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This version published online on July 2, 2009
Molecular Endocrinology, doi:10.1210/me.2008-0448
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Submitted on December 2, 2008
Accepted on June 26, 2009

Involvement of 4E-BP1 in the protection induced by HDLs on pancreatic beta cells

Jannick Pétremand, Natasa Bulat, Anne-Christine Butty, Carine Poussin, Sabine Rütti, Karin Au, Sujoy Ghosh, Vincent Mooser, Bernard Thorens, Jiang-Yan Yang, Christian Widmann*, and Gérard Waeber

Department of Physiology, Department of Cell Biology and Morphology, and Center for Integrative Genomics, Lausanne University, 1005 Lausanne, Switzerland; Department of Internal Medicine, University Hospital Center, and University of Lausanne, Switzerland; GlaxoSmithKline R&D Drug Discovery, Research Triangle Park NC and King of Prussia, PA 19406; Division of Endocrinology and Diabetes, University Hospital Zurich, Zurich, Switzerland

* To whom correspondence should be addressed. E-mail: Christian.Widmann{at}unil.ch.

High-density lipoproteins (HDLs) protect pancreatic {beta} cells against apoptosis. This property might relate to the increased risk to develop diabetes in patients with low HDL blood levels. The mechanisms by which HDLs protect {beta} cells are poorly characterized however. Here we used a transcriptomic approach to identify genes differentially modulated by HDLs in {beta} cells subjected to apoptotic stimuli. The transcript encoding 4E-BP1 was up-regulated by serum starvation and HDLs blocked this increase. 4E-BP1 inhibits cap-dependent translation in its non- or hypo-phosphorylated state but it looses this ability when hyper-phosphorylated. At the protein level, 4E-BP1 was also up-regulated in response to starvation and IL1{beta} and this was blunted by HDLs. While an ectopic increase of 4E-BP1 expression induced {beta} cell death, silencing 4E-BP1 increase with shRNAs inhibited the apoptotic-inducing capacities of starvation. HDLs can therefore protect {beta} cells by blocking 4E-BP1 protein expression but this is not the sole protective mechanism activated by HDLs. Indeed, HDLs blocked apoptosis induced by ER stress with no associated decrease in total 4E-BP1 induction. Although, HDLs favored the phosphorylation, and hence the inactivation of 4E-BP1 in these conditions, this appeared not to be required for HDL protection. Our results indicate that HDLs can protect {beta} cells through modulation of 4E-BP1 depending on the type of stress stimuli.


Key words: HDLs • Apoptosis • 4E-BP1 • Gene array • beta cells







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