Force generated by actomyosin contraction builds bridges between adhesive contacts.
Extracellular matrices in vivo are heterogeneous structures containing gaps that cells bridge with an actomyosin network. To understand the basis of bridging, we plated cells on surfaces patterned with fibronectin (FN)-coated stripes separated by non-adhesive regions. Bridges developed large tensions where concave cell edges were anchored to FN by adhesion sites. Actomyosin complexes assembled near those sites (both actin and myosin filaments) and moved towards the centre of the non-adhesive regions in a treadmilling network. Inhibition of myosin-II (MII) or Rho-kinase collapsed bridges, whereas extension continued over adhesive areas. Inhibition of actin polymerization (latrunculin-A, jasplakinolide) also collapsed the actomyosin network. We suggest that MII has distinct functions at different bridge regions: (1) at the concave edges of bridges, MIIA force stimulates actin filament assembly at adhesions and (2) in the body of bridges, myosin cross-links actin filaments and stimulates actomyosin network healing when breaks occur. Both activities ensure turnover of actin networks needed to maintain stable bridges from one adhesive region to another.
Department of Biological Sciences, Columbia University, New York, NY, USA.
Olivier M
OM
Rossier
Nils
N
Gauthier
Nicolas
N
Biais
Wynn
W
Vonnegut
Marc-Antoine
MA
Fardin
Philip
P
Avigan
Evan R
ER
Heller
Anurag
A
Mathur
Saba
S
Ghassemi
Michael S
MS
Koeckert
James C
JC
Hone
Michael P
MP
Sheetz
D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000737:chemistry* / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D007700:Kinetics; D009119:Muscle Contraction / Q000502:physiology*; D009218:Myosins / Q000737:chemistry / Q000378:metabolism; D054460:rho-Associated Kinases / Q000737:chemistry / Q000378:metabolism
D000199:Actins; D000205:Actomyosin; D054460:rho-Associated Kinases; D009218:Myosins