Abstract
Polymerization of actin, which is crucial for functions such as cell migration, membrane ruffling, cytokinesis, and endocytosis, must be tightly regulated in order to preserve an adequate supply of free actin monomers to respond to changing external conditions. The paper will describe mechanisms by which F-actin feeds back on its own assembly, thus regulating itself. I will present the experimental evidence for such feedback terms, discuss their use in current models of actin dynamics in cells, and present preliminary calculations for the role of feedback in transient endocytic actin patches. These calculations suggest a partial homeostasis of F-actin, in which the F-actin peak height depends only weakly on the actin filament nucleation rate.