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. IMPORTANCE CNF1 is a key toxin secreted by UPEC, which induces inflammation during UPEC infections. CNF1 is well known to activate Rho GTPases to disturb host cell signaling pathways. Macrophage reprogramming plays important roles in inflammation; however, the effect of CNF1 on macrophage polarization is not reported. This study demonstrated the role and mechanism of CNF1 in promoting M1 macrophage polarization during UPEC-induced acute kidney infections. Importantly, we identified Rho GTPase-independent effect of CNF1 as an adaptor on interfering with host cell signals and demonstrated that CNF1 exhibited LLPS to drive its interaction with host proteins, which improve our understanding of the UPEC-host interactions and UTI pathogenesis.
Keywords: CNF1; JAK-STAT1; liquid-liquid phase separation; macrophage polarization.