Evidence for a Role for Notch Signaling in the Cytokine-Dependent Survival of Activated T Cells

Bheeshmachar, Geetha and Purushotaman, Divya and Sade, Hadassah and Gunasekharan, Vigneshkumar and Rangarajan, Annapoorni and Sarin, Apurva (2006) Evidence for a Role for Notch Signaling in the Cytokine-Dependent Survival of Activated T Cells. In: The Journal of Immunology, 177 (8). pp. 5041-5050.

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Abstract

Peripheral T cell homeostasis results from a balance between factors promoting survival and those that trigger deletion of Ag-reactive cells. The cytokine IL-2 promotes T cell survival whereas reactive oxygen species (ROS) sensitize T cells to apoptosis. Two pathways of activated T cell apoptosis–one triggered by Fas ligand and the other by cytokine deprivation–depend on ROS, with the latter also regulated by members of the Bcl-2 family. Notch family proteins regulate several cell-fate decisions in metazoans. Ectopic expression of the Notch1 intracellular domain (NICD) in T cells inhibits Fas-induced apoptosis. The underlying mechanism is not known and the role, if any, of Notch in regulating apoptosis triggered by cytokine deprivation or neglect has not been examined. In this study, we use a Notch1/Fc chimera; a blocking Ab to Notch1 and chemical inhibitors of $\gamma$-secretase to investigate the role of Notch signaling in activated T cells of murine origin. We show that perturbing Notch signaling in activated $CD4^+/CD8 ^+$ T cells maintained in IL-2 results in the accumulation of ROS, reduced Akt/protein kinase B activity, and expression of the antiapoptotic protein $Bcl-xL$, culminating in apoptosis. A broad-spectrum redox scavenger inhibits apoptosis but T cells expressing mutant Fas ligand are sensitive to apoptosis. Activated T cells isolated on the basis of Notch expression $(Notch^+)$ are enriched for $Bcl-xL$ expression and demonstrate reduced susceptibility to apoptosis triggered by neglect or oxidative stress. Furthermore, enforced expression of NICD protects activated T cells from apoptosis triggered by cytokine deprivation. Taken together, these data implicate Notch1 signaling in the cytokine-dependent survival of activated T cells.

Item Type:	Journal Article
Publication:	The Journal of Immunology
Publisher:	The American Association of Immunologists, Inc.
Additional Information:	Copyright of this article belongs to The American Association of Immunologists, Inc.
Department/Centre:	Division of Biological Sciences > Molecular Reproduction, Development & Genetics
Date Deposited:	27 May 2008
Last Modified:	19 Sep 2010 04:45
URI:	http://eprints.iisc.ac.in/id/eprint/14057

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