Enrichment of the intracellular dolichol pool in isolated liver cells

Isolated hepatocytes were incubated with egg lecithin liposomes containing dolichol(C55), dolichol(C95), and dolichol phosphate(C55) in order to enrich intracellular membranes with these polyprenols. After incubation, the lipids were recovered from various membrane fractions and from the supernatant. The highest concentration was found in the microsomes. A part of the dolichol in microsomes, as well as in other fractions, was phosphorylated. This phosphorylation is mediated by the CTP-specific kinase that is present only on the outer surface of the microsomes and uses alpha-saturated polyprenols as substrates. The isolated microsomes enriched with dolichol in vivo exhibited increased lipid and protein glycosylation upon incubation with nucleotide sugars and it was demonstrated that the increased lipid glycosylation was due to transfer of the sugar to the exogenous incorporated dolichol.