Valuable insights into eukaryotic regulatory circuits can emerge from studying interactions of bacterial pathogens such as Helicobacter pylori with host tissues. H. pylori uses a type IV secretion system (T4SS) to deliver its CagA virulence protein to epithelial cells, where much of it becomes phosphorylated. CagA's phosphorylated and non‐phosphorylated forms each interact with host regulatory proteins to alter cell structure and cell fate. Kwok and colleagues1 showed that CagA destined for phosphorylation is delivered using host integrin as receptor and (...) H. pylori's CagL protein as an integrin‐specific adhesin, and that CagL–integrin‐binding activates the kinase cascade responsible for CagA phosphorylation. This research contributes to understanding infectious disease and the control of cell fates. BioEssays 30:515–520, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

Bacterial pathogens deliver effector proteins into host cells by deploying sophisticated secretion systems. This effector translocation during host‐pathogen interactions is a prerequisite for the manipulation of host cells and organisms and is important for pathogenesis. Analyses of dynamics and kinetics of translocation, subcellular localization, and cellular targets of effector proteins lead to understanding the mode of action and function of effector proteins in host‐pathogen interplay. This review provides an overview of biochemical and genetic tools that have been developed to study (...) protein effector translocation qualitatively or quantitatively. After introducing the challenges of analyses of effector translocation during host‐pathogen interaction, we describe various methods ranging from static visualization in fixed cells to dynamic live‐cell imaging of effector protein translocation. We show the main findings enabled by the approaches, emphasize the advantages and limitations of the methods, describe recent approaches that allow real‐time tracking of effector proteins in living cells on a single molecule level, and highlight open questions in the field to be addressed by application of new methods. (shrink)