Mechanosensing in actin stress fibers revealed by a close correlation between force and protein localization.
The mechanics of the actin cytoskeleton have a central role in the regulation of cells and tissues, but the details of how molecular sensors recognize deformations and forces are elusive. By performing cytoskeleton laser nanosurgery in cultured epithelial cells and fibroblasts, we show that the retraction of stress fibers (SFs) is restricted to the proximity of the cut and that new adhesions form at the retracting end. This suggests that SFs are attached to the substrate. A new computational model for SFs confirms this hypothesis and predicts the distribution and propagation of contractile forces along the SF. We then analyzed the dynamics of zyxin, a focal adhesion protein present in SFs. Fluorescent redistribution after laser nanosurgery and drug treatment shows a high correlation between the experimentally measured localization of zyxin and the computed localization of forces along SFs. Correlative electron microscopy reveals that zyxin is recruited very fast to intermediate substrate anchor points that are highly tensed upon SF release. A similar acute localization response is found if SFs are mechanically perturbed with the cantilever of an atomic force microscope. If actin bundles are cut by nanosurgery in living Drosophila egg chambers, we also find that zyxin redistribution dynamics correlate to force propagation and that zyxin relocates at tensed SF anchor points, demonstrating that these processes also occur in living organisms. In summary, our quantitative analysis shows that force and protein localization are closely correlated in stress fibers, suggesting a very direct force-sensing mechanism along actin bundles.
Colombelli
Julien
J
Cell Biology and Biophysics, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, D-69117 Heidelberg, Germany. julien.colombelli@irbbarcelona.org
Besser
Achim
A
Kress
Holger
H
Reynaud
Emmanuel G
EG
Girard
Philippe
P
Caussinus
Emmanuel
E
Haselmann
Uta
U
Small
John V
JV
Schwarz
Ulrich S
US
Stelzer
Ernst H K
EH
D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D003198:Computer Simulation; D004330:Drosophila / Q000196:embryology / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism; D004548:Elasticity; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D022001:Focal Adhesions / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D018398:Homeodomain Proteins / Q000378:metabolism; D053685:Laser Therapy; D040542:Mechanotransduction, Cellular / Q000187:drug effects; D051379:Mice; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D024507:Nonmuscle Myosin Type IIA / Q000037:antagonists & inhibitors / Q000378:metabolism; D048328:Potoroidae; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D022502:Stress Fibers / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D013314:Stress, Mechanical; D041701:Swiss 3T3 Cells; D013997:Time Factors; D014162:Transfection; D060589:Zyxin
D000199:Actins; D029721:Drosophila Proteins; D006576:Heterocyclic Compounds, 4 or More Rings; D018398:Homeodomain Proteins; D011993:Recombinant Fusion Proteins; C499520:Zyx protein, Drosophila; D060589:Zyxin; D049452:Green Fluorescent Proteins; C472645:blebbistatin; D024507:Nonmuscle Myosin Type IIA