Identification of cofilin, coronin, Rac and capZ in actin tails using a Listeria affinity approach.

Actin assembly is involved in cell motility and intracellular movement of Listeria monocytogenes. Induction of Listeria actin tails is mediated by the surface protein ActA. The N-terminal domain of ActA is sufficient for this function. Cell components known to play a role in the actin-based motility of Listeria are VASP (vasodilatator-stimulated phosphoprotein), the multiprotein Arp2/3 complex and cofilin. VASP interacts with the central domain of ActA. Proteins interacting with the N-terminal domain of ActA have not been identified. To identify novel host cell components of ActA-induced actin tails, we used bovine brain extracts and an affinity approach with Listeria as matrix. Several known components of Listeria tails were isolated including VASP, Arp3 and cofilin. Cofilin was identified by peptide sequencing, and cofilin recruitment and Listeria tail length were found to be pH-dependent, in agreement with its recently reported role in enhancing actin filament turnover. In addition, three proteins not previously known to be associated with Listeria tails, coronin, Rac and capZ, were identified in our affinity approach. In infected cells, the localization of the identified proteins was studied by immunofluorescence. Our findings suggest that these latter proteins, which are known to play critical roles in cellular actin rearrangements, may also be involved in the dynamics of Listeria-induced actin assembly.