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Characterization of macrophage adhesion molecule
1Center for Blood Research, Boston, Massachusetts 02115.
Abstract:
Macrophage adhesion molecule (MAM), an abundant surface molecule which functions in the adhesion and spreading of guinea pig macrophages on surfaces, is characterized as a heterodimer of the trypsin- and plasmin-sensitive glycopeptide gp160 (MAM-alpha) and the glycopeptide gp93 (MAM-beta). The density of MAM molecules is estimated at 630,000 per macrophage on the basis of quantitative binding of 125I-labeled monoclonal antibody. The glycopeptide subunits display microheterogeneity on isoelectrofocusing; the pI is 5.8-6.3 for gp160 (MAM-alpha) and 6.4-7.0 for gp93 (MAM-beta). A neutrophil gp160, gp93 molecule was shown to be indistinguishable from macrophage MAM on the basis of electrophoresis, isoelectrofocusing, and reactivity with 10 monoclonal antibodies. A related heterodimer of gp93 associated with a larger, antigenically different glycopeptide (gp180,gp93) was identified on circulating lymphocytes. Cumulative properties indicate that MAM is the guinea pig analogue of human Mo1 and mouse Mac-1.
Insights
Macrophage adhesion molecule (MAM) is a heterodimer crucial for guinea pig macrophage adhesion. This molecule is the guinea pig equivalent of human Mo1 and mouse Mac-1.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Macrophage adhesion molecule (MAM) is a key surface protein involved in macrophage adhesion and spreading.
- MAM is abundant on guinea pig macrophages, with an estimated density of 630,000 molecules per cell.
Purpose of the Study:
- To characterize the molecular structure and properties of Macrophage adhesion molecule (MAM).
- To identify potential analogues of MAM in other species.
Main Methods:
- Quantitative binding assays using 125I-labeled monoclonal antibody.
- Isoelectrofocusing to analyze glycopeptide subunits.
- Electrophoresis and reactivity testing with monoclonal antibodies.
Main Results:
- MAM is a heterodimer of gp160 (MAM-alpha) and gp93 (MAM-beta), sensitive to trypsin and plasmin.
- Glycopeptide subunits exhibit microheterogeneity with specific isoelectric points (pI).
- A gp160, gp93 molecule in neutrophils is identical to macrophage MAM; a related heterodimer (gp180,gp93) exists on lymphocytes.
Conclusions:
- Macrophage adhesion molecule (MAM) is structurally and functionally characterized.
- MAM is identified as the guinea pig homologue of human Mo1 and mouse Mac-1, suggesting conserved functions across species.