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Davoudian K, Bhattacharya S, Thompson D, Thompson M. Coupled Electrostatic and Hydrophobic Destabilisation of the Gelsolin-Actin Complex Enables Facile Detection of Ovarian Cancer Biomarker Lysophosphatidic Acid. Biomolecules 2023; 13:1426. [PMID: 37759826 PMCID: PMC10527313 DOI: 10.3390/biom13091426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 09/12/2023] [Accepted: 09/15/2023] [Indexed: 09/29/2023] Open
Abstract
Lysophosphatidic acid (LPA) is a promising biomarker candidate to screen for ovarian cancer (OC) and potentially stratify and treat patients according to disease stage. LPA is known to target the actin-binding protein gelsolin which is a key regulator of actin filament assembly. Previous studies have shown that the phosphate headgroup of LPA alone is inadequate to bind to the short chain of amino acids in gelsolin known as the PIP2-binding domain. Thus, the molecular-level detail of the mechanism of LPA binding is poorly understood. Here, we model LPA binding to the PIP2-binding domain of gelsolin in the gelsolin-actin complex through extensive ten-microsecond atomistic molecular dynamics (MD) simulations. We predict that LPA binding causes a local conformational rearrangement due to LPA interactions with both gelsolin and actin residues. These conformational changes are a result of the amphipathic nature of LPA, where the anionic phosphate, polar glycerol and ester groups, and lipophilic aliphatic tail mediate LPA binding via charged electrostatic, hydrogen bonding, and van der Waals interactions. The negatively-charged LPA headgroup binds to the PIP2-binding domain of gelsolin-actin while its hydrophobic tail is inserted into actin, creating a strong LPA-insertion pocket that weakens the gelsolin-actin interface. The computed structure, dynamics, and energetics of the ternary gelsolin-LPA-actin complex confirms that a quantitative OC assay is possible based on LPA-triggered actin release from the gelsolin-actin complex.
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Affiliation(s)
- Katharina Davoudian
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON M5S 3H6, Canada;
| | - Shayon Bhattacharya
- SSPC—The Science Foundation Ireland Research Centre for Pharmaceuticals, V94 T9PX Limerick, Ireland;
- Department of Physics, Bernal Institute, University of Limerick, V94 T9PX Limerick, Ireland
| | - Damien Thompson
- SSPC—The Science Foundation Ireland Research Centre for Pharmaceuticals, V94 T9PX Limerick, Ireland;
- Department of Physics, Bernal Institute, University of Limerick, V94 T9PX Limerick, Ireland
| | - Michael Thompson
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON M5S 3H6, Canada;
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2
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Illescas M, Peñas A, Arenas J, Martín MA, Ugalde C. Regulation of Mitochondrial Function by the Actin Cytoskeleton. Front Cell Dev Biol 2022; 9:795838. [PMID: 34993202 PMCID: PMC8725978 DOI: 10.3389/fcell.2021.795838] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 12/03/2021] [Indexed: 12/13/2022] Open
Abstract
The regulatory role of actin cytoskeleton on mitochondrial function is a growing research field, but the underlying molecular mechanisms remain poorly understood. Specific actin-binding proteins (ABPs), such as Gelsolin, have also been shown to participate in the pathophysiology of mitochondrial OXPHOS disorders through yet to be defined mechanisms. In this mini-review, we will summarize the experimental evidence supporting the fundamental roles of actin cytoskeleton and ABPs on mitochondrial trafficking, dynamics, biogenesis, metabolism and apoptosis, with a particular focus on Gelsolin involvement in mitochondrial disorders. The functional interplay between the actin cytoskeleton, ABPs and mitochondrial membranes for the regulation of cellular homeostasis thus emerges as a new exciting field for future research and therapeutic approaches.
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Affiliation(s)
- María Illescas
- Instituto de Investigación Hospital 12 de Octubre, Madrid, Spain
| | - Ana Peñas
- Instituto de Investigación Hospital 12 de Octubre, Madrid, Spain
| | - Joaquín Arenas
- Instituto de Investigación Hospital 12 de Octubre, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Miguel A Martín
- Instituto de Investigación Hospital 12 de Octubre, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Cristina Ugalde
- Instituto de Investigación Hospital 12 de Octubre, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
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3
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Polyphosphoinositides in the nucleus: Roadmap of their effectors and mechanisms of interaction. Adv Biol Regul 2019; 72:7-21. [PMID: 31003946 DOI: 10.1016/j.jbior.2019.04.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 04/02/2019] [Accepted: 04/03/2019] [Indexed: 01/01/2023]
Abstract
Biomolecular interactions between proteins and polyphosphoinositides (PPIn) are essential in the regulation of the vast majority of cellular processes. Consequently, alteration of these interactions is implicated in the development of many diseases. PPIn are phosphorylated derivatives of phosphatidylinositol and consist of seven species with different phosphate combinations. PPIn signal by recruiting proteins via canonical domains or short polybasic motifs. Although their actions are predominantly documented on cytoplasmic membranes, six of the seven PPIn are present within the nucleus together with the PPIn kinases, phosphatases and phospholipases that regulate their turnover. Importantly, the contribution of nuclear PPIn in the regulation of nuclear processes has led to an increased recognition of their importance compared to their more accepted cytoplasmic roles. This review summarises our knowledge on the identification and functional characterisation of nuclear PPIn-effector proteins as well as their mode of interactions, which tend to favour polybasic motifs.
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Szatmári D, Xue B, Kannan B, Burtnick LD, Bugyi B, Nyitrai M, Robinson RC. ATP competes with PIP2 for binding to gelsolin. PLoS One 2018; 13:e0201826. [PMID: 30086165 PMCID: PMC6080781 DOI: 10.1371/journal.pone.0201826] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 07/23/2018] [Indexed: 01/08/2023] Open
Abstract
Gelsolin is a severing and capping protein that targets filamentous actin and regulates filament lengths near plasma membranes, contributing to cell movement and plasma membrane morphology. Gelsolin binds to the plasma membrane via phosphatidylinositol 4,5-bisphosphate (PIP2) in a state that cannot cap F-actin, and gelsolin-capped actin filaments are uncapped by PIP2 leading to filament elongation. The process by which gelsolin is removed from PIP2 at the plasma membrane is currently unknown. Gelsolin also binds ATP with unknown function. Here we characterize the role of ATP on PIP2-gelsolin complex dynamics. Fluorophore-labeled PIP2 and ATP were used to study their interactions with gelsolin using steady-state fluorescence anisotropy, and Alexa488-labeled gelsolin was utilized to reconstitute the regulation of gelsolin binding to PIP2-containing phospholipid vesicles by ATP. Under physiological salt conditions ATP competes with PIP2 for binding to gelsolin, while calcium causes the release of ATP from gelsolin. These data suggest a cycle for gelsolin activity. Firstly, calcium activates ATP-bound gelsolin allowing it to sever and cap F-actin. Secondly, PIP2-binding removes the gelsolin cap from F-actin at low calcium levels, leading to filament elongation. Finally, ATP competes with PIP2 to release the calcium-free ATP-bound gelsolin, allowing it to undergo a further round of severing.
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Affiliation(s)
- Dávid Szatmári
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
- University of Pécs, Medical School, Department of Biophysics, Pécs, Hungary
| | - Bo Xue
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
- Department of Biochemistry, National University of Singapore, Singapore, Singapore
- NUS Synthetic Biology for Clinical and Technological Innovation (SynCTI), Life Sciences Institute, National University of Singapore, Singapore, Singapore
| | - Balakrishnan Kannan
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
| | - Leslie D. Burtnick
- Department of Chemistry and Centre for Blood Research, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
| | - Beáta Bugyi
- University of Pécs, Medical School, Department of Biophysics, Pécs, Hungary
- Szentágothai Research Center, Pécs, Hungary
| | - Miklós Nyitrai
- University of Pécs, Medical School, Department of Biophysics, Pécs, Hungary
- Szentágothai Research Center, Pécs, Hungary
| | - Robert C. Robinson
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
- Department of Biochemistry, National University of Singapore, Singapore, Singapore
- Research Institute for Interdisciplinary Science, Okayama University, Okayama, Japan
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5
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Wu CY, Lin MW, Wu DC, Huang YB, Huang HT, Chen CL. The role of phosphoinositide-regulated actin reorganization in chemotaxis and cell migration. Br J Pharmacol 2014; 171:5541-54. [PMID: 25420930 DOI: 10.1111/bph.12777] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 04/15/2014] [Accepted: 05/07/2014] [Indexed: 12/12/2022] Open
Abstract
UNLABELLED Reorganization of the actin cytoskeleton is essential for cell motility and chemotaxis. Actin-binding proteins (ABPs) and membrane lipids, especially phosphoinositides PI(4,5)P2 and PI(3,4,5)P3 are involved in the regulation of this reorganization. At least 15 ABPs have been reported to interact with, or regulated by phosphoinositides (PIPs) whose synthesis is regulated by extracellular signals. Recent studies have uncovered several parallel intracellular signalling pathways that crosstalk in chemotaxing cells. Here, we review the roles of ABPs and phosphoinositides in chemotaxis and cell migration. LINKED ARTICLES This article is part of a themed section on Cytoskeleton, Extracellular Matrix, Cell Migration, Wound Healing and Related Topics. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-24.
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Affiliation(s)
- C-Y Wu
- Department of Biological Science, National Sun Yat-sen University, Kaohsiung, Taiwan; Doctoral Degree Program in Marine Biotechnology, National Sun Yat-sen University and Academia Sinica, Kaohsiung, Taiwan
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Kapus A, Janmey P. Plasma membrane--cortical cytoskeleton interactions: a cell biology approach with biophysical considerations. Compr Physiol 2013; 3:1231-81. [PMID: 23897686 DOI: 10.1002/cphy.c120015] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
From a biophysical standpoint, the interface between the cell membrane and the cytoskeleton is an intriguing site where a "two-dimensional fluid" interacts with an exceedingly complex three-dimensional protein meshwork. The membrane is a key regulator of the cytoskeleton, which not only provides docking sites for cytoskeletal elements through transmembrane proteins, lipid binding-based, and electrostatic interactions, but also serves as the source of the signaling events and molecules that control cytoskeletal organization and remolding. Conversely, the cytoskeleton is a key determinant of the biophysical and biochemical properties of the membrane, including its shape, tension, movement, composition, as well as the mobility, partitioning, and recycling of its constituents. From a cell biological standpoint, the membrane-cytoskeleton interplay underlies--as a central executor and/or regulator--a multitude of complex processes including chemical and mechanical signal transduction, motility/migration, endo-/exo-/phagocytosis, and other forms of membrane traffic, cell-cell, and cell-matrix adhesion. The aim of this article is to provide an overview of the tight structural and functional coupling between the membrane and the cytoskeleton. As biophysical approaches, both theoretical and experimental, proved to be instrumental for our understanding of the membrane/cytoskeleton interplay, this review will "oscillate" between the cell biological phenomena and the corresponding biophysical principles and considerations. After describing the types of connections between the membrane and the cytoskeleton, we will focus on a few key physical parameters and processes (force generation, curvature, tension, and surface charge) and will discuss how these contribute to a variety of fundamental cell biological functions.
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Affiliation(s)
- András Kapus
- Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada.
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7
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Nag S, Larsson M, Robinson RC, Burtnick LD. Gelsolin: The tail of a molecular gymnast. Cytoskeleton (Hoboken) 2013; 70:360-84. [DOI: 10.1002/cm.21117] [Citation(s) in RCA: 149] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 05/24/2013] [Indexed: 12/14/2022]
Affiliation(s)
| | - Mårten Larsson
- Institute of Molecular and Cell Biology, A*STAR; Singapore
| | | | - Leslie D. Burtnick
- Department of Chemistry and Centre for Blood Research; Life Sciences Institute, University of British Columbia; Vancouver; British Columbia; Canada
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8
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Slabbaert JR, Khuong TM, Verstreken P. Phosphoinositides at the Neuromuscular Junction of Drosophila melanogaster: A Genetic Approach. Methods Cell Biol 2012; 108:227-47. [DOI: 10.1016/b978-0-12-386487-1.00012-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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9
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Disruption of blastomeric F-actin: a potential early biomarker of developmental toxicity in zebrafish. Mol Cell Biochem 2011; 353:283-90. [PMID: 21461911 DOI: 10.1007/s11010-011-0797-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Accepted: 03/17/2011] [Indexed: 01/21/2023]
Abstract
The expression of at least some biomarkers of toxicity is generally thought to precede the appearance of frank pathology. In the context of developmental toxicity, certain early indicators may be predictive of later drastic outcome. The search for predictive biomarkers of toxicity in the cells (blastomeres) of an early embryo can benefit from the fact that for normal development to proceed, the maintenance of blastomere cellular integrity during the process of transition from an embryo to a fully functional organism is paramount. Actin microfilaments are integral parts of blastomeres in the developing zebrafish embryo and contribute toward the proper progression of early development (cleavage and epiboly). In early embryos, the filamentous actin (F-actin) is present and helps to define the boundary of each blastomere as they remain adhered to each other. In our studies, we observed that when blastomeric F-actin is depolymerized by agents like gelsolin, the blastomeres lose cellular integrity, which results in abnormal larvae later in development. There are a variety of toxicants that depolymerize F-actin in early mammalian embryos, the later consequences of which are, at present, not known. We propose that very early zebrafish embryos (~5-h old) exposed to such toxicants will also respond in a like manner. In this review, we discuss the potential use of F-actin disruption as a predictive biomarker of developmental toxicity in zebrafish.
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10
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Liu Z, Klaavuniemi T, Ono S. Distinct roles of four gelsolin-like domains of Caenorhabditis elegans gelsolin-like protein-1 in actin filament severing, barbed end capping, and phosphoinositide binding. Biochemistry 2010; 49:4349-60. [PMID: 20392036 DOI: 10.1021/bi100215b] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Caenorhabditis elegans gelsolin-like protein-1 (GSNL-1) is a new member of the gelsolin family of actin regulatory proteins [Klaavuniemi, T., Yamashiro, S., and Ono, S. (2008) J. Biol. Chem. 283, 26071-26080]. It is an unconventional gelsolin-related protein with four gelsolin-like (G) domains (G1-G4), unlike typical gelsolin-related proteins with three or six G domains. GSNL-1 severs actin filaments and caps the barbed end in a calcium-dependent manner similar to that of gelsolin. In contrast, GSNL-1 has properties different from those of gelsolin in that it remains bound to F-actin and does not nucleate actin polymerization. To understand the mechanism by which GSNL-1 regulates actin dynamics, we investigated the domain-function relationship of GSNL-1 by analyzing activities of truncated forms of GSNL-1. G1 and the linker between G1 and G2 were sufficient for actin filament severing, whereas G1 and G2 were required for barbed end capping. The actin severing activity of GSNL-1 was inhibited by phosphatidylinositol 4,5-bisphosphate (PIP2), and a PIP2-sensitive domain was mapped to G1 and G2. At least two actin-binding sites were detected: a calcium-dependent G-actin-binding site in G1 and a calcium-independent G- and F-actin-binding site in G3 and G4. These results reveal both conserved and different utilization of G domains between C. elegans GSNL-1 and mammalian gelsolin for actin regulatory functions.
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Affiliation(s)
- Zhongmei Liu
- Department of Pathology and Department of Cell Biology, Emory University, Atlanta, Georgia 30322, USA
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11
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Brzeska H, Guag J, Remmert K, Chacko S, Korn ED. An experimentally based computer search identifies unstructured membrane-binding sites in proteins: application to class I myosins, PAKS, and CARMIL. J Biol Chem 2010; 285:5738-47. [PMID: 20018884 PMCID: PMC2820801 DOI: 10.1074/jbc.m109.066910] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2009] [Revised: 12/01/2009] [Indexed: 11/06/2022] Open
Abstract
Programs exist for searching protein sequences for potential membrane-penetrating segments (hydrophobic regions) and for lipid-binding sites with highly defined tertiary structures, such as PH, FERM, C2, ENTH, and other domains. However, a rapidly growing number of membrane-associated proteins (including cytoskeletal proteins, kinases, GTP-binding proteins, and their effectors) bind lipids through less structured regions. Here, we describe the development and testing of a simple computer search program that identifies unstructured potential membrane-binding sites. Initially, we found that both basic and hydrophobic amino acids, irrespective of sequence, contribute to the binding to acidic phospholipid vesicles of synthetic peptides that correspond to the putative membrane-binding domains of Acanthamoeba class I myosins. Based on these results, we modified a hydrophobicity scale giving Arg- and Lys-positive, rather than negative, values. Using this basic and hydrophobic scale with a standard search algorithm, we successfully identified previously determined unstructured membrane-binding sites in all 16 proteins tested. Importantly, basic and hydrophobic searches identified previously unknown potential membrane-binding sites in class I myosins, PAKs and CARMIL (capping protein, Arp2/3, myosin I linker; a membrane-associated cytoskeletal scaffold protein), and synthetic peptides and protein domains containing these newly identified sites bound to acidic phospholipids in vitro.
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Affiliation(s)
- Hanna Brzeska
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA.
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12
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Saarikangas J, Zhao H, Lappalainen P. Regulation of the actin cytoskeleton-plasma membrane interplay by phosphoinositides. Physiol Rev 2010; 90:259-89. [PMID: 20086078 DOI: 10.1152/physrev.00036.2009] [Citation(s) in RCA: 362] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The plasma membrane and the underlying cortical actin cytoskeleton undergo continuous dynamic interplay that is responsible for many essential aspects of cell physiology. Polymerization of actin filaments against cellular membranes provides the force for a number of cellular processes such as migration, morphogenesis, and endocytosis. Plasma membrane phosphoinositides (especially phosphatidylinositol bis- and trisphosphates) play a central role in regulating the organization and dynamics of the actin cytoskeleton by acting as platforms for protein recruitment, by triggering signaling cascades, and by directly regulating the activities of actin-binding proteins. Furthermore, a number of actin-associated proteins, such as BAR domain proteins, are capable of directly deforming phosphoinositide-rich membranes to induce plasma membrane protrusions or invaginations. Recent studies have also provided evidence that the actin cytoskeleton-plasma membrane interactions are misregulated in a number of pathological conditions such as cancer and during pathogen invasion. Here, we summarize the wealth of knowledge on how the cortical actin cytoskeleton is regulated by phosphoinositides during various cell biological processes. We also discuss the mechanisms by which interplay between actin dynamics and certain membrane deforming proteins regulate the morphology of the plasma membrane.
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Affiliation(s)
- Juha Saarikangas
- Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
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13
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Best MD, Zhang H, Prestwich GD. Inositol polyphosphates, diphosphoinositol polyphosphates and phosphatidylinositol polyphosphate lipids: Structure, synthesis, and development of probes for studying biological activity. Nat Prod Rep 2010; 27:1403-30. [DOI: 10.1039/b923844c] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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14
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Richer SM, Stewart NK, Webb SA, Tomaszewski JW, Oakley MG. High affinity binding to profilin by a covalently constrained, soluble mimic of phosphatidylinositol-4,5-bisphosphate micelles. ACS Chem Biol 2009; 4:733-9. [PMID: 19639958 DOI: 10.1021/cb900121r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Phosphoinositide (PI) lipids are essential regulators of a wide variety of cellular functions. We present here the preparation of a multivalent analogue of a phosphatidylinositol-4,5-bisphosphate (PIP(2)) micelle containing only the polar headgroup portion of this lipid. We show that this dendrimer binds to the cytoskeletal protein profilin with an affinity indistinguishable from that of PIP(2), despite the fact that profilin discriminates between PIP(2) and its monomeric hydrolysis product inositol-1,4,5-triphosphate (IP(3)) under physiological conditions. These data demonstrate that the diacylglycerol (DAG) moiety of PIP(2) is not required for high-affinity binding and suggest that profilin uses multivalency as a key means to distinguish between the intact lipid and IP(3). The class of soluble membrane analogues described here is likely to have broad applicability in the study of protein.PI interactions.
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Affiliation(s)
- Sarah M. Richer
- Department of Chemistry, Indiana University, 212 South Hawthorne Drive, Bloomington, Indiana 47405
| | - Nichole K. Stewart
- Department of Chemistry, Indiana University, 212 South Hawthorne Drive, Bloomington, Indiana 47405
| | - Sarah A. Webb
- Department of Chemistry, Indiana University, 212 South Hawthorne Drive, Bloomington, Indiana 47405
| | - John W. Tomaszewski
- Department of Chemistry, Indiana University, 212 South Hawthorne Drive, Bloomington, Indiana 47405
| | - Martha G. Oakley
- Department of Chemistry, Indiana University, 212 South Hawthorne Drive, Bloomington, Indiana 47405
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15
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Johnson CM, Rodgers W. Spatial Segregation of Phosphatidylinositol 4,5-Bisphosphate (PIP(2)) Signaling in Immune Cell Functions. IMMUNOLOGY, ENDOCRINE & METABOLIC AGENTS IN MEDICINAL CHEMISTRY 2008; 8:349-357. [PMID: 19956793 PMCID: PMC2771939 DOI: 10.2174/187152208787169233] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phosphatidylinositol 4,5-bisphosphate (PIP(2)) is a prevalent phosphoinositide in the inner leaflet of the plasma membrane. PIP(2) associates with an ever-growing list of proteins, and participates in a variety of cellular processes. PIP(2) signaling to the actin cytoskeleton transduces specific signals necessary for changes in morphology, motility, endocytosis, exocytosis, phagocytosis, and cell activation. The mechanism(s) by which PIP(2) signaling pathways are specific is a topic of intense investigation. One working model is the compartmentalization of PIP(2)-mediated signaling by concentrating PIP(2) in cholesterol-dependent membrane rafts, therefore providing spatial and temporal regulation. Here we discuss properties of PIP(2) signaling to the actin cytoskeleton in immune cell functioning, the association of PIP(2) cellular pools with membrane rafts, and recent work investigating models for compartmentalization of PIP(2)-mediated signaling in membrane rafts to the actin cytoskeleton.
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Affiliation(s)
- Corey M. Johnson
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation
| | - William Rodgers
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation
- Departments of Microbiology and Immunology, & Pathology, University of Oklahoma Health Sciences Center
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16
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Richer SM, Stewart NK, Tomaszewski JW, Stone MJ, Oakley MG. NMR Investigation of the Binding between Human Profilin I and Inositol 1,4,5-Triphosphate, the Soluble Headgroup of Phosphatidylinositol 4,5-Bisphosphate. Biochemistry 2008; 47:13455-62. [DOI: 10.1021/bi801535f] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sarah M. Richer
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, and Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
| | - Nichole K. Stewart
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, and Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
| | - John W. Tomaszewski
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, and Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
| | - Martin J. Stone
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, and Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
| | - Martha G. Oakley
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, and Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
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17
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Ono S. Mechanism of depolymerization and severing of actin filaments and its significance in cytoskeletal dynamics. INTERNATIONAL REVIEW OF CYTOLOGY 2007; 258:1-82. [PMID: 17338919 DOI: 10.1016/s0074-7696(07)58001-0] [Citation(s) in RCA: 212] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The actin cytoskeleton is one of the major structural components of the cell. It often undergoes rapid reorganization and plays crucial roles in a number of dynamic cellular processes, including cell migration, cytokinesis, membrane trafficking, and morphogenesis. Actin monomers are polymerized into filaments under physiological conditions, but spontaneous depolymerization is too slow to maintain the fast actin filament dynamics observed in vivo. Gelsolin, actin-depolymerizing factor (ADF)/cofilin, and several other actin-severing/depolymerizing proteins can enhance disassembly of actin filaments and promote reorganization of the actin cytoskeleton. This review presents advances as well as a historical overview of studies on the biochemical activities and cellular functions of actin-severing/depolymerizing proteins.
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Affiliation(s)
- Shoichiro Ono
- Department of Pathology, Emory University, Atlanta, GA 30322, USA
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18
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Osborn TM, Dahlgren C, Hartwig JH, Stossel TP. Modifications of cellular responses to lysophosphatidic acid and platelet-activating factor by plasma gelsolin. Am J Physiol Cell Physiol 2006; 292:C1323-30. [PMID: 17135294 DOI: 10.1152/ajpcell.00510.2006] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Gelsolin is a highly conserved intracellular actin-binding protein with an extracellular isoform, plasma gelsolin (pGSN). Blood concentrations of pGSN decrease in response to diverse tissue injuries. Depletion of pGSN to critical levels precedes and often predicts complications of injuries such as lung permeability changes and death. Administration of recombinant pGSN ameliorates such complications and reduces mortality in animal models. One proposed mechanism for pGSN's protective effects is that it inhibits inflammatory mediators generated during primary injuries, since pGSN binds bioactive mediators, including lysophospatidic acid (LPA) and endotoxin in vitro. However, no direct evidence in support of this hypothesis has been available. Here we show that recombinant pGSN modestly inhibited LPA-induced P-selectin upregulation by human platelets in the presence of albumin (P < 0.0001). However, physiologically relevant pGSN concentrations inhibit platelet-activating factor (PAF)-mediated P-selectin expression by up to 77% (P < 0.0001). pGSN also markedly inhibited PAF-induced superoxide anion (O(2)(-)) production of human peripheral neutrophils (PMN) in a concentration-dependent manner (P < 0.0001). A phospholipid-binding peptide derived from pGSN (QRLFQVKGRR) also inhibited PAF-mediated O(2)(-) generation (P = 0.024). Therefore, pGSN interferes with PAF- and LPA-induced cellular activation in vitro, suggesting a mechanism for the protective role of pGSN in vivo.
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Affiliation(s)
- Teresia M Osborn
- Translational Medicine Division/ Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, 75 Francis St., Boston, MA 02115, USA.
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19
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Smith J, Diez G, Klemm AH, Schewkunow V, Goldmann WH. CapZ-lipid membrane interactions: a computer analysis. Theor Biol Med Model 2006; 3:30. [PMID: 16914033 PMCID: PMC1564000 DOI: 10.1186/1742-4682-3-30] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2006] [Accepted: 08/16/2006] [Indexed: 12/03/2022] Open
Abstract
Background CapZ is a calcium-insensitive and lipid-dependent actin filament capping protein, the main function of which is to regulate the assembly of the actin cytoskeleton. CapZ is associated with membranes in cells and it is generally assumed that this interaction is mediated by polyphosphoinositides (PPI) particularly PIP2, which has been characterized in vitro. Results We propose that non-PPI lipids also bind CapZ. Data from computer-aided sequence and structure analyses further suggest that CapZ could become partially buried in the lipid bilayer probably under mildly acidic conditions, in a manner that is not only dependent on the presence of PPIs. We show that lipid binding could involve a number of sites that are spread throughout the CapZ molecule i.e., alpha- and beta-subunits. However, a beta-subunit segment between residues 134–151 is most likely to be involved in interacting with and inserting into lipid membrane due to a slighly higher ratio of positively to negatively charged residues and also due to the presence of a small hydrophobic helix. Conclusion CapZ may therefore play an essential role in providing a stable membrane anchor for actin filaments.
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Affiliation(s)
- James Smith
- Friedrich-Alexander-University of Erlangen-Nuremberg Center for Medical Physics and Technology, Biophysics Group Henkestrasse 91, 91052 Erlangen, Germany
| | - Gerold Diez
- Friedrich-Alexander-University of Erlangen-Nuremberg Center for Medical Physics and Technology, Biophysics Group Henkestrasse 91, 91052 Erlangen, Germany
| | - Anna H Klemm
- Friedrich-Alexander-University of Erlangen-Nuremberg Center for Medical Physics and Technology, Biophysics Group Henkestrasse 91, 91052 Erlangen, Germany
| | - Vitali Schewkunow
- Friedrich-Alexander-University of Erlangen-Nuremberg Center for Medical Physics and Technology, Biophysics Group Henkestrasse 91, 91052 Erlangen, Germany
| | - Wolfgang H Goldmann
- Friedrich-Alexander-University of Erlangen-Nuremberg Center for Medical Physics and Technology, Biophysics Group Henkestrasse 91, 91052 Erlangen, Germany
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20
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Urosev D, Ma Q, Tan ALC, Robinson RC, Burtnick LD. The structure of gelsolin bound to ATP. J Mol Biol 2006; 357:765-72. [PMID: 16469333 DOI: 10.1016/j.jmb.2006.01.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2005] [Revised: 12/29/2005] [Accepted: 01/04/2006] [Indexed: 11/17/2022]
Abstract
Calcium activation of the actin-modifying properties of gelsolin is sensitive to ATP. Here, we show that soaking calcium-free gelsolin crystals in ATP-containing media results in ATP occupying a site that spans the two pseudosymmetrical halves of the protein. ATP binding involves numerous polar and hydrophobic contacts and is identical for the two copies of gelsolin related by non-crystallographic symmetry within the crystal. The gamma-phosphate of ATP participates in several charge-charge interactions consistent with the preference of gelsolin for ATP, as a binding partner, over ADP. In addition, disruption of the ATP-binding site through Ca2+ activation of gelsolin reveals why ATP binds more tightly to the inactive molecule, and suggests how the binding of ATP may modulate the sensitivity of gelsolin to calcium ions. Similarities between the ATP and PIP2 interactions with the C-terminal half of gelsolin are evident from their overlapping binding sites and in that both molecules bind more tightly in the absence of calcium ions. We propose a model for how PIP2 may bind to calcium-free gelsolin based on the ATP-binding site.
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Affiliation(s)
- Dunja Urosev
- Department of Chemistry and Centre for Blood Research, The University of British Columbia, Vancouver, BC V6T 1Z1, Canada
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21
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Abstract
Phosphoinositide phosphates (PIPs) correspond to phosphorylated derivatives of phosphatidylinositol (PI). Despite their relatively low abundance in the plasma membrane, PIPs play a crucial role as precursors of second messengers and are themselves important signaling and targeting molecules. Indeed, modulation of levels of PIPs affects, for example, cortical actin organization, membrane dynamics, and cell migration. The focus of this review is on selected interesting targets of PIPs. Those proteins that bind PIPs and are involved in regulation of actin assembly, actin membrane linkage, and actin contractility are discussed, as well as those that are involved in signaling, such as small GTPases, protein kinases, and phosphatases, or in regulation of membrane dynamics.
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Affiliation(s)
- Verena Niggli
- Department of Pathology, University of Bern, CH-3010 Bern, Switzerland.
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Méré J, Chahinian A, Maciver S, Fattoum A, Bettache N, Benyamin Y, Roustan C. Gelsolin binds to polyphosphoinositide-free lipid vesicles and simultaneously to actin microfilaments. Biochem J 2005; 386:47-56. [PMID: 15527423 PMCID: PMC1134765 DOI: 10.1042/bj20041054] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Gelsolin is a calcium-, pH- and lipid-dependent actin filament severing/capping protein whose main function is to regulate the assembly state of the actin cytoskeleton. Gelsolin is associated with membranes in cells, and it is generally assumed that this interaction is mediated by PPIs (polyphosphoinositides), since an interaction with these lipids has been characterized in vitro. We demonstrate that non-PPI lipids also bind gelsolin, especially at low pH. The data suggest further that gelsolin becomes partially buried in the lipid bilayer under mildly acidic conditions, in a manner that is not dependent of the presence of PPIs. Our data also suggest that lipid binding involves a number of sites that are spread throughout the gelsolin molecule. Linker regions between gelsolin domains have been implicated by other work, notably the linker between G1 and G2 (gelsolin domains 1 and 2 respectively), and we postulate that the linker region between the N-terminal and C-terminal halves of gelsolin (between G3 and G4) is also involved in the interaction with lipids. This region is compatible with other studies in which additional binding sites have been located within G4-6. The lipid-gelsolin interactions reported in the present paper are not calcium-dependent, and are likely to involve significant conformational changes to the gelsolin molecule, as the chymotryptic digest pattern is altered by the presence of lipids under our conditions. We also report that vesicle-bound gelsolin is capable of binding to actin filaments, presumably through barbed end capping. Gelsolin bound to vesicles can nucleate actin assembly, but is less active in severing microfilaments.
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Affiliation(s)
- Jocelyn Méré
- *UMR 5539 (CNRS) Laboratoire de motilité cellulaire (Ecole Pratique des Hautes Etudes), Université de Montpellier 2, Place E. Bataillon, CC107, 34095 Montpellier Cedex 5, France
| | - Anne Chahinian
- *UMR 5539 (CNRS) Laboratoire de motilité cellulaire (Ecole Pratique des Hautes Etudes), Université de Montpellier 2, Place E. Bataillon, CC107, 34095 Montpellier Cedex 5, France
| | - Sutherland K. Maciver
- †School of Biomedical and Clinical Laboratory Sciences, Division of Biomedical Sciences, College of Medicine, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, Scotland, U.K
| | - Abdellatif Fattoum
- ‡Centre de Recherches de Biochimie Macromoléculaire, FRE 2593 (CNRS), 1919 rte de Mende, 34293 Montpellier Cedex 5, France
| | - Nadir Bettache
- *UMR 5539 (CNRS) Laboratoire de motilité cellulaire (Ecole Pratique des Hautes Etudes), Université de Montpellier 2, Place E. Bataillon, CC107, 34095 Montpellier Cedex 5, France
| | - Yves Benyamin
- *UMR 5539 (CNRS) Laboratoire de motilité cellulaire (Ecole Pratique des Hautes Etudes), Université de Montpellier 2, Place E. Bataillon, CC107, 34095 Montpellier Cedex 5, France
| | - Claude Roustan
- *UMR 5539 (CNRS) Laboratoire de motilité cellulaire (Ecole Pratique des Hautes Etudes), Université de Montpellier 2, Place E. Bataillon, CC107, 34095 Montpellier Cedex 5, France
- To whom correspondence should be addressed (email )
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23
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Burtnick LD, Urosev D, Irobi E, Narayan K, Robinson RC. Structure of the N-terminal half of gelsolin bound to actin: roles in severing, apoptosis and FAF. EMBO J 2004; 23:2713-22. [PMID: 15215896 PMCID: PMC514944 DOI: 10.1038/sj.emboj.7600280] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2004] [Accepted: 05/26/2004] [Indexed: 11/08/2022] Open
Abstract
The actin filament-severing functionality of gelsolin resides in its N-terminal three domains (G1-G3). We have determined the structure of this fragment in complex with an actin monomer. The structure reveals the dramatic domain rearrangements that activate G1-G3, which include the replacement of interdomain interactions observed in the inactive, calcium-free protein by new contacts to actin, and by a novel G2-G3 interface. Together, these conformational changes are critical for actin filament severing, and we suggest that their absence leads to the disease Finnish-type familial amyloidosis. Furthermore, we propose that association with actin drives the calcium-independent activation of isolated G1-G3 during apoptosis, and that a similar mechanism operates to activate native gelsolin at micromolar levels of calcium. This is the first structure of a filament-binding protein bound to actin and it sets stringent, high-resolution limitations on the arrangement of actin protomers within the filament.
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Affiliation(s)
- Leslie D Burtnick
- Department of Chemistry and Centre for Blood Research, The University of British Columbia, Vancouver, BC, Canada
| | - Dunja Urosev
- Department of Chemistry and Centre for Blood Research, The University of British Columbia, Vancouver, BC, Canada
| | - Edward Irobi
- Department of Medical Biochemistry and Microbiology, Uppsala Biomedical Center, Uppsala University, Uppsala, Sweden
| | - Kartik Narayan
- Department of Medical Biochemistry and Microbiology, Uppsala Biomedical Center, Uppsala University, Uppsala, Sweden
| | - Robert C Robinson
- Department of Medical Biochemistry and Microbiology, Uppsala Biomedical Center, Uppsala University, Uppsala, Sweden
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24
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Biswas RS, Baker DA, Hruska KA, Chellaiah MA. Polyphosphoinositides-dependent regulation of the osteoclast actin cytoskeleton and bone resorption. BMC Cell Biol 2004; 5:19. [PMID: 15142256 PMCID: PMC441372 DOI: 10.1186/1471-2121-5-19] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2004] [Accepted: 05/13/2004] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND Gelsolin, an actin capping protein of osteoclast podosomes, has a unique function in regulating assembly and disassembly of the podosome actin filament. Previously, we have reported that osteopontin (OPN) binding to integrin alphavbeta3 increased the levels of gelsolin-associated polyphosphoinositides, podosome assembly/disassembly, and actin filament formation. The present study was undertaken to identify the possible role of polyphosphoinositides and phosphoinositides binding domains (PBDs) of gelsolin in the osteoclast cytoskeletal structural organization and osteoclast function. RESULTS Transduction of TAT/full-length gelsolin and PBDs containing gelsolin peptides into osteoclasts demonstrated: 1) F-actin enriched patches; 2) disruption of actin ring; 3) an increase in the association polyphosphoinositides (PPIs) with the transduced peptides containing PBDs. The above-mentioned effects were more pronounced with gelsolin peptide containing 2 tandem repeats of PBDs (PBD (2)). Binding of PPIs to the transduced peptides has resulted in reduced levels of PPIs association with the endogenous gelsolin, and thereby disrupted the actin remodeling processes in terms of podosome organization in the clear zone area and actin ring formation. These peptides also exhibited a dominant negative effect in the formation of WASP-Arp2/3 complex indicating the role of phosphoinositides in WASP activation. The TAT-PBD gelsolin peptides transduced osteoclasts are functionally defective in terms of motility and bone resorption. CONCLUSIONS Taken together, these data demonstrate that transduction of PBD gelsolin peptides into osteoclasts produced a dominant negative effect on actin assembly, motility, and bone resorption. These findings indicate that phosphoinositide-mediated signaling mechanisms regulate osteoclast cytoskeleton, podosome assembly/disassembly, actin ring formation and bone resorption activity of osteoclasts.
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Affiliation(s)
- Rajat S Biswas
- Department of Biomedical Sciences, University of Maryland, Baltimore, Maryland 21201, USA
| | - De Anna Baker
- Department of Biomedical Sciences, University of Maryland, Baltimore, Maryland 21201, USA
| | - Keith A Hruska
- Department of Pediatrics, Washington University, St. Louis, MO 63110, USA
| | - Meenakshi A Chellaiah
- Department of Biomedical Sciences, University of Maryland, Baltimore, Maryland 21201, USA
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25
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Abstract
Lipid signaling by phosphoinositides (PIP(n)s) involves an array of proteins with lipid recognition, kinase, phosphatase, and phospholipase functions. Understanding PIP(n) pathway signaling requires identification and characterization of PIP(n)-interacting proteins. Moreover, spatiotemporal localization and physiological function of PIP(n)-protein complexes must be elucidated in cellular and organismal contexts. For protein discovery to functional elucidation, reporter-linked phosphoinositides or tethered PIP(n)s have been essential. The phosphoinositide 3-kinase (PI 3-K) signaling pathway has recently emerged as an important source of potential "druggable" therapeutic targets in human pathophysiology in both academic and pharmaceutical environments. This review summarizes the chemistry of PIP(n) affinity probes and their use in identifying macromolecular targets. The process of target validation will be described, i.e., the use of tethered PIP(n)s in determining PIP(n) selectivity in vitro and in establishing the function of PIP(n)-protein complexes in living cells.
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Affiliation(s)
- Glenn D Prestwich
- Department of Medicinal Chemistry, The University of Utah, 419 Wakara Way, Suite 205, Salt Lake City, UT 84108, USA.
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26
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Abstract
Phosphoinositides [PPIs, which collectively refer to phosphorylated derivatives of phosphatidylinositol (PI)] have a pivotal role as precursors to important second messengers and as bona fide signaling and scaffold targeting molecules. This review focuses on recent advances that elucidate how PPIs, particularly PI(4,5)P2 (PIP2), directly regulate the actin cytoskeleton in vivo by modulating the activity and targeting of actin regulatory proteins. The role of PIP2 in stimulating actin polymerization and in establishing cytoskeleton-plasma membrane linkages is emphasized. In addition, the review presents tantalizing evidence that suggests how binding of selected cytoskeletal proteins to membrane PPIs may promote PPI clustering into raft lipid microdomains, alter their accessibility to other proteins, and even distort the bilayer conformation. These actions have profound implications for many other PPI-regulated membrane functions that are beginning to be uncovered, and they suggest how PPIs can mediate crosstalk between the actin cytoskeleton and an expanding spectrum of essential cellular functions.
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Affiliation(s)
- Helen L Yin
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390, USA.
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27
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Kanungo J, Kozmik Z, Swamynathan SK, Piatigorsky J. Gelsolin is a dorsalizing factor in zebrafish. Proc Natl Acad Sci U S A 2003; 100:3287-92. [PMID: 12629212 PMCID: PMC152284 DOI: 10.1073/pnas.0634473100] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2002] [Indexed: 01/03/2023] Open
Abstract
The gene for gelsolin (an actin-binding, cytoskeletal regulatory protein) was shown earlier to be specialized for high corneal expression in adult zebrafish. We show here that zebrafish gelsolin is required for proper dorsalization during embryogenesis. Inhibition of gelsolin expression by injecting fertilized eggs with a specific morpholino oligonucleotide resulted in a range of concentration-dependent ventralized phenotypes, including those lacking a brain and eyes. These were rescued by coinjection of zebrafish gelsolin or chordin (a known dorsalizing agent) mRNAs, or human gelsolin protein. Moreover, injection of gelsolin mRNA or human gelsolin protein by itself dorsalized the developing embryos, often resulting in axis duplication. Injection of the gelsolin-specific morpholino oligonucleotide enhanced the expression of Vent mRNA, a ventral marker downstream of bone morphogenetic proteins, whereas injection of gelsolin mRNA enhanced the expression of chordin and goosecoid mRNAs, both dorsal markers. Our results indicate that gelsolin also modulates embryonic dorsalventral pattern formation in zebrafish.
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Affiliation(s)
- Jyotshnabala Kanungo
- Laboratory of Molecular and Developmental Biology, National Eye Institute, National Institutes of Health, 6 Center Drive, Bethesda, MD 20892, USA
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28
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Chou J, Stolz DB, Burke NA, Watkins SC, Wells A. Distribution of gelsolin and phosphoinositol 4,5-bisphosphate in lamellipodia during EGF-induced motility. Int J Biochem Cell Biol 2002; 34:776-90. [PMID: 11950594 DOI: 10.1016/s1357-2725(01)00177-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
During induced cell motility the actin cytoskeleton at the leading edge must undergo constant reorganization. Recently, phosphoinositides have been shown to be central to cytoskeleton-membrane linkages and actin organization and turnover. Epidermal growth factor (EGF) receptor (EGFR)-mediated cell motility requires phospholipase C-gamma (PLCgamma), hydrolysis of phosphoinsotide 4,5-bisphosphate (PIP(2)) and subsequent release of gelsolin. We hypothesized this led to the mobilization of PIP(2)-binding proteins which modify the actin cytoskeleton and thus sought to determine whether the leading edge was a site of active PIP(2) hydrolysis and gelsolin redistribution to cytoskeleton. Herein, we report that during EGF-induced motility, the leading edge's submembranous region constitutes a distinct subcellular locale. The relevant phosphoinositide composition of this space was determined by probing with an antibody to PIP(2) and a green fluorescence protein (GFP)-tagged pleckstrin homology (PH) domain of PLCdelta (GFP-PH) that recognizes both PIP(2) and inositol 1,4,5-trisphosphate (IP(3)). PIP(2) was absent from leading lamellipodia despite an increase in IP(3) generation, suggesting an increase in PIP(2) hydrolysis at the leading edge. Visualized with immunofluorescence, gelsolin preferentially concentrated near the leading edge in a punctate fashion. Examining the Triton X-insoluble actin cytoskeleton fractions, we observe a PLCgamma-dependent increase of gelsolin incorporation upon EGF stimulation. At a molecular level, field emission scanning electron microscopy (FE-SEM) shows that gelsolin incorporates preferentially into the submembranous actin arcs at the leading edge of the lamellipodia. Together these data suggest a model of PIP(2) hydrolysis at the leading edge causing a localized release of PIP(2)-binding proteins-particularly gelsolin-that drives cytoskeletal rearrangement and protrusion.
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Affiliation(s)
- Jeffrey Chou
- Department of Pathology, University of Pittsburgh, 713 Scaife Street, Pittsburgh, PA 15261, USA
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29
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Chen R, Kang VH, Chen J, Shope JC, Torabinejad J, DeWald DB, Prestwich GD. A monoclonal antibody to visualize PtdIns(3,4,5)P(3) in cells. J Histochem Cytochem 2002; 50:697-708. [PMID: 11967281 DOI: 10.1177/002215540205000511] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P(3)] is a second messenger produced in response to agonist stimulation. Traditionally, visualization of phosphoinositide polyphosphates (PtdInsP(n)) in living cells is accomplished using chimeric green fluorescent protein (GFP)-pleckstrin homology (PH) domain proteins, while PtdInsP(n) quantitation is accomplished by extraction and separation of radiolabeled cellular PtdInsP(n)s. Here we describe preparation of a covalent protein-PtdIns(3,4,5)P(3) immunogen, characterization of binding selectivity of an anti-PtdIns(3,4,5)P(3) IgM, and immunodetection of PtdIns(3,4,5)P(3) in stimulated mammalian cells. This antibody has greater than three orders of magnitude selectivity for binding PtdIns(3,4,5)P(3) relative to its precursor, phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)), and is therefore optimal for studies of cell function. The immunodetection in platelet-derived growth factor (PDGF)-stimulated NIH 3T3 cells was benchmarked against HPLC analysis of [3H]-myo-inositol-labeled cellular PtdInsP(n)s. In addition, the changes in subcellular amounts and localizations of both PtdIns(3,4,5)P(3) and PtdIns(4,5)P(2) in stimulated NIH 3T3 fibroblasts and human neutrophils were observed by immunofluorescence. In insulin- or PDGF-stimulated fibroblasts, PtdIns(3,4,5)P(3) levels increased in the cytoplasm, peaking at 10 min. In contrast, increases in the PtdIns(4,5)P(2) levels were detected in nuclei, corresponding to the production of new substrate following depletion by phosphoinositide (PI) 3-kinase.
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Affiliation(s)
- Riyan Chen
- Center for Cell Signaling, Salt Lake City, Utah 84108, USA
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30
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Li X, Rivas MP, Fang M, Marchena J, Mehrotra B, Chaudhary A, Feng L, Prestwich GD, Bankaitis VA. Analysis of oxysterol binding protein homologue Kes1p function in regulation of Sec14p-dependent protein transport from the yeast Golgi complex. J Cell Biol 2002; 157:63-77. [PMID: 11916983 PMCID: PMC2173257 DOI: 10.1083/jcb.200201037] [Citation(s) in RCA: 200] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Oxysterol binding proteins (OSBPs) comprise a large conserved family of proteins in eukaryotes. Their ubiquity notwithstanding, the functional activities of these proteins remain unknown. Kes1p, one of seven members of the yeast OSBP family, negatively regulates Golgi complex secretory functions that are dependent on the action of the major yeast phosphatidylinositol/phosphatidylcholine Sec14p. We now demonstrate that Kes1p is a peripheral membrane protein of the yeast Golgi complex, that localization to the Golgi complex is required for Kes1p function in vivo, and that targeting of Kes1p to the Golgi complex requires binding to a phosphoinositide pool generated via the action of the Pik1p, but not the Stt4p, PtdIns 4-kinase. Localization of Kes1p to yeast Golgi region also requires function of a conserved motif found in all members of the OSBP family. Finally, we present evidence to suggest that Kes1p may regulate adenosine diphosphate-ribosylation factor (ARF) function in yeast, and that it may be through altered regulation of ARF that Kes1p interfaces with Sec14p in controlling Golgi region secretory function.
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Affiliation(s)
- Xinmin Li
- Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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31
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Abstract
Several cytoskeletal proteins have been shown to interact in vitro with, and in some cases are regulated by, specific membrane lipids. In some cases, evidence for in situ interactions has been provided. The molecular basis for such interactions is now being unravelled. At least five structurally distinct types of lipid-binding sites in cytoskeletal proteins have been identified. However, our understanding of the physiological role of such interactions is still limited. Precise knowledge about the binding-site structures and the actual amino acid residues involved should now enable the expression of mutant proteins that specifically lack the ability to interact with lipids. The impact of these mutations on protein location and function can then be assessed.
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Affiliation(s)
- V Niggli
- Dept of Pathology, University of Bern, Murtenstrasse 31, CH-3010 Bern, Switzerland.
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