Intracellular pathogens and the actin cytoskeleton

Many pathogens actively exploit the actin cytoskeleton during infection. Th is exploitation may take place during entry into mammalian cells after enga gement of a receptor and/or as series of signaling events culminating in th e engulfment of the microorganism. Although actin rearrangements are a comm on feature of most internalization events (e.g. entry of Listeria, Salmonel la, Shigella, Yersinia, Neisseria, and Bartonella), bacterial and other cel lular factors involved in entry are specific to each bacterium. Another ste p during which pathogens harness the actin cytoskeleton takes place in the cytosol, within which some bacteria (Listeria, Shigella, Rickettsia) or vir uses (vaccinia virus) are able to move. Movement is coupled to a polarized actin polymerization process, with the formation of characteristic actin ta ils. Increasing attention has focused on this phenomenon due to its strikin g similarity to cellular events occurring at the leading edge of locomoting cells. Thus pathogens are convenient systems in which to study actin cytos keleton rearrangements in response to stimuli at the plasma membrane or ins ide cells.