Metabolism of Exogenous Gangliosides in Cerebellar Granule Cells, Differentiated in Culture

The metabolism of exogenous gangliosides in the CNS has been investigated using cerebellar granule cells in culture as a model. For this purpose, GM2 and GM1, both isotopically radiolabeled at the level of the terminal sugar residue or of the long chain base moiety, were administered to differentiated cells for a 15-h pulse, and their metabolic fate was followed in a time course protocol. At each time investigated (1, 2, and 4 days after the pulse), several compounds, besides the ones administered, were detected: (a) GM2 (only after GM1 was given), GM3, lactosylceramide, glucosylceramide, and ceramide, all products of ganglioside stepwise catabolism; (b) GM1 (only after GM2 was given), GD1a, GD1b, O-Ac-GT1b, and GT1b, that is, gangliosides more complex than the one administered; and (c) sphingomyelin. The compounds derived from ganglioside catabolism and sphingomyelin were detected only after administration of long chain base-labeled precursors, whereas the others were found regardless of the labeling position of the precursor. In addition, radioactivity was incorporated in the delipidized residue when sugar-labeled gangliosides were given to cells. Besides qualitative differences, quantitative ones were found after administration of the different precursors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in the Ganglioside Long-Chain Base Composition of Rat Cerebellar Granule Cells During Differentiation and Aging in Culture

Abstract: Changes in the ganglioside long-chain base (LCB) composition in rat cerebellar granule cells in culture were studied during differentiation and aging. The total native ganglioside mixtures, extracted from the cells maintained in culture up to 22 days, were fractionated by reversed-phase HPLC, each ganglioside homogeneous in the oligosaccharide chain as well as in the LCB being quantified. Two main LCBs were components of the ganglioside species of cultured cells, the C18:1 LCB and the C20:1 LCB. The content of C20:1 ganglioside molecular species was low and quite constant during differentiation, comprising ∼8% of the total ganglioside species content, the C20:1 LCB appearing to be represented more in the ganglioside of the "b series" (GD1b, GT1b, and GQ1b) than in the "a series" (GM1 and GD1a). During aging in culture, for 8–22 days, the content of the C20:1 species of all gangliosides increased, being more pronounced for GM1 and GD1a.