Analysis of the local organization and dynamics of cellular actin networks JOURNAL OF CELL BIOLOGY. September 2013

By Weiwei Luo1, Cheng-han Yu1, Zi Zhao Lieu1, Jun Allard2,3, Alex Mogilner2,3, Michael P. Sheetz1,4, and Alexander D. Bershadsky1,5

Journal of Cell Biology  202, 7 1057-73  September 30, 2013
doi: 10.1083/jcb.201210123

Abstract

Sasha JCB Sept2013(2)

The dynamic reorganization of F-actin and myosin II was visualized using Lifeact-Ruby and EGFP-tagged MRLC (EGFP-MRLC). MEFs were plated on fibronectin-patterned glass coverslips and then treated with 200 nM LatA. The cell area was marked as the yellow contour.

 

Actin filaments, with the aid of multiple accessory proteins, self-assemble into a variety of network patterns. We studied the organization and dynamics of the actin network in nonadhesive regions of cells bridging fibronectin-coated adhesive strips. The network was formed by actin nodes associated with and linked by myosin II and containing the formin disheveled-associated activator of morphogenesis 1 (DAAM1) and the cross-linker filamin A (FlnA). After Latrunculin A (LatA) addition, actin nodes appeared to be more prominent and demonstrated drift-diffusion motion. Superresolution microscopy revealed that, in untreated cells, DAAM1 formed patches with a similar spatial arrangement to the actin nodes. Node movement (diffusion coefficient and velocity) in LatA-treated cells was dependent on the level and activity of myosin IIA, DAAM1, and FlnA. Based on our results, we developed a computational model of the dynamic formin-filamin-actin asters that can self-organize into a contractile actomyosin network. We suggest that such networks are critical for connecting distant parts of the cell to maintain the mechanical coherence of the cytoplasm.

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Author Affiliations:
1.      Mechanobiology Institute, National University of Singapore, Singapore 117411, Republic of Singapore
2.      Department of Neurobiology, Physiology, and Behavior
3.      Department of Mathematics, University of California at Davis, Davis, CA 95616
4.      Department of Biological Sciences, Columbia University, New York, NY 10027
5.      Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel

Correspondence to Alexander D. Bershadsky: alexander.bershadsky@weizmann.ac.il