Energetics and Kinetics of Cooperative Cofilin–Actin Filament Interactions

Cao, Wenxiang; Goodarzi, Jim P.; Cruz, Enrique M. De La

doi:10.1016/j.jmb.2006.06.019

Cited by 98 publications

(165 citation statements)

References 36 publications

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“…36 Ions have long been known to stabilize the polymer form of actin through polysteric linkage (i.e. salt polymerizes actin monomers).…”

Section: Discussionmentioning

confidence: 99%

“…interactions that bridge filament subunits). In the case of cofilin, the stabilizing ion-actin interactions are replaced with net interactions that are non-or de-stabilizing 36 .…”

Section: Discussionmentioning

confidence: 99%

“…Recombinant human non-muscle cofilin-1 was purified as described. 4,14,36 Cofilin-decorated actin filaments (2-10 µM) were made by adding cofilin at a concentration ≥10 times the value needed to reach half maximum saturation of actin. 4 Equilibrated samples were rapidly diluted five-to ten-fold into KMI 6.6 buffer supplemented with 30 µg mL −1 glucose, 100 µg mL −1 catalase and 10 mM glucose directly on a 70% ethanol-cleaned glass microscope slide.…”

Section: Protein and Sample Preparationmentioning

confidence: 99%

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

McCullough

Blanchoin

Martiel

et al. 2008

Journal of Molecular Biology

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203

247

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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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“…36 Ions have long been known to stabilize the polymer form of actin through polysteric linkage (i.e. salt polymerizes actin monomers).…”

Section: Discussionmentioning

confidence: 99%

“…interactions that bridge filament subunits). In the case of cofilin, the stabilizing ion-actin interactions are replaced with net interactions that are non-or de-stabilizing 36 .…”

Section: Discussionmentioning

confidence: 99%

Section: Protein and Sample Preparationmentioning

confidence: 99%

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

McCullough

Blanchoin

Martiel

et al. 2008

Journal of Molecular Biology

Self Cite

203

247

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“…Thus, cofilin occupancy compromises the geometry and cation coordination of the predicted stiffness site. The overlapping binding sites and allosteric interactions give rise to strong thermodynamic coupling between cofilin binding and cation release (20).…”

Section: Significancementioning

confidence: 99%

“…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).…”

mentioning

confidence: 99%

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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Modeling capping protein FRAP and CALI experiments reveals in vivo regulation of actin dynamics

et al. 2010

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To gain insights on cellular mechanisms regulating actin polymerization, we used the Virtual Cell to model FRAP and chromophore assisted laser inactivation (CALI) experiments on EGFPcapping protein (EGFP-CP). Modeling the FRAP kinetics demonstrated that the in vivo rate for the dissociation of CP from actin filaments is much faster (~0.1 s −1 ) than that measured in vitro (0.01-0.0004 s −1 ). The CALI simulation revealed that in order to induce sustainable changes in cell morphology after CP inactivation, the cells should exhibit anti-capping ability. We included the VASP protein as the anti-capping agent in the modeling scheme. The model predicts that VASP affinity for barbed ends has a cooperative dependence on the concentration of VASPbarbed end complexes. This dependence produces a positive feedback that stabilizes the complexes and allows sustained growth at clustered filament tips. We analyzed the range of laser intensities that are sufficient to induce changes in cell morphology. This analysis demonstrates that FRAP experiments with EGFP-CP can be performed safely without changes in cell morphology, because, the intensity of the photobleaching beam is not high enough to produce the critical concentration of free barbed ends that will induce filament growth before diffusional replacement of EGFP-CP occurs.

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Energetics and Kinetics of Cooperative Cofilin–Actin Filament Interactions

Cited by 98 publications

References 36 publications

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

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

Modeling capping protein FRAP and CALI experiments reveals in vivo regulation of actin dynamics

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