Sphingolipid-enriched membrane domains from rat cerebellar granule cells differentiated in culture. A compositional study.
Sphingolipid-enriched membrane domains, characterized by a particular protein and lipid composition, have been detected in a variety of cells. However, limited data are available concerning these domains in neuronal cells. We analyzed the lipid and protein composition of a sphingolipid-enriched membrane fraction prepared from primary rat cerebellar granule cells differentiated in culture. Although the protein content of this fraction was only 1.4% of total cellular protein, 60% of the gangliosides, 67% of the sphingomyelin, 50% of the ceramide, and 40% of the cholesterol were located in this fraction. The protein pattern of the sphingolipid-enriched domain fraction was dramatically different from that associated with the cell homogenate. This fraction contained 25% of the tyrosine-phosphorylated proteins and was enriched in two proteins with apparent molecular masses of 135 and 15 kDa. 12% of cellular glycerophospholipids were located in the fraction, with phosphatidylcholine having the highest enrichment. The molar ratio between proteins, glycerophospholipids, cholesterol, sphingomyelin, ceramide and gangliosides in cerebellar granule cells was 1.6:41.6:6. 1:1.3:0.3:1 in the cell homogenate and 0.04:8.3:4.0:1.4:0.2:1 in the sphingolipid-enriched membrane fraction. These data indicate that selected proteins segregate with sphingolipids in specialized domains in the membrane of cultured neurons.
Prinetti
A
A
Study Center for the Functional Biochemistry of Brain Lipids, Department of Medical Chemistry and Biochemistry, Laboratorio Interdisciplenane Tecnologie Avanzate-Segrate, The Medical School, University of Milan, 20090 Milano, Italy.
Chigorno
V
V
Tettamanti
G
G
Sonnino
S
S
D000818:Animals; D002454:Cell Differentiation; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology*; D002855:Chromatography, Thin Layer; D003594:Cytoplasmic Granules; D004591:Electrophoresis, Polyacrylamide Gel; D008715:Methionine / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013107:Sphingolipids / Q000032:analysis*; D013110:Sphingosine / Q000032:analysis
D010710:Phosphates; D013107:Sphingolipids; D008715:Methionine; D013110:Sphingosine