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Article ; Online: The PKR/P38/RIPK1 Signaling Pathway as a Therapeutic Target in Alzheimer’s Disease

Jacques Hugon / Claire Paquet

International Journal of Molecular Sciences, Vol 22, Iss 3136, p

2021 Volume 3136

Abstract: Neuropathological lesions in Alzheimer’s disease (AD) include amyloid plaques formed by the accumulation of amyloid peptides, neurofibrillary tangles made of hyperphosphorylated tau protein, synaptic and neuronal degenerations, and neuroinflammation. The ...

Abstract	Neuropathological lesions in Alzheimer’s disease (AD) include amyloid plaques formed by the accumulation of amyloid peptides, neurofibrillary tangles made of hyperphosphorylated tau protein, synaptic and neuronal degenerations, and neuroinflammation. The cause of AD is unknown, but according to the amyloid hypothesis, amyloid oligomers could lead to the activation of kinases such as eukaryotic translation initiation factor 2-alpha kinase 2 (PKR), p38, and receptor-interacting serine/threonine-protein kinase 1 (RIPK1), which all belong to the same stress-activated pathway. Many toxic kinase activations have been described in AD patients and in experimental models. A p38 mitogen-activated protein kinase inhibitor was recently tested in clinical trials but with unsuccessful results. The complex PKR/P38/RIPK1 (PKR/dual specificity mitogen-activated protein kinase kinase 6 (MKK6)/P38/MAP kinase-activated protein kinase 2 (MK2)/RIPK1) is highly activated in AD brains and in the brains of AD transgenic animals. To delineate the implication of this pathway in AD, we carried out a search on PubMed including PKR/MKK6/p38/MK2/RIPK1, Alzheimer, and therapeutics. The involvement of this signaling pathway in the genesis of AD lesions, including Aβ accumulations and tau phosphorylation as well as cognitive decline, is demonstrated by the reports described in this review. A future combination strategy with kinase inhibitors should be envisaged to modulate the consequences for neurons and other brain cells linked to the abnormal activation of this pathway.
Keywords	Alzheimer ; kinases ; signaling pathways ; neuroinflammation ; combination therapy ; Biology (General) ; QH301-705.5 ; Chemistry ; QD1-999
Subject code	571
Language	English
Publishing date	2021-03-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Cerebrospinal Fluid Alpha-Synuclein Improves the Differentiation between Dementia with Lewy Bodies and Alzheimer’s Disease in Clinical Practice

Matthieu Lilamand / Josué Clery / Agathe Vrillon / François Mouton-Liger / Emmanuel Cognat / Sinead Gaubert / Claire Hourregue / Matthieu Martinet / Julien Dumurgier / Jacques Hugon / Elodie Bouaziz-Amar / Claire Paquet

International Journal of Molecular Sciences, Vol 23, Iss 13488, p

2022 Volume 13488

Abstract: Background: Alpha-synuclein, abnormally aggregated in Dementia with Lewy Bodies (DLB), could represent a potential biomarker to improve the differentiation between DLB and Alzheimer’s disease (AD). Our main objective was to compare Cerebrospinal Fluid ( ... ...

Abstract	Background: Alpha-synuclein, abnormally aggregated in Dementia with Lewy Bodies (DLB), could represent a potential biomarker to improve the differentiation between DLB and Alzheimer’s disease (AD). Our main objective was to compare Cerebrospinal Fluid (CSF) alpha-synuclein levels between patients with DLB, AD and Neurological Control (NC) individuals. Methods: In a monocentric retrospective study, we assessed CSF alpha-synuclein concentration with a validated ELISA kit (ADx EUROIMMUN) in patients with DLB, AD and NC from a tertiary memory clinic. Between-group comparisons were performed, and Receiver Operating Characteristic analysis was used to identify the best CSF alpha-synuclein threshold. We examined the associations between CSF alpha-synuclein, other core AD CSF biomarkers and brain MRI characteristics. Results: We included 127 participants (mean age: 69.3 ± 8.1, Men: 41.7%). CSF alpha-synuclein levels were significantly lower in DLB than in AD (1.28 ± 0.52 ng/mL vs. 2.26 ± 0.91 ng/mL, respectively, p < 0.001) without differences due to the stage of cognitive impairment. The best alpha-synuclein threshold was characterized by an Area Under the Curve = 0.85, Sensitivity = 82.0% and Specificity = 76.0%. CSF alpha-synuclein was associated with CSF AT(N) biomarkers positivity ( p < 0.01) but not with hippocampal atrophy or white matter lesions. Conclusion: CSF Alpha-synuclein evaluation could help to early differentiate patients with DLB and AD in association with existing biomarkers.
Keywords	alpha-synuclein ; Dementia with Lewy Bodies ; Alzheimer’s disease ; neurodegenerative disorders ; biomarker discovery ; Biology (General) ; QH301-705.5 ; Chemistry ; QD1-999
Subject code	610
Language	English
Publishing date	2022-11-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Biomarker profiles of Alzheimer's disease and dynamic of the association between cerebrospinal fluid levels of β-amyloid peptide and tau.

Aysha S Mohamed Lafirdeen / Emmanuel Cognat / Severine Sabia / Claire Hourregue / Matthieu Lilamand / Aline Dugravot / Elodie Bouaziz-Amar / Jean-Louis Laplanche / Jacques Hugon / Archana Singh-Manoux / Claire Paquet / Julien Dumurgier

PLoS ONE, Vol 14, Iss 5, p e

2019 Volume 0217026

Abstract: Objective To investigate the relationship between cerebrospinal fluid (CSF) β-amyloid peptide (Aβ42) and CSF Tau in a large population of patients referred to memory clinics for investigation of cognitive dysfunction. Methods We analyzed Alzheimer's ... ...

Abstract	Objective To investigate the relationship between cerebrospinal fluid (CSF) β-amyloid peptide (Aβ42) and CSF Tau in a large population of patients referred to memory clinics for investigation of cognitive dysfunction. Methods We analyzed Alzheimer's disease (AD) biomarkers in CSF taken from 3565 patients referred to 18 French memory clinics. Patients were classified into four profiles according to levels of CSF biomarkers (A: amyloidosis, N: neurodegeneration). The association between CSF Tau and CSF Aβ42 were analyzed using general linear regression models, in the overall population and stratified by biomarkers profiles. We compared linear and quadratic models using Akaike information criterion. We also assessed change in biomarker profiles in a subset of patients who had 2 assessments of biomarkers. Results CSF Tau was negatively associated with CSF Aβ42 in the overall population, following a non-linear quadratic model. However, the nature of this association was different in the 4 profiles: positive association in A-N- profile, negative association in A-N+ and A+N+ profiles, lack of association in A+N- patients. When considering patients with longitudinal data on profiles, 36% of those initially classified as A-N+ evolved to an A+N+ profile. Conclusions The nature of the association between CSF Aβ42 and CFS Tau depends on the A/N profiles of patients. These results suggest an increase in CSF Aβ42 early in the disease before its decline while tau pathology progresses, this pattern is particularly observed in non-APOE4 subjects. This phenomenon may explain why some patients with neurodegeneration only markers convert to an AD profile (A+N+) over time.
Keywords	Medicine ; R ; Science ; Q
Subject code	616
Language	English
Publishing date	2019-01-01T00:00:00Z
Publisher	Public Library of Science (PLoS)
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: PKR modulates abnormal brain signaling in experimental obesity.

Mariko Taga / François Mouton-Liger / Malha Sadoune / Sarah Gourmaud / Jenny Norman / Marion Tible / Sylvie Thomasseau / Claire Paquet / James A R Nicoll / Delphine Boche / Jacques Hugon

PLoS ONE, Vol 13, Iss 5, p e

2018 Volume 0196983

Abstract: Metabolic disorders including obesity and type 2 diabetes are known to be associated with chronic inflammation and are obvious risk factors for Alzheimer's disease. Recent evidences concerning obesity and diabetes suggest that the metabolic inflammasome ( ...

Abstract	Metabolic disorders including obesity and type 2 diabetes are known to be associated with chronic inflammation and are obvious risk factors for Alzheimer's disease. Recent evidences concerning obesity and diabetes suggest that the metabolic inflammasome ("metaflammasome") mediates chronic inflammation. The double-stranded RNA-dependent protein kinase (PKR) is a central component of the metaflammasome. In wild type (WT) and PKR-/- mice, blood glucose, insulin and lipid levels and the brain expression of the phosphorylated components of the metaflammasome-PKR, JNK, IRS1 and IKKbeta-were studied after the induction of obesity by a high fat diet (HFD). The results showed significant increased levels of activated brain metaflammasome proteins in exposed WT mice but the changes were not significant in PKR-/- mice. In addition, gain weight was observed in WT mice and also in PKR-/- mice exposed to HFD. Increased blood insulin level was more accentuated in PKR -/- mice. The modulation of PKR activity could be an appropriate therapeutic approach, aimed at reducing abnormal brain metabolism and inflammation linked to metabolic disorders in order to reduce the risk of neurodegeneration.
Keywords	Medicine ; R ; Science ; Q
Subject code	616
Language	English
Publishing date	2018-01-01T00:00:00Z
Publisher	Public Library of Science (PLoS)
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Inhibition of the inflammatory response to stress by targeting interaction between PKR and its cellular activator PACT

Stephanie Dabo / Patrick Maillard / Milagros Collados Rodriguez / Marianne Doré Hansen / Sabrina Mazouz / Donna-Joe Bigot / Marion Tible / Geneviève Janvier / Olivier Helynck / Patricia Cassonnet / Yves Jacob / Jacques Bellalou / Anne Gatignol / Rekha C. Patel / Jacques Hugon / Hélène Munier-Lehmann / Eliane F. Meurs

Scientific Reports, Vol 7, Iss 1, Pp 1-

2017 Volume 15

Abstract: Abstract PKR is a cellular kinase involved in the regulation of the integrative stress response (ISR) and pro-inflammatory pathways. Two N-terminal dsRNA Binding Domains (DRBD) are required for activation of PKR, by interaction with either dsRNA or PACT, ...

Abstract	Abstract PKR is a cellular kinase involved in the regulation of the integrative stress response (ISR) and pro-inflammatory pathways. Two N-terminal dsRNA Binding Domains (DRBD) are required for activation of PKR, by interaction with either dsRNA or PACT, another cellular DRBD-containing protein. A role for PKR and PACT in inflammatory processes linked to neurodegenerative diseases has been proposed and raised interest for pharmacological PKR inhibitors. However, the role of PKR in inflammation is subject to controversy. We identified the flavonoid luteolin as an inhibitor of the PKR/PACT interaction at the level of their DRBDs using high-throughput screening of chemical libraries by homogeneous time-resolved fluorescence. This was further validated using NanoLuc-Based Protein Complementation Assay. Luteolin inhibits PKR phosphorylation, the ISR and the induction of pro-inflammatory cytokines in human THP1 macrophages submitted to oxidative stress and toll-like receptor (TLR) agonist. Similarly, luteolin inhibits induction of pro-inflammatory cytokines in murine microglial macrophages. In contrast, luteolin increased activation of the inflammasome, in a PKR-independent manner. Collectively, these data delineate the importance of PKR in the inflammation process to the ISR and induction of pro-inflammatory cytokines. Pharmacological inhibitors of PKR should be used in combination with drugs targeting directly the inflammasome.
Keywords	Medicine ; R ; Science ; Q
Subject code	610
Language	English
Publishing date	2017-11-01T00:00:00Z
Publisher	Nature Publishing Group
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Hepatitis C virus reveals a novel early control in acute immune response.

Noëlla Arnaud / Stéphanie Dabo / Daisuke Akazawa / Masayoshi Fukasawa / Fumiko Shinkai-Ouchi / Jacques Hugon / Takaji Wakita / Eliane F Meurs

PLoS Pathogens, Vol 7, Iss 10, p e

2011 Volume 1002289

Abstract: Recognition of viral RNA structures by the intracytosolic RNA helicase RIG-I triggers induction of innate immunity. Efficient induction requires RIG-I ubiquitination by the E3 ligase TRIM25, its interaction with the mitochondria-bound MAVS protein, ... ...

Abstract	Recognition of viral RNA structures by the intracytosolic RNA helicase RIG-I triggers induction of innate immunity. Efficient induction requires RIG-I ubiquitination by the E3 ligase TRIM25, its interaction with the mitochondria-bound MAVS protein, recruitment of TRAF3, IRF3- and NF-κB-kinases and transcription of Interferon (IFN). In addition, IRF3 alone induces some of the Interferon-Stimulated Genes (ISGs), referred to as early ISGs. Infection of hepatocytes with Hepatitis C virus (HCV) results in poor production of IFN despite recognition of the viral RNA by RIG-I but can lead to induction of early ISGs. HCV was shown to inhibit IFN production by cleaving MAVS through its NS3/4A protease and by controlling cellular translation through activation of PKR, an eIF2α-kinase containing dsRNA-binding domains (DRBD). Here, we have identified a third mode of control of IFN induction by HCV. Using HCVcc and the Huh7.25.CD81 cells, we found that HCV controls RIG-I ubiquitination through the di-ubiquitine-like protein ISG15, one of the early ISGs. A transcriptome analysis performed on Huh7.25.CD81 cells silenced or not for PKR and infected with JFH1 revealed that HCV infection leads to induction of 49 PKR-dependent genes, including ISG15 and several early ISGs. Silencing experiments revealed that this novel PKR-dependent pathway involves MAVS, TRAF3 and IRF3 but not RIG-I, and that it does not induce IFN. Use of PKR inhibitors showed that this pathway requires the DRBD but not the kinase activity of PKR. We then demonstrated that PKR interacts with HCV RNA and MAVS prior to RIG-I. In conclusion, HCV recruits PKR early in infection as a sensor to trigger induction of several IRF3-dependent genes. Among those, ISG15 acts to negatively control the RIG-I/MAVS pathway, at the level of RIG-I ubiquitination.These data give novel insights in the machinery involved in the early events of innate immune response.
Keywords	Immunologic diseases. Allergy ; RC581-607 ; Biology (General) ; QH301-705.5
Subject code	570
Language	English
Publishing date	2011-10-01T00:00:00Z
Publisher	Public Library of Science (PLoS)
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Age and the association between apolipoprotein E genotype and Alzheimer disease

Hana Saddiki / Aurore Fayosse / Emmanuel Cognat / Séverine Sabia / Sebastiaan Engelborghs / David Wallon / Panagiotis Alexopoulos / Kaj Blennow / Henrik Zetterberg / Lucilla Parnetti / Inga Zerr / Peter Hermann / Audrey Gabelle / Mercè Boada / Adelina Orellana / Itziar de Rojas / Matthieu Lilamand / Maria Bjerke / Christine Van Broeckhoven /

Lucia Farotti / Nicola Salvadori / Janine Diehl-Schmid / Timo Grimmer / Claire Hourregue / Aline Dugravot / Gaël Nicolas / Jean-Louis Laplanche / Sylvain Lehmann / Elodie Bouaziz-Amar / Alzheimer’s Disease Neuroimaging Initiative / Jacques Hugon / Christophe Tzourio / Archana Singh-Manoux / Claire Paquet / Julien Dumurgier

PLoS Medicine, Vol 17, Iss 8, p e

A cerebrospinal fluid biomarker-based case-control study.

2020 Volume 1003289

Abstract: Background The ε4 allele of apolipoprotein E (APOE) gene and increasing age are two of the most important known risk factors for developing Alzheimer disease (AD). The diagnosis of AD based on clinical symptoms alone is known to have poor specificity; ... ...

Abstract	Background The ε4 allele of apolipoprotein E (APOE) gene and increasing age are two of the most important known risk factors for developing Alzheimer disease (AD). The diagnosis of AD based on clinical symptoms alone is known to have poor specificity; recently developed diagnostic criteria based on biomarkers that reflect underlying AD neuropathology allow better assessment of the strength of the associations of risk factors with AD. Accordingly, we examined the global and age-specific association between APOE genotype and AD by using the A/T/N classification, relying on the cerebrospinal fluid (CSF) levels of β-amyloid peptide (A, β-amyloid deposition), phosphorylated tau (T, pathologic tau), and total tau (N, neurodegeneration) to identify patients with AD. Methods and findings This case-control study included 1,593 white AD cases (55.4% women; mean age 72.8 [range = 44-96] years) with abnormal values of CSF biomarkers from nine European memory clinics and the American Alzheimer's Disease Neuroimaging Initiative (ADNI) study. A total of 11,723 dementia-free controls (47.1% women; mean age 65.6 [range = 44-94] years) were drawn from two longitudinal cohort studies (Whitehall II and Three-City), in which incident cases of dementia over the follow-up were excluded from the control population. Odds ratio (OR) and population attributable fraction (PAF) for AD associated with APOE genotypes were determined, overall and by 5-year age categories. In total, 63.4% of patients with AD and 22.6% of population controls carried at least one APOE ε4 allele. Compared with non-ε4 carriers, heterozygous ε4 carriers had a 4.6 (95% confidence interval 4.1-5.2; p < 0.001) and ε4/ε4 homozygotes a 25.4 (20.4-31.2; p < 0.001) higher OR of AD in unadjusted analysis. This association was modified by age (p for interaction < 0.001). The PAF associated with carrying at least one ε4 allele was greatest in the 65-70 age group (69.7%) and weaker before 55 years (14.2%) and after 85 years (22.6%). The protective effect of APOE ε2 ...
Keywords	Medicine ; R
Subject code	616
Language	English
Publishing date	2020-08-01T00:00:00Z
Publisher	Public Library of Science (PLoS)
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Seasonal plasticity of cognition and related biological measures in adults with and without Alzheimer disease

Andrew S P Lim / Chris Gaiteri / Lei Yu / Shahmir Sohail / Walter Swardfager / Shinya Tasaki / Julie A Schneider / Claire Paquet / Donald T Stuss / Mario Masellis / Sandra E Black / Jacques Hugon / Aron S Buchman / Lisa L Barnes / David A Bennett / Philip L De Jager

PLoS Medicine, Vol 15, Iss 9, p e

Analysis of multiple cohorts.

2018 Volume 1002647

Abstract: Background There are few data concerning the association between season and cognition and its neurobiological correlates in older persons-effects with important translational and therapeutic implications for the diagnosis and treatment of Alzheimer ... ...

Abstract	Background There are few data concerning the association between season and cognition and its neurobiological correlates in older persons-effects with important translational and therapeutic implications for the diagnosis and treatment of Alzheimer disease (AD). We aimed to measure these effects. Methods and findings We analyzed data from 3,353 participants from 3 observational community-based cohort studies of older persons (the Rush Memory and Aging Project [MAP], the Religious Orders Study [ROS], and the Minority Aging Research Study [MARS]) and 2 observational memory-clinic-based cohort studies (Centre de Neurologie Cognitive [CNC] study at Lariboisière Hospital and the Sunnybrook Dementia Study [SDS]). We performed neuropsychological testing and, in subsets of participants, evaluated cerebrospinal fluid AD biomarkers, standardized structured autopsy measures, and/or prefrontal cortex gene expression by RNA sequencing. We examined the association between season and these variables using nested multiple linear and logistic regression models. There was a robust association between season and cognition that was replicated in multiple cohorts (amplitude = 0.14 SD [a measure of the magnitude of seasonal variation relative to overall variability; 95% CI 0.07-0.23], p = 0.007, in the combined MAP, ROS, and MARS cohorts; amplitude = 0.50 SD [95% CI 0.07-0.66], p = 0.017, in the SDS cohort). Average composite global cognitive function was higher in the summer and fall compared to winter and spring, with the difference equivalent in cognitive effect to 4.8 years' difference in age (95% CI 2.1-8.4, p = 0.002). Further, the odds of meeting criteria for mild cognitive impairment or dementia were higher in the winter and spring (odds ratio 1.31 [95% CI 1.10-1.57], p = 0.003). These results were robust against multiple potential confounders including depressive symptoms, sleep, physical activity, and thyroid status and persisted in cases with AD pathology. Moreover, season had a marked effect on cerebrospinal fluid Aβ 42 ...
Keywords	Medicine ; R
Subject code	150
Language	English
Publishing date	2018-09-01T00:00:00Z
Publisher	Public Library of Science (PLoS)
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Article ; Online: Cerebrospinal fluid PKR level predicts cognitive decline in Alzheimer's disease.

Julien Dumurgier / Francois Mouton-Liger / Pauline Lapalus / Magali Prevot / Jean-Louis Laplanche / Jacques Hugon / Claire Paquet / Groupe d’Investigation du Liquide Cephalorachidien (GIL) Study Network

PLoS ONE, Vol 8, Iss 1, p e

2013 Volume 53587

Abstract: The cerebrospinal fluid (CSF) levels of the proapoptotic kinase R (PKR) and its phosphorylated PKR (pPKR) are increased in Alzheimer's disease (AD), but whether CSF PKR concentrations are associated with cognitive decline in AD patients remain unknown. ... ...

Abstract	The cerebrospinal fluid (CSF) levels of the proapoptotic kinase R (PKR) and its phosphorylated PKR (pPKR) are increased in Alzheimer's disease (AD), but whether CSF PKR concentrations are associated with cognitive decline in AD patients remain unknown. In this study, 41 consecutive patients with AD and 11 patients with amnestic mild cognitive impairment (aMCI) from our Memory Clinic were included. A lumbar puncture was performed during the following month of the clinical diagnosis and Mini-Mental State Examination (MMSE) evaluations were repeated every 6 months during a mean follow-up of 2 years. In AD patients, linear mixed models adjusted for age and sex were used to assess the cross-sectional and longitudinal associations between MMSE scores and baseline CSF levels of Aβ peptide (Aβ 1-42), Tau, phosphorylated Tau (p-Tau 181), PKR and pPKR. The mean (SD) MMSE at baseline was 20.5 (6.1) and MMSE scores declined over the follow-up (-0.12 point/month, standard error [SE] = 0.03). A lower MMSE at baseline was associated with lower levels of CSF Aβ 1-42 and p-Tau 181/Tau ratio. pPKR level was associated with longitudinal MMSE changes over the follow-up, higher pPKR levels being related with an exacerbated cognitive deterioration. Other CSF biomarkers were not associated with MMSE changes over time. In aMCI patients, mean CSF biomarker levels were not different in patients who converted to AD from those who did not convert.These results suggest that at the time of AD diagnosis, a higher level of CSF pPKR can predict a faster rate of cognitive decline.
Keywords	Medicine ; R ; Science ; Q
Subject code	616
Language	English
Publishing date	2013-01-01T00:00:00Z
Publisher	Public Library of Science (PLoS)
Document type	Article ; Online
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Article ; Online: Hepatitis C virus controls interferon production through PKR activation.

Noëlla Arnaud / Stéphanie Dabo / Patrick Maillard / Agata Budkowska / Katerina I Kalliampakou / Penelope Mavromara / Dominique Garcin / Jacques Hugon / Anne Gatignol / Daisuke Akazawa / Takaji Wakita / Eliane F Meurs

PLoS ONE, Vol 5, Iss 5, p e

2010 Volume 10575

Abstract: Hepatitis C virus is a poor inducer of interferon (IFN), although its structured viral RNA can bind the RNA helicase RIG-I, and activate the IFN-induction pathway. Low IFN induction has been attributed to HCV NS3/4A protease-mediated cleavage of the ... ...

Abstract	Hepatitis C virus is a poor inducer of interferon (IFN), although its structured viral RNA can bind the RNA helicase RIG-I, and activate the IFN-induction pathway. Low IFN induction has been attributed to HCV NS3/4A protease-mediated cleavage of the mitochondria-adapter MAVS. Here, we have investigated the early events of IFN induction upon HCV infection, using the cell-cultured HCV JFH1 strain and the new HCV-permissive hepatoma-derived Huh7.25.CD81 cell subclone. These cells depend on ectopic expression of the RIG-I ubiquitinating enzyme TRIM25 to induce IFN through the RIG-I/MAVS pathway. We observed induction of IFN during the first 12 hrs of HCV infection, after which a decline occurred which was more abrupt at the protein than at the RNA level, revealing a novel HCV-mediated control of IFN induction at the level of translation. The cellular protein kinase PKR is an important regulator of translation, through the phosphorylation of its substrate the eIF2alpha initiation factor. A comparison of the expression of luciferase placed under the control of an eIF2alpha-dependent (IRES(EMCV)) or independent (IRES(HCV)) RNA showed a specific HCV-mediated inhibition of eIF2alpha-dependent translation. We demonstrated that HCV infection triggers the phosphorylation of both PKR and eIF2alpha at 12 and 15 hrs post-infection. PKR silencing, as well as treatment with PKR pharmacological inhibitors, restored IFN induction in JFH1-infected cells, at least until 18 hrs post-infection, at which time a decrease in IFN expression could be attributed to NS3/4A-mediated MAVS cleavage. Importantly, both PKR silencing and PKR inhibitors led to inhibition of HCV yields in cells that express functional RIG-I/MAVS. In conclusion, here we provide the first evidence that HCV uses PKR to restrain its ability to induce IFN through the RIG-I/MAVS pathway. This opens up new possibilities to assay PKR chemical inhibitors for their potential to boost innate immunity in HCV infection.
Keywords	Medicine ; R ; Science ; Q
Subject code	570
Language	English
Publishing date	2010-05-01T00:00:00Z
Publisher	Public Library of Science (PLoS)
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