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Pasteurella multocida toxin and Bordetella bronchiseptica dermonecrotizing toxin elicit similar effects on cultured
T Ohnishi1, Y Horiguchi, M Masuda
1Department of Bacterial Toxinology, Research Institute for Microbial Disease, Osaka University, Japan.
Abstract:
We compared the effects of Pasteurella multocida toxin (PMT) with Bordetella bronchiseptica dermonecrotizing toxin (DNT) at a cellular level under same conditions. Both PMT and DNT cause actin stress fiber formation in MC3T3-E1 cells which is known to be regulated by the small GTP-binding protein Rho. DNT induced mobility shifts of Rho on SDS-polyacrylamide gel electrophoresis, indicating direct modification as reported elsewhere. In contrast, no alternations in the electrophoretic mobility of Rho were found in lysates from PMT-treated cells. PMT but not DNT increased the intracellular level of inositol phosphates, indicating the elevation of phospholipase C (PLC) activity in the PMT-treated cells. These results indicate that PMT does not have Rho as a target but activates PLC. The formation of actin stress fiber by PMT seems to be stimulated through the indirect activation of Rho, which resides downstream of PLC, PMT and DNT seem to elicit similar toxic effects, at least in part, through the activation of Rho.
Insights
Pasteurella multocida toxin (PMT) and Bordetella bronchiseptica dermonecrotizing toxin (DNT) both induce actin stress fiber formation. PMT activates phospholipase C (PLC), indirectly activating Rho, while DNT directly modifies Rho.
Area of Science:
- Cellular Biology
- Toxicology
- Molecular Biology
Background:
- Pasteurella multocida toxin (PMT) and Bordetella bronchiseptica dermonecrotizing toxin (DNT) are bacterial toxins with significant cellular effects.
- Both toxins are known to induce actin stress fiber formation in eukaryotic cells, a process regulated by the small GTP-binding protein Rho.
- Understanding the distinct molecular mechanisms of these toxins is crucial for elucidating their pathogenic roles.
Purpose of the Study:
- To compare the cellular effects of PMT and DNT under identical experimental conditions.
- To investigate the specific molecular targets and pathways activated by PMT and DNT.
- To determine whether PMT and DNT converge on the Rho signaling pathway despite potential differences in their mechanisms.
Main Methods:
- MC3T3-E1 cells were treated with purified PMT and DNT.
- Actin stress fiber formation was visualized using microscopy.
- Rho protein modification was assessed via SDS-polyacrylamide gel electrophoresis.
- Intracellular inositol phosphate levels were measured to assess phospholipase C (PLC) activity.
Main Results:
- Both PMT and DNT induced actin stress fiber formation in MC3T3-E1 cells.
- DNT directly modified Rho, as evidenced by mobility shifts on SDS-PAGE.
- PMT treatment led to increased intracellular inositol phosphates, indicating activation of PLC, but did not alter Rho electrophoretic mobility.
- PMT appears to activate Rho indirectly, downstream of PLC activation.
Conclusions:
- PMT and DNT elicit similar cellular effects, such as actin stress fiber formation, through Rho activation.
- PMT's mechanism involves the activation of PLC, leading to indirect Rho activation, whereas DNT directly modifies Rho.
- These findings highlight distinct yet convergent pathways utilized by bacterial toxins to manipulate host cell cytoskeleton.