Nexilin is a dynamic component of Listeria monocytogenes and enteropathogenic Escherichia coli actin-rich structures

The bacterial pathogens Listeria monocytogenes and enteropathogenic Escherichia coli (EPEC) generate motile actin-rich structures (comet tails and pedestals) as part of their infectious processes. Nexilin, an actin-associated protein and a component of focal adhesions, has been suggested to be involved in actin-based motility. To determine whether nexilin is commandeered during L. monocytogenes and EPEC infections, we infected cultured cells and found that nexilin is crucial for L. monocytogenes invasion as levels of internalized bacteria were significantly decreased in nexilin-targeted siRNA-treated cells. In addition, nexilin is a component of the machinery that drives the formation of L. monocytogenes comet tails and EPEC pedestals. Nexilin colocalizes with stationary bacteria and accumulates at the distal portion of comet tails and pedestals of motile bacteria. We also show that nexilin is crucial for efficient comet tail formation as cells pre-treated with nexilin siRNA generate malformed comet tails, whereas nexilin is dispensable during EPEC pedestal generation. These findings demonstrate that nexilin is required for efficient infection with invasive and adherent bacteria and is key to the actin-rich structures these microbes generate.