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You searched for subject:(Molecular clutch). Showing records 1 – 3 of 3 total matches.

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University of Oxford

1. Brown, Mostyn T. Control of the unidirectional motor in Rhodobacter sphaeroides.

Degree: PhD, 2009, University of Oxford

The control of the flagellar motor in Rhodobacter sphaeroides was investigated. Unlike most flagellar motors which are controlled by reversing the direction of rotation, the R. sphaeroides motor is controlled via a stop-start mechanism. Advanced optical microscopy was employed alongside genetic, biochemical, and behavioural techniques. High-resolution measurements of rotating beads on flagellar stubs revealed that the R. sphaeroides motor is similar to its E. coli counterpart, rotating counterclockwise at comparable torques/speeds (1,300 pNnm/rad at stall torque), and exhibiting transient step changes in speed. The mean stop duration, mean stop frequency (number of stops per s), and run bias (fraction of time spent rotating) of wild-type at steady-state were 0.66 ± 1.01 s, 0.31 ± 0.19 s-1, and 0.80 ± 0.20, respectively. Manipulating signal inputs to the motor genetically, or by exposing cells to chemotactic stimuli revealed that (i) without chemotactic stimulation the motor rotates continuously, (ii) phosphorylated CheYs are required to stop the motor, and (iii) the chemotaxis system cannot control the speed of rotation of the motor (termed chemokinesis) as previously reported. Complementation studies revealed that CheY3, CheY4, and CheY5 are functionally equivalent. The copy numbers per cell of important CheYs were found to vary greatly under the conditions tested (<1,000, ~3,000, ~60,000 for CheY3, CheY4, and CheY6 respectively). To determine how CheY-P binding causes the motor to stop, external force (viscous flow or optical tweezers) was applied to chemotactically stopped motors. CheY-P binding might either cause the torque-generating units to disengage from the rotor, analogous to a clutch, or trigger the rotor to jam, analogous to a brake. The rotor resisted re-orientation during a chemotactic stop implying that the motor was held in a locked state. The value of torque resisting forward motion (keeping it locked) was estimated to be 2-3 x stall torque (2,500-4,000 pNnm/rad). Furthermore beads attached to flagellar stubs stop at fixed angles for several seconds, showing no large-scale Brownian motion. Step analysis revealed that these stop events occur at 27-28 discrete angles around the motor, which most likely reflect the periodicity of the rotor (i.e. copies of FliG). This represents the first experimental resolution of steps in the rotation of a wild-type bacterial flagellar motor with a full complement of torque-generating units.

Subjects/Keywords: 579; Molecular biophysics (biochemistry); rhodobacter; flagellar motor; flagellum; clutch; brake; chemotaxis

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APA (6th Edition):

Brown, M. T. (2009). Control of the unidirectional motor in Rhodobacter sphaeroides. (Doctoral Dissertation). University of Oxford. Retrieved from http://ora.ox.ac.uk/objects/uuid:1e9aa2bb-0e16-45df-9164-fd859a724157 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504318

Chicago Manual of Style (16th Edition):

Brown, Mostyn T. “Control of the unidirectional motor in Rhodobacter sphaeroides.” 2009. Doctoral Dissertation, University of Oxford. Accessed August 10, 2020. http://ora.ox.ac.uk/objects/uuid:1e9aa2bb-0e16-45df-9164-fd859a724157 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504318.

MLA Handbook (7th Edition):

Brown, Mostyn T. “Control of the unidirectional motor in Rhodobacter sphaeroides.” 2009. Web. 10 Aug 2020.

Vancouver:

Brown MT. Control of the unidirectional motor in Rhodobacter sphaeroides. [Internet] [Doctoral dissertation]. University of Oxford; 2009. [cited 2020 Aug 10]. Available from: http://ora.ox.ac.uk/objects/uuid:1e9aa2bb-0e16-45df-9164-fd859a724157 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504318.

Council of Science Editors:

Brown MT. Control of the unidirectional motor in Rhodobacter sphaeroides. [Doctoral Dissertation]. University of Oxford; 2009. Available from: http://ora.ox.ac.uk/objects/uuid:1e9aa2bb-0e16-45df-9164-fd859a724157 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504318


University of Minnesota

2. Chan, Clarence Elvin. Cellular adhesion dynamics: investigation of molecular clutch attachment and force transmission.

Degree: PhD, Biomedical Engineering, 2008, University of Minnesota

As the major structural element of the cell, the cytoskeleton plays a vital role in response and transmission of forces in both extracellular and intracellular environments. For instance, in cell motility, the cell utilizes a host of proteins to physically link F-actin to the extracellular substrate, allowing the cell to exert traction forces as well as probe the mechanics of its local environment. During mitosis, the cell constructs a mitotic spindle, using microtubules and kinetochores to exert forces that segregate sister chromatids. Ultimately, understanding how cells build these robust molecular machines for unique tasks could one day lead to therapeutics that treat disease causing dysfunctions in these vital cellular processes. In order to explore how molecular clutches work in concert with the cytoskeleton to exert forces and maintain attachment under load, we developed a mechano-chemical cellular adhesion dynamics framework to simulate these processes. In the case of cellular motility, we find that a "motor-clutch" mechanism exhibits substrate-stiffness sensitive dynamics. On soft substrates, motor-clutch motility exhibits "load-and-fail" dynamics that lead to higher rates of retrograde flow and lower traction force transmission compared to stiff substrates. We confirm these predictions experimentally using embryonic chick forebrain neurons (ECFNs) plated on compliant polyacrylamide gels (PAGs) demonstrating that a motor clutch system could be the basis of cellular mechanosensing. We also use cellular adhesion dynamics to explore kinetochore-microtubule attachment during mitosis to identify what properties might be important in maintaining attachment during mitosis. We show that molecular clutch microtubule-lattice diffusion is important for relieving clutch stresses, prolonging bond life-times and minimizing detachment forces. Furthermore, molecular clutches that preferentially associate with interdimer interfaces, rather than with intradimer interfaces, promote robust kinetochore attachment by preventing the more distal, attachment-promoting linkers from becoming nonproductive. These findings help further our understanding of the mechanochemical basis of kinetochore attachment and mitosis, a process essential throughout development.

Subjects/Keywords: Cellular adhesion dynamics; Focal adhesions; Integrins; Kinetochores; Molecular clutch; Biomedical Engineering

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APA (6th Edition):

Chan, C. E. (2008). Cellular adhesion dynamics: investigation of molecular clutch attachment and force transmission. (Doctoral Dissertation). University of Minnesota. Retrieved from http://purl.umn.edu/58039

Chicago Manual of Style (16th Edition):

Chan, Clarence Elvin. “Cellular adhesion dynamics: investigation of molecular clutch attachment and force transmission.” 2008. Doctoral Dissertation, University of Minnesota. Accessed August 10, 2020. http://purl.umn.edu/58039.

MLA Handbook (7th Edition):

Chan, Clarence Elvin. “Cellular adhesion dynamics: investigation of molecular clutch attachment and force transmission.” 2008. Web. 10 Aug 2020.

Vancouver:

Chan CE. Cellular adhesion dynamics: investigation of molecular clutch attachment and force transmission. [Internet] [Doctoral dissertation]. University of Minnesota; 2008. [cited 2020 Aug 10]. Available from: http://purl.umn.edu/58039.

Council of Science Editors:

Chan CE. Cellular adhesion dynamics: investigation of molecular clutch attachment and force transmission. [Doctoral Dissertation]. University of Minnesota; 2008. Available from: http://purl.umn.edu/58039

3. Dos Santos Carvalho, Steve Francois. Morpho-functional impact of Vangl2 on hippocampus development : Impact morpho-fonctionnel de Vangl2 sur le développement de l’hippocampe.

Degree: Docteur es, Neurosciences, 2016, Bordeaux

La Polarité Cellulaire Planaire (PCP) est une voie de signalisation originellement identifiée chez les invertébrés pour son rôle dans l’établissement d’une asymétrie cellulaire perpendiculaire à l’axe apico‐basal. Elle définit une polarité dans le plan d’un épithélium et coordonne cette polarité dans tout l'épithélium. L'activation de la voie PCP conduit à une réorganisation ducyto squelette en passant par une modulation des zones d'adhésion, régulant ainsi la forme et les mouvements des cellules. La voie de signalisation de la PCP est conservée tout au long de l'évolution jusqu'au mammifères, et contrôle la morphogénèse de divers tissus dont les tissus épithéliaux et mésenchymateux, ainsi que pour les tissues cardiaques, osseux, pulmonaire ou encore rénaux, mais aussi le système nerveux pour n'en citer que quelques‐uns.Afin d'identifier le rôle de vangl2, un des gènes centraux de la PCP, dans la mise en place de la circuiterie hippocampale, nous avons créé un modèle murin où vangl2 est supprimé de façon conditionnelle (cKO) dans le télencéphale à des stades précoces de l’embryogénèse. J’ai d'abord montré que Vangl2 est enrichi dans les neurones immatures de la zone sous granulaire du DG, ainsi que dans l’arborisation des neurites (axones et dendrites) des cellules granulaires (CG) du gyrus denté (DG) de l’hippocampe. Ainsi, Vangl2 est enrichi dans le stratum lucidum (sl), une région dense en contacts synaptiques entre le DG et le CA3. Dans cette région a lieu une synapse très particulière entre l'axone des CG, la fibre moussue (Mf) qui forme des boutons géants (MfB) et les excroissances épineuse (TE) issues de la partie proximale des dendrites apicaux. L'analyse structurale et ultra structurale de ces épines démontre que l'élargissement et la complexification de la synapse MfB/TE est bloquée dans nos mutants, alors que les zones actives (PSD) des épines sont présentes, mais réorganisées. De façon intéressante,dans une zone plus distale des dendrites des neurones du CA3 (sl), les épines sont, elles, plus grosses, suggérant un remodelage complexe du réseau en l'absence de vangl2. Enfin, j’ai pu montrer que ces défauts morphologiques étaient corrélés à des problèmes de mémoire complexe (mémoire déclarative) qui dépendent de l’hippocampe mais aussi du cortex. Cette étude montre pour la première fois l’importance du signal PCP dans maturation in vivo d’un circuit hippocampique spécifique ainsi que ces conséquences cognitives. D'autres résultats in vitro montrent que la suppression de vangl2 augmente la vitesse de déplacement des cônes de croissance sur des substrats de N‐cadhérine. J’ai utilisé la microscopie en super résolution spt‐PALM‐TIRF pour montrer que cette augmentation de croissance est inversement proportionnelle à la vitesse du flux rétrograde d’actine. Des expériences de FRAP permettent de suggérer que les molécules de N‐cadhérine engagées dans des interactions hémophiliques (adhésion) est plus importante dans les mutants vangl2 Je propose que Vangl2 contrôle le recyclage et la stabilité des protéines… Advisors/Committee Members: Montcouquiol, Mireille (thesis director).

Subjects/Keywords: Polarité Cellulaire Planaire; Vangl2; N-cadhérine; Cône de croissance; Croissance neuronale; Adhésion; Flux rétrograde d’actine; Embrayage Moléculaire; Hippocampe; Gyrus Denté; CA3; Fibre Moussue; Bouton Fibre Moussue; Excroissance épineuse; PSD; Mémoire de Travail; Mémoire déclarative; Planar Cell Polarity; Vangl2; N-cadherin; Growth cone; Neuronal outgrowth; Adhesion; Actin Retrograde Flow; Molecular Clutch; Hippocampus; Dentate Gyrus; CA3; Mossy Fiber; Mossy Fiber Bouton; Thorny Excrescence; PSD; Working Memory; Declarative Memory

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Dos Santos Carvalho, S. F. (2016). Morpho-functional impact of Vangl2 on hippocampus development : Impact morpho-fonctionnel de Vangl2 sur le développement de l’hippocampe. (Doctoral Dissertation). Bordeaux. Retrieved from http://www.theses.fr/2016BORD0276

Chicago Manual of Style (16th Edition):

Dos Santos Carvalho, Steve Francois. “Morpho-functional impact of Vangl2 on hippocampus development : Impact morpho-fonctionnel de Vangl2 sur le développement de l’hippocampe.” 2016. Doctoral Dissertation, Bordeaux. Accessed August 10, 2020. http://www.theses.fr/2016BORD0276.

MLA Handbook (7th Edition):

Dos Santos Carvalho, Steve Francois. “Morpho-functional impact of Vangl2 on hippocampus development : Impact morpho-fonctionnel de Vangl2 sur le développement de l’hippocampe.” 2016. Web. 10 Aug 2020.

Vancouver:

Dos Santos Carvalho SF. Morpho-functional impact of Vangl2 on hippocampus development : Impact morpho-fonctionnel de Vangl2 sur le développement de l’hippocampe. [Internet] [Doctoral dissertation]. Bordeaux; 2016. [cited 2020 Aug 10]. Available from: http://www.theses.fr/2016BORD0276.

Council of Science Editors:

Dos Santos Carvalho SF. Morpho-functional impact of Vangl2 on hippocampus development : Impact morpho-fonctionnel de Vangl2 sur le développement de l’hippocampe. [Doctoral Dissertation]. Bordeaux; 2016. Available from: http://www.theses.fr/2016BORD0276

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