Dissertations / Theses on the topic 'Actin'
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Wang, Hui. "Structural studies of actin and actin-binding proteins." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/10916.
Full textHull, Richard Alan. "Actin and actin-binding proteins in higher plants." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279874.
Full textHeisler, David Bruce. "Role of Actin and Actin-binding Proteins in the Pathogenesis of Actin-targeting Bacterial Toxins." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1501519777175964.
Full textGholami, Azam. "Actin-based motility." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-72151.
Full textYeoh, Sharon I.-Wen. "Molecular interactions of human actin depolymerizing factor and cofilin with actin." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621255.
Full textGallinger, Julia. "WH2 domains and actin variants as multifunctional organizers of the actin cytoskeleton." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-161698.
Full textAktin ist als Bestandteil des Zytoskeletts eines der häufigsten Proteine in allen eukaryontischen Zellen. Eine genaue Regulation des Mikrofilamentsystems ist essentiell für Zellform, Zellmigration, Zellteilung und Membrandynamik. Ziel dieser Arbeit war (1) die Funktion von ausgewählten Aktin Bindedomänen in der Regulation des Aktin Zytoskeletts zu untersuchen und (2) die Funktion von Aktinvarianten zu verstehen. WH2 Domänen (WH2, Wiskott-Aldrich Syndrom Protein Homologie 2) sind kurze, konservierte Sequenzmotive (ca. 20 Aminosäuren), welche bevorzugt monomere Aktinmoleküle binden. Von besonderem Interesse waren Drosophila melanogaster Spire-WH2 und Mus musculus CAP2-WH2 Konstrukte. Das Protein Spire enthält vier WH2 Domänen (A-B-C-D) wohingegen CAP2 (Cyclase-assoziiertes Protein 2) nur eine WH2 Domäne besitzt. Diese WH2 Domänen können unter bestimmten Bedingungen (1) die Aktinpolymerisation stimulieren, (2) Aktinfilamente zerstückeln und (3) Aktinmonomere sequestrieren. Für die Nukleation der Aktinpolymerisation müssen mindestens zwei hintereinander angeordnete WH2 Domänen vorhanden sein und unterstöchiometrische Mengen an WH2 Domänen im Vergleich zur Aktinkonzentration vorliegen. Bei höheren WH2 Konzentrationen überwiegt die Sequestrierungsaktivität. Polymerisationsexperimente mit vorgefertigten SpireWH2-Aktin Komplexen bestätigen, dass diese Komplexe für die beobachtete Nukleation der Aktinpolymerisation verantwortlich sind. Im Gegensatz zu ungebundenen WH2 Domänen sind diese WH2-Aktin Komplexe selbst bei überstöchiometrischen WH2 Konzentrationen äußerst effiziente Nukleatoren. Alle untersuchten WH2 Konstrukte zeigen die bereits bekannte Bindung an G-Aktin, können aber auch vorgeformte Aktinfilamente sogar auseinanderreißen. Diese letztere und besonders auffällige Eigenschaft von WH2 Domänen wurde in fluorometrischen, viskometrischen und TIRF Experimenten nachgewiesen. Anscheinend ist die Affinität der WH2 Domänen zu Aktinmonomeren so stark, dass sie diese aus den Filamenten entfernen können und damit ganze Filamente und Filamentbündel zerstückeln. Für die Multifunktionalität der analysierten konservierten WH2 Domänen spricht zusammenfassend, dass sie neben der Aktinfilament Nukleation auch Filamente und Filamentbündel innerhalb von Sekunden fragmentieren können. Diese Daten wurden in Kollaboration mit den Gruppen Prof. Dr. Tad Holak und Prof. Dr. Robert Huber (Martinsried) durch kristallographische Versuchsansätze bestätigt. Neben den gut untersuchten konventionellen Aktinisoformen liegen oft auch Aktinvarianten vor, deren Funktion bisher unbekannt ist. Der Modellorganismus Dictyostelium discoideum besitzt mit seinen 41 Aktinen und Aktin-verwandten Proteinen ein umfangreiches „Aktinom”. Dazu gehört auch das Protein Filaktin (105 KDa), eine besonders außergewöhnliche Aktinvariante, die neben der konservierten Aktin-ähnlichen Domäne zusätzlich einen verlängerten N-Terminus mit einer definierten Domänenstruktur besitzt. Homologe von Filaktin wurden bisher in Dictyosteliden und einigen pathogenen Entamoeben identifiziert. Im zweiten Teil dieser Arbeit wurden die Funktionen von Filaktin in vivo und in vitro analysiert. Immunfluoreszenz Experimente zeigen, dass Filaktin mit konventionellem Aktin kolokalisiert und zusätzlich im Zytoplasma an Vesikel-artigen Strukturen zu sehen ist. Ein besonderes Merkmal von Filaktin ist zudem, dass es Teil von Stress-induzierten, intranukleären, stäbchenförmigen Proteinaggregaten, sogenannten „nuclear rods” ist. Für umfassende in vitro Experimente wurden rekombinante Filaktin Konstrukte mithilfe von Sf9 Insektenzellen exprimiert. Die Ergebnisse von fluorometrischen und viskometrischen Experimenten deuten darauf hin, dass die Aktin Domäne von Filaktin Aktinmonomere sequestrieren oder sogar Aktinfilamente verkappen kann. Gelfiltrationsexperimente ergaben zusätzlich, dass Filaktin wohl als Tetramer vorliegt. Außerdem verbinden Protein-Interaktionsstudien Filaktin mit dem ESCRT Signalweg (Endosomal Sorting Complexes Required for Transport), der unter anderem bei der Entstehung von multivesikulären Körpern wichtig ist. Zusammengefasst besteht das Mikrofilamentsystem vermutlich hauptsächlich aus konventionellen Aktinen, wohingegen spezielle Aktinvarianten andere zusätzliche und sogar Zytoskelett-unabhängige Funktionen übernehmen können.
Broderick, Michael James Francis. "The utrophin-actin interface." Thesis, University of Glasgow, 2005. http://theses.gla.ac.uk/30889/.
Full textMcGrath, James L. (James Lionel). "Actin dynamics in the cell cytoplasm and the role of actin associated proteins." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50446.
Full textSingh, Anish D. "Regulation and function of the non-muscle [beta]-actin and [gamma]-actin genes." Phd thesis, Department of Paediatrics and Child Health, Faculty of Medicine, 2004. http://hdl.handle.net/2123/11556.
Full textKruth, Karina Annette. "Effects of three deafness-causing gamma-actin mutations on actin structure and function." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/1475.
Full textHayot, Caroline. "Mise au point d'une stratégie pharmacologique originale pour l'obtention de composés anti-cancéreux anti-migratoires." Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210860.
Full textDans la première partie de notre travail, nous avons analysé les effets anti-angiogéniques et anti-migratoires des agents anti-tubuline. Nous avons confirmé que le Taxol® présentait une action anti-angiogénique à des concentrations non-cytotoxiques. Nous avons ensuite démontré que d’autres agents anti-tubuline exerçaient la même action que le Taxol®, et que cette action leur était spécifique. Nous avons montré que certains de ces agents étaient également capables de réduire la migration de lignées cellulaires tumorales, toujours à des concentrations non-cytotoxiques, et que cette action pouvait s’exercer via une affectation du cytosquelette d’actine.
Dans la deuxième partie du présent travail, nous avons démontré l’importance de la mise au point d’une approche pharmacologique originale permettant l’identification de composés à action anti-migratoire puisque l’outil utilisé par le U.S. National Cancer Institute pour le criblage de nouvelles molécules anti-cancéreuses ne permet pas de discerner l’activité anti-migratoire des molécules testées.
Enfin dans la troisième partie de ce travail, après avoir souligné la raison du choix de l’actine comme cible pour inhiber la migration cellulaire, nous avons développé une stratégie pharmacologique in vitro originale de découverte de composés anti-actine à activité anti-migratoire. Grâce à une approche divisée en plusieurs étapes, à savoir un essai de cytotoxicité, une étude de la dynamique de la polymérisation d’actine en tubes ou sur cellules entières, et des essais de migration bidimensionnelle sur cellules individuelles ou sur population cellulaire, nous avons montré d’une part que des molécules connues pour affecter le cytosquelette actinique étaient capables d’affecter la migration cellulaire, et d’autre part que la méthodologie que nous avons développée permettait bien l’identification de composés affectant l’actine et capables de réduire la migration de cellules tumorales. En conclusion, cette stratégie in vitro pourrait être utilisée dans l’identification de nouvelles molécules à activité anti-migratoire pour lutter contre le cancer.
Doctorat en sciences pharmaceutiques
info:eu-repo/semantics/nonPublished
Storz, Tobias-Alexander. "Statische und dynamische Lichtstreuung an Lösungen von Aktinfilamenten." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963434861.
Full textGlenz, Martin H. "Heterodimere F-actin capping proteine." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981289509.
Full textOsborn, Eric A. (Eric Alan) 1975. "Actin remodeling in motile cells." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28600.
Full textIncludes bibliographical references.
Non-muscle cell shape change and motility depend primarily on the dynamics and distributions of cytoplasmic actin. In cells, actin cycles between monomeric and polymeric phases tightly regulated by actin binding proteins that control cellular architecture and movement. Here, we characterize actin remodeling in shear stress stimulated endothelial cells and in actin networks reconstituted with purified proteins. Fluid shear stress stimulation induces endothelial cells to elongate and align in the direction of applied flow. Alignment requires 24 h of exposure to flow, but the cells respond within minutes to flow by diminishing their movements by 50%. Although movement slows, actin filament turnover times and the amount of polymerized actin in cells decreases, increasing actin filament remodeling in individual cells composing a confluent endothelial monolayer to levels used by disperse, non-confluent cells for rapid movement. Hours later, motility returns to pre-shear stress levels, but actin remodeling remains highly dynamic in many cells. We conclude that shear stress initiates a cytoplasmic actin remodeling response that is used to modify endothelial cell shape instead of bulk cell translocation. We determine the steady state dynamics of purified actin filament networks in the entangled state and after orthogonal cross-linking with filamins using a novel, non-perturbing fluorescence system. Human filamin A or Dictyosteliun discoidium filamin slow actin filament turnover by [approximately] 50% and recruit much of a significant population of actin oligomers that we measure are present in polymerized purified actin solutions into the immobile filament fraction. Surprisingly, these observations occur at very low stoichiometry to actin, approximately requiring only one
(cont.) filamin molecule bound per actin filament, similar to the amount required for actin filament gelation in vitro. Networks formed with filamin truncates localize this activity to the actin binding domain and reveal that dimerization and orthogonal cross-linking are not required for dynamic stabilization. Re-expression of filamin A with or without the actin binding domain in human melanoma cells that naturally lack this protein support the findings in purified actin networks. These results indicate that filamin cross-linking stabilizes filament dynamics by, slowing filament subunit cycling rates and by either decreasing spontaneous filament fragmentation or promoting filament annealing.
by Eric A. Osborn.
Ph.D.
McGrath, James L. (James Lionel). "Measuring actin dynamics in endothelium." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/38015.
Full textAhrens, S. "Extracellular actin in innate immunity." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1433762/.
Full textMarzook, Noorul Bishara. "Lights, Camera, Actin: Divergent roles of beta- and gamma-cytoplasmic actin in vaccinia virus infection." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/16859.
Full textFerrer, Jorge M. 1976. "Mapping the actin and actin binding proteins interactions : from micromechanics to single molecule force spectroscopy." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40950.
Full textIncludes bibliographical references.
Mechanical forces play an important role in cell morphology, orientation, migration, adhesion and can even induce apoptosis. The eukaryotic cell is equipped with a dynamic frame, known as the cytoskeleton, that provides the cell's structural integrity in order to sustain and react to such forces. Therefore, understanding the mechanical properties of the cytoskeleton is an important step towards building models describing cell behavior. Filamentous actin (F-actin), as one of the major constituents of the cytoskeleton, has been the target of extensive in vitro studies to determine its mechanical properties in bulk. However, there is still a lack in the understanding of how the molecular interactions between F-actin and the proteins that arrange these filaments into networks regulate the dynamic properties of the cytoskeleton Here we present a novel, single molecule assay to test the rupture force of a complex formed by an actin binding protein (ABP) linking two actin filaments. We readily demonstrate the adaptability of this assay by testing it with two different ABPs: filamin, a crosslinker, and a-actinin, a bundler. We measured rupture forces of 28-73 pN and 30-56 pN for filamin/actin and a-actinin/actin respectively, suggesting that the former is a slightly stronger interaction. Moreover, since no ABP unfolding events were observed at our force levels, our results suggest that ABP unbinding is a more relevant mechanism than unfolding for the temporal regulation of the mechanical properties of the actin cytoskeleton. In addition, we explore the micro-scale properties of F-actin networks reconstituted in vitro.
(cont.) Using imaging and microrheology techniques we characterized the effects of filament length and degree of crosslinking on the structural arrangement and mechanical properties of F-actin networks. We found that the mechanical properties of these networks are length-scale dependent. Also, when probed with active methods, the F-actin networks exhibited strain hardening followed by a gradual softening at forces -30 pN, in good agreement with the single molecule rupture force of 28-73 pN. Thus, with the combination of single molecule and network studies, we can expand the knowledge-base on the regulation and control of the cellular machinery starting from the molecular building blocks.
by Jorge M. Ferrer.
Ph.D.
Sofia, Denise Michela. "Characterization of profilin and actin depolymerizing factors expression and function in the testis." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:16-opus-76643.
Full textJeffries, T. E. "The use of pyrene-labelled actin to investigate the interaction between actin and other muscle proteins." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384441.
Full textWear, Martin Alexander. "Biochemical studies on gelsolin : actin complexes and experiments to form a minimal, defined-length actin filament." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/23253.
Full textMatthews, Jermey N. A. "Thermodynamics and relaxation during actin polymerization." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2346.
Full textThesis research directed by: Chemical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
Moniz, de Sa Mario. "The evolution of angiosperm actin genes." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/10062.
Full textNiedermayer, Thomas. "On the depolymerization of actin filaments." Phd thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2013/6360/.
Full textAktin ist eines der am häufigsten vorkommenden und am stärksten konservierten Proteine in eukaryotischen Zellen. Dieses globuläre Protein bildet lange Filamente, die zu einer großen Vielfalt von Netzwerken innerhalb des Zellskeletts führen. Die dynamische Reorganisation dieser Netzwerke, die entscheidend für Zellbewegung, Zelladhäsion, und Zellteilung ist, basiert auf der Polymerisation (dem Aufbau) und der Depolymerisation (dem Abbau) von Aktinfilamenten. Aktin bindet ATP, welches innerhalb des Filaments auf einer Zeitskala von einigen Minuten in ADP hydrolysiert wird. Da ADP-Aktin schneller vom Filamentende dissoziiert als ATP-Aktin, sollte ein Filament mit der Zeit instabiler werden. Neuere Experimente, in denen abrupte dynamische Änderungen während der Filamentdepolymerisation beobachtet wurden, deuten jedoch auf ein gegenteiliges Verhalten hin: Die Aktinfilamente werden mit der Zeit zunehmend stabiler. Mehrere Mechanismen für diese Stabilisierung wurden bereits vorgeschlagen, von strukturellen Übergängen des gesamten Filaments bis zu Wechselwirkungen der Filamentenden mit dem experimentellen Aufbau. Das zentrale Thema der vorliegenden Dissertation ist die Aufklärung der unerwarteten Unterbrechungen der Depolymerisation. Dies geschieht durch eine Kombination von experimentellen und theoretischen Untersuchungen. Mit Hilfe neuer Depolymerisationexperimente mit einzelnen Filamenten bestätigen wir zunächst, dass die Filamente plötzlich aufhören zu schrumpfen und bestimmen die Zeit, die von der Einleitung der Depolymerisation bis zum Auftreten der ersten Unterbrechung vergeht. Diese Zeit unterscheidet sich von Filament zu Filament und stellt eine stochastische Größe dar. Wir untersuchen daraufhin verschiedene hypothetische Mechanismen, welche die beobachteten Unterbrechungen verursachen könnten. Die Mechanismen können experimentell nicht direkt unterschieden werden, haben jedoch verschiedene Verteilungen für die Zeit bis zur ersten Unterbrechung zur Folge. Wir berechnen die jeweiligen Verteilungen, indem wir die zugrundeliegenden stochastischen Prozesse modellieren. Ein Vergleich mit der gemessenen Verteilung zeigt, dass der plötzliche Abbruch des Depolymerisationsprozesses weder auf eine Blockade der Enden, noch auf einen kollektiven strukturellen Übergang des gesamten Filaments zurückzuführen ist. An Stelle dessen postulieren wir einen lokalen Übergangsprozess, der an zufälligen Stellen innerhalb des Filaments auftritt. Die Kombination von weiteren experimentellen Ergebnissen und unserem theoretischen Ansatz bestätigt die Vorstellung eines lokalen Übergangsmechanismus und identifiziert den Übergang als die photo-induzierte Bildung eines Aktindimers innerhalb des Filaments. Nicht fluoreszenzmarkierte Aktinfilamente zeigen keine Unterbrechungen, woraus folgt, dass ältere Filamente in vivo durch die ATP-Hydrolyse destabilisiert werden. Die Destabilisierung zeigt sich durch die Beschleunigung der Depolymerisation vor der Unterbrechung. Im letzten Teil der vorliegenden Arbeit untersuchen wir diese Beschleunigung mit theoretischen Methoden, um auf den Mechanismus der ATP-Hydrolyse zu schließen. Wir zeigen, dass die Hydrolyserate von ATP innerhalb des Filaments konstant ist, was dem sogenannten zufälligen Hydrolysemechanismus entspricht und im Gegensatz zum sogenannten vektoriellen Mechanismus steht.
Thangavelu, Madan. "The actin gene family of tobacco." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335212.
Full textBegg, Carolyn E. "Studies of mouse actin genomic clones." Thesis, University of Glasgow, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280030.
Full textCarrel, Hyman A. (Hyman Andrew) 1979. "Giant vesicles compressed by actin polymerization." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/16646.
Full textIncludes bibliographical references (p. 45-46).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Actin polymerization plays a critical role in generating propulsive force to drive many types of cell motility. The discovery of actin based motility of the bacterial pathogen Listeria monocytogenes has lead to clearer understandings of the essential ingredients required for cell motility. The biophysical mechanisms by which these proteins generate forces is the subject of intense investigation. A novel system to study force generation by this polymerization engine is introduced by combining the well characterized mechanical properties of synthetic Giant Vesicles with the well understood biochemistry of actin polymerization. Giant Vesicles mimic the structural features of eukaryotic cell membranes. We find that Giant Vesicles coated with a protein that catalyzes actin polymerization form thick actin shells which produce a compressive force. The polymerization force directed at the membrane interface causes the membrane to rupture. In the resulting collapse we find that the shell thickens inward with a constant radial velocity and is characterized by radial lines of lipid and actin. We show that actin polymerization is the primary force driving the collapse.
by Hyman A. Carrel.
S.M.
Shin, Jennifer Hyunjong 1974. "Dynamics and statics of actin assemblies." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27043.
Full textIncludes bibliographical references (p. 95-101).
The conversion of chemical energy into mechanical forces that powers cell movements is a ubiquitous theme across biology. The acrosome reaction of Limulus sperm is a simple example of such a dynamical transformation where a 60 [mu]m-long crystalline bundle of actin filaments, tightly cross-linked by actin bundling protein scruin, straightens from a coiled conformation and extends from the cell in five seconds. This spring-like mechanism represents a third type of actin-based motility that is distinctly different from the better known polymerization or myosin-driven processes. To identify the basis and mechanism for this movement, we examine the possible sources of chemical and mechanical energy and show that the stored elastic energy alone is sufficient to drive the reaction. We also provide an estimate of the maximum force generated during the uncoiling by stalling the bundle using an agarose gel. Finally, we provide a simple mathematical model that rationalizes the dynamics of uncoiling. Motivated by the very stiff cross-linking in the bundle induced by scruin, we next turn to a model system of scruin mediated cross-linked actin networks where the elastic response is dominated by the properties of actin. While the biological significance of the actin cross-linking proteins is well documented, little is known about how bundling and cross-linking quantitatively affects the microstructure and mechanical properties of actin networks. We quantify the effect of scruin on actin networks using imaging techniques, co-sedimentation assays. multi-particle tracking (MPT), and bulk rheology and demonstrate how a simple entropic elasticity model for a semi-flexible polymer network explains the linear elastic regime of the actin-scruin network.
by Jennifer Hyunjong Shin.
Ph.D.
Lee, Hyungsuk. "Mechanical properties of F-actin network." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/50588.
Full textIncludes bibliographical references.
Cells sense, generate and respond to forces in their surroundings through cytoskeletal dynamics. Actin, the most abundant protein found in eukaryotic cells, is organized into various cytoskeletal structures that provide physical support for the cell and play important roles in numerous cellular processes. Assembly of F-actin into higher-order structures is regulated by over 100 actin binding proteins (ABPs). Although extensive measurements to estimate the mechanical properties of ABP/F-actin networks showed that they are nonlinear and viscoelastic, a full understanding of the origin of such fascinating behaviors is lacking. This thesis presents a multi-scale approach to identify the factors that determine the mechanical properties of F-actin networks from the macroscopic level to the single-molecule level. The mechanical properties of F-actin networks were probed by passive and active methods using optical tweezers. For the passive approach the thermal fluctuations of colloidal spheres are monitored to estimate the frequency-dependent complex shear modulus of an F-actin network. In the active approach, the response of an embedded microsphere to a driving force is tracked to obtain the strain-dependent viscoelasticity. The developed methods were applied to F-actin networks cross-linked with various ABPs such as filamin and a -actinin, with and without gelsolin to control filament length. Microstructures of those networks were also characterized in terms of filament length, mesh size, and degree of bundling.
(cont.) Comparison between cross-linked F-actin with two different length scales of actin filament suggested that network connectivity is another critical parameter in determining mechanical properties. To better understand how the cross-linking protein responds to an external force, a single molecule assay was used to measure the rupture force of a complex formed by an ABP filamin linking two actin filaments. Both force-induced unbinding and unfolding of filamin were observed at the critical force of 70 ± 23pN and 57 ± 19pN, respectively, although unbinding occurred more frequently. Similar pulling experiments were also performed on cross-linked F-actin networks and an abrupt transition was observed in the force trace indicating network rupture. The critical forces at transitions exhibited a similar loading-rate dependence to that observed for rupture forces in the single molecule measurements. Nonlinear behavior observed in strain-dependent microrheology was found to be irreversible. Combined results of molecular unbinding, network rupture, and irreversible network properties suggest that unbinding rather than unfolding is a dominant mechanism governing the mechanical properties of cross-linked F-actin networks. In addition, the mechanical behavior of F-actin networks subjected to an external prestress was investigated using a shear device. Visualization of sheared F-actin networks showed the structural evolution including mesh deformation, filament alignment, and network rupture.
(cont.) Measurement of mechanical properties as a function of external strain demonstrated that some regions exhibited strain-hardening while the others showed strain-softening. Aligned stretching of actin filaments observed at high strain seemed to play a role in strain-stiffening. By comparing the behaviors of an F-actin network cross-linked with wildtype and mutant FLNa, it was demonstrated how molecular structure of the ABP alters the mechanical behavior of F-actin network.
by Hyungsuk Lee.
Ph.D.
Robertson, Alec 1974. "Material properties of actin filament bundles." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/46628.
Full textIncludes bibliographical references (p. 119-127).
Actin is an ubiquitous structural protein fundamental to such biological processes as cell motility and muscle contraction. Our model system is the acrosomal process of the Limulus sperm which extends a 60 ýtm long actin bundle during reproduction. It is an example of a biological spring where the force of elongation derives from twist energy stored within the bundle during spermatogenesis. In addition to actin the acrosome comprises only one other protein: scruin, an actin-binding protein specific to Limulus that decorates and crosslinks actin filaments into a crystalline bundle. Our goal is to reconstitute the structure of the acrosome using these two proteins in order to further elucidate the role of scruin in actin bundle crosslinking.A multi-scale approach is presented wherein the bending rigidity of scruin bundles and their constituent filaments are probed individually, then inter-related by simple mechanical models. Material properties of filaments and bundles are measured using a combination of optical tweezers, electron and fluorescence microscopy. We find that scruin bundles reconstituted from acrosome fragments display an ordered structure, with a bending rigidity orders of magnitude higher than their individual filaments. Actin bundles formed by depletion exhibit similar behavior, revealing an intrinsic regime of coupled actin bundle formation. Bundle elastic moduli are eight orders of magnitude stiffer than reconstituted networks and an order of magnitude softer than the native acrosome, highlighting scruin's ability to dictate a wide range of material properties depending on the formation conditions.
by Alec P. Robertson.
Ph.D.
Brown, Jennifer. "Investigating the actin cytoskeleton in cancer." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7266/.
Full textLieleg, Oliver. "Model systems of the actin cortex." kostenfrei, 2008. http://mediatum2.ub.tum.de/doc/672641/672641.pdf.
Full textScoville, Damon Charles. "Filament dynamics and actin binding factors." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1693066541&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Full textHu, Xiaohua. "Actin polymerization dynamics at the leading edge." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/39940.
Full textPh. D.
Gallinger, Julia [Verfasser], and Michael [Akademischer Betreuer] Schleicher. "WH2 domains and actin variants as multifunctional organizers of the actin cytoskeleton / Julia Gallinger. Betreuer: Michael Schleicher." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://d-nb.info/1043906355/34.
Full textBuencamino, Raphael Hector Domingo. "Novel roles of actin binding proteins in Listeria monocytogenes actin-based motility revealed within a cellular context." Diss., Search in ProQuest Dissertations & Theses. UC Only, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3297798.
Full textUhde, Jörg. "Mikrorheometrie passiver und aktiver Aktinnetzwerke." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972234802.
Full textBaroni, Luciana. "Caracterização molecular da actina do Apicomplexa Neospora caninum." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/60/60135/tde-25022013-103829/.
Full textNeospora caninum is an Apicomplexan protozoan that infects, among a whole range of intermediate hosts, bovine where it is emerging as a relevant cause of reproductive problems and abortion in dairy and beef cattle. As obligatory intracellular organisms, parasites from Apicomplexa Phylum use their own active locomotion system to move and invade host cells. This mechanism is driven by the actin/myosin motor known as gliding motility, localized between the plasma and the inner membrane complex. Studies involving this locomotion and invasion system have been conducted mainly in Toxoplasma gondii and Plasmodium spp. To our knowledge there is no publication involving actin in N. caninum, so this work was outlined and involved the cloning and expression of the sequence NcAct201-310, initiating the characterization of actin of N. caninum (NcAct). The sequence NcAct was obtained from the Database ToxoDB, and a comparison of actins from Apicomplexa-related revealed total identity of NcAct with TgACT1 (100% identity). With other species, NcAct has higher identity/similarity with Eimeria tenella actin (97%/99%), followed by Plasmodium falciparum actin PfACT1 (93%/97%), Babesia bovis actin (86%/94%) and PfACT2 (80%/92%). When localized with the antibody anti-?-actin C4, NcAct is presented as two bands of 43 and 45 kDa in 1D acrylamide gel and as nine isoforms in 2D acrylamide gel. All these findings were confirmed by mass spectrometry (MS/MS). Moreover, NcAct localizes predominantly in the peripheric region of N. caninum tachyzoites. This distribution is altered after incubation of the tachyzoites with 5 ?M of jasplakinolide (JAS) or 2 ?M of cytochalasin D (CytD). Finally through fractionating assay of monomeric (actin-G) and filamentous (actin-F), we demonstrated that JAS is capable of increasing the quantity of actin-F in N. caninum tachyzoites.
Wang, Hong. "Regulation of actin polymerization by cell-matrix adhesion complexes : a biochemical study of the talin-vinculin complex Integrin-bound talin head inhibits actin filament barbed-end elongation Talin and vinculin combine their individual activities to trigger actin assembly The C-terminal domain of EFA6A interacts directly with F-actin and assembles F-actin bundles." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS132.
Full textTo migrate efficiently in different tissues, cells must sense and adapt to variations of the mechanical properties of their environment. In this adaptive process, focal adhesions (FAs) strengthen their link with the extracellular matrix and the actin cytoskeleton. The force-dependent association of the actin binding proteins talin and vinculin could reinforce actin anchoring to FAs by controlling actin assembly though an unknown mechanism. Previous studies showed that vinculin contains a single actin-binding domain (ABD) which binds to actin filaments, caps actin filament barbed-ends and nucleates actin filaments. Talin also contains three ABDs but their ability to regulate actin assembly was not known before this project. The global objective of this PhD project was to determine the precise mechanisms by which the force-dependent talin-vinculin complex controls actin assembly. In a first part of this PhD project, as a prerequisite to the study of the talin-vinculin complex, I finished the characterization of talin. I demonstrated that the N-terminal ABD1 of talin blocks the elongation of actin filament barbed ends observed in fluorescent microscopy (TIRFM), whereas ABD2 and ABD3 do not affect actin dynamics. In the second and main part of this project, I determined the activity of the talin-vinculin complex. Because force is required to trigger vinculin association to talin, and because both proteins are autoinhibited, it has so far been difficult to determine the ability of the talin-vinculin complex to regulate actin polymerization. Therefore, we first designed talin and vinculin mutants that associate constitutively into a stable complex. By combining fluorescence spectroscopy, binding assays and single filament observation in TIRF microscopy, we determined the activities of these mutants and their complex on actin dynamics. Our study first revealed that the three activities of vinculin are controlled by specific auto-inhibitory contacts. We also show that helix deletions along the rod domain of talin expose neighboring vinculin-binding sites, mimicking the mechanical stretching of talin. The binding of these talin and vinculin mutants forms a complex that nucleates filaments capped at their barbed ends. The characterization of a series of complexes, in which vinculin and talin are deleted from various ABDs, reveals the contribution of each protein in this mechanism. Altogether our data suggest a mechanism for the force-dependent reinforcement of actin anchoring in FAs
Badaoui, Magid. "Multi-scale analysis of the mechanics of branched actin material." Electronic Thesis or Diss., Université Paris Cité, 2023. http://www.theses.fr/2023UNIP7074.
Full textPolymerization of actin filaments against membranes can generate significant forces, leading to endocytosis in yeast or to the formation of lamellipodium protrusions at the leading edge of motiles cells like keratocytes. This polymerization is thermodynamically favorable, as the addition of a monomer is accompanied by a decrease in chemical potential. However, filament growth slows down when a stress opposes its growth, with a stall force of a few pN. While this picture is well established for a single filament, it is not clear how it translates to a network of hundreds of filaments like the lamellipodium. More generally, understanding the emergence of large-scale characteristics from molecular properties remains a major challenge in biology. Thus, the overall aim of this thesis is to understand the emergence of the mechanical properties of branched actin from a numerical, theoretical and statistical point of view. To achieve this, we rely on numerical simulations of large-scale networks in which macroscopic characteristics can be measured. In the first part of our work, we use stochastic simulations (Langevin dynamics) to create growing branched networks subjected to external mechanical stress, mimicking the resistance of the extracellular matrix. Specifically, we investigate on how stationary properties of the system are determined by both stall force and stress. For a network made of filaments with an infinite stall force, the growth velocity exhibits a maximum when the stress tends towards zero and then decreases as a power law of the stress. A mechanical theory of branched networks based on filaments entanglement agrees with this power law. The maximum value at low stress can be explained by the drag of the network, which becomes the main determining factor here. By studying more realistic filaments, we show that there is a stall force threshold above which movement is possible. This threshold is proportional to the external stress. Finally, to better understand the low-stress regime, we studied free-growing networks and showed that they self-adapt by slowing down and densifying. In the second part, we aim at quantify the information that can be obtained from statistics carried out on numerous simulations. More specifically, we seek to identify the combinations of parameters (e.g. actin stiffness, filament length) that most influence the observables of our branched system (e.g. density). To identify them, we apply tools from information theory to the statistics generated by our simulations, which have been repeated by applying small modifications to the parameters. Based on previous work on microtubule dynamics, we have calculated the associated Fisher information matrix (FIM), which quantifies the observable-parameter dependence. By assuming that each observable locally follows a normal distribution, and by a better use of simulation statistics, we were able to obtain a more efficient calculation of the FIM. Analysis of the eigenvectors and eigenvalues of the FIM provides a hierarchy of sensitivity modes in the parameter space, which can be interpreted geometrically as the direction in which network characteristics can be most influenced by the parameters. Thus, we characterize our branched system with its main sensitivity modes, corresponding to an effective dimension of our system. We find that this system has two effective dimensions, which has been confirmed using analytical models
Huber, Florian. "Emergent structure formation of the actin cytoskeleton." Doctoral thesis, Universitätsbibliothek Leipzig, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-86666.
Full textHsu, C. R. "Characterisation of a Salmonella actin-binding protein." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604683.
Full textBai, Limiao, and 白利苗. "In silico simulation of actin-based motility." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B46429116.
Full textSchnauß, Jörg. "Self-assembly effects of filamentous actin bundles." Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-179722.
Full textFörster, Florian. "Targeting the actin cytoskeleton with natural compounds." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-168914.
Full textMcAnulty, Ciaron. "Actin gene variability in different porcine breeds." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250527.
Full textMurtagh, Michael Stephen. "Electron microscopy of actin and thin filaments." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421969.
Full textGedge, Lucinda J. E. "Actin in the nuclei of mammalian cells." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400260.
Full textDrouin, Guy. "The evolution of actin genes in potato." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330216.
Full textFox, Helen Mary. "Toca-1 driven actin polymerisation at membranes." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/275610.
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