Related Experiment Videos
Defect of calmodulin-binding protein in expression of interleukin-1 beta gene by LPS-nonresponder C3H/HeJ mouse
Y Terada1, H Shinomiya, M Nakano
1Department of Microbiology, Jichi Medical School, Tochigi-ken, Japan.
Abstract:
Peritoneal macrophages of Lipopolysaccharide (LPS)-refractory C3H/HeJ mouse failed to express the mRNA coding interleukin 1 (IL-1) beta when stimulated by the Ca2+ ionophore A23187 or LPS, though macrophages of LPS-responsive C3H/He responded to these stimulants. These results suggest that the defect of the response in C3H/HeJ macrophages toward LPS stimulation may be related to the Ca2+-dependent signal pathway. The extracts from the C3H/HeJ macrophages showed normal activities of both protein kinase C (PKC) and calmodulin (CaM) in comparison with those from LPS-responsive C3H/He macrophages. However, one species of CaM-binding proteins could hardly be detected by the cross-linking assay with 125I-CaM in C3H/HeJ macrophages stimulated by LPS. These results suggest that the LPS-refractory site in C3H/HeJ macrophages is related to the lack of this CaM-binding protein, and the Ca2+-dependent CaM system may play an important role in the activation of cells by LPS.
Insights
Lipopolysaccharide (LPS)-refractory mice exhibit a defect in interleukin-1 beta (IL-1β) production. This points to a deficiency in a specific calmodulin-binding protein crucial for LPS-induced cellular activation.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Lipopolysaccharide (LPS) is a key component of Gram-negative bacteria that triggers immune responses.
- Interleukin-1 beta (IL-1β) is a critical cytokine involved in inflammation and immune signaling.
- C3H/HeJ mice are known for their refractory response to LPS, unlike LPS-responsive strains.
Purpose of the Study:
- To investigate the molecular basis of LPS unresponsiveness in C3H/HeJ mouse macrophages.
- To identify the specific signaling pathway defect responsible for the lack of IL-1β production.
Main Methods:
- Primary peritoneal macrophages were isolated from LPS-refractory C3H/HeJ and LPS-responsive C3H/He mice.
- Cells were stimulated with LPS or the Ca2+ ionophore A23187.
- mRNA expression of IL-1β was quantified.
- Protein kinase C (PKC) and calmodulin (CaM) activities were assessed.
- A cross-linking assay using 125I-CaM was performed to detect CaM-binding proteins.
Main Results:
- C3H/HeJ macrophages failed to express IL-1β mRNA upon stimulation with LPS or A23187, while C3H/He macrophages responded normally.
- PKC and CaM activities were comparable between the two mouse strains.
- A specific CaM-binding protein was significantly reduced or absent in LPS-stimulated C3H/HeJ macrophages.
Conclusions:
- The LPS-refractory phenotype in C3H/HeJ macrophages is linked to the deficiency of a particular CaM-binding protein.
- The Ca2+-dependent calmodulin system appears to play a vital role in LPS-induced macrophage activation.