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Protein phosphorylation in murine peritoneal macrophages induced by infection with Salmonella species
S Saito1, H Shinomiya, M Nakano
1Department of Microbiology, Jichi Medical School, Tochigi-ken, Japan.
Abstract:
Infection of peritoneal macrophages from C3H/HeN and C3H/HeJ mice with Salmonella typhimurium or S. enteritidis induced extensive phosphorylation in a set of proteins with molecular masses of 85, 72, 35, 30, and 23 kDa, which were different from those induced by bacterial lipopolysaccharide. The phosphorylated proteins of 35, 30, and 23 kDa (pp35, pp30, and pp23, respectively) originated from the infecting bacteria, because living bacteria could induce these phosphorylated proteins themselves, and no induction of the proteins occurred in macrophages after phagocytosis of heat-killed or UV-irradiated organisms. When the infected macrophages were disrupted and separated into bacterial and macrophage debris fractions, pp85 and pp72 remained in the macrophage debris fraction, with none in the bacterial fraction. Induction of pp85 and pp72 in infected macrophages was inhibited in the presence of chloramphenicol but not cytochalasin D, suggesting that bacterial growth in the macrophages is necessary for induction of both proteins. Neither of these proteins could be detected in macrophages infected with Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, or Listeria monocytogenes. These results support the view that phosphorylation of the 85- and 72-kDa proteins occurs in the macrophages during the early phases of the interaction between Salmonella organisms and macrophages. The functions of specific proteins remain to be clarified.
Insights
Salmonella infection triggers specific protein phosphorylation in mouse macrophages, with some proteins originating from bacteria and others from the host cells. Bacterial growth is essential for host protein induction.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Salmonella species are significant intracellular pathogens.
- Understanding host-pathogen interactions at the molecular level is crucial for developing effective treatments.
Purpose of the Study:
- To investigate protein phosphorylation changes in macrophages upon Salmonella infection.
- To differentiate between bacterial and host-derived phosphorylated proteins.
Main Methods:
- Peritoneal macrophages from C3H/HeN and C3H/HeJ mice were infected with Salmonella typhimurium or S. enteritidis.
- Phosphorylation patterns were analyzed using techniques to separate bacterial and macrophage components.
- Inhibition studies were performed using chloramphenicol and cytochalasin D.
Main Results:
- Salmonella infection induced phosphorylation of 85, 72, 35, 30, and 23 kDa proteins, distinct from lipopolysaccharide-induced changes.
- Phosphorylated proteins of 35, 30, and 23 kDa originated from live bacteria.
- Phosphorylated proteins of 85 and 72 kDa were host-derived and required bacterial growth for induction.
- These host proteins were specific to Salmonella infection, not observed with other bacteria like E. coli or S. aureus.
Conclusions:
- Salmonella infection induces distinct host and bacterial protein phosphorylation events in macrophages.
- Host protein phosphorylation (pp85, pp72) depends on bacterial viability and growth within macrophages.
- Further research is needed to elucidate the functions of these phosphorylated proteins in host-pathogen interactions.