title: RNA interference-mediated silencing of synaptotagmin IX, but not synaptotagmin I, inhibits dense-core vesicle exocytosis in PC12 cells.
abstract: Although PC12 cells express three synaptotagmin isoforms (Syts I, IV and IX), all of which have been proposed to regulate dense-core vesicle exocytosis, it remains unknown which of the Sytisoforms acts as the major Ca2+ sensor for dense-core vesicle exocytosis. In the present study, it has been shown by immunoaffinity purification and immunocytochemistry that Syts I and IX, but not Syt IV, are present on the same secretory vesicles in PC12 cells. Silencing of Syt IX with specific small interfering RNA significantly reduced high KCl-dependent neuropeptide Y secretion from PC12 cells, whereas silencing of Syt I with specific small interfering RNA had no significant effect. The results indicate that Syts I and IX are not functionally equivalent and that Syt IX, and not Syt I, is indispensable for the regulation of Ca2+-dependent dense-core vesicle exocytosis in PC12 cells.
authors.affiliation: Fukuda Initiative Research Unit, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Fukuda
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D002460:Cell Line; D005089:Exocytosis / Q000235:genetics / Q000502:physiology*; D005786:Gene Expression Regulation / Q000235:genetics / Q000502:physiology; D020868:Gene Silencing / Q000502:physiology; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D016716:PC12 Cells / Q000737:chemistry* / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D022142:Secretory Vesicles / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D050863:Synaptotagmin I; D050857:Synaptotagmins
chemical_list: D002135:Calcium-Binding Proteins; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; D050863:Synaptotagmin I; C494312:Syt1 protein, rat; C483193:Syt9 protein, rat; D050857:Synaptotagmins