The GTPase RalA regulates different steps of the secretory process in pancreatic beta-cells.

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Serval ID
serval:BIB_6AE6AA12C61A
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
The GTPase RalA regulates different steps of the secretory process in pancreatic beta-cells.
Journal
PloS one
Author(s)
Ljubicic S., Bezzi P., Vitale N., Regazzi R.
ISSN
1932-6203[electronic]
Publication state
Published
Issued date
2009
Peer-reviewed
Oui
Volume
4
Number
11
Pages
e7770
Language
english
Notes
Publication types: Journal Article ; Research Support, Non-U.S. Gov't
Publication Status: epublish
Abstract
BACKGROUND: RalA and RalB are multifuntional GTPases involved in a variety of cellular processes including proliferation, oncogenic transformation and membrane trafficking. Here we investigated the mechanisms leading to activation of Ral proteins in pancreatic beta-cells and analyzed the impact on different steps of the insulin-secretory process. METHODOLOGY/PRINCIPAL FINDINGS: We found that RalA is the predominant isoform expressed in pancreatic islets and insulin-secreting cell lines. Silencing of this GTPase in INS-1E cells by RNA interference led to a decrease in secretagogue-induced insulin release. Real-time measurements by fluorescence resonance energy transfer revealed that RalA activation in response to secretagogues occurs within 3-5 min and reaches a plateau after 10-15 min. The activation of the GTPase is triggered by increases in intracellular Ca2+ and cAMP and is prevented by the L-type voltage-gated Ca2+ channel blocker Nifedipine and by the protein kinase A inhibitor H89. Defective insulin release in cells lacking RalA is associated with a decrease in the secretory granules docked at the plasma membrane detected by Total Internal Reflection Fluorescence microscopy and with a strong impairment in Phospholipase D1 activation in response to secretagogues. RalA was found to be activated by RalGDS and to be severely hampered upon silencing of this GDP/GTP exchange factor. Accordingly, INS-1E cells lacking RalGDS displayed a reduction in hormone secretion induced by secretagogues and in the number of insulin-containing granules docked at the plasma membrane. CONCLUSIONS/SIGNIFICANCE: Taken together, our data indicate that RalA activation elicited by the exchange factor RalGDS in response to a rise in intracellular Ca2+ and cAMP controls hormone release from pancreatic beta-cell by coordinating the execution of different events in the secretory pathway.
Pubmed
Web of science
Open Access
Yes
Create date
21/01/2010 8:03
Last modification date
20/08/2019 14:25
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