Limits...
Hepatitis C virus infection activates an innate pathway involving IKK-α in lipogenesis and viral assembly.

Li Q, Pène V, Krishnamurthy S, Cha H, Liang TJ - Nat. Med. (2013)

Bottom Line: Here we describe a new nuclear factor κB (NF-κB)-independent and kinase-mediated nuclear function of IKK-α in HCV assembly.HCV, through its 3' untranslated region, interacts with DEAD box polypeptide 3, X-linked (DDX3X) to activate IKK-α, which translocates to the nucleus and induces a CBP/p300-mediated transcriptional program involving sterol regulatory element-binding proteins (SREBPs).This innate pathway induces lipogenic genes and enhances core-associated lipid droplet formation to facilitate viral assembly.

View Article: PubMed Central - PubMed

Affiliation: Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, US National Institutes of Health, Bethesda, Maryland, USA.

ABSTRACT
Hepatitis C virus (HCV) interacts extensively with host factors to not only establish productive infection but also trigger unique pathological processes. Our recent genome-wide siRNA screen demonstrated that IκB kinase-α (IKK-α) is a crucial host factor for HCV. Here we describe a new nuclear factor κB (NF-κB)-independent and kinase-mediated nuclear function of IKK-α in HCV assembly. HCV, through its 3' untranslated region, interacts with DEAD box polypeptide 3, X-linked (DDX3X) to activate IKK-α, which translocates to the nucleus and induces a CBP/p300-mediated transcriptional program involving sterol regulatory element-binding proteins (SREBPs). This innate pathway induces lipogenic genes and enhances core-associated lipid droplet formation to facilitate viral assembly. Chemical inhibitors of IKK-α suppress HCV infection and IKK-α-induced lipogenesis, offering a proof-of-concept approach for new HCV therapeutic development. Our results show that HCV uses a novel mechanism to exploit intrinsic innate responses and hijack lipid metabolism, which may contribute to high chronicity rates and the pathological hallmark of steatosis in HCV infection.

Show MeSH

Related in: MedlinePlus

Role IKKα in HCV infection. (a) Image illustration and quantitative analyses of HCV core staining part-one and part-two. Red: HCV core, blue: cell nuclei. Magnification 20 ×. (b) Efficacies of various IKKα siRNAs in silencing IKKα and restraining HCV RNA production. Values were normalized as relative to nontargeting siRNA (siNT) control. (c) Effect of IKKα depletion on infectious HCV production and secretion, assessed by limiting dilution assay. (d) Effect of over-expression of IKKα on HCV infection. (e) Effect of over-expression of the kinase-defective HA-IKKα KM on HCV infection. (f,g) Effects of wedelolactone (30 µM) and IKK inhibitor XII (10 µM) on HCV production (f) and viral infectivity (g). (h,i) Dose-response effects of wedelolactone and IKK inhibitor XII on HCV RNA production and secretion in Huh7.5.1 cells (h) and PHHs (i). Error bars represent ± s.d. of triplicate experiments. (a,f) Scale bars represent 100 µm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3676727&req=5

Figure 1: Role IKKα in HCV infection. (a) Image illustration and quantitative analyses of HCV core staining part-one and part-two. Red: HCV core, blue: cell nuclei. Magnification 20 ×. (b) Efficacies of various IKKα siRNAs in silencing IKKα and restraining HCV RNA production. Values were normalized as relative to nontargeting siRNA (siNT) control. (c) Effect of IKKα depletion on infectious HCV production and secretion, assessed by limiting dilution assay. (d) Effect of over-expression of IKKα on HCV infection. (e) Effect of over-expression of the kinase-defective HA-IKKα KM on HCV infection. (f,g) Effects of wedelolactone (30 µM) and IKK inhibitor XII (10 µM) on HCV production (f) and viral infectivity (g). (h,i) Dose-response effects of wedelolactone and IKK inhibitor XII on HCV RNA production and secretion in Huh7.5.1 cells (h) and PHHs (i). Error bars represent ± s.d. of triplicate experiments. (a,f) Scale bars represent 100 µm.

Mentions: We applied a two-part viral infection protocol to characterize host dependencies associated with both early (part-one) and late (part-two) stages of HCV life cycle19. The effect of IKKα silencing was more pronounced in part-two (>85% inhibition) than part-one (~60% inhibition), implicating that IKKα acts more on the late stage of viral infection (Fig. 1a and Supplementary Fig. 1a). The effect of IKKα depletion was confirmed by testing four individual siRNAs of the pool (Fig. 1b and Supplementary Fig. 1b). Expression of a siRNA-resistant IKKα mutant (HA-IKKα MUT) restored HCV infection in IKKα siRNA-treated cells (Supplementary Fig. 1c), further validating the phenotype-specific role of IKKα in HCV infection.


Hepatitis C virus infection activates an innate pathway involving IKK-α in lipogenesis and viral assembly.

Li Q, Pène V, Krishnamurthy S, Cha H, Liang TJ - Nat. Med. (2013)

Role IKKα in HCV infection. (a) Image illustration and quantitative analyses of HCV core staining part-one and part-two. Red: HCV core, blue: cell nuclei. Magnification 20 ×. (b) Efficacies of various IKKα siRNAs in silencing IKKα and restraining HCV RNA production. Values were normalized as relative to nontargeting siRNA (siNT) control. (c) Effect of IKKα depletion on infectious HCV production and secretion, assessed by limiting dilution assay. (d) Effect of over-expression of IKKα on HCV infection. (e) Effect of over-expression of the kinase-defective HA-IKKα KM on HCV infection. (f,g) Effects of wedelolactone (30 µM) and IKK inhibitor XII (10 µM) on HCV production (f) and viral infectivity (g). (h,i) Dose-response effects of wedelolactone and IKK inhibitor XII on HCV RNA production and secretion in Huh7.5.1 cells (h) and PHHs (i). Error bars represent ± s.d. of triplicate experiments. (a,f) Scale bars represent 100 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3676727&req=5

Figure 1: Role IKKα in HCV infection. (a) Image illustration and quantitative analyses of HCV core staining part-one and part-two. Red: HCV core, blue: cell nuclei. Magnification 20 ×. (b) Efficacies of various IKKα siRNAs in silencing IKKα and restraining HCV RNA production. Values were normalized as relative to nontargeting siRNA (siNT) control. (c) Effect of IKKα depletion on infectious HCV production and secretion, assessed by limiting dilution assay. (d) Effect of over-expression of IKKα on HCV infection. (e) Effect of over-expression of the kinase-defective HA-IKKα KM on HCV infection. (f,g) Effects of wedelolactone (30 µM) and IKK inhibitor XII (10 µM) on HCV production (f) and viral infectivity (g). (h,i) Dose-response effects of wedelolactone and IKK inhibitor XII on HCV RNA production and secretion in Huh7.5.1 cells (h) and PHHs (i). Error bars represent ± s.d. of triplicate experiments. (a,f) Scale bars represent 100 µm.
Mentions: We applied a two-part viral infection protocol to characterize host dependencies associated with both early (part-one) and late (part-two) stages of HCV life cycle19. The effect of IKKα silencing was more pronounced in part-two (>85% inhibition) than part-one (~60% inhibition), implicating that IKKα acts more on the late stage of viral infection (Fig. 1a and Supplementary Fig. 1a). The effect of IKKα depletion was confirmed by testing four individual siRNAs of the pool (Fig. 1b and Supplementary Fig. 1b). Expression of a siRNA-resistant IKKα mutant (HA-IKKα MUT) restored HCV infection in IKKα siRNA-treated cells (Supplementary Fig. 1c), further validating the phenotype-specific role of IKKα in HCV infection.

Bottom Line: Here we describe a new nuclear factor κB (NF-κB)-independent and kinase-mediated nuclear function of IKK-α in HCV assembly.HCV, through its 3' untranslated region, interacts with DEAD box polypeptide 3, X-linked (DDX3X) to activate IKK-α, which translocates to the nucleus and induces a CBP/p300-mediated transcriptional program involving sterol regulatory element-binding proteins (SREBPs).This innate pathway induces lipogenic genes and enhances core-associated lipid droplet formation to facilitate viral assembly.

View Article: PubMed Central - PubMed

Affiliation: Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, US National Institutes of Health, Bethesda, Maryland, USA.

ABSTRACT
Hepatitis C virus (HCV) interacts extensively with host factors to not only establish productive infection but also trigger unique pathological processes. Our recent genome-wide siRNA screen demonstrated that IκB kinase-α (IKK-α) is a crucial host factor for HCV. Here we describe a new nuclear factor κB (NF-κB)-independent and kinase-mediated nuclear function of IKK-α in HCV assembly. HCV, through its 3' untranslated region, interacts with DEAD box polypeptide 3, X-linked (DDX3X) to activate IKK-α, which translocates to the nucleus and induces a CBP/p300-mediated transcriptional program involving sterol regulatory element-binding proteins (SREBPs). This innate pathway induces lipogenic genes and enhances core-associated lipid droplet formation to facilitate viral assembly. Chemical inhibitors of IKK-α suppress HCV infection and IKK-α-induced lipogenesis, offering a proof-of-concept approach for new HCV therapeutic development. Our results show that HCV uses a novel mechanism to exploit intrinsic innate responses and hijack lipid metabolism, which may contribute to high chronicity rates and the pathological hallmark of steatosis in HCV infection.

Show MeSH
Related in: MedlinePlus