LECTIN-MEDIATED UPTAKE OF LYSOSOMAL HYDROLASES BY GENETICALLY DEFICIENT HUMAN-FIBROBLASTS

Human placental hexosaminidase B and β-galactosidase are not readily taken up by human fibroblasts in culture. However, fibroblasts manifesting genetically determined deficiencies of these lysosomal hydrolases may be induced to take them up by treatment of the cells with the lectin, concanavalin A (ConA). Hexosaminidase B and β-galactosidase become associated with ConA-treated cells at 4 °C and 37 °C. However, the enzyme which becomes cell-associated at 4 °C is readily removed by treatment of the cell with the haptene sugar α-methy lmannoside, while enzyme which becomes cell-associated at 37 °C cannot be removed by haptene treatment. The amount of hexosaminidase B which becomes cell-associated increases with increasing lectin concentration up to a level of about 100 μg/ml and plateaus thereafter. The amount of hexosaminidase B which becomes cell-associated after treatment of the cell with a fixed amount of lectin displays a sigmoidal dependence on enzyme concentration. After treatment of Sandhoff disease cells with ConA and hexosaminidase B at 37 °C, enzyme activity can be localized within the cell by a histochemical technique. These observations are interpreted as an initial binding of enzyme to multivalent lectin molecules located at the cell surface followed by an endocytotic process leading to internalization of both lectin and lectin-bound enzyme. Our results suggest that lectins may be useful tools for manipulating the enzyme content of cells in culture. © 1979.