Actin-based motility and cell-to-cell spread of Listeria monocytogenes

Abstract

Listeria monocytogenes has evolved the ability to exploit its host's actin cytoskeleton to power movement within and between cells without exiting from the cell, enabling it to evade the immune response. This remarkable adaptation requires the expression of a single bacterial surface protein, called ActA, that performs two key functions. It activates the host Arp2/3 complex, which promotes the nucleation of actin filaments at the bacterial surface and the organization of filaments into branched networks. Moreover, it recruits host Ena/VASP proteins and profilin, which stimulate actin filament elongation. Together these cellular factors promote the assembly of actin comet tails that recruit additional host cytoskeletal proteins that control filament bundling, terminate polymerization, and promote depolymerization. The assembly of the comet tail is essential for coupling actin polymerization to the force that drives bacterial propulsion. The process of bacterial motility can be reconstituted in vitro, facilitating a relatively complete understanding of the biochemical and biophysical mechanisms of actin polymerization and force generation. This chapter presents a review of the experiments that have led to our current understanding of the molecular mechanisms of L. monocytogenes' motility and spread.