MicroRNA target Fc receptors to regulate Ab-dependent Ag uptake in primary macrophages and dendritic cells
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Published on: May 31, 2018
Afsar Raza Naqvi1, Jezrom B Fordham1, Salvador Nares2
1Department of Periodontics, University of Illinois at Chicago, Chicago, IL, USA.
Abstract:
Phagocytosis commences with particle internalization and culminates with the activation of innate and adaptive immune responses. However, the role of miRNAs in phagocytosis remains largely unknown. In this study, we examined the role of miR-24, miR-30b and miR-142-3p in Ab Fc receptor (FcR)-mediated phagocytosis by macrophages (MΦ) and dendritic cells (DC). The expression of these miRNAs was reduced following phagocytosis of both IgG-opsonized beads and Escherichia coli, indicating their regulatory role in the process. Further, overexpression of these miRNAs impaired the uptake of IgG-coated latex beads, which corroborated the reduced secretion of the pro-inflammatory cytokines TNF-α and IL-8 and down-regulation of PKC-α, as well as superoxide-generating enzyme NADPH oxidase 2 expression level. Mechanistically, MΦ and DC transfected with miRNA mimics show marked reduction in expression of FcRs including FCGR2A, FcɛR1G and FCER2. We show that FcɛR1G expression is not affected at the transcription level, rather it is post-transcriptionally regulated by miR-30b. Finally, we demonstrate that siRNA-mediated knockdown of FcɛR1G leads to reduced uptake of IgG-opsonized beads, indicating its involvement on Ab-mediated phagocytosis. These results uncover miR-24, miR-30b and miR-142-3p as an essential component of FcR-mediated phagocytosis and associated innate immune responses.
Insights
MicroRNAs (miRNAs) regulate antibody (Ab) Fc receptor (FcR)-mediated phagocytosis. This study reveals miR-24, miR-30b, and miR-142-3p are crucial for macrophage and dendritic cell phagocytic activity.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Phagocytosis is a key cellular process involving particle uptake and immune activation.
- The role of microRNAs (miRNAs) in phagocytosis, particularly Fc receptor (FcR)-mediated phagocytosis, is not well understood.
- Investigating miRNA involvement can elucidate novel regulatory mechanisms in innate and adaptive immunity.
Purpose of the Study:
- To investigate the role of miR-24, miR-30b, and miR-142-3p in Fc receptor (FcR)-mediated phagocytosis by macrophages (MΦ) and dendritic cells (DC).
- To elucidate the molecular mechanisms by which these miRNAs regulate phagocytosis and associated immune responses.
Main Methods:
- Quantitative analysis of miRNA expression in MΦ and DC after phagocytosis.
- Overexpression and knockdown studies of specific miRNAs and Fc receptor genes.
- Measurement of cytokine secretion (TNF-α, IL-8) and expression of key proteins (PKC-α, NADPH oxidase 2).
- Assessment of Fc receptor (FCGR2A, FcɛR1G, FCER2) expression at transcriptional and post-transcriptional levels.
Main Results:
- Expression of miR-24, miR-30b, and miR-142-3p decreased following phagocytosis of IgG-opsonized beads and Escherichia coli.
- Overexpression of these miRNAs impaired IgG-coated latex bead uptake, reduced pro-inflammatory cytokine secretion, and decreased PKC-α and NADPH oxidase 2 expression.
- miRNA mimics reduced Fc receptor expression, with miR-30b specifically regulating FcɛR1G post-transcriptionally.
- Knockdown of FcɛR1G reduced IgG-opsonized bead uptake.
Conclusions:
- miR-24, miR-30b, and miR-142-3p are essential regulators of Fc receptor-mediated phagocytosis in macrophages and dendritic cells.
- These miRNAs influence key downstream signaling molecules and Fc receptor expression, impacting innate immune responses.
- The findings reveal a novel post-transcriptional regulatory role for miR-30b in FcɛR1G expression during phagocytosis.
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