The glycosylceramides of the nematodeCaenorhabditis elegans contain an unusual, branched‐chain sphingoid base

Abstract

Caenorhabditis elegans was cultured in semi-defined medium containing yeast extract, soy peptone, glucose, hemoglobin, Tween 80, and sitosterol. Monoglycosylceramides were chromatographically purified from nematode extracts. Their structures were elucidated with mass spectrometry, nuclear magnetic resonance spectroscopy, and analysis of methanolysis products of the parent cerebrosides. The glycosylceramides were unusual in that the only long-chain sphingoid base detected was an iso-branched compound with a C-4 double bond (i.e., 15-methyl-2-aminohexadec-4-en-1,3-diol). Glucose was the only sugar moiety detected. The fatty acids consisted of a series of primarily straight-chain, saturated, 2-hydroxylated C20-C26 acids; some iso-branched analogs also occurred. The sphingomyelins of C. elegans were also hydrolyzed, and the same iso-branched C17 compound was the only sphingoid base detected. This is the first structural analysis of a nematode glycosphingolipid and the first report of an organism in which the long-chain sphingoid bases are entirely iso-branched.

Expression of ceramide glucosyltransferases, which are essential for glycosphingolipid synthesis, is only required in a small subset ofC. eleganscells

“…Additional studies show that mutations in genes involved in oligosaccharide addition to GSLs suppress gain-of-function mutations in lin-12/Notch, implying that complex GSLs act as positive regulators of Notch signalling (Katic et al, 2005). Recent work shows that mutations in genes required for the synthesis of C17 branched-chain fatty acids -which are normally incorporated into the GSL backbone -cause arrest at the first larval stage (L1) (Chitwood et al, 1995;Kniazeva et al, 2004;Entchev et al, 2008;Kniazeva et al, 2008). Mutant animals carrying these mutations have altered levels of C17 ceramides, as well as unusual ceramides (Entchev et al, 2008).…”

Protection of C. elegans from Anoxia by HYL-2 Ceramide Synthase

“…Simultaneous deletion of both hyl-1 and hyl-2 is lethal (10). Sphingolipids from C. elegans are somewhat different from their counterparts in other eukaryotes because they contain exclusively isosphingoid bases (14), which are presumably used by the dihydroceramide synthases from worms. Nevertheless, hyl-1 can complement the loss of function of yeast LAG1 and LAC1 (15).…”

“…In many organisms, multiple ceramide synthases are expressed, each displaying fatty acylCoA specificity to produce a diversity of ceramides differing in their fatty acyl chains (18)(19)(20). Ceramides are the precursors for sphingolipids, including sphingomyelins, which are present in C. elegans (14). We quantified the major ceramide (Cer) and sphingomyelin (SM) species of C. elegans N2, hyl-1(ok976), and hyl-2(gnv1) animals by electrospray ionization mass spectrometry (ESI-MS).…”

Characterization of free endogenous C14 and C16 sphingoid bases from Drosophila melanogaster

“…Sphingolipids have been most thoroughly characterized in mammalian cells, in which the predominant molecular species of free LCBs are C 18 and C 20 sphingosine (Sph) and C 18 and C 20 dihydrosphingosine (DHS), and in Saccharomyces cerevisiae , in which the predominant molecular species are C 18 and C 20 phytosphingosine and C 18 and C 20 DHS (7)(8)(9)(10)(11). Sphingolipid molecular structures have also been determined for numerous other species (12)(13)(14)(15)(16)(17)(18)(19). However, in most of the latter, the sphingoid backbone structures have been determined through degradative analysis of higher order sphingolipids, whereas the structural characterization and quantitation of LCB signaling molecules have not been reported.…”