Cooperative Effects of Cofilin (ADF) on Actin Structure Suggest Allosteric Mechanism of Cofilin Function

Bobkov, Andrey A.; Mühlrád, András; Pavlov, Dmitry; Kokabi, Kaveh; Yilmaz, Atilgan; Reisler, Emil

doi:10.1016/j.jmb.2005.11.072

Cited by 79 publications

(95 citation statements)

References 37 publications

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“…Different sizes of clusters have been suggested, depending on the methods used to generate the data (9,14). The direct observation of cooperative binding in this study showed that the on-rate of cofilin binding is elevated in the vicinity (65 nm) of long (>0.4 s), nonconjunctive binding at 10 nM cofilin, which corresponds to ca.…”

Section: Discussionmentioning

confidence: 83%

“…Biochemical analyses of the kinetics of cofilin binding to actin filaments suggest that the conformational changes induced by cofilin binding affect further binding of cofilin to the actin filament (8). Differential scanning calorimetric study of cofilin-actin complexes indicates that the allosteric destabilization of the actin filament by cofilin binding is propagated over a long distance (128 subunits) along the actin filament (9,10). Electron microscopic studies show that the actin filaments are either fully decorated with cofilin or bare in the same micrograph (4,7), suggesting that the binding of cofilin to the actin filament is highly cooperative.…”

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confidence: 99%

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Single-molecule imaging and kinetic analysis of cooperative cofilin–actin filament interactions

Hayakawa

Sakakibara

Sokabe

et al. 2014

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

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The actin filament-severing protein actin depolymerizing factor (ADF)/cofilin is ubiquitously distributed among eukaryotes and modulates actin dynamics. The cooperative binding of cofilin to actin filaments is crucial for the concentration-dependent unconventional modulation of actin dynamics by cofilin. In this study, the kinetic parameters associated with the cooperative binding of cofilin to actin filaments were directly evaluated using a singlemolecule imaging technique. The on-rate of cofilin binding to the actin filament was estimated to be 0.06 μM −1 ·s −1 when the cofilin concentration was in the range of 30 nM to 1 μM. A dwell time histogram of cofilin bindings decays exponentially to give an offrate of 0.6 s −1 . During long-term cofilin binding events (>0.4 s), additional cofilin bindings were observed in the vicinity of the initial binding site. The on-rate for these events was 2.3-fold higher than that for noncontiguous bindings. Super-high-resolution image analysis of the cofilin binding location showed that the on-rate enhancement occurred within 65 nm of the original binding event. By contrast, the cofilin off-rate was not affected by the presence of prebound cofilin. Neither decreasing the temperature nor increasing the viscosity of the test solution altered the onrates, off-rates, or the cooperative parameter (ω) of the binding. These results indicate that cofilin binding enhances additional cofilin binding in the vicinity of the initial binding site (ca. 24 subunits), but it does not affect the off-rate, which could be the molecular mechanism of the cooperative binding of cofilin to actin filaments.cooperativity | fluctuations | non-nearest-neighbor | non-Arrhenius | superresolution C ofilin (1, 2) induces actin disassembly by severing actin filaments at concentrations below the equilibrium dissociation constant, whereas it facilitates actin nucleation at higher concentrations (3). This concentration-dependent modulation of cofilin activity is presumably due to its cooperative binding to actin filaments (4). In the wider sense, understanding the cooperative interactions between proteins is essential for understanding the regulation of enzymes (5, 6). However, the dynamic protein interactions that endow proteins with cooperativity in solution have not been directly imaged and analyzed. In this study, we focused on the molecular mechanism underlying the cooperative binding of cofilin to actin filaments using high-resolution optical microscopy.There is a general agreement that the binding of cofilin to actin filaments changes the conformation of the actin filaments. Electron microscopic observations reveal that the binding of cofilin to actin filaments increases their twist (4, 7). Biochemical analyses of the kinetics of cofilin binding to actin filaments suggest that the conformational changes induced by cofilin binding affect further binding of cofilin to the actin filament (8). Differential scanning calorimetric study of cofilin-actin complexes indicates that the allosteric destabilization of ...

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Section: Discussionmentioning

confidence: 83%

mentioning

confidence: 99%

Single-molecule imaging and kinetic analysis of cooperative cofilin–actin filament interactions

Hayakawa

Sakakibara

Sokabe

et al. 2014

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

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“…14,[20][21][22]33 Cofilin binding leads to the reorganization of subdomain 2, 9-11 and disrupts (longitudinal and lateral) filament subunit contacts. [11][12][13]34,35 It is, therefore, likely that the overall reduction in filament stiffness associated with cofilin binding arises from changes in the filament elasticity (E) and geometry (I) achieved by modulating the strength and redistribution of the intra-and intersubunit bonds.…”

Section: Resultsmentioning

confidence: 99%

Cofilin Increases the Bending Flexibility of Actin Filaments: Implications for Severing and Cell Mechanics

McCullough

Blanchoin

Martiel

et al. 2008

Journal of Molecular Biology

203

254

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We determined the flexural (bending) rigidities of actin and cofilactin filaments from a cosine correlation function analysis of their thermally driven, two-dimensional fluctuations in shape. The persistence length of actin filaments is 9.8 µm, corresponding to a flexural rigidity of 0.040 pN µm 2 . Cofilin binding lowers the persistence length ∼5-fold to a value of 2.2 µm and the filament flexural rigidity to 0.0091 pN µm 2 . That cofilin-decorated filaments are more flexible than native filaments despite an increased mass indicates that cofilin binding weakens and redistributes stabilizing subunit interactions of filaments. We favor a mechanism in which the increased flexibility of cofilin-decorated filaments results from the linked dissociation of filament-stabilizing ions and reorganization of actin subdomain 2 and as a consequence promotes severing due to a mechanical asymmetry. Knowledge of the effects of cofilin on actin filament bending mechanics, together with our previous analysis of torsional stiffness, provide a quantitative measure of the mechanical changes in actin filaments associated with cofilin binding, and suggest that the overall mechanical and forceproducing properties of cells can be modulated by cofilin activity.

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“…Filaments with bound cofilin have altered twist (8, 9) and are more compliant in both bending and twisting than bare filaments (10-13). It has been suggested that deformations in filament shape promote fragmentation at or near regions of topological and mechanical discontinuities, such as boundaries between bare and cofilin-decorated segments along partially decorated filaments (5,12,(14)(15)(16)(17)(18).Cations modulate actin filament structure and mechanical properties (19) and cofilin dissociates filament-associated cations (20), leading us to hypothesize that cation-binding interactions regulate filament severing by cofilin. Cations bind filaments at two discrete and specific sites positioned between adjacent subunits along the long-pitch helix of the filament (19, 21).…”

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Site-specific cation release drives actin filament severing by vertebrate cofilin

Kang

Bradley

Cao

et al. 2014

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

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Actin polymerization powers the directed motility of eukaryotic cells. Sustained motility requires rapid filament turnover and subunit recycling. The essential regulatory protein cofilin accelerates network remodeling by severing actin filaments and increasing the concentration of ends available for elongation and subunit exchange. Although cofilin effects on actin filament assembly dynamics have been extensively studied, the molecular mechanism of cofilin-induced filament severing is not understood. Here we demonstrate that actin filament severing by vertebrate cofilin is driven by the linked dissociation of a single cation that controls filament structure and mechanical properties. Vertebrate cofilin only weakly severs Saccharomyces cerevisiae actin filaments lacking this "stiffness cation" unless a stiffness cation-binding site is engineered into the actin molecule. Moreover, vertebrate cofilin rescues the viability of a S. cerevisiae cofilin deletion mutant only when the stiffness cation site is simultaneously introduced into actin, demonstrating that filament severing is the essential function of cofilin in cells. This work reveals that site-specific interactions with cations serve a key regulatory function in actin filament fragmentation and dynamics.cytoskeleton | persistence length | mechanics | electron cryomicroscopy A ctin polymerization powers the directed motility of eukaryotic cells and some pathogenic bacteria (1-3). Actin assembly also plays critical roles in endocytosis, cytokinesis, and establishment of cell polarity. Sustained motility requires filament disassembly and subunit recycling. The essential regulatory protein cofilin severs actin filaments (4-6), which accelerates actin network reorganization by increasing the concentration of filament ends available for subunit exchange (7).Cofilin binding alters the structure and mechanical properties of filaments, which effectively introduces local "defects" that compromise filament integrity and promote severing (5). Filaments with bound cofilin have altered twist (8, 9) and are more compliant in both bending and twisting than bare filaments (10-13). It has been suggested that deformations in filament shape promote fragmentation at or near regions of topological and mechanical discontinuities, such as boundaries between bare and cofilin-decorated segments along partially decorated filaments (5,12,(14)(15)(16)(17)(18).Cations modulate actin filament structure and mechanical properties (19) and cofilin dissociates filament-associated cations (20), leading us to hypothesize that cation-binding interactions regulate filament severing by cofilin. Cations bind filaments at two discrete and specific sites positioned between adjacent subunits along the long-pitch helix of the filament (19, 21). These cation binding sites are referred to as "polymerization" and "stiffness" sites based on their roles in filament assembly and mechanics, respectively. These discrete sites bind both monovalent and divalent cations with a range of affinities (low millimolar f...

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Cooperative Effects of Cofilin (ADF) on Actin Structure Suggest Allosteric Mechanism of Cofilin Function

Cited by 79 publications

References 37 publications

Single-molecule imaging and kinetic analysis of cooperative cofilin–actin filament interactions

Single-molecule imaging and kinetic analysis of cooperative cofilin–actin filament interactions

Cofilin Increases the Bending Flexibility of Actin Filaments: Implications for Severing and Cell Mechanics

Site-specific cation release drives actin filament severing by vertebrate cofilin

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