Bacterial virulence proteins as tools to rewire kinase pathways in yeast and immune cells

Virulence factors from two bacteria are used to reprogram intracellular signalling in yeast and immune T cells, illustrating how pathogens can provide a toolkit to engineer cells for biotechnological or therapeutic applications. Virulence proteins are a useful resource Effector proteins developed by bacterial pathogens to subvert host systems have potential uses in cell engineering for biotechnological or therapeutic applications. For example, many proteins from pathogens with the type III secretion system interfere with mitogen-activated protein kinase (MAPK) pathways. MAPK pathways are central to many eukaryotic responses, so agents capable of modulating them could have many uses — in biotechnological cells such as yeast, in immune cells engineered for adoptive immunotherapy, or to suppress cell growth associated with cancer, for instance. As a proof of principle, Wendell Lim and colleagues use two bacterial virulence factors, OspF from Shigella flexneri and YopH from Yersinia pestis , to modulate MAPK signalling in yeast and human immune cells. Bacterial pathogens have evolved specific effector proteins that, by interfacing with host kinase signalling pathways, provide a mechanism to evade immune responses during infection 1 , 2 . Although these effectors contribute to pathogen virulence, we realized that they might also serve as valuable synthetic biology reagents for engineering cellular behaviour. Here we exploit two effector proteins, the Shigella flexneri OspF protein 3 and Yersinia pestis YopH protein 4 , to rewire kinase-mediated responses systematically both in yeast and mammalian immune cells. Bacterial effector proteins can be directed to inhibit specific mitogen-activated protein kinase pathways selectively in yeast by artificially targeting them to pathway-specific complexes. Moreover, we show that unique properties of the effectors generate new pathway behaviours: OspF, which irreversibly inactivates mitogen-activated protein kinases 4 , was used to construct a synthetic feedback circuit that shows novel frequency-dependent input filtering. Finally, we show that effectors can be used in T cells, either as feedback modulators to tune the T-cell response amplitude precisely, or as an inducible pause switch that can temporarily disable T-cell activation. These studies demonstrate how pathogens could provide a rich toolkit of parts to engineer cells for therapeutic or biotechnological applications.