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Biomedical subjects

M Inbar

Publications and source records attributed to M Inbar.

100 records · Page 6Linked to original sources
PubMed1971

A specific metabolic activity on the surface membrane in malignant cell-transformation.

The carbohydrate-binding protein, Concanavalin A (Con A), binds to glucose- or mannose-like sites on the cell-surface membrane. Unless the cells are treated with trypsin, this protein agglutinates malignantly transformed cells, but not normal cells. The transformed cells were agglutinated at 24 degrees C but not at 4 degrees C. Transformed and normal cells treated with trypsin were agglutinated at both 24 degrees C and 4 degrees C with high concentrations of Con A (500 mug/ml), but only at 24 degrees C with low concentrations (5 mug/ml). The same number of Con A molecules were bound to normal and transformed cells at both temperatures. The results indicate that the site for Con A on the surface membrane contains two activities, a component that binds Con A molecules (B) and a component that determines agglutination (A). B is not temperature sensitive and is active in normal and transformed cells, whereas A, which is temperature sensitive, is in an active form only in transformed cells. A can be activated by trypsin, and the increased activity per cell allows agglutination at 4 degrees C with a high, but not with a low, concentration of Con A. Agglutination of transformed cells by wheat-germ agglutinin, which binds to N-acetyl-D-glucosamine-like sites, and by soybean agglutinin, which binds to N-acetyl-D-galactosamine-like sites, was not temperature sensitive. Thus, the temperature-sensitive component A is specific for Con A, and malignant transformation of normal cells, which results in agglutinability by Con A, is associated with the activation of a specific temperature-sensitive activity on the surface membrane.

Agglutination Tests↗
PubMed1969

Interaction of the carbohydrate-binding protein concanavalin A with normal and transformed cells.

It has been shown that the carbohydrate-binding protein concanavalin A (ConA) can agglutinate leukemic cells and cells transformed by polyoma virus, simian virus 40, chemical carcinogens, and X-irradiation. This protein did not agglutinate normal cells under the same conditions. The agglutination was reversed by competition with alpha-methyl-D-glucopyranoside (alpha-MG), a carbohydrate that strongly binds to ConA, but not by the carbohydrates alpha-methyl-L-fucopyranoside or N-acetylglucosamine, with no binding or weak binding to ConA. Destruction of the alpha-MG binding sites of the native protein by removal of bivalent metal ions abolished the agglutination produced by the native protein. The treatment of cells with trypsin resulted in the agglutination of normal cells by ConA and a decrease of agglutinability of transformed cells. When nonagglutinating untransformed 3T3 cells were infected with simian virus 40 and normal rat cells were infected with polyoma virus, the infected cells became agglutinable several days after virus infection. The percentage of cells agglutinated, about 50 per cent, was much higher than the percentage of cells hereditarily transformed. The results indicate that the surface membrane of transformed cells contains sites that interact with the alpha-MG binding sites of ConA, that such sites can be found on the surface membrane of normal cells after treatment with trypsin, and that the change in the surface structure from normal to transformed occurs in cells that are abortively transformed.

Agglutination↗