Research Spotlight: Formation of Tubules and Helical Ribbons by Ceramide Phosphoethanolamine-Containing Membranes

Posted on March 01, 2021


Tubules

Galactosylceramide (GalCer) is one of the few natural lipids that form helical ribbons in an aqueous solution. This process is important for the wrapping of axons in myelin in mammals. In invertebrates such as Drosophila, specialized glial cells ensheath axons since they do not have myelin. This axonal wrapping via glial cells has been studied in Drosophila, and ceramide phosphoethanolamine (CPE) was identified as a key component. CPE is a phosphosphingolipid analog of sphingomyelin and is the major sphingolipid in insects and some protozoa. As a comparison, CPE only makes up between 0.002 and 0.02 mole percent of the total phospholipid concentration in mammals.

Toshi and the research team studied the morphology of CPE-containing membranes and reported that CPE:phosphocholine (PC) mixtures tend to naturally form tubules and helical ribbons. The formation of tubules and helical ribbons was shown to depend on the N-linked acyl chain length and incubation conditions. When using only milk CPE with primary N-acyl chain lengths of 22:0, 23:0, and 24:0, the suspension exhibited amorphous aggregation. When using an equimolar mixture of milk CPE and di18:1 PC, the suspension readily exhibited helical structures. When varying the ratio of milk CPE to di18:1 PC, the findings revealed that mixtures with a CPE concentration above 50% exhibited dominantly helical structures.

Using equimolar concentrations of milk CPE with di18:1 PE, di16:0 PE, and cholesterol, respectively, these mixtures all exhibited amorphous aggregates rather than helical structures. Interestingly, equimolar suspensions of di18:1 PC and d17:1/N-12:0 CPE, di18:1 PC and d17:1/N-16:0 CPE, and di18:1 PC and N-18:1 CPE formed tubules. Suspensions with d18:1/N-24:0 CPE and d18:1/N-24:1 CPE formed helical structures. This shows that medium and long N-acyl chain CPEs prefer tubule formation while very long N-acyl chain CPEs prefer formation of helical ribbons. This is consistent with what was seen when using milk CPE in the CPE:PC mixtures.

Taken together, these results suggest that, like GalCer, CPE may play a role in stabilizing glial cells through the spontaneous formation of tubules and helices.

Toshi’s team was able to study the morphology of CPE:PC mixtures and how they might be involved in the ensheathement of invertebrate axons thanks to Avanti’s ultra pure lipid products. This study took advantage of Avanti’s Sphingomyelin, Phosphatidyethanolamine, Phosphatidylcholine, and Phosphatidylserine products.

If you’re looking to do research with sphingolipids or phospholipids, Avanti should be your first choice!

To check out the complete research article from Toshi and team, click HERE!


Image Credit: Original Research Publication