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Side-binding proteins modulate actin filament dynamics.

Crevenna AH, Arciniega M, Dupont A, Mizuno N, Kowalska K, Lange OF, Wedlich-Söldner R, Lamb DC - Elife (2015)

Bottom Line: In this study, using direct visualization of single actin filament elongation, we show that actin polymerization kinetics at both filament ends are strongly influenced by the binding of proteins to the lateral filament surface.We also show that the pointed-end has a non-elongating state that dominates the observed filament kinetic asymmetry.Tuning elongation kinetics by exploiting the malleability of the filament structure may be a ubiquitous mechanism to generate a rich variety of cellular actin dynamics.

View Article: PubMed Central - PubMed

Affiliation: Physical Chemistry, Department of Chemistry and Center for Nanoscience, Ludwig-Maximilians-Universität München, Munich, Germany.

ABSTRACT
Actin filament dynamics govern many key physiological processes from cell motility to tissue morphogenesis. A central feature of actin dynamics is the capacity of filaments to polymerize and depolymerize at their ends in response to cellular conditions. It is currently thought that filament kinetics can be described by a single rate constant for each end. In this study, using direct visualization of single actin filament elongation, we show that actin polymerization kinetics at both filament ends are strongly influenced by the binding of proteins to the lateral filament surface. We also show that the pointed-end has a non-elongating state that dominates the observed filament kinetic asymmetry. Estimates of flexibility as well as effects on fragmentation and growth suggest that the observed kinetic diversity arises from structural alteration. Tuning elongation kinetics by exploiting the malleability of the filament structure may be a ubiquitous mechanism to generate a rich variety of cellular actin dynamics.

No MeSH data available.


Related in: MedlinePlus

The distribution of the time to the first elongation pause at 300 nM free actin concentration.The distribution of the observed time to the first pause for depolymerizing pointed-ends at the lowest tether density (blue bar), at medium to high tether density (pooled data, red bars), or predicted using a model for light-induced dimerization (gray bars, see ‘Materials and methods’).DOI:http://dx.doi.org/10.7554/eLife.04599.015
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fig4s2: The distribution of the time to the first elongation pause at 300 nM free actin concentration.The distribution of the observed time to the first pause for depolymerizing pointed-ends at the lowest tether density (blue bar), at medium to high tether density (pooled data, red bars), or predicted using a model for light-induced dimerization (gray bars, see ‘Materials and methods’).DOI:http://dx.doi.org/10.7554/eLife.04599.015

Mentions: The low density used for these experiments and the observed pauses on freely swiveling actin filaments (pointed-end only) rules out surface effects (Kuhn and Pollard, 2005) as the determining cause for the pauses at the ends. Another possible source of pauses is light-induced photo-dimerization. From the work of Niedermayer et al. (2012), it is possible to quantitatively predict the accumulated fraction of filaments where depolymerization has been paused as a consequence of exposure to light (Figure 4—figure supplement 2). In contrast with this prediction, we observed all swiveling filament pointed-ends, under depolymerizing conditions, to be in a kinetically inactive state at the beginning of image acquisition (N = 40, Figure 4—figure supplement 2). Only in the presence of a medium to high density of tethering proteins did we observe depolyermization of pointed-ends (12 of 55, Figure 4—figure supplement 2).


Side-binding proteins modulate actin filament dynamics.

Crevenna AH, Arciniega M, Dupont A, Mizuno N, Kowalska K, Lange OF, Wedlich-Söldner R, Lamb DC - Elife (2015)

The distribution of the time to the first elongation pause at 300 nM free actin concentration.The distribution of the observed time to the first pause for depolymerizing pointed-ends at the lowest tether density (blue bar), at medium to high tether density (pooled data, red bars), or predicted using a model for light-induced dimerization (gray bars, see ‘Materials and methods’).DOI:http://dx.doi.org/10.7554/eLife.04599.015
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4375888&req=5

fig4s2: The distribution of the time to the first elongation pause at 300 nM free actin concentration.The distribution of the observed time to the first pause for depolymerizing pointed-ends at the lowest tether density (blue bar), at medium to high tether density (pooled data, red bars), or predicted using a model for light-induced dimerization (gray bars, see ‘Materials and methods’).DOI:http://dx.doi.org/10.7554/eLife.04599.015
Mentions: The low density used for these experiments and the observed pauses on freely swiveling actin filaments (pointed-end only) rules out surface effects (Kuhn and Pollard, 2005) as the determining cause for the pauses at the ends. Another possible source of pauses is light-induced photo-dimerization. From the work of Niedermayer et al. (2012), it is possible to quantitatively predict the accumulated fraction of filaments where depolymerization has been paused as a consequence of exposure to light (Figure 4—figure supplement 2). In contrast with this prediction, we observed all swiveling filament pointed-ends, under depolymerizing conditions, to be in a kinetically inactive state at the beginning of image acquisition (N = 40, Figure 4—figure supplement 2). Only in the presence of a medium to high density of tethering proteins did we observe depolyermization of pointed-ends (12 of 55, Figure 4—figure supplement 2).

Bottom Line: In this study, using direct visualization of single actin filament elongation, we show that actin polymerization kinetics at both filament ends are strongly influenced by the binding of proteins to the lateral filament surface.We also show that the pointed-end has a non-elongating state that dominates the observed filament kinetic asymmetry.Tuning elongation kinetics by exploiting the malleability of the filament structure may be a ubiquitous mechanism to generate a rich variety of cellular actin dynamics.

View Article: PubMed Central - PubMed

Affiliation: Physical Chemistry, Department of Chemistry and Center for Nanoscience, Ludwig-Maximilians-Universität München, Munich, Germany.

ABSTRACT
Actin filament dynamics govern many key physiological processes from cell motility to tissue morphogenesis. A central feature of actin dynamics is the capacity of filaments to polymerize and depolymerize at their ends in response to cellular conditions. It is currently thought that filament kinetics can be described by a single rate constant for each end. In this study, using direct visualization of single actin filament elongation, we show that actin polymerization kinetics at both filament ends are strongly influenced by the binding of proteins to the lateral filament surface. We also show that the pointed-end has a non-elongating state that dominates the observed filament kinetic asymmetry. Estimates of flexibility as well as effects on fragmentation and growth suggest that the observed kinetic diversity arises from structural alteration. Tuning elongation kinetics by exploiting the malleability of the filament structure may be a ubiquitous mechanism to generate a rich variety of cellular actin dynamics.

No MeSH data available.


Related in: MedlinePlus