Boland, Sebastian, Sampaio, Julio, L., Zagoriy, Vyacheslav, Fritsche, Raphael, Reimann, Jakob, Lubken, Tilo, Knolker, Hans-Joachim, Penkov, Sider, Czerwonka, Regina, Schmidt, Ulrike, Kurzchalia, Teymuras, V.
[
International Worm Meeting,
2017]
Caenorhabditis elegans (C. elegans) cannot synthesize cholesterol de novo, and requires exogenous cholesterol to progress through its four larval stages. Previously, we showed that worms grown for 2 generations in the absence of cholesterol arrest early in development. This suggests that maternal contributions of sterols are exploitable only in the first generation, but sterol reservoirs are either depleted or inaccessible by the second generation. Here, we present a novel class of phosphorylated glycosphingolipids, which we coined phosphoethanolamine glucosylceramides (PEGCs), that can overcome the sterol deprivation-induced larval arrest. However, they are not direct substitutes for cholesterol because they rescue larval arrest in only one additional generation. Instead, we propose a new model where larval arrest in the second generation of continious sterol deprivation is due not to depletion of internal reservoirs, but a failure to mobilize those reservoirs for promoting growth/development through PEGCs-induced mobilization of internal sterol pools. More precisely, we found that NPC1 and DAF-7 mutants, which display a Daf-c phenotype due to an impaired sterol transport to places of DA synthesis, are rescued by feeding PEGC. Moreover, the biosynthesis of PEGC depends on functional NPC1 and TGF- beta , indicating that these proteins control larval development at least partly through promoting increases in PEGC. Furthermore, glucosylceramide deficiency dramatically reduced PEGC amounts; however, the resulting developmental arrest could be rescued by over-saturation of food with cholesterol. This indicates that PEGC is a major regulator of cholesterol utilization in C. elegans and, thus, of development. The remarkable similarity in sterol trafficking between C. elegans and other metazoans, including mammals, suggests PEGCs might be conserved regulators of sterol transport.