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MFR, a putative receptor mediating the fusion of macrophages
C Saginario1, H Sterling, C Beckers
1Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA.
Abstract:
We had previously identified a macrophage surface protein whose expression is highly induced, transient, and specific, as it is restricted to actively fusing macrophages in vitro and in vivo. This protein is recognized by monoclonal antibodies that block macrophage fusion. We have now purified this protein and cloned its corresponding cDNA. This protein belongs to the superfamily of immunoglobulins and is similar to immune antigen receptors such as the T-cell receptor, B-cell receptor, and viral receptors such as CD4. We have therefore named this protein macrophage fusion receptor (MFR). We show that the extracellular domain of MFR prevents fusion of macrophages in vitro and therefore propose that MFR belongs to the fusion machinery of macrophages. MFR is identical to SHPS-1 and BIT and is a homologue of P84, SIRPalpha, and MyD-1, all of which have been recently cloned and implicated in cell signaling and cell-cell interaction events.
Insights
Researchers identified a novel macrophage fusion receptor (MFR) crucial for cell fusion. Blocking MFR inhibits macrophage fusion, revealing its role in the fusion machinery.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- A previously identified macrophage surface protein is specifically expressed on fusing macrophages.
- Monoclonal antibodies targeting this protein inhibit macrophage fusion.
Purpose of the Study:
- To purify and clone the cDNA of the macrophage fusion protein.
- To characterize the protein's function and its role in macrophage fusion.
Main Methods:
- Protein purification and cDNA cloning.
- Analysis of protein homology to immunoglobulin superfamily members.
- In vitro assays using extracellular MFR domain to assess fusion inhibition.
Main Results:
- The macrophage fusion protein was purified and its cDNA cloned, naming it macrophage fusion receptor (MFR).
- MFR belongs to the immunoglobulin superfamily, showing similarity to immune antigen receptors (TCR, BCR) and viral receptors (CD4).
- The extracellular domain of MFR was shown to inhibit macrophage fusion in vitro, indicating its role in the fusion machinery.
Conclusions:
- Macrophage fusion receptor (MFR) is a key component of the macrophage fusion machinery.
- MFR's structural similarity to immune receptors suggests a role in cell-cell interactions and signaling.
- MFR is identical to SHPS-1 and BIT, and homologous to P84, SIRPalpha, and MyD-1, linking it to broader cell signaling pathways.