THE ENTEROHEMORRHAGIC ESCHERICHIA COLI EFFECTOR PROTEIN NLEF BINDS MAMMALIAN HOST PROTEINS

Abstract

The extracellular human pathogens enterohemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC) and the related mouse pathogen Citrobacter rodentium inject type III secretion system (T3SS) effector proteins to promote their replication, survival and transmission. The mechanisms of action and the host targets of T3SS effectors are under active investigation because of their importance to bacterial virulence. The non-locus of enterocyte effacement (LEE)-encoded protein F, NleF, contributes to E. coli and Citrobacter colonization of animals through an unclear mechanism. Here we sought to characterize the host binding partners of NleF. Using a yeast two-hybrid screen, we identified a set of mammalian proteins as NleF-binding partners including Tmp21, a type-I integral membrane protein and COPI-vesicle receptor involved in trans-Golgi network function. We confirmed this interaction using bacterial two-hybrid, immunoprecipitation and bimolecular fluorescence complementation (BiFC). To consider the effects of NleF on protein trafficking, we expressed a temperature-sensitive vesicular stomatitis virus glycoprotein (VSVG) with temperature dependent localization and monitored protein trafficking. We determined that NleF does not block, but rather slows the intracellular trafficking of VSVG from endoplasmic reticulum to Golgi.