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Myosin II contributes to cell-scale actin network treadmilling through network disassembly


Crawling locomotion of eukaryotic cells is achieved by a process dependent on the actin cytoskeleton1: protrusion of the leading edge requires assembly of a network of actin filaments2, which must be disassembled at the cell rear for sustained motility. Although ADF/cofilin proteins have been shown to contribute to actin disassembly3, it is not clear how activity of these locally acting proteins could be coordinated over the distance scale of the whole cell. Here we show that non-muscle myosin II has a direct role in actin network disassembly in crawling cells. In fish keratocytes undergoing motility, myosin II is concentrated in regions at the rear with high rates of network disassembly. Activation of myosin II by ATP in detergent-extracted cytoskeletons results in rear-localized disassembly of the actin network. Inhibition of myosin II activity and stabilization of actin filaments synergistically impede cell motility, suggesting the existence of two disassembly pathways, one of which requires myosin II activity. Our results establish the importance of myosin II as an enzyme for actin network disassembly; we propose that gradual formation and reorganization of an actomyosin network provides an intrinsic destruction timer, enabling long-range coordination of actin network treadmilling in motile cells.

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Figure 1: Myosin II in keratocytes co-localizes with the primary sites of actin network disassembly.
Figure 2: Inhibition of myosin II blocks inward flow and alters the pattern of disassembly of the actin network.
Figure 3: Jasplakinolide specifically halts actin dynamics of cells in which myosin II is inhibited.
Figure 4: Actin network disassembly in the rear of detergent-extracted keratocyte cytoskeletons is ATP dependent and blebbistatin sensitive, consistent with a direct role for myosin II in this process.


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We thank M. J. Footer for the gift of purified GST–villin, A. Mogilner and S. Sivaramakrishnan for discussions, and Z. Pincus, N. Dye and T. Y.-C. Tsai for reading the manuscript. C.A.W. and J.A.T. were supported by National Institutes of Health grant R01AI067712 (J.A.T.). M.A.T. and E.L.B. were supported by National Institutes of Health grant T32GM007276. G.M.A. was supported by the Stanford Medical Scientist Training Program. P.T.Y. was supported by a Howard Hughes Medical Institute Predoctoral Fellowship, Stanford Graduate Fellowship and a Skye International Foundation Scholarship. K.T.A. was supported by a National Science Foundation Graduate Research Fellowship. K.K. was a Damon Runyon Fellow supported by the Damon Runyon Cancer Research Foundation (DRG-#1854-05). K.T.A., L.J. and G.D. were supported by National Institutes of Health grants U54GM64346 and U01GM67230 (G.D.). J.A.T. was supported by the Howard Hughes Medical Institute.

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Authors and Affiliations



C.A.W., M.A.T. and J.A.T. conceived and designed the experiments. C.A.W. and P.T.Y. performed FSM on untreated motile keratocytes. C.A.W. performed the pharmacological manipulation experiments, FSM observation and the analysis. L.J. and G.D. developed the flow tracking algorithm specific to the needs of this analysis. C.A.W. and P.T.Y. developed methods and software to integrate the flow tracking algorithm with these experiments and analysis. K.T.A., C.A.W. and G.D. developed algorithms for the F-actin turnover analysis. E.L.B. imaged myosin II localization. G.M.A., K.K. and E.L.B. collected the cell speed data and observed fixed cells under the different treatments; G.M.A. and C.A.W. analysed these data. M.A.T. performed experiments on detergent-extracted cytoskeletons and analysed the results. M.A.T., C.A.W. and J.A.T. wrote the paper. All authors discussed the results and commented on the manuscript.

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Correspondence to Julie A. Theriot.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Notes 1-3, Supplementary Figures 1-6 with legends, captions for Supplementary Movies 1-4 and References. (PDF 5572 kb)

Supplementary Movie 1

This movie shows that myosin II inhibition alters actin network flow (see Supplementary Information file for full caption). (MOV 20825 kb)

Supplementary Movie 2

This movie shows that inward traction force generation requires myosin II activity (see Supplementary Information file for full caption). (MOV 8661 kb)

Supplementary Movie 3

This movie shows that jasplakinolide halts actin dynamics of cells in which myosin II is inhibited (see Supplementary Information file for full caption). (MOV 15729 kb)

Supplementary Movie 4

This movie shows that actin network disassembly in the rear of detergent-extracted keratocyte cytoskeletons is ATP-dependent and blebbistatin-sensitive (see Supplementary Information file for full caption). (MOV 424 kb)

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Wilson, C., Tsuchida, M., Allen, G. et al. Myosin II contributes to cell-scale actin network treadmilling through network disassembly. Nature 465, 373–377 (2010).

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