(c) Simplified overview of phosphatidyl choline (PC) metabolism in C. elegans. P-choline, phosphorylcholine; CDP-choline, cytidyldiphosphate choline; PC, phosphatidylcholine; PS, phosphatidylserine; PS DC, phosphatidylserine decarboxylase; PE, phosphatidylethanolamine; Ptd-MeEtn, phosphatidylmonomethylethylamine. Intermediates whose levels are altered in
hpl-2 mutant worms compared to wild type are shown in red. (e) Metabolism of sphingomyelin and ceramide. De novo sphingomyelin synthesis is mediated by sphingomyelin synthase (SMS), which transfers the phosphorylcholine moiety from phosphatidylcholine (PC) onto ceramide, forming sphingomyelin and diacylglycerol (DAG). In C. elegans there are three SMS genes,
sms-1, -2, and -3. Ceramide can be generated either by the action of sphingomyelinase (SMase) or by de novo synthesis through the enzyme ceramide synthase (CerS,
lagr-1,
hyl-1 and
hyl-2 in C. elegans). (f)
hpl-2 regulates
sms-3 mRNA levels.
hpl-2/N2 ratios for sphingomyelin synthase sms genes at different developmental stages. Experiments were performed on three independent synchronized L3 cultures and on two adult and embryonic cultures. Reference genes are
pmp-3 and
cdc-42. Normalization was performed using the mean of both reference genes. Data are the mean of independent biological replicas.