A Dual-Targeting T6SS DNase Drives Bacterial Antagonism and Eukaryotic Apoptosis via the cGAS-STING-TNF Axis.

The Type VI secretion system (T6SS) is a key virulence mechanism utilized by many Gram-negative bacteria to mediate the microbial competition and host pathogenesis. Despite the identification of diverse T6SS effectors targeting eukaryotic or prokaryotic cells, the trans-kingdom T6SS effectors that simultaneously target both eukaryotic and prokaryotic cells remain rarely reported. In this study, it is demonstrated that Yersinia pseudotuberculosis (Yptb) T6SS secretes a DNase effector, TkeA, which induces apoptosis in host cells. The translocation of TkeA into host cells causes nuclear DNA damage. This, in turn, activates the DNA-sensing cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway. The activation of the cGAS-STING pathway by TkeA subsequently triggers apoptosis in host cells via extrinsic pathways, with tumor necrosis factor (TNF) signaling playing a critical role. Additionally, TkeA enhances bacterial competition by targeting rival bacteria, thereby promoting host colonization. These findings reveal that the transkingdom T6SS effector TkeA executes a "one weapon, two battlefields" strategy, acting as a trans-kingdom effector that enhances interbacterial competition while inducing apoptosis in host cells through the activation of the cGAS-STING-TNF axis. This highlights a previously unrecognized dimension of bacterial virulence strategies and expands the understanding of host-pathogen interactions involving T6SS effectors.