Translocation of enterohemorrhagic Escherichia coli effector Tir to the plasma membrane via host Golgi apparatus

The translocated intimin receptor (Tir) is a canonical type III secretion system effector, secreted by the enterohemorrhagic Escherichia coli (E. coli). This receptor alters the regular cellular processing of host cells, to promote intracellular bacterial replication and evasion of the host immune system. Tir is translocated and integrated into the host cell plasma membrane, a process required for its pathogenic activity in these cells, however, the underlying mechanisms of how this occurs remain to be elucidated. The present study used immunofluorescence and immunoelectron microscopy to demonstrate that the Tir of enterohemorrhagic E. coli was localized to the plasma membrane and colocalized with the 58K Golgi protein of the host cells. Treatment with brefeldin A destroyed the Golgi structure, inhibited the formation of actin pedestal and blocked the localization of Tir on the host cell plasma membrane. The results of the present study suggested that Tir is translocated to the host plasma membrane in a Golgi-dependent manner. It may mimic the activities of eukaryotic secretory proteins in order to make use of the Golgi apparatus for transportation and integration into the plasma membrane. These findings reveal a novel trafficking pathway for the translocation of bacterial secretory effectors to their specific subcellular compartments.