An Apical-Type Trafficking Pathway Is Present in Cultured Oligodendrocytes but the Sphingolipid-enriched Myelin Membrane Is the Target of a Basolateral-Type Pathway

AUTOR(ES)

de Vries, Hans

FONTE

The American Society for Cell Biology

RESUMO

Myelin sheets originate from distinct areas at the oligodendrocyte (OLG) plasma membrane and, as opposed to the latter, myelin membranes are relatively enriched in glycosphingolipids and cholesterol. The OLG plasma membrane can therefore be considered to consist of different membrane domains, as in polarized cells; the myelin sheet is reminiscent of an apical membrane domain and the OLG plasma membrane resembles the basolateral membrane. To reveal the potentially polarized membrane nature of OLG, the trafficking and sorting of two typical markers for apical and basolateral membranes, the viral proteins influenza virus–hemagglutinin (HA) and vesicular stomatitis virus–G protein (VSVG), respectively, were examined. We demonstrate that in OLG, HA and VSVG are differently sorted, which presumably occurs upon their trafficking through the Golgi. HA can be recovered in a Triton X-100-insoluble fraction, indicating an apical raft type of trafficking, whereas VSVG was only present in a Triton X-100-soluble fraction, consistent with its basolateral sorting. Hence, both an apical and a basolateral sorting mechanism appear to operate in OLG. Surprisingly, however, VSVG was found within the myelin sheets surrounding the cells, whereas HA was excluded from this domain. Therefore, despite its raft-like transport, HA does not reach a membrane that shows features typical of an apical membrane. This finding indicates either the uniqueness of the myelin membrane or the requirement of additional regulatory factors, absent in OLG, for apical delivery. These remarkable results emphasize that polarity and regulation of membrane transport in cultured OLG display features that are quite different from those in polarized cells.

Documentos Relacionados

• N-Terminal Protein Acylation Confers Localization to Cholesterol, Sphingolipid-enriched Membranes But Not to Lipid Rafts/Caveolae
• Two large glycosylated polypeptides found in myelinating oligodendrocytes but not in myelin.
• Myelin-associated glycoprotein, a cell adhesion molecule of oligodendrocytes, is phosphorylated in brain.
• An Endosome-to-Plasma Membrane Pathway Involved in Trafficking of a Mutant Plasma Membrane ATPase in Yeast
• The lysomal trafficking of sphingolipid activator proteins (SAPs) is mediated by sortilin