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Toxins Dec 2023iota-toxin is composed of two separate proteins: a binding protein (Ib) that recognizes a host cell receptor and promotes the cellular uptake of a catalytic protein and... (Review)
Review
iota-toxin is composed of two separate proteins: a binding protein (Ib) that recognizes a host cell receptor and promotes the cellular uptake of a catalytic protein and (Ia) possessing ADP-ribosyltransferase activity that induces actin cytoskeleton disorganization. Ib exhibits the overall structure of bacterial pore-forming toxins (PFTs). Lipolysis-stimulated lipoprotein receptor (LSR) is defined as a host cell receptor for Ib. The binding of Ib to LSR causes an oligomer formation of Ib in lipid rafts of plasma membranes, mediating the entry of Ia into the cytoplasm. Ia induces actin cytoskeleton disruption via the ADP-ribosylation of G-actin and causes cell rounding and death. The binding protein alone disrupts the cell membrane and induces cytotoxicity in sensitive cells. Host cells permeabilized by the pore formation of Ib are repaired by a Ca-dependent plasma repair pathway. This review shows that the cellular uptake of iota-toxin utilizes a pathway of plasma membrane repair and that Ib alone induces cytotoxicity.
Topics: Animals; Chlorocebus aethiops; Clostridium perfringens; Biological Transport; Actins; Vero Cells; ADP Ribose Transferases
PubMed: 38133199
DOI: 10.3390/toxins15120695 -
ACS Synthetic Biology Aug 2022Engineering synthetic cells has a broad appeal, from understanding living cells to designing novel biomaterials for therapeutics, biosensing, and hybrid interfaces. A...
Engineering synthetic cells has a broad appeal, from understanding living cells to designing novel biomaterials for therapeutics, biosensing, and hybrid interfaces. A key prerequisite to creating synthetic cells is a three-dimensional container capable of orchestrating biochemical reactions. In this study, we present an easy and effective technique to make cell-sized porous containers, coined actinosomes, using the interactions between biomolecular condensates and the actin cytoskeleton. This approach uses polypeptide/nucleoside triphosphate condensates and localizes actin monomers on their surface. By triggering actin polymerization and using osmotic gradients, the condensates are transformed into containers, with the boundary made up of actin filaments and polylysine polymers. We show that the guanosine triphosphate (GTP)-to-adenosine triphosphate (ATP) ratio is a crucial parameter for forming actinosomes: insufficient ATP prevents condensate dissolution, while excess ATP leads to undesired crumpling. Permeability studies reveal the porous surface of actinosomes, allowing small molecules to pass through while restricting bigger macromolecules within the interior. We show the functionality of actinosomes as bioreactors by carrying out protein translation within them. Actinosomes are a handy addition to the synthetic cell platform, with appealing properties like ease of production, inherent encapsulation capacity, and a potentially active surface to trigger signaling cascades and form multicellular assemblies, conceivably useful for biotechnological applications.
Topics: Actins; Adenosine Triphosphate; Artificial Cells; Nucleotides; Polymers
PubMed: 35948429
DOI: 10.1021/acssynbio.2c00290 -
American Journal of Physiology. Cell... May 2021Ion channels in plasma membrane play a principal role in different physiological processes, including cell volume regulation, signal transduction, and modulation of... (Review)
Review
Ion channels in plasma membrane play a principal role in different physiological processes, including cell volume regulation, signal transduction, and modulation of membrane potential in living cells. Actin-based cytoskeleton, which exists in a dynamic balance between monomeric and polymeric forms (globular and fibrillar actin), can be directly or indirectly involved in various cellular responses including modulation of ion channel activity. In this mini-review, we present an overview of the role of submembranous actin dynamics in the regulation of ion channels in excitable and nonexcitable cells. Special attention is focused on the important data about the involvement of actin assembly/disassembly and some actin-binding proteins in the control of the epithelial Na channel (ENaC) and mechanosensitive Piezo channels whose integral activity has a potential impact on membrane transport and multiple coupled cellular reactions. Growing evidence suggests that actin elements of the cytoskeleton can represent a "converging point" of various signaling pathways modulating the activity of ion transport proteins in cell membranes.
Topics: Actin Cytoskeleton; Actins; Animals; Cell Membrane; Epithelial Sodium Channels; Humans; Ion Channel Gating; Ion Channels; Mechanotransduction, Cellular; Protein Conformation; Structure-Activity Relationship
PubMed: 33471624
DOI: 10.1152/ajpcell.00368.2020 -
International Journal of Molecular... Jul 2021The primary function of the endothelial cells (EC) lining the inner surface of all vessels is to regulate permeability of vascular walls and to control exchange between... (Review)
Review
The primary function of the endothelial cells (EC) lining the inner surface of all vessels is to regulate permeability of vascular walls and to control exchange between circulating blood and tissue fluids of organs. The EC actin cytoskeleton plays a crucial role in maintaining endothelial barrier function. Actin cytoskeleton reorganization result in EC contraction and provides a structural basis for the increase in vascular permeability, which is typical for many diseases. Actin cytoskeleton in non-muscle cells presented two actin isoforms: non-muscle β-cytoplasmic and γ-cytoplasmic actins (β-actins and γ-actins), which are encoded by ACTB and ACTG1 genes, respectively. They are ubiquitously expressed in the different cells in vivo and in vitro and the β/γ-actin ratio depends on the cell type. Both cytoplasmic actins are essential for cell survival, but they perform various functions in the interphase and cell division and play different roles in neoplastic transformation. In this review, we briefly summarize the research results of recent years and consider the features of the cytoplasmic actins: The spatial organization in close connection with their functional activity in different cell types by focusing on endothelial cells.
Topics: Actins; Animals; Cytoplasm; Endothelial Cells; Humans
PubMed: 34360602
DOI: 10.3390/ijms22157836 -
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 -
Journal of Biosciences 2020As a tumor suppressor, p53 preserves genomic integrity in eukaryotes. However, limited evidence is available for the p53 shuttling between the cytoplasm and nucleus....
As a tumor suppressor, p53 preserves genomic integrity in eukaryotes. However, limited evidence is available for the p53 shuttling between the cytoplasm and nucleus. Previous studies have shown that β-actin polymerization negatively regulates p53 nuclear import through its interaction with p53. In this study, we found that DNA damage induces both β-actin and p53 accumulation in the nucleus. β-actin knockdown impaired the nuclear transport of p53. Additionally, β-actin could interact with p53 which was enhanced in response to genotoxic stress. Furthermore, N terminal deletion mutants of p53 shows reduced levels of association with β-actin. We further identified Ser15, Thr18 and Ser20 of p53 are critical to the β-actin: p53 interaction, which upon mutation into alanine abrogates the binding. Taken together, this study reveals that β-actin regulates the nuclear import of p53 through protein-protein interaction.
Topics: Actins; Active Transport, Cell Nucleus; Antineoplastic Agents, Phytogenic; Cell Line, Tumor; DNA Damage; Etoposide; Gene Expression Regulation, Neoplastic; Humans; Tumor Suppressor Protein p53
PubMed: 32098913
DOI: No ID Found -
ELife Sep 2023As cells migrate and experience forces from their surroundings, they constantly undergo mechanical deformations which reshape their plasma membrane (PM). To maintain...
As cells migrate and experience forces from their surroundings, they constantly undergo mechanical deformations which reshape their plasma membrane (PM). To maintain homeostasis, cells need to detect and restore such changes, not only in terms of overall PM area and tension as previously described, but also in terms of local, nanoscale topography. Here, we describe a novel phenomenon, by which cells sense and restore mechanically induced PM nanoscale deformations. We show that cell stretch and subsequent compression reshape the PM in a way that generates local membrane evaginations in the 100 nm scale. These evaginations are recognized by I-BAR proteins, which triggers a burst of actin polymerization mediated by Rac1 and Arp2/3. The actin polymerization burst subsequently re-flattens the evagination, completing the mechanochemical feedback loop. Our results demonstrate a new mechanosensing mechanism for PM shape homeostasis, with potential applicability in different physiological scenarios.
Topics: Actins; Cell Membrane; Homeostasis
PubMed: 37747150
DOI: 10.7554/eLife.72316 -
Seminars in Cell & Developmental Biology Jun 2020Actin is one of the most abundant and essential intracellular proteins that mediates nearly every form of cellular movement and underlies such key processes as... (Review)
Review
Actin is one of the most abundant and essential intracellular proteins that mediates nearly every form of cellular movement and underlies such key processes as embryogenesis, tissue integrity, cell division and contractility of all types of muscle and non-muscle cells. In mammals, actin is represented by six isoforms, which are encoded by different genes but produce proteins that are 95-99 % identical to each other. The six actin genes have vastly different functions in vivo, and the small amino acid differences between the proteins they encode are rigorously maintained through evolution, but the underlying differences behind this distinction, as well as the importance of specific amino acid sequences for each actin isoform, are not well understood. This review summarizes different levels of actin isoform-specific regulation in cellular and developmental processes, starting with the nuclear actin's role in transcription, and covering the gene-level, mRNA-level, and protein-level regulation, with a special focus on mammalian actins in non-muscle cells.
Topics: Actins; Animals; Cells; Growth and Development; Humans; Protein Isoforms
PubMed: 32001148
DOI: 10.1016/j.semcdb.2019.12.003 -
JCI Insight Aug 2020Actin γ 2, smooth muscle (ACTG2) R257C mutation is the most common genetic cause of visceral myopathy. Individuals with ACTG2 mutations endure prolonged...
Actin γ 2, smooth muscle (ACTG2) R257C mutation is the most common genetic cause of visceral myopathy. Individuals with ACTG2 mutations endure prolonged hospitalizations and surgical interventions, become dependent on intravenous nutrition and bladder catheterization, and often die in childhood. Currently, we understand little about how ACTG2 mutations cause disease, and there are no mechanism-based treatments. Our goal was to characterize the effects of ACTG2R257C on actin organization and function in visceral smooth muscle cells. We overexpressed ACTG2WT or ACTG2R257C in primary human intestinal smooth muscle cells (HISMCs) and performed detailed quantitative analyses to examine effects of ACTG2R257C on (a) actin filament formation and subcellular localization, (b) actin-dependent HISMC functions, and (c) smooth muscle contractile gene expression. ACTG2R257C resulted in 41% fewer, 13% thinner, 33% shorter, and 40% less branched ACTG2 filament bundles compared with ACTG2WT. Curiously, total F-actin probed by phalloidin and a pan-actin antibody was unchanged between ACTG2WT- and ACTG2R257C-expressing HISMCs, as was ultrastructural F-actin organization. ACTG2R257C-expressing HISMCs contracted collagen gels similar to ACTG2WT-expressing HISMCs but spread 21% more and were 11% more migratory. In conclusion, ACTG2R257C profoundly affects ACTG2 filament bundle structure, without altering global actin cytoskeleton in HISMCs.
Topics: Actin Cytoskeleton; Actins; Cell Movement; Cells, Cultured; Collagen; Gene Expression Regulation; Humans; Intestinal Pseudo-Obstruction; Muscle Contraction; Muscle, Smooth; Mutation
PubMed: 32814715
DOI: 10.1172/jci.insight.140604 -
Biochemical Society Transactions Feb 2023The actin cytoskeleton plays a key role in cell migration and cellular morphodynamics in most eukaryotes. The ability of the actin cytoskeleton to assemble and... (Review)
Review
The actin cytoskeleton plays a key role in cell migration and cellular morphodynamics in most eukaryotes. The ability of the actin cytoskeleton to assemble and disassemble in a spatiotemporally controlled manner allows it to form higher-order structures, which can generate forces required for a cell to explore and navigate through its environment. It is regulated not only via a complex synergistic and competitive interplay between actin-binding proteins (ABP), but also by filament biochemistry and filament geometry. The lack of structural insights into how geometry and ABPs regulate the actin cytoskeleton limits our understanding of the molecular mechanisms that define actin cytoskeleton remodeling and, in turn, impact emerging cell migration characteristics. With the advent of cryo-electron microscopy (cryo-EM) and advanced computational methods, it is now possible to define these molecular mechanisms involving actin and its interactors at both atomic and ultra-structural levels in vitro and in cellulo. In this review, we will provide an overview of the available cryo-EM methods, applicable to further our understanding of the actin cytoskeleton, specifically in the context of cell migration. We will discuss how these methods have been employed to elucidate ABP- and geometry-defined regulatory mechanisms in initiating, maintaining, and disassembling cellular actin networks in migratory protrusions.
Topics: Cryoelectron Microscopy; Actins; Actin Cytoskeleton; Cytoskeleton; Microfilament Proteins; Cell Movement
PubMed: 36695514
DOI: 10.1042/BST20220221