scholarly journals Biomolecular condensates undergo a generic shear-mediated liquid-to-solid transition

2020 ◽  
Author(s):  
Yi Shen ◽  
Francesco Simone Ruggeri ◽  
Daniele Vigolo ◽  
Ayaka Kamada ◽  
Seema Qamar ◽  
...  
Keyword(s):  
Phase Transition ◽  
Liquid Phase ◽  
Rna Binding ◽  
Cell Signalling ◽  
Physical Factors ◽  
Transition Control ◽  
Cell Functions ◽  
Fused In Sarcoma ◽  
Wide Range ◽  
Liquid To Solid Transition

A wide range of systems containing proteins have been shown to undergo liquid-liquid phase separation (LLPS) forming membraneless compartments, such as processing bodies1, germ granules2, stress granules3 and Cajal bodies4. The condensates resulting from this phase transition control essential cell functions, including mRNA regulation, cytoplasm structuring, cell signalling and embryogenesis1–4. RNA-binding Fused in Sarcoma (FUS) protein is one of the most studied systems in this context, due to its important role in neurodegenerative diseases5–7. It has recently been discovered that FUS condensates can undergo an irreversible phase transition which results in fibrous aggregate formation6. Gelation of protein condensates is generally associated with pathology. One case where liquid-to-solid transition (LST) of liquid-liquid phase separated proteins is functional, however, is that of silk spinning8,9, which is largely driven by shear, but it is not known what factors control the pathological gelation of functional condensates. Here we show that four proteins and one peptide system not related to silk, and with no function associated with fibre formation, have a strong propensity to undergo LST when exposed to even low levels of mechanical shear comparable to those found inside a living cell, once present in their liquid-liquid phase separated forms. Using microfluidics to control the application of mechanical shear, we generated fibres from single protein condensates and characterized their structures and material properties as a function of shear stress. Our results inform on the molecular grammar underlying protein LST and highlight generic backbone-backbone hydrogen bonding constraints as a determining factor in governing this transition. Taken together, these observations suggest that the shear plays an important role in the irreversible phase transition of liquid-liquid phase separated droplets, shed light on the role of physical factors in driving this transition in protein aggregation related diseases, and open a new route towards artificial shear responsive biomaterials.

scholarly journals Picornaviruses and RNA Metabolism: Local and Global Effects of Infection

2019 ◽  
Vol 93 (21) ◽  
Author(s):  
Autumn C. Holmes ◽  
Bert L. Semler
Keyword(s):  
Host Cell ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Foot And Mouth Disease ◽  
Rna Metabolism ◽  
Cell Nuclei ◽  
Cell Functions ◽  
Mouth Disease Virus ◽  
Wide Range ◽  
Positive Strand Rna

ABSTRACT Due to the limiting coding capacity for members of the Picornaviridae family of positive-strand RNA viruses, their successful replication cycles require complex interactions with host cell functions. These interactions span from the down-modulation of many aspects of cellular metabolism to the hijacking of specific host functions used during viral translation, RNA replication, and other steps of infection by picornaviruses, such as human rhinovirus, coxsackievirus, poliovirus, foot-and-mouth disease virus, enterovirus D-68, and a wide range of other human and nonhuman viruses. Although picornaviruses replicate exclusively in the cytoplasm of infected cells, they have extensive interactions with host cell nuclei and the proteins and RNAs that normally reside in this compartment of the cell. This review will highlight some of the more recent studies that have revealed how picornavirus infections impact the RNA metabolism of the host cell posttranscriptionally and how they usurp and modify host RNA binding proteins as well as microRNAs to potentiate viral replication.

scholarly journals Identification and characterization of differentially active pools of type IIα phosphatidylinositol 4-kinase activity in unstimulated A431 cells

2003 ◽  
Vol 376 (2) ◽  
pp. 497-503 ◽  
Author(s):  
Mark G. WAUGH ◽  
Shane MINOGUE ◽  
Deena BLUMENKRANTZ ◽  
J. Simon ANDERSON ◽  
J. Justin HSUAN
Keyword(s):  
Kinase Activity ◽  
Cell Signalling ◽  
Cell Types ◽  
Intrinsic Activity ◽  
A431 Cells ◽  
Cell Functions ◽  
Subcellular Membrane ◽  
Phosphatidylinositol Kinase ◽  
Wide Range ◽  
Phosphatidylinositol 4

The seven known polyphosphoinositides have been implicated in a wide range of regulated and constitutive cell functions, including cell-surface signalling, vesicle trafficking and cytoskeletal reorganization. In order to understand the spatial and temporal control of these diverse cell functions it is necessary to characterize the subcellular distribution of a wide variety of polyphosphoinositide synthesis and signalling events. The predominant phosphatidylinositol kinase activity in many mammalian cell types involves the synthesis of the signalling precursor, phosphatidylinositol 4-phosphate, in a reaction catalysed by the recently cloned PI4KIIα (type IIα phosphatidylinositol 4-kinase). However the regulation of this enzyme and the cellular distribution of its product in different organelles are very poorly understood. This report identifies the existence, in unstimulated cells, of two major subcellular membrane fractions, which contain PI4KIIα possessing different levels of intrinsic activity. Separation of these membranes from each other and from contaminating activities was achieved by density gradient ultracentrifugation at pH 11 in a specific detergent mixture in which both membrane fractions, but not other membranes, were insoluble. Kinetic comparison of the purified membrane fractions revealed a 4-fold difference in Km for phosphatidylinositol and a 3.5-fold difference in Vmax, thereby indicating a different mechanism of regulation to that described previously for agonist-stimulated cells. These marked differences in basal activity and the occurrence of this isozyme in multiple organelles emphasize the need to investigate cell signalling via PI4KIIα at the level of individual organelles rather than whole-cell lysates.

scholarly journals Microenvironments created by liquid-liquid phase transition control the dynamic distribution of bacterial division FtsZ protein

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Begoña Monterroso ◽  
Silvia Zorrilla ◽  
Marta Sobrinos-Sanguino ◽  
Christine D. Keating ◽  
Germán Rivas
Keyword(s):  
Phase Transition ◽  
Liquid Phase ◽  
Liquid Phase Transition ◽  
Dynamic Distribution ◽  
Transition Control ◽  
Ftsz Protein ◽  
Bacterial Division

scholarly journals The phase separation-dependent FUS interactome reveals nuclear and cytoplasmic function of liquid-liquid phase separation

2019 ◽  
Author(s):  
Stefan Reber ◽  
Helen Lindsay ◽  
Anny Devoy ◽  
Daniel Jutzi ◽  
Jonas Mechtersheimer ◽  
...  
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Rna Binding ◽  
Mitochondrial Gene ◽  
Liquid Phase Separation ◽  
Fused In Sarcoma ◽  
Damage Repair ◽  
Interaction Partners ◽  
Lateral Sclerosis ◽  
Liquid Liquid Phase Separation

AbstractLiquid-liquid phase separation (LLPS) of proteins and RNAs has emerged as the driving force underlying the formation of membrane-less organelles. Such biomolecular condensates have various biological functions and have been linked to disease. One of the best studied proteins undergoing LLPS is Fused in Sarcoma (FUS), a predominantly nuclear RNA-binding protein. Mutations in FUS have been causally linked to Amyotrophic Lateral Sclerosis (ALS), an adult-onset motor neuron disease, and LLPS followed by aggregation of cytoplasmic FUS has been proposed to be a crucial disease mechanism. In spite of this, it is currently unclear how LLPS impacts the behaviour of FUS in cells, e.g. its interactome. In order to study the consequences of LLPS on FUS and its interaction partners, we developed a method that allows for the purification of phase separated FUS-containing droplets from cell lysates. We observe substantial alterations in the interactome of FUS, depending on its biophysical state. While non-phase separated FUS interacts mainly with its well-known interaction partners involved in pre-mRNA processing, phase-separated FUS predominantly binds to proteins involved in chromatin remodelling and DNA damage repair. Interestingly, factors with function in mitochondria are strongly enriched with phase-separated FUS, providing a potential explanation for early changes in mitochondrial gene expression observed in mouse models of ALS-FUS. In summary, we present a methodology that allows to investigate the interactome of phase-separating proteins and provide evidence that LLPS strongly shapes the FUS interactome with important implications for function and disease.

RNA-Binding Proteins and Translation in Neurodegenerative Disease

2020 ◽  
Author(s):  
Kent E. Duncan
Keyword(s):  
Neurodegenerative Diseases ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Fragile X ◽  
Potential Contribution ◽  
Fused In Sarcoma ◽  
Specific Mrnas ◽  
Ataxia Syndrome ◽  
Research Frontiers

Both RNA-binding proteins (RBPs) and translation are increasingly implicated in several neurodegenerative diseases, but their specific roles in promoting disease are not yet fully defined. This chapter critically evaluates the evidence that altered translation of specific mRNAs mediated by RNA-binding proteins plays an important role in driving specific neurodegenerative diseases. First, diseases are discussed where a causal role for RNA-binding proteins in disease appears solid, but whether this involves altered translation is less clear. The main foci here are TAR DNA-binding protein (TDP-43) and fused in sarcoma (FUS) in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Subsequently, diseases are presented where altered translation is believed to contribute, but involvement of RNA-binding proteins is less clear. These include Huntington’s and other repeat expansion disorders such as fragile X tremor/ataxia syndrome (FXTAS), where repeat-induced non-AUG-initiated (RAN) translation is a focus. The potential contribution of both canonical and non-canonical RBPs to altered translation in Parkinson’s disease is discussed. The chapter closes by proposing key research frontiers for the field to explore and outlining methodological advances that could help to address them.

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