is in large part due to experimental challenges underlying studies of OS-membrane interactions due to their dynamic and transient nature. Here, we address this challenge by using a suite of microfluidics-based assays that enable in-solution quantification of OS-membrane interactions. We find that OS bind more strongly to highly curved, rather than flat, lipid membranes. By comparing the membrane-binding properties of OS and monomeric S (MS), we further demonstrate that OS bind to membranes with up to 150-fold higher affinity than their monomeric counterparts. Moreover, OS compete with and displace bound MS from the membrane surface, suggesting that disruption to the functional binding of MS to membranes may provide an additional toxicity mechanism in PD. These findings present a unique binding mechanism of oligomers to model membranes, which can potentially be targeted to inhibit the progression of PD. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=62 SRC="FIGDIR/small/533646v2_ufig1.gif" ALT="Figure 1"> View larger version (10K): org.highwire.dtl.DTLVardef@4ab089org.highwire.dtl.DTLVardef@18c0709org.highwire.dtl.DTLVardef@220077org.highwire.dtl.DTLVardef@4c85b9_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2022

A Kinetic Map of the Influence of Biomimetic Lipid Membrane Models on Aβ42 Aggregation

The aggregation of the amyloid {beta} peptide (A{beta}) is one of the major molecular hallmarks of Alzheimers disease. Although A{beta} deposits have been mostly observed extracellularly, various studies have reported the presence of also intracellular A{beta} assemblies. Because these intracellular A{beta} aggregates might play a role in the onset and progression of Alzheimers disease, it is important to investigate their possible origins at different locations of the cell along the secretory pathway of the amyloid precursor protein (APP), from which A{beta} is derived by proteolytic cleavage. Since lipid bilayers have been shown to promote the aggregation of A{beta}, in this study we measure the effects of the lipid membrane composition on the in vitro aggregation kinetics of the 42-residue form of A{beta} (A{beta}42). By using small unilamellar vesicles modelling cellular membranes at different locations, including the inner and outer leaflets of the plasma membrane, late endosomes, the endoplasmic reticulum (ER), and the Golgi apparatus, we show that A{beta}42 aggregation is inhibited by the ER and Golgi membranes. These results provide a preliminary map of the possible effects of the membrane composition in different cellular locations on A{beta} aggregation, and suggest the presence of an evolutionary optimization of lipid composition to prevent the intracellular aggregation of A{beta}.

biophysics↗