Biophysics of actin filament severing by cofilin

Elam, W. Austin; Kang, Hyeran; Cruz, Enrique M. De La

doi:10.1016/j.febslet.2013.01.062

Cited by 93 publications

(106 citation statements)

References 65 publications

Supporting

Mentioning

100

Contrasting

Order By: Relevance

“…A previous biochemical study implied that a small cluster of cofilin formed at low concentrations of cofilin (10-100 nM) and effectively severed actin filaments (8). This idea is supported by our observation of changes in actin filament fluorescence intensity caused by long-lasting cofilin binding, which presumably reflects conformational changes in actin filaments (35) that may lead to severing with additional cofilin binding.…”

Section: Discussionsupporting

confidence: 87%

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.

View full text Add to dashboard Cite

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 ...

show abstract

Section: Discussionsupporting

confidence: 87%

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.

View full text Add to dashboard Cite

show abstract

“…Alteration of WT yeast actin filament flexibility and severing by yeast cofilin must originate from E167-and stiffness cation-independent perturbations. However, the severing activities of both yeast and vertebrate cofilins correlate with the ability to alter filament mechanical properties (12), favoring a shared mechanical mechanism for severing (5,11,12,15,19,41). These differences among cofilin orthologs are presumably explained by their relatively low sequence identity (∼40%), which may afford yeast cofilin with additional or distinct (yeast) actin interactions from vertebrate cofilin (42).…”

Section: Significancementioning

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.

Self Cite

View full text Add to dashboard Cite

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...

show abstract

“…Estimates of the length over which cofilininduced conformational changes and cooperative binding interactions propagate along actin vary, ranging from N = 1-2 up to N > 100 subunits (3,5,(12)(13)(14)(15)(16)(17)(18)(19)(20). Equilibrium (3,6,12,21) and transient kinetic (12,14) binding data are well described by models invoking positive cooperativity between nearest neighbors (N = 1-2).…”

mentioning

confidence: 99%

The actin filament twist changes abruptly at boundaries between bare and cofilin-decorated segments

Huehn

Cao

Elam

et al. 2018

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

Cofilin/ADF proteins are actin-remodeling proteins, essential for actin disassembly in various cellular processes, including cell division, intracellular transport, and motility. Cofilins bind actin filaments cooperatively and sever them preferentially at boundaries between bare and cofilin-decorated (cofilactin) segments. The cooperative binding to actin has been proposed to originate from conformational changes that propagate allosterically from clusters of bound cofilin to bare actin segments. Estimates of the lengths over which these cooperative conformational changes propagate vary dramatically, ranging from 2 to >100 subunits. Here, we present a general, structure-based method for detecting from cryo-EM micrographs small variations in filament geometry (i.e. twist) with single subunit precision. How these variations correlate with regulatory protein occupancy reveals how far allosteric, conformational changes propagate along filaments. We used this method to determine the effects of cofilin on the actin filament twist. Our results indicate that cofilin-induced changes in filament twist propagate only 1-2 subunits from the boundary into the bare actin segment, independently of the boundary polarity (i.e. irrespective of whether or not the bare actin segment flanks the pointed or barbed end side of the boundary) and the pyrene fluorophore labeling of actin. These observations indicate that the filament twist changes abruptly at boundaries between bare and cofilin-decorated segments, thereby constraining mechanistic models of cooperative actin filament interactions and severing by cofilin. The methods presented here extend the capability of cryo-EM to analyze biologically relevant deviations from helical symmetry in actin as well as other classes of linear polymers.

show abstract

Biophysics of actin filament severing by cofilin

Cited by 93 publications

References 65 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

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

The actin filament twist changes abruptly at boundaries between bare and cofilin-decorated segments

Contact Info

Product

Resources

About