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Expression of a 120,000 dalton protein during tumoricidal activation in murine peritoneal macrophages
Abstract:
Modulation of protein expression during interferon-gamma (IFN-gamma)-lipopolysaccharide (LPS)-mediated macrophage tumoricidal activation has been examined by metabolic radiolabeling of various murine peritoneal macrophage populations with [35S]methionine followed by SDS-PAGE analysis. Although both IFN-gamma and LPS are capable of stimulating the expression of several proteins when used independently, combined treatment induced the enhanced or de novo expression of a 120,000 dalton polypeptide. The expression of this protein was synergistically regulated by both IFN-gamma and LPS in a manner strongly reminiscent of the functional synergism that these two agents exhibit with respect to induction of tumoricidal activity. p120 expression could be seen first at approximately 3 hr after the addition of both agents, reached optimal expression by 6 hr, and maintained elevated synthesis for up to 24 hr. This time course corresponds closely to that seen for the acquisition of tumoricidal competence. Macrophages elicited in the primed state of activity in vivo with methyl vinyl ether co-polymer II (MVE-II) did not express p120, but could be induced to do so when treated with low doses of LPS. Under similar conditions, MVE-II-elicited cells also acquire tumoricidal activity. Macrophages obtained from mice chronically infected with bacillus Calmette-Guerin constitutively expressed both p120 and cytolytic activity. If such macrophages were cultured for 24 hr, the expression of both events decayed and was lost, but could be restored by treatment with low doses of LPS. Thus the data support a strong correlation between the expression by macrophages of a novel 120,000 dalton protein and the expression of tumor cytotoxicity.
Insights
Researchers identified a novel 120,000 dalton protein (p120) whose expression in macrophages correlates with tumor cell killing. This protein
Area of Science:
- Immunology
- Molecular Biology
- Cellular Biology
Background:
- Macrophage activation is crucial for anti-tumor immunity.
- Interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS) synergistically activate macrophages for tumoricidal activity.
- Protein expression changes during this activation process are not fully understood.
Purpose of the Study:
- To investigate protein expression modulation during IFN-gamma and LPS-mediated macrophage tumoricidal activation.
- To identify specific proteins correlated with macrophage tumoricidal function.
Main Methods:
- Murine peritoneal macrophages were metabolically radiolabeled with [35S]methionine.
- Protein expression was analyzed using SDS-PAGE.
- Macrophage populations were stimulated with IFN-gamma and/or LPS.
Main Results:
- Combined IFN-gamma and LPS treatment induced de novo expression of a 120,000 dalton polypeptide (p120).
- p120 expression was synergistically regulated by both cytokines, mirroring functional synergism in tumoricidal activity.
- p120 expression kinetics (onset at 3 hr, peak at 6 hr) correlated with the acquisition of tumoricidal competence.
- p120 expression was inducible in MVE-II-elicited macrophages and constitutively present in BCG-infected macrophages, both associated with tumoricidal activity.
Conclusions:
- A novel 120,000 dalton protein (p120) is strongly correlated with macrophage-mediated tumor cytotoxicity.
- p120 expression serves as a potential molecular marker for activated tumoricidal macrophages.
- The findings provide insights into the molecular mechanisms underlying macrophage anti-tumor responses.