The effector protein Hcp1 of avian pathogenic Escherichia coli causes mitochondrial dysfunction by interacting with...

The pathogenic mechanisms of virulence factors in avian pathogenic Escherichia coli (APEC) targeting eukaryotic cells have gained extensive attention. Hemolysin co-regulatory protein (Hcp), a key element for the secretion of the type VI secretion system (T6SS), functions as an effector protein mediating attacks on host cells. Mitochondria in eukaryotic cells are increasingly considered key participants in host-pathogen interactions. While Hcp in APEC has been extensively studied, the potential for Hcp1, one of the core proteins in the hcp family, to modulate mitochondrial function during infection remains unexplored. In this study, we discovered that the deletion of hcp1 influences bacterial biological characteristics and is critical for bacterial virulence. Previous studies have shown that bacterial virulence factors can interfere with mitochondrial function. Therefore, we further investigated the impact of Hcp1 on cellular mitochondria. After incubating Hcp1 with HD-11 cells, we observed a significant decrease in the mitochondrial membrane potential, an increase in the mitochondrial Ca^2 + concentration, elevated levels of reactive oxygen species, and a reduction in ATP levels, suggesting that Hcp1 induces mitochondrial dysfunction in HD-11 cells. To evaluate the molecular mechanisms underlying mitochondrial dysfunction, we employed LC-MS/MS to identify mitochondria-associated proteins potentially interacting with Hcp1, and PHB2 was identified as a candidate. Protein and molecular docking results demonstrated strong binding activity between Hcp1 and PHB2, and co-immunoprecipitation confirmed their interaction. In summary, T6SS effector protein Hcp1 influences the pathogenicity of APEC, potentially by interacting with PHB2 to induce HD-11 cells' mitochondrial dysfunction.