Scaling of F-Actin Network Rheology to Probe Single Filament Elasticity and Dynamics

Gardel, M. L.; Shin, Jennifer Hyunjong; MacKintosh, F. C.; Mahadevan, L.; Matsudaira, PA; Weitz, D. A.

doi:10.1103/physrevlett.93.188102

Cited by 189 publications

(228 citation statements)

References 27 publications

Supporting

Mentioning

200

Contrasting

Unclassified

Order By: Relevance

“…In the absence of any ABPs, the elasticity of single actin filaments and their entangled solutions is purely entropic (32). In the presence of ABPs that lead to cross-linking, the elasticity of the resultant network of semiflexible filaments can also be entropic in origin (33,34).…”

Section: Discussionmentioning

confidence: 99%

Relating microstructure to rheology of a bundled and cross-linked F-actin networkin vitro

Shin

Gardel

Mahadevan

et al. 2004

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

Self Cite

190

175

View full text Add to dashboard Cite

The organization of individual actin filaments into higher-order structures is controlled by actin-binding proteins (ABPs). Although the biological significance of the ABPs is well documented, little is known about how bundling and cross-linking quantitatively affect the microstructure and mechanical properties of actin networks. Here we quantify the effect of the ABP scruin on actin networks by using imaging techniques, cosedimentation assays, multiparticle tracking, and bulk rheology. We show how the structure of the actin network is modified as the scruin concentration is varied, and we correlate these structural changes to variations in the resultant network elasticity.F -actin is one of the most important participants in maintaining the mechanical integrity of eukaryotic cells. In vivo, actin filaments rarely exist as isolated single filaments but instead associate into bundles or networks, in concert with Ͼ60 different actin binding proteins (ABPs), to influence cell shape, division, adhesion, and motility (1-4). The elastic modulus of cytoplasmic actin gels is estimated to be of order 100-1,000 Pa (5), and the gel must be able to sustain shear stresses of up to 1,000 Pa for proper cell functions (6). This large elasticity cannot result exclusively from a network of actin alone; in vitro, solutions of entangled actin filaments are weak elastic solids. For example, a solution of actin filaments at a concentration of 24 M has an elastic modulus of only 0.1 Pa and breaks under a shear stress of Ͻ0.1 Pa (7,8). Therefore, the properties of the actin cytoskeleton must be regulated predominantly by ABPs. Modest changes in the concentration of ABPs can significantly modify the structure of the network because they can both bundle and cross-link the actin filaments. These structural changes can lead to concomitant change in the mechanical properties, dramatically enhancing the mechanical rigidity (9-13). The changes in structure occur over a large range of length scales, ranging from a few nanometers, the size of an ABP, to several micrometers, the length of an individual actin filament. The dearth of techniques that probe the structure and properties over this range of length scales has limited our ability to determine the modifications caused by the ABPs and to identify their critical contributions. As a result, a quantitative understanding of how the changes in mechanical stiffness are correlated with structure remains elusive.In this study, we probe the changes in structure and mechanical properties of a F-actin network as a function of ABP concentration. We use electron microscopy (EM) to measure structural changes on the nanometer scale and confocal microscopy to measure structural changes on the micrometer scale. We exploit the technique of multiparticle tracking (MPT), by using small nonbinding particles to directly probe the variations in mesh size with changing ABP concentration, and compare the results with the analysis of images obtained with confocal microscopy. Moreover, we employ MPT to probe the loc...

show abstract

Section: Discussionmentioning

confidence: 99%

Relating microstructure to rheology of a bundled and cross-linked F-actin networkin vitro

Shin

Gardel

Mahadevan

et al. 2004

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

Self Cite

190

175

View full text Add to dashboard Cite

show abstract

“…1; this is in sharp contrast to F-actin networks formed with rigid cross-links, where G 0 increases significantly, varying as G 0 R 3 [13]. Moreover, the dissipation is significant as G 00 remains comparable to G 0 as the FLNa concentration is increased; this also contrasts sharply with rigidly crosslinked F-actin networks, where the relative magnitude of G 00 to G 0 decreases with increased R [12].…”

mentioning

confidence: 83%

“…However, the rheological properties of in vitro F-actin networks are quite different from those of cells: the magnitude of the elastic modulus typically underestimates that measured in cells, often by several orders of magnitude. In addition, unlike the linear behavior assumed for cells [1][2][3]10], the viscoelasticity of F-actin networks is linear only for very small deformations; like most semiflexible biopolymers [11], it rapidly becomes strongly nonlinear with increasing deformation [5,9,12,13]. One possible cause for this discrepancy is the fact that, in vivo, F-actin is cross-linked with a variety of actin-binding proteins (ABP's), which are essential in determining the elastic properties of the cytoskeleton.…”

mentioning

confidence: 99%

Stress-Dependent Elasticity of Composite Actin Networks as a Model for Cell Behavior

et al. 2006

Self Cite

View full text Add to dashboard Cite

“…1,2 Actin filament shows a variety of morphologies in cytoplasm, especially in conjunction with membrane. It has been considered that actin filaments form assembly together with structural proteins such as α-actinin, fimbrin and scruin.…”

Section: Introductionmentioning

confidence: 99%

Structural transition of actin filament in a cell-sized water droplet with a phospholipid membrane

Hase

Yoshikawa

2006

The Journal of Chemical Physics

View full text Add to dashboard Cite

Actin filament, F-actin, is a semiflexible polymer with a negative charge, and is one of the main constituents on cell membranes. To clarify the effect of cross-talk between a phospholipid membrane and actin filaments in cells, we conducted microscopic observations on the structural changes in actin filaments in a cell-sized (several tens of micrometers in diameter) water droplet coated with a phospholipid membrane such as phosphatidylserine (PS; negatively-charged head group) or phosphatidylethanolamine (PE; neutral head group) as a simple model of a living cell membrane. With PS, actin filaments are distributed uniformly in the water phase without adsorption onto the membrane surface between 2 and 6 mM Mg 2+ , while between 6 and 12 mM Mg 2+ , actin filaments are adsorbed onto the inner membrane surface. With PE, actin filaments are uniformly adsorbed onto the inner membrane surface between 2 and 12 mM Mg 2+ . With both PS and PE membranes, at Mg 2+ concentrations higher than 12 mM, thick bundles are formed in the bulk water droplet accompanied by the dissolution of actin filaments from the membrane surface. The attraction between actin filaments and membrane is attributable to an increase in the translational entropy of counterions accompanied by the adsorption of actin filaments onto the membrane surface. These results suggest that a microscopic water droplet coated with phospholipid can serve as an easy-to-handle model of cell membranes.

show abstract

Scaling of F-Actin Network Rheology to Probe Single Filament Elasticity and Dynamics

Cited by 189 publications

References 27 publications

Relating microstructure to rheology of a bundled and cross-linked F-actin networkin vitro

Relating microstructure to rheology of a bundled and cross-linked F-actin networkin vitro

Stress-Dependent Elasticity of Composite Actin Networks as a Model for Cell Behavior

Structural transition of actin filament in a cell-sized water droplet with a phospholipid membrane

Contact Info

Product

Resources

About