WASP-related proteins, Abi1 and Ena/VASP are required for Listeria invasion induced by the Met receptor

Internalisation of the pathogenic bacterium Listeria monocytogenes involves interactions between the invasion protein InIB and the hepatocyte growth factor receptor, Met. Using colocalisation studies, dominant-negative constructs and small interfering RNA (siRNA), we demonstrate a cell-type-dependent requirement for various WASP-related proteins in Listeria entry and InIB-induced membrane ruffling. The WAVE2 isoform is essential for InIB-induced cytoskeletal rearrangements in Vero cells. In HeLa cells, WAVE1, WAVE2 and N-WASP cooperate to promote these processes. Abi1, a key component of WAVE complexes, is recruited at the entry site in both cell types and its inactivation by RNA interference impairs InlB-mediated processes. Ena/VASP proteins also play a role in Listeria internalization, and their deregulation by sequestration or overexpression, modifies actin cups beneath entering particles. Taken together, these results identify the WAVE complex, N-WASP and Ena/VASP as key effectors of the Met signalling pathway and of Listeria entry and highlight the existence of redundant and/or cooperative functions among WASP-family members.