Different metabolic recycling of the lipid components of exogenous sulphatide in human fibroblasts.
Cultured human fibroblasts were fed with two differently labelled sulphatide molecules [one labelled on C-3 of the sphingosine (Sph) moiety [( Sph-3H]sulphatide), the second on C-1 of stearic acid [( stearoyl-14C]sulphatide)], and the intracellular metabolic fate of radioactivity was monitored. Incorporated radioactivity was almost all recovered in the total lipid extract, regardless of the labelling position of the added sulphatide; however, large differences in the level of incorporation occurred among labelled glycosphingolipids. For example, sphingomyelin was present as the major radiolabelled lipid after [Sph-3H]-sulphatide incubation, but was detectable only in trace amounts after [stearoyl-14C]sulphatide administration; in the latter case the radioactivity was located predominantly in glycerophospholipids. From this finding it can be inferred that the free long-chain base (sphingosine) that originates from lysosomal catabolism of sulphatide is mainly, and quite specifically, utilized for sphingomyelin biosynthesis, whereas the ceramide moiety is not; conversely the fatty acid released from ceramide is non-specifically re-utilized for phospholipid biosynthesis.
Department of Medical Chemistry and Biochemistry, Medical School, University of Milan, Italy.
M
M
Trinchera
U
U
Wiesmann
M
M
Pitto
D
D
Acquotti
R
R
Ghidoni
D002250:Carbon Radioisotopes; D002478:Cells, Cultured; D002855:Chromatography, Thin Layer; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D050356:Lipid Metabolism; D010743:Phospholipids / Q000096:biosynthesis; D013109:Sphingomyelins / Q000096:biosynthesis; D013110:Sphingosine / Q000378:metabolism; D013229:Stearic Acids / Q000378:metabolism; D013433:Sulfoglycosphingolipids / Q000378:metabolism*; D014316:Tritium
D002250:Carbon Radioisotopes; D010743:Phospholipids; D013109:Sphingomyelins; D013229:Stearic Acids; D013433:Sulfoglycosphingolipids; D014316:Tritium; C031183:stearic acid; D013110:Sphingosine