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Regulation of Protein Kinase R (PKR) activation during cell stress by TRBP phosphorylation
Author(s) -
Chukwurah Evelyn Ekene,
Patel Rekha C
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.647.10
Subject(s) - protein kinase r , eif 2 kinase , phosphorylation , stress granule , microbiology and biotechnology , protein kinase a , autophosphorylation , biology , kinase , integrated stress response , activator (genetics) , translation (biology) , biochemistry , mitogen activated protein kinase kinase , cyclin dependent kinase 2 , messenger rna , receptor , gene
A crucial component of cellular stress response is the attenuationof protein synthesis by phosphorylation of the α‐subunit of the eukaryotictranslation initiation factor, eIF2. This allows the cell to mount anappropriate response to the stressful conditions, while minimizing energyexpended on protein translation. However, a prolonged eIF2α phosphorylation dueto sustained stressful conditions results in the induction of apoptosis. PKR is one of four well‐characterized serine‐threoninekinases responsible for mediating translation inhibition in response to viralinfection, endoplasmic reticulum (ER) stress, oxidative stress, and serumstarvation. During these conditions, PKR is activated via interaction either withdouble stranded RNA (dsRNA) generated during viral infections or with itscellular activator PACT ( P rotein Act ivator of PKR), resulting in itsautophosphorylation, activation of its catalytic function, and subsequent eIF2αphosphorylation. PKR's kinase activity is inhibited by the double stranded RNA binding protein TRBP ( T AR R NA B inding P rotein) by a direct interaction, as well as by sequestration of PKR's dsRNA activators and PACT, there by preventing PKR autophosphorylation and downstream protein translation inhibition. Various studies have linked dysregulation of PKR activation with various neuro degenerative and neuromuscular disorders. Recent findings indicate that TRBP also inhibits PKR inother cellular contexts (i.e. mitosis, obesity), but suggest that its abilityto inhibit PKR is dependent on various post‐translational modifications that significantly alter its binding affinity for PKR and ultimately affect PKRactivation in those contexts. We investigated changes in both PKR‐TRBP interactions and TRBP‐mediated PKR inhibition during cell stress. We used various biochemical methods to study TRBP phosphorylation, its interaction with PKR, and effect on PKR's kinase activity. Various phospho‐mimetic and phospho‐defective mutants of TRBP were used to examine the role of phosphorylation in mediating PKRinhibition. Our results indicate a functional role of TRBP phosphorylation inregulating PKR activation in response to cellular stress, and elucidate animportant mechanism by which the deleterious sustained response to stress is down regulated.