Enteropathogenic Escherichia coli (EPEC) is a gram-negative bacterium that can be found in the lower intestine of humans and it is associated with acute gastroenteritis. EPEC relies on type III secretion system (T3SS) or injectisome to deliver effector proteins directly into the host cells. The importance of this T3SS relies on the fact that its basic structure is shared among different pathogenic organisms as Yersinia spp. or Salmonella spp.
Once the T3SS is assembled, translocators and chaperones interact to mediate the recognition and attachment of the bacteria to the gut cells and effector proteins are released to cause disease onset.
Three different parts can be distinguished in the T3SS: the basal structure, the needle complex and the translocation pore. The needle complex is the part of the T3SS that connects the bacterial outer membrane with the host cell membrane. The full assembly of the needle of the T3SS is crucial for the delivery of the effectors without which the bacterial infection won’t be developed.
Using the single molecule confocal microscopy and protein – protein interaction assay, here we study the oligomerisation/aggregation propensity of the different components of the needle complex and the way the proteins interact. We also test the capacity of these proteins to allow membrane penetration and form the translocation pore or the way that their co-expressions modify their normal behaviour.
The next step in this study would be to analyse the way EPEC effectors are able to disrupt multiple pathways in the host cell and validate the host targets using proteomics. Here we mainly target the effectors involved in actin reorganization, cell-to-cell junction formation and apoptosis pathways, as these are the pathways profoundly affected during EPEC infection. Eventually, we will perform live cell imaging to follow the impact of the effectors inside the cells.