Phosphomimetic S3D cofilin binds but only weakly severs actin filaments
| Autor: | Wenxiang Cao, Ewa Prochniewicz, David D. Thomas, Charles V. Sindelar, Teresa T. Bonello, Hyeran Kang, Gregory A. Voth, Enrique M. De La Cruz, Peter W. Gunning, Andrew Huehn, Anthony C. Schramm, Glen M. Hocky, Karina Negrón, Jean Garcia, W. Austin Elam |
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| Rok vydání: | 2017 |
| Předmět: |
0301 basic medicine
Cell division Cooperativity macromolecular substances Molecular Dynamics Simulation environment and public health Biochemistry Protein filament 03 medical and health sciences Serine Phosphorylation Molecular Biology Actin Chemistry Cryoelectron Microscopy Molecular Mimicry Cell Biology Actin filament severing Cofilin Actin cytoskeleton Actin Cytoskeleton 030104 developmental biology Actin Depolymerizing Factors Microscopy Fluorescence Biophysics Molecular Biophysics Protein Binding |
| Zdroj: | Journal of Biological Chemistry. 292:19565-19579 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.m117.808378 |
| Popis: | Many biological processes, including cell division, growth, and motility, rely on rapid remodeling of the actin cytoskeleton and on actin filament severing by the regulatory protein cofilin. Phosphorylation of vertebrate cofilin at Ser-3 regulates both actin binding and severing. Substitution of serine with aspartate at position 3 (S3D) is widely used to mimic cofilin phosphorylation in cells and in vitro. The S3D substitution weakens cofilin binding to filaments, and it is presumed that subsequent reduction in cofilin occupancy inhibits filament severing, but this hypothesis has remained untested. Here, using time-resolved phosphorescence anisotropy, electron cryomicroscopy, and all-atom molecular dynamics simulations, we show that S3D cofilin indeed binds filaments with lower affinity, but also with a higher cooperativity than wild-type cofilin, and severs actin weakly across a broad range of occupancies. We found that three factors contribute to the severing deficiency of S3D cofilin. First, the high cooperativity of S3D cofilin generates fewer boundaries between bare and decorated actin segments where severing occurs preferentially. Second, S3D cofilin only weakly alters filament bending and twisting dynamics and therefore does not introduce the mechanical discontinuities required for efficient filament severing at boundaries. Third, Ser-3 modification (i.e. substitution with Asp or phosphorylation) “undocks” and repositions the cofilin N terminus away from the filament axis, which compromises S3D cofilin's ability to weaken longitudinal filament subunit interactions. Collectively, our results demonstrate that, in addition to inhibiting actin binding, Ser-3 modification favors formation of a cofilin-binding mode that is unable to sufficiently alter filament mechanical properties and promote severing. |
| Databáze: | OpenAIRE |
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