Internalization of Shigella flexneri into HeLa cells occurs without an increase in cytosolic Ca super(2+) concentration

Pathogenic Shigella flexneri invades epithelial cells through directed phagocytosis. The role of intracellular free calcium ((Ca super(2+)) sub(i)) as a signal for this process was tested. No variation in the (Ca super(2+)) sub(i) could be detected by using the fluorescent indicator fura 2 to measure the (Ca super(2+)) sub(i) in HeLa cells during the invasion process. In addition, neither clamping nor maximal decreasing or increasing of the (Ca super(2+)) sub(i) of HeLa cells had any effect on their susceptibility to invasion. These data demonstrate that (Ca super(2+)) sub(i) is not a signal for S. flexneri) directed phagocytosis in HeLa cells.