Kinase suppressor of Ras-1 protects intestinal epithelium from cytokine-mediated apoptosis during inflammation
Fang Yan, … , M. Kay Washington, D. Brent Polk
Fang Yan, … , M. Kay Washington, D. Brent Polk
Published November 1, 2004
Citation Information: J Clin Invest. 2004;114(9):1272-1280. https://doi.org/10.1172/JCI21022.
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Article Cell biology

Kinase suppressor of Ras-1 protects intestinal epithelium from cytokine-mediated apoptosis during inflammation

Abstract

TNF plays a pathogenic role in inflammatory bowel diseases (IBDs), which are characterized by altered cytokine production and increased intestinal epithelial cell apoptosis. In vitro studies suggest that kinase suppressor of Ras-1 (KSR1) is an essential regulatory kinase for TNF-stimulated survival pathways in intestinal epithelial cell lines. Here we use a KSR1-deficient mouse model to study the role of KSR1 in regulating intestinal cell fate during cytokine-mediated inflammation. We show that KSR1 and its target signaling pathways are activated in inflamed colon mucosa. Loss of KSR1 increases susceptibility to chronic colitis and TNF-induced apoptosis in the intestinal epithelial cell. Furthermore, disruption of KSR1 expression enhances TNF-induced apoptosis in mouse colon epithelial cells and is associated with a failure to activate antiapoptotic signals including Raf-1/MEK/ERK, NF-κB, and Akt/protein kinase B. These effects are reversed by WT, but not kinase-inactive, KSR1. We conclude that KSR1 has an essential protective role in the intestinal epithelial cell during inflammation through activation of cell survival pathways.

Authors

Fang Yan, Sutha K. John, Guinn Wilson, David S. Jones, M. Kay Washington, D. Brent Polk

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Figure 1

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TNF induces apoptosis in KSR1–/– mouse colon epithelium in vivo. Mice we...
TNF induces apoptosis in KSR1–/– mouse colon epithelium in vivo. Mice were injected with TNF or PBS for the indicated times. Paraffin-embedded colon tissues were studied for apoptosis using ISOL staining. (A) Apoptotic nuclei labeled with peroxidase were visualized using DIC microscopy. Arrowheads indicate ISOL-labeled apoptotic nuclei. (B) The number of apoptotic nuclei found per 100 colonic glands. (C) Caspase-3 activity was determined by immunohistochemistry using anti–active caspase-3 antibody. Arrowheads indicate examples of caspase-3–positive cells detected by peroxidase. KSR1 expression in the gastrointestinal tract was determined by Western blot analysis of mucosal lysates (D) and immunohistochemistry (E). The arrow in E points to the transitional section of KSR1 expression in IL-10+/–KSR1+/– mouse colon. d, distal; p, proximal; SI, small intestine; Cec, cecum; C, colon. The data shown here are representative of 5 different experiments. Magnification, ×40.