Quantitative measurements of integrin-mediated adhesion to extracellular matrix

Integrin-mediated adhesion is based on the binding of integrins to immobilized ligands either in the extracellular matrix or on the surface of adjacent cells. The strength of adhesion is determined primarily by the number of adhesive bonds that form. Integrins have also been described as signaling receptors. Like adhesion, signals from integrins receptors can depend on the number of integrins that are bound to substrate attached ligands. The common methods for measuring cell adhesion are only capable of measuring initial interactions because the multivalent nature of adhesive bonds when the cell is considered as a unit, these assays reach plateau levels. To measure adhesive integrin-ligand bonds, a spinning disc device is described in which the mean cell detachment force is proportional to the number of adhesive bonds. Particularly as the field has moved from identification of integrins and their ligands into the analysis of adhesion and its relationship to cell signaling, it is important to shift to assays that relate the extracellular binding to the intracellular signals. Specific plans, methods, and analytic strategies are provided to apply this technology to current problems in integrin biology. At present, this is the only published approach that will provide good measures of the number of adhesive bonds that can be generally applied.