Cell Spreading and Focal Adhesion Dynamics are Regulated by Spacing of Integrin Ligands

¹ University of Heidelberg
² The Weizmann Institute of Science
³ Massachusetts Institute of Technology
⁴ TU Muenchen

^* To whom correspondence should be addressed. E-mail: ada.cavalcanti-adam{at}urz.uni-heidelberg.de.

Submitted on May 23, 2006
Revised on August 17, 2006
Accepted on 8 January 2007

	Abstract

Integrin-mediated adhesion is regulated by multiple features of the adhesive surface, including its chemical composition, topography and physical properties. In this study we investigated integrin lateral clustering, as a mechanism to control integrin functions, by characterizing the effect of nanoscale variations in the spacing between adhesive RGD ligands on cell spreading, migration and focal adhesion dynamics. For this purpose, we used nanopatterned surfaces, containing RGD-biofunctionalized gold-dots, surrounded by passivated gaps. By varying the spacing between the dots, we modulated the clustering of the associated integrins. We show that cell-surface attachment is not sensitive to pattern density, while the formation of stable focal adhesions and persistent spreading is. Thus cells plated on 108 nm-spaced pattern exhibit delayed spreading with repeated protrusion-retraction cycles compared to cells growing on a 58 nm pattern. Cell motility on these surfaces is erratic and non-persistent, leaving thin membrane tethers bound to the RGD pattern. Dynamic molecular profiling indicated that the adhesion sites formed with the 108 nm pattern undergo rapid turnover and contain reduced levels of zyxin. These findings indicate that a critical RGD density is essential for the establishment of mature and stable integrin adhesions which, in turn, induce efficient cell spreading and formation of focal adhesions.

Key Words: cell adhesion, cell motility, extracellular matrix, focal adhesions, nanotechnology

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