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Reversibility and Viscoelastic Properties of Micropillar Supported and Oriented Magnesium Bundled F-Actin.

Maier T, Haraszti T - PLoS ONE (2015)

Bottom Line: Understanding the bundling kinetics of actin filaments is important in the formation of various cytoskeletal structures, such as filopodia and stress fibers.Microparticles attached to the filaments allowed the measurement of thermal motion, and we found that bundling takes place at lower concentrations than previously found in 3-dimensional actin gels, i.e. actin filaments formed bundles in the presence of 5-12 mM of magnesium chloride in a time-dependent manner.The filaments also displayed long term stability for up to hours after removing the magnesium ions from the buffer, which suggests that there is an extensive hysteresis between cation induced crosslinking and decrosslinking.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Intelligent Systems, Department of New Materials and Biosystems, Heisenberg str. 3, D-70569 Stuttgart, Germany; University of Heidelberg, Institute of Physical Chemistry, Department of Biophysical Chemistry, Im Neuenheimer Feld 253, D-69120 Heidelberg, Germany.

ABSTRACT
Filamentous actin is one of the most important cytoskeletal elements. Not only is it responsible for the elastic properties of many cell types, but it also plays a vital role in cellular adhesion and motility. Understanding the bundling kinetics of actin filaments is important in the formation of various cytoskeletal structures, such as filopodia and stress fibers. Utilizing a unique pillar-structured microfluidic device, we investigated the time dependence of bundling kinetics of pillar supported free-standing actin filaments. Microparticles attached to the filaments allowed the measurement of thermal motion, and we found that bundling takes place at lower concentrations than previously found in 3-dimensional actin gels, i.e. actin filaments formed bundles in the presence of 5-12 mM of magnesium chloride in a time-dependent manner. The filaments also displayed long term stability for up to hours after removing the magnesium ions from the buffer, which suggests that there is an extensive hysteresis between cation induced crosslinking and decrosslinking.

No MeSH data available.


Related in: MedlinePlus

Apparent spring constants.ky perpendicular to the bundling axis, before bundling (red), after bundled by 10–12 mMMgCl2 ions (green) and 3 hours after rinsing with the ion removal buffer (blue). There are three clear cases when the stiffness of the bundle returned back or became less than the original value. In all other cases, the bundles remained stiffer than the initial value. (Semilogarithmic plot of 15 bead positions measured in 3 independent experiments. The errors are estimated from the Gaussian fit of the position distributions.)
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pone.0136432.g005: Apparent spring constants.ky perpendicular to the bundling axis, before bundling (red), after bundled by 10–12 mMMgCl2 ions (green) and 3 hours after rinsing with the ion removal buffer (blue). There are three clear cases when the stiffness of the bundle returned back or became less than the original value. In all other cases, the bundles remained stiffer than the initial value. (Semilogarithmic plot of 15 bead positions measured in 3 independent experiments. The errors are estimated from the Gaussian fit of the position distributions.)

Mentions: Fig 5 compares the ky values obtained using nonlinear fitting before bundling, after bundling and 3 hours after EDTA treatment. After washing the loosely bound Mg2+ ions away, the elasticity remains close to the values obtained after bundling in general, much higher than their initial values indicating that the bundling process was not reversed. In four cases however, ky returned or was even less than its value before the divalent cations were introduced (e.g. bead numbers 1, 12, 14, 15).


Reversibility and Viscoelastic Properties of Micropillar Supported and Oriented Magnesium Bundled F-Actin.

Maier T, Haraszti T - PLoS ONE (2015)

Apparent spring constants.ky perpendicular to the bundling axis, before bundling (red), after bundled by 10–12 mMMgCl2 ions (green) and 3 hours after rinsing with the ion removal buffer (blue). There are three clear cases when the stiffness of the bundle returned back or became less than the original value. In all other cases, the bundles remained stiffer than the initial value. (Semilogarithmic plot of 15 bead positions measured in 3 independent experiments. The errors are estimated from the Gaussian fit of the position distributions.)
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4556452&req=5

pone.0136432.g005: Apparent spring constants.ky perpendicular to the bundling axis, before bundling (red), after bundled by 10–12 mMMgCl2 ions (green) and 3 hours after rinsing with the ion removal buffer (blue). There are three clear cases when the stiffness of the bundle returned back or became less than the original value. In all other cases, the bundles remained stiffer than the initial value. (Semilogarithmic plot of 15 bead positions measured in 3 independent experiments. The errors are estimated from the Gaussian fit of the position distributions.)
Mentions: Fig 5 compares the ky values obtained using nonlinear fitting before bundling, after bundling and 3 hours after EDTA treatment. After washing the loosely bound Mg2+ ions away, the elasticity remains close to the values obtained after bundling in general, much higher than their initial values indicating that the bundling process was not reversed. In four cases however, ky returned or was even less than its value before the divalent cations were introduced (e.g. bead numbers 1, 12, 14, 15).

Bottom Line: Understanding the bundling kinetics of actin filaments is important in the formation of various cytoskeletal structures, such as filopodia and stress fibers.Microparticles attached to the filaments allowed the measurement of thermal motion, and we found that bundling takes place at lower concentrations than previously found in 3-dimensional actin gels, i.e. actin filaments formed bundles in the presence of 5-12 mM of magnesium chloride in a time-dependent manner.The filaments also displayed long term stability for up to hours after removing the magnesium ions from the buffer, which suggests that there is an extensive hysteresis between cation induced crosslinking and decrosslinking.

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Intelligent Systems, Department of New Materials and Biosystems, Heisenberg str. 3, D-70569 Stuttgart, Germany; University of Heidelberg, Institute of Physical Chemistry, Department of Biophysical Chemistry, Im Neuenheimer Feld 253, D-69120 Heidelberg, Germany.

ABSTRACT
Filamentous actin is one of the most important cytoskeletal elements. Not only is it responsible for the elastic properties of many cell types, but it also plays a vital role in cellular adhesion and motility. Understanding the bundling kinetics of actin filaments is important in the formation of various cytoskeletal structures, such as filopodia and stress fibers. Utilizing a unique pillar-structured microfluidic device, we investigated the time dependence of bundling kinetics of pillar supported free-standing actin filaments. Microparticles attached to the filaments allowed the measurement of thermal motion, and we found that bundling takes place at lower concentrations than previously found in 3-dimensional actin gels, i.e. actin filaments formed bundles in the presence of 5-12 mM of magnesium chloride in a time-dependent manner. The filaments also displayed long term stability for up to hours after removing the magnesium ions from the buffer, which suggests that there is an extensive hysteresis between cation induced crosslinking and decrosslinking.

No MeSH data available.


Related in: MedlinePlus