Force Generation by Cytoskeletal Filament End-Tracking Proteins

Dickinson, Richard B.; Caro, Luzelena; Purich, Daniel L.

doi:10.1529/biophysj.104.045211

Cited by 121 publications

(146 citation statements)

References 63 publications

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“…15 These latter experiments directly validated the kinetic model for assembly proposed seven years earlier by Dickinson et al 11 It is now widely accepted that insertional polymerization by NPFs is how actin filaments are assembled within cell protrusions at the leading edge of a crawling tissue cell, if not every else as well in vivo. Hence, chemical engineering modeling and analysis revealed the essential mechanism of actin-filament assembly in vivo, which is widely relevant to a multitude of cellular functions, and helped turn the field to the actual mechanism long before direct experimental confirmation.…”

Section: ■ the Value Of Chemical Engineering "Thinking"supporting

confidence: 54%

Chemical Engineering Principles in the Field of Cell Mechanics

Dickinson

Lele

2015

Ind. Eng. Chem. Res.

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The field of cell mechanics involves problems at the interface of mechanics, molecular transport, biochemical kinetics, thermodynamics, and cell biology. We argue that chemical engineering training is uniquely suited for fruitful research in the field by discussing three examples in the research area. Cell mechanics is already well-represented in many chemical engineering departments and promises to be a vibrant subarea in the profession.

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Section: ■ the Value Of Chemical Engineering "Thinking"supporting

confidence: 54%

Chemical Engineering Principles in the Field of Cell Mechanics

Dickinson

Lele

2015

Ind. Eng. Chem. Res.

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“…At any time, one end-tracking module from one VASP tetramer is tethered to the filament barbed end region while the GAB domains of three other VASP tetramers are available for monomer delivery. However, the free energy of ATP hydrolyses appears not to be required for release of the end-tracking clamp, thereby acting as a passive actoclampin motor (23,31), although this finding does not rule out a potential role of ATP hydrolysis in facilitating VASP-mediated filament assembly from PFN-actin at concentrations found in vivo. The units in the lattice are symmetric and overlapping, so that each VASP tetramer can tether or deliver actin monomers to four neighboring actin filaments.…”

Section: Discussionmentioning

confidence: 86%

“…It is derived from the "actoclampin" model of actin filament end-tracking proteins (22)(23)(24), in which processive and tethered elongation is achieved Significance Ena/VASP proteins are tetramers that drive the processive elongation of actin filaments. Because Ena/VASP proteins are implicated in motility, embryogenesis, and cancer, it is mandatory to understand their molecular mechanism.…”

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confidence: 99%

Distinct VASP tetramers synergize in the processive elongation of individual actin filaments from clustered arrays

Brühmann

Ushakov

Winterhoff

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Ena/VASP proteins act as actin polymerases that drive the processive elongation of filament barbed ends in membrane protrusions or at the surface of bacterial pathogens. Based on previous analyses of fast and slow elongating VASP proteins by in vitro total internal reflection fluorescence microscopy (TIRFM) and kinetic and thermodynamic measurements, we established a kinetic model of Ena/VASP-mediated actin filament elongation. At steady state, it entails that tetrameric VASP uses one of its arms to processively track growing filament barbed ends while three G-actin-binding sites (GABs) on other arms are available to recruit and deliver monomers to the filament tip, suggesting that VASP operates as a single tetramer in solution or when clustered on a surface, albeit processivity and resistance toward capping protein (CP) differ dramatically between both conditions. Here, we tested the model by variation of the oligomerization state and by increase of the number of GABs on individual polypeptide chains. In excellent agreement with model predictions, we show that in solution the rates of filament elongation directly correlate with the number of free GABs. Strikingly, however, irrespective of the oligomerization state or presence of additional GABs, filament elongation on a surface invariably proceeded with the same rate as with the VASP tetramer, demonstrating that adjacent VASP molecules synergize in the elongation of a single filament. Additionally, we reveal that actin ATP hydrolysis is not required for VASP-mediated filament assembly. Finally, we show evidence for the requirement of VASP to form tetramers and provide an amended model of processive VASPmediated actin assembly in clustered arrays.actin | Ena/VASP | TIRF | cluster | formin

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“…The ''actoclampin'' model (4,5) proposes that the adhesive bonds are never broken, and instead that the bacterium advances through the discrete, ATP-hydrolysis-driven advancement of ''end-clamping'' proteins that bind the bacterium to the elongating ends of actin filaments. In this case, the biochemical rates of hydrolysis and filament growth reactions determine the rate of movement.…”

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confidence: 99%

Adhesion controls bacterial actin polymerization-based movement

Soo

Theriot²

2005

Proc. Natl. Acad. Sci. U.S.A.

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As part of its infectious life cycle, the bacterial pathogen Listeria monocytogenes propels itself through the host-cell cytoplasm by triggering the polymerization of host-cell actin near the bacterial surface, harnessing the activity of several cytoskeletal proteins used during actin-based cell crawling. To distinguish among several classes of biophysical models of actin-based bacterial movement, we used a high-throughput tracking technique to record the movement of many individual bacteria during temperature shifts. The speed of each bacterium varied strongly with temperature, closely following the Arrhenius rate law. Among bacteria, the prefactor A of the Arrhenius dependence unexpectedly varied exponentially with apparent activation energy, E a, over a wide range (8 -21 kcal͞mol), reminiscent of the ''rate compensation effect'' of classical catalytic reactions. Average E a were increased for mutant bacteria deficient in binding Ena͞VASP proteins and bacteria moving in diluted extract. These two effects were additive. The observed temperature and rate compensation effects are consistent with a class of simple kinetic models in which the bacterium advances through the thermally driven, cooperative breakage of groups of adhesive bonds on its surface. The estimated number of coupled adhesive bonds N on the bacterial surface varies between 10 and 40 bonds. In contrast to other models, this model correctly predicts an experimentally observed negative correlation between bacterial speed and actin gel density. The idea that speed depends on adhesion, rather than polymerization, suggests several alternative mechanisms by which known cytoskeletal regulatory proteins could control cellular movement.ActA ͉ Listeria ͉ motility M any types of eukaryotic cells, including immune system lymphocytes, neurons, and cancer cells, use the forces generated by polymerizing actin filament networks to change shape and to move. In the actin polymerization-based movement of intracellular bacterial pathogens such as Listeria monocytogenes, individual bacteria harness the same cytoskeletal machinery to move within the host-cell cytoplasm (1).Several classes of biophysical models have been proposed to explain the mechanism of actin polymerization-based movement. The models differ in which steps in the motility cycle are proposed to control the rate of bacterial movement.The ''tethered elastic Brownian ratchet'' model (2) proposes that a large force generated by the network of polymerizing actin filaments in the ''comet tail'' behind the bacterium continuously induces the breakage of individual adhesive bonds between the bacterium and the surrounding actin gel, pushing the bacterium forward. In this model, bacteria move at the speed at which propulsive and adhesive forces are balanced; this equilibrium velocity depends strongly on the specific properties of actin polymerization and adhesion. The related ''elastic gel '' model (3) proposes that the elastic expansion of the actin gel behind the bacterium also contributes to propulsion, ''s...

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Force Generation by Cytoskeletal Filament End-Tracking Proteins

Cited by 121 publications

References 63 publications

Chemical Engineering Principles in the Field of Cell Mechanics

Chemical Engineering Principles in the Field of Cell Mechanics

Distinct VASP tetramers synergize in the processive elongation of individual actin filaments from clustered arrays

Adhesion controls bacterial actin polymerization-based movement

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