Dataset Information

NS5A Promotes Constitutive Degradation of IP3R3 to Counteract Apoptosis Induced by Hepatitis C Virus.

ABSTRACT: FBXL2 targets IP3R3 for ubiquitin-mediated degradation to limit Ca2+ flux to mitochondria and, consequently, apoptosis. Efficient replication of hepatitis C virus (HCV) requires geranylgeranylation of FBXL2. Here, we show that the viral protein NS5A forms a trimeric complex with IP3R3 and FBXL2, unmasking IP3R3's degron in the absence of inositol 1,4,5-trisphosphate (IP3) stimulation. FBXL2 knockdown or expression of a stable IP3R3 mutant causes persistent Ca2+ flux and sensitizes cells to apoptosis, resulting in the inhibition of viral replication. Importantly, the effect of FBXL2 silencing is rescued by depleting IP3R3, but not p85?, another established FBXL2 substrate, indicating that the anti-HCV effect of FBXL2 knockdown is largely due to IP3R3 stabilization. Finally, disruption of the FBXL2-NS5A-IP3R3 complex using somatic cell genetics or pharmacologic inhibition results in IP3R3 stabilization and suppression of HCV replication. This study reveals an IP3-independent molecular mechanism through which HCV promotes IP3R3 degradation, thereby inhibiting virus-induced apoptosis and establishing chronic infection.

SUBMITTER: Kuchay S

PROVIDER: S-EPMC6247906 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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NS5A Promotes Constitutive Degradation of IP3R3 to Counteract Apoptosis Induced by Hepatitis C Virus.

Kuchay Shafi S Saeed Mohsan M Giorgi Carlotta C Li Jie J Hoffmann Hans-Heinrich HH Pinton Paolo P Rice Charles M CM Pagano Michele M

Cell reports 20181001 4

FBXL2 targets IP3R3 for ubiquitin-mediated degradation to limit Ca2+ flux to mitochondria and, consequently, apoptosis. Efficient replication of hepatitis C virus (HCV) requires geranylgeranylation of FBXL2. Here, we show that the viral protein NS5A forms a trimeric complex with IP3R3 and FBXL2, unmasking IP3R3's degron in the absence of inositol 1,4,5-trisphosphate (IP3) stimulation. FBXL2 knockdown or expression of a stable IP3R3 mutant causes persistent Ca2+ f ...[more]

PMID: 30355490

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Project description:Hepatitis C virus (HCV) infection is accompanied by increased oxidative stress and endoplasmic reticulum stress as a consequence of viral replication, production of viral proteins, and pro-inflammatory signals. To overcome the cellular stress, hepatocytes have developed several adaptive mechanisms like anti-oxidant response, activation of Unfolded Protein Response and autophagy to achieve cell survival. These adaptive mechanisms could both improve or inhibit viral replication, however, little is known in this regard. In this study, we investigate the mechanisms by which hepatocyte-like (Huh7) cells adapt to cellular stress in the context of HCV protein overexpression and oxidative stress. Huh7 cells stably expressing individual HCV (Core, NS3/4A and NS5A) proteins were treated with the superoxide anion donor menadione to induce oxidative stress. Production of reactive oxygen species and activation of caspase 3 were quantified. The activation of the eIF2α/ATF4 pathway and changes in the steady state levels of the autophagy-related proteins LC3 and p62 were determined either by quantitative polymerase chain reaction (qPCR) or Western blotting. Huh7 cells expressing Core or NS5A demonstrated reduced oxidative stress and apoptosis. In addition, phosphorylation of eIF2α and increased ATF4 and CHOP expression was observed with subsequent HCV Core and NS5A protein degradation. In line with these results, in liver biopsies from patients with hepatitis C, the expression of ATF4 and CHOP was confirmed. HCV Core and NS5A protein degradation was reversed by antioxidant treatment or silencing of the autophagy adaptor protein p62. We demonstrated that hepatocyte-like cells expressing HCV proteins and additionally exposed to oxidative stress adapt to cellular stress through eIF2a/ATF4 activation and selective degradation of HCV pro-oxidant proteins Core and NS5A. This selective degradation is dependent on p62 and results in increased resistance to apoptotic cell death induced by oxidative stress. This mechanism may provide a new key for the study of HCV pathology and lead to novel clinically applicable therapeutic interventions.

Dataset Information

NS5A Promotes Constitutive Degradation of IP3R3 to Counteract Apoptosis Induced by Hepatitis C Virus.

Publications

NS5A Promotes Constitutive Degradation of IP3R3 to Counteract Apoptosis Induced by Hepatitis C Virus.

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