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Cytosolic HMGB1 controls the cellular autophagy/apoptosis checkpoint during inflammation.

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2015

J Clin Invest. 2015 Feb 2. pii: 76344. doi: 10.1172/JCI76344. [Epub ahead of print]

Cytosolic HMGB1 controls the cellular autophagy/apoptosis checkpoint during inflammation.

X Zhu;JS Messer;Y Wang;F Lin;CM Cham;J Chang;TR Billiar;MT Lotze;DL Boone;EB Chang

Department of Medicine, University of Chicago, Chicago, Illinois, USA. Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, Massachusetts, USA. Department of Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.

Service type: Knockout mice

Abstract

The intracellular protein HMGB1 is released from cells and acts as a damage-associated molecular pattern molecule during many diseases, including inflammatory bowel disease (IBD); however, the intracellular function of HMGB1 during inflammation is poorly understood. Here, we demonstrated that cytosolic HMGB1 regulates apoptosis by protecting the autophagy proteins beclin 1 and ATG5 from calpain-mediated cleavage during inflammation. Colitis in mice with an intestinal epithelial cell-specific Hmgb1 deletion and patients with IBD were both characterized by increased calpain activation, beclin 1 and ATG5 cleavage, and intestinal epithelial cell (IEC) death compared with controls. In vitro cleavage assays and studies of enteroids verified that HMGB1 protects beclin 1 and ATG5 from calpain-mediated cleavage events that generate proapoptotic protein fragments. Together, our results indicate that HMGB1 is essential for mitigating the extent and severity of inflammation-associated cellular injury by controlling the switch between the proautophagic and proapoptotic functions of beclin 1 and ATG5 during inflammation. Moreover, these studies demonstrate that HMGB1 is pivotal for reducing tissue injury in IBD and other complex inflammatory disorders.

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