Sphingosine Facilitates SNARE Complex Assembly and Activates Synaptic Vesicle Exocytosis

Abstract

SummarySynaptic vesicles loaded with neurotransmitters fuse with the plasma membrane to release their content into the extracellular space, thereby allowing neuronal communication. The membrane fusion process is mediated by a conserved set of SNARE proteins: vesicular synaptobrevin and plasma membrane syntaxin and SNAP-25. Recent data suggest that the fusion process may be subject to regulation by local lipid metabolism. Here, we have performed a screen of lipid compounds to identify positive regulators of vesicular synaptobrevin. We show that sphingosine, a releasable backbone of sphingolipids, activates synaptobrevin in synaptic vesicles to form the SNARE complex implicated in membrane fusion. Consistent with the role of synaptobrevin in vesicle fusion, sphingosine upregulated exocytosis in isolated nerve terminals, neuromuscular junctions, neuroendocrine cells and hippocampal neurons, but not in neurons obtained from synaptobrevin-2 knockout mice. Further mechanistic insights suggest that sphingosine acts on the synaptobrevin/phospholipid interface, defining a novel function for this important lipid regulator.

SNARE tagging allows stepwise assembly of a multimodular medicinal toxin

“…To test the effect of LcTd-SNARE-Rbd on neurotransmitter release, we used a 96-well glutamate release assay that allows simultaneous comparison of multiple factors (22). Fig.…”

CaV1.3 as pacemaker channels in adrenal chromaffin cells: Specific role on exo- and endocytosis?

“…77 In bovine chromaffin cells, the mechanism of action involves sphingosine and originates at the intracellular site. 78 The phenomenon is lost when applying repeated stimuli. 79 Concerning the role of Ca 2+ channels in sustaining endocytosis, a preferential coupling of LTCCs to endocytosis has been recently proposed: Ca 2+ -entry through LTCCs in bovine chromaffin cells is more effective in triggering endocytosis than exocytosis.…”

Exploring the binding dynamics of BAR proteins

“…We propose to study the effects of BAR proteins in cultured cells. For example, melanotrophs, pituitary cells from the pars intermedia, are a convenient cell type to study effects of lipids or proteins on the cumulative exocytosis in a cell [32]. A 300 second cytosol dialysis by a pipette solution containing BAR proteins should be sufficient to elicit an increase/decrease in C m , as is sufficient in the case where we use a pipette containing high-Ca 2+ solution (Fig.…”