Host cell mTORC1 is required for HCV RNA replication

Stöhr, Stefanie; Costa, Rui; Sandmann, Lisa; Westhaus, Sandra; Pfaender, Stephanie; Anggakusuma,; Dazert, Eva; Meuleman, Philip; Vondran, Florian W. R.; Manns, Michael P.; Steinmann, Eike; Hahn, Thomas von; Ciesek, Sandra

doi:10.1136/gutjnl-2014-308971

Cited by 48 publications

(45 citation statements)

References 39 publications

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“…Furthermore, such inactivation and the downstream inhibition of the PI3/Akt/mTOR pathway resulted in HCV-induced autophagy (14), which may contribute to membrane rearrangements to accommodate replication complexes (15,16). Similar results have been recently observed using mTOR inhibitors (17). How the transition of Akt/PKB from an early-activated plasma membrane-bound form to a cytoplasm location takes place is not known.…”

supporting

confidence: 67%

“…A deeper knowledge of the NS5B-Akt/PKB molecular interaction could be used to design small-molecule inhibitors directed to interfere with this critical connection, by analogy to the proposed new Bcl-2 inhibitors for cancer treatment (46). Furthermore, Akt/PKB inhibitors currently undergoing clinical trials could be useful for HCV infection treatment, as it has been recently showed for those inhibiting mTORC1 (17). Taken together, these results highlight the importance of the PI3K/Akt/mTOR pathway in HCV infection.…”

Section: Discussionmentioning

confidence: 99%

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Hepatitis C Virus RNA-Dependent RNA Polymerase Interacts with the Akt/PKB Kinase and Induces Its Subcellular Relocalization

Valero

Sabariegos

Cimas

et al. 2016

Antimicrob Agents Chemother

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i Hepatitis C virus (HCV) interacts with cellular components and modulates their activities for its own benefit. These interactions have been postulated as a target for antiviral treatment, and some candidate molecules are currently in clinical trials. The multifunctional cellular kinase Akt/protein kinase B (PKB) must be activated to increase the efficacy of HCV entry but is rapidly inactivated as the viral replication cycle progresses. Viral components have been postulated to be responsible for Akt/PKB inactivation, but the underlying mechanism remained elusive. In this study, we show that HCV polymerase NS5B interacts with Akt/ PKB. In the presence of transiently expressed NS5B or in replicon-or virus-infected cells, NS5B changes the cellular localization of Akt/PKB from the cytoplasm to the perinuclear region. Sequestration of Akt/PKB by NS5B could explain its exclusion from its participation in early Akt/PKB inactivation. The NS5B-Akt/PKB interaction represents a new regulatory step in the HCV infection cycle, opening possibilities for new therapeutic options. As an obligate parasite, HCV usurps cellular functions and pathways to complete its replication cycle, and some of these routes are related to cell cycle control (2). The Akt/protein kinase B (PKB) family of serine/threonine protein kinases are involved in several signaling pathways that can impact the outcome of viral infections. Akt/PKB resides in the cytosol in an inactive conformation. Initial stimulation of the cell causes activation of a cell surface receptor and subsequently phosphorylation of phosphatidylinositol 3-kinase (PI3K). Activated PI3K is responsible of the formation of phosphatidylinositol(3,4,5)-trisphosphate second messenger. Akt interacts with these phosphoinositides and is recruited to the membrane, where it can be fully activated by PDK1 and other kinases. The Akt/PKB pathway is involved in processes as disparate as nutrient metabolism, regulation of protein synthesis, autophagy, and the balance of apoptosis versus cell survival and proliferation, the latter being critical for the outcome of viral infections (3-6). Akt/PKB can influence the virus-host interaction by several mechanisms. The translational repressors 4E-BPs are eukaryotic translation initiation factor 4E (eIF4E)-binding proteins that prevent cap-dependent translation of cellular mRNAs. Akt/PKB is needed for the inactivation of 4E-BPs, which occurs through a phosphorylation reaction that requires FRAP/mammalian target of rapamycin (mTOR) and results in activation of cellular translation (7). Akt/PKB is the downstream target of the lipid kinase PI3K, and both are involved in cell proliferation and apoptosis. In infections of neuronal cells by dengue virus serotype 2 (dengue-2) and Japanese encephalitis virus, PI3K played an antiapoptotic role, and the blocking of PI3K activation enhanced virus-induced cytopathology with no effect on virus production (8). These multiple effects of Akt/PKB can modulate cap-versus internal ribosome entry site (IRES)-dependent translatio...

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supporting

confidence: 67%

Section: Discussionmentioning

confidence: 99%

Hepatitis C Virus RNA-Dependent RNA Polymerase Interacts with the Akt/PKB Kinase and Induces Its Subcellular Relocalization

Valero

Sabariegos

Cimas

et al. 2016

Antimicrob Agents Chemother

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“…mTORC2 contains mTOR, GβL, and rictor and directly phosphorylates the prosurvival kinase Akt/PKB, but its cellular function is just beginning to be understood (37). Recently, Stöhr et al (38) reported that the host cell mTORC1/raptor is required for HCV replication, rather than suppression of HCV replication. To clarify the seemingly contradictory roles of mTOR in their and our studies, we dissected the antiviral effects of raptor (mTORC1) and rictor (mTORC2) downstream of DAPK.…”

Section: Discussionmentioning

confidence: 99%

Pegylated IFN-α suppresses hepatitis C virus by promoting the DAPK-mTOR pathway

Liu

Yang

Hsu

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Death-associated protein kinase (DAPK) has been found to be induced by IFN, but its antiviral activity remains elusive. Therefore, we investigated whether DAPK plays a role in the pegylated IFN-α (peg-IFN-α)-induced antiviral activity against hepatitis C virus (HCV) replication. Primary human hepatocytes, Huh-7, and infectious HCV cell culture were used to study the relationship between peg-IFN-α and the DAPK-mammalian target of rapamycin (mTOR) pathways. The activation of DAPK and signaling pathways were determined using immunoblotting. By silencing DAPK and mTOR, we further assessed the role of DAPK and mTOR in the peg-IFN-α-induced suppression of HCV replication. Peg-IFN-α up-regulated the expression of DAPK and mTOR, which was associated with the suppression of HCV replication. Overexpression of DAPK enhanced mTOR expression and then inhibited HCV replication. In addition, knockdown of DAPK reduced the expression of mTOR in peg-IFN-α-treated cells, whereas silencing of mTOR had no effect on DAPK expression, suggesting mTOR may be a downstream effector of DAPK. More importantly, knockdown of DAPK or mTOR significantly mitigated the inhibitory effects of peg-IFN-α on HCV replication. In conclusion, our data suggest that the DAPK-mTOR pathway is critical for anti-HCV effects of peg-IFN-α.H epatitis C virus (HCV) infection is a major health problem worldwide that may lead to chronic hepatitis, liver cirrhosis, hepatocellular carcinoma, and liver failure (1). Although the development of direct antiviral agents (DAAs), such as HCV protease and polymerase inhibitors, has revolutionized the treatment of HCV infection (2, 3), considering the high cost of IFN-free DAAs, combination therapy with pegylated IFN-α (peg-IFN-α) and ribavirin (RBV) may remain for a while, especially in countries with limited medical resources (4-6). However, many HCV patients fail combination therapy of peg-IFN-α and RBV, and determinants of the responsiveness to IFN have not been fully understood. Therefore, it is scientifically important to identify biomarkers or mechanisms for prediction of the IFN response in patients with hepatitis C.Type I IFNs are a family of pleiotropic cytokines with known antiviral, antiproliferative, and immunomodulatory functions exerted on a wide range of cell types. IFNs bind to its receptor and lead to activation of the Janus kinase-signal transducer and activator of transcription (STAT) pathway, resulting in the association of phosphorylated STATs with IFN regulatory factor-9 to form a transcriptional activator complex, which subsequently translocates to the nucleus and activates an array of IFN-stimulated genes, such as dsRNA-dependent protein kinase (PKR), 2′,5′-oligoadenylatesynthesase, p56, and myxovirus resistance protein A (MxA) (7). Through the action of these IFN-induced genes, IFN-α confers an antiviral state on hepatocytes and exerts its anti-HCV activity in patients with chronic hepatitis C. However, the full function of the IFN-induced genes in suppression of HCV replication has not yet been compr...

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“…Whichever the cause, it is remarkable that in both cases, HCV infection did not recurred despite the start and maintenance of immunosuppressive therapy. On the other hand, although recent report suggested a possible role of mTOR in favouring viral decay [7], this issue remains controversial based on a thorough review of the current literature.…”

Section: Discussionmentioning

confidence: 99%