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

The metabolism of two radiolabelled glycosphingolipids, lactosylceramide and GM1 ganglioside, in differentiated and undifferentiated HT-29 cells is reported. Both lactosylceramide and GM1 ganglioside were demonstrated to be extensively catabolized in undifferentiated cells, as deduced by the relative amount of the compounds formed along the degradative pathway. Conversely, in differentiated cells both precursors were utilized as substrates for sugar-chain elongation. Furthermore we were unable to detect any significant difference in the activity of CMP-NeuAc:GM1 alpha 2-->3sialyltransferase, a Golgi key enzyme for the glycosylation of glycosphingolipids, between the two cell populations. Taken together with our previous results on the differentiation-dependent trimming of high-mannose N-linked glycoproteins in HT-29 cells, one can 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.