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Soybean agglutinin binds a 160-kDa rat macrophage membrane glycoprotein and enhances cell differentiation and
W Krugluger1, T Lucas, M Köller
1Institute of General and Experimental Pathology, AKH, Vienna, Austria.
Abstract:
Mature macrophages (M phi) differ from other rat leukocytes by their ability to bind soybean agglutinin (SBA). In this study we identify the SBA-binding structure on rat bone marrow-derived M phi (BMDM phi). Precipitation of iodinated membrane proteins from rat bone marrow cells (BMC) and BMDM phi with SBA revealed a major glycoprotein of Mr 160 kDa on BMDM phi but not on BMC. In addition minor bands migrating at 70 and 26 kDa were seen. Stimulation of BMDM phi with 100 nM SBA induced a decrease in surface density of Thy1.1 (MRC OX7) and His54 and an increase in the expression of MRC OX6 (RT1.B/I-A), MRC OX17 (RT1.D/I-E), MRC OX41 (gp 110/120), MRC OX42 (CD11b/c), Macl (CD11b/CR3) and Mac2 (galectin-3/IgE binding protein) antigen. Expression of other M phi differentiation antigens recognized by mAb MRC OX43 (M phi, endothelial cells) and ED9 (M phi/CD14 like) were not significantly altered. BMDM phi derived from cultures with M phi colony-stimulating factor (M-CSF) and SBA showed increased oxidative burst and phagocytic activity compared to cells cultured with M-CSF alone. Our data suggest that binding of a 160-kDa membrane glycoprotein on M phi by N-acetylgalactosamine-specific lectins stimulates M phi differentiation and activation.
Insights
Mature macrophages bind soybean agglutinin (SBA) via a 160-kDa glycoprotein. This interaction stimulates macrophage differentiation and enhances phagocytic activity, suggesting a role for lectin binding in immune cell activation.
Area of Science:
- Immunology
- Cell Biology
Background:
- Mature macrophages (M phi) possess unique lectin-binding properties, distinguishing them from other leukocytes.
- Soybean agglutinin (SBA) is a lectin known to bind specifically to N-acetylgalactosamine residues.
Purpose of the Study:
- To identify the specific structure on rat bone marrow-derived macrophages (BMDM phi) responsible for SBA binding.
- To investigate the functional consequences of SBA binding on macrophage differentiation and activation.
Main Methods:
- Proteomic analysis using SBA precipitation of iodinated membrane proteins from rat bone marrow cells and BMDM phi.
- Flow cytometry to assess changes in surface antigen expression following SBA stimulation.
- Functional assays measuring oxidative burst and phagocytic activity in M phi cultured with M-CSF and SBA.
Main Results:
- A major 160-kDa glycoprotein was identified as the primary SBA-binding structure on BMDM phi.
- SBA stimulation led to altered expression of key macrophage differentiation antigens (e.g., MRC OX6, MRC OX42, Mac2).
- BMDM phi treated with M-CSF and SBA exhibited enhanced oxidative burst and phagocytic activity compared to M-CSF alone.
Conclusions:
- The 160-kDa membrane glycoprotein is crucial for SBA binding on rat macrophages.
- N-acetylgalactosamine-specific lectin binding to this glycoprotein promotes M phi differentiation and activation, impacting cellular functions.