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Regulation of insulin granule turnover in pancreatic beta-cells by cleaved ICA512.
J. Biol. Chem. 283, 33719-33729 (2008)
Insulin maintains homeostasis of glucose by promoting its uptake into cells from the blood. Hyperglycemia triggers secretion of insulin from pancreatic beta-cells. This process is mediated by secretory granule exocytosis. However, how beta-cells keep granule stores relatively constant is still unknown. ICA512 is an intrinsic granule membrane protein, whose cytosolic domain binds beta2-syntrophin, an F-actin-associated protein, and is cleaved upon granule exocytosis. The resulting cleaved cytosolic fragment, ICA512-CCF, reaches the nucleus and up-regulates the transcription of granule genes, including insulin and ICA512. Here, we show that ICA512-CCF also dimerizes with intact ICA512 on granules, thereby displacing it from beta2-syntrophin. This leads to increased granule mobility and insulin release. Based on these findings, we propose a model whereby the generation of ICA512-CCF first amplifies insulin secretion. The ensuing reduction of granule stores would then increase the probability of newly generated ICA512-CCF to reach the nucleus and enhance granule biogenesis, thus allowing beta-cells to constantly adjust production of granules to their storage size and consumption. Pharmacological modulation of these feedback loops may alleviate deficient insulin release in diabetes.
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Publikationstyp
Artikel: Journalartikel
Dokumenttyp
Wissenschaftlicher Artikel
Sprache
englisch
Veröffentlichungsjahr
2008
HGF-Berichtsjahr
0
ISSN (print) / ISBN
0021-9258
e-ISSN
1083-351X
Zeitschrift
Journal of Biological Chemistry, The
Quellenangaben
Band: 283,
Heft: 48,
Seiten: 33719-33729
Verlag
American Society for Biochemistry and Molecular Biology
Begutachtungsstatus
Peer reviewed
Institut(e)
Institute of Pancreatic Islet Research (IPI)
PubMed ID
18824546
Erfassungsdatum
2008-12-31