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Synaptotagmin III isoform is compartmentalized in pancreatic beta-cells and has a functional role in exocytosis.
- Source :
-
Diabetes . Mar2000, Vol. 49 Issue 3, p383-391. 9p. 3 Black and White Photographs, 3 Graphs. - Publication Year :
- 2000
-
Abstract
- Synaptotagmin is involved in Ca2+-regulated secretion and has been suggested to serve as a general Ca2+ sensor on the membrane of secretory vesicles in neuronal cells. Insulin exocytosis from the pancreatic beta-cell is an example of a Ca2+-dependent secretory process. Previous studies of pancreatic beta-cells were unable to show presence of synaptotagmin I. We now present biochemical and immunohistochemical data showing that synaptotagmin III is present in pancreatic beta-cells as well as in the insulin-secreting cell line HIT-T15 and in rat insulinoma. By subcellular fractionation, we found synaptotagmin III in high-density fractions together with insulin and secretogranin I, indicating colocalization of synaptotagmin III and insulin in secretory granules. We could also show that blockade of synaptotagmin III by a specific antibody inhibited Ca2+-induced changes in beta-cell membrane capacitance, suggesting that synaptotagmin III is part of the functional protein complex regulating beta-cell exocytosis. The synaptotagmin III antibody did not affect the activity of the voltage-gated L-type Ca2+-channel. These findings are compatible with the view that synaptotagmin III, because of its distinct localization in the pancreatic beta-cell, functionally modulates insulin exocytosis. This indicates that synaptotagmin may have a general role in the regulation of exocytosis not only in neuronal cells but also in endocrine cells. [ABSTRACT FROM AUTHOR]
- Subjects :
- *MEMBRANE proteins
*EXOCYTOSIS
*CELL compartmentation
*PHYSIOLOGY
Subjects
Details
- Language :
- English
- ISSN :
- 00121797
- Volume :
- 49
- Issue :
- 3
- Database :
- Academic Search Index
- Journal :
- Diabetes
- Publication Type :
- Academic Journal
- Accession number :
- 2892016
- Full Text :
- https://doi.org/10.2337/diabetes.49.3.383