Actin filament nucleation by endosomes, lysosomes and secretory vesicles

Intracellular pathogens such as Listeria monocytogenes and vaccinia virus p ropel themselves through the cytoplasm of mammalian cells by nucleating act in filaments. Recently, actin assembly has also been shown to power the mov ement of intracellular vesicles, and this may be a mechanism underlying end omembrane movement in a variety of physiological contexts. Surprisingly, cl ass I myosins have been found to play important roles in both actin nucleat ion and endomembrane trafficking.