101
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Kemp JP, Brieher WM. The actin filament bundling protein α-actinin-4 actually suppresses actin stress fibers by permitting actin turnover. J Biol Chem 2018; 293:14520-14533. [PMID: 30049798 DOI: 10.1074/jbc.ra118.004345] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 07/21/2018] [Indexed: 01/07/2023] Open
Abstract
Cells organize actin filaments into contractile bundles known as stress fibers that resist mechanical stress, increase cell adhesion, remodel the extracellular matrix, and maintain tissue integrity. α-actinin is an actin filament bundling protein that is thought to be essential for stress fiber formation and stability. However, previous studies have also suggested that α-actinin might disrupt fibers, making the true function of this biomolecule unclear. Here we use fluorescence imaging to show that kidney epithelial cells depleted of α-actinin-4 via shRNA or CRISPR/Cas9, or expressing a disruptive mutant make more massive stress fibers that are less dynamic than those in WT cells, leading to defects in cell motility and wound healing. The increase in stress fiber mass and stability can be explained, in part, by increased loading of the filament component tropomyosin onto stress fibers in the absence of α-actinin, as monitored via immunofluorescence. We show using imaging and cosedimentation that α-actinin and tropomyosin compete for binding to F-actin and that tropomyosin shields actin filaments from cofilin-mediated disassembly in vitro and in cells. Perturbing tropomyosin in cells lacking α-actinin-4 results in a complete loss of stress fibers. Our results with α-actinin-4 on stress fiber organization are the opposite of what might have been predicted from previous in vitro biochemistry and further highlight how the complex interactions of multiple proteins competing for filament binding lead to unexpected functions for actin-binding proteins in cells.
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Affiliation(s)
| | - William M Brieher
- From the Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, Urbana, Illinois 61801
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102
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Abstract
The actin cytoskeleton provides not only the underpinning for cell architecture but also mechanical force and the ability to drive movement of cells and their organelles. It is tempting to think of it simply as a set of stable structural elements, but nothing could be further from the truth. The cells of our bodies are continually remodelling their architecture by responding to a range of imposed biomechanical forces and intracellular functional demands. Studies of the dynamic and functional properties of the actin cytoskeleton have been dominated by a focus on actin and the view that actin filaments are essentially 'generic'. However, the 'other' component of most actin filaments in animals - tropomyosin - is coming into prominence. With this discovery is the realisation that far from being generic, actin filaments have their own functional individuality provided to them by their associated tropomyosin. This is changing the way we understand and study the actin cytoskeleton and has delivered a new therapeutic opportunity in what had come to be considered a 'no-go zone'.
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Affiliation(s)
- Peter W Gunning
- School of Medical Sciences, University of New South Wales, Sydney, NSW, 2052, Australia.
| | - Edna C Hardeman
- School of Medical Sciences, University of New South Wales, Sydney, NSW, 2052, Australia.
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103
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Hilton DM, Aguilar RM, Johnston AB, Goode BL. Species-Specific Functions of Twinfilin in Actin Filament Depolymerization. J Mol Biol 2018; 430:3323-3336. [PMID: 29928893 DOI: 10.1016/j.jmb.2018.06.025] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 05/28/2018] [Accepted: 06/12/2018] [Indexed: 11/16/2022]
Abstract
Twinfilin is a highly conserved member of the actin depolymerization factor homology (ADF-H) protein superfamily, which also includes ADF/Cofilin, Abp1/Drebrin, GMF, and Coactosin. Twinfilin has a unique molecular architecture consisting of two ADF-H domains joined by a linker and followed by a C-terminal tail. Yeast Twinfilin, in conjunction with yeast cyclase-associated protein (Srv2/CAP), increases the rate of depolymerization at both the barbed and pointed ends of actin filaments. However, it has remained unclear whether these activities extend to Twinfilin homologs in other species. To address this, we purified the three mouse Twinfilin isoforms (mTwf1, mTwf2a, mTwf2b) and mouse CAP1, and used total internal reflection fluorescence microscopy assays to study their effects on filament disassembly. Our results show that all three mouse Twinfilin isoforms accelerate barbed end depolymerization similar to yeast Twinfilin, suggesting that this activity is evolutionarily conserved. In striking contrast, mouse Twinfilin isoforms and CAP1 failed to induce rapid pointed end depolymerization. Using chimeras, we show that the yeast-specific pointed end depolymerization activity is specified by the C-terminal ADF-H domain of yeast Twinfilin. In addition, Tropomyosin decoration of filaments failed to impede depolymerization by yeast and mouse Twinfilin and Srv2/CAP, but inhibited Cofilin severing. Together, our results indicate that Twinfilin has conserved functions in regulating barbed end dynamics, although its ability to drive rapid pointed end depolymerization appears to be species-specific. We discuss the implications of this work, including that pointed end depolymerization may be catalyzed by different ADF-H family members in different species.
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Affiliation(s)
- Denise M Hilton
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA 02454, USA
| | - Rey M Aguilar
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA 02454, USA
| | - Adam B Johnston
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA 02454, USA
| | - Bruce L Goode
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA 02454, USA.
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104
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Edhager AV, Povlsen JA, Løfgren B, Bøtker HE, Palmfeldt J. Proteomics of the Rat Myocardium during Development of Type 2 Diabetes Mellitus Reveals Progressive Alterations in Major Metabolic Pathways. J Proteome Res 2018; 17:2521-2532. [PMID: 29847139 DOI: 10.1021/acs.jproteome.8b00276] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Congestive heart failure and poor clinical outcome after myocardial infarction are known complications in patients with type-2 diabetes mellitus (T2DM). Protein alterations may be involved in the mechanisms underlying these disarrays in the diabetic heart. Here we map proteins involved in intracellular metabolic pathways in the Zucker diabetic fatty rat heart as T2DM develops using MS based proteomics. The prediabetic state only induced minor pathway changes, whereas onset and late T2DM caused pronounced perturbations. Two actin-associated proteins, ARPC2 and TPM3, were up-regulated at the prediabetic state indicating increased actin dynamics. All differentially regulated proteins involved in fatty acid metabolism, both peroxisomal and mitochondrial, were up-regulated at late T2DM, whereas enzymes of branched chain amino acid degradation were all down-regulated. At both onset and late T2DM, two members of the serine protease inhibitor superfamily, SERPINA3K and SERPINA3L, were down-regulated. Furthermore, we found alterations in proteins involved in clearance of advanced glycation end-products and lipotoxicity, DCXR and CBR1, at both onset and late T2DM. These proteins deserve elucidation with regard to their role in T2DM pathogenesis and their respective role in the deterioration of the diabetic heart. Data are available via ProteomeXchange with identifiers PXD009538, PXD009554, and PXD009555.
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Affiliation(s)
- Anders Valdemar Edhager
- Research Unit for Molecular Medicine, Department of Clinical Medicine , Aarhus University and Aarhus University Hospital , 8200 , Aarhus N , Denmark
| | | | - Bo Løfgren
- Department of Cardiology , Aarhus University Hospital , 8200 , Aarhus N , Denmark.,Institute for Experimental Clinical Research , Aarhus University , 8000 , Aarhus C , Denmark
| | - Hans Erik Bøtker
- Department of Cardiology , Aarhus University Hospital , 8200 , Aarhus N , Denmark
| | - Johan Palmfeldt
- Research Unit for Molecular Medicine, Department of Clinical Medicine , Aarhus University and Aarhus University Hospital , 8200 , Aarhus N , Denmark
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105
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Ehler E. Actin-associated proteins and cardiomyopathy-the 'unknown' beyond troponin and tropomyosin. Biophys Rev 2018; 10:1121-1128. [PMID: 29869751 PMCID: PMC6082317 DOI: 10.1007/s12551-018-0428-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 05/18/2018] [Indexed: 02/06/2023] Open
Abstract
It has been known for several decades that mutations in genes that encode for proteins involved in the control of actomyosin interactions such as the troponin complex, tropomyosin and MYBP-C and thus regulate contraction can lead to hereditary hypertrophic cardiomyopathy. In recent years, it has become apparent that actin-binding proteins not directly involved in the regulation of contraction also can exhibit changed expression levels, show altered subcellular localisation or bear mutations that might lead to hereditary cardiomyopathies. The aim of this review is to look beyond the troponin/tropomyosin mechanism and to give an overview of the different types of actin-associated proteins and their potential roles in cardiomyocytes. It will then discuss recent findings relevant to their involvement in heart disease.
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Affiliation(s)
- Elisabeth Ehler
- Randall Centre for Cell and Molecular Biophysics (School of Basic and Medical Biosciences), London, UK. .,School of Cardiovascular Medicine and Sciences, British Heart Foundation Research Excellence Centre, King's College London, Room 3.26A, New Hunt's House, Guy's Campus, London, SE1 1UL, UK.
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106
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Barnes DE, Watabe E, Ono K, Kwak E, Kuroyanagi H, Ono S. Tropomyosin isoforms differentially affect muscle contractility in the head and body regions of the nematode Caenorhabditis elegans. Mol Biol Cell 2018; 29:1075-1088. [PMID: 29496965 PMCID: PMC5921574 DOI: 10.1091/mbc.e17-03-0152] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 02/21/2018] [Accepted: 02/23/2018] [Indexed: 11/11/2022] Open
Abstract
Tropomyosin, one of the major actin filament-binding proteins, regulates actin-myosin interaction and actin-filament stability. Multicellular organisms express a number of tropomyosin isoforms, but understanding of isoform-specific tropomyosin functions is incomplete. The nematode Caenorhabditis elegans has a single tropomyosin gene, lev-11, which has been reported to express four isoforms by using two separate promoters and alternative splicing. Here, we report a fifth tropomyosin isoform, LEV-11O, which is produced by alternative splicing that includes a newly identified seventh exon, exon 7a. By visualizing specific splicing events in vivo, we find that exon 7a is predominantly selected in a subset of the body wall muscles in the head, while exon 7b, which is the alternative to exon 7a, is utilized in the rest of the body. Point mutations in exon 7a and exon 7b cause resistance to levamisole--induced muscle contraction specifically in the head and the main body, respectively. Overexpression of LEV-11O, but not LEV-11A, in the main body results in weak levamisole resistance. These results demonstrate that specific tropomyosin isoforms are expressed in the head and body regions of the muscles and contribute differentially to the regulation of muscle contractility.
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Affiliation(s)
- Dawn E. Barnes
- Department of Pathology, Department of Cell Biology, and Winship Cancer Institute, Emory University, Atlanta, GA 30322
| | - Eichi Watabe
- Laboratory of Gene Expression, Medical Research Institute, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
| | - Kanako Ono
- Department of Pathology, Department of Cell Biology, and Winship Cancer Institute, Emory University, Atlanta, GA 30322
| | - Euiyoung Kwak
- Department of Pathology, Department of Cell Biology, and Winship Cancer Institute, Emory University, Atlanta, GA 30322
| | - Hidehito Kuroyanagi
- Laboratory of Gene Expression, Medical Research Institute, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
| | - Shoichiro Ono
- Department of Pathology, Department of Cell Biology, and Winship Cancer Institute, Emory University, Atlanta, GA 30322
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107
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Woodman S, Trousdale C, Conover J, Kim K. Yeast membrane lipid imbalance leads to trafficking defects toward the Golgi. Cell Biol Int 2018; 42:890-902. [PMID: 29500884 DOI: 10.1002/cbin.10956] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 02/24/2018] [Indexed: 12/19/2022]
Abstract
Protein recycling is an essential cellular process involving endocytosis, intracellular trafficking, and exocytosis. In mammalian systems membrane lipids, including cholesterol, sphingolipids, and phospholipids, play a pivotal role in protein recycling. To address this role in budding yeast, Saccharomyces cerevisiae, we utilized GFP-Snc1, a v-SNARE protein serving as a fluorescent marker for faithfully reporting the recycling pathway. Here we demonstrate results that display moderate to significant GFP-Snc1 recycling defects upon overexpression or inactivation of phospholipid, ergosterol, and sphingolipid biosynthesis enzymes, indicating that the homeostasis of membrane lipid levels is prerequisite for proper protein recycling. By using a truncated version of GFP-Snc1 that cannot be recycled from the plasma membrane, we determined that abnormalities in Snc1 localization in membrane lipid overexpression or underexpression mutants are not due to defects in the synthetic/secretory pathway, but rather in the intracellular trafficking pathway. We found that membrane lipid imbalance resulted in an accumulation of the late endosome marker Vps10-GFP, indicating trafficking from the endosomes to the Golgi may be being hindered, preventing recycling to the plasma membrane. To elucidate the possible mechanism for this trafficking hindrance, we stained the actin cytoskeleton, then quantified the percentage of cells with visible actin cables. Compared to wild-type cells, membrane lipid mutant cells exhibited lower levels of actin cables, indicating the actin cytoskeleton is disrupted upon membrane lipid imbalance. Taken together, our results show that impairment of proper recycling may be due to disruption of the actin cytoskeleton, which causes trafficking hindrance between the endosomes and Golgi.
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Affiliation(s)
- Sara Woodman
- Missouri State University, 901 S National Ave., Springfield, Missouri
| | - Christopher Trousdale
- Missouri State University, 901 S National Ave., Springfield, Missouri.,Washington University in St. Louis, 1 Brookings Dr., St. Louis, Missouri
| | - Justin Conover
- Missouri State University, 901 S National Ave., Springfield, Missouri.,Iowa State University, Ames, Iowa
| | - Kyoungtae Kim
- Missouri State University, 901 S National Ave., Springfield, Missouri.,Iowa State University, Ames, Iowa
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108
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Barua B, Sckolnick M, White HD, Trybus KM, Hitchcock-DeGregori SE. Distinct sites in tropomyosin specify shared and isoform-specific regulation of myosins II and V. Cytoskeleton (Hoboken) 2018; 75:150-163. [PMID: 29500902 PMCID: PMC5899941 DOI: 10.1002/cm.21440] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 02/07/2018] [Accepted: 02/19/2018] [Indexed: 12/25/2022]
Abstract
Muscle contraction, cytokinesis, cellular movement, and intracellular transport depend on regulated actin-myosin interaction. Most actin filaments bind one or more isoform of tropomyosin, a coiled-coil protein that stabilizes the filaments and regulates interactions with other actin-binding proteins, including myosin. Isoform-specific allosteric regulation of muscle myosin II by actin-tropomyosin is well-established while that of processive myosins, such as myosin V, which transport organelles and macromolecules in the cell periphery, is less certain. Is the regulation by tropomyosin a universal mechanism, the consequence of the conserved periodic structures of tropomyosin, or is it the result of specialized interactions between particular isoforms of myosin and tropomyosin? Here, we show that striated muscle tropomyosin, Tpm1.1, inhibits fast skeletal muscle myosin II but not myosin Va. The non-muscle tropomyosin, Tpm3.1, in contrast, activates both myosins. To decipher the molecular basis of these opposing regulatory effects, we introduced mutations at conserved surface residues within the six periodic repeats (periods) of Tpm3.1, in positions homologous or analogous to those important for regulation of skeletal muscle myosin by Tpm1.1. We identified conserved residues in the internal periods of both tropomyosin isoforms that are important for the function of myosin Va and striated myosin II. Conserved residues in the internal and C-terminal periods that correspond to Tpm3.1-specific exons inhibit myosin Va but not myosin II function. These results suggest that tropomyosins may directly impact myosin function through both general and isoform-specific mechanisms that identify actin tracks for the recruitment and function of particular myosins.
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Affiliation(s)
- Bipasha Barua
- Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854
| | - Maria Sckolnick
- Department of Molecular Physiology & Biophysics University of Vermont, Burlington, VT 05405
| | - Howard D. White
- Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA 23507
| | - Kathleen M. Trybus
- Department of Molecular Physiology & Biophysics University of Vermont, Burlington, VT 05405
| | - Sarah E. Hitchcock-DeGregori
- Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854
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109
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Gunning PW, Hardeman EC. Tropomyosin-directed tuning of myosin motor function: Insights from mutagenesis. Cytoskeleton (Hoboken) 2018. [DOI: 10.1002/cm.21441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- P. W. Gunning
- School of Medical Sciences; UNSW; Sydney New South Wales 2052 Australia
| | - E. C. Hardeman
- School of Medical Sciences; UNSW; Sydney New South Wales 2052 Australia
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110
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Masedunskas A, Appaduray MA, Lucas CA, Lastra Cagigas M, Heydecker M, Holliday M, Meiring JCM, Hook J, Kee A, White M, Thomas P, Zhang Y, Adelstein RS, Meckel T, Böcking T, Weigert R, Bryce NS, Gunning PW, Hardeman EC. Parallel assembly of actin and tropomyosin, but not myosin II, during de novo actin filament formation in live mice. J Cell Sci 2018; 131:jcs.212654. [PMID: 29487177 DOI: 10.1242/jcs.212654] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 02/12/2018] [Indexed: 01/04/2023] Open
Abstract
Many actin filaments in animal cells are co-polymers of actin and tropomyosin. In many cases, non-muscle myosin II associates with these co-polymers to establish a contractile network. However, the temporal relationship of these three proteins in the de novo assembly of actin filaments is not known. Intravital subcellular microscopy of secretory granule exocytosis allows the visualisation and quantification of the formation of an actin scaffold in real time, with the added advantage that it occurs in a living mammal under physiological conditions. We used this model system to investigate the de novo assembly of actin, tropomyosin Tpm3.1 (a short isoform of TPM3) and myosin IIA (the form of non-muscle myosin II with its heavy chain encoded by Myh9) on secretory granules in mouse salivary glands. Blocking actin polymerization with cytochalasin D revealed that Tpm3.1 assembly is dependent on actin assembly. We used time-lapse imaging to determine the timing of the appearance of the actin filament reporter LifeAct-RFP and of Tpm3.1-mNeonGreen on secretory granules in LifeAct-RFP transgenic, Tpm3.1-mNeonGreen and myosin IIA-GFP (GFP-tagged MYH9) knock-in mice. Our findings are consistent with the addition of tropomyosin to actin filaments shortly after the initiation of actin filament nucleation, followed by myosin IIA recruitment.
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Affiliation(s)
| | | | | | | | - Marco Heydecker
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia.,Membrane Dynamics, Department of Biology, Technische Universität Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany
| | - Mira Holliday
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | | | - Jeff Hook
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | - Anthony Kee
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | - Melissa White
- South Australian Genome Editing, Facility Robinson Research Institute, University of Adelaide, Adelaide, SA 5005, Australia
| | - Paul Thomas
- South Australian Genome Editing, Facility Robinson Research Institute, University of Adelaide, Adelaide, SA 5005, Australia
| | - Yingfan Zhang
- NHLBI, National Institutes of Health, Bethesda, MD 20892, USA
| | | | - Tobias Meckel
- Membrane Dynamics, Department of Biology, Technische Universität Darmstadt, Schnittspahnstrasse 3, 64287 Darmstadt, Germany
| | - Till Böcking
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | - Roberto Weigert
- Laboratory of Cellular and Molecular Biology, CCR, National Cancer Institute, Bethesda, MD 20892, USA
| | - Nicole S Bryce
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | - Peter W Gunning
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | - Edna C Hardeman
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
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111
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Kee AJ, Chagan J, Chan JY, Bryce NS, Lucas CA, Zeng J, Hook J, Treutlein H, Laybutt DR, Stehn JR, Gunning PW, Hardeman EC. On-target action of anti-tropomyosin drugs regulates glucose metabolism. Sci Rep 2018; 8:4604. [PMID: 29545590 PMCID: PMC5854615 DOI: 10.1038/s41598-018-22946-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 03/01/2018] [Indexed: 01/09/2023] Open
Abstract
The development of novel small molecule inhibitors of the cancer-associated tropomyosin 3.1 (Tpm3.1) provides the ability to examine the metabolic function of specific actin filament populations. We have determined the ability of these anti-Tpm (ATM) compounds to regulate glucose metabolism in mice. Acute treatment (1 h) of wild-type (WT) mice with the compounds (TR100 and ATM1001) led to a decrease in glucose clearance due mainly to suppression of glucose-stimulated insulin secretion (GSIS) from the pancreatic islets. The impact of the drugs on GSIS was significantly less in Tpm3.1 knock out (KO) mice indicating that the drug action is on-target. Experiments in MIN6 β-cells indicated that the inhibition of GSIS by the drugs was due to disruption to the cortical actin cytoskeleton. The impact of the drugs on insulin-stimulated glucose uptake (ISGU) was also examined in skeletal muscle ex vivo. In the absence of drug, ISGU was decreased in KO compared to WT muscle, confirming a role of Tpm3.1 in glucose uptake. Both compounds suppressed ISGU in WT muscle, but in the KO muscle there was little impact of the drugs. Collectively, this data indicates that the ATM drugs affect glucose metabolism in vivo by inhibiting Tpm3.1's function with few off-target effects.
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Affiliation(s)
- Anthony J Kee
- School of Medical Sciences, UNSW Sydney, Sydney, NSW, 2052, Australia
| | - Jayshan Chagan
- School of Medical Sciences, UNSW Sydney, Sydney, NSW, 2052, Australia
| | - Jeng Yie Chan
- Garvan Institute of Medical Research, St Vincent's Hospital, UNSW Sydney, Sydney, NSW, Australia
| | - Nicole S Bryce
- School of Medical Sciences, UNSW Sydney, Sydney, NSW, 2052, Australia
| | - Christine A Lucas
- School of Medical Sciences, UNSW Sydney, Sydney, NSW, 2052, Australia
| | - Jun Zeng
- MedChemSoft Solutions, Level 3 Brandon Park Drive, Wheelers Hill, 3150, VIC, Australia
| | - Jeff Hook
- School of Medical Sciences, UNSW Sydney, Sydney, NSW, 2052, Australia
| | - Herbert Treutlein
- Sanoosa Pty. Ltd., 35 Collins Street, Melbourne, 3000, VIC, Australia
| | - D Ross Laybutt
- Garvan Institute of Medical Research, St Vincent's Hospital, UNSW Sydney, Sydney, NSW, Australia
| | - Justine R Stehn
- School of Medical Sciences, UNSW Sydney, Sydney, NSW, 2052, Australia
- Novogen Pty Ltd, 502/20 George St, Hornsby, NSW, 2077, Australia
| | - Peter W Gunning
- School of Medical Sciences, UNSW Sydney, Sydney, NSW, 2052, Australia
| | - Edna C Hardeman
- School of Medical Sciences, UNSW Sydney, Sydney, NSW, 2052, Australia.
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112
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Masters TA, Tumbarello DA, Chibalina MV, Buss F. MYO6 Regulates Spatial Organization of Signaling Endosomes Driving AKT Activation and Actin Dynamics. Cell Rep 2018; 19:2088-2101. [PMID: 28591580 PMCID: PMC5469940 DOI: 10.1016/j.celrep.2017.05.048] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 04/05/2017] [Accepted: 05/12/2017] [Indexed: 02/06/2023] Open
Abstract
APPL1- and RAB5-positive signaling endosomes play a crucial role in the activation of AKT in response to extracellular stimuli. Myosin VI (MYO6) and two of its cargo adaptor proteins, GIPC and TOM1/TOM1L2, localize to these peripheral endosomes and mediate endosome association with cortical actin filaments. Loss of MYO6 leads to the displacement of these endosomes from the cell cortex and accumulation in the perinuclear space. Depletion of this myosin not only affects endosome positioning, but also induces actin and lipid remodeling consistent with endosome maturation, including accumulation of F-actin and the endosomal lipid PI(3)P. These processes acutely perturb endosome function, as both AKT phosphorylation and RAC-dependent membrane ruffling were markedly reduced by depletion of either APPL1 or MYO6. These results place MYO6 and its binding partners at a central nexus in cellular signaling linking actin dynamics at the cell surface and endosomal signaling in the cell cortex.
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Affiliation(s)
- Thomas A Masters
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
| | - David A Tumbarello
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
| | - Margarita V Chibalina
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
| | - Folma Buss
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK.
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113
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Repetto O, De Re V, De Paoli A, Belluco C, Alessandrini L, Canzonieri V, Cannizzaro R. Identification of protein clusters predictive of tumor response in rectal cancer patients receiving neoadjuvant chemo-radiotherapy. Oncotarget 2018; 8:28328-28341. [PMID: 28423701 PMCID: PMC5438653 DOI: 10.18632/oncotarget.16053] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 02/27/2017] [Indexed: 12/26/2022] Open
Abstract
Preoperative neoadjuvant chemoradiotherapy (nCRT) is the gold standard in locally advanced rectal cancer, only 10–30% of patients achieving benefits. Currently, there is a need of a reliable selection of markers for the identification of poor or non-responders prior to therapy. In this work, we compared protein profiles before therapy of patients differing in their responses to nCRT to find novel predictive markers of response to therapy. Patients were grouped into 3 groups according to their tumor regression grading (TRG) after surgery: 'TRG 1–2′, good responders, 'TRG 3′ and 'TRG 4′, poor responders. Paired surgical specimens of rectal cancer and healthy (histologically confirmed) rectal tissues from 15 patients were analysed before nCRT by two dimensional difference in gel electrophoresis followed by mass spectrometry. Thirty spots were found as differentially expressed (p < 0.05). Among them, 3 spots (spots 471, 683 and 684) showed an increased amount of protein in poor responders compared with good responders, and they were more tumor associated compared with healthy tissues. Proteins of these spots were identified as fibrinogen ß chain fragment D, actin isoforms, B9 and B5 serpins, cathepsin D isoforms and peroxiredoxin-4. In an independent validation set of 20 rectal carcinomas we validated the increased fibrinogen ß chain abundance before nCRT in poor responders by immunoblotting. In conclusion, we propose a risk-stratification tool in predicting the response to nCRT treatment in rectal cancer based on the quantity of these proteins.
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Affiliation(s)
- Ombretta Repetto
- Facility of Bio-Proteomics, Immunopathology and Cancer Biomarkers, IRCCS CRO National Cancer Institute, Aviano, Italy
| | - Valli De Re
- Facility of Bio-Proteomics, Immunopathology and Cancer Biomarkers, IRCCS CRO National Cancer Institute, Aviano, Italy
| | - Antonino De Paoli
- Radiation Oncology, IRCCS CRO National Cancer Institute, Aviano, Italy
| | - Claudio Belluco
- Surgical Oncology, IRCCS CRO National Cancer Institute, Aviano, Italy
| | | | | | - Renato Cannizzaro
- Renato Cannizzaro, Gastroenterology, IRCCS CRO National Cancer Institute, Aviano, Italy
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114
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Tropomyosin 2 heterozygous knockout in mice using CRISPR-Cas9 system displays the inhibition of injury-induced epithelial-mesenchymal transition, and lens opacity. Mech Ageing Dev 2018; 171:24-30. [PMID: 29510160 DOI: 10.1016/j.mad.2018.03.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 01/28/2018] [Accepted: 03/01/2018] [Indexed: 01/16/2023]
Abstract
The process of epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) after cataract surgery contributes to tissue fibrosis, wound healing and lens regeneration via a mechanism not yet fully understood. Here, we show that tropomyosin 2 (Tpm2) plays a critical role in wound healing and lens aging. Posterior capsular opacification (PCO) after lens extraction surgery was accompanied by elevated expression of Tpm2. Tpm2 heterozygous knockout mice, generated via the clustered regularly interspaced short palindromic repeat/Cas9 (CRISPR/Cas9) system showed promoted progression of cataract with age. Further, injury-induced EMT of the mouse lens epithelium, as evaluated histologically and by the expression patterns of Tpm1 and Tpm2, was attenuated in the absence of Tpm2. In conclusion, Tpm2 may be important in maintaining lens physiology and morphology. However, Tpm2 is involved in the progression of EMT during the wound healing process of mouse LECs, suggesting that inhibition of Tpm2 may suppress PCO.
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115
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The clinical significance and biological function of tropomyosin 4 in colon cancer. Biomed Pharmacother 2018; 101:1-7. [PMID: 29455030 DOI: 10.1016/j.biopha.2018.01.166] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Revised: 01/31/2018] [Accepted: 01/31/2018] [Indexed: 01/06/2023] Open
Abstract
Tropomyosin 4 (TPM4) has been found to be dys-regulated, and function as oncogene or anti-oncogene in human cancers. However, there was no report on the clinical significance and biological function of TPM4 in colon cancer. This study was designed to investigate the clinical value and biological function of TPM4 in colon cancer. Thus, we detected the TPM4 expression in colon cancer clinical samples, and conducted the gain-of-function in colon cancer cell lines. In our results, TPM4 mRNA and protein expressions were reduced in colon cancer tissues and cell lines compared with normal colon tissues and colon epithelial cell line, respectively. TPM4 protein low-expression was obviously associated with clinical stage, T classification (invasion depth), N classification (lymph node metastasis), distant metastasis and differentiation. Survival analysis showed low-expression of TPM4 was an unfavorable independent prognostic factor for colon cancer patients. Moreover, the experiments in vitro suggested up-regulated TPM4 expression suppressed colon cancer cell migration, invasion and metastasis-associated gene expression including MMP-2, MMP-9 and MT1-MMP, but had no effect on cell proliferation. In conclusion, TPM4 is associated with clinical progression in colon cancer patient and acts as a tumor suppressor in colon cancer cell.
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116
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Zhai Q, Fu Z, Hong Y, Yu X, Han Q, Lu K, Li H, Dou X, Zhu C, Liu J, Lin J, Li G. iTRAQ-Based Comparative Proteomic Analysis of Adult Schistosoma japonicum from Water Buffalo and Yellow Cattle. Front Microbiol 2018; 9:99. [PMID: 29467732 PMCID: PMC5808103 DOI: 10.3389/fmicb.2018.00099] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 01/16/2018] [Indexed: 01/08/2023] Open
Abstract
Schistosomiasis japonicum is one of the most severe zoonotic diseases in China. Water buffalo and yellow cattle are important reservoir hosts and the main transmission sources of Schistosoma japonicum in endemic areas. The susceptibility of these two hosts to schistosome infection is different, as water buffaloes are less susceptible to S. japonicum than yellow cattle. In this study, iTRAQ-coupled LC-MS/MS was applied to compare the protein expression profiles of adult schistosomes recovered from water buffalo with those of yellow cattle. A total of 131 differentially expressed proteins (DEPs) were identified, including 46 upregulated proteins and 85 downregulated proteins. The iTRAQ results were confirmed by Western blotting and quantitative real-time PCR. Further analysis indicated that these DEPs were primarily involved in protein synthesis, transcriptional regulation, protein proteolysis, cytoskeletal structure and oxidative stress response processes. The results revealed that some of the differential expression molecules may affect the development and survival of schistosomes in these two natural hosts. Of note, this study provides useful information for understanding the interplay between schistosomes and their final hosts.
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Affiliation(s)
- Qi Zhai
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
- Key Laboratory of Animal Parasitology of Ministry of Agriculture, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Zhiqiang Fu
- Key Laboratory of Animal Parasitology of Ministry of Agriculture, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Yang Hong
- Key Laboratory of Animal Parasitology of Ministry of Agriculture, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Xingang Yu
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
- Key Laboratory of Animal Parasitology of Ministry of Agriculture, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Qian Han
- Key Laboratory of Animal Parasitology of Ministry of Agriculture, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Ke Lu
- Key Laboratory of Animal Parasitology of Ministry of Agriculture, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Hao Li
- Key Laboratory of Animal Parasitology of Ministry of Agriculture, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Xuefeng Dou
- Key Laboratory of Animal Parasitology of Ministry of Agriculture, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Chuangang Zhu
- Key Laboratory of Animal Parasitology of Ministry of Agriculture, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Jinming Liu
- Key Laboratory of Animal Parasitology of Ministry of Agriculture, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Jiaojiao Lin
- Key Laboratory of Animal Parasitology of Ministry of Agriculture, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Guoqing Li
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
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117
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Chengappa P, Sao K, Jones TM, Petrie RJ. Intracellular Pressure: A Driver of Cell Morphology and Movement. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2018; 337:185-211. [PMID: 29551161 DOI: 10.1016/bs.ircmb.2017.12.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Intracellular pressure, generated by actomyosin contractility and the directional flow of water across the plasma membrane, can rapidly reprogram cell shape and behavior. Recent work demonstrates that cells can generate intracellular pressure with a range spanning at least two orders of magnitude; significantly, pressure is implicated as an important regulator of cell dynamics, such as cell division and migration. Changes to intracellular pressure can dictate the mechanisms by which single human cells move through three-dimensional environments. In this review, we chronicle the classic as well as recent evidence demonstrating how intracellular pressure is generated and maintained in metazoan cells. Furthermore, we highlight how this potentially ubiquitous physical characteristic is emerging as an important driver of cell morphology and behavior.
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Affiliation(s)
| | - Kimheak Sao
- Drexel University, Philadelphia, PA, United States
| | - Tia M Jones
- Drexel University, Philadelphia, PA, United States
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118
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Rynkiewicz MJ, Prum T, Hollenberg S, Kiani FA, Fagnant PM, Marston SB, Trybus KM, Fischer S, Moore JR, Lehman W. Tropomyosin Must Interact Weakly with Actin to Effectively Regulate Thin Filament Function. Biophys J 2018; 113:2444-2451. [PMID: 29211998 DOI: 10.1016/j.bpj.2017.10.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 09/13/2017] [Accepted: 10/05/2017] [Indexed: 10/18/2022] Open
Abstract
Elongated tropomyosin, associated with actin-subunits along the surface of thin filaments, makes electrostatic interactions with clusters of conserved residues, K326, K328, and R147, on actin. The association is weak, permitting low-energy cost regulatory movement of tropomyosin across the filament during muscle activation. Interestingly, acidic D292 on actin, also evolutionarily conserved, lies adjacent to the three-residue cluster of basic amino acids and thus may moderate the combined local positive charge, diminishing tropomyosin-actin interaction and facilitating regulatory-switching. Indeed, charge neutralization of D292 is connected to muscle hypotonia in individuals with D292V actin mutations and linked to congenital fiber-type disproportion. Here, the D292V mutation may predispose tropomyosin-actin positioning to a myosin-blocking state, aberrantly favoring muscle relaxation, thus mimicking the low-Ca2+ effect of troponin even in activated muscles. To test this hypothesis, interaction energetics and in vitro function of wild-type and D292V filaments were measured. Energy landscapes based on F-actin-tropomyosin models show the mutation localizes tropomyosin in a blocked-state position on actin defined by a deeper energy minimum, consistent with augmented steric-interference of actin-myosin binding. In addition, whereas myosin-dependent motility of troponin/tropomyosin-free D292V F-actin is normal, motility is dramatically inhibited after addition of tropomyosin to the mutant actin. Thus, D292V-induced blocked-state stabilization appears to disrupt the delicately poised energy balance governing thin filament regulation. Our results validate the premise that stereospecific but necessarily weak binding of tropomyosin to F-actin is required for effective thin filament function.
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Affiliation(s)
- Michael J Rynkiewicz
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts
| | - Thavanareth Prum
- Department of Biological Sciences, University of Massachusetts-Lowell, Lowell, Massachusetts
| | - Stephen Hollenberg
- Department of Biological Sciences, University of Massachusetts-Lowell, Lowell, Massachusetts
| | - Farooq A Kiani
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts
| | - Patricia M Fagnant
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont
| | - Steven B Marston
- National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Kathleen M Trybus
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont
| | - Stefan Fischer
- Computational Biochemistry Group, IWR, Heidelberg University, Heidelberg, Germany
| | - Jeffrey R Moore
- Department of Biological Sciences, University of Massachusetts-Lowell, Lowell, Massachusetts
| | - William Lehman
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts.
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120
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Manaenko A, Yang P, Nowrangi D, Budbazar E, Hartman RE, Obenaus A, Pearce WJ, Zhang JH, Tang J. Inhibition of stress fiber formation preserves blood-brain barrier after intracerebral hemorrhage in mice. J Cereb Blood Flow Metab 2018; 38:87-102. [PMID: 27864464 PMCID: PMC5757435 DOI: 10.1177/0271678x16679169] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Intracerebral hemorrhage (ICH) represents the deadliest subtype of all strokes. The development of brain edema, a consequence of blood-brain barrier (BBB) disruption, is the most life-threatening event after ICH. Pathophysiological conditions activate the endothelium, one of the components of BBB, inducing rearrangement of the actin cytoskeleton. Upon activation, globular actin assembles into a filamentous actin resulting in the formation of contractile actin bundles, stress fibers. The contraction of stress fibers leads to the formation of intercellular gaps between endothelial cells increasing the permeability of BBB. In the present study, we investigated the effect of ICH on stress fiber formation in CD1 mice. We hypothesized that ICH-induced formation of stress fiber is triggered by the activation of PDGFR-β and mediated by the cortactin/RhoA/LIMK pathway. We demonstrated that ICH induces formation of stress fibers. Furthermore, we demonstrated that the inhibition of PDGFR-β and its downstream reduced the number of stress fibers, preserving BBB and resulting in the amelioration of brain edema and improvement of neurological functions in mice after ICH.
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Affiliation(s)
- Anatol Manaenko
- 1 Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA, USA.,2 Department of Neurology, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Peng Yang
- 1 Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA, USA.,3 Department of Emergency Surgery, the First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China
| | - Derek Nowrangi
- 1 Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA, USA
| | - Enkhjargal Budbazar
- 1 Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA, USA
| | - Richard E Hartman
- 4 Department of Psychology, Loma Linda University, Loma Linda, CA, USA
| | - Andre Obenaus
- 5 Department of Pediatrics, Loma Linda University, Loma Linda, CA, USA
| | - William J Pearce
- 1 Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA, USA
| | - John H Zhang
- 1 Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA, USA.,6 Department of Anesthesiology, Loma Linda University, Loma Linda, CA, USA.,7 Department of Neurosurgery, Loma Linda University, Loma Linda, CA, USA
| | - Jiping Tang
- 1 Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA, USA
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121
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Suchowerska AK, Fok S, Stefen H, Gunning PW, Hardeman EC, Power J, Fath T. Developmental Profiling of Tropomyosin Expression in Mouse Brain Reveals Tpm4.2 as the Major Post-synaptic Tropomyosin in the Mature Brain. Front Cell Neurosci 2017; 11:421. [PMID: 29311841 PMCID: PMC5743921 DOI: 10.3389/fncel.2017.00421] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 12/14/2017] [Indexed: 12/14/2022] Open
Abstract
Nerve cell connections, formed in the developing brain of mammals, undergo a well-programmed process of maturation with changes in their molecular composition over time. The major structural element at the post-synaptic specialization is the actin cytoskeleton, which is composed of different populations of functionally distinct actin filaments. Previous studies, using ultrastructural and light imaging techniques have established the presence of different actin filament populations at the post-synaptic site. However, it remains unknown, how these different actin filament populations are defined and how their molecular composition changes over time. In the present study, we have characterized changes in a core component of actin filaments, the tropomyosin (Tpm) family of actin-associated proteins from embryonal stage to the adult stage. Using biochemical fractionation of mouse brain tissue, we identified the tropomyosin Tpm4.2 as the major post-synaptic Tpm. Furthermore, we found age-related differences in the composition of Tpms at the post-synaptic compartment. Our findings will help to guide future studies that aim to define the functional properties of actin filaments at different developmental stages in the mammalian brain.
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Affiliation(s)
- Alexandra K Suchowerska
- Neurodegeneration and Repair Unit, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Sandra Fok
- Neurodegeneration and Repair Unit, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Holly Stefen
- Neurodegeneration and Repair Unit, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia.,Neuron Culture Core Facility, University of New South Wales, SydneyNSW, Australia
| | - Peter W Gunning
- Cellular and Genetic Medicine Unit, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Edna C Hardeman
- Cellular and Genetic Medicine Unit, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - John Power
- Translational Neuroscience Facility, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Thomas Fath
- Neurodegeneration and Repair Unit, School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia.,Neuron Culture Core Facility, University of New South Wales, SydneyNSW, Australia
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122
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Pathan-Chhatbar S, Taft MH, Reindl T, Hundt N, Latham SL, Manstein DJ. Three mammalian tropomyosin isoforms have different regulatory effects on nonmuscle myosin-2B and filamentous β-actin in vitro. J Biol Chem 2017; 293:863-875. [PMID: 29191834 PMCID: PMC5777259 DOI: 10.1074/jbc.m117.806521] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 11/16/2017] [Indexed: 12/19/2022] Open
Abstract
The metazoan actin cytoskeleton supports a wide range of contractile and transport processes. Recent studies have shown how the dynamic association with specific tropomyosin isoforms generates actin filament populations with distinct functional properties. However, critical details of the associated molecular interactions remain unclear. Here, we report the properties of actomyosin–tropomyosin complexes containing filamentous β-actin, nonmuscle myosin-2B (NM-2B) constructs, and either tropomyosin isoform Tpm1.8cy (b.–.b.d), Tpm1.12br (b.–.b.c), or Tpm3.1cy (b.–.a.d). Our results show the extent to which the association of filamentous β-actin with these different tropomyosin cofilaments affects the actin-mediated activation of NM-2B and the release of the ATP hydrolysis products ADP and phosphate from the active site. Phosphate release gates a transition from weak to strong F-actin–binding states. The release of ADP has the opposite effect. These changes in dominant rate-limiting steps have a direct effect on the duty ratio, the fraction of time that NM-2B spends in strongly F-actin–bound states during ATP turnover. The duty ratio is increased ∼3-fold in the presence of Tpm1.12 and 5-fold for both Tpm1.8 and Tpm3.1. The presence of Tpm1.12 extends the time required per ATP hydrolysis cycle 3.7-fold, whereas it is shortened by 27 and 63% in the presence of Tpm1.8 and Tpm3.1, respectively. The resulting Tpm isoform–specific changes in the frequency, duration, and efficiency of actomyosin interactions establish a molecular basis for the ability of these complexes to support cellular processes with widely divergent demands in regard to force production, capacity to move processively, and speed of movement.
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Affiliation(s)
| | | | | | | | | | - Dietmar J Manstein
- From the Institute for Biophysical Chemistry and .,the Division for Structural Biochemistry, Hannover Medical School, 30625 Hannover, Germany
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123
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Temperature sensitive point mutations in fission yeast tropomyosin have long range effects on the stability and function of the actin-tropomyosin copolymer. Biochem Biophys Res Commun 2017; 506:339-346. [PMID: 29080743 PMCID: PMC6269162 DOI: 10.1016/j.bbrc.2017.10.109] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 10/20/2017] [Indexed: 11/25/2022]
Abstract
The actin cytoskeleton is modulated by regulatory actin-binding proteins which fine-tune the dynamic properties of the actin polymer to regulate function. One such actin-binding protein is tropomyosin (Tpm), a highly-conserved alpha-helical dimer which stabilises actin and regulates interactions with other proteins. Temperature sensitive mutants of Tpm are invaluable tools in the study of actin filament dependent processes, critical to the viability of a cell. Here we investigated the molecular basis of the temperature sensitivity of fission yeast Tpm mutants which fail to undergo cytokinesis at the restrictive temperatures. Comparison of Contractile Actomyosin Ring (CAR) constriction as well as cell shape and size revealed the cdc8.110 or cdc8.27 mutant alleles displayed significant differences in their temperature sensitivity and impact upon actin dependent functions during the cell cycle. In vitro analysis revealed the mutant proteins displayed a different reduction in thermostability, and unexpectedly yield two discrete unfolding domains when acetylated on their amino-termini. Our findings demonstrate how subtle changes in structure (point mutations or acetylation) alter the stability not simply of discrete regions of this conserved cytoskeletal protein but of the whole molecule. This differentially impacts the stability and cellular organisation of this essential cytoskeletal protein. Cloning, expression and characterisation of fission yeast temperature sensitive tropomyosin mutants. Detailed in vitro analysis on the impact of temperature upon these mutants. Comparison with in vivo impact of mutations upon actin ring function within the fission yeast. Demonstrates that subtle changes in structure alter the long range stability of Tropomyosin containing polymers.
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124
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Chen YY, Chan KM. Transcriptional inhibition of TCDD-mediated induction of cytochrome P450 1A1 and alteration of protein expression in a zebrafish hepatic cell line following the administration of TCDD and Cd 2. Toxicol Lett 2017; 282:121-135. [PMID: 29107029 DOI: 10.1016/j.toxlet.2017.10.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 10/24/2017] [Accepted: 10/25/2017] [Indexed: 12/27/2022]
Abstract
We studied the effects of Cd2+ on TCDD-mediated induction of the cytochrome P450 1A1 (cyp1a1) gene using a zebrafish liver cell line (ZFL). Our results showed that Cd2+ inhibited the TCDD-mediated induction of the cyp1a1 protein, enzyme activity, and mRNA expression level. Cd2+ also down-regulated levels of the aryl hydrocarbon receptor (ahr2) and the aryl hydrocarbon receptor nuclear translocator 2b (arnt2b) mRNAs. Compared with TCDD (3nM) treatment alone, co-treatment with Cd2+ (0-30μM) and TCDD (3nM) significantly inhibited the activity of the luciferase reporter gene constructs harboring the distal promoter region (P-2626/-2009) of CYP1A1 and the synthetic 3XRE gene promoter. This indicates that Cd2+ decreased the level of TCDD-induced cyp1a1 through transcriptional inhibition. Proteomic analysis was also used to evaluate the effect of Cd2+ on TCDD-altered protein expression in ZFL cells. The identified proteins are mainly enzymes of the glycolysis pathway and proteasomes, and have anti-oxidative and anti-stress effects.
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Affiliation(s)
- Ying Ying Chen
- School of Life Sciences, Faculty of Science, Chinese University, Sha Tin, Hong Kong
| | - King Ming Chan
- School of Life Sciences, Faculty of Science, Chinese University, Sha Tin, Hong Kong.
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125
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Kee AJ, Bryce NS, Yang L, Polishchuk E, Schevzov G, Weigert R, Polishchuk R, Gunning PW, Hardeman EC. ER/Golgi trafficking is facilitated by unbranched actin filaments containing Tpm4.2. Cytoskeleton (Hoboken) 2017; 74:379-389. [PMID: 28834398 DOI: 10.1002/cm.21405] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 07/31/2017] [Accepted: 08/16/2017] [Indexed: 01/14/2023]
Abstract
We have identified novel actin filaments defined by tropomyosin Tpm4.2 at the ER. EM analysis of mouse embryo fibroblasts (MEFs) isolated from mice expressing a mutant Tpm4.2 (Tpm4Plt53/Plt53 ), incapable of incorporating into actin filaments, revealed swollen ER structures compared with wild-type (WT) MEFs (Tpm4+/+ ). ER-to-Golgi, but not Golgi-to-ER trafficking was altered in the Tpm4Plt53/Plt53 MEFs following the transfection of the temperature sensitive ER-associated ts045-VSVg construct. Exogenous Tpm4.2 was able to rescue the ER-to-Golgi trafficking defect in the Tpm4Plt53/Plt53 cells. The treatment of WT MEFs with the myosin II inhibitor, blebbistatin, blocked the Tpm4.2-dependent ER-to-Golgi trafficking. The lack of an effect on ER-to-Golgi trafficking following treatment of MEFs with CK666 indicates that branched Arp2/3-containing actin filaments are not involved in anterograde vesicle trafficking. We propose that unbranched, Tpm4.2-containing filaments have an important role in maintaining ER/Golgi structure and that these structures, in conjunction with myosin II motors, mediate ER-to-Golgi trafficking.
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Affiliation(s)
- Anthony J Kee
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Nicole S Bryce
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Lingyan Yang
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Elena Polishchuk
- Telethon Institute of Genetics and Medicine, Naples 80131, Italy
| | - Galina Schevzov
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Roberto Weigert
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892
| | - Roman Polishchuk
- Telethon Institute of Genetics and Medicine, Naples 80131, Italy
| | - Peter W Gunning
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Edna C Hardeman
- School of Medical Sciences, UNSW Sydney, Sydney, NSW 2052, Australia
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126
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Bonnet A, Lambert G, Ernest S, Dutrieux FX, Coulpier F, Lemoine S, Lobbardi R, Rosa FM. Quaking RNA-Binding Proteins Control Early Myofibril Formation by Modulating Tropomyosin. Dev Cell 2017; 42:527-541.e4. [PMID: 28867488 DOI: 10.1016/j.devcel.2017.08.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 06/26/2017] [Accepted: 08/03/2017] [Indexed: 10/24/2022]
Abstract
Skeletal muscle contraction is mediated by myofibrils, complex multi-molecular scaffolds structured into repeated units, the sarcomeres. Myofibril structure and function have been extensively studied, but the molecular processes regulating its formation within the differentiating muscle cell remain largely unknown. Here we show in zebrafish that genetic interference with the Quaking RNA-binding proteins disrupts the initial steps of myofibril assembly without affecting early muscle differentiation. Using RNA sequencing, we demonstrate that Quaking is required for accumulation of the muscle-specific tropomyosin-3 transcript, tpm3.12. Further functional analyses reveal that Tpm3.12 mediates Quaking control of myofibril formation. Moreover, we identified a Quaking-binding site in the 3' UTR of tpm3.12 transcript, which is required in vivo for tpm3.12 accumulation and myofibril formation. Our work uncovers a Quaking/Tpm3 pathway controlling de novo myofibril assembly. This unexpected developmental role for Tpm3 could be at the origin of muscle defects observed in human congenital myopathies associated with tpm3 mutation.
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Affiliation(s)
- Aline Bonnet
- IBENS, Institut de Biologie de l'Ecole Normale Supérieure, 75005 Paris, France; INSERM U1024, 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France.
| | - Guillaume Lambert
- IBENS, Institut de Biologie de l'Ecole Normale Supérieure, 75005 Paris, France; INSERM U1024, 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France
| | - Sylvain Ernest
- IBENS, Institut de Biologie de l'Ecole Normale Supérieure, 75005 Paris, France; INSERM U1024, 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France
| | - François Xavier Dutrieux
- IBENS, Institut de Biologie de l'Ecole Normale Supérieure, 75005 Paris, France; INSERM U1024, 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France
| | - Fanny Coulpier
- INSERM U1024, 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France; IBENS, Institut de Biologie de l'Ecole Normale Supérieure, Plateforme Génomique, 75005 Paris, France
| | - Sophie Lemoine
- INSERM U1024, 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France; IBENS, Institut de Biologie de l'Ecole Normale Supérieure, Plateforme Génomique, 75005 Paris, France
| | - Riadh Lobbardi
- IBENS, Institut de Biologie de l'Ecole Normale Supérieure, 75005 Paris, France; INSERM U1024, 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France
| | - Frédéric Marc Rosa
- IBENS, Institut de Biologie de l'Ecole Normale Supérieure, 75005 Paris, France; INSERM U1024, 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France.
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127
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Lappalainen P. Actin-binding proteins: the long road to understanding the dynamic landscape of cellular actin networks. Mol Biol Cell 2017; 27:2519-22. [PMID: 27528696 PMCID: PMC4985253 DOI: 10.1091/mbc.e15-10-0728] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 06/14/2016] [Indexed: 11/17/2022] Open
Abstract
The actin cytoskeleton supports a vast number of cellular processes in nonmuscle cells. It is well established that the organization and dynamics of the actin cytoskeleton are controlled by a large array of actin-binding proteins. However, it was only 40 years ago that the first nonmuscle actin-binding protein, filamin, was identified and characterized. Filamin was shown to bind and cross-link actin filaments into higher-order structures and contribute to phagocytosis in macrophages. Subsequently many other nonmuscle actin-binding proteins were identified and characterized. These proteins regulate almost all steps of the actin filament assembly and disassembly cycles, as well as the arrangement of actin filaments into diverse three-dimensional structures. Although the individual biochemical activities of most actin-regulatory proteins are relatively well understood, knowledge of how these proteins function together in a common cytoplasm to control actin dynamics and architecture is only beginning to emerge. Furthermore, understanding how signaling pathways and mechanical cues control the activities of various actin-binding proteins in different cellular, developmental, and pathological processes will keep researchers busy for decades.
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Affiliation(s)
- Pekka Lappalainen
- Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
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128
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Sui Z, Gokhin DS, Nowak RB, Guo X, An X, Fowler VM. Stabilization of F-actin by tropomyosin isoforms regulates the morphology and mechanical behavior of red blood cells. Mol Biol Cell 2017; 28:2531-2542. [PMID: 28720661 PMCID: PMC5597325 DOI: 10.1091/mbc.e16-10-0699] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 07/14/2017] [Accepted: 07/14/2017] [Indexed: 01/17/2023] Open
Abstract
The absence of Tpm3.1 in red blood cells (RBCs) induces a compensatory increase in Tpm1.9 and abnormally stable F-actin in the membrane skeleton, with reduced association of Band 3 and glycophorin A, leading to a compensated hemolytic anemia with abnormal RBC shapes and mechanical properties. The short F-actins in the red blood cell (RBC) membrane skeleton are coated along their lengths by an equimolar combination of two tropomyosin isoforms, Tpm1.9 and Tpm3.1. We hypothesized that tropomyosin’s ability to stabilize F-actin regulates RBC morphology and mechanical properties. To test this, we examined mice with a targeted deletion in alternatively spliced exon 9d of Tpm3 (Tpm3/9d–/–), which leads to absence of Tpm3.1 in RBCs along with a compensatory increase in Tpm1.9 of sufficient magnitude to maintain normal total tropomyosin content. The isoform switch from Tpm1.9/Tpm3.1 to exclusively Tpm1.9 does not affect membrane skeleton composition but causes RBC F-actins to become hyperstable, based on decreased vulnerability to latrunculin-A–induced depolymerization. Unexpectedly, this isoform switch also leads to decreased association of Band 3 and glycophorin A with the membrane skeleton, suggesting that tropomyosin isoforms regulate the strength of F-actin-to-membrane linkages. Tpm3/9d–/– mice display a mild compensated anemia, in which RBCs have spherocytic morphology with increased osmotic fragility, reduced membrane deformability, and increased membrane stability. We conclude that RBC tropomyosin isoforms directly influence RBC physiology by regulating 1) the stability of the short F-actins in the membrane skeleton and 2) the strength of linkages between the membrane skeleton and transmembrane glycoproteins.
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Affiliation(s)
- Zhenhua Sui
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037
| | - David S Gokhin
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037
| | - Roberta B Nowak
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037
| | - Xinhua Guo
- Laboratory of Membrane Biology, New York Blood Center, New York, NY 10065
| | - Xiuli An
- Laboratory of Membrane Biology, New York Blood Center, New York, NY 10065.,School of Life Science, Zhengzhou University, Henan, Zhengzhou 450001, China
| | - Velia M Fowler
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037
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129
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Shin H, Kim D, Helfman DM. Tropomyosin isoform Tpm2.1 regulates collective and amoeboid cell migration and cell aggregation in breast epithelial cells. Oncotarget 2017; 8:95192-95205. [PMID: 29221121 PMCID: PMC5707015 DOI: 10.18632/oncotarget.19182] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 06/20/2017] [Indexed: 02/06/2023] Open
Abstract
Metastasis dissemination is the result of various processes including cell migration and cell aggregation. These processes involve alterations in the expression and organization of cytoskeletal and adhesion proteins in tumor cells. Alterations in actin filaments and their binding partners are known to be key players in metastasis. Downregulation of specific tropomyosin (Tpm) isoforms is a common characteristic of transformed cells. In this study, we examined the role of Tpm2.1 in non-transformed MCF10A breast epithelial cells in cell migration and cell aggregation, because this isoform is downregulated in primary and metastatic breast cancer as well as various breast cancer cell lines. Downregulation of Tpm2.1 using siRNA or shRNA resulted in retardation of collective cell migration but increase in single cell migration and invasion. Loss of Tpm2.1 is associated with enhanced actomyosin contractility and increased expression of E-cadherin and β-catenin. Furthermore, inhibition of Rho-associated kinase (ROCK) recovered collective cell migration in Tpm2.1-silenced cells. We also found that Tpm2.1-silenced cells formed more compacted spheroids and exhibited faster cell motility when spheroids were re-plated on 2D surfaces coated with fibronectin and collagen. When Tpm2.1 was downregulated, we observed a decrease in the level of AXL receptor tyrosine kinase, which may explain the increased levels of E-cadherin and β-catenin. These studies demonstrate that Tpm2.1 functions as an important regulator of cell migration and cell aggregation in breast epithelial cells. These findings suggest that downregulation of Tpm2.1 may play a critical role during tumor progression by facilitating the metastatic potential of tumor cells.
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Affiliation(s)
- HyeRim Shin
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
| | - Dayoung Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
| | - David M Helfman
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
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130
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Neri L, Lasa M, Elosegui-Artola A, D'Avola D, Carte B, Gazquez C, Alve S, Roca-Cusachs P, Iñarrairaegui M, Herrero J, Prieto J, Sangro B, Aldabe R. NatB-mediated protein N-α-terminal acetylation is a potential therapeutic target in hepatocellular carcinoma. Oncotarget 2017; 8:40967-40981. [PMID: 28498797 PMCID: PMC5522283 DOI: 10.18632/oncotarget.17332] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 04/04/2017] [Indexed: 01/02/2023] Open
Abstract
The identification of new targets for systemic therapy of hepatocellular carcinoma (HCC) is an urgent medical need. Recently, we showed that hNatB catalyzes the N-α-terminal acetylation of 15% of the human proteome and that this action is necessary for proper actin cytoskeleton structure and function. In tumors, cytoskeletal changes influence motility, invasion, survival, cell growth and tumor progression, making the cytoskeleton a very attractive antitumor target. Here, we show that hNatB subunits are upregulated in in over 59% HCC tumors compared to non-tumor tissue and that this upregulation is associated with microscopic vascular invasion. We found that hNatB silencing blocks proliferation and tumor formation in HCC cell lines in association with hampered DNA synthesis and impaired progression through the S and the G2/M phases. Growth inhibition is mediated by the degradation of two hNatB substrates, tropomyosin and CDK2, which occurs when these proteins lack N-α-terminal acetylation. In addition, hNatB inhibition disrupts the actin cytoskeleton, focal adhesions and tight/adherens junctions, abrogating two proliferative signaling pathways, Hippo/YAP and ERK1/2. Therefore, inhibition of NatB activity represents an interesting new approach to treating HCC by blocking cell proliferation and disrupting actin cytoskeleton function.
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Affiliation(s)
- Leire Neri
- Gene Therapy and Regulation of Gene Expression Program, Centro de Investigación Médica Aplicada, Universidad de Navarra, Pamplona, Spain
| | - Marta Lasa
- Gene Therapy and Regulation of Gene Expression Program, Centro de Investigación Médica Aplicada, Universidad de Navarra, Pamplona, Spain
| | | | - Delia D'Avola
- Liver Unit, Clínica Universidad de Navarra, Centro de Investigación Biomédica en Red en el Área Temática de Enfermedades Hepáticas y Digestivas (Ciberehd), Pamplona, Spain
- Instituto de Investigación Sanitaria de Navarra (IdiSNA), Pamplona, Spain
| | - Beatriz Carte
- Gene Therapy and Regulation of Gene Expression Program, Centro de Investigación Médica Aplicada, Universidad de Navarra, Pamplona, Spain
| | - Cristina Gazquez
- Gene Therapy and Regulation of Gene Expression Program, Centro de Investigación Médica Aplicada, Universidad de Navarra, Pamplona, Spain
| | - Sara Alve
- Department of Biology, CBMA-Centre of Molecular and Environmental Biology, University of Minho, Campus de Gualtar, Braga, Portugal
| | - Pere Roca-Cusachs
- Institute for Bioengineering of Catalonia, Barcelona, Spain
- University of Barcelona, Barcelona, Spain
| | - Mercedes Iñarrairaegui
- Liver Unit, Clínica Universidad de Navarra, Centro de Investigación Biomédica en Red en el Área Temática de Enfermedades Hepáticas y Digestivas (Ciberehd), Pamplona, Spain
- Instituto de Investigación Sanitaria de Navarra (IdiSNA), Pamplona, Spain
| | - Jose Herrero
- Liver Unit, Clínica Universidad de Navarra, Centro de Investigación Biomédica en Red en el Área Temática de Enfermedades Hepáticas y Digestivas (Ciberehd), Pamplona, Spain
- Instituto de Investigación Sanitaria de Navarra (IdiSNA), Pamplona, Spain
| | - Jesús Prieto
- Gene Therapy and Regulation of Gene Expression Program, Centro de Investigación Médica Aplicada, Universidad de Navarra, Pamplona, Spain
- Liver Unit, Clínica Universidad de Navarra, Centro de Investigación Biomédica en Red en el Área Temática de Enfermedades Hepáticas y Digestivas (Ciberehd), Pamplona, Spain
| | - Bruno Sangro
- Liver Unit, Clínica Universidad de Navarra, Centro de Investigación Biomédica en Red en el Área Temática de Enfermedades Hepáticas y Digestivas (Ciberehd), Pamplona, Spain
- Instituto de Investigación Sanitaria de Navarra (IdiSNA), Pamplona, Spain
| | - Rafael Aldabe
- Gene Therapy and Regulation of Gene Expression Program, Centro de Investigación Médica Aplicada, Universidad de Navarra, Pamplona, Spain
- Instituto de Investigación Sanitaria de Navarra (IdiSNA), Pamplona, Spain
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131
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Khaitlina S, Tsaplina O, Hinssen H. Cooperative effects of tropomyosin on the dynamics of the actin filament. FEBS Lett 2017; 591:1884-1891. [PMID: 28555876 DOI: 10.1002/1873-3468.12700] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 05/19/2017] [Accepted: 05/22/2017] [Indexed: 12/26/2022]
Abstract
Tropomyosin (Tpm) plays an important role in regulating the organisation and functions of the actin cytoskeleton. Here, we describe a new approach to analyse the effects of Tpm on actin dynamics. Using F-actin proteolytically modified within the DNase-binding loop (ECP-actin), we show that Tpm binding almost completely suppresses the increased subunit exchange intrinsic for this F-actin. The effect is both concentration-dependent and cooperative, with half-maximal inhibition observed at about a 1 : 50 Tpm : actin ratio. Tpm decreases not only the number concentration of ECP-actin filaments, but also the rate of the filament subunit exchange. Our data suggest that Tpm regulates the dynamics of actin filaments by an allosteric strengthening of intermonomer contacts in the actin filament, and that this mechanism may be involved in the modulation of cytoskeletal dynamics.
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Affiliation(s)
| | | | - Horst Hinssen
- Faculty of Biology, University of Bielefeld, Bielefeld, Germany
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132
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Jégou A, Romet-Lemonne G. Single Filaments to Reveal the Multiple Flavors of Actin. Biophys J 2017; 110:2138-46. [PMID: 27224479 DOI: 10.1016/j.bpj.2016.04.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 03/26/2016] [Accepted: 04/01/2016] [Indexed: 11/29/2022] Open
Abstract
A number of key cell processes rely on specific assemblies of actin filaments, which are all constructed from nearly identical building blocks: the abundant and extremely conserved actin protein. A central question in the field is to understand how different filament networks can coexist and be regulated. Discoveries in science are often related to technical advances. Here, we focus on the ongoing single filament revolution and discuss how these techniques have greatly contributed to our understanding of actin assembly. In particular, we highlight how they have refined our understanding of the many protein-based regulatory mechanisms that modulate actin assembly. It is now becoming apparent that other factors give filaments a specific identity that determines which proteins will bind to them. We argue that single filament techniques will play an essential role in the coming years as we try to understand the many ways actin filaments can take different flavors and unveil how these flavors modulate the action of regulatory proteins. We discuss different factors known to make actin filaments distinguishable by regulatory proteins and speculate on their possible consequences.
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Affiliation(s)
- Antoine Jégou
- Institut Jacques Monod, CNRS, Université Paris Diderot, Université Sorbonne Paris Cité, Paris, France
| | - Guillaume Romet-Lemonne
- Institut Jacques Monod, CNRS, Université Paris Diderot, Université Sorbonne Paris Cité, Paris, France.
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133
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Maninova M, Caslavsky J, Vomastek T. The assembly and function of perinuclear actin cap in migrating cells. PROTOPLASMA 2017; 254:1207-1218. [PMID: 28101692 DOI: 10.1007/s00709-017-1077-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 01/09/2017] [Indexed: 05/24/2023]
Abstract
Stress fibers are actin bundles encompassing actin filaments, actin-crosslinking, and actin-associated proteins that represent the major contractile system in the cell. Different types of stress fibers assemble in adherent cells, and they are central to diverse cellular processes including establishment of the cell shape, morphogenesis, cell polarization, and migration. Stress fibers display specific cellular organization and localization, with ventral fibers present at the basal side, and dorsal fibers and transverse actin arcs rising at the cell front from the ventral to the dorsal side and toward the nucleus. Perinuclear actin cap fibers are a specific subtype of stress fibers that rise from the leading edge above the nucleus and terminate at the cell rear forming a dome-like structure. Perinuclear actin cap fibers are fixed at three points: both ends are anchored in focal adhesions, while the central part is physically attached to the nucleus and nuclear lamina through the linker of nucleoskeleton and cytoskeleton (LINC) complex. Here, we discuss recent work that provides new insights into the mechanism of assembly and the function of these actin stress fibers that directly link extracellular matrix and focal adhesions with the nuclear envelope.
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Affiliation(s)
- Miloslava Maninova
- Institute of Microbiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 00, Prague, Czech Republic
| | - Josef Caslavsky
- Institute of Microbiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 00, Prague, Czech Republic
| | - Tomas Vomastek
- Institute of Microbiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 00, Prague, Czech Republic.
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134
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Desouza-Armstrong M, Gunning PW, Stehn JR. Tumor suppressor tropomyosin Tpm2.1 regulates sensitivity to apoptosis beyond anoikis characterized by changes in the levels of intrinsic apoptosis proteins. Cytoskeleton (Hoboken) 2017; 74:233-248. [PMID: 28378936 DOI: 10.1002/cm.21367] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 03/03/2017] [Accepted: 03/28/2017] [Indexed: 01/15/2023]
Abstract
The actin cytoskeleton is a polymer system that acts both as a sensor and mediator of apoptosis. Tropomyosins (Tpm) are a family of actin binding proteins that form co-polymers with actin and diversify actin filament function. Previous studies have shown that elevated expression of the tropomyosin isoform Tpm2.1 sensitized cells to apoptosis induced by cell detachment (anoikis) via an unknown mechanism. It is not yet known whether Tpm2.1 or other tropomyosin isoforms regulate sensitivity to apoptosis beyond anoikis. In this study, rat neuroepithelial cells overexpressing specific tropomyosin isoforms (Tpm1.7, Tpm2.1, Tpm3.1, and Tpm4.2) were screened for sensitivity to different classes of apoptotic stimuli, including both cytoskeletal and non-cytoskeletal targeting compounds. Results showed that elevated expression of tropomyosins in general inhibited apoptosis sensitivity to different stimuli. However, Tpm2.1 overexpression consistently enhanced sensitivity to anoikis as well as apoptosis induced by the actin targeting drug jasplakinolide (JASP). In contrast the cancer-associated isoform Tpm3.1 inhibited the induction of apoptosis by a range of agents. Treatment of Tpm2.1 overexpressing cells with JASP was accompanied by enhanced sensitivity to mitochondrial depolarization, a hallmark of intrinsic apoptosis. Moreover, Tpm2.1 overexpressing cells showed elevated levels of the apoptosis proteins Bak (proapoptotic), Mcl-1 (prosurvival), Bcl-2 (prosurvival) and phosphorylated p53 (Ser392). Finally, JASP treatment of Tpm2.1 cells caused significantly reduced Mcl-1, Bcl-2 and p53 (Ser392) levels relative to control cells. We therefore propose that Tpm2.1 regulates sensitivity to apoptosis beyond the scope of anoikis by modulating the expression of key intrinsic apoptosis proteins which primes the cell for death.
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Affiliation(s)
- Melissa Desouza-Armstrong
- Department of Anatomy, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, Australia
| | - Peter W Gunning
- Department of Anatomy, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, Australia
| | - Justine R Stehn
- Department of Anatomy, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, Australia.,Novogen Ltd. Hornsby, Sydney, New South Wales, 2077, Australia
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135
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Gray KT, Kostyukova AS, Fath T. Actin regulation by tropomodulin and tropomyosin in neuronal morphogenesis and function. Mol Cell Neurosci 2017; 84:48-57. [PMID: 28433463 DOI: 10.1016/j.mcn.2017.04.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 04/06/2017] [Accepted: 04/11/2017] [Indexed: 12/26/2022] Open
Abstract
Actin is a profoundly influential protein; it impacts, among other processes, membrane morphology, cellular motility, and vesicle transport. Actin can polymerize into long filaments that push on membranes and provide support for intracellular transport. Actin filaments have polar ends: the fast-growing (barbed) end and the slow-growing (pointed) end. Depolymerization from the pointed end supplies monomers for further polymerization at the barbed end. Tropomodulins (Tmods) cap pointed ends by binding onto actin and tropomyosins (Tpms). Tmods and Tpms have been shown to regulate many cellular processes; however, very few studies have investigated their joint role in the nervous system. Recent data directly indicate that they can modulate neuronal morphology. Additional studies suggest that Tmod and Tpm impact molecular processes influential in synaptic signaling. To facilitate future research regarding their joint role in actin regulation in the nervous system, we will comprehensively discuss Tpm and Tmod and their known functions within molecular systems that influence neuronal development.
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Affiliation(s)
- Kevin T Gray
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington, United States; School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Alla S Kostyukova
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington, United States.
| | - Thomas Fath
- School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia.
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136
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Zhao JY, Zhao XT, Sun JT, Zou LF, Yang SX, Han X, Zhu WC, Yin Q, Hong XY. Transcriptome and proteome analyses reveal complex mechanisms of reproductive diapause in the two-spotted spider mite, Tetranychus urticae. INSECT MOLECULAR BIOLOGY 2017; 26:215-232. [PMID: 28001328 DOI: 10.1111/imb.12286] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Although a variety of factors underlying diapause have been identified in arthropods and other organisms, the molecular mechanisms regulating diapause are still largely unknown. Here, to better understand this process, we examined diapause-associated genes in the two-spotted spider mite, Tetranychus urticae, by comparing the transcriptomes and proteomes of early diapausing and reproductive adult females. Amongst genes underlying diapause revealed by the transcriptomic and proteomic data sets, we described the noticeable change in Ca2+ -associated genes, including 65 Ca2+ -binding protein genes and 23 Ca2+ transporter genes, indicating that Ca2+ signalling has a substantial role in diapause regulation. Other interesting changes in diapause included up-regulation of (1) glutamate receptors that may be involved in synaptic plasticity changes, (2) genes involved in cytoskeletal reorganization including genes encoding each of the components of thick and thin filaments, tubulin and members of integrin signalling and (3) genes involved in anaerobic energy metabolism, which reflects a shift to anaerobic energy metabolism in early diapausing mites.
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Affiliation(s)
- J-Y Zhao
- Department of Entomology, Nanjing Agricultural University, Nanjing, China
| | - X-T Zhao
- Department of Entomology, Nanjing Agricultural University, Nanjing, China
| | - J-T Sun
- Department of Entomology, Nanjing Agricultural University, Nanjing, China
| | - L-F Zou
- Beijing Genomics Institute-Shenzhen, Shenzhen, China
| | - S-X Yang
- Department of Entomology, Nanjing Agricultural University, Nanjing, China
| | - X Han
- Department of Entomology, Nanjing Agricultural University, Nanjing, China
| | - W-C Zhu
- Department of Entomology, Nanjing Agricultural University, Nanjing, China
| | - Q Yin
- Beijing Genomics Institute-Shenzhen, Shenzhen, China
| | - X-Y Hong
- Department of Entomology, Nanjing Agricultural University, Nanjing, China
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137
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Ulke-Lemée A, Sun DH, Ishida H, Vogel HJ, MacDonald JA. Binding of smoothelin-like 1 to tropomyosin and calmodulin is mutually exclusive and regulated by phosphorylation. BMC BIOCHEMISTRY 2017; 18:5. [PMID: 28320308 PMCID: PMC5359911 DOI: 10.1186/s12858-017-0080-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 03/15/2017] [Indexed: 12/11/2022]
Abstract
Background The smoothelin-like 1 protein (SMTNL1) can associate with tropomyosin (Tpm) and calmodulin (CaM), two proteins essential to the smooth muscle contractile process. SMTNL1 is phosphorylated at Ser301 by protein kinase A during calcium desensitization in smooth muscle, yet the effect of SMTNL1 phosphorylation on Tpm- and CaM-binding has yet to be investigated. Results Using pull down studies with Tpm-Sepharose and CaM-Sepharose, we examined the interplay between Tpm binding, CaM binding, phosphorylation of SMTNL1 and calcium concentration. Phosphorylation greatly enhanced the ability of SMTNL1 to associate with Tpm in vitro; surface plasmon resonance yielded a 10-fold enhancement in KD value with phosphorylation. The effect on CaM binding is more complex and varies with the availability of calcium. Conclusions Combining both CaM and Tpm with SMTNL1 shows that the binding to both is mutually exclusive. Electronic supplementary material The online version of this article (doi:10.1186/s12858-017-0080-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Annegret Ulke-Lemée
- Department of Biochemistry & Molecular Biology, University of Calgary, Cumming School of Medicine, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada
| | - David Hao Sun
- Department of Biochemistry & Molecular Biology, University of Calgary, Cumming School of Medicine, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada
| | - Hiroaki Ishida
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1 N4, Canada
| | - Hans J Vogel
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1 N4, Canada
| | - Justin A MacDonald
- Department of Biochemistry & Molecular Biology, University of Calgary, Cumming School of Medicine, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada.
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138
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Christensen JR, Hocky GM, Homa KE, Morganthaler AN, Hitchcock-DeGregori SE, Voth GA, Kovar DR. Competition between Tropomyosin, Fimbrin, and ADF/Cofilin drives their sorting to distinct actin filament networks. eLife 2017; 6. [PMID: 28282023 PMCID: PMC5404920 DOI: 10.7554/elife.23152] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 03/09/2017] [Indexed: 12/15/2022] Open
Abstract
The fission yeast actin cytoskeleton is an ideal, simplified system to investigate fundamental mechanisms behind cellular self-organization. By focusing on the stabilizing protein tropomyosin Cdc8, bundling protein fimbrin Fim1, and severing protein coffin Adf1, we examined how their pairwise and collective interactions with actin filaments regulate their activity and segregation to functionally diverse F-actin networks. Utilizing multi-color TIRF microscopy of in vitro reconstituted F-actin networks, we observed and characterized two distinct Cdc8 cables loading and spreading cooperatively on individual actin filaments. Furthermore, Cdc8, Fim1, and Adf1 all compete for association with F-actin by different mechanisms, and their cooperative association with actin filaments affects their ability to compete. Finally, competition between Fim1 and Adf1 for F-actin synergizes their activities, promoting rapid displacement of Cdc8 from a dense F-actin network. Our findings reveal that competitive and cooperative interactions between actin binding proteins help define their associations with different F-actin networks. DOI:http://dx.doi.org/10.7554/eLife.23152.001 Cells use a protein called actin to provide shape, to generate the forces needed for cells to divide, and for many other essential processes. Inside a cell, individual actin proteins join up to form long filaments. These actin filaments are organized in different ways to make networks that have distinct properties, each tailored for a specific process. For instance, bundles of straight actin filaments help a cell to divide, whereas a network of branched actin filaments allows cells to move. The different proteins that bind to actin filaments influence how quickly actin filaments are assembled and organized into networks. Therefore, many of the properties of an actin filament network are due to the actin binding proteins that are associated with it. Two actin binding proteins called fimbrin and cofilin associate with a type of actin filament network known as the actin patch. A third actin binding protein called tropomyosin associates with a different network that forms a ring. It is not known how particular actin binding proteins choose to associate with one actin network instead of another. Christensen et al. used a fluorescence microscopy technique to study how fimbrin, cofilin and tropomyosin associate with different actin networks in a single-celled organism called fission yeast. This technique involved incubating actin and actin binding proteins together in a microscope chamber. The experiments show that some actin binding proteins, like tropomyosin, cooperate to bind to actin. Individual tropomyosin molecules find it difficult to bind actin filaments on their own, but once one tropomyosin molecule is attached to the filament, others rapidly join to coat the filament. On the other hand, some actin-binding proteins compete for binding to filaments. For example, the binding of fimbrin to actin filaments causes tropomyosin to be removed from the actin network. Further experiments revealed that fimbrin and cofilin work with each other to rapidly generate a dense actin network and displace tropomyosin. Together, the findings of Christensen et al. suggest that competitions between actin binding proteins determine which actin binding proteins are associated with an actin network. The next challenge is to understand how the most competitive actin-binding proteins are kept off actin networks where they do not belong. Further studies will shed light on how these interactions cause large changes in how the cell is organized. DOI:http://dx.doi.org/10.7554/eLife.23152.002
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Affiliation(s)
- Jenna R Christensen
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, United States
| | - Glen M Hocky
- Department of Chemistry, The University of Chicago, Chicago, United States.,James Franck Institute, The University of Chicago, Chicago, United States
| | - Kaitlin E Homa
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, United States
| | - Alisha N Morganthaler
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, United States
| | - Sarah E Hitchcock-DeGregori
- Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, United States
| | - Gregory A Voth
- Department of Chemistry, The University of Chicago, Chicago, United States.,James Franck Institute, The University of Chicago, Chicago, United States.,Computation Institute, The University of Chicago, Chicago, United States.,Institute for Biophysical Dynamics, The University of Chicago, Chicago, United States
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, United States.,Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, United States
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139
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Eastwood TA, Baker K, Brooker HR, Frank S, Mulvihill DP. An enhanced recombinant amino-terminal acetylation system and novel in vivo high-throughput screen for molecules affecting α-synuclein oligomerisation. FEBS Lett 2017; 591:833-841. [PMID: 28214355 PMCID: PMC5396276 DOI: 10.1002/1873-3468.12597] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 02/13/2017] [Accepted: 02/14/2017] [Indexed: 01/19/2023]
Abstract
Amino‐terminal acetylation is a ubiquitous protein modification affecting the majority of eukaryote proteins to regulate stability and function. We describe an optimised recombinant expression system for rapid production of amino terminal‐acetylated proteins within bacteria. We go on to describe the system's use in a fluorescence based in vivo assay for use in the high‐throughput screen to identify drugs that impact amino‐terminal acetylation‐dependent oligomerisation. These new tools and protocols will allow researchers to enhance routine recombinant protein production and identify new molecules for use in research and clinical applications.
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Affiliation(s)
| | - Karen Baker
- School of Biosciences, University of Kent, Canterbury, UK
| | | | - Stefanie Frank
- School of Biosciences, University of Kent, Canterbury, UK
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140
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Gateva G, Kremneva E, Reindl T, Kotila T, Kogan K, Gressin L, Gunning PW, Manstein DJ, Michelot A, Lappalainen P. Tropomyosin Isoforms Specify Functionally Distinct Actin Filament Populations In Vitro. Curr Biol 2017; 27:705-713. [PMID: 28216317 PMCID: PMC5344678 DOI: 10.1016/j.cub.2017.01.018] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Revised: 12/14/2016] [Accepted: 01/10/2017] [Indexed: 12/28/2022]
Abstract
Actin filaments assemble into a variety of networks to provide force for diverse cellular processes [1]. Tropomyosins are coiled-coil dimers that form head-to-tail polymers along actin filaments and regulate interactions of other proteins, including actin-depolymerizing factor (ADF)/cofilins and myosins, with actin [2, 3, 4, 5]. In mammals, >40 tropomyosin isoforms can be generated through alternative splicing from four tropomyosin genes. Different isoforms display non-redundant functions and partially non-overlapping localization patterns, for example within the stress fiber network [6, 7]. Based on cell biological studies, it was thus proposed that tropomyosin isoforms may specify the functional properties of different actin filament populations [2]. To test this hypothesis, we analyzed the properties of actin filaments decorated by stress-fiber-associated tropomyosins (Tpm1.6, Tpm1.7, Tpm2.1, Tpm3.1, Tpm3.2, and Tpm4.2). These proteins bound F-actin with high affinity and competed with α-actinin for actin filament binding. Importantly, total internal reflection fluorescence (TIRF) microscopy of fluorescently tagged proteins revealed that most tropomyosin isoforms cannot co-polymerize with each other on actin filaments. These isoforms also bind actin with different dynamics, which correlate with their effects on actin-binding proteins. The long isoforms Tpm1.6 and Tpm1.7 displayed stable interactions with actin filaments and protected filaments from ADF/cofilin-mediated disassembly, but did not activate non-muscle myosin IIa (NMIIa). In contrast, the short isoforms Tpm3.1, Tpm3.2, and Tpm4.2 displayed rapid dynamics on actin filaments and stimulated the ATPase activity of NMIIa, but did not efficiently protect filaments from ADF/cofilin. Together, these data provide experimental evidence that tropomyosin isoforms segregate to different actin filaments and specify functional properties of distinct actin filament populations. Stress-fiber-associated tropomyosin isoforms segregate to different actin filaments Tropomyosin isoforms bind F-actin with different dynamics Dynamic tropomyosin isoforms activate non-muscle myosin II Stable tropomyosin isoforms protect actin filaments from ADF/cofilin
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Affiliation(s)
- Gergana Gateva
- Institute of Biotechnology, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
| | - Elena Kremneva
- Institute of Biotechnology, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
| | - Theresia Reindl
- Institute for Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany
| | - Tommi Kotila
- Institute of Biotechnology, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
| | - Konstantin Kogan
- Institute of Biotechnology, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
| | - Laurène Gressin
- Biosciences and Biotechnology Institute of Grenoble, LPCV/CNRS/CEA/UGA/INRA, 38054 Grenoble, France
| | - Peter W Gunning
- Oncology Research Unit, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Dietmar J Manstein
- Institute for Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany
| | - Alphée Michelot
- Aix-Marseille University, CNRS, IBDM, 13284 Marseille, France
| | - Pekka Lappalainen
- Institute of Biotechnology, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland.
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141
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Filopodia formation and endosome clustering induced by mutant plus-end-directed myosin VI. Proc Natl Acad Sci U S A 2017; 114:1595-1600. [PMID: 28143933 DOI: 10.1073/pnas.1616941114] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Myosin VI (MYO6) is the only myosin known to move toward the minus end of actin filaments. It has roles in numerous cellular processes, including maintenance of stereocilia structure, endocytosis, and autophagosome maturation. However, the functional necessity of minus-end-directed movement along actin is unclear as the underlying architecture of the local actin network is often unknown. To address this question, we engineered a mutant of MYO6, MYO6+, which undergoes plus-end-directed movement while retaining physiological cargo interactions in the tail. Expression of this mutant motor in HeLa cells led to a dramatic reorganization of cortical actin filaments and the formation of actin-rich filopodia. MYO6 is present on peripheral adaptor protein, phosphotyrosine interacting with PH domain and leucine zipper 1 (APPL1) signaling endosomes and MYO6+ expression causes a dramatic relocalization and clustering of this endocytic compartment in the cell cortex. MYO6+ and its adaptor GAIP interacting protein, C terminus (GIPC) accumulate at the tips of these filopodia, while APPL1 endosomes accumulate at the base. A combination of MYO6+ mutagenesis and siRNA-mediated depletion of MYO6 binding partners demonstrates that motor activity and binding to endosomal membranes mediated by GIPC and PI(4,5)P2 are crucial for filopodia formation. A similar reorganization of actin is induced by a constitutive dimer of MYO6+, indicating that multimerization of MYO6 on endosomes through binding to GIPC is required for this cellular activity and regulation of actin network structure. This unique engineered MYO6+ offers insights into both filopodia formation and MYO6 motor function at endosomes and at the plasma membrane.
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142
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Pleines I, Woods J, Chappaz S, Kew V, Foad N, Ballester-Beltrán J, Aurbach K, Lincetto C, Lane RM, Schevzov G, Alexander WS, Hilton DJ, Astle WJ, Downes K, Nurden P, Westbury SK, Mumford AD, Obaji SG, Collins PW, Delerue F, Ittner LM, Bryce NS, Holliday M, Lucas CA, Hardeman EC, Ouwehand WH, Gunning PW, Turro E, Tijssen MR, Kile BT. Mutations in tropomyosin 4 underlie a rare form of human macrothrombocytopenia. J Clin Invest 2017; 127:814-829. [PMID: 28134622 PMCID: PMC5330761 DOI: 10.1172/jci86154] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 12/01/2016] [Indexed: 01/12/2023] Open
Abstract
Platelets are anuclear cells that are essential for blood clotting. They are produced by large polyploid precursor cells called megakaryocytes. Previous genome-wide association studies in nearly 70,000 individuals indicated that single nucleotide variants (SNVs) in the gene encoding the actin cytoskeletal regulator tropomyosin 4 (TPM4) exert an effect on the count and volume of platelets. Platelet number and volume are independent risk factors for heart attack and stroke. Here, we have identified 2 unrelated families in the BRIDGE Bleeding and Platelet Disorders (BPD) collection who carry a TPM4 variant that causes truncation of the TPM4 protein and segregates with macrothrombocytopenia, a disorder characterized by low platelet count. N-Ethyl-N-nitrosourea–induced (ENU-induced) missense mutations in Tpm4 or targeted inactivation of the Tpm4 locus led to gene dosage–dependent macrothrombocytopenia in mice. All other blood cell counts in Tpm4-deficient mice were normal. Insufficient TPM4 expression in human and mouse megakaryocytes resulted in a defect in the terminal stages of platelet production and had a mild effect on platelet function. Together, our findings demonstrate a nonredundant role for TPM4 in platelet biogenesis in humans and mice and reveal that truncating variants in TPM4 cause a previously undescribed dominant Mendelian platelet disorder.
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Affiliation(s)
- Irina Pleines
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Australia
| | - Joanne Woods
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
- NHS Blood and Transplant, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Stephane Chappaz
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Australia
| | - Verity Kew
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
- NHS Blood and Transplant, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Nicola Foad
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
- NHS Blood and Transplant, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - José Ballester-Beltrán
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
- NHS Blood and Transplant, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Katja Aurbach
- Institute of Experimental Biomedicine, University Hospital and Rudolf Virchow Center, University of Wuerzburg, Wuerzburg, Germany
| | - Chiara Lincetto
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
- NHS Blood and Transplant, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Rachael M. Lane
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
| | - Galina Schevzov
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Warren S. Alexander
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Australia
| | - Douglas J. Hilton
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Australia
| | - William J. Astle
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
- NHS Blood and Transplant, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Kate Downes
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
- NHS Blood and Transplant, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Paquita Nurden
- Institut Hospitalo-Universitaire LIRYC, Plateforme Technologique d’Innovation Biomédicale, Hôpital Xavier Arnozan, Pessac, France
| | - Sarah K. Westbury
- School of Clinical Sciences, University of Bristol, Bristol, United Kingdom
| | - Andrew D. Mumford
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, United Kingdom
| | - Samya G. Obaji
- Arthur Bloom Haemophilia Centre, School of Medicine, Cardiff University, Heath Park, Cardiff, United Kingdom
| | - Peter W. Collins
- Arthur Bloom Haemophilia Centre, School of Medicine, Cardiff University, Heath Park, Cardiff, United Kingdom
| | - NIHR BioResource
- NIHR BioResource–Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Fabien Delerue
- Transgenic Animal Unit, Mark Wainwright Analytical Centre, University of New South Wales, Sydney, Australia
| | - Lars M. Ittner
- Transgenic Animal Unit, Mark Wainwright Analytical Centre, University of New South Wales, Sydney, Australia
| | - Nicole S. Bryce
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Mira Holliday
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Christine A. Lucas
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Edna C. Hardeman
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Willem H. Ouwehand
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
- NHS Blood and Transplant, Cambridge Biomedical Campus, Cambridge, United Kingdom
- NIHR BioResource–Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge, United Kingdom
- Human Genetics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, United Kingdom
| | - Peter W. Gunning
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Ernest Turro
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
- NHS Blood and Transplant, Cambridge Biomedical Campus, Cambridge, United Kingdom
- Medical Research Council Biostatistics Unit, Cambridge Institute of Public Health, Cambridge, United Kingdom
| | - Marloes R. Tijssen
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
- NHS Blood and Transplant, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Benjamin T. Kile
- Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Australia
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143
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Abstract
Tropomyosin is the archetypal-coiled coil, yet studies of its structure and function have proven it to be a dynamic regulator of actin filament function in muscle and non-muscle cells. Here we review aspects of its structure that deviate from canonical leucine zipper coiled coils that allow tropomyosin to bind to actin, regulate myosin, and interact directly and indirectly with actin-binding proteins. Four genes encode tropomyosins in vertebrates, with additional diversity that results from alternate promoters and alternatively spliced exons. At the same time that periodic motifs for binding actin and regulating myosin are conserved, isoform-specific domains allow for specific interaction with myosins and actin filament regulatory proteins, including troponin. Tropomyosin can be viewed as a universal regulator of the actin cytoskeleton that specifies actin filaments for cellular and intracellular functions.
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144
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Tanja Mierke C. Physical role of nuclear and cytoskeletal confinements in cell migration mode selection and switching. AIMS BIOPHYSICS 2017. [DOI: 10.3934/biophy.2017.4.615] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
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145
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Abstract
Coiled coils appear in countless structural contexts, as appendages to small proteins, as parts of multi-domain proteins, and as building blocks of filaments. Although their structure is unpretentious and their basic properties are understood in great detail, the spectrum of functional properties they provide in different proteins has become increasingly complex. This chapter aims to depict this functional spectrum, to identify common themes and their molecular basis, with an emphasis on new insights gained into dynamic aspects.
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Affiliation(s)
- Marcus D Hartmann
- Max Planck Institute for Developmental Biology, Spemannstraße 35, 72076, Tübingen, Germany.
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146
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Goldman CH, Gonsalvez GB. The Role of Microtubule Motors in mRNA Localization and Patterning Within the Drosophila Oocyte. Results Probl Cell Differ 2017; 63:149-168. [PMID: 28779317 DOI: 10.1007/978-3-319-60855-6_7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Messenger RNA (mRNA) localization is a powerful and prevalent mechanism of post-transcriptional gene regulation, enabling the cell to produce protein at the exact location at which it is needed. The phenomenon of mRNA localization has been observed in many types of cells in organisms ranging from yeast to man. Thus, the process appears to be widespread and highly conserved. Several model systems have been used to understand the mechanism by which mRNAs are localized. One such model, and the focus of this chapter, is the egg chamber of the female Drosophila melanogaster. The polarity of the developing Drosophila oocyte and resulting embryo relies on the specific localization of three critical mRNAs: gurken, bicoid, and oskar. If these mRNAs are not localized during oogenesis, the resulting progeny will not survive. The study of these mRNAs has served as a model for understanding the general mechanisms by which mRNAs are sorted. In this chapter, we will discuss how the localization of these mRNAs enables polarity establishment. We will also discuss the role of motor proteins in the localization pathway. Finally, we will consider potential mechanisms by which mRNAs can be anchored at their site of localization. It is likely that the lessons learned using the Drosophila oocyte model system will be applicable to mRNAs that are localized in other organisms as well.
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Affiliation(s)
- Chandler H Goldman
- Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1459 Laney Walker Blvd., CB2917, Augusta, GA, 30912, USA
| | - Graydon B Gonsalvez
- Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1459 Laney Walker Blvd., CB2917, Augusta, GA, 30912, USA.
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147
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Appaduray MA, Masedunskas A, Bryce NS, Lucas CA, Warren SC, Timpson P, Stear JH, Gunning PW, Hardeman EC. Recruitment Kinetics of Tropomyosin Tpm3.1 to Actin Filament Bundles in the Cytoskeleton Is Independent of Actin Filament Kinetics. PLoS One 2016; 11:e0168203. [PMID: 27977753 PMCID: PMC5158027 DOI: 10.1371/journal.pone.0168203] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 11/28/2016] [Indexed: 12/23/2022] Open
Abstract
The actin cytoskeleton is a dynamic network of filaments that is involved in virtually every cellular process. Most actin filaments in metazoa exist as a co-polymer of actin and tropomyosin (Tpm) and the function of an actin filament is primarily defined by the specific Tpm isoform associated with it. However, there is little information on the interdependence of these co-polymers during filament assembly and disassembly. We addressed this by investigating the recovery kinetics of fluorescently tagged isoform Tpm3.1 into actin filament bundles using FRAP analysis in cell culture and in vivo in rats using intracellular intravital microscopy, in the presence or absence of the actin-targeting drug jasplakinolide. The mobile fraction of Tpm3.1 is between 50% and 70% depending on whether the tag is at the C- or N-terminus and whether the analysis is in vivo or in cultured cells. We find that the continuous dynamic exchange of Tpm3.1 is not significantly impacted by jasplakinolide, unlike tagged actin. We conclude that tagged Tpm3.1 may be able to undergo exchange in actin filament bundles largely independent of the assembly and turnover of actin.
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Affiliation(s)
- Mark A. Appaduray
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, New South Wales, Australia
| | - Andrius Masedunskas
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, New South Wales, Australia
| | - Nicole S. Bryce
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, New South Wales, Australia
| | - Christine A. Lucas
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, New South Wales, Australia
| | - Sean C. Warren
- The Kinghorn Cancer Center, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Paul Timpson
- The Kinghorn Cancer Center, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Jeffrey H. Stear
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, New South Wales, Australia
| | - Peter W. Gunning
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, New South Wales, Australia
| | - Edna C. Hardeman
- Cellular and Genetic Medicine Unit, School of Medical Sciences, UNSW Australia, Sydney, New South Wales, Australia
- * E-mail:
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148
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Nicovich PR, Janco M, Sobey T, Gajwani M, Obeidy P, Whan R, Gaus K, Gunning PW, Coster AC, Böcking T. Effect of surface chemistry on tropomyosin binding to actin filaments on surfaces. Cytoskeleton (Hoboken) 2016; 73:729-738. [PMID: 27783462 DOI: 10.1002/cm.21342] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 10/24/2016] [Accepted: 10/25/2016] [Indexed: 01/29/2023]
Abstract
Reconstitution of actin filaments on surfaces for observation of filament-associated protein dynamics by fluorescence microscopy is currently an exciting field in biophysics. Here we examine the effects of attaching actin filaments to surfaces on the binding and dissociation kinetics of a fluorescence-labeled tropomyosin, a rod-shaped protein that forms continuous strands wrapping around the actin filament. Two attachment modalities of the actin to the surface are explored: where the actin filament is attached to the surface at multiple points along its length; and where the actin filament is attached at one end and aligned parallel to the surface by buffer flow. To facilitate analysis of actin-binding protein dynamics, we have developed a software tool for the viewing, tracing and analysis of filaments and co-localized species in noisy fluorescence timelapse images. Our analysis shows that the interaction of tropomyosin with actin filaments is similar for both attachment modalities. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Philip R Nicovich
- ARC Centre of Excellence in Advanced Molecular Imaging and EMBL Australia Node in Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Miro Janco
- ARC Centre of Excellence in Advanced Molecular Imaging and EMBL Australia Node in Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Tom Sobey
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Mehul Gajwani
- ARC Centre of Excellence in Advanced Molecular Imaging and EMBL Australia Node in Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Peyman Obeidy
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Renee Whan
- Biomedical Imaging Facility, University of New South Wales, Sydney, Australia
| | - Katharina Gaus
- ARC Centre of Excellence in Advanced Molecular Imaging and EMBL Australia Node in Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Peter W Gunning
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Adelle Cf Coster
- School of Mathematics and Statistics, University of New South Wales, Sydney, Australia
| | - Till Böcking
- ARC Centre of Excellence in Advanced Molecular Imaging and EMBL Australia Node in Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney, Australia
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149
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Alioto SL, Garabedian MV, Bellavance DR, Goode BL. Tropomyosin and Profilin Cooperate to Promote Formin-Mediated Actin Nucleation and Drive Yeast Actin Cable Assembly. Curr Biol 2016; 26:3230-3237. [PMID: 27866892 DOI: 10.1016/j.cub.2016.09.053] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 09/01/2016] [Accepted: 09/26/2016] [Indexed: 01/06/2023]
Abstract
Tropomyosins comprise a large family of actin-binding proteins with critical roles in diverse actin-based processes [1], but our understanding of how they mechanistically contribute to actin filament dynamics has been limited. We addressed this question in S. cerevisiae, where tropomyosins (Tpm1 and Tpm2), profilin (Pfy1), and formins (Bni1 and Bnr1) are required for the assembly of an array of actin cables that facilitate polarized vesicle delivery and daughter cell growth. Formins drive cable formation by promoting actin nucleation and by accelerating actin filament elongation together with profilin [2]. In contrast, how tropomyosins contribute mechanistically to cable formation has been unclear, but genetic studies demonstrate that Tpm1 plays a more important role than Tpm2 [3, 4]. Here, we found that loss of TPM1 in strains lacking BNR1, but not BNI1, leads to severe defects in cable formation, polarized secretion, and cell growth, suggesting that TPM1 function is required for proper Bni1-mediated cable assembly. Furthermore, in vitro total internal reflection fluorescence (TIRF) microscopy demonstrated that Tpm1 strongly enhances Bni1-mediated, but not Bnr1-mediated, actin nucleation without affecting filament elongation rate, whereas Tpm2 has no effects on Bni1 or Bnr1. Tpm1 stimulation of Bni1-mediated nucleation also requires profilin and its interactions with both G-actin and formins. Together, these results demonstrate that yeast Tpm1 works in concert with profilin to promote formin-dependent nucleation of actin cables, thus expanding our understanding of how specific tropomyosin isoforms influence actin dynamics.
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Affiliation(s)
- Salvatore L Alioto
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA 02454, USA
| | - Mikael V Garabedian
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA 02454, USA
| | - Danielle R Bellavance
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA 02454, USA
| | - Bruce L Goode
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA 02454, USA.
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Veeranan-Karmegam R, Boggupalli DP, Liu G, Gonsalvez GB. A new isoform of Drosophila non-muscle Tropomyosin 1 interacts with Kinesin-1 and functions in oskar mRNA localization. J Cell Sci 2016; 129:4252-4264. [PMID: 27802167 DOI: 10.1242/jcs.194332] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 10/05/2016] [Indexed: 12/16/2022] Open
Abstract
Recent studies have revealed that diverse cell types use mRNA localization as a means to establish polarity. Despite the prevalence of this phenomenon, much less is known regarding the mechanism by which mRNAs are localized. The Drosophila melanogaster oocyte provides a useful model for examining the process of mRNA localization. oskar (osk) mRNA is localized at the posterior of the oocyte, thus restricting the expression of Oskar protein to this site. The localization of osk mRNA is microtubule dependent and requires the plus-end-directed motor Kinesin-1. Unlike most Kinesin-1 cargoes, localization of osk mRNA requires the Kinesin heavy chain (Khc) motor subunit, but not the Kinesin light chain (Klc) adaptor. In this report, we demonstrate that a newly discovered isoform of Tropomyosin 1, referred to as Tm1C, directly interacts with Khc and functions in concert with this microtubule motor to localize osk mRNA. Apart from osk mRNA localization, several additional Khc-dependent processes in the oocyte are unaffected upon loss of Tm1C. Our results therefore suggest that the Tm1C-Khc interaction is specific for the osk localization pathway.
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Affiliation(s)
- Rajalakshmi Veeranan-Karmegam
- Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1459 Laney Walker Blvd, Augusta, GA 30912, USA
| | - Devi Prasad Boggupalli
- Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1459 Laney Walker Blvd, Augusta, GA 30912, USA
| | - Guojun Liu
- Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1459 Laney Walker Blvd, Augusta, GA 30912, USA
| | - Graydon B Gonsalvez
- Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, 1459 Laney Walker Blvd, Augusta, GA 30912, USA
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