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- Title
Localization and functional role of synaptotagmin III in insulin secretory vesicles in pancreatic beta-cells.
- Authors
Mizuta, Masanari; Kurose, Takeshi; Miki, Takashi; Shoji-Kasai, Yoko; Takahashi, Masami; Seino, Susumu; Matsukura, Shigeru; Mizuta, M; Kurose, T; Miki, T; Shoji-Kasai, Y; Takahashi, M; Seino, S; Matsukura, S
- Abstract
Pancreatic beta-cells secrete insulin by Ca2+-triggered exocytosis of insulin-containing large dense-core vesicles. Synaptotagmin is a Ca2+/phospholipid-binding protein and is a good candidate for the Ca2+ sensor for exocytosis of synaptic vesicles in neurons. In the present study, we generated a polyclonal antibody against synaptotagmin III, and found that synaptotagmin III immunoreactivity was present at high levels in insulin-containing pancreatic islet cells and insulin-secreting clonal MIN6 cells. In subcellular fractionations of MIN6 cells, synaptotagmin III was recovered in the vesicular fractions containing both insulin and vesicle-associated membrane protein-2 (VAMP-2), but not in synaptophysin-positive fractions. The secretory vesicles immunoprecipitated by anti-VAMP-2 antibody contained synaptotagmin III and insulin. In addition, treatment of streptolysin-O-permeabilized MIN6 cells with anti-synaptotagmin III antibody significantly inhibited Ca2+-triggered insulin secretion. These results indicate that synaptotagmin III is localized in insulin-containing dense-core vesicles in pancreatic beta-cells, and further strongly suggest that synaptotagmin III is the Ca2+ sensor in the exocytosis of insulin secretory vesicles.
- Publication
Diabetes, 1997, Vol 46, Issue 12, p2002
- ISSN
0012-1797
- Publication type
journal article
- DOI
10.2337/diab.46.12.2002