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Updated: Aug 9, 2026
Bone Marrow-derived Macrophage Production
Published on: November 22, 2013
Down-modulation through protein kinase C-alpha of lipopolysaccharide-induced expression of membrane CD14 in mouse
1Molecular Immunophysiology Unit, URA-1961 of the National Center for Scientific Research, Pasteur Institute, Paris, France.
Abstract:
We have previously shown that stimulation of mouse bone marrow granulocytes (BMC) by lipopolysaccharide (LPS) induces the expression of CD14. We found here that phorbol 12-myristate 13-acetate (PMA) blocks this LPS effect. The aim of this study was to investigate the mechanism by which PMA can block the LPS signaling pathway in BMC. The unmodified binding of a radiolabeled LPS in PMA-treated cells indicated that the PMA effect was not the consequence of a shedding or an internalization of the LPS receptor, but was rather due to a biochemical event that follows the interaction of LPS with its receptor. The observations that a selective activator of protein kinase C (PKC)-alpha (sapintoxin D) mimics the PMA effect, whereas a selective PKC-alpha inhibitor (Ro-320432) antagonizes this effect, suggest a regulatory role of PKC-alpha in the LPS signaling pathway in mouse BMC.
Insights
Phorbol 12-myristate 13-acetate (PMA) blocks lipopolysaccharide (LPS) induced CD14 expression in mouse bone marrow granulocytes (BMC). This blockage occurs downstream of LPS receptor binding, implicating protein kinase C-alpha in LPS signaling.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Lipopolysaccharide (LPS) stimulation of mouse bone marrow granulocytes (BMC) induces CD14 expression.
- Phorbol 12-myristate 13-acetate (PMA) has been observed to inhibit this LPS-induced effect.
Purpose of the Study:
- To elucidate the mechanism by which PMA inhibits LPS signaling in BMC.
- To investigate the role of protein kinase C-alpha (PKC-alpha) in this inhibitory pathway.
Main Methods:
- Radiolabeled LPS binding assays were performed on PMA-treated BMC.
- Selective PKC-alpha activator (sapintoxin D) and inhibitor (Ro-320432) were used to probe the signaling pathway.
Main Results:
- PMA treatment did not affect LPS receptor binding or internalization.
- Sapintoxin D mimicked the inhibitory effect of PMA on LPS signaling.
- Ro-320432 reversed the inhibitory effect of PMA, suggesting PKC-alpha involvement.
Conclusions:
- PMA inhibits LPS signaling in BMC via a post-receptor binding mechanism.
- Protein kinase C-alpha plays a regulatory role in the LPS signaling pathway in mouse BMC.
