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Proc Natl Acad Sci U S A. 2017 Oct 3;114(40):10648-10653. doi: 10.1073/pnas.1701136114.

Actin retrograde flow actively aligns and orients ligand-engaged integrins in focal adhesions.

Author information

1
Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543.
2
Physiology Course, Marine Biological Laboratory, Woods Hole, MA 02543.
3
Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD 20892.
4
National Centre for Biological Sciences, Bangalore 560065, Karnataka, India.
5
Eugene Bell Center, Marine Biological Laboratory, Woods Hole, MA 02543.
6
Division of Infection Medicine, Lund University, SE-221 84 Lund, Sweden.
7
Program in Cellular and Molecular Medicine, Children's Hospital, Boston, MA 02115.
8
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
9
Department of Biochemistry, University of Washington, Seattle, WA 98195.
10
Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195.
11
Institute for Molecular Science, Okazaki 444-8585, Japan.
12
Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543; watermancm@nhlbi.nih.gov.

Abstract

Integrins are transmembrane receptors that, upon activation, bind extracellular ligands and link them to the actin filament (F-actin) cytoskeleton to mediate cell adhesion and migration. Cytoskeletal forces in migrating cells generated by polymerization- or contractility-driven "retrograde flow" of F-actin from the cell leading edge have been hypothesized to mediate integrin activation for ligand binding. This predicts that these forces should align and orient activated, ligand-bound integrins at the leading edge. Here, polarization-sensitive fluorescence microscopy of GFP-αVβ3 integrins in fibroblasts shows that integrins are coaligned in a specific orientation within focal adhesions (FAs) in a manner dependent on binding immobilized ligand and a talin-mediated linkage to the F-actin cytoskeleton. These findings, together with Rosetta modeling, suggest that integrins in FA are coaligned and may be highly tilted by cytoskeletal forces. Thus, the F-actin cytoskeleton sculpts an anisotropic molecular scaffold in FAs, and this feature may underlie the ability of migrating cells to sense directional extracellular cues.

KEYWORDS:

cell migration; fluorescence polarization microscopy; mechanosensing

PMID:
29073038
PMCID:
PMC5635867
DOI:
10.1073/pnas.1701136114
[Indexed for MEDLINE]
Free PMC Article

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