N-WASP is an important protein for the actin-based motility of Shigella flexneri in the infected epithelial cells.

quently spread within and between the cells are a prerequisite for causing dysentery. The capacity of the bacteria to spread in the cytoplasm and then move into adjacent epithelial cells is know as intra / intercellular spreading, respectively, and requires the bacterial functions encoded by the virG (icsA) gene (1, 2, 3). After invasion of epithelial cells, Shigella become surrounded by F-actin. This F-actin •hclot•hthen rearranges into a tail which remains stationary in the cytoplasm and is left behind by bacteria moving ahead, in which the VirG protein recruits host components and mediate actin polymerization, which is thought to serve as the propulsive force (4, 5). The movement of S. flexneri within the host cells resembles the formation of filopodium of locomoting cells, since those are mediated by actin polymerization and cause membrane protrusions (2, 5). However, so far no known protein has been reported to be specifically involved in both phenomena. Several host proteins such as vinculin, plastin (fimbrin), filamin, ƒ¿ -actinin, profilin (6), VASP (7) have been identified as being associated with the F-actin tail generated by intracellular S. flexneri (8, 9, 10). Amongst these proteins, only vinculin can directly interact with VirG, in which the 95 kDa vinculin head domain interacting with the VirG a-domain is involved in promoting the formation of actin tail from intracellular Shigella (10). However, vinculin is not only associated with Shigella actin tail but is also widely distributed in focal adhesions, filopodia and lamellipodia (11). Recently, N-WASP was identified as the Ash/Grb2 binding protein in brain, but its expression was also noted in other tissues including the colon (12, 13). The sequence of N-WASP is