Brefeldin A Limits N‐Hexanoylsphingosine‐Induced Accumulation of Natural Ceramide via the Salvage Pathway by Enhancing Glucosylation

Abstract

Cells actively metabolize exogenously administered N-hexanoylsphingosine (C6-Cer) to natural (i.e. long-chain) ceramide (LC-Cer) via the sphingosine (Sph) salvage pathway, namely via C6-Cer deacylation and Sph reacylation with a long-chain fatty acid. Based on the observation that the mycotoxin brefeldin A (BFA), a Golgi complex disassembler, impairs C6-Cer-evoked LC-Cer accumulation, it has been hypothesized that the integrity of the above-mentioned organelle might be necessary for C6-Cer processing via the salvage pathway and that BFA might block the phenomenon at the step short-chain ceramide deacylation. The present study shows that BFA indeed attenuates C6-Cer-evoked LC-Cer accumulation in human neurotumor CHP-100 cells: evidence is however provided that the phenomenon is not due to impaired synthesis of LC-Cer, but to its enhanced conversion to glucosylceramide. The possibility is discussed that this outcome might be a consequence of the BFA well-established property to induce the merging of the cis-Golgi region with endoplasmic reticulum, namely the compartments in which glucosylceramide synthase and ceramide synthases have been reported to reside.