Oligodendrocyte-substratum adhesion activates the synthesis of specific lipid species involved in cell signaling.
Ovine oligodendrocytes (OLGs) undergo biochemical and morphological changes following attachment to polylysine. Autoradiographs of two-dimensional thin-layer chromatograms of [14C]Gal-labeled OLG cultures revealed that attachment of OLGs to a polylysine substratum and their subsequent morphological differentiation is accompanied by an increased synthesis of multiple forms of galactosylceramide, sulfogalactosylceramide, and both sulfogalactosyl- and galactosyl-diglycerides, together with an array of complex sialoglycosphingolipids, predominantly GM2 ganglioside. As previously reported, overall lipid synthesis measured by [14C]acetate incorporation into glycerophosphatides, sphingomyelin, and neutral lipids also increased dramatically for up to 60 days (last time point examined) following OLG-substratum adhesion, reflecting membrane growth. Attachment was associated with a rapid augmentation in the synthesis of ethanolamine plasmalogen from 12 to 27% within 24 hr to reach a 35% plateau at 30 days and remain constant thereafter. In contrast, the plasmalogen content of phosphatidylcholine remained constant at 3-5%. This rapid increase in lipid synthesis (especially in the ethanolamine plasmalogen content following attachment) closely paralleled increased diacylglycerol (DAG) production and protein kinase C-dependent phosphorylation of both myelin basic protein and 2',3'-cyclic nucleotide phosphohydrolase. Labeling studies indicated that the major source of [3H]arachidonate-labeled DAG following attachment was from phosphatidylinositol turnover (and to a lesser extent phosphatidylcholine) rather than polyphosphoinositides or plasmalogens. Enhanced lipid synthesis is not only required for the production of membranes in these myelin-producing cells but is also a source of second messengers required in the posttranslational modification of key myelin and cellular proteins.
Vartanian
T
T
Department of Biochemistry and Molecular Biology, University of Chicago, Illinois.
Szuchet
S
S
Dawson
G
G
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology; D004075:Diglycerides / Q000096:biosynthesis; D006028:Glycosphingolipids / Q000096:biosynthesis; D050356:Lipid Metabolism; D009836:Oligodendroglia / Q000378:metabolism / Q000502:physiology*; D010743:Phospholipids / Q000378:metabolism; D010770:Phosphotransferases / Q000378:metabolism; D015398:Signal Transduction
D004075:Diglycerides; D006028:Glycosphingolipids; D010743:Phospholipids; D016718:Arachidonic Acid; D010770:Phosphotransferases