Triggered phagocytosis by Salmonella: bacterial molecular mimicry of RhoGTPase activation/deactivation.

Salmonella Typhimurium uses the type III secretion system encoded in the Salmonella pathogenicity island I (SPI-1 TTSS) to inject toxins (effector proteins) into host cells. Here, we focus on the functional mechanism of three of these toxins: SopE, SopE2, and SptP. All three effector proteins change the GTP/GDP loading state of RhoGTPases by transient interactions. SopE and SopE2 mimic eukaryotic G-nucleotide exchange factors and thereby activate RhoGTPase signaling pathways in infected host cells. In contrast, a domain of SptP inactivates RhoGTPases by mimicking the activity of eukaryotic GTPase-activating proteins. The Salmonella-host cell interaction provides an excellent example for the use of molecular mimicry by bacterial pathogens.