Regulation of endocytosis, exocytosis, and shape by membrane tension.

Abstract

In general, the physical properties of membranes have often been suggested as significant factors in regulating biological functions. Membrane receptors are often concentrated in domains, and their lateral aggregation has been linked to functional activation. Stretch-activated channels and osmoregulatory responses all have a clear mechanical component. Furthermore, membranes can exert very significant forces through thread-like tethers, as evidenced by the retraction fibers that migrating cells or rolling lymphocytes generate. We have recently characterized the forces that cells exert on membrane tethers as a function of the cell state (Dai and Sheetz 1995). Those forces are significantly greater than the forces that single motor molecules can generate. For example, in the neuronal growth cone, a tether membrane similar in size to a filopodium creates a 7 pN force on the bead used to form it. Single myosin molecules generate a peak force of approximately 3 pN and possibly even less under...