title: Localized sphingolipid signaling at presynaptic terminals is regulated by calcium influx and promotes recruitment of priming factors.
abstract: Activity-dependent changes in presynaptic function represent a critical mechanism by which synaptic strength is controlled. However, how changes in synaptic activity couple to presynaptic components to control synaptic vesicle release and recycling are poorly understood. Sphingosine kinase (SphK) is a sphingolipid metabolic enzyme whose activity-dependent recruitment to membrane regions within presynaptic terminals promotes neurotransmitter release. Here, we show that synaptic recruitment of SPHK-1, the SphK ortholog in Caenorhabditis elegans, is mediated by presynaptic calcium influx. Quantitative fluorescence imaging of live presynaptic terminals reveals that blocking presynaptic calcium influx reduces synaptic SPHK-1 abundance whereas increasing calcium influx increases SPHK-1 synaptic abundance. CALM-1, the calcium and integrin binding protein ortholog, colocalizes with SPHK-1 at release sites and regulates muscarinic-mediated synaptic SPHK-1 recruitment. We identify two additional sphingolipid metabolic enzymes that are concentrated at presynaptic terminals, and mutants lacking one of these, HYL-1/ceramide synthase, have defects in synaptic transmission and in synaptic vesicle cycling. Finally, we show that SPHK-1 activity is required for the recruitment of the priming protein UNC-13/Munc13 to presynaptic terminals following activation by muscarinic signaling. These findings suggest that calcium-dependent regulation of local S1P metabolism at synapses may be an important mechanism by which synaptic vesicle priming factors are recruited to release sites to promote synaptic transmission.
authors.affiliation: Zilkha Neurogenetic Institute, University of Southern California, Keck School of Medicine, Los Angeles, California 90033, USA.
authors.forename: Jason P
authors.initials: JP
authors.lastname: Chan
authors.forename: Derek
authors.initials: D
authors.lastname: Sieburth
mesh_terms: D000448:Aldicarb / Q000494:pharmacology; D000818:Animals; D001115:Arecoline / Q000494:pharmacology; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins; D018679:Cholinergic Agonists / Q000494:pharmacology; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D009046:Motor Neurons / Q000187:drug effects / Q000378:metabolism; D009154:Mutation; D061848:Optical Imaging / Q000379:methods; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism*; D013107:Sphingolipids / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000235:genetics; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism; D000099157:Sphingosine Kinase
chemical_list: D000448:Aldicarb; D001115:Arecoline; D029742:Caenorhabditis elegans Proteins; D002118:Calcium; D002352:Carrier Proteins; D018679:Cholinergic Agonists; D002800:Cholinesterase Inhibitors; D010088:Oxidoreductases; D017853:Phosphotransferases (Alcohol Group Acceptor); D013107:Sphingolipids; D000099157:Sphingosine Kinase; C083141:phorbol ester binding protein; C108138:dihydroceramide desaturase