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Title

Synaptotagmin VII splice variants alpha, beta, and delta are expressed in pancreatic beta-cells and regulate insulin exocytosis

Authors
Duhamel, Dominique L.
Iezzi, Mariella
Fukuda, Mitsunori
Published in FASEB Journal. 2008, vol. 22, no. 1, p. 194-206
Abstract Synaptotagmins (SYT) are calcium-binding proteins that participate in regulated exocytosis. Although SYTI to IX isoforms are expressed in insulin-producing cell lines, hitherto only SYTIX has been associated with native beta-cell insulin granules and implicated in exocytosis. SYTVII was also proposed to regulate insulin exocytosis, but its subcellular location and number of alternative splice variants produced remain controversial. Only transcripts of SYTVII alpha, beta, and a novel splice variant delta are expressed in beta-cells and INS-1E cells. Western blotting revealed that INS-1E cells predominantly produced SYTVII alpha and low levels of SYTVII beta, whereas SYTVII delta was undetectable. The protein colocalized with insulin granules but not with synaptic-like microvesicles. Overexpression of SYTVII alpha resulted in decreased insulin granule content with a concomitant translocation of the variant to the plasma membrane, while SYTVII beta retained largely a granular pattern. Overexpressed SYTVII delta exhibited a distribution different to that of insulin granules and inhibited exocytosis when assessed by whole cell patch clamp capacitance recording. Silencing of SYTVII alpha by targeted RNA interference suppressed secretion, while repression of beta slightly increased release. Our results demonstrate that SYTVII is expressed on insulin granules and that only SYTVII alpha is implicated in exocytosis under physiological conditions.
Keywords AnimalsBase SequenceCalcium/metabolismCell LineDNA PrimersExocytosis/physiologyGlucose/metabolismInsulin/metabolismIslets of Langerhans/metabolismMaleRNA SplicingRatsRats WistarRecombinant Proteins/genetics/metabolismReverse Transcriptase Polymerase Chain ReactionSynaptotagmins/genetics/metabolism/physiology
Identifiers
PMID: 17709608
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Article (Author postprint) (847 Kb) - document accessible for UNIGE members only Limited access to UNIGE
Other version: http://www.fasebj.org/cgi/content/full/22/1/194
Structures
Research group Migration cellulaire (645)
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(ISO format)
GAUTHIER, Benoît et al. Synaptotagmin VII splice variants alpha, beta, and delta are expressed in pancreatic beta-cells and regulate insulin exocytosis. In: FASEB Journal, 2008, vol. 22, n° 1, p. 194-206. https://archive-ouverte.unige.ch/unige:759

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Deposited on : 2009-02-11

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