TNFα induces survival through the FLIP-L-dependent activation of the MAPK/ERK pathway

F Marques-Fernandez,N Llecha-Cano,V J Yuste,L Planells-Ferrer,S Reix,K Mo Galenkamp,J X Comella,R Gozzelino,J Lopez-Soriano,R S Moubarak

doi:10.1038/cddis.2013.25

Abstract

Activation of tumor necrosis factor receptor-1 can trigger survival or apoptosis pathways. In many cellular models, including the neuronal cell model PC12, it has been demonstrated that inhibition of protein synthesis is sufficient to render cells sensitive to apoptosis induced by TNFα. The survival effect is linked to the translocation of the transcription factor nuclear factor-kappa B (NF-κB) to the nucleus and activation of survival-related genes such as FLICE-like inhibitory protein long form (FLIP-L) or IAPs. Nonetheless, we previously reported an NF-κB-independent contribution of Bcl-xL to cell survival after TNFα treatment. Here, we demonstrate that NF-κB-induced increase in FLIP-L expression levels is essential for mitogen-activated protein kinases/extracellular signal-regulated kinases (MAPK/ERK) activation. We demonstrate that FLIP-L behaves as a Raf-1 activator through both protein–protein interaction and Raf-1 kinase activation, without the requirement of the classical Ras activation. Importantly, prevention of FLIP-L increase by NF-κB inhibition or knockdown of endogenous FLIP-L blocks MAPK/ERK activation after TNFα treatment. From a functional point of view, we show that inhibition of the MAPK/ERK pathway and the NF-κB pathway are equally relevant to render PC12 cells sensitive to cell death induced by TNFα. Apoptosis induced by TNFα under these conditions is dependent on jun nuclear kinase1/2 JNK1/2-dependent Bim upregulation. Therefore, we report a previously undescribed and essential role for MAPK/ERK activation by FLIP-L in the decision between cell survival and apoptosis upon TNFα stimulation.

Highlights

The binding of TNF-alpha (TNFa) to its receptor tumor necrosis factor receptor-1 (TNFR1) can alternatively induce cell death or survival and differentiation through the formation of two sequential complexes.[9]
As maximal caspase activation is reached after 24 h of TNFa treatment, cell death was determined by counting of apoptotic nuclei at the same time point (Figure 1b), revealing that PC12 cells overexpressing the super-repressor (SR-IkBa) plasmid and treated with TNFa undergo apoptosis when compared with cells expressing the control plasmid (Neo)
We describe the regulation of MAPK/ERK activation by TNFa in the neuronal PC12 cells

Summary

Introduction

The binding of TNF-alpha (TNFa) to its receptor tumor necrosis factor receptor-1 (TNFR1) can alternatively induce cell death or survival and differentiation through the formation of two sequential complexes.[9]. FLIP-L protects from DR-induced apoptosis in a wide range of cellular models.[21,22,23] While the antiapoptotic role of FLIP-L is well established in the immune system,[24,25,26] only a couple of reports have shown that FLIP-L controls embryonic motoneurons apoptosis during development[27] and protects neurons against in vivo ischemia and in vitro glucose deprivation-induced cell death.[28] We have recently established that FLIP-L is crucial for neurotrophin-induced neurite outgrowth through its interaction with Trk receptors, inducing the activation of both NF-kB and mitogen-activated protein kinases/extracellular signal-regulated kinases (MAPK/ERK) pathways.[29] We demonstrated that FLIP-L function in neurotrophin-induced differentiation is independent from its antiapoptotic role. We sought to determine the role of FLIP-L in DR-induced survival and apoptotic pathway

Methods

Results

Conclusion