title: Sphingomyelin derivatives increase the frequency of microvesicle and granule fusion in chromaffin cells.
abstract: Sphingomyelin derivatives like sphingosine have been shown to enhance secretion in a variety of systems, including neuroendocrine and neuronal cells. By studying the mechanisms underlying this effect, we demonstrate here that sphingomyelin rafts co-localize strongly with synaptosomal-associated protein of 25Kda (SNAP-25) clusters in cultured bovine chromaffin cells and that they appear to be linked in a dynamic manner. In functional terms, when cultured rat chromaffin cells are treated with sphingomyelinase (SMase), producing sphingomyelin derivatives, the secretion elicited by repetitive depolarizations is enhanced. This increase was independent of cell size and it was significant 15min after initiating stimulation. Interestingly, by evaluating the membrane capacitance we found that the events in control untreated cells corresponded to two populations of microvesicles and granules, and the fusion of both these populations is clearly enhanced after treatment with SMase. Furthermore, SMase does not increase the size of chromaffin granules. Together, these results strongly suggest that SNARE-mediated exocytosis is enhanced by the generation of SMase derivatives, reflecting an increase in the frequency of fusion of both microvesicles and chromaffin granules rather than an increase in the size of these vesicles.
authors: Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas, Sant Joan d'Alacant, Alicante 03550, Spain.
authors: V
authors: V
authors: García-Martínez
authors: Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, 41009 Sevilla, Spain.
authors: M A
authors: MA
authors: Montes
authors: Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas, Sant Joan d'Alacant, Alicante 03550, Spain.
authors: J
authors: J
authors: Villanueva
authors: Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas, Sant Joan d'Alacant, Alicante 03550, Spain.
authors: Y
authors: Y
authors: Gimenez-Molina
authors: Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, 41009 Sevilla, Spain.
authors: G A
authors: GA
authors: de Toledo
authors: Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-Consejo Superior de Investigaciones Científicas, Sant Joan d'Alacant, Alicante 03550, Spain. Electronic address: luisguti@umh.es.
authors: L M
authors: LM
authors: Gutiérrez
mesh_terms: D000818:Animals; D055592:Biophysical Phenomena / Q000187:drug effects; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D055252:Cell-Derived Microparticles / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000166:cytology* / Q000187:drug effects; D002837:Chromaffin Granules / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D025802:Electric Capacitance; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008854:Microscopy, Electron; D018408:Patch-Clamp Techniques; D050600:SNARE Proteins / Q000378:metabolism; D013108:Sphingomyelin Phosphodiesterase / Q000494:pharmacology; D013109:Sphingomyelins / Q000378:metabolism*; D018709:Statistics, Nonparametric; D050825:Synaptosomal-Associated Protein 25 / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D050600:SNARE Proteins; D013109:Sphingomyelins; D050825:Synaptosomal-Associated Protein 25; D049452:Green Fluorescent Proteins; D013108:Sphingomyelin Phosphodiesterase
keywords: cell capacitance; chromaffin cells; exocytosis; neurotransmission; sphingomyelin