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Published on: April 27, 2018
Study of Lawsonia intracellularis interactions with cell culture mitochondria
Dong Wei1, Zhouyurong Fan1, Hong Zhou1
1MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
Abstract:
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.
Insights
Lawsonia intracellularis infection elongates host cell mitochondria, boosting bacterial numbers. The Omp2 protein inhibits ERK1/2 signaling, linking mitochondrial shape to bacterial proliferation.
Area of Science:
- Microbiology
- Cell Biology
- Molecular Biology
Background:
- Lawsonia intracellularis is an obligate intracellular bacterium impacting host cell mitochondria.
- Mitochondrial function is crucial for host cell physiology and bacterial proliferation.
- The interaction between L. intracellularis and host mitochondria is not well understood.
Purpose of the Study:
- To investigate how L. intracellularis manipulates host cell mitochondria for its proliferation.
- To elucidate the molecular mechanisms underlying L. intracellularis-induced mitochondrial alterations.
Main Methods:
- Indirect immunofluorescence assay (IFA) to examine mitochondrial morphology and bacterial load.
- Quantitative PCR (qPCR) to assess intracellular bacterial load.
- Western blot analysis to investigate protein expression and phosphorylation.
Main Results:
- L. intracellularis infection induced mitochondrial elongation in McCoy cells.
- Increased intracellular L. intracellularis load correlated with elongated mitochondria.
- The L. intracellularis outer membrane protein Omp2 inhibited ERK1/2 phosphorylation, leading to mitochondrial elongation.
- Omp2 interacted with macrophage migration inhibitory factor (MIF), suppressing MIF-induced ERK1/2 phosphorylation.
Conclusions:
- Mitochondrial morphology significantly influences L. intracellularis proliferation.
- The Omp2 protein plays a key role in regulating mitochondrial dynamics and bacterial load.
- Omp2-mediated inhibition of ERK1/2 signaling, involving MIF, is a mechanism for L. intracellularis to promote its intracellular survival and replication.
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