Transmembrane cooperative linkage in cellular adhesion.

Various dynamic cellular activities require precise regulation of extracellular adhesion. Here we propose a simple thermodynamic model that does not depend on affinity regulation of transmembrane adhesion molecules but, rather, is based on the principles of collision-limited reactions. We show that the number of transmembrane adhesion molecules forming extracellular bonds depends on the degree of cytoskeletal damping of their lateral mobility (translational entropy) within the plane of the plasma membrane. This type of transmembrane cooperativity between cytoskeletal linkage and the number of extracellular bonds does not require high affinities to the cytoskeleton (micromolar range) and will be particularly effective at low extracellular affinities of adhesion molecules (millimolar range).