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International Journal of Molecular... Feb 2023To date, it has been shown that the phenomenon of liquid-liquid phase separation (LLPS) underlies many seemingly completely different cellular processes. This provided a... (Review)
Review
To date, it has been shown that the phenomenon of liquid-liquid phase separation (LLPS) underlies many seemingly completely different cellular processes. This provided a new idea of the spatiotemporal organization of the cell. The new paradigm makes it possible to provide answers to many long-standing, but still unresolved questions facing the researcher. In particular, spatiotemporal regulation of the assembly/disassembly of the cytoskeleton, including the formation of actin filaments, becomes clearer. To date, it has been shown that coacervates of actin-binding proteins that arise during the phase separation of the liquid-liquid type can integrate G-actin and thereby increase its concentration to initiate polymerization. It has also been shown that the activity intensification of actin-binding proteins that control actin polymerization, such as N-WASP and Arp2/3, can be caused by their integration into liquid droplet coacervates formed by signaling proteins on the inner side of the cell membrane.
Topics: Actins; Polymerization; Microfilament Proteins; Actin Cytoskeleton; Cytoskeleton
PubMed: 36834689
DOI: 10.3390/ijms24043281 -
The Journal of Clinical Investigation Feb 2020KBTBD13 is a protein expressed in striated muscle whose precise function is unknown. Work by de Winter et al. in this issue of the JCI provides evidence that KBTBD13...
KBTBD13 is a protein expressed in striated muscle whose precise function is unknown. Work by de Winter et al. in this issue of the JCI provides evidence that KBTBD13 localizes to the sarcomere and can directly bind actin. A mutation in KBTBD13 that is associated with nemaline myopathy alters the protein's effects on actin, apparently increasing thin-filament stiffness and ultimately depressing contractile force and relaxation rate. We discuss here the implications of this new sarcomeric protein, some alternate explanations for the effects of KBTBD13R408C, and the advantages of using computational models to interpret functional data from muscle.
Topics: Actins; Humans; Kinetics; Microfilament Proteins; Muscle Proteins; Muscle, Skeletal; Myopathies, Nemaline; Sarcomeres
PubMed: 31904591
DOI: 10.1172/JCI132954 -
Journal of Cell Science Jan 2024The actin cytoskeleton performs multiple cellular functions, and as such, actin polymerization must be tightly regulated. We previously demonstrated that reversible,...
The actin cytoskeleton performs multiple cellular functions, and as such, actin polymerization must be tightly regulated. We previously demonstrated that reversible, non-degradative ubiquitylation regulates the function of the actin polymerase VASP in developing neurons. However, the underlying mechanism of how ubiquitylation impacts VASP activity was unknown. Here, we show that mimicking multi-monoubiquitylation of VASP at K240 and K286 negatively regulates VASP interactions with actin. Using in vitro biochemical assays, we demonstrate the reduced ability of multi-monoubiquitylated VASP to bind, bundle, and elongate actin filaments. However, multi-monoubiquitylated VASP maintained the ability to bind and protect barbed ends from capping protein. Finally, we demonstrate the electroporation of recombinant multi-monoubiquitylated VASP protein altered cell spreading morphology. Collectively, these results suggest a mechanism in which ubiquitylation controls VASP-mediated actin dynamics.
Topics: Actin Cytoskeleton; Actins; Microfilament Proteins; Neurons; Phosphoproteins
PubMed: 38277158
DOI: 10.1242/jcs.261527 -
Anatomical Record (Hoboken, N.J. : 2007) Dec 2018The actin cytoskeleton has long been recognized as a crucial sub-cellular filament system that is responsible for governing fundamental events ranging from cell division...
The actin cytoskeleton has long been recognized as a crucial sub-cellular filament system that is responsible for governing fundamental events ranging from cell division and muscle contraction to whole cell motility and the maintenance of tissue integrity. Consequently, it is not surprising that this network is the focus of over 100,000 different manuscripts. Alterations in the actin cytoskeleton lead to an assortment of diseases and serve as a target for a variety of pathogens. Here we have brought together a collection of primary research articles and reviews that underscore the broad influence this filament system has on organisms. Anat Rec, 301:1986-1990, 2018. © 2018 Wiley Periodicals, Inc.
Topics: Actin Cytoskeleton; Actins; Animals; Cell Movement; Humans; Microfilament Proteins
PubMed: 30312025
DOI: 10.1002/ar.23960 -
Cell Communication and Signaling : CCS Jun 2018TRIO and F-actin-binding protein (TRIOBP) also referred to as Tara, was originally isolated as a cytoskeleton remodeling protein. TRIOBP-1 is important for regulating... (Review)
Review
TRIO and F-actin-binding protein (TRIOBP) also referred to as Tara, was originally isolated as a cytoskeleton remodeling protein. TRIOBP-1 is important for regulating F-actin filament reorganization. TRIOBP variants are broadly classified as variant-1 or - 4 and do not share exons. TRIOBP variant-5 contains all exons. Earlier studies indicated that TRIOBP-4/5 mutation is a pivotal element of autosomal recessive nonsyndromic hearing loss. However, recent studies provide clues that TRIOBP variants are associated with other human diseases including cancer and brain diseases. In this review, recent functional studies focusing on TRIOBP variants and its possible disease models are described.
Topics: Brain; Disease; Genetic Variation; Hearing Loss; Humans; Microfilament Proteins; Neoplasms
PubMed: 29890989
DOI: 10.1186/s12964-018-0237-y -
Molecular Biology of the Cell Oct 2023Myosin-1s are monomeric actin-based motors that function at membranes. Myo1 is the single myosin-1 isoform in that works redundantly with Wsp1-Vrp1 to activate the...
Myosin-1s are monomeric actin-based motors that function at membranes. Myo1 is the single myosin-1 isoform in that works redundantly with Wsp1-Vrp1 to activate the Arp2/3 complex for endocytosis. Here, we identified Ank1 as an uncharacterized cytoplasmic Myo1 binding partner. We found that in cells, Myo1 dramatically redistributed from endocytic patches to decorate the entire plasma membrane and endocytosis was defective. Biochemical analysis and structural predictions suggested that the Ank1 ankyrin repeats bind the Myo1 lever arm and the Ank1 acidic tail binds the Myo1 TH1 domain to prevent TH1-dependent Myo1 membrane binding. Indeed, Ank1 overexpression precluded Myo1 membrane localization and recombinant Ank1 reduced purified Myo1 liposome binding in vitro. Based on biochemical and cell biological analyses, we propose budding yeast Ank1 and human OSTF1 are functional Ank1 orthologs and that cytoplasmic sequestration by small ankyrin repeat proteins is a conserved mechanism regulating myosin-1s in endocytosis.
Topics: Humans; Schizosaccharomyces pombe Proteins; Ankyrin Repeat; Schizosaccharomyces; Myosins; Actins; Cytoskeletal Proteins; Microfilament Proteins
PubMed: 37531259
DOI: 10.1091/mbc.E23-06-0233 -
Microbiology Spectrum Sep 2021The deep-branching protozoan parasite Giardia lamblia is the causative agent of the intestinal disease giardiasis. Consistent with its proposed evolutionary position,...
The deep-branching protozoan parasite Giardia lamblia is the causative agent of the intestinal disease giardiasis. Consistent with its proposed evolutionary position, many pathways are minimalistic or divergent, including its actin cytoskeleton. is the only eukaryote known to lack all canonical actin-binding proteins. Previously, our lab identified a number of noncanonical Giardia lamblia actin (Actin) interactors; however, these proteins appeared to interact only with monomeric or globular actin (G-actin) rather than with filamentous actin (F-actin). To identify F-actin interactors, we used a chemical cross-linker to preserve native interactions followed by an anti-Actin antibody, protein A affinity chromatography, and liquid chromatography coupled to mass spectrometry. We found 46 putative actin interactors enriched under the conditions favoring F-actin. Data are available via ProteomeXchange with identifier PXD026067. None of the proteins identified contain known actin-interacting motifs, and many lacked conserved domains. Each potential interactor was then tagged with the fluorescent protein mNeonGreen and visualized in live cells. We categorized the proteins based on their primary localization; localizations included ventral disc, marginal plate, nuclei, flagella, plasma membrane, and internal membranes. One protein from each of the six categories was colocalized with Actin using immunofluorescence microscopy. We also co-immunoprecipitated one protein from each category and confirmed three of the six potential interactions. Most of the localization patterns are consistent with previously demonstrated Actin functions, but the ventral disc represents a new category of actin interactor localization. These results suggest a role for Actin in ventral disc function, which has previously been controversial. Giardia lamblia is an intestinal parasite that colonizes the small intestine and causes diarrhea, which can lead to dehydration and malnutrition. actin (Actin) has a conserved role in cells, despite being a highly divergent protein with none of the conserved regulators found in model organisms. Here, we identify and localize 46 interactors of polymerized actin. These putative interactors localize to a number of places in the cell, underlining Actin's importance in multiple cellular processes. Surprisingly, eight of these proteins localize to the ventral disc, 's host attachment organelle. Since host attachment is required for infection, proteins involved in this process are an appealing target for new drugs. While treatments for exist, drug resistance is becoming more common, resulting in a need for new treatments. and human systems are highly dissimilar, thus drugs specifically tailored to proteins would be less likely to have side effects.
Topics: Actins; Giardia lamblia; Giardiasis; Host-Parasite Interactions; Humans; Microfilament Proteins; Protein Binding; Protozoan Proteins
PubMed: 34287056
DOI: 10.1128/Spectrum.00558-21 -
Neural Plasticity 2016Structural plasticity of excitatory synapses is a vital component of neuronal development, synaptic plasticity, and behaviour. Abnormal development or regulation of... (Review)
Review
Structural plasticity of excitatory synapses is a vital component of neuronal development, synaptic plasticity, and behaviour. Abnormal development or regulation of excitatory synapses has also been strongly implicated in many neurodevelopmental, psychiatric, and neurodegenerative disorders. In the mammalian forebrain, the majority of excitatory synapses are located on dendritic spines, specialized dendritic protrusions that are enriched in actin. Research over recent years has begun to unravel the complexities involved in the regulation of dendritic spine structure. The small GTPase family of proteins have emerged as key regulators of structural plasticity, linking extracellular signals with the modulation of dendritic spines, which potentially underlies their ability to influence cognition. Here we review a number of studies that examine how small GTPases are activated and regulated in neurons and furthermore how they can impact actin dynamics, and thus dendritic spine morphology. Elucidating this signalling process is critical for furthering our understanding of the basic mechanisms by which information is encoded in neural circuits but may also provide insight into novel targets for the development of effective therapies to treat cognitive dysfunction seen in a range of neurological disorders.
Topics: Animals; Brain; Dendritic Spines; Humans; Microfilament Proteins; Monomeric GTP-Binding Proteins; Neuronal Plasticity; Neurons; Signal Transduction
PubMed: 26989514
DOI: 10.1155/2016/3025948 -
Scientific Reports Mar 2022Protein assembly plays an important role throughout all phyla of life, both physiologically and pathologically. In particular, aggregation and polymerization of proteins...
Protein assembly plays an important role throughout all phyla of life, both physiologically and pathologically. In particular, aggregation and polymerization of proteins are key-strategies that regulate cellular function. In recent years, methods to experimentally study the assembly process on a single-molecule level have been developed. This progress concomitantly has triggered the question of how to analyze this type of single-filament data adequately and what experimental conditions are necessary to allow a meaningful interpretation of the analysis. Here, we developed two analysis methods for single-filament data: the visitation analysis and the average-rate analysis. We benchmarked and compared both approaches with the classic dwell-time-analysis frequently used to study microscopic association and dissociation rates. In particular, we tested the limitations of each analysis method along the lines of the signal-to-noise ratio, the sampling rate, and the labeling efficiency and bleaching rate of the fluorescent dyes used in single-molecule fluorescence experiments. Finally, we applied our newly developed methods to study the monomer assembly of actin at the single-molecule-level in the presence of the class II nucleator Cappuccino and the WH2 repeats of Spire. For Cappuccino, our data indicated fast elongation circumventing a nucleation phase whereas, for Spire, we found that the four WH2 motifs are not sufficient to promote de novo nucleation of actin.
Topics: Actin Cytoskeleton; Actins; Microfilament Proteins; Polymerization
PubMed: 35304498
DOI: 10.1038/s41598-022-08245-6 -
Molecular Microbiology Sep 2021For the protist parasite Entamoeba histolytica, endocytic processes, such as phagocytosis, are essential for its survival in the human gut. The actin cytoskeleton is...
For the protist parasite Entamoeba histolytica, endocytic processes, such as phagocytosis, are essential for its survival in the human gut. The actin cytoskeleton is involved in the formation of pseudopods and phagosomal vesicles by incorporating a number of actin-binding and modulating proteins along with actin in a temporal manner. The actin dynamics, which comprises polymerization, branching, and depolymerization is very tightly regulated and takes place directionally at the sites of initiation of phagocytosis. Formin and profilin are two actin-binding proteins that are known to regulate actin cytoskeleton dynamics and thereby, endocytic processes. In this article, we report the participation of formin and profilin in E. histolytica phagocytosis and propose that these two proteins interact with each other and their sequential recruitment at the site is required for the successful completion of phagocytosis. The evidence is based on detailed microscopic, live imaging, interaction studies, and expression downregulation. The cells downregulated for expression of formin show absence of profilin at the site of phagocytosis, whereas downregulation of profilin does not affect formin localization.
Topics: Actin Cytoskeleton; Actins; Animals; CHO Cells; Cricetulus; Entamoeba histolytica; Formins; Gene Expression Regulation; Humans; Microfilament Proteins; Phagocytosis; Phagosomes; Profilins; Protozoan Proteins
PubMed: 34278607
DOI: 10.1111/mmi.14787