Glycolysis promotes caspase-3 activation in lipid rafts in T cells

Michael A Secinaro,Vikas Anathy,Michael P Murphy,Ralph C Budd,Oliver Dienz,Angela Logan,Jonathan E Boyson,Karen A Fortner

doi:10.1038/s41419-017-0099-z

Abstract

Resting T cells undergo a rapid metabolic shift to glycolysis upon activation in the presence of interleukin (IL)-2, in contrast to oxidative mitochondrial respiration with IL-15. Paralleling these different metabolic states are striking differences in susceptibility to restimulation-induced cell death (RICD); glycolytic effector T cells are highly sensitive to RICD, whereas non-glycolytic T cells are resistant. It is unclear whether the metabolic state of a T cell is linked to its susceptibility to RICD. Our findings reveal that IL-2-driven glycolysis promotes caspase-3 activity and increases sensitivity to RICD. Neither caspase-7, caspase-8, nor caspase-9 activity is affected by these metabolic differences. Inhibition of glycolysis with 2-deoxyglucose reduces caspase-3 activity as well as sensitivity to RICD. By contrast, IL-15-driven oxidative phosphorylation actively inhibits caspase-3 activity through its glutathionylation. We further observe active caspase-3 in the lipid rafts of glycolytic but not non-glycolytic T cells, suggesting a proximity-induced model of self-activation. Finally, we observe that effector T cells during influenza infection manifest higher levels of active caspase-3 than naive T cells. Collectively, our findings demonstrate that glycolysis drives caspase-3 activity and susceptibility to cell death in effector T cells independently of upstream caspases. Linking metabolism, caspase-3 activity, and cell death provides an intrinsic mechanism for T cells to limit the duration of effector function.

Highlights

The balance of cell proliferation and cell death is critical for the maintenance of stable cell numbers and tissue homeostasis
IL-15 induces mitochondrial reactive oxygen species (ROS) and glutathionylation of caspase-3 To investigate the influence of cell metabolism on caspase activity, we initially modeled two metabolic states in vitro using cytokines that are known to promote very different levels of glycolysis following T-cell activation: IL2, which upregulates glycolysis, and IL-15, known to induce a non-glycolytic state of mitochondrial respiration[12]
Complex I is known to generate reactive oxygen species (ROS)[26], and we determined that IL-15 induced a greater amount of mitochondrial ROS compared to IL-2 (Fig. 1d) as measured using the mitochondria-targeted probe mitoboronic acid (MitoB)[27]

Summary

Introduction

The balance of cell proliferation and cell death is critical for the maintenance of stable cell numbers and tissue homeostasis. It is perhaps not surprising that these opposing processes may be mechanistically linked in various cell types, including cancer[1,2]. T lymphocytes undergo a period of very rapid proliferation. During this expansion, T cells become susceptible to T-cell receptor (TCR) restimulationinduced cell death (RICD)[3,4]. The link between proliferation and susceptibility to death remains poorly understood[5]. Changes in cellular metabolism are well recognized to play a critical role during an effective immune response

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Results

Conclusion