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Am J Physiol Endocrinol Metab (September 15, 2009). doi:10.1152/ajpendo.00217.2009
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Submitted on April 1, 2009
Revised on September 14, 2009
Accepted on September 15, 2009

Deletion of Fas in the Pancreatic {beta} Cells Leads to Enhanced Insulin Secretion

Diana Choi1, Anna Radziszewska1, Stephanie A Schroer1, Nicole Liadis1, Yunfeng Liu1, Yi Zhang1, Patrick PL Lam1, Laura Sheu1, Zhenyue Hao2, Herbert Gaisano1, and Minna Woo1*

1 University of Toronto
2 Advanced Medical Discovery Institute

* To whom correspondence should be addressed. E-mail: mwoo{at}uhnres.utoronto.ca.

Fas/Fas ligand belongs to the tumor necrosis factor superfamily of receptors/ligands and is best known for its role in apoptosis. However, recent evidence supports its role in other cellular responses, including proliferation and survival. While Fas has been implicated as an essential mediator of {beta}-cell death in the pathogenesis of type 1 diabetes, the essential role of Fas specifically in pancreatic {beta} cells has been found to be controversial. Moreover, the role of Fas on {beta}-cell homeostasis and function is not clear. The objective of this study is to determine the role of Fas specifically in {beta} cells under both physiological and diabetes models. Mice with Fas deletion specifically in the {beta} cells were generated using the Cre-loxP system. Cre-mediated Fas deletion was under the control of the rat insulin promoter. Absence of Fas in {beta} cells leads to complete protection against FasL-induced cell death. However, Fas is not essential in determining {beta}-cell mass or susceptibility to streptozotocin- or HFD-induced diabetes. Importantly, Fas deletion in {beta} cells leads to increased p65 expression, enhanced glucose tolerance and glucose-stimulated insulin secretion, with increased exocytosis as manifested by increased changes in membrane capacitance, and increased expression of syntaxin1A, vamp2, and munc18a. Together, our study shows that Fas in the {beta} cells indeed plays an essential role in the canonical death receptor-mediated apoptosis, but is not essential in regulating {beta}-cell mass or diabetes development. However, {beta}-cell Fas is critical in the regulation of glucose homeostasis through regulation of the exocytosis machinery.







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