Interactions of Bacterial Toxin CNF1 and Host JAK1/2 Driven by Liquid-Liquid Phase Separation Enhance Macrophage Polarization

Urinary tract infections (UTIs) are a global public health concern, which is mainly caused by uropathogenic Escherichia coli (UPEC). Cytotoxic necrotizing factor 1 (CNF1) is a key UPEC toxin and regulates multiple host cellular processes through activating the Rho GTPases; however, the effect of CNF1 on macrophage polarization remains unknown. Here, we found that CNF1 promoted M1 macrophage polarization through regulating NF-κB and JAK-STAT1 signaling pathways in kidney at an early stage of acute UTIs. Notably, we identified CNF1 could directly interact with JAK1/2 through its domain without Rho GTPases activation, which induced JAK1/2 phosphorylation, subsequent STAT1 activation and M1 polarization. Moreover, CNF1 exhibited liquid-liquid phase separation (LLPS) to induce a CNF1-JAK1/2 complex, promoting macrophage reprogramming. These findings highlight the LLPS-dependent and Rho GTPase-independent effect of CNF1 as an adaptor on interfering with host cell signals.