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Direct observation of α-actinin tension and recruitment at focal adhesions during contact growth

Ye N1, Verma D2, Meng F3, Davidson MW4, Suffoletto K2, Hua SZ5.

Exp Cell Res. 2014;327(1):57-67.

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1Department of Physiology and Biophysics, SUNY-Buffalo, Buffalo, NY 14260, USA; Department of Mechanical and Aerospace Engineering, SUNY-Buffalo, Buffalo, NY 14260, USA.

2Department of Mechanical and Aerospace Engineering, SUNY-Buffalo, Buffalo, NY 14260, USA.

3Department of Physiology and Biophysics, SUNY-Buffalo, Buffalo, NY 14260, USA.

4National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA; Department of Biological Science, Florida State University, Tallahassee, FL 32310, USA.and

5Department of Physiology and Biophysics, SUNY-Buffalo, Buffalo, NY 14260, USA; Department of Mechanical and Aerospace Engineering, SUNY-Buffalo, Buffalo, NY 14260, USA. Electronic address: [email protected]

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Abstract 

Adherent cells interact with extracellular matrix via cell-substrate contacts at focal adhesions. The dynamic assembly and disassembly of focal adhesions enables cell attachment, migration and growth. While the influence of mechanical forces on the formation and growth of focal adhesions has been widely observed, the force loading on specific proteins at focal adhesion complex is not clear. By co-expressing force sensitive α-actin in FRET probes and fluorescence labeled paxillin in MDCK cells, we have simultaneously observed the time-dependent changes in tension in α-actin in and the dynamics of focal adhesion during cell migration. We show that increase in tension in α-actinin at the focal adhesion coincides with elongation of the adhesion in its growth phase. The enlargement of focal adhesion is through a force sensitive recruitment of α-actinin and paxillin to the adhesion sites. Changes in α-actinin tension and correlated relocation of α-actinin in an active adhesion also guide the growth direction of the adhesion. The results support the model that cytoskeletal tension is coupled to focal adhesion via the linking protein, α-actinin at the adhesion complex. Lysophosphatidic acid caused an immediate increase in α-actinin tension followed by drastic focal adhesion formation and elongation. Application of Rho-ROCK inhibitor, Y27632, resulted in reversible reduction in tension in α-actinin and disassociation of focal adhesion, suggesting the involvement of myosin-II mediated contractile force in the focal adhesion dynamics. These findings suggest that α-actinin not only serves as a physical linker between cytoskeleton and integrin, but also participates in force transmission at adhesion sites to facilitate adhesion׳s growth.

Copyright © 2014 Elsevier Inc. All rights reserved.

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Figure Legend

The dynamic assembly and disassembly of focal adhesions enables cell attachment, migration and growth. In this paper, the researchers have directly measured the α-actinin tension and recruitment at focal adhesions during contact growth by co-expressing force sensitive FRET probes and fluorescence labeled paxillin in MDCK cells. The results show that focal adhesion growth is dynamically correlated to the increase in α-actinin tension and its recruitment. Change in FA growth direction is facilitated by force-dependent α-actinin translocation. These findings suggest that α-actinin not only serves as a physical linker between cytoskeleton and integrin, but also participates in force transmission at adhesion sites to facilitate adhesion’s growth.

Ye, N., Verma, D., Meng, F., Davidson, M.W., Suffoletto, K. & Hua, S.Z. Direct observation of alpha-actinin tension and recruitment at focal adhesions during contact growth. Experimental cell research 327, 57-67 (2014).

 

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