Cellular actin networks grow by ATP-actin addition at filament barbed ends and have long been presumed to depolymerize at their pointed ends, primarily after filaments undergo “aging” (ATP hydrolysis and Pi release). The cytosol contains high levels of actin monomers, which favors assembly over disassembly, and barbed ends are enriched in ADP-Pi actin. For these reasons, the potential for a barbed end depolymerization mechanism in cells has received little attention. Here, using microfluidics-assisted TIRF microscopy, we show that mouse twinfilin, a member of the ADF-homology family, induces depolymerization of ADP-Pi barbed ends even under assembly-promoting conditions. Indeed, we observe in single reactions containing micromolar concentrations of actin monomers the simultaneous rapid elongation of formin-bound barbed ends and twinfilin-induced depolymerization of free barbed ends. The data show that twinfilin catalyzes dissociation of subunits from ADP-Pi barbed ends and thereby bypasses filament aging prerequisites to disassemble newly polymerized actin filaments.
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4 January 2021
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November 23 2020
Twinfilin bypasses assembly conditions and actin filament aging to drive barbed end depolymerization
Shashank Shekhar,
1
Department of Biology, Brandeis University, Waltham, MA
2
Department of Biochemistry, Brandeis University, Waltham, MA
Correspondence to Shashank Shekhar: shekhar@emory.edu
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Gregory J. Hoeprich,
1
Department of Biology, Brandeis University, Waltham, MA
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Jeff Gelles,
Jeff Gelles
2
Department of Biochemistry, Brandeis University, Waltham, MA
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Bruce L. Goode
1
Department of Biology, Brandeis University, Waltham, MA
Bruce L. Goode: goode@brandeis.edu
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Shashank Shekhar
1
Department of Biology, Brandeis University, Waltham, MA
2
Department of Biochemistry, Brandeis University, Waltham, MA
Gregory J. Hoeprich
1
Department of Biology, Brandeis University, Waltham, MA
Jeff Gelles
2
Department of Biochemistry, Brandeis University, Waltham, MA
Bruce L. Goode
1
Department of Biology, Brandeis University, Waltham, MA
Correspondence to Shashank Shekhar: shekhar@emory.edu
Bruce L. Goode: goode@brandeis.edu
*
S. Shekhar and G.J. Hoeprich contributed equally to this paper.
Received:
June 03 2020
Revision Received:
October 06 2020
Accepted:
October 29 2020
Online Issn: 1540-8140
Print Issn: 0021-9525
Funding:
Brandeis University
(NO AWARD)
National Institutes of Health
(R35 GM134895, R01 GM098143)
National Science Foundation
(142038)
© 2020 Shekhar et al.
2020
This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms/). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 International license, as described at https://creativecommons.org/licenses/by-nc-sa/4.0/).
J Cell Biol (2021) 220 (1): e202006022.
Article history
Received:
June 03 2020
Revision Received:
October 06 2020
Accepted:
October 29 2020
Citation
Shashank Shekhar, Gregory J. Hoeprich, Jeff Gelles, Bruce L. Goode; Twinfilin bypasses assembly conditions and actin filament aging to drive barbed end depolymerization. J Cell Biol 4 January 2021; 220 (1): e202006022. doi: https://doi.org/10.1083/jcb.202006022
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