THE METABOLIC PROCESSING OF GLYCOSPHINGOLIPIDS IN HT-29 CELLS IS DIFFERENTIATION-DEPENDENT

The metabolism of two radiolabelled glycosphingolipids, lactosylcerami de and GM1 ganglioside, in differentiated and undifferentiated HT-29 c ells is reported. Both lactosylceramide and GM1 ganglioside were demon strated to be extensively catabolized in undifferentiated cells, as de duced by the relative amount of the compounds formed along the degrada tive pathway. Conversely, in differentiated cells both precursors were utilized as substrates for sugar-chain elongation. Furthermore we wer e unable to detect any significant difference in the activity of CMP-N euAc:GM1 alpha 2-->3sialyltransferase, a Golgi key enzyme for the glyc osylation of glycosphingolipids, between the two cell populations. Tak en together with our previous results on the differentiation-dependent trimming of high-mannose N-linked glycoproteins in HT-29 cells, one c an suggest that common steps control the anabolic/catabolic balance of these two classes of glycoconjugates as a function of differentiation . (C) 1994 Academic Press, Inc.