Identification of a major poly‐ N ‐acetyllactosamine‐containing cell‐surface glycoprotein of mouse teratocarcinoma cells

Mouse teratocarcinoma F9 cells were induced to primitive endoderm differentiation with retinoic acid, and poly‐ N ‐acetyllactosamine‐containing surface glycoproteins were identified by radiolabelling endo‐β‐galactosidase‐cleavable glycans with galactosyltransferase and radiolabelled UDP‐galactose. One major radiolabelled band with an apparent size of 250–500 kDa was identified which differed from the known poly‐ N ‐acetyllactosamine‐containing glycoproteins laminin, fibronectin, lysosome‐associated membrane protein (LAMP)‐1 and LAMP‐2. This acidic glycoprotein, resistant to glycosaminoglycan‐degrading enzymes and proteases, was purified by extraction and phase partition with Triton X‐114, octyl Sepharose and Helix pomatia lectin chromatography. The purified glycoprotein could be digested by endo‐β‐galactosidase and glycopeptide N ‐glycosidase F to an apparent size of 160–240 kDa. During retinoic‐acid‐induced differentiation into primitive endoderm cells, the glycoprotein showed a several‐fold increase and a broadening to an apparent size of 200–> 700 kDa. The glycoprotein was no longer detected in retinoic‐acid and dibutyryl‐cAMP‐treated cells which had undergone further differentiation to parietal endoderm cells, nor in the permanently differentiated parietal endoderm line F9‐AC. The results suggest that the glycoprotein is a major carrier of poly‐ N ‐acetyllactosamine chains on differentiating teratocarcinoma F9 cells, and that its expression as revealed by the poly‐ N ‐acetyllactosamine labelling method is regulated by the stage of cellular differentiation.