Cellular regulation of actin network assembly

Actin is a defining feature of eukaryotes, where it commonly is one of the most abundant proteins. Actin filaments participate in biological processes ranging from amoeboid movements of protozoa and human white blood cells to muscle contraction. Some of these processes including muscle contraction and cytokinesis require motor proteins of the myosin family, which move along actin filament tracks. Other motile processes, including the extension of pseudopods, are driven by the regulated assembly and disassembly of a network of actin filaments that pushes forward the plasma membrane. External stimuli, acting through a variety of cell surface receptors, control these reactions, allowing cells to move toward attractive stimuli and away from harm. The purpose of this primer is to explain how actin polymerizes and how cells use regulatory proteins to control this process.