title: Direct observation of α-actinin tension and recruitment at focal adhesions during contact growth.
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-actinin FRET probes and fluorescence labeled paxillin in MDCK cells, we have simultaneously observed the time-dependent changes in tension in α-actinin 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.
authors.affiliation: Department of Physiology and Biophysics, SUNY-Buffalo, Buffalo, NY 14260, USA; Department of Mechanical and Aerospace Engineering, SUNY-Buffalo, Buffalo, NY 14260, USA.
authors.forename: Nannan
authors.initials: N
authors.lastname: Ye
authors.affiliation: Department of Mechanical and Aerospace Engineering, SUNY-Buffalo, Buffalo, NY 14260, USA.
authors.forename: Deepika
authors.initials: D
authors.lastname: Verma
authors.affiliation: Department of Physiology and Biophysics, SUNY-Buffalo, Buffalo, NY 14260, USA.
authors.forename: Fanjie
authors.initials: F
authors.lastname: Meng
authors.affiliation: National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA; Department of Biological Science, Florida State University, Tallahassee, FL 32310, USA.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Davidson
authors.affiliation: Department of Mechanical and Aerospace Engineering, SUNY-Buffalo, Buffalo, NY 14260, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Suffoletto
authors.affiliation: Department of Physiology and Biophysics, SUNY-Buffalo, Buffalo, NY 14260, USA; Department of Mechanical and Aerospace Engineering, SUNY-Buffalo, Buffalo, NY 14260, USA. Electronic address: zhua@buffalo.edu.
authors.forename: Susan Z
authors.initials: SZ
authors.lastname: Hua
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology; D003599:Cytoskeleton / Q000378:metabolism; D004285:Dogs; D022001:Focal Adhesions / Q000378:metabolism*; D016023:Integrins / Q000378:metabolism; D061985:Madin Darby Canine Kidney Cells; D024462:Myosin Type II / Q000378:metabolism; D051419:Paxillin / Q000378:metabolism
chemical_list: D000199:Actins; D016023:Integrins; D051419:Paxillin; D024462:Myosin Type II
keywords: Cytoskeleton; FRET; Focal adhesions; Mechanical force; α-Actinin
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