The Rockefeller University Press

Cell adhesion is a critical development that spurred the evolu-tion of metazoans and is integrated into virtually all physiological functions, from energy and metabolism to movement and defense against invasive organisms. Adhesion receptors share with other cell surface receptors, such as the tyrosine kinase growth factor or G-protein–coupled receptors, the ability to transmit extracel-lular signals into cells (Menko and Boettiger, 1987). However, their primary function is mechanical and their signaling function appears to devolve from their adhesive function (Friedland et al., 2009). The mechanical function of adhesion receptors involves both the number of bound receptors and their spatial distribution on the cells. The strength of adhesion is determined primarily by the number of adhesive bonds (bonds between cell surface adhe-sion receptors and cell or extracellular matrix–bound ligands). Because cells need to move and change shape, they need to var