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Binding of Red Clover Isoflavones to Actin as A Potential Mechanism of Anti-Metastatic Activity Restricting the Migration of Cancer Cells. Molecules 2018; 23:molecules23102471. [PMID: 30261641 PMCID: PMC6222305 DOI: 10.3390/molecules23102471] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Revised: 09/18/2018] [Accepted: 09/25/2018] [Indexed: 11/17/2022] Open
Abstract
Actin functions are crucial for the ability of the cell to execute dynamic cytoskeleton reorganization and movement. Nutraceuticals that form complexes with actin and reduce its polymerization can be used in cancer therapy to prevent cell migration and metastasis of tumors. The aim of this study was to evaluate the ability of isoflavones to form complexes with actin. Docking simulation and isothermal titration calorimetry were used for this purpose. The formation of complexes by hydrogen bonds, hydrophobic and π-π interactions was demonstrated. Interactions occurred at the ATP binding site, which may limit the rotation of the actin molecule observed during polymerization and also at the site responsible for contacts during polymerization, reducing the ability of the molecule to form filaments. The greatest therapeutic potential was demonstrated by isoflavones occurring in red clover sprouts, i.e., biochanin A and formononetin, being methoxy derivatives of genistein and daidzein.
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Meiring JC, Bryce NS, Wang Y, Taft MH, Manstein DJ, Liu Lau S, Stear J, Hardeman EC, Gunning PW. Co-polymers of Actin and Tropomyosin Account for a Major Fraction of the Human Actin Cytoskeleton. Curr Biol 2018; 28:2331-2337.e5. [DOI: 10.1016/j.cub.2018.05.053] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 04/20/2018] [Accepted: 05/17/2018] [Indexed: 01/14/2023]
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3
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Cofilin-induced cooperative conformational changes of actin subunits revealed using cofilin-actin fusion protein. Sci Rep 2016; 6:20406. [PMID: 26842224 PMCID: PMC4740740 DOI: 10.1038/srep20406] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 12/31/2015] [Indexed: 11/19/2022] Open
Abstract
To investigate cooperative conformational changes of actin filaments induced by cofilin binding, we engineered a fusion protein made of Dictyostelium cofilin and actin. The filaments of the fusion protein were functionally similar to actin filaments bound with cofilin in that they did not bind rhodamine-phalloidin, had quenched fluorescence of pyrene attached to Cys374 and showed enhanced susceptibility of the DNase loop to cleavage by subtilisin. Quantitative analyses of copolymers made of different ratios of the fusion protein and control actin further demonstrated that the fusion protein affects the structure of multiple neighboring actin subunits in copolymers. Based on these and other recent related studies, we propose a mechanism by which conformational changes induced by cofilin binding is propagated unidirectionally to the pointed ends of the filaments, and cofilin clusters grow unidirectionally to the pointed ends following this path. Interestingly, the fusion protein was unable to copolymerize with control actin at pH 6.5 and low ionic strength, suggesting that the structural difference between the actin moiety in the fusion protein and control actin is pH-sensitive.
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4
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A small molecule inhibitor of tropomyosin dissociates actin binding from tropomyosin-directed regulation of actin dynamics. Sci Rep 2016; 6:19816. [PMID: 26804624 PMCID: PMC4726228 DOI: 10.1038/srep19816] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 12/07/2015] [Indexed: 12/26/2022] Open
Abstract
The tropomyosin family of proteins form end-to-end polymers along the actin filament. Tumour cells rely on specific tropomyosin-containing actin filament populations for growth and survival. To dissect out the role of tropomyosin in actin filament regulation we use the small molecule TR100 directed against the C terminus of the tropomyosin isoform Tpm3.1. TR100 nullifies the effect of Tpm3.1 on actin depolymerisation but surprisingly Tpm3.1 retains the capacity to bind F-actin in a cooperative manner. In vivo analysis also confirms that, in the presence of TR100, fluorescently tagged Tpm3.1 recovers normally into stress fibers. Assembling end-to-end along the actin filament is thereby not sufficient for tropomyosin to fulfil its function. Rather, regulation of F-actin stability by tropomyosin requires fidelity of information communicated at the barbed end of the actin filament. This distinction has significant implications for perturbing tropomyosin-dependent actin filament function in the context of anti-cancer drug development.
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Aggeli D, Kish-Trier E, Lin MC, Haarer B, Cingolani G, Cooper JA, Wilkens S, Amberg DC. Coordination of the filament stabilizing versus destabilizing activities of cofilin through its secondary binding site on actin. Cytoskeleton (Hoboken) 2014; 71:361-79. [PMID: 24943913 PMCID: PMC4241054 DOI: 10.1002/cm.21178] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 05/29/2014] [Indexed: 11/08/2022]
Abstract
Cofilin is a ubiquitous modulator of actin cytoskeleton dynamics that can both stabilize and destabilize actin filaments depending on its concentration and/or the presence of regulatory co-factors. Three charge-reversal mutants of yeast cofilin, located in cofilin's filament-specific secondary binding site, were characterized in order to understand why disruption of this site leads to enhanced filament disassembly. Crystal structures of the mutants showed that the mutations specifically affect the secondary actin-binding interface, leaving the primary binding site unaltered. The mutant cofilins show enhanced activity compared to wild-type cofilin in severing and disassembling actin filaments. Electron microscopy and image analysis revealed long actin filaments in the presence of wild-type cofilin, while the mutants induced many short filaments, consistent with enhanced severing. Real-time fluorescence microscopy of labeled actin filaments confirmed that the mutants, unlike wild-type cofilin, were functioning as constitutively active severing proteins. In cells, the mutant cofilins delayed endocytosis, which depends on rapid actin turnover. We conclude that mutating cofilin's secondary actin-binding site increases cofilin's ability to sever and de-polymerize actin filaments. We hypothesize that activators of cofilin severing, like Aip1p, may act by disrupting the interface between cofilin's secondary actin-binding site and the actin filament.
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Affiliation(s)
- Dimitra Aggeli
- SUNY Upstate Medical University, Department of Biochemistry and Molecular Biology, 750 E. Adams Street, Syracuse, NY 13159
| | - Erik Kish-Trier
- University of Utah, Department of Biochemistry, 15 N Medical Drive East, Salt Lake City, UT 84112-5650
| | - Meng Chi Lin
- Early Embryogenesis Lab, Center for Developmental Biology, Riken, Japan
| | - Brian Haarer
- SUNY Upstate Medical University, Department of Biochemistry and Molecular Biology, 750 E. Adams Street, Syracuse, NY 13159
| | - Gino Cingolani
- Thomas Jefferson University, Department of Biochemistry and Molecular Biology, 233 South 10th Street, Philadelphia, PA 19107
| | - John A. Cooper
- Washington University in St. Louis, Department of Cell Biology and Physiology, 660 South Euclid Avenue, St. Louis, MO 63110
| | - Stephan Wilkens
- SUNY Upstate Medical University, Department of Biochemistry and Molecular Biology, 750 E. Adams Street, Syracuse, NY 13159
| | - David C. Amberg
- SUNY Upstate Medical University, Department of Biochemistry and Molecular Biology, 750 E. Adams Street, Syracuse, NY 13159
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6
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Kardos R, Nevalainen E, Nyitrai M, Hild G. The effect of ADF/cofilin and profilin on the dynamics of monomeric actin. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:2010-9. [PMID: 23845993 DOI: 10.1016/j.bbapap.2013.06.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2012] [Revised: 05/22/2013] [Accepted: 06/13/2013] [Indexed: 11/19/2022]
Abstract
The main goal of the work was to uncover the dynamical changes in actin induced by the binding of cofilin and profilin. The change in the structure and flexibility of the small domain and its function in the thermodynamic stability of the actin monomer were examined with fluorescence spectroscopy and differential scanning calorimetry (DSC). The structure around the C-terminus of actin is slightly affected by the presence of cofilin and profilin. Temperature dependent fluorescence resonance energy transfer measurements indicated that both actin binding proteins decreased the flexibility of the protein matrix between the subdomains 1 and 2. Time resolved anisotropy decay measurements supported the idea that cofilin and profilin changed similarly the dynamics around the fluorescently labeled Cys-374 and Lys-61 residues in subdomains 1 and 2, respectively. DSC experiments indicated that the thermodynamic stability of actin increased by cofilin and decreased in the presence of profilin. Based on the information obtained it is possible to conclude that while the small domain of actin acts uniformly in the presence of cofilin and profilin the overall stability of actin changes differently in the presence of the studied actin binding proteins. The results support the idea that the small domain of actin behaves as a rigid unit during the opening and closing of the nucleotide binding pocket in the presence of profilin and cofilin as well. The structural arrangement of the nucleotide binding cleft mainly influences the global stability of actin while the dynamics of the different segments can change autonomously.
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Affiliation(s)
- Roland Kardos
- University of Pécs, Medical School, Department of Biophysics, Szigeti str. 12, Pécs H-7624, Hungary; Szentágothai Research Center, Ifjúság str. 34, Pécs H-7624, Hungary
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7
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Elam WA, Kang H, De la Cruz EM. Biophysics of actin filament severing by cofilin. FEBS Lett 2013; 587:1215-9. [PMID: 23395798 DOI: 10.1016/j.febslet.2013.01.062] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 01/25/2013] [Accepted: 01/28/2013] [Indexed: 11/16/2022]
Abstract
The continuous assembly and disassembly of actin filament networks is vital for cellular processes including division, growth, and motility. Network remodeling is facilitated by cofilins, a family of essential regulatory proteins that fragment actin filaments. Cofilin induces net structural changes in filaments that render them more compliant in bending and twisting. A model in which local stress accumulation at mechanical discontinuities, such as boundaries of bare and cofilin-decorated filament segments, accounts for the cofilin concentration dependence of severing, including maximal activity at sub-stoichiometric binding densities. Real-time imaging of cofilin-mediated filament severing supports the boundary-fracture model. The severing model predicts that fragmentation is promoted by factors modulating filament mechanics (e.g. tethering, cross-linking, or deformation), possibly explaining enhanced in vivo severing activities.
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Affiliation(s)
- W Austin Elam
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
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8
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Fan J, Saunders MG, Haddadian EJ, Freed KF, De La Cruz EM, Voth GA. Molecular origins of cofilin-linked changes in actin filament mechanics. J Mol Biol 2013; 425:1225-40. [PMID: 23352932 DOI: 10.1016/j.jmb.2013.01.020] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 01/14/2013] [Accepted: 01/16/2013] [Indexed: 10/27/2022]
Abstract
The actin regulatory protein cofilin plays a central role in actin assembly dynamics by severing filaments and increasing the concentration of ends from which subunits add and dissociate. Cofilin binding modifies the average structure and mechanical properties of actin filaments, thereby promoting fragmentation of partially decorated filaments at boundaries of bare and cofilin-decorated segments. Despite extensive evidence for cofilin-dependent changes in filament structure and mechanics, it is unclear how the two processes are linked at the molecular level. Here, we use molecular dynamics simulations and coarse-grained analyses to evaluate the molecular origins of the changes in filament compliance due to cofilin binding. Filament subunits with bound cofilin are less flat and maintain a significantly more open nucleotide cleft than bare filament subunits. Decorated filament segments are less twisted, thinner (considering only actin), and less connected than their bare counterparts, which lowers the filament bending persistence length and torsional stiffness. Using coarse-graining as an analysis method reveals that cofilin binding increases the average distance between the adjacent long-axis filament subunit, thereby weakening their interaction. In contrast, a fraction of lateral filament subunit contacts are closer and presumably stronger with cofilin binding. A cofilactin interface contact identified by cryo-electron microscopy is unstable during simulations carried out at 310K, suggesting that this particular interaction may be short lived at ambient temperatures. These results reveal the molecular origins of cofilin-dependent changes in actin filament mechanics that may promote filament severing.
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Affiliation(s)
- Jun Fan
- Department of Chemistry, James Franck Institute, Computation Institute, University of Chicago, 5735 South Ellis Avenue, Chicago, IL 60637, USA
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9
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Lu JX, Xiang YF, Zhang JX, Ju HQ, Chen ZP, Wang QL, Chen W, Peng XL, Han B, Wang YF. Cloning, soluble expression, rapid purification and characterization of human Cofilin1. Protein Expr Purif 2012; 82:186-91. [DOI: 10.1016/j.pep.2012.01.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 01/03/2012] [Accepted: 01/03/2012] [Indexed: 10/14/2022]
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10
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Hild G, Bugyi B, Nyitrai M. Conformational dynamics of actin: effectors and implications for biological function. Cytoskeleton (Hoboken) 2010; 67:609-29. [PMID: 20672362 PMCID: PMC3038201 DOI: 10.1002/cm.20473] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2010] [Accepted: 07/15/2010] [Indexed: 12/30/2022]
Abstract
Actin is a protein abundant in many cell types. Decades of investigations have provided evidence that it has many functions in living cells. The diverse morphology and dynamics of actin structures adapted to versatile cellular functions is established by a large repertoire of actin-binding proteins. The proper interactions with these proteins assume effective molecular adaptations from actin, in which its conformational transitions play essential role. This review attempts to summarise our current knowledge regarding the coupling between the conformational states of actin and its biological function.
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Affiliation(s)
- Gábor Hild
- Department of Biophysics, University of Pécs, Faculty of Medicine, Pécs, Szigeti str. 12, H-7624, Hungary
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11
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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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12
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Böhl M, Tietze S, Sokoll A, Madathil S, Pfennig F, Apostolakis J, Fahmy K, Gutzeit HO. Flavonoids affect actin functions in cytoplasm and nucleus. Biophys J 2007; 93:2767-80. [PMID: 17573428 PMCID: PMC1989700 DOI: 10.1529/biophysj.107.107813] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Based on the identification of actin as a target protein for the flavonol quercetin, the binding affinities of quercetin and structurally related flavonoids were determined by flavonoid-dependent quenching of tryptophan fluorescence from actin. Irrespective of differences in the hydroxyl pattern, similar Kd values in the 20 microM range were observed for six flavonoids encompassing members of the flavonol, isoflavone, flavanone, and flavane group. The potential biological relevance of the flavonoid/actin interaction in the cytoplasm and the nucleus was addressed using an actin polymerization and a transcription assay, respectively. In contrast to the similar binding affinities, the flavonoids exert distinct and partially opposing biological effects: although flavonols inhibit actin functions, the structurally related flavane epigallocatechin promotes actin activity in both test systems. Infrared spectroscopic evidence reveals flavonoid-specific conformational changes in actin which may mediate the different biological effects. Docking studies provide models of flavonoid binding to the known small molecule-binding sites in actin. Among these, the mostly hydrophobic tetramethylrhodamine-binding site is a prime candidate for flavonoid binding and rationalizes the high efficiency of quenching of the two closely located fluorescent tryptophans. The experimental and theoretical data consistently indicate the importance of hydrophobic, rather than H-bond-mediated, actin-flavonoid interactions. Depending on the rigidity of the flavonoid structures, different functionally relevant conformational changes are evoked through an induced fit.
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Affiliation(s)
- Markus Böhl
- Institute of Zoology, Technical University Dresden, D-01062 Dresden, Germany
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13
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Ono S. Mechanism of depolymerization and severing of actin filaments and its significance in cytoskeletal dynamics. INTERNATIONAL REVIEW OF CYTOLOGY 2007; 258:1-82. [PMID: 17338919 DOI: 10.1016/s0074-7696(07)58001-0] [Citation(s) in RCA: 212] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The actin cytoskeleton is one of the major structural components of the cell. It often undergoes rapid reorganization and plays crucial roles in a number of dynamic cellular processes, including cell migration, cytokinesis, membrane trafficking, and morphogenesis. Actin monomers are polymerized into filaments under physiological conditions, but spontaneous depolymerization is too slow to maintain the fast actin filament dynamics observed in vivo. Gelsolin, actin-depolymerizing factor (ADF)/cofilin, and several other actin-severing/depolymerizing proteins can enhance disassembly of actin filaments and promote reorganization of the actin cytoskeleton. This review presents advances as well as a historical overview of studies on the biochemical activities and cellular functions of actin-severing/depolymerizing proteins.
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Affiliation(s)
- Shoichiro Ono
- Department of Pathology, Emory University, Atlanta, GA 30322, USA
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14
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Dedova IV, Nikolaeva OP, Safer D, De La Cruz EM, dos Remedios CG. Thymosin beta4 induces a conformational change in actin monomers. Biophys J 2005; 90:985-92. [PMID: 16272441 PMCID: PMC1367123 DOI: 10.1529/biophysj.105.063081] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Using fluorescence resonance energy transfer spectroscopy we demonstrate that thymosin beta(4) (tbeta(4)) binding induces spatial rearrangements within the small domain (subdomains 1 and 2) of actin monomers in solution. Tbeta(4) binding increases the distance between probes attached to Gln-41 and Cys-374 of actin by 2 A and decreases the distance between the purine base of bound ATP (epsilonATP) and Lys-61 by 1.9 A, whereas the distance between Cys-374 and Lys-61 is minimally affected. Distance determinations are consistent with tbeta(4) binding being coupled to a rotation of subdomain 2. By differential scanning calorimetry, tbeta(4) binding increases the cooperativity of ATP-actin monomer denaturation, consistent with conformational rearrangements in the tbeta(4)-actin complex. Changes in fluorescence resonance energy transfer are accompanied by marked reduction in solvent accessibility of the probe at Gln-41, suggesting it forms part of the binding interface. Tbeta(4) and cofilin compete for actin binding. Tbeta(4) concentrations that dissociate cofilin from actin do not dissociate the cofilin-DNase I-actin ternary complex, consistent with the DNase binding loop contributing to high-affinity tbeta(4)-binding. Our results favor a model where thymosin binding changes the average orientation of actin subdomain 2. The tbeta(4)-induced conformational change presumably accounts for the reduced rate of amide hydrogen exchange from actin monomers and may contribute to nucleotide-dependent, high affinity binding.
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Affiliation(s)
- Irina V Dedova
- Muscle Research Unit, Institute for Biomedical Research, University of Sydney, New South Wales, Australia
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15
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De La Cruz EM. Cofilin binding to muscle and non-muscle actin filaments: isoform-dependent cooperative interactions. J Mol Biol 2004; 346:557-64. [PMID: 15670604 DOI: 10.1016/j.jmb.2004.11.065] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2004] [Revised: 11/19/2004] [Accepted: 11/23/2004] [Indexed: 11/19/2022]
Abstract
I have monitored equilibrium binding of human cofilin to rabbit skeletal muscle (alpha) and human non-muscle (85% beta, 15% gamma) actin filaments from the quenching of pyrene actin fluorescence. Filament binding is cooperative and stoichiometric (i.e. one cofilin molecule per actin subunit) for both actin isoforms. The Hill coefficient for binding to betagamma-actin filaments (n(H)=3.5) is greater than for muscle actin (n(H)=2.3). Analysis of equilibrium binding using a nearest-neighbor cooperativity model indicates that the intrinsic affinities for binding to an isolated site are comparable (10-14 microM) for both filament isoforms but the cooperative free energy is greater for binding betagamma-actin filaments. The predicted cofilin cluster sizes and filament binding densities are small at concentrations of cofilin where efficient filament severing is observed, indicating that a few bound cofilin molecules are sufficient to destabilize the filament lattice and promote fragmentation. The analysis used in this study provides a framework for evaluating proton and ion linkage and effects of regulatory proteins on cofilin binding and severing of actin filaments.
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Affiliation(s)
- Enrique M De La Cruz
- Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA.
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16
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Rommelaere H, Waterschoot D, Neirynck K, Vandekerckhove J, Ampe C. A method for rapidly screening functionality of actin mutants and tagged actins. Biol Proced Online 2004; 6:235-249. [PMID: 15514698 PMCID: PMC524212 DOI: 10.1251/bpo94] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2004] [Revised: 09/23/2004] [Accepted: 10/01/2004] [Indexed: 11/26/2022] Open
Abstract
Recombinant production and biochemical analysis of actin mutants has been hampered by the fact that actin has an absolute requirement for the eukaryotic chaperone CCT to reach its native state. We therefore have developed a method to rapidly screen the folding capacity and functionality of actin variants, by combining in vitro expression of labelled actin with analysis on native gels, band shift assays or copolymerization tests. Additionally, we monitor, using immuno-fluorescence, incorporation of actin variants in cytoskeletal structures in transfected cells. We illustrate the method by two examples. In one we show that tagged versions of actin do not always behave native-like and in the other we study some of the molecular defects of three beta-actin mutants that have been associated with diseases.
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Affiliation(s)
- Heidi Rommelaere
- Flanders Interuniversity Institute for Biotechnology (VIB 09) and Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University. B-9000 Gent. Belgium
| | - Davy Waterschoot
- Flanders Interuniversity Institute for Biotechnology (VIB 09) and Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University. B-9000 Gent. Belgium
| | - Katrien Neirynck
- Flanders Interuniversity Institute for Biotechnology (VIB 09) and Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University. B-9000 Gent. Belgium
| | - Joël Vandekerckhove
- Flanders Interuniversity Institute for Biotechnology (VIB 09) and Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University. B-9000 Gent. Belgium
| | - Christophe Ampe
- Flanders Interuniversity Institute for Biotechnology (VIB 09) and Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University. B-9000 Gent. Belgium
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17
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Dedova IV, Nikolaeva OP, Mikhailova VV, dos Remedios CG, Levitsky DI. Two opposite effects of cofilin on the thermal unfolding of F-actin: a differential scanning calorimetric study. Biophys Chem 2004; 110:119-28. [PMID: 15223149 DOI: 10.1016/j.bpc.2004.01.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2003] [Revised: 01/24/2004] [Accepted: 01/27/2004] [Indexed: 11/25/2022]
Abstract
Differential scanning calorimetry was used to examine the effects of cofilin on the thermal unfolding of actin. Stoichiometric binding increases the thermal stability of both G- and F-actin but at sub-saturating concentrations cofilin destabilizes F-actin. At actin:cofilin molar ratios of 1.5-6 the peaks corresponding to stabilized (66-67 degrees C) and destabilized (56-57 degrees C) F-actin are observed simultaneously in the same thermogram. Destabilizing effects of sub-saturating cofilin are highly cooperative and are observed at actin:cofilin molar ratios as low as 100:1. These effects are abolished by the addition of phalloidin or aluminum fluoride. Conversely, at saturating concentrations, cofilin prevents the stabilizing effects of phalloidin and aluminum fluoride on the F-actin thermal unfolding. These results suggest that cofilin stabilizes those actin subunits to which it directly binds, but destabilizes F-actin with a high cooperativity in neighboring cofilin-free regions.
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Affiliation(s)
- Irina V Dedova
- Muscle Research Unit, Department of Anatomy and Histology, The University of Sydney, NSW 2006 Sydney, Australia
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18
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Galkin VE, Orlova A, VanLoock MS, Shvetsov A, Reisler E, Egelman EH. ADF/cofilin use an intrinsic mode of F-actin instability to disrupt actin filaments. ACTA ACUST UNITED AC 2003; 163:1057-66. [PMID: 14657234 PMCID: PMC2173606 DOI: 10.1083/jcb.200308144] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Proteins in the ADF/cofilin (AC) family are essential for rapid rearrangements of cellular actin structures. They have been shown to be active in both the severing and depolymerization of actin filaments in vitro, but the detailed mechanism of action is not known. Under in vitro conditions, subunits in the actin filament can treadmill; with the hydrolysis of ATP driving the addition of subunits at one end of the filament and loss of subunits from the opposite end. We have used electron microscopy and image analysis to show that AC molecules effectively disrupt one of the longitudinal contacts between protomers within one helical strand of F-actin. We show that in the absence of any AC proteins, this same longitudinal contact between actin protomers is disrupted at the depolymerizing (pointed) end of actin filaments but is prominent at the polymerizing (barbed) end. We suggest that AC proteins use an intrinsic mechanism of F-actin's internal instability to depolymerize/sever actin filaments in the cell.
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Affiliation(s)
- Vitold E Galkin
- Department of Biochemistry and Molecular Genetics, University of Virginia Health Sciences Center, Jordan Hall, Charlottesville, VA 22908-0733, USA
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dos Remedios CG, Chhabra D, Kekic M, Dedova IV, Tsubakihara M, Berry DA, Nosworthy NJ. Actin binding proteins: regulation of cytoskeletal microfilaments. Physiol Rev 2003; 83:433-73. [PMID: 12663865 DOI: 10.1152/physrev.00026.2002] [Citation(s) in RCA: 700] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The actin cytoskeleton is a complex structure that performs a wide range of cellular functions. In 2001, significant advances were made to our understanding of the structure and function of actin monomers. Many of these are likely to help us understand and distinguish between the structural models of actin microfilaments. In particular, 1) the structure of actin was resolved from crystals in the absence of cocrystallized actin binding proteins (ABPs), 2) the prokaryotic ancestral gene of actin was crystallized and its function as a bacterial cytoskeleton was revealed, and 3) the structure of the Arp2/3 complex was described for the first time. In this review we selected several ABPs (ADF/cofilin, profilin, gelsolin, thymosin beta4, DNase I, CapZ, tropomodulin, and Arp2/3) that regulate actin-driven assembly, i.e., movement that is independent of motor proteins. They were chosen because 1) they represent a family of related proteins, 2) they are widely distributed in nature, 3) an atomic structure (or at least a plausible model) is available for each of them, and 4) each is expressed in significant quantities in cells. These ABPs perform the following cellular functions: 1) they maintain the population of unassembled but assembly-ready actin monomers (profilin), 2) they regulate the state of polymerization of filaments (ADF/cofilin, profilin), 3) they bind to and block the growing ends of actin filaments (gelsolin), 4) they nucleate actin assembly (gelsolin, Arp2/3, cofilin), 5) they sever actin filaments (gelsolin, ADF/cofilin), 6) they bind to the sides of actin filaments (gelsolin, Arp2/3), and 7) they cross-link actin filaments (Arp2/3). Some of these ABPs are essential, whereas others may form regulatory ternary complexes. Some play crucial roles in human disorders, and for all of them, there are good reasons why investigations into their structures and functions should continue.
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Affiliation(s)
- C G dos Remedios
- Institute for Biomedical Research, Muscle Research Unit, Department of Anatomy and Histology, University of Sydney, Australia.
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Bobkov AA, Muhlrad A, Kokabi K, Vorobiev S, Almo SC, Reisler E. Structural effects of cofilin on longitudinal contacts in F-actin. J Mol Biol 2002; 323:739-50. [PMID: 12419261 DOI: 10.1016/s0022-2836(02)01008-2] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Structural effects of yeast cofilin on skeletal muscle and yeast actin were examined in solution. Cofilin binding to native actin was non-cooperative and saturated at a 1:1 molar ratio, with K(d)<or=0.05 microM for both CaATP-G-actin and F-actin. Cofilin binding enhanced the fluorescence of dansyl ethylenediamine (DED) attached to Gln41 on the DNase I binding loop of skeletal muscle F-actin and decreased the fluorescence of AEDANS at Cys41 on yeast Q41C/C374S mutant F-actin. However, cofilin had no effect on the spectral properties of DED or AEDANS on CaATP-G-actin. Fluorescence energy transfer (FRET) from tryptophan residues to DED at Gln41 on skeletal muscle actin and to AEDANS at Cys41 on yeast Q41C/C374S actin was decreased by cofilin binding to F- but not to G-actin. Cofilin inhibited strongly the rate of interprotomer disulfide cross-linking of Cys41 to Cys374 on yeast Q41C mutant F-actin. Binding of cofilin enhanced excimer formation between pyrene probes attached to Cys41 and Cys374 on Q41C F-actin. These results indicate that cofilin alters the interface between subdomains 1 and 2 and shifts the DNase I binding loop away from subdomain 1 of an adjacent actin protomer. Cofilin reduced FRET from tryptophan residues to 4-azido-2-nitrophenyl-putrescine (ANP) at Gln41 in skeletal muscle F-but not in G-actin. However, following the interprotomer cross-linking of Gln41 to Cys374 in F-actin by ANP, cofilin binding did not change FRET from the tryptophan residues to ANP. This suggests that cofilin binding and the conformational effect on F-actin are not coupled tightly. Overall, this study provides solution evidence for the weakening of longitudinal, subdomain 2/1 contacts in F-actin by cofilin.
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Affiliation(s)
- Andrey A Bobkov
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA.
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