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Cytoskeletal coherence requires myosin-IIA contractility
Yunfei Cai1, Olivier Rossier, Nils C Gauthier
1Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
Journal of Cell Science
|January 14, 2010
Summary
Nonmuscle myosin-II (NMII) contraction of actin filaments creates a coherent cytoskeleton essential for cell shape and motility. Loss of NMII activity fragments the cytoplasm, highlighting its role in maintaining cellular integrity.
Area of Science:
- Cell Biology
- Cytoskeletal Dynamics
- Biophysics
Background:
- Maintaining cytoplasmic physical connections is vital for cell motility, shape, and tissue development.
- The mechanism of force transmission across the cytoplasm without stress fibers remains unclear.
Purpose of the Study:
- To investigate the role of nonmuscle myosin-II (NMII) in establishing cytoplasmic coherence.
- To understand how NMII contraction influences cytoskeletal network integrity and force transmission.
Main Methods:
- Inhibition of NMII activity using Rho kinase inhibitors, blebbistatin, caldesmon overexpression, and NMIIA RNAi.
- Chromophore-assisted laser inactivation (CALI) to locally inhibit NMII.
- Observation of cell spreading dynamics, traction forces, and cytoskeletal organization.
Main Results:
- NMII contraction of actin filaments establishes a coherent cytoskeletal network.
- Inhibition of NMII leads to loss of symmetric traction forces, cell spreading, and cytoplasm fragmentation into 'C' or dendritic shapes.
- Loss of cytoplasmic coherence correlates with the disappearance of circumferential actin bundles, with actin polymerization being necessary but microtubules and intermediate filaments being dispensable.
Conclusions:
- Nonmuscle myosin-II (NMII) is essential for generating a coherent actin network through circumferential actin bundles.
- These bundles mechanically link peripheral cytoskeletal elements, crucial for force generation during cell spreading.
- NMII activity is critical for maintaining cellular integrity and preventing cytoplasm fragmentation.
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