Nonmuscle myosin IIA-dependent force inhibits cell spreading and drives F-actin flow.
Nonmuscle myosin IIA (NMM-IIA) is involved in the formation of focal adhesions and neurite retraction. However, the role of NMM-IIA in these functions remains largely unknown. Using RNA interference as a tool to decrease NMM-IIA expression, we have found that NMM-IIA is the major myosin involved in traction force generation and retrograde F-actin flow in mouse embryonic fibroblast cells. Quantitative analyses revealed that approximately 60% of traction force on fibronectin-coated surfaces is contributed by NMM-IIA and approximately 30% by NMM-IIB. The retrograde F-actin flow decreased dramatically in NMM-IIA-depleted cells, but seemed unaffected by NMM-IIB deletion. In addition, we found that depletion of NMM-IIA caused cells to spread at a higher rate and to a greater area on fibronectin substrates during the early spreading period, whereas deletion of NMM-IIB appeared to have no effect on spreading. The distribution of NMM-IIA was concentrated on the dorsal surface and approached the ventral surface in the periphery, whereas NMM-IIB was primarily concentrated around the nucleus and to a lesser extent at the ventral surface in cell periphery. Our results suggest that NMM-IIA is involved in generating a coherent cytoplasmic contractile force from one side of the cell to the other through the cross-linking and the contraction of dorsal actin filaments.
Cai
Yunfei
Y
Department of Biological Sciences, Columbia University, New York, New York, USA.
Biais
Nicolas
N
Giannone
Gregory
G
Tanase
Monica
M
Jiang
Guoying
G
Hofman
Jake M
JM
Wiggins
Chris H
CH
Silberzan
Pascal
P
Buguin
Axel
A
Ladoux
Benoit
B
Sheetz
Michael P
MP
D000199:Actins / Q000502:physiology*; D000818:Animals; D002465:Cell Movement / Q000502:physiology*; D002478:Cells, Cultured; D005347:Fibroblasts / Q000502:physiology*; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D051379:Mice; D020409:Molecular Motor Proteins / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D024507:Nonmuscle Myosin Type IIA / Q000502:physiology*; D013314:Stress, Mechanical
D000199:Actins; D020409:Molecular Motor Proteins; D024507:Nonmuscle Myosin Type IIA