scholarly journals Intrinsic Disorder-Based Emergence in Cellular Biology: Physiological and Pathological Liquid-Liquid Phase Transitions in Cells

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 990 ◽  
Author(s):  
April L. Darling ◽  
Boris Y. Zaslavsky ◽  
Vladimir N. Uversky
Keyword(s):  
Phase Transitions ◽  
Phase Separation ◽  
Liquid Phase ◽  
Intrinsic Disorder ◽  
Living Cells ◽  
Cellular Biology ◽  
Physiological Functions ◽  
Pathological Conditions ◽  
Liquid Liquid Phase Separation ◽  
In Cells

The visible outcome of liquid-liquid phase transitions (LLPTs) in cells is the formation and disintegration of various proteinaceous membrane-less organelles (PMLOs). Although LLPTs and related PMLOs have been observed in living cells for over 200 years, the physiological functions of these transitions (also known as liquid-liquid phase separation, LLPS) are just starting to be understood. While unveiling the functionality of these transitions is important, they have come into light more recently due to the association of abnormal LLPTs with various pathological conditions. In fact, several maladies, such as various cancers, different neurodegenerative diseases, and cardiovascular diseases, are known to be associated with either aberrant LLPTs or some pathological transformations within the resultant PMLOs. Here, we will highlight both the physiological functions of cellular liquid-liquid phase transitions as well as the pathological consequences produced through both dysregulated biogenesis of PMLOs and the loss of their dynamics. We will also discuss the potential downstream toxic effects of proteins that are involved in pathological formations.

scholarly journals Prion-Like Proteins in Phase Separation and Their Link to Disease

Biomolecules ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1014
Author(s):  
Macy L. Sprunger ◽  
Meredith E. Jackrel
Keyword(s):  
Protein Folding ◽  
Phase Transitions ◽  
Phase Separation ◽  
Liquid Phase ◽  
Protein Misfolding ◽  
Solid Phase ◽  
Liquid Phase Separation ◽  
Therapeutic Approaches ◽  
Important Physiological Process ◽  
Liquid Liquid Phase Separation

Aberrant protein folding underpins many neurodegenerative diseases as well as certain myopathies and cancers. Protein misfolding can be driven by the presence of distinctive prion and prion-like regions within certain proteins. These prion and prion-like regions have also been found to drive liquid-liquid phase separation. Liquid-liquid phase separation is thought to be an important physiological process, but one that is prone to malfunction. Thus, aberrant liquid-to-solid phase transitions may drive protein aggregation and fibrillization, which could give rise to pathological inclusions. Here, we review prions and prion-like proteins, their roles in phase separation and disease, as well as potential therapeutic approaches to counter aberrant phase transitions.

scholarly journals Taurine suppresses liquid-liquid phase separation of lysozyme protein

2021 ◽  
Author(s):  
Kanae Tsubotani ◽  
Sayuri Maeyama ◽  
Shigeru Murakami ◽  
Stephen W Schaffer ◽  
Takashi Ito
Keyword(s):  
Phase Separation ◽  
Polyethylene Glycol ◽  
Critical Temperature ◽  
Liquid Phase ◽  
Liquid Phase Separation ◽  
Compatible Osmolyte ◽  
Hen Egg ◽  
Liquid Liquid Phase Separation ◽  
In Cells

AbstractTaurine is a compatible osmolyte that infers stability to proteins. Recent studies have revealed that liquid-liquid phase separation (LLPS) of proteins underlie the formation of membraneless organelles in cells. In the present study, we evaluated the role of taurine on LLPS of hen egg lysozyme. We demonstrated that taurine decreases the turbidity of the polyethylene glycol-induced crowding solution of lysozyme. We also demonstrated that taurine attenuates LLPS-dependent cloudiness of lysozyme solution with 0.5 or 1M NaCl at a critical temperature. Moreover, we observed that taurine inhibits LLPS formation of a heteroprotein mix solution of lysozyme and ovalbumin. These data indicate that taurine can modulate the formation of LLPS of proteins.

scholarly journals Liquid-liquid phase separation and morphology of internally mixed dicarboxylic acids/ammonium sulfate/water particles

2011 ◽  
Vol 11 (10) ◽  
pp. 29141-29194 ◽  
Author(s):  
M. Song ◽  
C. Marcolli ◽  
U. K. Krieger ◽  
A. Zuend ◽  
T. Peter
Keyword(s):  
Phase Transitions ◽  
Phase Separation ◽  
Liquid Phase ◽  
Ammonium Sulfate ◽  
Particle Surface ◽  
Dicarboxylic Acids ◽  
Liquid Phase Separation ◽  
Model Systems ◽  
Second Phase ◽  
Liquid Liquid Phase Separation

Abstract. Knowledge of the physical state and morphology of internally mixed organic/inorganic aerosol particles is still largely uncertain. To obtain more detailed information on liquid-liquid phase separation (LLPS) and morphology of the particles, we investigated complex mixtures of atmospherically relevant dicarboxylic acids containing 5–7 carbon atoms (C5, C6 and C7) having oxygen-to-carbon atomic ratios (O:C) of 0.80, 0.67, and 0.57, respectively, mixed with ammonium sulfate (AS). With micrometer-sized particles of C5/AS/H2O, C6/AS/H2O and C7/AS/H2O as model systems deposited on a hydrophobically coated substrate, laboratory experiments were conducted for various organic-to-inorganic dry mass ratios (OIR) using optical microscopy and Raman spectroscopy. When exposed to cycles of relative humidity (RH), each system showed significantly different phase transitions. While the C5/AS/H2O particles showed no LLPS with OIR = 2:1, 1:1 and 1:4 down to 20% RH, the C6/AS/H2O and C7/AS/H2O particles exhibit LLPS upon drying at RH 50% to 85% and ~90%, respectively, via spinodal decomposition, growth of a second phase from the particle surface or nucleation-and-growth mechanisms depending on the OIR. This suggests that LLPS commonly occurs within the range of O:C<0.7 in tropospheric organic-inorganic aerosols. To support the comparison and interpretation of the experimentally observed phase transitions, thermodynamic equilibrium calculations were performed with the AIOMFAC model. For the C7/AS/H2O and C6/AS/H2O systems, the calculated phase diagrams agree well with the observations while for the C5/AS/H2O system LLPS is predicted by the model at RH below 60% and higher AS concentration, but was not observed in the experiments. Both core-shell structures and partially engulfed structures were observed for the investigated particles, suggesting that such morphologies might also exist in tropospheric aerosols.

Liquid-liquid phase separation in biology: mechanisms, physiological functions and human diseases

2020 ◽  
Vol 63 (7) ◽  
pp. 953-985 ◽  
Author(s):  
Hong Zhang ◽  
Xiong Ji ◽  
Pilong Li ◽  
Cong Liu ◽  
Jizhong Lou ◽  
...  
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Liquid Phase Separation ◽  
Human Diseases ◽  
Physiological Functions ◽  
Liquid Liquid Phase Separation

scholarly journals Liquid–Liquid Phase Separation in Crowded Environments

2020 ◽  
Vol 21 (16) ◽  
pp. 5908 ◽  
Author(s):  
Alain A. M. André ◽  
Evan Spruijt
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Macromolecular Crowding ◽  
Liquid Phase Separation ◽  
The Impact ◽  
Crowded Environments ◽  
Liquid Liquid Phase Separation ◽  
In Cells

Biomolecular condensates play a key role in organizing cellular fluids such as the cytoplasm and nucleoplasm. Most of these non-membranous organelles show liquid-like properties both in cells and when studied in vitro through liquid–liquid phase separation (LLPS) of purified proteins. In general, LLPS of proteins is known to be sensitive to variations in pH, temperature and ionic strength, but the role of crowding remains underappreciated. Several decades of research have shown that macromolecular crowding can have profound effects on protein interactions, folding and aggregation, and it must, by extension, also impact LLPS. However, the precise role of crowding in LLPS is far from trivial, as most condensate components have a disordered nature and exhibit multiple weak attractive interactions. Here, we discuss which factors determine the scope of LLPS in crowded environments, and we review the evidence for the impact of macromolecular crowding on phase boundaries, partitioning behavior and condensate properties. Based on a comparison of both in vivo and in vitro LLPS studies, we propose that phase separation in cells does not solely rely on attractive interactions, but shows important similarities to segregative phase separation.

scholarly journals Concentration and dosage sensitivity of proteins driving liquid-liquid phase separation

2021 ◽  
Author(s):  
Nazanin Farahi ◽  
Tamas Lazar ◽  
Shoshana J. Wodak ◽  
Peter Tompa ◽  
Rita Pancsa
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Liquid Phase Separation ◽  
Condensate Formation ◽  
Associated Proteins ◽  
Liquid Liquid Phase Separation ◽  
In Cells ◽  
Dosage Sensitivity

AbstractLiquid-liquid phase separation (LLPS) is a molecular process that leads to the formation of membraneless organelles (MLOs), i.e. functionally specialized liquid-like cellular condensates formed by proteins and nucleic acids. Integration of data on LLPS-associated proteins from dedicated databases revealed only modest overlap between them and resulted in a confident set of 89 human LLPS driver proteins. Since LLPS is highly concentration-sensitive, the underlying experiments are often criticized for applying higher-than-physiological protein concentrations. To clarify this issue, we performed a naive comparison of in vitro applied and quantitative proteomics-derived protein concentrations and discuss a number of considerations that rationalize the choice of apparently high in vitro concentrations in most LLPS studies. The validity of in vitro LLPS experiments is further supported by in vivo phase-separation experiments and by the observation that the corresponding genes show a strong propensity for dosage sensitivity. This observation implies that the availability of the respective proteins is tightly regulated in cells to avoid erroneous condensate formation. In all, we propose that although local protein concentrations are practically impossible to determine in cells, proteomics-derived cellular concentrations should rather be considered as lower limits of protein concentrations, than strict upper bounds, to be respected by in vitro experiments.

An intrinsically disordered pathological prion variant Y145Stop converts into self-seeding amyloids via liquid–liquid phase separation

2021 ◽  
Vol 118 (45) ◽  
pp. e2100968118
Author(s):  
Aishwarya Agarwal ◽  
Sandeep K. Rai ◽  
Anamika Avni ◽  
Samrat Mukhopadhyay
Keyword(s):  
Phase Transitions ◽  
Phase Separation ◽  
Liquid Phase ◽  
Phase Behavior ◽  
Intrinsically Disordered Proteins ◽  
Liquid Phase Separation ◽  
Disordered Proteins ◽  
Cell Physiology ◽  
Intrinsically Disordered ◽  
Liquid Liquid Phase Separation

Biomolecular condensation via liquid–liquid phase separation of intrinsically disordered proteins/regions (IDPs/IDRs) along with other biomolecules is proposed to control critical cellular functions, whereas aberrant phase transitions are associated with a range of neurodegenerative diseases. Here, we show that a disease-associated stop codon mutation of the prion protein (PrP) at tyrosine 145 (Y145Stop), resulting in a truncated, highly disordered, N-terminal IDR, spontaneously phase-separates into dynamic liquid-like droplets. Phase separation of this highly positively charged N-terminal segment is promoted by the electrostatic screening and a multitude of weak, transient, multivalent, intermolecular interactions. Single-droplet Raman measurements, in conjunction with an array of bioinformatic, spectroscopic, microscopic, and mutagenesis studies, revealed a highly mobile internal organization within the liquid-like condensates. The phase behavior of Y145Stop is modulated by RNA. Lower RNA:protein ratios promote condensation at a low micromolar protein concentration under physiological conditions. At higher concentrations of RNA, phase separation is abolished. Upon aging, these highly dynamic liquid-like droplets gradually transform into ordered, β-rich, amyloid-like aggregates. These aggregates formed via phase transitions display an autocatalytic self-templating characteristic involving the recruitment and binding-induced conformational conversion of monomeric Y145Stop into amyloid fibrils. In contrast to this intrinsically disordered truncated variant, the wild-type full-length PrP exhibits a much lower propensity for both condensation and maturation into amyloids, hinting at a possible protective role of the C-terminal domain. Such an interplay of molecular factors in modulating the protein phase behavior might have much broader implications in cell physiology and disease.

scholarly journals Observations on hygroscopic growth and phase transitions of mixed 1, 2, 6-hexanetriol/(NH4</sub>)<sub>2</sub>SO<sub>4</sub> particles: Investigation of liquid-liquid phase separation (LLPS) dynamic process and mechanism and secondary LLPS

2021 ◽  
Author(s):  
Shuai-Shuai Ma ◽  
Zhe Chen ◽  
Shu-Feng Pang ◽  
Yun-Hong Zhang
Keyword(s):  
Phase Transitions ◽  
Phase Separation ◽  
Liquid Phase ◽  
Liquid Phase Separation ◽  
Solution Phase ◽  
High Time Resolution ◽  
Hygroscopic Growth ◽  
Inorganic Particles ◽  
Inorganic Components ◽  
Liquid Liquid Phase Separation

Abstract. Atmospheric aerosols consisting of organic and inorganic components may undergo liquid-liquid phase separation (LLPS) and liquid-solid phase transitions during ambient relative humidity (RH) fluctuation. However, the knowledge of dynamic phase evolution processes for mixed organic-inorganic particles is scarce. Here we present a universal and visualized observation on LLPS, efflorescence and deliquescence transitions as well as hygroscopic growth of mixed 1, 2, 6-hexanetriol/ammonium sulfate (AS) particles with different organic-inorganic mole ratios (OIR = 1:4, 1:2, 1:1, 2:1 and 4:1) with the high time resolution (0.5 s), using an optical microscope with a video camera. The optical images suggest that an inner AS solution phase is surrounded by an outer organic-rich phase after LLPS for all mixed particles. The LLPS mechanism for particles with different OIRs differs, meanwhile, multiple mechanisms may dominate successively in individual particles with a certain OIR, somewhat inconsistent with earlier observations by literature. More importantly, another phase separation in inner AS solution phase, defined as secondary LLPS here, is observed for OIR = 1:1, 1:2 and 1:4 particles. The secondary LLPS may be attributed to the formation of more concentrated AS inclusions in the inner phase, and becomes more obvious with decreasing RH and increasing AS mole fraction. Furthermore, the changes in size and amount of AS inclusions during LLPS are quantitatively characterized, which further illustrate the equilibrium partitioning process of organic and inorganic components. The experimental results have significant implications for revelation of complex phase transitions of internally mixed atmospheric particles and evaluation of liquid-liquid and liquid-solid equilibria in thermodynamic models.

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