Interaction of Double-stranded RNA-dependent Protein Kinase (PKR) with the Death Receptor Signaling Pathway in Amyloid β (Aβ)-treated Cells and in APPSLPS1 Knock-in Mice

Julien Couturier,Milena Morel,Raymond Pontcharraud,Bernard Fauconneau,Marc Paccalin,Virginie Gontier,Guylène Page

doi:10.1074/jbc.m109.041954

Julien Couturier, Milena Morel + Show 5 more

Open Access

https://doi.org/10.1074/jbc.m109.041954

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Abstract

For 10 years, research has focused on signaling pathways controlling translation to explain neuronal death in Alzheimer Disease (AD). Previous studies demonstrated in different cellular and animal models and AD patients that translation is down-regulated by the activation of double-stranded RNA-dependent protein kinase (PKR). Among downstream factors of PKR, the Fas-associated protein with a death domain (FADD) and subsequent activated caspase-8 are responsible for PKR-induced apoptosis in recombinant virus-infected cells. However, no studies have reported the role of PKR in death receptor signaling in AD. The aim of this project is to determine physical and functional interactions of PKR with FADD in amyloid-beta peptide (Abeta) neurotoxicity and in APP(SL)PS1 KI transgenic mice. In SH-SY5Y cells, results showed that Abeta42 induced a large increase in phosphorylated PKR and FADD levels and a physical interaction between PKR and FADD in the nucleus, also observed in the cortex of APP(SL)PS1 KI mice. However, PKR gene silencing or treatment with a specific PKR inhibitor significantly prevented the increase in pT(451)-PKR and pS(194)-FADD levels in SH-SY5Y nuclei and completely inhibited activities of caspase-3 and -8. The contribution of PKR in neurodegeneration through the death receptor signaling pathway may support the development of therapeutics targeting PKR to limit neuronal death in AD.

Highlights

Alzheimer Disease (AD)2 is the leading cause of dementia in the elderly, affecting 25 million people in the world with about 5% of genetic origin
Fas-associated protein with a death domain (FADD) could be involved in apoptosis through its nuclear localization by interacting with the methylCpG binding domain protein 4 (MDB4), a protein known to be implicated in DNA repair, but that could promote apoptosis when associated with FADD [14]
Physical Interaction between PKR and FADD in amyloid ␤ peptide (A␤)42treated SH-SY5Y Cells—Previous studies demonstrated that the Thr451 phosphorylated site in the PKR activation loop was required in vivo and in vitro for high-level kinase activity [23]

Summary

Introduction

Alzheimer Disease (AD) is the leading cause of dementia in the elderly, affecting 25 million people in the world with about 5% of genetic origin. For 10 years, research has focused on pathways controlling translation [1,2,3,4,5] They revealed that activated double-stranded RNA-dependent protein kinase (PKR), which phosphorylates the ␣-subunit of eIF2, was associated with degenerating neurons in AD brains (6 – 8). The levels of phosphorylated forms of PKR and eIF2␣ were significantly increased in AD cellular models exposed to A␤42 [2, 5] in the brain of AD transgenic mice [1, 9] and in lymphocytes of AD patients [10] These modifications were negatively correlated with cognitive and memory test scores performed in AD patients [3, 10, 11]. PKR inhibitory treatments prevented the nuclear translocation of FADD and significantly decreased caspase-3 and -8 activities induced by A␤ neurotoxicity

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