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Robaszkiewicz K, Wróbel J, Moraczewska J. Troponin and a Myopathy-Linked Mutation in TPM3 Inhibit Cofilin-2-Induced Thin Filament Depolymerization. Int J Mol Sci 2023; 24:16457. [PMID: 38003645 PMCID: PMC10671271 DOI: 10.3390/ijms242216457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 11/10/2023] [Accepted: 11/13/2023] [Indexed: 11/26/2023] Open
Abstract
Uniform actin filament length is required for synchronized contraction of skeletal muscle. In myopathies linked to mutations in tropomyosin (Tpm) genes, irregular thin filaments are a common feature, which may result from defects in length maintenance mechanisms. The current work investigated the effects of the myopathy-causing p.R91C variant in Tpm3.12, a tropomyosin isoform expressed in slow-twitch muscle fibers, on the regulation of actin severing and depolymerization by cofilin-2. The affinity of cofilin-2 for F-actin was not significantly changed by either Tpm3.12 or Tpm3.12-R91C, though it increased two-fold in the presence of troponin (without Ca2+). Saturation of the filament with cofilin-2 removed both Tpm variants from the filament, although Tpm3.12-R91C was more resistant. In the presence of troponin (±Ca2+), Tpm remained on the filament, even at high cofilin-2 concentrations. Both Tpm3.12 variants inhibited filament severing and depolymerization by cofilin-2. However, the inhibition was more efficient in the presence of Tpm3.12-R91C, indicating that the pathogenic variant impaired cofilin-2-dependent actin filament turnover. Troponin (±Ca2+) further inhibited but did not completely stop cofilin-2-dependent actin severing and depolymerization.
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Affiliation(s)
| | | | - Joanna Moraczewska
- Department of Biochemistry and Cell Biology, Faculty of Biological Sciences, Kazimierz Wielki University in Bydgoszcz, 85-671 Bydgoszcz, Poland; (K.R.); (J.W.)
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2
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Dahlstroem C, Paraschiakos T, Sun H, Windhorst S. Cryo-EM structures of actin binding proteins as tool for drug discovery. Biochem Pharmacol 2023:115680. [PMID: 37399949 DOI: 10.1016/j.bcp.2023.115680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 06/29/2023] [Accepted: 06/29/2023] [Indexed: 07/05/2023]
Abstract
Cellular actin dynamic is controlled by a plethora of actin binding proteins (ABPs), including actin nucleating, bundling, cross-linking, capping, and severing proteins. In this review, regulation of actin dynamics by ABPs will be introduced, and the role of the F-actin severing protein cofilin-1 and the F-actin bundling protein L-plastin in actin dynamics discussed in more detail. Since up-regulation of these proteins in different kinds of cancers is associated with malignant progression of cancer cells, we suggest the cryogenic electron microscopy (Cryo-EM) structure of F- actin with the respective ABP as template for in silico drug design to specifically disrupt the interaction of these ABPs with F-actin.
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Affiliation(s)
- Christian Dahlstroem
- Department of Biochemistry and Signal Transduction, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, D-20246 Hamburg
| | - Themistoklis Paraschiakos
- Department of Biochemistry and Signal Transduction, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, D-20246 Hamburg
| | - Han Sun
- Structural Chemistry and Computational Biophysics Group, Leipniz-Forschungsinstitut für Moekulare Pharmakologie, Robert-Rössle-Strasse 10, D-13125, Berlin; Institute of Chemistry, Technical University of Berlin, D-10623, Berlin
| | - Sabine Windhorst
- Department of Biochemistry and Signal Transduction, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, D-20246 Hamburg.
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3
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Baroni L, Pereira LM, Maciver SK, Yatsuda AP. Functional characterisation of the actin-depolymerising factor from the apicomplexan Neospora caninum (NcADF). Mol Biochem Parasitol 2018; 224:26-36. [PMID: 30040977 DOI: 10.1016/j.molbiopara.2018.07.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 07/15/2018] [Accepted: 07/15/2018] [Indexed: 01/20/2023]
Abstract
Neospora caninum is an apicomplexan parasite that causes infectious abortion in cows. As an obligate intracellular parasite, N. caninum requires a host cell environment to survive and replicate. The locomotion and invasion mechanisms of apicomplexan parasites are centred on the actin-myosin system to propel the parasite forwards and into the host cell. The functions of actin, an intrinsically dynamic protein, are modulated by actin-binding proteins (ABPs). Actin-depolymerising factor (ADF) is a ubiquitous ABP responsible for accelerating actin turnover in eukaryotic cells and is one of the few known conserved ABPs from apicomplexan parasites. Apicomplexan ADFs have nonconventional properties compared with ADF/cofilins from higher eukaryotes. In the present paper, we characterised the ADF from N. caninum (NcADF) using computational and in vitro biochemical approaches to investigate its function in rabbit muscle actin dynamics. Our predicted computational tertiary structure of NcADF demonstrated a conserved structure and phylogeny with respect to other ADF/cofilins, although certain differences in filamentous actin (F-actin) binding sites were present. The activity of recombinant NcADF on heterologous actin was regulated in part by pH and the presence of inorganic phosphate. In addition, our data suggest a comparatively weak disassembly of F-actin by NcADF. Taken together, the data presented herein represent a contribution to the field towards the understanding of the role of ADF in N. caninum and a comparative analysis of ABPs in the phylum Apicomplexa.
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Affiliation(s)
- Luciana Baroni
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café, s/n, 14040-930, Ribeirão Preto, SP, Brazil
| | - Luiz M Pereira
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café, s/n, 14040-930, Ribeirão Preto, SP, Brazil
| | - Sutherland K Maciver
- Centre for Discovery Brain Sciences, Biomedical Sciences, Edinburgh Medical School, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, Scotland, United Kingdom
| | - Ana P Yatsuda
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café, s/n, 14040-930, Ribeirão Preto, SP, Brazil.
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4
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Tanaka K, Takeda S, Mitsuoka K, Oda T, Kimura-Sakiyama C, Maéda Y, Narita A. Structural basis for cofilin binding and actin filament disassembly. Nat Commun 2018; 9:1860. [PMID: 29749375 PMCID: PMC5945598 DOI: 10.1038/s41467-018-04290-w] [Citation(s) in RCA: 108] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2017] [Accepted: 04/18/2018] [Indexed: 11/26/2022] Open
Abstract
Actin depolymerizing factor (ADF) and cofilin accelerate actin dynamics by severing and disassembling actin filaments. Here, we present the 3.8 Å resolution cryo-EM structure of cofilactin (cofilin-decorated actin filament). The actin subunit structure of cofilactin (C-form) is distinct from those of F-actin (F-form) and monomeric actin (G-form). During the transition between these three conformations, the inner domain of actin (subdomains 3 and 4) and the majority of subdomain 1 move as two separate rigid bodies. The cofilin–actin interface consists of three distinct parts. Based on the rigid body movements of actin and the three cofilin–actin interfaces, we propose models for the cooperative binding of cofilin to actin, preferential binding of cofilin to ADP-bound actin filaments and cofilin-mediated severing of actin filaments. Cofilin is a small actin-binding protein that accelerates actin turnover by disassembling actin filaments. Here the authors present the 3.8 Å cryo-EM structure of a cofilin-decorated actin filament and discuss mechanistic implications.
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Affiliation(s)
- Kotaro Tanaka
- Structural Biology Research Center, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
| | - Shuichi Takeda
- Structural Biology Research Center, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
| | - Kaoru Mitsuoka
- Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, 7-1 Mihogaoka, Ibaraki, Osaka, 567-0047, Japan
| | - Toshiro Oda
- Faculty of Health and Welfare, Tokai Gakuin University, Nakakirino-cyo 5-68, Kakamigahara, Gifu, 504-8511, Japan
| | - Chieko Kimura-Sakiyama
- Structural Biology Research Center, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan.,Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, 1-3 Miyakodani, Tatara, Kyotanabe, Kyoto, 610-0394, Japan
| | - Yuichiro Maéda
- Structural Biology Research Center, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan.,Toyota Physical and Chemical Research Institute, 41-1, Yokomichi, Nagakute, Aichi, 480-1192, Japan
| | - Akihiro Narita
- Structural Biology Research Center, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan.
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5
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Raz-Ben Aroush D, Ofer N, Abu-Shah E, Allard J, Krichevsky O, Mogilner A, Keren K. Actin Turnover in Lamellipodial Fragments. Curr Biol 2017; 27:2963-2973.e14. [PMID: 28966086 DOI: 10.1016/j.cub.2017.08.066] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 07/21/2017] [Accepted: 08/29/2017] [Indexed: 10/18/2022]
Abstract
Actin turnover is the central driving force underlying lamellipodial motility. The molecular components involved are largely known, and their properties have been studied extensively in vitro. However, a comprehensive picture of actin turnover in vivo is still missing. We focus on fragments from fish epithelial keratocytes, which are essentially stand-alone motile lamellipodia. The geometric simplicity of the fragments and the absence of additional actin structures allow us to characterize the spatiotemporal lamellipodial actin organization with unprecedented detail. We use fluorescence recovery after photobleaching, fluorescence correlation spectroscopy, and extraction experiments to show that about two-thirds of the lamellipodial actin diffuses in the cytoplasm with nearly uniform density, whereas the rest forms the treadmilling polymer network. Roughly a quarter of the diffusible actin pool is in filamentous form as diffusing oligomers, indicating that severing and debranching are important steps in the disassembly process generating oligomers as intermediates. The remaining diffusible actin concentration is orders of magnitude higher than the in vitro actin monomer concentration required to support the observed polymerization rates, implying that the majority of monomers are transiently kept in a non-polymerizable "reserve" pool. The actin network disassembles and reassembles throughout the lamellipodium within seconds, so the lamellipodial network turnover is local. The diffusible actin transport, on the other hand, is global: actin subunits typically diffuse across the entire lamellipodium before reassembling into the network. This combination of local network turnover and global transport of dissociated subunits through the cytoplasm makes actin transport robust yet rapidly adaptable and amenable to regulation.
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Affiliation(s)
- Dikla Raz-Ben Aroush
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Noa Ofer
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel; Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Enas Abu-Shah
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel; Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Jun Allard
- Department of Mathematics, Center for Complex Biological Systems and Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697, USA
| | - Oleg Krichevsky
- Physics Department and Ilse Kats Center for Nanoscience, Ben-Gurion University, Beer-Sheva 84105, Israel
| | - Alex Mogilner
- Courant Institute of Mathematical Sciences and Department of Biology, New York University, New York, NY 10012, USA.
| | - Kinneret Keren
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel; Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 32000, Israel; Network Biology Research Laboratories, Technion-Israel Institute of Technology, Haifa 32000, Israel.
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Zhu J, Nan Q, Qin T, Qian D, Mao T, Yuan S, Wu X, Niu Y, Bai Q, An L, Xiang Y. Higher-Ordered Actin Structures Remodeled by Arabidopsis ACTIN-DEPOLYMERIZING FACTOR5 Are Important for Pollen Germination and Pollen Tube Growth. MOLECULAR PLANT 2017; 10:1065-1081. [PMID: 28606871 DOI: 10.1016/j.molp.2017.06.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 06/02/2017] [Accepted: 06/05/2017] [Indexed: 06/07/2023]
Abstract
Dynamics of the actin cytoskeleton are essential for pollen germination and pollen tube growth. ACTIN-DEPOLYMERIZING FACTORs (ADFs) typically contribute to actin turnover by severing/depolymerizing actin filaments. Recently, we demonstrated that Arabidopsis subclass III ADFs (ADF5 and ADF9) evolved F-actin-bundling function from conserved F-actin-depolymerizing function. However, little is known about the physiological function, the evolutional significance, and the actin-bundling mechanism of these neofunctionalized ADFs. Here, we report that loss of ADF5 function caused delayed pollen germination, retarded pollen tube growth, and increased sensitive to latrunculin B (LatB) treatment by affecting the generation and maintenance of actin bundles. Examination of actin filament dynamics in living cells revealed that the bundling frequency was significantly decreased in adf5 pollen tubes, consistent with its biochemical functions. Further biochemical and genetic complementation analyses demonstrated that both the N- and C-terminal actin-binding domains of ADF5 are required for its physiological and biochemical functions. Interestingly, while both are atypical actin-bundling ADFs, ADF5, but not ADF9, plays an important role in mature pollen physiological activities. Taken together, our results suggest that ADF5 has evolved the function of bundling actin filaments and plays an important role in the formation, organization, and maintenance of actin bundles during pollen germination and pollen tube growth.
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Affiliation(s)
- Jingen Zhu
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Qiong Nan
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Tao Qin
- State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Dong Qian
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Tonglin Mao
- State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Shunjie Yuan
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Xiaorong Wu
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Yue Niu
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Qifeng Bai
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Lizhe An
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Yun Xiang
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
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7
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Al Haj A, Mazur AJ, Buchmeier S, App C, Theiss C, Silvan U, Schoenenberger CA, Jockusch BM, Hannappel E, Weeds AG, Mannherz HG. Thymosin beta4 inhibits ADF/cofilin stimulated F-actin cycling and hela cell migration: Reversal by active Arp2/3 complex. Cytoskeleton (Hoboken) 2013; 71:95-107. [DOI: 10.1002/cm.21128] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Revised: 04/17/2013] [Accepted: 12/10/2013] [Indexed: 12/19/2022]
Affiliation(s)
- Abdulatif Al Haj
- Department of Anatomy and Molecular Embryology; Ruhr-University; Bochum Germany
| | | | - Sabine Buchmeier
- Cell Biology Group; Institute of Zoology; Technical University of Braunschweig; Germany
| | - Christine App
- Institute of Biochemistry; University of Erlangen; Erlangen Germany
| | | | - Unai Silvan
- Maurice E. Müller Institute for Structural Biology, Biocenter; Basel Switzerland
| | | | - Brigitte M. Jockusch
- Cell Biology Group; Institute of Zoology; Technical University of Braunschweig; Germany
| | - Ewald Hannappel
- Institute of Biochemistry; University of Erlangen; Erlangen Germany
| | - Alan G. Weeds
- MRC Laboratory of Molecular Biology and Trinity College; Cambridge United Kingdom
| | - Hans Georg Mannherz
- Department of Anatomy and Molecular Embryology; Ruhr-University; Bochum Germany
- Department of Physical Biochemistry; Max-Planck-Institute of Molecular Physiology; Dortmund Germany
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Chen CK, Benchaar SA, Phan M, Grintsevich EE, Loo RRO, Loo JA, Reisler E. Cofilin-induced changes in F-actin detected via cross-linking with benzophenone-4-maleimide. Biochemistry 2013; 52:5503-9. [PMID: 23862734 DOI: 10.1021/bi400715z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cofilin is a member of the actin depolymerizing factor (ADF)/cofilin family of proteins. It plays a key role in actin dynamics by promoting disassembly and assembly of actin filaments. Upon its binding, cofilin has been shown to bridge two adjacent protomers in filamentous actin (F-actin) and promote the displacement and disordering of subdomain 2 of actin. Here, we present evidence for cofilin promoting a new structural change in the actin filament, as detected via a switch in cross-linking sites. Benzophenone-4-maleimide, which normally forms intramolecular cross-linking in F-actin, cross-links F-actin intermolecularly upon cofilin binding. We mapped the cross-linking sites and found that in the absence of cofilin intramolecular cross-linking occurred between residues Cys374 and Asp11. In contrast, cofilin shifts the cross-linking by this reagent to intermolecular, between residue Cys374, located within subdomain 1 of the upper protomer, and Met44, located in subdomain 2 of the lower protomer. The intermolecular cross-linking of F-actin slows the rate of cofilin dissociation from the filaments and decreases the effect of ionic strength on cofilin-actin binding. These results are consistent with a significant role of filament flexibility in cofilin-actin interactions.
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Affiliation(s)
- Christine K Chen
- Department of Chemistry and Biochemistry, Molecular Biology Institute and Biological Chemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
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9
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Schönichen A, Mannherz HG, Behrmann E, Mazur AJ, Kühn S, Silván U, Schoenenberger CA, Fackler OT, Raunser S, Dehmelt L, Geyer M. FHOD1 is a combined actin filament capping and bundling factor that selectively associates with actin arcs and stress fibers. J Cell Sci 2013; 126:1891-901. [PMID: 23444374 DOI: 10.1242/jcs.126706] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Formins are actin polymerization factors that are known to nucleate and elongate actin filaments at the barbed end. In the present study we show that human FHOD1 lacks actin nucleation and elongation capacity, but acts as an actin bundling factor with capping activity toward the filament barbed end. Constitutively active FHOD1 associates with actin filaments in filopodia and lamellipodia at the leading edge, where it moves with the actin retrograde flow. At the base of lamellipodia, FHOD1 is enriched in nascent, bundled actin arcs as well as in more mature stress fibers. This function requires actin-binding domains located N-terminally to the canonical FH1-FH2 element. The bundling phenotype is maintained in the presence of tropomyosin, confirmed by electron microscopy showing assembly of 5 to 10 actin filaments into parallel, closely spaced filament bundles. Taken together, our data suggest a model in which FHOD1 stabilizes actin filaments by protecting barbed ends from depolymerization with its dimeric FH2 domain, whereas the region N-terminal to the FH1 domain mediates F-actin bundling by simultaneously binding to the sides of adjacent F-actin filaments.
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Affiliation(s)
- André Schönichen
- Department of Physical Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany.
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10
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Müller M, Mazur AJ, Behrmann E, Diensthuber RP, Radke MB, Qu Z, Littwitz C, Raunser S, Schoenenberger CA, Manstein DJ, Mannherz HG. Functional characterization of the human α-cardiac actin mutations Y166C and M305L involved in hypertrophic cardiomyopathy. Cell Mol Life Sci 2012; 69:3457-79. [PMID: 22643837 PMCID: PMC11115188 DOI: 10.1007/s00018-012-1030-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 04/22/2012] [Accepted: 05/07/2012] [Indexed: 11/25/2022]
Abstract
Inherited cardiomyopathies are caused by point mutations in sarcomeric gene products, including α-cardiac muscle actin (ACTC1). We examined the biochemical and cell biological properties of the α-cardiac actin mutations Y166C and M305L identified in hypertrophic cardiomyopathy (HCM). Untagged wild-type (WT) cardiac actin, and the Y166C and M305L mutants were expressed by the baculovirus/Sf9-cell system and affinity purified by immobilized gelsolin G4-6. Their correct folding was verified by a number of assays. The mutant actins also displayed a disturbed intrinsic ATPase activity and an altered polymerization behavior in the presence of tropomyosin, gelsolin, and Arp2/3 complex. Both mutants stimulated the cardiac β-myosin ATPase to only 50 % of WT cardiac F-actin. Copolymers of WT and increasing amounts of the mutant actins led to a reduced stimulation of the myosin ATPase. Transfection of established cell lines revealed incorporation of EGFP- and hemagglutinin (HA)-tagged WT and both mutant actins into cytoplasmic stress fibers. Adenoviral vectors of HA-tagged WT and Y166C actin were successfully used to infect adult and neonatal rat cardiomyocytes (NRCs). The expressed HA-tagged actins were incorporated into the minus-ends of NRC thin filaments, demonstrating the ability to form hybrid thin filaments with endogenous actin. In NRCs, the Y166C mutant led after 72 h to a shortening of the sarcomere length when compared to NRCs infected with WT actin. Thus our data demonstrate that a mutant actin can be integrated into cardiomyocyte thin filaments and by its reduced mode of myosin interaction might be the basis for the initiation of HCM.
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Affiliation(s)
- Mirco Müller
- Institute for Biophysical Chemistry, OE 4350, Hannover Medical School, 30625 Hannover, Germany
| | - Antonina Joanna Mazur
- Department of Anatomy and Molecular Embryology, Ruhr-University, Universitätsstrasse 150, 44780 Bochum, Germany
- Present Address: Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, 51-148 Wroclaw, Poland
| | - Elmar Behrmann
- Department of Physical Biochemistry, Max-Planck-Institute for Molecular Physiology, 44227 Dortmund, Germany
| | - Ralph P. Diensthuber
- Institute for Biophysical Chemistry, OE 4350, Hannover Medical School, 30625 Hannover, Germany
| | - Michael B. Radke
- Institute for Biophysical Chemistry, OE 4350, Hannover Medical School, 30625 Hannover, Germany
| | - Zheng Qu
- Department of Anatomy and Molecular Embryology, Ruhr-University, Universitätsstrasse 150, 44780 Bochum, Germany
| | - Christoph Littwitz
- Department of Physiology, Stritch School of Medicine, Loyola University Chicago, Chicago, USA
| | - Stefan Raunser
- Department of Physical Biochemistry, Max-Planck-Institute for Molecular Physiology, 44227 Dortmund, Germany
| | - Cora-Ann Schoenenberger
- Maurice E. Müller Institute for Structural Biology, Biozentrum, University of Basel, 4046 Basel, Switzerland
| | - Dietmar J. Manstein
- Institute for Biophysical Chemistry, OE 4350, Hannover Medical School, 30625 Hannover, Germany
| | - Hans Georg Mannherz
- Department of Anatomy and Molecular Embryology, Ruhr-University, Universitätsstrasse 150, 44780 Bochum, Germany
- Department of Physical Biochemistry, Max-Planck-Institute for Molecular Physiology, 44227 Dortmund, Germany
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11
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Wiggan O, Shaw AE, DeLuca JG, Bamburg JR. ADF/cofilin regulates actomyosin assembly through competitive inhibition of myosin II binding to F-actin. Dev Cell 2012; 22:530-43. [PMID: 22421043 DOI: 10.1016/j.devcel.2011.12.026] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Revised: 12/30/2011] [Accepted: 12/31/2011] [Indexed: 11/29/2022]
Abstract
The contractile actin cortex is important for diverse fundamental cell processes, but little is known about how the assembly of F-actin and myosin II motors is regulated. We report that depletion of actin depolymerizing factor (ADF)/cofilin proteins in human cells causes increased contractile cortical actomyosin assembly. Remarkably, our data reveal that the major cellular defects resulting from ADF/cofilin depletion, including cortical F-actin accumulation, were largely due to excessive myosin II activity. We identify that ADF/cofilins from unicellular organisms to humans share a conserved activity to inhibit myosin II binding to F-actin, indicating a mechanistic rationale for our cellular results. Our study establishes an essential requirement for ADF/cofilin proteins in the control of normal cortical contractility and in processes such as mitotic karyokinesis. We propose that ADF/cofilin proteins are necessary for controlling actomyosin assembly and intracellular contractile force generation, a function of equal physiological importance to their established roles in mediating F-actin turnover.
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Affiliation(s)
- O'Neil Wiggan
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA.
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12
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Abstract
Cofilin/ADF proteins play key roles in the dynamics of actin, one of the most abundant and highly conserved eukaryotic proteins. We used cryoelectron microscopy to generate a 9-Å resolution three-dimensional reconstruction of cofilin-decorated actin filaments, the highest resolution achieved for a complex of F-actin with an actin-binding protein. We show that the cofilin-induced change in the filament twist is due to a unique conformation of the actin molecule unrelated to any previously observed state. The changes between the actin protomer in naked F-actin and in the actin-cofilin filament are greater than the conformational changes between G- and F-actin. Our results show the structural plasticity of actin, suggest that other actin-binding proteins may also induce large but different conformational changes, and show that F-actin cannot be described by a single molecular model.
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13
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Munsie L, Caron N, Atwal RS, Marsden I, Wild EJ, Bamburg JR, Tabrizi SJ, Truant R. Mutant huntingtin causes defective actin remodeling during stress: defining a new role for transglutaminase 2 in neurodegenerative disease. Hum Mol Genet 2011; 20:1937-51. [PMID: 21355047 PMCID: PMC3080606 DOI: 10.1093/hmg/ddr075] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Huntington's disease (HD) is caused by an expanded CAG tract in the Interesting transcript 15 (IT15) gene encoding the 350 kDa huntingtin protein. Cellular stresses can trigger the release of huntingtin from the endoplasmic reticulum, allowing huntingtin nuclear entry. Here, we show that endogenous, full-length huntingtin localizes to nuclear cofilin–actin rods during stress and is required for the proper stress response involving actin remodeling. Mutant huntingtin induces a dominant, persistent nuclear rod phenotype similar to that described in Alzheimer's disease for cytoplasmic cofilin–actin rods. Using live cell temporal studies, we show that this stress response is similarly impaired when mutant huntingtin is present, or when normal huntingtin levels are reduced. In clinical lymphocyte samples from HD patients, we have quantitatively detected cross-linked complexes of actin and cofilin with complex formation varying in correlation with disease progression. By live cell fluorescence lifetime imaging measurement–Förster resonant energy transfer studies and western blot assays, we quantitatively observed that stress-activated tissue transglutaminase 2 (TG2) is responsible for the actin–cofilin covalent cross-linking observed in HD. These data support a direct role for huntingtin in nuclear actin re-organization, and describe a new pathogenic mechanism for aberrant TG2 enzymatic hyperactivity in neurodegenerative diseases.
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Affiliation(s)
- Lise Munsie
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1200 Main Street West, Hamilton, Ontario, Canada L8N3Z5
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14
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Identification of a cofilin-like actin-binding site on translationally controlled tumor protein (TCTP). FEBS Lett 2010; 584:4756-60. [DOI: 10.1016/j.febslet.2010.10.054] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Revised: 10/20/2010] [Accepted: 10/23/2010] [Indexed: 11/19/2022]
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15
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Modulation of actin filament dynamics by actin-binding proteins residing in lamellipodia. Eur J Cell Biol 2010; 89:402-13. [DOI: 10.1016/j.ejcb.2009.10.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2007] [Revised: 09/24/2009] [Accepted: 10/01/2009] [Indexed: 11/19/2022] Open
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16
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Lang AE, Schmidt G, Schlosser A, Hey TD, Larrinua IM, Sheets JJ, Mannherz HG, Aktories K. Photorhabdus luminescens toxins ADP-ribosylate actin and RhoA to force actin clustering. Science 2010; 327:1139-42. [PMID: 20185726 DOI: 10.1126/science.1184557] [Citation(s) in RCA: 168] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The bacterium Photorhabdus luminescens is mutualistically associated with entomopathogenetic nematodes. These nematodes invade insect larvae and release the bacteria from their intestine, which kills the insects through the action of toxin complexes. We elucidated the mode of action of two of these insecticidal toxins from P. luminescens. We identified the biologically active components TccC3 and TccC5 as adenosine diphosphate (ADP)-ribosyltransferases, which modify unusual amino acids. TccC3 ADP-ribosylated threonine-148 of actin, resulting in actin polymerization. TccC5 ADP-ribosylated Rho guanosine triphosphatase proteins at glutamine-61 and glutamine-63, inducing their activation. The concerted action of both toxins inhibited phagocytosis of target insect cells and induced extensive intracellular polymerization and clustering of actin. Several human pathogenic bacteria produce related toxins.
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Affiliation(s)
- Alexander E Lang
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany
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17
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Mannherz HG, Hannappel E. The beta-thymosins: intracellular and extracellular activities of a versatile actin binding protein family. ACTA ACUST UNITED AC 2009; 66:839-51. [PMID: 19405116 DOI: 10.1002/cm.20371] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The beta-thymosins are N-terminally acetylated peptides of about 5 kDa molecular mass and composed of about 40-44 amino acid residues. The first member of the family, thymosin beta4, was initially isolated from thymosin fraction 5, prepared in five steps from calf thymus. Thymosin beta4 was supposed to be specifically produced and released by the thymic gland and to possess hormonal activities modulating the immune response. Various paracrine effects have indeed been reported for these peptides such as cardiac protection, angiogenesis, stimulation of wound healing, and hair growth. Besides these paracrine effects, it was noted that beta-thymosins occur in high concentration in the cytoplasm of many eukaryotic cells and bind to the cytoskeletal component actin. Subsequently it became apparent from in vitro experiments that they preferentially bind to monomeric (G-)actin and stabilize it in its monomeric form. Due to this ability the beta-thymosins are the main intracellular actin sequestering factor, i.e., they posses the ability to remove monomeric actin from the dynamic assembly and disassembly processes of the actin cytoskeleton that constantly occur in activated cells. In this review we will concentrate on the intracellular activity and localization of the beta-thymosins, i.e., their modulating effect on the actin cytoskeleton.
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Affiliation(s)
- Hans Georg Mannherz
- Department of Anatomy and Embryology, Ruhr-University, D-44780 Bochum, Germany.
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18
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Chan C, Beltzner CC, Pollard TD. Cofilin dissociates Arp2/3 complex and branches from actin filaments. Curr Biol 2009; 19:537-45. [PMID: 19362000 DOI: 10.1016/j.cub.2009.02.060] [Citation(s) in RCA: 154] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Revised: 02/16/2009] [Accepted: 02/17/2009] [Indexed: 10/20/2022]
Abstract
BACKGROUND Actin-based cellular motility requires spatially and temporally coordinated remodeling of a network of branched actin filaments. This study investigates how cofilin and Arp2/3 complex, two main players in the dendritic nucleation model, interact to produce sharp spatial transitions between densely branched filaments and long, unbranched filaments. RESULTS We found that cofilin binding reduces both the affinity of actin filaments for Arp2/3 complex and the stability of branches. We used fluorescence spectroscopy to measure the kinetics of cofilin association with filaments and the resulting dissociation of Arp2/3 complex and TIRF microscopy to visualize filament severing and the loss of actin filament branches. Cofilin severs filaments optimally when few actin subunits are occupied but dissociates branches rapidly only at higher occupancies. Effective debranching is nevertheless achieved, as a result of cooperative binding and reduced affinity of Arp2/3 complex for the filament, at cofilin concentrations below those required for direct competition. CONCLUSIONS Cofilin rapidly dissociates Arp2/3 complex and branches by direct competition for binding sites on the actin filament and by propagation of structural changes in the actin filament that reduce affinity for Arp2/3 complex.
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Affiliation(s)
- Chikio Chan
- Department of Molecular Cellular, Yale University, PO Box 208103, New Haven, CT 06520-8103, USA
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19
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The effects of ADF/cofilin and profilin on the conformation of the ATP-binding cleft of monomeric actin. Biophys J 2009; 96:2335-43. [PMID: 19289059 DOI: 10.1016/j.bpj.2008.12.3906] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Revised: 12/03/2008] [Accepted: 12/08/2008] [Indexed: 11/20/2022] Open
Abstract
Actin depolymerizing factor (ADF)/cofilin and profilin are small actin-binding proteins, which have central roles in cytoskeletal dynamics in all eukaryotes. When bound to an actin monomer, ADF/cofilins inhibit the nucleotide exchange, whereas most profilins accelerate the nucleotide exchange on actin monomers. In this study the effects of ADF/cofilin and profilin on the accessibility of the actin monomer's ATP-binding pocket was investigated by a fluorescence spectroscopic method. The fluorescence of the actin bound epsilon-ATP was quenched with a neutral quencher (acrylamide) in steady-state and time dependent experiments, and the data were analyzed with a complex form of the Stern-Volmer equation. The experiments revealed that in the presence of ADF/cofilin the accessibility of the bound epsilon-ATP decreased, indicating a closed and more compact ATP-binding pocket induced by the binding of ADF/cofilin. In the presence of profilin the accessibility of the bound epsilon-ATP increased, indicating a more open and approachable protein matrix around the ATP-binding pocket. The results of the fluorescence quenching experiments support a structural mechanism regarding the regulation of the nucleotide exchange on actin monomers by ADF/cofilin and profilin.
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20
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Levitsky DI, Pivovarova AV, Mikhailova VV, Nikolaeva OP. Thermal unfolding and aggregation of actin. FEBS J 2008; 275:4280-95. [DOI: 10.1111/j.1742-4658.2008.06569.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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21
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Roubelakis MG, Pappa KI, Bitsika V, Zagoura D, Vlahou A, Papadaki HA, Antsaklis A, Anagnou NP. Molecular and proteomic characterization of human mesenchymal stem cells derived from amniotic fluid: comparison to bone marrow mesenchymal stem cells. Stem Cells Dev 2008; 16:931-52. [PMID: 18047393 DOI: 10.1089/scd.2007.0036] [Citation(s) in RCA: 180] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Human mesenchymal stem cells (hMSCs) constitute a population of multipotent adherent cells able to give rise to multiple mesenchymal lineages such as osteoblasts, adipocytes, or chondrocytes. So far, the most common source of MSCs has been the bone marrow (BM); however BM-MSC harvesting and processing exhibits major drawbacks and limitations. Thus, identification and characterization of alternative sources of MSCs are of great importance. In the present study, we isolated and expanded fetal MSCs from second-trimester amniotic fluid (AF). We documented that these cells are of embryonic origin, can differentiate under appropriate conditions into cell types derived from all three germ layers, and express the pluripotency marker Oct-4, the human Nanog protein, and the stage-specific embryonic antigen-4 (SSEA-4). Furthermore, we systematically tested the immunophenotype of cultured MSCs by flow cytometry analysis using a wide variety of markers. Direct comparison of this phenotype to the one derived from cultured BM-MSCs demonstrated that cultured MSCs from both sources exhibit similar expression patterns. Using the two-dimensional gel electrophoresis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) approach, we have generated for the first time the protein map of cultured AF-MSCs by identifying 261 proteins, and we compared it directly to that of cultured BM-MSCs. The functional pattern of the identified proteins from both sources was similar. However, cultured AF-MSCs displayed a number of unique proteins related to proliferation and primitive phenotype, which may confer to the distinct features of the two types. Considering the easy access to this new cell source and the yield of expanded MSCs for stem cell research, AF may provide an excellent source of MSCs both for basic research and for potential therapeutic applications.
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Affiliation(s)
- Maria G Roubelakis
- Cell and Gene Therapy Laboratory, Centre of Basic Research II, Biomedical Research Foundation of the Academy of Athens (BRF), Athens, Greece
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22
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Grintsevich EE, Benchaar SA, Warshaviak D, Boontheung P, Halgand F, Whitelegge JP, Faull KF, Loo RRO, Sept D, Loo JA, Reisler E. Mapping the cofilin binding site on yeast G-actin by chemical cross-linking. J Mol Biol 2008; 377:395-409. [PMID: 18258262 DOI: 10.1016/j.jmb.2007.12.073] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Revised: 12/27/2007] [Accepted: 12/28/2007] [Indexed: 11/25/2022]
Abstract
Cofilin is a major cytoskeletal protein that binds to both monomeric actin (G-actin) and polymeric actin (F-actin) and is involved in microfilament dynamics. Although an atomic structure of the G-actin-cofilin complex does not exist, models of the complex have been built using molecular dynamics simulations, structural homology considerations, and synchrotron radiolytic footprinting data. The hydrophobic cleft between actin subdomains 1 and 3 and, alternatively, the cleft between actin subdomains 1 and 2 have been proposed as possible high-affinity cofilin binding sites. In this study, the proposed binding of cofilin to the subdomain 1/subdomain 3 region on G-actin has been probed using site-directed mutagenesis, fluorescence labeling, and chemical cross-linking, with yeast actin mutants containing single reactive cysteines in the actin hydrophobic cleft and with cofilin mutants carrying reactive cysteines in the regions predicted to bind to G-actin. Mass spectrometry analysis of the cross-linked complex revealed that cysteine 345 in subdomain 1 of mutant G-actin was cross-linked to native cysteine 62 on cofilin. A cofilin mutant that carried a cysteine substitution in the alpha 3-helix (residue 95) formed a cross-link with residue 144 in actin subdomain 3. Distance constraints imposed by these cross-links provide experimental evidence for cofilin binding between actin subdomains 1 and 3 and fit a corresponding docking-based structure of the complex. The cross-linking of the N-terminal region of recombinant yeast cofilin to actin residues 346 and 374 with dithio-bis-maleimidoethane (12.4 A) and via disulfide bond formation was also documented. This set of cross-linking data confirms the important role of the N-terminal segment of cofilin in interactions with G-actin.
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Affiliation(s)
- Elena E Grintsevich
- Department of Chemistry and Biochemistry, University of California-Los Angeles, CA, USA
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23
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Kamal JKA, Chance MR. Modeling of protein binary complexes using structural mass spectrometry data. Protein Sci 2007; 17:79-94. [PMID: 18042684 DOI: 10.1110/ps.073071808] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
In this article, we describe a general approach to modeling the structure of binary protein complexes using structural mass spectrometry data combined with molecular docking. In the first step, hydroxyl radical mediated oxidative protein footprinting is used to identify residues that experience conformational reorganization due to binding or participate in the binding interface. In the second step, a three-dimensional atomic structure of the complex is derived by computational modeling. Homology modeling approaches are used to define the structures of the individual proteins if footprinting detects significant conformational reorganization as a function of complex formation. A three-dimensional model of the complex is constructed from these binary partners using the ClusPro program, which is composed of docking, energy filtering, and clustering steps. Footprinting data are used to incorporate constraints-positive and/or negative-in the docking step and are also used to decide the type of energy filter-electrostatics or desolvation-in the successive energy-filtering step. By using this approach, we examine the structure of a number of binary complexes of monomeric actin and compare the results to crystallographic data. Based on docking alone, a number of competing models with widely varying structures are observed, one of which is likely to agree with crystallographic data. When the docking steps are guided by footprinting data, accurate models emerge as top scoring. We demonstrate this method with the actin/gelsolin segment-1 complex. We also provide a structural model for the actin/cofilin complex using this approach which does not have a crystal or NMR structure.
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Affiliation(s)
- J K Amisha Kamal
- Center for Proteomics and Mass spectrometry, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
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24
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Lee SH, Hayes DB, Rebowski G, Tardieux I, Dominguez R. Toxofilin from Toxoplasma gondii forms a ternary complex with an antiparallel actin dimer. Proc Natl Acad Sci U S A 2007; 104:16122-7. [PMID: 17911258 PMCID: PMC2042172 DOI: 10.1073/pnas.0705794104] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many human pathogens exploit the actin cytoskeleton during infection, including Toxoplasma gondii, an apicomplexan parasite related to Plasmodium, the agent of malaria. One of the most abundantly expressed proteins of T. gondii is toxofilin, a monomeric actin-binding protein (ABP) involved in invasion. Toxofilin is found in rhoptry and presents an N-terminal signal sequence, consistent with its being secreted during invasion. We report the structure of toxofilin amino acids 69-196 in complex with the host mammalian actin. Toxofilin presents an extended conformation and interacts with an antiparallel actin dimer, in which one of the actins is related by crystal symmetry. Consistent with this observation, analytical ultracentrifugation analysis shows that toxofilin binds two actins in solution. Toxofilin folds into five consecutive helices, which form three relatively independent actin-binding sites. Helices 1 and 2 bind the symmetry-related actin molecule and cover its nucleotide-binding cleft. Helices 3-5 bind the other actin and constitute the primary actin-binding region. Helix 3 interacts in the cleft between subdomains 1 and 3, a common binding site for most ABPs. Helices 4 and 5 wrap around actin subdomain 4, and residue Gln-134 of helix 4 makes a hydrogen-bonding contact with the nucleotide in actin, both of which are unique features among ABPs. Toxofilin dramatically inhibits nucleotide exchange on two actin molecules simultaneously. This effect is linked to the formation of the antiparallel actin dimer because a construct lacking helices 1 and 2 binds only one actin and inhibits nucleotide exchange less potently.
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Affiliation(s)
- Sung Haeng Lee
- Department of Physiology, University of Pennsylvania School of Medicine, 3700 Hamilton Walk, Philadelphia, PA 19104-6085
| | - David B. Hayes
- Boston Biomedical Research Institute, 64 Grove Street, Watertown, MA 02472; and
| | - Grzegorz Rebowski
- Department of Physiology, University of Pennsylvania School of Medicine, 3700 Hamilton Walk, Philadelphia, PA 19104-6085
| | - Isabelle Tardieux
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8104, Institut Cochin, 75014 Paris, France
| | - Roberto Dominguez
- Department of Physiology, University of Pennsylvania School of Medicine, 3700 Hamilton Walk, Philadelphia, PA 19104-6085
- To whom correspondence should be addressed. E-mail:
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25
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Kamal JKA, Benchaar SA, Takamoto K, Reisler E, Chance MR. Three-dimensional structure of cofilin bound to monomeric actin derived by structural mass spectrometry data. Proc Natl Acad Sci U S A 2007; 104:7910-5. [PMID: 17470807 PMCID: PMC1876546 DOI: 10.1073/pnas.0611283104] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cytoskeletal protein, actin, has its structure and function regulated by cofilin. In the absence of an atomic resolution structure for the actin/cofilin complex, the mechanism of cofilin regulation is poorly understood. Theoretical studies based on the similarities of cofilin and gelsolin segment 1 proposed the cleft between subdomains 1 and 3 in actin as the cofilin binding site. We used radiolytic protein footprinting with mass spectrometry and molecular modeling to provide an atomic model of how cofilin binds to monomeric actin. Footprinting data suggest that cofilin binds to the cleft between subdomains 1 and 2 in actin and that cofilin induces further closure of the actin nucleotide cleft. Site-specific fluorescence data confirm these results. The model identifies key ionic and hydrophobic interactions at the binding interface, including hydrogen-bonding between His-87 of actin to Ser-89 of cofilin that may control the charge dependence of cofilin binding. This model and its implications fill an especially important niche in the actin field, owing to the fact that ongoing crystallization efforts of the actin/cofilin complex have so far failed. This 3D binary complex structure is derived from a combination of solution footprinting data and computational approaches and outlines a general method for determining the structure of such complexes.
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Affiliation(s)
- J. K. Amisha Kamal
- *Center for Proteomics, Case Western Reserve University School of Medicine, Cleveland, OH 44106; and
| | - Sabrina A. Benchaar
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, CA 90095
| | - Keiji Takamoto
- *Center for Proteomics, Case Western Reserve University School of Medicine, Cleveland, OH 44106; and
| | - Emil Reisler
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, CA 90095
| | - Mark R. Chance
- *Center for Proteomics, Case Western Reserve University School of Medicine, Cleveland, OH 44106; and
- To whom correspondence should be addressed. E-mail:
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26
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Eulitz D, Mannherz HG. Inhibition of deoxyribonuclease I by actin is to protect cells from premature cell death. Apoptosis 2007; 12:1511-21. [PMID: 17468836 DOI: 10.1007/s10495-007-0078-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Deoxyribonuclease I (Dnase1) is the major extracellular endonuclease. It is secreted by digestive glands into the alimentary tract and into the plasma, lacrimal fluid and urine by hepatocytes, lacrimal glands and renal proximal tubular cells, respectively. In many species the activity of Dnase1 is inhibited by monomeric actin. However, the biological significance of this high affinity interaction is unknown. We generated a Dnase1 mutant with extremely reduced actin binding capacity. EGFP-constructs of wild-type and mutant Dnase1 were transfected into MCF-7 breast cancer cells and apoptosis or necrosis was induced by staurosporine or oxidative stress. During apoptosis faster chromatin fragmentation occurred in cells transfected with mutant Dnase1. When wt (wild-type)- or mutated Dnase1 were added to cells after induction of necrosis, faster chromatin degradation occurred in the presence of mutant Dnase1. Inclusion of actin under these conditions inhibited chromatin degradation by wt- but not by mutated Dnase1. Thus, inhibition of Dnase1 by actin may serve as a self-protection mechanism against premature DNA degradation during cell damage.
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Affiliation(s)
- Dirk Eulitz
- Department of Anatomy and Embryology, Ruhr-University Bochum, Germany.
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