PKC\u03b6 phosphorylates TRAF2 to protect against intestinal ischemia\u2013reperfusion\u2013induced injury

Wei Zhou,Zhenlu Li,Jihong Yao,Guangzhi Wang,Wasim Qasim,Dongcheng Feng,Xiaofeng Tian,Zhao Chen,Wenzhi Tan,Shili Ning,Yang Li

doi:10.1038/cddis.2017.310

Abstract

Intestinal ischemia–reperfusion (I/R) is a common clinical problem that occurs during various clinical pathological processes. Excessive apoptosis has an indispensable role in intestinal I/R injury. Tumor necrosis factor receptor-associated factor 2 (TRAF2) and PKCζ have an essential role in apoptosis. Here, we aimed to investigate the effects of PKCζ and TRAF2 and to explore the correlation between PKCζ and TRAF2 in intestinal I/R injury. Mice were subjected to intestinal I/R injury in vivo. In vitro experiments were conducted by treating Caco-2 cells with hypoxia/reoxygenation (H/R) stimulation to simulate intestinal I/R. Intestinal tissue samples and Caco-2 cells were examined using various approaches. Intestinal I/R induced the membrane translocation and phosphorylation of PKCζ. Pretreatment with the PKCζ activator phosphatidylcholine remarkably attenuated gut injury by suppressing apoptosis. H/R induced PKCζ to combine with TRAF2, which was phosphorylated by PKCζ at Ser55, but not at Ser11, under intestinal I/R or H/R conditions. In addition, TRAF2 Ser55 phosphorylation increased cell survival by inhibiting cell apoptosis in the H/R model. Mechanistically, TRAF2 Ser55 phosphorylation promoted NF-κB activation but suppressed c-Jun activation in Caco-2 cells under H/R conditions. The results of this study demonstrate that the PKCζ/TRAF2 pathway represents a novel protective mechanism against intestinal I/R injury. Therefore, the PKCζ/TRAF2 pathway is a novel target for potential treatments of intestinal I/R injury-related diseases.

Highlights

PKCζ have an essential role in apoptosis
H/R induced PKCζ to combine with TRAF2, which was phosphorylated by PKCζ at Ser[55], but not at Ser[11], under intestinal I/R or H/R conditions
Research has indicated that TRAF2 KO mouse embryonic fibroblasts (MEFs) are resistant to cell death induced by reactive oxygen species (ROS),[19] suggesting that TRAF2 can promote ROS-induced cell death

Summary

Introduction

PKCζ have an essential role in apoptosis. Here, we aimed to investigate the effects of PKCζ and TRAF2 and to explore the correlation between PKCζ and TRAF2 in intestinal I/R injury. TRAF2 Ser[55] phosphorylation increased cell survival by inhibiting cell apoptosis in the H/R model. Tumor necrosis factor (TNF) receptor-associated factor (TRAF) proteins are adaptor molecules that associate the TNF receptor family with a variety of signaling pathways related to cell survival and cellular responses to stress.[14]. Previous studies revealed that TRAF2, which is a representative member of the TRAF family, promoted cell survival in response to TNF-α stimulation.[15] In addition, TRAF2 depletion augmented hepatocyte apoptosis via Fas/CD95,16 implying that TRAF2 has a role in suppressing apoptosis in the liver. PKCζ phosphorylates TRAF2 at Ser[55] in response to TNF-α stimulation, which allows the phosphorylated TRAF2 to suppress apoptosis, leading to inhibition of TNF-α-induced cell death in MEFs.[20] in this study, we sought to investigate the role of the PKCζ/TRAF2 signaling pathway in intestinal I/R injury

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Conclusion