Reelin affects the lipid composition of the neuronal plasma membrane

The neuronal plasma membrane is composed of versatile lipid molecules with distinct biophysical characteristics and functions. Among them, sphingomyelin (SM) influences the localization and functions of various proteins including GPI-anchored proteins. Therefore, elucidation of the mechanisms that regulate the SM amount is important for understanding the mechanisms that control neuronal morphology and information transmission. Reelin is a secreted protein that regulates neuronal morphology and dynamics. We previously found that the embryonic brain of Reelin-deficient mice shows aberrant lipid compositions. Reelin activates Fyn tyrosine kinase and, in non-neuronal cells, the activation of Fyn is known to increase the SM amount. We hypothesized that Reelin affects the SM amount in neurons. Here we aim to clarify the effect of Reelin on the amount of SM of the neuronal plasma membrane.Primary cultured neurons treated with Reelin were more strongly stained by Equinatoxin2-GFP, an SM-specific probe, than control neurons, indicating that Reelin increases the amount of SM in the plasma membrane. Reelin also increased the amount of GPI-anchored protein Thy-1 on the plasma membrane, while it did not affect its whole amount in the neurons. Non-targeted lipidomics analysis on the postsynaptic density regions revealed that the composition of phosphatidylcholine, ceramide, and diacylglycerol, which are lipid species involved in SM metabolism, was altered in Reelin-deficient mice. These results suggest that Reelin increases the amount of SM in the plasma membrane and affects neuronal function.