Identification of a 185 kd Maclura pomifera agglutinin binding glycoprotein as a candidate for a differentiation marker for alveolar type II cells in adult rat lung.

In adult rat lung the lectin Maclura pomifera agglutinin (MPA) binds apically to alveolar type II (ATII) cells but not to alveolar type I (ATI) cells. This suggests that the presence of MPA binding glycoproteins might be a criterion by which to distinguish the differentiated state of these two adult alveolar epithelial cells. The authors therefore studied MPA binding glycoproteins of ATII cells, comparing, biochemically and cytochemically, MPA binding glycoproteins in freshly isolated ATII cells with those in cultures of ATII cells that are "dedifferentiating" or have "dedifferentiated" as a result of growth on tissue culture plasticware. A MPA binding glycoprotein (185 kd) that is present in freshly isolated "differentiated" ATII cells and then is subsequently lost as isolated ATII cells "dedifferentiate" in tissue culture has been identified. This 185 kd MPA binding glycoprotein alone, or expressed in conjunction with other proteins, is a candidate for a differentiation marker for ATII cells. Preliminary data suggests that this 185 kd MPA binding glycoprotein is not found in ATI cells.