Cytoskeletal coherence requires myosin-IIA contractility.
Maintaining a physical connection across cytoplasm is crucial for many biological processes such as matrix force generation, cell motility, cell shape and tissue development. However, in the absence of stress fibers, the coherent structure that transmits force across the cytoplasm is not understood. We find that nonmuscle myosin-II (NMII) contraction of cytoplasmic actin filaments establishes a coherent cytoskeletal network irrespective of the nature of adhesive contacts. When NMII activity is inhibited during cell spreading by Rho kinase inhibition, blebbistatin, caldesmon overexpression or NMIIA RNAi, the symmetric traction forces are lost and cell spreading persists, causing cytoplasm fragmentation by membrane tension that results in 'C' or dendritic shapes. Moreover, local inactivation of NMII by chromophore-assisted laser inactivation causes local loss of coherence. Actin filament polymerization is also required for cytoplasmic coherence, but microtubules and intermediate filaments are dispensable. Loss of cytoplasmic coherence is accompanied by loss of circumferential actin bundles. We suggest that NMIIA creates a coherent actin network through the formation of circumferential actin bundles that mechanically link elements of the peripheral actin cytoskeleton where much of the force is generated during spreading.
Cai
Yunfei
Y
Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
Rossier
Olivier
O
Gauthier
Nils C
NC
Biais
Nicolas
N
Fardin
Marc-Antoine
MA
Zhang
Xian
X
Miller
Lawrence W
LW
Ladoux
Benoit
B
Cornish
Virginia W
VW
Sheetz
Michael P
MP
D000199:Actins / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D051379:Mice; D041681:NIH 3T3 Cells; D024507:Nonmuscle Myosin Type IIA / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors
D000199:Actins; D006576:Heterocyclic Compounds, 4 or More Rings; C472645:blebbistatin; D054460:rho-Associated Kinases; D024507:Nonmuscle Myosin Type IIA