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MafB enhances the phagocytic activity of RAW264.7 macrophages by promoting Fcgr3 expression
Takako Nemoto1, Yoko Shibata1, Sumito Inoue1
1Department of Cardiology, Pulmonology, and Nephrology, Yamagata University School of Medicine, Yamagata, Japan.
Abstract:
This study was designed to investigate whether MafB influences the phagocytic activity of macrophages by modulating the expression of the Fc receptors for IgG (FcγRs), Fcgr2b and Fcgr3. In macrophages, FcγRs are critical for the phagocytosis of opsonized pathogens. Of these receptors, Fcgr3 has been shown to play an important role in host defense. As a model to evaluate the mechanism by which MafB influences phagocytosis, we utilized a macrophage cell-line that constitutively expresses a MafB-specific short hairpin (sh)RNA (RAW264.7-MafB-shRNA). Specifically, the levels of Fc receptor mediated-phagocytosis and the levels of FcγRs surface expression were evaluated by flow cytometry analysis, while quantitative real-time PCR analysis was utilized to examine the mRNA expression levels of FcγRs. Compared to the control cell population, RAW264.7-MafB-shRNA cells exhibited significant reductions in Fcgr3 expression and Fc receptor-mediated phagocytosis, but no difference in Fcgr2b expression. Likewise, there was markedly decreased surface expression of Fcgr3 antigen, but not Fcgr2b antigen, in RAW264.7-MafB-shRNA, compared to the control cells. Meanwhile, the observed reduction in the phagocytic activity of the MafB-shRNA-expressing cells was attenuated by ectopic expression of Fcgr3. Together, the results presented here indicate that MafB influences the phagocytic activity of macrophages by promoting Fcgr3, but not Fcgr2b, expression.
Insights
The transcription factor MafB enhances macrophage phagocytosis by increasing Fc gamma receptor 3 (Fcgr3) expression. This study shows MafB is crucial for Fcgr3-mediated phagocytic activity against pathogens.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Macrophages are key immune cells involved in phagocytosis of pathogens.
- Fc gamma receptors (FcγRs) on macrophages mediate the uptake of opsonized particles.
- Fcgr3 plays a significant role in host defense mechanisms.
Purpose of the Study:
- To investigate the role of the transcription factor MafB in regulating macrophage phagocytic activity.
- To determine if MafB influences the expression of Fc gamma receptors (FcγRs), specifically Fcgr2b and Fcgr3.
- To elucidate the mechanism by which MafB affects Fc receptor-mediated phagocytosis.
Main Methods:
- Utilized a macrophage cell line (RAW264.7) engineered to express MafB-specific short hairpin RNA (shRNA).
- Assessed Fc receptor-mediated phagocytosis and FcγRs surface expression using flow cytometry.
- Quantified FcγRs mRNA expression levels via quantitative real-time PCR.
Main Results:
- Macrophages with reduced MafB expression showed significantly decreased Fcgr3 mRNA and surface protein levels.
- MafB knockdown resulted in impaired Fc receptor-mediated phagocytosis.
- No significant changes in Fcgr2b expression or phagocytic activity were observed.
- Restoring Fcgr3 expression attenuated the reduction in phagocytic activity caused by MafB knockdown.
Conclusions:
- MafB positively regulates the expression of Fcgr3 in macrophages.
- MafB significantly influences macrophage phagocytic activity through the promotion of Fcgr3 expression.
- MafB's role in Fcgr3 regulation is critical for effective host defense against pathogens.
