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Differential metabolism and trafficking of sphingolipids in differentiated versus undifferentiated HT29 cells
Author(s) -
Babia Teresa,
Kok Jan Willem,
Hulstaert Caesar,
De Weerd Henk,
Hoekstra Dick
Publication year - 1993
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.2910540519
Subject(s) - sphingolipid , sphingomyelin , ceramide , lactosylceramide , sphingosine , biochemistry , glycolipid , lipid raft , cell culture , metabolism , biology , cell , chemistry , microbiology and biotechnology , cholesterol , receptor , apoptosis , genetics
Abstract Trafficking and metabolism of sphingolipids were examined in undifferentiated (G + ) and differentiated (G + reversed) HT29 human colon adenocarcinoma cell lines. Metabolic experiments employing a fluorescently labeled sphingolipid precursor, 6‐[ N ‐(7‐nitro‐2,1,3‐benzoxadiazol‐4‐yl)amino]hexanoylceramide (C 6 ‐NBD‐ceramide) revealed that both qualitative and quantitative differences exist in sphingolipid synthesis between the 2 cell lines. One of the C 6 ‐NBD‐sphingolipids synthesized in G + cells is not found in the G + reversed cells. Furthermore, the ratio of the 2 main products, C 6 ‐NBD‐glucosyiceramide and C 6 ‐NBD‐sphingomyelin, differs: in G + cells glucosylceramide is by far the main product, whereas G + reversed cells synthesize C 6 ‐NBD‐sphingomyelin in slight excess. Once established, these ratios of sphingolipids are quickly restored metabolically when distortion of the ratio is caused by experimental manipulation. This indicates that they represent a true metabolic equilibrium situation of the 2 sphingolipids in these cells, while the distinct ratios are mainly determined by the NBD‐lipid pool in the plasma membrane. Preferential synthesis and transfer of glucosylceramide from its site of synthesis to the cell surface do not occur when the plasma membrane pool of glucosylceramide is selectively removed. This suggests that instantaneous replenishment via specific signalling is probably not involved as a mechanism in re‐establishing perturbed lipid pools. In conjunction with observations on distinct lipid trafficking pathways of glucosylceramide in G + and G + reversed cells, the present metabolic studies emphasize a relation between the expression of this glycolipid and the state of differentiation of HT29 cells.