Structural Effects of Cofilin on Longitudinal Contacts in F-actin

Bobkov, Andrey A.; Mühlrád, András; Kokabi, Kaveh; Vorobiev, S.M.; Almo, Steven C.; Reisler, Emil

doi:10.1016/s0022-2836(02)01008-2

Cited by 66 publications

(113 citation statements)

References 46 publications

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“…On cofilin decoration of F-actin, the longitudinal contacts between subdomains 1 and 2 of adjacent actin monomers are destabilized (Bobkov et al, 2002;Galkin et al, 2003). Similar loss of longitudinal contacts have been observed at the pointed ends of undecorated actin filaments, suggesting that cofilin binding maintains a preexisting destabilized conformation of the actin filament (Galkin et al, 2003).…”

Section: Introductionmentioning

confidence: 60%

A Genetic Dissection of Aip1p's Interactions Leads to a Model for Aip1p-Cofilin Cooperative Activities

Clark

Teply

Haarer

et al. 2006

MBoC

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Actin interacting protein 1 (Aip1p) and cofilin cooperate to disassemble actin filaments in vitro and are thought to promote rapid turnover of actin networks in vivo. The precise method by which Aip1p participates in these activities has not been defined, although severing and barbed-end capping of actin filaments have been proposed. To better describe the mechanisms and biological consequences of Aip1p activities, we undertook an extensive mutagenesis of AIP1 aimed at disrupting and mapping Aip1p interactions. Site-directed mutagenesis suggested that Aip1p has two actin binding sites, the primary actin binding site lies on the edge of its N-terminal ␤-propeller and a secondary actin binding site lies in a comparable location on its C-terminal ␤-propeller. Random mutagenesis followed by screening for separation of function mutants led to the identification of several mutants specifically defective for interacting with cofilin but still able to interact with actin. These mutants suggested that cofilin binds across the cleft between the two propeller domains, leaving the actin binding sites exposed and flanking the cofilin binding site. Biochemical, genetic, and cell biological analyses confirmed that the actin binding-and cofilin binding-specific mutants are functionally defective, whereas the genetic analyses further suggested a role for Aip1p in an early, internalization step of endocytosis. A complementary, unbiased molecular modeling approach was used to derive putative structures for the Aip1p-cofilin complex, the most stable of which is completely consistent with the mutagenesis data. We theorize that Aip1p-severing activity may involve simultaneous binding to two actin subunits with cofilin wedged between the two actin binding sites of the N-and C-terminal propeller domains.

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Section: Introductionmentioning

confidence: 60%

A Genetic Dissection of Aip1p's Interactions Leads to a Model for Aip1p-Cofilin Cooperative Activities

Clark

Teply

Haarer

et al. 2006

MBoC

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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%

“…4) and twisting 14 mechanics (Table 1) indicates that cofilin binding disrupts stabilizing contacts between filament subunits and/or enhances their conformational dynamics, both of which have been documented extensively for the cofilin-actin filament interaction. [9][10][11][12][13][14]35 We favor a mechanism in which the cofilin-linked changes in filament bending and twisting mechanics (Table 1) are mediated largely through the reorganization of actin subdomain 2, since the conformation of this region influences the subunit longitudinal contacts and filament flexibility, 33 and is modulated by cofilin binding. [9][10][11] Molecular dynamics simulations 22 indicate that filament lateral contacts are also dependent on the actin subdomain 2 conformation.…”

Section: Discussionmentioning

confidence: 99%

“…[9][10][11][12][13][14]35 We favor a mechanism in which the cofilin-linked changes in filament bending and twisting mechanics (Table 1) are mediated largely through the reorganization of actin subdomain 2, since the conformation of this region influences the subunit longitudinal contacts and filament flexibility, 33 and is modulated by cofilin binding. [9][10][11] Molecular dynamics simulations 22 indicate that filament lateral contacts are also dependent on the actin subdomain 2 conformation. Therefore, the weakening of longitudinal and lateral filament contacts with cofilin binding [10][11][12][13][14] could be mediated through interaction with actin subdomain 2.…”

Section: Discussionmentioning

confidence: 99%

“…Structural and biochemical analysis demonstrates that cofilin alters the filament subunit tilt 7 and increases the filament helical twist, 8 increases the disorder of actin subdomain 2 9 and the DNase-binding loop, 10 disrupts the subdomain 1 to 2 interface of adjacent subunits along the long pitch helix, 11 and weakens stabilizing lateral contacts. 12,13 Cofilin binding lowers the actin filament torsional stiffness, so cofilin-decorated filaments twist more easily than native filaments.…”

Section: Introductionmentioning

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

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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Severing of F-actin by yeast cofilin is pH-independent

Pavlov

Mühlrád

Cooper

et al. 2006

Cell Motil. Cytoskeleton

Self Cite

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Cofilin plays an important role in actin turnover in cells by severing actin filaments and accelerating their depolymerization. The role of pH in the severing by cofilin was examined using fluorescence microscopy. To facilitate the imaging of actin filaments and to avoid the use of rhodamine phalloidin, which competes with cofilin, α-actin was labeled with tetramethylrhodamine cadaverine (TRC) at Gln 41 . The TRC-labeling inhibited actin treadmilling strongly, as measured by εATP release. Cofilin binding, detected via an increase in light scattering, and the subsequent conformational change in filament structure, as detected by TRC fluorescence decay, occurred 2-3 times faster at pH 6.8 than at pH 8.0. In contrast, actin filaments severing by cofilin was pH-independent. The pH-independent severing by cofilin was confirmed using actin labeled at Cys 374 with Oregon Green ® 488 maleimide. The depolymerization of actin by cofilin was faster at high pH.

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Structural Effects of Cofilin on Longitudinal Contacts in F-actin

Cited by 66 publications

References 46 publications

A Genetic Dissection of Aip1p's Interactions Leads to a Model for Aip1p-Cofilin Cooperative Activities

A Genetic Dissection of Aip1p's Interactions Leads to a Model for Aip1p-Cofilin Cooperative Activities

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

Severing of F-actin by yeast cofilin is pH-independent

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