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 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.

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 Liquid-liquid phase separation of full-length prion protein initiates conformational conversion in vitro

2020 ◽  
Author(s):  
Hiroya Tange ◽  
Daisuke Ishibashi ◽  
Takehiro Nakagaki ◽  
Yuzuru Taguchi ◽  
Yuji O. Kamatari ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Separation ◽  
Liquid Phase ◽  
Prion Protein ◽  
Solid Phase ◽  
Terminal Region ◽  
Liquid Phase Separation ◽  
Solid Phase Transition ◽  
Liquid Liquid Phase Separation

AbstractPrion diseases are characterized by accumulation of amyloid fibrils. The causative agent is an infectious amyloid that is comprised solely of misfolded prion protein (PrPSc). Prions can convert PrPC to proteinase-resistant PrP (PrP-res) in vitro; however, the intermediate steps involved in the spontaneous conversion remain unknown. We investigated whether recombinant prion protein (rPrP) can directly convert into PrP-res via liquid-liquid phase separation in the absence of PrPSc. We found that rPrP underwent liquid-liquid phase separation at the interface of the aqueous two-phase system (ATPS) of polyethylene glycol (PEG) and dextran, whereas single-phase conditions were not inducible. Fluorescence recovery assay after photobleaching revealed that the liquid-solid phase transition occurred within a short time. The aged rPrP-gel acquired proteinase-resistant amyloid accompanied by β-sheet conversion, as confirmed by western blotting, Fourier transform infrared spectroscopy, and Congo red staining. The reactions required both the N-terminal region of rPrP (amino acids 23-89) and kosmotropic salts, suggesting that the kosmotropic anions may interact with the N-terminal region of rPrP to promote liquid-liquid phase separation. Thus, structural conversion via liquid–liquid phase separation and liquid–solid phase transition are intermediate steps in the conversion of prions.

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.

scholarly journals Spider silk self-assembly via modular liquid-liquid phase separation and nanofibrillation

2020 ◽  
Vol 6 (45) ◽  
pp. eabb6030
Author(s):  
Ali D. Malay ◽  
Takehiro Suzuki ◽  
Takuya Katashima ◽  
Nobuaki Kono ◽  
Kazuharu Arakawa ◽  
...  
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Self Assembly ◽  
Spider Silk ◽  
Solid Phase ◽  
Silk Gland ◽  
Liquid Phase Separation ◽  
Hierarchical Organization ◽  
Amino Terminal ◽  
Liquid Liquid Phase Separation

Spider silk fiber rapidly assembles from spidroin protein in soluble state via an incompletely understood mechanism. Here, we present an integrated model for silk formation that incorporates the effects of multiple chemical and physical gradients on the different spidroin functional domains. Central to the process is liquid-liquid phase separation (LLPS) that occurs in response to multivalent anions such as phosphate, mediated by the carboxyl-terminal and repetitive domains. Acidification coupled with LLPS triggers the swift self-assembly of nanofibril networks, facilitated by dimerization of the amino-terminal domain, and leads to a liquid-to-solid phase transition. Mechanical stress applied to the fibril structures yields macroscopic fibers with hierarchical organization and enriched for β-sheet conformations. Studies using native silk gland material corroborate our findings on spidroin phase separation. Our results suggest an intriguing parallel between silk assembly and other LLPS-mediated mechanisms, such as found in intracellular membraneless organelles and protein aggregation disorders.

scholarly journals Capillary flow experiments for thermodynamic and kinetic characterization of protein liquid-liquid phase separation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Emil G. P. Stender ◽  
Soumik Ray ◽  
Rasmus K. Norrild ◽  
Jacob Aunstrup Larsen ◽  
Daniel Petersen ◽  
...  
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Amyloid Fibrils ◽  
Capillary Flow ◽  
Solid Phase ◽  
Liquid Phase Separation ◽  
Dead Box ◽  
Phase Concentration ◽  
Liquid Liquid Phase Separation

AbstractLiquid-liquid phase separation or LLPS of proteins is a field of mounting importance and the value of quantitative kinetic and thermodynamic characterization of LLPS is increasingly recognized. We present a method, Capflex, which allows rapid and accurate quantification of key parameters for LLPS: Dilute phase concentration, relative droplet size distributions, and the kinetics of droplet formation and maturation into amyloid fibrils. The binding affinity between the polypeptide undergoing LLPS and LLPS-modulating compounds can also be determined. We apply Capflex to characterize the LLPS of Human DEAD-box helicase-4 and the coacervate system ssDNA/RP3. Furthermore, we study LLPS and the aberrant liquid-to-solid phase transition of α-synuclein. We quantitatively measure the decrease in dilute phase concentration as the LLPS of α-synuclein is followed by the formation of Thioflavin-T positive amyloid aggregates. The high information content, throughput and the versatility of Capflex makes it a valuable tool for characterizing biomolecular LLPS.

scholarly journals Observations on hygroscopic growth and phase transitions of mixed 1, 2, 6-hexanetriol ∕ (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> particles: investigation of the liquid–liquid phase separation (LLPS) dynamic process and mechanism and secondary LLPS during the dehumidification

2021 ◽  
Vol 21 (12) ◽  
pp. 9705-9717
Author(s):  
Shuaishuai Ma ◽  
Zhe Chen ◽  
Shufeng Pang ◽  
Yunhong 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 of LLPS, efflorescence and deliquescence transitions as well as hygroscopic growth of laboratory-generated 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 high time resolution (0.5 s) using an optical microscope operated 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 is found to be distinct; meanwhile, multiple mechanisms may dominate successively in individual particles with a certain OIR, somewhat inconsistently with previously reported observations. More importantly, another phase separation in the 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 number of AS inclusions during LLPS are quantitatively characterized, which further illustrate the equilibrium partitioning process of organic and inorganic components. These experimental results have significant implications for the revelation of complex phase transitions of internally mixed atmospheric particles and evaluation of liquid–liquid and liquid–solid equilibria in thermodynamic models.

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

2012 ◽  
Vol 12 (5) ◽  
pp. 2691-2712 ◽  
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, 6, and 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.

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