Trafficking of Acetyl-C16-Ceramide-NBD with Long-Term Stability and No Cytotoxicity into the Golgi Complex

The Golgi complex plays a prominent role in the modification and sorting of lipids and proteins, and is a highly dynamic organelle that is dispersed and rearranged before and after mitosis. Several reagents including 4-nitrobenzo-2-oxa-1,3-diazole-labeled C6-ceramide (NBD-C6-ceramide, a ceramide having an NBD-bound C6-N-acyl chain) and Golgi-specific proteins that emit fluorescence are used as Golgi markers. In the present study, we synthesized a new ceramide analog, acetyl-C16-ceramide-NBD (a ceramide having an acetylated C-1 hydroxyl group, C16-N-acyl chain, and NBD-bound C15-sphingosine), and showed that it preferentially accumulated in the Golgi complex without cytotoxicity for over 24 h. Pathways for cellular uptake and interorganelle trafficking of acetyl-C16-ceramide-NBD were investigated. Acetyl-C16-ceramide-NBD was transported to the Golgi complex via ceramide transport proteins. In contrast to NBD-C6-ceramide, acetyl-C16-ceramide-NBD was resistant to ceramide metabolic enzymes such as sphingomyelin synthase and glucosylceramide synthase. Because of its weaker cytotoxicity and resistance to ceramide metabolic enzymes, the localization of the Golgi complex could be observed in acetyl-C16-ceramide-NBD-labeled cells before and after mitosis.