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LPS induces selective translocation of protein kinase C-beta in LPS-responsive mouse macrophages, but not in
H Shinji1, K S Akagawa, T Yoshida
1Tokyo Institute for Immunopharmacology Inc., Japan.
Abstract:
Translocation of protein kinase C (PKC) after PMA or LPS stimulation has been studied in thioglycolate (TGC)-elicited murine peritoneal macrophages. Among the PKC subtypes we examined (alpha, beta, gamma, delta, and epsilon) by indirect immunostaining and immunoblot analysis, conventional PKC-beta, as well as novel PKC-delta and PKC-epsilon were found to exist in TGC-elicited C3H/HeN mouse macrophages. Translocation of PKC-beta to the Triton-stable cytoskeleton could be seen in macrophages after stimulation by both PMA and LPS. On the other hand, novel PKCs redistributed only after PMA stimulation. Macrophages obtained from LPS-nonresponsive C3H/HeJ mice also exhibited PKC-beta, and the m.w., cellular distribution, and cellular content of this enzyme could not be distinguished from those of C3H/HeN macrophages. These macrophages exhibited PKC-delta and PKC-epsilon, as did the C3H/HeN macrophages. In these macrophages, however, LPS did not induce any remarkable change in the intracellular distribution of PKC-delta and PKC-epsilon or PKC-beta, whereas PMA was able to induce the translocation of PKC-beta to the cytoskeleton. These results suggest that LPS stimulation induces selective redistribution of PKC-beta in LPS-responsive macrophages, whereas a defect related to LPS unresponsiveness exists in C3H/HeJ mouse macrophages before the PKC activation. Translocation of PKC-beta can be understood to be an important event in LPS signaling in macrophages.
Insights
Lipopolysaccharide (LPS) stimulation causes protein kinase C-beta (PKC-beta) to move in macrophages. This PKC-beta translocation is a key event in LPS signaling, but is defective in LPS-unresponsive mice.
Area of Science:
- Immunology
- Cellular Biology
- Molecular Biology
Background:
- Protein kinase C (PKC) plays a crucial role in cellular signaling pathways.
- Understanding PKC subtype behavior during immune cell activation is essential for deciphering immune responses.
- Thioglycolate-elicited murine peritoneal macrophages are a model system for studying macrophage activation.
Purpose of the Study:
- To investigate the translocation of different protein kinase C (PKC) subtypes in response to phorbol 12-myristate 13-acetate (PMA) and lipopolysaccharide (LPS) stimulation.
- To compare PKC behavior in LPS-responsive (C3H/HeN) and LPS-nonresponsive (C3H/HeJ) mouse macrophages.
- To determine the role of PKC-beta translocation in LPS signaling.
Main Methods:
- Indirect immunostaining and immunoblot analysis were used to examine PKC subtypes (alpha, beta, gamma, delta, epsilon).
- Murine peritoneal macrophages from C3H/HeN and C3H/HeJ mice were stimulated with PMA and LPS.
- Intracellular distribution of PKC subtypes was analyzed before and after stimulation.
Main Results:
- Conventional PKC-beta, novel PKC-delta, and PKC-epsilon were identified in C3H/HeN macrophages.
- LPS and PMA induced PKC-beta translocation to the cytoskeleton in C3H/HeN macrophages.
- Novel PKCs only redistributed after PMA stimulation in C3H/HeN macrophages.
- LPS failed to induce significant PKC redistribution in C3H/HeJ macrophages, despite the presence of PKC subtypes.
- PMA induced PKC-beta translocation in C3H/HeJ macrophages, indicating a defect specific to LPS signaling.
Conclusions:
- LPS stimulation selectively induces PKC-beta redistribution in LPS-responsive macrophages.
- A defect in LPS unresponsiveness exists in C3H/HeJ macrophages prior to PKC activation.
- PKC-beta translocation is a critical event in the lipopolysaccharide (LPS) signaling pathway in macrophages.