Catch bonds in adhesion.

One of the most exciting discoveries in biological adhesion is the recent and counter-intuitive observation that the lifetimes of some biological adhesive bonds, called catch bonds, are enhanced by tensile mechanical force. At least two types of adhesive proteins have been shown to form catch bonds--blood proteins called selectins and a bacterial protein called FimH. Both mediate shear-enhanced adhesion, in which cells bind more strongly at high shear than at low shear. Single-molecule experiments and cell-free assays have now clearly demonstrated that catch bonds exist and mediate shear-enhanced adhesion. However, the mechanics of cellular organelles also contribute to shear-enhanced adhesion by modulating the force applied to catch bonds. This review examines how individual catch bond behavior contributes to shear-enhanced cellular adhesion for the two best-understood examples. The lessons from these systems offer design principles for understanding other types of shear-enhanced adhesion and for engineering nanostructured force-dependent adhesives out of catch bonds.