LAMP-1 DOES NOT ACQUIRE THE LARGE POLYLACTOSAMINOGLYCANS CHARACTERISTIC OF F9 CELLS

Although F9 cells labelled with [H-3]glucosamine synthesize many glyco proteins that bind to Datura stramonium agglutinin-agarose, only a sma ll proportion of these were immunoprecipitated with monoclonal antibod ies to lamp-I and lamp-2 (lamp = lysosomal membrane protein). Differen tiation of F9 cells by retinoic acid increased labelling of all Datura stramonium-bound glycoproteins, including lamp-I and lamp-2. Although the large polylactosaminoglycans excluded from Bio-Gel P-6 that are c haracteristic of F9 cells were obtained from total glycoproteins, litt le of these large polylactosaminoglycans was found on lamp-1 and lamp- 2. There was no increase in large polylactosaminoglycans of lamp-I and lamp-2 after retinoic acid treatment, but an increase in the size of small polylactosaminoglycans (included on Bio-Gel P-6) and tri- and te tra-antennary complex oligosaccharides. Therefore, other factors besid es the expression of specific glycosyltransferases determine the exten t of elongation of polylactosaminoglycans on lysosomal membrane protei ns.