[Cell adhesion and the cytoskeleton]

Most cells have macromolecules on their outer surface that are specialized for adhesion. Cells can attach to another cell and/or various extracellular matrix components. When tissue culture cells attach to the substrate, they form a specialized structure called adhesion plaque. At the cytoplasmic side of the adhesion plaque, stress fibers terminate, forming an electron-dense plasma membrane undercoat structure. Integrin is localized to the adhesion plaque and this is a transmembrane protein that connects the cytoskeleton to the extracellular matrix. Endothelial cells in vivo have stress fibers, and we have recently found that the ends of these stress fibers also terminate at a structure similar to the adhesion plaque of cultured cells. It appears, therefore, that endothelial cells in vivo employ similar, if not identical, mechanism for adhesion as the one used by tissue culture cells.