Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 110, Issue 48, Pages 19372-19377Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1307405110
Keywords
FRET biosensor; intracellular tension; substrate rigidity
Categories
Funding
- National Institutes of Health [HL098472, HL109142, GM106403, NS063405, GM072744, GM065918]
- National Science Foundation [CBET0846429]
- Beckman Laser Institute, Inc.
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Matrix mechanics controls cell fate by modulating the bonds between integrins and extracellular matrix (ECM) proteins. However, it remains unclear how fibronectin (FN), type 1 collagen, and their receptor integrin subtypes distinctly control force transmission to regulate focal adhesion kinase (FAK) activity, a crucial molecular signal governing cell adhesion/migration. Here we showed, using a genetically encoded FAK biosensor based on fluorescence resonance energy transfer, that FN-mediated FAK activation is dependent on the mechanical tension, which may expose its otherwise hidden FN synergy site to integrin alpha 5. In sharp contrast, the ligation between the constitutively exposed binding motif of type 1 collagen and its receptor integrin alpha 2 was surprisingly tension-independent to induce sufficient FAK activation. Although integrin alpha subunit determines mechanosensitivity, the ligation between alpha subunit and the ECM proteins converges at the integrin beta 1 activation to induce FAK activation. We further discovered that the interaction of the N-terminal protein 4.1/ezrin/redixin/moesin basic patch with phosphatidylinositol 4,5-biphosphate is crucial during cell adhesion to maintain the FAK activation from the inhibitory effect of nearby protein 4.1/ezrin/redixin/moesin acidic sites. Therefore, different ECM proteins either can transmit or can shield from mechanical forces to regulate cellular functions, with the accessibility of ECM binding motifs by their specific integrin alpha subunits determining the biophysical mechanisms of FAK activation during mechanotransduction.
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