Double-Stranded RNA-Dependent Protein Kinase Links Pathogen Sensing with Stress and Metabolic Homeostasis

Department of Genetics & Complex Diseases, Harvard School of Public Health, Boston, MA 02115, USA.
Cell (Impact Factor: 32.24). 02/2010; 140(3):338-48. DOI: 10.1016/j.cell.2010.01.001
Source: PubMed


As chronic inflammation is a hallmark of obesity, pathways that integrate nutrient- and pathogen sensing pathways are of great interest in understanding the mechanisms of insulin resistance, type 2 diabetes, and other chronic metabolic pathologies. Here, we provide evidence that double-stranded RNA-dependent protein kinase (PKR) can respond to nutrient signals as well as endoplasmic reticulum (ER) stress and coordinate the activity of other critical inflammatory kinases such as the c-Jun N-terminal kinase (JNK) to regulate insulin action and metabolism. PKR also directly targets and modifies insulin receptor substrate and hence integrates nutrients and insulin action with a defined pathogen response system. Dietary and genetic obesity features marked activation of PKR in adipose and liver tissues and absence of PKR alleviates metabolic deterioration due to nutrient or energy excess in mice. These findings demonstrate PKR as a critical component of an inflammatory complex that responds to nutrients and organelle dysfunction.

Download full-text


Available from: Masato Furuhashi,
  • Source
    • "PKR activation also regulates the activity of transcriptional factors that include STATs (signal transducer and activation of transcription factors), IkB/NFkB , p53, and interferon regulatory factor-1 (IRF-1) and also MAP kinases that play a role in cell growth, development, differentiation, and death [26] [27]. Recent studies implicated PKR in inflammasome activation and also suggested as a core component of putative metabolic inflammasome consisting of major elements of inflammatory signaling and insulin action [28] [21]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Tyrosine phosphorylation of insulin receptor beta (IRβ) in insulin treated HepG2 cells is inversely correlated to ser(51) phosphorylation in the alpha-subunit of eukaryotic initiation factor 2 (eIF2α) that regulates protein synthesis. Insulin stimulates interaction between IRβ and PKR, double stranded RNA-dependent protein kinase, also known as EIF2AK2, and phosphorylation of tyrosine residues in PKR, as analyzed by immunoprecipitation and pull down assays using anti-IRβ and anti-phosphotyrosine antibodies, recombinant IRβ and immunopurified PKR. Further polyIC or synthetic double stranded RNA-induced threonine phosphorylation or activation of immunopurified and cellular PKR is suppressed in the presence of insulin treated purified IRβ and cell extracts. Acute, but not chronic, insulin treatment enhances tyrosine phosphorylation of IRβ, its interaction with PKR and tyrosine phosphorylation of PKR. In contrast, lipopolysaccharide that stimulates threonine phosphorylation of PKR and eIF2α phosphorylation and AG 1024, an inhibitor of the tyrosine kinase activity of IRβ, reduces PKR association with the receptor, IRβ in HepG2 cells. These findings therefore may suggest that tyrosine phosphorylated PKR plays a role in the regulation of insulin induced protein synthesis and in maintaining insulin sensitivity, whereas, suppression of polyIC-mediated threonine phosphorylation of PKR by insulin compromises its ability to fight against virus infection in host cells. Copyright © 2015. Published by Elsevier Inc.
    Archives of Biochemistry and Biophysics 08/2015; 585. DOI:10.1016/ · 3.02 Impact Factor
  • Source
    • "Cells were then treated with 0.2 mM LA for 48 h, a concentration that can be achieved in human blood plasma after ingestion of a supplement [21]. LA was dissolved in ethanol to prepare a stock solution of 100 mM, and glucose was dissolved in water to prepare a solution of 1 M. Palmitic acid (PA) was prepared as previously described [22]. For cell transfection, 1.5 g of plasmid DNAs was transfected into McA cells as previously described [23] "
    [Show abstract] [Hide abstract]
    ABSTRACT: The activation of sterol regulatory element binding proteins (SREBPs) is regulated by insulin-induced genes 1 and 2 (Insig-1 and Insig-2) and SCAP. We previously reported that feeding R-α-lipoic acid (LA) to Zucker diabetic fatty (ZDF) rats improves severe hypertriglyceridemia. In this study, we investigated the role of cyclic AMP-responsive element binding protein H (CREBH) in the lipid-lowering mechanism of LA and its involvement in the SREBP-1c and Insig pathway. Incubation of McA cells with LA (0.2 mM) or glucose (6 mM) stimulated activation of CREBH. LA treatment further induced mRNA expression of Insig-1 and Insig-2a, but not Insig-2b, in glucose-treated cells. In vivo, feeding LA to obesity-induced hyperlipidemic ZDF rats activated hepatic CREBH and stimulated transcription and translation of Insig-1 and Insig-2a. Activation of CREBH and Insigs induced by LA suppressed processing of SREBP-1c precursor into nuclear SREBP-1c, which subsequently inhibited expression of genes involved in fatty acid synthesis, including FASN, ACC and SCD-1, and reduced triglyceride (TG) contents in both glucose-treated cells and ZDF rat livers. Additionally, LA treatment also decreased abundances of very low density lipoprotein (VLDL)-associated apolipoproteins, apoB100 and apoE, in glucose-treated cells and livers of ZDF rats, leading to decreased secretion of VLDL and improvement of hypertriglyceridemia. This study unveils a novel molecular mechanism whereby LA lowers TG via activation of hepatic CREBH and increased expression of Insig-1 and Insig-2a to inhibit de novo lipogenesis and VLDL secretion. These findings provide novel insight into the therapeutic potential of LA as an anti-hypertriglyceridemia dietary molecule. Copyright © 2015 Elsevier Inc. All rights reserved.
    The Journal of nutritional biochemistry 05/2015; 26(9). DOI:10.1016/j.jnutbio.2015.03.011 · 3.79 Impact Factor
  • Source
    • "JNK activity was found induced in many tissues of obese and insulinresistant mice (Hirosumi et al. 2002) (Fig. 2). Mechanistically, JNK activation can occur through the induction of endoplasmic reticulum stress (Hotamisligil 2010), depending on the activity of double-stranded RNA-dependent protein kinase (PKR) (Nakamura et al. 2010). Alternatively, saturated fatty acids through binding of toll-like receptors (Shi et al. 2006; Tsukumo et al. 2007) or through activation of the protein kinase C-mediated activation of the mixed-lineage protein kinase (MLK) group of MAP kinase kinase kinases (MAPKKKs) (Kant et al. 2013) may also activate JNK. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Low-grade inflammation is an established pathological condition that contributes to the development of obesity, insulin resistance and type 2 diabetes. Metabolic inflammation is dependent on multiple signalling events. In an overnutrition state, canonical inflammatory pathways are induced by inflammatory cytokines and lipid species. They can also be triggered through inflammasome activation as well as through cellular stress provoked by the unfolded protein response at the endoplasmic reticulum as well as by reactive oxygen species. In this chapter, we summarize the current knowledge about signalling events within the cell and describe how they impact on metabolic inflammation and whole-body metabolism. We particularly highlight the interplay between different signalling pathways that link low-grade inflammation responses to the inactivation of the insulin receptor pathway, ultimately leading to insulin resistance, a hallmark of type 2 diabetes.
    Handbook of experimental pharmacology 04/2015; DOI:10.1007/164_2015_4
Show more