-
Molecular Biology of the Cell Nov 1995
Review
Topics: Actin Cytoskeleton; Actin Depolymerizing Factors; Actins; Amino Acid Sequence; Animals; Cytoskeleton; Humans; Microfilament Proteins; Models, Structural; Molecular Sequence Data; Nerve Tissue Proteins
PubMed: 8589446
DOI: 10.1091/mbc.6.11.1423 -
Molecular Biology of the Cell Aug 2020Villin is a major actin-bundling protein that assembles the brush border of intestinal and renal epithelial cells. The villin "headpiece" domain and the actin-binding...
Villin is a major actin-bundling protein that assembles the brush border of intestinal and renal epithelial cells. The villin "headpiece" domain and the actin-binding residues within it regulate its actin-bundling function. Substantial experimental and theoretical information about the three-dimensional structure of the isolated villin headpiece, including a description of the actin-binding residues within the headpiece, is available. Despite that, the actin-bundling site in the full-length (FL) villin protein remains unidentified. We used this existing villin headpiece nuclear magnetic resonance data and performed mutational analysis and functional assays to identify the actin-bundling site in FL human villin protein. By careful evaluation of these conserved actin-binding residues in human advillin protein, we demonstrate their functional significance in the over 30 proteins that contain a villin-type headpiece domain. Our study is the first that combines the available structural data on villin headpiece with functional assays to identify the actin-binding residues in FL villin that regulate its filament-bundling activity. Our findings could have wider implications for other actin-bundling proteins that contain a villin-type headpiece domain.
Topics: Actins; Amino Acid Sequence; Amino Acids; Animals; Binding Sites; Carrier Proteins; Cytoskeleton; Dogs; HeLa Cells; Humans; Madin Darby Canine Kidney Cells; Microfilament Proteins; Protein Binding; Protein Domains; Protein Structure, Tertiary
PubMed: 32520642
DOI: 10.1091/mbc.E20-02-0158 -
PLoS Genetics Jan 2017During cytokinesis, a contractile ring generates the constricting force to divide a cell into two daughters. This ring is composed of filamentous actin and the motor...
During cytokinesis, a contractile ring generates the constricting force to divide a cell into two daughters. This ring is composed of filamentous actin and the motor protein myosin, along with additional structural and regulatory proteins, including anillin. Anillin is a required scaffold protein that links the actomyosin ring to membrane and its organizer, RhoA. However, the molecular basis for timely action of anillin at cytokinesis remains obscure. Here, we find that phosphorylation regulates efficient recruitment of human anillin to the equatorial membrane. Anillin is highly phosphorylated in mitosis, and is a substrate for mitotic kinases. We surveyed function of 46 residues on anillin previously found to be phosphorylated in human cells to identify those required for cytokinesis. Among these sites, we identified S635 as a key site mediating cytokinesis. Preventing S635 phosphorylation adjacent to the AH domain disrupts anillin concentration at the equatorial cortex at anaphase, whereas a phosphomimetic mutant, S635D, partially restores this localization. Time-lapse videomicroscopy reveals impaired recruitment of S635A anillin to equatorial membrane and a transient unstable furrow followed by ultimate failure in cytokinesis. A phosphospecific antibody confirms phosphorylation at S635 in late cytokinesis, although it does not detect phosphorylation in early cytokinesis, possibly due to adjacent Y634 phosphorylation. Together, these findings reveal that anillin recruitment to the equatorial cortex at anaphase onset is enhanced by phosphorylation and promotes successful cytokinesis.
Topics: Cell Membrane; Cytokinesis; HeLa Cells; Humans; Microfilament Proteins; Mutation; Phosphorylation; Protein Processing, Post-Translational
PubMed: 28081137
DOI: 10.1371/journal.pgen.1006511 -
EMBO Reports Sep 2017Primary cilia are sensory, antennae-like organelles present on the surface of many cell types. They have been involved in a variety of diseases collectively termed...
Primary cilia are sensory, antennae-like organelles present on the surface of many cell types. They have been involved in a variety of diseases collectively termed ciliopathies. As cilia are essential regulators of cell signaling, the composition of the ciliary membrane needs to be strictly regulated. To understand regulatory processes at the ciliary membrane, we report the targeting of a genetically engineered enzyme specifically to the ciliary membrane to allow biotinylation and identification of the membrane-associated proteome. Bioinformatic analysis of the comprehensive dataset reveals high-stoichiometric presence of actin-binding proteins inside the cilium. Immunofluorescence stainings and complementary interaction proteomic analyses confirm these findings. Depolymerization of branched F-actin causes further enrichment of the actin-binding and actin-related proteins in cilia, including Myosin 5a (Myo5a). Interestingly, Myo5a knockout decreases ciliation while enhanced levels of Myo5a are observed in cilia upon induction of ciliary disassembly. In summary, we present a novel approach to investigate dynamics of the ciliary membrane proteome in mammalian cells and identify actin-binding proteins as mechanosensitive components of cilia that might have important functions in cilia membrane dynamics.
Topics: Actins; Animals; Cilia; Computational Biology; Gene Expression Regulation; Gene Knockout Techniques; Humans; Membrane Proteins; Membranes; Microfilament Proteins; Myosins; Proteome; Proteomics; Signal Transduction
PubMed: 28710093
DOI: 10.15252/embr.201643846 -
The Biochemical Journal Aug 2004Cortactin was first identified over a decade ago, and its initial characterization as both an F-actin binding protein and v-Src substrate suggested that it was likely to... (Review)
Review
Cortactin was first identified over a decade ago, and its initial characterization as both an F-actin binding protein and v-Src substrate suggested that it was likely to be a key regulator of actin rearrangements in response to tyrosine kinase signalling. The recent discovery that cortactin binds and activates the actin related protein (Arp)2/3 complex, and thus regulates the formation of branched actin networks, together with the identification of multiple protein targets of the cortactin SH3 domain, have revealed diverse cellular roles for this protein. This article reviews current knowledge regarding the role of cortactin in signalling to the actin cytoskeleton in the context of these developments.
Topics: Actins; Animals; Cortactin; Humans; Microfilament Proteins; Signal Transduction
PubMed: 15186216
DOI: 10.1042/BJ20040737 -
Current Biology : CB Feb 2004A novel actin-binding protein, Shroom, localises to precisely those cells that will constrict during cranial neural tube closure and appears pivotal in regulating the... (Review)
Review
A novel actin-binding protein, Shroom, localises to precisely those cells that will constrict during cranial neural tube closure and appears pivotal in regulating the apical constrictions that drive epithelial foldings in vertebrate embryos.
Topics: Actins; Animals; Central Nervous System; Epithelium; Gene Expression Regulation; Mice; Microfilament Proteins; Morphogenesis
PubMed: 15027465
DOI: No ID Found -
FEBS Letters Sep 2020Cytoskeletal remodeling is indispensable for the development and maintenance of neuronal structures and functions. However, the molecular machinery that controls the...
Cytoskeletal remodeling is indispensable for the development and maintenance of neuronal structures and functions. However, the molecular machinery that controls the balance between actin polymerization and depolymerization during these processes is incompletely understood. Here, we report that coronin 2B, a conserved actin-binding protein, is concentrated at the tips of developing dendrites and that knockdown of coronin 2B inhibits the growth of dendrites. Importantly, coronin 2B interacts with actin and reduces the F-actin/G-actin ratio. Furthermore, the coiled-coil domain of coronin 2B is required for its oligomerization, thus confining coronin 2B to neurite tips. Our findings collectively suggest that coronin 2B is important for promoting dendrite outgrowth by limiting the speed of actin polymerization at growth cones.
Topics: Actins; Animals; Cytoskeleton; Growth Cones; HEK293 Cells; Humans; Mice; Microfilament Proteins; Protein Domains
PubMed: 32692409
DOI: 10.1002/1873-3468.13886 -
The actin cytoskeleton as a pivotal molecular basis for cell motility: letter from the guest editor.Cell Adhesion & Migration 2011
Topics: Actins; Cell Movement; Cytoskeleton; Microfilament Proteins
PubMed: 21350331
DOI: 10.4161/cam.5.2.15257 -
Biochimica Et Biophysica Acta Jan 1999The number of actin binding proteins for which (part of) the three-dimensional structure is known, is steadily increasing. This has led to a picture in which defined... (Review)
Review
The number of actin binding proteins for which (part of) the three-dimensional structure is known, is steadily increasing. This has led to a picture in which defined structural modules with actin binding capacity are shared between different actin binding proteins. A classification of these based on their common three-dimensional modules appears a logical future step and in this review we provide an initial list starting from the currently known structures. The discussed cases illustrate that a comparison of the similarities and variations within the common structural actin binding unit of different members of a particular class may ultimately provide shortcuts for defining their actin target site and for understanding their effect on actin dynamics. Within this concept, the multitude of possible interactions by an extensive, and still increasing, list of actin binding proteins becomes manageable because they can be presented as variations upon a limited number of structural themes. We discuss the possible evolutionary routes that may have produced the present array of actin binding modules.
Topics: Actins; Amino Acid Sequence; Animals; Binding Sites; Evolution, Molecular; Humans; Microfilament Proteins; Models, Molecular; Molecular Sequence Data; Protein Conformation; Sequence Homology, Amino Acid; Structure-Activity Relationship
PubMed: 9990286
DOI: 10.1016/s0167-4889(98)00152-9 -
The FEBS Journal Sep 2008Iba2 is a homolog of ionized calcium-binding adapter molecule 1 (Iba1), a 17-kDa protein that binds and cross-links filamentous actin (F-actin) and localizes to membrane... (Comparative Study)
Comparative Study
Iba2 is a homolog of ionized calcium-binding adapter molecule 1 (Iba1), a 17-kDa protein that binds and cross-links filamentous actin (F-actin) and localizes to membrane ruffles and phagocytic cups. Here, we present the crystal structure of human Iba2 and its homodimerization properties, F-actin cross-linking activity, cellular localization and recruitment upon bacterial invasion in comparison with Iba1. The Iba2 structure comprises two central EF-hand motifs lacking bound Ca2+. Iba2 crystallized as a homodimer stabilized by a disulfide bridge and zinc ions. Analytical ultracentrifugation revealed a different mode of dimerization under reducing conditions that was independent of Ca2+. Furthermore, no binding of Ca2+ up to 0.1 mM was detected by equilibrium dialysis. Correspondingly, Iba EF-hand motifs lack residues essential for strong Ca2+ coordination. Sedimentation experiments and microscopy detected pronounced, indistinguishable F-actin binding and cross-linking activity of Iba1 and Iba2 with induction of F-actin bundles. Fluorescent Iba fusion proteins were expressed in HeLa cells and co-localized with F-actin. Iba1 was recruited into cellular projections to a larger extent than Iba2. Additionally, we studied Iba recruitment in a Shigella invasion model that induces cytoskeletal rearrangements. Both proteins were recruited into the bacterial invasion zone and Iba1 was again concentrated slightly higher in the cellular extensions.
Topics: Actins; Amino Acid Sequence; Calcium; Calcium-Binding Proteins; Crystallography, X-Ray; DNA-Binding Proteins; Dimerization; HeLa Cells; Humans; Microfilament Proteins; Models, Molecular; Molecular Sequence Data; Sequence Alignment; Shigella
PubMed: 18699778
DOI: 10.1111/j.1742-4658.2008.06605.x