title: The synaptic ribbon is a site of phosphatidic acid generation in ribbon synapses.
abstract: Ribbon synapses continuously transmit graded membrane potential changes into changes of synaptic vesicle exocytosis and rely on intense synaptic membrane trafficking. The synaptic ribbon is considered central to this process. In the present study we asked whether tonically active ribbon synapses are associated with the generation of certain lipids, specifically the highly active signaling phospholipid phosphatidic acid (PA). Using PA-sensor proteins, we demonstrate that PA is enriched at mouse retinal ribbon synapses in close vicinity to the synaptic ribbon in situ. As shown by heterologous expression, RIBEYE, a main component of synaptic ribbons, is responsible for PA binding at synaptic ribbons. Furthermore, RIBEYE is directly involved in the synthesis of PA. Using various independent substrate binding and enzyme assays, we demonstrate that the B domain of RIBEYE possesses lysophosphatidic acid (LPA) acyltransferase (LPAAT) activity, which leads to the generation of PA from LPA. Since an LPAAT-deficient RIBEYE mutant does not recruit PA-binding proteins to artificial synaptic ribbons, whereas wild-type RIBEYE supports PA binding, we conclude that the LPAAT activity of the RIBEYE(B) domain is a physiologically relevant source of PA generation at the synaptic ribbon. We propose that PA generated at synaptic ribbons likely facilitates synaptic vesicle trafficking.
authors: Department of Neuroanatomy, Institute for Anatomy and Cell Biology, Saarland University Medical School, Homburg/Saar, 66421 Homburg/Saar, Germany. dr.karin.schwarz@uks.eu
authors: Karin
authors: K
authors: Schwarz
authors: Sivaraman
authors: S
authors: Natarajan
authors: Nawal
authors: N
authors: Kassas
authors: Nicolas
authors: N
authors: Vitale
authors: Frank
authors: F
authors: Schmitz
mesh_terms: D000217:Acyltransferases / Q000378:metabolism; D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D056970:Co-Repressor Proteins; D003208:Concanavalin A / Q000378:metabolism; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4 / Q000235:genetics / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D010712:Phosphatidic Acids / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics; D012160:Retina / Q000166:cytology; D051245:Retinal Bipolar Cells / Q000378:metabolism / Q000648:ultrastructure; D013569:Synapses / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D013570:Synaptic Membranes / Q000187:drug effects / Q000378:metabolism*; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism*; D014162:Transfection; D014364:Tryptophan / Q000235:genetics / Q000378:metabolism
chemical_list: D056970:Co-Repressor Proteins; D008081:Liposomes; D009419:Nerve Tissue Proteins; D010712:Phosphatidic Acids; D010743:Phospholipids; D003208:Concanavalin A; D049452:Green Fluorescent Proteins; D014364:Tryptophan; D000429:Alcohol Oxidoreductases; C421248:CTBP2 protein, human; D000217:Acyltransferases; D019908:Proto-Oncogene Proteins c-raf; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4