title: Regulation of integrin adhesions by varying the density of substrate-bound epidermal growth factor.
abstract: Substrates coated with specific bioactive ligands are important for tissue engineering, enabling the local presentation of extracellular stimulants at controlled positions and densities. In this study, we examined the cross-talk between integrin and epidermal growth factor (EGF) receptors following their interaction with surface-immobilized Arg-Gly-Asp (RGD) and EGF ligands, respectively. Surfaces of glass coverslips, modified with biotinylated silane-polyethylene glycol, were functionalized by either biotinylated RGD or EGF (or both) via the biotin-NeutrAvidin interaction. Fluorescent labeling of the adhering A431 epidermoid carcinoma cells for zyxin or actin indicated that EGF had a dual effect on focal adhesions (FA) and stress fibers: at low concentrations (0.1; 1 ng/ml), it stimulated their growth; whereas at higher concentrations, on surfaces with low to intermediate RGD densities, it induced their disassembly, leading to cell detachment. The EGF-dependent dissociation of FAs was, however, attenuated on higher RGD density surfaces. Simultaneous stimulation by both immobilized RGD and EGF suggest a strong synergy between integrin and EGFR signaling, in FA induction and cell spreading. A critical threshold level of EGF was required to induce significant variation in cell adhesion; beyond this critical density, the immobilized molecule had a considerably stronger effect on cell adhesion than did soluble EGF. The mechanisms underlying this synergy between the adhesion ligand and EGF are discussed.
authors.affiliation: Department of Molecular Cell Biology, Weizmann Institute of Science, 76100, Rehovot, Israel.
authors.forename: Tamar
authors.initials: T
authors.lastname: Shahal
authors.forename: Benjamin
authors.initials: B
authors.lastname: Geiger
authors.forename: Iain E
authors.initials: IE
authors.lastname: Dunlop
authors.forename: Joachim P
authors.initials: JP
authors.lastname: Spatz
mesh_terms: D002448:Cell Adhesion; D045744:Cell Line, Tumor; D020099:Coated Materials, Biocompatible; D004815:Epidermal Growth Factor / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D023822:Tissue Engineering / Q000379:methods
chemical_list: D020099:Coated Materials, Biocompatible; D016023:Integrins; D004815:Epidermal Growth Factor