p53 up-regulated modulator of apoptosis (PUMA) activation contributes to pancreatic β-cell apoptosis induced by proinflammatory cytokines and endoplasmic reticulum stress

Abstract

Type 1 diabetes is an autoimmune disorder characterized by chronic inflammation and pancreatic β-cell loss. Here, we demonstrate that the proinflammatory cytokine interleukin-1β, combined with interferon-γ, induces the expression of the Bcl-2 homology 3 (BH3)-only activator PUMA (p53 up-regulated modulator of apoptosis) in β-cells. Transcriptional activation of PUMAis regulated by nuclear factor-κB and endoplasmic reticulum stress but is independent of p53. PUMA activation leads to mitochondrial Bax translocation, cytochrome c release, and caspase-3 cleavage resulting in β-cell demise. The antiapoptotic Bcl-XL protein is localized mainly at the mitochondria of the β-cells and antagonizesPUMAaction, but Bcl-XL is inactivated by the BH3-only sensitizer DP5/Hrk in cytokine-exposed β-cells. Moreover, a pharmacological mimic of the BH3-only sensitizer Bad, which inhibits Bcl-XL and Bcl-2, induces PUMA dependent β-cell death and potentiates cytokine-induced apoptosis. Our data support a hierarchical activation of BH3-only proteins controlling the intrinsic pathway of β-cell apoptosis in the context of inflammation and type 1 diabetes. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.