Localized reprogramming of Rab GTPases at the Shigella containing vacuole to trigger vacuolar rupture by mechanotransduction – RabReprogram

Shigella is an intracellular pathogen representing an important public health threat. Despite extensive research, there is no universal vaccine against Shigella infections and there is a rise in antibiotic resistance. Shigella targets non-phagocytic epithelial cells of the gut, where it escapes from the bacterial containing vacuole (BCV) upon cell invasion. BCV rupture is a key event for virulence, since Shigella is only able to proliferate once it has gained access to the host cytosol. Previously, the subversion of Rab GTPases that are recruited to in situ formed macropinosomes in the vicinity of the BCV orchestrate contacts with the BCV and enhance release of the bacteria into the cytosol. How the BCV itself is involved in these processes has remained unclear. Here we will investigate Rab GTPase subversion directly at the BCV. Based on strong preliminary data, we will study the direct post-translational modification of one specific Rab GTPase by a bacterial effector protein. We hypothesize that this Rab reprogramming elicits a spatially confined signaling cascade involving Rab effectors and cytoskeletal components to induce mechanical forces. These forces are important to rip the BCV apart, to transport the membrane remnants away from the invading bacterium, and to leave the bacterium “naked” in the cytosol for infection progression. We will apply cutting-edge methodologies for the study of the molecular events of this process including advanced in cellulo cryo tomography. Our work will decipher the molecular details of the key steps around BCV rupture, and it will open possibilities for rational development of host-targeted antimicrobial approaches.