Study of Lawsonia intracellularis interactions with cell culture mitochondria.

Lawsonia intracellularis is an important obligate intracellular bacterium. It localizes in close proximity to mitochondria within host cells. Mitochondria regulate diverse physiological processes in host cells, thereby significantly affecting the intracellular proliferation of bacteria. However, how L. intracellularis interacts with mitochondria to promote its own proliferation remains unclear. In this study, the mitochondrial morphology of McCoy cells infected with L. intracellularis was examined by indirect immunofluorescence assay (IFA), and L. intracellularis infection was found to induce mitochondrial elongation. Subsequently, the intracellular L. intracellularis load was assessed by IFA and qPCR following the alteration of mitochondrial morphology. The results showed that the intracellular L. intracellularis load was increased in cells with elongated mitochondria and decreased in cells with fragmented mitochondria. Western blot analysis revealed that the L. intracellularis outer membrane protein Omp2 inhibited ERK1/2 phosphorylation. This inhibition led to a reduction in Drp1 protein levels, thereby inducing mitochondrial elongation. Furthermore, Omp2 interacted with macrophage migration inhibitory factor (MIF), an upstream regulator of ERK1/2, and Omp2 suppressed MIF-induced ERK1/2 phosphorylation, suggesting that MIF is involved in the Omp2-mediated regulation of ERK1/2 phosphorylation.