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Identification of macrophage external membrane proteins and their possible role in cell adhesion
Abstract:
Starch-activated mouse peritoneal macrophages (STpMAC) plated on plastic demonstrate the adhesive properties typical for activated pMAC: attaching as round cells and, within 15 min, spreading out with marginal membrane ruffles. These attached STpMAC were labeled by lactoperoxidase-catalysed 125I surface iodination, sodium dodecyl-sulfate-lysed, and the lysates electrophoresed on polyacrylamide gels which were examined by autoradiography. The STpMAC morphological phenotype correlates with the labeling of a particular protein (195,000, estimated mol wt). Normal pMAC (NpMAC), from unstimulated mice, do not spread and do not display the 195,000 band. Both pMAC band patterns, including the 195,000 band, are relatively resistant to trypsin digestion, as is pMAC adhesion itself trypsin-resistant. Neither class of pMAC exhibits fibronectin (Cell Adhesion Factor, LETS protein) which is a component in the adhesive matrix of cells forming trypsin-sensitive monolayers. When pMAC are tested against antifibronectin antibody, these cells do not give immunofluorescent staining. In summary, two functions in pMAC adhesion, enzyme resistance and the ability to spread, appear related to molecular properties distinctive for pMAC surface protein.
Insights
Starch-activated mouse peritoneal macrophages (STpMAC) exhibit unique adhesive properties, including spreading and enzyme resistance, linked to a distinct 195,000 molecular weight surface protein. This protein is absent in normal peritoneal macrophages (NpMAC).
Area of Science:
- Cell Biology
- Immunology
- Protein Chemistry
Background:
- Mouse peritoneal macrophages (pMAC) are immune cells with adhesive functions.
- Activated pMAC exhibit distinct morphological and adhesive characteristics compared to normal pMAC (NpMAC).
Purpose of the Study:
- To investigate the molecular basis of adhesion in starch-activated mouse peritoneal macrophages (STpMAC).
- To identify specific surface proteins associated with STpMAC adhesive properties.
Main Methods:
- STpMAC and NpMAC were cultured on plastic.
- Surface iodination using lactoperoxidase, cell lysis, SDS-PAGE, and autoradiography were employed.
- Trypsin digestion and antifibronectin antibody immunofluorescence were used to assess protein and cell surface characteristics.
Main Results:
- STpMAC demonstrated spreading and marginal membrane ruffles, unlike NpMAC.
- A specific 195,000 molecular weight protein band was detected in STpMAC but not in NpMAC.
- Both STpMAC adhesion and the 195,000 protein band showed resistance to trypsin digestion.
- Neither STpMAC nor NpMAC exhibited fibronectin on their surface.
Conclusions:
- The adhesive functions of STpMAC, including spreading and trypsin resistance, are associated with a unique 195,000 MW surface protein.
- This protein is a distinguishing molecular feature of activated peritoneal macrophages.
- Peritoneal macrophages do not appear to utilize fibronectin in their adhesive matrix.