Pfkfb1 Selectively Identifies Macrophages Harboring Intracellular Growing Bacteria

Through releasing virulence molecules into host cells, intracellular bacteria interfere with host cellular functions and grow in the cells that engulf them. To ensure survival and virulence, these pathogens also manipulate host factors, but this process is not fully understood. In this study, we investigated the host molecular mechanisms required for intracellular bacterial growth in macrophages using Salmonella typhimurium (Salmonella) infection model and bacterial division reporter system. Upon Salmonella infection, Protein Phosphatase 6 (Pp6) was significantly reduced in macrophages containing growing bacteria. Conditional knockout of Pp6 increased host susceptibility to Salmonella-mediated killing, which was attributed to the poor resistance in Pp6-deficient macrophages. MicroRNA-31 (miR-31) was identified as a negative regulator of Pp6, and its conditional deletion promoted Salmonella clearance. Moreover, a yeast two-hybrid screening identified 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 1 (Pfkfb1), a key metabolic regulator, as a substrate of Pp6. Pp6-deficient macrophages exhibited elevated Pfkfb1 expression. Furthermore, we found that macrophages containing growing Salmonella exclusively exhibited high Pfkfb1 expression. Pfkfb1 deletion reduced bacterial growth, likely due to increased NO levels, while also downregulating arginase-1 (Arg-1) expression and impairing arginine biosynthesis and metabolism in macrophages. Together, we investigated the role of Pp6-Pfkfb1 axis in orchestrating host metabolic adaptions and intracellular bacterial survival, which may provide therapeutic targets for infectious diseases against intracellular multidrug-resistant bacteria.