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Histochemistry and Cell Biology Nov 2020Actin is a conserved cytoskeletal protein with essential functions. Here, we review the state-of-the-art reagents, tools and methods used to probe actin biology and... (Review)
Review
Actin is a conserved cytoskeletal protein with essential functions. Here, we review the state-of-the-art reagents, tools and methods used to probe actin biology and functions in zebrafish embryo and larvae. We also discuss specific cell types and tissues where the study of actin in zebrafish has provided new insights into its functions.
Topics: Actins; Animals; Zebrafish
PubMed: 33095903
DOI: 10.1007/s00418-020-01932-3 -
Current Opinion in Cell Biology Feb 1996Small GTP-binding proteins of the Rho family appear to integrate extracellular signals from diverse receptor types and initiate rearrangements of F-actin. Active members... (Review)
Review
Small GTP-binding proteins of the Rho family appear to integrate extracellular signals from diverse receptor types and initiate rearrangements of F-actin. Active members of the Rho family, Rho and Rac, are now joined by Cdc42 which induces filopodia. Downstream of the Rho family proteins, actin polymerization may be induced by an increase in the availability of actin filament barbed ends. Actin organization may be affected by exposure of actin-binding sites on proteins such as vinculin and ezrin.
Topics: Actins; Signal Transduction
PubMed: 8791404
DOI: 10.1016/s0955-0674(96)80050-0 -
Trends in Biochemical Sciences Jun 2019Actin is one of the most abundant proteins in eukaryotic cells and the main component of the microfilament system. It plays essential roles in numerous cellular... (Review)
Review
Actin is one of the most abundant proteins in eukaryotic cells and the main component of the microfilament system. It plays essential roles in numerous cellular activities, including muscle contraction, maintenance of cell integrity, and motility, as well as transcriptional regulation. Besides interacting with various actin-binding proteins (ABPs), proper actin function is regulated by post-translational modifications (PTMs), such as acetylation, arginylation, oxidation, and others. Here, we explain how actin PTMs can contribute to filament formation and stability, and may have additional actin regulatory functions, which potentially contribute to disease development.
Topics: Actins; Animals; Cytoskeleton; Humans; Microfilament Proteins; Protein Processing, Post-Translational
PubMed: 30611609
DOI: 10.1016/j.tibs.2018.11.010 -
Current Opinion in Cell Biology Feb 2013Now that many genomes have been sequenced, a central concern of cell biology is to understand how the proteins they encode work together to create living matter. In... (Review)
Review
Now that many genomes have been sequenced, a central concern of cell biology is to understand how the proteins they encode work together to create living matter. In vitro studies form an essential part of this program because understanding cellular functions of biological molecules often requires isolating them and reconstituting their activities. In particular, many elements of the actin cytoskeleton were first discovered by biochemical methods and their cellular functions deduced from in vitro experiments. We highlight recent advances that have come from in vitro studies, beginning with studies of actin filaments, and ending with multi-component reconstitutions of complex actin-based processes, including force-generation and cell spreading. We describe both scientific results and the technical innovations that made them possible.
Topics: Actin Cytoskeleton; Actins; Biomimetic Materials; Cell Shape; Movement
PubMed: 23267766
DOI: 10.1016/j.ceb.2012.11.007 -
Annual Review of Biophysics 2010The dynamic nature of actin in cells manifests itself constantly. Polymerization near the cell edge is balanced by depolymerization in the interior, externally induced... (Review)
Review
The dynamic nature of actin in cells manifests itself constantly. Polymerization near the cell edge is balanced by depolymerization in the interior, externally induced actin polymerization is followed by depolymerization, and spontaneous oscillations of actin at the cell periphery are frequently seen. I discuss how mathematical modeling relates quantitative measures of actin dynamics to the rates of underlying molecular level processes. The dynamic properties addressed include the rate of actin assembly at the leading edge of a moving cell, the disassembly rates of intracellular actin networks, the polymerization time course in externally stimulated cells, and spontaneous spatiotemporal patterns formed by actin. Although several aspects of actin assembly have been clarified by increasingly sophisticated models, our understanding of rapid actin disassembly is limited, and the origins of nonmonotonic features in externally stimulated actin polymerization remain unclear. Theory has generated several concrete, testable hypotheses for the origins of spontaneous actin waves and cell-edge oscillations. The development and use of more biomimetic systems applicable to the geometry of a cell will be key to obtaining a quantitative understanding of actin dynamics in cells.
Topics: Actins; Cell Movement; Cell Physiological Phenomena; Energy Metabolism; Protein Multimerization
PubMed: 20462375
DOI: 10.1146/annurev.biophys.093008.131207 -
The FEBS Journal Dec 2022When the plasma membrane (PM) detaches from the underlying actin cortex, the PM expands according to intracellular pressure and a spherical membrane protrusion called a... (Review)
Review
When the plasma membrane (PM) detaches from the underlying actin cortex, the PM expands according to intracellular pressure and a spherical membrane protrusion called a bleb is formed. This bleb retracts when the actin cortex is reassembled underneath the PM. Whereas this phenomenon seems simple at first glance, there are many interesting, unresolved cell biological questions in each process. For example, what is the membrane source to enlarge the surface area of the PM during rapid bleb expansion? What signals induce actin reassembly for bleb retraction, and how is cytoplasmic fluidity regulated to allow rapid membrane deformation during bleb expansion? Furthermore, emerging evidence indicates that cancer cells use blebs for invasion, but little is known about how molecules that are involved in bleb formation, expansion, and retraction are coordinated for directional amoeboid migration. In this review, we discuss the molecular mechanisms involved in the regulation of blebs, which have been revealed by various experimental systems.
Topics: Humans; Actins; Calcium; Cell Membrane; Cytoplasm; Cytoskeleton
PubMed: 34614290
DOI: 10.1111/febs.16220 -
Metallomics : Integrated Biometal... Jan 2012Although the number of papers about "vanadium" has doubled in the last decade, the studies about "vanadium and actin" are scarce. In the present review, the effects of... (Review)
Review
Although the number of papers about "vanadium" has doubled in the last decade, the studies about "vanadium and actin" are scarce. In the present review, the effects of vanadyl, vanadate and decavanadate on actin structure and function are compared. Decavanadate (51)V NMR signals, at -516 ppm, broadened and decreased in intensity upon actin titration, whereas no effects were observed for vanadate monomers, at -560 ppm. Decavanadate is the only species inducing actin cysteine oxidation and vanadyl formation, both processes being prevented by the natural ligand of the protein, ATP. Vanadyl titration with monomeric actin (G-actin), analysed by EPR spectroscopy, reveals a 1:1 binding stoichiometry and a K(d) of 7.5 μM(-1). Both decavanadate and vanadyl inhibited G-actin polymerization into actin filaments (F-actin), with a IC(50) of 68 and 300 μM, respectively, as analysed by light scattering assays, whereas no effects were detected for vanadate up to 2 mM. However, only vanadyl (up to 200 μM) induces 100% of G-actin intrinsic fluorescence quenching, whereas decavanadate shows an opposite effect, which suggests the presence of vanadyl high affinity actin binding sites. Decavanadate increases (2.6-fold) the actin hydrophobic surface, evaluated using the ANSA probe, whereas vanadyl decreases it (15%). Both vanadium species increased the ε-ATP exchange rate (k = 6.5 × 10(-3) s(-1) and 4.47 × 10(-3) s(-1) for decavanadate and vanadyl, respectively). Finally, (1)H NMR spectra of G-actin treated with 0.1 mM decavanadate clearly indicate that major alterations occur in protein structure, which are much less visible in the presence of ATP, confirming the preventive effect of the nucleotide on the decavanadate interaction with the protein. Putting it all together, it is suggested that actin, which is involved in many cellular processes, might be a potential target not only for decavanadate but above all for vanadyl. By affecting actin structure and function, vanadium can regulate many cellular processes of great physiological significance.
Topics: Actins; Cysteine; Ethenoadenosine Triphosphate; Nuclear Magnetic Resonance, Biomolecular; Oxidation-Reduction; Vanadates
PubMed: 22012168
DOI: 10.1039/c1mt00124h -
Journal of Biomolecular Structure &... May 2023Polymerization and depolymerization of actin play an essential role in eukaryotic cells. Actin exists in cells in both monomeric (G-actin) and filamentous (polymer,...
Polymerization and depolymerization of actin play an essential role in eukaryotic cells. Actin exists in cells in both monomeric (G-actin) and filamentous (polymer, F-actin) forms. Actin binding proteins (ABPs) facilitate the transition between these two states, and their interactions with these two states of actin are critical for actin-based cellular processes. Rapid depolymerization of actin is assisted in the brain and/or other cells by its oxidation by the enzyme Mical (yielding Mox-actin), and/or by the binding of Inverted Formin 2 (INF2) - which can also accelerate filaments formation. At their stoichiometric molar ratio INF2 and actin yield the 8S complex (consisting of 4 actin monomers: 2 INF2 dimer molecules). Using biochemical and biophysical methods, we investigate the structural arrangement of actin in the 8S particles and the interaction of INF2 with actin and Mox-actin. To that end, we show 2 D class averages of 8S particles obtained by negative staining electron microscopy. We also show that: (i) 8S particles can seed rapid actin assembly; (ii) Mox-actin and INF2 form 8S particles at proteins ratios similar to those of unoxidized actin; (iii) chemical crosslinkings suggest that actin monomers are in a parallel orientation in the 8S particles of both actin and Mox-actin; and (iv) INF2 accelerates the disassembly of Mox-F-actin. Our results provide better understanding of actin's arrangement in the 8S particles formed during actin depolymerization and in the early polymerization stages of both actin and Mox-actin.Communicated by Ramaswamy H. Sarma.
Topics: Actins; Formins; Microfilament Proteins; Actin Cytoskeleton
PubMed: 35343388
DOI: 10.1080/07391102.2022.2050947 -
IUBMB Life Oct 2005Actin participates in many important biological processes. Currently, intensive investigation is being carried out in a number of laboratories concerning the function of... (Review)
Review
Actin participates in many important biological processes. Currently, intensive investigation is being carried out in a number of laboratories concerning the function of actin in these processes and the molecular basis of its functions. We present a glimpse into four of these areas: actin-like proteins in bacterial cells, actin in the eukaryotic nucleus, the conformational plasticity of the actin filament, and finally, Arp2/3-dependent regulation of actin filament branching and creation of new filament barbed ends.
Topics: Actin-Related Protein 2-3 Complex; Actins; Animals; Cell Nucleus; Escherichia coli Proteins; Humans; Models, Molecular; Protein Conformation; Saccharomyces cerevisiae Proteins; Wiskott-Aldrich Syndrome Protein
PubMed: 16223708
DOI: 10.1080/15216540500306991 -
Biophysical Journal Aug 2019The assembly of actin filaments and filament networks generate forces that drive cell and vesicle movement. These structures and the comprising actin filaments must be...
The assembly of actin filaments and filament networks generate forces that drive cell and vesicle movement. These structures and the comprising actin filaments must be mechanically stable to sustain these forces and maintain their structural integrity. Filaments in these dynamic structures must also be disassembled to recycle and replenish the pool of actin monomers available for polymerization. Actin-severing proteins such as cofilin and contractile myosin motor proteins fragment these nominally stable structures. We developed a mesoscopic-length-scale actin filament model to investigate force-induced filament fragmentation. We show that fragmentation in our model occurs at curvatures similar to previous measurements of fragmentation within (cofil)actin and actin-cofilactin boundaries. Boundaries between bare and cofilin-decorated segments are brittle and fragment at small bending and twisting deformations. Extending filaments disperses strain uniformly over subunit interfaces, and filaments fragment with no detectable partial rupture or plastic deformation. In contrast, bending or twisting filaments imposes nonuniform interface strain and leads to partial interface rupture, accelerating filament fragmentation. As a result, the rupture force under compressive loads is an order of magnitude lower than under tensile loads. Partial interface rupture may be a primary mechanism of accelerating actin filament fragmentation by other actin-destabilizing proteins.
Topics: Actin Cytoskeleton; Actins; Biomechanical Phenomena; Kinetics; Protein Binding; Protein Subunits; Stress, Mechanical
PubMed: 31301801
DOI: 10.1016/j.bpj.2019.06.018