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Expression and localisation of synaptotagmin isoforms in endocrine beta-cells: their function in insulin exocytosis

Gut, A
Fukuda, M
Mikoshiba, K
Published in Journal of Cell Science. 2001, vol. 114, no. Pt 9, p. 1709-16
Abstract Exocytosis of insulin containing Large Dense Core Vesicles (LDCVs) from pancreatic beta-cells and derived cell lines is mainly controlled by Ca(2+). Several lines of evidence have demonstrated a role of the Ca(2+)- and phospholipid-binding protein synaptotagmin (syt) in this event. Synaptotagmins form a large protein family with distinct affinities for Ca(2+) determined by their two C(2) domains (C(2)A/B). Except for the well-characterized isoforms I and II, their role is still unclear. We have used here insulin-secreting cells as a model system for LDCV exocytosis to gain insight into the function of synaptotagmins. Immunocytochemical analysis revealed that of the candidate Ca(2+) sensors in LDCV exocytosis, syt III was not expressed in primary beta-cells, whereas syt IV was only found adjacent to the TGN. However, syt V-VIII isoforms were expressed at different levels in various insulin-secreting cells and in pancreatic islet preparations. In streptolysin-O permeabilized primary beta-cells the introduction of recombinant peptides (100 nM) corresponding to the C(2) domains of syt V, VII and VIII, but not of syt III, IV or VI, inhibited Ca(2+)-evoked insulin exocytosis by 30% without altering GTP gamma S-induced release. Our observations demonstrate that syt III and IV are not involved in the exocytosis of LDCVs from primary beta-cells whereas V, VII and VIII may mediate Ca(2+)-regulation of exocytosis.
Keywords AnimalsCalcium-Binding ProteinsCell LineExocytosisInsulin/metabolismIslets of Langerhans/cytology/metabolismMaleMembrane Glycoproteins/metabolismNerve Tissue Proteins/metabolismProtein Isoforms/metabolismRatsRats, WistarSynaptotagmins
PMID: 11309201
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GUT, A et al. Expression and localisation of synaptotagmin isoforms in endocrine beta-cells: their function in insulin exocytosis. In: Journal of Cell Science, 2001, vol. 114, n° Pt 9, p. 1709-16. https://archive-ouverte.unige.ch/unige:34827

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Deposited on : 2014-03-18

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