Researchers at the Helmholtz Centre for Infection Research (HZI) have identified the molecule that enables the enterohemorrhagic E. coli to move across the surface of a host cell and reproduce without being flushed out. They found that a host cell molecule called IRSp53 enables a connection between the bacterial effectors, Tir and EspFU.
“The prerequisite for this signal pathway is a special secretion system—a sort of molecular syringe, through which the bacteria insert entire proteins in the host cell,” explains Theresia Stradal, Ph.D., head of the signal transduction and motility research group at HZI.
The researchers were trying to understand how Tir and EspFU enter into contact with one another in the host cell. They found that IRSp53 gathers on the cell surface, directly beneath the bacteria sitting on it and then draws Tir and EspFU from the bacterium into the host cell.
The host cell then presents Tir on its surface, and the bacterium recognizes this molecule thus adhering to the host cell. EspFU then triggers the signal for local actin conversion into a mobile base, or pedestal. This acts as a secure anchor for the bacterium but still allows it to move across the cell surface. “Cells in which IRSp53 is lacking are no longer able to form pedestals for the bacteria,” adds Markus Ladwein, Ph.D., also of HZI.
The article is published on March 19 in Cell Host & Microbe.