Sphingomimetic multiple sclerosis drug FTY720 activates vesicular synaptobrevin and augments neuroendocrine secretion

Frederic D Darios,Robert Zorec,Luis M Gutiérrez,Ege T Kavalali,Virginia García-Martinez,Jernej Jorgacevski,Elena Nosyreva,Charlotte Leese,Ajda Flašker,Manjot Bal,José Villanueva,Bazbek Davletov

doi:10.1038/s41598-017-05948-z

Abstract

Neurotransmission and secretion of hormones involve a sequence of protein/lipid interactions with lipid turnover impacting on vesicle trafficking and ultimately fusion of secretory vesicles with the plasma membrane. We previously demonstrated that sphingosine, a sphingolipid metabolite, promotes formation of the SNARE complex required for membrane fusion and also increases the rate of exocytosis in isolated nerve terminals, neuromuscular junctions, neuroendocrine cells and in hippocampal neurons. Recently a fungi-derived sphingosine homologue, FTY720, has been approved for treatment of multiple sclerosis. In its non-phosphorylated form FTY720 accumulates in the central nervous system, reaching high levels which could affect neuronal function. Considering close structural similarity of sphingosine and FTY720 we investigated whether FTY720 has an effect on regulated exocytosis. Our data demonstrate that FTY720 can activate vesicular synaptobrevin for SNARE complex formation and enhance exocytosis in neuroendocrine cells and neurons.

Highlights

The sphingolipid signalling pathway plays an important role in the brain function and pathophysiology of diverse neurological diseases[1,2,3,4]
We tested whether amine-containing positively-charged lipid compounds could upregulate vesicular synaptobrevin for SNARE complex formation as was reported recently for sphingosine[23]
Synaptic vesicles were purified from rat brain synaptosomes by flotation and incubated with synaptobrevin’s partner proteins – syntaxin and SNAP25 that normally reside in the plasma membrane

Summary

Introduction

The sphingolipid signalling pathway plays an important role in the brain function and pathophysiology of diverse neurological diseases[1,2,3,4]. A synthetic analogue of sphingosine, FTY720 known as fingolimod, has been investigated extensively for clinical use in the last decade and recently approved for the treatment of multiple sclerosis, the most common inflammatory disorder of the CNS5, 6. It has been demonstrated that non-phosphorylated FTY720 can be taken up by neurons increasing long-term potentiation in electrophysiological recordings from hippocampal slices[22]. Since sphingosine was recently shown to act as a stimulator of neuronal exocytosis[23,24,25], it is conceivable that FTY720 could affect release of neurotransmitters and hormones. We recently reported that sphingosine, a releasable backbone of sphingolipids, can activate vesicular synaptobrevin for protein assembly and upregulates exocytosis in neuroendocrine cells and in hippocampal neurons[23]. We demonstrate that FTY720 is as effective as sphingosine in activating vesicular synaptobrevin and stimulating neuronal and neuroendocrine exocytosis

Methods

Results

Conclusion